Parameter Optimization of Combustor Dump Diffuser Based on RSM

At present, dump diffuser is basically adopted in the combustion chamber of aeroengine. The total pressure loss in it may account for 30% or even higher in the combustion chamber. So it is necessary to optimize various geometric parameters in dump diffuser. In order to solve the problem of increasing experimental cost due to multi-parameter optimization, response surface method (RSM) was used to study the performance of dump diffuser’s three geometric parameters at three inlet Mach numbers (Ma = 0.27, 0.20 and 0.10), namely pre-diffuser expansion angle, dump gap ratio and side wall expansion angle. The ratio of static pressure recovery coefficient to total pressure loss coefficient was used to compare the performance of the diffuser. Also the distribution of entropy production rate was used to obtain the pressure loss in the diffuser and analyze the causes. Then the response model was established and the response equation was solved to obtain the combined parameters corresponding to the optimal solution. Finally, the optimization results were predicted and verified. We can see that the influence of three geometric parameters on the diffuser performance is the prediffuser expansion angle, dump gap ratio and the side wall expansion angle in descending order. Compared with the initial average performance, the optimized results under three working conditions are improved by 47.93%, 48.70% and 69.49%, and the relative errors are all less than 6.5%, showing high accuracy.