The present paper has derived 2-D turbulent boundray layer differential equations including the effects rotation and curvature to solve gas-phase flow in Blade-to-Blade stream plane of centrifugal fans. Using single-phase-correlation model, we caculate the trails solid particles in blade channel and the balde erosion impacted by solid particles. The computation results show that this boundray layer method agree with practical situations better than the potential flow computation model. It is suitable for engineering caculation.