Theoretical Study of the effects of Ignition Delay on the Performance of DI Diesel Engine

Abstract

The ignition delay in a diesel engine is defined as the time (or crank angle) interval between the start of injection and the start of combustion. The start of injection is usually taken as the time when the injector needle lifts off its seal. The start of combustion is more difficult to determine precisely.  Both physical and chemical processes must take place before a significant fraction of the chemical energy of the injected liquid fuel is released. The physical processes are: the atomization of the liquid fuel jet, the vaporization of the fuel droplets, the mixing of fuel vapor with air. The chemical processes are the pre-combustion reactions of the fuel, air, residual gas mixture which lead to auto ignition. These processes are affected by engine design and operating variables.