无导叶对转涡轮尾缘激波对燃气入侵机理的影响研究

Due to asymmetric distribution of external mainstream pressure induced by rotor trailing shocks, the gas ingestion mechanism between conventional turbines and vaneless contra-rotating turbines is different from each other. In this condition, the influence of the trailing shock on the gas ingestion in a vaneless contra-rotating turbine will be investigated in this project: the effect of the railing shock on circumferential distribution of static pressures in the turbine rim seal will be analyzed. After that, the influence of rim pressure gradient on sealing performance of the turbine disk and the effect of the gas ingestion on the endwall losses will be explored. At last, the couple optimization design method of the rim sealing and turbine aerodynamic design will be conducted based on the previous results. The numerical simulation and analysis are used in this project to clarify the coupling relationships between the trailing shock strength and rim static pressure circumferential distribution, and to enhance the physical understanding of mechanisms in which the trailing shock affect the evolving of the vortex structure in the contra-rotating turbine disks, and to reveal the potential link between gas ingestion and losses caused by passage vortex. In this way, the optimization design rules of rim seal and aerodynamic design of the contra-rotating turbine will also be established. All the works in this project will benefit for improving the efficiency of aero-engine, and decreasing the fuel consumption, and reducing the amount of cooling airs.

针对转子尾缘复杂激波波系引起的轮缘静压周向非均匀分布，导致无导叶对转涡轮燃气入侵机理不同于常规涡轮的问题，本项申请采用数值方法，研究尾缘激波对无导叶对转涡轮轮缘间隙处静压周向分布规律的影响机理及规律，分析轮缘静压的改变对无导叶对转涡轮燃气入侵的影响机制、尾缘激波作用下燃气入侵对端壁损失的影响效应，在此基础上形成无导叶对转涡轮轮缘密封与涡轮气动性能耦合优化设计方法。项目预期将揭示尾缘激波强度与轮缘静压周向复杂变化规律之间的内在关联，阐明尾缘激波作用下对转盘腔内涡系结构的形成演化机理，澄清对转涡轮燃气入侵对端壁通道涡强度及损失的影响效应。项目的研究成果可以为减少冷却空气需求量、提高发动机效率、降低发动机耗油率提供一定的理论支撑。

为明晰尾缘激波诱发的静压非均匀分布对无导叶对转涡轮转转盘腔燃气入侵机理的影响效应，本项目采用数值方法研究了对转盘腔燃气入侵机制、盘腔冷气入射及轮缘几何对涡轮气动性能的作用规律，研究发现：1）无导叶对转涡轮高压转子尾缘激波会导致局部静压升高，引起高温燃气入侵盘腔。高压转子尾迹、尾缘激波与低压转子前缘压力势场的非定常干涉效应会强化轮毂面静压的周向非均匀分布，进而导致燃气入侵加剧，转转盘腔封严冷气需求随之增加。高压转子尾迹、尾缘激波扫掠整个轮缘间隙，导致轮缘间隙周期性经历冷气出流-燃气入侵-冷气出流的变化过程，燃气入侵的位置沿着圆周方向移动，显著区别于常规涡轮转静盘腔的燃气入侵现象。2）无导叶对转涡轮等熵效率随盘腔封严冷气量的增加呈现出先增加后减小的变化趋势，最佳冷气量下涡轮效率提升1.09%。封严冷气流量较小时，冷气出流诱发的再压缩效应降低高压转子尾缘激波强度及损失，减小低压转子轮毂通道涡强度及其诱发的气动损失，改善了对转涡轮气动性能；当封严冷气流量继续增加，冷气与主流的掺混损失逐渐增大，且低压转子攻角由正变负，端区损失与边界层分离损失增加，因而对转涡轮性能随封严冷气流量的增加而降低。3）对转涡轮轮缘几何修正，使得高压转子轮缘处的高压区向下游迁移，减小了盘腔内部流动阻力，减小了主流与盘腔内的压差，减弱了冷气出流的阻力，改善了对转盘腔的封严效果、提升了对转涡轮气动性能。项目研究成果可为减少对转盘腔冷气用量、提升无导叶对转涡轮气动性能提供理论支撑，为航空发动机推重比的进一步增大提供技术储备。