Gaseous fueling of an adapted commercial automotive spark-ignition engine: Simplified thermodynamic modeling and experimental study running on hydrogen, methane, carbon monoxide and their mixtures

•Gaseous fuels of possible renewable origin can be used to run spark-ignition engines.•Performance depends more on the air–fuel equivalence ratio than on the gas nature.•The fuel nature mainly affected the air-to-fuel equivalence ratio that could be used.•The 20 % CH4–80 % H2 blend can be used within a very broad range of mixtures with air.•A zero-dimensional thermodynamic model captures the main trends of fuels’ behaviour. In the present work, methane, carbon monoxide, hydrogen and the binary mixtures 20 % CH4–80 % H2, 80 % CH4–20 % H2, 25 % CO–75 % H2 (by volume) were considered as fuels of a naturally aspirated port-fuel injection four-cylinder Volkswagen 1.4 L spark-ignition (SI) engine. The interest in these fuels lies in the fact that they can be obtained from renewable resources such as the fermentation or gasification of residual biomasses as well as the electrolysis of water with electricity of renewable origin in the case of hydrogen. In addition, they can be used upon relatively easy modifications of the engines, including the retrofitting of existing internal combustion engines. It has been found that the engine gives similar performance regardless the gaseous fuel nature if the air–fuel equivalence ratio (λ) is the same. Maximum brake torque and mean effective pressure values within 45–89 N·m and 4.0–8.0 bar, respectively, have been obtained at values of λ between 1 and 2 at full load, engine speed of 2000 rpm and optimum spark-advance. In contrast, the nature of the gaseous fuel had great influence upon the range of λ values at which a fuel (either pure or blend) could be used. Methane and methane-rich mixtures with hydrogen or carbon monoxide allowed operating the engine at close to stoichiometric conditions (i.e. 1