Method for reducing pollutant emissions and consumption of an engine

To reduce pollutant emissions and consumption of passenger cars diesel engines multiple injection strategies are applied. Assuming constant cylinder and bowl geometry and constant rail pressure the variation of the number of injections, injection quantity of each injection and separation between two consecutive injections are the major parameters to be optimised. Furthermore, a single injection is applied with a shaped injection rate by a rise in injection pressure, equal to that observed in cam controlled injection systems. The needle lift can be modified for piezo driven common rail injection systems. Both methods are compared in terms of pollutant emission, fuel consumption and robustness. Experiments were carried out on single cylinder research engines. Multiple injection strategies with large hydraulic dwell times were compared with a short dwell setting simulating a "rate shaped" single injection. Rate shaping was implemented performing multiple injections with hydraulic dwell times close to or equal zero.