Search Results

As automotive exhaust emission standards have become more stringent and emission control technologies have advanced over the years, accurately measuring the resulting near zero emissions has become increasingly difficult. To improve measurement accuracy, enhancements have been made to the conventional Constant Volume Sampling system (CVS) and to the analytical instrumentation This study included the evaluation of a CVS enhancement. Specifically, a prototype air filter was utilized to enhance the performance of a CVS by reducing non-methane hydrocarbons (NMHC) from dilution air at ambient temperature. Also incorporated into this study was the assessment of a Bag Mini-Dilute (BMD), a relatively new sampling system developed for measuring low-level vehicle emissions. The BMD can be used as an alternative to the CVS and has been approved for emission measurement by the United States Environmental Protection Agency (US EPA) and the California Air Resources Board (ARB.)

This report describes tests of a fuel additive in a medium-duty, high-swirl, direct-injection diesel engine. The additive was found to have little influence on general combustion performance or on NOx emissions. On the other hand, it had a profound effect on particulate emissions. This was most clear under high load where particle emissions are highest. Here, when the engine was switched from running on the base fuel to the additive treated fuel, particle emissions at first increased and then fell to levels about 40% lower (by particle volume) than those initially produced by the base fuel. The additive had a long lasting effect. After running with the additive for about 25 hours, emission levels with the base fuel were only slightly higher than those with the additive treated fuel. We believe that the additive action is associated with a combination of cleaning and surface conditioning. More work should be done to understand the relative importance of these two mechanisms.