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Oddities in determining burning rate on basis of closed vessel tests of single base propellant

Leciejewski Z. K.

Journal of Theoretical and Applied Mechanics

2014

Vol. 52 nr 2

313--321

The proper determination of parameter values defining the dependence of the burning rate r of smokeless propellant on gas pressures p surrounding the burning grains constitutes one of the goals of experimental pyrostatic (closed vessel) testing. The aim of the hereby paper is the analysis of results of experimental closed vessel tests realized in the context of isolating possible oddities in determining the relation r(p). During the experimental tests, a single base propellant with grains of different or similar combustible layer thickness e1 was burned while implementing identical or various loading conditions. Identical ignition systems were used in both instances. The results of experimental tests and theoretical analysis performed permit a more complete verification of the assumptions with regard to proper realization of pyrostatic comparative tests and prove additionally that closed vessel tests should be focused in the direction of “dedicated” tests.

Experimental Study of Possibilities for Employment of Linear Form of Burning Rate Law to Characterise the Burning Process of Fine-Grained Propellants

Leciejewski Z. K.

Central European Journal of Energetic Materials

2008

Vol. 5, nr 1

45-61

In the paper the linear form of burning rate law r=r1źp, describing changes (in proportion to pressure p) in burning rate of propellants is reviewed. The linear form is one of many (but very popular) forms of burning rate law predicted to analysis and computer simulations of propellant gun systems operating and design process of gun. Coeffcient r1 of the linear form is usually calculated on the basis of average dimensions of grain (layer of burnt propellant) and integrated experimental pressure-time curve. Recorded picture of pressure of propellant gas mixture is an effect of closed vessel test. It is assumed that value of coeffcient r1 is constant (for given type of propellant) regardless of value of propellant gas pressure. Different fne-grained propellants (single-base and double-base) were fred in closed vessel tests to determine their burning rate behaviour. The variations in mass of igniter pad (black powder) at the same value of loading density were used. The results of experimental tests and calculations presented in this paper show signifcant infuence of the used type of ignition system (mass of black powder) on burning rate (coeffcient r1) of propellant. The differences in calculations of propellant burning rate and computer simulations of pressure-travel history inside the barrel of a propellant gun system indicate that there are limitations to the validity of the linear form approach particularly for fne-grained propellants.