Research On Aerodynamic Performance Of Dump Diffuser In Axial Flow Combuster

The dump diffuser is an important part of the combustion chamber.Compared to the traditional Pneumatic diffuser,it has the characteristics of short length,compact structure and it is insensitive to distortion of inlet flow field.So it is widely used in modern aviation engines.But because of the existence of the dump region,the total pressure loss of the dump diffuser is higher and its performance is greatly reduced.This paper focuses on how to improve the aerodynamic performance of dump diffuser.The effects of several geometric factors and aerodynamic factors are studied to provide the basis for the design of dump diffuser and the selection of aerodynamic parameters.In order to raise the reliability of the study results,the experimental method are used to test the aerodynamic performance of several geometries and investigate the influence of each factor on their performance.Numerical simulations are used to verify the conclusions at the same time.In terms of geometric factors,the influence of divergence ratio and dump gap on its performance is mainly studied.In terms of aerodynamic factors,we studied the influence of inlet mach number,velocity distribution and flow distribution on the aerodynamic performance.In addition,the PIV experiment were carried out to measure the flow field of the pre-diffuser and the dump region.Within the parameters of this paper,the following conclusions are obtained:(1)The divergence ratio and the dump gap have a great influence on the aerodynamic performance of the dump diffuser.As the divergence ratio increases,the total pressure loss of pre-diffuser and whole decreases first then increases.The static pressure recovery coefficient first increases and then decreases.As the dump gap increases,the total pressure loss of pre-diffuser and whole decreases but the static pressure recovery coefficient increases.(2)With the increase in the inlet mach number,the total pressure loss of diffuser gradually increases.But the static pressure recovery coefficient is basically unchanged.(3)With the increase in the flow distribution,the total pressure loss appears to decrease first and then increase.The static pressure recovery coefficient is just the opposite.(4)The distribution of velocity has important influence on the performance of dump diffuser.(5)The CFD are used to simulate the typical structures and analyzed the geometric factors and aerodynamic factors on the performance of dump diffuser.Compared to the experiment,the numerical simulation results are consistent with the experimental results.