Analysis of the Lubrication Condition of a Crosshead Pin Bearing of a Large Marine Diesel Engine

The main function of the crosshead bearing of a crosshead engine is to transmit the load from the connecting rod, which is directly attached to the piston of the engine, through a second rod to the guide shoe, which bears the entire crosshead. Apart from this function it enables the large normal forces, which are usually borne by the piston skirt in the case of a trunk piston engine, to be transmitted to the guide shoe from which it is subsequently transmitted to the rails along which the guide shoe glides. The dynamics of the crosshead bearing is such that the bearing pin is subjected to very low levels of incomplete rotation resembling that executed by a pendulum over a reduced arc. The bearing is also subjected to the load in only one direction. These operating conditions augur poorly for the formation of the hydrodynamic oil film necessary to support the imposed load. This type of bearing is therefore susceptible to considerable friction losses and significant wear as a result of lack of the capacity to generate lubrication film. This paper evaluates a model to determine the levels of achievable hydrodynamic film and the measures introduced to generate a hydrostatic squeeze lubricating film in the bearing as a result of the introduction of high pressure oil during part of the operating cycle of the engine.