Numerical simulation of infrared signature emitted by liquid rocket plume using wide band k-distribution model

A new wide band k-distribution model has been developed and used to investigate infrared radiation signatures of liquid rocket plume in some detectors' working spectrum regions, in which the temperature and the gas molar concentration fields are solved using engineering empirical formulations. Based on the line parameters in HITEMP database, absorption coefficient variables of water vapor and carbon dioxide corresponding to 12-point Gauss-Lobatto quadrature points are derived and expressed as a simple formulation. The absorption coefficient variables of mixture are obtained by summing the absorption coefficient variables of individual gas species under the hypothesis that the k-distributions are statistically uncorrelated. Its validity for the numerical prediction of liquid rocket plume radiation is verified by comparison with line-by-line approach (LBL). Compared with line-by-line calculations, the maximum relative errors of the new band model are less than 10 % in the detectors' working spectrum regions, while the computational time of the new band model is less than 1/1000 of LBL. The effects of fly parameter on infrared radiation signatures of liquid rocket plume are studied using the new model. The results showed that the integral radiation intensities of liquid rocket plume increase with the nozzle exit temperature, Mach number and the ratio of nozzle exit pressure to atmospheric pressure. The radiation intensity variation trend for liquid rocket plume with altitude is different for different detectors' working spectrum regions.