In the multi-blade fan, there is the large re-circulation region near the front shroud. Hien the flow in the impeller is fairly varied in span direction. We proposed the prediction method for the flow characteristics of the multi-blade fan, in which it is considered the re-circulation region and the flow variation in span-direction. The two-step procedure is proposed. The first step is the potential flow procedure that is included the vortex ring and the source. It can be roughly estimated the meridian flow distribution in span direction and the scale of the re-circulation region. The next step is the correction of the first step. It is proposed the criterion that the static pressure is kept constant in span direction. The blade load, which is estimated with the quasi-one dimensional empirical method, makes the span-wise width modified at the outlet of the impeller. The flow characteristics out of the blade passage were estimated. The predicted results were examined with the experiments and the references. The scale of the re-circulation region is predicted well. The flow characteristics of the impeller are roughly predicted.
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