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Increasingly stringent emission limits for commercial vehicles in the EU as of 2005 will most probably require exhaust gas aftertreatment. Particulate traps are one possible route. They are set to become a widespread treatment for the control of PM emissions from diesels due to the continuing concern over the health effects. No other technology can achieve comparable levels of efficiency in removing PM. However, reliable particulate trap regeneration under all possible driving conditions presents a problem that has not been solved satisfactorily yet. Especially with vehicles that are being operated in urban areas in stop & go mode (buses, delivery vans, garbage collectors), the problem arises that exhaust gas temperatures are not high enough to regenerate the filter via passive measures. One remedy would be to integrate an active regeneration system, e.g. a full-flow burner, which is presented in this paper.

The paper reports on the development of cost effective active regeneration aids as a “worst case solution” for implementation in diesel particulate traps, particularly with respect to long time vehicle operation in the inner-city at very low exhaust gas temperature level. Two different principles of active measures were investigated: heating the entire exhaust gas by fuel burner to initiate the soot burning or applying so called “hot spot” heating by electrical heaters to start the regeneration of the loaded trap. Both methods may be combined with engine management measures to lower the necessary energy input. Based on this investigation, several systems have been developed and tested on modern diesel engines for passenger cars at steady state and dynamic operation at difficult conditions such as low speed and very low load close to idle. Advantages and disadvantages of the systems are reported.

The paper reports on the development of cost effective active regeneration aids as a “worst case solution” for implementation in diesel particulate traps, particularly with respect to long time vehicle operation in the inner-city at very low exhaust gas temperature level. Two different principles of active measures were investigated: heating the entire exhaust gas by fuel burner to initiate the soot burning or applying so called “hot spot” heating by electrical heaters to start the regeneration of the loaded trap. Both methods may be combined with engine management measures to lower the necessary energy input. Based on this investigation, several systems have been developed and tested on modern diesel engines for passenger cars at steady state and dynamic operation at difficult conditions such as low speed and very low load close to idle. Advantages and disadvantages of the systems are reported.

Diesel engines belong to the most efficient power sources for any kind of on-road vehicle, but especially in Europe increasingly for passenger cars. However, more stringent exhaust emission regulations, which will come into force world-wide in industrialised countries during the first decade of the next century will require NOx and particulate emissions to be reduced by up to 60% and more from today's levels. To meet these future emission standards particularly for heavier passenger vehicles, such as SUVs, Pickup Trucks and Light Commercial Vehicles, as well as for heavy luxury class passenger cars, the application of new technologies including advanced exhaust gas aftertreatment systems will be indispensable, especially in view of maintaining the thermal efficiency of diesel engines relative to gasoline engines.

The paper reports on the outcome of a still on-going joint-research project with the objective of establishing a demonstrator high speed direct injection (HSDI) diesel engine in a Sport Utility Vehicle (SUV) which allows to exploit the effectiveness of new engine and aftertreatment technologies for reducing exhaust emissions to future levels of US/EPA Tier 2 and Euro 4. This objective should be accomplished in three major steps: (1) reduce NOx by advanced engine technologies (cooled EGR, flexible high pressure common rail fuel injection system, adapted combustion system), (2) reduce particulates by the Continuous Regeneration Trap (CRT), and (3) reduce NOx further by a DeNOx aftertreatment technology. The current paper presents engine and vehicle results on step (1) and (2), and gives an outlook to step (3).

Diesel exhaust gas contains low molecular aliphatic carbonyl compounds and strongly smelling organic acids, which are known to have an irritant influence on eyes, nose and mucous membranes. Thus, diesel exhaust aftertreatment has to be considered more critically than that of gasoline engines, with respect to the formation of undesired by-products. The results presented here have been carried out as research work sponsored by the German Research Association for Internal Combustion Engines (FVV). The main objective of the three year project was to evaluate the behaviour of current and future catalyst technology on the one hand (oxidation catalyst, CRT system, SCR process), and regulated and certain selected non-regulated exhaust gas emission components and exhaust gas odour on the other hand.

The paper reports on a study performed as a joint project between Rhodia, Renault Automobiles and AVL and deals with the application of a sintered metal trap (SMT) whose regeneration is supported by the use of a Ce-based fuel-borne catalyst installed on a delivery van equipped with a conventional IDI/NA diesel engine. For demonstration purpose, a trap protection strategy was developed with the aim to minimize the trap loading and thus the consequent fuel consumption penalty that can be observed for worst-case low speed driving scenarios. Measures to temporarily increase the exhaust gas temperature during inner-city driving and therefore to initiate the start of regeneration were successfully applied. MAJOR EFFORT IS BEING currently undertaken to develop and apply advanced aftertreatment systems to meet future proposed exhaust gas emission standards for passenger cars, LDT and HD diesel engines.

The paper reports on achievements obtained in an ongoing development program which is part of a european EUREKA joint research project named EFFLED (EFFicient Low Emission Diesel) being performed at AVL in cooperation with the companies DAF Trucks, Serck Heat Transfer, Robert Bosch and the Community of the City of Rotterdam. The main objective of this project is the development and refinement of a venturi supported exhaust gas recirculation (EGR) system for a turbocharged and intercooled heavy-duty (HD) diesel engine enabling map controlled cooled EGR rates which are high enough to achieve future low NOx emission standards at acceptable fuel consumption level. In addition to EGR, further technologies have been investigated, which may be required to meet future exhaust emission standards.

The paper reports on the results of a joint research program performed at Rhône-Poulenc and AVL concerning a passive trap system with Cerium (Ce) as a new patented fuel additive in conjunction with an engine management control system to increase the exhaust gas temperature for initiating regeneration under practically all engine application conditions. Investigations were carried out on a 12L DI/TCI HD diesel engine which meets the US94 emission standards. From the work done the most effective combination of the engine control measures has been established as an apprepriate solution to increase the exhaust gas temperature up to 400 deg. C. at minimum penalty with respect to emissions and fuel consumption. Furthemore, the influence of Cerium on engine-out emissions and fuel consumption has been investigated. It could be shown that by using Cerium, the fuel consumption improves on average by about 2 percent.

The paper deals with problems arising on the one hand from aplying diesel oxidation catalyst for minimizing HC emission at low exhaust gas temperatures prevailing in the European city driving cycle and on the other hand in preventing sulphate formation in the oxidation catalyst at higher temperatures as they appear e.g. in the ECE R49 13-mode certification cycle. The main parameters influencing the catalyst efficiency - exhaust gas temperature level, sulphur content in the fuel and catalyst specifications - are discussed and new solutions to fulfill the conflicting requirements are presented. The use of a highly active catalyst for exhaust gas treatment only up to the temperature limit of sulphates formation and by-passing it in the high temperature range appears to be a viable solution.

This paper reports on research and development work conducted at AVL to determine the NOx-reduction potential of in-cylinder charge conditions, fuel injection system parameters, exhaust gas recirculation, fuel formulation, and exhaust gas aftertreatment by catalyst. Based on these findings, development options are derived and assigned to the various future emission standards in USA, Europe and Japan.

This paper deals with development and optimization of combustion process, cold start system and exhaust after-treatment carried out on the steady state and transient test bed as well as with vehicle development on chassis dynamometer and on the road at standard ambient temperatures and under cold conditions of a) SPFI or MPFI-SI engine with catalyst (closed loop), neat ethanol fuelled, compared to b) glow plug assisted direct injection methanol engine equipped with oxidation catalyst. The main emphasis is laid on the optimization of the cold start behaviour with and w/o catalyst in order to obtain low emissions, primarily during the first phase of the FTP 75 cycle. The emission results show that with both engine types the achievement of US-1994 limits will be possible, including a very low aldehyde emission.

The paper describes the development of methanol fueled engines for passenger cars and light duty trucks working both on the compression ignition and glow plug assisted ignition principle. Special emphasis was laid on development and optimization of the combustion process for both the glow plug assisted and the compression ignition system, the application of the engine management system and the development of the exhaust after-treatment under steady state conditions on the engine dynamometer. The transient engine development in the test car was carried out on chassis dynamometer and under road conditions. The glow plug assisted direct injection methanol engine was in addition equipped with oxidation catalysts for this development program.

The paper describes the research work concerning the investigation and optimization of oxidation catalysts for diesel engines, especially for passenger cars and light duty trucks. The investigations carried out both in the laboratory and on the chassis dynamometer with different engine types (DI and IDI as well as natural aspirated and turbocharged) demonstrate the influence of a number of important catalyst design parameters on catalytic converion of soluble particulate content and gaseous emissions (HC, CO and S02) (e.g. precious metal content, washcoat formulation, space velocity, cell density, substrate material, different exhaust gas temperatures, variable oxygen and sulphur dioxide content) with fresh and aged catalysts.

Different qualities of diesel fuels have been tested in naturally aspirated IDI engines and turbocharged DI engines to determine the effect on exhaust emissions (NOx, CO, HC, PAH, particulates, sulfates and smoke) and combustion characteristics (heat release, ignition delay) under cold ambient conditions. Measurements were made during engine warm-up and under steady state operating conditions at ambient temperatures between -20°C and +20°C. The startability was tested down to -30°C. The results showed that the behaviour of the diesel engine is dependent on engine design, the lubricant used and the fuel properties. Low viscosity and good flow properties of the fuel are important for starting - more important than cetane number, for example. Fuel consumption and exhaust emissions at the beginning of the warm-up period increased considerably as the starting temperature was reduced.