Influences of wedge geometry incorporated oil-grooves on lubrication characteristics for crosshead-pin bearings

Because the crosshead-pin bearing for large size two-stroke diesel engines oscillates within a small angle at a low speed and is always subject to a high downward load, the hydrodynamic oil film is very thin. The recent tendency to raise the engine power using compact engines continues to increase the lubrication severity of the bearing. It is thus very important to improve the load carrying capacity of the bearing. In the present study, calculations were carried out to clarify the lubrication characteristics for the crosshead-pin bearing with a very low clearance ratio and wedge geometry incorporated oil-grooves. Reducing the bearing clearance ratio is advantageous for enhancing squeeze action on the entirety of the bearing pads, thereby decreasing the oil film pressure. However, this also has a negative aspect of reducing wedge action, causing the oil film thickness to decrease. Even when the clearance ratio becomes very low. incorporating a wedge geometry on both sides of the oil-grooves is an effective means to improve wedge action, and thereby to increase the oil film thickness without a significant raise in the oil film pressure.