跨声速涡轮轮缘复合封严结构的数值研究

Numerical Investigation on Composite Rim Seal Configurations of Transonic Turbine

关键词:  高压涡轮  燃气入侵  转静盘腔  复合封严  FFT频谱分析

Key words:  High pressure turbine  Hot gas ingestion  Rotor-stator cavity  Composite rim seal  Fast Fourier transform

摘要:

为了保护航空发动机涡轮盘，阻止高温燃气向盘腔内部深入，破坏核心部件，通常将压气机冷气引入转静盘腔，以抵抗高温燃气入侵，并对涡轮部件进行冷却。本文利用非稳态与稳态数值计算方法，研究了跨声速涡轮设计工况（Re?>10⁷）下的两种复合封严结构：静盘存在封严环的覆叠封严和动盘带封严齿的咬合封严结构，并与轴向封严结构进行对比。在本文所研究的范围内，对非稳态计算进行快速傅里叶变换（FFT）的结果表明：跨声速涡轮流动中，叶栅通道存在由激波引起的高压区，导致了燃气的剧烈入侵，因而在特征信号频谱中f/f_blade=2处存在峰值，这是跨声速涡轮燃气入侵最显著的特点。稳态计算证明复合封严结构封严性能良好。静盘封严环将盘腔分割为上下两个容腔，入侵容腔滞留了绝大部高温燃气，故高半径处封严效率较低，但盘腔低半径处封严效率明显提高。在冷气流量系数C_w≈996时，两种复合封严结构在r/b=0.96以下都能达到很高的封严效率。咬合封严能够增加燃气流动阻力，有效减小封严冷气使用量。但是，由于跨声速工况下剧烈的燃气入侵，两种封严结构在冷气流量系数从C_w=199逐渐增大到2000时，高半径处封严效率并没有明显的提高，封严效率仅提高了20%~30%。

Abstract:

In aerospace science and technology， to resist the ingestion of hot gas and protect the turbine disk from ablation， the coolant flow of the compressor is introduced into the rotor-stator cavity. A numerical investigation on flow characteristics of two composite rim seal configurations （lip seal and bite seal） operating at transonic condition （Re?>10⁷） under unsteady and steady simulation is presented， in the meantime comparison with axial rim seal in terms of sealing performance is carried out. In detail， the Fast Fourier Transform （FFT） reveals the sealing characteristics of transonic turbine stage. The high-pressure zone at the vane suction side caused by shock wave intensifies the hot gas ingestion， with a peak of pressure signal at f/f_blade=2. Shock wave induced ingress is a unique property for transonic turbine stage. On the other hand， the two composite rim seals obtained higher sealing efficiency than the axial seal. The disk cavity is divided into ingestion cavity and buffer cavity by the sealing ring on the static disk. Although， High radius region gains rather low sealing efficiency due to most of the hot gas being trapped in the ingestion cavity， while low radius region gains a rather high sealing efficiency， especially the region below r/b=0.96 gains a sealing efficiency of nearly 100% with coolant flow rate C_w≈996. Still， bite rim seal can produce greater flow resistance and thus reduce the consumption of coolant flow. Finally， at high radius， the sealing efficiency only increases by 20%~30% when C_w increases from 199 to 2000， that means both of the two composite structures cannot get significant improvement in the ingestion cavity， due to the drastic gas ingestion under transonic condition.