Composition of Particulate Matter Emitted from Lean Burn Gas Engine with Pre-chamber Spark-plug Ignition System and Comparing Emissions with Those from Diesel Engines

Abstract

When investigating the sources of particulate matter (PM) and its reduction methods, it is important to clarify its composition. In this study, PM emitted from a lean burn gas engine with a pre-chamber spark plug ignition system was analyzed by quantifying emission factors of PM components, namely Elemental Carbon (EC), Organic Carbon (OC), sulfate and nitrate, as well as “the other components” . These emission factors were compared with previous results of PM constituents emitted from diesel engines in an attempt to gauge how this gas engine could contribute to reducing PM emissions. At 75% engine load, the percentages of EC, OC, sulfate and nitrate in PM were less than 3%, 70%, less than 1% and 10% respectively with the other components being the remaining 18%. The low proportion of EC was caused by lean fuel conditions inside the gas engine. OC, which accounted for a majority of PM, is thought to have derived from vaporized lubricant oil. A slight amount of sulfur may have originated in either sulfur contents in lubricant oil or odorous components in city gas. At any engine load, the gas engine’s PM emissions were more than 70% lower than those from diesel engines. Two-thirds of reductions in PM emissions came from EC and the remaining one-third were due to a drop in emissions of the other components.