Investigation of Infrared Image Prediction for Subsonic Exhaust Plume

An infrared imaging prediction model of exhaust plume was developed to understanding the infrared characteristics of exhaust plume. The method is based on the irradiance calculation of all pixels on the focal plane array. In order to compute the irradiance incident on each pixel, the gas radiation transfer path in the plume for the instantaneous field of view (IFOV) corresponds to the pixel was solved by the simultaneous equation of a cylinder which covers the exhaust plume and the line of sight. Radiance for the transfer path was calculated by equation of radiation transfer for nonscattering gas. The radiative properties of combustion were computed by Malkmus model with EM2C narrow band database(25cm-1). The pressure, species concentration for the path was determination by CFD analysis. The relatively intensity of each pixel was transferred to color in the display according to gray map coding and hot map coding. Infrared image of the exhaust plumes from a subsonic axisymmetric nozzle was predicted with the model. By changing the parameters, such as FOV and space resolution , the image of different imaging system can be predicted for varying relatively position of camera and the plume.