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Atomization and Sprays
IF: 1.262 5-Year IF: 1.518 SJR: 0.814 SNIP: 1.18 CiteScore™: 1.6

ISSN Print: 1044-5110
ISSN Online: 1936-2684

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Atomization and Sprays

DOI: 10.1615/AtomizSpr.v19.i3.10
pages 207-234


Z. van Romunde
Department of Mechanical Engineering, University College London,Torrington Place, London WC1E 7JE, UK
Pavlos Aleiferis
Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, United Kingdom


Maximum benefits from gasoline direct-injection systems can only be achieved by precisely controlling the atomization and evaporation processes of the fuel within the cylinder of an internal combustion engine. These requirements place considerable demands on the fuel injection hardware, in particular the injector. In addition the variable conditions of fuel properties, fuel temperature, and in-cylinder pressure interact to affect the fuel spray formation and development. This work seeks to understand and quantify these interactions and their working mechanisms for the latest generation of direct-injection gasoline multihole injectors by examining the fuel spray in a static rig in which each of these parameters can be independently altered. Five types of fuels with different grades of volatility were studied for a range of fuel temperatures (20−120° C) and gas pressures (0.55.0 bar). The fuels included various grades of gasoline, iso-octane, and a multicomponent model fuel blended specifically to mimic gasoline but also suitable for in-cylinder laser-induced fluorescence measurements. The fuel pressure was kept constant at 150 bar throughout the experiments. Measurements of key spray parameters (such as plume penetration and cone angle) showed that the main mechanism affecting spray development in a quiescent environment was dependent on the amount of superheat of the lowest volatility components in the fuel for the prevailing gas pressure and fuel temperature conditions. A high amount of superheat led to the rapid and disruptive, near-spontaneous, vaporization of the fuel as it was ejected from the nozzle. The migration of fuel vapor to the low-pressure regions between the spray plumes acted to draw the plumes together to form a single, high-penetration-rate plume in the extreme case. This contraction of the global spray form has been termed "spray collapse." The lack of high superheat and the single boiling point of iso-octane was manifested in markedly different, less collapsed spray form, which carries implications when characterizing an engine or injector using only such a single-component model fuel. The variability of the fuel spray from injection to injection was not affected appreciably by operating conditions, suggesting a certain level of "random" small variability due to the injection event and spray breakup itself, or from injector internal effects.