An Approximation Method in Theory of Unsteady Rate of Burning of Powder

摘要

A change in pressure will change the combustion rate of powder. A quasi-steady condition appears when the change in pressure is slow, so that the temperature-profile in the heated layer of powder can follow the changes in pressure. When the pressure is changing rapidly, the temperature-profile in the powder is lagging behind the pressure and the combustion rate of the powder will differ from a quasi-steady rate. Analytical expressions are derived with the aid of an approximate method of integral relationships for unsteady combustion rate of a powder-model whose combustion rate is determined only by the pressure and the temperature gradient at the surface of the condensation phase. Cases of both instantaneous and exponential changes in pressure are examined. Conditions favoring the extinguishing of burning powder during a drop in pressure are determined. A comparison is given with the results of a numerical calculation. Cases of linear and exponential relationships between the steady combustion rate of powder and its initial temperature were investigated. (Author)