1. Description of the phenomena involved

In a compression-ignition engine, between the end of the transfer phase and the release of heat induced by the combustion of the air/fuel mixture, a succession of physical and chemical phenomena are brought into play (figure 1 ).

• When the intake valves close, the enclosed charge is characterized by its pressure (supercharging), temperature (intake air cooling, recirculated gases, residual gases) and composition (recirculated gases, residual gases). This is phase 1 in figure