高压涡轮工作叶片内部流场特性试验研究

为研究变工况特性下涡轮叶片内部通道流场特性，选取高压涡轮二级工作叶片内部通道作为研究对象，在5种不同的进口雷诺数（Re）工况下，利用TRPIV（时序PIV）技术对通道内的流场特性进行了试验研究。Re变化为32426～64700，模拟了飞行循环过程中的若干典型工况。在先进加工技术的辅助下，保留了真实叶型约束下的完整内冷三通道带肋结构，捕捉到一些不同于常规截面两通道模型等简化模型中的流动现象，包括：弯头区域不对称主流分离结构和非对称二次涡系。通过数据分析，明确了高、低雷诺数下流动特性的差异。在高Re工况条件下，弯头出口附近的冲击区域增大；对于第一通道内的二次流，在接近弯头位置处，横向速度分量会导致纵向涡对的强度被削弱，高Re工况下拥有更加剧烈的影响，极有可能削弱吸力面的换热强度。

Experimental Study on Internal Flow Field of High-Pressure Turbine Working Blade

Typical internal cooling design of high-pressure turbine blades was commonly conducted at a design working condition, including the selection of structure parameters, calculation of exterior wall temperature and strength assessment of whole structure. However, it was ignored for the internal cooling characteristics under other working conditions in a flying cycle. To fill the void, in present work, the flow characteristics inside of coolant channel of a 2_^nd stage high-pressure turbine blade have been experimentally studied under five different Reynolds numbers, by means of advanced Time-resolved Particle Image Velocimetry (TRPIV) technology. The inlet Reynolds number ranges from 32,426 to 64,700, several typical working conditions in a flying cycle. A ribbed three-pass coolant channel featuring the actual blade geometry and film outflows was manufactured as the test model, where the special flow details were successfully captured, different from the typical flow in simplified two-pass passages with regular cross-sections. These flow features mainly included the asymmetrical flow separation of main flow orientation and asymmetric secondary vortices downstream of bend, which can provide the important guidance for the precise design of cooling structures. In addition, the comparisons have revealed the significant differences of flow characteristics under low and high Reynolds numbers. Larger flow impingement region can be generated under the higher Re condition, indicating the larger probability of local thermal damage, caused by the more uneven wall temperature distribution and hence the larger thermal stress. For the secondary flow in the first passage, near the bend, the strength of longitudinal vortex-pair can be significantly weakened by the transverse component of streamwise velocity. The more dramatic impact can be formed under the high Re condition, leading to the reduced heat transfer coefficient at suction side.