间隙主动控制系统中冷却空气管换热特性实验研究

Experimental Studies on Heat Transfer Characteristics in Air Cooling Pipe of Turbine Tip Clearance Control System

关键词:  主动间隙控制  冷却空气管  换热特性  冲击间距 

Key words:  Active clearance control  Air cooling pipe  Heat transfer characteristics  Impingement distance

摘要:

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。 

Abstract:

Experiments were carried out to investigate the heat transfer characteristics in the air cooling pipe with 1∶1simplified model, which is widely applied as a part of active clearance control system in the civil aero-engine. Inlet Reynolds number, impingement distance and space between holes which were designed by Similarity criteria were changed to study the local and average Nusselt number on impingement target plate. It is found in experiments that although the distance among these arranged impingement holes in air cooling pipe is constant, the distribution of temperature on the impingement target plate is quite different, and the maximum difference of the local Nusselt number can be 300%.The experimental results show that local Nusselt number increases with the central angle increasing due to the nonuniform air flow rate distribution. With the inlet Renolds number increasing,the local and average Nusselt number on impingement target plate also increase. All the results show that smaller Nusselt number can be achieved with the larger impinging distance H and the ratio of space between holes to hole’s diameter L/d.