Ignition and combustion of boron particles

Direct combustion of recyclable metal fuels for zero-carbon heat and power

https://www.yang.gatech.edu/publications/Journal/PECS%20(Beckstead,%202007).pdf

Modeling of combustion and ignition of solid-propellant ingredients

Solid propellants: AP/HTPB composite propellants

A comprehensive theoretical/numerical model for treating AP/HTPB composite-propellant combustion in a rocket-motor environment is presented. The formulation takes into account the conservation equations in both the gas and condensed phases, and accommodates finite-rate chemical kinetics and variable thermophysical properties. The processes in the two phases are coupled at the surface to determine the propellant burning behavior. An asymptotic analysis based on a large activation-energy approximation for the condensed-phase decomposition is applied to help resolve the combustion wave structure in the interfacial layer. A simplified global reaction is employed to characterize the final diffusion flame between the decomposition products of AP and the pyrolysis products of HTPB. Only laminar flows are considered here, to avoid complications arising from turbulence. A detailed parametric study is conducted on the gas-phase flame structures of AP/HTPB composite propellants. The dependence of burning rate, flame...

http://www.yang.gatech.edu/publications/Journal/CST%20(2008,%20AP-HTPB,%20Cai).pdf

A Model of AP/HTPB Composite Propellant Combustion in Rocket-Motor Environments

PE Nomenclature = heat capacity of the gases = boron heat capacity = oxide heat capacity = heat absorbed by reaction of B2O3 with H2O = heat absorption associated with surface reaction(s) (per unit mass of boron) = heat of vaporization of B2O3 = particle burning mass flux = heat release associated with gas-phase reaction(s) (per unit mass of oxygen) = heat release of B + B2O3 reaction = particle radius = molar rate of boron consumption = molar evaporation rate of boric oxide = molar rate of removal of B2O3 by water reaction = time = particle temperature = effective surroundings radiation temperature = particle surface temperature — ambient temperature = oxide layer thickness = ambient oxygen mass fraction = surroundings absorptivity = particle emissivity = boron density = boric oxide density = density-diffusivity product = Stef an-Boltzmann constant

Ignition and Combustion of Boron Particles and Clouds

Model for Steady-State Combustion of Unimodal Composite Solid Propellants.

: An experimental apparatus designed for measurement of erosive burning rates at crossflow velocities up to Mach 1 has been used to determine the erosive burning characteristics of seven propellant formulations with systematically varied properties. A composite propellant erosive burning model based on the bending of columnar diffusion flames gives reasonably good agreement with the measured erosive burning data over a wide range of conditions, breaking down only in regions where the fuel-oxidizer gas stream mixing does not control burning rate. Propellant base (no-crossflow) burning rate is found to have a predominant effect on sensitivity to crossflow (higher- burning-rate formulations being considerably less sensitive) whether the base burning rate differences are produced by oxidizer particle size variation, oxidizer/fuel ratio variation, or use of catalysts. Comparison of erosive burning predictions using the erosive burning model described herein with flow profiles expected to prevail in the test apparatus to predictions using profiles believed to exist in cylindrically-perforated motor grains indicate that erosive burning may be considerably less for a given mainstream crossflow velocity in such a motor than in the typical erosive burning test apparatus, a result quite important to extrapolation of test apparatus erosive burning data to actual motor conditions.

Erosive Burning of Composite Solid Propellants: Experimental and Modeling Studies

: Development of solid rocket motor designs which result in high velocity flows of product gases across burning propellant surfaces(notably, nozzleless rocket motors) is leading to increased occurrence of erosive burning. In this paper, a physically realistic picture of the effect of such crossflow on composite propellant combustion, based on the bending of columnar diffusion flames by the crossflow, is presented. This bending results in shifting of the diffusion flame heat release zone toward the surface, with consequent increased heat feedback flux from this flame to the surface and thus increased burning rate. A relatively simple analytical model based on this picture is developed for prediction of propellant burnings rate as a function of pressure and crossflow velocity, given only zero-crossflow burning rate versus pressure data. Model predictions and experimental results are compared, with reasonably good agreement being found. (Author)

Merrill K. King

Papers

Ignition and Combustion of Boron Particles and Clouds

Model for Steady-State Combustion of Unimodal Composite Solid Propellants.

Erosive Burning of Composite Solid Propellants: Experimental and Modeling Studies

A Model of Erosive Burning of Composite Propellants

Comment on ''spin effects on rocket nozzle performance.''