Search Results

A unique time-resolved Fourier Transform InfraRed (FTIR) spectrometry technique has been developed to obtain full mid-IR lubricant spectra directly from the ring-pack region of a firing, single cylinder, diesel engine. Initial studies of the detailed spectra show a growth of oxidation products, as indicated by a strong carbonyl absorption peak, observed to increase with load close to the top ring location, for both power and exhaust strokes. Similarly, the formation of alcohol, ketone, aldehyde and carboxylate oxidation products is accessible. Thus it is possible to gauge gross changes to lubricant composition as a function of spatial location through the ring-pack, engine stroke and the severity of engine operation.

Mid-infrared reflection-absorption spectroscopy, has been applied for the first time to the measurement of lubricant degradation products in the ring pack of a firing single-cylinder, IDI diesel. An IR-transmitting window, mounted in the cylinder wall, enables illumination of the moving piston by a broadband IR source located on the engine exterior. Light reflected from the piston is analysed in three wavebands to measure carbonyl oxidation products and oil volumes. Intra-cycle observations reveal differences in the apparent extent of lubricant oxidation between strokes and at different spatial locations in the ring pack. The data are interpreted in terms of a non-homogeneous sample.

A piston ring-pack lubrication model has been developed which takes into account both lubricant viscosity/temperature and viscosity/shear rate variations. In addition, lubricant starvation of the upper piston rings, due to restriction of the oil supply by the lower rings, has been included. Inputs to the model include piston ring profiles (measured using Talysurf profilometry) and gas pressure distributions throughout the ring-pack. The latter were calculated using the (known) combustion chamber pressure diagram at the relevant engine operating conditions. The model was validated by comparing predicted oil film thicknesses with those measured using a laser-induced fluorescence technique on a Caterpillar-1Y73 single-cylinder diesel engine. The engine was run at a range of speeds with two different, fully formulated, multigrade lubricants, and the oil film thickness under each of the piston rings was measured.

An optical technique using laser-induced fluorescence (LIF) has been developed to measure the oil film thickness between a fixed point on the cylinder-liner and the piston of a single-cylinder diesel engine. Details are presented of an experimental layout for acquiring fluorescence data from the engine and a strategy for their conversion to oil film thickness. Engine tests have shown that the oil film thickness in the liner/piston contact depends critically on the temperature dependence of the oil viscosity and hence is sensitive to the engine's speed and torque output condition. Oil film thickness measurements were made for two fully formulated lubricants, a 15W/40 Universal Diesel Engine Oil (UDEO) and a 10W/30 Super High Performance Diesel Oil (SHPDO). From these oil film thickness measurements the analysis was extended so as to estimate the oil volumes present between the cylinder-liner and different portions of the piston as they pass the measurement point.