Development of Performance Correlations using ACFD Method for 2-D Curved Diffuser

Abstract

Diffuser is a fluid mechanical device which allows the recovery of pressure energy from the fluid flow on the outlay of kinetic energy. Performance of turning diffuser is evaluated primarily by pressure recovery coefficient, and flow uniformity,. The varying of geometrical and operating parameters could alter the performance of the diffuser. Hence, this study aims to investigate the effect of angle of turn, on 2-D curved diffuser performance and to develop performance correlations. The angle of turn was varied from 30°to 180°. The evaluation for performance of the curved diffusers was done by using ANSYS Fluent with the most appropriate turbulence model of Reynolds Stress Model (RSM) added with enhanced wall treatment of + =1.0. Performance correlations in terms of pressure recovery and flow uniformity were developed by implementing Asymptotic Computational Fluid Dynamics (ACFD) technique. Pressure recovery of the curved diffusers showed a declining pattern by approximately 79.5% while flow uniformity shows higher distortion up to 52.6% with the increase of angle of turn from 30°to 180°. Hence, it has been proven that the increase of angle of turn has affected the performance of curved diffuser significantly. The ACFD performance correlations has provided acceptable deviations to both CFD and experimental results.

Effect of Angle of Turn on Loss Characteristics and Flow Rectification of Curve Diffuser

“…Three (3) turbulence models (Standard k-, Renormalization Group k- and Realizable k-epsilon) adopted enhanced wall treatment were considered for the validation. A turbulence model that could provide the least discrepancies with similarity of flow characteristics to the experimental case [10][11][12][14][15][16] was chosen for the intensive simulation.…”

“…Three k- turbulence models (ske, rngke, rke) were considered to simulate the case with the best model opted from validation. Pressure recovery coefficient (Cp) and flow uniformity index (out) are the parameters used to assess the performance [5][6][7][8][9][10][11][12][13][14][15][16][17]:…”

“…Curve diffusers with an angle of turn (30 o , 90 o , 120 o , 150 o , 180 o ), area ratio (1.60, 2.16, 4.00) and inflow Reynolds number (5.934x10 4 , 8.163x10 4 , 1.783x10 5 ) are considered. These ranges of variables are opted to serve common operating settings of curve diffuser for subsonic applications such as wind tunnel and HVAC systems [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Effect of Expansion Direction/Area Ratio on Loss Characteristics and Flow Rectification of Curve Diffuser

“…There are abundant works done previously to investigate the effects of geometrical and operating parameters on diffuser performances [10][11][12][13][14][15][16][17][18][19][20], but none has focused on the effects of area ratio (AR) configured with different expansion directions, i.e. 2D expansion (z-direction), 3D expansion (x-and z-direction), 2D expansion (x-direction) and inflow Reynolds Number (Rein).…”

“…Therefore, this study aims to numerically investigate the effects of expansion directions of 90 o curve diffuser with AR= 1.2, 1.6, 2.16, 3.0, 4.0 and Rein= 5.934 × 10 4 , 8.163 × 10 4 , 1.783 × 10 5 on pressure recovery and flow uniformity. These ranges of variables are opted to serve common operating settings of curve diffuser for subsonic applications such as wind tunnel and HVAC systems [7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”