In-Service Emissions from Model Year 2012 Hydraulic Hybrid and Model Year 2008 Conventional Diesel Package Delivery Trucks

摘要

In-service emissions measurements were conducted on two package delivery trucks: one model year 2008 FCCC MT-55 conventional diesel and one model year 2012 FCCC MT-55 hydraulic hybrid (HHV). Mass emissions of CO_2, CO, NO_x, PM, and THC from the HHV and the conventional diesel test vehicle were each measured under conditions closely simulating normal package delivery operation. The HHV demonstrated a 29.4% improvement in fuel economy and a 17.4% reduction in CO_2 emissions compared to the conventional diesel vehicle. The HHV showed its best potential in operating areas characterized by low driving speeds and high number of stops (“pick-up and delivery”) with a 40.5% improvement in fuel economy and a 21.2% reduction in CO_2 emissions. Depending on operating conditions such as terrain, driver behavior and driving / traffic conditions, some fuel saving were achieved on operating areas characterized by high driving speeds and low number of stops (“highway / arterial”), but savings remained small. While the different EPA emission certification levels prevented the direct comparison of NO_x emissions between the conventional diesel truck and the HHV, testing demonstrated that the HHV produced 62.6% less NO_x per mile on the “highway / arterial” return than on the outbound trip. The analysis of the exhaust temperature of the HHV showed that this large difference in NO_x emissions per mile was probably attributable to the low SCR catalyst temperature at the beginning of the trip.