ANÃLISE DE DESEMPENHO E DE EMISSÕES EM UM MOTOR DE COMBUSTÃO INTERNA ALIMENTADO COM BIOGÃS

Resumo

The present work aims to optimize the performance of an internal combustion engine fueled with biogas. Tests were carried out in a 4 kW Otto cycle engine-generator powered initially with three different fuels: gasoline, compressed natural gas (CNG) and biogas. Fuel consumption and emissions were measured at four different engine nominal power loads (25%, 50%, 75% and 100%). In the performed tests, the values of CO and HC emissions measured with biogas were lower than the results obtained in the tests carried out with the CNG. NOx emissions were higher in the tests performed with CNG due to the higher temperatures reached during the combustion process. The presence of CO2 in the biogas has a diluent effect, which decreases the temperature in the combustion chamber. The biogas presented higher fuel consumption due to its low calorific value. In a second phase, more detailed tests were performed with the engine running on biogas only. Since biogas has specific characteristics, some engine parameters have been modified to determine its influence on engine performance and emissions. The studied parameters were the air-fuel ratio and the spark ignition timing. For both parameters studied a decrease in specific fuel consumption and an increase in overall efficiency was observed.