Comparative Analysis of Real-Driving Emission Characteristics of Euro 7 Hybrid Electric Vehicles at Varied Ambient Temperatures.

In this study, the emission characteristics of a Euro 7 hybrid electric vehicle (HEV) were experimentally investigated under real-driving test cycles at different ambient temperatures using a climate-controlled chassis dynamometer. The total and transient emissions of particulate number (PN), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and ammonia (NH3) were compared at -7 and 23 °C. The results showed that while CO, HC, NOx, and PN emissions remained within Euro 7 limits at both temperatures, NH3 emissions exceeded the standards, indicating a need for improved aftertreatment technologies and control strategies. At -7 °C, CO emissions increased by 72.9% and HC emissions rose by 89.4% compared to those at 23 °C, with CO consistently exhibiting higher transient emissions throughout the test cycle. In contrast, NOx and NH3 emissions were 58.8% and 18.8% lower at -7 °C, respectively, although both displayed significant transient spikes during cold starts. PN10 and PN23 emissions showed minimal temperature dependence in total measurements but presented higher initial transient levels at -7 °C before reversing this trend after engine stabilization. The findings demonstrate substantial temperature effects on hybrid vehicle emissions, highlighting in particular the challenges of cold-start conditions and the need for NH3 control solutions. This study provides valuable data for understanding real-world emission behavior under different environmental conditions, although further research with expanded temperature ranges and vehicle configurations would enhance the practical applicability of the findings.