Mechanical and environmental performance evaluation of a Spark Ignition Engine with high compression ratio fueled whit Biogas, Methane and Hydrogen blends

Abstract

Use of renewable fuels from sources other than fossils takes on importance as energy sources, such as biogas. Exclusive engines of biogas have a high economic cost, and little commercial availability for low powers. In this study, we used a compression ignition engine work as spark ignition. Mechanical and environmental performance of a stationary 1550 cm³, 20 kW@3000 rpm nominal power, 15.5:1 compression ratio, diesel engine converted to spark ignition is analyzed. The engine is coupled to a resistance bank simulating engine load by power generation. The engine was fixed at 1800 rpm at 4 kW, which corresponds to 57% of the engine load at a 0.852 bar atmospheric pressure in the Medellín city. The engine was fueled with methane (CH4) and carbon dioxide (CO₂) mixtures in order to simulate at common biogas composition (60% CH₄ - 40% CO₂), and enriched biogas (70% CH₄ - 30% CO₂ y 80% CH₄ - 20% CO₂). Hydrogen was added in small amounts (0%, 5%, 10% and 15% on volumetric basis). The addition of hydrogen enhances the combustion rates, extends the flammability limits, and contributes to the reduction greenhouse gases like CO₂ and pollutants such as CO and unburned hydrocarbons. However, hydrogen increases NO and NO₂ emissions. It was found that the addition of 15% hydrogen improves the combustion properties when using a lean fuel mixture, relative equivalence ratio of 0.822 for pure biogas, while for biogas-hydrogen mixtures no significant improvements in the mechanical and environmental behavior of the engine were found.