The next part of the analysis centers around the air-fuel mixture ratio, presented here as Equivalence Ratio. In this simulation, the fuel rich zones are seen as equiv_ratio > 1, while lean zones are seen as < 1. Again, to help quantify this more exactly, we have computed an isovolume where equiv_ratio > 1, and graphed it as a percentage of total volume as a function of time. You can see the fuel rich zones initially appear along the spray injection locations, followed by a relatively rich zone towards the top of the domain. In the two animations presented below, we can see there are two large regions of very rich air-fuel mixture, which needs to be monitored closely.