EGR interna para redução do trabalho de bombeamento em um motor ignição por centelha de injeção direta

Abstract

The constant increase in the price of petroleum-derived fuels during the pandemic period and the need to reduce greenhouse gas emissions demand more efficient spark-ignition combustion engines. Governmental programs such as the one entitled ROTA2030 aim to support technological development in the automotive sector, promoting the use of biofuels, such as ethanol, in order to reduce dependence on fossil fuels and emission levels. The use of more efficient combustion engines through the combination of downsizing concepts, direct fuel injection and mechanisms that independently control the events of the camshaft of valves, are alternatives to maximize the efficiency of spark ignition engines, mainly in partial loads, where the load control method throttles the air admitted for engine power control, resulting in high pumping losses, precisely in the largest portion of operation of a vehicle in an urban cycle. Strategies that allow the retention of a greater fraction of residual gases in the combustion chamber contribute to the reduction of pumping work due to the addition of inert gases, however, high concentrations can cause combustion instability. In this sense, the present work aims to investigate the influence of the symmetrical variation of the opening and closing events of the intake and exhaust valves, causing high overlap conditions as a strategy to retain residual gases in the cylinder, to reduce the pumping work of the engine. The results show gains in energy conversion efficiency at partial loads with high valve overlap, which consequently raises the levels of residual gases present in the combustion chamber.