Experimental Analysis of Infrared Cooling Characteristics of Wall-attached Nozzle

Aiming at the problem of infrared radiation in the 8-14 μm band of ships, a water curtain spray method was adopted to attenuate the infrared radiation intensity of a target, and an infrared thermal imager was employed to build a wall attached nozzle test system. Through comparative design experiments, the influences of different spraying distances, total spray flow rates, and temperatures of the steel plates on the infrared cooling characteristics of the wall nozzles were analyzed. The test results show that when the target steel plate is in the hollow area, and the boundary between the hollow area and the coverage area, the infrared cooling rates are 2.03 and 3.31℃/min, respectively. When the target steel plate was in the coverage area, there were non-overlapping and overlapping areas in the spray. The maximum cooling rate of the non-overlapping area was 6.18℃/min, and the cooling rate of the overlapping area under the same radius was 6.54℃/min. The infrared cooling time in the overlapping zone was 40 s, which was 32 s shorter than that in the non-overlapping zone. Moreover, an increase in the total spray flow resulted in a significant increase in cooling of the steel plate. The higher the initial temperature of the steel plate, the higher the cooling rate of the wall nozzle. In addition, the temperature difference between the steel plates inside and outside the water curtain can reach up to 8.49℃. Studies have shown that the water curtain spray formed by a wall-attached nozzle can effectively cover the surface temperature of the steel plate, reduce the infrared detectability of the ship surface, and realize water curtain spray stealth. These results provide a technical reference for improving the infrared stealth performance of ships.