Infrared radiation modeling of NO, OH, CO, H2O, and CO2 for emissivity/radiance prediction at high temperature

•An infrared radiation modeling of NO, OH, CO, H2O, and CO2 for spectral calculations was devised.•Line-by-line method was applied with the use of up-to-date spectroscopic parameters and recent radiation databases.•The effect of room air absorption on calculated spectra was examined.•Simulated results were well matched with available experimental data.

In the present study, infrared radiation modeling of NO, OH, CO, H2O, and CO2 molecules was devised based on a line-by-line method by utilizing a structured radiation analysis package, SPRADIAN07, coupled with up-to-date spectroscopic parameters and recent high-resolution radiation databases. An infrared calculation module was newly implemented in SPRADIAN07 for simulating the emissivity/radiance of NO and OH. The line positions of NO and OH molecules were determined by diagonalizing the Hamiltonian matrices of each molecule. The Einstein coefficients were obtained from either radiation databases or available calculated temperature-related line intensities. H2O, CO2, and CO were also modeled based on the high-resolution radiation databases, HITEMP2010 and CDSD-4000. When the line-by-line calculations were performed using the radiation databases, a parallel computing technique based on PC clusters was adopted for fast and efficient evaluation. The line-by-line model devised in the present study was validated by comparing the results with existing measurements. The simulations with room air absorption composed of H2O and CO2 were also carried out. The spectra taken from a plasma torch and those from a rocket plume were calculated by utilizing the present radiation model. It was shown that the calculated spectra are in good agreement with observed ones.