Master's Thesis Defense

Jean Pecquet 

(Advisor: Prof. Menon)

Large Eddy Simulation of Solid-Fuel Ramjet Combustion

On

Monday, April 21 

1:00 p.m. 

Montgomery Knight Building 325

Abstract 

Ramjet propulsion is uniquely suited to high-speed atmospheric flight compared to other means of propulsion like turbine and rocket engines. Solid-fuel ramjets (SFRJs) offer many potential advantages, including reduced size and weight, improved cost effectiveness, and higher performance, but also present many modeling challenges. Solid fuels for SFRJ applications are typically polymers, whose thermal degradation and combustion involves phase change and complex chemical reactions in the condensed and gaseous phases. Unlike liquid-fueled combustors in which the rate of fuel injection is carefully regulated, the rate at which the solid fuel undergoes thermal degradation, and its gaseous products become available for combustion depends entirely on the heat flux from the flame region to the solid fuel surface. In turn, the rate of solid fuel consumption affects the fuel-air ratio and the flame characteristics, which also strongly depend on the inlet conditions, themselves a function of flight speed, altitude, and other factors.

The SFRJ flow field is characterized by a recirculation region and a shear layer at the entrance of the combustor, contributing to the unsteadiness of the flow. Large-eddy simulation (LES) is required to properly capture these dynamic features, but few LES studies have been conducted yet. The research presented in this dissertation aims to establish a simple LES framework with reduced-order gas-phase chemical kinetics and a semi-empirical model for the solid fuel regression rate using a standard solid fuel, hydroxyl-terminated polybutadiene (HTPB). Comparison of the numerical results to measurements of chemiluminescence, temperature, species concentration, and regression rate show reasonable agreement. The framework is then applied to another combustor using a model fuel, polyoxymethylene (POM), to evaluate similarities and differences in their combustion characteristics.

Committee

· Prof. Suresh Menon – School of Aerospace Engineering (advisor)

· Prof. Joseph Oefelein – School of Aerospace Engineering

· Prof. Wenting Sun – School of Aerospace Engineering