• RCCI is a promising low-temperature combustion strategy offering a pathway to high-efficiency clean combustion using in-cylinder blending of fuels with different auto-ignition characteristics. (Earlier post.) RCCI provides combustion control by varying fuel reactivity using two fuels with different reactivities—for example, the port fuel injection of gasoline (mixed with intake air, as in spark-ignition engines) and multiple direct-injections of diesel fuel into combustion chamber later during compression (as in diesel engines).

• GCI uses low-octane gasoline in diesel (compression ignition) engines to achieve very high efficiency while reducing the cost of diesel engines by lowering injection pressures and requiring less expensive exhaust aftertreatment. (E.g., earlier post.)

QuantLogic has developed an adaptive dual-fuel injector to enable direct injections of both gasoline/E85 and diesel fuel on-demand from a single injector. This technology, the development of which was supported by Small Business Innovation Research (SBIR) grants, was designed to reduce the fuel system cost and enable advanced combustion on practical engines.

To perform the optimizations, the team used the University of Wisconsin Engine Research Center KIVA code coupled with a multiobjective genetic algorithm. Model validation was performed by comparing simulation results to conventional diesel, reactivity controlled compression ignition, and gasoline compression ignition combustion, and the validated model was used to develop an optimum reactivity controlled compression ignition–gasoline compression ignition combustion strategy.

The reactivity controlled compression ignition (RCCI) optimization results showed that by direct injecting both gasoline and diesel fuel, rather than using a combination of port- and direct-injection technology, the gasoline quantity can be held at a high percentage across the range of loads considered.

In this study, the mode-weighted gasoline percentage was 91%. At the lightest load point, direct injecting the gasoline delivered optimum results, whereas for the other load points, premixing the gasoline yielded the optimum results.

RCCI combustion gave a cycle-averaged improvement of 33% in gross indicated efficiency over conventional diesel combustion. The cycle-averaged NO_x and soot emissions were reduced by 95% and 75%, respectively. To demonstrate operation over the entire operating map, an optimization was performed at a high-speed–high-load (16 bar, 2500 r/min) condition.

Optimization results also showed that a gross indicated efficiency of 46.4% with near zero NO_x and soot emissions could be achieved using gasoline compression ignition at this load point.

Resources

• Chaitanya Kavuri, Sage L Kokjohn, David T Klos and Deyang Hou (2015) “Blending the benefits of reactivity controlled compression ignition and gasoline compression ignition combustion using an adaptive fuel injection system”International Journal of Engine Research doi: 10.1177/1468087415615255