A numerical investigation has been conducted for an axisymmetric dump diffuser combustor after the validation of an asymmetric diffuser test case. The dump combustor is a simplified geometry of a typical lean-burn combustor in a modern civil aero-engine gas turbine. The aerodynamic performance of the dump diffuser combustor is analyzed with an emphasis on two common performance parameters: static pressure recovery and total pressure loss. The former is essential to maintain high-pressure air flow across the liner, whereas the latter involves the specific fuel consumption of the aero-engine. At first, the effects of geometrical parameters of the dump diffuser combustor are investigated. A high diffuser angle seems to be detrimental to both static pressure recovery and total pressure loss. On the other hand, a high dump gap ratio is beneficial on the aerodynamic performance point of view. However, all these desired characteristics are subject to mechanical constraints and their implications on specific consumption. An optimum value of those parameters should exist for a given desired aerodynamics performance. The majority of previous researches, including the first part of this study, has been carried out with the uniform inlet conditions due to a typical independent design cycle of each component. The effects of compressor exit conditions are usually not considered in the early stage design process. In the second part of this study, various inlet conditions representing a more realistic compressor exit condition such as inlet symmetrical and asymmetrical boundary layer thickness are investigated. The performance of an asymmetrical configuration with a thin boundary layer thickness near the outer annulus is almost comparable to that of its uniform counterpart. Therefore, the recent observations open a new design space for the combustor design engineer to improve the combustor’s performance based on the conditions of compressor exit.


Numerical Investigation of Dump Diffuser Combustor Performance at Uniform and Non-Uniform Inlet Conditions

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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