Abstract
Particulate emission from internal combustion engines is a complex phenomenon that needs to be understood in order to identify its main factors. To this end, it appears necessary to study the impact of unburned gases, called blow-by gases, which are reinjected into the engine intake system. A series of transient tests demonstrate their significant contribution since the particle emissions of spark-ignition engines are 1.5 times higher than those of an engine without blow-by with a standard deviation 1.5 times greater. After analysis, it is found that the decanter is not effective enough to remove completely the oil from the gases. Tests without blow-by gases also have the advantage of having a lower disparity, and therefore of being more repeatable. It appears that the position of the “endgap” formed by the first two rings has a significant impact on the amount of oil transported towards the combustion chamber by the backflow, and consequently on the variation of particle emissions. For this engine and for this transient, 57% of the particulate emissions are related to the equivalence ratio, while 31% are directly related to the ability of the decanter to remove the oil of the blowby gases and 12% of the emissions come from the backflow. The novelty of this work is to relate the particles fluctuation to the position of the endgap ring.
Highlights
The reduction of pollutant emissions, and the soot particles emitted by internal combustion engines, is essential for human health
Strictly identical, carried out on a turbocharged spark-ignition engine with direct injection have highlighted the significant impact of particle emissions linked to blow-by gases and the endgap ring position
- even equipped with a two-way oil separator (Low pressure and High pressure), this engine emits 1.5 times more particles with a standard deviation that decreases by 33% compared to a configuration without blow-by gases
Summary
The reduction of pollutant emissions, and the soot particles emitted by internal combustion engines, is essential for human health. The soot particles come from the combustion or pyrolysis at high temperatures of unburned fuel This unburned fuel has several origins [1]: - Incomplete combustion. - The oil film on the cylinder wall It absorbs unburned fuel, which can be released after combustion. Cheng et al [1] have specified that, in a steady state, 0.6% of the total fuel injected would pass through the piston rings and the cylinder wall to end up in the oil pan. If all of the blow-by gases are recycled, that is to say the oil is removed and the gases are reinjected at the intake for a new cycle, there would be only 1.8% of unburned fuel that would be emitted in the atmosphere in the form of soot particles [1]
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