Thermal radiation from solid propellant rocket motor plume

Özen, Güzide
Radiation emitted from rocket plumes plays a significant role in quantifying infrared (IR) radiative signature which is essential for identification and tracking of rockets. Prediction of plume radiation necessitates simultaneous solution of conservation equations for mass, momentum, energy, chemical species and radiant energy to provide input data for the radiation code. This is carried out by a Computational Fluid Dynamics (CFD) solver. As CFD solvers are CPU time expensive, an accurate and CPU efficient solution method of radiative transfer equation (RTE) and a less accurate but CPU efficient radiative property estimation technique are usually employed in these solvers. However, radiation code for prediction of plume radiation necessitates an accurate and CPU efficient solution method of RTE as well as a highly accurate wavelength dependent radiative property estimation technique. Therefore, predictive accuracy and CPU efficiency of RTE solvers and radiative property estimation techniques were first evaluated by applying the code to different 3-D enclosures containing non-grey, absorbing-emitting-scattering media and benchmarking their predictions against reference solutions and measurements. Comparisons reveal that as RTE solver Discrete Ordinates Method (DOM) for both CFD solver and radiation code and as radiative property estimation techniques Spectral Line-based Weighted Sum of Grey Gases (SLW) and Statistical Narrow-Band Correlated-k (SNBCK) for CFD solver and radiation code, respectively, satisfy the requirements. This was followed by running the CFD solver, ANSYS FLUENT v.15.0 with and without radiation in order to see the effect of radiation on the input data provided to the radiation code. CFD solver without radiation was found to be accurate and CPU efficient. Radiation code based on DOM with SNBCK for gas and Mie Theory for particles was developed to predict plume radiation for non-aluminized and aluminized propellants. For non-aluminized propellant, the prediction accuracy and computational efficiency of radiation code was tested by comparing its predictions with measurements available in the literature. Predictions were found to be in good agreement with measured data. Predictions of spectral radiant intensity under aluminized propellant case were found to be higher than those of non-aluminized propellant due to the use of higher temperature profiles and radiative properties of particles under aluminized propellant case.