Influence of geometric modeling of exhaust diffuser on aerodynamic design of heavy-duty gas turbine

Abstract

As a core component of gas turbines, the aerodynamic performance of the exhaust diffuser directly impacts turbine efficiency. Connected to the last-stage outlet, it guides the airflow while facilitating kinetic energy recovery. However, its structural volume not only increases the overall dimensions of the gas turbine but also restricts equipment compactness and layout flexibility. To address this, the numerical simulation method (based on the shear stress transfer model) is used to design the key geometric parameters of a gas turbine exhaust diffuser, including the inclination angle of the support plate, the shape of the tail cone and the expansion angle of the outer cone. The results show that the designed swept-back strut significantly improves the flow in the annular diffuser channel and affects the back pressure of the upstream turbine. By designing the tail cone shape and its length, the position of the maximum diffuser section of the diffuser can be changed, and the aerodynamic performance of the diffuser can be improved. The change in the flare angle of the outer cone does not affect the position of the maximum diffuser section, but with the increase of the angle, the aerodynamic performance of the diffuser decreases. In this studied, the maximum static pressure recovery coefficient per unit area of the diffuser is increased by 31.03%, the total pressure loss coefficient is reduced by 34.09%, while the length of the diffuser can be shortened by 30.34%, and the outlet area can be reduced by 20.27%.