Numerical Investigation of flow through Annular Diffusing Duct

In the present investigation the distribution of mean velocity, static pressure and total pressure are experimentally studied on an annular curved diffuser of 37.5° angle of turn with an area ratio of 1.273 at Reynolds number 1.85 x 10 based on inlet diameter and mass average inlet velocity. The experimental results then were numerically validated with the help of Fluent and then a series of parametric investigations are conducted with same centre line length and inlet diameter but with different area ratios varying from 1.25 to 2.0 with change in angle of turn from 30o to 75o.The velocity distribution shows high velocity fluids shifted and accumulated at the concave wall of the exit section due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The maximum values of the mass average static pressure recovery and total pressure loss are 27% and 18% compared to the predicted results of 31% and 21% respectively, which shows a good agreement between the experimental and predicted results. From the parametric investigation it is observed that static pressure recovery increases up to an area ratio of 2 and pressure recovery decreases steadily up to angle of turn 75o. The coefficient of total pressure loss almost remains constant with the change in area ratio and angle of turn for similar inlet