HIDE LTLEflb

NBSIR 87-3549

A Survey of Electronic

Measurement Needs Below 10 MHz

John R. Sorrells

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Electronics and Electrical Engineering

Electrosystems Division

Gaithersburg, MD 20899

February 1987

Issued June 1987

U.S. DEPARTMENT OF COMMERCE

“QC

100

• U56

87-3549

1987

C.2

IUREAU OF STANDARDS

NBSIR 87-3549

•Research Information Center

National Bureau of Standards

Gaithersburg, Maryland 20899

A SURVEY OF ELECTRONIC

MEASUREMENT NEEDS BELOW 10 MHz

John R. Sorrells

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Electronics and Electrical Engineering

Electrosystems Division

Gaithersburg, MD 20899

February 1987

Issued June 1987

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

EXECUTIVE SUMMARY

This report presents the results of a survey conducted by the Center for

Electronics and Electrical Engineering to assess the measurement needs of the

electronics industry at frequencies from dc to 10 MHz. The purpose of the

survey was to obtain information that can be used in planning and implementing

NBS programs to develop new or improved calibration services or measurement

methods to support industry needs.

In conducting the survey, the Center received cooperation and assistance from

the following organizations: the IEEE Instrumentation and Measurements

Society, the Electronic Industries Association, the National Conference of

Standards Laboratories, the American Physical Society, and the Instrument

Society of America. These organizations provided comments and suggestions on the survey questionnaire, and/or provided membership mailing lists for use in

soliciting survey participation.

The survey vehicle was a seven-part questionnaire that elicited information

regarding (1) the respondent’s type of organization or business, (2) the

principal reasons for needing NBS measurement support, (3) the measurement

needs for critical electrical quantities, (4) the usage and support of

measuring instruments or devices, (5) needs related to automatic test

equipment or complex measurement systems, (6) concerns with conducted

electromagnetic interference, and (7) the effectiveness of mechanisms for

communicating or interacting with NBS. Space was also provided for the

respondents to enter "other" responses or provide additional comments if

desired.

Questionnaires were returned by a total of 527 respondents, representing most

segments of the electronics industry. The largest number of responses came from organizations involved with test equipment or instruments, followed by

aerospace organizations, and independent test, repair, or calibration service

organizations.

The largest percentage of respondents indicated that their organizations need

NBS measurement support to meet government requirements. However, there was a strong expression of need for NBS assistance to support R&D and other

production-related activities.

The responses to Section C of the questionnaire indicated that the measurement

of many of the more basic quantities such as voltage, current, resistance,

capacitance, frequency, etc., were of critical importance and that

new/improved measurement methods or NBS calibration services are needed for

many quantities already supported by NBS measurement services. Further study

is planned to determine the implications of these responses.

Also in Section C, 33% of the respondents indicated that they were familiar

with the NBS calibration services described in NBS Special Publication 250 and

51% indicated that their organizations use such services.

iii
The responses to Section D of the questionnaire regarding the usage and

need for support of measuring instruments or devices correlates well with

those regarding electrical quantities. Those instruments or devices involved

in the measurement of basic quantities ranked high on the usage list. Also,

many of the instruments were perceived to require new or improved

characterization methods or NBS calibration services.

Responses to the questions regarding the respondents’ involvement with

automatic test equipment or complex measurement systems and with conducted

electromagnetic interference indicate that these are important technical areas

needing NBS support. In particular, there is a strong expression of needs for

practical support such as calibration and test guides, documented measurement

methods, definitions and terminology, and characterization/measurement

techniques in these areas.

The four communication means used most by the respondents to obtain

information on NBS programs and services were indicated to be NBS reports/

special publications, journal publications, conf erences/workshops/seminars

,

and specific requests. Others such as staff interactions, media releases, and

technical committees were ranked somewhat less important. For each of the

listed communication means, some percentage of the respondents indicated a need for improvement.

A final question of the survey asked if NBS has provided the necessary support

when requested by the respondent’s organization. There were 259 responses to

this question, with 92% affirmative answers.

Twenty-seven percent of the respondents provided additional comments regarding

specific measurement needs or general metrology-related issues. A common

theme in these comments was the need to learn more about NBS services,

programs, and activities.

The appendices of this report include a copy of the survey questionnaire, a listing of the responding organizations, lists of various "other" responses,

and histograms of the responses regarding measurement requirements (accuracy

vs. frequency or time) for the electrical quantities listed in the

questionnaire. Essentially all of the data derived from the survey are tabulated and presented either in the body of the report or in the appendices.

The results of this survey will be provided to all participants and made

available to other interested parties. Internally, the results will be used

to plan NBS programs and establish priorities for responding to the

measurement needs of the electronics industry.

iv
TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY iii

TABLE OF CONTENTS v LIST OF FIGURES vi

LIST OF TABLES vi

ABSTRACT 1

1. INTRODUCTION 1

2. THE QUESTIONNAIRE 2

3. SUMMARY OF RESPONSES 3

Section A, Organization/Business 3

Section B. Organizational Needs 4

Section C. Basic Electrical Quantities 6

Section D. Precision Instruments /Devices 14

Section E. ATE/Complex Measurement Systems 20

Section F. Conducted Electromagnetic Interference (CEMI). ... 22

Section G. Communications /Interact ions 23

Section H. Additional Comments 27

4. CONCLUSIONS 28

5. ACKNOWLEDGMENTS 30

APPENDIX A 31

APPENDIX B 39

APPENDIX C 47

APPENDIX D 81

APPENDIX E 82

APPENDIX E. 2 83

v
Page

LIST OF FIGURES

Figure 1. Requirements from survey and NBS

capabilities for voltage 10

LIST OF TABLES

Table 1. Distribution of responses by type of

organization/business 3

Table 2. Overall ranking of reasons for needing NBS

measurement support 4

Table 3. Reasons for needing NBS measurement support

as ranked by each type of organization/business 5 Table 4. Overall ranking of electrical quantities,

based on the number of Section C responses 6

Table 5. Section C responses indicating the need for

a new/ improved measurement method or an NBS

calibration service 8

Table 6. Top eleven quantities based on the number of

responses indicating the need for an NBS

calibration service 9

Table 7. Top eleven quantities based on the number of

responses indicating the need for a new/improved measurement method 11

Table 8. Percentage of respondents familiar with NBS

calibration services —classified by type of

organization 12

Table 9. Percentage of respondents using NBS calibration

services —classified by type of organization 13

Table 10. Ranking of instruments /devices, based on number

of users (Section D responses). Usage data for

each instrument /device is also shown 15

Table 11. Top eleven instruments or devices based on the

number of responses indicating their use as a standard 16

Table 12. Number of responses indicating the need for a new/improved characterization method or NBS

calibration service for the instrument /devices

.

Ranking is the same as in Table 11 17

vi
Page

LIST OF TABLES (contd.)

Table 13. Top eleven instruments or devices based on the number of responses indicating the need

for an NBS calibration service 18

Table 14. Top eleven instruments or devices based on the number of responses indicating the need

for new/improved characterization methods 19

Table 15. Summary of responses regarding respondents'

involvement with ATE or complex measurement

systems . 20

Table 16. Summary of responses regarding types of ATE

or complex measurement systems with which

respondents are involved 20

Table 17. Summary of responses regarding the usefulness

of possible NBS outputs related to ATE or complex measurement systems. 21

Table 18. Summary of responses regarding the manufacture

or use of CEMI-related equipment 22

Table 19. Summary of responses regarding the usefulness

of possible NBS outputs related to CEMI 23

Table 20. Summary of responses regarding the communication

means used by respondents to obtain information

on NBS programs and services 24

Table 21. Ranking of communication means by type of

organization/business. .... 25

Table 22. Summary of responses indicating the need to

improve the given communication means. . 26

vii
<
A SURVEY OF ELECTRONIC MEASUREMENT NEEDS BELOW 10 MHz

John R. Sorrells

Abstract

The results of a survey to assess the measurement needs of the

electronics industry over the frequency range from dc to 10 MHz

are presented. The questionnaire used in the survey covered three

broad areas of measurement needs: (1) basic electrical quantities

and related precision instruments, (2) automatic test equipment

and other complex measurement systems, and (3) conducted electromagnetic interference. The data provided by 527 respondents are summarized, and the results of various analyses are described.

Several conclusions, suggested by the analyses, are also discussed.

Key words: automatic test equipment; ATE; complex measurement systems;

electrical quantities; electronic measurement needs; precision

instruments; questionnaire; survey

1. Introduction

In 1985 the NBS Center for Electronics and Electrical Engineering (CEEE) began

plans for conducting an electronic measurement needs survey, and, in August of

that year, received formal approval from the Office of Management and Budget to

proceed with the endeavor. The objective of the survey was to elicit

information from the electronics industry pertaining to current and future

measurement needs that might require NBS measurement support, particularly from

the Electrosystems Division. Thus, the survey questionnaire focused primarily

on the assessment of measurement needs over the frequency range from dc to 10 MHz.

The first step in conducting the survey was the development of a suitable

questionnaire — one that covered both general and specific areas of concern. Several versions were prepared, revised, and subjected to internal review before

a final draft was produced. By prior arrangements, copies of this draft were

sent to representatives of the IEEE Instrumentation and Measurements Society,

the National Conference of Standards Laboratories (NCSL), and the Electronic

Industries Association for their review and comments. Copies were also provided

to individuals within NBS who were aware of the proposed survey and interested

in the results. In response, we received thoughtful comments and constructive

suggestions on the draft questionnaire from thirteen representatives in these

organizations. All comments and suggestions were given careful consideration,

and, where feasible, incorporated into the final version of the questionnaire.

With the approval and cooperation of the appropriate authorities, more than

11,500 advance letters were mailed to members of the IEEE Instrumentation and

Measurement Society, the Electronic Industries Association, the National

Conference of Standards Laboratories, the Instrument and Measurement Science

Group of the American Physical Society, and three divisions of the Instrument
2

Society of America, The advance letters gave a brief description of the

planned survey, and asked the recipient to return a pre-addressed post card

if he or she were interested in participating. Twelve percent (1418) of the

letter recipients requested and received a copy of the survey questionnaire.

Of these, 527 (37%) were completed and returned to NBS.

The following sections of this report summarize the results of the survey.

Section 2 discusses the format and structure of the questionnaire and the

purpose of each set of questions; Section 3 gives a summary of the responses

and presents tabulations of some of the data and cross-correlation results;

and Section 4 presents a discussion of conclusions that are based on' our interpretation of the data.

2. The Questionnaire

A copy of the questionnaire and its cover letter are included in Appendix A.

The questionnaire is composed of seven major sections. Section A requests

information on the respondent's organization or business. Section B asks the

respondent to identify the principal reasons why his or her organization needs

measurement support from NBS. Section C seeks to identify and quantify the

respondent's specific measurement needs. In this section, the respondent is

asked to identify electrical quantities whose measurement is critical in his

or her operation and to indicate the required accuracy and frequency ranges.

The respondent is also asked to indicate if a new or improved measurement

method or calibration service is needed for the listed quantities. Similar

information is requested for several time-domain quantities. Two final

questions in this section pertain to the respondent's awareness of existing

NBS calibration services and the use of those services by his or her

organization. Section D contains a list of instruments or devices that are commonly used for measuring electronic or electrical quantities and requests

information on how they are used by the respondent's organization. The

respondent was also asked to indicate if a characterization method or calibration service is needed for any of the listed instruments.

The questions in sections E and F are more general in scope than in the

preceding sections and are aimed at assessing the measurement needs of

organizations involved with automatic test equipment or complex measurement

systems and with conducted electromagnetic interference. In both of these

sections, the respondent is asked to identify the nature of his or her

organization's involvement, and to estimate the usefulness of possible NBS

outputs in each area. The questions in Section G are aimed at determining

the primary mechanisms by which the respondent's organization communicates

or interacts with NBS and the effectiveness of those mechanisms and of NBS

support on prior measurement problems. Finally, Section H provides space

for additional comments and for optional information regarding the

respondent's name and affiliation.

For most questions, space was provided for the respondent to enter an "other"

response or specific comments.
3. Summary of Responses

This section contains summaries of the responses to each part of the

questionnaire, as well as the results of several analyses to determine

cross-correlations between certain responses.

The following data presentations are arranged according to the sections of the

questionnaire. Where percentages are used to report the data, it is indicated

whether the figure is based on the total number of questionnaires returned, or on the number of responses to that particular question. In some instances,

the total number of responses to a given question is also reported.

Section A. Organization/Business

As stated above, 527 questionnaires were completed and returned during the

survey. Of these, 84 were submitted anonymously. The organizations

represented by the remaining respondents are listed in Appendix B. A

breakdown of these according to the categories listed in Section A is shown

below. Since many respondents checked more than one category, the sum of the

percentages is greater than 100 percent.

Table 1. Distribution of responses by type of organization/business

Organiz at ion/ Business

Section A

Responses

Percent of

Questionnaires

Returned (527)

Test Equipment /Instruments 132 25

Aerospace 79 15

Independent test, repair, 45 9

calibration service

Military 43 8

Electronic Components 42 8

University 42 8

Electric Power 36 7 Other Government 30 6

National Laboratory 26 5

Computer Equipment 25 5 Medical Electronics 24 5

Consumer Electronics 20 4

Telecommunication 19 4

Automotive 17 3

Other 99 19

Excluding the "Other" category, the largest percentage of responses came from

organizations involved in Test Equipment /Instruments and Aerospace. The most

common businesses listed in the "Other" category were R&D and consulting. The

remainder of the "Other" list includes a wide variety of organizations

involved in such business as pharmaceuticals, machinery, nuclear power,

chemicals, oil, gas, and the manufacture of various products.
Section B. Organizational Needs

- 4 -

In this section, the respondent was asked to indicate the principal reasons

why his or her organization needs measurement support from NBS. All respondents

(527) answered this section of the questionnaire, and generally checked more

than one category.

Table 2. Overall ranking of reasons for needing NBS measurement support.

Reason for Needing NBS Support

Section B

Responses

Percent of

Questionnaires

Returned (527)

1 . To meet government requirements,

e.g., for traceability

384 73

2. To support R&D 250 47

3. To improve quality control

in production

209 40

4. To improve product reliability 172 33

5. To assist in development of

product specifications

166 31

6 • To support development of voluntary

standards

147 28

7. To improve product compatibility 129 24

8 . To meet requirements of foreign

governments /buyers

92 17

9. To ensure market equity 88 17

10. To increase productivity 82 16

11. To reduce the cost of reaching

buyer/seller agreement

51 10

12. Other 33 6

A large percentage of the respondents indicated that their organizations need

NBS measurement support to meet government requirements. However, 47 percent

of the respondents indicated they need NBS support to support R&D, and more than 30 percent indicated a need for support in production-related activities.

This suggests that NBS measurement support is considered important and necessary

by many organizations in helping to solve some of the practical problems involved

in developing and producing reliable products.
5

Although 33 respondents listed "other" reasons for needing NBS support, most

of these were variations or restatements of those given in the above list.

Some of the new reasons cited were "to improve personnel safety," "to develop

standards in new areas of technology," and "to increase reliability in the

nuclear power area.

To obtain further insight into the question of organizational needs, the

responses for this section were tabulated and ranked according to type of

organization/ business.

In the table below, the needs ranked first, second, and third by each type of

organization are shown. In each column, the numbers 1 through 11 refer to the

overall ranking of the eleven listed needs; the numbers in parenthesis indicate

the percentage of organizations in each category that ranked the need either

first, second, or third in importance.

Table 3. Reasons for needing NBS measurement support

as ranked by each type of organization/business

Type of Organization Needs Ranking

1st 2nd 3rd

Aerospace 1 (90) 2 (56) 3 (42)

Automotive 1 (94) 3 (41) 2,4,6 (29)

Computer Equipment 1 (68) 3 (60) 7 (56)

Consumer Electronics 1 (85) 3 (65) 9 (55)

Electric Power 1 (83) 3 (42) 4 (39)

Electronic Components 1 (83) 3 (60) 6 (48)

Independent test, repair, calib. service 1 (89) 3 (44) 6 (36)

Medical Electronics 1 (67) 3 (54) 2,4 (38)

National Laboratory 2 (77) 1 (46) 6 (27)

Military 1 (86) 2 (44) 4 (28)

Other Government 1 (80) 2 (47) 4 (43)

Telecommunications 1 (63) 6 (59) 3 (53)

Test Equipment /Instruments 1 (77) 3,5

(46)

2 (38)

University 2 (79) 1 (33) 6 (21)

With only two exceptions, all types of organizations ranked the need to meet

government requirements as their top concern; the exceptions were National

Laboratories and Universities, both of which ranked the support of R&D as their

principal need for NBS support. The need to improve quality control in

production was ranked second in importance by eight of the fourteen organization

types, and the support of R&D was ranked second by Aerospace, Military, and Other

Government organizations. Third place rankings included six of the eleven needs

categories.
6

Section C. Basic Electrical Quantities

This section of the questionnaire collected the largest body of data and

undoubtedly required the greatest investment of time by the respondents. From

a list of 33 quantities, each respondent was asked to identify those of critical

importance to his or her organization, and, for those so identified, to indicate

the required measurement accuracy, the frequency or time range of concern, and

the type of NBS support needed (measurement method or calibration service). As

shown, the number of responses varied by an order of magnitude, depending upon the

electrical quantity.

In the following table, the electrical quantities are ranked in descending order,

based on the number of respondents who indicated that the quantity is critical to

his or her operation by indicating their accuracy vs. frequency (or time)

requirements. As can be seen, the quantities receiving the highest percentage of

responses are many of the more basic ones.

Table 4. Overall ranking of electrical quantities, based on the number of

Section C responses.

Electrical Quantity

1. Voltage

2. Resistance

3. Current

4. Capacitance

5. Frequency

6. Voltage, transient

7. Rise/fall time

8. Power

9. Current, transient

10. Inductance

11. Delay time

12. Phase

13. Impedance

14. Magnetic Field Strength

15. Settling Time

16. Harmonic Distortion

17. Acquisition Time

18. Leakage Current

19. Conductance

20 . Noise Amplitude

21. Electric Field Strength

22. Power Factor

23. Quality Factor

24. Dissipation Factor

25. Reactive Power

26. Linearity, Differential

27. Linearity, Integral

28. Energy

29. Percent Modulation, AM

30. Percent Modulation, FM

31. Phase Noise

32. Admittance

33. Effective Bits

Percent of

Section C Questionnaires

Responses Returned (527)

404 77

332 63

323 61

250 47

237 45

235 45

224 43

172 33

167 32

164 31

149 28

132 25

125 24

121 23

118 22

100 19

96 18

87 17

85 16

85 16

81 15

78 15

74 14

71 13

64 12

62 12

61 12

60 11

58 11

56 11

42 8

42 8

36 7
7

Thirty-three respondents listed "other" quantities whose measurement they

considered important to their operations. This list contained few repeats and

included both physical and electrical quantities such as charge, pressure,

optical power, wavelength, force, permittivity, duty cycle, baseline offset,

delay time jitter, and transient resistance.

Quantities receiving the highest percentage of responses were also the quantities

that appeared near the top of the two lists in Section C of the questionnaire,

and, thus, might be expected to receive a greater number of responses. However,

this does not appear to be the case since many of the more derived quantities

such as rise/fall time, phase, harmonic distortion, etc. were also considered to

be of critical importance, and they appeared later in the list.

The responses regarding required measurement accuracies and frequencies also

varied considerably, depending upon the quantity to be measured. For example,

for some of the more basic quantities such as voltage, current, and resistance,

many respondents indicated the need for high accuracy measurements (0.001% and

0.0001%) over the full range of frequencies, but with the greatest need being for

dc measurements. For other quantities such as power, reactive power, and power

factor, the highest measurement accuracy required was 0.001% and the frequency

ranges of most concern were those encompassing the standard power frequencies (60

and 400 Hz). For frequency measurements, the respondents indicated the

greatest need for the most accurate (0.0001%) measurements at the highest

frequency (1 MHz - 10 MHz) range addressed by the survey.

For the interested reader, a complete summary of the accuracy vs. frequency data

for all of the listed quantities is presented in Appendix C.

The responses regarding the need for new or improved measurement methods or calibration services for the electrical quantities are tabulated in the following

table. Here the quantities are again ranked by the number of responses received,

and the number of responses indicating the need for a measurement method or calibration service are listed. Many respondents indicated a need for both.

Quantities that are followed by an asterisk are those for which a routine NBS

calibration service or special test is available for certain levels of accuracy

and certain ranges of frequency or time.
8

Table 5. Section C responses indicating the need for a new/improved

measurement method or an NBS calibration service.

Quantity

Number Needing

Section C NBS Calib.

Responses Meas. Method Service

1. Voltage* 404 88 148

2. Resistance* 332 51 110

3. Current* 323 71 87

4. Capacitance* 250 49 85

5. Frequency* 237 33 65

6. Voltage, transient 235 82 47

7. Rise, fall time* 224 72 48

8. Power* 172 28 45

9. Current, transient 167 56 24

10. Inductance* 164 30 49

11. Delay Time* 149 41 28

12. Phase* 132 32 35

13. Impedance 125 28 32

14. Magnetic Field Strength* 121 47 32

15. Settling Time 118 41 24

16. Harmonic Distortion 100 27 22

17. Acquisition Time 96 32 17

18. Leakage Current 87 23 20

19. Conductance 85 15 20

20. Noise Amplitude 85 40 28

21. Electric Field Strength 81 34 17

22. Power Factor 78 16 17

23. Quality Factor 74 25 25

24. Dissipation Factor 71 22 24

25. Reactive Power 64 9 15

26. Linearity, differential 62 20 18

27. Linearity, integral 61 20 15

28. Energy* 60 8 10

29. Percent Modulation, AM 58 15 12

30. Percent Modulation, FM 56 13 10

31. Phase Noise 42 15 10

32. Admittance 42 7 9

33. Effective Bits 36 14 10

Although the numbers vary from quantity to quantity, on the average,

approximately half of those responding to Section C indicated the need for a new

or improved measurement method or an NBS calibration service for the listed

quantities. These results imply that approximately half of the respondents who

consider the measurement of a given quantity critical to their operation, also

believe existing measurement methods and NBS calibration services need

improvement. Since NBS already provides calibration services or special tests

for more than a third of the quantities, the data could also be interpreted as an indication that NBS should do more to make the user community aware of

available services. The responses to some of the other survey questions tend

to support this interpretation.
J - 9 -

To explore the significance of these results further, the quantities were

ranked according to the number of responses indicating a need for an NBS

calibration service. Listed below are the eleven quantities that comprise

the upper third of that rank. Quantities that are followed by an asterisk

are those for which a routine 1NBS calibration service or special test is

available.

Table 6. Top eleven quantities based on the number of responses

indicating the need for an NBS calibration service.

Section C Number Needing NBS

Quantity Responses Calibration Service

1 . Voltage* 404 148

2. Resistance* 332 110

3. Current* 323 87

4. Capacitance* 250 85

5. Frequency* 237 65

6. Inductance* 164 49

7. Rise/fall time* 224 48

8. Voltage/ transient 235 47

9. Power* 172 45

10. Phase* 132 35

11. Impedance 125 32

There are two points worth noting about the above list. First, nine of the

eleven quantities (all but phase and impedance) also appear in the upper third

of table 4, where the quantities are ranked according to the percentage of

total respondents who indicated that the quantity is critically important to

his or her organization. Second, except for transient voltage and impedance,

all of these quantities are ones for which an NBS calibration service or special

test is available.

To determine if NBS is already providing services at the accuracies and frequencies

of interest indicated by the survey, NBS is conducting further analyses. In these

analyses, the measurement needs indicated by the survey data will be compared with

the measurement services currently offered by NBS to determine where differences or similarities exist. As an example, the results of such an analysis for voltage are discussed below.

An example of how the survey data can be utilized for NBS planning purposes is

illustrated by the requirements/capability charts for voltage, given in figure 1.

As a starting point. Appendix C provides a histogram of the number of responses

regarding measurement requirements (accuracy vs. frequency or time) for all of the

quantities listed in the questionnaire. For voltage, the 404 responses are seen to

be distributed, with the higher accuracy requirements at dc and the lower frequency

ranges. Tables 5 and 6 above indicate that 148 of the respondents indicated the

need for an NBS calibration service for voltage. The first chart in figure 1 shows

the voltage measurement requirements of these respondents, where the heavy border

encloses the areas where the number of responses were at least 20 percent of the
o)H-s

—r

-<oi>^cooj>

10

REQUIREMENTS/CAPABILITIES - VOLTAGE

O.OOI%

0. 0001 %

1 %

0. 1 %

0. 01 %

0. 001 %

0. 0001 %

0 . 00001 %

63

1 %

0 . 1 %

0. 01 %

0. 001 %

0.0001 %

0 . 00001 %

8

Voltage requirements of 148

respondents heeding an NBS

calibration service for voltage,

DC voltage measurements and indirect

AC voltage measurements Via AC-DC

difference of TVCs (existing NBS calibration

services).

Note:

V - Routine and special tests * •- Best uncertainty available using

NBS Voltage Calibration System. %

0- Best uncertainty available at IV by

direct comparison to the National

Standard of voltage.

Voltage measurements directly via best

available calibrators and DVMs (proposed

NBS calibration services).

* Best uncertainty available

within (but not necessarily over)

the entire frequency range.

Figure 1. Requirements from survey and NBS capabilities for voltage.
11 -

maximum value of 63 (i.e., 12 or higher). As can be seen, the requirements

are generally focused at the 0.1% through 0.001% accuracy limits, with 0.0001%

(1 ppm) needed at dc. In the 1-10 MHz frequency band, 0.1% to 0.01% accuracy

is required.

The second chart in figure 1 gives an approximate description of the existing

NBS calibration service capabilities for dc voltage measurements, as well as ac voltage measurements. The latter are supported indirectly by means of ac-dc

difference measurements of thermal voltage converters. The 0.1 ppm (0.00001%)

accuracy limit at dc is achieved by a special test that requires the use of

precision dc transfer standards which have the requisite stability, low

temperature coefficient, and mechanical ruggedness. The 10 ppm (0.001%)

accuracy limit shown from dc through 100 kHz is achievable only as a special

ac-dc difference test for voltages from 5V to 100V, 100 Hz to 20 Hz, provided

that the performance of the instrument under test is adequate. A 200 ppm

(0.02%) accuracy limit occurs above 100 kHz to 500 kHz, and 300 ppm (0.03%) is

the accuracy limit from 500 kHz to 1 MHz. From 1 MHz to 10 MHz, the accuracy

limit varies between 300-500 ppm (0.03-0.05%).

The third chart in figure 1 describes the NBS capabilities now planned for

providing a proposed new NBS calibration service for measuring voltage

directly. Consequently, this proposed new NBS service would be responsive to

the needs expressed in Section D of the questionnaire for the calibration of

voltmeters and calibrators. In general, the limit to the accuracy available

will depend upon the uncertainty (indicated by the black dots) of the NBS

Voltage Calibration System (VCS) , and the stability of the calibrator or voltmeter standard under test. The VCS is capable of high accuracy over a voltage range from several millivolts to one kilovolt, at frequencies ranging

from near dc to 10 MHz, with measurement uncertainties estimated to be 10-20 ppm

(0.001-0.002%) in the midrange of voltage amplitudes and frequencies. Thus, it

appears that the proposed new NBS calibration service would meet most of the

voltage requirements expressed by the survey respondents.

In another analysis of the data provided in Section C, the quantities were

ranked according to the number of responses indicating a need for a new or improved measurement method. Again, the eleven quantities comprising the upper

third of that rank are listed in the table below, where asterisks identify

those for which an NBS calibration service or special test is available.

Table 7. Top eleven quantities based on the number of responses

indicating the need for a new/improved measurement method.

Quantity

Section C Number Needing

Responses Measurement Method

1. Voltage*

2. Voltage, transient

3. Rise/fall time*

4. Current*

5. Current, transient

6. Resistance*

7. Capacitance*

8. Magnetic Field Strength*

9. Delay Time*

10. Settling Time

11. Noise Amplitude

404 88

235 82

224 72

323 71

167 56

332 51

250 49

121 47

149 41

118 41

85 40
12

As shown in table 7, when the quantities are ranked by this means, a different

set of eleven from that shown in table 6 appears at the top. Since two of

these (rise/fall time and delay time) are supported by NBS for frequencies

above 10 MHz, these results appear to indicate a need for new/improved

measurement methods for these two quant itites in the low frequency regimes.

The transient voltage, transient current, noise amplitude and settling time

quantities are dynamic, derived quantities for which new/improved measurement

methods could be developed under present and future NBS research programs.

Question Cll of this section asks the respondent if he or she is familiar

with the calibration services currently offered by NBS and described in

Special Publication 250. Of the 527 respondents, only 33% answered "yes” to

this question. These responses were broken down by type of organization and

are shown in the table below.

Table 8. Percentage of respondents familiar with NBS calibration

services — classified by type of organization.

Organization Type

Total

Responses

"Yes"

Responses

Percentage

of "Yes"

Responses

1. Aerospace

2. Automotive

3. Computer Equipment

4. Consumer Electronics

5. Electric Power

6. Electronic Components

7. Independent Test, Repair,

Calibration Service

8. Medical Electronics

9. National Laboratory

10. Military

11. Other Government

12. Telecommunication

13. Test equipment/instruments

14. University

15. Other

74 27 36

14 7 50

21 9 43

18 4 22

31 9 29

39 10 26

42 23 55

20 8 40

24 5 21

40 15 38

27 9 33

19 7 37

120 29 24

39 5 13

92 28 30
13 -

Seventy-nine percent of the respondents who said they are familiar with NBS

calibration services described in SP250 also said that their organization

uses those services (question C12) or normally seeks NBS assistance on measurement problems (question G3). Conversely, only 44% of the respondents

who were not familiar with NBS calibration services said their organizations

use NBS calibration services or seek NBS measurement assistance.

These results suggest rather strongly that efforts are needed to increase

public awareness of available NBS calibration services.

Question C12 asks the respondent if his or her organization uses any of the

NBS calibration services. Of the 327 respondents, 51 percent answered "yes"

to this question. These responses were also broken down by type of

organization and are tabulated below.

Table 9. Percentage of respondents using NBS calibration

services — classified by type of organization.

Organization Type

Total

Responses

"Yes"

Responses

Percentage

of "Yes"

Responses

1. Aerospace 71 42 59

2. Automotive 16 12 75

3. Computer Equipment 20 9 45

4. Consumer Electronics 18 8 44

5. Electric Power 30 17 57

6. Electronic Components 37 14 38

7. Independent Test, Repair,

Calibration Service

44 29 66

8. Medical Electronics 19 11 58

9. National Laboratory 20 14 70

10 . Military 41 29 71

11. Other Government 26 15 58

12. Telecommunication 17 10 59

13. Test equipment/ instruments 122 67 55

14. University 40 8 20

15. Other 89 32 36

It is interesting to note that more respondents answered "yes" to this

question than to Cll. We assume this to mean that some respondents knew that

their organizations use one or more of NBS calibration services but were not

necessarily aware of or familiar with the full range of calibration services

offered by NBS and described in Special Publication 250.
14 -

Section D. Precision Instruments/Devices

This section of the survey is closely related to the previous section on electrical quantities since it requests information on instruments or devices

that are commonly used to measure those quantities. The questions in this

section focus on how the instruments or devices are used by the respondent’s

organization and the need for new/improved characterization methods or NBS

calibration services for the instruments.

The data regarding the use of the instruments or devices is tabulated in the

following table, where the instruments are ranked in descending order,' according

to the number of responses received indicating that the instrument is used either

in general purpose applications or as a standard by the respondent's

organization. Here, the number of responses was generally somewhat higher than

those received for the basic electrical quantities themselves. It is noteworthy

that function generators, signal generators, pulse generators, counter-timers,

frequency meters, oscillators, and spectrum analyzers were considered to be of

critical importance. Since these instruments did not appear near the top of the

list in the questionnaire, this ranking shows that the number of responses

received is not related to the order in which the instruments/devices were listed

in the questionnaire.

Seventy respondents also listed "other” instruments or devices which they

considered important to their measurement operations. This list is given in

Appendix D and includes a wide variety of items.

The figures in the two columns to the right of the table indicate the number of

respondents that use the ins trument /device as a general purpose instrument, or as a standard. While NBS does not generally offer calibration services for general

purpose equipment, it does calibrate many types of precision instruments or devices that are used as standards. Furthermore, using NBS calibrations,

industrial laboratories calibrate other instruments that are themselves used as lower echelon standards. Thus, those on the list that are reported to be used

most heavily as standards are of greater importance to NBS plans for measurement

support.
15 -

Table 10. Ranking of instruments /devices, based on number of

users (Section D responses). Usage data for each

instrument /device is also shown.

Ins t rument / Devi ce

Number Using as Number of General

Users Purpose Standard

1. Voltmeters 446 395 240

2. Multimeters 445 415 130

3. Function Generators 339 315 65

4. Calibrators 338 129 274

5. Counter-timers 333 295 122

6. Signal Generators 332 305 95

7. Frequency Meters 319 275 136

8. Oscillators 303 281 82

9. Pulse Generators 299 275 57

10. Spectrum Analyzers 288 266 60

11. Oscilloscopes, 283 268 60

real time/analog

12. A/D Converters 278 262 50

13. Instrumentation Amplifiers 272 258 51

14. Current Shunts 259 180 158

15. Oscilloscopes, digitizing 248 234 27

16. D/A Converters 245 229 47

17. Impedance Meters 237 201 61

18. Wattmeters 209 179 77

19. Waveform Recorders 203 196 28

20. Distortion Analyzers 180 148 58

21. Phase Angle Meters 168 147 54

22. Instrument Transformers 164 128 71

23. Sample/hold amplifiers 149 145 19

24 . Q Meters 133 116 28

25. Noise Analyzers 119 110 22

26. Power Factor Meters 95 82 25

27. CEMI Meters /recorders 94 90 13

28. Watthour Meters 84 69 36

29. CEMI High Voltage Generators 80 72 15

30. Watt Converters 71 59 23

31. Var/Varhour Meters 51 44 17

Several additional analyses were performed on the data submitted in this

section. For the following analysis, the instrument /devices were ranked

according to the number of respondents (for a given instrument or device) who

indicated their usage as a standard. The instruments in the upper third of the

rank are listed in the table below. Those followed by an asterisk are ones for

which an NBS calibration service or special test is available.
16 -

Table 11. Top eleven instruments or devices based on the number

of responses indicating their use as a standard.

Instrument /Device

Section D Number Using

Responses as a Standard

1 . 2 . 3.

4.

5.

6 . 7.

8 . 9.

10 . 11 .

Calibrators

Voltmeters

Current Shunts*

Frequency Meters

Multimeters

Counter- timers

Signal Generators

Oscillators*

Wattmeters*

Instrument Transformers*

Function Generators

338 274

446 240

259 158

319 136

445 130

333 122

332 95

303 82

209 77

164 71

339 65

It is interesting to note that four of the instruments/devices on this list are supported by an NBS calibration service or special test. Models of

current shunts, instrument transformers, wattmeters, and oscillators having

sufficient precision and stability are used by NBS as standards in performing

special tests or calibration services for the quantities of resistance,

ratio, power and frequency. Calibrators, which strongly appear at the top of

the list, are also used extensively now as standards for supporting voltage,

current, and resistance measurements. However, voltmeters and multimeters

are also emerging as instruments capable of serving as standards for these

basic quantities. Frequency meters and counter-timers are used, of course,

as standards for measuring frequency and time intervals (such as delay time

and settling time), both of which quantities were shown to be of critical

interest in the discussion on quantitites (Section C of the survey). The

fact that signal generators and function generators appear on this list

indicates that these instruments are apparently being used as standards for

supporting various frequency and time-domain analysis quantities.

The responses regarding the need for new/improved characterization methods

or NBS calibration services for instruments/devices are summarized in the

following table, where again, the instruments are ranked according to the

number of responses received in Section D regarding the use of these

instruments. The figures in the two right-most columns of the table show

the number of respondents that indicated a need for a new/ improved

characterization method or NBS calibration service. As shown, the indicated

needs vary significantly, depending upon the type of instrument /device.
17

Table 12. Number of responses indicating the need for a new/ improved

characterization method or NBS calibration service for the

instruraents/devices. Ranking is the same as in Table 11.

Number Needing

Section D Char. NBS Calib.

Instrument/Device Responses Method Service

1. Voltmeters

2. Multimeters

3. Function Generators

4. Calibrators

5. Counter-timers

6. Signal Generators

7. Frequency Meters

8. Oscillators

9. Pulse Generators

10. Spectrum Analyzers

11. Oscilloscopes,

real time/analog

12. A/D Converters

13. Instrumentation Amplifiers

14 . Current Shunts

15. Oscilloscopes, digitizing

16. D/A Converters

17. Impedance Meters

18. Wattmeters

19. Waveform Recorders

20. Distortion Analyzers

21. Phase Angle Meters

22. Instrument Transformers

23. Sample/hold amplifiers

24. Q Meters

25. Noise Analyzers

26. Power Factor Meters

27. CEMI Meters/recorders

28. Watthour Meters

29. CEMI High Voltage Generators

30. Watt Converters

31. Var/Varhous Meters

446 41 67

445 36 42

339 24 16

338 38 59

333 25 30

332 23 20

319 25 33

303 18 13

299 21 19

288 34 25

283 23 21

278 48 21

272 31 12

259 28 31

248 29 17

245 38 13

237 24 19

209 24 32

203 18 16

180 22 9

168 21 22

164 17 26

149 15 2

133 17 12

119 17 9

95 13 15

94 13 8

84 13 18

80 14 9

71 10 6

51 8 8

To explore these results further, the instruments and devices were reranked

according to the number of respondents for a given type who indicated the need

for NBS calibration services. The instruments /devices comprising the upper

third of that rank are listed below, in descending order. Those followed by an asterisk are ones for which an NBS calibration service is available.
18 -

Table 13. Top eleven instruments or devices based on the number of

responses indicating the need for an NBS calibration service.

Ins t rument / Devi ce Section D Number Needing NBSResponses Calib. Service

Voltmeters 446 67

Calibrators 338 59

Multimeters 445 42

Frequency Meters 319 33

Wattmeters* 209 32

Current Shunts* 259 31

Counter-timers 333 30

Instrument transformers* 164 26

Spectrum Analyzers 288 25

Phase Angle Meters* 168 22

A/D Converters* 278 21

Once again voltmeters, calibrators, and multimeters appear at the top of the

list. This correlates well with the results of Section C where voltage,

resistance, and current ranked at the top of the list of quantities in need of

NBS measurement support. As discussed in Section C, a proposed new NBS

calibration service would make use of the best available high accuracy

voltmeters and calibrators to provide a capability for measuring voltage

directly. The fact that wattmeters and current shunts are high on the list is

also in agreement with Section C results where the need for measuring current

and power received relatively high ranking. As indicated earlier in Table 11,

frequency meters and counter-timers are used by many respondents as standards,

which suggests that there is considerable interest in having an NBS

calibration service for these instruments as well. It is also interesting to

note that this list is quite similar to that in table 11, except for spectrum

analyzers, phase angle meters, and A/D converters. This suggests that there

is interest in having these instruments and devices traceable to NBS

standards.

The fact that several instruments or devices on this list are presently

supported by NBS calibration services or special tests suggests that further

analysis is required to determine specific user needs relative to the NBS

services.

In another analysis of the results from Section D, the instrument /devices were

ranked according to the number of respondents for a given item who indicated

the need for a new/ improved characterization method. The instruments or devices comprising the upper third of that rank are listed in the following

table, and those for which an NBS calibration service or special test is

available are followed by an asterisk.
19 -

Table 14. Top eleven instruments or devices based on the number

of responses indicated the need for new/improved

characterization methods.

Instrument/ Devi ce

Number Needing

Section D Improved

Responses Char. Method

A/D Converters* 278 48

Voltmeters 446 41

Calibrators 338 38

D/A Converters* 245 38

Multimeters 445 36

Spectrum Analyzers 288 34

Instrumentation Amplifiers 272 31

Oscilloscopes, digitizing 248 29

Current Shunts* 259 28

Counter- timers 333 25

Frequency Meters 319 25

For those instruments /devices marked by an asterisk in the above list, NBS is

presently working on better characterization methods for use in the

calibration services now offered. These results would seem to indicate a need

for better dissemination of NBS methodology for those items. Most of the

other instruments /devices have also appeared on the earlier tables analyzing

their usage as standards and the need for NBS calibration services. The

appearance of instrumentation amplifiers and digitizing oscilloscopes in

this table would seem to imply that these items are more general purpose in

usage, and mostly in need of better characterization methods.
20

Section E. ATE/ Complex Measurement System

In this section, the respondent was asked to provide information regarding his

or her organization’s involvement, if any, with automatic test equipment (ATE)

or complex measurement systems. The responses to the first question are tabulated below, where the number of responses are given together with the

percentage with respect to the total number of respondents (527).

Table 15. Summary of responses regarding respondents’ involvement

with ATE or complex measurement systems.

Involvement Capacity

Responses to

Question 1

Percent of

Questionnaires

Returned (527)

Equipment User 304 58

Instrument Manufacturer 90 17

Systems Manufacturer 88 17

Software Designer 88 17

ATE Manufacturer 68 13

Standards Developer 50 9

Other 51 10

As shown above, the largest majority of the respondents are users of ATE or complex measurement systems, but there is also a fair degree of involvement in

the remaining categories. A listing of the 51 responses entered under ’’Other"

is given in Appendix E.

The second question of this section asked the respondent to identify the types

of ATE or complex measurement systems with which his or her organization is

involved. The responses are summarized below, using the same notation as the

previous table.

Table 16. Summary of responses regarding types of ATE or complex

measurement systems with which respondents are involved.

Percent of

Responses to Questionnaires

Equipment Type Question 2 Returned (527)

General Purpose Testers 189 36

Automatic Calibration Systems 182 35

Passive Component Testers 124 24

Functional Board Testers 112 21

Active Component Testers (incl. VLSI) 89 17

In-circuit Board Testers 70 13

Computer Systems Testers 69 13

Other 46 9
21 -

The entries under "Other” included a variety of equipment types -— some general

purpose in nature and some for making specific measurements. These are also

given in Appendix E.In the final part of this section, several possible NBS

outputs pertaining to ATE or complex measurement systems are listed and the

respondent is asked to rate the usefulness to his or her organization as "extremely valuable," "useful," or "not useful." These responses are summarized

in the following table where the figures in each column represent the percentage

of total respondents (527) who gave the indicated rating.

Table 17. Summary of responses regarding the usefulness of possible

NBS outputs related to ATE or complex measurement systems.

Percent of

Questionnaires Returned (527)

Possible NBS Outputs

Extremely

Valuable Useful Both*

Not

Useful

Practical calibration/ test guides 39 30 69 2 Documented measurement methods, 38 29 67 2

definitions, terminology

Development of new standards for ATE 20 29 49 9

Theoretical calibration/ test strategies 19 33 52 6

Technical contributions to voluntary 19 31 50 6

standards organizations

Calibration services for ATE standards 17 32 49 10

*Sum of "extremely valuable" and "useful" responses.

Here, the usefulness of two of the listed outputs were rated well above the

others; namely, "practical calibration/ test guides" and "documented measurement

methods, definitions, terminology." This appears to be a strong expression of

need for documented outputs and assistance that offer straightforward solutions

to practical problems. Furthermore, the generally high level of response to

this entire section of the questionnaire suggests the need for NBS research and

support in this area.
22

Section F. Conducted Electromagnetic Interference (CEMI)

As in the previous section, the questions in this section focus on a specific

area of electronic technology. The first question asks for information on how

the respondent’s organization is involved, if at all, with problems associated

with CEMI. More specifically, the respondent is asked to indicate if his or her

organization is a manufacturer and/or user of certain types of equipment or participates in developing voluntary standards for CEMI. In the following table,

the responses to this question are presented in terms of the percentage of total

respondents (527) answering a given query.

Table 18. Summary of responses regarding the manufacture or use

of CEMI-related equipment.

Equipment Type

Protective Devices

Detection/Measurement Instruments

Potentially Susceptible Equipment

Potentially Interfering Equipment

Percent of

Questionnaires Returned (527)

Manufacturer User Both

3 39 4

4 40 4

14 31 9

13 26 9

Five percent of the respondents indicated their involvement in voluntary

standards development, and 11 respondents (2%) listed "other" types

of involvement. The latter included such activities as "effects on living

organisms," "evaluation of EMC," "effects of education," and "evaluation of

tests.

In the final part of this section, the respondents again were asked to

evaluate the usefulness of several possible NBS outputs, relative to CEMI.

Those responses are tablulated below.
23 -

Table 19. Summary of responses regarding the usefulness of

possible NBS outputs related to CEMI.

Percent of

Questionnaires Returned (527)

Possible NBS Output

Extremely

Valuable Useful Both*

Not

Usef

Documented measurement methods, 32 29 61 2 definitions, terminology

Techniques for measuring CEMI signals 26 34 60 2

Techniques for characterizing CEMI sources 18 32 50 5

Test methods for protective devices 17 31 48 4

Calibration services for CEMI standards 13 25 38 8

Technical contributions to voluntary 11 25 36 6

standards organizations

*Sum of "extremely valuable" and "useful" responses.

As in Section F, the strongest need appears to be for practical measurement

methods and techniques. The level of response to questions in this section

suggests an awareness of and concern for CEMI-related problems, as well as a need for NBS support.

Section G. Communications /Interactions

The questions in this section are aimed at assessing the effectiveness of

communications and interactions between the respondent’s organization and

NBS. In question one, several communication mechanisms are listed and the

respondent is asked to indicate those that are used to obtain information

about NBS programs and services. Eighty-nine percent (470) of the

respondents answered this question, and generally checked more than one category. Their responses are summarized in the following table, where the

communication means are ranked according to the number of responses to

question 1.
24

Table 20. Summary of responses regarding the communication means used

by respondents to obtain information on NBS programs and

services.

Question 1 Percentage of

Communication Means Responses Total Responses (470)

1. NBS reports/special publications 271 58

2. Journal publications 268 57

3 • Conferences /workshops /seminars 210 45

4. Specific requests 207 44

5. Staff interactions 137 29

6. Media releases 108 23

7. Technical committees 78 17

8. Other 44 9

As shown above, the four communication means that were ranked most important

overall by the respondents are NBS reports/special publications, journal

publications, conferences/workshops/seminars, and specific requests. The

top three and others on the list are ones which obviously can be influenced

by internal policies and actions at NBS. These results suggest that the

dissemination of research results and other NBS outputs via NBS reports,

special publications, journal publications, and technical conferences,

workshops, or seminars should continue to receive special emphasis.

Under "Other," 20 respondents listed the National Conference of Standards

Laboratories (NCSL) as their source of information about NBS, and five

respondents entered "none." Additional means listed under "Other" included

manufacturers, vendors, and organizations such as IEEE, the Aerospace

Guidance and Metrology Center (AGMC) and the Calibration Coordination Group

( CCG)

To explore the results from this question further, the responses were broken

down by type of organization. These results are shown in the following table

where the numbers in each column refer to the overall ranking of the eight

listed communication means.

I

j Ml
J

J - 25 -

Table 21. Ranking of communi cation means by

type of organization/business*

Rank Based on Usage

Organization/ Business 1st 2nd 3rd 4th 5th 6 th 7th 8th

Aerospace 1 2 4 3 5 6 7 8

Automotive 1 4 2 3 6 7 5 8

Computer Equipment 2 3 1 4 6 7 5 8

Consumer Electronics 2 4 3 5 1 6 7 8

Electric Power 1 2 4 3 5 7 6 8

Electronic Components 1 2 3 4 6 5 7 8

Independent Test/Repair

Calibration Service

3 1 2 4 5 7 6 8

Medical Electronics 1 2 4 3 6 5 7 8

National Laboratory 1 5 4 3 2 7 6 8

Military 1 3 2 4 5 6 7 8

Other Government 2 1 3 4 5 6 7 8

Telecommunication 2 3 4 1 5 7 6 8

Test Equipment /Instruments 1 2 3 4 5 6 7 8

University 2 1 4 5 3 6 7 8

Other 2 1 4 3 6 5 7 8

This table shows some interesting variations in the relative importance of the

given communication means to different types of organizations. For example, for

all but three types of organizations, the four most-used communication means are

NBS reports/special publications, journal publications, conferences/workshops/

seminars, and specific requests. The three exceptions are consumer electronics,

national laboratories, and universities, all of which ranked staff interactions

as one of their four most used communication means.
26 -

The second question in Section G asked the respondent to indicate whether

or not the listed communication means are effective in keeping his or her

organization informed about NBS, and to identify those that should be

improved. There were 470 responses to the first part of the question of

which 54% were "yes" answers. A total of 217 respondents answered "no" to

the question and indicated a need for greater emphasis on, or improvement

in, the communication means. These latter responses are tabulated below

where the percentage of the 217 respondents who indicated the need for

improvement is given for each communication means. Eighty-six percent of the respondents who said the listed communicatibn means

are not effective also said their organizations do not use NBS calibration

services (question C12) and do not normally seek NBS assistance on measurement

problems (question G3).

Table 22. Summary of responses indicating the need

to improve the given communication means.

Communication Means

Percentage of Respondents (217)

indicating improvements needed

NBS reports/special publications 70

Journal publications 35

Media releases 29

Cohf erences/workshops/ seminars 25

Technical committees 8

Specific requests 7 Staff interactions 6

Other 3

It is interesting to note that the two communication means that were reported

to be used the most (NBS reports/special publications and journal publications)

are the same ones that were perceived by the most respondents to need improvement

or greater emphasis. This may be an indication that many of the responding

organizations would like to receive more of these publications.

Most of the respondents (471) answered question 3 which asked if his or her

organization normally seeks NBS assistance on calibration or measurement

problems. Of these, 34% answered "yes." This figure agrees almost exactly

with the response to an earlier question (C. 11) where 33% of the respondents

said they were familiar with NBS calibration services. One could conclude

from these results that more organizations would probably make use of NBS

services if they were aware of the available services.

The final question in this section asks if NBS has provided the necessary

support when requested by the respondent’s organization. There were 259

responses to this question, with 92% (239) of the respondents giving a "yes" answer.
27

Section H. Additional Comments

In this section, space was provided for additional general comments, and the

respondent was encouraged to elaborate on key measurement needs that NBS should

meet and to provide estimates of any economic benefits that would result. Twenty

seven percent (143) of the respondents took the time to provide comments that

ranged in length from a few words to several paragraphs. NBS has considered all

comments carefully and appreciates the time invested by respondents in providing

them.

These comments varied greatly from respondent to respondent and included

discussions of very specific measurement needs (for both electrical and physical

quantities) as well as general metrology-related issues. By far the most common

theme was the expression of needs to learn more about NBS services, programs, and

activities. Some 17% of the comments addressed this subject. One respondent

stated that the discontinuation of the NBS publication DIMENSIONS has been a severe loss to his organization.

Eleven respondents expressed their satisfaction with NBS services and support,

while three respondents voiced complaints about the services. Two of the latter

complained about long turnaround times for NBS calibrations, and the third said

that the calibration fees are too high.

Other measurement quantities or technology areas that received multiple comments

are listed below in alphabetical order.

Measurement Concern

Number of

Comments

Automatic Test Equipment 6

AC Current 4

AC/DC Voltage 7

Capacitance 4

Conducted Electromagnetic Interference 3

Optical Power 3

Quality Factor (Q) 3

Resistance 5

Time domain quantities 3
28 -

4. Conclusions

In this summary report, tabulations of essentially all of the raw data are presented, along with the results of several cross-correlation analyses and

listings of such items as responding organizations and items entered under

"Other” categories. Further analyses of the data are needed and will be

performed to extract additional information or meaning. However, at this

point we believe the results lead to and support the following conclusions:

1. A majority of the respondents cited the need to meet government

requirements for traceability as their principal reason for

needing NBS measurement support. In addition, there was a strong expression of need for NBS measurement support by

organizations involved in research and in the development,

production, and quality control of products. This is borne

out by the responses received in Section B of the questionnaire

which suggest that the measurement services offered by NBS should

address and be applicable to the practical problems encountered

by this segment of industry.

2. Additional analysis of the data from Section C is required in

order to further assess its significance and its impact upon NBS

calibration services and research programs. For each of the 33

listed electrical quantities, some number of the respondents

considered its measurement critical to their operations, and

indicated the need for new/improved measurement methods and

calibration services. Since the measurement needs of all

respondents for all of the quantities cannot be addressed

simultaneously, some order of priority must be assumed. Thus, we believe it is appropriate to focus on those quantities that are included in Tables 6 and 7, which are the top eleven

identified by the most respondents as needing improved

measurement methods or NBS calibration services. By providing

an analysis on these quantities of interest, similar to that

given for voltage in Section C of this report, the desired

guidance for planning NBS measurement programs can be developed.

In addition to voltage, the quantities that should receive

further analysis include resistance, current, capacitance,

frequency, inductance, rise/fall time, transient voltage, power,

phase, impedance, delay time, and settling time. Many of these

are quantities for which NBS already offers calibration services

or special tests. Some of these services may need improvements

to achieve higher accuracies and/or broader frequency ranges.

Some may be adequate but need to be publicized better. Other

quantities on the list are ones for which NBS calibration

services or improved measurement methods could be developed

under existing or future research programs.
29

3. The responses received for Section D of the questionnaire

show that all of the instruments and devices that are listed

are used by some organizations as general purpose equipment,

as standards, or as both. Also, in all cases, some of these users indicated the need for a new/ improved characterization

method or an NBS calibration service. Those instruments or devices that are most widely used as standards and for which

there is the greatest need for improved characterization

methods or calibration services are the ones that should be

given primary consideration in NBS plans. Instruments or devices that meet these criteria are listed in Tables 11,

13, and 14 and include calibrators, voltmeters, multimeters,

current shunts, frequency meters, counter-timers, signal

generators, oscillators, wattmeters, instrument transformers,

function generators, phase meters, spectrum anmalyzers, A/D

converters, D/A converters, instrument amplifiers, and

digitizing oscilloscopes. Six of these instruments/devices

are supported by existing NBS calibration services or special

tests, namely, current shunts, wattmeters, instrument

transformers, phase meters, A/D converters, and D/A converters.

Also, many of the others are calibrated by industrial or commercial laboratories using standards that are traceable

to NBS. We believe these results indicate the need for a thorough review of the measurement capabilities of the

instruments listed above, compared to the characterization

methods and calibration services that are presently available.

Those instruments whose capabilities exceed the capabilities

of existing characterization methods or calibration services

would be candidates for NBS to address in its technical

programs. In those cases where existing documented

characterization methods or calibration services appear to

be adequate, better methods to disseminate and publicize

these methods and services should be considered.

4. We believe that the level of response to the questions on ATE/

Complex Measurement Systems and on Conducted Electromagnetic

Interference indicate a need for NBS programs in these areas. Fifty-eight percent of the responding organizations indicated

that they are now using ATE or complex measurement systems,

and many others indicated their involvement with various

aspects of such systems. Likewise, a relatively high

percentage of responding organizations reported their

involvement with CEMI technology as users or manufacturers

of instruments and equipment. The responses on both subjects

indicate that the respondents want NBS programs that place

special emphasis on the development and dissemination of

practical guides, techniques, and test/calibration methods.

These results also support anecdotal information received

from various conferences, inquiries, informal suggestions

from calibration clients, etc.
30

5. A large number of organizations that apparently need and could

use NBS measurement support are not aware of, or are only

vaguely familiar with, existing NBS programs and services.

Furthermore, from some of the comments received in Section H,

this situation does not appear to be peculiar to CEEE, but to

apply to NBS in general. These results suggest that existing

programs and mechanisms for publicizing NBS activities and

services need improvement.

The above conclusions are those that are most apparent from our analysis of the

results thus far. Further analyses, aimed at resolving questions about the

implications of certain responses, are planned. In addition, we can foresee a continuing need to review and study the data to extract specific information in

certain areas. Thus, the usefulness of the survey results will continue into the

future.

5. Acknowledgments

Our special thanks go to Thomas Leedy, Ann Lovett, and Dawna Whitworth for their

diligent and patient efforts in developing and debugging the software programs

for extracting, processing, and analyzing the survey data. We also appreciate

the extensive support provided by Jennifer Muse and Betty Meiselraan in data

entry, mail preparation, and preparing this report. The contributions of these

individuals were essential to the timely completion of this project.

Many other people also provided valuable assistance and suggestions. Internally,

J. French, R. Powell, B. Bell, and 0. Petersons were very helpful in drafting and

revising the survey questionnaire. Barry Bell provided additional assistance in

analyzing and interpreting the survey data. Also, G. Tassey, B. Belanger, and

J. Mayo-Wells provided constructive comments and suggestions.

Without the cooperation and help provided by representatives of several external

organizations, it is doubtful that the survey could have been carried out.

Mr. Fred Ligouri of the IEEE Instrumentation and Measurement Society, Mr. R. B. England of NCSL, Mr. Jack Kinn of the Electronic Industries Association, and

Mr. Lawrence Rubin of the American Physical Society all endorsed the program and

lent their support by providing mailing labels for their members and

participating in the review and critique of the questionnaire. Mr. Ted Plum of

the Instrument Society of Anerica provided valuable support by coordinating our first mailing to 5000 members of his Society.
- 31-

APPENDIX A - QUESTIONNAIRE

OMB Approval No.: 0652-0022

Expiration Date: September, 1986

SURVEY OF ELECTRONIC MEASUREMENT NEEDS BELOW 10 MHz

by the

National Bureau of Standards

Center for Electronics and Electrical Engineering

Metrology Building, Room B-162

Gaithersburg, MD 20899

Thank you for returning the postcard indicating that you wish to participate

in this survey.

The purpose of the survey is to determine how the National Bureau of Standards

can best support the current and future measurement requirements of your

organization. You can help by completing the parts of the survey that apply

to your measurement needs

The survey seeks information in the low frequency domain from DC to 10 MHz for

three broad areas of measurement need: (1) basic electrical quantities and

related precision instruments, (2) automatic test equipment and other complex

measurement systems, and (3) conducted electromagnetic interference.

Measurement needs at frequencies above 10 MHz, including those in the

microwave and mil lime ter -wave domains, are the subject of a separate study.

The survey findings will help NBS plan research programs that provide

documented measurement methods and calibration services for industry and

Government. These services support quality control, productivity, marketplace

equity, international competitiveness, and other goals important to the U.S.

economy. NBS seeks to support, rather than compete with, the private sector.

NBS is not a regulatory agency.

Other important sources of information will also be considered in NBS

planning, including the 1982 National Measurement Requirements Survey of the

National Conference of Standards Laboratories.

If you find that the questions in the survey do not adequately cover your

measurement needs, please describe those needs in the comments section at the

end of the survey.

Your response to this survey is entirely voluntary and may be submitted

anonymously, if you wish. Please call John Sorrells if you have any questions

(301-921-2727). Thank you for your assistance.

Electrical Engineering

U.S. Department of Commerce

National Bureau of Standards

NBS- 1215

( 1

- 86 )
- 32 - A. Your Organization/Business

1. D Aerospace

2. D Automotive

3. Computer Equipment

4. Consumer Electronics

5. Electric Power

6. D Electronic Components

7. Independent test, repair,

calibration service

8. D Medical Electronics

9. n

10.

11.

12.

13.

14.

15.

National Laboratory

Military

Other government

Telecommunication

Test Equipment/Instruments

University

Other:

B. Organizational Needs

Please indicate the principal reasons why your organization needs measurement support from NBS. Check

all categories that apply.

1. D To reduce the cost of reaching buyer/seller agreement.

2. D To ensure market equity.

3. D To meet government requirements, e.g., for traceability.

4. D To meet requirements of foreign governments/buyers.

5. D To assist in development of product specifications.

6. D To support development of voluntary standards.

7. G To support R&D.

8. To improve quality control in production.

9. To increase productivity.

10. D To improve product reliability.

11. To improve product compatibility.

12. Other:
33 -

C. Basic Electrical Quantities

If the measurement of one or more quantities in the following list is critically important in your operations,

indicate the frequency and accuracy ranges of most concern by entering an accuracy code letter in the

appropriate frequency column. If a new/improved measurement method* or NBS calibration service** is needed, place a check in the appropriate “NEEDS” column. For example, if you were concerned with

measuring ac voltage to an accuracy of 0.1% at a frequency of 5 MHz and need a calibration service for your reference standards, you would enter the letter “b” in the “1 MHz-10 MHz” frequency column and

place a check in the “Cal. Service” column for “Voltage.” Further comments can be entered, if desired.

Accuracy Code Letters Frequency Needs

Comments

1. Voltage I I I I I 1 I I |__J

2. Current

3. Resistance

4. Capacitance

5. Conductance

6. Dissipation Factor

7. Inductance ~~~

8. Impedance

9. Admittance

10. Quality Factor (Q)

11. Power

12. Reactive Power

13. Power Factor

14. Energy

15. Phase

16. Linearity, Integral

17. Linearity, Differential 18. Effective Bits 19. Frequency

20. Phase Noise

21. Harmonic Distortion 22. Percent Modulation, AM

23. Percent Modulation, FM

24. Noise Amplitude

25. Electric Field Strength

26. Magnetic Field Strength

21. Leakage Current

28. Others:

29.

“

30.

31.

*ln the context of this survey, a measurement method is defined as a published technique for the

measurement of a given quantity, employing appropriate standards.

**ln the context of this survey, a calibration service is defined as a service for determining the errors of instrument or device standards submitted to NBS.

a - 1%

b - 0.1%

c - 0.01%

d - 0.001%

e - 0.0001%

QUANTITY
C. Basic Electrical Quantities (Cont’d.)

For the following time-domain quantities, note that the frequency ranges have been replaced by time

ranges. Otherwise, the procedure for entering your response is unchanged.

Accuracy Code Letters Time Needs

a - 1 % d - Oj

b - 0.1% e - Oj c - 0.01%

QUANTITY

1. Voltage, transient

2. Current, transient

3. Rise/Fall Time

4. Settling Time

5. Delay Time ~

6. Acquisition Time7. Others:

_8 . _9.

10 .

1 1

.

Are you familiar with the calibration services currently offered by NBS and described in Special

Publication 250? D Y D N

12.

Does your organization use any of the NBS calibration services? D Y D N
35

D. Precision Instruments/Devices

If an instrument or device in the following list is important to your measurement operations, indicate how it is used by placing a check in the appropriate “USE” column(s). If a new/improved characterization method*

or NBS calibration service is needed, place a check in the appropriate “NEEDS” column.

Use Needs

INSTRUMENT/DEVICE Comments

1. Voltmeters

2. Multimeters

3. Calibrators

4. Impedance Meters

5. Q Meters

6. Wattmeters

7. Watt Converters

8. Var/Varhour meters

9. Power factor meters

10. Watthour meters

1 1 . Phase angle meters

12. Current shunts

13. Instrument transformers

14. A/D Converters

15. D/A Converters

16. Sample/hold amplifiers

17. Instrumentation amplifiers

18. Waveform recorders

19. Oscilloscopes

a. real time/analog storage

b. digitizing 20. Frequency meters

21. Function generators

22. Oscillators

23. Pulse generators

24. Counter-timers

25. Signal generators

26. Distortion analyzers

27. Spectrum analyzers

28. Noise analyzers

29. Conducted EMI instruments

a. high voltage generators

b. meters/recorders

30. Others:

31.

32. L_

*ln the context of this survey, a characterization method is defined as a published procedure for evaluating

the performance of an instrument or device, employing appropriate standards.
- 36 -

E. ATE/Complex Measurement Systems

In what capacity is your organization involved with automatic test equipment (ATE) or complex measurement

systems? Please check all categories that apply.

1. D Systems Manufacturer

2. EH Software Designer

3. D Standards Developer

4. D Instrument Manufacturer

5. D ATE Manufacturer

6. EH Equipment User

7. Other:

With what types of ATE/Complex Measurement Systems is your organization involved?

8.

EH Passive component testers

9.

EH Functional board testers

10. General purpose testers

(for instruments, avionics, etc.)

11. EH Automatic calibration systems

12. EH Active component testers (including VLSI)

13. EH In-circuit board testers

14. EH Computer systems testers

15. EH Other:

Indicate the usefulness to your organization of the following possible NBS outputs for ATE/Complex

Measurement Systems. Circle E for extremely valuable, U for useful, X for not useful, or leave blank if you

have insufficient information to judge.

16. Theoretical calibration/test strategies

17. Practical calibration/test guides

18. Calibration services for ATE standards*

19. Development of new standards* for ATE

20. Documented measurement methods, definitions, terminology

21. Technical contributions to voluntary standards organizations

22. Other:

E

E

E

E

E

E

E

E

E

U

U

u

u

u

u

uu

u

X

X

X

X

X

X

X

X

X

*As used here, an ATE standard is defined as an instrument or device used for the accurate generation/

measurement of electrical quantities and especially adapted for ATE.
37

F. Conducted Electromagnetic Interference (CEMI)*

In what capacity is your organization involved with the problems associated with CEMI? Please check all categories that apply.

1. Protective Devices a. D Manufacturer

2. Detection/Measurement Instruments

3. Potentially Susceptible Equipment

4. Potentially Interfering Equipment

5. Voluntary Standards Development

6. Other:

a. D Manufacturer

a. D Manufacturer

a. Manufacturer

b. D User

b. D User

b. User

b. User

Indicate the usefulness to your organization of the following possible outputs from NBS. Circle E for extremely useful, circle U for useful, circle X for not useful, or leave blank if you have insufficient information to judge.

7. Test methods for protective devices E U

8. Techniques for characterizing CEMI sources, e.g., source impedance E U

9. Techniques for measuring CEMI signals E U

10. Calibration services for CEMI standards** E U

1 1 . Documented measurement methods, definitions, terminology E U

12. Technical contributions to voluntary standards organizations E U

13. Other:

X

X

X

X

X

X

E U X

E U X

E U X

*ln the context of this survey, CEMI is defined as any unwanted signal that enters a system by means of power lines, signal lines, or other conducting paths.

**As used here, a CEMI standard is defined as an instrument or device used for the accurate generation/

measurement of electrical quantities involved in CEMI testing.
- 38 -

G. Communications/Interactions

1

.

By what means does your organization obtain/receive information regarding

programs and sen/ices? Please check all categories that apply.

a. EH Staff interactions

b. D Conferences/workshops/seminars

c. D NBS reports/special publications

d. D Journal publications

e. D Technical committees

f. EH Specific requests

g. D Media releases

h. D Other:

2. Are the above mechanisms effective in keeping your organization informed about NBS activities, services, and results? D Y EH N

If not, which ones should be improved or receive greater emphasis? Please circle the appropriate letter designations: a. b. c. d. e. f. g. h.

3. If your organization has a calibration or measurement problem does it normally seek assistance from

NBS? Y N

4. In those cases where your organization has requested NBS help in solving a calibration or measurement

problem, has NBS provided the necessary support? Y D N

H. Additional Comments

Please elaborate on key measurement needs you want NBS to meet; as an aid in establishing work

priorities, provide, if possible, an estimate of economic benefit to your organization or the nation if NBS

meets those needs. Use the back of this form if you need additional space.

Optional Information:

Name of person responding: Tel.:

Organizaton:

Address (for mailing survey findings):

Are you willing to be contacted by NBS for further information? EH Y N

Note: Survey responses should be returned in the enclosed envelope. Anonymous respondents can receive a summation of survey findings by sending a separate request to NBS at the address on the cover page.
39

APPENDIX B - PARTICIPATING ORGANIZATIONS

A SQUARE D COMPANY

AAI CORP.

ABBOTT LABORATORIES

ACME ELECTRIC CORP.

ADC TELECOMMUNICATIONS

ADVANCED PERIPHALS INC.

AIR FORCE WEAPONS LAB

AIRE SEARCH

AIRE SEARCH MFG. CO.

ALLISON GAS TURBINE DIV. GM

ALLIS. CHALMERS HYDRO, INC.

ALPHA INDUSTRIES

AMADOR CORP.

AMERICAN CRITICAL CARE

AMERICAN EDWARDS LABS

AMERICAN TECHNICAL CERAMICS CORP.

AMTRAK

AMXTM-CW-WS

ANADRILL/SCHLUMBERGER

ANALOG DEVICES

ANALOG DEVICES SEMICONDUCTOR

ANALOGIC- INDUSTRIAL TECH. GROUP

ANR STORAGE CO.

APPLIED SENSORS INTERNATIONAL

ARCO OIL & GAS CO. MEASUREMENT DEPT.

ARGONNE NATIONAL LAB

ARLO ALASKA INC.

ARVIN/CALSPAN ATC.

ASTRA CORP.

ATEAM CORP.

ATKINS TECHNICAL INC.

AUSTRON INC.

AVCO SYSTEMS DIVISION

AXIOM TECHNOLOGY, INC.

BAILEY CONTROLS CO.

BALLANTINE LABORATORIES

BARNANT / COLE-PARME

BARRIOS TECHNOLOGY INC.

BATTELLE MEMORIAL INSTITUTE

BATTELLE NORTHWEST LABORATORIES

BDM CORP.

BEAR MEDICAL SYSTEMS

BEARD ENGINEERING, INC.

BELL HELICOPTER TEXTRON CANADA

BENDIX FIELD ENGR. CORP. - DEPT. OF ENERGY

BERGAN MERCY HOSPITAL

BIOMAGNETIC TECHNOLOGIES, INC.

BIO-TEX INSTRUMENTS INC.

BKC CONSULTANTS

BLACKBURN - A DIV. OF FL INDUSTRIES, INC.
40

BOEING MILITARY AIRPLANE CO.

BONNEVILLE POWER ADMINISTRATION

BORG WARNER RESEARCH

BROOKHAVEN NATIONAL LABORATORIES

BRUNSWICK CORP.

BTI

CABLE SYSTEMS INC.

CALIFORNIA MICROWAVE INC.

CALVIN COLLEGE

CANADIAN GENERAL ELECTRIC

CAP INTEL INSTRUMENTS INC.

CATALYST RESEARCH, DIV. MSA

CATEC

CATERPILLAR, INC.

CENTURION INSTRUMENT CO.

CERTIFIED MEASUREMENTS, INC.

CHEMISTRY DEPT. , JOHNS HOPKINS UNIVERSITY

CITY OF TACOMA, WA, DEPT. OF UTILITIES

CLARK COUNTY HEALTH DISTRICT

COILCRAFT INC.

COLORADO CRYSTAL CORP.

COLORADO STATE UNIVERSITY

COLUMBIA ENGINEERING

COMMERCIAL RADIO CO.

COMMONWEALTH EDISON CO.

COMPUTER INSTRUMENTS CORP.

COMSAT LABORATORIES

CONSULTANT

CORNING GLASS WORKS

CORPUS CHRISTI PETROCHEMICAL CO.

CUMMING ENGINE CO.

C . E . D

.

DATRON INSTRUMENTS LTD.

DEPT. OF LABOR MINE SAFETY & HEALTH ADMIN.

DUQUENSE LIGHT CO.

DICKSON CO.

DICONIX, A KODAK COMPANY

DIGITAL EQUIPMENT CORP.

DODIG

DORIC SCIENTIFIC

DRAVO ADVANCED TECHNOLOGY

DUKE POWER CO.

DYNAMIC SCIENCES

EASTMAN KODAK APPARATUS DIVISION

EATON CORP. ENGR. & RES.

ECTRON CORP.

E G & G OCEAN PRODUCTS

E G & G/EM INC.

EIL INSTRUMENTS, INC.

EIP MICROWAVE

ELECTRO RENT CORP.

ELECTRO SCIENTIFIC INDUSTRIES, INC.

ELECTROMAGNETIC SCIENCES

ELECTRONIC CONTROLS DESIGN
41

ELECTRO-MECHANICS

ELERY F. BUCKLEY

ELI LILLY & CO.

ERFO

ESC ELECTRONICS CORP.

ETHICON, INC.

E-A-R DIV. /CABOT CORP.

E-M INSTRUMENTS

E-SYSTEMS UNIT 4 84322

E. G. & G. IDAHO INC.

E. I. DU PONT DE NEMOURS & CO.

FAIRCHILD SEMICONDUCTOR

FLORIDA SOLAR ENERGY CENTER

FLOW SYSTEMS, INC.

FMC CORP

FORD MOTOR CO.

FOTEC , INC.

FREQUENCY AND TIME SYSTEMS

FTS

GEC AVIONICS

GENERAL CABLE CO.

GENERAL DYNAMICS ELECTRONICS

GENERAL DYNAMICS/CONVAIR

GENERAL DYNAMICS/ELEC. BOAT DIV.

GENERAL DYNAMICS /FT. WORTH DIVISION

GENERAL ELECTRIC

GENERAL ELECTRIC NUCLEAR ENERGY BUS. ORG.

GENRAD INC.

GENRAD, SEMICONDUCTOR TEST DIV.

GIORDANO ASSOC. IND.

GOULD OSD

GUIDED WAVE, INC.

GUILDLINE INSTRUMENTS INC.

HARRIS SEMICONDUCTOR

HARRY DIAMOND LABORATORIES

HEKIMIAN LABORATORIES, INC.

HEWLETT PACKARD

HEWLETT PACKARD CO. - LOVELAND INSTR. DIV

HEWLETT PACKARD MEMORY DIV.

HNB INTERSTATE

HONEYWELL INC.

HONEYWELL INFO. SYSTEMS

HONEYWELL OPTOELECTRONICS

HONEYWELL STANDARDS LAB.

HOTTINGER BALDWIN MEASUREMENTS, INC.

HUGHES AIRCRAFT

HUGHES OPTICAL

I & E MAINT. ENG. INC.

IBM

IBM CORP. , GPD

IFR INC.

INCAL SERVICES

INSTRULAB, INC.

INSTRUMENTATION SERVICE, WYETH LABS
42

INTEL CORP.

INTERNATIONAL JENSEN, INC.

ITI CO.

ITT CORP.

ITT TELECOM

I. S.A.

JOHN FLUKE MFG. CO.

JOHN TYLER COMMUNITY COLLEGE

JOHNS HOPKINS APPLIED PHYSICS LABORATORY

JOHNS HOPKINS UNIVERSITY

JOHNS HOPKINS UNIVERSITY, DEPT. OF PHYSICS

JOMAR SYSTEMS

JOY MANUFACTURING

J. A. JONES APPLIED RESEARCH

KAMAN SCIENCES CORP.

KAMAN TEMPO

KEITHLEY INSTRUMENTS INC.

KISTLER INSTRUMENT CORP.

KNOPP, INC.

KOLLMORGEN CORP. PHOTO RESEARCH DIV.

KOLLSMAN INSTRUMENT CO.

LAWRENCE LIVERMORE NATIONAL LABORATORY

LEDFORD MACHINE & GAGE LAB

LEWIS ELECTRONIC INSTRUMENTATION

LFE CORP. INSTRUMENTS DIV.

LITTON ELECTRON DEVICES

LMSC RES. LAB

LOCKHEED GEORGIA CO.

LOCKHEED MISSILES AND SPACE COMPANY

LOCKHEED SPACE OPERATIONS CO.

LOCKHEED-CALIFORNIA CO.

LOCKHEED/EMSCO, JOHNSON SPACE CENTER

LORD CORP. R&D CENTER

LOS ALAMOS NATIONAL LABORATORY

LOS ANGELES PIERCE COLLEGE

LOTUS DEVELOPMENT CORP.

LTX CORP.

MACK TRUCKS INC.

MAGNAVOX CO.

MAGNAVOX GOV. & INDUST. ELEC. CO.

MAGNETIC MEASUREMENTS ENGINEERING

MARATHON OIL GULF COAST REGION ELECTRONICS

MAROTTA SCIENTIFIC

MATSUSHITA/ PANASONIC

MAXWELL LABORATORIES

MCDONNELL DOUGLAS

MEDTRONIC INC.

METROLOGY-AIRE SEARCH MANUFACTURING

MIAMI HEART INSTITUTE

MICRO SWITCH

MICROMANIPULATION CO.

MICROSEM CORP.

MILES LABS-AMES DIVISION

MILES LABS, INC.

MINE SAFETY APPLIANCES CO.
43

MINNESOTA DEPT. OF HEALTH

MISSISSIPPI POWER AND LIGHT, GRAND GULF NUCLEAR

MIT LINCOLN LABORATORY

MKS INSTRUMENTS

MOLYTEK, INC.

MORTON THIOKOL INC.

MOTOROLA COMMUNICATIONS

MOTOROLA GOVERNMENT ELEC. GROUP

MOTOROLA INC.

MOTOROLA SPS

MTS SYSTEMS CORP.

MT. SINAI MEDICAL CENTER

MUSTANG FUEL CO.

M-TRONICS, INC.

M/A COM MILLIMETER PRODUCTS, INC.

NASA

NASA LANGLEY RES. CTR.

NASA LYNDON B. JOHNSON SPACE CENTER

NASA RESEARCH CENTER

NASA-NTF

NASA, AMES RESEARCH CENTER

NAVAL AIR REWORK FACILITY

NAVAL AVIONICS CENTER

NAVAL ORDNANCE STATION

NAVAL RESEARCH LABORATORY

NAVAL SHIP SYS. ENGR. STA. (CODE 052E)

NAVY PRIMARY STANDARDS DEPT.

NAVY PRIMARY STANDARDS LABORATORY

NEWTON INSTRUMENT CO.

NIAGARA MOHAWK POWER CO.

NMERI/CERF

NORDSON CORPORATION

NORDSON CORP. PMA DIVISION

NORTHERN STATES POWER

NORTHROP DSD

NORTHROP PRECISION PRODUCTS DIVSION

NORTHRUP CORP., AIRCRAFT DIV.

NORTHWEST REGIONAL CALIBRATION CTR.

N.A.P. CONSUMER ELECTRONICS CORP.

OECO CORP.

OHIO EDISON CO.

OHIO STATE UNIVERSITY

ONEAC CORP.

ONTARIO HYDRO

OPUS ENGINEERING & SOFTWARE

ORLANDO TECHNOLOGY, INC.

ORMOND INC.

PALL CORP.

PHILLIPS ULTRASOUND

PHOTO RESEARCH DIV.

PICOSECOND PULSE LABS INC.

PIERCE CO. UTILITIES

PITTSBURG STATE UNIVERSITY

PITTSBURGH CORNING CORP.
44

PRECISION MEASUREMENT

PREMIER MICROWAVE CO.

PROCESS & INSTRUMENTS CORP.

PUGET SOUND NAVAL SHIPYARD

PUGET SOUND POWER & LIGHT CO.

P.S.E. & RESEARCH CORP.

QVS INC.

Q-DOT, INC.

RAMSEY ENGINEERING CO.

RAYTHEON CO.

RAYTHEON CO. MISSILE SYSTEMS DIV.

RCA ASTRO-ELECTRONICS

RCA CONSUMER ELECTRONICS

RCA CORP.

RCA LABORATORIES

RCA-SSD

RCA, PMEL/E

RD TECHNOLOGY INC.

RED RIVER ARMY DEPOT

RELIANCE ELECTRIC CO. - MSE

RESURRECTION HOSPITAL

RETLIF TESTING LABORATORIES

REXNORD CHEMICAL PRODUCTS INC.

ROCHESTER GAS & ELECTRIC CORP.

ROCKWELL ENG. CO.

ROCKWELL HANFORD OPERATION

ROCKWELL INTERNATIONAL

ROCKWELL INTERNATIONAL, CTSD

ROCKWELL INTERNATIONAL, ROCKY FLATS

ROSEMOUNT, INC.

ROSS ENGINEERING CORP.

ROTEK INSTRUMENT CORP.

ROTTER ENGINEERING

RUSKA INSTRUMENT CORP.

RUTHERFORD RESEARCH

SACRAMENTO MUNICIPAL UTILITY DISTRICT

SANDIA NATIONAL LABORATORIES

SANGAMO WESTON, INC.

SARGENT INDUSTRIES

SASKATCHEWAN POWER CORP.

SCANTEK IND.

SECURITY TAG SYSTEMS INC.

SENSOTEC, INC.

SENTRY TEST SYSTEMS

SENTRY VHSIC

SEQUENCE, INC.

SHEPARD SCIENTIFIC

SIMCO ELECTRONICS

SOLAR ENERGY RESEARCH INST.

SOUTHWEST RESEARCH INSTITUTE

SOUTH CAROLINA ELECTRIC AND GAS

SPECTRA-PHYSICS, INC.

SPERRY

SPERRY, COMPUTER SYSTEMS DIV.
.

STONE & WEBSTER ENGINEERING CORP.

STUBBS OVERBECK & ASSOCIATES, INC.

SUN TEQ ENGINEERING INC.

SUND STRAND ATG.

SUNDSTRAND DATA CONTROL, INC.

STATE UNIVERSITY OF NEW YORK- BUFFALO

SVERDRUP & PARCEL ASSOC.

SYNERGY, INC.

SYNETIC DESIGN CO.

SYSTEM TEST

S. SENSIPER

TECHNICAL SERVICE LABORATORY

TEKTRONIX, INC.

TELEDYNE RYAN ELECTRONICS

TELEDYNE SYSTEMS CO.

TENNESSEE TECH. UNIVERSITY

TERADYNE INC.

TETTEX INSTRUMENTS INC.

TEXAS INSTRUMENTS, INC.

TEXAS STATE TECHNICAL INSTITUTE

THE BOEING CO.

THE CITADEL

THE UNIVERSITY OF TULSA

THERMO ELECTRIC (CANADA) LTD.

THERMOMETRICS INC.

TIGER COMMUNICATIONS

TMDE BRANCH, U. S. ARMY

TRACOR, INC.

TRANSMAT I ON INC.

TRAVENOL LABORATORIES INC.

TRIPLETT CORP.

TRW

TRW DSSG

TUDOR TECHNOLOGY INC.

UAB EE DEPT.

UNIVERSITY OF CALIFORNIA AT BERKELEY

UNION CARBIDE CORP.

UNIVERSITY OF NEW MEXICO, NMERI

UNIVERSITY OF ARIZONA

UNIVERSITY OF ARKANSAS

UNIVERSITY OF LA VERNE

UNIVERSITY OF PITTSBURGH

UNIVERSITY OF SASKATCHEWAN

UNIVERSITY OF SOUTH FLORIDA

UNIVERSITY OF WASHINGTON

UNIVERSITY OF MINNESOTA

U. S. AIR FORCE

U. S. ARMY ARDC IEB NSD PAD

U. S. ARMY AREA TMDE SUPPORT OPERATION

U. S. GEOLOGICAL SURVEY, WRD

U. S. INSTRUMENT RENTALS

U.S.A. AREA CALIBRATION & REPAIR CTR.

USAF QUALITY ASSURANCE

UNIVERSITY OF TEXAS AT ARLINGTON
46

U. S. NAVAL ACADEMY

U. S. GEOLOGICAL SURVEY, WRD

U. S. NAVY CALIBRATION LABORATORY

U. S. WINDPOWER INC.

VALCOR ENG. CORP.

VARIAN ASSOCIATES

VECTRON LABS INC.

VEDA INC.

VI SHAY

VOGELMAN DEVELOPMENT CO.

WEAC

WESTINGHOUSE ADVCD. ENERGY SYSTEMS DIV.

WESTERN ENGINE CO.

WEYERHAUSER FORESTRY RESEARCH

WILLIAMS INTERNATIONAL CORP.

WYANN TECHNOLOGY CORP.

YELLOW SPRINGS INST. CO.

3M COMPANY

55 AMS/MAAP
47

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81 -

Appendix D - "Other" Instruments/Devices

Listed by Respondents in Section D

Ammeters

Flux Meters

Current Generators

Resistance Meters

Mircroammeters

Optical Radiance Instruments

Colorimeters

Temperature Guages

Ratio Bridges

Thermocouples

Antennas

10-volt References

Thermopiles

Fluke 752A Divider

RTD Thermometry

Resistors

TV C

Electrostatic Voltmeters

Avtron Model T53

Accelerometers

Moisture Monitors

Primary Frequency Standard

Fiber Optic Power Meters

Transformer Comparators

Gauss Meters

Syncro/digital Converters

Wideband H.V. Divider

Angle (mechanical)

RTD

EM Field Sensors

Standard Cells

Fluke 732A Voltage Reference

Reference Voltage Diodes

Electric Field Probe

Network Analyzers

Capacitance Bridges

Microwave Attenuators

Microwave Power Meters

Power Amplifiers

Potential Divider, L&N Model 4399

Milliohmeters

Lock-in Amplifiers

Timing Equipment

Programmable Voltage Supplies

Resistance Standards

Sound Level Meters

Chromatograph

Hi-pot Tester

Cesium Standard

Shake Tables

Scaler Ratemeter

Data Loggers

Capacitors /inductors

Magnetic Field Probe

Strain Guage Devices

Voltage Dividers

Analog Tape Recorders

Charge Amplifier
82 -

Appendix E - "Other” Types of Involvement With

ATE/Complex Measurement Systems

For in-plant use For cal lab use

In-house ATE

Diagnostic X-Ray testing

Design for in-house use

Standards lab automation

Equipment specifications

Designer of small systems

Purchase for repair operations

Consultant to manufacturers

Component manufacturers

Instrument distributor

Diagnostics for scientific instruments

Calibrations

Medical equipment and standards

Custom ATE for specific products

ATE master calibration station

Build for internal use

ATE calibration support

In-house development

Evaluate and advise

Sales

Automated calibration systems

Research

Systems engineering

R&D ATE for government systems

Watthour billing meter

Sales - service and calibration

R&D Laboratory

Education and research

Maintainer /calibrator

Instrumentation/sensor testing

Consultants

Measurement Systems education

Data acquisition process controls

Government specification writers

General systems engineering for the Air Force

Design of prototype ATE

Consumer /user
83 -

Appendix E.2 - "Other" ATE/Complex Measurement Equipment

listed by respondents in Section E

Mechanical component testers

Materials

TEM call control

TEMPEST

Fiber optic components

Spectrophotometry

Magnetic field quality

Data acquisition of pressure

EMI measurement systems

Microwave test systems

Specific equipment testers

Emulators

Oscillator testers

Quadrupole mass spectrometer

Electrical properties of living cells

GO/nogo systems

EMC tests

Probers/C-V plotters

Computerized EMP measurements

Satellite test systems

Process monitors

Computer controlled measurement systems

Cable testers

Biomedical test systems

Diagnostic/ pro gnostic

TV measurements

Comparator board testers

Specialized product testers

Transient recorders

Process control - analytical

Fiber optic test and measurement

Data acquisition

Destructive tests

R&D test systems

Sensor test consoles

Testing DC/AC inverters

Instrumentation systems

Ballistic data acquisition

Plant control monitoring

Steel wire rope testers

System performancew testers
.
MBS-1 14A (REV. 2-80

U.s. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 87-3549

2. Performing Organ. Report No. 3. Publication Date JUNE 1987

4. TITLE AND SUBTITLE

Summary Report on a Survey of Electronic Measurement Needs Below 10 MHz

5. AUTHOR(S)

John R. Sorrells

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s) national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State. ZIP)

10. SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

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12. KEY WORDS (Six to twelve entries; alphabetical order; capi ta I i ze only proper names; and separate key words by semicolon s) automatic test equipment; ATE; complex measurement systems; electrical quantities;

electronic measurement needs; precision instruments; questionnaire; survey

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PUBLICATIONS

NBSIR 87-3550

Mixing in Variable Density,

Isothermal Turbulent Flow and

Implications for Chemically

Reacting Turbulent Flows

William M. Pitts Takashi Kashiwagi

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

May 1987

30

37 - 387

.2

Supported in part by:

.S. Air Force

'ffice of Scientific Research

NBSIR 87-3550

MIXING IN VARIABLE DENSITY,

ISOTHERMAL TURBULENT FLOWS

AND IMPLICATIONS FOR CHEMICALLY

REACTING TURBULENT FLOWS

Research Information Center

National Bureau of Standards

Gaithersburg, Maryland 20899

fee

Qoioo

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William M. Pitts Takashi Kashiwagi

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

May 1987

Supported in part by:

U.S. Air Force

Office of Scientific Research

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
TABLE OF CONTENTS

Page

List of Tables iii

List of Figures iv

Abstract 1

1. Introduction 1

2. Project Objectives 2

3. Research Accomplishments 3

3.1 Diagnostic Development 3

3.1.1 Concentration Measurement Using

Rayleigh Light Scattering 4

3.1.2 Simultaneous Concentration and Velocity

Measurement 5 3.1.3 Development of a Digital Line Camera

for Concentration Measurement . : 9

3.2 Characterization of Mixing and Velocity

Behavior in Axisymmetric Jets 14

3.2.1 Mixing in a Turbulent, Axisymmetric

Jet of Methane 14

3.2.2 Simultaneous Measurements of Concentration

and Velocity in a Propane Jet 15

3.2.3 Density and Reynolds Number Effects on

Mixing in Axisymmetric Jets 16

4. Importance of Isothermal Studies to an Improved

Understanding of Turbulent Reacting Flows 21

4.1 Similarity of Mixing in Isothermal and Reacting

Flows 22

4.2 Lift-Off and Blow-Out of Turbulent Jet Diffusion

Flames 23

4.3 Application of Isothermal Findings to Turbulent

Mixing in Combustion Regions of Turbulent Jet Flames 28

4.4 Reynolds Number Effects in Diffusion Flames 31

5. Summary 32

6. References 34

7. Tables 39

8 . Figures 40

ii
LIST OF TABLES

Table 1. Experimental parameters

Page

39

iii
LIST OF FIGURES

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

The experimental configuration for real-time Rayleigh

light scattering "point" measurements of concentration in

binary gas mixtures is shown schematically. The flow

system consists of a 6.35 mm diameter pipe with a sharpened edge enclosed within a 100 X 100 cm2 square

cylinder

The quality of the data which can be acquired utilizing

the Rayleigh light scattering technique for concentration

is demonstrated. Radial profiles of concentration (in

both mole and mass fraction terms) are plotted for a turbulent CH4 jet flowing into a slow coflow of air. The

downstream distance is z/ro = 35 and the Reynolds number

is 3950 44

Partial time -resolved data records recorded during a simultaneous Rayleigh light scattering and hot- film

anemometry experiment are reproduced for a propane jet

(Re - 3960) flowing into a slow coflow of air. The

observation volume is located on the jet centerline at

z/rQ - 31.5. The light scattering signals have been

calibrated and are plotted in terms of mole fraction of

propane . The raw data for the anemometer output is

plotted along with the velocity calculated utilizing the

calibrations of film response to changes in velocity and

gas composition 45

The correlation is shown for the heat transfer from a hot-wire as a function of flow velocity for nine

different gases. Experimental measurements are

nondimensionalized by the use of the Nusselt number and

Reynolds number. Corrections have been included for heat

losses to the prongs of the hot-wire and thermal slip and

accommodation effects at the surface of the probe. (KB ) X and (Ka ) x are coefficients which are necessary to

compensate for variations in molecular properties from

gas to gas 46

The camera which has been developed for recording realtime Rayleigh light scattering intensity along a line is

shown. The top portion indicates the major components

and their configuration. The actual appearance of the

camera is shown below 47

Page

43

iv
Page

Figure

Figure

Figure

Figure

Figure

Figure

6. The overall experimental configuration for real-time

measurements of concentration along a line in turbulent

flows is represented. Rayleigh light scattering is

induced along a line in the flow field by the Ar+ ion

laser. Light scattering at 90° is recorded by the

digital line camera system consisting of the line camera

shown in figure 5, suitable interfaces, and a data

acquisition minicomputer 48

7. An example of time-resolved line measurements of propane

mole fraction across a turbulent jet of propane (Re =

3960) flowing into a coflow of air is reproduced.

Propane mole fraction is represented by a seven level

gray scale. The downstream position is 5 diameters and

the line read out rate is 830 Hz 49

8. Time-averaged radial profiles of propane mole fraction

are shown for five downstream positions in the

development region of a propane (Re = 3960) jet flowing

into a slow coflow of air. The growth of the boundary

layers on either side of the potential core with

increasing z and decrease of centerline concentration at

the end of the potential core can be clearly observed.

It is interesting to note that the data displayed

represents 164,000 individual concentration measurements

which were recorded during 1.54 s of actual acquisition

time 50

9. The apparatus for recording time -resolved shadowgraphs is

represented schematically. The light pulse generated by

the chopper has a temporal profile which is triangular in

shape and has a total duration of 310 /is 51

10. Three time -resolved shadowgraphs are shown for a SF6 jet

(Re = 3950) flowing into a slow coflow of air. Three

different downstream positions recorded at different

times are represented. Note particularly the formation

of a fountain by the SF6 at a downstream position of ~

37.5 ro

* 52

11. Shadowgraphs are reproduced for jets of SF6 (Re = 7890

and 11,860) entering slow coflows of air. For each jet

four views of the flow recorded at different times and

positions in the jet are superimposed. Note that the

fine scale turbulence becomes more pronounced with

increasing Re, but that the overall spreading rate of

the jet does not appear to be affected 53

v
Page

Figure 12 . Five sets of superimposed shadowgraphs are shown for

jets of one gas flowing into a second gas. With the

exception of the SF6 flow, the Reynolds numbers are

roughly the same. The effects of variations in the

global density ratio appear as changes in the

development region of the flow and modifications in the

eddy structure at downstream positions where the flows

are close to fully- developed

Figure 13 . Superimposed shadowgraphs are reproduced for propane

jets at three Re entering into slow coflows of air. The

development of finer turbulent scales with increasing Re

can be clearly seen. It is also evident that increasing

the Re results in a shortening of the distance required

for the development of vortical structures near the

nozzle. The overall spreading behavior of the jets is

independent of Re supporting the supposition that

entrainment is determined by large scale turbulent

structures

Figure 14. Values of Y0 /Ym (Yc = Yra is the centerline concentration

at z/ro and YQ is the mass fraction of jet fluid at the

jet exit) are plotted as a function of z/rQ for six

different jet/coflow gas combinations. The solid lines

are linear least squares fits of the results. Note the

decreasing slopes and upstream movement of the virtual

origins (z where YQ /YC

-* 0) which occur as the

jet/coflow density ratio is increased

Figure 15. Predicted values of inverse centerline mass fraction

(denoted as 1/Cm ) based on the analysis of Thring and

Newby [35] are plotted as functions of z/ro for the six

jet/coflow gas pairs which have been experimentally

investigated. Comparison of figures 14 and 15 shows

that there is good agreement between prediction and

experiment *. . . Figure 16. Values of centerline unmixedness are plotted as a function of z/ro for the six jet/coflow gas pairs

listed. Values of Y^/Ym for each jet approach a common

asymptote of « 0.23, but the flow distance required

increases dramatically as the jet/coflow density ratio

increases

Figure 17. The centerline unmixedness values shown in figure 16 are replotted as a function of z/r£

. The collapse of the

data onto a single curve suggests that r £ is the proper

scaling parameter for correlating the growth of

unmixedness in these variable density flows

54

55

56

57

58

59

vi
Page

Figure 18. Centerline unmixedness values for three different Re

jets of propane entering slow coflows of air are plotted

as functions of z/rQ

. Flows at higher Re require longer

flow distances in order to achieve the asymptotic value

of unmixedness even though the value of the asymptote

does not change

Figure 19 . The concentration contour corresponding to that for

which the laminar flame speed of an ethylene/air mixture

is a maximum (YL =0.073) is plotted as functions of

z/ro and r/ro

. The virtual origin for the plot is

assumed to be at z = 0. Two representations are shown.

On the right the radial and axial axes have the same

scaling, while on the left the radial scale is expanded

by a factor of 3

Figure 20. Experimental values [47] of lift-off height (h) are

plotted against jet exit velocity for turbulent jet

flames of methane , ethylene , and propane . These

measured values are compared with values (solid lines)

predicted using eq (5) and the known velocity and mixing

behaviors of the jets. The agreement is excellent. . . Figure 21. Experimental [53] (symbols) and calculated values

(lines) of blow out velocity are plotted as a function

of jet radius for axisymmetric turbulent jet flames of

five organic fuels . Calculated values are derived by

using eqs (6) and (7)

The agreement of the predicted

values with experiment is very good

Figure 22. Approximate radial density profiles for three

nondimens ional downstream distances are shown for

turbulent jet diffusion flames of hydrogen and a typical

organic fuel (methane) . These curves are based on

measurements reported by several different authors

[63,67]

60

61

62

63

64

vii

ABSTRACT

This report summarizes the research findings of a project which has been

jointly funded by the Air Force Office of Scientific Research and the National

Bureau of Standards. The goal of the research was to improve the fundamental

understanding of chemically reacting turbulent flow. The approach which was

taken was to investigate mixing in variable density flows in order to better

understand the role of local density fluctuations (which result from chemical

heat release) on the turbulent mixing behavior. The development of new

experimental diagnostics having excellent spatial and temporal resolution is

described. These techniques have been utilized to investigate a wide range of

mixing properties in variable density flows. These results are summarized

along with a discussion of their importance to an improved understanding of

chemically reacting flow.

1. INTRODUCTION

This report summarizes the major findings of a four-year study on

chemically reacting turbulent flow. This project was jointly funded by the

Air Force Office of Scientific Research (contract numbers ISSA-83-00012 , ISSA84-00005, ISSA-85-00012 , and ISSA-86-00008) and the National Bureau of

Standards. The period covered is October 1, 1982 to September 30, 1986.

In the following sections the overall objectives of the research project

are discussed, significant research accomplishments are listed and briefly

described, and the significance of the findings to the understanding of

chemically reacting turbulent flow is discussed.

1
2 . PROJECT OBJECTIVES

The primary objective of this research program was the improvement of the

fundamental understanding of chemically reacting turbulent flow. The most

complicated aspect of this problem is the complex coupling of fluid mechanics

and heat release which occurs for most flows in this class. Despite intense

efforts for several decades, this complicated process has remained poorly

characterized. This is unfortunate since chemically reacting turbulent flows

are of paramount importance in a wide range of combustion devices and other

chemical reactors which have military and industrial significance. An

improved understanding of the interactions of fluid dynamics and heat release

is not only necessary to improve device efficiencies and contribute to the

conservation of dwindling fuel and feed stocks, but also to allow new types of

designs which can limit the release of undesirable pollutants.

In order to meet the above objective an approach was chosen in which the

effects of global density variations on turbulent mixing of axisymmetric jets

were investigated. This path was chosen since it was felt that one of the

major sources of coupling between heat release and fluid motion in a turbulent

flow is through the density variations introduced by chemical heat release.

In order to characterize these effects, it is first necessary to understand

the effects of global density differences.

The study of mixing in variable density, turbulent flows (or any

turbulent flow for that matter) is complicated by the wide range of spatial

and temporal scales which are of importance. These scales vary from the full

dimensions of the flow field down to the smallest scales where turbulent

dissipation occurs. It is clear that in order to obtain an improved

characterization of these processes diagnostics having high spatial and

2
temporal resolution are required. Since suitable diagnostics were not

available, an important secondary goal for the project became the development

of new experimental techniques for the study of concentration and velocity

fluctuations in variable density flows. The importance of large scale

turbulent structures in these flows fields necessitated the development of

multi -point diagnostics capable of high temporal and spatial resolution. A

digital line camera was designed and a prototype constructed. Preliminary

experiments utilizing the camera have been encouraging and development is

continuing

3. RESEARCH ACCOMPLISHMENTS

In the subsection which follows , the development of new diagnostics are

described. The findings of an extensive study of mixing in variable density

turbulent flows are then summarized. Work in this laboratory, as well as elsewhere, has demonstrated the importance of these findings to an improved

understanding of chemically reacting turbulent flow. This point is discussed

in the last subsection.

3 . 1 DIAGNOSTIC DEVELOPMENT

Throughout the course of this project there was an emphasis on the

acquisition of real-time data having high spatial resolution and accuracy.

Very few suitable experimental techniques were available and a great deal of

effort was directed toward the development of unique capabilities for the

measurement of concentration and velocity in variable density flow fields.

Significant progress has been made on the development of the necessary

diagnostic tools.

3
3.1.1 Concentration Measurement Using Rayleigh Light Scattering

The development of Rayleigh light scattering as a real-time diagnostic of

concentration fluctuations within small spatial volumes of turbulent binary

gas mixtures was completed during the very early stages of the project period.

Building on earlier work [1,2] it was demonstrated [3,4] that Rayleigh light

scattering can be utilized to measure a wide range of properties in these flow

fields

.

The intensity of light scattered by a gas is proportional to the Rayleigh

scattering cross section. This scattering cross section is in turn related to

the index of refraction of the gas. Since the refractive indices of

individual gases vary, scattering intensity varies from gas to gas. For

mixtures, the scattering cross sections for the different gases are additive.

A measurement of scattering intensity from a binary gas mixture, following

calibration in the pure components, allows the concentrations of the two gases

in the observation volume to be determined.

Figure 1 shows the experimental apparatus which was developed for

Rayleigh light scattering measurements. In order to test this system, realtime concentration data were recorded in the turbulent flow field formed by an

axisymmetric jet of methane (Re - 4130) flowing into a slow coflow of air. It

was demonstrated [3,4] that this system is capable of recording real-time

measurements of methane concentration at data rates as high as 10 kHz for

observation volumes as small as 0.0003 mm3

. The accuracy of individual

measurements was estimated to be » 1.9% at the highest data rate.

From the resulting real-time data records such flow properties as the

time -averaged concentration, root mean square (RMS) in the concentration

fluctuations, and the concentration skewness and kurtosis were calculated.

4
Figure 2 shows the behavior of the time -averaged methane concentration in the

radial direction for a downstream distance of 30 r0

. By using fast Fourier

transform analysis it was also possible to calculate the frequency spectrum

and correlation functions for the concentration fluctuations

The availability of real-time data allowed a determination of whether or not jet fluid was present in the imaged volume during the observation time.

In this manner, the intermittency function (based on the presence or absence

of jet fluid) could be determined and then utilized to provide conditionallysampled measurements for the properties described above.

Even though the results [3,4] of this work were of a preliminary nature,

they represented the most extensive and complete set of data for a variable

density flow available in the literature at the time of their publication.

Where comparisons were possible, results [3,4] were found to be in excellent

agreement with measurements reported in the literature.

3.1.2 Simultaneous Concentration and Velocity Measurement

The development of the Rayleigh light scattering technique provided a powerful means for monitoring concentration behavior in a turbulent flow field

of two gases. However, in order to more fully characterize turbulent behavior

in variable density flows, measurements for velocity are also required. Of

particular importance is the capability for simultaneous measurements of

concentration and velocity which allows such parameters as the cross- correlation coefficient (Ruc ) of velocity and concentration to be calculated.

Such correlations are very important since they often appear in models which

attempt to provide closure for the Navier- Stokes equations and in treatments

which utilize Favre averaging [5]. Such measurements have been very difficult

5
to make in the past and very few comparisons between theoretical estimates and

experimental findings are available.

Either of two techniques, hot-wire anemometry (HWA) and laser Doppler

veloclmetry (LDV) , are usually employed for real-time velocity measurement.

LDV requires seeding of the flow with particles. This results in a strong Mie

scattering which completely obscures the Rayleigh light scattering signal

necessary for concentration measurement. Even though experiments have

demonstrated that simultaneous measurements of concentration and velocity are possible in lightly seeded flows [6]

,

it has not been possible to make realtime measurements. For this reason, HWA was chosen as the velocity

diagnostic.

HWA in variable density flows is complicated by the variations in

molecular thermal conductivity which occur as the composition of the gases

around the probe changes. As a result, the response of the HWA is not only

sensitive to velocity changes, but also to concentration variations. This

sensitivity has been used as the basis for probes designed to measure

concentration in binary gas mixtures [7], By combining two probes having

different heat transfer properties it has also been possible to make

simultaneous measurements of concentration and velocity [8,9], However, these

measurements require extensive calibrations and data manipulation and have not

come into widespread or routine use. By combining the HWA and Rayleigh light scattering techniques it is

possible to mitigate some of the limitations of HWA for velocity measurements

in variable density flow fields consisting of two gases. The Rayleigh light

scattering technique provides real-time concentration measurements which can

be utilized to correct the response of the HWA for variations in gas

6
composition once the velocity probe has been calibrated in a series of

mixtures. The necessary calibrations are considerably simpler than those

required when two hot-wires are employed. Limitations of such an approach

include the need for an obtrusive probe and the necessity of physically

separating the observation volume for the Rayleigh light scattering and the

position of the hot-wire (to avoid scattering)

Experimental work [10] has shown that the limitations mentioned above are not serious and that the combination of Rayleigh light scattering and HWA can

be utilized for accurate, real-time measurement of concentration and velocity

in variable density flows. Figure 3 shows an example of the real-time

behavior of concentration and velocity for a turbulent jet of propane flowing

into a coflow of air. Such data records were utilized to calculate timeaverages, rms values, and cross-correlation values for the velocity and

concentration fluctuations of propane and methane jets. In all cases the

experimental measurements were in excellent agreement [10] with the limited

data available in the literature.

The measurements reported in [10] are for a single hot-wire (or hot- film)

aligned so that the probe is sensitive to velocity in the axial direction of

the jet flows. It is possible to also utilize an "X-probe" consisting of two

wires oriented at 45° in order to measure both the axial and radial components

of velocity. During the past year the response of such a probe to variable

density flows as well as the effects of flow direction have been extensively

investigated. In the near future this X-probe will be combined with the

Rayleigh light scattering system in order to form an experimental system which

can make real-time measurements of concentration and two components of

velocity in variable density flow fields. This system will be capable of

7
characterizing variable density turbulent flow fields to a degree which has

heretofore been impossible.

As part of the calibration work necessary to employ these HWA probes,

various correlations available in the literature for the heat loss from a cylinder were considered. It was discovered that none of these correlations

were successful in correlating an extensive series of calibrations performed

in ten different gases [11,12]. The most widely quoted correlation for

different gases utilized a correction based on the Prandtl number (Pr) to

correct for variations in molecular properties [13-15] . This correlation was

found to be unsatisfactory for the gases investigated during this study.

Extensive analysis [11,12] of the data showed that it is necessary to consider

the temperature dependence of the molecular properties in order to obtain

accurate correlations. Figure 4 is a plot of the heat transfer behavior (in

terms of the nondimens ional Nusselt number) as a function of flow velocity (in

terms of the nondimens ional Reynolds number based on the probe diameter) . The

correlation of the results for the nine gases shown is excellent.

Other heat transfer characteristics such as thermal slip and surface

accommodation were also investigated during the course of this study [11,12].

In particular, it was shown that the heat transfer from a cylinder to helium

is strongly influenced by surface accommodation. Using theories previously

developed for treating this process [16] it was possible to correct the

measurements for this effect and obtain an accurate correlation of the heat

transfer behavior of helium with the results for other gases. The helium data

included in figure 4 have been analyzed in this manner. The measurements also

yielded an vastly improved understanding of the dependence of the heat

8
transfer process on Re and transitions in flow behavior which occur as the Re

is varied.

The manuscripts which resulted from this work [10,11,12] are not only

significant for their importance to researchers who wish to utilize HWA in

different gases, but are also important for the much wider field of heat

transfer. The results considerably modify current concepts concerning the

role of molecular properties in heat transfer behavior.

Extensive measurements [17] have also been made for mixtures of gases.

For these mixtures the procedure described above does not provide accurate

correlations for the heat transfer measurements. Systematic variations are observed with the mole fractions of the components which have tentatively been

ascribed to the effects of thermal diffusion on the heat transfer behavior.

If thermal diffusion is indeed the source of the variations, it is required

that its effects on heat transfer be roughly ten times larger than reported in

the literature. Dr. Howard Baum is currently developing a theory [17] for

this process which is designed to allow a test of this hypothesis.

3.1.3 Development of a Digital Line Camera for Concentration Measurement

The flow diagnostic techniques described above are designed to allow

accurate point measurements of velocity and concentration. Measurements

utilizing these techniques as well as findings in other laboratories have

suggested the importance of large scale structures for mixing in turbulent

flows such as axisymmetric jets. The availability of real-time point

measurements allows some characterization of these structures through the

determination of intermittency functions and conditional sampling. However,

such measurements provide very limited information about individual structures

9
and their role in the entrainment of surrounding gases. Clearly, simultaneous

measurements at many different points in space would provide much more

information concerning the structure and role of these large scale structures

in the turbulent mixing process

.

Recently there has been a great deal of research activity (e.g., [18-23])

on the development of optical diagnostics which are capable of nonobtrusive

,

multi-point measurements in flow fields. Such imaging experiments have been

reported along lines [18], in planes [19-21], and in three dimensions [23]. A

wide range of optical processes such as Rayleigh [19,23], Raman [20], Mie

scattering [19] and fluorescence [18,21,22] have been employed. Even though

there are exceptions, most of these experiments are characterized by the need

for image intensification (due to the relative insensitivity of the solidstate detectors which are usually employed) and the use of high-powered lasers

which provide sufficient signal levels to allow the optical measurements, but

which limit the experiments to low repetition rates.

Due to the ability of imaging experiments to provide a more complete

characterization of large scale structures in turbulent flows, it was clear

that a system utilizing Rayleigh light scattering for quantitative mass

fraction measurement would be very useful. A short proposal was prepared and

the necessary funding for the development of a digital line camera system was

provided internally by the National Bureau of Standards. Note that a similar

unintensified system has been utilized for concentration measurements in a water jet [22]

.

A set of design goals were developed for the camera. The most important

of these are listed here:

1. A spatial resolution of 400 fxm along the line.

10
2 . Line readout rates greater than a kHz

3 . Concentration measurements having an absolute accuracy of a few percent.

4. Utilization of an existing CW Ar ion laser and data

acquisition system.

5. Use of commercially- available components.

The first three of these goals were chosen to be consistent with the

capabilities of our experimental system for single point measurements of

concentration. The last two were required to minimize the cost of the system

and simplify its design and construction. These criteria were found to be in

competition with one another and it was necessary to make compromises in the

design of the camera.

An analysis [24] of the intensity of scattered light from the Ar+ ion

laser beam and the sensitivity of commercially available solid-state line

detectors indicated that image intensification would be required in order for

the line camera to operate at the required data rates. This requirement

turned out to be the most difficult technical challenge of the camera design.

There are two major types of image intensifiers available commercially.

These are known as generation I (gen I) and generation II (gen II) . Gen I

tubes consist of a photocathode, accelerating and focusing electronics for

electrons emitted by the photocathode, and a phosphor screen. The optical

gain of the device results from the fact that a single accelerated electron

striking the phosphor screen results in the production of many photons.

Gen II tubes are similar to gen I tubes with the exception that a microchannel plate (MCP) is inserted between the photocathode and the phosphor

screen. The MCP is an active device which can produce electron gains of

11
103 -10A

. Since the channels which form the MCP are aligned, any electron

"image" present on the input face is maintained at the other end of the MCP.

Electrons emitted by the photocathode of a gen II image intensifier are focused (either by proximity or electrically) onto the MCP and the resulting

amplified electron image from the MCP is focused onto a photocathode. Since

the MCP provides a very high gain, a single gen II image intensifier has a much higher light gain than a single gen I tube. It is necessary to cascade

two or three gen I tubes in order to obtain intensification comparable to a single gen II tube.

In most flow imaging experiments reported thus far gen II tubes have been

utilized. However we discovered [24] that for real-time imaging there is a serious problem due to the maximum light output which can be generated by this

type of image intensifier. This limitation results from the limited output

current of the individual channels of the MCP. Calculations indicated that

the maximum brightness which can be generated by a gen II tube is comparable

to that available from the Rayleigh light scattering experiment and is not

sufficient for real-time detection using commercial, solid-state line

detectors. Since only moderate light gains were necessary, a gen I tube was

chosen as the image intensifier. These tubes can operate at much higher

current levels than the second generation devices and can therefore produce

more intense light outputs.

Measurements at data rates greater than a kHz also require consideration

of the response time of the phosphor screen used in the intensifier. The P-20

phosphor employed for standard tubes has a long-lived tail in its temporal

decay and for this reason is unsuitable for this application. A P-47 phosphor

screen was chosen instead. This screen has a submicrosecond lifetime, but it

12
is less efficient than P-20 and the overall gain of a single stage is

significantly reduced. The final selection for the image intensifier

consisted of two stages of gen I tubes equipped with P-47 phosphor screens. The detector chosen for the camera was a Reticon RL128S* line detector

which consists of 128 pixels on 25 \im centers. A 4:1 reduction fiber optic

taper was utilized to couple the detector and the image intensifier. The

camera was completed by the addition of a f/I . 9 1:1 focusing lens for imaging

the scattered light onto the image intensifier. With this arrangement each

pixel corresponds to a 100 fim length of the image so that the entire line

image covers 12.8 mm. Figure 5 shows a schematic for the prototype camera. The line detector is equipped with electronics which generate voltages

that are proportional to the light detected during the integration period on

an individual pixel. The voltages for the 128 pixels appear sequentially on

the output. These voltages are digitized and stored in the memory of a minicomputer. Since the maximum data rate for the acquisition system used is

333 kHz, the maximum line read-out rate is limited to 2.2 kHz. Figure 6 shows

the overall system for line measurements of concentration including the

digital line camera, the flow system, and the Ar+ ion laser.

In order to test the system, line measurements of propane mole fraction

for a propane jet flowing into a slow coflow of air have been recorded.

Figure 7 shows an example of the concentration behavior across the radial

profile of the jet at a downstream distance of 5 jet diameters and a line

read-out rate of 837 Hz. The total data acquisition time was « 300 ms. Even

* Certain commercial equipment, instruments, or materials are identified in

this paper in order to adequately specify the experimental procedure. Such

identification does not imply recommendation or endorsement by the National

Bureau of Standards nor does it imply the instruments or equipment are necessarily the best available for the purpose.

13
though the time resolution is not sufficient to fully resolve small details,

the importance of large scale structures is clear. The results of such

measurements can be time-averaged to yield the contour of the radial profile.

Figure 8 shows the results for five downstream positions. The growth and

spread of the turbulent boundary layers is evident.

While the performance of the initial camera prototype has been very

encouraging, it has not been possible to reach the full time resolution

potential of the camera due to limitations in the gain of the image

intensifier. A new, three -stage tube has been ordered and will be installed

shortly. This gen I image intensifier will provide a higher gain due to the

additional stage of amplification. It is also equipped with P-46 phosphor

screens which have the same short lifetime properties of P-47, but which have

outputs at longer wavelengths (green) . Green light is more efficiently

transmitted by the fiber optic taper and detected more efficiently by the line

scanner. This modification should therefore increase the sensitivity of the

tube significantly.

3.2 CHARACTERIZATION OF MIXING AND VELOCITY BEHAVIOR IN AXISYMMETRIC JETS

3.2.1 Mixing in a Turbulent, Axisymmetric Jet of Methane

As part of the development of Rayleigh light scattering as a diagnostic

for concentration, extensive measurements of such flow properties as timeaveraged concentration, unmixedness, skewness, kurtosis, concentration

fluctuation spectra, and correlation functions were made [3,4]. The existence

of time -resolved data records also allowed the intermittency functions for the

flow field to be determined and from these it was possible to generate

conditionally- averaged measurements of these flow properties.

14
Data were recorded at various positions along the jet centerline and

across the radial profile of the jet for one downstream position (z/ro = 35).

In all cases where literature sources were available for comparison there was

excellent agreement. The availability of real-time data allowed the existence

of large-scale ramp -like structures in the intermittent region of the flow

field to be identified. Such structures are believed [25,26] to be the

primary mechanism by which jet entrainment occurs and for this reason their

characterization is crucial.

Even though the findings of the study [3,4] were of a preliminary nature,

they were chosen for comparison purposes with conserved scalar measurements in

a hydrogen jet flame [27,28]. These authors felt the measurements were the

most complete and accurate available at the time. A remarkable similarity was

found between mixing in the isothermal and combusting flows. The significance

of this finding is discussed below.

3.2.2 Simultaneous Measurements of Concentration and Velocity

in a Propane Jet

As a test of the combined hot -probe anemometry and Rayleigh light

scattering diagnostic, real-time concentration and velocity data were recorded

in jet flows of propane entering a slow coflow of air [10]. Preliminary

measurements which were recorded are significant due to the limited number of

such measurements which have been reported in the literature for variable

density flows. For instance, time-averaged measurements of centerline

velocity showed that the data could be fit in the form

Uo/Uc - Ku (z-z0 )/re (1)

15
where r A least squares fit e is the effective radius defined as (p0 /p«,)

1/2 r0 . of the results gave - 0.082 which is close to the value of 0.081

recommended by both List [29] and Chen and Rodi [30]. Values of the

correlation coefficients for velocity and concentration were also calculated

as a function of downstream position. Literature comparisons were very scare,

but measurements by Antonia et al. [31], Chevray and Tutu [32], and Catalano

et al. [33] showed that values of Ruc measured in this study were consistent

with previous measurements. The findings suggest that Eluc grows to an

asymptotic value of « 0.39 on the jet centerline in this variable density

flow.

3.2.3 Density and Reynolds Number Effects on Mixing

in Axisymmetric Jets

An extensive study [34] of the effects of density and Reynolds number

variations on mixing in turbulent axisymmetric jets was performed.

Qualitative information concerning the flows was obtained using time -resolved

shadowgraphs while Rayleigh light scattering was utilized to investigate

quantitatively the centerline mixing behavior. Table 1 lists the gas pairs

investigated in this study, the ratio of jet to coflow densities, Re based on

the jet diameter, and whether or not shadowgraph and Rayleigh data were taken.

Figure 9 shows the experimental arrangement used to record shadowgraphs

of the variable density jet flows. The diameter of the shadowgraphs is 76 mm

and the light pulse has a measured FWHM of 165 ps with a total duration of 310

/zs. It must be remembered that shadowgraphs provide an integrated view of the

flow field and that the signal is proportional to the second derivative of the

index of refraction variations which occur along the path of the light beam.

16
For these reasons, extreme caution must be utilized in drawing conclusions

from such photographs. However, with this in mind, it is possible to

characterize some of the effects of density and Reynolds number variations on

jet mixing behavior from the series of shadowgraphs which have been recorded.

Figure 10 provides a dramatic example of the effects of density

differences on the mixing behavior of a turbulent jet. Shadowgraph are shown

for a jet flow of sulfur hexafluoride into air with Re = 3950. The initial

jet density is 5.1 times higher than that of the surrounding air. As is

clearly shown by the shadowgraph covering the downstream region from z/ro = 25

to 45 , the initial momentum of the jet is not high enough to overcome the

negative buoyancy (the jet is orientated vertically) of the flow and the jet

forms a fountain with jet fluid falling back through the surrounding coflow.

Interestingly, as can be seen in figure 11, this effect disappears for Re of

7890 and 11860.

Shadowgraphs for flows covering jet to coflow density ratios of 0.14 to

5.1 are shown in figure 12. The following conclusions have been drawn

concerning the effects of density and Re differences on mixing in these flows

from these and other shadowgraphs

1. The initial density ratio effects the shape of the vortices at

downstream positions in the flow field. Increasing density ratios

result in lengthening of vortices in the axial direction.

2. Changes in the density ratio effect the initial development of

turbulence in the jets. For smaller values of po /pt0 the flow

distance required for initial growth of vortices is shorter.

Figure 13 shows shadowgraphs recorded for jet flows of propane into air

at three different Re. From these photographs as well as those shown in

figure 11, the general effects of changes in Re can be summarized as

1. As the Re is increased the turbulent structures in the flow field

extend to smaller scales.

17
2. Increasing the Re has very little effect on the angle of spread for

a given gas pair.

3 . Turbulent structures develop at shorter flow distances as the Re is

increased.

Even though the shadowgraphs provided qualitative information concerning

mixing in variable density turbulent flows, very little quantitative

information could be obtained. Rayleigh light scattering was utilized to

perform quantitative measurements of fluid concentration behavior along the

centerlines of the jets.

Time -averaged concentration measurements provide an excellent example of

how significantly density differences can modify mixing. Figure 14 shows

experimental values of inverse time-averaged mass fraction (1/Ym ) plotted as a function of nondimens ionalized downstream position for different jets having a wide range of density ratio. The data fall on straight lines having slopes

which decrease with increasing density ratio and virtual origins (value of z where 1/Ym extrapolates to zero) which move upstream as the density ratio

increases

.

In the early 1950 's Thring and Newby [35] suggested that the centerline

mixing behavior of axisymmetric turbulent jets could be correlated using an

expression which can be written as

1/Ym - Kc z/re + (pa /P0

- DK' (2)

where r £ is the effective radius defined earlier and Kc and K' are constants

which are determined by radial integrations of velocity and concentration

across the flow field. This equation can be derived utilizing conservation

equations and assuming self- similarity . It is strictly valid only for

downstream positions where ~p m ~ pQ .

18
The predicted behavior of plots of 1/Ym versus z/r0 using eq (2) are shown in figure 15 for Kc - 0.114 and K' - 0.5. Comparison with the

experimental results in figure 14 shows that there is excellent agreement.

The dependence of the slopes of the plots on p 0 /pm has been documented in the

literature previously (e.g., [36,37]), but to our knowledge, this is the first

time that the predicted dependence of z

Q on the this parameter has been

confirmed.

Similar data were recorded for axisymmetric jets in which the Reynolds

number was varied. These measurements showed that the principal effect of

increasing the Re was to shift the virtual origin, z

0

, downstream. Slopes of

plots of 1/Ym versus z/ro were independent of Re. This suggests that the

centerline mixing behavior in these flow fields is due primarily to large

scale turbulent structures which should be independent of Re (i.e., inviscid

flow)

The availability of time-resolved measurements allowed the behavior of

centerline unmixedness (defined as the RMS of the concentration fluctuations,

, divided by Ym ) to be determined as a function of p Q /pm and Re. Figure 16

is a plot of Y^/Ym versus z/rQ for six variable density flows. It is clear

that in each case unmixedness values are approaching a common asymptote of «

0.23, but that the flow distance required to attain this value is strongly

dependent on p 0 /pa with higher ratio flows requiring longer flow distances.

There are very few measurements or theoretical predictions of unmixedness in

variable density flows reported in the literature. This study was the first

to provide data for a wide range of p0 /pm . In order to gain some understanding of the role of density ratio on the

flow distance required to attain the unmixedness asymptote, the experimental

19
values of Y^/Ym were replotted as a function of z/re as shown in figure 17.

It is clear that plotting the data in this manner results in a collapse of the

growth curves for unmixedness and that re serves as a scaling parameter for

the growth. This conclusion is surprising in that the unmixedness development

is occurring in a flow region where the condition "pm « pQ is not met and the

development which leads to the definition of re is not strictly valid. At the

same time it does suggest that r e is a true scaling parameter which not only

results in a collapse of time -averaged data, but also scales the development

of turbulent structure in the flow field.

Similar measurements in C3 H8 /air (see fig. 18) and SF6 /air flows have

shown that the asymptotic value of unmixedness is independent of Re, but that

the flow distance required to attain the asymptote increases as the Re is

increased. The longer flow distances required for turbulence growth in the

higher Re flows results in the downstream shifts of the virtual origins

observed for plots of 1/Ym as functions of z/ro

. The observed Re dependence

of the flow distance required to attain fully- developed flow was surprising

since fully -developed turbulent behavior is generally associated with high Re.

The independence of the asymptotic value of Y,J/Ym on Re once again highlights

the importance of large scale structures in turbulent mixing behavior.

It was hypothesized [34] that the longer flow distances required for

fully- developed flow at higher Re is connected with development of smaller

scale vortices in the flow fields at higher Re. If a "pseudo- equilibrium”

exists between the different vortical scales, a longer flow distance would be

required for the entire turbulent structure to come into equilibrium at the

higher Re. More sophisticated experiments will be necessary to test this

hypothesis. Whether or not this hypothesis is correct, a more complete

20
characterization of the growth of centerline unmixedness in these flows is

required so that parameters which control the growth of turbulence in flow

fields can be identified.

The time records were also used to calculate skewness (third moment) and

kurtosis values (fourth moment) for concentration fluctuations. Distinct

effects of density ratio were observed on the centerline behavior of these

parameters, but in the absence of theoretical guidance it was not possible to

relate these variations to physical modifications of the mixing behavior.

The manuscript which was written to describe these results [34] contains

extensive comparison with previous literature findings. Generally,

quantitative agreement is excellent. Possible sources of disagreement, such

as the effects of buoyancy and the use of a coflow, were also analyzed and

were generally found to be minor perturbations . It was concluded that the

results are indicative of mixing behavior in free axisymmetric jets. The use

of a wide range of density ratios and Re resulted in the identification of

dependencies in the mixing behavior which had not been reported previously.

4. IMPORTANCE OF ISOTHERMAL STUDIES TO AN IMPROVED

UNDERSTANDING OF TURBULENT REACTING FLOWS

The significance of findings from the isothermal flow studies for

improving the understanding of the more complicated case of chemically

reacting flows was considered where appropriate. These analyses resulted in a more clearly defined perception of the role of density variations (both global

and local) in chemically reacting turbulent flows. Consideration of mixing

behavior in the isothermal mixing regions of lifted and blown out turbulent

jet diffusion flames resulted in new correlation procedures for describing

these stabilization characteristics and suggested new physical models to

21
understand the behaviors . The role of local Re variations on mixing in

chemically reacting turbulent flows has been assessed. These points are

discussed in this section.

4.1 Similarity of Mixing in Isothermal and Reacting Flows

Numerical data from the original Rayleigh light scattering study of

methane [3,4] were provided to investigators at General Electric Corporate

Research and Development Center for comparison with extensive experimental

measurements recorded for a turbulent hydrogen jet flames. Drake et al.

[27,28] found that radial profiles of the first four moments of concentration

fluctuations (time -average , RMS , skewness , and kurtosis) for the isothermal

and reacting flow (in terms of the conserved scalar concentration, [38])

were very similar. Such agreement suggests that heat release and combustion

have very little effect on the probability distribution functions (PDF) of

scalar mixing in turbulent reacting flows. This conclusion is extremely

important because it implies that the results of isothermal mixing studies can

be applied directly to chemically reacting turbulent flows and thus provides

additional justification for the approach taken in our own study. Theorists

have long used isothermal mixing results as the basis for models of chemically

reacting turbulent flow [39].

Drake et al. [27,28] also utilized the isothermal results of our earlier

study along with their own findings to test a parametric expression developed

by Effelsberg and Peters [40] which divided the conserved scalar PDF into

nonturbulent , fully turbulent, and superlayer parts. These authors concluded

that the measurements were not consistent with this model since the results

required that more than 50% of the PDF be due to superlayer contributions . An

22
alternate interpretation was offered in which the "apparent" superlayer was

attributed to the presence of large scale "ramp -like" structures in the flow

field. Such structures have been observed in time records recorded in our earlier work [3,4] and by other researchers (e.g., [31,41,42]).

4.2 Lift-off and Blow-Out of Turbulent Jet Diffusion Flames

There are certain properties of combusting jets for which isothermal

findings are directly applicable. In particular, lift-off and blow out of

turbulent jet diffusion flames must depend on the concentration and velocity

behavior of the turbulent flow upstream of the region where combustion or blow

out occurs. The results of our isothermal studies as well as other findings

available in the literature have been utilized [54] to develop a procedure

which is capable of accurately predicting experimental lift-off heights as a function of jet exit velocity and blow out velocities as a function of jet

diameter for turbulent jet diffusion flames of many different fuels.

Interestingly, only time -averaged properties have been considered and it has

not been necessary to consider the actual turbulent behavior of the flow.

This is significant since most theoretical treatments either assume flame

stability is due to an equilibrium of flow velocities and turbulent flame

speeds (which depend on small scale turbulent structure) [43-47] or to flame

extinction processes in small scale structures [48-51]

A radically different explanation for flame stability has been suggested

by Broadwell et al. [52]. These researchers have argued that flame stability

is determined by the reentrainment of hot combustion gases (expelled by the

passage of earlier large scale structures) by large scale structures in the

flow field. These gases are rapidly mixed with the jet gases and if the

23
turbulent mixing time, r

d is longer than the chemical ignition time, r

c

, of

the fuel/air mixture in the jet, the structure will be ignited and the

combustion stabilized. When the mixing time becomes shorter than the chemical

reaction time (r c > r

d ) combustion can no longer be sustained.

The impetus for our investigation of flame stability mechanism was the

extensive experimental investigations of lift-off [47] and blow out [53] of

turbulent jet flames by Kalghatgi. He found that his results for lift-off

heights as a function of velocity for different fuels were well correlated by

an expression which can be approximated as

h - Ch (U0 /(Sb )J ax )i/0 (p8 /p.) 1 - s

. (3)

where Ch is a constant, (Sb ) max is the maximum laminar flame speed for the

fuel and air, and the density term is an approximation for a more complicated

expression. The form of this equation was based on dimensional analysis. The

inclusion of uQ in the expression reflects the important role small scale

turbulent structures are believed to play in this stability behavior.

Blow out velocities as a function of jet diameter were found to have a similar dependence on density and uQ [53]. This correlation can be written as

(U0 )b - Cb r,(Sb )S. x /(Y.^0 (p0 /p.) 1 - 5 ), (4)

where Cb is a constant and Ys is the mass fraction of fuel in a stoichiometric

mixture with air.

Attempts to predict the exponent of 1.5 for the density ratios in eqs (3)

and (4) in terms of the known concentration and velocity fields of isothermal,

variable density turbulent jets were not successful. On the other hand,

correlations in which the term vQ (p0 /pm ) x • 5 were omitted from eqs (3) and (4)

24
were found to accurately correlate Kalghatgi's experimental findings. The

simplicity of these correlations suggested that the time-averaged properties

of the flow field might be employed to predict lift-off heights and blow out

velocities. Subsequent calculations [54] have shown this to be the case. The first step in the procedure is to calculate the time -averaged mass

fraction contour in the flow field along which the laminar flame speed is a maximum. Both theory [43-45] and measurements [44,45,55] in turbulent jet

flames have shown that the most probable location for the shortest distance

between the nozzle and the instantaneous flame position is along this contour.

Figure 19 shows the form of this contour for an ethylene jet. In order to

make these calculations , the centerline mixing behavior is taken from our

variable density study and the radial behavior is based on expressions given

in Chen and Rodi's book [30], Shifts in virtual origin with density ratio and

Re have been ignored.

An empirical procedure was then utilized to derive an expression for the

local velocity (UL ) along the contour which results in the proper dependencies

[47] of lift-off heights on jet diameter (nearly independent) and exit

velocity (linearly dependent) . The resulting expression has the form

U, - Ci'z2 (Sb )£ a:[ Yf/re (5)

where YL is the mass fraction of fuel necessary for (Sb ) max . The

corresponding velocity at the jet exit is then calculated utilizing the known

axial and radial dependencies for velocity [30]. Cb

' is a constant parameter

which has the units of an inverse kinematic viscosity. In order to determine

Cb

' a single experimental measurement of h for ethylene from the turbulent jet

25
flame data of Kalghatgi [47] was utilized. A value of CjJ - 0.0484 s/cm2

resulted.

This calculational procedure was utilized to calculate values of the

lift-off height as a function of exit velocity for different fuels. Figure 20

reproduces the results of the calculation [54] for fuel jets of methane,

ethylene, and propane and compares the predictions with the experimental

results of Kalghatgi [47]. The agreement is excellent.

The success of the calculational procedure in reproducing the

experimental findings for lift-off heights of turbulent jet diffusion flames

suggests that small scale vortices may not be important in flame stability

since only global mixing properties which are independent of Re have been

utilized. The role of small scale structures cannot be total discounted since

it is possible that their properties may be correlated with the variables

included in eq (5) in some manner. The fluctuation properties of the

concentration and velocity in the radial positions where these calculations

have been made are not well enough characterized to test this

.

The form of eq (5) is consistent with the model for turbulent combustion

suggested by Broadwell et al. [52] in which flame stability is determined by

the behavior of large scale turbulent structures. However, it should be noted

that the authors reported, but did not test, an expression for lift-off

heights which is not consistent with the experimental observations of

Kalghatgi [47]

.

If their model is correct, eq. (5) suggests that the chemical

reaction time is inversely proportional to (Sb ) 2 ax and that the turbulent

mixing time is proportional to z

2 /r€

. The latter proportionality suggests

that two lengths scales are necessary to characterize the mixing time; one

which increases as z/r€ and a second which scales as z. It has already been

26
shown that z/r€ is the proper nondimens ionalizing length scale for centerline

mixing. Previous studies [30,36] have concluded that the radial spreading

rate as a function of downstream distance is linearly dependent on z and

independent of density ratio. It is therefore expected that r

d will scale

with the product of z and z/r€

. The appearance of the Y

2 in eq (5) is at first perplexing. Calculations

have shown that it serves to make the calculated values of Uo independent of

Yl

. This is consistent with the absence of this parameter in the correlation

shown in figure 20 and suggests that r

d may be independent of radial position

in these flows

It was possible to extend this calculational procedure to the prediction

of blow out velocities [54]. It is known [44,45,53] that blow out occurs in

these flames well before the contour represented in figure 19 reaches the jet

centerline. This suggests that flame extinction occurs when

UL > Ub , (6)

where Ub is a well-defined velocity. In order to reproduce the experimental

finding of Kalghatgi [53] for (UQ ) b as functions of jet radius and fuel it is

necessary that

Ub - Cb (Sb )£ ai r0. (7)

A value of Cb = 1.5 s/cm2 was determined using one of Kalghtgi's experimental

measurements [53] . Figure 21 compares predicted blow out behaviors (solid

lines) with Kalghatgi' s experimental results for five fuels. The agreement is

outstanding

27
Broadwell et al. [52] showed that their hypothesis concerning the role of

large scale structures in the stability of turbulent jet diffusion flames led

to an expression which also accurately correlated Kalghatgi's [53] blow out

data. Equation (7) is very similar to their development with the exception

that it is based on the local flow velocity while Broadwell et al. [52] found

it necessary to assume that flame extinction occurred when the centerline mass

fraction fell to some constant percentage of the value for stoichiometric

burning. The similarity of the two expressions lends support to their flame

stability theory.

4.3 Application of Isothermal Findings to Turbulent Mixing in

Combusting Regions of Turbulent Jet Flames

The similarity of the isothermal measurements of turbulent structure

[3,4] and those made in a hydrogen/air diffusion flame [27,28] suggests that

the combustion process may not significantly alter turbulent mixing behavior.

If this is the case, it is expected that the principal effect of combustion on

turbulent mixing arises from the density variations induced by heat release.

In an earlier manuscript [54] the role of these density fluctuations on

mixing in turbulent jet flames has been discussed. Several particular cases

were identified for which these density variations might be expected to

approximate those in isothermal flows having global density variations. As

summarized here, experimental findings suggest this approach may have some

validity in certain downstream positions of combusting flow fields.

Figure 22 is a representation of radial density profiles in turbulent jet

flames of hydrogen and a typical hydrocarbon (methane) . One of the

interesting aspects of the hydrogen jet flame is that the heated products and

the cold fuel have very nearly the same densities. In the near field of the

28
jet, combustion occurs primarily in the outer regions of the flow so that the

density is constant over nearly the full radial range of the turbulent flow.

For this reason, the mixing behavior of the flow near the jet exit should be

very similar to that observed for a constant density, isothermal flow.

Experimental evidence supporting or contradicting this conclusion was not

available in the literature.

Similar arguments lead to a different conclusion for the near- field

mixing behavior in hydrocarbon turbulent jet diffusion flames. Since the

heated combustion products are much less dense than the cold fuel, in the near

field the flow consists of a dense inner turbulent jet flowing into

considerably less dense surroundings (see fig. 22). This view is supported by

shadowgraphs recorded by Wohl et al. [56] and by the recent schlieren study of

Savas and Gollahalli [57] which show a more dense turbulent fuel jet entering

an apparently laminar, less dense surroundings.

Several groups (e.g., [58] and [59]) have recorded concentration

measurements in the near fields of both isothermal and combusting jets of

hydrocarbon fuel gases. In general, the flame jets have longer potential

cores, develop turbulent behavior further downstream, and have centerline fuel

mass fractions which fall off less rapidly with downstream distance than in

the corresponding isothermal flows . Based on the isothermal findings

discussed above, these behaviors are exactly those expected for a dense jet

flowing into less dense surroundings.

As the combusting jet move further downstream the most likely position

for combustion moves closer to the centerline and the radial density profiles

are modified. In the case of the hydrogen flame the result is that the

central part of radial profile has a density which remains nearly constant,

29
but in the outer regions of the flow there is a rapid increase in density (see

fig. 22, z/ro = 80). The condition necessary for the application of the

isothermal findings (namely, p* « pm ) is not fulfilled and it is not expected

that the centerline decay will obey a relation having the form of eq (2).

Detailed measurements of conserved scalar concentrations in turbulent jet

flames of hydrogen are available [60,61]. In general, the authors have not

analyzed their data in the form suggested by eq (2)

,

but it appears that the

centerline decay of conserved hydrogen concentration does not have a hyperbolic fall off with increasing downstream distance.

In the case of hydrocarbon fuels Hans Kremer (as described by Ebrahimi

and Kleine [59] and Lenze and Gunther [62]) has developed an analysis

procedure similar to that described here to predict the fall off of the

centerline conserved scalar concentration. Ebrahimi and Kleine [59] have

shown that this analysis gives accurate predictions of f along the jet

centerline for 20 < z/rQ < 100 when pa was assumed to be that for heated

combustion gases (Tf = 1600 K, p f /p

4.9).

For larger downstream distances was found to fall off more quickly than

predicted. The authors attributed this to a buoyancy effect (i.e., an

increase in jet momentum). However, it is possible that the analysis fails

due to changes in the radial density profiles which invalidate the conditions

for which eq (2) was derived. As figure 22 shows, the radial density profiles

for the hydrocarbon flame are greatly modified at large downstream distances

(e.g., z/ro = 160). Such radial profiles cannot be considered as that of

either a heavy jet into light surroundings or for a constant density jet. In

order to predict the centerline behavior of in this flow region it may be

necessary to have a better understanding of the effects of local density

30
variations on turbulent mixing. Further experimentation is required to

clarify the roles buoyancy- induced momentum and radial density profiles on

turbulent mixing.

For regions of turbulent jet flames where direct comparisons of

isothermal mixing results are valid, it should also be possible to predict

centerline values of unmixedness. Measurements of unmixedness in several

different jet flames are available [59-61,63]. These suggest that unmixedness

levels in turbulent jet diffusion flames are of the same order as measured in

isothermal flows, but there are systematic variations in most of the

measurements which make direct quantitative comparison impossible.

As the above discussion suggests, isothermal measurements in variable

density flows can provide important insights into the mixing behaviors of

turbulent jet diffusion flames. Further work is required to determine for

which conditions direct comparisons are valid and when it will be necessary to

allow for local radial density variations due to the heat release of

combustion.

4.4 Reynolds Number Effects in Diffusion Flames

The investigation of Re effects on mixing in variable density flows has

important implications for mixing in turbulent jet diffusion flames [54]It

is well known that local Reynolds numbers , Re^^ , for turbulent flames are much

lower than calculated based on the room temperature properties of the flow at

the nozzle. This is due to the large increase in kinematic viscosity which

occurs when gases are heated.

The isothermal studies [34] have shown that the centerline mixing

behavior is independent of Re except for downstream shifts in virtual origins

31
and longer flow distances required to attain asymptotic values of unmixedness

which are found with increasing Re. This suggests that the mixing behavior of

these turbulent flow fields is determined by large scale structures and that

as long as the local Reynolds number is high enough to insure the development

of large scale vortices, mixing in combustion regions of the flow field will

be independent of ReL

. This conclusion is supported by the observations of

Becker and Yamazaki [64] who noted that flame lengths of turbulent jet

diffusion flames were independent of ReL even when the turbulent structure was

"fairly primitive, having little more than an appropriate large-eddy

structure"

.

For isothermal flows it has been shown that centerline unmixedness

attains asymptotic behavior over shorter flow distances at lower Re. This

suggests that for the lower Re characteristic of combusting flows, the flow

field should be able to respond to density fluctuations resulting from heat

release over relatively short flow distances. This conclusion may be very

helpful in understanding and predicting the effects of local density

variations on mixing in complex chemically reacting flows.

5. SUMMARY

During the four years of this joint AFOSR/NBS research program

significant progress has been made toward the goal of improving the

understanding of chemically reacting turbulent flow. The results of

experiments in this laboratory as well as measurements elsewhere on turbulent

jet diffusion flames have justified the original choice to investigate flows

having global density differences. It is anticipated that the experimental

findings and the data base which were generated will be utilized by

32
researchers who are attempting to develop calculational procedures for

describing chemically reacting flows. The real-time nature of the studies and

the conclusion that vortical structures are modified by global density

differences will be of particular interest for workers who are attempting to

develop sophisticated calculational procedures to describe the time behavior

of turbulent flows (e.g., see [65] and [66]).

During the past four years the use of Rayleigh light scattering for

characterizing turbulent mixing behavior in isothermal, variable temperature,

and combusting flows has become more widespread and many laboratories are now

utilizing the technique. It is gratifying that the original careful

characterization of the technique in this laboratory has contributed to this

growth. It is anticipated that the development of new diagnostics for

simultaneous point measurement of concentration and velocity and for line

measurements of concentration will lead to further utilization of this unique

and powerful technique.

33
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[1] Graham, S.C.; Grant, A.J.; and Jones, J.M. AIAA J. 12(8): 1140-1142; 1974

Augus t

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[2] Dyer, T.M. AIAA J . 17(8): 912-914; 1979 August.

[3] Pitts, William M. ; Kashiwagi, Takashi. The application of laser- induced

Rayleigh light scattering to the study of turbulent mixing, Nat. Bur.

Stand. (U.S.) NBSIR 83-2641; 1983 January. 114 p.

[4] Pitts, William M. ; Kashiwagi, Takashi. J. Fluid Mech. 141: 391-429;

1984 April.

[5] Hinze, J.O. Turbulence. 2nd ed. New York: McGraw-Hill; 1975. 800 p.

[6] Schefer, R.W. ; Dibble, R.W. AIAA J . 23(7): 1070-1078; 1985 July.

[7] Brown, G.L.; Rebollo, M.R. AIAA J . 10(5): 649-652; 1972 May.

[8] Way, J.; Libby, P.A. AIAA J. 34(8): 1567-1573; 1971 August.

[9] McQuaid, J.; Wright, W. Inti. J. Heat Mass Transfer. 17(2): 341-349;

1974 February.

[10] Pitts, William M. ; McCaffrey, Bernard J.; Kashiwagi, Takashi. "A New

Diagnostic for Simultaneous, Time-Resolved Measurements of Concentration

and Velocity in Simple Turbulent Flow Systems," Presented at the Fourth

Symposium on Turbulent Shear Flows, Karlsruhe, W. Germany; 1983 September

12-14.

[11] Pitts, William M. ; McCaffrey, Bernard J. Response behavior of hot-wires

and films to flows of different gases. Nat. Bur. Stand. (U.S.) NBSIR 85-

3203; 1985 July. 123 p.

[12] Pitts, William M. ; McCaffrey, Bernard J. J. Fluid Mech. 169: 465-512;

1986 August.

[13] Wu, P.; Libby, P.A. Inti. J. Heat Mass Transfer. 14(8): 1071-1077; 1971

Augus t

.

[14] McQuaid, J.; Wright, W. Inti. J. Heat Mass Transfer. 16(4): 819-828; 1973

April

.

[15] Simpson, R.L. ; Wyatt, W.G. ; J. Phys. E: Sci. Instrum. 6(10): 981-987;

1973 October.

[16] Andrews, G.E.; Bradley, D. ; Hundy, G.F. Inti. J. Heat Mass Transfer.

15(10): 1765-1786; 1972 October.

34
[17] Baum, Howard R. ; McCaffrey, Bernard J.; Pitts, William M. unpublished

work.

[18] Alden, M. ; Edner, H. ; Holmstedt, G.; Svanberg, S.; Hogberg, T. Appl.

Optics. 21(7): 1236-1240; 1982 April 1.

[19] Escoda, M.C.; Long, M.B. AIAA J. 21(1): 81-84; 1983 January.

[20] Long, M.B.; Fourguette, D.C.; Escoda, M.C.; Layne, C.B. Optics Lett.

8(5): 244-246; 1983 May.

[21] Kychakoff, G. ; Howe, R.D.

Hanson, R.K.Drake, M.C.; Pitz, R.W.

Lapp,

M.; Penney, C.M. Science. 224(4647): 382-384; 1984 April 27.

[22] Koochesfahani, M.M; Dimotakis, P.E. AIAA J . 23(11): 1700-1707; 1985

November

[23] Yip, B.; Long, M.B. Optics Lett. 11(2): 64-65; 1986 February.

[24] Pitts, William M. Development of a line camera for real-time measurements

of concentration in turbulent flow fields. Proceedings of the

International Congress on Applications of Lasers and Electro-Optics:

Flow and Particle Diagnostics; Vol. 58; The Laser Institute of America;

1986 November 10-13. 7-15.

[25] Gibson, C.H.; Friehe, C.A.; McConnell, S.O. Phys . Fluids. 20(10, pt. 2):

S156-S167; 1977 October.

[26] Chevray, R. Prog. Energy Combust. Sci. 8(4): 303-315; 1982.

[27] Drake, M.C.; Shyy, W. ; Pitz, R.W. Superlayer contribution to conserved

scalar PDFS in a H2 turbulent jet diffusion flame. Presented at the Fifth

Symposium on Turbulent Shear Flows; Ithaca, New York; 1985 August 7-9.

[28] Drake, M.C.; Pitz, R.W.

Shyy, W. J. Fluid Mech. 171: 27-51; 1986

October

[29] List, E.J. Mechanics of turbulent buoyant jets and plumes. Turbulent Jets

and Plumes, W. Rodi, ed. New York: Pergamon Press; 1982. 1-68.

[30] Chen, C.J.; Rodi, W . Vertical turbulent buoyant jets- -a review of

experimental data. New York: Pergamon Press; 1980. 88 p.

[31] Antonia, R.A.

Prabhu, A.; Stephenson, S.E. J. Fluid Mech. 72(3): 455-

480; 1975 December 9.

[32] Chevray, R. ; Tutu, N.K. J. Fluid Mech. 88(1): 133-160; 1978 Septemer 13.

[33] Catalano, G.D.; Morton, J.B.; Humphris, R.R. AIAA J . 14(9): 1157-1158;

1976 September.

35
[34] Pitts, William M. Effects of global density and Reynolds number

variations on mixing in turbulent, axisymmetric jets. Nat. Bur. Stand.

(U.S.) NBSIR 86-3340; 1986. 172 p.

[35] Thring, M.W. ; Newby, M.P. Combustion length of enclosed turbulent jet

flames. Fourth symposium (inti) on combustion. Pittsburgh, PA: The

Standing Committee on Combustion; 1953. 789-796.

[36] Sunavala, P.D.; Hulse, C.; Thring, M.W. Com. Flame. 1(2): 179-193; 1972

June

.

[37] Wilson* R.A.M. ; Danckwerts , P.V. Chem. Eng. Science. 19: 885-895; 1964.

[38] Bilger, R.W. Prog. Energy Com. Science. 1(2/3): 87-109; 1976.

[39] Williams, F.A. Combustion Theory, 2nd ed. Reading, MA: Benjamin/Cummings;

1985. 680 p.

[40] Effelsberg, E.; Peters, N. Com. Flame. 50(3): 351-360: 1983 April.

[41] Gibson, C.H.; Chen, C.C.; Lin, S.C. AIAA J . 6(4): 642-649; 1968 April.

[42] Screenivasan, K. R. ; Tavoularis, S. J. Fluid Mech. 101(4): 783-795; 1980

December 29.

[43] Vanquickenborne , L. ; van Tiggelen, A. Com. Flame. 10(1): 59-69; 1966

March

.

[44] Hall, L. ; Horch, K. ; Gunther, R. Brenns toff -Wdrme -Kraft . 32(1): 26-31;

1980 January.

[45] Gunther, R. ; Horch, K. ; Lenze, B. The stabilization mechanism of free jet

diffusion flames. First specialist meeting (inti) of the combustion

institute. Pittsburgh, PA: The Combustion Institute; 1981. 117-122.

[46] Eickoff, H. ; Lenze, B. ; , and Leuckel, W. Experimental investigation on

the stabilization of jet diffusion flames. Twentieth symposium (inti) on

combustion. Pittsburg, PA: The Combustion Institute; 1984. 311-318.

[47] Kalghatgi, G.T. Com. Science. Tech. 41(1+2): 17-29; 1984.

[48] Byggst/yl, S.; Magnussen, B.F. A model for flame extinction in turbulent

flow. Turbulent Shear Flows 4, eds . Bradbury, L.J.S. et al . , SpringerVerlag , Berlin; 1985. 381-395.

[49] Janicka, J.; Peters, N. Prediction of turbulent jet diffusion flame liftoff using a PDF transport equation. Nineteenth symposium (inti) on

combustion. Pittsburg, PA: The Combustion Institute; 1982. 367-374.

[50] Peters, N. ; Williams, F.A. AIAA J . 21(3): 423-429; 1983 March.

36
[51] Peters, N. Partially premixed diffusion flamelets in non-premixed

turbulent combustion. Twentieth symposium (inti) on combustion.

Pittsburgh, PA: The Combustion Institute; 1984. 353-360.

[52] Broadwell, J.E.; Dahm, W.J.A.; Mungal, M.G. Blowout of turbulent

diffusion flames. Twentieth symposium (inti) on combustion. Pittsburgh,

PA: The Combustion Institute; 1984. 303-310.

[53] Kalghatgi , G.T. Com. Science Tech. 26(5 and 6): 233-239; 1981.

[54] Pitts, William M. The effects of global density and Reynolds number

variations on mixing in turbulent, axisymmetric j ets- - implications for

turbulent jet diffusion flames. Proceedings of the 2nd ASME/JSME Joint

Thermal Engineering Conference, Book #10219S, Volume 1; Honolulu, HI 1987

March 23-27.

[55] Sobiesiak, A. ; Brzustowski, T.A.

On the structure of the stabilization

region of lifted turbulent diffusion flames. Presented at the 1986 Spring

Meeting of the Western States Section of the Combustion Institute, Banff,

Canada; 1986 April 27-30.

[56] Wohl , K. ; Gazley, C.; Kapp, N. Diffusion Flames. Third symposium on

combustion, flame, and explosion phenomena. Baltimore, MD: Williams and

Wilkins; 1949. 288-300.

[57] Savas , 0.; Gollahalli, S.R. AIAA J. 24(7): 1137-1140; 1986 July.

[58] Chigier, N.A.

Strokin, V. Com. Science Tech. 9(3 and 4): 111-118; 1974.

[59] Ebrahimi, I.; Kleine, R. The nozzle fluid concentration fluctuation field

in round turbulent free jets and jet diffusion flames. Sixteenth

symposium (inti) on combustion. Pittsburgh, PA: The Combustion Institute;

1977. 1711-1723.

[60] Kennedy, I.M.; Kent, J.H. Measurements of a conserved scalar in turbulent

jet diffusion flames. Seventeenth symposium (inti) on combustion.

Pittsburgh, PA: The Combustion Institute; 1979. 279-287.

[61] Drake, M.C.; Bilger, R.W.

and Starner, S.H. Raman measurements and

conserved scalar modeling in turbulent diffusion flames. Nineteenth

symposium (inti) on combustion. Pittsburgh, PA: The Combustion Institute;

1982. 459-467.

[62] Lenze, B. and Gunther, R. Brennstoff -W&rme -Kraft . 27(10): 387-394; 1975

October

[63] Gunther, R. Prog. Energy Com. Science. 9(1/2): 105-154; 1983.

[64] Becker, H.A. and Yamazaki, S. Com. Flame. 33(2): 123-149; 1978.

[65] Grinstein, F.F.; Oran, E.S.; Boris, J.P. AIAA J. 25(1): 92-98; 1987

J anuary

37
[66] Ghoniem, A.F. and Sethian, J.A. AIAA J. 25(1): 168-171: 1987 January.

[67] Lockwood, F.C. and Moneib, H.A. Com. Flame. 47(3): 291-314; 1982

September

.

38
TABLE 1

Experimental Parameters

Jet/Coflow PQ /P* Re Experiments (R - Rayleigh, S — Shadowgraph)

He/air 0.14 3950 R, S

CH4 /air 0.55 3950 R, S

c3 h8 /co2 1.02 3960 R, S

C3 H8 /air 1.55 3960 R, S

C3 H8 /air 1.55 7890 R, S

C3 H8 /air 1.55 11860 R, S

CFa /air 3.01 3960 R

CFA /air 3.01 7920 R

SF6 /air 5.11 3950 R,S

SF6 /air 5.11 7890 R, S

SFg/air 5.11 11860 R,S

SFg/He 37.0 3960 R, S

39
FIGURE CAPTIONS

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

The experimental configuration for real-time Rayleigh light

scattering "point" measurements of concentration in binary gas

mixtures is shown schematically. The flow system consists of a 6.35 mm diameter pipe with a sharpened edge enclosed within a 100 X

100 cm2 square cylinder.

The quality of the data which can be acquired utilizing the

Rayleigh light scattering technique for concentration is

demonstrated. Radial profiles of concentration (in both mole and

mass fraction terms) are plotted for a turbulent CHA jet flowing

into a slow coflow of air. The downstream distance is z/ro = 35

and the Reynolds number is 3950.

Partial time -resolved data records recorded during a simultaneous

Rayleigh light scattering and hot- film anemometry experiment are

reproduced for a propane jet (Re = 3960) flowing into a slow coflow

of air. The observation volume is located on the jet centerline at

z/rQ = 31.5. The light scattering signals have been calibrated and

are plotted in terms of mole fraction of propane. The raw data for

the anemometer output is plotted along with the velocity calculated

utilizing the calibrations of film response to changes in velocity

and gas composition.

The correlation is shown for the heat transfer from a hot-wire as a function of flow velocity for nine different gases. Experimental

measurements are nondimens ionalized by the use of the Nusselt

number and Reynolds number. Corrections have been included for

heat losses to the prongs of the hot-wire and thermal slip and

accommodation effects at the surface of the probe. (KB ) x and (KA ) X are coefficients which are necessary to compensate for variations

in molecular properties from gas to gas

.

The camera which has been developed for recording real-time

Rayleigh light scattering intensity along a line is shown. The top

portion indicates the major components and their configuration.

The actual appearance of the camera is shown below.

The overall experimental configuration for real-time measurements

of concentration along a line in turbulent flows is represented.

Rayleigh light scattering is induced along a line in the flow field

by the Ar+ ion laser. Light scattering at 90° is recorded by the

digital line camera system consisting of the line camera shown in

figure 5, suitable interfaces, and a data acquisition minicomputer.

An example of time -resolved line measurements of propane mole

fraction across a turbulent jet of propane (Re = 3960) flowing into

a coflow of air is reproduced. Propane mole fraction is

represented by a seven level gray scale. The downstream position

is 5 diameters and the line read out rate is 830 Hz.

40
Figure 8

Time -averaged radial profiles of propane mole fraction are shown

for five downstream positions in the development region of a propane (Re = 3960) jet flowing into a slow coflow of air. The

growth of the boundary layers on either side of the potential core

with increasing z and decrease of centerline concentration at the

end of the potential core can be clearly observed. It is

interesting to note that the data displayed represents 164,000

individual concentration measurements which were recorded during

1.54 s of actual acquisition time.

Figure 9

The apparatus for recording time -resolved shadowgraphs is

represented schematically. The light pulse generated by the

chopper has a temporal profile which is triangular in shape and has

a total duration of 310 /is.

Figure 10. Three time -resolved shadowgraphs are shown for a SF6 jet (Re =

3950) flowing into a slow coflow of air. Three different

downstream positions recorded at different times are represented.

Note particularly the formation of a fountain by the SF6 at a downstream position of « 37.5 ro

. Figure 11. Shadowgraphs are reproduced for jets of SF6 (Re = 7890 and 11,860)

entering slow coflows of air. For each jet four views of the flow

recorded at different times and positions in the jet are

superimposed. Note that the fine scale turbulence becomes more

pronounced with increasing Re, but that the overall spreading rate

of the jet does not appear to be affected.

Figure 12Five sets of superimposed shadowgraphs are shown for jets of one

gas flowing into a second gas . With the exception of the SF6 flow, the Reynolds numbers are roughly the same. The effects of

variations in the global density ratio appear as changes in the

development region of the flow and modifications in the eddy

structure at downstream positions where the flows are close to

fully- developed

Figure 13

Superimposed shadowgraphs are reproduced for propane jets at three

Re entering into slow coflows of air. The development of finer

turbulent scales with increasing Re can be clearly seen. It is

also evident that increasing the Re results in a shortening of the

distance required for the development of vortical structures near

the nozzle. The overall spreading behavior of the jets is

independent of Re supporting the supposition that entrainment is

determined by large scale turbulent structures.

Figure 14

Values of Y /Ym (Y„ = Ym is the centerline concentration at z/r

and Y0 is the mass fraction of jet fluid at the jet exit) are

plotted as a function of z/ro for six different jet/coflow gas

combinations. The solid lines are linear least squares fits of

the results. Note the decreasing slopes and upstream movement of

the virtual origins (z where YQ /YC

-* 0) which occur as the

jet/coflow density ratio is increased.

41
Figure 15

.

Predicted values of inverse centerline mass fraction (denoted as 1/Cm ) based on the analysis of Thring and Newby [35] are plotted

as functions of z/ro for the six jet/coflow gas pairs which have

been experimentally investigated. Comparison of figures 14 and 15

shows that there is good agreement between prediction and

experiment

.

Figure 16

.

Values of centerline unmixedness are plotted as a function of z/ro for the six jet/coflow gas pairs listed. Values of Y^/Ym for each

jet approach a common asymptote of « 0.23, but the flow distance

required increases dramatically as the jet/coflow density ratio

increases

.

Figure 17

.

The centerline unmixedness values shown in figure 16 are replotted

as a function of z/r£

. The collapse of the data onto a single

curve suggests that r£ is the proper scaling parameter for

correlating the growth of unmixedness in these variable density

flows

.

Figure 18

.

Centerline unmixedness values for three different Re jets of

propane entering slow coflows of air are plotted as functions of

z/ro

. Flows at higher Re require longer flow distances in order

to achieve the asymptotic value of unmixedness even though the

value of the asymptote does not change.

Figure 19

.

The concentration contour corresponding to that for which the

laminar flame speed of an ethylene/air mixture is a maximum (Y1 = 0.073) is plotted as functions of z/ro and r/ro

. The virtual

origin for the plot is assumed to be at z = 0 . Two

representations are shown. On the right the radial and axial axes have the same scaling, while on the left the radial scale is

expanded by a factor of 5

.

Figure 20. Experimental values [47] of lift-off height (h) are plotted

against jet exit velocity for turbulent jet flames of methane,

ethylene, and propane. These measured values are compared with

values (solid lines) predicted using eq. (5) and the known

velocity and mixing behaviors of the jets. The agreement is

excellent

.

Figure 21. Experimental [53] (symbols) and calculated values (lines) of blow

out velocity are plotted as a function of jet radius for

axisymmetric turbulent jet flames of five organic fuels.

Calculated values are derived by using eqs . (6) and (7). The

agreement of the predicted values with experiment is very good.

Figure 22. Approximate radial density profiles for three nondimens ional

downstream distances are shown for turbulent jet diffusion flames

of hydrogen and a typical organic fuel (methane) . These curves

are based on measurements reported by several different authors

[63,67].

42
BEAM

EXPANDER

Figure 1. The experimental configuration for real-time Rayleigh light

scattering measurements of concentration.

43
44

Figure

2.

Radial

profiles

of

concentration

are

plotted

for

a

turbulent

CHA

jet

flowing

into

a

slow

coflow
U

(m/s)

E

(volts)

HOT-FILM OUTPUT

CALCULATED VELOCITY

Figure 3. Partial time-resolved data records recorded during a simultaneous

Rayleigh light scattering and hot- film anemometry experiment.

45
x(vX)-°n N

x

in6

<D OZ

46

Figure

4.

The

correlation

is

shown

for

the

heat

transfer

from

a

hot-wire

as

a

function

of

velocity

for

nine

different

gases.
RET I

CON

LINE

SCANNER %

0)

a:LU

a: »—

LU U.

Q. »—* cx: (/) i- 21

LU o K i—

Z

i—

M

a.o LU

CD a a: LU z

CD i—

i—

LL

••

a:>

Hi

47

Figure

5.

The

camera

for

recording

real-time

Rayleigh

light

scattering

intensity

along a

line

is

shown.
Enclosure

48

Figure

6.

The

overall

experimental

configuration

for

real-time

measurements

of

concentration

along

a

line

in

turbulent

flows

.
0*0 N to

* * » o o o

(s) ©uu!X

O

r—

II

49

An

example

of

time

-

resolved

line

measurements

of

mole

fraction

across

a

turbulent

jet

ofC
UOjpDJJ 9|0|A| eUDdoJJ

P96DJ9AD-9UJIX

o

50

Figure

8.

Time-averaged

radial

profiles

of

mole

fraction

are

shown

for

a

propane

jet

flowing

into

air.
51

Figure

9.

The

apparatus

for

recording

time-resolved

shadowgraphs

is

represented

schematically
50r

d

Figure 10. Three time-resolved shadowgraphs are shown for a SFg jet (Re =

3950) flowing into a slow coflow of air.

52
a) SF6 /air b) SF6 /air

n Re = 7890 Re = 1 1860

6 °r —i—i—i—r i—i—i—i—r n 60

r/ r0 r/ r0

Figure 11. Shadowgraphs are reproduced for jets of SF6 entering slow coflows

of air.

53
He/air

b)

CH4

/air

c)C3H8

/C02

d)C3H8

/air

e)

SF6

/air

Re=

3950

Re=

3950

Re=

3960

Re=

3960

Re=

7890

54

Figure

12.

Superimposed

shadowgraphs

are

shown

for

jets

of

one

gas

flowing

into a

second

gas.
)C3H8 /

air

b)C3H8

/air

c)C3H8

/air

Re=

3960

Re=

7930

Re=

11880

55

Figure

13.

Superimposed

shadowgraphs

for

propane

jet

at

three

Re

entering

slow

coflows

of

air.
56

Figure

14.

Values

ofYo /Ym

are

plotted

asa

function

of

z/ro

for

six

different

jet/coflow

gas

combinations.
I

Figure 15. Predicted values of inverse centerline mass fraction based on the

analysis of Thring and Newby.

57
58

Figure

16.

Values

of

centerline

unmixedness

are

plotted

as

a

function

of

z/r

o

for

the

jet/coflow

pairs

listed.
'A/7

59

Figure

17

.

The

centerline

unmixedness

values

shown

in

figure

16

are

replotted

as

a

function

of

z/r

e
- <

<

_ <$J

<1

_Lm

CMo

*v«cw

o <

1 xo

<x O

<3<3 x O

. o

x O

<J O

x O

<3 <J O

x O

<3 <3

<3 O

x O

OO

<$3

o

CM

in

o

iu

<3 x

o

o

m

o

a/7

o

CD

O

m

o

o o 00

CD fO oo — o

CD cn *— "M1 ’ m \ II II II o OO 31 <D a> Q> cm cm cm o <3 X o - 30 N

o

CM

_ o

o

o

60

Figure

18.

Centerline

unmixedness

values

for

three

different

Re

jets

of

propane

entering

slow

coflows

of

air

are

plotted

as

functions

of

z/r

o

.
Figure 19. The concentration contour for which the laminar flame speed of an ethylene/air mixture is a maximum.

61
25 -

Figure 20. Experimental values of lift-off height (h) are plotted against jet

exit velocity.

62
Figure 21. Experimental [53] (symbols) and calculated values (lines) of blow

out velocity are plotted.

63
( e

w/6>|)cJ

64

Figure

22.

Approximate

radial

profiles

for

three

nondimens

ional

downstream

distances

are

shown

for

turbulent

jet

diffusion

flames

of

hydrogen

and

a

typical

organic

fuel

(methane).
I

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR-87/3550

2. Performing Organ. Report No. 3. Publication Date JUNE 1987

4. TITLE AND SUBTITLE

Mixing in Variable Density, Isothermal Turbulent Flow and Implications for

Chemically Reacting Turbulent Flows

5. AUTHOR(S)

William M. Pitts and Takashi Kashiwagi

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. national bureau of standards ISSA-86-00008

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State, ZIP)

Air Force Office of Scientific Research

Bolling AFB

Building 410

Washington, DC 20332

10. SUPPLEMENTARY NOTES

U Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

This report summarizes the research findings of a project which has been

jointly funded by the Air Force Office of Scientific Research and the National

Bureau of Standards. The goal of the research was to improve the fundamental

understanding of chemically reacting turbulent flow. The approach which was

taken was to investigate mixing in variable density flows in order to better

understand the role of local density fluctuations (which result from chemical

heat release) on the turbulent mixing behavior. The development of new

experimental diagnostics having excellent spatial and temporal resolution is

described. These techniques have been utilized to investigate a wide range of

mixing properties in variable density flows. These results are summarized

along with a discussion of their importance to an improved understanding of

chemically reacting flow.

L2. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) concentration fluctuations; concentration measurement; density effects

digital

line earner

flow visualization; hot wire anemometry; jst flames; Rayleigh

light scattering; Reynolds number; turbulent flames; velocity measurement

13. AVAILABILITY

DTI Unlimited

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