To meet greenhouse gas (GHG) emission target, automotive manufacturers should popularize low carbon emission technology including GDI (Gasoline Direct Injection) system. However, recent studies have shown that excessive nanoparticle emissions were emitted from GDI vehicles compared to PFI (Port Fuel Injection) vehicles. The nanoparticle emissions have been regulated as particle mass (PM) and particle number (PN) due to adverse effects on human body. As more stringent emissions regulations expected in the future, a lot of researchers make an effort on reducing nanoparticle emissions from GDI engine.
One of the many ways to decrease nanoparticle emission from GDI engine is to use alternative fuel. As a eco-friendly fuel, LPG (Liquefied Petroleum Gas) is one of the promising alternative fuels due to following advantages (1) relatively low fuel price (2) potential for reducing emissions (3) low carbon dioxide (CO2) emission due to its low carbon content. Additionally, LPG has superior vaporization characteristics which produced less wall-wetting phenomena and better performance in air-fuel mixture formation. Therefore, with downsizing and turbo charging technologies, applying LPG fuel has potential to improve power performance and nanoparticle emission characteristics at the same time.
This study used turbo charged 2.0L 4-cylinder LPG direct injection engine(T-LPDi) which is converted from turbo charged gasoline direct injection engine(T-GDI). For analysis on combustion phenomena and nanoparticle emissions (particle number) of T-LPDi engine, in-cylinder pressure and exhaust gas were measured under engine dynamometer test. For an in-depth study on nanoparticle emission characteristics, DMS-500 (Cambustion co., MK-II) was used to investigate size-resolved real-time nanoparticle emissions. Also, various engine control parameters were swung to understand the effects of the control parameters on combustion and nanoparticle characteristics.
Under the part-load test, PN emissions of T-LPDi engine were reduced 98.0% compared to that of T-GDI. Furthermore, CO2 emissions from T-LPDi engine were 10.3% lower than that from T-GDI engine.