Infrared Stealth Of Heat Source Target Based On Cold Plate And Stealth Film

With the booming development of the infrared detection technology and the continuous improvement of the detection performance,the survivability of the weapons on the ground has been greatly threatened,especially the heat source targets with a high power engine,such as tanks and armored cars.In order to elude infrared detection,the temperature control technology based on a cold plate and the emissivity regulation technology based on a dielectric/metal/dielectric multilayer film were proposed in this paper to reduce the infrared radiation characteristics of heat source targets and realize the infrared stealth.In order to obtain the infrared radiation characteristics of a heat source target,an armored car was selected as the typical heat source target.Its infrared radiation characteristics in different states were collected at different distances and analyzed.It was found that the main heat source lied in the exhaust pipe.In the stable operation of the armored car,the infrared radiation temperature of the exhaust pipe in the wavelength range of 8?14 ?m was up to 67.9 ?,which was 41.2? higher than that of the ground surface.Based on the analysis for the infrared radiation characteristics of the heat source target,an infrared stealth method using a cold plate to shield the infrared characteristics of heat sources was put forward.Firstly,the influences of structure and operating parameters of cold plates on the thermal shielding performance of the heat source targets were investigated by means of experiments.After that,the simulation models of the horizontal and vertical cold plates were constructed and verified by the experimental results.Based on the simulation models,the factors that affect the temperature control effect of the cold plates were discussed in detail,including the flow channel layout,the thickness of channel,the inlet volumetric flow rate and the thickness of thermal insulation material attached to the hot surface of the cold plate.The results demonstrated that as the number of flow passes increased,the temperature uniformity of the cold surface could be improved,but it would result in an increase in the flow resistance between the inlet and the outlet.Furthermore,the thickness of channel had little effect on the thermal shielding performance.What's more,increasing the inlet volumetric flow rate or the thickness of thermal insulation material is an effective way to improve the thermal shielding performance of the cold plate.However,it is necessary to consider the increase of the flow power consumption when increasing the flow rate.Finally,the infrared stealth performance of the cold plate in the outdoor environment was studied by means of experiment.The results indicated that the average temperature difference between the system surface and the ground surface was less than 3.8? when the heat source target at 84.4?was shielded by a cold plate.In order to achieve the visible and infrared compatible stealth,the emissivity regulation technology based on a dielectric/metal/dielectric multilayer film was proposed.The ZnS/Ag/ZnS film was determined according to material selection and structure design,and the influence of each layer thickness on the visible transmittance and the infrared reflectance was analyzed by the transfer matrix method.The results showed that as the thickness of the outer ZnS increased,the position of the transmission peak would shift toward the long wave,while the infrared reflectance was almost unchanged.With the increase of Ag layer thickness,the visible transmittance was lower and the infrared reflectivity was higher.As the thickness of the inner ZnS layer increased,the transmittance of visible light decreased,while the infrared reflectance was almost unchanged.The luminous transmittance of the optimized ZnS(40 nm)/Ag(14 nm)/ZnS(45 nm)multilayer film is 0.92,and the average reflectance in the infrared atmosphere window(3?5?m and 8?14 ?m)is 0.95.In addition,the preparation technology of ZnS/Ag/ZnS film was explored,and ZnS(35 nm)/Ag(17 nm)/ZnS(35 nm)film was prepared by vacuum thermal evaporation.The corresponding luminous transmittance is 0.882 and the average infrared reflectance is 0.968,which indicates that the visible-infrared compatible stealth was realized.In order to make the heat source target radiate heat through the non-atmospheric window(5?8 ?m),the periodic hole array were introduced into the ZnS/Ag/ZnS film,and the influence of the structure parameters of the hole array was analyzed by the FDTD method.The results demonstrated that the transmission peak of the designed thin film was mostly located in the 5?8 ?m region and the transmittance at 5.57 ?m was up to 0.872,implying that the heat source target can radiate heat to the external environment through the non-atmospheric window.