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An attempt is made to develop solenoid operated injectors for diesel engines, to inject natural gas directly into the combustion chamber at high pressure. These new injectors have the size of conventional diesel injectors with small but powerful solenoids located in the former spring chamber, and the spring is moved to a location closer to the nozzle. To provide fast opening and closing of the nozzle, a multiobjective optimization method is used to select the design variables of the injector. The mathematical model used for optimization is developed with the help of experimental results obtained from the solenoid force measurements at transient conditions. The optimization results did show good dynamic performance of the injector, despite the use of a small size solenoid actuator.

Contemporary high speed diesel engines require a compromise regarding the size of fuel nozzle orifices which should be small enough to assure a good fuel atomization at low engine speed, and large enough to provide the engine with high fuel dose at maximum power. Calculations were made to predict the dynamic response of a closed diesel injector within its unstable operation range. The pressure in the seat chamber under the needle was established as the key factor to simulate the injector's behaviour. It was measured at different flow conditions and used in calculations. After applying an optimization method, it was possible to predict how the design parameters of an injector should be changed in order to obtain the best dimentional configuration which improves the fuel atomization at low engine speed.