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Technical Paper

Use of a PPS Sensor in Evaluating the Impact of Fuel Efficiency Improvement Technologies on the Particle Emissions of a Euro 5 Diesel Car

The effect of “Start & Stop” and “Gear Shift Indicator” - two widespread fuel saving technologies - on fuel consumption and particle emissions of a Euro 5 passenger car is evaluated in this paper. The vehicle was subjected to a series of different driving cycles, including the current (NEDC) and future (WLTC) cycles implemented in the European type approval procedure at cold and hot start condition and particle number was measured with an AVL Particle Counter. In addition, we have utilized two Pegasor Particle Sensor units positioned in different locations along the sampling line to assess the impact of the sampling location on the particle characteristics measured during highly transient events. The results showed that the particle number emission levels over the WLTC were comparable to the NEDC ones, whereas NOx emissions were more than twofold higher. Both fuel saving technologies can lead to reduced fuel consumption and, subsequently CO2 emissions, in the order of 5%.
Journal Article

Use of a Catalytic Stripper as an Alternative to the Original PMP Measurement Protocol

The Particle Measurement Programme (PMP) developed an exhaust particle number measurement protocol that has been adopted by current light duty vehicle emission regulations in Europe. This includes thermal treatment of the exhaust aerosol to isolate solid particles only and a number counting device with a lower cutpoint of 23 nm to avoid measurement of smaller particles that may affect the repeatability of the measurement. In this paper, we examine a potential alternative to the PMP system, where the thermal treatment is replaced by a catalytic stripper (CS). This offers oxidation and not just evaporation of the volatile components. Alternative sampling systems, either fulfilling the PMP recommendations or utilizing a CS, have been explored in terms of their volatile particle removal efficiency. Tests have been conducted on diesel exhaust, diesel equipped with DPF and gasoline direct injection emissions.
Technical Paper

Sampling Conditions Effects on Real-Time Particle Measurements from a Light Duty Vehicle

The effect of sampling conditions on the diesel exhaust aerosol characteristics has been studied so far with the application of Electrostatic Classifiers under steady state conditions. This paper aims at examining the same effects with application of an Electrical Low Pressure Impactor under transient engine operating conditions. Explanation of the results obtained takes into account the different operational characteristics of this new technique (recorded magnitude, size range and resolution). The study confirms particle formation in the dilution tunnel and downstream of a DPF and also coagulation of liquid particles in the tunnel. However, separation of the liquid particle phase has led to modification of the aerosol properties in a direction which may be conversely recorded by instruments based on different operation principles.
Technical Paper

Performance Evaluation of a Novel Sampling and Measurement System for Exhaust Particle Characterization

This paper presents a novel partial flow sampling system for the characterization of airborne exhaust particle emissions. The sampled aerosol is first conditioned in a porous dilutor and then subsequent ejector dilutors are used to decrease its concentration to the range of the instrumentation used. First we examine the sensitivity of aerosol properties to boundary sampling conditions. This information is then used to select suitable sampling parameters to distinguish both the nucleation and the accumulation mode. Selecting appropriate sampling parameters, it is demonstrated that a distinct nucleation mode can be formed and measured with different instruments. Using these parameters we examine the performance of the system over transient vehicle operation. Additionally, we performed calculations of particle losses in the various components of the system which are then used to correct signals from the instruments.
Technical Paper

Particle Emissions Characteristics of Different On-Road Vehicles

Due to the stringent emission standards set worldwide, particulate matter (PM) emissions from diesel vehicles have been significantly curtailed in the last decade, and are expected to be reduced even further in the future. This evolution has brought forward two main issues: whether PM emissions should only be regulated for diesel vehicles and whether gasoline powered vehicles can be further neglected from PM emission inventories. This paper addresses these issues comparing the characteristics of particle emissions from a current diesel passenger car, a gasoline one and two small two-wheelers. It is shown that the gasoline car is a negligible source of particle emissions while the two-wheelers may be even more significant particle sources than the diesel car.
Technical Paper

Overview of the European “Particulates” Project on the Characterization of Exhaust Particulate Emissions from Road Vehicles: Results for Heavy Duty Engines

This paper presents an overview of the results on heavy duty engines collected in the “PARTICULATES” project, which aimed at the characterization of exhaust particle emissions from road vehicles. The same exhaust gas sampling and measurement system as employed for the measurements on light duty vehicles [1] was used. Measurements were made in three labs to evaluate a wide range of particulate properties with a range of heavy duty engines and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The sample consisted of 10 engines, ranging from Euro-I to prototype Euro-V technologies. The same core diesel fuels were used as in the light duty programme, mainly differentiated with respect to their sulphur content. Additional fuels were tested by some partners to extend the knowledge base.
Technical Paper

Overview of the European “Particulates” Project on the Characterization of Exhaust Particulate Emissions From Road Vehicles: Results for Light-Duty Vehicles

This paper presents an overview of the results on light duty vehicles collected in the “PARTICULATES” project which aimed at the characterization of exhaust particle emissions from road vehicles. A novel measurement protocol, developed to promote the production of nucleation mode particles over transient cycles, has been successfully employed in several labs to evaluate a wide range of particulate properties with a range of light duty vehicles and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The vehicle sample consisted of 22 cars, including conventional diesels, particle filter equipped diesels, port fuel injected and direct injection spark ignition cars. Four diesel and three gasoline fuels were used, mainly differentiated with respect to their sulfur content which was ranging from 300 to below 10 mg/kg.
Technical Paper

Modeling the Interactions Of Soot and SCR Reactions in Advanced DPF Technologies with Non-homogeneous Wall Structure

The pressure for compact and efficient deNO systems has led to increased interest of incorporating SCR coatings in the DPF walls. This technology could be very attractive especially if high amounts of washcoat loadings could be impregnated in the DPF porous walls, which is only possible with high porosity filters. To counterbalance the filtration and backpressure drawbacks from such high porosity applications, the layered wall technology has already been proposed towards minimizing soot penetration in the wall and maximizing filtration efficiency. In order to deal with the understanding of the complex interactions in such advanced systems and assist their design optimization, this paper presents an advanced modeling framework and selected results from simulation studies trying to illustrate the governing phenomena affecting deNO performance and passive DPF regeneration in the above combined systems.
Journal Article

Impact of FAME Content on the Regeneration Frequency of Diesel Particulate Filters (DPFs)

Modern diesel vehicles utilize two technologies, one fuel based and one hardware based, that have been motivated by recent European legislation: diesel fuel blends containing Fatty Acid Methyl Esters (FAME) and Diesel Particulate Filters (DPF). Oxygenates, like FAME, are known to reduce PM formation in the combustion chamber and reduce the amount of soot that must be filtered from the engine exhaust by the DPF. This effect is also expected to lengthen the time between DPF regenerations and reduce the fuel consumption penalty that is associated with soot loading and regeneration. This study investigated the effect of FAME content, up to 50% v/v (B50), in diesel fuel on the DPF regeneration frequency by repeatedly running a Euro 5 multi-cylinder bench engine over the European regulatory cycle (NEDC) until a specified soot loading limit had been reached.
Technical Paper

Experimental Investigation of Cyclic Variability on Combustion and Emissions of a High-Speed SI Engine

Cyclic combustion variability (CCV) is an undesirable characteristic of spark ignition (SI) engines, and originates from variations in gas motion and turbulence, as well as from differences in mixture composition and homogeneity in each cycle. In this work, the cycle to cycle variability on combustion and emissions is experimentally investigated on a high-speed, port fuel injected, spark ignition engine. Fast response analyzers were placed at the exhaust manifold, directly downstream of the exhaust valve of one cylinder, for the determination of the cycle-resolved carbon monoxide (CO) and nitric oxide (NO) emissions. A piezoelectric transducer, integrated in the spark-plug, was also used for cylinder pressure measurement. The impact of engine operating parameters, namely engine speed, load, equivalence ratio and ignition timing on combustion and emissions variability, was evaluated.
Technical Paper

Experimental Evaluation of the Fuel Consumption and Emissions Reduction Potential of Low Viscosity Lubricants

Reducing fuel consumption and emissions from road transport is a key factor for tackling global warming, promoting energy security and sustaining a clean environment. Several technical measures have been proposed in this aspect amongst which the application of low viscosity engine lubricants. Low viscosity lubricants are considered to be an interesting option for reducing fuel consumption (and CO2 emissions) throughout the fleet in a relatively cost effective way. However limited data are available regarding their actual “real-world” performance with respect to CO2 and other pollutant emissions. This study attempts to address the issue and to provide experimental data regarding the benefit of low viscosity lubricants on fuel consumption and CO2 emissions over both the type-approval and more realistic driving cycles.
Technical Paper

Effect of a DPF and Low Sulfur Lube Oil on PM Physicochemical Characteristics from a Euro 4 Light Duty Diesel Vehicle

This paper studies the effect of a Catalyzed Diesel Particle Filter (CDPF) on the emission profile of a Euro 4 diesel vehicle operated on low sulfur fuel and lubrication oil. The vehicle was tested in its original configuration and with the CDPF retrofitted in place of its main underbody catalyst. Experiments included steady state tests, the certification cycle and real-world high speed transient driving conditions. Measurements included total particle mass collected on Teflon-coated filters, total particle number measured by a condensation particle counter, size distributions determined by a Scanning Mobility Particle Sizer and chemical analysis of the mass collected for elemental and organic carbon, ions, PAHs, and trace elements. Results showed that the vehicle complies with the Euro 4 emission limits when tested over the type-approval NEDC, but it emits more nitrogen oxides and, in some cases, more particulate matter when tested over real-world test cycles.
Technical Paper

Effect of Speed and Speed-Transition on the Formation of Nucleation Mode Particles from a Light Duty Diesel Vehicle

This work studies the formation of nucleation mode (NM) particles from a Euro 3 passenger car operating on 280 ppm wt. sulfur fuel, during on-road plume chasing and in the laboratory. The vehicle produced a distinct NM when its speed exceeded 100 km/h in both sampling environments. A higher particle number (up to 8 times) after 4 min at constant speed was measured when this speed was approached from a lower than from a higher speed. The variability in the measurement of NM particles was explained using literature information on sulfur-to-sulfate conversion over a catalyst and, in particular, on the extent and rate of sulfate storage and release mechanisms. All evidence led to the conclusion that storage and release processes take several minutes to conclude after a step-wise change in speed and have significant implications in the total particle number measurements during steady-speed testing.
Technical Paper

Effect of Lube Oil on the Physicochemical Characteristics of Particulate Matter Emitted from a Euro 4 Light Duty Diesel Vehicle

This paper investigates the effect of lubrication oil on the physical and chemical characteristics of the particulate matter (PM) emitted from a Euro 4 diesel vehicle. Two different lubrication oils were examined. A fully synthetic ACEA grade B3 service-fill oil of low sulfur content (1760 ppm wt.) falling into the OW-40 SAE viscosity grade and a mineral ACEA B2-98 motor oil of high sulfur (8890 ppm wt.), falling into the 15W-40 SAE viscosity grade. To exclude interferences from the fuel derived sulfur, a rather sulfur-free fuel (< 10 ppm wt.) was used in the experiments. The experiments included steady state tests, the certification cycle and real-world highspeed transient driving conditions. The properties measured included total particle mass collected on Teflon-coated filters, total particle number measured by a condensation particle counter, size distributions determined by a scanning mobility particle sizer.
Technical Paper

Diesel Particle Exhaust Emissions from Light Duty Vehiclesand Heavy Duty Engines

Diesel engines are widespread in both passenger car and heavy duty truck applications. However, despite that the combustion concepts are similar in the two cases, the engine calibration required for compliance with the different emission standards leads to distinct particle emission behavior from the two categories. This paper compares the exhaust particle emissions from heavy duty engines with typical diesel passenger cars of similar emission standard and/or emission control technology. Measurements were conducted with the same sampling system and sampling protocol to avoid interferences induced by the sampling methodology. A range of particle properties were studied, including mass, number of solid and total particles and total particle surface. For comparability, the results are expressed per unit of exhaust volume, per unit of fuel consumed and per unit of distance driven.
Technical Paper

Comparative Assessment of Two Different Sampling Systems for Particle Emission Type-Approval Measurements

The Particle Measurement Programme (PMP), initiated from different Member States, aims at developing a method and sampling recommendations for a particle number-based emission standard, to support future emission regulation in Europe. In this paper we applied two different commercially available dilution systems (an FPS from Dekati Ltd and an MD19-2E from Matter Engineering AG) to record the particle emissions of a Euro II and a Euro III diesel passenger car. The latter was also fitted with a diesel particle filter (DPF) to simulate future emission levels. At their present development stage, both dilution systems failed to totally comply with all requirements of the PMP protocol. The main problems appeared to be the lack of accurate determination of the dilution ratio and the inability to reach the desired dilution temperature.
Journal Article

Application of the Pegasor Particle Sensor for the Measurement of Mass and Particle Number Emissions

The Pegasor Particle Sensor (PPS) is a small and lightweight sensor that can be used directly in raw exhaust to provide the mass and number concentration of exhaust aerosol. Its operation principle is based on the electrical charging of exhaust aerosol and determination of particle concentration by measuring the charge accumulated on the particles. In this paper we have applied the PPS in a variety of vehicle exhaust configurations to evaluate its performance characteristics. First, the output signal of the instrument was calibrated with diesel exhaust to deliver either the mass or the number concentration of exhaust aerosol. Linear response with the soot mass concentration measured by a Photo Acoustic Soot Sensor and number concentration measured by an Electrical Low Pressure Impactor was established.
Technical Paper

Applicability of the Pegasor Particle Sensor to Measure Particle Number, Mass and PM Emissions

The Pegasor Particle Sensor (PPS) has been earlier presented by Ntziachristos et al. (SAE Paper 2011-01-0626) as a novel small and robust instrument that can be directly installed in the exhaust line to measure exhaust particles without any dilution. The instrument is based on the electrical detection of aerosol. It is increasingly being used to measure exhaust particles from engines and vehicles with different exhaust configurations. In this study, a number of tests have been conducted using two sensors in parallel, one directly installed in the tailpipe and one installed in the CVS, side by side to the PM sampling filter. Aim of the study was to make recommendations on the proper use of the sensor and to check how the sensor signal compares to particulate mass, soot concentration, and particle number. A first finding is that external heating has to be provided to the sensor to avoid condensation.
Journal Article

A New Constant Dilution Ratio Concept for Vehicle and Engine Exhaust Particle Sampling

This paper presents a new concept of a partial flow sampling system (PFSS), involving a two-stage dilutor which operates at underpressure, while exhaust is sampled through a capillary. The sample flowrate is in the order of few cubic centimeters per minute. Due to the low flowrate, no tight fixation is required between the exhaust line and the capillary inlet. The dilutor may sample from an opening in the exhaust line which freely exhausts to ambient pressure. As a result, the PFSS operates at constant pressure conditions even upstream of diesel particle filters (DPF). A straightforward mathematical model is then developed to calculate the dilution ratio (DR), depending on the dilution air flowrate and the dilutor underpressure. The model is validated using CO2 as a trace gas, and a very good agreement is demonstrated between the calculated and the measured DR values.