变几何低压涡轮气动性能研究

Research on Variable Geometry Low Pressure Turbine Aerodynamic Performance

关键词:  变几何涡轮  厚前缘  后加载  负攻角  大扩张角  端壁径向间隙

Key words:  Variable geometry turbine  Thick leading edge  Aft-loading  Negative incidence  Large expansion angle  Endwall radial gap

摘要:

为了探索变几何涡轮气动设计方案，导向器与动叶均采用厚前缘与后加载型叶片设计以及动叶进口负攻角设计。为了提高涡轮输出功，低压涡轮采用了大流道扩张角设计。应用数值方法对此设计涡轮进行了不同导向器开度以及有无导向器端壁径向间隙的涡轮气动性能与流场结构特性研究，并对大流道扩张角的导向器端壁径向间隙变化进行了理论分析。结果表明在设计点工况下，基本涡轮效率为0.903，相对折合流量为1.006，满足设计需求；大流道扩张角下，导向器端壁径向间隙对涡轮性能影响很大；在设计工况下，随着导向器开度的逐渐关小，涡轮主要气动参数反力度降低，通流流量下降，而效率变化相对较小，有利于调节发动机工作状态。在非设计工况下，涡轮效率随膨胀比变化亦相对较小。可见此设计变几何涡轮给发动机带来较大收益。

Abstract:

To explore the variable geometry turbine aerodynamic design plan， the thick leading edge and aft-loading blade is used both in the rotor and stator， and inlet negative incidence design is adopted by the rotor. In addition， the large expansion angle of meridional channel were used in low pressure turbine to improve the output power. Aerodynamic performance and flow filed of the turbine were analyzed by numerical method at the different stator opening with the stator radial gap or not， and the variation of endwall radial gap was analyzed at large expansion angle of meridional channel condition by the theoretical method. It is shown that at the design point the basic turbine efficiency is 0.903， and the relative corrected mass flow is 1.006 which both meet the design requirement. However， the endwall radial gap has a large influence on the turbine performance at large expansion angle of meridional channel condition. At the design condition， with the stator generally closed， the main aerodynamic parameter of reaction is decreased， the mass flow is reduced shapely， and the variation of efficiency is relatively small which will lead to the engine working condition being changed obviously. At off design condition， the efficiency variation also is small with the expansion ratio changed. It is visible that the variable geometry turbine will bring great advantages to the engine.