涡轮间隙泄漏涡破碎对损失的影响

采用数值方法联合标准k-ω两方程湍流模型求解雷诺平均Navier-Stokes方程组，研究了不同间隙高度下GE-E³（Energy Efficient Engine）涡轮第一级动叶顶部间隙泄漏涡（TLV）的破碎特性及其对泄漏损失的影响。首先描述了泄漏涡的破碎现象，并对其动力学特性进行了理论分析，接着研究了间隙高度对泄漏涡结构及破碎特性的影响，最后对泄漏涡破碎与损失的关系进行了探讨。研究结果表明：涡轮叶顶间隙泄漏涡具有不稳定特性，当泄漏涡具有足够的强度可以克服通道涡卷吸形成完整涡结构时，在叶片后半部分逆压区发生了涡破碎现象，带来了额外的涡破碎损失；间隙高度对泄漏涡破碎位置的影响比较明显，在大间隙下泄漏涡趋于相对稳定；叶顶泄漏流产生的掺混损失以泄漏涡的破碎为标志分为两个阶段，大量的掺混损失发生在泄漏涡破碎之后，这也是叶顶泄漏流产生损失的主要部分。

Effect of Tip Leakage Vortex Breakdown on Losses in Turbines

Numerical investigation is performed to simulate the tip leakage vortex (TLV) breakdown characteristics and its effect on leakage losses in the first-stage rotor blade of GE-E³ (Energy Efficient Engine) turbines at various tip clearances, by solving the Reynolds-averaged Navier-Stokes equations in conjunction with a standard k-ω two-equation turbulence model. The tip leakage vortex breakdown phenomenon and its dynamics are analyzed; so are the effects of tip clearance height on the tip leakage vortex structure and the vortex breakdown characteristics. Furthermore, the relationship between the tip leakage vortex breakdown and losses is investigated. Numerical results show that the turbine tip leakage vortex is unstable. When the tip leakage vortex has sufficient strength to overcome the entrainment of the tip passage vortex, and forms a complete vortex structure, the tip leakage vortex breakdown is initiated in the adverse-pressure region of the second half of the rotor blade, which leads to extra vortex breakdown losses. The tip clearance height has a great impact on the vortex breakdown location, and the tip leakage vortex tends to be relatively stable at large tip clearances. The tip mixing losses are divided into two stages marked by the tip leakage vortex breakdown. A lot of mixing losses occur after the tip leakage vortex breakdown, which is the main part of the tip mixing losses.