R. K. Sigman

Bio: R. K. Sigman is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Ammonium perchlorate & Finite element method. The author has an hindex of 17, co-authored 31 publications receiving 833 citations.

The effects of bimodal aluminum with ultrafine aluminum on the burning rates of solid propellants

Abstract: Burning rates were measured for aluminized composite propellants with different aluminum (Al) sizes(monomodal distribution) and with bimodal Al distributions containing various amounts of ultrafine Al (UFAl). Enhanced rates were found for fine Al, with the enhancement increases for reduced Al size. The fine Al also burned in an intense region very close to the propellant surface, suggesting improved heat feedback in the form of radiation and conduction. Major modification of the burning rate could be achieved with moderate amounts of UFAl. Results obtained with various fine oxidizer particle sizes and mass fractions suggest that the degree of burning-rate modification depends on the ability to ignite the UFAl, for example, with leading-edge flames, as well as the availability of oxidizer near the Al-containing regions of the propellant.

Mechanism of Burning Rate Enhancement of Composite Solid Propellants by Ferric Oxide

Abstract: This paper reports a series of experimental studies performed on sandwich propellants, wherein a matrix lamina of particulate oxidizer and polymeric binder is sandwiched between two ammonium perchlorate (AP) laminae. The catalyst (ferric oxide ) is incorporated in the matrix lamina. The variables are pressure (0.345‐ 6.9 MPa), matrix lamina thickness, catalyst concentration, matrix mixture ratio, types of oxidizer and binder, and the dispersion ability of the catalyst. The combined results indicate that, under the conditions tested, near-surface reactions associated with the particulate AP/binder contact lines on the burning surface assume signie cance in the presence of the catalyst. These reactions are further augmented by the presence of the leading-edge portion of the diffusion e ame above the interface of the matrix and AP laminae.

Intermittent Burning of Ammonium Perchlorate-Hydrocarbon Binder Monomodal Matrixes, Sandwiches, and Propellants

Abstract: The onset of the midpressure extinction of certain formulations (termed matrixes) of ammonium perchlorate (AP) of monomodal particle size distribution and hydroxyl-terminated polybutadiene binder, in the pressure range around 2-5 MPa, is examined. These matrixes, besides being tested in isolation, have been included in between AP laminas to form sandwiches and mixed with coarse AP particles to form high solids-loading (87.5%) non-aluminized propellants. The burning rates of the sandwiches show abnormal trends with pressure such as low or negative exponents in ranges corresponding to the onset of the midpressure extinction of their respective matrixes. The propellants exhibit this behavior to a lesser degree. Quenched surfaces (self-extinguished or intentionally interrupted during burning) of all the three types of samples were analyzed using a scanning electron microscope, and the burning history of the samples was captured with a high-speed digital camera. The results indicate the prevalence of intermittent burning of the matrixes as the pressure is varied across the boundary between continuous burning and self-extinction (burn/no-burn boundary) of the matrixes. The burning surfaces are marked by extreme three dimensionality coupled with a redistribution of the fine AP particles and the binder. The observations are explained based on the combined effects of the need for the AP particles and the binder to accumulate relative to each other on the burning surface depending on the difference in their pyrolysis rates and the existence of the binder in a molten state on the burning surface.

Combustion of Nano Aluminum Particles (Review)

Abstract: Nano aluminum particles have received considerable attention in the combustion community; their physicochemical properties are quite favorable as compared with those of their micron-sized counterparts. The present work provides a comprehensive review of recent advances in the field of combustion of nano aluminum particles. The effect of the Knudsen number on heat and mass transfer properties of particles is first examined. Deficiencies of the currently available continuum models for combustion of nano aluminum particles are highlighted. Key physicochemical processes of particle combustion are identified and their respective time scales are compared to determine the combustion mechanisms for different particle sizes and pressures. Experimental data from several sources are gathered to elucidate the effect of the particle size on the flame temperature of aluminum particles. The flame structure and the combustion modes of aluminum particles are examined for wide ranges of pressures, particle sizes, and oxidizers. Key mechanisms that dictate the combustion behaviors are discussed. Measured burning times of nano aluminum particles are surveyed. The effects of the pressure, temperature, particle size, and type and concentration of the oxidizer on the burning time are discussed. A new correlation for the burning time of nano aluminum particles is established. Major outstanding issues to be addressed in the future work are identified.