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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.

The Diffusion Size Classifier (DiSC) is a new instrument to measure number concentration and average diameter of nanometer sized particles in the size range 10 - 200nm. It is small, easily portable and battery operated and therefore well suited for field measurements. The measurement range is suitable for ambient air concentrations (1000 - 500000 particles/cm3); together with a diluter it can be used for emission measurements. The number concentrations measured with DiSC agree well with those measured with a condensation particle counter. The response time is short enough to measure transient engine operation. The DiSC is therefore a useful instrument for number concentration measurements in non-laboratory settings.

The UN-ECE Particle Measurement Programme (PMP) has considerably gained momentum since the European Commission published the regulation details of Euro 5/6 for light duty vehicles, including a limit value for the number of particles emitted from passenger car tailpipes, to be enforced as early as Euro 5. A PMP-compliant particle number counting system retrieves its exhaust gas sample from a CVS tunnel and consists of two dilution stages before and after an evaporation tube, and a condensation particle counter. For each of these systems, compliance with the PMP guidelines has to be proved in terms of measurement performance. A required key property is the system's ability to evaporate liquid and volatile exhaust gas components, while properly transmitting solid particles to the number counter. Particle Number Count is able to distinguish between different filling states of a DPF as well as between DPF substrates with different porosity.

A modern HD-Diesel engine for construction machines, Liebherr D 934L (120kW) was set-up for a monofuel operation with crude, cold pressed rapeseed oil (ROR)*). The engine was equipped with a supplementary fuel filtration, supplementary engine & fuel heating for cold start and an appropriate fuel temperature control for the engine operation. A special lube oil was applied. After an extensive basic research of emissions including nanoparticles and energy consumption some adaptations of engine setting were performed: modification of the camshaft to eliminate the internal EGR (same valve timing and lift), earlier start of injection (SOI) at high- and full load, application of a combined exhaust gas aftertreatment system DPF+SCR, testing of DPF+SCR according to the VERT quality verification procedure.

The “Reproducible Exhaust Simulator” (REXS) is a new combustion soot generator, based on the principle of a laminar diffusion flame. Soot is extracted from the stabilized flame by rapid cooling with dilution air. Due to its combustion origin, REXS soot is very similar to Diesel soot in terms of particle morphology, chemistry and size distribution, while its stability is far better than that of a Diesel engine. The soot generator can be operated against rising backpressure from a loading filter. A case study for the quality control of filter elements from mass production is presented. REXS soot is fed into filter samples, and their filtration characteristics are assesses using established nanoparticle measuring techniques. Filtration efficiency of 3 samples exceeded 99.99%, but decreased to some 99.5% for a short time after regeneration events. Leaks in the filter substrate, simulated by boring holes of 0.7 mm2 each into some end plugs, increased particle penetration 100-400 fold.

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.

Decreased particle concentrations in vehicle exhaust due to the use of particulate traps pose new challenges to particle measurement methods in terms of sensitivity and repeatability. In the present paper nanoparticle measurement methods are compared to gravimetric and coulometric analysis of filter samples from CVS sampling with special attention to the consequences for the measurement of DPF efficiency. Repeatability and sensitivity of the methods are assessed, and the influence of dilution and sampling is investigated. It is shown that the repeatability of nanoparticle measurement methods is of the same order as that of PM measurement. In terms of sensitivity, nanoparticle methods are by three orders of magnitude better than today's PM and EC measurement. This provides a much better signal-to-noise ratio, especially when particle emissions are very low.

The increasing use of diesel particulate filters (DPF) as the most effective exhaust after-treatment method to reduce particle emissions from internal combustion engines emphasises the need for new particle measurement methods beyond gravimetric. Following a guideline of the Swiss EPA to extend particle measurement to particle size, number concentration and surface concentration, a group of European countries, joined by Japan, have initiated a large-scale investigation of particle metric and measurement methods, the “Particulate Measurement Programme” (PMP). Under the auspices of the UNECE Group of Experts on Pollution and Energy (GRPE), PMP aims at finding a particle metric that is more sensitive to the toxicologically relevant sub-micron particles and that is to supplement, or even replace, gravimetric as future certification standard for particle emissions.

Decreased particle concentration due to the use of particulate traps poses new challenges to particle measurement methods in terms of sensitivity and repeatability. In the present paper nanoparticle measurement methods are compared to gravimetric and Coulmetric analysis of filter samples from CVS sampling. Repeatability and sensitivity of the methods are assessed, and the influence of dilution and sampling is investigated. It is shown that the repeatability of nanoparticle measurement methods is of the same order as that of PM measurement. In terms of sensitivity, nanoparticle methods are by three orders of magnitude better than today's PM and EC measurement. This provides a much better signal-to-noise ratio, especially when particle emissions are very low. While a gravimetric “zero” measurement may still contain a lot of nanoparticles, a “zero” with a nanoparticle method is by a factor 1000 closer to particle free air.

Swiss EPA and European occupational health authorities have sponsored the development of a new sampling and measuring system designed to fulfil future requirements of differentiated particle analysis in field use and for certification purposes. The system suppresses the formation of condensates by applying hot dilution. Solid carbonaceous particles are distinguished from ash particles by means of two different sensors. Particles are size classified by their mobility; their active surface is measured. The measurable size ranges from less than 10 nm to 1 micrometer. The detection limit corresponds to a mass concentration of elemental carbon (EC) of about 0.1 μg/m3. The time resolution of 1 second is suitable for on-line analysis of particulate emission during all types of transient cycles, even no-load acceleration. The system includes a compact diluter with tunable dilution factor from 30 to 3000.

NanoMet is a new technique for on-line characterization of nanoparticle size and composition and their diffusion behavior. NanoMet consists of a pocket size diluter with tunable dilution ratio, a sampling interface for high concentration measurements and two on-line sensors. Simultaneous operation of the two sensors yields both the active surface (corona discharge diffusion charging sensor, DC) and the active surface times material coefficient (photoelectric aerosol sensor, PAS). Division of the readings provides the material coefficient which turns out to be characteristic of the particle source. Thus, information on source and toxicity of the aerosol is obtained. Thanks to the diluter and the sensitivity of the sensors the measurable concentration range stretches from (vehicle) raw emissions to ambient air / occupational exposure measurements. A particle sizing unit with a diffusion battery and a centrifuge is under development. NanoMet measures particles in-situ, i.e. as aerosol.