Effects of Fuel Sulfur Content and Dilution Conditions on Engine PM Emissions under Transient Conditions

Abstract

The U.S. has introduced ultra low sulfur diesel fuel in 2007 and by 2010 will completely replace the current low-sulfur diesel fuel which has a sulfur content of less than 500 ppm. As a result, most diesel engines, including new and aged ones, are currently implementing ULSD. Thus, it is important to understand how ULSD will affect these engines’ emissions, especially under transient conditions when the load, speed, exhaust gas temperature, and primary dilution ratio change continuously. This study is to assess the effects of fuel sulfur content and aging condition on PM emissions under transient conditions. Combinations of fuels and primary dilutions were used. The primary dilution was accomplished by a CFV-CVS, a system which maintains proportional sampling throughout temperature excursions and is designed for engine emission certification. Data were collected by a Scanning Mobility Particle Sizer and an Engine Exhaust Particle Sizer for steady-state and transient testing, respectively. Although the steady-state results show reasonable agreement with previous studies, the transient results display significant discrepancy when ULSD and LSD were used with the high primary dilution ratio.