Pulsed charged sprays: application to DISI engines during early injection
International Journal for Numerical Methods in Engineering, 58, (3), . (doi:10.1002/nme.794).
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Numerical predictions of the temporal evolution of pulsed sprays, typical of those used in gasoline direct injection spark ignition engines are presented, with the novelty that the drops are electrically charged. The rate of spray expansion, in terms of the fraction of maximum possible spray charge for a typical engine timescale, is investigated. The engine timescale chosen is the time available between spray injection and ignition, and for a low-speed engine operation, with injection during the intake stroke. The aim is to quantify the amount of electric charge, required to spread the spray throughout the engine cylinder, without causing excessive piston and wall impingement, prior to hypothetical ignition. It is found that experimentally realizable amounts of electric charge are sufficient to cause spray expansion throughout the engine cylinder within the timescale permitted. Also noted is a segregation of the smaller drops from their larger cousins, by virtue of the known non-linear variation in drop charge with drop mass. Since it is known that pulsed fuel injectors producing charged sprays of insulating liquids are a reality then electric charge seems to be a viable route to control and optimize in-cylinder mixture distribution and hence engine performance, robustness and emissions.
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