Showing papers on "Burn rate (chemistry) published in 1981"

A model for solid propellant combustion

Abstract: A model has been developed to describe the combustion characteristics of composite solid propellants. The model is based on several new concepts. First, the oxidizer and binder have different surface temperatures rather than a single averaged temperature that has previously been assumed. Second, the overall burn rate is calculated from a time averaged approach rather than the conventional space averaging used in most propellant combustion models. A key contribution in the time averaging approach is use of an ignition delay time for the oxidizer. Third, a generalized flame standoff distance has been developed based on a modified Burke-Schumann diffusion flame analysis. The analysis accounts for variable oxidizer/fuel (O/F) ratio that differing oxidizer size fractions can experience. The analysis shows that the primary diffusion flame can extend over either the oxidizer or the fuel depending on the local O/F ratio. Calculated results for a series of HMX composite propellants show several key trends and excellent agreement when compared to experimental data. The propellants vary in oxidizer particle size and concentration over a range of pressures and temperatures. The model indicates that the fuel binder has a more significant influence than previously thought.

Experimental and theoretical study of the effects of pressure and crossflow velocity on composite propellant burning rate

Abstract: A model for prediction of burning rates of composite (ammonium perchlorate oxidizer) propellants has been developed. In addition, an experimental device for measuring effects of crossflow on burning rate has been used to characterize eight propellants with systematicall, varied formulation parameters. Model predictions of no-crossflow burning rate-pressure behavior agree very well with data, while agreement between erosive burning predictions and data is generally good. The dominant factor influencing composite propellant burning rate sensitivity to crossflow is the base (no-crossflow) burning rate (lower base rate leading to increased sensitivity) with other factors having at most second order effects outside their influence on base rate. Three formulations with widely variant compositional and ingredient particle size parameters, but nearly identical base burning characteristics, exhibited very similar crossflow behavior.

Jet-propelled missile with single propellant-explosive

Abstract: A spin-stabilized spherical jet-propelled missile is disclosed for use in combination with a launching apparatus which includes rotary means for rotating the missile and release means for releasing the missile after a period of initial spinup. The missile includes a housing, an exhaust nozzle on the housing, and a pressure chamber within the housing in communication with the exhaust nozzle. A single explosive compound is disposed as a singular mass within the housing and has a burn surface exposed in the pressure chamber. An impact fuze is disposed on the housing remote from the burn surface of the explosive compound for detonating the explosive compound on impact of the missile. Initial burning of a portion of the explosive compound at said burn surface is effective to drive gases through the exhaust nozzle and to the rotary means of the launching apparatus during spinup, and during flight of the missile, and the fuze is effective to detonate the remainder of the explosive compound on subsequent impact of the missile. The single explosive compound comprises a double based propellant including a high energy plasticizer, such as a nitrated plasticizer, in combination with a high explosive, such as an HMX crystalline explosive, to give a relatively slow burn rate and a relatively high detonating rate.

Motor Vehicle Non-Crash Fires

Abstract: Various data sources on non-crash fires are reviewed with reference to previous studies. Fire department responses to motor vehicle fires reported in 1976-1977 within Michigan are analyzed. It is recommended that some form of industry standard be established that considers smoke emission, toxicity of gas by-products of combustion, and ignition sources as well as burn rate of materials. Such a standard could be flexible and adaptable to changes in vehicle design and new processes and materials.

Combustion Processes in Consolidated Propellants

Abstract: : The use of consolidated or compacted conventional gun propellants offers the ballistician the opportunity for significant performance increases through effective use of very high loading densities on the order of 1.2 g/cc. Such loading densities will only be effective, however, if accompanied by an increase in surface area progressivity. We report the results of an experimental program surveying the effects of ignition stimulus and compaction density on the combustion of simple wafers of consolidated charges of single and double base propellants. We have found that sample confinement, surface inhibition, and grain geometric factors, have significant effects on charge break-up and propellant mass burning rate. In effect, the samples can behave with strong surface area progressivity. With a knowledge of the base grain propellant linear burning rate, independently arrived at, we have extracted instantaneous surface area profiles for burning consolidated propellants. The progressive character of the gas generation rate from burning consolidated charge samples can be explained on the basis of 'macroscopic progressivity' defined as the controlled release of surface area through a continuous deconsolidation process.