This dissertation is an investigation into the effects of natural convection on the combustion process of a spreading flame in a gravitational environment. The flame is spreading into an opposing flow of oxidizer over a solid fuel. This is approached as a steady state problem with coordinates fixed at the tip of the flame. This investigation incorporates the use of experimental data, numerical simulations and a simplified approach to develop a better understanding of combustion. The focus of the material presented can be separated in two components: First, a well validated forced flow numerical model is used to evaluate flame structure for the natural convection configuration. A simplified approach is developed and compared to the numerical model for flame structure and flame spread rates in chapters 2 and 3. Critical parameters controlling flame spread such as pressure, fuel thickness, oxygen concentration, and strength of gravitational field are widely varied. In the thermal regime, where this simplified approach applies, comparisons between experimental data, numerical solutions and simplified approach predictions are excellent. The numerical model is also compared to experimental data outside the thermal regime including a prediction of the regression rate of the solid fuel and gas phase characteristics. Second, a hybrid two-color pyrometry technique is developed and used to analyze flame structure for experiments in a microgravity environment. Images of flame intensity are calibrated and converted into temperature profiles for various opposed flow velocities and oxygen concentration. Numerical simulations are used to demonstrate various approximate techniques and their accuracies. The experimental images are used in conjunction with the numerical simulation to determine the temperature profiles and the partial pressure of carbon dioxide. Techniques are discussed on how to improve the results for future experiments by modifying the filter bandwidth selections. Through a greater understanding of the physics and controlling mechanisms for flame spread, the ability to control fire and the establishment of comprehensive guidelines for fire safety will be realized. This dissertation is another step toward that goal.

This book provides an introduction to understanding combustion, the burning of a substance that produces heat and often light, in microgravity environments-i.e., environments with very low gravity such as outer space. Readers are presented with a compilation of worldwide findings from fifteen years of research and experimental tests in various low-gravity environments, including drop towers, aircraft, and space. Microgravity Combustion is unique in that no other book reviews low- gravity combustion research in such a comprehensive manner. It provides an excellent introduction for those researching in the fields of combustion, aerospace, and fluid and thermal sciences. * An introduction to the progress made in understanding combustion in a microgravity environment * Experimental, theoretical and computational findings of current combustion research * Tutorial concepts, such as scaling analysis * Worldwide microgravity research findings

This book provides an introduction to understanding combustion, the burning of a substance that produces heat and often light, in microgravity environments-i.e., environments with very low gravity such as outer space. Readers are presented with a compilation of worldwide findings from fifteen years of research and experimental tests in various low-gravity environments, including drop towers, aircraft, and space.Microgravity Combustion is unique in that no other book reviews low- gravity combustion research in such a comprehensive manner. It provides an excellent introduction for those researching in the fields of combustion, aerospace, and fluid and thermal sciences.* An introduction to the progress made in understanding combustion in a microgravity environment* Experimental, theoretical and computational findings of current combustion research* Tutorial concepts, such as scaling analysis* Worldwide microgravity research findings

An experimental program was conducted to study the burning of laminar gas jet diffusion flames in a zero-gravity environment. The tests were conducted in the Lewis Research Center 2.2-Second Zero-Gravity Facility. The photographic results indicated that a sudden decrease in gravity level from 1 to 0 effected an immediate reduction in the length of the flame. Continued time in zero gravity resulted in the flame expanding away from the burner until extinguishment appeared to occur. Nondimensionalization of the governing flow equation yielded the parameters used to correlate the buoyancy effects.