Experimental study on the transient thermal characteristics of an integrated deflector under the periodic impingement of a supersonic flame jet

The flow deflector effectively facilitates thermal spreading and the split of high-temperature gas flow from jet impingement. In this study, we developed two samples of integrated deflectors with four layers. The first sample consisted of a composite of silicon carbide reinforced with carbon fiber (C/SiC), carbon aerogel, silica aerogel, and a sandwich corrugated plate. The second sample replaced carbon aerogel with lithium fluoride (LiF), a high-temperature composite material of phase change. Under the periodic impingement of a supersonic flame jet, the transient thermal response of the two deflectors was investigated experimentally. The thermal image of the impinged surface was obtained by an infrared camera. After four periods, the periodic temperature variation in this surface stabilized. The thermal disturbance propagated and attenuated gradually from the impinged surface to the corrugated plate back surface. The back surface temperature of corrugated plate increased monotonically with impingement period without any fluctuation. The entire temperature of the deflector was effectively controlled in the range from 3400 K (the total gas temperature) to 480 K at the centerpoint of the back surface of the sandwich corrugated plate without incurring thermal damage. The deflector temperature level and the ablation rate of the impingement surface were lowered further using LiF as a thermal shield layer because of its high storage of latent energy.