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The two major problems of diesel emission control are the reduction of nitrogen oxides and particulates. This paper describes experimental investigations to achieve both a separation of soot particles as well as a catalytic NOx reduction with hydrocarbons under lean diesel exhaust gas conditions. For that purpose a diesel particle trap is coated with a catalyst based on a Pt containing zeolite. Preliminary studies have been performed on the catalytic NOx reduction to evaluate the efficiency of a Pt/zeolite system as well as to establish the impact of operation conditions on the catalyst performance. The activity of the prepared samples (catalytic coating on particle trap) has been determined under model gas test conditions. Much attention has been focussed on the steady-state kinetics of the surface processes. Another aspect considered is the N2O formation which can be reduced, when alkali-earth or rare-earth oxides are added to the catalyst system.

The effects of in-cylinder water injection on a direct injection (DI) Diesel engine were studied using a computational fluid dynamics (CFD) program based on the Kiva-3v code. The spray model is validated against experimental bomb data with good agreement for vapor penetration as a function of time. It was found that liquid penetration increased approximately 35% with 23% of the fuel volume replaced by water, due mostly to the increase in latent heat of vaporization. Engine calculations were compared to experimental results and showed very good agreement with pressure, ignition delay and fuel consumption. Trends for emissions were accurately predicted for both 44% and 86% load conditions. Engine simulations showed that the vaporization of liquid water as well as a local increase in specific heat of the gas around the flame resulted in lower Nitrogen Oxide emissions (NOx) and soot formation rates.

The combustion process of a heavy-duty DI-Diesel truck engine has been investigated using numerical simulation. The numerical modeling was based on an improved version of the KIVA-2 engine simulation code, employing a modified characteristic time-scale combustion model and a modified Kelvin-Helmholtz spray atomization model. The NO-formation process was modeled using the extended thermal Zeldovich mechanism. The simulation efforts included the effects of different injection characteristics such as varying the injection rate profile or number of injection holes and sizes. The physical sub-models used to improve the simulation of the mixture-formation and the combustion process were validated through comparison with single-cylinder engine experiments. Special attention was given to accurately model the in-cylinder flame propagation of the individual sprays and their effect on thermal NO-formation. All simulations were based on full load cases at medium speed.

Multi-dimensional modelling of the flow and combustion promises to become a useful optimisation tool for IC engine design. Currently, the total simulation time for an engine cycle is measured in weeks to months, thus preventing the routine use of CFD in the design process. Here, we shall describe three tools aimed at reducing the simulation time to less than a week. The rapid template-based mesher produces the computational mesh within 1-2 days. The parallel flow solver STAR-CD performs the flow simulation on a similar time-scale. The package is completed with COVISEMP, a parallel post-processor which allows real-time interaction with the data.

High over-all efficiency, good performance together with low impact on environment and low lifecycle-costs are the major demands of truck engine customers. To fulfill these high demands, the potential of an SNCR (selective non catalytic reduction) process for NOx reduction as an alternative to catalytic exhaust treatment systems has been examined in this investigation [1]. Aqueous urea was used as the reducing species. The experimental tests were carried out on a heavy duty single cylinder research engine. The tests confirmed the applicability of a homogeneous non-catalytic selective reduction process. By injecting aqueous urea directly into the combustion chamber a maximum NOx reduction of 65% could be achieved at full load and increased exhaust gas temperature.

The application of statistical analysis methods and simulation techniques through the concept stages of a truck engine development process, in order to assist with decision making, is reported in this paper. Aspects of single cylinder engine, combustion system development and the subsequent use of modelling and simulation, to predict multi-cylinder engine behaviour, is described. Finally, the inclusion of vehicle commercial and operational information is shown to provide insights into the likely mix of technical strategies for future truck engines in the UK vehicle parc. It is seen that, in the near future especially in Europe, the likely solution for truck engines will be a mix of EGR and SCR techniques both of which will include the use of particulate filtration. However, the extent of the commercially viable application of this strategy is very dependent upon likely future market prices for the various aftertreatment and fuel technologies.

For meeting 21st-century exhaust emission standards for HD diesel engines, new methods are necessary for reducing NOx and PM emissions without increasing fuel consumption. The stratified diesel fuel-water-diesel fuel (DWD) injection in combination with exhaust gas recirculation (EGR) is as a means for NOx and PM reduction without any negative effect on fuel economy. The investigation was performed on a charged HD single-cylinder direct-injection diesel engine with a modern low-swirl combustion system, 4-valve technology and high pressure injection. The application of DWD injection combined with EGR resulted in a 60 percent lower NOx emission at full load and a 75 percent reduced NOx emission at part load when compared with present day (EURO II) technology. This was achieved without any fuel economy penalty, but with an additional PM emission reduction.

Using an engine simulation code (WAVE) combined with statistical experimental design and optimisation techniques, the potential of a combined Miller cycle and internal EGR heavy duty engine for future truck applications (Euro 3 and 4) has been assessed. The practical issues related to a suitable variable valve timing or actuation system and boosting strategy have been considered. It is found that, whilst internal EGR levels suitable for future European emissions legislation cycles are possible, the boost pressures needed at high load to maintain a suitable air/fuel ratio when running a valve timing strategy to give acceptable levels of in-cylinder temperature (via the Miller system) are beyond the capabilities of current technology. It is believed, however, that such a system may still be suitable for application in markets which have duty cycles less dependent upon full load operation, for example Japan and, possibly, the USA.