Question - What Are The Problems Associated With Effective Lubrication Of The Liner And Piston Assembly Of A Large Slow Speed Engine ?
Answer -
The effective lubrication of the cylinder liner and piston assembly requires a constant lubricant feed over the whole liner surface, and that piston movement will generate the oil pressures required to separate the surfaces.
However in the real situation the following problems occur:
- The oil is injected at defined points which can lead to an oversupply at the feed points, and an under supply away from these points
- The residual fuel normally used contains acids and abrasives that will reduce the lubrication properties of the oil
- The normal operation of the piston will cause the piston movement to stop at top dead centre, causing any oil pressure developed between the ring and liner to collapse
- The high temperatures present at top dead centre reduce the effectiveness of the lubricant
- The feed rate of the lubricant is regulated usually by the speed of the engine, which will cause a mismatch between actual lube oil requirements over a wide range of engine operation, with usually too little an amount of oil injected at low loads and during engine load changes.