Abstract According to the design requirements of high-temperature combustion chamber, an advanced shaped hole structure was designed for film cooling. Numerical method was applied in this study to investigate the flow and heat transfer characteristics of shaped holes and compared with those of cylindrical holes. The influence of the forward expansion angle of shaped holes on the flow and heat transfer was studied. The results show that compared to cylindrical holes, the diffused structure of shaped holes decreases the momentum of jet flow, improves the adhesion characteristics of the cooling air film, increases the diffusion of the coolant air outflow and improves the cooling efficiency between adjacent columns of holes in the lateral direction. When the forward expansion angle increases, the expansion section induced the flow vortex, which reduces the radial velocity of coolant flow and enhances the diffusion of cooling air film both in streamwise and spanwise directions. However, as the forward expansion angle increases further, the scale of vortex inside the shaped hole grows. Too large vortex inside the shaped hole increases the coolant eject angle, which weakens the film covering effect. Additionally, the shaped hole results in an increase in lateral spreading and enhances the cooling effect between adjacent columns of the film hole. The enhancement of the film cooling characteristics is due to the change in the shape of the film hole, resulting in the enhancement of the flow vortex, which induces complicated secondary flow.

中文翻译：

---

前扩角对异形孔气膜冷却特性的影响

摘要 根据高温燃烧室的设计要求，设计了一种先进的异形孔结构进行气膜冷却。本研究采用数值方法研究了异形孔的流动和传热特性，并与圆柱孔的流动和传热特性进行了比较。研究了异形孔的前扩角对流动和传热的影响。结果表明，与圆柱孔相比，异形孔的扩散结构降低了射流的动量，改善了冷却空气膜的粘附特性，增加了冷却空气流出的扩散，提高了相邻孔列之间的冷却效率在横向。当前向膨胀角增大时，膨胀段产生涡流，这降低了冷却剂流动的径向速度，并增强了冷却空气膜在流动方向和展向方向上的扩散。然而，随着前向膨胀角的进一步增大，异形孔内的涡旋规模增大。异形孔内涡流过大，会增加冷却液喷射角度，削弱薄膜覆盖效果。此外，异形孔导致横向扩展的增加并增强了膜孔相邻列之间的冷却效果。薄膜冷却特性的增强是由于薄膜孔形状的变化，导致流动涡流增强，从而诱发复杂的二次流。随着前向膨胀角的进一步增大，异形孔内的涡旋尺度增大。异形孔内涡流过大，会增加冷却液喷射角度，削弱薄膜覆盖效果。此外，异形孔导致横向扩展的增加并增强了膜孔相邻列之间的冷却效果。薄膜冷却特性的增强是由于薄膜孔形状的变化，导致流动涡流增强，从而诱发复杂的二次流。随着前向膨胀角的进一步增大，异形孔内的涡旋尺度增大。异形孔内涡流过大，会增加冷却液喷射角度，削弱薄膜覆盖效果。此外，异形孔导致横向扩展的增加并增强了膜孔相邻列之间的冷却效果。薄膜冷却特性的增强是由于薄膜孔形状的变化，导致流动涡流增强，从而诱发复杂的二次流。异形孔导致横向扩展的增加，并增强了膜孔相邻列之间的冷却效果。薄膜冷却特性的增强是由于薄膜孔形状的变化，导致流动涡流增强，从而诱发复杂的二次流。异形孔导致横向扩展的增加，并增强了膜孔相邻列之间的冷却效果。薄膜冷却特性的增强是由于薄膜孔形状的变化，导致流动涡流增强，从而诱发复杂的二次流。