The effects of engine operating parameters on a diesel engine were investigated with the measurements of inter-ring gas pressure, cylinder pressure, and oil film thickness. Explanations of the data were augmented where possible by the application of a computer program, RINGPAK, which was used to simulate ring motion. An analysis of the radial motion of the top compression ring was performed to determine whether the blow-back mechanism caused by radial ring collapse occurred.
There were two methods used to obtain inter-ring gas pressure. These were: using a linkage telemetry system in which the pressure transducer was mounted in the piston, and using a liner-based system in which 13 pressure transducers were mounted at differential circumferential and axial locations in the liner.
The oil film thicknesses along the liner were measured at several locations using two unique designs for capacitance probes. The first design was a horizontally oriented rectangular electrode which demonstrated a high sensitivity for a given spatial resolution. The second design was a vertically oriented rectangular electrode which was capable of measuring oil film thicknesses over a large crank angle range.
The experimental and analytical results of this study showed that ring collapse did not occur for the engine conditions run. The analytical results demonstrated that the phenomena of ring lift (a blow-back mechanism) could occur on the engine studied in this dissertation.
The radial ring motion of the top compression ring was shown to be strongly correlated with the pressure difference between the inter-ring gas pressure and the cylinder pressure. When this pressure difference was greater than or equal to zero, the oil film thicknesses could increase substantially.
The measured inter-ring gas pressure showed high variability between data bursts. An explanation for this variability was analytically predicted to be the effect of ring rotation, intermittent oil accumulation within the inter-ring volume, and the extent to which the engine was warmed up.
Trends were observed with respect to speed and load. The inter-ring gas pressure had higher pressure magnitudes at lower speeds and higher loads. The oil film thicknesses on the liner demonstrated increased film thicknesses with speed.