The fluid centerline temperature profiles are presented in Figure 8 along the length of the burner with preheating, combustion, and post-combustion or cooling regions. For most cases studied, burners exhibit similar combustion characteristics that are summarized here. There are three regions in these burners, namely preheating, combustion, and post-combustion or cooling regions. The width of these regions changes as a function of operating conditions, and their distinction is not always as sharp. In the preheating region, the wall temperature is significantly higher than the fluid temperature, so energy transfers from the wall to the fluid. The wall thermal conductivity is significantly larger than that of the fluid mixture, so most of the upstream conductive heat flux occurs within the walls of the reactor. This energy is brought upstream from the post-combustion region where walls are considerably hot. Since the mixture warms up from the wall towards the centerline, ignition occurs near the wall and the flame stabilizes at the centerline. This ignition mode is different from the case where outside preheating is used to ignite the mixture. In the latter case, ignition occurs at the centerline. Once the fluid reaches the ignition temperature, there is an inflection point in the temperature profile. The mixture combusts rapidly, releasing heat, which causes a sharp rise in the fluid temperature in the combustion region. The combustion zone is relatively narrow, a characteristic of highly activated reactions. Even at these relatively small scales, the transverse heat transfer within the fluid is much slower than the rate of heat release so that the fluid centerline temperature in this zone approaches approximately the adiabatic flame temperature. Combustion at the lower adiabatic flame temperature produces a correspondingly lesser amount of nitrogen oxides production. In the post-combustion region, after the reactants are consumed, the reaction stops, the fluid cools down to the wall temperature, and the walls are cooled by exterior heat losses. There are no significant axial or transverse gradients within this zone. In non-adiabatic cases, both the fluid and the wall would eventually reach room temperature in sufficiently long burners. In some cases, the maximum fluid temperature exceeds the adiabatic flame temperature of butane-air mixture computed for room temperature. Traditional continuous stirred tank reactor or plug flow reactor analysis suggests that this is impossible to achieve with one-step chemistry. However, in this distributed model, the wall acts as a conduit for heat transfer from the hot exiting products to the cold entering reactants. This link results in a heat recycle within the system, which increases the temperatures near the inlet and allows a maximum temperature that is greater than the adiabatic flame temperature. Because of the overall energy conservation, the exiting fluid temperature is in these cases lower than the adiabatic flame temperature.