Conjugate heat transfer analysis of methane/air premixed flame – Wall interaction: A study on effect of wall material

Abstract

Conjugate heat transfer analyses of methane/air premixed flames propagating toward walls are performed without employing any wall model in terms of one- and two-dimensional numerical simulations, and the flame-wall interaction is investigated in detail. To describe the combustion reaction of methane, a two-step global reaction model is used. In one-dimensional numerical simulations, the effects of wall material, i.e., the insulation and Al alloy, and ambient pressure on the wall heat flux are investigated. In two-dimensional numerical simulations, on the other hand, the effect of turbulence on the wall heat flux is investigated. The results of the one-dimensional numerical simulations show that the wall heat flux on the insulation wall is higher than that on the Al alloy wall at the moment the flame reaches the wall. Thereafter, the heat flux on both walls rapidly reduces, however heat flux on the insulation wall reduces more than that on the Al alloy wall, because the gas temperature gradient on the insulation wall becomes smaller. This reduction effect of the wall heat flux due to the insulation is more efficient at higher pressure conditions, and reaches 1.8 % at 4 MPa. On the other hand, the two-dimensional numerical simulations show that the propagation speed in the vicinity of the wall after the flame first reaches the wall is slower in the turbulent case than that in the laminar case. This is due to the fact that the advection of the flame front with high temperature toward the unburnt side is suppressed by the turbulent eddies.