风车状态下转子性能及通道内流动分析

为探究低展弦比压气机转子在风车状态下由压气机模式向涡轮模式转化过程中性能、内部流场结构以及气动损失的演化过程,提出了一种基于叶片和流体间能量传递的简化数值计算方法,以获得某转速下的风车状态临界流量点。在数值模拟的基础上,重点对比了同一转速线上压气机工况点(小流量工况)、风车临界点和涡轮工况点下叶尖泄漏损失的演化机制,同时探究了叶片通道内流动分离的演化过程。 结果显示,随着转速的增加,转子风车状态临界流量呈现近似线性的变化趋势。而同转速下随流量增大,叶尖泄漏流从吸力面流向压力面,并与压力面上的低能量流体进行掺混,造成了流动堵塞。同时,从压气机模式转向涡轮模式的过程中,叶尖区域的流动分离从吸力面分离转变为压力面分离,随后分离强度和尺寸逐渐增大,造成的气动损失显著增加;而在轮毂区域,流动分离始终保持吸力面分离,其分离尺度沿径向有所发展。

Aerodynamic performance of compressor rotor and flow analysis at windmilling condition

To explore the evolutions of inner flow structure and aerodynamic losses in a low-aspect ratio compressor rotor operating from compressor condition to highly loaded windmilling condition (turbine condition), a simplified numerical calculation method based on energy transfer between rotor blade and working fluid was employed to capture the critical windmill points at low rotational speeds. Due attention was paid on comparisons of the evolutions of tip leakage loss and the flow separations in the blade passage at the compressor condition, critical windmill point and turbine condition on a speedline. It was found that the rotor operating mass flow for critical windmill point showned a nearly linear variation trend with the increment of rotating speed. At the same time, with the rotor operating from the compressor to turbine condition, the tip leakage flow traveled across the clearance from the suction surface to the pressure surface at turbine conditions and mixed with the low-momentum fluids on the pressure surface, resulting in flow blockages near the casing endwall. In the meanwhile, the tip flow separation switched from suction surface separation to pressure surface separation, and both the intensity and size gradually increased, leading to higher aerodynamic losses. In the hub region, the flow separation was kept on the suction surface and the size of the separation has presented a growth in the radial direction near the trailing edge.