Spray characterization of like-on-like doublet impinging rocket injectors

Abstract

Spray cliaracterization by laseidiagnostics h a s iniproved drastically, since the early 1970's when the last major rocker injector cliaracterizarion work occun'ed. An assessment of th is earlier experimental work by Ferrenberg, et at., resulted in the following conclusions:' __ The irestilts of an investigation to characterize spi-ays generated by like-on-like doublet impinging injectors are described. This injector configuration i s being considei-ed foiuse i n a liquid/liquidigas tripropellant I-ocker combustot-. However, since a wide range of liquid propeities, liquid flow rates, and chamber densities were used in this investigation, t l i e results are iiot l imited to a specific application Experimental fluid properties and flow conditions were generally far from those of a rocket injector. Existing correlations were eniuirical and can't be exI tended witl i i i i i icl i confidence beyond t l i e variable range oveiwhich they wei-e developed. Sprays were characterized using phorograplir. a Malvel-n Droplet Size Analyzer, and an Aei-oiiietricr Phase Doppler Paificle Analyzer (PDPA), Acorrelation was developed to predict the spray Sauter Mean Diameter (SMD) and the Mass Median Diameter (MMD) as a function of injector operating conditions and fluid properties. The constaiits and exponents were obtained by multiple i-egression of f l ie Malverii Droplet Size Analyzer iiieasiii-eiiieiits. liitrocluctiori The tripropellant rocket engine cycle uses liquid oxygen (OJ. gaseous or liqriid hydrocarbon. and gaseous hydrogen (H2) as t l ie propellants and is believed io have t l ie following benefits: Operatiolh at higher chamber pressures due to the' superior cooling characteristics of H2. Elimination of carbon deposition and fouling probl e m in the turbopump, since Hz can be used as t l ie gas generator fuel. Reduction of combustion instability risks due to the enhancement of tl ie combustion process by H, addit ion e The proposed liquidiliquidigas tripropellant combination i s liquid OJliquid RPl/gaseous Hz. A like-on-like doublet impinging injector is a possible candidate for use in a liquidlliquid/gas tripropellant rocker combustor. This itijector configtiratioti would lhave thr-ee manifolds, one for each liquid and one for H2. The two oxidizer streams would impinge on each other and the two fuel streanis would impinge on each other at separate locations. The H2 i s added through a woven wire niesli faceplate * AlAA MEMRER Copyrighr 1990 hy Uniretl Trclmologirs Corpor;xion. Published hy $lie Americnn I i i s i i lme of Aerwwr ics anti AsirOiiautiCS. Inc.. will) permission Earlier measurement techniques had problems \vliicli resulted in data of questionable accuracy. Fei-renberg, et a l . and Louniie have recently used advanced. laser diagnostics to characterize rocket injector^.'-^ This work coiitiiiites the process of t l i e interrogation of sprays generated by rocket injectors with advanced laser diagnostics. The objective of tl ie work described in t l i i s paper was to detertiiitie the spray characteristics of like-on-like doublet impinging injectors with fluids and flow conditions as close to rocket injector conditions as possible. The United Teclinologies Research Center (UTRC) High Pressure Spray Facility was used during this investigation. This facility has been used in other rocket injector spray studies.? T h e effect of liquid properties, chamber conditions, and flow conditions on t l ie spray character of like-on-like doublet impinging rocket injectors was investigated using photographs, a Malverii Droplet Size Analyzer, and an Aerometrics Phase Doppler Panicle Analyzer (PDPA) Experinienta! Facility The UTRC High Pressure Spray Facility was used during this investigation. This facility was designed to allow the use of various liquid siiiiulants and the nieasurenient of droplet sizes at high pressure. The High Pressure Spray Faciliry f low system is shown in Fig. 1. Either low velocity (0.9 mis to 8 mis (3 fps to 27 fps)) NZ or air can be used as t l i e bulk gas which flows through the facility. This bulk gas can be heated up to 540 C (1000 F) by an electric resistance air heater. The i l ia in roles of tl ie bulk gas are to help reiiiove the spray from t l ie test section and to keep the windows clear of liquid. The spray i s generared in the test section which has a window on each side to allow, optical access. The facility can operate