Quasi-One-Dimensional Theoretical Analysis Of Ejector Mode Of Rocket-Based Combined Cycle Engine

In the study of the Ejector Mode of Rocket-Based Combined Cycle ( RBCC ) engine, it's a simple, fast and effective research approach to build up a quasi-one-dimensional simplified theoretical calculation & analysis model. With the simplified model of a strutjet-mixer( constant cross section )-diffuser style for RBCC Ejector Mode as an object, this paper applied the classical ejector theory to studying the operation trends, fundamental performances and parameter effects of the RBCC Ejector Mode for the case without secondary combustion, and made a reasonable design for the fundamental parameters of the RBCC Ejector Mode. Here presented the major content below.To begin with, the characteristics of the common ejector and the RBCC Ejector Mode were reviewed, and their correlations and distinctions were summarized. At the aim of widening the classical ejector theory and applying it to the study of the RBCC Ejector Mode, a quasi-one-dimensional theoretical calculation & analysis model for the case without secondary combustion was built up.As to the problem of the double-solution of the Mach number at the mixer outlet of a supersonic ejector, which was not solved theoretically in the ejector history, a criterion was put forward to identify the solutions of the Mach number at the mixer outlet, according to the physical process of streams'passing through the divergent section. The criterion was validated with the help of a set of experimental data from a literature. Results of some preliminary applications indicated, with the strut-mixer area ratio ofψ=10% and the ejector-nozzle outflow Mach number of M 1=3.0, if the total pressure of the primary flow p0 1 was higher than 5 MPa, the Mach number at the mixer outlet must be supersonic. And it's the main innovation in the paper.With the effects of the back pressure of the outflow and the total pressures of the secondary and primary flow being taken into consideration, the operation regimes of the RBCC Ejector Mode were distinguished, and their parameter conditions and transformation trends were also discussed in detail. Moreover, the effects of deviating from the 3rd critical regime on the fundamental performances of the RBCC Ejector Mode were studied. The thrust-economy performances for each critical regime were compared and concluded. As to the RBCC Ejector mode without secondary combustion, the analyses indicated that the 3rd critical regime showed the optimal thrust-economy performances because of comparatively higher performances for inner-thrust, inner-thrust-augmentation and propellant-pecific- impule than another two critical regimes. The effects of some key parameters on the ( 2nd & 3rd ) critical ejector coefficient were discussed in detail and the possibilities of achieving each critical regime were analyzed. In the framework of the 3rd critical regime, the effects of the parameters of the primary-nozzle on the fundamental performances of the RBCC Ejector Mode were discussed. Further, with the optimal thrust-economy performances in the 3rd critical regime as a target function, a set of preliminary arrangements were made for the fundamental parameters of the RBCC Ejector Mode. The results indicated, for the instances ofΠ0=40, 60, 80 and 100, a set of corresponding values for the ejector-nozzle outflow Mach number M 1 were supposed to be 2.98, 3.20, 3.35 and 3.47 respectively, and the values for the strut-mixer area ratioψwere supposed to be 0.18, 0.16, 0.14 and 0.13 respectively.