Study on the mechanism of lubricating oil vapor effects on the performance of a low-speed two-stroke diesel engine

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Journal of Dalian Maritime University ›› 2025, Vol. 51 ›› Issue (4) : 67-79.

LIU Yanxin¹, LI Qingbo^*1, PIAO Jicheng², JIANG Han¹

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Abstract

Focusing on the impact of lubricating oil vapor on low-speed two-stroke diesel engine performance, this study employed a combined approach of numerical simulation and bench testing. By developing an engine model and a lubricating oil vapor model, and coupling the combustion mechanism with physical parameters of diesel fuel and lubricating oil components, we revealed how the introduction of lubricating oil vapor triggers reorganization of the radical network, thereby influencing combustion characteristics and emission behaviors. The results showed that the introduction of lubricant vapor led to an increase in H/HOOH (hydrogen and hydroperoxyl radicals) and a decrease in O/OH (oxygen and hydroxyl radicals), which prolonged the stagnant combustion period of diesel fuel (CA0-10 increased by 1.1°CA) and accelerated the process of main combustion period (CA10-90 decreased by 4.84°CA). The increase of H radicals promoted the hydrogenation of soot precursors and inhibited soot nucleation and surface growth, resulting in an 18% decrease in peak soot emissions. In contrast, the reduction of OH radicals weakened the process of CO oxidation to CO₂ deep conversion, resulting in a 6.8% decrease in peak CO emissions. The H/O radicals triggered the recombination of hydrocarbons through hydrocarbon cleavage, resulting in a 5.8% increase in peak unburned hydrocarbons (HC). The H/O/HO₂ radical cycle accelerated thermal nitrogen oxide (NO_x) generation kinetics, resulting in an 8% increase in NO_Xemissions.

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diesel engine / lubricating oil vapor / radicals / combustion performance / emission pattern

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LIU Yanxin, LI Qingbo, PIAO Jicheng, JIANG Han. Study on the mechanism of lubricating oil vapor effects on the performance of a low-speed two-stroke diesel engine[J]. Journal of Dalian Maritime University. 2025, 51(4): 67-79

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