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This paper describes the principle of operation of a novel capacitance based transducer which is employed in a bench mounted turbocharger to identify oil leakage from the “piston-ring” seal at the turbine end of the shaft. Some preliminary data relating to “vacuum-to-leak” conditions are presented along with graphs which illustrate the filling of the transducer. Finally, the design modifications which will be required if the transducer is to be used for leak detection in a turbocharger mounted on a firing engine, are briefly outlined.

Transducers based on capacitance and inductance measurement techniques have been used to make extensive measurements of the lubricant film thickness between the piston rings and liner of an I.C. engine. It was found that ring operating film thicknesses were not stable but suffered both gradual and abrupt changes, even under apparently stable engine operating conditions. It is postulated that these effects arise as a result of two effects; ring spin and secondary piston motion. The paper also presents evidence for cavitation effects. However this evidence is inconclusive and further work is planned to examine the effects more rigorously.

This paper examines the influences of a non-circular bore and circumferential variations in face profile on piston ring performance. It is shown that both circumferential variation of ring face profile and bore shape significantly influence operating oil film thickness, ring friction and oil transport during the engine cycle. Experimental measurements of ring film thickness in an engine simulator show encouraging agreement with predictions of the model.