Investigating the Effect of Operating Variables and Engine Lubricant Viscosity on Engine Friction- A DOE Approach 2011-28-0052

Engine components are exposed to various lubrication regimes such as hydrodynamic, elasto-hydrodynamic, boundary and mixed lubrication during engine operation. In each of these regimes, the factors which influence engine friction are different. Hydrodynamic friction is influenced by lubricant rheology, film thickness and sliding speed of interacting surfaces, whereas boundary and elasto-hydrodynamic friction is a function of surface properties like roughness and hardness and the type of friction modifier used in engine lubricant. So the principal factors which influence engine friction power are speed, load, surface topography of engine components, oil viscosity, oil temperature and type of friction modifiers used. Experimental studies on an off-highway diesel engine were conducted to investigate the effect of engine oil viscosity and engine operating conditions on engine friction power. A full factorial design of experiments (DOE) was formulated to analyze some of the important parameters by which engine friction power influenced significantly. Three factors; speed, load and oil viscosity were chosen as variables with each factor having two levels. Statistical analysis of the test results revealed that the engine speed and speed-load combination are the most significant factors on which engine friction is strongly influenced. Also it has been observed that there is reduction in engine friction power at high speed when lower viscosity grade engine oil was used instead of the recommended viscosity grade engine oil.