Validação de modelos computacionais de um motor de ignição por centelha com comando de válvulas totalmente variável operando com etanol

Abstract

Commitment to move towards sustainability leads to the search of internal combustion engines new fuels and viable strategies to reduce the emission of greenhouse gases. Biofuels become a viable solution due to their renewable replacement and environmental and economic benefits. Studies show that there is an increase in the indicated efficiency of spark ignition engines when operated without throttling through the use of variable valve timing strategies. The use of these strategies brings reductions in pumping work losses. Over the last few decades, several strategies have been proposed to increase engine performance. In this work, computational models of a research single-cylinder spark ignition engine equipped with a fully variable electro-hydraulic valve actuation system operating on ethanol and using different valve timing strategies were developed and validated. The computational simulation was performed using a one-dimensional finite volume software specific for internal combustion engines. The modeling technique used was TPA (three pressure analysis). This model seeks to simulate the real engine gas exchange condition by using experimental data of instantaneous pressure and flow temperature in the intake and exhaust manifolds as boundary conditions. The instantaneous cylinder pressure is used to calculate the rate of heat release during combustion, and as a comparative validation parameter. The valve strategies used in the previously carried out experiment were positive valve overlap and negative valve overlap. Different loads, from 2.0 to 9.0 bar IMEP at 1500 rpm, were evaluated for each strategy. Models for both strategies were validated, deviations between simulated and experimental validation parameters were presented, and a comparative analysis present a greater gain in efficiency with NVO in condition of 3 bar IMEP.