Turbulent Flows in a Two-Dimensional 180° -Curved Diffuser With a Guide Vane

Numerical and experimental investigations of the flow in a two-dimensional 180°-curved diffuser, with a guide vane interposed in the diffuser, is presented to clarify their characteristic and to improve the curved diffuser performance. Particular attention is focused on the effect of the variation in the interposed position of the guide vane on the flow field and pressure recovery. Measurements for mean longitudinal and transverse velocity profiles as well as the wall static pressure are performed at different downstream stations. Comparisons are made between the present measurements for the diffuser with a guide vane and without a guide vane [10]. The numerical investigation is based on the solution of the governing equations using a finite volume technique employing SIMPLE algorithm on co-located body-fitted grids. The two-equation model of turbulence, standard k-ε model, and the modified k-ε model [15] are employed in this investigation. The study indicated that the emerging velocity distribution is more uniform than that associated with flow in the diffuser without a guide vane. The presence of a guide vane is shown to suppress the formation of the region of flow separation, as a consequence, the performance of the diffuser is improved. The overall pressure recovery is 54% of the inlet dynamic pressure. The comparison between the numerical and experimental results indicates that the modified k-ε model satisfactorily predicts the overall characteristics of the flow in the diffuser. Numerical predictions show that the best position for a guide vane is positioning the vane towards the convex wall of the diffuser. Diffusers with a guide van at B/W₁ = 0.25 to 0.333 give the highest-pressure recovery coefficient.