Mass‐ and momentum transfer in hydrogen/air and methane/air mixtures

Abstract

In this article we present results for the viscosity and the mass transfer rates of hydrogen/ air, hydrogen/oxygen, methane/air and methane/oxygen mixtures in the temperature range from 1000 to 7000 K and a pressure range from lo3 to lo6 Pa. In addition, the combustion ratio is varied from 0 to 03. The transport properties are calculated from the first order solution of the Chapman Enskog approach to the Boltzmann equation, assuming chemical equilibrium composition. An extensive literature study was performed to derive experimental and/or theoretically based data for the respective binary interaction potentials. The values of the collision integrals, as derived from a complex numerical integration procedure, are correlated to an approximation formula. In addition, the exact solutions of the kinetic theory are compared to frequently used empirical mixture rules. For the mixture viscosity an easy approximation formula is deduced from the gas-kinetic theory.

Energy transfer in hydrogen/air and methane/air mixtures

“…[l I]) lead to the formulation of the inelastic collision terms as functions of the relaxation times ~i J n~,~ and ~i j n~*~~~, as well as the partition functions Qint,i. The type of the resulting equation is identical to that of the integral of the elastic collision as given in [9]. The complete method and the resulting integral equations are described in detail by Pascal [7].…”

“…The dynamic viscosity of a mixture, the binary diffusion, and the multi-component diffusion in a mixture are only weakly affected by the thermal nonequilibrium. They do not differ from known solutions and are, therefore, discussed in the first part of this article [9]. All terms contributing to the molecular heat conductivity are affected strongly by the thermal nonequilibrium.…”

“…This value corresponds to a chemically frozen mixture condition. The second term describes the transport of enthalpy concerning the mass flow, also called conductivity due to reaction [9]. The third and fourth terms describe thermal diffusion effects, the third summand describes the Soret effect and the fourth one the Dufour effect.…”

“…The heat conductivity due to translation in a gas mixture with v components can be described by a v-dimensional linear equation system as already applied for the viscosity q and the diffusive mass flux j in [9].…”

“…The vector j t corresponds to the solution vector of the diffusion matrix for concentration and pressure diffusion given in [9]. As constant pressure is assumed for chemical equilibrium, pressure diffusion can be neglected for all following considerations.…”