Optimization of gasoline compression ignition combustion with ozone addition and two-stage direct-injection at middle loads

Abstract

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.

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

“…That report showed that an O 3 concentration of 1000 ppm or more was needed to enhance the ignition. 18 This O 3 concentration is considerably higher than that used to enhance the combustion of premixed gasoline components, that is less than 100 ppm, 10,11,[15][16][17] and considerable energy amounts are consumed to generate the O 3 concentration above 1000 ppm. 19 The differences in the required O 3 concentration between the gasoline components and the natural gas would suggest that the oxidation reactions of larger hydrocarbons are more likely to be affected by the O-radicals.…”

“…12–15 The ignition enhancement effects due to the O 3 addition have also been utilized in gasoline compression ignition (GCI) engines employing a two-stage direct injection strategy, in which the first injection is implemented before the O 3 decomposition to make the first injected fuel react with the O-radicals, and the ignition delay of the second injection is controlled by the temperature increase and the chemical species generated due to the first fuel injection. 9,16,17…”

“…[12][13][14][15] The ignition enhancement effects due to the O 3 addition have also been utilized in gasoline compression ignition (GCI) engines employing a two-stage direct injection strategy, in which the first injection is implemented before the O 3 decomposition to make the first injected fuel react with the O-radicals, and the ignition delay of the second injection is controlled by the temperature increase and the chemical species generated due to the first fuel injection. 9,16,17 Nishida et al 18 introduced O 3 into the intake air together with natural gas and injected diesel fuel directly into the cylinder near top dead center. That report showed that an O 3 concentration of 1000 ppm or more was needed to enhance the ignition.…”

Prospects of Controlled Auto-Ignition Based Thermal Propulsion Units for Modern Gasoline Vehicles

“…ii Using high-ON fuels, such as ethanol, to prolong ignition delay and thus allow operation at high compression ratios. Christensen et al [107] realised stable CAI, albeit at relatively low loads, using ethanol in an engine with a very high compression ratio of 21:1. iii Introducing radical producing species, such as ozone, in the intake air [117] or partially reforming the injected fuel via low-temperature heat release [100] to lower AI temperature.…”