............ _... r .a,_

NASA Technical Memgran_um 102432 .........

Scattered,Light Scanner Measurements

of Cryogenic Liquid-Jet Breakup

Robert D. Ingebo and Donald __R.Buchele _ _ ,

Lewis Research Center

Cleveland,- Ohio ..........

Prepared for the

Second International Congress on Optical Particle Sizing

sponsored by Arizona State University

Tempe, Arizona, March 5-9, 1990

(NASA-TM-IO2432) SCATT_RE D-L TGHT SCANNER

MEASUREMENTS OF C_YNGENTC LIQUID-JET @R!:AKUP

(NASA) 14 p CSCL 14B

r3135

Nq0-22021

Unclas

0266122

https://ntrs.nasa.gov/search.jsp?R=19900012705 2017-09-11T14:10:01+00:00Z

SCATTERED-LIGHT SCANNER MEASUREMENTS OF CRYOGENIC LIQUID-JET BREAKUP

Robert D. Ingebo and Donald R.Buchele

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

ABSTRACT

The effect of highly turbulent Mach 1 gasflow and high thermal-gradients on drop size measurements was investigated with a scattered-light scanner. The instrument, developed at NASA Lewis

Research Center, was used to measure characteristic drop diameters of cryogenic-liquid sprays. By

correcting for gas-turbulence and thermal-gradient affects, it was possible to obtain good reproducible data with the scattered-light scanner. Tests were conducted primarily in the aerodynamicstripping regime of liquid-jet atomization and it was found that the loss of small droplets due to

vaporization and dispersion had a marked effect on dropsize measurements. The Sauter mean, D32,

and volume median, Dv. 5, drop diameters were measured and correlated with nitrogen gas flow rate,

Hn, to give the following general expression; Dc I: C W_"33 where the reciprocal characteristic

diameter and gas flow rate are in cm-l and g/sec, respectively. The correlating coefficient, C, was

,I.33

evaluated and gave the following expressions: D3_ = 210 W_"33 and Uv. 5 , at a downstream

distance of x = 1.3 cm.

The nitrogen-gas flow rate exponent of 1.33 is the same as that predicted by atomization theory

for liquid-jet breakup in high velocity gasflow. However, when the sprays were sampled farther

downstream of the atomizer, at distances of x - 2.5 and 4.5 cm, the exponent for Wn decreased to

1.2 and 0.9, respectively. This was attributed to the loss of small droplets due to vaporization

when values of x exceeded 1.3 cm.

NOMENCLATURE

b

c

Dc

D'

c

Di

Dr. 5

D32

D31

k

Nn

NF

n

v

dropsize parameter in Nukiyama-Tanasawa expression, cm

drop size parameter in Rosin-Rammler expression, cm

characteristic drop diameter measured for entire spray, cm

characteristic drop diameter for line-of-sight measurements, cm

diameter of ith drop, cm

volume median drop diameter, cm

, n_3t'_ -'-_ _2 Sauter mean drop diameter _-'_i ui _--_inui ' cm

volume-linear mean drop diameter, L_-_inD_/_'-'_inDi] 0"5, cm

correlation coefficient, sec/g-cm

exponent for Nukiyama-Tanasawa drop size distribution expression

exponent for Rosin-Rammler drop size distribution expression

number of droplets

volume fraction of droplets having diameter x
W weight flow of fluid, lb/sec or g/sec

x droplet diameter in drop size distribution expressions, cm

x axial downstream spray sampling distance, cm

Subscripts

n nitrogen gas

w water

INTRODUCTION

New drop size measurement techniques are needed to overcome the many difficulties encountered

in studies of fuel spray combustion in rocket and gas-turbine combustors and icing cloud formation

in wind tunnels. In the task of characterizing liquid sprays, one of the major difficulties encountered with optical instruments is the occurrence of high droplet vaporization rates. Detailed

knowledge of fuel spray characteristics is especially needed at the point of initial spray formation close to the atomizer orifice and the effect of vaporization on the spray must be known. From

this information, accurate initial conditions can be established for modelling the fuel spray combustion process or the formation of ice on airfoils.

The presence of high velocity and high thermal gradients also contribute to the difficulty of

obtaining accurate measurements of characteristic drop diameters, i.e., Sauter mean diameter, D32.

For example, a drop size measuring technique using forward light-scattering, i.e., a Malvern instrument, was modified by Dodge and Cerwin, l to study evaporating fuel sprays in air at temperatures as

high as 700 K. With no spray present, the instrument picked up background noise due to thermally

induced density gradients in the gas phase, To correct for this, the distribution of light was

obtained by using only the outer 24 channels of a 30 channel detector to measure light scattered

mainly from the smaller particles. As a result, it was stated that the light distribution "follows

the shape expected for the scattering from a spray" and the usefulness of the instrument was extended to include drop size measurements of evaporating sprays at distances relatively close to the

atomizer.

Numerous investigators have obtained experimental drop size data and correlated it with relative velocity, i.e., gas velocity relative to liquid velocity and also with liquid properties, as

given in Refs. 2 to 8. Some of the correlations do not agree very well with atomization theory

which is generally attributed to the fact that measurement techniques and drop sizing instruments

have yet to be developed and standardized to the extent that good agreement might be expected. In

the present study, the entire spray cross section was sampled with a 4.4 by 1.9 cm rectangular

laser beam at three axial locations downstream of the atomizer. Also, a 0.30 by 1,9 cm narrow

laser beam was used to scan across the spray cross section and the characteristic drop s%ze D32

was determined at three different atomizing-gas flow rates. Drop size distribution exponents for

the Rosin-Rammler and Nukiyama-Tanasawa drop size distribution expressions were also determined

with the scattered light scanner.
ORIGINAL PAGE

BLACK AND WHIT£ PHOT.OGRAP.H

APPARATUS AND PROCEDURE

A pneumatic two-fluid atomizer was mounted in the test section as shown in Figs. 1 and 2.

optical path of the scattered-light scanner and a detailed diagram of the atomizer are shown in

Figs. 2 and 3. respectively.

The

0.01 cM-DIAM-_

/ 1 MW LASER

FIGURE 1. - APPARATUS AND AUXILLIARY EQUIPMENT.

AIR

LIOU|D NITROGEN -_- _"_

NITROGEN

GAS-_]_ _q_.... _ATOMIZER, I)o = 0.564 CM

1 t _\ I rLIGIITSCATTERING

Z I /_., i // ANGLE O, 13 RAD -_ 10 CM _-f_

5.0 CM-DI/Vfl _ X, SPRAY / r 7.5 cM-DIAM /. 7,5 CM-DIAM

, CM // _ SCANNER-,, i" _FILTER

IH I MULTIPLIER

TIMER II L"-_J

LAMP_ II "-MOTOR

, C>Uq

F'----61 CM --_ JI _TIMER : --- 22 cm --- DETECTOR

- -- 58 CM........

FIGIIRE2. - ATMOSPIIERICPRESSURETEST SECTIONAND OPTICALPATIIOF SCATTEREI)-LIGIIT SCANNER.
NITROGENINSIDE

DIAMETER GAS-_

, I JNOllLEORIFICE

LIQUID NITROGEN DIAMETER iI_I

0.663 CMJ

FIGURE 3. - DIAGRAM OF PNEUMATIC TWO-FLUID

ATOMIZER.

The Scattered-Liqht Scanner

The optical system of the scattered-light scanner is shown in Fig. 2. The instrument measures

scattered-light as a function of scattering angle by repeatedly sweeping a variable-length slit in

the focal plane of the collecting lens. The data obtained is scattered-light energy as a function

of the scattering angle relative to the laser-beam axis, This method of particle size measurement

is similar to that given in Ref. 9 and it is described in detail in Ref. lO.

Data processing consists, as shown in Fig. 4, of locating four points on a plot of scatteredlight energy which is normalized to the maximum energy and plotted against scattering angle. The

points are used to evaluate Sauter mean, volume median, volume linear and 75-percent volume drop

diameters. In Ref. I0, it is demonstarated that the four characteristic drop diameters and the dispersion of drop sizes are substantially independent of particle size distribution function. For a

typical measurement, the scan is repeated 60 times per second to average out any temporal variations in the energy curve.

I.O

CIIARACTERISTIC RELATIVE

DIAMEER ENERGY

Dr.75 0.85

Dr.5 0.73

D32 O. J12

D31 O,2h

I

L DvO.5

DvO.75

D31

.005 .010 .015

LIGHT SCATTER ANGLE, RAD

FIGURE h. - TYPICAL SCATTERE[)-LIGIil

ENERGY CURVE WITIIFOUR CIIARACTERISTIC DIAMETERS.
Spray pattern affects were minimized by measuring characteristic drop diameters for the entire

spray cross section. Reproducibility of characteristic drop size measurements was shown in Ref. 8

to be within ±5 percent. Calibration was accomplished with five sets of nonosized polystyrene

spheres having diameters of 8, 12, 25, 50 and lO0 pm. Since the sprays were sampled very close to

the atomizer orifice, they contained a relatively high number-density of very small drops. As a

result, the light-scattering measurements required correction for multiple scattering as described

in Refs. lO and II for the case of high number-density sprays. Drop size measurements were also

corrected as described in Ref. lO to include Mie scattering theory when very small characteristic

droplet diameters, i.e., <lO pm, were measured•

In the first part of the present study, the entire spray cross section was sampled with a

4.4 by 1.9-cm rectangular laser beam, Later, the long dimension of the laser beam was reduced from

4.4 to 0.64 cm and the smaller laser beam was used to sample the spray at various traverse positions and at three different atomizing-gas flow rates. When measurements of the characteristic

drop size of cryogenic liquid nitrogen sprays were first attempted, it was found that good reproduicible measurements were much more difficult to obtain with cryogenic sprays than with water

sprays. This was attributed to excessively high temperature gradients in the gas-film surrounding

the droplets caused by a temperature difference of 216 K, i.e., Tg - Tl = 293 - 77 K = 216 K.

Density variations caused by high temperature gradients deflected the laser beam and caused a spike

to appear on the light energy curve as shown in Fig. 5(a). To reduce the amplitude of the large

spike, the laser beam was moved 0.6 mm from the path of the rotating variable-length slit shown in

Fig. 2. This adjustment, described in detail in Ref. 12, causes a distortion of the true scattered

light wave shape at a small scatter angle, which is corrected by instrument calibration. The spike

was reduced as shown in Fig. 5(b) by computations employing the equations given in Ref. lO. As a

result, it was possible to obtain good reproducible drop size data for cryogenic sprays with the

scattered-light scanning instrument.

1.25 --

1.00

.75

• 50

.25

i +-_

.25 ,50 .75 1.0 1.25

I

1.50x10 "2 O

._BACKGROUNI) CURVE

I'" ._CORRECTED CURVF

I

.25 .50 ,75 1.0 1,25

LIGHT SCATTER ANGLE. RAD

(a) UNCORRECTED CURVE, (b) BACKGROUND CURVE AND CORRECTED DRIVE,

FIGURE 5. - ENERGY CURVES UNCORRECTED AND CORRECTED FOR BACKGROUND LIGHT-SCATTERING DUE lO DIGU GAS-PI_SE TEMPERATURE-GRADIENTS,

1.50x10 "2
Experimental Procedure

The test section, scattered-light scanner and auxiliary equipment are shown in Fig. I. Air

supplied at ambient temperature, 293 K, passed through the 15.24 cm inside diameter test section

which exhausted to the atmosphere. The test section was l m in length and a 5.0B cm diameter

orifice was used to measure airflow rate in the test section. A flow of dry air at a velocity of

5 m/see was maintained in the test section to aid in transporting small droplets through the laser

beam. This prevented ambient humid air from contacting the spray and thereby avoided the formation

of ice particles in the laser beam.

The atomizer shown in Fig. 2 was mounted at the center line of the test duct and operated over

pressure ranges of 0.2 to l.O MPa for both liquid nitrogen and the atomizing nitrogen gas. Liquid

nitrogen sprays were injected downstream into the airflow just upstream of the duct exit. The

sprays were sampled at distances of 1.3, 2.5 and 4.5 cm downstream of the atomizer orifice with a

4.4 by 1.9 cm rectangular laser beam produced by the aperture shown in Fig. 2. A diagram of the

pneumatic two-fluid nozzle used in this study is shown in Fig. 3.

Liquid nitrogen, LN2, at a temperature of 77 K measured with an I.C. thermocouple, was axially

injected into the airstream at a flow of 76.5 g/see, as indicated by a turbine flow meter. Nitrogen gas was then turned on to atomize the LN2 jet and weight flow rate was measured with a 0.51 cm

diameter sharp-edge orifice. After the air, nitrogen gas and LN2 flow rates were set, characteristic drop diameters and exponents for drop size distribution expressions were determined from

measurements made with the scattered-light scanner.

EXPERIMENTAL RESULTS

A two-fluid atomizer using liquid and gaseious nitrogen was tested to determine the effect of

axial sampling distance on characteristic dropsize. Also, exponents for Rosin-Rammler and NukiyamaTanasawa dropsize distribution expressions were determined.

Effect of Sampl_!ng_Distance on Dropsize Measurement

The entire spray cross section was sampled at axial distances of 1.3, 2.5 and 4.5 cm downstream of the atomizer orifice, i.e., x = 1.3, 4.5 and 4.5 cm where x is the distance from the

atomizer orifice to the center line of the laser beam. Liquid nitrogen flow rate was held approximately constant at 76.5 g/see. Characteristic drop diameters D32 and Dv.5 were measured and

plotted against nitrogen gas flow rate, Wn, as shown in Figs. 6(a) and (b). This plot shows the

following relationships for the Sauter mean, D32 and volume median, Dv.5, drop diameters:

-1 D -I ~ W1 .33

D32 and v.5 n

D3_ and D -I ~ W1"2 v.5 n

-I D -I ~ wO.9 D32 and v.5 n

at downstream distances of x : 1.3, 2.5 and 4.5 cm, respectively. The preceding expression,

D31 and Dvl.5 - Win"33

as obtained at x = 1.3 cm, agrees very well with that given by atomization theory for liquid-jet breakup in the regime of aerodynamic-stripping.13
ORIGINAL PAGE IS

OE_ POOR (_ALITY

T

z

u

2000 _

1500

lo00

300

800

7001

Go0

500

qO0 I

300

2

,=>

i I

3

L L____L_J

5 6 7 8 9 10

i I

3 5 E 7 8 9 10

NITROGEN GAS FLOWRATE, g/sEe

(a) SAUTER MEAN DIA_IETER, D)2. (b) VOLUME MEDIAN DIA/4[TER, Dv.5.

FIGURE 6. - CORRELATION OF CHARACTERISTIC DROP DIAMETERS WITII GAS FLOWRATE, LIQUID NITROGEN FLOWRATE OF 76,5 g/sEc.

Also, it was concluded from these results that measurements obtained at x = 1.3 cm, were not

appreciably affected by vaporization and dispersion of the very small droplets as compared with

measurements made farther downstream from the atomizer orifice. Values of the exponent, n,

obtained in other experimental studies are also shown in Table ] for comparison with atomization

theory. 13

Comparison of Characteristic Dropsize Expressions

Characteristic drop diameters, D32 and Dv.5 were determined for liquid-nitrogen sprays sampled at downstream distances of 1.3, 2.5 and 4.5 cm. In Figs. 7(a), (b) and (c), the reciprocals

oF the characteristic drop diameters, with units of cm-l, are plotted against nitrogen-gas flow

rate raised to the exponent a, which was determined from Fig. 6 as a function of the spray sampling

distance x. From the plots shown in Fig. 7, the values of the correlation coefficient k were

determined and the following general expression was derived:

D- l = k Wa

C n

where Dc

of 1.3 cm,

-I

D32

is the characteristic drop diameter of a liquid-nitrogen spray.

the following dropsize expressions were obtained:

= 210 N133

n

At a sampling distance

D -1 N1.33 v.5 : 150 n
TABLE I. - VELOCITY EXPONENT, N, FOR

LIQUID-NITROGEN JET BREAKUP IN

MACH I GASFLOW, Dc ~ V_ n.

Source Exponent

Theoryl3'

Present study, _: 1.3 cm

Weiss and Worsham3

Wolfe and Anderson 4

Kim and Marshall 5

Nuk__iyamaand Tanasawa 6

x = 5 to 25 cm

Lorenzetto and Lefebvre 7

1.33

1.33

al .33

1.33

al .14

1.0

l.O

aWax sphere dropsize data.

2800 m

24o0-

2ooo16oo

1200

0

80O

-- 400

0 D321 = 210 Wn 1'33

[] Dr.-IS : 150 Wnl.)3

o

o o

2 _ 6 B

W_ ._'3, (glsec)1.33

(a) AT SAMPLING DISTANCE, _, OF i.3 CM.

I

I0

D,i'o,9o.o, 2 /P

-- O Dv._ " 150 Wn 1'2 0

_ 0

2 t_ G 8 10 12 14

W 1,2, (g/sEc)i.2

(b) AT SAMPLING DISTANCE, _, OF 2.5 Cm.

I

16

0 D321 = 2_I0 Wn 0'9

-- D -I

[] v.S = ISO Wn 0"9

2 4 6 8

WOn'9, (g/sEe) 0.9

(C) AT SAMPLING DISTANCE, _(, OF 4.5 CM.

FIGURE 7. - COMPARISON OF ClIARACTERISTIC DROP DIAMETERS AT LIQUID NITROGEN FLOWRATE OF 76.5 g/sEe.

The correlation coefficient, k, nitrogen gasflow rate exponent, a, are given in Table 2 for comparison. It is interesting to note that at any of the two sampling distances, the value of k varied

by only ±lO percent whereas the exponent a changed from 1.33 to 0.9 when _ was increased from

1.3 to 4.5 cm. This indicated that vaporization of the small droplets had only a minor effect on

the correlation coefficient k but a major effect on the exponent a.

i

Measurement of Characteristic Drop Diameter, D32

The laser beam height of the scattered-light scanner was reduced from 1.9 to 0.32 cm and

i

line-of-sight measurements of characteristic drop diameter D32 were obtained at several vertical

locations in each liquid-nitrogen spray. Values of %2 are plotted against vertical location as

shown in Fig. 8. This type of measurement was obtained for the two-fluid atomizer at constant liquid nitrogen flow rate, and for three different atomizing gas flow rates, at an axial downstream

sampling distance of x = 1.3 cm.
TABLE2. - COEFFICIENT, k ANDEXPONENT, a, FOR

CHARACTERISTIC DROPDIAMETERXPRESSION,

-- a w,

Dcl = kWn,

Sampling location, T, cm

Exponent, a

Coefficient, k, for

characteristic diameter

D32

Dv.5

1.3

l.33

210

150

2.5

1.20

190

150

*WLN2 = 76.5 g/cm.

4.5

.90

240

lBO

20

-- 16

wn, 9/SEC

<) 1.82

I I 1 1 J

•64 .32 0 -. 32 .64 -. 96

DISTANCE FROM LIQUID JET CENTERLINE, CM

FIGURE 8. - SPRAY PROFILE FOR TWO-FLUID ATOMIZER AT X = 1.3 CM,

i

Minimum values of D32 at the liquid-jet center line were reduced nearly one-third i.e.,

from approximately 18.5 to 12.3 wm, when nitrogen gas flow rate was increased from l.B2 to

i

2.72 g/sec. A similar reduction in D32 occurred in the upper and lower fringes of the sprays. The

asymetry of the spray shape was attributed to the effect of gravity on the drops and also a possible

slight misalignment of the center tube of the atomizer.

Characteristic Exponents for Dropsize Distribution E_xpresslons

The scattered-light scanner gave data for the exponent Nr, which appears in the Rosin-Rammler

expression as follows:

Nr-I N

dv Nrx e_(X/C ) r

dx = N-_

C
Data were also obtained for the exponent Nn, which appears in the Nukiyama-Tanasawa expression as

follows:

6/Nn _bxNn

dv b x5 e

dx - (6/N n)

From a plot of the data obtained with the two-fluid atomizer, as shown in Fig. 9, the

Following relation was determined:

0.5

Nr - 2.83 Nn

which is similar to the expression derived in Ref. l for water sprays. Thus, it was found that

although the downstream distance, x, was varied from 1.3 to 4.5 cm, the relation between the exponents was not appreciably affected by vaporization and dispersion of the small droplets.

z:

L_J

3 --

0

O

o

X, CM

1.3

I

.2 .tl .G .8 l,O 2

EXPONENT.Nn

FIGURE9. - CORREtATIONOF EXPONENTSFOR ROSIN-RAMMLERAND NUKIYAMATANASAWAEXPRESSIONS.

CONCLUDING REMARKS

Investigating the fluid mechanics of liquid-nitrogen jet breakup in highvelocity gasflow is

considerably more difficult than studying the formation of water sprays. This is primarily due to

the fact that the surface temperature of liquid-nitrogen jets used in the present study was always

near its boiling point which is approximately ?? K. Since the atomizing gas used in this study was

at room temperature, approximately 293 K, this created large temperature gradients that deflected

the laser beam, i.e., caused beam steering to occur, when characteristic drop diameters were

measured with the scattered-light scanner. This problem was minimized in the present investigation

by moving the laser beam away from the slit in the scattered-light scanner optical system.

Characteristic drop diameters of cryogenic liquid-nitrogen sprays were measured with a scattered-light scanning instrument at a distance of 1.3 cm downstream of the orifice of a pneumatic

two-fluid atomizer. Values of D32 and D 5 were obtained and correlated with nitrogen gas flow

rate raised to the 1.33 power. This exponent of 1.33 is the same as that derived theoretically in

Ref. 12 for liquid-jet atomization in the aerodynamic-stripping regime of breakup. The fact that

experimental results agreed well with atomization theory was attributed to a negligible loss of

small droplets due to vaporization and dispersion affects. These affects were not negligible at a

10
distance of 4.5 cm downstream of the atomizer orifice, where the exponent decreased to a value of

0.9. When the laser beam was positioned at a distance of less than 1.3 cm from the atomizer, characteristic dropsize increased very markedly due to incomplete breakup of the liquid jet. With the

two-fluid atomizer, at a liquid-nitrogen flowrate of 76.5 g/sec and at a sampling distance of

1.3 cm, the following expressions for characteristic drop diameter of the initial liquid-nitrogen

spray were obtained:

-l = 210 W1"33 and D -l _ 150 WI'33

D32 n v.5 n

which agree well with atomization theory for liquid-jet breakup in high-velocity gasflow.

Line-of-sight through the sprays were also made with the scattered-light scanner. Such data

are useful in comparing the performance of similar atomizers by providing information concerning

the spatial pattern of dropsize characteristics within the spray cross-section. Reproducibility of

the spray data was within ±5 percent. Also, it was found that experimental values of the exponents Nn and Nr, for the dropsize distribution expressions, were not appreciably affected when

the sampling distance, x, was varied from 1.3 to 4.5 cm downstream of the atomizer orifice.

REFERENCES

I. L.G. Dodge and S.A. Cerwin, "Extending the Applicability of Diffraction-Based Drop Sizing

Instruments," in Liquid Particle Size Measurement Techniques, ASTM-STP-84B, J.M. Tishkoff, R.D.

Ingebo, and J.B. Kennedy, eds., (American Society for Testing Materials, Philadelphia, PA,

1984) pp. 72-81.

2. R.A. Mugele and H.D. Evans, "Droplet Size Distribution in Sprays," Ind. Enq_ Chem., 43,

1317-1324 (1951).

3. M.A. Weiss and C.H. Worsham, "Atomization in High Velocity Airstreams," Am. Rocket Soc. J., 29,

252-259 (1959).

4. H.E. Wolfe and W.H. Anderson, "Aerodynamic Break-up of Liquid Drops," Proceedinqs of the 5th

International Shock Tube S.ygposium, Z.I. Slawsky, J.F. Moulton, Jr., and W.S. Filler, eds.,

(Naval Ordnance Lab., White Oak, MD, 1965) pp. 1145-1169 (Avail. NTIS, AD-638011).

5. K.Y. Kim and W.R. Marshall Jr., "Drop Size Distributions from Pneumatic Atomizers," AIChE J.,

17, 575-584 (1971).

6. S. Nukiyama and Y. Tanasawa, "Experiments on the Atomization of Liquids by Means of an Air

Stream, Parts Ill-IV," Trans. Soc. Mech. Enq. Jpn., 5, 63-75 (1939).

7. G.E. Lorenzetto and A.H. Lefebvre, "Measurements of Drop Size on a Plain-Jet Airblast Atomizer,"

AIAA J., 15, 1006-1010 (1977).

8. R.D. Ingebo, "Experimental and Theoretical Effects of Nitrogen Gas Flow Rate on Liquid-Jet Atomization," J. Propulsion Power, 4, 406-411 (1988).

9. J. Swithenbank, J.M. Beer, D.S. Taylor, D. Abbot, and G.C. McCreath, "A Laser Diagnostic

Technique for the Measurement of Droplet and Particle Size Distribution," in Experimental Diagnostics in Gas Phase Combustion System___s,"B.T. Zinn, ed., Progress in Astronautics and Aeronautics, Vol. 53, (AIAA, New York, 1977), pp. 421-447.

I]
10. D.R.Buchele,"Particle Sizing ByWeightedMeasurements of ScatteredLight," NASATM-I00968,

1988.

11. P.G.Felton, A.A. Hamidi,andA.K. Algal, "Measurement of DropsizeDistribution in DenseSprays

ByLaserDiffraction," in 3rd International Conference on Liquid Atomisation and Spray Systems

(ICLASS 1985), Vo1. 2, P. Eisenklam and A. Yule, eds., (Institute of Energy, London, 1985),

pp. IVA/4/I-IVA/4/II.

12. D.R. Buchele, "Particle Sizing by Measurement of Forward-Scattered Light at Two Angles,"

NASA TP-2156, 19B3.

13. M. Adelberg, "Mean Drop Size Resulting from the Injection of a Liquid Jet Into a High-Speed Gas

Stream," AIAA J., 6, 1143-I147 (196B).

12
National Aeronautics and

Space Administration

1. Report No. 2. Government Accession No.

NASA TM- 102432

4. Title and Subtitle

Scattered-Light Scanner Measurements of Cryogenic Liquid-Jet Breakup

7. Author(s)

Robert D. Ingebo and Donald R. Buchele

9. Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

3. Recipient's Catalog No.

5. Report Date

6. Performing Organization Code

8. Performing Organization Report No.

E-5200

10. Work Unit No.

505-62-21

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. SponsoringAgencyCode

Report Documentation Page

15. Supplementary Notes

Prepared for the Second International Congress Optical Particle Sizing sponsored by Arizona State University,

Tempe, Arizona, March 5-9, 1990.

16. Abstract

-___=_

The effect of highly turbulent Mach I gas_ow and high thermal-gradients on drop size measurements was

investigated with a scattered-light scanner. The instrument, developed at NASA Lewis Research Center, was used

to measure characteristic drop diameters or cryogenic-liquid sprays. By correcting for gas:-t_rbulence and thermal-"

gradient affects, it was possible to obtain good reproducible data with the scattered-light scanner. Tests were

conducted primarily in the aerodynamic-stripping regime of liquid-_-et atomization and it was found that the loss

of small droplets due to vaporization and dispersion had a marked effect on drop size measurements. The Sauter

mean, D32, and volume median, Dr.5, drop diameters were measured and correlated with nitrogen gas flow rate,

W,, to give the following _nera3 expression; D_ 1 = C W 1'33 where thereciprocal characteristic diameter and

gas flowrate are in cm-1 and g/see, respectively. The correlating coefficient, C, was evaluated and gave the

= W 1.33 following expressions: D3_ 1 = 210 --nVOVl'33and DT.1 150 --n , at a downstream distance ofx = 1.3 cm. The

nitrogen-gas flowrate exponent of 1.33 is the same as that predicted by atomization theory for liquid-jet breakup

in high velocity gasflow. However, when the sprays were sampled farther downstream of the atomizer, at

distances of x = 2.5 and 4.5 cm, the exponent for Wn decreased 1.2 and 0.9, respectively. This was attributed to

the loss of small droplets due to vaporization when _alues of x exceeded 1.3 cm.

17. Key Words (Suggested by Author(s))

Light scattering; Particle sizing; Liquid-jet breakup;

Cryogenic liquids; Multiphase flow; Sprays

19. Security Classif. (of this report)

Unclassified

18. Distribution Statement

Unclassified- Unlimited

Subject Category 35

20. Security Classif. (of this page)

Unclassified

21. No. of pages

14

NASAFORM162SOCTe_ *For sale by the National Technical Information Service, Springfield, Virginia 22161

22. Price*

A03