Characterization of the Diesel Soot Oxidation Process through an Optimized Thermogravimetric Method

Abstract

A thermogravimetric analyzer (TGA) was used to oxidize real diesel soot produced in a modern four-cylinder, turbo-charged, diesel engine equipped with a common rail injection system. In the first part of the study, a large amount of soot produced with a variety of diesel fuels of current and future interest and in typical engine modes was collected. A thorough test matrix was designed and executed in the TGA to develop an optimized oxidation method, which allows for the determination of oxidation profiles, characteristic temperatures, and Arrhenius kinetic parameters. Such parameters are critical for modeling diesel filter regeneration and designing more efficient regeneration techniques. A comparison of this method to others proposed in previous literature is made, and the advantages are pointed out. In the second part, diesel and biodiesel soot produced in three engine operating modes (low, medium, and high load) was evaluated with the proposed method. The results showed that the effect of the fuel on the oxidation process was more significant than that of the engine mode. Biodiesel soot oxidation occurred at lower temperatures, proving the possibilities that this fuel offers for achieving more efficient filter regeneration. Although differences in the activation energy of diesel and biodiesel soot were not large, the oxidation rates of biodiesel soot were, on average, 1 order of magnitude above those of diesel soot.