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Experimental Study on Cooling Efficiency of Hypersonic Optical Window
Author(s): Qi Mi, ShiHe Yi, Zhao Xinhai, Bo Zhang, XiaoGe Lu
Keywords: Optical window; Supersonic film; Injection nozzles; Cooling efficiency
The cooling effectiveness of optical window restricts the imaging quality of hypersonic vehicles. This study focuses on the supersonic film cooling efficiency on the optical window of a blunt cone. The experiments were conducted in the Mach8 gun wind tunnel with a total temperature of 900K and a total pressure of 9MPa. Three tangential 2D nozzles with different combinations of slot height and Mach number were designed to detect the film cooling length under different injection pressures. The heat flux on window surface was measured by Thin Film Gauges and the flow field was monitored by schlieren technique. The results showed that the cooling length of film was positively correlated with the Mach number and slot height of the nozzle. However, the higher the Mach number and the higher slot the nozzles were, the greater mass flow rate of injection was demanded. Therefore, the main factor that determines the cooling length was the mass flow rate. When the jet pressure matched the mainstream, the window was completely cooled, and the minimum mass flow rate was required when the slot height was 5mm and the jet Mach number was 2.5. If the pressure ratio of jet continues to increase, the heat flux density could be furtherly reduced, but the cooling efficiency of film injection decreased. Besides, the increase of jet pressure resulted in thickening the mixing layer, which enhanced the heat insulation effect and reduced the heat flux as a result.

Journal of Applied Fluid Mechanics

The Journal of Applied Fluid Mechanics (JAFM) is an international, peer-reviewed journal which covers a wide range of theoretical, numerical and experimental aspects in fluid mechanics. The emphasis is on the applications in different engineering fields rather than on pure mathematical or physical aspects in fluid mechanics. Although many high quality journals pertaining to different aspects of fluid mechanics presently exist, research in the field is rapidly escalating.