Carlo Beatrice

New findings on combustion behavior of oxygenated synthetic diesel fuels

Abstract New results were obtained on pollutants evolution during the combustion of four oxygenated fuels, whichwere compared with n-tetradecane and n-octane combustion. Three different techniques were adopted on a single cylinder direct injection diesel engine, equipped with optical accesses: two-colour pyrometry for the measurement of in-cylinder soot loading, high speed cinematography for the visualization and analysis of spray and combustion, fast sampling valve for the measurements of in-cylinder combustion products. In particular, the sampling line downstream of the fast sampling valve was adapted for the in-cylinder aldheydes measurements. Heat release analysis and fast sampling valve have shown that CO2 formation rate and heat release rate during the diffusion phase of combustion increase with the fuel oxygen content. Acetylene concentrations are influenced by fuel cetane number and oxygen content but, at the same fuel cetane number, they decrease when oxygen content increases. In-cylinder aldheyd...

Experimental Characterization of Combustion Behaviour of New Diesel Fuels for Low Emission Engines

Some oxygenated hydrocarbons were tested as pure fuels in two different DI diesel engines, and their emission potential was compared to n-tetradecane combustion. Two colours pyrometry method was used to infer in-cylinder sooting tendency of tested fuels. Pure pyrolysis of the same fuels was also investigated in a conventional shock lube at high temperature (1700–2500 K) and pressure (9–13 bar), using light scattering/extinction methods. All oxygenated compounds tested in the engines exhibited a strong decrease of soot loading compared with tetradecane combustion. The long soot induction times, as measured in shock tube experiments, and the oxygen content of the fuel molecules seem to provide a plausible explanation of soot lacking in oxygenated fuels combustion. Emission measurements at the exhaust of a four cylinder engine fully confirm the trends obtained by two colours pyrometry and shock tube experiments. As a matter of fact, the oxygenated synthetic fuels strongly reduce both gaseous and total partic...

Application of a reduced kinetic model for soot formation and burnout in three-dimensional diesel combustion computations

Using a modified version of the Kiva-2 code, three-dimensional computations of combustion and soot formation were performed, burning tetradecane and n -heptane in a direct injection, naturally aspirated diesel engine. A coupled soot formation and combustion model is proposed. Assuming acetylene as the crucial pyrolitic species, the model takes into acount the fuel-to-acetylene pyrolysis, acetylene oxidation, soot nucleation, and surface growth and soot oxidation. The numerical predictions are compared with the expermental data of heat-release patterns and with the in-cylinder measurements of acetylene concentration and soot volume fraction. C 2 H 2 data were collected using a fast-acting valve, while soot loading was measured with the two-color technique. The improved code is able to predict correctly the combustion and heat-release patterns of the two fuels without any retuning of the model constants. The computational results demonstrate that the reduced kinetic soot model is capable of predicting, with satisfactory accuracy, the local amount of soot and pyrolytic products in the combustion chamber, keeping the main features of the diesel combustion.

Proinflammatory effects of diesel exhaust nanoparticles on scleroderma skin cells.

Autoimmune diseases are complex disorders of unknown etiology thought to result from interactions between genetic and environmental factors. We aimed to verify whether environmental pollution from diesel engine exhaust nanoparticulate (DEP) of actually operating vehicles could play a role in the development of a rare immune-mediated disease, systemic sclerosis (SSc), in which the pathogenetic role of environment has been highlighted. The effects of carbon-based nanoparticulate collected at the exhaust of newer (Euro 5) and older (Euro 4) diesel engines on SSc skin keratinocytes and fibroblasts were evaluated in vitro by assessing the mRNA expression of inflammatory cytokines (IL-1α, IL-6, IL-8, and TNF-α) and fibroblast chemical mediators (metalloproteases 2, 3, 7, 9, and 12; collagen types I and III; VEGF). DEP was shown to stimulate cytokine gene expression at a higher extent in SSc keratinocytes versus normal cells. Moreover, the mRNA gene expression of all MMPs, collagen types, and VEGF genes was significantly higher in untreated SSc fibroblasts versus controls. Euro 5 particle exposure increased the mRNA expression of MMP-2, -7, and -9 in SSc fibroblasts in a dose dependent manner and only at the highest concentration in normal cells. We suggest that environmental DEP could trigger the development of SSc acting on genetically hyperreactive cell systems.

Assessment of the Effect of Low Cetane Number Fuels on a Light Duty CI Engine: Preliminary Experimental Characterization in PCCI Operating Condition

The goal of this paper is to acquire insight into the influence of cetane number (CN) and fuel oxygen on overall engine performance in the Premixed Charge Compression Ignition (PCCI) combustion mode.

Assessment of Closed-Loop Combustion Control Capability for Biodiesel Blending Detection and Combustion Impact Mitigation for an Euro5 Automotive Diesel Engine

The present paper describes the results of a cooperative research project between GM Powertrain Europe and Istituto Motori - CNR aimed at studying the impact of both fresh and highly oxidized Rapeseed Methyl Ester (RME) at different levels of blending on performance, emissions and fuel consumption of modern automotive diesel engines featuring Closed-Loop Combustion Control (CLCC). In parallel, the capability of this system to detect the level of biodiesel blending through the use of specific detection algorithms was assessed. The tests were performed on the recently released 2.0L Euro5 GM diesel engine for passenger car application equipped with embedded pressure sensors in the glow plugs. Various blends of fresh and aged RME with reference diesel fuel were tested, notably 20% RME by volume (B20), 50% (B50) and pure RME (B100). The tests on the multi-cylinder engine were carried out in a wide range of engine operating points for the complete characterization of the biodiesel performance in the New European Driving Cycle (NEDC). The results highlighted that there is not appreciable difference in terms of performance and emission between fresh and oxidized biodiesel, at all levels of blending. On the other hand, the capability of the CLCC control to detect biodiesel blending with reasonable accuracy and to implement the corrective actions for avoiding emission drift and performance losses was successfully demonstrated.

Low Cetane Number Renewable Oxy-fuels for Premixed Combustion Concept Application: Experimental Investigation on a Light Duty Diesel Engine

This paper illustrates the results of an experimental study on the impact of a low cetane number (CN) oxygenated fuel on the combustion process and emissions of a light-duty (LD) single-cylinder research engine. In an earlier study, it was concluded that cyclic oxygenates consistently outperformed their straight and branched counterparts at equal oxygen content and with respect to lowering soot emissions. A clear correlation was reported linking soot and CN, with lower CN fuels leading to more favorable soot levels. It was concluded that a lower CN fuel, when realized by adding low reactive cyclic oxygenates to commercial diesel fuel, manifests in longer ignition delays and thus more premixing. Ultimately, a higher degree of premixing, in turn, was thought to suppress soot formation rates. Such compounds have the advantage to be stable in blends with fossil diesel fuel, to have a boiling point close to the diesel fuel range, and have the potential to be produced in a renewable way from lignin , which has a similar hexagonal hydrocarbon basis, albeit in polymer form. Lignin is currently a widely available second generation biomass waste stream, found in for example the paper pulp industry and cellulosic ethanol plants. In the present work, blends of diesel and cyclohexanone were tested in a LD single cylinder research diesel engine in order to evaluate its effects on the combustion process and pollutant emissions, employing both conventional (i.e. mixing-controlled) combustion (at medium/high engine loads) and premixed combustion (at medium/low loads). The results suggest that the combination of low CN and fuel oxygen appears to have a favorable impact on both fuel efficiency and overall emissions in premixed-mode. For mixing-controlled combustion, at medium/high engine loads, the negative effects of low CN (e.g. retarded combustion phasing) can be overcome with an appropriate calibration of the injection parameters. The high unburnt hydrocarbon emissions at low load, conversely, require a further development of the combustion system design, as well as the after-treatment device. Finally, to realize a more and more precise control of the in-cylinder air-fuel charge, before and during the combustion, the future PCCI fuels have to be tailored to the specific combustion process characteristics. In this framework, renewable low CN oxygenated fuels might function as an enabler for PCCI combustion engines.

In-Cylinder Soot and NOx Concentration Measurements in D.I. Diesel Engine Fed by Fuels of Varying Quality

Selected measurements of the in-cylinder soot loading and the gaseous combustion products for ten different innovative fuels, burned in a D.I. diesel engine are presented and discussed. All the fuels which were tested have a very low sulfur content, so the insoluble fraction of the particulate is mainly composed of soot. Two different measure techniques are applied: the two-color pyrometry optical method and the fast sampling of gaseous products in the combustion chamber. A priori and experimental uncertainties relative to the reduction of the data obtained with the two-color measurements are preliminarily investigated. The main results which were obtained are: (a) in pure paraffin fuels the measured soot loading strongly depends upon the cetane number; (b) only in lower (< 58) cetane number fuels the soot loading depends on the aromatic fuel content; (c) tests performed with the fast sampling technique confirm the main trends found when performing measurements with the two-color technique.

Two-Colour Pyrometry Measurements of Soot Loading in a Diesel Engine Burning Model Fuels of Varying Quality

ABSTRACT In the present paper the two-colour technique is applied to study the in-cylinder soot volume fraction evolution in a Direct Injection Diesel engine. A preliminary analysis of the theoretical uncertainty involved in performing the two-colour soot emission measurements is carried out. It is found that, with interference filters at 600 and 1000 nm, and reducing the data with the appropriate numerical algorithm, the total accuracy about soot temperature and volume fraction-values is confined respectively under ± 57 K and ± 30%. The in-cylinder measurements are performed at fixed engine angular speed and injected fuel mass, varying the injection timing and the fuel quality. Employing the two-colour pyrometry technique the following results can be obtained: a) the fuel cetane number controls the soot loading of paraffinic fuels; b) at a fixed level of cetane number (up to 58) the fuel aromatic content strongly influences the engine soot loading amount, but, at a further increase of cetane number (over...

Analysis of Particle Mass and Size Emissions from a Catalyzed Diesel Particulate Filter during Regeneration by Means of Actual Injection Strategies in Light Duty Engines

The diesel particulate filters (DPF) are considered the most robust technologies for particle emission reduction both in terms of mass and number. On the other hand, the increase of the backpressure in the exhaust system due to the accumulation of the particles in the filter walls leads to an increase of the engine fuel consumption and engine power reduction. To limit the filter loading, and the backpressure, a periodical regeneration is needed. Because of the growing interest about particle emission both in terms of mass, number and size, it appears important to monitor the evolution of the particle mass and number concentrations and size distribution during the regeneration of the DPFs. For this matter, in the presented work the regeneration of a catalyzed filter was fully analyzed. Particular attention was dedicated to the dynamic evolution both of the thermodynamic parameters and particle emissions. The measurements were performed at the exhaust of a Euro 5 CR Diesel engine equipped with a Close Coupled DPF. The regeneration process was investigated in a point representative of an extraurban engine operating condition. The regeneration was managed by the electronic control unit (ECU). In particular, an injection calibration was implemented taking into account the engine and the filter features. The particle size distribution evolution during regeneration phase was measured in the size range 5-1000 nm using a differential mobility spectrometer. The particle mass concentration was monitored by means of a microsoot sensor. Particle mass and number concentrations strongly increase during the regeneration process. Moreover, a high concentration of the number of particles smaller than 30nm was observed in some critical phases of the regeneration process.