The Cooling Effect of Combustor Exit Louver Scheme on a Transonic Nozzle Guide Vane Endwall

The ever-increasing combustor exit temperature in modern turbine engine designs raises cooling challenges for the nozzle guide vane (NGV). Due to the complexity of NGV cooling design, the cooling effect from the upstream combustor cooling features can prove valuable. This study investigates, experimentally and numerically, the cooling effect of a louver cooling scheme near the combustor exit on the NGV endwall. Wind tunnel testing and computational fluid dynamics simulation are carried out with engine-representative conditions of an exit Mach number of 0.85, an exit Reynolds number of 1.5 × 10⁶, an inlet turbulence intensity of 16%, and a density ratio of 2.1. Various coolant mass flow ratios from 1% to 4% are tested to demonstrate the effect of the coolant rate. For the geometry studied, the results found a critical mass flow ratio between 1% and 2%. When exceeding this rate, the coolant forms a uniform film, providing satisfactory coverage upstream of the NGV passage inlet. For the cooling of the NGV passage, the mass flow ratio of the range investigated is insufficient for desirable cooling performance. The pressure side endwall proves the most difficult for the coolant to reach. In addition, the fishmouth cavity at the combustor–NGV interface causes a three-dimensional cavity vortex that transports the coolant in the pitch-wise direction. The coolant transport pattern is dependent on the coolant mass flow ratio. Based on the results, the authors propose combining this louver scheme with the upstream jump cooling scheme for a desirable NGV cooling system.