支撑板构型提升燃气轮机排气扩压器气动性能研究

Study on the Strut Structure in Improving Aerodynamic Performance of Gas Turbine Exhaust Diffuser under Different Inlet Preswirls

为提升排气扩压器的气动性能,基于燃气轮机排气扩压器典型支撑板结构,提出了带有弯度的直列支撑板(结构B)和弯扭支撑板(结构C)2种新构型支撑板。采用数值求解三维Reynolds-Averaged Navier-Stokes(RANS)的方法研究了2种新构型支撑板在4种进气预旋下对排气扩压器气动性能的影响。基于安装典型结构支撑板的排气扩压器的实验测量数据,验证了数值方法的有效性。研究表明:进气预旋为0.35和0.48时,3种不同形状支撑板对排气扩压器总压损失系数没有产生明显的影响,但由于结构B支撑板附近的分离流对出口流动结构影响更大,使得动压系数显著降低,进而导致静压恢复系数下降。结构C支撑板则没有对排气扩压器的静压恢复系数产生明显影响。随着进气预旋增加,结构B和结构C支撑板显著减弱了轮毂附近的角区分离流,使得总压损失系数下降的同时,动压系数有所增加。相比于原始结构支撑板,结构B和结构C支撑板在进气预旋为0.64和0.89时显著增大了排气扩压器的静压恢复系数,其中结构C支撑板将静压恢复系数分别提升16%和23%。所提出的结构C支撑板能够有效提高大进气预旋下排气扩压器的气动性能,有效拓宽了排气扩压器的高效工作范围。

To improve the aerodynamic performance of the exhaust diffuser,two new types of struts:bend strut(structure B)and twist strut(structure C),are proposed in this paper for comparison with the strut of a conventionally typical structure.The aerodynamic performance of the exhaust diffuser with these new struts at four different inlet pre-swirls is numerically computed and analyzed using three-dimensional Reynolds-averaged Navier-Stokes(RANS)solutions.The numerical approach is validated based on the experimental measurement data of the exhaust diffuser with the strut of a conventionally typical structure.The results show that when the inlet pre-swirl is 0.35 and 0.48,the struts of these three types of structure have no significant effect on the total pressure loss coefficient of the exhaust diffuser.However,the separation flow near Structure B has a greater impact on the outlet flow,resulting in a significant decrease in the dynamic pressure coefficient,which in turn leads to a decrease in the static pressure recovery coefficient.Structure C has no significant effect on the static pressure recovery coefficient of the exhaust diffuser.With the increase of the inlet pre-swirl,Structures B and C significantly weaken the corner separation flow near the hub,so that the total pressure loss coefficient decreases while the dynamic pressure coefficient increases.Compared with the strut of a conventionally typical structure,Structures B and C significantly increase the static pressure recovery coefficient of the exhaust diffuser when the inlet pre-swirl is 0.64 and 0.89,and Structure C increases the static pressure recovery coefficient by 16%and 23%respectively.Namely,Structure C can improve the aerodynamic performance of the exhaust diffuser at high inlet pre-swirls and widen its efficient operating range.