Measurement of the Oil Film Thickness Between the Cylinder Liner and the Piston Rings in a Heavy Duty Directly Injected Diesel Engine

An electrical capacitance measuring method has been used to obtain the cylinder liner oil film thicknesses for various speeds and loads in a heavy duty directly injected diesel engine.

Interesting facts have been observed:

• Increased oil film thickness for the top ring distance to wall during idling.
• A gas pocket appearing between top ring and liner at increasing speeds and loads
• movement of the piston in the liner when combustion sets in, the motion is not parallel.
• temperature seems to have little effect on the oil film thickness.

A computer model of the top ring showed good conformance with the measurements over the speed and load range, but the calculated oil film thickness is about 3 to 6 times higher.