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Combustion, Explosion and Shock Waves

2016 year, number 2

Effect of Heat Transfer Conditions on the Critical Pressure of Metal Ignition in Oxygen

V. I. Bolobov
St. Petersburg Mining University, St. Petersburg,199106 Russia
Keywords: критическое давление возгорания, кислород, инициаторы возгорания, фрагменты разрушения, титановые сплавы, коэффициент теплоотдачи, critical pressure of ignition, oxygen, ignition initiators, fracture fragments, titanium alloys, heat transfer coefficien

Abstract

Experimental data on the critical pressure of ignition of titanium alloy fragments in gaseous oxygen are analyzed. The fragments are obtained after fracture of alloy samples in the dynamic mode (p2*) and under natural convection conditions (p1*). The results are analyzed with allowance for the heat transfer coefficients from material ignition initiators under similar conditions. Based on the shape of the experimental thermograms of plate cooling, the coefficient of heat transfer from microcraters with a juvenile surface formed due to knockout of metal particles from the plate by the high-velocity flow is found: α2 ~ 11 W(m2 × K). The value of α2 is close to the value of this coefficient calculated with the use of the coefficient α1 ~ 5 kW/(m2 × K) of heat transfer from titanium rod microfragments (with the size of the order of metal grains) formed during titanium rod fracture in oxygen under conditions of natural convection with allowance for the ratio p2*/p1*.