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Abstract(s)
Os motores são máquinas engenhadas para entregar energia mecânica, movimento essencial às mais diversas tarefas que ditam o ritmo da sociedade. Os motores de combustão interna, invariavelmente presentes no nosso cotidiano são o destino de boa parte da energia utilizada pela humanidade, no entanto, uma parcela considerável da potência gerada nesse tipo de motor é consumida pelo trabalho de atrito na própria máquina. Este trabalho apresenta um modelo de cálculo para a previsão da potência de atrito num motor rotativo a combustão interna, tecnologia atualmente em desenvolvimento pela empresa KEYOU GmbH. O trabalho de atrito num motor de combustão interna é usualmente dividido em três componentes; trabalho de bombeamento, trabalho de fricção e trabalho de acessórios. O primeiro grupo, que consiste na energia utilizada para bombear os fluidos na admissão e exaustão do motor, é calculado pelas leis da mecânica dos fluidos para escoamento em dutos. O segundo grupo, que trata da fricção no contato de componentes em movimento relativo foi modelado matematicamente através pelas equações da tribologia para atrito viscoso. Por fim, o terceiro grupo que é o trabalho executado pelo motor para a operação de componentes auxiliares, foi modelado pelas leis da mecânica dos fluidos, quando os auxiliares são bombas dos sistemas de lubrificação e refrigeração, e pelo rendimento do alternador quando tratam-se de acessórios elétricos O modelo cumpre os requisitos do projeto pela adaptabilidade e fácil operação, com resultados em concordância com os disponíveis na bibliografia. Num motor de 1 l à velocidade de 3500 RPM o modelo prevê que 10,4 kW, cerca de 20 % da potência útil, é desperdiçada sob a forma de atrito. O maior componente desta perda é o trabalho de fricção, seguido pelo trabalho de bombeamento e o trabalho de acessórios. O modelo também aponta que a potência de atrito aumenta com o aumento da velocidade de operação, um reflexo da contribuição da fricção hidrodinâmica existente no sistema.
Engines are engineered to deliver mechanical energy, the movement which is essential to a wide range of tasks driven by society’s activities. Internal combustion engines are seen on a daily basis and consume a great amount of the energy humanity uses; however, the friction work consumes a great part of the power generated in an internal combustion engine. This paper introduces a model to predict the friction power in an internal combustion rotary engine, which is currently in development by the company KEYOU GmbH. It is common to subdivide the friction work in three main groups; pumping work, rubbing friction work and accessory work. The first group concerns about the energy to pump the fluids into and out of the engine at the inlet and exhaust strokes, fluid mechanics laws for internal ducts flow have been used to model it. The second one deals with the friction generated by the rubbing contact between components in relative motion, it was mathematically written using the tribology equations for viscous friction. The accessory work which is the work performed by the engine to power the auxiliary components, has been coped with the fluid mechanics laws, when the model deals with lubrication and cooling system pumps, and by the alternator efficiency, when it is about the electric accessories. The model fulfills the project requirements, due to its adaptability and straight forward use, with results in accordance to those found in the bibliography. For a 1 l engine operating at 3500 RPM, this friction model predicts a waste of 10.4 kW, about 20 % of the useful engine power, as friction power. The largest component is related to rubbing friction, followed by pumping and accessory work. The model also points out that the size of the friction power increases with the engine speed, as a result of the great amount of hydrodynamic friction in the system.
Engines are engineered to deliver mechanical energy, the movement which is essential to a wide range of tasks driven by society’s activities. Internal combustion engines are seen on a daily basis and consume a great amount of the energy humanity uses; however, the friction work consumes a great part of the power generated in an internal combustion engine. This paper introduces a model to predict the friction power in an internal combustion rotary engine, which is currently in development by the company KEYOU GmbH. It is common to subdivide the friction work in three main groups; pumping work, rubbing friction work and accessory work. The first group concerns about the energy to pump the fluids into and out of the engine at the inlet and exhaust strokes, fluid mechanics laws for internal ducts flow have been used to model it. The second one deals with the friction generated by the rubbing contact between components in relative motion, it was mathematically written using the tribology equations for viscous friction. The accessory work which is the work performed by the engine to power the auxiliary components, has been coped with the fluid mechanics laws, when the model deals with lubrication and cooling system pumps, and by the alternator efficiency, when it is about the electric accessories. The model fulfills the project requirements, due to its adaptability and straight forward use, with results in accordance to those found in the bibliography. For a 1 l engine operating at 3500 RPM, this friction model predicts a waste of 10.4 kW, about 20 % of the useful engine power, as friction power. The largest component is related to rubbing friction, followed by pumping and accessory work. The model also points out that the size of the friction power increases with the engine speed, as a result of the great amount of hydrodynamic friction in the system.
Description
Keywords
Motor de Combustão Interna Modelo para o Trabalho de Atrito Motor Rotativo Eficiência Atrito Internal Combustion Engine Friction Work Model Rotary Engine Efficiency Friction