非均匀叶顶动态间隙对轴流压气机流动失稳机制影响研究

Compared with the compressor designed based on the ideal axisymmetric assumption, the real operating conditions may have a significant impact on its aerodynamic performance, especially its stability, which makes it deviate from the ideal design state, and brings potential safety hazards to the stable operation of aeroengine or gas turbine. This project focuses on the effect of non-uniform tip dynamic clearance on the flow instability mechanism of compressors under real conditions. Firstly, the dynamic clearance measurement technology based on blade tip timing principle BTT and the developed dynamic clearance description mathematical model are used to measure the dynamic characteristics of non-uniform clearance distribution around the rotor. Secondly, the synchronous measurement methods of dynamic clearance measurement of BTT and dynamic pressure sensor array are developed to achieve the synchronous acquisition of dynamic clearance information and unsteady flow information. The circumferential flow redistribution, disturbance propagation and stall initiation characteristics in the compressor end-wall region under dynamic non-uniform tip clearance are experimentally studied. Finally, by adopting the hybrid strategy of dynamic clearance deformed mesh and sliding mesh, the numerical simulation of the compressor flow in the whole annulus under dynamic non-uniform tip clearance is carried out, and the complex unsteady flow in the end-wall region and the spatio-temporal evolution characteristics of vortices structures under the stall initiation process are described in detail. By comparing with the uniform clearance conditions, the mechanism of compressor flow instability under dynamic non-uniform clearance is revealed. It provides a scientific basis for improving the stability of compressor.

相比基于理想轴对称假设设计的压气机，真实运行条件可能对其气动性能尤其是稳定性产生显著影响，使其偏离理想的设计状态，进而给航空发动机或燃气轮机的稳定运行带来安全隐患。本项目重点研究真实条件下非均匀叶顶动态间隙对压气机流动失稳机制的影响。首先，借助基于叶尖定时原理BTT的动态间隙测试技术，结合开发的动态间隙描述数学模型，实现对转子整周非均匀间隙分布动态特性的测量；其次，发展BTT动态间隙测试和动态压力传感器阵列的同步测试手段，实现动态间隙信息与非定常流动信息的同步获取，试验研究动态非均匀叶顶间隙下压气机端区周向流动匹配、扰动传播规律及失速始发特征；最后，采取动态间隙变形网格与滑移网格混合策略，开展动态非均匀间隙下压气机全环流动数值仿真，细致刻画失速始发过程中端区复杂非定常流动、涡系结构时空演化特征，与均匀间隙情况对比分析，揭示动态非均匀间隙下压气机流动失稳机理。为提升压气机稳定性提供科学依据。

本项目“非均匀叶顶动态间隙对轴流压气机流动失稳机制影响研究”（批准号51906205），已先进航空发动机压缩部件为牵引，以真实非均匀间隙压气机为对象，通过试验和仿真两个方面，研究非均匀叶顶间隙对压气机气动性能和流动失稳机制的影响。首先基于体积力理论，建立了描述间隙非均匀特性的数学模型，形成了针对周向非均匀间隙条件下压气机全环三维流场的高效数值仿真方法。在对仿真方法验证的基础上，针对转子偏心条件下轴流压气机开展数值仿真研究，获得了不同偏心率对压气机气动性能及稳定性的影响规律。进一步，基于现有轴流压气机试验台建立了间隙区域非定常流动及扰动传播测试平台，开展了叶顶间隙区域流场非定常扰动动态压力测试研究和叶顶间隙区域三维非定常流动结构PIV测试研究，获得了非定常扰动周向传播规律以及失速先兆发展为失速团的动态演化特征，发现了小间隙区域对大间隙区域产生的非稳态流动具有稳定作用。最后，发展了针对三维流场仿真模型的非均匀间隙网格拓扑划分策略，开展了非均匀间隙条件压气机全环非定常仿真分析，获得了非均匀间隙变化对压气机气动性能及内部复杂流动的影响规律和机理，揭示了间隙非定常流动作用下的压气机流动失稳机理，建立针对周向非均匀动态间隙条件的全局失稳准则。