Experimental investigation of relationship between flange height and flanged diffuser performances

Flange height is between the geometric futures of the diffuser that contributes efficiently in improving diffuser performances. Results obtained from experimental data show a critical ratio (Flange height/Inlet section diffuser diameter = 0.2) has been found. Beyond this value, due to the remoteness of vortices from the flange, the flange height seems to be without significant effect on increasing wind velocity. It was be demonstrated that when a flange is mounted at the diffuser outlet section, two contra-rotating vortices were created at this location. These two vortices move away from each other in the flow direction as the flange height increases and they seem to lengthen in the streamwise direction and to extend in the two directions when the flange height becomes taller.