Showing papers on "Burn rate (chemistry) published in 1969"

Extinguishment of solid propellants by rapid depressurization

Abstract: : A new theory for extinction by depressurization of AP composite propellants is employed to predict the rate of pressure decrease required to achieve flame-out and to rationalize the effects of various composition parameters on the ease of extinguishment The research is concentrated mainly on the 'temporary' extinguishment behavior of solid propellants, but a re- ignition theory is also presented Attention is given in this theory to the proper derivation of the nonsteady heat feedback from the gaseous flame zone to the burning surface Included in the model are the essential physical and chemical rate processes of the granular diffusion flame model, as deduced from the steady state burning characteristics A brief study of double-base propellants which indicates that they are considerably easier to extinguish than composite propellants concludes this report A rough model for the burning of double-base propellants is presented which further indicates the importance of the flame structure in determining the extinguishment characteristics of solid propellants

Aluminized composite solid-propellant burning rates in acceleration fields

Abstract: The average burning rates of a parametric series of propellants were determined in acceleration fields up to 1000 g using a combustion bomb mounted on a centrifuge. The propellant strands were burned at 500, 1000, and 1500 psia with the acceleration field directed normal and into the burning surface. Acceleration caused a time-dependent increase of as much as 100% in the burning rate of relatively slow-burning aluminized propellants. The relative amount of burning-rate increase for the various propellants was strongly dependent on the amount of aluminum retained on the propellant surface during burning. The burning rates of two very fast-burning propellants were found to be essentially accelerationindependent. OLID-PROPELLANT rocket motors are currently being used in applications which subject the metallized propellant grains to acceleration fields. The propellant burning rates increase appreciably when the acceleration field is imposed normal and into the burning surface.1'2 Postfire inspections of motors containing metallized propellants have revealed the presence of metal and/or metal oxide residue in the motor cases. The propellant burning-rate increase and the retention of residue appear to be interrelated. The review and abstracting of the literature on the effects of acceleration on solid-propell ant performance are presented in Refs. 3 and 4. Although progress has been made toward an understanding of some aspects of burning-rate augmentation in acceleration fields, it was believed that additional experimental studies with well-controlled propellant parameters would yield valuable insight. A parametric series of aluminized propellants was formulated to establish the importance of some of the propellant parameters that could be controlled to minimize the effects of acceleration. The objectives of this investigation were twofold. The first objective was to obtain the quantitative effect of acceleration on the burning rate of the propellants as a function of propellant composition, acceleration level, and time. The second objective was to obtain quantitative information on the amount of aluminum and/or aluminum oxide residue retained in the inhibitor case as a function of propellant -composition, acceleration level, pressure level, and propellant burning rate.

Combustion instability of solid propellants

Abstract: Experimental data has been obtained from two T-burners and an L^* burner over a range of frequencies from 10 cps to 8000 cps and from 25 psia to 1000 psia. From these data the response of the propellants to a pressure perturbation has been calculated and has been found to be consistent between burners. The results have been interpreted as a response function surface with burning rate and frequencies as independent variables. The data indicates that for a given pressure level the response function has a peak value at a frequency that increases as pressure increases. The magnitude of this peak height varies with pressure so that there is a localized peak in the response function surface for a given propellant. The results are in qualitative agreement with theoretical studies in that the models also predict a maximum value in the response function. However, they also predict that this magnitude should be approximately a constant and not dependent on the pressure and frequency to the extent observed in the present study. The results obtained for an aluminized propellant indicate that presence of metal in the combustion zone greatly influences both the magnitude of the response function peak as well as its location.

Some Problems in the Unsteady Burning of Solid Propellants

Abstract: : The model of uniformly distributed combustion in the gas phase is used as the basis for examining several features of unsteady burning. As a zeroth approximation the flame zone begins at the solid-gas interface and responds linearly and quasi-statistically to changes of pressure only. Three deviations from this behavior are then examined: the combustion zone is displaced from the surface, the energy release responds to fluctuations of temperature and the response is not quasi-static. It appears that the assumption that the burning begins immediately at the surface can lead to significant changes, more important than the assumption that the energy release responds to changes of pressure only, especially in the interpretation of experimental data. The problem of nonquasi-static behavior, i.e., processes in the gas phase do not follow precisely impressed changes of pressure, is formulated as an expansion in frequency. Approximate results seem to be consistent with existing information.

Pressure level control system for a solid propellant rocket motor

Abstract: A system for controlling the operating pressure and thrust of a solid propellant rocket motor which includes a propellant cutter that extends through the burning surface of the solid propellant to increase on command the burning surface area and thereby increase the burning rate of the solid propellant.

Thermodynamic reaction drive

Abstract: A thermodynamic reaction drive or rocket engine which employs liquefiable solid propellant. An alkali metal, which is used as the propellant, is stored in the fuel tank of the rocket engine in the solid state and then, whenever engine operation is desired, liquefied by heating to the necessary temperature. The liquid propellant is fed from the fuel tank through a De Laval nozzle into the mixing or combustion chamber where it is combined with an oxidizer. The propellant, which can be forced through the nozzle primarily by means of its own vapor pressure, is changed over at the nozzle into a two-phase flow. The oxidizer, which is simultaneously introduced into the mixing chamber at a higher pressure than the pressure in the chamber, effects the combustion of the propellant so that the internal energy of the products of combustion may be converted to kinetic energy in an appropriate thrust nozzle.

Burn rate testing apparatus

Abstract: An apparatus for testing the burn rate between two spaced apart points on a sample of material. It includes an angularly adjustable support holder, an electrically ignited torch supplied with an independent supply of oxygen, a flame shutter between the torch and the sample holder and photocells positioned to sense ignition of the test material and the rate of burn between two spaced apart points on the material.

Nonlinear solid propellant burning rate behavior during abrupt pressure excursions.

Abstract: Solid propellant burning rate behavior during abrupt environmental pressure excursions, using transient combustion model

Remarks on extinguishment and the response function for a burning solid propellant.

Abstract: T HE presence of small amplitude pressure oscillations in a solid rocket chamber depends mainly upon the interaction between the vibrations and the combustion processes occurring in the thin region adjacent to the solid. Often the behavior seems to be dominated by the influence of pressure fluctuations; this is conveniently expressed in terms of the response function (mf/in)/(p'/p), the ratio of a small change in mass flux to a small change of pressure. Most calculations lead to results that can be put in the form1 for harmonic oscillations

A technique for controlling the position of a burning solid-propellant sample in a combustion bomb

Abstract: Position control of burning solid nonmetallized propellant strand in combustion bomb using closed loop servomechanism

An Investigation of the Effects of Acceleration on the Burning Rates of Solid Propellants

Abstract: : The acceleration sensitivity of aluminized and nonmetallized composite and double-base propellants were investigated. A review of previous experimental findings and current analytical models was also conducted. An investigation was conducted to determine the cause(s) for the differences in burning rate augmentation data reported by various investigators. Strand length (burn time) was found to be the dominant factor. Lead and copper additives commonly found in double-base propellants were found to decrease the burning rate with increasing acceleration. Burning rate instability was also obtained at high accelerations. The addition of aluminum increased the burning rate at any given acceleration.

Measurement of Erosive Burning Rates

Abstract: : A new technique for measuring average erosive burning rates of a propellant fired under realistic motor conditions is described. By utilizing a small test motor attached as a blast tube to a large gas generator, a minimal amount of test propellant is required. Hence the technique is attractive for evaluating or ranking the erosive-burning tendencies of compositions in a propellant development program. Erosive burning rates were measured for a CTPB- based composite propellant. Excellent correlation was found between the erosive burning rate, Mach number at the tail end of the propellant grain, and chamber pressure. The erosive burning rates measured in the test motors were independent of the composition of the gas-generator propellant. Application of the data in the design of an erosive-burning propellant grain has not been made.