Presence "Cross Flow Fan" of the vortex, the output of the impeller creates a circulating flow in the vortex, the air flow within the impeller line circular arc. Therefore, the impeller outer circumference of the flow rate at each point is inconsistent, closer to the vortex center, the greater the speed, the more close to the volute, the speed is smaller. Fan in the outlet air flow rate and pressure is not uniform, and thus the fan flow coefficient and pressure coefficient is an average value. Vortex position on "Cross Flow Fan" greater impact on performance, close to the center of the vortex circumference and near the volute tongue, better performance fan impeller; vortex center far from the vortex of the tongue, the regional circular flow increases, "Cross Flow Fan" reduce efficiency, increase the degree of flow instability.