High Fidelity Radiative Thermal Transport Simulations of a Scramjet Propulsion System.

Abstract

Scramjets are a type of air breathing propulsion system that have the potential to efficiently provide thrust for atmospheric vehicles at high speeds. Defining the operational limits of a scramjet is difficult to do through flight testing or ground experiments. Computational simulations of a scramjet can include a wide range of conditions that are likely to be encountered by an operational system. Furthermore, the probability of undesirable events can be determined by quantifying the uncertainty of numerical simulations and the sensitivity of those simulations to input variable variance. This thesis utilizes high fidelity models of radiative thermal transport to accurately determine the radiative heat flux in a scramjet propulsion system and quantify the uncertainty of the results as part of a larger effort to define the operational limits of a scramjet. The Implicit Monte Carlo method is used to simulate radiative thermal transport, and tabulated results from line by line calculations are used to define interaction probabilities between thermal radiation and the gaseous medium in a scramjet. Three dimensional simulation results of the radiative heat flux resulting from combustion products inside a scramjet combustion chamber and nozzle are presented. Uncertainty in these results due to the transport model are quantified, and uncertainties due to known uncertainties in the data used to define radiation interactions are modeled based on a sensitivity analysis of radiative heat flux in one dimensional simulations. Simulation results of radiative heat flux are compared to results from a discrete ordinates method using a correlated-k spectral model, which will be used to perform a sensitivity analysis of radiative heat flux to the variations of thermodynamic variables in future work. Finally, a new method of correcting an error in the sampling of spatial emission locations in time dependent stochastic particle based methods is presented. Radiative thermal transport results utilizing this method are compared to a typically used correction method.