A numerical investigation on the effect of wall thermal conductivity on flame stability and combustion efficiency in a mesoscale channel filled with fibrous porous medium

Premixed CH4/air combustion in a mesoscale channel filled with fibrous porous medium was numerically investigated. First, the accuracy of numerical model was verified by experimental results. Then, the effect of wall thermal conductivity on the standing wave (i.e., stationary flame) was examined. It is shown that both upper and lower limits for the standing wave regime rise with the increase of wall thermal conductivity. The quantitative analysis reveals that there are two major factors that are responsible for this phenomenon. On one hand, the heat recuperation via the upstream channel wall is enhanced at a larger wall thermal conductivity, which can increase the burning velocity of incoming mixture. On the other hand, the near-wall “dead space” grows wider at a larger wall thermal conductivity due to the decrease of wall temperature level. Thus, in order to get a new balance between the incoming mixture velocity and burning velocity, or to shrink the near-wall “dead space”, a larger inlet velocity is required. Additionally, the wider “dead space” results in a sharp drop in combustion efficiency at a larger wall thermal conductivity. In conclusion, for small channels filled with fibrous porous media, a solid wall of relatively small thermal conductivity is preferable.