Effects of Nonaxisymmetric Tip Clearance on Axial Compressor Performance and Stability
Effects of Nonaxisymmetric Tip Clearance on Axial Compressor Performance and Stability
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DOI：
10.1115/1.2841774
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发表时间：
1998-10
影响因子：
1.7
通讯作者：
M. Graf;T. S. Wong;E. Greitzer;F. E. Marble;C. Tan;Hyoun-Woo Shin;D. Wisler
中科院分区：
文献类型：
--
作者：
M. Graf;T. S. Wong;E. Greitzer;F. E. Marble;C. Tan;Hyoun-Woo Shin;D. Wisler
通过实验和理论分析研究了叶顶周向间隙不均匀对轴流压气机性能和稳定性的影响。建立了具有非轴对称叶顶间隙的压气机性能理论模型，并利用该模型在一台四级低速压气机上进行了一系列实验。实验和计算结果清楚地揭示了压气机非轴对称叶顶间隙响应的主要物理特征和控制参数。研究发现，失速余量的损失比按平均净空估算的损失要严重得多。事实上，失速点更接近于在最大净空水平上进行均匀净空时获得的失速点。叶尖间隙的周向长度尺度(以及伴随的流动不对称性)是决定降低失速裕度的重要因素。对于相同的平均间隙，基波波长等于压气机周长的非对称性比波长等于压气机周长的一半的非对称性的峰值压升损失高50%。间隙不对称对峰值效率的影响要小得多；测量得到的最大效率下降不到0.4%，而不对称间隙导致的峰值压力升高下降了8%。因此，非轴对称叶尖间隙的效率损失接近于在周向平均水平上具有均匀间隙时的效率损失。理论模型准确地捕捉到了与间隙不对称相关的稳态压力升降和稳定工作范围的减小。它还很好地描述了观察到的趋势：(I)速度不对称性随着压气机流量的减小而增大，(Ii)间隙不对称性的影响随着间隙分布的主导波长的减小而减小。时间分辨数据表明，预失速传播扰动在压气机环隙中的空间结构被很好地描述，稳定性极限过程可以与这些扰动模式的非定常结构联系在一起。该模型还被用于参数研究，以确定间隙的周向分布、稳态压气机压升特性和系统动态参数对压气机性能和稳定性的影响。对间隙不对称性的敏感性随着频率的降低而急剧下降，随着峰值压力的升高和峰值附近特性曲率的增加而增加。
The effects of circumferentially nonuniform tip clearance on axial compressor performance and stability have been investigated experimentally and analytically. A theoretical model for compressor behavior with nonaxisymmetric tip clearance has been developed and used to design a series of first-of-a-kind experiments on a four-stage, low-speed compressor. The experiments and computational results together show clearly the central physical features and controlling parameters of compressor response to nonaxisymmetric tip clearance. It was found that the loss in stall margin was more severe than that estimated based on average clearance. The stall point was, in fact, closer to that obtained with uniform clearance at the maximum clearance level. The circumferential length scale of the tip clearance (and accompanying flow asymmetry) was an important factor in determining the stall margin reduction. For the same average clearance, the loss in peak pressure rise was 50 percent higher for an asymmetry with fundamental wavelength equal to the compressor circumference than with wavelength equal to one-half the circumference. The clearance asymmetry had much less of an effect on peak efficiency; the measured maximum efficiency decrease obtained was less than 0.4 percent compared to the 8 percent decrease in peak pressure rise due to the asymmetric clearance. The efficiency penalty due to nonaxisymmetric tip clearance was thus close to that obtained with a uniform clearance at the circumferentially averaged level. The theoretical model accurately captured the decreases in both steady-state pressure rise and stable operating range which are associated with clearance asymmetry. It also gave a good description of the observed trends of: (i) increasing velocity asymmetry with decreasing compressor flow, and (ii) decreasing effect of clearance asymmetry with decreasing dominant wavelength of the clearance distribution. The time-resolved data showed that the spatial structure of the prestall propagating disturbances in the compressor annulus was well represented and that the stability limiting process could be linked to the unsteady structure of these disturbance modes. The model was also utilized for parametric studies to define how compressor performance and stability are affected by the circumferential distribution of clearance, steady-state compressor pressure-rise characteristic, and system dynamic parameters. Sensitivity to clearance asymmetry was found to fall off strongly with the (asymmetry-related) reduced frequency and to increase with peak pressure rise and increasing curvature of the characteristic near the peak.