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A theory of multicomponent diffusion based on Fick's law is proposed, in which, when writing the Maxwell–Stefan equations, a multicomponent mixture appears to consist of two components: the isolated substance and all the others with average characteristics. The number of diffusion coefficients is significantly reduced, a method for calculating them is indicated, and they strongly depend on the concentration of the mixture components. Based on the results of this theory, we simulated the combustion of a stoichiometric H2/O2 mixture. For each component, large chemical works are carried out with variable signs, but in total they partially destroy each other. The analysis of the effect of changing the composition of the mixture on the transfer processes, temperature, and combustion rate was carried out. [ABSTRACT FROM AUTHOR]

Study of the practice of using solid rocket fuels and explosives has determined the existence of an increase in the combustion rate due to turbulence. However, this rule is violated in the case of small-scale turbulence produced by the gasification zone of solid fuel. The incoming heat from the gas phase is partially consumed to maintain the chemical reaction of gasification and partially returns to the gas phase. If the return energy of turbulent motion is high, then the combustion rate decreases. [ABSTRACT FROM AUTHOR]

A solution is obtained to the problem of determining the conditions of hydrodynamic stability in the presence of flow of gaseous combustion products over the propellant gasification surface. The cross-flow has a small gradient along the direction of motion. Analysis of the obtained dispersion equation shows that hydrodynamic instability with oscillations develops. The transfer coefficients of natural turbulence are represented as the sum of two terms: the first is responsible for the transfer in the absence of cross-flow, and the second takes into account the enhancement of transport processes in the case of cross-flow. Their dependence on the initial temperature of solid propellant combustion predicts a reduction in the negative erosion effect in accordance with experimental data. Accounting for the relaxation time of the evaporation process has a stabilizing effect. In the limit of strong relaxation, this leads to oscillatory stability (in the absence of crossflow) where the perturbations neither grow nor decay. However, arbitrarily weak cross-flow leads to instability. [ABSTRACT FROM AUTHOR]

A model for solid propellant gasification is proposed which contains a two-phase medium in an intermediate stage. The formation of the gas phase proceeds in two ways: chemical reactions result in gaseous products, which, in turn, initiate the formation of bubbles in which vapor forms from the liquid phase of the propellant. Gaseous products play an important role only in the very early stage of bubble development; their critical pressure is used to determine the minimum size of gas-phase nuclei. The bubble volume grows primarily by evaporation of the liquid phase. A kinetic equation for the bubble concentration and the necessary boundary conditions are formulated. Arguments are given suggesting that a temperature maximum cannot occur in the gasification zone and that natural turbulence can be generated by collapsing bubbles. The sound produced by solid propellant combustion is explained by the collapse of a huge number of microscopic bubbles. If the processes in the two-phase zone are neglected, the formulated system of equations is transformed into the Belyaev-Zel'dovich model equations. [ABSTRACT FROM AUTHOR]