The flow in the cross flow fan is different from conventional turbo-machinery. The air passes the blades twice and the motion of the blades forms an eccentric vortex within the impeller. It is presented in this paper that the flow in the cross flow fan is divided to four parts; inflow, outflow, casing and tongue parts. The blade load is large in the outflow part and the circumferential variation of it is large. The pressure rise in the fan is higher at the short tongue than at the original tongue, but the efficiency is opposite to the pressure rise characteristics. The eccentric vortex emerges near the tongue in the impeller, and when the short tongue is used, the position of it moves to the outflow part. The energy increment in the impeller is different in circumferential position, that it is very large at the outflow part. The form of the eccentric vortex is closely relating to the fan performance, but the strength of it is not so large relating to it.
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