Multiphase Flows and Combustion
Modeling of Laminar Spray Flames
Laminar spray flames are fundamental to spray flame modeling, and they are accessible to experiments. Their structures may also be used in turbulent spray simulations in the frame of the spray flamelet model. This enables consideration of detailed chemical reaction mechanisms in these turbulent spray systems, and thus the prediction of pollutant formation and soot precursors.
Figures 1 and 2 display two different spray flame structures for the simulation of a methanol spray with carrier gas air directed against an air stream. Here, two different spray flame structures have been found for the first time for the same initial and boundary conditions (multiple solutions). Figure 1 shows two flame zones whereas in Fig. 2, the air-sided flame is extinguished. For pure gas flames, the latter case represents the cold solution in pure gas flames. In spray flames, in both cases, the spray-sided gas flame persists which accounts for the evaporation of the injected spray.
Figure 3 shows the maximum flame temperature in dependence of the strain rate on the fuel side of the configuration. It can be seen that the spray-sided flames are structurally identical.
The gas-sided flames of Fig. 1 have been compared to pure gas flames, and it is found that the flames are structurally identical, too. This fact can be used in the flamelet modeling of turbulent spray flames to simplify their implementation into the turbulent spray combustion model.