Paper 12: Hydrodynamic Theory of Dynamically Loaded Bearings and its Application to Engine Bearing Design

Abstract

In recent years the hydrodynamic theory of dynamically loaded engine bearings has been developed to such an extent that calculations of bearing behaviour under all kinds of loads can be made with good correlation to experimental results and field experience. In addition to these calculations, experiments have been performed to determine the influence of variables in practical bearings such as oil-inlet pressure or temperature, the shape of the oil inlet, and the quantity of the lubricant. At the engine-design stage, engine-bearing behaviour can be predicted by using calculations based on hydrodynamic theory. Some examples are given to show that the load-carrying capacity and consequently the reliability of engine bearings can be increased by using these calculation methods on a digital computer and with a variation of bearing characteristics, such as dimensions, clearance, oil pressure, temperature, and viscosity, or with a variation of load characteristics such as magnitude or direction of counterweight-mass forces, gas pressure, and firing order. Very good correlation is obtained between these predictions and real engine-bearing behaviour in fast-running diesel engines, as measured by radioactive tracer methods. Many German diesel-engine producers are using these calculations in an early stage of engine design.