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Four of these Particulate Reduction Systems (PMS) were tested on a passenger car and one of them on a HDV. Expectation of the research team was that they would reach at least a PM-reduction of 30% under all realistic operating conditions. The standard German filter test procedure for PMS was performed but moreover, the response to various operating conditions was tested including worst case situations. Besides the legislated CO, NOx and PM exhaust-gas emissions, also the particle count and NO2 were measured. The best filtration efficiency with one PMS was indeed 63%. However, under critical but realistic conditions filtration of 3 of 4 PMS was measured substantially lower than the expected 30 %, depending on operating conditions and prior history, and could even completely fail. Scatter between repeated cycles was very large and results were not reproducible. Even worse, with all 4 PMS deposited soot, stored in these systems during light load operation was intermittently blown-off.

A well balanced use of alternative fuels is an important objective for a sustainable development of individual transportation worldwide. Several countries have objectives to substitute a part of the energy of traffic by ethanol as the renewable energy source. Investigations of limited and unregulated emissions of two 2-S scooters with gasoline-ethanol blend fuels have been performed in the present work according to the measuring procedures, which were established in the previous research in the Swiss Scooter Network (since 2000). The investigated fuels contained ethanol (E), in the portion of 5, 10, 15 and 20% by volume. The investigated 2-S scooters represented a newer and an older 2-stroke technology with carburettor. The newer one was investigated with and without catalyst and the older one only in the original state without catalyst.

Increasing concern, about the health risk due to solid aerosols from engine combustion, has provoked more stringent imission limits, for soot particles in the range of pulmonary intrusion, at critical work-places (e.g. tunnel sites, see Table 1). Within the scope of the joint European project VERT, these emissions were characterized and their effective curtailment through exhaust gas after-treatment investigated. Diesel engines, irrespective of design and operating point, emit solid particulates in the range of 100 nm, at concentrations above 10 million particulates per cm3. Engine tests showed that a drastic curtailment of pulmonary intruding particulates seems not feasible by further development of the engine combustion, nor by reformulation of fuels, nor by deployment of oxidation catalytic converters. Particulate traps, however, can curtail the total solid particulate count, in the fine particulate range 15-500 nm, by more than two orders of magnitude.

New Diesel exhaust gas aftertreatment systems, with combined DPF*) and deNOx (mostly SCR) systems represent a very important step towards zero emission Diesel fleet. These combined systems are already offered today by several suppliers for retrofitting of HD vehicles. Reliable quality standards for those quite complex systems are urgently needed to enable decisions of several authorities. The present report informs about the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles and NOx), which was started in Nov. 2006 with the objective to introduce the SCR-, or combined DPF+SCR-systems in the VERT verification procedure. Examples of results for some of the investigated systems are given. These investigations included parameters, which are important for the VERT quality testing: besides the regulated gaseous emissions several unregulated components such as NH3, NO2 and N2O were measured.

1 Analysis of limited and nonlimited emissions of scooters was performed during several research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS*). Small scooters, which are very much used in the congested centers of the European cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investiga-tions of a Peugeot scooter with TSDI (Two Stroke Direct Injection) were per-formed and the emissions were compa-red to the other 2-S & 4-S scooters. As nonlimited emissions the nanopar-ticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet*). The measurements were both: at steady state and at transient operating conditions.

1 During the research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to to the European project ARTEMIS*) analysis of limited and nonlimited emissions of motorcycles was performed. Exhaust emissions measurements of two motorcycles without catalyst: 4-stroke 750 cc and 1100 cc have been performed in the present work. Identical driving cycles have been repeated and the influence of the cooling duration on the emissions at cold start was investigated. A cold start in the temperature range of 20 ÷ 25 °C can be regarded as a “summer cold start”. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS and NanoMe**). The measurements were performed at steady state and at transient operating conditions. The present work cleared up several details about the emissions of strong motorized motorcycles.

1 A methodology for correctly matching trap systems to the vehicle types was developed within the scope of a feasibility study to retrofit the entire Swiss fleet of on-road HDV. Representative test vehicles from 11 vehicle categories were equipped with high capacity data loggers during a period of 4-6 weeks. Statistical evaluation of exhaust temperatures indicate that data on averages, peaks and frequency distributions alone can be misleading, because these tend to over-estimate the available exhaust enthalpy. Analysis of dwell time intervals, at certain temperature levels, is a better method to assess the energy available for the regeneration. Such verification of duty cycles is indispensable before retrofitting traps and choosing either active or passive regeneration systems.

1 Analysis of limited and nonlimited emissions of scooters was performed during several research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS *). Small scooters, which are very much used in the congested centers of the European cities are a remarkable source of air pollution. Therefore every effort to reduce the emissions is an important contribution to improve the air quality in urban centers. In the present work detailed investigations of a Peugeot scooter with TSDI (Two Stroke Direct Injection) were performed and the emissions were compared to the other 2-S & 4-S scooters. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet *). The measurements were both: at steady state and at transient operating conditions.

Particulate traps are mechanical devices for trapping soot, ash and mineral particles, to curtail emissions from Diesel engines. The filtration effectiveness of traps can be defined, independent of the pertinent engine, as a function of the particle size, space velocity and operating temperature. This method of assessment lowers cost of certifying traps for large-scale retrofitting projects [1,2]. VERT [3] is a joint project of several European environmental and occupational health agencies. The project established a trap-verification protocol that adapts industrial filtration standards [4] to include the influence of soot burden and trap regeneration phenomena. Moreover, it verifies possible catalytic effects from coating substrates and deposited catalytic active material from engine wear or fuel/ lubricant additives.

1 Small scooters are very much used in the congested centers of the European cities. Even if there is a continuous technical progress, the small two-wheelers are a remarkable source of air pollution. During the research programs of the Swiss Federal Office of Environment Forests and Landscape (FOEFL) - and as a contribution to the European project ARTEMIS *) analysis of limited and nonlimited emissions of scooters was performed. Exhaust emissions measurements of two Scooters: 4-stroke 125 cc and 2-stroke 50 cc have been performed with and without catalyst. Identical driving cycles have been repeated and the influence of the cooling duration on limited the emissions at cold start was investigated. A cold start in the temperature range of 20 - 25 °C can be regarded as a “summer cold start”. As nonlimited emissions the nanoparticulate emissions at cold and warm operating conditions were measured by means of SMPS, ELPI and NanoMet *).

By means of catalysts, either coatings or fuel-borne, the temperature level for triggering the combustion of soot stored in particulate traps can be lowered from 600°C to 300°C, in case of CRT even to 250°C; but even that may fail, if in dense traffic application of a city-bus only 150 - 200°C are attained - similar situations of low load duty cycles exist in most other applications too. Mere passive regeneration may then not be sufficient, active support is needed. This paper presents an “active” method applicable to any Diesel engine to increase the exhaust temperature whenever required: load of Diesel engines is controlled by the fuel flow only; consequently, excess of air above stochiometric requirement is increasing from λ = 1.5 to λ = 8 with decreasing load, which is in fact the principal cause of the low temperature at light loads.

Primary measures, to reduce the NOx emissions from diesel engines, penalize the fuel consumption and aggravate the CO2 problem. Instead, an after-treatment system is proposed that permits optimum combustion and yet reduces the NOx by more than 95%. Such installations are in operation for more than five years. Successful deployment on a short-haul ferry, subject to highly cyclic operation, began in Spring 1992. The chief features are high space-velocity (25,000 1/h), urea as non-toxic reactant and rapid transient response. The attained results counter the misgivings about the SCR catalysis. Development aims at further halving the size thus facilitating service in off-highway vehicles such as locomotives and earth-movers. The integration of particulate traps using knitted micro-fibers is under development.

Ceramic fibers, in a knitted structure, offer an elastic deep-filter medium having a very high specific surface. The robustness of this trap, and its invulnerability to thermo-shock, was demonstrated during a further year of development and tests. By using new manufacturing techniques, the filtration efficiency was further improved, pressure losses reduced, and the required volume diminished. New insight was obtained regarding the employment of the fiber medium for catalysis. The filter concept permits regeneration either electrically or by fuel-additives. The layout versatility facilitates deployment on vehicular and stationary engines, in the pre-turbo position, too.

Metallic substances, usually added to fuel as organic compounds are, as fuel additives proven to curtail particulate emissions from diesel engines and, as fuel borne catalysts (FBC), to promote regeneration of particle traps. During combustion, these substances form catalytic metal oxides and exit the combustion chamber as ultra-fine solid clusters in the mobility diameter range of 5-30 nm. Particles of this size and composition have a health impact and should not enter the respiratory air. FBC should therefore only be used together with particle traps, which can efficiently collect these metal oxide particles at all operating conditions. This and other requirements are stipulated in the VERT suitability tests for particle trap systems. The approval procedure includes a particle size-specific analysis to verify trap penetration in trace quantities.

The development of particulate-traps for big engines is more difficult than for automobile applications. The usual placement, after the turbocharger, necessitates complex solutions to challenges in size, flow distribution and regeneration. The placement of the particulate trap ahead of the turbocharger has technical and financial advantages, and has previously been extensively investigated, but did not prevail because of poor reliability of the monolithic traps. This paper investigates the knitted fiber trap, a mechanically and thermically dependable unit, developed for integration into the engine. A modular design makes the trap very compact. Filtration rate and pressure loss are satisfactory. The filter element has not shown any weakness. A typical deficiency of this application, that needs further investigation, is worsening of the engine's transient response by the thermal inertia of the filter material.

High levels of particulate emissions from Diesel engines, in tunnel construction sites, force the aftertreatment of exhaust gases with particulate traps. Sub-micron particulates are suspected to be carcinogenic. Hence, the size distribution of particulates was compared for different particulate trap systems. The two extreme types are the ceramic monolith surface filter and the typical deep-bed filter of knitted fiber. These two types have distinctly different properties. The gravimetric evaluation of both systems show comparable efficiencies around 90%. If, instead, the particle count is evaluated: the efficiency of the surface filter drops below 70%, whereas that of the deep-bed filter increases. The spectral analysis of distinct solid particulates shows that the efficiency of the surface filter deteriorates for particles smaller than 100 nm. The toxicological consequences are disquieting.

Knitted fiber particulate traps facilitate deep-bed structures. These have excellent filtration properties, particularly for ultra-fine particulates. They are also suitable as substrate for catalytic processes. The two characteristics are: high total surface area of the filaments, and good mass transfer. These are prerequisites for intense catalytic activity. The deposited soot is uniformly distributed. Therefore, temperature peaks are avoided during regeneration. The tested coatings lower the regeneration temperature by about 200°C to burn-off temperatures below 350°C. Further improvements seem attainable. Thus, a purely passive regeneration appears feasible for most applications. The system is autonomous and cost effective. However, in extreme low load situations, e.g. city bus services, the necessary exhaust temperatures are not attained. Hence, burners or electrical heating is necessary for trap regeneration.

There is growing concern about the risk potential of Diesel particulates. This prompted two Swiss R&D projects focused on the capabilities of different soot trap concepts for filtering finest particulates. Eight different filter media, some in numerous variants, were tested on four different Diesel engines. All traps attained their gravimetric target. However, there are noticeable performance differences for finest particulates at or smaller than 50 nm. Fiber deep filters seem to be noticeably better than other filter types. If the carcinogens are mainly the finest particulates, then this criterion may become important in future trap evaluation.

Microfibers with high specific micro-surface can be knitted into two-dimensional structures with large internal porosity. Catalytically active metals can be deposited on the fibers with high dispersion by wet-impregnation, sol-gel or CVD, respectively. These microfiber knits may be used for exhaust gas treatment systems with a triple function: particle filtration, gas conversion and muffling. The total oxidation of propane on Pd and Pt coated fibers has been studied as a test reaction. Conversion temperature could be remarkably reduced compared to cellular structures. For a bimetallic (Pt-Pd) coating, the activity is independent of humidity or oxygen concentration. Thus a catalytic converter based on micro-fiber knits appears feasible. Its high mass and heat transfer prevent hot spots. And it functions as submicron filter for combustion aerosols. Integrated electric heating can also be provided in case of low gas temperatures. First tests on engines show promising results.