Abstract
This paper describes the design of a test apparatus which simulates the lubrication of large, slow, two-stroke marine engines in which the ring pack is lubricated by means of injectors supplying lubricant above the piston. The equipment is able to control lubricant injection parameters (volume, frequency, etc.) and employs capacitance based lubricant film thickness transducers to allow instantaneous oil film thickness and film extent around the compression ring to be investigated on a stroke-by-stroke basis. It is demonstrated that the equipment can be used to study the development of lubricating films on successive strokes under differing injection strategies. Time varying changes in lubricating film thickness and film extent have been measured and the rate at which the lubricant spreads across the cylinder wall has also been investigated. It has been observed that increases in oil-film thickness are strongly linked to the transition from starved to fully-flooded inlet conditions and that net lubricant transport rates along different parts of the cylinder can be evaluated from measured data.
Highlights
Large, slow, two-stroke, marine, diesel engines are typically used to power merchant vessels such as container ships and supertankers
A reliable method to quantitively evaluate flow rate of lubricant moving between different points within the cylinder due to the various transport mechanisms operating within the ring pack has proved more challenging
This volume is evaluated using film-thickness and film extent data from oil-film thickness sensors on each cycle. When these data are monitored during a transient phase in lubricating film conditions, for example during a test from an initially dry cylinder, or following a change in engine conditions/lubricant flow rate, the volume changes measured at a series of sensors positioned axially along the cylinder liner allow the lubricant transport to be computed
Summary
Slow, two-stroke, marine, diesel engines are typically used to power merchant vessels such as container ships and supertankers. These engines conventionally incorporate a crosshead, which serves two functions. The lubrication system for the piston-ring packs of modern, twostroke, marine engines normally consists of some form of arrangement to spray lubricant into the cylinder at a position above the piston when the piston is in the lower part of the cylinder. Lubricant flows into the cylinder at a steady rate through a “quill” system consisting of a series of holes and channels in the cylinder with the passage of the ring pack helping to distribute the lubricant both axially and circumferentially. It is desirable to reduce the use of cylinder lubricants from both economic and environmental/health reasons
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