Can lubricant oil promote undesired self-ignition of the charge in hydrogen engines?

Abstract

Hydrogen utilization in internal combustion engines is deemed a viable solution for promoting a rapid transition towards a carbon-free mobility, especially for those hard-to-electrify applications. However, critical aspects still poorly understood remain and need to be investigated in order to accelerate the development of such a promising technology. Some of these might originate from the undesired but unavoidable participation of lubricant oil to the combustion process. The present work aims at ascertaining if the lubricant oil chemical characteristics can be at the basis of the onset of certain uncontrolled self-ignition modes of the charge. Considering a lubricant oil droplet suspended in a H2/air environment, an analytical model was developed to derive essential information about mixture composition and thermodynamic conditions that might establish where oil contamination occurs. The results were used to initialize zero-dimensional numerical simulations performed in the OpenSMOKE++ framework with the aim of highlighting charge reactivity variations induced by the presence of oil vapour in the vicinity of an oil droplet. A reduced chemical model, developed for this very purpose in a previous recent work, was employed in the simulations for emulating the reactivity properties of the H2/oil/air mixture.