Study On Infrared Characteristics Of Solid Propellant Plumes

Strong infrared radiation from solid rocket motor plume is an important characteristic signal of aircraft, which can be used to detect the military target, and to monitor engine mechanical failure. Therefore, the study of infrared radiation characteristics from plume is of great importance for infrared detection guidance technology and military stealth technology, as well as improving design of solid propellant formulations.The propellant combustion is a dramatically unsteady process. The passive remote sensing FTIR spectroscopy technology was used in this paper to do in-depth analysis of infrared radiation characteristics of the propellant flame in real time, in situ and efficiently.First, the linear and nonlinear multi-point calibration methods of FTIR spectrometer were carried out to explore the instrument response function variation with temperature, resolution, aperture. The results showed that through multi-point non-linear calibration, the infrared emission spectra could be more accurately obtained. Under the same test distance, the instrument response function reduced with the decrease of spectral resolution, and increased with increase of the aperture. When the instrument received weak signal, the instrument response function decreased with increasing temperatures; When the instrument received strong signal, the instrument response function increases slowly with increasing temperature, and finally maintained to a steady state.Second, the infrared radiation characteristics of two kinds of solid propellant plume were studied. The infrared emission spectra of the combustion plumes were recoreded with an MR-254 FTIR spectrometer, which were calibrated and calculated to get the plume radiation energy distributions, plume temperatures, and concentrations of gaseous combustion products. Results showed that the total radiation energy of the aluminized propellant was 106.767W/sr which is higher than that of the NEPE propellant of 61.084W/Sr. The calculated plume temperatures of two kinds of propellants based on molecular rotation-vibration fine structure spectra of gaseous products are close to actual temperatures. The temperature of the aluminized and NEPE propellant plume were 3500K and 1500K, and the actual temperature are 3000K and 1400K. According to the Lambert Beer’s law, the concentration of propellant combustion gas main products were calculated, which could be applied to the improvement of composite propellant, and for scientists to develop the propellant of high energy and low characteristic signal.Last, a plume temperature calibration software was programmed in this paper, which calculats the emissivity of the plume by calibrating the temperature data from chromothermometer and infrared thermal imaging, thus the actual temperatures of the plume were inferred. The results showed that this calibration method which recieved the emissivity was reliable.