Performance and Environmental Assessment of Hybrid Electric Vehicle with Power-Split Device Under Quasi-Realistic Operating Conditions

Hybrid electric vehicles aim to both increase fuel efficiency and reduce carbon emissions by combining an internal combustion engine and an electric motor. However, integrating these two power sources most efficiently requires complex engineering and design decisions. The performance and environmental impact of hybrid electric vehicles depend not only on the efficiency of the engines but also on the vehicle's operating conditions and powertrain design. Therefore, understanding how hybrid electric vehicles perform in real-world scenarios and thoroughly examining the factors that affect their performance is critical for future vehicle designs. This study presents a performance and environmental assessment of a series-parallel hybrid electric vehicle (HEV) under quasi-realistic operating conditions. We considered the influence of resistance forces on the demanded traction force. For a real vehicle, performance characteristic curves were derived through calculations utilizing actual performance maps of the internal combustion engine, electric motor, and generator. Furthermore, the impact of power-split mechanism design parameters on vehicle performance was investigated. While keeping the planetary gear unit's gear ratio constant, the angular velocity ratio (ω_R/ω_s) between the ring gear and sun gear was evaluated. Findings indicate that a low ω_R/ω_s value enhances the effective hybridization factor but limits the vehicle's ability to reach desired high velocities. Conversely, a high ω_R/ω_s increases battery power demand to achieve the required vehicle power. From an environmental perspective, a high ω_R/ω_s value proved more advantageous for CO2 equivalent emissions. These findings offer valuable guidance for HEV designers.