抄録
Interest in diesel-powered passenger cars is rising in the United States, along with the desire to reduce the nation's dependence on imported petroleum. As a result, operating diesel vehicles on fuels blended with biodiesel is also gaining attention. One of several factors to consider when operating a vehicle on biodiesel blends is understanding the performance and impact of the fuel on the emission control system. This paper documents the impact of biodiesel blends on engine-out emissions as well as overall system performance in terms of emission control system calibration and overall system efficiency. The testing platform is a light-duty, high-speed, direct-injection diesel engine with a Euro 4 base calibration in a 1700-kg sedan vehicle. It employs a second-generation common-rail injection system with a peak pressure of 1600 bar, as well as cooled high-pressure exhaust gas recirculation. The study includes three different fuels: U.S. ultra-low-sulfur diesel (ULSD) base fuel and B20 prepared from soy-derived biodiesel. The study also includes two different emission control systems (ECS): oxides of nitrogen (NO_x) adsorber catalyst (NAC) with a diesel particle filter (DPF), and selective catalytic reduction with a DPF. This paper focuses primarily on NAC calibration, regeneration, and desulfurization; DPF regeneration and preliminary emissions, focusing on NO_x; and fuel economy results. The NAC ECS aged to end-of-life conditions showed efficiencies in the mid-80% range, thus allowing operation within Tier 2 Bin 5 emission standards for both intermediate and useful life conditions. Results of the vehicle chassis tests showed some NO_x benefits when operating on B20 fuel blends with the NAC ECS. This is a result of calibration work being performed using the 20% biodiesel fuel blend. The higher exhaust temperatures resulting from the use of ULSD resulted in lower ECS effectiveness with the NAC. The average tailpipe results when operating the vehicle on B20 were in the range of 0.03 g/mi, while the emissions with ULSD averaged below 0.05 g/mi with larger cycle-to-cycle variability.
