Investigation of film cooling performance of the V-shaped cratered diffusion hole on the guide shield of the exhaust system

The guide shield is positioned on the exterior of the bearing strut of the turbine rear frame, serving the dual purpose of insulating from hot gas and providing rectification. However, the guide shield still faces the severe risk of the external high-temperature environment for the advanced aero-engine. The conventional cylindrical hole exhibits inadequate spanwise cooling performance. To enhance film cooling effectiveness (η) for the guide shield, a new type of V-shaped cratered diffusion (VSCD) hole is proposed in this paper. The η of the guide shield is measured by the pressure-sensitive paint (PSP) technique. The effect of the density ratio (DR = 1.0, 1.5, and 2.6) and blowing ratio (BR = 0.5, 0.75, 1.0, 1.25, and 1.5) on the η of the guide shield is considered. Furthermore, the interaction of the mainstream and the coolant also is predicted by the numerical simulation with the RANS method. The results indicate that the VSCD hole can decline the jet momentum of the cooling film, which greatly increases the adhesion of the coolant on the central line of the hole. The introduction of the V-shaped crater creates a diversion effect, leading to the emergence of areas with the heightened η on both sides of the outlet of the V-shaped crater. Increasing the DR of the coolant, the η of all the guide shields is dramatically enhanced. As the BR grows, the coverage of the coolant on the guide shield is raised, whereas, the growth ratio gradually decreases. Compared to cylindrical holes, VSCD holes exhibit more pronounced advantages at higher BRs. At BRs of 0.5, 1.0, and 1.5, the area-average η values increase by 18.2%, 20.7%, and 24.5% respectively for VSCD holes. The proposed VSCD hole can significantly improve the η and provide an optional scheme for efficient cooling of the guide shield under practical conditions.