3 - Mixture formation, combustion and pollutant emissions in high-speed direct-injection diesel engines

Abstract

This chapter deals with mixture formation, combustion and pollutant emissions in high-speed direct injection (HSDI) diesel engines. In the first part of the chapter the fundamentals of mixture preparation are covered. The physics of spray formation, spray propagation and their characterisation by global values like spray angle and penetration are described in detail. It is shown that fuel atomisation, characterised by droplet diameter, plays a fundamental role in mixture formation. Further, air entrainment as a second important factor governing mixture preparation is discussed in combination with air-distributed and fuel-distributed mixture preparation, combustion chamber design, in-cylinder flow (swirl, turbulence, etc.) and injection rate. It is shown that there is a clear relationship between injection pressure, swirl number, combustion chamber design, number of nozzle holes and nozzle hole diameter.