The Study Of The Multi-staged Supersonic Combustor Evaluation And Optimization

For single-stage dual-mode scramjet combustor, with the restrained geometry and maximum static temperature boundary, when it works in low Mach number at stoichiometric ratio, the back pressure caused by the combustion will push the shocktrain out of the isolator, which results in the inlet-unstart. The multi-staged combustor can solve the problem that the fuel equivalence ratio of a single-staged combustor is limited by the inlet-unstart. when the incoming flow Mach number is high(such as the Mach number 6 or 7), the maximum static temperature in the combustor caused by a high fuel equivalence ratio is beyond the material temperature ceiling, while the cooling system cannot meet the requirements. Thus a better engine performance will be acquired by a properly distribution of the heat release under the constrains of temperature and the inlet-unstart.In this paper, the dual-mode scramjet with multi-staged combustor is analyzed, Two-dimensional flow field is calculated by using FLUENT to study the influence of the heat release distribution in the combustor on the inner flow characteristics and the performance parameters of the dual-mode engine. The performance changing regulation of the dual-mode scramjet working at a wide range of free-flow Mach numbers are analyzed to obtain the working boundary and the mode distribution character under different flow conditions by using a one-dimensional engine model created by MATLAB/ Simulink. It is found that the combustion mode transition boundary, the inlet-unstart boundary and the temperature ceiling are different at the different flow conditions. Besides, the changing regulations of the engine optimal performances vary from each other under the different flow conditions and different total equivalence ratios: in terms of the engine uninstall thrust, the fuel equivalence under lower flow Mach number condition tends to be relatively higher in the second combustor stage and relatively lower in the first combustor stage. Nevertheless under the higher Mach flow conditions, the heat release tends to concentrate in the upstream.Based on the analysis of the engine characteristics under different working conditions, dual-mode scramjet performance parameters are optimized by using Genetic Algorithm according to different optimization purposes. The geometric configuration and the heat release distribution of the multi-staged combustor of the dual-mode scramjet which correspond to the optimal performance parameters are acquired. There is some reference value of the optimization results to the optimization of combustor geometric configuration and the heat release distribution.