高压涡轮尾切凹槽叶尖冷却换热特性

为研究尾切凹槽状涡轮叶片叶尖的表面换热,通过瞬态风洞实验得到无冷却和带除尘孔两种情况下叶尖表面传热系数,并将其与数值模拟结果进行对比,实验结果的不确定度小于5%。分析叶尖间隙流场情况,无冷却时,由于腔底的空腔涡和凸肩壁的分离泡,高表面传热系数集中在压吸力侧凸肩和腔底前缘处;腔底后半段沿压力侧存在条状低表面传热系数分布。有除尘孔冷却时,冷却气体分为高低能两股流体,高能流体随泄漏流流出,造成吸力侧凸肩存在多段高表面传热系数集中分布;低能流体紧贴凹槽压力侧向后流动,对应位置冷却效率可达0.4以上。 

Cooling and heat transfercharacteristics of high-pressure turbine blade with cutback squealer tip

In order to study the surface heat transfer of turbine blades with cutback squealer tip, surface heat transfer coefficient was investigated experimentally through a transient wind tunnel experiment for an uncooled blade and a blade with dust purge holes. The experimental outcome was compared with the numerical simulation result. The uncertainty of the experiment was less than 5%. By analyzing the over tip leakage (OTL) flow condition, it revealed that on the uncooled blade tip, due to the cavity vortex and the separation bubbles, high surface heat transfer coefficient values were scattered on squealer rims of both pressure side (PS) and suction side (SS), and on cavity floor near the leading edge. A strip of low surface heat transfer coefficient values appeared onthe PS of the second half cavity. In the cooled case, coolant flow from dust purge holes was separated into two parts. The high-energy fluid merged into the OTL flow, resulting in multiple high surface heat transfer coefficient distributions on the SS rim, while the low-energy fluid flowed backward along the SS of the cavity. Cooling effectiveness can reach over 0.4 in this region.