複數薄膜冷卻孔在引擎葉片上的熱傳分析

Abstract

自從燃汽渦輪機問世後，不論是在民生或是軍事上對於人類的生活都有非常大的影響，因此，為了保護渦輪機葉片避免發生熱損壞的薄膜冷卻法日漸成為重要之課題。本文以二維可壓縮流流體探討並處理複雜外型的引擎葉片之暫態熱傳分析，且在數值方法中加入了沉浸邊界法，以此方法可以在直角坐標系統中模擬複數管道之引擎葉片的複雜外型。 以壓力為入口條件的冷卻流體由複數薄膜冷卻管道流出，每個管道所分配到的流量不盡相同，冷卻流體流出管道後與主流進行熱交換，在壁面上形成低溫保護膜，可藉此觀察葉片附近之流場與渦流的分佈，並且探討此低溫保護層對壁面的保護效果，並以薄膜冷卻效率做為比較的基準。由結果可以觀察出並不存在一個固定的吹洩比能在全域都有最好的薄膜冷卻效率，而需因位置在迎風面或是被封面進行調整。

Turbine blades in a gas turbine engine must withstand high temperature and pressure that easily causes the blade broken. In order to protect turbine blades from the situation, a film cooling method has been always employed on the turbine blade. This study simulates the complex configuration of turbine blades with the 2-D compressible flow, and applies the immersed boundary method to the simulation. Because of the immersed boundary method, a complex configuration with structured grid can be simulated, and it is better than unstructured grids used to simulate the complex configuration. Cooling fluids are issued from high pressure chamber inside the turbine to the outside surface of the blades. Because the pressure difference on each point on the turbine blade is not the same, each film cooling hole has different coolant mass flow rate that leads different kinds of vorticities when the cooling fluids mix with the hot gas. As a result, different heat transfer mechanisms are observed on the pressure and suction side.