Computational optimization of a reactivity controlled compression ignition (RCCI) combustion system considering performance at multiple modes simultaneously

The optimization study resulted in an optimum CR of 13.1 with a bowl geometry that has two distinctive regions to benefit the low load and high load operating conditions, respectively. Results also showed that a narrow spray angle for diesel fuel and a wide spray angle for gasoline would be necessary to target the two different regions in the bowl. The optimal fueling strategy had very low gasoline percentage at low load (∼15% of the total fuel mass) and a high gasoline percentage (∼92% of the total fuel mass) at the high load condition. From the study on the effect of weighting the efficiencies, it was found that when low load is given a higher weighting, a higher CR piston (CR ∼15.7) was chosen as the optima while giving a higher weighting to high load led to a lower CR (CR ∼11.8) piston as the optima. Results also showed that prioritizing one load highly over the other would yield a bowl geometry that negatively affects the performance at the other load condition - indicating that an optimization must consider both the operating modes simultaneously.