Ozone (O3) was introduced into the intake air to control the ignition in a gasoline compression ignition (GCI) engine. An early fuel injection at −68 °CA ATDC was adopted to mix the fuel with the reactive O-radicals decomposed from the O3, before the reduction of the O-radicals due to their recombination would take place. The second injection was implemented near top dead center to optimize the profile of the heat release rate. The engine experiments were performed around the indicated mean effective pressure (IMEP) of 0.67 MPa with a primary reference fuel, octane number 90 (PRF90), maintaining the 15% intake oxygen concentration with the EGR. The quantity of the first injection, the second injection timing as well as the ozone concentration were changed as experimental parameters. The results showed that the GCI operation with the ozone addition makes it possible to reduce the maximum pressure rise rate while attaining high thermal efficiency, compared to that without the ozone. Appropriate combinations of the ozone concentration and the first injection quantity achieve low smoke and NOx emissions. Further, the ozone-assisted GCI operation was compared with conventional diesel operation. The results showed that the indicated thermal efficiency of the ozone-assisted GCI combustion is slightly lower than that of the conventional diesel combustion, but that GCI assisted with ozone is highly advantageous to the smoke and NOx emissions.

No abstract

Here, ozone (O3) was introduced into the intake air in a natural gas fueled engine ignited by diesel fuel, a natural gas–diesel dual fuel engine, to utilize the reactive O-radicals decomposed from the O3 for the promotion of the ignition and for improvements in the thermal efficiency and exhaust emissions. The engine experiments were performed over a range of equivalence ratios of the natural gas in a single cylinder engine. The timing of the pilot injection of the diesel fuel was varied from early in the compression stroke to near top dead center to examine the changes in the effects of the O3 addition on the ignition and combustion with the pilot injection timing while varying the O3 concentration. The results showed that the combination of the O3 addition and the early pilot injection is a means to improve the thermal efficiency and unburned emissions with a small amount of O3. Further, the improvement in the thermal efficiency and the reduction of the unburned hydrocarbons with the O3 addition are more pronounced for lower equivalence ratios of natural gas, while the O3 addition has a limited effect on the thermal efficiency and the unburned hydrocarbons for higher equivalence ratios of the natural gas.