[american institute of aeronautics and astronautics 10th aiaa/nal-nasda-isas international space...

(c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.

A01 -28014 AIAA-2001-1773AIAA/NAL-NASDA-ISAS 10th International SpacePlanes and Hypersonic Systems and Technologies

24-27 April 2001

Hydrogen Concentration Measurements ofSupersonic Hydrogen-Air Shear Layer

Using Catalytic ReactionTakakage ARAP, Jiro KASAHARA*, Fuminori SAKIMA *, Junji MIURA *,Takayuki AMI *

Muroran Institute of Technology, Muroran 050-8585, Japan

Harunori NAGATA^Hokkaido University, Sapporo 060-8628, Japan

To investigate development of an air-hydrogen supersonic shear layer and distributionof hydrogen concentration, a hydrogen jet was injected into a cold air supersonic free-st reem in a paralell direction. The free stream Mach number was about 1.81. Usinga catalytic reaction on a thin platinum wire, heat release due to catalytic reaction, aheat transfer coefficient and hydrogen concentration were measured. It was shown thatthe paralell injection was found to affect on mixing condition. The effect of paralellinjection on hydrogen concentration profile was clarified. It seemed that there was thestoichiometric condition at the outer edge of shear layer. It was confirmed that thediffusion of Hydrogen, including turbulent mixing, had an effect of flow configuration.

NomenclatureH height of backward-facing stepM Mach numberMc convective Mach numberP supplied electric powerQ heat release due to catalytic reactionq H2 jet to freestream momentum ratio

= />H2^H2/Poo^LT temperatureu mean steamwise velocityx flow direction

and distance from backward-facing stepy horizontal direction and distancez vertical direction

and height from lower wallp density(j) equivalent ratio

Subscripts

9H2

gashydrogen gas

* Associate Professor, Senior Member AIAA, [email protected], Phone/Fax 81-143-46-5367

t Research Associate, Member AIAA* Graduate Student§ Associate Professor, Member AIAA, Email na-

[email protected], Phone 81-11-706-7193/Fax 81-11-706-7889

Copyright © 2001 by the American Institute of Aeronauticsand Astronautics, Inc. All rights reserved.

Ni NickelPt Platinumw walloo free stream just before step

Introduction

IT is important in the study of scramjet engines tounderstand the mixing process in supersonic mix-

ing layers.1 So far, many experimental and numericalstudies have been conducted to clarify the mixing pro-cess in supersonic mixing layers.

Numerous fuel injection schemes have been inves-tigated. Typical methods included axial injectionthrough steps in the combustor wall, transverse orangled injection through wall orifices, and injectionthrough ramps. A review is provided by Bogdanoff.2

Most experimental studies about mixing process havefocused on the velocity distributions with in the mixinglayer3 and also flow visualization results.4 Meanwhile,numerical results have been able to give the spatialdata of equivalence ratio of hydrogen (hydrogen con-centration profile).5 There is less experimental dataof distribution of equivalence ratio in the mixing layerdue to measurement difficulties.

The present study proposes a new evaluation tech-nique for the hydrogen concentration in hydrogen-airsupersonic flow. We have reported the new techniquefor the evaluation of turbulent supersonic mixing layerusing catalytic reaction on constant high temperature

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AMERICAN INSTITUTE OF AERONAUTICS AND ASTRONAUTICS PAPER 2001-1773


upper wall

boundary layerexpansion fenxshock wave

Pt or Ni wireshear layer

temperature control circuitFig. 1 Schematic of flow field.

Afoo=1.81

AfooF=1.81 Step Hydrogen inj ection

HydrogenFig. 2 Schematic of injection slit configuration.

platinum wire.6"9 In this paper, this technique hasbeen developed and is applied to measure hydrogenconcentration in the flow field produced by hydrogeninjection from two dimensional slit into a supersonicflow.

Experimental Apparatus and MethodExperimental apparatus

A suction-type supersonic wind tunnel was used inthe present study. Figure 1 shows the schematic ofthe flow field. The freest ream Mach number at thestep was M — 1.81. Working time of the wind tunnelwas about 10 seconds. The step height was of H = 3mm. Test section conditions are computed assumingisentropic flow through the supersonic nozzle. For thisstudy, the test section static temperature and pressurewere about 180 k and 17.3 kPa, respectively. The hy-drogen was injected into the freestream in a parallel

direction from a slit, which located at the backwardfacing step as shown in Fig. 2. The width and lengthof the slit was of 1.1 mm and 18 mm, respectively. Hy-drogen jet to freestream momentum flux ratio, 9, wasabout 2.3. The convective Mach number10 Mc wasabout 0.485.

Nanopulse (about 30xlO~9 s)11 schlieren pho-tographs of the flow field were made. Features ofinterest include the thickness of the boundary layer,shock structure, and the downstream development ofthe mixing layer.

The probe for measuring hydrogen consentration isshown in Fig. 1. This probe has a thin platinum ornickel wire of 10 mm long and 0.1 mm diameter, andwas connected to an electric circuit for constant tem-perature. In the hydrogen-air supersonic mixing layer,there was an electrically heated platinum wire, on

2 OP 6



a) no injection.

Hydrogen

b) Hydrogen injection.

Fig. 3 Shlieren photographs of flow field.

which catalytic reaction occurs. Catalytic heat releaserate was measured by adapting the technique of con-stant temperature type hot-wire anemometeres. Theprobe can go to the z direction. The measurement wasconducted at x = 31, 61 and 91 mm locations.

Hydrogen consentration measurementHeat release due to catalytic reaction

The energy balance of a thin wire in the flow fieldis given as follows;

(1)

where,Q(W): heat release due to catalytic reactionP(W): supplied power to a thin wire of Pt/NiT(K): mean temperature of a thin wireTW(K): mean temperature of wallTg(K): temperature of freestream<7i(W/K4): coefficient in Eq.(l) (heat radiation)(72(W/K): coefficient in Eq.(l) (heat convection)

heat loss due to heat conduction.

If a thin nickel wire is used, there is no heat release

due to the catalytic reaction in any cases so that Q isneglected. Hence, Eq.(l) yields

Pm = C1(T*-T$,) + Ct(T-T,) + Qte (2)

While, in the case of using a platinum wire, Q is not ne-glected because there is the possibility of heat releasedue to the catalytic reaction. Then, Eq.(l) yields

Q + PPt = - T9) + Qtc (3)

The temperature of platinum and nickel wire are keptunder the constant and same value by using the elec-tric circuit, respectively. Assuming above, Eq.(2) andEq.(3) were combined to give

Q = PNi - Ppt (4)

The each temperature of platinum and nickel wirewere set to the same value of about 870 K. Then,the difference between Ppt and PNI was controlled towithin 5% in the free stream. The effect of differenceof the thermal conductivity of platinum and nickel wasneglected, because assuming the temperature gradientof 106 K/m in the thin wire, Qtcm - QtCFb « 0.16 W,that is within 3% of P.

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0 2 4 6 8 0 2 4 6 8 0 2 4 6 8P [W] P [W] P [W]

Fig. 4 Supplied electric power.

Procedure of Hydrogen consentration measuremnetSince the transfer rate of molecules to the platinum

wire surface controls the catalytic heat release rate, thecatalytic heat release rate was almost proportional tothe hydrogen concentration for <f> < 1. On the otherhand it was proportional to oxygen consentration for</> > 1, where <j) is equivalent ratio. The procedure ofgetting hydrogen concentration was as follows;9

1. Energy balance of a hot wire of nickel was as-sumed as same as Eq.(2) to calculate the suppliedelectric power numerically. Then, as comparedsupplied electric power for nickel wire with ex-perimental results, the thermal conductivity andtemperature distribution of hot wire was given.

2. Using the given thermal conductivity, the temper-ature distribution of a platinum wire and catalyticheat release were calculated.

3. As comparing catalytic heat release of numericalresult with experimental one, and also, assum-ing the similarity of heat and mass transfer, thehydrogen concentration in supersonic flow was in-troduced.

Our previous study of Ref. 9 showed that the errorof measurement had within 2% for the case of usingpremixed gas of air and hydrogen, and this methodwas very good technique for evaluating hydrogen con-sentration in supersonic flow.

Results and DiscussionsFlow structure

Figure 3 shows the typical result of the flow fieldobtained from the flow visualization technique ofschlieren method. The flow was from left to right.Figures 3(a) and 3(b) show without injection case andparallel injection case, respectively. In Fig. 3(a), The

incoming boundary layer separated at the step gener-ating Prandtl-Meyer expansion fan. It was also shownin Fig. 3(b) that the coming boundary layer separatedat the step struck the hydrogen jet, so that the shockwave generated at the injection slit.

Catalytic reaction

Figure 4 shows the typical result of suplied electricpower to the hot wire with constant temperature. InFig. 4, symbol O means the result of Pt wire case and• means Ni wire case result. Since the temperature ofNi wire and Pt wire were equal, the difference betweenthe supplied electric power to Ni and Pt wire gave theheat release due to catalytic reaction. Because thecatalytic reaction occurs only on Pt wire surface. Forexample, the supplied electric power of Pt wire caseand Ni wire case were almost equal for z > 6 mm atx = 31 mm position. It means that there was no heatrelease on Pt wire for the region of z > 6 mm, that is,there was no hydrogen molecular in that flow region.

Figure 5 shows the heat release along the z direc-tion due to catalytic reaction measured by adaptingthe techniwue of constant temperature type hot-wireanemometers as mentioned above. The regions wherethere was the hydron molecullar were about z < 6 mm,z < 9 mm and z < 13 mm for x = 31 mm, x = 61mm and x = 91 mm, respectively. It means that theregime where hydrogen exist expanded as z increaseddue to mixing. It was also found that the maximamvalues of heat release for all cases were almost equel,about 1.8 W. Therefore, at this z position for eachcases, equvalence ratio $ would be 1.

Heat transfer coefficient

Figure 6 shows the heat transfer coefficient distribu-tions on z-direction at the there streamwise positions,x = 31, 61 and 91 mm. Heat transfer rate is re-lated with flow velocity and thermal conductivity ofthe fluid. The freestream seemed to be uniform so

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30

6 25i*"1, **~f

N

20

15

10

5

0

. , . . .i x=31mm

IIII

, \1<P, ,0 1 2

Q[W]

, | , , ii x=61mm

Ic1

°o______£__

0 1 2

Q[W]

, | , , ,i x=91mm

1S\

I, : 8 , ,

0 1 2Q[W]

30

20

15

10

Fig. 5 Profile of heat release due to catalytic reaction.

I

[x=31mm

I I I

1 [x=91mm

I I2000 3000 4000

a [W/(m2-K)]2000 3000 4000

a [W/(m2-K)J2000 3000 4000

a [W/(m2-K)]Fig. 6 Distribution of heat transfer coefficient.

that heat transfer coefficient on the wire was uniformfor z = 13 ~ 27 mm at x = 61 mm position in Fig. 6.Heat transfer coefficient decreased gradually as z de-creased from z = 13 to 8 mm because the flow velocitydecreased gradually due to the shear layer. Then, heattransfer coefficient increased as z decreased from z= 8 to 2 mm due to the increasing of the hydrogenconcentration because the thermal conductivity of thehydrogen is larger than one's of the air. Heat transfercoefficient decreased again as z decreased from 8 to1 mm because the flow velocity decreased and hydro-gen concentration decreased. As above mentioned, theheat transfer coefficient distribution introduced thesome informations of flow field including velocity andhydrogen concentration.

Hydrogen Concentration

Figure 7 shows the results of the hydrogen con-centration profile, the density gradient obtained by

schlieren photographs, and heat release rate due tocatalytic reaction. It was found that the region of theexistence of hydrogen molecular spreads to z-directionas the measurement position changed to downstream(goes to x-direction). On the other hand, the max-imum value of the hydrogen concentration decreasedas the measurement position changed to downstream.The gray scale distribution related with the densitygradient of flow would introduce the shear layer re-gion. For example of results of x = 31 mm and 61mm locations, the maximum point of hydrogen con-centration located in the middle of the shear layer. Aschanging the measurement position to downstream ofx — 91 mm location, the maximum point of hydrogenconcentration moved to the edge of the shear layer.It meant that the mixing of air and hydrogen devel-oped rapidly and hydrogen diffused and entrained tothe main flow.

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H

25 50 25 50 25 50

(a)x =

0 256gray scale

31mm

0 256gray scale

(b)x = 61 mm

0 256gray scale

(c) x = 91 mm

Fig. 7 Hydrogen consentration profile.

ConclusionsTwo-dimensional sonic Hydrogen jet was injected in

parallel into a cold air supersonic flow (M^ — 1.81) toinvestigate the development of an air-hydrogen super-sonic shear layer. Catalytic reaction on a platinumwire was used to measure the heat release rate sothat the heat transfer coefficient and hydrogen con-centration was obtained. It was clarified that the newtechnique of hydrogen measurement method, whichwas proposed in the present study, was found to beuseful and easy to evaluate the hydrogen concentra-tion in supersonic mixing flow field. The change of thehydrogen concentration profile was also clarified quan-titatively, and the relation between mixing phenomenaand flow pattern was discussed.

AcknowledgmentsThis research was supported, in part, by the Min-

istry of Education, Science, Sports and Culture,Grant-in-Aid for Scientific Research (C), 09651006,1997, and 11650938, 1999.

References1Nishioka, M. and Sunami, T., "Some Thoughts and Exper-

iments on the Supersonic Mixing Enhancement," Nagare, Jour-nal of Japan Society of Fluid Mechanics, Vol. 14, No. 5, Oct.1995, pp. 377-389, (in Japanese).

2Bogdanoff, D. W., "Advanced Injection and Mixing Tech-niques for Scramjet Combustion," Journal of Propulsion andPower, Vol. 10, No. 2, 1994, pp. 183-190.

3Arai, T., Sugiyama, H., and Uno, N., "Mixing Enhance-ment by Normal Gas Injection in Supersonic Mixing Layer,"Fluid Mechanic and Us Applications, Vol. 39, 1997, pp. 301-308.

4Schetz, J. A., Hawkins, P. P., and Lehman, H., "Structureof Highly Unexpanded Transverse Jets in a Supersonic Stream,"AIAA Journal, Vol. 5, No. 5, 1967, pp. 882-884.

5Deshaies, B., Figueria Da Silva, L. F., and Rene-Corail, M.,"Some Generic Problems Related to Combustion of Hydrogenand Air in Supersonic Flows," Fluid Mechanic and Its Applica-tions, Vol. 39, 1997, pp. 15-42.

6Arai, T., Endo, A., Nagata, H., Sugiyama, H., and Morita,S., "Catalytic Combustion of Transverse Hydrogen Jet Injec-tion behind a Rear-Facing Step into a Cold Supersonic Flow,"Trans. of JSME (B), Vol. 63, No. 614, 1997, pp. 3318-3324, (inJapanese).

7Arai, T. and Nagata, H., Endo, A., Sugiyama, H., Morita,S., and Hosokawa, H., "Evaluation of Supersonic Turbulent Mix-ing using Catalytic Combustion of Constant Temperature PtWire," Trans. of JSME (B), Vol. 64, No. 619, 1998, pp. 793-799, (in Japanese).

8Arai, T., Morita, S., Nagata, H., and Sugiyama, H., "H2concentration Profile in Cold Supersonic Hydrogen-Air MixingLayer (Evaluation using Catalytic Reaction on Constant Tem-perature Pt Wire," AIAA Paper 98-1623, April 1998, In AIAA8th International Space Planes and Hypersonic Systems andTechnologies Conference.

9Nagata, H., Sakai, M., Arai, T., Totani, T., and Kudo, L,"Evaluation of Mass Transfer Coefficient and Hydrogen Con-centration in Supersonic Flow by using Catalytic Reaction,"Proceedings of 28th International Symposium on Combustion,Combustion Institute, Aug. 2000.

10Bogdanoff, D. W., "Compressibility effects in TurbulentShear Layer," AIAA Journal, Vol. 26, No. 6, 1983, pp. 926-927.

nTada, K., Miyashiro, S., Takayama, K., Kleine, H., andGronig, H., "Development of Nanosecond Spark Source," Jour-nal of Japan Soc. Aero. Space Sci., Vol. 43, No. 501, 1995,pp. 582-585, (in Japanese).

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