Efeito da composição do biogás nas emissões e performance de um motor de combustão interna

Abstract

The search for renewable energy sources has increased in recent years due to increasing pollution from fossil fuels. Aiming at the reuse of agricultural residues and industrial processes, the use of biomass for energy purposes is highlighted. Biogas is one of the products generated by anaerobic digestion of biomass and the presence of methane in its composition gives it fuel characteristics. Among the other gases that make up biogas, carbon dioxide is also present in high concentrations. The present work aimed to analyze the influence of biogas concentration as fuel in a spark-ignition internal combustion engine. A theoretical approach was developed using Python software with the Cantera chemical reaction library. The methodology applied in the numerical simulation was validated with experimental results of a real biogas engine. The results show that biogas concentration promotes direct influences on combustion engine emissions and operating parameters. For a biogas with high methane content there are important gains in efficiency, exhaust temperature and output power. But, there is also a significant increase in emissions of major pollutants. Thus, a simpler purifying biogas, used here with 70% by volume methane and 30% by volume carbon dioxide, proved to be a viable alternative. In this biogas there were gains in efficiency and exhaust temperature and the increases in emissions were smaller.