Showing papers on "Burn rate (chemistry) published in 1976"

Flame-Spreading and Combustion in Packed Beds of Propellant Grains

Abstract: This paper is concerned with the prediction of the pressure history during the process of flame-spreading and combustion of solid-propellant grains as would occur, for example in a gun cartridge. Solution of the governing conservation equations for the two-phase media requires the use of empirical relations to account for the physical processes of momentum and energy interaction between the solid grains and hot propellant gas. The results indicate the extreme importance of these interaction relations on the predictions of the pressure and velocity field. and at the other is a projectile which will begin to move at a given prescribed pressure. This '"piston" then moves through a long length of channel of the same cross section as the cham- ber, in order that the flow processes following piston motion can be followed. A predescribed igniter mass flow provides gaseous products which, in turn, ignite the bed. Since solid propellants have high burning rates, the rate of gas generation within the chamber is high. Therefore, the pressure is rising rapidly during this flame-spreading process. The pressure rises enhances the pressure-dependent burning rate of the propellant, the result of which is a rapidly accelerating combustion process, with generally steep gradients along the length of the chamber. This gradient results in a high-velocity flow of the gases toward the piston end and into the unburned portion of the propellant. Hence, the flame-spreading and pressurization is rapid, and the entire burn is completed in a matter of milliseconds, if the ignition source is strong enough. Looking at flow process taking place, one may determine the effect on the particle bed. The hot igniter gases initially are driven into a quiescent bed of propellant particles. These ignite the particles nearest the igniter source. The mass generation and subsequent pressurization occur, and a flowfield develops within the chamber. The propellant par- ticles exert a drag force on the flowing gases and are ac- celerated. As shot-start pressure is approached, the entire bed usually has been set into motion.J Throughout the burn, the particles continue to decrease in size as they burn. Kuo and Summerfield2 have pioneered the analysis of packed-bed solid-propellant combustion.

Steerable extraction rocket

Abstract: A steerable rocket motor for towing a load or extracting an aircrew memberrom a disabled aircraft, regardless of aircarft attitude or altitude. The rocket motor is formed from a hollow cylindrical thin walled casing containing a high burn rate propellant and having a plurality of rocket nozzles at one end. The rocket nozzles are positioned around the circumference of the rocket body and are angled to thrust outward and toward the load or aircrew member being towed. A thrust control proportions thrust among the plurality of nozzles for controlling the pitch and yaw of the rocket. Position and rate sensing apparatus informs the thrust control regarding rocket attitude to enable the rocket to steer a predefined desirable flight trafectory. One or more lines are attached to the rocket and are adapted to be fastened to the load or aircrew member being towed.

Radial end burner rocket motor

Abstract: A rocket motor grain consisting of a one-piece solid base propellant divided into an aft end section having a central cavity extending throughout its length, a forward end section having a central longitudinal cavity filled with a propellant having a substantially higher burning rate than the base propellant and a central web section being defined between the forward and aft end sections. This radial end burning rocket motor grain provides a means for utilizing high energy and high density propellants which have high burning rates in a manner such that the burning rate effects can be offset to provide enhanced motor performance without the sacrifice of high energy. After initiation of the rocket motor grain, the aft end section and central web section begin burning together to provide the desired mass flow rate, followed by initiation of a higher burning rate propellant in the forward section. Thereafter, the higher burning rate propellant, being consumed at a much higher rate than the base propellant of the forward section, forms a cylindrical radial burning port therein, thereby extending the motor burn time.

Multi-flame fuel burner for liquid and gaseous fuels

Abstract: A multi-flame fuel burner comprises a plurality of air-atomizing fuel nozzles and sources of pressurized gas and liquid and gaseous fuels associated with each nozzle. A flame spreader is employed in combination with each air-atomizing nozzle to stabilize and shape the flame. The number of nozzles and associated flame spreaders are set to provide the desired burn rate.

Solid Propellant Ignition and Other Unsteady Combustion Phenomena Induced by Radiation

Abstract: : Experimental and analytical investigations were conducted to understand the ignition and nonsteady burning processes that occur at and near the propellant surface, to determine the connection between the ignitability of a propellant and its other nonsteady combustion characteristics, to quantify the peculiarities of radiative ignition, and to develop a means of ranking propellant ignitability. As a result of these investigations, radiative ignition processes have been explained for a wide variety of propellant and test conditions. The stability properties of heterogeneous combustion waves were considered for linear and nonlinear situations. Nonlinear (large disturbances) solid propellant stability boundaries can be immediately defined from the knowledge of the associated restoring function. The restoring function is a property strictly dependent on the nature of the solid propellant.

Critical Review: Modeling of Acceleration Effects on Solid Propellant Combustion

Abstract: Acceleration fields normal and into burning solid propellant surfaces have been observed to cause marked increases, often time-dependent, in their regression rates. Models have been developed for prediction of this burning rate augmentation as a function of various parameters for metalized propellants and non-metalized composite propellants. Most of the metalized propellant models are invalid in that they assume a steady-state involving a finite number of metal agglomerates of constant size controlling the burning rate by formation of pits which lead the burning: in reality, such a steady-state cannot be achieved and flooding of the propellant surface with metal occurs. One model does present a reasonable approach to treating the transient behavior in a semiquantitative fashion, although the problem of calculating agglomerate size as a function of time and various independent parameters is not resolved. Two models of the interaction for nonmetalized propellants appear to be physically unrealistic.

Ignition system used in testing solid propellant compositions for smokelessness

Abstract: This invention is an igniter for solid rocket propellants that is used when testing propellant compositions for smokiness. The igniter has a charge of solid propellant in the form of small, generally spherical particles or thin sheets so as to have a large total burning surface and thin web. The composition of the igniter propellant is same or similar to that of the propellant being tested so that true smokiness of the test propellant can be ascertained. Upon ignition, the igniter propellant charge burns rapidly in an igniter combustion chamber and produces a high internal pressure. The hot gases produced by this combustion of the igniter propellant discharge through an orifice in an igniter chamber wall and flow onto the surface of the main propellant being ignited.

Active binder propellants incorporating burning rate catalysts

Abstract: New propellant compositions characterized by the addition of certain simple salts and double salts, both metallic and non-metallic, having the B10 H10 -2 anion in common, are taught herein to function as a class of burn rate catalysts, and not as fuels, when combined with a category of propellants known as nitrocellulose base propellants. Additionally, unique forms of the simple salts, created by coprecipitation of the simple salt with an oxidizer, constitute a third class of burn rate enhancers herein.

Erosive Burning of Composite Propellants

Abstract: : Increasing use of solid rocket motors with low port-to-throat area ratios, including the ultimate case of nozzleless motors, is leading to increased occurrence and severity of burning rate augmentation due to flow of propellant products across burning propellant surfaces (erosive burning) A review of the literature regarding this phenomenon indicates a lack of systematic data defining the effects of propellants formulation variables on the sensitivity of burning rate to crossflow velocity and the absence of a realistic predictive model for composite propellant burning rate-pressure-velocity relationships In this paper, a physically realistic picture of the effect of crossflow velocity on composite propellant combustion is presented and a relatively simple analytical model based upon this picture is developed for prediction of composite propellant burning rate as a function of pressure and crossflow velocity, given only the burning rate-pressure relationship in the absence of cross-flow In addition, hardware developed for testing erosive burning effects at cross flow Mach numbers up to 10 is described and a planned systematic test matrix is defined Preliminary test results are included and compared with predictions made using the aforementioned analytical model

Theoretical prediction of erosive burning characteristics of solid rocket propellant based on burning rate dependence of pressure and initial temperature and its energetic characteristics

Abstract: New theoretical method for prediction of erosive burning characteristics of solid propellant, using known ballistic and thermodynamic data only, is presented. Method is based on modified Lenoir-Robillard formula, and is applicable for composite and double base propellants, with or without negative erosion effect. Method is confirmed using experimental data of numerous authors.

Investigation of Titanium Combustion Characteristics and Suppression Techniques

Abstract: : This test program studies the burning characteristics of titanium under air flow conditions. The flat plate titanium samples are ignited by molten titanium from an electrically heated ignitor. Air flow conditions that support sustained combustion of a single sample are determined. The burn rate is measured on all tests with steady state burning. Argon gas is shown to be a feasible extinguishing agent for a titanium fire. Quick injection of a sufficient amount of argon gas to maintain a 60% concentration by volume of argon results in quick suppression by oxygen depletion. Carbon dioxide (CO2), a common fire extinguishing agent, is shown to sustain titanium burning at an accelerated rate. The ultraviolet (UV) radiation emitted by burning titanium is shown to be of a sufficient intensity for existing UV fire detectors to detect at reasonable distances.