高压涡轮圆柱孔状径向轮缘密封封严特性的数值研究

Numerical Study on Sealing Characteristics of High-Pressure Turbine Cylindrical Hole Radial Rim Seal

关键词:  高压涡轮  封严性能  燃气入侵  径向轮缘密封  圆柱孔

Key words:  High-pressure turbine  Sealing performance  Mainstream ingestion  Radial rim seal  Cylindrical hole

摘要:

径向轮缘密封结构在增大主流燃气入侵阻力同时也会阻碍封严冷气的向上输送，为此提出了一种在径向轮缘密封的径向内齿上打孔来改善其封严性能的设计思路。针对Lisa1.5级高压涡轮实验台，设计了一种传统和五种带孔新型的径向轮缘密封，采用数值模拟方法评定了圆柱孔孔径D和孔心距S_h对封严性能的影响，并揭示了其改变封严特性的流动机理。结果表明：在设计封严冷气量工况下，相较于传统的径向轮缘密封结构，D为0.375mm和0.5mm的圆柱孔状径向轮缘密封具有更好的封严性能，其喷射的冷气与主流冷气混合后形成“屏障”，阻止燃气的进一步入侵，使得封严效率分别提高大约2%和4%；S_h为0.75mm和1.825mm圆柱孔状径向轮缘密封可以提高封严效率4%左右，但S_h为0.75mm的密封结构会在盘腔内发生回流现象，导致燃气扩散，而S_h为1.825mm的密封结构由于圆柱孔远离燃气率先入侵位置，可以有效地阻碍燃气在盘腔内的入侵。因此，D为0.5mm以及S_h为1.825mm的圆柱孔状轮缘密封是本文研究获得的最优设计方案。

Abstract:

The traditional radial rim seal increases the mainstream ingestion resistance but it also hinders the upward transportation of the sealing flow. So a new design idea of drilling holes in the radial inner teeth of radial rim seal was proposed， which ducting sealing flow upward through the cylindrical holes. Taking the Lisa 1.5 high-pressure turbine as the research object， a traditional radial rim seal and five cylindrical hole radial rim seals are designed. Numerical simulation was carried out to evaluate the sealing performance of these rim seal and uncover the associated influence of the diameter and axial position of the cylindrical hole on flow mechanism. The results show that， compared to traditional radial rim seal ，the cylindrical hole radial rim seal with the hole diameter of 0.375mm and 0.5mm can increase the sealing effectiveness by 2% and 4% ，respectively. And cylindrical hole radial rim seal with hole center distance 0.75mm and 1.825mm can also increase the sealing effectiveness by 4%， respectively. Close examination of the flow field reveals that cylindrical hole rim seal with the hole diameter of 0.375mm and 0.5mm inject the sealing flow upward through the cylindrical hole and mix with mainstream sealing flow to form a ‘barrier’ to increase the mainstream ingestion resistance. The cylindrical hole rim seal with the 0.75mm hole center distance can occur the phenomenon of backflow in the disc cavity，leading to ingestion diffusion. Whereas the cylindrical hole radial rim seal with the 1.825mm hole center distance can effectively prevent the ingestion in the disk cavity ，because the cylindrical hole is away from the position where the gas first invades. In this paper，cylindrical hole radial rim seal with the 0.5mm hole diameter and 1.825mm hole center distance is the optimal design scheme.