Unsteady Flow Analysis of a Highly Loaded High-Pressure Turbine of a Gas Turbine Engine

Advanced fighter aircraft requires a gas turbine engine with high thrust to weight ratio of the order 10 and low specific fuel consumption of the order 0.7 (kg/kg-hr) to meet the high maneuverability, long range, and low life cycle cost requirements. To meet high thrust to weight ratio and low specific fuel consumption, aero gas turbine engine demands high turbine entry temperature and high turbine efficiency. In order to reduce design cycle time typically, a turbo machinery design process is carried out with the assumption that the flow is steady. However, the fluid flow in turbo machinery is highly three-dimensional and inherently unsteady due to stator–rotor interactions through wakes, potential flow, and shock interactions. In this paper, an attempt is made to analyze the unsteady flow in a transonic High-Pressure (HP) turbine which is having high blade loading and low aspect ratio, and is designed for an advanced engine. The calculations are performed by using ANSYS-CFX, which is a commercial software. This software solves three-dimensional Navier–Stokes equations. Structured grids are used in this analysis and turbulence is modeled by using k–ω SST turbulence model. Sliding interface models are used for unsteady simulation studies to analyze the flow field of the turbine stage. Numerical study shows that total-to-total efficiency of the HP turbine stage decreases by 0.4% due to unsteadiness as compared to steady state.