孔布局对切向发散结构综合冷却效率的影响

Effects of Hole Arrangement on Overall Cooling Effectiveness for Tangential Effusion Cooling

关键词:  燃气轮机  孔布局  切向发散  综合冷却效率  热流固耦合

Key words:  Gas turbine  Hole arrangement  Tangential effusion  Overall cooling effectiveness  Conjugate heat transfer

摘要:

为了进一步提高燃气轮机燃烧室冷却效率，采用热流固耦合方法以及Realizable k-ε模型，在两种吹风比下，对4种不同布局的切向发散冷却结构的流动和传热特性进行了对比分析。研究结果表明，在吹风比2.2时，冷却射流之间相互独立，孔布局对切向发散冷却结构的影响较小。在吹风比10.4时，正对排列结构的冷却射流交叉互补，更易形成全覆盖冷却气膜；而采用交叉排列结构由于各排冷却射流互相叠加，抬升涡增强使得冷却射流脱离壁面，导致展向均匀性变差且综合冷却效率降低。沿轴向等间距比“前密后疏”排列的综合冷却效率峰值更高。正对且等间距排列结构具有最佳的冷却效果，随着吹风比的增大，综合冷却效率提升幅度最大为17.6%，比交叉排列的两种结构综合冷却效率高出约46%。基于模拟结果拟合了正对且等间距孔布局的首排孔冷却效率关联式，试验值与模拟结果的误差在±2%以内。

Abstract:

In order to further improve the cooling performance of gas turbine combustion chamber， the flow and heat transfer characteristics of four different arrangements of tangential effusion holes were compared and analyzed by using the conjugate heat transfer method and Realizable k-ε model under different blow ratios. The results show that the cooling jets are independent of each other， and the effusion hole arrangements have little effect on the overall cooling effectiveness at the blow ratio of 2.2. As the blow ratio increases to 10.4， the cooling jets of the front-to-back-aligned arrangement cross and complement each other， making it easier to form a full-coverage cooling film. The overall cooling effectiveness is significantly improved with the front-to-back-aligned arrangement， while the cross-aligned arrangement increases the lifting height of the cooling jets due to the interaction between the adjacent rows of cooling jets. This results in poor spreading uniformity and overall cooling effectiveness. Equal spacing along the axial direction results in higher peak overall cooling effectiveness than the arrangement of “dense front and sparse rear”. The arrangement with front-to-back-aligned and equal spacing has the best cooling performance. And as the effusion cooling consumption increases， the overall cooling effectiveness increases by a maximum of 17.6%， which is about 46% higher than that of the two cross-aligned arrangements. The correlation equation for the overall cooling effectiveness of the first row of holes was fitted based on the simulation results for the arrangement of front-to-back and equal spacing aligned. The correlation was in good agreement with the experimental results with a relative error of less than 2%.