A one-dimensional model for the motor oil-fuel dilution under gasoline engine boundary conditions

Abstract

Nowadays the climate change caused by the green-house effect increasing is a world-wide issue with which scientists have to face. Being the passenger vehicles filled with fossil fuels, the emission of the carbon dioxide green-house gas is unavoidable. In order to slowdown both the global warming and the fossil fuels wasting, lower fuel consumptions, thus high efficiency engines, are required. Currently, the coupled use of downsizing and direct injection in spark ignited engines meets both high efficiency and power-demand requirements. Being downsized engines more compact, the distance between the injector and the engine walls are shorter. Thus, depending on the engine operating condition, the fuel spray wall impingement may occur leading to the formation of a liquid fuel film. If the wall impingement occurs against the cylinder liner wall, which is wetted by a thin oil layer, the motor oil and the landed fuel dilute until the piston arrival. At this time, the mass transport by diffusion have promoted the creation of an oil-fuel mixture. Thus, while thicker part of the mixture layer is scraped into the piston top land crevice, the thinner, whose properties are degraded by the fuel contamination, remains on the cylinder liner. The mixture accumulated inside the crevice may be scattered due to the piston inertia leading to the oil detachment and transport in the combustion chamber. The latter may cause both abnormal combustions named preignitions at high loads and increased particulate emissions at low loads, cold states, and cat-heating. This paper reports the implementation of a onedimensional numerical model for the dilution between fuel and motor oil in a stroke of a gasoline engine. The model aims to give the composition of the oil-fuel mixture both on the cylinder liner after the piston arrival and in the piston top land crevice.

Hydrogen Application as a Fuel in Internal Combustion Engines

“…This model can be run as a stand-alone tool for global analysis and supporting tool paired with CFD codes for local and three-dimensional leak analysis. To model the hydrogen-lubricant interaction, a one-dimensional code was developed that simulates the dilution between lubricating oil and deposited liquid fuel [49,50]. It considers the mass diffusion between the two liquids, and their heating and evaporation by heat exchange with both walls and with the gases inside the combustion chamber.…”

A Numerical Methodology to Test the Lubricant Oil Evaporation and Its Thermal Management-Related Properties Derating in Hydrogen-Fueled Engines

“…Furthermore, the Authors implemented the liquid fuel as a multicomponent mixture with different diffusion rate for each component. In [17] Mariani et al the Authors presented an improved version of the model by Zhang for the oil-fuel dilution analysis by enhancing the features of the diffusion model with the use of a new hybrid deep neural networks methodology for predicting the binary diffusion coefficient between engine oils and typical gasoline fuels. Furthermore, additional care was placed in the mixing rules for the calculation of the oil-fuel mixture properties depending on both temperature and composition.…”

“…Finally, the normal boiling point of the lubricant oil is calculated with a dedicated sub-model, being evaporation properties not additive. The sub-model is based on the zero-dimensional distillation model developed by Mariani et al [17], which is based on the works of Slavinskaya et al [31] and Abianeh et Al. [32], allowing to evaluate the first boiling temperature by means of a pure thermodynamic model.…”

Application of a One-Dimensional Dilution and Evaporation Lubricant Oil Model to Predict Oil Evaporation under Different Engine Operative Conditions Considering a Large Hydrogen-Fuelled Engine

“…These compositions are needed as inputs in a mass and thermal diffusion and evaporation numerical model, now briefly described. This model relies on a previous work by the present authors [20] and allows to evaluate the lubricant oil evaporation, while accounting for the mutual diffusion among its components and the temperature dependency of its properties during the working cycle of a hydrogen-fuelled ICE. The computational domain is composed by the cylinder liner wall, the lubricant oil layer and a moving boundary to address lubricant oil evaporation, thus, the layer thickness reduction during the simulation.…”

“…They used a lubricant oil surrogate based on n-hexadecane and developed a reduced reaction mechanism that allowed to discover that lubricant oil significantly facilitates the mixture ignition at lower temperatures with respect to those typical of hydrogen autoignition. Concerning lubricant oil -fuel dilution and fuel evaporation, Mariani et al [20] [21] developed a one-dimensional lubricant oil -fuel dilution model which is able to qualitatively predict the lubricant oil deterioration due to fuel impact on the cylinder liner wall. Though, attention must be paid on the fact that these models does not account for lubricant oil evaporation, being the characteristic temperatures of gasoline combustion lower with respect to hydrogen combustion, thus not enabling oil evaporation.…”