熵产控制体方法对压气机近零间隙流动损失的演变规律

以澄清近零间隙流动结构及流动损失随间隙的变化规律为目标,提出熵产控制体分析方法,可精确量化流场任意位置的局部不可逆损失.数值模拟发现,间隙在0.4%叶高范围内(称近零间隙)效率水平最高且出现一对应峰值效率最高的最佳非零间隙.熵产控制体分析表明:通道内总熵产随间隙变化规律与效率一致;间隙变化对动叶端区20%~80%弦长范围内的熵产改变最为明显,主导了总熵产的变化;间隙变化时熵产改变的流动区域不同,这是由于动叶端区主导损失的流动结构发生改变造成的.进一步结合流场结构,探讨近零间隙流动损失演变的可能原因:间隙为零时壁面剪切力是造成损失的主导因素;最佳间隙时流动均匀,损失最小. 

Entropy generation control volume method and its application into flow loss evolution in a compressor with near zero tip clearance

To clarify the variation of the flow structure and the flow loss of the near zero tip clearance, a method for analysis of the entropy generation control volume was presented, which could accurately quantify the local irreversible loss of the flow field at any position. The numerical simulation showed the efficiency was at high level when the tip clearance was within 0.4% span(called near zero tip clearance), and there was an optimal non zero tip clearance where efficiency reached maximum. Entropy generation control volume analysis showed that the total entropy generation in the passage was consistent with the efficiency when tip clearance changed;the entropy generation varied evidently at 20%-80% chord of rotor tip region, dominating the total entropy generation; with the change of tip clearance, the entropy generation of different flow regions varied differently, primarily owing to the change of the flow structure in the rotor tip region. Furthermore, the flow field structure was studied. When the tip clearance was zero, the wall shear stress was the dominant factor of the loss; when the clearance was optimal, the flow was uniform, and the loss was minimal.