Numerical Investigation of 180o Curved Diffuser Performance by Varying Geometrical and Operating Parameters

Abstract

The geometry of a curved diffuser often inviting the flow to separate. The flow separation phenomenon plays a vital role in the recovery of pressure inside the diffuser. Besides, the geometrical and operating aspects of a curved diffuser have always been taken into consideration in most relatable researches. Pressure recovery and flow uniformity of a steady, developed entering turbulent flow of a circularsectioned 180° curved diffuser has been investigated numerically by varying geometrical and operating parameters. The curved diffuser with area ratio (2, 3 and 4), radius of inlet and curvature of respectively 50 mm and 180 mm was considered. Different values of Reynolds number 6 × 10 4 , 12 × 10 4 , 18 × 10 4 , 24 × 10 4 , and 30 × 10 4 were tested in every area ratio set. ANSYS code Fluent was used to run the simulation by considering different turbulence models, i.e. the standard kturbulence model (std k-), Spalart-Allmaras turbulence model (SA), k-kl-transition turbulence model and transition SST model. The present work proposed the curved diffuser with AR=2 operated at Re=6x10 4 as the optimum set of parameters, with minimal flow separation occurring in the system.

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.…”

“…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

“…For validation, ske turbulence model adopted both standard and enhanced wall treatment was considered. Previous experimental work by Rasidi et al, [15] was referred to validate the best model to represent the case. As shown in Figure 4, ske turbulence model equipped with enhanced wall treatment resembles well the experimental case with a deviation percentage of approximately 0.83%.…”

“…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].…”