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

Martínez, Santiago; Irimescu, Adrian; Merola, Simona Silvia; Lacava, Pedro Teixeira; Curto-Riso, Pedro

doi:10.3390/en10091337

Cited by 40 publications

(17 citation statements)

References 57 publications

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“…It is important to note that pressure was directly taken from the pressure transducer. Meanwhile, the temperature was estimated with the first law of thermodynamics coupled with a heat and mass transfer model [34]. The results show the same trend between fuels in laminar and turbulent flame speed.…”

Section: Optical Investigationsmentioning

confidence: 84%

“…Two different setups were used, one for high-luminosity flames (methane and pure syngas at λ = 1.0) with f/32 and the other with f/5.6 for diluted syngas and lean methane combustion. In spite of the fact that this approach has the disadvantage that flame luminosity between mixtures cannot be quantitatively compared, it avoids the risk of damage to the equipment and has no effect on the analysis of flame morphology parameters [34].…”

Section: Thermodynamic and Optical Measurementsmentioning

confidence: 99%

“…The National Instruments Vision Development Module was used for image post-processing by using an in-house algorithm [34]. Figure 3 shows the main steps of the procedure, from the original image to the outline flame front extraction.…”

Section: Thermodynamic and Optical Measurementsmentioning

confidence: 99%

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Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

et al. 2019

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To mitigate the increasing concentration of carbon dioxide in the atmosphere, energy production processes must change from fossil to renewable resources. Bioenergy utilization from agricultural residues can be a step towards achieving this goal. Syngas (fuel obtained from biomass gasification) has been proved to have the potential of replacing fossil fuels in stationary internal combustion engines (ICEs). The processes associated with switching from traditional fuels to alternatives have always led to intense research efforts in order to have a broad understanding of the behavior of the engine in all operating conditions. In particular, attention needs to be focused on fuels containing relatively high concentrations of hydrogen, due to its faster propagation speed with respect to traditional fossil energy sources. Therefore, a combustion study was performed in a research optical SI engine, for a comparison between a well-established fuel such as methane (the main component of natural gas) and syngas. The main goal of this work is to study the effect of inert gases in the fuel mixture and that of air dilution during lean fuelling. Thus, two pure syngas blends (mixtures of CO and H2) and their respective diluted mixtures (CO and H2 with 50vol% of inert gases, CO2 and N2) were tested in several air-fuel ratios (stoichiometric to lean burn conditions). Initially, the combustion process was studied in detail by traditional thermodynamic analysis and then optical diagnostics were applied thanks to the optical access through the piston crown. Specifically, images were taken in the UV-visible spectrum of the entire cycle to follow the propagation of the flame front. The results show that hydrogen promotes flame propagation and reduces its distortion, as well as resulting in flames evolving closer to the spark plug. All syngas blends show a stable combustion process, even in conditions of high air and fuel dilution. In the leanest case, real syngas mixtures present a decrease in terms of performance due to significant reduction in volumetric efficiency. However, this condition strongly decreases pollutant emissions, with nitrogen oxide (NOx) concentrations almost negligible.

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Section: Optical Investigationsmentioning

confidence: 84%

Section: Thermodynamic and Optical Measurementsmentioning

confidence: 99%

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Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

et al. 2019

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“…Martinez et al [19] studied the flame front propagation in an optical GDI engine under stoichiometric and lean burn conditions using cycle resolved digital imaging. The data was first exported as 8-bit grey-level images and pre-processed to adjust the contrast and brightness with respect to the maximum intensity value.…”

Section: Introductionmentioning

confidence: 99%

Turbulent Flame Geometry Measurements in a Mass-Production Gasoline Direct Injection Engine

Villani

Aquino

2020

Energies

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Direct optical access to the combustion chamber of a gasoline direct injection (GDI) engine provides extremely valuable information about the combustion process. Experimental measurements of the geometric characteristics of the turbulent flame—such as the flame radius, flame center, flame edges and flame brush thickness—are of fundamental interest in support of the development and validation of any combustion model. To determine the macroscopic properties of sprays and flames, visualization and digital image processing techniques are typically used in controlled experimental setups like single-cylinder optical engines or closed vessels, while optical measurements on mass-production engines are more uncommon. In this paper the optical experimental setup (consisting of a high-speed camera, a laser light source and a data acquisition system) used to characterize the planar turbulent flame propagation in the cylinder of a 3.5 L GDI V6 mass-production engine, is described. The image acquisition process and the image processing that is necessary to evaluate the geometric characteristics of the propagating flame front, which are usually omitted in the referenced literature, are reported in detail to provide a useful guideline to other researchers. The results show that the step-by-step algorithm and the calculation formulae proposed allow to retrieve clear visualizations of the propagating flame front and measurements of its geometrical properties.

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“…Therefore, a potential alternative is the mix of both concepts to achieve a stable combustion process, with low particle emission and without losing performance. Some authors have studied this strategy of homogeneous in-cylinder charge with single [16,17], and multiple injections [18][19][20] in the intake and early compression stroke. Marseglia et al [18] found that the split injection strategy introduces positive effects with respect to the single injection case, such as the reduction of coefficient of variation of the indicate mean effective pressure (COVIMEP), tendency to knock, carbon monoxide emissions, as well as soot formation.…”

Section: Introductionmentioning

confidence: 99%

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

2019

Self Cite

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Direct-injection in spark-ignition engines has long been recognized as a valid option for improving fuel economy, reducing CO2 emissions and avoiding knock occurrence due to higher flexibility in control strategies. However, problems associated with mixture formation are responsible for soot emissions, one of the most limiting factors of this technology. Therefore, the combustion process and soot formation were investigated with different injection strategies on a gasoline direct injection (GDI) engine. The experimental analysis was realized on an optically accessible single cylinder engine when applying single, double and triple injection strategies. Moreover, the effect of fuel delivery phasing was also scrutinized by changing the start of the injection during late intake- and early compression-strokes. The duration of injection was split in different percentages between two or three pulses, so as to obtain close to stoichiometric operation in all conditions. The engine was operated at fixed rotational speed and spark timing, with wide-open throttle. Optical diagnostics based on cycle resolved digital imaging was applied during the early and late stages of the combustion process. Detailed information on the flame front morphology and soot formation were obtained. The optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. The results suggest that the split injection of the fuel has advantages in terms of reduction of soot formation and NOx emissions and a similar combustion performance with respect to the single injection timing. Moreover, an early injection resulted in higher rates of heat release and in-cylinder pressure, together with a reduction of soot formation and flame distortion. The double injection strategy with higher percentage of fuel injected in the first pulse and early second injection pulse showed the best results in terms of combustion evolution and pollutant emissions. For the operative condition studied, a higher time for mixture homogenization and split of fuel injected in the intake stroke shows the best results.

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

Cited by 40 publications

References 57 publications

Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

Turbulent Flame Geometry Measurements in a Mass-Production Gasoline Direct Injection Engine

Flame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine

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