City Research Online

Abstract

This paper investigates the complex multiphase flow developing inside the micro-orifices of diesel injector nozzles during pilot injection. High speed micro-visualisations of a transparent serial production nozzle tip replica are used to record the multiphase flow inside the flow orifices as well as nearnozzle spray development. The physical processes taking place are explained with the aid of a three-phase (liquid, vapour and air) homogeneous mixture model utilized in the context of Large Eddy Simulations. Phase-change due to cavitation is considered with a model based on the Rayleigh-Plesset equation, while compressibility of all the phases is accounted for. Numerical simulations shed light on the interaction between the vortex flow and cavitation formation that take place simultaneously with air entrainment from the surrounding environment into the injector’s sac volume during the injection and the dwell time between successive injections. The experimentally observed flow phenomena are well captured by the simulation model. In particular the compression of pre-existing air bubbles inside the injector’s sac volume during the injector opening, cavitation vapor condensation and air suction after the needle closure are well reproduced.

Publication Type:	Article
Additional Information:	© Elsevier 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Publisher Keywords:	LES, Multiphase flow, Cavitation, Fuel Injection, Pilot injection, Air entrainment
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TL Motor vehicles. Aeronautics. Astronautics
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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