Study On Combustion And Flow Characteristics Of A Ramjet Swirling Trapped Vortex Combustor

Swirling trapped vortex combustor?STVC?which combines swirl and cavity to stabilize flame is put forward.Compared with a combustor with single flame stabilizing mode,flame stabilizing effect of STVC is more remarkable under the condition of high-speed inlet flow of ramjet combustor.In this paper,the numerical simulation method is adopted to study the STVC's flow and combustion characteristics in depth.The factors such as cavity structure size,inlet swirling strength,cavity fuel injection mechanism and performance of double cavity combustor under the ramjet condition,is taken into consideration.The aim of research is to provide a design idea for engineering.At first,the different cavity structure size and inlet swirl strength were simulated and discussed.The results showed that when L/D=0.72,H/D=0.5 and S=0.1 were selected,the drag coefficient of cavity was the smallest,a stable single vortex was formed in cavity,and the total pressure recovery coefficient of combustor was high.Therefore,an appropriate combination of cavity structure size and inlet swirl strength under the current flow condition was L/D=0.72,H/D=0.5 and S=0.1.On this basis,the mechanism of fuel injection in the cavity of combustor chamber was studied.By simulating fifteen different kinds of gaseous fuel injector positions,the results showed that in case10(y_fore=37mm,y_back=30mm),case11(y_fore=37mm,y_back=37mm)and case12(y_fore=37mm,y_back=42mm),the total pressure recovery coefficient under the nonreacting flowfields was higher than other conditions.However,the fuel injector positions effect on the combustion efficiency and total pressure recovery coefficient under reacting flowfields was negligible.In order to further analyze the combustor's performance with different total equivalence ratio,four different gaseous fuel massflow conditions were selected under the previous three fuel injector positions.The calculation results showed that the combustion efficiency was above 90%except for the extremely poor fuel conditions,and the combustion performance was better under the case 12 condition.In addition,the combustion performances of liquid fuel jet were analyzed under the same three kinds of injector positions.The results showed that the total pressure recovery coefficient of combustion chamber was higher than 80%,and the combustion efficiency was above 99%,which preliminarily proved the feasibility of liquid fuel combustion.In order to further improve the flame stability of the combustor,based on the original structure of the combustor,a dual cavity swirl trapped vortex combustor was designed and its performance was studied.The results showed that whether liquid fuel or gaseous fuel was injected,the introduction of cavity II could ensure the fuel combustion more efficient in shorter distance,which was beneficial to shorten the length of the combustor and improve the thrust-weight ratio of the engine.At the same time,the combustion efficiency maintained above 97%.