Structured Catalysts for Soot Combustion for Diesel Engines

E. D. BANÚS; M.A. ULLA; E.E. MIRÓ; V.G. MILT

Diesel Engine - Combustion, Emissions and Condition Monitoring

InTech Open

Año: 2012; p. 117 - 142

For diesel fuel, low volatility and excellent ignitability make it difficult to broaden the engine load range and optimize engine thermal efficiency. In light of increasingly stringent diesel emissions limits, changes in conventional combustion mode, addition of active elements to the fuel or after treatment of exhaust gases are needed.Concerning changes in combustion mode, research efforts have been invested into Homogeneous Charge Compression Ignition (HCCI) combustion as an alternative to conventional diesel combustion. The implementation of HCCI combustion in direct injection diesel engines using early, multiple and late injection strategies has been studied. Governing factors in HCCI operations such as injector characteristics, injection pressure, piston bowl geometry, compression ratio, intake charge temperature, exhaust gas recirculation (EGR) and supercharging or turbocharging has been discussed. Also, the effects of design and operating parameters on HCCI diesel emissions were investigated. Although much advancement has been achieved in this research field over the last decade, large scale adoption of HCCI diesel engines in commercial vehicles is currently not possible. The main challenges facing HCCI diesel engines are its limited operational range, lack of direct control of combustion phasing and increased HC and CO emissions, as reported in some applications.Cerium-based compounds have been used as diesel fuel additives, in order to lower PM emissions and to enhance oxidation rates. Also, oxygenated compounds, as 1,1-diethoxyethane, have been tested as additives to reduce PM in an automotive diesel engine. Nevertheless, engine tests showed an insensitive effect on gaseous pollutant emissions (HC, CO and NOx).Improvements in diesel engine designs will not be enough to meet the requirements of future legislation for both soot and NOx. Therefore, after treatment technologies are the object of intense research efforts. A variety of technologies have been proposed to abate NOx and soot; the combination of filters and combustion catalysts for particle removal and catalytic traps for nitric oxide reduction are among the most investigated of those technologies.