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The combined exhaust gas aftertreatment systems (DPF+SCR) are the most efficient way and the best available technology (BAT) to radically reduce the critical Diesel emission components particles (PM&NP) and nitric oxides (NOx). SCR (selective catalytic reduction) is regarded as the most efficient deNOx-system, diesel particle filters are most efficient for soot abatement. Today, several suppliers offer combined systems for retrofitting of HD vehicles. Quality standards for those quite complex systems and especially for retrofit systems are needed to enable decisions of several authorities and to estimate the potentials of improvements of the air quality in highly populated agglomerations. The present paper informs about the VERTdePN *) quality test procedures, which were developed in an international network project with the same name 2007-2011 (VERT … Verification of Emission Reduction Technologies; dePN … decontamination, disposal of PM / NP and of NOx).

Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Like ethanol, butanol can be produced as a biomass-based renewable fuel or from fossil sources. In the research project, DiBut (Diesel and butanol) addition of butanol to Diesel fuel was investigated from the points of view of engine combustion and of influences on exhaust aftertreatment systems and emissions. One investigated engine (E1) was with emission class “EU Stage 3A” for construction machines, another one, engine (E2) was HD Euro VI. The most important findings are: with higher butanol content, there is a lower heat value of the fuel and there is lower torque at full load.

Analysis of non-legislated engine-emission components, with different exhaust-gas after-treatment techniques, is an important air quality objective. This paper reports the results for various nitrogen oxides, ammonia and differentiated hydrocarbons emitted at part load from a small 4-S SI engine. It was operated with gasoline, with CNG and with two different three-way catalytic converters. CNG produces less HC and less aromatics. But the HC conversion rate is insufficient. This is due to the lower exhaust gas temperatures, at part load with CNG, and due to the higher stability of light HCs. CNG affects the λ-regulation window, of the investigated system, such that the NOx conversion rate is lowered. In the rich domain of the λ-regulation window, the NO & NOx emissions after catalyst were lowest, while the NH₃ formation was most intense, and vice versa.

The selective catalytic reduction SCR is extensively used for NOx reduction of recent HD-vehicles. There are some manufacturers and some applications of SCR as retrofit systems (mostly for the low emission zones LEZ and in combination with a DPF). In charge of Swiss authorities AFHB investigated several SCR-systems, or (DPF+SCR)-systems on HD-vehicles and proposed a simplified quality test procedure of those systems. This procedure can especially be useful for the admission of retrofit systems but it can also be helpful for the quality check of OEM-systems. The project name was TeVeNOx - Testing of Vehicles with NOx reduction systems. In the present paper the test procedures will be described and some specific results will be discussed.

Limited and nonlimited emissions of scooters were analysed during several annual research programs of the Swiss Agency of Environment Forests and Landscape (SAEFL, BUWAL)*). Small scooters, which are very much used in the congested centers of several 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 particle emissions of different 2-stroke scooters with direct injection and with carburetor were performed. The nanoparticulate emissions with different lube oils and fuels were measured by means of SMPS, (CPC) and NanoMet *). Also the particle mass emission (PM) was measured with the same method as for Diesel engines. Extensive analyses of PM-residuum for PAH & SOF/INSOF, as well as for VOC were carried out in an international project network.

In the diesel sector the fatty acid methyl esters (FAME's) - in Europe mostly RME (rapeseed methyl ester) and in US mostly SME (soja oil methyl ester) - are used as a various share, % volume blends with the diesel fuel (B5, B7, B10, B20, Bxx). The present joint project focuses on RME being the most important representative of the biofuels of 1st generation in Europe. The influences of RME blend fuels on emissions and on lube oil deterioration are emphasized. Emissions were investigated on a modern engine with exhaust gas aftertreatment devices like SCR and (DPF+ SCR). Beside the legally limited exhaust emission components some non-legislated like NO₂, N₂O, NH₃ and nanoparticles were measured at stationary and dynamic engine operation.

In order to analyze the processes during the gas exchange in the engine, knowledge of pressure states in both inlet and outlet is required. This pressure measuring is known as “low pressure indication”. In the present work, three examples of controlling the quality of low pressure measurement are presented. An insight in the pressure waves in exhaust pipe, especially in the exhaust blow-off is given. It was shown that: a small inaccuracy of measurement, lower than 10 mbar can be attained, the asymmetric course of the exhaust pulse can clearly be verified, and a protection screen for a sensor exposed to the exhaust blow-off pressure wave can be a tool to optimize between longlife and accuracy. The most important statements are: both presented methods of low pressure indication - the direkt and the indirect yield the results with highest accuracy.

The Swiss 1998 Ordinance on Air Pollution Control (OAPC) mandates curtailment of carcinogenic Diesel particle emissions at construction sites [4]. In addition particle traps are compulsory at underground workplaces [3]. In compliance, more than 6,000 Diesel engines were retrofitted with different particle trap systems. Many traps surpassed 99% filtration efficiency, from the beginning, and secondary emissions were mostly prevented. However, trap failure due to mechanical and thermal damage was initially rather high at about 10%. By Y-2000 the failure rate was halved to about 6%. Thanks to focussed improvements, the Y-2003 statistics show yearly failures of “only” about 2%. The Swiss target is to retrofit 15,000 construction machines with traps, fully compliant with environmental directives, having 5,000 operating hours durability and failure rates below 1%. Construction machines have much higher PM-emission factors than trucks, and are operated more intensely than tractors.

Advances in emission control technologies have demanded development of new ceramic chemistries and improved microstructures in catalytic substrates and especially in diesel particulate filters. High porosity filters are desirable, as they decrease engine backpressure and enable application of advanced catalysts including, but not limited to, multi-functional filters (MFF). A significant recent development has been in the use of ceramic fibers to create cross-linked microstructures in extruded honeycomb ceramics. This development allows high porosities to be attained while maintaining mechanical strength. However, according to the World Health Organization, certain classes of ceramic fibers are considered to have adverse health effects if released in air and inhaled.

The progressing exhaust gas legislation for on- and off-road vehicles includes gradually the nanoparticle count limits. The invisible nanoparticles from different emission sources penetrate like a gas into the living organisms and may cause several health hazards. The present paper shows some results of a modern chain saw with & without oxidation catalyst, with Alkylate fuel and with different lube oils. The measurements focused specially on particulate emissions. Particulates were analysed by means of gravimetry (PM) and granulometry SMPS (PN). In this way the reduction potentials with application of the best materials (fuel, lube oil, ox-cat.) were indicated. It has been shown that the particle mass (PM) and the particle numbers (PN), which both consisting almost exclusively of unburned lube-oil, can attain quite high values, but can be influenced by the lube oil quality and can be considerably reduced with an oxidation catalyst.

Further efforts to reduce the air pollution from traffic are undertaken worldwide and the filtration of exhaust gas will also be increasingly applied on gasoline cars (GPF1 … gasoline particle filter). In the present paper, some results of investigations of nanoparticles from four MPI gasoline cars are represented. The measurements were performed at vehicle tailpipe and in CVS-tunnel. Moreover, two variants of GPF were investigated on a high-emitting modern vehicle, including analytics of PAH and attempts of soot loading in road application. The modern MPI vehicles can emit a considerable amount of PN, which in some cases attains the level of Diesel exhaust gas without DPF and can pass over the actual European limit value for GDI (6.0 x 1011 #/km). The GPF-technology offers in this respect further poten-tials to reduce the PN-emissions of traffic.

By the intense inflammation and high combustion rates in the spark ignition engine oscillatory combustion is formed, similarly to the diesel engine. The oscillation is particularly marked in the engines with divided combustion chamber, due to the rapid combustion caused by the turbulence generated in the prechamber nozzles. Oscillatory combustion and knocking are two different phenomena with different causes. It will be tried in this paper to clarify the reasons of formation of pulsating combustion and the parameters which influence it. Also the differences between the oscillatory combustion and knocking in the gasoline engines and the influence of turbulence on knocking will be shown.

A filter system is presented which allows the reduction of the concentration of ultrafine particles in vehicle cabins to very low levels. The original ventilation system is switched to the recirculation mode and all cabin intake air is supplied via a retrofitted filter system. Tests with a variety of different vehicles (from passenger cars to coaches) show the efficiency of the system.

In the present paper some results of investigations of nanoparticles from five DI gasoline cars are represented. The measurements were performed at vehicle tailpipe and in CVS-tunnel. Moreover, five variants of “vehicle - GPF” were investigated. These results originate from the project GasOMeP (Gasoline Organic & Metal Particulates), which focused on metal-nanoparticles (including sub 20nm) from gasoline cars with different engine technologies. The PN-emission level of the investigated GDI cars in WLTC without GPF is in the same range of magnitude very near to the actual limit value of 6.0 × 1012 #/km. With the GPF’s with better filtration quality, it is possible to lower the emissions below the future limit value of 6.0 × 1011 #/km. There is no visible nuclei mode and the ultrafine particle concentrations below 10mm are insignificant. Some of the vehicles show at constant speed operation a periodical fluctuation of the NP-emissions, as an effect of the electronic control.

NO₂ is much more toxic than NO. The average proportion of NO₂ in exhaust gases of vehicles increases significantly due to the use of oxidation catalysts and catalytic coatings in the exhaust gas systems during the last decades combined with generalization of using low sulfur fuels. Diesel oxidation catalysts (DOC) and Pt-containing DPF coatings are widely used to support the regeneration of particle filters, being a source of strongly increased production of NO₂. The present work shows some examples and summarizes the experiences in this matter performed at the Laboratories for IC-Engines & Exhaust Emissions Control (AFHB) of the University of Applied Sciences Biel-Bienne, Switzerland, during some research activities on engine dynamometers in the years 2010-2012.

Concern for engine particle emission led to EC regulations of the number of solid particles emitted by LDV and HDV. However, all conventional piston-driven combustion engines emit metal oxide particles of which only little is known. The main sources are abrasion between piston ring and cylinder, abrasion of bearing, cams and valves, catalyst coatings, metal-organic lubrication oil additives, and fuel additives. While abrasion usually generates particles in the μm range, high concentrations of nanosize metal oxide particles are also observed, probably resulting from nucleation processes during combustion. In general, metal oxides, especially from transition metals, have high surface reactivity and can therefore be very toxic, especially nanosize particles, which evidently provide a high specific bioactive surface and are suspected to penetrate into the organism. Hence, these particles must be scrutinized for quantity, size distribution and composition.

All internal combustion piston engines emit solid nanoparticles. Some are soot particles resulting from incomplete combustion of fuels, or lube oil. Some particles are metal compounds, most probably metal oxides. A major source of metal compound particles is engine abrasion. The lube oil transports these abraded particles into the combustion zone. There they are partially vaporized and ultrafine oxide particles formed through nucleation [1]. Other sources are the metallic additives to the lube oil, metallic additives in the fuel, and debris from the catalytic coatings in the exhaust-gas emission control devices. The formation process results in extremely fine particles, typically smaller than 50 nm. Thus they intrude through the alveolar membranes directly into the human organism. The consequent health risk necessitates a careful investigation of these emissions and effective curtailment.

1 In the present work investigations of a 7.8 liter-TC-IC-IVECO-CNG engine were performed with single point (SPI) *) and with multipoint (MPI) gas injection systems. Three types of MPI injectors available on the market were compared for stationary and transient engine operation. There are several advantages of MPI e.g. better possibility to equalize the air-fuel-ratio of the cylinders, optimization of the gas injection timing and of the gas pressure for different operating conditions. With different injector types there are different optimum injection timings, due to different injection durations, but at the optimum conditions there is little difference in the combustion quality. The injectors with higher flow rate can cause more λ-excursions in the dynamic response and with sudden changes of the gas pressure.

Diesel exhaust gas aftertreatment systems, which include the selective catalytic reduction (SCR)*) for reduction of NOx are necessary to fulfil the latest legal requirements and are extensively used in the heavy duty (HD) sector. The present paper informs about some results obtained with SCR and with SDPF (a DPF with SCR-coating) on a medium duty research engine Iveco F1C. Beside the limited gaseous emission components NH3, NO2 and N2O were measured. The analysis of nanoparticle emissions was performed with SMPS and CPC. The integration of functions of filtration and NOx-reduction in one element of exhaust aftertreatment system offers several advantages and is widely investigated and considered as a market solution.

As a result of increased use of catalytic exhaust aftertreatment systems of vehicles and the low-sulfur Diesel fuels there is an increasing share of nitrogen dioxide NO2 in the ambient air of several cities. This is in spite of lowering the summary nitric oxides NOx emissions from vehicles. NO2 is much more toxic than nitrogen monoxide NO and it will be specially considered in the next legal testing procedures. There are doubts about the accuracy of analyzing the reactive substances from diluted gas and this project has the objective to show how NO2 is changing as it travels down through the exhaust- and the CVS systems. For legal measurements of NO2 a WLTP-DTP subgroup (Worldwide Light Duty Test Procedures - Diesel Test Procedures) proposed different combinations of NOx-analyzers and analysis of NO and NOx. Some of these set-ups were tested in this work.