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.