多腔室凹槽对涡轮叶顶流动传热特性影响的数值研究

现代航空发动机为获得更大输出功率和推重比，涡轮进口温度不断提高，因此高温燃气在无围带动叶叶顶间隙的泄漏引起叶顶热负荷急剧增加，甚至导致叶片烧蚀、失效，严重影响涡轮运行安全。为降低叶顶热负荷，抑制泄漏流，本文以GE-E3第一级叶栅为研究对象，通过求解三维Reynolds-Averaged Navier-Stokes (RANS）方程和湍流模型研究了多腔室凹槽对叶顶流动传热性能的影响。研究结果表明:在多腔室凹槽中，叶顶换热系数随着叶顶空腔数量的增加而逐渐减小，凹槽腔室内刮削涡可有效降低泄漏流量。格栅结构在凹槽中起到“气动篦齿”作用，在0至20%的流向区域内泄漏流控制效果显著。Case7的叶顶换热系数最小，比Case1降低了40.44％；Case2和Case3可显著抑制叶顶泄漏量，与Case1相比分别降低了33.82％、28.90％。

Numerical Investigations of Multi-Cavity Tip Effects on Turbine Blade Tip Flow and Heat Transfer Characteristics

In modern aero-engine, the turbine inlet temperature is gradually increased to pursue higher power and thrust-to-weight ratio. High-temperature gas leaks through the gap clearance between the blade tip and the shroud surface, causing the heat load increase dramatically to the tip region. This process is always accompanied by ablation and failure occur in the blades. In order to reduce the heat load and leakage flow rate in turbine blade tip region, The present research focus on the first stage of GE-E3 turbine, applies the rib structure to the blade tip. three-dimensional Reynolds-Averaged Navier-Stokes(RANS) and standard turbulent model were adopted in all the present computations. The effects of multi-cavity tip on the blade tip leakage flow and heat transfer characteristic were numerically investigated. The numerical results show that as the number of cavities increased the heat-transfer coefficients increased on the multi-cavity tip surface, and the scraping vortex in the cavity can effectively control the leakage flow. An aero-labyrinth liked sealing effect is formed by the grid structure, which has obvious leakage flow control effect in 0-20% stream-wise region. Results also showed that Case7 obtained the smallest heat transfer coefficient on the blade tip and reduction40.44% compared with that of the flat tip (Case1). A remarkable decrease of leakage flow is observed within Case2 and Case3, which are respectively reduced by 33.82% and 28.90% compared to the Case1.