Burn rate (chemistry)

About: Burn rate (chemistry) is a research topic. Over the lifetime, 847 publications have been published within this topic receiving 8908 citations. The topic is also known as: Burning rate.

Solid propellant combustion mechanisms and flame structure

Abstract: AP and HMX are the two oxidizers used most often in modern solid propellants, either composite propellants or composite modified double base propellants. Although the two oxidizers have very similar combustion characteristics as monopropellants, they lead to significantly different characteristics when combined with binders to form propellants. Also, different characteristics result depending on the particular binder system used. This paper discusses various flame structures and mechanisms that apparently lead to these similarities and differences, with emphasis on the qualitative effects of flame structure on combustion mechanisms. For AP composite propellants, the primary flame is more energetic than the monopropellant flame, leading to an increase in burn rate over the monopropellant rate. This also leads to a very strong particle size dependence. In contrast the HMX primary flame is less energetic than the HMX monopropellant flame and ultimately leads to a propellant rate significantly less than the monopropellant rate in composite propellants. In HMX composite propellants the primary flame apparently robs energy from the monopropellant flame leading to a reduced rate with little particle size dependence. In double base propellants HMX has little effect on the burning rate.

Solid propellant diffusion flame structure

Abstract: Laser-supported deflagration of ADN, AP, HNF, TNA, RDX, or HMX in sandwich configurations with various energetic and nonenergetic binders was studied. Planar laser-induced fluorescence (PLIF) was used to measure the two-dimensional NH, OH, and CN species profiles for these sandwiches. For the HNF sandwiches, obvious diffusion flames were present at low pressure, but they were weak, further from the surface than the HNF monopropellant flame, and not expected to be burn-rate controlling. ADN was found to have diffusion flames with energetic binders at low pressures, but they were very far from the surface. The high burn rate of ADN at pressures above 3 atm left the binder behind, and the diffusion flames became weak. AP showed clear evidence for strong close diffusion flames with binders and even with other oxidizers. The combination of HMX or TNA with AP leads to obvious diffusion flame interactions: the highly reactive AP-decomposition products accelerated the nitramine dark zone kinetics and caused the secondary flame to hold on the interface region. This leads to higher heat feedback in the interface region and a somewhat faster nitramine regression rate. TNA, RDX, and HMX were not found to have any diffusion flames with energetic or nonenergetic binders: the monopropellant flame was lifted in the region around the binder. These results imply that ADN, HNF, TNA, RDX, and HMX propellants will not have the clear particle size ballistic tailorability seen with AP propellants, because diffusion flames appear to be strong and close to the surface (and therefore burn-rate controlling) only in AP propellants.

Azide-free gas generant compositions and processes

Abstract: Composition and process for inflating an automobile or aircraft occupant safety restraint bag which reduces the toxicity of the gases produced by gas generants. A relatively low energy nitrogen containing fuel is combined with a burn rate accelerator, such as an alkali metal salt, to form an azide-free gas generant composition which lowers the combustion temperature of the gas generants while also maintaining a rapid burn rate, thereby reducing toxicity of the resultant gases.

Size and Shape of Ammonium Perchlorate and their Influence on Properties of Composite Propellant

Abstract: Most of the composite propellant compositions contain solid loading up to 86 per cent. The main solid ingredients of composite propellant are ammonium perchlorate (AP) and aluminium powder. Therefore, it is a must to characterise these to improve processibility and quality of composite propellant. Effect of particle size on propellants slurry viscosity and ballistic parameters are well documented, however, the effect of oxidizer particle shape is not reported. In the present study, different methods for size and shape characterisation are discussed and effect of size and shape of AP on composite propellant properties are studied. The data indicate that as size of AP decreases, propellant slurry viscosity increases and burn rate increases. The particles having higher shape factor provides less endof mix (EOM) viscosity of propellant slurry and burn rate. Further, effect of size of ground AP on shape is also investigated. From the data thus obtained, it is inferred that as size of ground AP decreases, shape factor decreases, and particles become more irregular in shape.Defence Science Journal, 2009, 59(3), pp.294-299, DOI:http://dx.doi.org/10.14429/dsj.59.1523

Apparatus for suppressing a fire

Abstract: An apparatus for suppressing a fire comprises a gas generator containing a propellant and a fire suppressant as a mixture of compacted powders. The average diameter of a fire suppressant particle is larger than the average diameter of a propellant particle and the larger fire suppressant particles form discrete cooling sites that do not dramatically reduce the propellant burn rate.