COMPATIBILITY OF 3-D TURNING DIFFUSERS BY MEANS OF VARYING AREA RATIOS AND OUTLET-INLETCONFIGURATIONS

Combined turning and diffusing is often associated with detrimental flow phenomena that contribute to losses induced by the very nature of its geometry. This paper aims to investigate the compatibility of using 3-D turning diffusers in improving pressure recovery and flow uniformity by means of varying area ratios (AR) and outlet-inlet configurations (W2/W1, X2/X1). There were three cases considered; (i) Case-A (reference): 2-D turning diffuser (AR=2.0, W2/W1=2.0, X2/X1=1.0), (ii) Case-B: 3-D turning diffuser (AR=2.0, W2/W1=1.5, X2/X1=1.3) and (iii) Case-C: 3-D turning diffuser (AR=4.0 W2/W1=1.5 and X2/X1=2.7). Inflow Reynolds Number (Re) approximately of 20 was applied. The experimental rig was set up with the diffuser models fabricated using acrylic. Particle Image Velocimetry (PIV) was used to acquire the velocity profile and visualize the flow structure in the diffusers. Digital manometer with resolution of 0.1Pa provided pressure values. Results show pressure recovery (Cp) of respectively 0.3, 0.1 and 0.5 gained for Case A, B and C. In terms of flow uniformity, standard deviations (σu) of 2.04E-03, 3.14E-03 and 2.57E-03 were recorded, respectively. There was a reduction in terms of recovery and uniformity when a 3D turning diffuser with an AR=2.0 was introduced. Whereas, the compatibility of 3-D turning diffuser with an AR=4.0 seems more promising. The results obtained in this study will be used to validate the CFD codes. The intensive CFD simulation by means of varying other geometry configurations in the event of different inflow Reynolds number will be carried out in future.