Study on the Performance of a Novel Air-bleeding Aerodynamic Combustor Diffuser

Abstract

The pressure ratio of a compressor increases when the engine performance is improved, which leads to a higher air velocity in the combustion chamber. This aggravates the pressure loss in a conventional diffuser, which is proportional to the square of the inlet velocity. It is, therefore, an urgent need for a new diffuser technology. Regardless of whether high-temperature, or low-pollution, combustion chambers are being used, the significant difference when compared with other chambers is the notable increase in the combustion air and its entry through the dome of the flame tube. However, the increased amount of air in the dome causes a mismatch between the diffuser outlet and the dome intake of the flame tube. Therefore, to solve the problem of an excessive total pressure loss and a mismatch of the intake air in the combustor, a novel air-bleeding aerodynamic diffuser has here been proposed. The effects of various parameters (including the number of air-bleed holes, the position of the first row of holes, and the position of the second row of holes) and their interactions on the performance of this diffuser have then been investigated by using the experimental design presented by Taguchi. The maximum static pressure recovery was achieved by using a genetic algorithm combined with the CFD method. Among the three parameters, the results revealed that the position of the first row of holes had the largest impact on the performance of the diffuser. Also, the optimal values of the three parameters varied for the inlet Mach numbers 0.10, 0.15, and 0.20. The relative difference between the predicted values and the values obtained by the numerical simulations were all below 3%, which showed the reliability of the predictions. As compared with the reference case, the optimized results for the three working conditions increased by 19.16%, 21.38%, and 40.62%, respectively.

Keywords

• gas turbine combustor
• combustor diffuser
• diffuser performance
• optimization
• flow characteristics
• air bleeding aerodynamic diffuser