Investigation On Detonation-Wave/Boundary-Layer Interactions In Supersonic Flows

Detonation-wave/boundary-layer interactions(DWBLI)in supersonic flows is an important flow and combustion regime for the oblique detonation engine(ODE).It can significantly influence local combustion and stabilization of the oblique detonation wave(ODW)and thus the engine performance.Since ODE is still at conceptual stage,what people know about DWBLI is now far from enough in contrast to that of shock-wave/boundary-layer interactions(SWBLI).In this paper,DWBLI is investigated through combination of theoretical analysis,numerical simulation and experiments.First,the reflection of an oblique detonation wave(ODW)in inviscid supersonic flows was studied.Basic ODW's equations with varying specific heat ratio(gamma)and the detonation polar were analyzed.The polar expression of ODW's reflection was discussed via two-and three-shock theories,confirming the regular reflection domain,Mach reflection domain and double solution domain within which the regular reflection is unstable and hysteresis phenomenon exists.It was pointed out that the ODW's stabilization domain shrinks in a confined room because of its reflection on the wall.The applicability of two-and three-shock theories was discussed and it was discovered that the two-and three-shock theories had their own limitations when used in the ODW's reflection problem,which was due to the discrepancy of the single-front hypothesis of two-and three-shock theories and the truth of non single-front of a detonation wave.The theories are quasi correct when the detonation wave is near the chemical equilibrium limit.Otherwise,the application of two-and three-shock theories would bring in considerable errors.The reflection of an incident ODW under viscous condition and the DWBLI were studied.Wave characteristics of the flow field of DWBLI were analyzed.Possible wave combinations were pointed out and numerically investigated.Results showed that both adverse pressure gradients and chemical reactions in separation zone affect the separation scales.Chemical reactions in separation zone makes the separation scales increase and the flow near separation point non isentropic.Thus,the pressure plateau of DWBLI flow field cannot be predicted using the free-interaction theory.It was pointed out that the separation wave style(shock wave or detonation)could influence the pressure plateau and the scales of the separation zone.When the separation wave is respectively a shock wave and a detonation,the plateau of the separation region is higher for the former than for the latter.This is because the reaction of the separation region for the former is more violent than for the latter,and thus the non isentropic effect for the former is also stronger.Meanwhile,the scales of the separation region is smaller for the former than for the latter.The reason is that the higer pressure of the separation region for the former provides stronger resistance against the total adverse pressure gradients.The hysteresis phenomenon of ODW's reflection under viscous condition was investigated.It was shown through polar analysis that the viscous reflection solutions were much different from inviscid ones.Moreover,the different separation wave styles lead to different reflection solutions.In the numerical simulations,turbulence intensity of incoming flow can significantly influence the hysteresis phenomenon.For low turbulence intensity or a laminar flow,the hysteresis phenomenon can be obtained through numerical simulations.However,for high turbulence intensity,It cannot be obtained in simulations and the regular and Mach reflection would transit to each other in a successive manner.Whether this phenomenon is true in physics is to be validated in experiments.Ramp-induced DWBLI(RDWBLI)was studied thereafter.The initiation of an ODW was experimentally investigated in a high-enthalpy supersonic premixed wind tunnel.Key factors of ODW's initiation was analyzed and it was discovered that the Mach number and temperature of incoming flow both had positive and negative effects on ODW's initiation.The experiment also discovered that the boundary layer effect can significantly influence the morphology of an ODW.That is,for small scales of separation,the ODW is at an abrupt manner and for large scales of separation,it is at a smooth manner and for middle scales of separation,it is at an intermittent abrupt manner.This boundary layer effect was also confirmed through numerical simulation.Besides,the RDWBLI flow fied was compared to that of incident-ODW/boundary-layer interactions,which showed that such two types of flow field were similar only when the styles of sepration waves were the same.Finally,the initiation and propagation of detonation in other types of shear flows were investigated.The characteristics of the flow field of ODW/cavity-shear-layer interactions was analyzed.It was discovered that the ODW after reattachment of cavity shear layer had the structure of double slip lines.The initiation and stabilization of an ODW in nonuniform flows were studied.Results showed that the ODW presented satisfactory adaption to the nonuniformity,realizing its initiation and stabilization.This is of benefit to the ODE at high flight Mach numbers because the requirement for uniformity of incoming flow is considerably reduced.Besides,detonation initiation and propagation through over-expansion shock wave in a supersonic flow was numerically validated.The initial propagation velocity of detonation after initiation increases with the back pressure,and it rapidly decades in its later propagation process.