Design And Analysis Of Exhaust Diffuser Of Gas Turbine Afterburner Using CFD
The exhaust diffuser is a part of an afterburner of the gas turbine engine which decreases the velocity of gases
coming from the low pressure turbine. The decrease in velocity is required to reduce afterburner cold and hot total pressure
loss and to increase flame stability. It helps in better flow control and diffusion in exhaust diffuser leading to increased thrust
and combustion efficiency. The present work deals with design and analysis of an exhaust diffuser of gas turbine afterburner.
In this study, a baseline diffuser configuration has been designed using 1-D empirical relations. The baseline diffuser
configuration has been incorporated into a practical afterburner and the performance of the exhaust diffuser evaluated under
non-reacting condition using CFD. Further the diffuser modifications have been carried out using CFD to arrive at a
configuration which gives minimum total pressure loss and Mach number. Commercial CFD software, ANSYS FLUENT
has been used for the CFD analysis. A significant improvement in performance has been obtained by managing the contours
of the diffuser and length. Further a reacting flow analysis has been carried out for the finalized afterburner configuration in
order to study the performance of diffuser and the afterburner under reacting (combustion) flow condition. From the
analysis, total temperature rise, velocity of flow and thrust of the afterburner has been determined. In addition, the CFD
analysis has been extended for different engine bypass ratio and different engine flight conditions of the afterburner to
evaluate the diffuser performance.
Index Terms— Afterburner, Exhaust diffuser, CFD, Non-reacting and Reacting flow.