垂直横流通道内槽型截面孔气膜冷却特性数值研究

Numerical Investigation on Film Cooling Characteristics of Slot-Sectional Holes in Perpendicular Cross-Flow Channels

关键词:  气膜冷却  垂直横流  槽型截面孔  数值研究  燃气轮机

Key words:  Film cooling  Cross-flow  Slot-sectional hole  Numerical investigation  Gas turbine

摘要:

为了揭示燃气透平动叶内部横流通道对不同截面形状气膜孔的影响机理，采用数值方法对比研究了典型扇形孔和槽型截面孔在垂直横流通道内的气膜冷却特性。四种槽型截面孔包括2种梭型扩张孔（上游壁外凸、下游壁外凸）和2种半圆侧壁矩形扩张孔（计量段截面宽度1.7D，2.0D），气膜孔直径D均为3mm。三种垂直横流通道均为8D×4D矩形通道，分为无肋光滑通道、45°和135°带肋通道，肋间距与孔间距均为8D。数值结果表明：在中高吹风比下，四种槽型截面孔的气膜冷却效果均显著优于扇形孔，光滑通道中差距最大，45°肋通道中差距最小，其中大截面宽度矩形扩张孔的气膜冷却效果在三种横流通道中均最高。由于强的横向扩张，下游壁外凸的梭形扩张孔的气膜冷却效果受横流影响弱，在三种横流通道中的变化幅度最小。四种槽形截面孔的展向平均气膜冷却效果在45°和135°带肋通道中变化均不大，即肋角度对槽形截面孔气膜冷却效果影响较小。四种槽型截面孔中高吹风比下的出流系数在无肋通道中均高于扇形孔，在带肋通道中五种孔型的出流系数差别很小。

Abstract:

In order to reveal the influencing mechanism of the internal cross-flow channel in gas turbine rotor blade on the film holes with various cross-sectional shapes， the film cooling performance of slot-sectional holes and typical fan-shaped hole in perpendicular cross-flow channels were conducted using numerical methods. Four slot-sectional holes included two fusiform diffusion holes （respectively the up- and downstream wall outer convex） and two rectangular diffusion holes （respectively the cross-sectional width 1.7D and 2.0D）， the diameter D of simulated holes were 3mm. Three cross-flow channels included a smooth channel， a 45° and a 135° ribbed channel. The cross-sectional size of three cross-flow channels were 8D×4D， and the rib pitch was 8D the same as the hole pitch. The simulated results indicated that， under moderate and high blowing ratios， the film cooling effectiveness of four slot-sectional holes is superior to fan-shaped hole significantly， in which the magnitude difference in the smooth cross-flow channel is the largest， while the magnitude difference is the smallest in the 45° ribbed cross-flow channel. The rectangular diffusion hole with a larger cross-sectional width produces the highest film cooling effectiveness in each cross-flow channel. Because of intense spanwise expansion， the fusiform diffusion hole with an outer convex downstream wall behaves the smallest variation magnitude of film cooling effectiveness in three cross-flow channels. The spanwise averaged film cooling effectiveness of four slot-sectional holes varies little in 45° and 135° ribbed channels， that is， the change of rib angle has a weak influence on the film cooling effectiveness of slot-sectional holes. The discharge coefficients of the four slot-sectional holes under moderate and high blowing ratios are higher than those of the fan-shaped holes in the smooth channel， while it has less difference in the ribbed channels.