Design and Analysis of Annular Exhaust Diffuser forJet Engines

Abstract

ower and efficiency of the gas turbines depends highly on the performance of the exhaust turbine diffuser. To build a high efficient diffuser gas turbine we need to consider the flow through unsteady interaction with the high and low pressure rotating stage of the turbine, which create swirl flow. Study of various literature shows that there is room for improvement to enhance turbine performance. Since diffuser is the hub which deals with varying degrees of swirl. Swirl flow in diffuser section will create problems like, pressure loss during flowing across struts and reducing transitional Reynolds number renders the flow to turbulent which is not favourable. Annular diffuser with spokes and struts designed to recover pressure and to convert the swirl flow into laminar thereby increasing the transitional Reynolds number, which are favourable in increasing the turbine performance. The flow is simulated by k-ε model with the help of ANSYS Workbench. A scaled model of typical gas turbine exhaust diffuser which consists of annular diffuser with spokes and struts is investigated experimentally. A radial swirl generator is used to set up swirling flow at the inlet. A part of differences attributing to the diffuser spokes and struts are neglected to reduce the complexity in calculation. In this work both numerical and experimental results validated and concluded that the turning the excessive swirl flow into laminar flow with the advantage of avoiding turbulent flow, increase the transitional Reynolds number.