Diffusion Flame Studies of Solid Fuels with Nitrous Oxide
Open Access
- Author:
- Nardozzo, Paige Kristeen
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 25, 2016
- Committee Members:
- Richard A Yetter, Thesis Advisor/Co-Advisor
- Keywords:
- Combustion
Diffusion Flame
Hybrid Rockets
Solid Fuel
Nitrous Oxide - Abstract:
- Fundamental counterflow combustion studies and static-fired rocket motor experiments were conducted to investigate baseline solid fuel (hydroxyl-terminated polybutadiene, HTPB) and aluminized solid fuel combustion under varied pressure environments using gaseous oxygen (GOx) and nitrous oxide (N2O). Combustion experiments were coupled with a detailed model developed to understand GOx and N2O combustion with pyrolyzing HTPB under pressurized environments. The pressure influence on N2O decomposition is studied in detail describing the flame structure, and solid fuel combustion. Counterflow combustion experiments and model results show solid fuel regression rate increases with pressure for a fixed momentum flux. The flame structure thins, due to the faster kinetics, and shifts towards the regressing fuel surface with increasing pressure. Flame temperature increases with pressure as well, due to decreasing radical formation, increasing the surface temperature gradient, resulting in enhancement of solid fuel pyrolysis. Heat release from N2O decomposition and pyrolyzed fuel oxidation occurs in two distinct stages under atmospheric conditions, while at elevated pressure (1.827 MPa) the exothermic peak associated with oxidation becomes distributed over a wide spatial domain containing many reactions with large exothermicities. The flame structure with N2O exhibits the same trends as O2 following decomposition. Leakage of O2 and NO into the fuel pyrolysis zone also decreases with increasing pressure, indicating faster reaction rates. Over the range of pressures investigated, the diffusion flame produced by combustion of HTPB pyrolysis and N2O decomposition products was always positioned on the oxidizer side of the stagnation plane, which also shifted toward the fuel surface with increasing pressure. Aluminized solid fuel combustion experiments coupled with spectroscopic analysis of the flame zone detected AlO emission only when combusted with gaseous oxygen, indicating ignition of the aluminum was not achieved using N2O, and/or significant amounts of aluminum were not leaving the fuel surface. With both oxidizers, aluminum was observed to collect in the melt layer formed on the solid fuel surface. Motor combustion experiments were conducted to evaluate the propulsive performance of N2O/HTPB and N2O/aluminized HTPB system having a 6.5 and 26 µm Al particle size, with loading up to 10% by weight. Average linear regression rates were observed to increase by 15% over the HTPB baseline for an average N2O momentum flux of 60 kg/m2s.