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针对民用发动机低压涡轮主动间隙控制系统中冷却空气管气流冲击机匣的典型结构,建立1∶1简化试验模型并开展换热特性试验研究。试验中依据相似准则确定试验工况,通过改变进口Re数、孔排方式、冲击间距(即冷却管和机匣间距)等参数,分析了机匣表面局部和平均Nu数的分布和变化规律。试验中发现尽管冷却管上冲击孔沿周向均匀分布,机匣表面周向温度却存在明显的差异,对应局部换热系数相差可达3倍以上。试验数据表明:由于冷却管冲击孔周向出流流量不均匀,造成机匣表面局部Nu数随着对应圆心角的增加而逐步变大;当进口Re数增加后,冲击板面局部及平均Nu数均随之增大;试验工况下,机匣表面局部及平均Nu数均随冲击间距、冲击孔间距与孔径比(L/d)的增加而减小。
Aiming at the typical structure of the receiver of the cooling air pipe in the active clearance control system of the low pressure turbine of civil engine, a simplified test model of 1: 1 was established and the heat transfer characteristics were studied. The test conditions were determined according to similar criteria. The distribution and variation regularity of local and average Nu numbers on the casing surface were analyzed by changing parameters such as inlet Re number, pore row arrangement, impact spacing (ie, cooling tube and casing spacing). It was found in the experiment that although the impact holes on the cooling pipe are uniformly distributed in the circumferential direction, there are obvious differences in the circumferential temperature of the casing surface, corresponding to a difference of more than 3 times that of the corresponding local heat transfer coefficient. The experimental data show that the local Nu number of the casing surface gradually increases with the increase of the corresponding central angle due to the non-uniform flow of the outflow in the perforation of the cooling tube. When the inlet Re number increases, the local and average Nu Under the test conditions, the local and average Nu numbers of the casing surface both decrease with the increase of the impact distance and the ratio of the impact hole to the hole diameter (L / d).