Particulate Emission from Combustion of Diesel and Fischer−Tropsch Fuels: A Shock Tube Study

Abstract

Motor vehicle emissions have been identified as a major source of particulates, and have been associated with adverse health effects and decreased ambient air quality. Recent published studies have shown that Fischer−Tropsch fuels can reduce particulate emissions. The fuel composition, temperature, and pressure affect the kinetics of a chemical reaction and ultimately the yield of end products. To see how the above factors impact the particulate yields, D-2 diesel and two Fischer−Tropsch fuels, Shell MDS and Mossgas COD, were investigated in this study over a pressure range of 5 to 24 atm and temperature range of 1000 to 2300 °C. All experiments were conducted in a modified single-pulse reflected shock tube. Fuels were injected using a high-pressure liquid injector. The results from Leco carbon analysis indicated that for most test conditions, Shell MDS had the lowest particulate yield compared to D-2 diesel followed by Mossgas COD. At relatively low temperatures (∼1150 °C) and high temperatures (∼2250 °C) the particulate yields decreased for all fuels tested. At higher pressures an increase in particulate yield was observed. An attempt was made to correlate the observed difference in soot yields to physical properties and chemical composition of the investigated fuels. The results are well in agreement with previous studies that relate lower sulfur and aromatic contents to lower particulate yields for the test conditions studied. No direct benefit was seen from a high cetane number on particulate emissions.