Numerical Simulation of Gasoline and n-Butanol Combustion in an Optically Accessible Research Engine

Breda, Sebastiano; D'Adamo, Alessandro; Fontanesi, Stefano; D’Orrico, Fabrizio; Irimescu, Adrian; Merola, Simona Silvia; Giovannoni, Nicola

doi:10.4271/2017-01-0546

Cited by 35 publications

(26 citation statements)

References 18 publications

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“…In agreement with the literature [49,50], the change in the pressure near the spark plug determined a change in the linear tendency. As observed in previous works [25,39,40], flame kernel emission could be well distinguished at around 10 CADs after spark timing due to the luminosity of plasma induced between the spark plug's electrodes. After this time, the flame front propagated from the center of the combustion towards the cylinder walls.…”

Section: Resultssupporting

confidence: 57%

“…Nonetheless, this mechanism can be considered to have a relatively reduced influence on overall efficiency; to put things into perspective, a concentration of 100 ppm of n-hexane in burned gas (the basis for HC as n-hexane equivalent measurements performed in this study) is equivalent to around 0.5% of the fuel content of stoichiometric air-fuel mixtures. The evolution of nitrogen oxides can be related to the thermal effect [20,39,40] with the highest value for the stoichiometric combustion process. With lean mixtures, the two competing effects (i.e., higher concentration of oxygen and lower burned gas temperature) featured different weights, with temperature having the more prominent influence.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, the evidence of high-intensity flames in the intake valve region, near the injector, confirmed the presence of fuel deposits that burned when they interacted with the spark ignited flame front (Figure 10). In agreement with other studies, the deposits determined fuel-rich zones that slowed down the flame propagation [40]. In order to better investigate the effect, the image processing previously described was performed considering the sequences related to 25 consecutive cycles for all lambda values (from 1.0 to 1.6).…”

Section: Hcoh + Hν → H + Hco Hcoh + Hν → H + Hcomentioning

confidence: 99%

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Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

et al. 2017

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Lean fueling of spark ignited (SI) engines is a valid method for increasing efficiency and reducing nitric oxide (NO x ) emissions. Gasoline direct injection (GDI) allows better fuel economy with respect to the port-fuel injection configuration, through greater flexibility to load changes, reduced tendency to abnormal combustion, and reduction of pumping and heat losses. During homogenous charge operation with lean mixtures, flame development is prolonged and incomplete combustion can even occur, causing a decrease in stability and engine efficiency. On the other hand, charge stratification results in fuel impingement on the combustion chamber walls and high particle emissions. Therefore, lean operation requires a fundamentally new understanding of in-cylinder processes for developing the next generation of direct-injection (DI) SI engines. In this paper, combustion was investigated in an optically accessible DISI single cylinder research engine fueled with gasoline. Stoichiometric and lean operations were studied in detail through a combined thermodynamic and optical approach. The engine was operated at a fixed rotational speed (1000 rpm), with a wide open throttle, and at the start of the injection during the intake stroke. The excess air ratio was raised from 1 to values close to the flammability limit, and spark timing was adopted according to the maximum brake torque setting for each case. Cycle resolved digital imaging and spectroscopy were applied; the optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. Flame front propagation speed, flame morphology parameters, and centroid motion were evaluated through image processing. Chemical kinetics were characterized based on spectroscopy data. Lean burn operation demonstrated increased flame distortion and center movement from the location of the spark plug compared to the stoichiometric case; engine stability decreased as the lean flammability limit was approached.

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Section: Resultssupporting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Section: Hcoh + Hν → H + Hco Hcoh + Hν → H + Hcomentioning

confidence: 99%

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Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

et al. 2017

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“…Wall wetting is directly related to load, meaning that as engine output is increased at fixed rotational speed, larger quantities of fuel need to be injected; several mechanisms during air-fuel mixture formation contribute to complex effects on charge distribution during combustion, that can be identified through combined experimental and numerical investigations [18,19]. Mixture inhomogeneity plays a significant role during the initial stages of flame kernel development [20], but also influences the occurrence of abnormal combustion phenomena due to autoignition [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

et al. 2017

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Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms involved in the formation of carbonaceous structures during combustion and their evolution in the exhaust line. In-cylinder pressure was recorded in combination with cycle-resolved flame imaging, gaseous emissions and particle size distribution. This complete characterization was performed at three injection phasing settings, with butanol and commercial gasoline. Optical accessibility from below the combustion chamber allowed visualization of diffusive flames induced by fuel deposits; these localized phenomena were correlated to observed changes in engine performance and pollutant species. With gasoline fueling, minor modifications were observed with respect to combustion parameters, when varying the start of injection. The alcohol, on the other hand, featured marked sensitivity to the fuel delivery strategy. Even though the start of injection was varied in a relatively narrow crank angle range during the intake stroke, significant differences were recorded, especially in the values of particle emissions. This was correlated to the fuel jet-wall interactions; the analysis of diffusive flames, their location and size confirmed the importance of liquid film formation in direct injection engines, especially at medium and high load.

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“…Wall wetting is directly related to load, meaning that as engine output is increased at fixed rotational speed, larger quantities of fuel need to be injected; several mechanisms during air-fuel mixture formation contribute to complex effects on charge distribution during combustion, that can be identified through combined experimental and numerical investigations [18], [19]. Mixture inhomogeneity plays a significant role during the initial stages of flame kernel development [20], but also influences the occurrence of abnormal combustion phenomena due to autoignition [21], [22], [23]. The use of alternative fuels is another aspect that needs to be considered from a wide perspective [24].…”

Section: Introductionmentioning

confidence: 99%

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

Merola¹,

Irimescu²,

Iorio³

et al. 2017

Preprint

Self Cite

View full text Add to dashboard Cite

Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms involved in the formation of carbonaceous structures during combustion and their evolution in the exhaust line. In-cylinder pressure was recorded in combination with cycle-resolved flame imaging, gaseous emissions and particle size distribution. This complete characterization was performed at three injection phasing settings, with butanol and commercial gasoline. Optical accessibility from below the combustion chamber, allowed visualization of diffusive flames induced by fuel deposits; these localized phenomena were correlated to observed changes in engine performance and pollutant species. With gasoline fueling, minor modifications were observed with respect to combustion parameters, when varying the start of injection. The alcohol, on the other hand, featured marked sensitivity to the fuel delivery strategy. Even though the start of injection was varied in a relatively narrow crank angle range during the intake stroke, significant differences were recorded, especially in the values of particle emissions. This was correlated to the fuel jet-wall interactions; the analysis of diffusive flames, their location and size confirmed the importance of liquid film formation in direct injection engines, especially at medium and high load.

show abstract

Numerical Simulation of Gasoline and n-Butanol Combustion in an Optically Accessible Research Engine

Cited by 35 publications

References 18 publications

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

Flame Front Propagation in an Optical GDI Engine under Stoichiometric and Lean Burn Conditions

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

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