The effect of lean on the inlet flow of a single blade row was studied with the dimensionality reduction method

and the mechanism for lean improving endwall condition was explained by the inlet flow change. The circumferential fluctuation(CF) source items were obtained through the derivation of the circumferentially averaged Navier-Stokes(N-S)equations. The radial and circumferential components of the CF sources existed yet before the blade passage with a uniform incoming flow

representing the magnitude of the inlet CF. Different leaned cascade models were numerically calculated and circumferentially averaged. The results indicate that lean could change the magnitude and distribution of the CF source items before the blade passage

leading to the radial migration of the inlet flow. The positive lean diverts the inlet flow from hub to tip and improves the endwall condition

while the negative lean has a contrary effect.The inlet CF sources are also affected by the aerodynamic parameters such as the inlet Mach number

blade solidity and stagger angle. Neither an over-high inlet Mach number nor an over-wide stagger angle is good for the effect of blade lean on the inlet flow.