Combustion of solid fuels in a diffusion flame enviroment
Open Access
- Author:
- Burger, Christopher Michael
- Area of Honors:
- Aerospace Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Richard Yetter, Thesis Supervisor
Philip John Morris, Thesis Honors Advisor - Keywords:
- Counterflow
Combustion
Diffusion Flame - Abstract:
- Fundamental combustion studies were performed in a pressurized counterflow burner using Hydroxyl-Terminated Polybutadiene (HTPB) and gaseous oxygen. The goal of the study was to explore whether or not diffusion flame combustion in a counterflow configuration correlated well to diffusion flame combustion in the cross-flow configuration of hybrid rockets. The oxidizer flow rate was varied throughout the study with mass flux values ranging from 7 to 112 kg/(m2s), while the chamber pressure was held at a target pressure of 200 psig. It was found at low values of oxidizer mass flux that the experimental regression rates of the HTPB correlated well to the predicted diffusion flame power law, commonly used for hybrid rocket motors. At higher oxidizer mass fluxes, however, the regression rate plateaued to a near-constant value that was independent of oxidizer mass flow rate. This plateau has not been encountered in lab-scale hybrid rocket motors tests; however, a similar effect has been observed slab burner experiments. A computational model created using CHEMKIN and GNU Octave was used to simulate the combustion process in a counterflow configuration. The purpose was to achieve a better understanding of the diffusion flame structure and chemistry. As oxidizer mass flux increases, the model indicates that the diffusion flame moves closer to the fuel surface. The model predicted the experimentally observed trends, with burning rate increasing with oxidizer flow rate and achieving a plateau at the highest flow conditions. Flame structure results from the model support the hypothesis that the location of the diffusion flame becomes increasingly invariant with increasing oxidizer mass flux.