Methane/hydrogen fueling a spark-ignition engine for studying NO, CO and HC emissions with a research CFD code

Kosmadakis, George; Rakopoulos, Dimitrios C.; Rakopoulos, C.D.

doi:10.1016/j.fuel.2016.08.040

Cited by 84 publications

(17 citation statements)

References 52 publications

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“…Several authors [7,8,[13][14][15][16][17] have studied syngas mixtures and compared them with conventional fuels (gasoline, natural gas, and hydrogen) in terms of engine performance, durability, combustion stability, and exhaust emissions. A reduction in efficiency and power was observed due to low energy density.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…Previous work adopting the described modelling framework lead to an overprediction of the early HRR. 37 In order to account for the transition during this phase from a initially laminar to fully developed turbulent flame, Rakopoulos and colleagues 31,49 assumed a laminar flame propagation for a flame that falls below a given critical radius for which it is assumed that turbulent eddies do not interact with the turbulent flame front, and fully turbulent flame speed above this radius. In their work, they fixed this radius at 4 mm and demonstrated good agreement with experimental data for the engine under consideration.…”

Section: Ignition and Early Flame Treatmentmentioning

confidence: 99%

“…Whereas experimentally a lot of work has been performed for hydrogen–methane admixtures, to the best knowledge of the authors, only a small number of three-dimensional computational fluid dynamics (CFD) investigations within IC engines considering admixtures can be found. A Reynolds-averaged Navier–Stokes (RANS) combustion model based on the turbulent flame speed closure of Zimont et al, 26 Lipatnikov and Chomiak 27 and Zimont 28 was presented in Rakopoulos et al 29 for pure hydrogen and extended to consider admixtures by blending the used laminar flame speed correlations for the mono component fuels in Kosmadakis et al 30,31 A fixed hydrogen fraction in the fuel of 10 and 30 vol% was considered, for which good agreement with the experimental data was reported. More recently, a laminar flame speed correlation for lean gasoline–hydrogen admixtures in combination with the extended coherent flame model (ECFM) was proposed in Iafrate et al 32 and successfully validated against engine test bench data in order to highlight the positive effects of small hydrogen addition for different loads.…”

Section: Introductionmentioning

confidence: 99%

Reactive computational fluid dynamics modelling of methane–hydrogen admixtures in internal combustion engines: Part I – RANS

Koch

Schürch

Wright

et al. 2020

International Journal of Engine Research

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The effects of hydrogen addition to internal combustion engines operated by natural gas/methane has been widely demonstrated experimentally in the literature. Already small hydrogen contents in the fuel show promising benefits with respect to increased engine efficiency, lower CO2 emissions, extended lean operating limits and a higher exhaust gas recirculation tolerance while maintaining the knock resistance of methane. In this article, the influence of hydrogen addition to methane on a spark ignited single cylinder engine is investigated. This article proposes a modelling approach to consider hydrogen addition within three-dimensional reactive computational fluid dynamics in order to establish a framework to gain further insights into the involved processes. Experiments have been performed on a single-cylinder spark-ignition engine situated at a test bed and cater as reference data for validating the proposed reactive computational fluid dynamics modelling approach based around the G-Equation combustion model. Within the course of the first part, crucial aspects relevant to the modelling of the mean engine cycle are highlighted. In this article, a simplified early combustion phase model which considers the transition towards a fully developed turbulent flame following ignition is introduced, along with a second submodel considering combined effects of the walls. The sensitivity of the combustion process towards the modelling approach is presented. The submodels were calibrated for a reference operating point, and a sweep in hydrogen content in the fuel as well as stoichiometric and lean operation has been considered. It is shown that the flame speed coefficient A appearing in the used turbulent flame speed closure, weighting the influence of the turbulent fluctuating speed [Formula: see text], has to be adjusted for different hydrogen contents. The introduced submodels allowed for significant improvement of the in-cylinder pressure and heat release rate evolution throughout all considered operating conditions.

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“…A cyclic variability sub-model has been recently added for capturing the relevant effects in spark-ignition engines [24], briefly described in the next sub-section for completeness. The other main sub-models of the CFD code have been validated against experimental data, and they concern the combustion processes with gaseous fuels [28], heat transfer [29] and crevices [30] with dedicated sub-models developed by the authors, and pollutant emissions models [29][30][31][32][33]. The simulations cover the closed engine cycle and start at IVC and finish at EVO.…”

Section: Highlights Of the Cfd Code And Its Main Sub-modelsmentioning

confidence: 99%

A Fast CFD-Based Methodology for Determining the Cyclic Variability and Its Effects on Performance and Emissions of Spark-Ignition Engines

Kosmadakis

Rakopoulos

2019

Energies

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A methodology for determining the cyclic variability in spark-ignition (SI) engines has been developed recently, with the use of an in-house computational fluid dynamics (CFD) code. The simulation of a large number of engine cycles is required for the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) to converge, usually more than 50 cycles. This is valid for any CFD methodology applied for this kind of simulation activity. In order to reduce the total computational time, but without reducing the accuracy of the calculations, the methodology is expanded here by simulating just five representative cycles and calculating their main parameters of concern, such as the IMEP, peak pressure, and NO and CO emissions. A regression analysis then follows for producing fitted correlations for each parameter as a function of the key variable that affects cyclic variability as has been identified by the authors so far, namely, the relative location of the local turbulent eddy with the spark plug. The application of these fitted correlations for a large number of engine cycles then leads to a fast estimation of the key parameters. This methodology is applied here for a methane-fueled SI engine, while future activities will examine cyclic variations in SI engines when fueled with different fuels and their mixtures, such as methane/hydrogen blends, and their associated pollutant emissions.

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Methane/hydrogen fueling a spark-ignition engine for studying NO, CO and HC emissions with a research CFD code

Cited by 84 publications

References 52 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

Reactive computational fluid dynamics modelling of methane–hydrogen admixtures in internal combustion engines: Part I – RANS

A Fast CFD-Based Methodology for Determining the Cyclic Variability and Its Effects on Performance and Emissions of Spark-Ignition Engines

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