支撑板结构对燃气轮机排气扩压器气动性能影响的数值研究

Numerical Study on Effects of Strut Structure on Aerodynamic Performance of Gas Turbine Exhaust Diffuser

关键词:  燃气轮机  排气扩压器  支撑板  静压恢复系数  数值模拟

Key words:  Gas turbine  Exhaust diffuser  Strut  Static pressure recovery coefficient  Numerical simulation

摘要:

支撑板结构直接影响燃气轮机排气扩压器的气动性能。采用求解三维RANS（Reynolds-Averaged Navier-Stokes）的方法，在考虑燃气涡轮末级叶片导致的气流预旋的条件下，探究了支撑板的数目、轴向位置、倾斜角度这三个几何参数对排气扩压器气动性能的影响，并基于正交试验原理，探究了不同几何参数对排气扩压器气动性能影响程度的差异。结果表明：支撑板数目的减少和轴向位置更靠近出口可以有效提升排气扩压器在不同进气预旋下的静压恢复系数，支撑板的倾斜设计在进气预旋小于0.48时，能有效提升排气扩压器的静压恢复系数，但在进气预旋大于0.48后，则会带来不利影响。基于正交试验原理的数值计算则表明，在进气预旋为0.12时，支撑板数目、轴向位置、倾斜角度三个因素变动对排气扩压器静压恢复系数的影响相近，进气预旋为0.35时，三者对静压恢复系数影响的贡献率分别为40.2%，30.9%，7.3%。进气预旋为0.89时，三者的贡献率分别为32.3%，22.2%，19.8%。

Abstract:

The strut structure directly affects the aerodynamic performance of the gas turbine exhaust diffuser. Considering the inlet pre-swirl caused by the last stage blade of the gas turbine， the three-dimensional Reynolds-Averaged Navier-Stokes （RANS） method is used to explore the influence of the number， axial position， and skewed angle of struts on the aerodynamic performance of the exhaust diffuser. At the same time， based on the principle of orthogonal test， this paper explores the difference of the influence degree of different geometry parameters on the aerodynamic performance of exhaust diffuser. The results show that the reduction in the number of struts and the axial position of strut closer to the outlet can effectively increase the static pressure recovery coefficient of the exhaust diffuser under different inlet pre-swirls. When the inlet pre-swirl is less than 0.48， the skewed design of the strut can effectively improve the static pressure recovery coefficient of the exhaust diffuser， but when the inlet pre-swirl is greater than 0.48， it will have an adverse effect. Numerical calculations based on the principle of orthogonal test show that when the inlet pre-swirl is 0.12， the number of struts， the axial position， and the skewed angle contribute similarly to the change in the static pressure recovery coefficient of the exhaust diffuser. When it is 0.35， the contribution rates of the three factors to the change of static pressure recovery coefficient are 40.2%， 30.9%， and 7.3%， respectively. When the inlet pre-swirl is 0.89， the contribution rates of the three factors are 32.3%， 22.2%， and 19.8%， respectively.