Search Results

The European research co-operation Lotus is presented. The main objectives of the project were i) to show the potential for a urea-based SCR system to comply with the EU standard of years 2005 and 2008 for heavy-duty Diesel engines for different driving conditions with optimal fuel consumption, ii) to reach 95 % conversion of NOx at steady state at full load on a Euro III engine, iii) to reach 75 % NOx reduction for exhaust temperatures between 200-300°C, and 85 % average NOx reduction between 200-500°C. The energy content of the consumed urea should not exceed 1.0 %, calculated as specific fuel consumption. These targets were met in May 2003 and the Lotus SCR system fulfilled the Euro V NOx legislative objectives for year 2008.

Diesel fuels have been tested in both a naturally aspirated and an externally supercharged single cylinder, air cooled KHD DI-diesel engine, to determine the influence of poor fuel quality on combustion and emissions. A thermodynamic analysis of the cylinder pressure was conducted and the emissions were measured both gaseous as well as the particle emission (by means of a dilution tunnel). Additionally, extensive cold start tests were conducted. Under steady state conditions the cetane number seems to be a good parameter which describes the ignition behavior of different fuels. At low load, a change in combustion and a high increase in CO, HC and particle emissions were found with decreasing cetane number. During cold starting and warming up, a clear deterioration of the emission and combustion characteristics was also observed with decreasing cetane number when basic fuels were used.

The deposits on intake valve tulips of spark ignition and diesel engines can produce an increase in fuel consumption and exhaust gas emission, a deterioration of the driving behavior as well as mechanical defects. The formation of these deposits is investigated with respect to different engine parameters and by using a commercially available leaded fuel without additives. The valve deposits are formed by composing and decomposing phenomena which occur in parallel. The composing elements are oil, particles coming from the combustion chamber via the internal exhaust gas recirculation and, partially, fuel components. The deposits are reduced by the liquid fuel coming in contact with the valve tulips and by a high rate of oil flow. To the end of a shorter test duration and less test efforts a short-time simulation to investigate the deposit formation on inlet valves will be described.

Diesel soot collected in a catalytically coated ceramic honeycomb trap, burns self-supporting, if the heat loss is less than the heat release due to soot oxidation. Experimental verification has been accomplished using a 4.66″ × 6″, 100 CPI trap. Ignition time and regeneration time are measured. At low speeds, a minimum ignition time of 15 s would be sufficient for the trap regeneration. An extended channel with an observation window is provided to allow examination of the regeneration. The soot is ignited at the beginning of the channel and the flame propagation is then observed. The soot burns through the channel in a match-like manner. Manganese and iron fuel additives are observed to have an effect on the mechanism of flame propagation.

A vehicle investigation programme was initiated to evaluate the influence of diesel fuel sulfur content on the performance of a DeNOx catalyst for NOx control. The programme was conducted with a passive DeNOx catalyst, selected for its good NOx reduction performance and two specially prepared fuels with different sulfur contents. Regulated emissions were measured and analysed during the course of the programme. The NOx conversion efficiency of the DeNOx catalyst increased from 14 to 26% over the new European test cycle when the sulfur content of the diesel fuel was reduced from 49 to 6 wt.-ppm. In addition the number and size of particles produced using 6 wt.-ppm sulfur fuel were measured by two different techniques: mobility diameter by SMPS and aerodynamic diameter by impactor. The influence of the assumed density of the particulate on the apparent diameters measured by the two techniques is discussed.