【作者】 杨国伟；

【导师】 吴艳辉；

【作者基本信息】 西北工业大学 ， 航空宇航推进理论与工程， 2018， 硕士

【摘要】 压气机失稳机理分析与稳定性控制是伴随着航空发动机发展的重要课题。本文以跨音转子Rotor35为研究对象,用三维数值模拟方法研究了该转子在不同工况下的流场特征,进而对压气机的失稳机制进行了总结分析。随后,对新型叶顶引气自循环机匣的扩稳能力与机理进行分析。最后,在转子叶顶加装具有不同布局形式的自循环处理机匣,探索最佳的机匣布局形式,并对自循环机匣的扩稳机制和造成不同布局形式下自循环机匣扩稳能力差异的原因进行进一步研究。首先,建立三通道计算模型,对原型机的流场特征与失稳机制进行分析。随着转子节流程度加深,叶顶流场的恶化趋势最为严重,转子失稳起始于叶顶区域。在转子流量减小的过程中,泄漏涡起始位置前移,激波逐渐脱体,使得泄漏涡逐渐丧失抵抗激波强逆压梯度的波面法向速度,进而在波后发生破碎。波涡干涉诱导出的低能流在通道进口压力面侧积聚,阻碍来流进入流道,压气机最终发生阻塞型失稳。低能团在叶顶的发展是非定常的,其发展过程会对压力面侧的叶片载荷产生周期性作用,使得相邻通道的泄漏量周期性发展,并进一步导致相邻通道波涡干涉所诱导出的低能团也呈现出与前一通道相似的发展规律。依次类推,构成了泄漏涡与低能团非定常发展的周向传播规律。然后,建立叶顶引气的自循环机匣模型,用占主流0.36%的引气量实现了3.33%的流量裕度提升,且基本不影响总压比和效率在近失稳工况前的特性分布,峰值效率仅降低了0.23%。自循环机匣激励叶顶流场的过程中,一方面会周期性降低叶片的进气攻角;另一方面可以直接激励泄漏流与波后低能团,将泄漏流和低能区向通道下游推进。这两种扩稳机制中,第二种起到了主导作用,并且激励波后低能团的扩稳效果要优于激励波前泄漏涡。自循环机匣在激励通道上游泄漏涡与低能团的同时,会增大吸力面尾缘分离程度,但整体上对叶顶流场仍然起到了改善作用,延缓了失稳发生。自循环机匣可以提高转子的承载能力,提高转子可承受的时均扩压因子,但当节流程度进一步加深,喷气对叶顶流场的周期性改善无法维持叶顶的通流能力时,与原型机的流场特征相似,转子再次发生阻塞型失稳。最后,建立具有不同引气形式的自循环机匣模型。无周向偏置,但轴向引气位置不同的三种自循环机匣,扩稳能力的差异由射流动量的大小决定。将叶顶正向偏置与两种栅后无偏置机匣布局形式进行对比,可以发现,桥路与流场耦合的非定常过程可以显著影响自循环机匣的扩稳能力。喷气量在时间和空间上集中于通道进口近压力面侧,可以获得更大的扩稳量。更多还原

【Abstract】 The analysis of compressor instability mechanism and stability control is an important issue accompanying the development of aero engine.In this paper,a transonic rotor Rotor35 is used as the research object.Three-dimensional numerical simulation is conducted to study the flow field characteristics of this rotor at different working conditions,so that the instability mechanism of the compressor is analyzed.Then,the stability enhancement capacity and mechanism of a new-type self recirculating casing which bleeds upon rotor blades are analyzed.Lastly,in order to explore the best casing structure form,the self recirculation casing with different structure is installed at tip region.In addition,the stability enhancement mechanism is studied further,and the reason why the stability enhancement capacity is difference among different casing structure is analyzed.First,three channels calculation model is established to analyze the flow field characteristics and the instability mechanism of the prototype.With the deepening of the rotor throttling,the deterioration trend of flow field at tip region is the most obvious,so the rotating stall begins at the top of blade.In the process of reducing flow rate,the starting position of tip leakage vortex moves forward,and the shock gradually detaches.These lead to the leakage vortex gradually losing its normal velocity resisting the strong inverse pressure gradient of the shock,which results in the leakage vertex breaki down behind the shock surface finally.The accumulation of low energy fluid at the pressure side of the tip,induced by interference between shock and vortex,prevents air coming into the channel,and then the compressor is characterized as blockage instability.The development of low energy cells at tip is unsteady,which affects the pressure distribution at pressure side of the passage periodically,and then the leakage flow and low energy cells coming from the interference between shock and vortex also present the similar development characteristics to the previous one in adjacent passage.This leads to the circumferential propagation mechanism of the unsteady development of the leakage vortex and the low energy cells.Secondly,the self recirculating casing model bleeding air at tip is established.The improvement of stall margin is achieved by 3.33% using only 0.36% of the main flow.It hardly affects the distribution of the total pressure ratio and efficiency characteristic lines before the near stall condition,and the peak efficiency is reduced by only 0.23%.On the one hand,the incidence angle can be periodically reduced through the periodic jet excitation.On the other hand,the leakage flow and low energy cells can be directly excited,and the leakage and low energy cells can be pushed down to the downstream channel.Among the two factors,the second one plays a major role,and the effects of exciting the low energy cells behind the shock surface is better than that of exciting leakage vertex in front of shock.The self recirculation casing enhances the separation on the suction surface at the same time,but overall,it still plays a positive role in the tip flow field,and delays the occurrence of instability.The bearing capacity of the rotor can be improved by the self recirculation casing,and the time average diffusion factor of the rotor can be increased.But when the throttling degree is further deepened,the benefit coming from periodic jet excitation can’t maintain the flow capacity of the tip,and then the rotor characterizes as blockage instability similar to the prototype.Finally,several self recirculating casing models with different air bleeding structure forms are established.The difference of the stability enhancement capacity among the three kinds of self recirculating casing with different axial bleeding positions,but without circumferential bias is determined by the magnitude of jet momentum.Through comparing the positive bias casing treatment form which bleeds from tip with the two kinds of casing treatment forms without circumferential bias which bleed behind rotor,it is found that the unsteady process of the coupling between the bridge and the tip flow field can significantly affect the stability enhancement capacity of the self recirculation casing.When the jet is concentrated on the region near pressure surface at the inlet of the channel,the capacity of stability enhancement can be stronger.更多还原