Investigação dos efeitos da razão ar-combustível na performance de um motor de ignição por centelha operando em carga parcial com hidrogênio

Abstract

Alternative fuels drive research in internal combustion engines to reduce carbon emissions and environmental impact caused by the mobility sector. With this aim, this study investigates the lean operation limits of a single-cylinder internal combustion engine for spark ignition research, using hydrogen as the fuel. The tests were conducted on a dynamometer bench at the Engine Laboratory of the Federal University of Santa Maria, with an engine speed of 1800 rpm under a condition of 2.5 bar indicated mean effective pressure. The influence of the air-fuel ratio on engine operation was investigated, starting from a fully open throttle condition with sufficient fuel injection to maintain the operating load. Four different air-fuel ratios were tested by varying the intake pressure through throttle valve closure to achieve richer air-fuel ratios. The established ratios were 1, 2, 3, and 4, corresponding to intake pressure values of 55, 70, 85, and 100.5 kPa. For each ratio, an ignition timing sweep was performed to find the maximum indicated efficiency ignition advance. It was possible to operate the engine under high air dilution conditions, with a maximum air-fuel ratio (lambda) of 4, approaching the stoichiometric limit. The enrichment of the mixture resulted in a reduction in combustion duration. However, load control through throttling directly impacted the operating efficiency.