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Technical Paper

Nanometric Particle Formation in Optically Accessible Engine Diesel

2001-03-05
2001-01-1258
In the last years, there has been an increasing concern on the emission of ultrafine particles in the atmosphere. A detailed study of formation and oxidation of these particles in the environment of the diesel cylinder presents many experimental difficulties due to the high temperatures, pressures and extremely reactive intermediate species. In this paper, in order to follow the different phases of diesel combustion process, high temporal and spatial resolution optical techniques were applied in the optically accessible chamber of diesel engine, at 2000 rpm and A/F=80:1 and 60:1. Simultaneous extinction, scattering and flame chemiluminescence measurements from UV to visible were carried out, in order to study the diesel combustion process from the droplet ignition to the formation of soot, through the growth of its precursors.
Technical Paper

The Role of Radical Species in Diesel Engine Auto-Ignition Detection

2001-03-05
2001-01-1003
Ignition delay in diesel engine combustion comprehends both a chemical and a physical amount, the first depending on fuel composition and charge temperature and pressure, the last resulting of time needed for the fuel to atomize, vaporize and mix with air. Control of this parameter, which is mandatory to weight the relative amount of premixed to diffusive stage of the hydrocarbon combustion, is here considered. Experimental measurements of flame intensity spectra obtained by in situ measurements on an optically accessible test device show the presence of peaks corresponding to radicals as OH and CH appearing at the pressure start of combustion. Since OH radicals result from chain branching reactions, a numerical simulation is performed based on a reduced kinetic scheme which allows to measure the branching agent concentration, and whose approximate nature is adequate to the proportion chemical aspects contribute to the overall delay.
Technical Paper

Cycle Resolved Measurements of Diesel Particulate by Optical Techniques

1994-10-01
941948
The capabilities of the spectral extinction and scattering technique to follow the time history of the particulate concentration in the exhaust of a Diesel engine were evaluated. Simultaneous measurements of extinction and scattering coefficients from UV to visible were performed at 1.5 m downstream the exhaust valve. The measurements were triggered with the exhaust valve lift. The exhaust stroke was divided in three time windows of 1 ms in which the optical signals of 100 consecutive cycles were detected. The mean diameter, the concentration and the properties of soot particles were evaluated. The cyclic variation of measurements was also estimated.
Technical Paper

A Study of Physical and Chemical Delay in a High Swirl Diesel System via Multiwavelength Extinction Measurements

1998-02-23
980502
The characterization of a turbulent diesel spray combustion process has been carried out in a divided chamber diesel system with optical accesses. Laser Doppler Anemometry, spectral extinction and flame intensity measurements have been performed from U.V., to visible from the start of injection to the end of combustion, at fixed air/fuel ratio and different engine speeds. Spatial distribution of fuel and vapor as well as the ignition location and soot distribution have been derived in order to study the mechanism of the air-fuel interaction and the combustion process. The analysis of results has shown that the high swirling motion transports the fuel towards the left part of the chamber and breaks up the jet into small droplets of different sizes and accelerates the fuel vaporization. Then, chemical and physical overlapped phases were observed during the ignition delay, contributing both to autoignition.
Technical Paper

Evaluation of the Effects of a New Combustion System and Catalyst on Engine Emissions

1990-10-01
902083
The present paper reports the results of an experimental investigation carried out on a four-stroke single- cylinder D.I. diesel engine (100 x 95mm bore x stroke) with the aim to evaluate the effects of a four-lobe square combustion chamber on the gaseous and particulate emissions. Fluid-dynamic behaviour of the axisymmetric toroidal and four-lobe square chambers was investigated by Laser Doppler Anemometry. Engine tests at 2000 and 3000 rpm for different start of combustion (SOC) and A/F ratio are reported. Particulate, HC and NOx emission index measured under different operating conditions are given. In addition, the volatile content of the particulates produced from the two chambers at various engine operative conditions was measured by thermogravimetric analysis (TGA). Finally, the catalytic activity of a metal-oxide-based catalyst in the combustion of particulate was also evaluated by TGA.
Technical Paper

Optical Characterization of the Combustion Process in a 4- Stroke Engine for 2-Wheel Vehicle.

2009-09-13
2009-24-0055
The match among the increasing performance demands and the stringent requirements of emissions and the fuel consumption reduction needs a strong evolution in the two-wheel vehicle technology. In particular, many steps forward should be taken for the optimization of modern small motorcycles and scooters at low engine speeds and high loads. To this aim, detailed understanding of thermo-fluid dynamic phenomena that occur in the combustion chamber is fundamental. In this work, low-cost solutions are proposed to optimize ported fuel injection spark ignition (PFI SI) engines for two-wheel vehicles. The solutions are based on the change of phasing and on the splitting of the fuel injection in the intake manifold. The experimental activities were carried out in the combustion chamber of a single-cylinder 4-stroke optical engine fuelled with European commercial gasoline. The engine was equipped with a four-valve head of a commercial scooter engine.
Technical Paper

Soot Particle Size Distribution~A Joint Work for Kinetic Modelling and Experimental Investigations

2005-09-11
2005-24-053
The intention of the presented work was to develop a new simulation tool that fits into a CFD (computational fluid dynamics) workflow and provides information about the soot particle size distribution. Additionally it was necessary to improve and use state-of-the-art measurement techniques in order to be able to gain more knowledge about the behavior of the soot particles and to validate the achieved simulation results. The work has been done as a joint research financed by the European Community under FP5.
Technical Paper

Diesel Exhaust Nanoparticles Characterization by Multiwavelength Techniques, Laser Induced Incandescence and ELPI

2005-09-11
2005-24-021
Two different optical techniques for detection, sizing and counting nanoparticles were applied to undiluted exhaust from 16 v–1900 cc Common Rail diesel engine upstream and downstream a Catalyzed Diesel Particulate Filter (CDPF): Broadband Ultraviolet–Visible Extinction and Scattering Spectroscopy (BUVESS) and Laser Induced Incandescence (LII). They are powerful “in situ” and non-intrusive techniques; they are able to measure mass concentration and size of particles, considering their chemical properties. BUVESS overcomes the intrinsic limitations of single wavelength techniques because it takes advantage of data at several wavelengths to retrieve primary particle size distribution. LII measures mean size of primary particles with a large dynamic range, not limited by aggregate size and by complex retrieving procedure.
Technical Paper

Soot Concentration and Particle Size in a DI CR Diesel Engine by Broadband Scattering and Extinction Measurements

2005-09-11
2005-24-013
Actual emission legislation limits strongly the amount of pollutant in the atmosphere from internal combustion engine. In particular diesel engines widely emit NOx and particulate matter (PM). The last one has principally a carbonaceous nature and presents micronic and submicronic particles extremely dangerous for human health since it could deposit in the lung. In this work, a technique based on broadband ultraviolet (UV) visible scattering and extinction is applied inside a transparent DI CR diesel engine in order to analyze the soot evolution and oxidation. The study is carried out with particular detail for different injection strategies characterized of two and three injections per cycle, Pre+Main and Pre+Main+Post, considering the late combustion before the exhaust stroke. The analysis is performed in terms of size, mass concentration, and chemical and physical nature.
Technical Paper

Nanoparticles Characterization at Spark Ignition Engine Exhaust

2005-09-11
2005-24-010
The aim of the paper is the characterization in terms of chemical and physical nature of particles at exhaust of spark ignition (SI) engine. Measurements were carried out at exhaust of 16v - 1.2 litre Port Fuel Injection Spark Ignition engine downstream a catalyst. The emission of nanoparticles was investigated by optical techniques and conventional methods. In particular laser induced incandescence (LII), and broadband multiwavelength extinction-scattering spectroscopy (BUVESS) were used. LII allowed the detection and sizing primary particles of carbonaceous nature. BUVESS measured particle size distribution by numerical procedure that took advantage by data at several wavelengths. The optical results were compared with those obtained by conventional methods like opacimeter for mass concentration and Electrical Low Pressure Impactor (ELPI) for sizing. Different engine operating conditions were selected in order to evaluate their influence on the particle nature and size distribution.
Technical Paper

Development and Experimental Validation of a Combustion Model with Detailed Chemistry for Knock Predictions

2007-04-16
2007-01-0938
Aim of this work is to develop a general purpose model for combustion and knocking prediction in SI engines, by coupling a thermo-fluid dynamic model for engine simulation with a general detailed kinetic scheme, including the low-temperature oxidation mechanism, for the prediction of the auto-ignition behavior of hydrocarbons. A quasi-D approach is used to describe the in-cylinder thermodynamic processes, applying the conservation of mass and energy over the cylinder volume, modeled as a single open system. The complex chemistry model has been embedded into the code, by using the same integration algorithm for the conservation equations and the reacting species, and taking into account their mutual interaction in the energy balance. A flame area evolution predictive approach is used to evaluate the turbulent flame front propagation as function of the engine operating parameters.
Technical Paper

Flame Diagnostics in the Combustion Chamber of Boosted PFI SI Engine

2007-09-16
2007-24-0003
The growing demands on fuel economy and always stricter limitations on pollutant emissions has increased the interest in the ignition phenomena to guarantee successful flame development for all the spark ignition (SI) engine operating conditions. The initial size and the growth of the flame have a strong influence on the further development of the combustion process. In particular, for the new FIAT generation of turbocharged SI engines, the first times of spark ignition combustion are not yet fully understood. This is mainly due to the missing knowledge concerning the detailed physical and chemical processes taking place during the all set of the flame propagation. These processes often occur simultaneously, making difficult the interpretation of measurements. In the present paper, flame dynamic was followed by UV-visible emission imaging in an optical SI engine.
Technical Paper

The Diesel Exhaust Aftertreatment (DEXA) Cluster: A Systematic Approach to Diesel Particulate Emission Control in Europe

2004-03-08
2004-01-0694
The DEXA Cluster consisted of three closely interlinked projects. In 2003 the DEXA Cluster concluded by demonstrating the successful development of critical technologies for Diesel exhaust particulate after-treatment, without adverse effects on NOx emissions and maintaining the fuel economy advantages of the Diesel engine well beyond the EURO IV (2000) emission standards horizon. In the present paper the most important results of the DEXA Cluster projects in the demonstration of advanced particulate control technologies, the development of a simulation toolkit for the design of diesel exhaust after-treatment systems and the development of novel particulate characterization methodologies, are presented. The motivation for the DEXA Cluster research was to increase the market competitiveness of diesel engine powertrains for passenger cars worldwide, and to accelerate the adoption of particulate control technology.
Technical Paper

Characterization of CR diesel exhaust by UV-visible extinction and scattering spectroscopy

2001-09-23
2001-24-0070
Non-intrusive diagnostic techniques based on broadband (190-550 nm) extinction and scattering spectroscopy were applied at undiluted exhaust Common- Rail (CR) diesel engine in real time. The influence of load and Exhaust Gas Recirculation (EGR) on soot mass concentration, size distribution of emitted particles and NO concentration was analyzed. NO concentration was evaluated by ""in-situ"" ultraviolet-visible absorption measurements and compared with those obtained by conventional analyzer. The extinction and scattering spectra were compared with those evaluated by the Lorenz-Mie model for spherical particles in order to retrieve the size, the number concentration of the emitted particles and particulate mass. The optical measurements showed that new generation diesel engines, in spite of a drastic reduction of the exhaust mass concentration, caused the emission in the atmosphere of high number concentration of carbonaceous nanoparticles.
Technical Paper

Multidimensional Modelling and Spectroscopic Analysis of the Soot Formation Process in a Diesel Engine

2002-07-09
2002-01-2161
Multidimensional simulation of the soot formation process in a diesel engine is realised exploiting quantitative measurements of the soot volume fraction and diameter obtained by optical techniques. Broadband extinction and scattering measurements are performed on an optically accessible 4-stroke engine where a forced air motion allows a strong prevalence of the premixed stage of combustion with respect to the non-premixed one. Two semi-empirical models for soot formation are tested in the numerical simulation, which is performed using a customized version of the KIVA-3 code. The need of furnishing coherent values of the soot particles density and mean diameter to the one of the two models requiring this kind of information, is highlighted and demonstrated to be crucial in avoiding over-prediction of the soot concentration.
Technical Paper

Thermo-Fluid Dynamic Modeling and Experimental Investigation of a Turbocharged Common Rail DI Diesel Engine

2005-04-11
2005-01-0689
The paper describes the results of a parallel 1D thermo-fluid dynamic simulation and experimental investigation of a DI turbocharged Diesel engine. The attention has been focused on the overall engine performances (air flow, torque, power, fuel consumption) as well as on the emissions (NO and particulate) along the after-treatment system, which presents a particulate filter. The 1D research code GASDYN for the simulation of the whole engine system has been enhanced by the introduction of a multi-zone quasi-dimensional combustion model for direct injection Diesel engines. The effect of multiple injections is taken into account (pilot and main injection). The prediction of NO and soot has been carried out respectively by means of a super-extended Zeldovich mechanism and by the Hiroyasu kinetic approach.
Technical Paper

Modelling of soot formation in diesel engines exploiting measurements of soot volume fraction and diameter

2001-09-23
2001-24-0011
Quantitative measurements of the soot volume fraction and diameter performed by spectroscopic techniques within the combustion chamber of a diesel engine are employed to aid multidimensional simulation of the soot formation and oxidation processes. By changing the start of fuel injection, two different operating conditions are considered, which are characterized by different relative importance of the premixed to the diffusive stage of the combustion process. Both the reduced models by Hiroyasu et al., and the one by Nagle and Strikland- Constable are employed within the numerical simulation. The reason of the peculiar over-prediction of soot concentration of the latter model is discussed and related to the need of furnishing coherent values of the soot particle density and mean diameter.
Journal Article

Effect of Injection Phasing on Valves and Chamber Fuel Deposition Burning in a PFI Boosted Spark-Ignition Engine

2008-04-14
2008-01-0428
A satisfactory answer to the future severe normative on emissions and to the market request for spark ignition engines seems to be the use of downsized engines for passenger cars. Downsizing permits the increase in engines power and torque without the increase in cylinder capacity. The downsizing benefits are evident at part loads; on the other hand, more work should be done to optimize boosted engines at higher and full load. To this goal, a detailed knowledge of the thermo-fluid dynamic processes that occur in the combustion chamber is fundamental. The aim of this paper is the experimental investigation of the effect of the fuel injection in the intake manifold on the combustion process and pollutant formation in a boosted spark ignition (SI) engine. The experiments were performed on a partially transparent single-cylinder port fuel injection (PFI) SI engine, equipped with a four-valve head and boost device.
Journal Article

Optical Investigations of the Abnormal Combustion in a Boosted Spark-ignition PFI Engine

2009-04-20
2009-01-0697
The flame front propagation in normal and abnormal combustion was investigated. Cycle-resolved flame emission imaging was applied in the combustion chamber of a port fuel injection boosted spark ignition engine. The engine was fuelled with a mixture of 90% iso-octane and 10% n-heptane by volume (PRF90). The effect of fuel injection phasing was studied. The combustion process was followed from the flame kernel formation until the opening of the exhaust valves. Different phenomena correlated to the abnormal combustion were analysed. Detailed information on ignition surfaces, end-gas auto-ignitions and knock were obtained. The appearance of autoignition centres in the end gas was evaluated in terms of timing, location and frequency of occurrence.
Journal Article

Use of Accelerometers for Spark Advance Control of SI Engines

2009-04-20
2009-01-1019
Electronic engine controls based on non-intrusive diagnostics can significantly help in complying with the stricter and stricter regulations on pollutants emissions and fuel consumption. The aim of this paper is the use of a low-cost linear capacitive accelerometer placed on the engine block for non-intrusive diagnosis of combustion process in spark ignition engines. In particular, good correspondences between the engine block vibrations and the combustion pressure signal were obtained. The angular position of pressure peak evaluated by accelerometer data can be used in a closed-loop control system for real time control of spark advance.
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