High Pressure Multiple Injection Spray Characteristics

In previous work, high injection pressures and multiple injections per engine stroke were shown to be effective at reducing the NOx and particulate emissions of DI Diesel engine combustion [1, 2].

A series of experiments were performed to study the effects of injection pressure, back pressure, and injection strategy on the spray characteristics for multiple injections. An injection system which was capable of multiple injections was used to introduce diesel fuel into a constant volume cold spray chamber. Parallel engine experiments were conducted using the same injectors as in this work [1, 2, 3]. In these engine tests, emissions (NOx and particulate) were measured. The engine experiments were used to develop the injector and chamber operating conditions for this work. The injection pressure was varied up to 90 MPa. The back pressure in the spray chamber was set with compressed argon gas, to make the density of the gas equal to the cylinder ensity at the start of injection of the combustion emission tests. Double and triple injections along with different dwells under the same injection pressure (90MPa), ambient density (27kg/m³) and similar fuel elivery (168 mg/inj) were analyzed to reveal the effect of multiple injections on spray tip penetration length, spray cone angle, and droplet size.