叶尖间隙泄漏对厘米级高亚声微型轴流涡轮性能的影响

针对某微型涡轮发动机(MTE)原理样机的直径为78.4mm的微型轴流涡轮,采用数值模拟手段研究了叶尖间隙泄漏对该厘米级高亚声微型轴流涡轮流场结构及涡轮性能的影响.结果表明:微型轴流涡轮相对叶尖间隙尺寸在3.1%~4.6%,明显高于常规轴流涡轮;微型轴流涡轮叶尖间隙泄漏涡影响范围较常规轴流涡轮扩大(至叶中高度),泄漏损失占涡轮级总损失的35%,也较常规轴流涡轮明显增大.研究获得了间隙尺寸对该厘米级高亚声微型轴流涡轮性能的影响规律,叶尖相对间隙尺寸每增加1%叶高,效率最快下降1.9%,其变化幅度较常规轴流涡轮更为明显.最后,根据工程安装的限制(离心力变形及热变形、轴承游隙、加工装配误差等),确定了一个较优的叶尖间隙(0.4mm),通过数值模拟获得了在该间隙下的涡轮性能参数:落压比为2.12,效率为0.87,流量为0.35kg/s.

Effect of tip clearance leakage on performance of centimetre-level high subsonic micro axial flow turbine

The effect of the tip leakage on the flow field structure and turbine performance of a 78.4mm diameter centimetre-level high subsonic micro axial flow turbine of a micro turbine engine(MTE) prototype was analyzed by numerical simulation. Results show that the relative tip clearance size of micro axial turbine is within the range of 3.1%-4.6%, which is higher than that of conventional axial flow turbine. The effect of tip leakage vortex extends towards the mid of the vanes, of which the leakage losses account for 35% of total losses of the turbine stage, showing a significant increase compared to the conventional axial flow turbine. Studies on the impacts of the law of the gap size of the centimetre-level high subsonic micro axial flow turbine have shown that, once the gap size for each increases by 1% of the blade height, the efficiency will decrease up to 1.9%, which is more distinct than the conventional turbine. Finally, an optimum gap size (0.4mm) was determined due to the restrictions of engineering installation (centrifugal deformation, thermal deformation, bearing clearance, machining and assembly errors, etc), and the performance parameter of the impeller was acquired by numerical simulation: total pressure ratio of 2.12, efficiency of 0.87, mass flow of 0.35kg/s.