延伸冲击孔冲击冷却流动与换热特性的数值研究

采用数值模拟方法研究了延伸冲击孔冲击冷却系统的冷却特性，分析了3个冲击雷诺数和5个冲击孔延伸长度对冲击腔内流动与换热特性的影响，给出了靶面努塞尔数分布、靶面压力分布、中心截面流速与综合换热性能的变化。结果表明：延伸冲击孔可以有效地防止横流对冲击射流的偏转作用，同时使射流出口更加贴近冲击靶面壁面，冲击速度更高，可以明显提高靶面的换热系数，并使整个靶面上的换热系数分布也更加均匀。冲击冷却的冷却性能随着冲击孔延伸长度的增加而增加，相较于传统冲击冷却（baseline），在L/d=2.5时靶面平均努塞尔数提升达15%以上，但压力损失也相对较高；对比不同延伸长度冲击孔的综合换热性能，发现存在最佳的L/d取值范围使冲击冷却系统获得最佳的综合冷却性能。在本研究范围内，最佳的L/d= 2.5。

Numerical Study on Flow and Heat Transfer Characteristics of Impingement Cooling with Extended Jet Holes

The cooling characteristics of an impingement cooling system with extended jet holes were studied using a commercial computational fluid dynamic software ANSYS-CFX. The effects of three impingement jet Reynolds numbers and five impingement hole extended lengths on the flow and heat transfer characteristics in the impingement cavity were analyzed. The changes of distributions of Nusselt number, pressure, central cross-section velocity and the resulting overall thermal perform were given in detail. The results showed that the cooling performance of impingement cooling increased with the increase of jet Reynolds number and the extended length of the jet hole. The extended jet hole can effectively prevent the deflection of crossflow to the impact jet. The extended impingement hole made the jet outlet closer to the wall, and the flow velocity was higher when it reached the target surface, which obviously improved the average Nusselt number on the target surface, resulting in the more uniform heat transfer distributions on the target surface. Compared with the traditional jet impingement configuration (baseline), the laterally-averaged Nusselt number on the target surface increased by more than 15% at L/d=2.5, but the penalty was higher pressure loss. In term of overall thermal performance, there was an optimal range of L/d, which made the impingement cooling system had the highest overall performance. In this study, the best L/d =2.5.