Experimental Analysis of the Influence of Water Injection Strategies on DISI Engine Particle Emissions
Increasing the efficiency of modern gasoline engines (with direct injection and spark-ignition - DISI) requires innovative approaches. The reduction of the engine displacement, accompanied by an increase of the mean pressure, is limited by the tendency of increasing combustion anomalies. Conventional methods for knock mitigation, on the contrary, have a negative effect on consumption and efficiency. A promising technology to solve these conflicting objectives is the injection of water. Both the indirect and the direct water injection achieve a significant reduction in the load temperature. The fuel enrichment can be reduced, whereby the operating range of the exhaust aftertreatment can be extended. In addition, water injection paves the way for an increase in the geometric compression ratio, which leads to an efficiency advantage even at partial load.