Analysis of the Increase Level of Vibration in an Internal Combustion Engine Due to the Degradation of the Lubricating Oil. 2019-01-0780
The objective of this work was to evaluate the vibration level of an internal combustion engine due to the degradation of the lubricating oil used in the engine. When analyzing vibrations in internal combustion engines, it is noticed that the greatest sources of vibrations are generated by combustion and mechanical forces. These forces occur over a wide frequency range and are transmitted to the outer surface of the engine through several paths, such as through the piston mechanism, connecting rod, crankshaft and engine block. As a result of the action of these forces, the external surfaces of the engine are subjected to vibrations of various amplitudes. The viscosity is the main property of automotive lubricant oils for internal combustion engines and it also indicates the degree of resistance a lubricant oil allows on two surfaces in relative motion. Lubricant oils undergo changes in their viscosity when subjected to temperature variation and mechanical stresses. These variations can be very different depending on each type of lubricant oils. The tests were performed on a bench dynamometer and a specific test cycle was used. Each engine with a specific fuel (ethanol or gasoline) and a specific lubricating oil (SAE 5W30, SAE 15W40 or SAE20W50) operated for 600 hours in a specific cycle of tests. Every 50 hours of testing, vibration level measurements were made at the extremities of the crankshaft and engine block, and a 100 ml sample of the lubricating oil was collected for analysis of the physical and chemical properties. The results show that the level of vibration increases with the time of use of the lubricant, and that this increase is very significant from the moment the viscosity has reached the minimum limit stipulated by the lubricant manufacturer. The type of fuel and viscosity of the lubricant influence the level of vibration in the engine. The results show that engine running on ethanol with lubricant of lower viscosity have the highest rates of vibration.
Claudio Marcio Santana, Jose Mautone, helder almeida