Hybrid Propulsion for Motorcycle Application to Reduce Engine-out Emissions: An Analytical-Experimental Investigation

All over the world, motorcycles represent an important share of motorized vehicles helping to meet daily urban transport needs, thus, particularly in urban contexts, two-wheelers impact to air pollution is significant. In a previous experimental investigation, emissions of regulated pollutants were measured in the exhaust of a four-stroke motorcycle belonging to the Euro-3 legislative category. Since exhaust emissions and fuel consumption are very sensitive to variations in vehicles instantaneous speed and acceleration, such experimental results are used in this research to recognize the kinematic parameters that cause higher CO and HC emissions. The hybrid electric propulsion is then proposed to reduce exhaust emissions in particular driving conditions which include high levels of acceleration with resultant sudden steep increase in engine speed. In such phases, in fact, an enrichment of the air/fuel mixture is needed which affects the catalyst conversion efficiency. Subsequently, the power requirements and the grade of electrical assistance in such driving situations are estimated by a procedure based on both the measured exhaust emissions and the kinematic parameters that characterize the driving dynamics collected during the experimental tests. Finally, the share of CO and HC emissions that could be saved utilizing a hybrid motorcycle instead of a conventional thermal motorcycle is calculated through an environmental analysis.