Research On Ir Suppressant Of Hot Exhaust With The Discrete Particles In Flight

Aircraft stealth technology determines not only the viability of combat aircraft, but also to ensure that finding and attacking the enemy before the war. Aerosol obscure is an effectual technique of I.R. suppression, which is applied to decrease the I.R. radiation of hot exhaust and hot nozzle in the bands from 3μm to 5μm and 8μm to 14μm.Based on the study and improvement on the calculation method, we reseach on the influencing factors and laws of aerosol obscure in flight through the numerical calculation. First, the software FLUENT is used to work out the flow field of the hot exhaust with paticles, and then a ray-tracing-method is applied to gain the radiation intensity of any spots in the space. In this paper, we calculate and analyze some conditions in flight of various parameters.The results show us that, with the increasing in flight speed, the aerosol cloud gets thinner, and so, the suppression capability gets reduced, but not linearly. And increasing the amount of spraying aerosol can efficiently enhance the suppresion capability. With the same spraying amount, C and SiO₂ are proved to be better, whose infraed suppression rate can be up to 80% when Ma=0.8 in flight. For the material C, when its diameter is 1μm, the suppression rate is the highest.On comparision, the spraying speed and angle don't significantly affect the discrete particle distribution and the infrared suppresion.In order to validate the calculation method, we carry on a serial of experiments on ground. An aerosol jet system is designed to release a layer of aerosol around the hot exhaust of engine. In the experiment, we mainly measure the infraed radiation before and after the aerosol spraying from 0°to 90°, here the materials SiO₂ and C are used. Finally, the experimental results are contrasted to the calculation ones, and thus the calculation method proves to be feasible.