Dissertação de Mestrado
Study of a bearing test bench capable to simulate wear in diesel start-stop engines
Fecha
2019-03-29Autor
Nathalia Duarte Souza Alvarenga Santos
Institución
Resumen
The growing concern about the environmental impacts of the automobile sector activities has increased governmental regulations regarding fuel consumption and emissions reduction, mainly in Europe, pioneer in the implementation of such regulations. Thereby, the automotive industry has been developing strategies to adapt itself to these new requirements, and in that sense, the use of start-stop systems in the vehicles has been increasing. This system aims to reduce emissions and fuel consumption by stopping the engine at idle conditions, whether at traffic lights or in traffic jams. Such a system, more widely applied for passenger vehicles, has also been introduced for medium duty vehicles such as buses and medium trucks with urban routes. A major challenge in the start-stop implementation, however, is the alteration of the stresses applied to core engine components, such as piston, piston rings and bearings, since the temperature variation and lubrication supply for them is intermittent with the cyclic engine shutdown. As durability tests for such components using common dynamometric test benches are extremely expensive and time consuming, new test strategies have been recently explored. In this work, the main goal was to support the installation of a bearing test bench developed by Daimler AG, simulating the operation of their medium duty MDEG engines, and analyze its first results. The test bench is basically composed of hydraulic cylinders simulating the combustion load and a crankshaft rotated by an electric motor. The first tests, discussed in this work, show the difficulties of developing new test methods, such as problems in the oil conditioning system, the development of an operation program similar to regular engines and the wear measurements, as well as the lack of data acquisition capacity. However, the work shows the great potential of such a test bench after the explored obstacles have been overcome, as a quick and simple way to test bearings, and possibly other core engine components. In addition, the work suggests that the association of this experiment with computational tools can provide even more complete results, further contributing to the development of engines capable to withstand the implementation of start-stop systems.