Approximate Calculation for Average Infrared Radiation Intensity of Straight Flow Exhaust System

With the rapid development of infrared detection and guidance technology, future fighter aircraft will face the search and detection of enemy aerial, air and ground all-round infrared detection systems. To determine the average infrared radiation intensity in the rear hemisphere of straight flow exhaust systems, an approximate calculation method was designed basing on limited data. This method was applied to conduct numerical simulations of the average infrared radiation intensity in the rear hemisphere for axisymmetric nozzles, two-dimensional convergent–divergent rectangular nozzles, and two-dimensional ejector nozzles. The innovative aspect of this method is that it can obtain the distribution of infrared radiation intensity in the rear hemisphere and the average infrared radiation intensity for the corresponding exhaust system using infrared radiation intensity data from typical detection planes, thereby significantly reducing calculation time. The results demonstrated that with this newly developed approximate calculation method, the error in the distribution of the average infrared radiation intensity for each model is generally within 10%, and the error in the average infrared radiation intensity is around 5%. These simulation calculation errors are acceptable for engineering applications.