1-D Numerical Model of a Spark Ignition Engine Fueled with Methanol for Off-Grid Charging Stations 2023-24-0098

The road transportation sector is undergoing significant changes, and new green scenarios for sustainable mobility are being proposed. In this context, a diversification of the vehicles’ propulsion, based on electric powertrains and/or alternative fuels and technological improvements of the electric vehicles charging stations, are necessary to reduce greenhouse gas emissions. The adoption of internal combustion engines operating with alternative fuels, like methanol, may represent a viable solution for overcoming the limitations of actual grid connected charging infrastructure, giving the possibility to realize off-grid charging stations. This work aims, therefore, at investigating this last aspect, by evaluating the performance of an internal combustion engine fueled with methanol for stationary applications, in order to fulfill the potential demand of an on off-grid charging station. In addition, the possibility to recover the thermal power from the exhaust gas for cogeneration applications is also investigated. The internal combustion engine is a turbocharged spark ignition with a 4.5 liter displacement, which develops a maximum rated power of 100 kW between 1500 and 2500 rpm. A 1-D numerical model was developed using the AVL-boost software to evaluate the main performance at different engine speeds and spark advances in terms of brake and thermal power, efficiency, specific fuel consumption and pollutant emissions. Model validation was carried out with literature data on a SI single cylinder engine. Afterwards, a multi-objective optimization was performed to define the spark advance that guarantees a suitable trade-off between the brake power, the thermal power recovered by the engine and NO_x emissions. Results show that methanol ensures considerable improvements in terms of performance with respect to gasoline. In particular, enhancements of 7.4% and 10.3% for the maximum brake torque and brake thermal efficiency were recorded, respectively. An optimal spark advance of 10°CA was selected as optimal value for the turbocharged spark ignition engine since it guarantees the maximum thermal power recovered from the exhaust gas, the minimum specific NO_x emissions and a brake power slightly lower than the maximum value.