The momentum flux ratio is the key parameter in determining spray characteristics and mixing efficiency of the propellants in rocket injectors. The spray characteristics of oxygencentered kerosene-swirl coaxial (OCKSC)injector have been experimentally investigated through cold flow tests in atmospheric pressure and high back pressure. Mainly 4 categoried conditions were investigated through the cold flow tests. The spray process was obtained from analysis of high resolution digital images, thus to achieve the spray angle. The liquid and gas discharge coefficient increased as the flow rate pressure drop increasing. The spray angle became narrow with momentum flux ratio increasing. And also the spray flow field was numerically simulated to assist the analysis on the experimental data. The hot firing tests were under investigation to receive the relations that combustion efficiencies decreased as the mixture ratio and momentum flux ratio increased were obtained by far. Different recess length will be investigated in the future. Nomenclature d in = Gas inlet orifice diameter d g = Gas post diameter d 0 = Outer injector diameter A inj = Liquid inlet spiral groove cross section area d gap = Gap height t lip = Gas post lip thickness L = Recess length l inj = Total injector length P 0 = Outer ambient pressure P is = Inter-space pressure P g = Gas pressure ̇ = Mass flow rate of the gas = Gas post pressure drop = Velocity of Gas post outlet g µ = Gas post discharge coefficient = Liquid post pressure drop ̇ = Mass flow rate of the liquid = Velocity of liquid post outlet l µ = Liquid post discharge coefficient J = Ratio of gas and liquid momentum flux *= Characteristic velocity 1 Graduate student, school of astronautics, onecangzhitao@hotmail.com 2 PHD student, school of astronautics, tianliangg@sina.com 3 PHD student, school of astronautics, zhushaohua@sa.buaa.edu.cn 4 Professor, school of astronautics, xuxu@buaa.edu.cn Downloaded by ROKETSAN MISSLES INC. on February 7, 2015 | http://arc.aiaa.org |

A GO 2 /kerosene ejector rocket chamber was designed and tested to meet the requirements of the direct-connection tests of the RBCC engine model, and its performance was experimentally and numerically evaluated. Such an ejector rocket chamber is required to operate in a very wide range of total mass flow (̇= .~. / ). To realize such a wide work range by one set of ejector rocket chamber, double-recessed-coax-swirl (DRSC) spray nozzles were firstly designed and installed in a low mass flow rate range (̇=~/ ) ejector rocket chamber. The rocket was tested both separately and jointly with the RBCC engine. The * of the rockets were ranged from 88% to 98%, and it was positively influenced by the momentum flux ratio and the pressure drop ratio of the injector. The improved spray nozzles were used and tested perfectly in the high mass flow rate range ejector rocket chamber. No thermal damage occurred under all operating conditions, and steadily operation was achieved as well. NomenclatureC * = characteristic velocity ℎ * = theory characteristic velocity * = experimental characteristic velocity p c = rocket chamber pressure ̇ = total mass flow rate ̇O = oxygen mass flow rate ̇k ero = kerosene mass flow rate ̇N = force coefficient in the y direction A t = Area of the throat O/F = mixture ratio =m o /m f O2 = flow coefficient of oxygen kero = flow coefficient of kerosene O2 = pressure upstream of the oxygen sonic nozzle kero = pressure upstream of the kerosene venturi tube * = characteristic velocity efficiency g = outlet pressure of the gas hole g = jet velocity of the gas l = outlet pressure of the kerosene channels la = axis jet velocity of the kerosene = momentum flux ratio Δ = pressure drop Δ = pressure drop ratio1 PHD student, school of astronautics, zhushaohua@sa.buaa.edu.cn 2 PHD student, school of astronautics, tianliangg@sina.com 3 Graduate student, school of astronautics, onecangzhitao@hotmail.com 4 Professor, school of astronautics,