Evaluation of a Numerical Method to Determine the Combustion Temperature of A Rocket Engine Simulator from OH Emission Spectra

The hydroxyl radical OH emission spectra generated by a rocket engine simulator have been recorded at various oxidizer (O2) pressures. Due to the Boltzmann distribution function and the effect of the linewidth on the lineshape, the calculated spectral line intensities are expected to be dependent upon the assumed temperatures and linewidth. The hydroxyl OH rotational spectra at various assumed temperatures with an optimal linewidth have been predicted and plotted. The line peak intensity ratios of three selected line peaks to the largest line peak have been computed. A polynomial fit process has been employed to establish an emperical relation between the line peak intensity ratios and the rotational temperatures. The line peak intensity ratios evaluated from the observed OH spectra along with the emperical relations have been used to determine the combustion temperature.