Gerhard Lepperhoff

Impact of Particulate Traps on the Hydrocarbon Fraction of Diesel Particles

Particulate traps reduce particle emissions through the physical filtration of solid, predominantly carbonaceous particles and decreasing particle-bound hydrocarbon emissions. Catalyst coated and uncoated traps were examined for their ability to reduce particle-bound hydrocarbons. At low exhaust temperatures some volatile hydrocarbons are particle-bound in the trap and are physically retained. These components become gaseous and are purged from the trap with sharp exhaust temperature rises. Oxidation catalysts considerably improve the ability of traps to decrease particle-bound hydrocarbon emissions, particularly PAH at low exhaust temperatures. Precious metal coated traps generate sulfate particles so that especially at high exhaust temperatures the overall filter efficiency can be reduced.

Influence on particles in diluted diesel engine exhaust gas

This paper presents the results of experimental and theoretical investigations on measuring particulate emissions of diesel engines in a dilution tunnel. The results offer a contribution to understanding the influence of several parameters on the particle phase of exhaust gas when diluted and mixed with air. These parameters include the exhaust gas temperature, the dilution ratio of the exhaust gas in the air, the mixture temperature, the flow and mixture conditions, the amount of filter loading and the filter material. In order to determine which physical/chemical processes dominate particle formation in diluted exhaust gas, the results of calculations in terms of condensation and adsorption are compared with the experimental findings. An increase in measured particulate concentrations is generally favoured by short sampling times, fast mixing processes, high exhaust gas temperatures, low mixture temperatures and low dilution ratios. Furthermore, the results show that adsorption of hydrocarbons to soot particles rather than condensation is the major influence on particulate formation.

Influences of Future Diesel Fuels on Combustion and Emissions of a Dl-Diesel Engine

Influence des carburants diesel de remplacement sur la combustion et les emissions polluantes des moteurs diesel a injection directe

Soot Formation and Oxidation in Diesel Engines

The formation of soot in diesel engine combustion is discussed. Different mechanisms of formation of soot corresponding to the different phases of diesel engine combustion, viz. soot formation in the fuel rich zones of the inhomogeneous premixed combustion, soot formation from the fuel injected into the flames, soot formation from the fuel injected into the burnt gases and, finally, soot oxidation, are identified. Some phenomena of soot formation in diesel engines are investigated experimentally by means of rapid sampling techniques and other experiments under diesel engine combustion conditions. From these experiments the need of further experiments for the investigation of single processes for soot formation under diesel engine combustion are concluded. Possible boundary conditions for the experiments are identified.

The influence of diesel fuel composition on gaseous and particulate emissions

A very efficient and promising approach to improve rapidly the pollutant emission behaviour of an existing diesel vehicle fleet is to optimise the fuel composition with regard to reduced pollutant formation. That is why a European research program was carried out to evaluate the potential of an optimised fuel composition. Twelve diesel-like fuels were composed performing lower aromatic concentrations and containing oxygenating components. A series-like modern passenger car CR DI diesel engine was operated on a test bench under various steady state conditions using these fuels and - for comparison - a diesel-typical reference fuel. Pollutant concentrations were measured in the tailpipe and in-cylinder. To get further information on the transient pollutant emission behaviour of the engine, the investigations were extended by vehicle tests (same engine) on a chassis dynamometer. For all experiments the HC, CO, CO2, NOx, O2 and PM concentrations were measured.