Investigation of an Advanced Combustion System for Stoichiometric Diesel to Reduce Soot Emissions 2019-01-0023
Diesel engines are losing market-share in the light-duty and small non-road segments, primarily due to the high relative cost of emissions control systems for lean-burn diesel engines. Advancements in gasoline engine technology have decreased the operating cost advantage of diesels to the extent that the high relative initial-cost disadvantage is now too large to sustain a strong business position. SwRI has focused several years of research efforts toward enabling diesel engine combustion systems to operate at stoichiometric conditions. This would allow the application of a low-cost three-way catalyst emission control system which has been well developed for gasoline spark-ignited engines. One of the main barriers of this combustion concept is the result of high smoke emissions from poor fuel/air mixing. The current study focuses on improving the combustion system by investigating different fuel/air mixing strategies that enhance charge gas – piston bowl interaction while simultaneously optimizing the fuel injection system. CFD simulations were first carried out to evaluate different piston bowl designs as well as injector nozzle designs with reduced hole diameters to introduce small spray droplets and simultaneously avoid locally fuel-rich regions within the cylinder chamber. The combination of selected nozzle and piston bowl design was then installed and tested in a common rail, direct injected diesel engine. By using proper injection strategy, it was demonstrated that smoke emissions were reduced significantly from baseline.
Avery Chase, Jason Miwa, Zainal Abidin, Khanh Cung
Southwest Research Institute
International Powertrains, Fuels & Lubricants Meeting