V. A. Strunin

Combustion mechanism of RDX and HMX and possibilities of controlling the combustion characteristics of systems based on them

Modeling of the combustion of cyclic nitramines (CNAs) has shown that their combustion proceeds by the same mechanism with the joint effect of the processes in the condensed and gas phases. The combustion characteristics of the pure substances can be changed only at low pressures by using catalysts acting in the condensed phase, and at high pressures, this problem is difficult to solve. The combustion of binary compositions [CNA + fuel (F) and CNA + ammonium perchlorate (AP)] and ternary compositions (AP + CNA + F) is considered. It is shown that the combustion mechanism and characteristics are determined by the chemical interaction and heat exchange between the reactants, which depend on the characteristic particle size in the system.

Combustion conditions of volatile materials decomposing in condensed and gas phases

A classical model of combustion conditions is presented in which conversion occurs only in the gas phase. This paper presents an approximate analytical approach to such a model of combustion, allowing investigations to be undertaken over a wide range of parameter variation and the combustion characteristics to be estimated sufficiently and simply, which is important for a multiparameter process. The conceptual aspect of the method of determing the combustion characteristics is described; the theoretical pressure dependences of the combustion characteristics are shown.

Modeling of HMX combustion

A mechanism of HMX combustion was proposed and the corresponding model was developed under the assumption that the combustion wave consists of two zones, with consideration given to the reaction of decomposition and vaporization of the initial energetic material in the condensed phase and the subsequent decomposition of its vapor in the gas phase. An analysis of the results showed that, at low pressures, the burning rate is largely determined by the exothermic decomposition of the material in the condensed phase, but at pressure above ∼20 atm, the processes in the gas phase begin to play an increasingly important role, where the limiting process is the bimolecular activation reaction with the subsequent dissociation of HMX accompanied by the secondary reactions between the products. A comparison of the calculation results with experimental data showed that the model adequately describes a number of characteristics of the combustion wave and ballistic properties, such as the burning rate and its sensitivity to pressure and initial temperature.

Specific Features of Combustion of Cellulose Nitrate and Inert Filler Based Composites

Combustion of composites based on granulated cellulose nitrates and containing, as fillers, aluminum oxide, silicon carbide, carbon, boron nitride, sodium chloride, zinc oxide, and tungsten particles, is studied. Burning rates under atmospheric pressure, combustion-front temperatures, and mass losses after complete combustion of the composites are measured. The dependence of the burning rate on the size of silicon-carbide particles is obtained. Models of solid and laminar combustion are used to predict combustion characteristics, which are in good agreement with experimental data. Some specific features of combustion of composites with particular fillers are explained.

Effect of catalysts on the combustion of layered systems

An experimental study is made of a “chemical arc”, a model layered system of solid components, between the end surfaces of which stationary combustion takes place. The rates of combustion of the components in ammonium perchlorate-polyether, ammonium perchlorate-polyethylene, and ammonium perchlorate-butyl rubber systems with catalytic additives (diethyl ferrocene, epoxyethyl ferrocene, and iron oxide) are measured as functions of the distance between the components. A maximum mass combustion velocity is found to exist as a result of the transition from a low velocity (kinetic) to a high velocity reaction regime. The data are in qualitative agreement with theory. The mechanism by which the catalysts affect the combustion characteristics is analyzed.

Influence of additives on the characteristics of the combustion of layered systems imitating composite propellants

This article is an overview, containing both new research data and results of published works. Using a layered system model that takes into account chemical processes and heat and mass transfer, proceeding in the one and two-zone combustion modes, we considered various types of combustion systems comprised of two components: base propellant and various additives, such as organic materials (decomposable, evaporable, oxidizeable), energetic materials, coolants, catalysts, and metals. Based on analytical-form results, the combustion characteristics are calculated as functions of the pressure, size of the components, and physicochemical properties of the system. In a number of cases, complex dependences are observed, for example, areas with an accelerated or retarded growth of the burning rate with increasing pressure, and extrema in the dependences. A comparison of calculation results with experimental data demonstrated a good qualitative agreement. The results can be used in developing solid rocket propellants with the required ballistic properties.