自循环机匣周向偏置对轴流压气机非定常流场的影响

Effects of Self-Recirculating Casing Circumferential Offset on Unsteady Flow Field of Axial Compressor

以NASA Rotor 35为研究对象,设置了15°,0°和-15°三种不同周向偏置度数的自循环机匣,利用NUMECA软件包进行三维非定常数值模拟,以研究机匣处理对压气机非定常流场的影响。计算结果表明,针对NASA Rotor 35,由通道激波与叶顶泄漏涡相互作用导致的失速,不同周向偏置角度的自循环机匣处理均能够较好地拓宽压气机的稳定工作范围,且几乎不影响压气机峰值效率。其中周向偏置15°的自循环机匣虽然流量裕度改进量最大,但是压气机的压比下降较大。周向偏置后自循环机匣的扩稳能力不再遵循传统上以回流量、喷嘴出口速度和自循环装置内的流动损失来关联扩稳效果的经验规律,而是由桥路和流场耦合的非定常过程导致的。其喷射和抽吸作用对叶顶流场的激励使得叶顶静压分布、泄漏流产生周期性波动,不同物理量峰值在时域上存在相位延迟。

NASA Rotor 35 is taken as the research object,three kinds of self-recirculating casings with different circumferential offset degrees(positive 15°,0°and negative 15°)are set up,and three-dimensional unsteady value simulation is carried out by using NUMECA software package to study the influence of casing treatment on unsteady flow field of compressor.The numerical simulation results show that for the stall of NASA Rotor 35 caused by the interaction of passage shock and tip leakage vortex,the different circumferential offset angles of the self-recirculating casing treatment can better expand the compressor stability to varying degrees,almost no penalty to compressor peak efficiency.The self-recirculating device in which the circumferential offset is 15°is the best of stall margin improvement(SMI),but the total pressure ratio of the compressor is obviously reduced.The SMI ability of the self-recirculating device after circumferential offset no longer follows the traditional empirical rule that stabilization effect is correlated with the circulating flow rate,the injector outlet speed and the flow loss in the self-recirculating device,but is caused by the unsteady processes of self-recirculating device and flow field coupling.The suction and jet action on the tip flow field causes the static pressure distribution and the tip leakage flow to periodically fluctuate,and there are phase delays at different physical quantity peaks.