Laser Ignition of Aluminum and Boron Based Powder Systems
A. G. Korotkikh1,2, I. V. Sorokin3, V. A. Arkhipov2
1National Research Tomsk Polytechnic University, Tomsk, 634050 Russia
2National Research Tomsk State University, Tomsk, 634050 Russia
3Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: powder, aluminum, amorphous boron, aluminum diboride, aluminum dodecaboride, oxidation, ignition delay time, ignition temperature
Abstract
Powders of various metals and boron are widely used in mixed fuel compositions to increase the combustion temperature and specific impulse of rocket engines. The article presents the results of an experimental study of the oxidation and ignition in air of ultrafine aluminum powders Alex, amorphous boron and microsized aluminum powders μAl, aluminum borides AlB2 and AlB12. Metal and boron powders were heated and ignited by a cw CO2 laser in the heat flux density range 65 ÷ 190 W/cm2. Based on thermal analysis data, it was found that the powder reactivity parameters are arranged in the following sequence (in descending order of activity): Alex ® B ® AlB12 ® AlB2 ® μAl. During the oxidation of amorphous boron and aluminum dodecaboride AlB12, the total specific heat release and the rate of mass change have maximum values. Alex, boron and AlB12 powders ignite more easily in air under the action of an external radiant source. Power exponent n as a function of the ignition delay time tign on the heat flux density tign ( q ) = Aq - n for μAl powders, AlB2 and AlB12 are approximately the same and equal to »2.0, for ultrafine Alex and boron powders it is lower and amounts to n = 1.5 and 1.0, respectively.
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