Investigation Of The Mixing Enhancement In Ejector Mode Of Strut-jet Engine

In recent years, the world regards RBCC (rocket based combined cycle) propulsionsystem as an effective way of single stage to orbit and reusable target, and carried outdepth research related to RBCC through a series of programs and projects. The RBCCcontains four work modes, one of them is the ejector mode, which is the optional powerprogram of RBCC take-off stage. Since this propulsion can achieve self-takeoff function,and can achieve the integration of the engine structure, the RBCC received lots ofconcerns. Aiming at the poor mixing effect in ejector mode, this paper mainly focus onnumerical simulation, experimental studies and theoretical analysis to study the mixingenhancement in RBCC ejector mode, mainly including mixing enhanced programdesign in RBCC ejector model, mixing enhanced project on the effects of strut-jetengine flow parameters and the strut-jet engine performance under cold flow conditionsthrough the simulation research and experimental research, the effect of the secondaryflow parameters on the engine performance as well as the effect of the mixingenhancement on the combustion efficiency through the simulation research.For the numerical simulation part, through the simulation of strut-jet engine modelunder cold flow conditions, the following main conclusions are made: in the differentmixing enhancement project， the lobed nozzle project is the superior to others, theequal-section project in the lobed nozzle has the optimal mixing effects, a lager thrustvalue, a lower compression ratio and a higher ejecting coefficient; in the study for thedifferent incoming flow parameters, as mach number of the primary increases, themixing effect become worse, the thrust is decreasing, and the ejecting coefficient isincreasing with the mach number increasing; in the study of different total pressure ofprimary flow, with the total pressure increasing the mixing effect of no mixingenhancement project and vortex project become good, but in the lobed nozzle project,when the total pressure is1Mpa and3Mpa, the mixing effect is the best, with the totalpressure increases the thrust increases, the ejecting coefficient decreases; in the studyfor the different Mach number of secondary flow, with the increase of Mach number insecondary flow, the mixing effect becomes good, the compression ratio of theequal-section lobed nozzle project is still minimal, the ejecting coefficient grows withthe increase of the secondary flow mach number. In the combustion simulation, theimportant conclusions are made as follows: the expansion and contraction part of thelobed nozzle produce different effects in the flow field behind; lobed nozzle projectpromotes the mixing effect in the cross-section, and increase the process of the reaction;in the lobed project, the lobes causes a certain energy loss, however, with the X/Lincreasing, due to the effect of the lobes, the combustion in the lobed project is betterthan the no mixing project, the energy generated is more than no mixing project, the average total temperature values in the cross section where X/L>6.67is higher than nomixing project; the thrust in the lobe project is more than the no mixing project.For the experimental part, the important conclusions are made as follows: themixing effect of the equal-section lobed nozzle project is the best, but there is alsoexistence of a larger total pressure loss; with the total pressure of the primary flowincreasing, mixing effect on the cross-section is improving, at the same time, the secondflow rate also varies, but the change is only slightly; with the increase of the secondaryentrance area, the second flow rate increases, the secondary flow rate changes little, inthe flow field mixing effect deteriorates in cross section.