NASA Contractor Report 181868 

THE NASA LANGLEY RESEARCH CENTER 

0.3-METER TRANSONIC CRYOGENIC TUNNEL T-P/Re-M 

CONTROLLER MANUAL 

S. Balakrishna and W. Allen Kilgore 

Vigyan Inc. 

Hampton, Virginia 23666-1325 

Contract NAS1-17919 

July 1989 

, 

(UASA-CR-181868) THE UASA LAU6LBT RESZARCE B89 -26869 

CEUTEE 0, PEETER TRAUSONIC CBYOGLYIC ZUBBBL 

T-P/Be-M COI'IROLLEE EALIOUAL (Vigyan Research Associates) 41 p CSCL 14B Unclas 

G3/09 0224574 
ChaDter details: page 

1. Introduction 

2. Microcomputer interface to 0.3-m TCT 

3. Microcomputer hardware and connections 

4. Microcomputer software 

5. Installation of control software on a PC/AT 

6. Operation of tunnel controller 

7. References 

List of figures: 

1. Display format for the controller monitor. 

2. Typical controller monitor display. 

1 

2 

7 

10 

13 

15 

18 

16 

17 

Appendices: 

A. List of input sensors and outputs for the controller. 19 

20 

C. Control program flowchart. 27 

B. Variable names in the T-P/Re-M control software of the 0.3-m TCT. 

D. Details of the monitor display for tunnel control. 32 

E. Input keyboard commands. 38 

Relevant Drawings: 

1. LD 662971 Rheostat Position Contrc)lli:r. 

2. LD 662972 System Interconnection. 

t 

i 
INTRODUCTION 

The 0.3-m Transonic Cryogenic Tunnel (TCT) located in Bldg. 1242 of the NASA Langley Research 

Center is a fan driven liquid nitrogen (LN,) operated pressure tunnel. The tunnel is capable of 

operating from 15 to 85 psia stagnation pressure, tunnel temperature from about 78 to 342 K, and 

Mach number ranging from 0.2 to about 1.0. Since May 1988, the tunnel has been under full 

automatic control of a 16 bit microcomputer. This document provides the details of the electronic 

interface to the tunnel sensors/actuators to a 16 bit microcomputer, the tunnel control software, the 

simulation software, installation of the control software on the microcomputer and other particulars 

essential for tunnel control software maintenance. The aim of the control software is to control the 

0.3-m TCT precisely to provide necessary aerodynamic testing conditions in the test section. The 

simulation software provides operator training capability. 

1 
MICROCOMPUTER INTERFACE TO 0.3-m TCT 

The microcomputer understands the physical status of the 0.3-m TCT by a set of highly accurate 

analog electrical signals from the tunnel which are converted to a numerical form through an 8 channel 

analog to digital converter (ADC). The ADC has a resolution of 1 in 65536 corresponding to 16 bits of 

information. The control commands from the microcomputer are in the form of current drive in the 

range 4-20 mA, 0-5 VDC or 1-5 VDC. The numerical commands are generated by the microcomputer 

and are converted to an electrical form through an 8 channel digital to analog converter (DAC). This 

DAC has a resolution of 1 in 4096 corresponding to 12 bits. Appendix A gives complete list of the 

sensors, their ranges and names. The microcomputer receives the tunnel status information from the 

following measuring devices. 

Tunnel stagnation pressure: 

The tunnel stagnation pressure is measured at the settling chamber by a capacitance type differential 

pressure transducer. 

range to provide 0-5 VDC for 0-6.8 atm which corresponds to a sensitivity of 1.366 V/atm. 

The output is signal conditioned by a Datametrics amplifier working on a fzxed 

This 

sensitivity is used in the tunnel control software. Any change in the transducer sensitivity must be 

reflected in the control software. 

Tunnel static pressure: 

The tunnel static pressure is measured at the constant area of the test section using a pitot tube with a 

capacitance type differential pressure transducer. The output is signal conditioned by a Datametrics 

amplifier working on a fixed range setting to provide 0-5 VDC for 0-6.8 atm which corresponds to a 

sensitivity of 1.366 V/atm. This sensitivity is used in the tunnel control software. Any change in the 

sensitivity must be reflected in the control software. 

2 
Liquid nitrogen pressure: 

The LN, pressure is measured by a bonded strain gauge type pressure transducer excited from a 

floating DC supply. The bridge output is amplified by a variable gain amplifier to provide a 

sensitivity of 2.6539 VDC/atm. This 

signal sensitivity is used in the tunnel control software. Any change in this sensitivity must be 

reflected in the control software. 

The output is filtered by a 10 Hz cutoff low pass amplifier. 

Tunnel gas stagnation temperature: 

The tunnel gas flow stagnation temperature is measured by a copper-constantan thermocouple 

(TRING-25) mounted on the thermocouple ring in the settling chamber. This is made of 0.023 inch 

diameter fine wire which provides good response. The thermocouple output is referred to a Kaye ice 

point reference. The signal output at this point is from -5.587 to 2.864 mV for 74.15 to 342.15 I(. 

This unbalanced signal is taken to a NEFF amplifier where the gain and offset are set to obtain a 

signal sensitivity of 0 VDC output at 74.15 K and 5 VDC at 342.12 K. The gain required is about 

591.65 and the offset necessary is about -3.305 volts. The amplifier output filter is set to 0-10 Hz low 

pass setting. This signal of 0-5 VDC is used by the tunnel controller for linearization and later use in 

the control laws. The linearization cannot be easily changed. Hence the thermocouple calibration for 

0-5 VDC must be maintained. 

Tunnel metal wall temperature: 

The tunnel wall temperature is an important sensor which provides a safe cooldown. This sensor is 

located at the third corner of the 0.3-m TCT on the external surface of the tunnel structure but 

internal to the insulation. It has been found to provide excellent average structural temperature data 

and control results. This is a 0.028 inch wire diameter copper-constantan thermocouple. The signal is 

referred to a Kaye ice point reference. The signal varies from -5.587 mV at 74.15 E; to 2.864 mV at 

342.12 K. This signal is signal conditioned in a NEFF amplifier with a gain of 591.65 and an offset of 

-3.305 volts to generate a signal sensitivity of0-5 VDC for 74.15 to 345.12 K temperature. The output 

3 
filter is set to 0-10 Hz low pass setting. This signal is linearized in the controller and its calibration 

should not -be changed. 

Screen pressure drop: 

The screen pressure drop is an important measurement of the 0.3-m TCT. If inadvertently moisture 

enters the tunnel while at temperatures below 273 K, the moisture is likely to condense on the antiturbulence screen and with flow this may damage the screen. The screen pressure drop is measured by 

a bonded strain gauge type pressure transducer. The transducer is excited from a Dc power supply 

and the output is amplified. The signal sensitivity of 1 VDC/psid. This is used in the controller to 

monitor’the moisture in the tunnel. Any change in the sensitivity must be reflected in the controller 

software. 

Liquid nitrogen injection valves #3531 and #3533: 

LN, is injected into the tunnel by the controller through a set of pneumatically driven diaphragm 

operated flow control valves. The electropneumatic converter comes with an internal power amplifier 

located on the body and is set to a 4-20 mA operation. The unit provides 3-15 psig output command 

which is power boosted before being fed to the spring loaded diaphragm. The valves work on the 100 

psia air supply energy. These valves are “air to open” type and require a signal to open. The valve 

full open to close time is about 0.6 seconds. This speed is essential for good control of the tunnel. Any 

deterioration of the valve speed should be corrected. The valve calibration must be maintained at 4 

mA for full close and 20 mA for full open. The microcomputer based tunnel controller generates 4-20 

mA signal drive based on this calibration. 

Liquid nitrogen pressure control valve #3535: 

The LN, pumping system has a closed circuit configuration with provision to return the unused LN,. 

The supply pressure is maintained by a back pressure valve in the return leg which is operated by a 

diaphragm driven control valve. The electropneumatic signal transducer device drives the valve and is 

4 
set to close at a 4 mA signal and to fully open at a 20 mA current signal. The pump characteristics 

are such that at full closed condition the line pressure is about 150 psia and full open condition is 90 

psia. The controller generates the 4-20 mA drive to the pressure control valve so as to maintain the 

line pressure constant at a set point. 

Gas discharge valves #3621 and #3622: 

0.3-m TCT has three remotely controlled 4 inch valves which discharge the tunnel gas. Two of these 

are operated by the microcomputer based tunnel controller. These valves have been modified for 

electrohydraulic operation using a 4 inch stroke hydraulic actuator, a 5 gpm servo valve and a position 

potentiometer. An analog closed loop controller provides the position control of each of these valves 

based on a set point command of 1 VDC for full close and 5 VDC for full open. The tunnel controller 

is designed based on this sensitivity of 1-5 VDC. Any change which affects this sensitivity must be 

avoided. The valve #3623 is not under the control of the microcomputer. 

Fan speed sensor: 

The fan speed is measured by an electro-optical counting system mounted on the tunnel fan shaft. The 

output of the photo device is brought to a Pioneer RPM signal sensor. The instrument is adjusted for 

CALIBRATION setting of 3.2 KHz and RANGE setting of 6.4 KHz. The output sensitivity ut this 

setting of 1.280 VDC/1000 rpm of the fan shaft. This sensitivity factor is used in the tunnel control 

software. Any change in this sensitivity must be reflected in the control software. 

Fan speed control: 

The 0.3-m TCT is driven by a 2 pole 3 phase induction motor supplied from a variable frequency 

generator. The motor speed control is obtained by varying the supply frequency from 10 to 96 Hz 

which corresponds to 600 to 5600 rpm on the tunnel shaft. Prolonged operation of the tunnel in the 

speed band of 3550-3650 rpm must be avoided. The frequency control is realized by a rheostat control 

which adjusts the field excitation of the DC motor driving the variable frequency generator. The 
rheostat is driven by an instrument position servomotor. The position servo accepts a command of 0-5 

VDC to provide 600-5600 rpm speed control. The DC supply to the rheostat bridge is 5 VDC. Both 

the bridge reference and the set point command are generated by the tunnei controller through a pair 

of buffer amplifiers to prevent loading the DAC unit. 

6 
MICROCOMPUTER HARDWARE AND CONNECTIONS 

The microcomputer system is mounted in the 0.3-m TCT control rack. The monitor shows through 

the front panel and the control keyboard is located in front of the monitor. The microcomputer system 

is located in the rack below the monitor. The microcomputer can be accessed only by removing the 

blank front panel below the monitor. The microcomputer unit is powered from an uninterrupted 115 V 

60 Hz supply. The two terminal boards DT 707 and DT 701-20 are located in the rear of the control 

rack. The terminals are wired as noted in drawing LD 662972. The details of the wiring, 

microcomputer, keyboard and monitor that are necessary for tunnel control operation are presented 

below. 

Hardware: 

1. Any PC/AT class microcomputer or similar clone can be used to perform as the 0.3-m 

TCT controller based on the software. The minimum configuration essential is that it should 

have a Phoenix BIOS, 512 kilobyte RAM, a 360 kilobyte or a 1.2 megabyte 5$ inch floppy 

drive, a hard disk, an enhanced color graphics monitor with its drive board, and a 5060 or 

101 keyboard. The microcomputer must have a minimum operating clock speed of 12 MHz. 

2. The tunnel interface is through an analog to digital converter (ADC). The software is 

based on the Data Translation DT 2801/5716A unit. This full size personal computer card is 

mounted on the system board of the PC/AT through the 62 pin bus connector. To perform 

as a part of the tunnel controller, the DT2801/5716A jumpers must be set for the following. 

i) Base Address &H2EC 

ii) AD conversion setting Bipolar 

iii) Input type Floating (DI) jumpers W3-W7 

The DA conversion functions, the Digital 1/0 functions and the clock on the DT 2801/5716A 

are NOT used in the controller operation. 

7 
3. The DT 2801/5716A ADC card must be connected to the terminal strip DT707 through 

the connector Ansley 609-5030 on the back panel of the PC/AT. The following table gives 

the pin connections and the signal to be connected from the tunnel data sensors and signal 

conditions with sensitivities discussed in the previous section. 

DT2801/5716 DT707 Polarity Transducer Amplifier 

Pin # terminal 

J1-1 CH 0 + Stagnation Pressure Datametrics 

J 1-2 CH8/0RET - Stagnation Pressure Datametrics 

J 1-3 CH 1 + Static Pressure Datametrics 

J 1-4 CH9/1RET - Static Pressure Datametrics 

J 1-5 CH 2 + TRING 25 NEFF 

J 1-6 CH 10/2 RET - TRING 35 NEFF 

J 1-7 CH 3 + Wall Temperature NEFF 

J 1-8 CH 11/3 RET - Wall Temperature NEFF 

J 1-9 CH 4 + Fan Speed Pioneer 

51-10 CH 12/4 RET - Fan Speed Pioneer 

J1-11 CH 5 + LN, Pressure 

51-12 CH 13/5 RET - LN, Pressure 

51-13 CH 6 + Screen AP 

J1-14 CH 14/6 RET - Screen AP 

4. The DT 2815 digital to analog conversion unit is plugged into the system board in the 

PC/AT microcomputer through the 62 pin connector. The unit must be configured as follows 

by use of the jumpers for using it to control the 0.3-m TCT controller: 

i> 

ii) 

iii) 

Base address 

Output range 

Output mode selection 

Ch 0 - current 

Ch 1 - current 

Ch 2 - current 

Ch 3 - voltage 

Ch 4 - voltage 

Ch 5 - voltage 

Ch 6 - voltage 

Ch 7 - not used 

&H224 

Unipolar E3-E4 and E5-E6 

Jumper settings 

jumper (E28 - E36) 

jumper (E27 - E35) 

jumper (E26 - E34) 

jumper (E17 - E27) 

jumper (E16 - E24) 

jumper (E15 - E23) 

jumper (E14 - E22) 

5. The DAC DT2815 must be connected to the terminal strip DT-701-20 through two EP047 

cables of eight foot length each. The connectors J1 and J2 at either end of the cable mating, 

the DT 2815 unit and the terminal strip are male-female pairs of 3M3421. The terminal strip 

8 
DT-701-20 is internally wired to provide a +12 VDC supply to the current outputs at pin J2- 

9 which carries the 12 volts supply from the computer and is internally wired to terminals 

T2, T4 and T6 of the terminal strip. The following table provides the connection details for 

the outputs. 

DT701-20 Actuator 

T1 #3531 

T2 #3531 

T3 #3533 

T4 #3533 

T5 #3535 

T6 #3535 

T18 #3621 

T19 #3621 

T42 #3622 

T43 #3622 

T44 

T45 

T46 Same as T44 

T47 

Signal to rheostat servo through buffer amp (ground) 

+ Signal to rheostat servo through buffer amp (0-5 VDC) 

Reference signal to rheostat servo (5 VDC) 

6. The keyboard is altered by physically deleting a few keys from the standard 101 keyboard. 

These keys are Control, Alternate, Delete, Print Screen, Scroll Lock, and Pause. This can be 

done by removing the spring loaded key pads and blanking the area. 

9 
MICROCOMPUTER SOFTWARE 

The software is available as three disks called CONTROL, SIMULATOR and BOOT. The software 

CONTROL alone is sufficient for operating the 0.3-m TCT. SIMULATOR is not used in tunnel 

control, but can be used for training the operators in using the controller on any PC/AT. BOOT is 

necessary only when the tunnel control software is to be maintained or modified. 

For using the PC/AT microcomputer as a tunnel controller, it should be set up as follows. The 

operating system MSDOS is loaded into the hard disk C. The tunnel control software 

CONTROL.EXE and the BASRUN.EXE are then loaded into disk C. No other soflware should be 

mounted in the system. The AUTOEXEC.BAT is set such that when the microcomputer is powered, 

the system boots itself on the MSDOS of disk C, and after booting the program, CONTROL.EXE is 

automatically loaded and executed. The microcomputer exclusively runs the CONTROL.EXE program 

all the time. This program needs to be stopped only when there is a need for a software update. 

CONTROL software: 

The 650 line software for tunnel control is written in BASIC for ease of understanding and 

modifications. The BASIC code of the tunnel controller program is available from the Facility 

Coordinator. This program is compiled and linked using the BASIC compiler to obtain 

CONTROL.EXE object code. The software is executed using the combination of CONTROL.EXE and 

BASRUN.EXE. Appendix B provides the list of the variables used in the tunnel control software. 

Appendix C provides a program flowchart. Appendix D provides details of the screen display format. 

SIMULATOR software: 

A tunnel simulation software is available on the diskette SIMULATOR. This simulation can run on 

any PC/AT with a color monitor. A PC/AT with about 10 MHz clock provides the correct speed and 

is preferred. The simulation package does not require the DT 2801/5716A or the DT 2815 cards. 

10 
1. Copy all the software in SIMULATOR to either the hard disk or to a backup disk using 

the COPY *.* command. The SIMULATOR disk consists of two files, SIM.EXE and 

BASRUN.EXE. The monitor displays the typical 

control display shown in figure 1. 

Type SIM and hit the “Return” key. 

2. The tunnel gas 

temperature is at 300 K, tunnel metal temperature is at 300 K, tunnel pressure is at 14.70 

psia and fan speed at zero. The LN, valve, gas discharge valve, and rheostat are at zero. 

The LN, pump is at 11.6 psia and the back pressure valve is fully open. The T-P/Re-i?l 

loops are on manual mode. 

The monitor shows starting conditions corresponding to the ambient. 

3. It provides a prompt with a 

flashing “,K”. The set point 300.0 is then loaded. A Return command transfers temperature 

set point to the loop and changes the mode to “AUTO”. Similarly, pressure loop can be 

commanded to “AUTOP” with letter “P” command which provides a flashing “,psian prompt 

and pressure can be set to 30.00 psia. “,rpm” 

prompt and a typical speed command of 2400 rpm slowly starts the tunnel by increasing the 

fan speed at a rate of 50 rpm/s. When the fan speed crosses 600 rpm, the temperature loop is 

enabled and the LN, pressure set point is switched to 136 psia (default). The tunnel now 

slowly starts off and stabilizes in automode at 300 K, 30 psia and a fan speed of 2400 rpm. 

The tunnel test section static pressure is displayed in psia, and varies with fan speed. The 

tunnel can be taken to any pressure, temperature and fan speed within its operating range by 

commanding the appropriate numbers. Appendix E gives a complete listing of all input 

commands. 

To load the required temperature, letter “T” is used. 

Letter command “N” provides a flashing 

4. Mach number mode can be addressed by the letter “M” command which transfers the fan 

speed loop to “AUTO” mode. 

11 
5. A tunnel cooldown can be practiced by commanding 100.0 K either at constant speed or 

at constant Mach number. The tunnel initially cools down the gas at about 20 K/minute 

and then follows the metal temperature cooling rate. The monitor displays the structural 

cooling rate GRAD in K/minute. The typical cooling rate at 30 psia and Mach number 

equal to 0.44 is about 3.4 K/minute. The cooldown rate can be increased by using a higher 

fan speed or a higher tunnel pressure. 

6. Reynolds number mode can be addressed by the letter “R” command which transfers 

pressure loop to “AUTORE” mode. This requires use of the correct chord data which can be 

loaded using letter command “C”. 

7. Letter command “B” allows setting of the LN, pressure between 100 and 150 psia. 

8. Letter command “D” allows the partial keyboard commands to be cleared. 

Exercising this simulator provides a good feel for operating the tunnel controller. The tunnel simulator 

controls and the 0.3-m TCT controller are duplicates of each other concerning the operator display and 

commands. Hence, no change in operating techniques is necessary when the actual tunnel is run. 

However, the dynamics of the tunnel process near tunnel choking conditions, (high Mach number) have 

not been duplicated, nor has the geometrical disturbances, (adaptive wall movements, angle of attack 

change, and drag rake movement). While operating the tunnel, these changes have to be kept in mind. 

12 
INSTALLATION OF CONTROL SOFTWARE ON A PC/AT 

1. Check the microcomputer system configuration to make sure that DT 2801/5716 A and 

DT 2815 cards are mounted with correct jumper configuration. Make sure that the keyboard 

is modified. 

2. Mount the MSDOS operating system in hard disk C. All other software must be deleted. 

3. Copy CONTROL.EXE and BASRUN.EXE to hard disk C. 

4. Modify AUTOEXEC.BAT to load automatically CONTROL.EXE for operation. 

5. Check the monitor screen to see if the correct display is shown when CONTROL.EXE is 

loaded. 

6. 

actual signals to make sure that all the displays are correct. 

The input signals can be checked by comparing the displayed tunnel variables with the 

Software modifications: 

1. The tunnel software modifications should be performed by a person who fully understands 

the BASIC code. This should be performed only with the knowledge and approval of the 

Facility Safety Head of 0.3-m TCT. The BASIC code for the tunnel controller is available 

from the Facility Coordinator. Need for software modification arises only if tunnel geometry 

changes, the sensors/actuators change, or the microcomputer operating clock speed changes. 

The software must then be compiled and linked to obtain a new CONTROL.EXE. 

2. Since the tunnel controller is always running, to stop the program the BOOT diskette 

must be put into drive A and the microcomputer power switched off and then switched on. 

The microcomputer will now boot to disk A. The microcomputer now is running MSDOS. 

13 
Change the drive to disk C. The new version should be copied on to drive C: as 

CONTROL.EXE. 

3. To restart the system, the BOOT diskette in A drive must be removed. Again the power 

must be switched off and then switched on. The system will automatically load the new 

program. 

14 
OPERATION OF TUNNEL CONTROLLER 

The microcomputer T-P/Re-M controller is switched on. The monitor needs to be studied first. If the 

display shows "SENSOR FAILURE", it means that one or more of the seven sensors is out of range. 

Typically, when the vacuum pump reference for the tunnel pressure sensors is not operating, a sensor 

failure exists. 

The seven sensors used for tunnel control are displayed on the screen. 

their calibration on the monitor screen. They are: 

These should be checked for 

1. Both the temperature sensors must read the ambient temperature of about 290 K, unless 

the tunnel is known to be at a colder temperature. 

2. The total and static pressure sensors must be calibrated using the Datametrics zero and 

range controls. 

3. The LN, pressure sensor reading and calibration must be checked. 

4. The PIONEER speed indicator has a CAL button. This signals 3200 rpm command and 

should be checked on the monitor. 

5. The calibration of the screen AP must also be checked. 

After the sensors are checked, the auto/manual switches for the vent valves #3621, #3622, as well as 

the LN,, valve switch for #3535 must be transferred to microcomputer control. The tertiary valve 

#3623 must be closed. 

Once all other ancillary systems and safety devices are checked, the tunnel is ready for operation. The 

operating procedure is very similar to the details in SIMULATOR section. However, before a cooldown 

starts, the tunnel needs to be purged of all the moisture. Hence, the tunnel is started at 300 K, 30 psia 

15 
and 2400 rpm. Once equilibrium conditions are reached, the tunnel is operated for five minutes. At 

the end of five minutes, the pressure set point is changed to 15 psia so that all the tunnel resident 

moisture is discharged. The tunnel is brought back to 30 psia. The tunnel is now ready for cooldown 

to any conditions, under automatic control. 

0.3-m TUNNEL T-P/R-M CONTROLLER 

Figure 1. Display format for the controller monitor. 

16 
0.3-m TUNNEL T-P/R-M CONTROLLER 

Figure 2.- Typical controller monitor display. 

17 
REFERENCES 

Balakrishna, S. ; and Kilgore, W. Allen : Microcomputer Based Controller for the Langley 0.3-Meter 

Transonic Cryogenic Tunnel. NASA CR 181808, March 1989. 

User Manual for DT 2801 Series, Single Board Analog and Digital 1/0 System for the IBM Presonal 

Computer. Data Translation, Inc., Eight Edition. October 1988. 

User Manual for DT 2815, D/A Converter Board, IBM PC/XT/AT Compatible. 

Inc., Second Edition, October 1987. 

Data Translation, 

18 
APPENDIX A 

LIST OF INPUT SENSORS FOR THE CONTROLLER 

OUTPUTS FROM THE CONTROLLER 

DAC( 1) ALQ 4-20 mA position drive valve #3531 

DAC(2) ALQ 4-20 mA position drive valve #3533 

DAC(3) ALN 4-20 mA position drive valve #3535 

DAC(4) AGVl 1-5 VDC position drive valve #3621 

DAC(5) AGV2 1-5 VDC position drive valve #3622 

DAC(6) SNRPM 0-5 VDC fan drive command Rheost servo 

DAC(7) I& 5 VDC fan drive reference Rheost ref.( 100%) 

19 
APPENDIX B 

VARIABLE NAMES IN THE T-P/Re-M CONTROL SOFTWARE OF THE 0.3-M TCT 

AA 

AEMP 

AGVl 

AGVlP 

AGV2 

ALN 

ALNl 

ALQ 

ALQP 

AUTOM 

AUTOP 

Keyboard input function. Combines the integer inputs H1, H2, H3, and H5 with proper 

decimal scaling for use in program calculations. 

Temporary data register output in DAC routine to check status. 

Area of GN, valve #l. Full open AGV1=1 and closed AGVl=O. 

Area of GN, valve #1, previous cycle value. 

Area of GN, valve #2. Full open AGV2=1 and closed AGV2=O. Valve #2 opens only 

when AGVl > 90% open and starts closing when AGVl < 70% open. Valve #2 moves 

at a rate of 1% per cycle. 

Area of LN, back pressure control valve. Full open ALN=l and closed ALN=O. 

Area of LN, back pressure control valve, previous cycle value. 

Area of LN, control valve. Full open ALQ=1 and closed ALQ=O. The command is for all 

the valves in parallel. 

Area of LN, control valve, previous cycle value. 

Logic state Mach number controller: 

AUTOM=l automatic Mach number control. 

AUTOMZO manual Mach number control. Corresponds to fan speed control. 

Logic state pressure controller: 

AUTOP=l automatic pressure control. 

AUTOP=O manual pressure control. 

AUTORE Logic state Reynolds number controller: 

AUTOT 

BEMP 

BSD 

CEMP 

AUTORE=l automatic Reynolds number control. Corresponds to automatic pressure 

control with the pressure set point generated by the Reynolds number regulation. 

AUTORE=O manual Reynolds number control. Corresponds to automatic pressure 

control. 

Temperature Controller: 

AUTOT=l automatic temperature control. 

AUTOTZO manual temperature control. 

Temporary status register output in DAC routine to check status. 

Dummy calculation to create a time delay between resetting the DAC and reading its 

status. Used only during initialization of DAC. BSD=SQR(7) 

Temporary status register output in DAC subroutine. 

20 
CGV 

CH 

CLQV 

D1 

D2 

D3 

D4 

D5 

DAC( 1) 

DAC(2) 

DAC(3) 

DAC(4) 

DAC(5) 

DAC(6) 

DAC(7) 

DAC(8) 

DEL 

DLP 

DLPC 

DRPM 

DR1 

DR2 

Ell 

E12 

E(1) 

E(2) 

Coefficient for GN, discharge valve. CGV=8 

Mean aerodynamic chord. Loaded through the keyboard using the “C” command. 

Default value is CH=0.1800 meters. 

Flow coefficient for LN, injection valve. CLQV=4 

Integer used in the LOCATE statements. D1 is added to MU to print properly the first 

digit of the variable loaded through the keyboard. 

Integer used in the LOCATE statements. D2 is added to MU to print properly the second 

digit of the variable loaded through the keyboard. 

Integer used in the LOCATE statements. D3 is added to MU to print properly the third 

digit of the variable loaded through the keyboard. 

Integer used in the LOCATE statements. D4 is added to MU to print properly the fourth 

digit of the variable loaded through the keyboard. 

Integer used in the LOCATE statements. D4 is added to MU to print properly the fifth 

digit of the variable loaded through the keyboard. 

Control variable ALQ output, (4-20 mA). DAC(l)=ALQ 

Control variable ALQ output, (4-20 mA). DAC(2)zALQ 

Control variable ALN output, (4-20 mA). DAC(3)=ALN 

Control variable AGVl output, (1-5 VDC). DAC(4)=AGV1 

Control variable AGV2 output, (1-5 VDC). DAC(5)=AGV2 

Control variable SNRPM output, (0-5 VDC). DAC(G)=SNRPM 

RPM/MACH controller output for Rheostat control. DAC(7)=1 for normal operation. 

DAC(7)=O for Rheostat control. 

Spare control variable channel. 

Cycle time step. DEL=O.l seconds. 

Difference in pressure across the screens of the tunnel settling chamber, (psia). 

DLP=E(7)+XDLP 

Maximum safe screen pressure drop allowed. DLPC=0.47+PP*MtM/(MF)-6 

Fan speed in RPM with a minimum limit of 100 rpm. DRPM=FRPM, DRPM>100 

Command output high integer buffer in DAC routine, (13 bit). 

Command output low integer buffer in DAC routine, (4 bit). 

Output from ADC of the tunnel total pressure for monitor display. 

Output from ADC of the tunnel static pressure for monitor display. 

Input millivolts from total pressure sensor. 

Input millivolts from static pressure transducer. 

21 
E(3) 

E(4) 

E(5) 

E(6) 

E(7) 

E@) 

ELP 

ELPl 

EM 

EN 

EP 

EPMl 

EPM2 

ET 

ETMl 

ETM2 

FB 

FBF 

FF 

FKW 

FLl 

FL2 

FL3 

FL4 

FL5 

Input millivolts from the total temperature thermocouple. 

Input millivolts from the tunnel metal wall temperature thermocouple. 

Input millivolts from the fan speed sensor in RPM. 

Input millivolts from LN, pressure transducer. 

Input millivolts from the screen pressure drop transducers. 

Spare input channel. 

Error in LN, pressure control, (atm). ELP=PLQ-SLQ 

Error in LN, pressure control, previous cycle value. 

Error in Mach number control. EM=SM-M 

Error in fan speed control, (rpm). EN=NCMDSl-FRPM 

Error in pressure control, (atm). EP=PP-SPR 

Error in pressure control, previous cycle value. 

Error in pressure control, twice previous cycle value. 

Error in temperature control, (kelvin). ET=TT-ST 

Error in temperature control, previous cycle value. 

Error in temperature control, twice previous cycle value. 

Fan bias, an equivalent of FKW in LN, flow. FB=FKW/(121+TT)/LF 

Product of FB and FF. FBF=FB*FF+O.S 

Feed forward logic integer. FF=1 the fan bias is fed forward as LN,. FF=O the fan bias 

is not fed forward as LN,. The feed forward is off during tunnel warm-ups. 

Estimated fan power released to gas, (kilowatts). 

FKW=llO*PP*(FRPM/lOOO)^2.26/SQR(TTMP) 

Logic flag. FL1=1 when the error in temperature control is less than 0.3 K. FLl=O 

corresponds to a larger temperature control error. 

Logic flag. FL2=1 when the metal temperature is within 24 K of the tunnel temperature 

set point. FL2=0 corresponds to a larger temperature difference. FLl*FL2=1 

corresponds to the temperature of the tunnel at the set point. 

Logic flag. FL3=1 when the error in pressure control is less than 0.005 atm. FL3=0 

corresponds to a larger pressure control error. 

Logic flag. FL4=1 when the error in Mach number less than 0.002. FL4=0 corresponds to 

larger Mach number control error. 

Logic flag. FL5=1 when the error in the LN, pressure control is less than 0.25 atm. 

FL5d corresponds to a larger LN, pressure error. 

22 
KIM 

KIN 

KIP 

KIT 

KMC 

KMGS 

KMM 

KP 

KPGS 

KPL 

KPM 

KPN 

KPP 

KPT 

KRE 

KT 

KTGS 

LCMDS 

LDPQ 

LF 

LMT 

LO 

LQ 

LU 

M 

MF 

MU 

MXT 

NCMDS 

Mach number control integral gain. KIM=O.O 

Fan speed control integral gain. KIN=0.4 

Pressure control integral gain. KIP=0.05 

Temperature control integral gain. KIT=O.10 

Constant corresponding to tunnel fan speed/test section coupling defined in the control 

analysis of the Mach number controller. KMC=520*SQR(TT)/PPA-0.035 

Mach number control gain schedule function. KMGS=KMC*KMM 

Mach number control gain. KMM=0.30 

Pressure control gain. KP=0.30 

Pressure control gain schedule function. KPGS=75O*KP/PP/SQR(TT) 

LN, pressure control proportional gain. KPL=0.2 

Mach number control proportional gain. KPM=4.50 

Fan speed control proportional gain. KPN=0.6 

Pressure control proportional gain. KPP=1.0 

Temperature control proportional gain. KPTz1.0 

Constant used for evaluating Reynolds number related functions. 

KRE=63714*CH*M/TTe 1.4/(MF)^2.1 

Temperature control gain factor. KTz0.04 

Temperature control gain schedule function. 

LN, valve area. Loaded through the keyboard using the “L” command. 

Difference between LN, pressure and total pressure. LDPQ=(PLQ-PP) 

LN, flow when LN, valve is full open. LF=CLQV*O.M76*SQR(LDPQ) 

Limiter for LN, flow. Used when the temperature difference between the tunnel metal 

wall and tunnel gas exceeds MXT. 

An output driving the DAC low buffer for final command. Low byte to data register in 

DAC routine. 

Product of ALQ and 100. LQ=ALQ*100 

Screen row numbers used in the LOCATE statements; for display. 

Tunnel flow Mach number in the test section based on the difference between total and 

static pressure. M=SQR(S*(PP/PS)’0.28571-5) 

Isentropic function of the tunnel flow Mach number. MF=( 1+0.2*M*M) 

Screen column numbers used in the LOCATE statements; for display. 

Maximum safe temperature difference allowed between tunnel gas and tunnel metal wall. 

Fan speed set point. Loaded through the keyboard using the “N” command. 

KTGS=DRPM*SQR(PP)*KT/3.O/TT/LF 

24 
IK 

IQ 

IW 

FL6 

FLlO 

FRPM 

GCMDS 

GF1 

GV1 

GV2 

H1 

H2 

H3 

H5 

HI 

&HSEC 

&H224 

&H225 

I 

IE 

J 

JJ 

JD 

K 

KDL 

KDP 

KDT 

KEN 

KIL 

Logic flag. FL6=1 when the pressure difference across the tunnel screens is unsafe. 

FL6=0 corresponds to a safe pressure difference. 

Logic flag. FL10=1 when a sensor fails. FL10=O corresponds to normal operation. A 

sensor failure will cause an emergency stop. 

Fan speed in RPM. FRPM=E(S)*XFRPM 

GN, discharge valve area. Loaded through the keyboard using the “G” command. 

Mass flow from the tunnel. GF1=2.725*CGV*PP/SQR(TT) 

Product of AGVl and 100. GVl=AGV1*100 

Product of AGV2 and 100. GV2=AGV2*100 

First integer of an input keyed during a variable input. 

Second integer of an input keyed during a variable input. 

Third integer of an input keyed during a variable input. 

Fourth integer of an input keyed during a variable input. 

High byte to DAC buffer of the DAC subroutine. 

Port number on the PC/AT microcomputer for ADC. 

Port number on the PC/AT microcomputer for DAC. 

Port number on the PC/AT microcomputer for DAC. 

Integer cycle counter used to print the screen borders. 

Logic flag. IE=1 corresponds to an emergency stop. IE=O corresponds to normal 

operation. 

Integer cycle counter used for output of DAC variables. 

Logic flag. IQ=1 corresponds to Rheostat control in RPM/MACH control. IQ=O 

corresponds to normal operation. 

Integer cycle counter, IW=40. Used in integrating the wall temperature gradient. Some 

control variables are displayed only once in 40 cycles. 

Integer variable that identifies type of input variable. 

Integer cycle counter for calculation of BSD. 

Integer cycle counter for printing certain variables every 4 cycles. 

Integer cycle counter for a 600 cycle beep. 

LN, pressure control derivative gain. KDL=O.O 

Pressure control derivative gain. KDPZO.0 

Temperature control derivative gain. KDT=O.O 

A gradient term limiting the RPM of the fan speed. 

LN, pressure control integral gain. KILZ0.20 

23 
NCMDSl Fan speed set point derived from NCMDS or other safety fan speed commands. 

PLQ LN, pressure, (atm). PL&=E(G)*XPLQ 

PLQUSCS LN, pressure, (psia). PLQUSCS=PLQ*14.696 

PP 

PPUSCS 

PS 

PSUSCS 

RE 

RIL 

RILMl 

RIM 

RIMMl 

RIN 

RINMl 

RIP 

RIPMl 

RIT 

RITM 1 

SAT 

SATl 

SLQ 

SLQSC 

SM 

SNRPM 

SP 

SPR 

SPRl 

SPRU 

SRE 

SRPM 

Total tunnel pressure, (atm). PP=E(l)*XPP 

Total tunnel pressure, (psia). PPUSCS=PP*14.696 

Tunnel static pressure, (atm). PS=E(2)*XPS 

Tunnel static pressure, (psia). PSUSCS=PS*l4.696 

Flow Reynolds number based on aerodynamic chord. RE=KRE*PP 

LN, control integral error, (atm-sec). 

LN, control integral error, previous cycle value. 

Mach number control integral error, (Mach-sec). 

Mach number control integral error, previous cycle value. 

Fan speed control integral error, (rpm-sec). 

Fan speed control error integral, previous cycle value. 

Pressure control integral error, (atm-sec). 

Pressure control integral error, previous cycle value. 

Temperature control integral error, (K-sec). 

Temperature control integral error, previous cycle value. 

Saturation temperature based on Jacobsens data, (kelvin). SAT=50+27.34*PSa0.296 

Saturation temperature for tunnel static pressure, (kelvin). SATl =SAT*MF 

LN, pressure control set point, (atm). SLQ=SLQSC/14.696 

LN, back pressure set point. Loaded through the keyboard using the “B” command. 

Default value is SLQSCz17 psi for fan “on” and 11 psi for fan “off“. 

Mach number set point. Loaded through the keyboard using the UMn command. 

Fan speed rheostat drive command normalized to one. SNRPM=SRPM/7500 

Tunnel total pressure set point, (psia). Loaded through the keyboard using the “P” 

command. 

Tunnel total pressure set point, (atm). SPR=SP/14.696 

Tunnel total pressure set point estimated from Reynolds number set point. Valid in 

automatic Reynolds number control mode. SPRl=SRE/KRE 

Tunnel total pressure set point estimated from Reynolds number set point, (psia). 

SPRU=SPR*14.696 

Reynolds number set point. Loaded through the keyboard using the “R” command. 

Fan speed command from control law, (rpm). 

25 
SRPMl 

ST 

ST1 

STP 

TMWL 

TMWL1 

TT 

TTMP 

WLG 

XDPL 

XFRPM 

XPLQ 

XPP 

XPS 

XRPM 

XX 

Z 

Fan speed command , previous cycle value. 

Tunnel total temperature set point. Based on a safe temperature for given tunnel 

conditions. Also, for the condition when TT and PP are high and the gas mass in the 

tunnel is inadequate to reach a desired temperature set point. 

Tunnel total temperature set point. Loaded through the keyboard using the "T" 

command. 

Total temperature set point ramp generator. Restricts the rate of temperature change to 

0.04 K/cycle or 24 K/minute. 

Tunnel metal wall temperature, (kelvin). 

Tunnel metal wall temperature, previous cycle value. 

Total temperature of tunnel gas, (kelvin). 

Total temperature of tunnel gas with a minimum limit of 80 K. TTMP=TT 

Rate of change for the tunnel metal wall temperature. Wall temperature gradient. 

Screen pressure drop transducer sensitivity. XDPL=1.000 

Fan speed sensor sensitivity. XFRPMz1280 

LN, pressure sensor sensitivity. XPLQ=2.6539 

Stagnation pressure transducer sensitivity. XPPz1.366 

Static pressure transducer sensitivity. XPS=1.366 

Fan constant. XRPM=KMC*SM*( 1-0.3tSM) 

Integer counter between 0 to 5. Represents the number of keyed in characters while 

inputing set points into the controller. 

Defined as an integer variable. 

ZDCHNL Analog to digital conversion channel number. 

ZDGAIN ADC gain switch at software level. 

ZOL# ADC output normalized to 5 volts. 

ZOLT# ADC output as a 16 bit binary number. 

ZOW Low byte of ADC output. 

ZIGH High byte of ADC output. 

ZTATUS Status of the ADC register. 

26 
APPENDIX C 

CONTROL PROGRAM FLOWCHART 

(Program available from Facility Coordinator) 

Dofho brro rddrorr 

and othor addroo0 

for ADC rnd DAC 

Wtlrl DAC 

STOP 

Doflw Stutlng Conrtantr 

1) Conrtrntr for Control Loop 2) Trrnrducor Crllbrrtlon 

5) Vrlvo Cooflklrntr 

+ 

Prht llrod ocroon prorontotlon 

In vrrlour colorr lor full rcroon 

Rotun ADC of rrvon Jgnrlr E(1) Io E(7) 

A 

Koyborrd Commondo: 

Cnglnoorhg Convorrlon 01 tho 

Korboud 

I 

27 

1 '1 
No 

b 

~ 

II J.1 thon 8Tl.AA 

II J.2 thon SP=AA 

I1 J4 lhon SM=AA 

I1 J=4 lhon SRE=AA 

It J-6 Ihon LCMDS'AA 

It +d 1h.n QCMDS-AA 

II 5.7 lhon NCMDS-AA 

I1 J-8 lhon CWAA 

it +O 1h.n SLOC=AA 

Paramotor Eatinration 

and bot Polnl buporvlalon: 

CalculaUon of Loop Funcllono 

M. MF. KRE. RE. SAT. SAW, LDPO 

LF. DRPM, KTQS, FKW, FB. SPR, SPR1 

SPR-SPRl 

I 

YO. 

1 No 

I 1 

I 

YO. 

Yar 

L 

I 

ST=TT-O.OZ 8T~TMWL-MXT 

28 
No 

Yanwl 

1 

I 

Con Opood Intogrol Control 

RIN+INMl*EN*DEL*KIN 

V 

0 RW1-KEN * RIN 4 RWbKEN * 6000 

Can 8pO.d Control Lor 

Control Law Roallrrtlon: 

(LN2 Prooruro) 

LN2 Intrgrd Control 

RIL-RILMl*ELP*KIL*DEL 

LhllO 0 to 1.0 

LN2 Control Low 

AUM<PL.ELP*KDL=(ELP-ELPM~)/DEL~~. LMtO 0 to loo% 

4 

30 
Control Law Roallratlon: 

(tomporatura) 

3- 

I If ET -6 ihon FF-0 I If ET 0 (hon FF-1 

I .L 

r 

I 

ALO-LCY081100 

Control Law Roallxatlon: 

(Prarauro) 

ON2 Into@ Control 

RIP=RIPMl*EP*KPQ8=DE=K~ 

Llmli8 0 to 1.0 

I mla 0 to 100% 

Manual - 

Umli Raio of AQVi io 6% por Iirrllon DAC(4) 

29 
I Dloplr y: 

Sofoty Monitor: 

1 

1 

1 

Prht rcroon vrrlrblmr 

on00 b 5 cyclor 01 oprrtlon 

Erthuto Wad arrdknt 

WLI (TYWL-TYWL1)IDEL 

Output of rovon rlgnrlr 

DAC(1) to DAC(7) 

U.morlr0 proront vrrlrblor a0 

31 
APPENDIX D 

DETAILS OF THE MONITOR DISPLAY FOR TUNNEL CONTROL 

(refer to figures 1 and 2) 

w1 

w2 

w3 

w4 

w5 

W6 

w7 

Displays the status of LN, control as “AUTO”. It cannot be changed. The LN, control is 

always on automatic mode. 

Displays the status of temperature control loop. Three modes are possible: 

“AUTO” in yellow for temperature control operation using temperature set point. 

“MANUAL” in yellow for LN, injection valve area control. 

“MANUAL” in red for emergency command. 

Displays status of pressure control loop. Four modes are possible: 

“AUTOP” in yellow for pressure control operation using pressure set point. 

‘AUTORE” in yellow for pressure control with Reynolds number generated pressure set point. 

“MANUAL” in yellow for GN, discharge valve area control. 

“MANUAL” in red for emergency command of 100% for GN, discharge valve position. 

Displays status of fan speed control. Three modes are possible: 

“AUTO” in yellow for fan speed control operation using Mach number set point. 

“MANUAL” in yellow for fan speed control using fan speed set point. 

“MANUAL” in red for emergency command of zero fan speed. 

Displays the LN2 pressure control set point. Set to 11 psia for fan speed below 580 rpm. 

Switches to 132 psia for fan speed 2 580 rpm. Is loaded from the keyboard by letter command 

“B”. Updated only on a new set point command. 

Displays the tunnel temperature control set point. Is loaded from the keyboard by letter 

command “T”. Updated only on a new command. 

Displays the tunnel temperature set point actually used as estimated by control law based on 

gas-metal temperature difference, set point magnitude and direction, tunnel trajectory 

direction. Updated every 0.3 seconds. 

32 
W8 Display of the tunnel pressure set point as desired by operator in ”AUTOP” mode. 

Is loaded from the keyboard by letter command “P”. Updated on a new set point command. 

Also displays pressure set point as estimated by Reynolds number when in ” AUTORE” mode. 

Updated every 0.3 seconds. 

W9 Displays Reynolds number set point desired by operator. Is loaded from the keyboard by letter 

command “R”. Updated on a new set point command. 

W10 Displays Mach number set point as desired by operator. Is loaded from the keyboard by letter 

command “M”. Updated on a new set point command. 

W11 Displays fan speed set point as desired by the operator. Is loaded from the keyboard by letter 

command “N”. Updated on a new set point command. 

W12 Displays the true LN, supply pressure measured by the transducer. Updated every 0.3 seconds. 

W13 Displays the true gas temperature in the tunnel settling chamber. Updated every 0.3 seconds. 

W14 Displays the true metal temperature on the tunnel aluminum shell at the third corner. 

Updated every 0.3 seconds. 

W15 Displays the tunnel total pressure measured in the tunnel settling chamber. 

Updated every 0.3 seconds. 

W16 Displays the tunnel flow Reynolds number based on the chord. If chord data is not given 

Reynolds number is based on default value of a chord of 0.1800 m. Updated every 0.3 seconds. 

W17 Displays the true flow Mach number in the test section using the difference between measured 

total and static pressures. For no flow conditions, the estimate is clipped to be > 0.001 to 

avoid arithmetic problems in program. Updated every 0.3 seconds. 

W18 Displays the true measured fan speed in RPM from the sensor. Updated every 0.3 seconds. 

33 
w19 

w20 

w21 

w22 

W23 

W24 

W25 

W26 

Displays the command to LN, back pressure valve generated by the LN, pressure control law. 

Display is in percent for 4-20 mA current drive. Updated every 0.3 seconds. 

Displays the command to the LN, injection valves in percent. This corresponds to 4-20 mA 

signal going to the coils. In ”AUTO” mode the command is from the temperature control law. 

In “MANUAL” the command is from position command, limited by metal-gas temperature 

difference. 

Displays the command to gas discharge electrohydraulically driven valve 1. 

In “AUTO” mode the drive is derived from the pressure control law. 

In “MANUAL” mode the driver is derived from the area control command. 

Display of 0-100% corresponds to 1-5 VDC set point commands to electrohydraulic valve 1. 

Display corresponds to gas discharge electrohydraulic valve 2 in “AUTO” mode. 

Display of 0-100% corresponds to 1-5 VDC set point command to electrohydraulic valve 2. 

Displays the fan speed rheostat position command in percent. This is the set point to the 

position servo driving the field coil of the variable frequency generator. 0-100% corresponds to 

0-5 VDC to position servo set point. 

Display area normally blank. When the fan speed is between 3550-3650 rpm, the display 

shows “SPEED BAND” to alert the operator about the singularity of the speed control system. 

Letter “B” enables this display with a flashing “,psian. Numeric inputs from the operator in 

format ###.# forms the LN, pressure set point and is displayed as loaded. Return command 

transfers it to the LN, control loop and clears the display. “D” command clears the display 

without transferring it to control. 

Letter “T” enables this display with a flashing “,K”. Numeric inputs from the operator in 

format ###.#, forms the temperature set point and is displayed as loaded. Return command 

transfers the set point to temperature control loop, transfers the control to “AUTO” and clears 

the display. “D” command clears the display without transferring it to control. 

34 
W27 Letter “L” enables this display with a flashing ”,% opn”. Numeric inputs from the operator in 

the format ##.##, forms the LN, valve area set point and is displayed as loaded. Return 

command transfers the set point to the controller, transfers control to “MANUAL” and clears 

the display. “D” command clears the display without transferring it to control. 

W28 Letter “P” enables this display with a flashing “,psia”. Numeric inputs from the operator in 

the format ##.##, forms the pressure set point and is displayed as loaded. Return command 

transfers the tunnel pressure set point to the controller, transfers the control to AUTOP and 

clears the display. “D” command clears the display without transferring it to control. 

W29 Letter “R” enables this display with a flashing “,miln/chrd”. Numeric inputs from the 

operator in the format ##.##, forms the Reynolds number set point and is displayed as 

loaded. Return command transfers the Reynolds number set point to the controller, takes the 

control to “AUTORE” and clears the display. “D” command clears the display without 

transferring it to control. 

W30 Letter “G” enables this display with a flashing “% opn”. Numeric inputs from the operator in 

the format ##.##, forms the discharge valve 1 position set point and is displayed as loaded. 

Return command transfers the set point to controller, transfers control to ”MANUAL” and 

clears the display. “D” command clears the display without transferring it to control. 

W31 Letter “C” enables this display with a flashing “,m”. Numeric inputs from the operator in the 

format .####, forms the model aerodynamic chord for Reynolds number estimation, and is 

displayed as loaded. Return transfers this chord to Reynolds number estimation and clears the 

display. “D” command clears the display without transferring it to control. 

W32 Letter “M” enables this display with a flashing “,Mach”. Numeric inputs from the operator in 

the format #.###, forms the Mach number set point and is displayed as loaded. Return 

command transfers the Mach number set point to the controller, transfers control to “AUTO” 

and clears the display. “D” command clears the display without transferring it to control. 

35 
w33 

w34 

w35 

W36 

w37 

W38 

w39 

W40 

Letter “N” enables this display with a flashing “,rpm”. Numeric inputs from the operator in 

the format ####., forms the fan speed set point and is displayed as loaded. Return 

command transfers the fan speed set point to the controller, transfers control to “MANUAL” 

and clears the display. “D” command clears the display without transferring it to control. 

Metal temperature time gradient as a cooling or a warm up rate in K/min is displayed in this 

block. This display is updated every 4 seconds since this time is required to average the 

gradient. 

This displays the saturation temperature of tunnel test section gas, based on the tunnel static 

pressure. Updated every 0.3 seconds. 

This displays the mean aerodynamic chord used for Reynolds number estimation. The chord 

of the model can be loaded though “C” command. Default chord is displayed in white whereas 

the chosen chord length is shown in yellow. Updated on a new command. 

This displays measured tunnel test section static pressure. Updated every 0.3 seconds. 

The measured pressure drop across the screen in the settling chamber is shown in this display 

area. The actual pressure drop is compared with an ideal pressure drop. If the actual pressure 

indicates on set of icing, this display starts flashing. 

This display is normally blank. When the sensors go out of meaningful signal range, this 

display shows “SENSOR FAILURE” in red. This clears by itself once the signals are normal. 

This display is normally blank. When the tunnel is on an emergency shutdown, this displays 

“EMERGENCY SHUTDOWN”. This can be cleared by “D” command or new set point 

commands, when the emergency condition no longer exists. 

fml On when the absolute value of LN, pressure loop error is less than 0.25 atm. 

Updated every 0.3 seconds. 

w] On when the absolute value of the tunnel temperature loop error is less than 0.2 K. 

Updated every 0.3 seconds. 

36 
[-I On when the absolute value of the pressure loop error is less than 0.006 atm. 

Updated every 0.3 seconds. 

ml On when the absolute value of Mach number loop error is less than 0.002. 

Updated every 0.3 seconds. 

37 
APPENDIX E 

INPUT KEYBOARD COMMANDS 

Input LN, back pressure set point. LN, back pressure set point format is ###.#, range 

is LN, pressure to 150 psia. 

Input mean aerodynamic chord. Chord format is .####, range is 0.010 to 0.400 meters. 

Delete the previous input keys memorized on screen and not yet executed. 

Input GN, discharge valve area. Takes the pressure controller and Reynolds number 

controller to manual control mode. GN, valve area format is ##.##, range is 

99.99%=full open to O%=closed. 

Input LN, valve area. Takes the temperature controller to manual mode. LN, valve area 

format is ##.##, range is 99.99%=full open to O%=closed. 

Input Mach number set point. Takes fan speed to automatic Mach number control mode. 

Mach number set point format is #.###, range is 0.150 to 0.995. 

Input fan speed set point. Takes the fan speed to manual Mach number control mode. 

Fan speed set point format is ####., range is 0 to 5600 rpm. 

Input pressure set point. Takes the controller to automatic pressure control mode and 

manual Reynolds number control mode. Pressure set point format is ##.##, range is 

14.7 to 88 psia. 

Input Reynolds number set point. Takes the pressure control to automatic Reynolds 

number control mode by generating the required pressure set point. Reynolds number set 

point format is ##.##, range is 1 to 50 million/chord. 

Input temperature set point. Takes the controller to automatic temperature control mode. 

Temperature set point format is ###.#, range is saturation temperature to 340 K. 

38 
Report Documentation Page 

1. Report No. 

NASA CR-181868 

2. Government Accession No. 

4. Title and Subtitle 

The NASA Langley Research Center 

0.3-m Transonic Cryogenic Tunnel T-P/Re-M 

Controller Manual 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of pages 

Unclassified Unclassified 40 

7. Authorls) 

S. Balakrishna and W. Allen Kilgore 

22. Price 

A03 

9. Performing Organization Name and Address 

Vigyan, Inc. 

30 Research Drive 

Hampton, VA 23666-1325 

12. Sponsoring Agency Name and Address 

National Aeronautics and Space Administration 

Langley Research Center 

Hampton, VA 23665-5225 

Langley Technical Monitor: Edward J. Ray 

15. Supplementary Notes 

3. Recipient's Catalog No. ! 

5. Report Date I 

July 1989 

6. Performing Organization Code 

~~ 

8. Psrforming Organization Report No. 

10. Worlt Unit No. 

505-61-01-09 

11. Contract or Grant No. 

NAS1-17919 

13. Type of Report and Period Covered 

Contractor Report 

14. Sponsoring hgency Code 

Abstract 

A new microcomputer based controller for the 0.3-m Transonic 

Cryogenic Tunnel (TCT) has been commissioned in 1988 and has reliably 

operated for more than a year. The tunnel stagnation pressure, gas 

stagnation temperature, tunnel wall structural temperature and flow 

Mach number are precisely controlled by the new controller in a 

stable manner. This report describes the tunnel control hardware, 

software, and the flow chart to assist in calibration of the sensors, 

actuators, and the controller real time functions. The software 

installation details are also presented. The report serves as the 

maintenance and trouble shooting manual for the 0.3-m TCT controller. 

17. Key Words (Suggested by Author(s)l I 18. Distribution Statement 

Cryogenic Wind Tunnel 

Microcomputer Controller 

Unclassified - Unlimited 

Subject Category: 09