Improvements in thermal efficiency and exhaust emissions with ozone addition in a natural gas-diesel dual fuel engine

Here, ozone (O-3) 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 O-3 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 O-3 addition on the ignition and combustion with the pilot injection timing while varying the O-3 concentration. The results showed that the combination of the O-3 addition and the early pilot injection is a means to improve the thermal efficiency and unburned emissions with a small amount of O-3. Further, the improvement in the thermal efficiency and the reduction of the unburned hydrocarbons with the O-3 addition are more pronounced for lower equivalence ratios of natural gas, while the O-3 addition has a limited effect on the thermal efficiency and the unburned hydrocarbons for higher equivalence ratios of the natural gas.