The Influence of Injection Rate Shaping on Diesel Fuel Sprays—An Experimental Study

Abstract

A current strategy in the development of direct injection (DZ) diesel engine combustion systems is the control and limitation of the initial 'premixed' combustion heat release ensuing from the auto-ignition of the injected fuel. This requires control of the amount of fuel vaporization and mixing taking place during the ignition delay time. Since the latter is determined by the fuel composition and the in-cylinder gas temperature, development efforts have focused on the injection of well-controlled, portwned fuel quantities prior to the ignition as a means of achieving the desired goal. This practice is becoming known as @el rate shaping'. Consequently, the fuel spray penetration during this period, fuel evaporation and mixture preparation, as well as the influence of in-cylinder air motion on mixture distribution, are main subjects of interest in affording insight into fuel rate shaping attempts. These have been addressed through a combined experimental and theoretical investigation of the spray characteristics associated with &@rent injection practices. The experimental investigations have been performed in an optically accessed spray research engine. Basic aspects of fuel spray tip penetration, time and location of auto-ignition and flame propagation have been recorded with a high-speed line-scan camera. The results provide the space and time-scale characteristics for the propagation, ignition and combustion of a selection of dieselfuer sprays. Investigations have been carried out for a conventional fuel injection system equipped with a set of diflerent single-hole injector nozzles, as well as for a dual-spring injector and an injector with a split injection device. The experimental results provide an insight into the propagation of the fuel spray front, yield qualitative information about its spatial and temporal distribution, and, in the case of split injection, show the interaction of the initial plot fuel portion with the main injection.

Fuel injection rate shaping and its effect on spray parameters in a direct-injection gasoline system

“…Such shaping of the injection process has been utilized in compression-ignition engines using electromagnetic (Hountalas et al 2002;Tanabe et al 2005) or piezoelectric injectors (Lee et al 2006;Shen et al 2014) for several years. The initially available simulation methods of time-varying fuel flow modeling (Boggavarapu and Singh 2011;Hountalas et al 2002;Juneja et al 2004;Winklhofer et al 1992) have now taken quite complicated shapes regarding the start of injection (Macian et al 2014;Mancaruso et al 2017;Rottmann et al 2009;Zhou et al 2018) and the way it ends (Koci et al 2015).…”