气膜冷却涡轮叶片前缘外换热系数的实验研究

EXPERIMENTAL INVESTIGATION OF EXTERNAL HEAT TRANSFER COEFFICIENTS ON FILM-COOLED TURBINE BLADE LEADING EDGE

关键词:  涡轮叶片  薄膜冷却  传热系数  实验

Key words:  Turbine blade  Film cooling  Heat transfer coefficient  Test

摘要:

本文利用扁圆柱头部模拟涡轮叶片前缘对四个具有不同几何角度气膜孔的模型,测定了无气膜时和有气膜时的外表面换热系数分布规律.通过比较表明:气膜冷却时由于二次流的扰动,破坏了主流的附面层,导致外换热系数增加,这种影响在气膜孔口附近表现得尤为显著,并随着吹风比的增大而增大.本文给出了四个模型的外换热系数变化与主流雷诺数、吹风比、无因次弧长的经验关系式.并认为设计气膜冷却叶片时必须考虑换热系数的变化.

Abstract:

A semicylinder nose is used in test models to simulate a turbine blade leading edge with film cooling.Four models with ejection holes at different angles and positions for film cooling are used in this paper.The external heat transfer coefficient distributions along the leading edge region with and without film cooling are measured separately.It is observed from the experiments that the main-stream boundary layer is damaged due to the existance of film jets, resulting in an enhancement of external heat transfer coefficients,especially in the vicinity of film holes.The effect of film cooling on external heat transfer coefficients increases with the blowing ratios of film jets.Four sets of empirical correlations of the enhancement of the external heat transfer coefficients showing their variations with the main stream Reynolds no,, ReD, blowing ratios, M, and nondimensional distances, x/d, are presented in this paper.