An Experimental Study of Cross Flow Fan : 2nd Report, Movements of Eccentric Vortex inside Impeller

Abstract

Relations between the shape of performance curve and flow pattern of cross flow fan are investigated. Total pressure distributions along inner periphery of impeller are measured by traversing a three-hole circular yaw probe. Output signals from a hot-wire probe fitted to impeller are photographed to show the relative flow through blades. Movements of the eccentric vortex inside impeller are measured by these methods, and the following results are obtained. When the flow rate decreases, the vortex center moves along the inner periphery of impeller towards the tongue over the flow rate corresponding to the maximum of ψt. Substantially different two types of flow patterns appear according as φ is larger than 0.3 or not. That is, when φ>0.3, the shape of tongue is the determining factor to the flow pattern, if casing of ordinary size are used. However, when φ<0.3, both the angle of delivery arc of impeller and the size of casing affect the pattern as well as fan performance.