Investigation on the suitability of conventional film hole under pulsed detonation incoming flow conditions

Abstract

As a novel and efficient engine, the pulse detonation engine will increasingly demand advanced cooling technology. Film cooling, widely utilized in conventional aero engines, is also anticipated to be employed in pulse detonation engines. However, further investigation is required to assess the suitability of conventional film holes for pulse detonation engines. This study determines the cooling characteristics of a plate with a single film hole in a pulse detonation engine operating at a frequency of 30Hz through numerical calculations. The types of film holes considered include cylindrical, fan-shaped, laid-back, laid-back fan-shaped, and converging-slot holes, all of which have a diameter of 1 mm and an inclination angle of 30°. The single pulse detonation period is divided into stages: initiation and detonation wave propagation, gas exhaust, and refilling. During the initiation and detonation wave propagation stage, the film hole exhibits a significant backflow phenomenon, with the magnitude of gas backflow positively correlated with the outlet area of the film hole. Notably, the converging-slot hole experiences the least amount of gas backflow, with an exit area 33 % smaller than that of cylindrical holes and a corresponding 18 % reduction in backflow enthalpy. Throughout the initiation and detonation wave propagation stage, the backflow gas carries an enthalpy ranging from 0.43 J to 0.63 J into each individual film hole. In the gas exhaust stage, the blowing ratio increases over time as the mainstream pressure decreases, leading to a rapid decline in the film cooling effectiveness of the cylindrical and laid-back holes. The converging-slot holes have the largest film covering area, thus exhibiting the highest film cooling effectiveness, which is 53 % higher than that of the cylindrical hole. In the refilling stage, the mainstream temperature reaches the same level as the secondary flow temperature, rendering the consideration of the cooling characteristics of the film hole unnecessary. Under the conditions of this study, the converging-slot hole is found to be most suitable for cooling the pulse detonation engine.