Hanwei Zhu

Bio: Hanwei Zhu is an academic researcher from University of California, Riverside. The author has contributed to research in topics: NOx & Diesel fuel. The author has an hindex of 4, co-authored 6 publications receiving 55 citations. Previous affiliations of Hanwei Zhu include Bourns College of Engineering.

European Regulatory Framework and Particulate Matter Emissions of Gasoline Light-Duty Vehicles: A Review

Abstract: The particulate matter (PM) emissions of gasoline vehicles were much lower than those of diesel vehicles until the introduction of diesel particulate filters (DPFs) in the early 2000s. At the same time, gasoline direct injection (GDI) engines started to become popular in the market due to their improved efficiency over port fuel injection (PFI) ones. However, the PM mass and number emissions of GDI vehicles were higher than their PFI counterparts and diesel ones equipped with DPFs. Stringent PM mass levels and the introduction of particle number limits for GDI vehicles in the European Union (EU) resulted in significant PM reductions. The EU requirement to fulfill the proposed limits on the road resulted to the introduction of gasoline particulate filters (GPFs) in EU GDI models. This review summarizes the evolution of PM mass emissions from gasoline vehicles placed in the market from early 1990s until 2019 in different parts of the world. The analysis then extends to total and nonvolatile particle number emissions. Care is given to reveal the impact of ambient temperature on emission levels. The discussion tries to provide scientific input to the following policy-relevant questions. Whether particle number limits should be extended to gasoline PFI vehicles, whether the lower limit of 23 nm for particle number measurements should be decreased to 10 nm, and whether low ambient temperature tests for PM should be included.

Real-world automotive emissions: Monitoring methodologies, and control measures

Abstract: Vehicular emissions make significant contribution to the total ambient airborne pollutants. Global warming and human health concerns are motivating researchers to come out with newer ways of controlling air pollution effectively. On the other hand, there are significant challenges in complying with current and upcoming vehicle emission regulations, which are quite stringent. It is therefore quite important to monitor vehicular emissions closely, which can facilitate adopting effective control measures when necessary, and also in predicting the impact of vehicular emissions on ambient air quality. Traditionally, dynamometers (both engine and chassis) testing has been used extensively to measure and monitor vehicular emissions, and the database generated has been used as input in modeling the traffic-related air quality impact. Even though standard driving cycles are followed in dynamometer tests attempting to closely replicate real-world driving conditions, they may not necessarily represent actual real-world driving conditions and emissions thereof. Therefore, in recent years, significant scientific efforts have been directed to measure and analyze real-world driving emissions (RDE) from vehicles. In this paper, the state-of-the-art techniques and methods for vehicular emissions monitoring under real-world driving conditions are reviewed and discussed in detail. Different vehicle emissions monitoring methods are presented in comparison to dynamometer-based measurements. Several influencing factors which affect on-road and in laboratory measurements are identified and discussed. Potential applications of different emission control strategies are reviewed. Finally, guidelines are formulated for effective vehicular emissions monitoring, and to minimize discrepancies between on-road and laboratory based measurements, in order to have a sustainable road transport system in future.