Research On Stealth Aircraft Exhaust Plume Infrared Detection Simulating Technique

With the increasing number of stealth aircraft using various stealth technologies and cruising at supersonic speed, most radar have had limited capacity to effectively detect them resently. If infrared detect system can be used to detect the stealth aircraft and obtain early warning, it can thus provide important basis to counter stealth aircraft.Not only is high-temperature exhaust plume the main infrared radiation source of stealth aircraft, but also it acts as fisrt-cosidered object of infrared stealth.So the research on high-temperature exhaust plume is of great significance.This thesis builds the model and simulates based on F-22 jet nozzle, and studies the plume infrared detection relevant technologies of stealth aircraft, which provides the theoretical and technical to the infrared detection and trace of the exhaust plume of stealth aircraft in near space platform. The detailed researches are as follows.(1)The infrared radiation intensity of the stealth aircraft are analyzed,building the geometric model of jet nozzle with GAMBIT software,discretizing the flow field calculation domain through grid partition, and getting temperature, pressure and other data of the exhaust plume flow field through the Fluent simulation. Given the unevenly distribution property of temperature, pressure and other features for the exhaust plume flow field and the spectrum selectivity of infrared radiation,we use C-G line approximation method to combine the line of sight direction and jet direction of the tail flame stratified flow field.This thesis calculates the infrared spectral transmittance of each layer of exhaust plume flow field which is layered from probing direction and flow fielddirection,and analyzes the influence of different stealth measures on the infrared radiation intensity of exhaust plume.And then, the infrared radiation of exhaust plume is calculated under different probing directions.(2)This thesis analyzes how the infrared radiation characteristics, atmospheric transmission characteristics and infrared detection system performance have influence on the operating distance of the infrared detection system. And the atmospheric transmittance calculation becomes a difficulty in calculation of operating distance of the infrared detection system. Although the atmospheric transmission model can be simulated with MODTRAN precisely, it is hard to call. Combining the MODTRAN calculation model of atmospheric transmittance under MODTRAN software with theimproved calculation model of operating distance of the infrared detection system by programming, we use successive approximation method to calculate the theoretical detectable distance from ground platform, air platform and near-space platform for probing stealth aircraft exhaust plume and analyze the advantages of near-space exploration platform to stealth aircraft.(3)Given the advantages of near-space exploration platform, the stealth aircraft exhaust plume is detected by using two detectors of near-space exploration platform.Also, azimuth data alignment is accomplished through adaptive ?-? filtering forecasting method, then the orientation of the target can be finished by noting the intersection of the ray that the targets located and the common perpendicular of the two rays as approximation of the target position. Finally, by using the function fitting of the double detector positioning distance and the radiation intensity of the tail flame, the recognition theory model of stealth aircraft is obtained.(4)Finally, in order to make the analysis of stealth aircraft plume infrared detection more convenient, the simulation software of stealth aircraft plume infrared detection system is developped by using hybrid programming with C++ and MATLAB,MODTRAN under the above-mentioned model.