Exploração do limite pobre em carga parcial de um motor ignição por centelha de injeção direta operando com etanol

Abstract

Stringent environmental legislation has demanded development of internal combustion engines towards higher thermal efficiency to reduce greenhouse gas emissions. Brazilian governmenta l programs like ROTA 2030 and RenovaBio drive the research and development of highly efficient engines fueled with biofuels, as sugarcane bioethanol, which has a near to zero carbon footprint. Some technologies such as gasoline direct injection, variable v alve train and turbocharging w ere implemented in downsized Spark Ignition engines to reach higher thermal efficiencies and decrease CO2 emissions. Homogeneous lean combustion in SI operation can improve fuel consumption and reduce exhaust gas emissions. To explore the limits of homogen eous lean combustion in SI engines, experimental tests were run to investigate performance, efficiency, combustion, and emission parameters of a multi cylinder Ford 1.0l Ti VCT EcoBoost engine fueled with hydrous ethanol. Hydrous ethanol is a commercial Br azilian fuel which has higher laminar flame speed and higher dilution tolerance than gasoline, and thus can increase combustion stability. P art load operation (bellow 8.0 bar IMEP) was explored at engine speed of 1500 rpm. Air to fuel ratio was varied from stoichiometric (lambda 1.0) to lambda 1.5. The lean l imit of stable homogeneous lean combustion (CoV of IMEP ≤ 3.0%) was archived with lambda 1.4. The lowest indicated load of 2.1 bar IMEP was limited in combustion stability at lambda 1.3. The maximum ind icated efficiency was 36.9% in indicated load of 8.0 b ar IMEP and lambda 1.4 The NOx emissions were 1.4 g/kWh at 4.0 bar IMEP and lambda 1.4.