Final work : Conception and investigation of new designs of pre-swirl nozzles manufactured with additive manufacturing

Abstract

Pre-swirl systems are important components for the internal cooling of turbomachinery. They allow to reduce the total relative temperature of the rotor disc and blades by feeding the rotor with a fast and tangential air. The gases exiting the combustion chamber can therefore have higher temperature, thus, increasing the overall efficiency of the turbomachinery. This thesis aims at investigating a new design of pre-swirl system from a jet engine high pressure turbine (HPT) core made with additive manufacturing (AM). Indeed, additive manufacturing presents many assets for the aeronautic industry as it offers new possibilities in terms of design while reducing the component mass. The study consists in 3D CFD analysis on Fluent for steady take-off operating conditions. The thermal, aerodynamic, integration and additive manufacturing requirements related to pre-swirl systems are detailed. This led to a pre-swirl system with a curved nozzle and a house shape cross section. Different geometry influence studies are conducted to investigate the new design. The influence of surface ratio between the nozzle inlet and throat surfaces and reduced radius R are examined. An air intake device (AID) located at the inlet of the nozzle is also studied. The configurations are compared to the radial pre-swirl system with vane nozzles of a HP turbine core representing the baseline configuration. The flow performances are evaluated in terms of outlet mass flow, discharge coefficient, throat Mach number and nozzle outlet swirl ratio. As preliminary results, the impact of the sub-chamber upstream of the pre-swirl system is studied. The transition between this chamber and the pre-swirl system can be assimilated to an elbow duct. This elbow duct introduces turbulences leading to performance losses. The influence studies have shown that a high surface ratio and a low reduced radius offer the best flow performances. Furthermore, the AID device reduces the losses at the nozzle inlet improving the performances. The comparison of all the AM nozzle configuration has shown that the configuration with the highest performances is R=0.2 with AID. However, the current AID design introduces mass to the assembly and doesn’t improve significantly the flow performances for low reduced radius configuration. Therefore, the selected optimum configuration is R=0.2 without AID. This configuration has a lower mass from 30% compared to the baseline configuration. However, in terms of flow performances, it shows lower results compared to the baseline configuration, especially for the Mach number and swirl ratio.