Recent progress in modeling solid propellant combustion

Abstract

Tremendous progress has been achieved in the last ten years with respect to modeling the combustion of solid propellants. The vastly increased performance of computing capabilities has allowed utilization of calculation approaches that were previously only conceptual. The paper will discuss three areas of emphasis: first, numerical modeling of premixed flames using detailed kinetic mechanisms; second, development of packing models to calculate a geometrical distribution of particles simulating a heterogeneous solid propellant; and finally, calculation of diffusion flame effects that are critical in the combustion of AP/hydrocarbon solid propellants.The capability of modeling premixed combustion using detailed kinetic mechanisms has been evolving and successfully applied to solid propellant ingredients based on a one-dimensional approach. Much of the early work was performed at Novosibirsk. The approach allows calculating the burning rate as a function of pressure but also the temperature sensitivity and spatial distributions of temperature and species concentrations. Generalized mechanisms have been developed and applied to many ingredients such as HMX, GAP, RDX, NG, AP, etc. The gas-phase kinetic mechanisms seem to represent the chemistry of these monopropellants and pseudo-propellants consistently well. The burning rates of these monopropellants vary by almost an order of magnitude but are essentially independent of the flame temperature. Various model calculations agree reasonably well with available experimental data.Recent work in the USA has been aimed at describing the geometrical packing of a solid propellant. These models represent significant progress toward such a description. Combining the packing model with a realistic flame model is still a significant challenge. Preliminary results are encouraging, but obviously further work is needed. Also, fundamental calculation of two-dimensional diffusion flames, incorporating realistic kinetics has progressed significantly. Recent results show encouraging promise toward simulating the minute detail involved in determining the burning rates of AP containing propellants.Key words: modeling, combustion, solid propellant, chemical kinetics. Abbreviations

Literature survey for a first choice of a fuel-oxidiser couple for hybrid propulsion based on kinetic justifications

“…The first one is linked to thermal decomposition in the solid phase with diffusion of light species in the reducer. This is, for example, the case of PMMA (under 773 K), and also of the oxidiser AP [17]. This phenomenon depends on the regression rate of the solid [19].…”

“…Transient phenomena in combustion, like temperature and pressure oscillations [15,16], could not be observed without pyrolysis kinetics. In comparison with hybrid propulsion, solid propulsion is more widely studied using a detailed kinetic approach [17].…”

“…However, this is not the most appropriate technique because of gradients lower than 50 K s -1 . In the hybrid rocket, the combustion heat release should be of the order of 10 7 K s -1 [17]. Flash pyrolysis system allows obtaining several thousand degrees per second by pyrolysing a sample deposited within a very thin electrically heated wire.…”

Critical Review of Phenomenological Models for Studying Transient Combustion of Solid Propellants

“…However, use of those models implies precise knowledge of numerous physicochemical characteristics of SP which are not available at present. It concerns first of all reliable description of the chemical reactions in the condensed phase and knowing the properties of energetic materials at enhanced temperatures [1]. In addition, there are great difficulties in justification of realistic boundary conditions at the burning surface, especially when analyzing the time dependent combustion regimes.…”

Modelagem da combustão da dinitramida de amônio por simulação computacional

“…No entanto, algumas condições de modelagem podem não ser passíveis de serem atingidas em experimentos laboratoriais. 19 Nas últimas décadas, as técnicas de modelagem de combustão e ignição de materiais energéticos evoluíram enormemente, 20 sendo aplicadas a diversos tipos de formulações de explosivos, propelentes, geradores de gases ou pirotécnicos. 21 Este procedimento de modelagem computacional considera efeitos como a distribuição de zonas reacionais em fases condensadas, radiação de espectros não-lineares e não-homogeneidade do propelente, para reações químicas energéticas formuladas, entre outros.…”