A coupled-inductor DC-DC converter with a high voltage gain is proposed in this paper to match the voltage of a fuel cell stack to a DC link bus. The proposed converter can minimize current ripples and can also achieve a high voltage gain by adjusting the duty cycle d and the turns ratio n of a coupled inductor. A passive lossless clamping circuit that is composed of one capacitor and one diode is employed, and this suppresses voltage spikes across the power device resulting from system leakage inductance. The operating principles and the characteristics of the proposed converter are analyzed and discussed. A 400-W experimental prototype was developed, and it had a wide voltage gain range (4–13.33) and a maximum efficiency of 95.12%.

Faults of the selective catalytic reduction (SCR) significantly exacerbate nitrogen oxide (NOx) emissions from heavy-duty vehicles, thereby posing a severe hazard to atmospheric environmental quality. Currently, the paucity of systematic studies on NOx emission degradation induced by typical SCR faults has severely hindered the advancement of precise emission regulation for heavy-duty vehicles in China. To address this critical gap, this study investigates the impact of typical SCR faults on NOx emission deterioration from heavy-duty vehicles. Initially, leveraging the China heavy-duty commercial vehicle test cycle as the benchmark, heavy-duty vehicle emission tests were designed and conducted under typical SCR faults. Emission datasets were acquired for three typical SCR faults—namely nozzle circuit disconnected fault, upstream temperature sensor inaccuracy fault, and urea-water replacement fault—as well as under normal operating conditions. Building upon these data, three representative scenarios were established by integrating vehicle operating condition, fuel consumption levels, and vehicle specific power states, enabling systematic quantification of the extent of NOx emission deterioration caused by each SCR fault. The findings reveal that the NOx emissions deterioration caused by urea-water replacement fault is the most severe, followed by nozzle circuit disconnected fault, and the impact of upstream temperature sensor inaccuracy fault is the least. This research provides crucial support for identifying key targets in emission control and enhancing the precision of heavy-duty vehicle emission regulation. Relevant authorities should prioritize cracking down on intentional non-compliant practices such as urea water substitution to safeguard a healthy and sustainable atmospheric environment.

In this study, a bench test was conducted employing the Worldwide Harmonized Light-duty Vehicles Test Cycle (WLTC) to investigate the emission rates of hydrocarbons (HCs), carbon monoxide (CO), and carbon dioxide (CO₂) with two different gasolines and five gasoline vehicles. The results indicated that compared with X gasoline, X+ gasoline led to a reduction in the emission rates of HC, CO, and CO₂, by 38%, 11%, and 7%, respectively, attributed to its lower aromatic hydrocarbon content, olefin content, and 90% evaporation temperature (T90), and higher oxygen content. X+ gasoline exhibited more emission reductions under both acceleration and deceleration conditions. The two gasolines showed consistent patterns: for X+ gasoline, the emission rates under acceleration conditions were significantly higher than those under deceleration conditions, by a factor of 14.9, 2.1, and 1.6 for HC, CO, and CO₂, respectively. Stronger Spearman correlations between vehicle specific power (VSP) and the emission rates were observed at higher speed (>80 km/h) of X, than those at medium speed (40–80 km/h) and lower speed (≤40 km/h), for both gasolines. Overall, the grey relation analysis revealed obvious heterogeneity between each of the seven fuel properties (RON, T10, T50, T90, Oxygen content, Aromatics content, Olefin content) and each of the three emission rates. However, slightly higher relational degrees were observed between HC emissions and aromatics or olefin contents, highlighting the need for lowering aromatics and olefin contents, thus reducing HC emissions.

Urea regulators (UR) have generally been employed against diesel trucks to save urea usage and thus contribute to the reduction in excessive emissions, while their usage is generally difficult to supervise and enforce. By conducting real driving emission measurements on a China IV heavy-duty diesel truck, a “trade-off” effect caused by UR was found between nitrogen oxides (NOx) and particle number (PN) emissions. The usage of UR contributes to 1.04 times higher NOx but 0.28 times lower PN emissions for the whole trip. In particular, the increasing effects on NOx are most efficient on the highway and least effectual on the urban road, while the decreasing effects on PN exhibit an opposite trend under different road types. From low- and medium- to the high-speed bin, the peak average vehicle-specific power NOx emission rates exhibit markedly increasing but slightly decreasing trends for the truck with and without UR, respectively. Furthermore, the NOx emissions in units of CO₂ and the linear correlational relationship between CO₂ and NOx instantaneous mass emission rates, especially those on the highway, are significantly enhanced. This study directly clarifies the effects of UR on real-world emissions, providing a scientific basis for the real-time identification of the malfunction of the selective catalytic reduction system.