Numerical Investigation On The Influence Of Helicopter Infrared Suppressor On Helicopter Infrared Characteristics

Helicopter infrared suppressor is an effective device to reduce the infrared radiation and therefore improve the performance of infrared stealth of helicopter.Numerical research on the influence of infrared suppressor on helicopter infrared characteristics was carried out in this paper.The main work is as follows:a)The pumping-mixing performance of different types of infrared suppressors was compared.b)The influence of different hovering rotor downwash velocity and different exhaust direction on the flow-field and temperature-field of helicopter was analyzed.c)Based on reverse Monte-Carlo method,the calculation model of target's infrared radiation characteristics was established,so the infrared radiation features of infrared suppressor and helicopter were evaluated.d)Two kinds of helicopter infrared stealth measures were put forward and the feasibility analysis was launched.Therefore,the results of this paper can provide the basis for both structure design of infrared suppressor and the stealth design of helicopter.The research results showed that,the infrared suppressor can effectively reduce the infrared feature of helicopter in 3-5?m band,and the lobed nozzle infrared suppressor has better pumping-mixing performance and infrared suppression effect.However,the suppressor's ejecting coefficient decreased by 30%after installed which indicates that the study on infrared suppressor should take the influence of helicopter into consideration and shall be based on the whole machine.Besides,under hover condition,the pumping capacity on the direction of vertical-up,slant-up 45° and horizontal respectively experienced down-going,a peak,up-going when the downwash velocity increased,and heating effect caused by exhaust gas on the tail beam of the fuselage is most obvious on the vertical-up direction and least in the horizontal direction.The direction of exhaust gas has obvious influence on the infrared characteristics of helicopter,while some certain angles would lead to the most evident infrared feature on each direction.Two kinds of stealth measures were proposed and evaluated based on the results above.It proved that adding covering shelter combination with reducing the emissivity of both lobed nozzle and curved mixing duct could effectively reduce the infrared radiation characteristics of helicopter in both horizontal and vertical directions,thus improving the infrared stealth performance of helicopter.