CFD Investigation of Vane Nozzle and Impeller Design for HPT Blade Cooling Air Delivery System

Abstract

In the design of a HPT blade cooling air delivery system, sufficient supply pressure and lower relative total temperature are required to guarantee HPT blades working properly in the high temperature environment. The pre-swirl vane nozzles and the radial impellers are used in the delivery system with lower radial location of pre-swirl nozzle to achieve the requirements. In this paper, CFD analysis is utilized for designing the vane nozzles and the radial impellers. Two HPT blade cooling air delivery systems were explored. The baseline is a system without impellers, and the alternative is a system with impellers. The results show that the impeller contributes to the delivery system by pumping effectiveness thus decreasing the extracted air pressure. The parity of swirl ratio between the flow and the broach slots is a main factor that decreases the system pressure loss, which can be improved by the radial impellers. The well-designed contoured radial-impeller vane with 30° front angle and 20° trailing angle is recommended in the blade cooling air delivery system design because of its good aerodynamic performance and closely radial outflow. The cascade vane nozzle with more than 70° angle turn is recommended in the pre-swirl nozzle design. It has a good aerodynamic performance with discharge coefficient greater than 0.99 and deviation angle less than 1.3°. The well-designed radial impeller pays big contributions to the blade cooling air delivery system with 11.4% increase of the thermal effectiveness and 10.2% decrease of the pressure loss versus the system without impellers.