【作者】 王凯；

【导师】 王仲奇； 王松涛；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2009， 博士

【摘要】 现代航空燃气涡轮发动机为了获得更高的推重比和热效率,不断提高涡轮前温度,精简涡轮级数。高温、高膨胀比必然带来涡轮内部流动的局部超声速。国际上先进气冷涡轮气动设计的理念是在不影响涡轮做功能力的前提下,实现叶片表面的冷却效果最大化。这使冷气与主流的掺混研究成为涡轮研究设计中的一个关键问题。本文主要对尾缘冷气喷射形式对流场的影响、考虑冷气喷射影响的叶型设计以及非定常条件下局部优化设计对流场的影响进行了深入分析和研究。本文首先通过对高压涡轮静叶尾缘不同方案的冷气喷射数值模拟,分析了不同冷气喷射方式以及不同冷气喷射量对于静叶尾缘激波强度和下游动叶流场的影响。研究发现,采用压力面尾缘斜劈缝冷却对于减弱尾缘激波强度,减小掺混损失,改善流场流动有优势。采用尾缘对开缝冷却,可以削弱尾迹涡对强度,减小尾迹损失,但是掺混损失较大。动叶进口气流角随着冷气注入量的增大而减小,冷气喷射对动叶栅顶部马赫数影响要较其他部分弱。然后,探讨了具有凹陷特征的跨声速气冷涡轮叶型以及在静叶吸力面激波反射点进行冷气喷射来削弱激波强度的可行性。结果表明,具有前缘凹陷特征的气冷涡轮叶型可以把冷却气体以冷气旋涡的形式控制在其凹陷部位;与传统叶型比较,新型叶型的主流流动较合理。在吸力面激波反射点附近喷射冷气是一种行之有效的控制激波强度的方法;冷气喷射位置位于激波反射点附近时注入冷气对减弱激波强度有积极作用。接着,本文又详细研究了有静叶尾缘冷气喷射条件下的跨音速高压涡轮级内的流动规律,探讨了静叶尾缘激波对于附面层分离以及下游动叶流动的影响、采用正弯静叶片后对于级内激波强度的削弱带来的积极影响以及上游静叶变化对于下游动叶流动的影响,为高压涡轮级内冷气与主流掺混对流动影响的研究提供了必要的知识储备和理论依据。实验研究不能完全模拟航空发动机的实际工作条件,利用数值模拟的优势深入研究涡轮叶片的实际工作状态具有很重要的工程意义,本文为了更加深入研究高压涡轮级内的真实流动特性,对无冷气喷射和有尾缘冷气喷射情况下的各种方案的涡轮高压级进行了详细的非定常数值模拟和分析。研究发现,跨音速涡轮静叶受非定常势流影响的主要区域集中在吸力面扩压段到尾缘区域,动叶表面压力的非定常波动非常明显,叶片负荷变化很大;静叶尾缘激波强度呈现周期性变化,相对来说尾缘激波的压力面分支受下游动叶周期性运动的影响较小;尾迹涡对的吸力面一侧涡受到动静叶间的非定常干扰影响较小,而压力面侧尾迹涡受非定常效应影响较大,旋涡强度变化较剧烈。尾迹传播方向随着下游势流的变化而产生相应的变化;采用正弯静叶片后,下游动叶中部截面的非定常波动幅度有所增强,动叶根部和顶部截面的静压波动幅度较采用直静叶时要小;当采用压力面斜劈缝冷却时,尾迹涡对的压力面一侧涡受非定常效应的影响较大;尾迹受到下游动叶势流影响传播方向也发生周期性的变化;当采用尾缘对开缝冷却时,尾迹涡对受到下游动叶势流影响非常小,且尾迹受到下游势流的影响也较小,尾迹传播方向的非定常波动幅度很小;静叶尾缘冷气喷射后下游动叶30%弦长前负荷减小,30%弦长后较静叶不喷冷气时负荷增大。更多还原

【Abstract】 In order to obtain higher thrust weight ratio, nowadays, aero engine improves inlet temperature of turbine and reduces turbine stage constantly. High temperature and high expansion ratio lead to local transonic in the turbine. The advanced air-cooled turbine aerodynamic design idea is to realize blade surface’s maximum cooling effect, base on there is not effect on performance ability of turbine. It makes the research of cooling air and main stream mixing become to a key problem in the turbine design. In this paper, the effect of trailing cool-air injection on flow field, the blade profile design which consider the cool-air injection effects and effect of unsteady local optimize design on flow field have been analyzed and studied in detail.At first, numerical simulations have been carried out on stator trailing cool-air injection in different schemes, the effects of different cool-air injection methods and different cool-air injection mass on the intensity of stator trailing shock wave and downstream rotor flow field have been analyzed. Result shows that, slot cooling on suction side of trailing edge can reduce the intensity of trailing shock wave and mixing loss, improve flow field. Slot cooling on trailing point can reduce the intensity of trailing vortex and trailing loss, but its mixing loss is bigger. Rotor’s inlet flow angle reduces with the mass increasing of cool-air injection. Effects of cool-air injection on the mach number of rotor blade shroud part is weaker than other parts.Secondly, the feasibility of a transonic air cooled turbine blade profile with depression feature at leading edge and injection cool-air at shock wave reflection point to reduce the intensity of shock wave has been researched. Results shows that, new blade profile can control the cool-air vortex in the depression part. Compared with traditional blade, new blade profile’s main flow is more reasonable. Injecting cool-air at shock wave reflection point is a feasibility method to reduce shock wave intensity. When cool-air has been injected near the shock wave reflection point, the cool-air injection has positive role on the reducing of shock wave intensity.Then, the flowing law of transonic high pressure turbine stage with stator trailing edge cooling has been studied in detail. The effects of stator trailing edge wave on the boundary layer separation and rotor’s flow field have been analyzed. Theory basis and knowledge reserve have been provided for the study of effects of cool-air and main flow mixing on flow. in high pressure turbine stage.Experimental study could not simulate the real working condition of aero engine entirely, so using the advantage of numerical simulation to study the real working condition of turbine blade has important project meaning. In this paper, in order to study the real working condition of flow field in high pressure turbine stage further, unsteady numerical simulations and system analyses have been carried out on different schemes of high pressure turbine stage with cool-air injection and without cooling. Results shows that, the effects of unsteady potential flow on stator is mainly in the range between suction side pressure expansion part and trailing edge part; the unsteady fluctuation on rotor’s surface is very obviously. Rotor’s loading change greatly. The intensity of shock wave at stator trailing edge become in periodicity. Relatively, the pressure side branch of trailing shock wave has been affected smaller by downstream rotor periodicity movement. There is small effect of rotor and stator’s unsteady interfere on suction side vortex of trailing edge vortexes, but the effect on pressure side trailing vortex is bigger and its vortex intensity changes acutely. The transfer direction of wake changes with the potential flow of downstream changing. After using positive bowed stator, the unsteady fluctuation of rotor’s mid-section has been increased, the fluctuations of rotor’s hub-section and shroud-section are smaller than using straight stator. When slot cooling on trailing edge of pressure side has been used, trailing vortexes’ pressure side branch has been influenced greater by unsteady effect and the wake’s spread direction changes periodically with the effects of rotor’s potential flow. When slot cooling on trailing point has been adopted, the potential flow of downstream rotor has very small effect on trailing vortexes and spread direction of wake. Cooling of stator trailing edge makes the rotor’s load reduce before 30% chord length and increase behind 30% chord length.更多还原