Finally, it is of interest to both aero-propulsion designers and experimentalists to recognize the non-uniform flow distribution at the fan exit plane. For designers, it is important to understand the details of the exhaust flow and its airfoil coupling effects through viscous entrainment, separation control, and thrust generation [22]. For experimentalists, it is critical that an adequate number of measurement locations are employed to obtain accurate prediction of overall total pressure rise. For example, as noted by Yu et al. [19], additional measurement locations at the exit diffuser were added to the earlier work of Seaton [52] and Cheng [53] to obtain more accurate experimental results.
Fig. 35 and Fig. 36 show CFD results of the total pressure ratio (denoted by PT), total temperature ratio (denoted by TT), and x-component velocity (denoted by Ux) as functions of vertical position along the diffuser exit at 4000 and 8000 rpm, respectively. In each figure, typical instantaneous profiles are plotted (denoted by the dashed lines) along with the time-averaged data (denoted by the solid lines). These figures clearly show that the exhaust flow is highly non-uniform, and the higher total pressure region is in the middle of the exhaust duct. For this particular cross-flow fan, spatial non-uniformity is much greater at 8000 than at 4000 rpm for all three values presented. In addition, the flow exiting the fan also has a high swirl velocity component as a result of the forward curved blading.