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In this article we present a design of a new miniaturized sensor with the capacity to measure exhaust particle concentrations on board vehicles and engines. The sensor is characterized by ultra-fast response time, high sensitivity, and a wide dynamic range. In addition, the physical dimensions of the sensor enable its placement along the exhaust line. The concentration response and temporal performance of a prototype sensor are discussed and characterized with aerosol laboratory test measurements. The sensor performance was also tested with actual engine exhaust in both chassis and engine dynamometer measurements. These measurements demonstrate that the sensor has the potential to meet and even exceed any requirements around the world in terms of on-board diagnostic (OBD) sensitivity and frequency of monitoring.

During the past few decades the exhaust emissions of diesel engines have significantly decreased due to efficient emissions regulation. Compared to the situation in the 1990s, the nitrogen oxide (NOx) and particulate matter (PM) emissions, the main challenges for diesel engines, are now reduced 80-95 % in many industrialized countries. To meet the demanding requirements, engine technologies have been updated and improved step by step. These improvements have also kept Specific Fuel Consumption (SFC) figures at a low level or they have even improved. The latter issue is of great significance for consumers (cost) and also for the environment (CO2). Nowadays many diesel engine fuel injection strategies rely on the use of exhaust after-treatment systems. Efficient and clean combustion is obtained by utilizing high injection pressure and advanced injection timing.

Particle emissions have been generally associated to diesel engines. However, spark-ignition direct injection (SI-DI) engines have been observed to produce notable amounts of particulate matter as well. The upcoming Euro 6 legislation for passenger cars (effective in 2014, stricter limit in 2017) will further limit the particulate emissions from SI engines by introducing a particle number emission (PN) limit, and it is not probable that the SI-DI engines are able to meet this limit without resorting to additional aftertreatment systems. In this study, the solid particle emissions of a SI-DI passenger car with and without an installed Particle Oxidation Catalyst (POC®) were studied over the New European Driving Cycle (NEDC) on a chassis dynamometer and over real transient acceleration situations on road. It was observed that a considerable portion of particle number emissions occurred during the transient acceleration phases of the cycle.

The effect of SCR on nanoparticle emissions has been a subject for some recent diesel particle emission related studies. In this study, the effect of after-treatment (DOC and SCR) on particle emissions was studied with a heavy-duty off-road diesel engine (emission level stage 3b with an SCR). A special “transient cold test cycle” (TCTC) was designed to describe the SCR system operation at low exhaust gas temperatures. The particle instrumentation made it possible to measure on-line the particle number concentration, particle size distribution and chemical composition of particles. The largest particle number concentrations were measured after the exhaust manifold. The exhaust after-treatment was observed to reduce the total particle number concentration by 82.5% with the DOC and 95.7% with the DOC+SCR.

The aim of this paper is to analyze the quantitative impact of fuel sulfur content on particulate oxidation catalyst (POC) functionality, focusing on soot emission reduction and the ability to regenerate. Studies were conducted on fuels containing three different levels of sulfur, covering the range of 6 to 340 parts per million, for a light-duty application. The data presented in this paper provide further insights into the specific issues associated with usage of a POC with fuels of higher sulfur content. A 48-hour loading phase was performed for each fuel, during which filter smoke number, temperature and back-pressure were all observed to vary depending on the fuel sulfur level. The Fuel Sulfur Content (FSC) affected also soot particle size distributions (particle number and size) so that with FSC 6 ppm the soot particle concentration was lower than with FSC 65 and 340, both upstream and downstream of the POC.

Under on-road driving conditions, the engine load and speed and the cooling effect of ambient air may affect the functioning of exhaust aftertreatment devices. In this paper, we studied the effects of these parameters on the functioning of the combination of a Diesel Oxidation Catalyst and a Particle Oxidation Catalyst (DOC+POC). In the engine tests, the engine load and speed were observed to affect the nonvolatile particle reduction efficiency curve of the DOC+POC; while the nonvolatile core particle (Dp ≺ 15 nm) reduction was high (97-99%) in all the engine test modes, the reduction of soot varied from 57% at low load to 70% at high load. Because the change in engine load and speed affected both the exhaust temperature and flow velocity, the effects of these parameters were measured separately in an aerosol laboratory.

State-of-art light duty diesel vehicles and heavy duty diesel engines are utilized in studying the effect of a novel particle oxidation catalyst (POC®) on particle emission. In addition to the regulated particulate matter (PM) emission measurement, a real time mass emission and particle number size distribution measurements are utilized in testing. The results show that the particle oxidation catalyst can have a significant decreasing effect on the diesel exhaust particle emissions. For example, in light duty applications PM reductions of 55-61% were achieved over the New European Driving Cycle (NEDC) when using a POC of same size as the engine volume. The usage of a DOC in combination with the POC ensures proper regeneration of the POC substrate. The size distribution measurements revealed that the particle number collection efficiency for smaller particles i.e. the nanoparticles was very high, being close to 100 %.