| || Computation of Flow through an Annular Diffuser and Volute Exhaust
Author : Arun, M.;Tulapurkara, E.G.;Sundararajan , T.
Source : Defence Science Journal ; Vol:56(2) ; 2006 ; pp 147-158
Subject : 621.438 Aircraft Gas Turbine Engines
Keywords : Conical diffuser;Annular diffuser;Swirl parameter;Turbulence models;Turbulent flow;Computer model;Computation;Diffusers
Abstract : Turbulent flow in a diffuser with swirl occurs in many commonly used fluid mechanical devices,eg, diffusers located downstream of a gas turbine, and in certain types of combustion chambers. Diffusers are widely used for converting kinetic energy to pressure, and a reliable prediction method of such flows with the required flow conditions would lead to the design of fluid machinery with improved efficiency. As a first step, turbulent swirling flow through a 12o included angle conical diffuser for a swirl parameter, m = 0.18 was numerically investigated using various turbulence models like standard k-e, RNG-based k-e, shear-stress transport (SST) k-w, and Reynolds stress model (RSM). Though the comparison between the experimental and the predicted mean velocity profile by RSM is superior to that by RNG k-e and SST models, the latter two models give closer comparison with the experimental pressure distribution. Subsequently, computation of flow inside a complex duct involving axisymmetric annular diffuser, transition from rectangular to circular cross section, and exit pipe have been carried out using RNG k-e and SST k-w models. The comparison of computed and experimental results indicates that the SST k-w model gives predictions with reasonable accuracy.