Comparison And Analysis Of Influences On Scramjet Combustor Performance

Hypersonic technology has developed widely in some countries around the world,combustor is a core part of the scramjet engine.This paper evaluated combustor performance,studied various influence factors on main parameters and combustion mode by numerical simulation methods.Based on unsteady quasi-one-dimensional Euler equations,the model accounted for variable area,fuel addition,variable specific heat,wall friction and heat loss and chemical equilibrium reactions,etc.Using Fortran language,one-dimensional program was obtained,which can calculate steady operating processes of combustor under indefinite shock location.The convective flux terms can be solved respectively by Roe or AUSM scheme.Fuel addition adapted the exponential mode.The source terms were solved by time splitting and second order Runge-Kutta method.Combustion used model where there are 13 species and 7 reactions,and introduced equilibrium constant method to calculate gas components and combustion releasing heat.This paper simulated the chemical reaction flow field of combustor by the time stepping approach,gained the results of the distributions law of Mach number,pressure ratio,static temperature,etc.compared with experiments from references,and analyzed the influence of oil-gas ratio,friction coefficient and pollutant compositions.The calculation results showed: Oil-gas ratio has a serious influence on combustion mode,but in common range friction coefficient has no substantial impact;Under the case of oil-gas ratio 0.35,static pressure and temperature are higher where inflow compositions contained water;One-dimensional program can provide rapid performance evaluation for scramjet combustor.Applying Fluent,this paper carried out multidimensional steady combustion flow field computation.Combustion model selected finite rate/eddy dissipation,turbulence model selected RNG K-?,this paper adapted density-based AUSM+ implicit algorithm when solving equation,and analyzed the influence of oil-gas ratio and pollutant compositions.Three-dimensional computation had results in good agreement with experiments from reference.Three-dimensional computation results such as pressure ratio,temperature,Mach were conducted mass-weighted average along the flow direction distribution.Compare with one-dimensional those showed: The changing tendency of parameters was in agreement with combustor operating mode;With oil-gas ratio increasing,fuel and disturbance caused by fuel injection spread to the upstream gradually,subsonic region expanded,combustor converted to thermodynamics choke;Under the case of oil-gas ratio 0.35,combustion main region diffused to main flow obviously when inflow compositions contained water.