Abstract
As a key component-connecting compressor and the entrance of combustion chamber, the diffuser is able to increase the pressure and slow down the airflow in order to promote efficient combustion as well as avoid a large amount of pressure loss. In this paper, experimental investigation and numerical studies have been carried out to understand the effects of air bleeding from dump region and dump gap ratio on the total pressure loss and static pressure recovery of the dump diffusers. The ultimate objective is optimizing the dump diffuser design to get the maximum static pressure recovery and minimum total pressure loss. A simplified test model is used to study the effect of the air bleeding from the outer dump region and the dump gap ratio on the total pressure loss and static pressure recovery in the dump diffuser. The impact of the dump gap ratio in the performance of the dump diffusers has also been discussed. Nearly all the pressure raise occurs in the prediffuser, and most of the total pressure loss occurs in the dump region. For the recirculating area in the dump region, the controllable vortex can be introduced. Bleeding air from the outer dump region can improve the velocity distribution near the flame tube. The results show that when 0.4% of the air is bled from outer dump region, the performance of the dump diffuser is optimal. Hence, the controllable vortex method is effective for improving the performance of the dump diffuser.
Highlights
The performance of an aircraft cannot be improved without the support of an aeroengine which directly determines the flight characteristic, and the combustor is one of the three key components of aeroengines, which directly affects the engine performance
The results indicate that the dump gap could affect the flow distribution and the total pressure loss
The pressure distributions of the top and under walls of the prediffuser and the flame tube are presented in Figures 13–15, and 16
Summary
The performance of an aircraft cannot be improved without the support of an aeroengine which directly determines the flight characteristic, and the combustor is one of the three key components of aeroengines, which directly affects the engine performance. With high-performance compressor, the compressed air at compressor outlet is accelerated to 170 m/s or higher. If the compressed air flows into the flame tube without being decelerated, it may cause serious problems on combustion stability and high total pressure loss. The gas turbine diffuser system is used to resolve the problems listed above. It is employed to decelerate the compressor discharge flow and distribute the air around the flame tube uniformly and stably. The diffusion process must be accomplished with minimum total pressure loss because these parasitic losses have an adverse effect on the thermal efficiency of the whole engine
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