Exam Question

(a) The primary purpose of lubrication is to prevent metal-to-metal contact between the liner and piston rings by forming an oil film. However, maintaining effective lubrication in a large slow-speed engine is challenging due to the following factors:
The piston speed varies throughout the cycle. At Top Dead Center (TDC), the piston speed is zero, making it difficult to maintain an effective oil film.
High temperatures at TDC, where combustion occurs, lead to oil film breakdown.
Residual fuel oils often contain impurities such as ash, sediments, and catalytic fines, which can break the oil film and cause abrasive wear.