Effect of Oil Additives and Fuel Concentration in Lubricating Oil on Abnormal Combustion of Supercharged SI Engine

Yota Nakayama; Junya Tanaka

doi:10.4271/2022-32-0007

The spark ignition engine with supercharger which is supplied the fuel directly in cylinder (SI engine) has a phenomenon of abnormal combustion as called Low Speed Pre-Ignition (LSPI). It has been reported that the LSPI would be related with lubricating oil and the ingredients of fuel and oil additives [1] [2]. The mechanism of LSPI does not clear sufficiently, especially, relation ignition source of LSPI with the lubricating oil additives and the fuel concentration in lubricating oil.

This research focuses on the source of LSPI which is autoignition of a lubricating oil droplet in cylinder. The effect of oil additives as Zn, Mo, Mg, Ca and concentration of fuel on autoignition of a lubricating oil droplet has been investigated. This research has been tried to evaluate the degree of autoignition fundamentally by using of electric furnace which has been heated an oil droplet. The experimental data show oil additives and fuel are strongly effect on autoignition and the data show the synergy effect of the both for autoignition, especially, the concentration of fuel between 20%vol. and 40%vol..

These experimental results have been evaluated by the activation energy E by Livengood-Wu integral. It has been suggested that the Zn and Mo oil additives prevent an oil droplet from igniting spontaneously. The oil additive of Ca and Mg in an oil droplet is little effect on autoignition.

The concentration of fuel in an oil droplet is more than 20%vol., the autoignition is accelerated significantly.

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Effect of Oil Additives and Fuel Concentration in Lubricating Oil on Abnormal Combustion of Supercharged SI Engine 2022-32-0007

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