Showing papers on "Burn rate (chemistry) published in 1974"

Role of Binders in Solid Propellant Combustion

Abstract: : The objective of this program was to investigate and define the effects of inert binder properties on composite solid propellant burning rate. Experimental pyrolysis data were obtained for many binders of practical interest over a wide range of heating rates and pressures, in several environmental gases, with and without 10-percent ammonium perchlorate (AP) contained in the sample, and in some cases with catalysts. These data were used to extract kinetics constants from Arrhenius plots, and heat of decomposition. In addition, motion pictures were taken of the pyrolyzing surface and gas samples were extracted for analysis. Pyrolysis kinetics varied between binders, but were found to be independent of pressure, the presence of AP, and the presence of burn rate catalysts; however, a chlorine gas environment had a material effect upon the results. All of the binders exhibited molten, boiling surfaces mingled with char, to varying degrees; the amount of char increased with AP present, and in chlorine. Relevant data were input to the Derr-Beckstead-Price combustion model in order to associate binder properties with known binder effects on burning rate. Although the effects were predictable, they stemmed from properties other than pyrolysis kinetics; however, the binder data as applied to the model revealed possible deficiencies in the model, which are discussed. It appears that the approach of combustion tailoring by binder modification would have to involve the gas phase combustion processes rather than surface pyrolysis. Therefore, future work concerning the role of binder should be directed toward the gas phase.

Low temperature gas generating compositions and methods

Abstract: A pyrotechnic powder composition comprising a mixture of an oxidizer powder and an oxygen bearing metal organic compound powder is used for inflating a passenger restraint bag for an automobile. Metals preferred for the metal organic compound have a free energy of oxidation less than the free energy of oxidation of carbon monoxide. An exemplary composition comprises a mixture of anhydrous nickel formate and potassium chlorate. When these react, substantial volumes of oxygen, carbon dioxide and water vapor are released for inflating a passenger restraint bag. The burning rate of the powder composition may be increased by including up to about 20 percent of an enhancer distributed in the powder and having a burn rate substantially higher than the burn rate of the powder composition.

Numerical Investigation of Nonlinear Axial Instabilities in Solid Rocket Motors

Abstract: : Nonlinear axial-mode combustion instability remains a serious problem in the development of solid propellant rocket motors. Although the use of metal- loaded solid propellants which produce solid particles in the flow has reduced the occurrence of high frequency instabilities, it has not eliminated the axial-mode intermediate frequency (100 - 1000 Hz.) problem. If such an instability reaches a large amplitude limit cycle, it may lead to an increase in mean chamber pressure and burning rate, excessive heat transfer rates, and a severe vibration level. The objective of this report is to investigate the complex coupling between the chamber flow conditions and the solid propellant combustion process which may lead to large amplitude longitudinal instabilities.

Flammability Limits and the Oscillatory Burning of Solid Propellants at Low Pressure.

Abstract: : A one-dimensional analysis of the small-amplitude oscillatory burning of a solid propellant has been developed. The analysis is based on a simplified flame model using quasi-steady gas-phase approximation. The difference between this analysis and previous analyses is that radiant heat loss from the burning surface has been included in the present theory. This heat loss produces significant qualitative and quantitative differences in the unsteady behaviour of solid propellants at low pressures. The effect of initial temperature on the stability of the combustion process has also been examined. (Modified author abstract)

Solid propellant sandwich deflagration analysis

Abstract: A theoretical solution has been obtained for the shape of a deflagrating ammonium perchlorate surface when it is adjacent to an inert, pyrolysing, dry binder. The eigenvalue, the regression rate, is shown to be independent of binder type and very close to the burn rate of pure AP, as has been experimentally observed. A slope discontinuity of the surface should exist at the binder-oxidizer interface and typical binders should incline very near to 90° to the nearly horizontal AP surface, at the junction of the two. The transition from AP to binder should take place on a distance scale of the order of microns and all results are quite insensitive to pressure level.

Development of a miniature solid propellant rocket motor for use in plume simulation studies

Abstract: A miniature solid propellant rocket motor has been developed to be used in a program to determine those parameters which must be duplicated in a cold gas flow to produce aerodynamic effects on an experimental model similar to those produced by hot, particle-laden exhaust plumes. Phenomena encountered during the testing of the miniature solid propellant motors included erosive propellant burning caused by high flow velocities parallel to the propellant surface, regressive propellant burning as a result of exposed propellant edges, the deposition of aluminum oxide on the nozzle surfaces sufficient to cause aerodynamic nozzle throat geometry changes, and thermal erosion of the nozzle throat at high chamber pressures. A series of tests was conducted to establish the stability of the rocket chamber pressure and the repeatibility of test conditions. Data are presented which define the tests selected to represent the final test matrix. Qualitative observations are also presented concerning the phenomena experienced based on the results of a large number or rocket tests not directly applicable to the final test matrix.

Synergistic and Novel Effects in Composite Solid Propellant Combustion.

Abstract: : This report summarizes experiments and analysis concerned with sandwich and cast composite solid propellant combustion. The ingredients used in the experiments are ammonium perchlorate as the oxidizer, hydroxyl terminated polybutadiene as the binder and four catalysts: Harshaw catalyst CU-0202, Fe2O3, ferrocene and iron blue. Cinephotomacrography and the fuze wire technique are used for combustion visualization and burn rate determination. Scanning electron microscopy is used for quenched sample visualization. Areas investigated are (a) analytical and experimental determination of synergistic catalytic effects in sandwich and propellant combustion, (b) the loading of ferrocene into the binder at the molecular level and its effect on sandwich combustion, (c) differential scanning calorimetry of catalyst laden binder and (d) analysis of sandwich deflagration.