Numerical Study On Air Throttling Influence On The Performance Of Combustion In The Scramjet Combustor

Fuel/air mixing、 ignition transient and flame stabilization are the keys indesigning scramjet combustor in a high-speed environment. Air throttling produces aproper shock train to improve the local temperature、local pressure and reduce thelocal Mach number, mix fuel and air effectively, facilitate ignition transient and flamestabilization. The effects of air throttling on scramjet combustor were studied bynumerical simulation solved by unsteady N-S equations and experimental methods.This study is consisted of five parts. The investigation on air throttling and thesignificance on air throttling are introduced in the first part. The numerical methods,unsteady N-S equations and solving methods included, and experiential facility withmeasure ways were discussed in the second part. The flow structure and fuel/airmixing on the scramjet combustor were studied in the third part, the study was basedon the inflow condition Ma=4, the flow structure and fuel/air mixing with andwithout air throttling in scramjet combustor were compared to show the results: aproper shock train is produced to improve the local temperature、local pressure andreduce the local Mach number, vorticities diffuse to the main flow path, fuel/air mixedwell. The study on air throttling influence of ignition transient and flame stabilizationin the scramjet combustor were researched in the fourth part, the evolution of thecarbon dioxide field in the scramjet combustor during the ignition transient(0~1ms)with and without air throttling was studied to show the results: ignition of thefuel(C2H4) is achieved successfully in both cases, but the flame diffuses to the mainflow path in the “with air throttling” case, the other one doesn’t, the flame is onlysteady in the shear layer near the wall. With the time goes on, the flame goes outgradually in the “without air throttling” case, but the flame goes on in the “with airthrottling” case, flame stabilization is achieved successfully in this case, the wallpressure calculated is matched to the experiential data well. The influence ofparameters of air throttling on the scramjet combustor, the flux、location and timeincluded, was discussed in the fifth part, the results show: parameters of air throttlinghave great effects on the air throttling result, choosing right parameters of airthrottling is very important.