Mechanistic Effects of Prelubrication and Lubricant Preheating on Lubrication and Wear in Diesel Engines During Subzero Cold Starts

Abstract

Abstract. Diesel engines have difficulty to cold start in severe cold environments. Prelubrication and preheating technologies are effective measures to address this issue. The present study examines the influence of the prelubrication amount, lubricant preheating temperatures, and oil gallery prefill fractions on diesel engines' low-temperature cold-start performance from lubrication and wear perspectives with flow simulations validated by bench tests. Results show that: (1) between 0 °C and −20 °C of ambient temperature, while the prefill fraction of the main oil gallery increases to 80% by prelubrication, the dry friction wear of the bearings at the far end of the oil gallery decreases by more than 50.5%; (2) at −50 °C of ambient temperature, dry friction ends in the early stage of engine startup if the lubricant is preheated to above 0 °C and the engine is prelubricated. The higher the oil temperature, the less the dry friction wear of bearings, but the wear amount barely decreases if the oil is preheated to above 40 °C; and (3) at −50 °C of ambient temperature, prefilling the main oil gallery to more than 80% significantly improved the bearing filling status. Increasing the main gallery prefill fraction from 20% to 100% can reduce the wear of bearings at the far ends by 56.8–85.4%. Considering both economy and performance, we recommend a cold-start strategy of preheating the lubricant to 40 °C and prefilling the main oil gallery to 80% by prelubrication.