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1

Nanoparticles characterisation at the spark ignition engine exhaust

Merola S. S., Tornatore C., Vaglieco B. M.

Journal of KONES

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2008

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Vol. 15, No. 3

347-355

EN

The particles at the exhaust of two Port Fuel Injection Spark Ignition (PFI-SI) engines were characterised in terms of number size distribution and chemical properties. Optical techniques based on the Laser Induced Incandescence (LII) and on the Broadband Ultraviolet - Visible Extinction and Scattering Spectroscopy (BUVESS) were applied. The optical results were compared with those obtained by Electrical Low Pressure Impactor (ELPI). The aim of the work was the characterisation of the nanoparticles emitted by Port Fuel Injection Spark Ignition (PFI - SI) engines in terms of number size distribution and chemical-physical properties. Two PFI - SI engines were used for the experiments: a four-cylinder engine and a research optically accessible single cylinder engine. The experiments were performed at the exhaust of a multi-cylinder SI engine equipped with a three way catalyst (TWC) and in the combustion chamber and at the exhaust of a single-cylinder optical engine. High number concentrations of nanoparticles (D less than 50 nm) were detected. The presence of carbonaceous particles at the exhausts was due to the ignition of the fuel film deposits on the intake valves and on the cylinder walls. This was demonstrated by the optical measurements performed in the combustion chamber of the research engine. Different engine operating conditions were considered.

2

Effect of the fuel injection splitting on the combustion process in a PFI boosted spark-ignition engine

Merola S. S., Sementa P., Tornatore C., Vaglieco B. M.

Journal of KONES

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2008

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Vol. 15, No. 4

331-339

EN

Future stringent legislation on emissions in combination with the market request of an increase in engine efficiency and optimization poses a great challenge to the engine and components manufacturers. The technologies developed in the last years for Spark Ignition (SI) engines such as turbocharging and variable valve actuation are not able to totally satisfy the future normative. More progress still has to be made in terms of in-cylinder combustion process and efficiency. The aim of this paper is the optimisation of a boosted SI engine in terms of performances, fuel consumption and pollutants emissions with low costs. The experimental activity was carried out on a port fuel injection SI optical engine, equipped with a commercial four-valve head. Innovative injection strategies were tested: in particular, single and double injections were performed when the intake valves were open. Optical techniques based on 2D-digital imaging were used to follow the fuel injection in the intake manifold and simultaneously the flame propagation in the combustion chamber. Conventional measurements of engine parameters and exhaust emissions completed the experimental investigations. The tests demonstrated that the double injection strategies were characterized by higher combustion process efficiency than single injection on. The injection splitting resulted a suitable solution for the reduction in pollutants concentration in the combustion chamber and at the exhaust with a good compromise between performance and fuel consumption.

3

Effect of the fuel injection pressure on the combustion process in a PFI boosted spark-ignition engine

Merola S. S., Sementa P., Tornatore C., Vaglieco B. M.

Journal of KONES

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2008

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Vol. 15, No. 4

341-349

EN

In this paper, low-cost solutions were proposed to reduce the fuel consumption in a boosted port fuel injection spark ignition (PFI SI) engine, taking into account the engine performances and the pollutants emission. To this purpose, the optical characterization of the fuel injection and of the combustion process was carried out in a PFI SI engine. The experiments were performed on a partially transparent single-cylinder SI engine, equipped with a four-valve head and an external boost device. The intake manifold was optically accessible through three holes that allowed the introduction of an endoscope and of optical fibres. The standard injection condition planned by the engine manufacturer was investigated; it consisted in the fuel injection at 3.5 bar when the intake valves were closed. Moreover, the fuel injection with open intake valves was tested; 3.5 and 6.5 bar fuel pressures were studied for open and closed valves conditions. Optical techniques based on 2D-digital imaging were used to follow the fuel injection spray in the intake manifold and the flame propagation in the combustion chamber. The results of in-cylinder optical investigations were correlated with the engine performances and with the exhaust emissions.

4

Effect of EGR on nanoprticles at Common-rail diesel engines exhaust

Merola S. S., Tornatore C., Vaglieco B. M.

Silniki Spalinowe

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2007

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R. 46, nr SC3

206-217

EN

In the last years, diesel emission control strategies based on engine design and after-treatment devices, have been very successful in the reduction of the total particulate mass and gaseous emissions. Nevertheless they have been significantly less effective in reducing the total number of particles. Thus, when EURO 5 will be introduced, it will be difficult to meet the emission standards with the present technologies. Nowadays diesel engines are equipped with the Exhaust Gas Recirculation (EGR) system that allows the reduction of thermal-Nitrogen Oxides but it could also influence particles emissions. For this reason, the aim of the present work is to evaluate the effect of EGR on the balance between the primary particles and the aggregates at the exhaust of diesel engines. The idea is to find out a relation between EGR percentage and the size of the emitted particles for every speed and load. Two different methodologies for detection, sizing and counting nanoparticles were used. Electrical Low Pressure Impactor (ELPI) measured the particle size distributions in the range 7 nm-10 μm, without distinction between primary particles and aggregates. Laser Induced Incandescence (LII) allowed to determine soot primary particles diameter. ELPI measurements pointed out the increasing of number concentration and size of particles with the EGR. The size distributions showed a maximum in the range of 54-91nm with negligible number of particles larger than 300 nm. For alt the conditions, an increase of number concentration of particles bigger than 54 nm and a reduction of smaller ones was measured. This was due to the agglomeration effect caused by the reintroduction of particles contained in the exhaust gases into the cylinder during the EGR. LII measurements showed that at fixed engine speed and for alt EGR values, the diameters of primary particles increased with engine load. Moreover smaller primary particles were formed at higher speed. With respect to EGR variation, for every condition the primary particles diameters increased due to the partial oxidation of soot recirculated in the combustion chamber ad the successive superficial growth. Taking into account the proposed results, for each engine operating condition, the best EGR value could be chosen taking into account the size distribution of the produced particles and not only the NOx-soot trade-off.

5

Effect of fuel film deposition on combustion process in PFI SI engine

Merola S. S., Sementa P., Tornatore C., Vaglieco B. M.

Journal of KONES

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2007

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Vol. 14, No. 3

395-402

EN

The present paper discusses the experimental investigations on the flame induced by fuel film deposition ignition in a single cylinder, ported fuel injection, four-stroke, over-boosted spark-ignition engine with a four-valve production head. The engine was optically accessible and equipped with a transparent quartz window in the bottom of the combustion chamber. 2D-digital imaging and UV-visible natural emission spectroscopy were used to follow the flame propagation in the combustion chamber. Two colour pyrometers were applied to evaluate flame temperature and soot concentration. Particulate matter and soot primary particles diameters were measured and correlated with the soot amount produced in the combustion chamber. The effect of the intake air pressure and injection phasing was investigated. Optical setup for spectroscopic measurements and visible digital imaging, visible flame emission detected in the chamber for the selected operating conditions, visible emission spectra measured at 60 CAD ASOS in the chamber, soot concentration measured at the selected operating conditions, integral soot concentration measured at the selected operating conditions, particulate mass concentration measured by the Opacimeter and particles number concentration measured by LII at the engine exhaust are presented in the paper.