The tip clearance between turbine blade and stationary casing leads to the exposure of blade tip to high temperature gas and contributes to a high thermal load in this region. Then it is necessary to perform cooling on the blade tip. Moreover, the tip leakage flow in a high speed brings complex aerothermal conditions to the blade tip. The blade tip film cooling on the transonic squealer tip is investigated in this research. The effects of tip and pressure-side coolant injections on the blade tip heat transfer are discussed. And the influences of total pressure ratio of coolant to main flow and endwall moving on the film cooling are considered. Firstly, the reliability of a commercial CFD code with different turbulence models was first validated by contrasting with the experimental results. The heat flux and isentropic Ma number predicted with the BSL k-ω model shows a better agreement with the test data. Then the mesh independency study was performed. The mesh with tip and pressure-side injection hole is generated by in-house code. For the tip without film cooling at outlet Mach number of 0.96, the squealer tip shows a high heat transfer at front of the tip cavity floor caused by the impingement of tip leakage flow, besides the suction-side rim has high heat transfer coefficient. With the tip coolant injection, the tip coolant is pushed towards the cavity pressure-side and provides better coverage in this region. At the front of cavity floor near suction-side, there is almost no coolant coverage then it shows little cooling effects. The coolant discharges from the tip over the suction-side rim thereby the heat transfer near the trailing edge is less affected by the tip coolant injection. With the pressure-side near tip film cooling, the coolant injection shows high film-cooling effectiveness at low coolant stagnation pressure and lift off blade surface at high coolant stagnation pressure. The endwall motion increases the total heat load of the blade tip by increase heat load at cavity floor and suction-side near tip region and the reduces film-cooling effectiveness.
Numerical Study of Blade Tip Cooling at High Speed With Tip and Pressure-Side Coolant Injections
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Zhou, Z, Wang, S, & Chen, S. "Numerical Study of Blade Tip Cooling at High Speed With Tip and Pressure-Side Coolant Injections." Proceedings of the ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. Volume 5A: Heat Transfer. Oslo, Norway. June 11–15, 2018. V05AT12A012. ASME. https://doi.org/10.1115/GT2018-75915
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