Validation of turbulent flame speed models for methane–air-mixtures at high pressure gas engine conditions

Ratzke, Ansgar; Schöffler, Tobias; Kuppa, Kalyan; Dinkelacker, Friedrich

doi:10.1016/j.combustflame.2015.04.011

Cited by 25 publications

(3 citation statements)

References 31 publications

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“…Determining the flame front impinges on the piston surface is also important when computing flame speed. Ratzke et al 31 discussed the importance of understanding the crank angle when the flame impinges on the piston surface. They derived a turbulent flame speed model from the mean in-cylinder pressure using a zonal cylinder model and showed that the in-cylinder pressure curve of the model was in good agreement with measurements until the flame front touched the piston surface.…”

Section: Image Processing and Calculation Of Flame Propertiesmentioning

confidence: 99%

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

Afkhami

Wang

Miers

et al. 2019

International Journal of Engine Research

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The current research experimentally studied flame speed and stretch under engine in-cylinder conditions. A direct-injection, spark-ignition, and optically accessible engine was utilized to image the flame propagation, and E10 was selected as the fuel. Also, three fuel–air mixtures (stoichiometric, lean, and rich) were examined. The flame front was located by processing high-speed images. This study introduces a novel approach for calculation of equivalent spherical flame radius for analysis of flame speed and stretch. Flame front propagation analysis showed that during the flame propagation period, the stretch decreased until the flame front touched the piston surface. This was a common trend for stoichiometric, lean, and rich mixtures, which occurred because the flame radius was the dominant factor in the stretch calculation. In addition, the rich fuel–air mixture showed a lower flame stretch compared to stoichiometric or lean mixture. This was the result of a lower Markstein number for the rich fuel–air mixture. To study the sensitivity of different fuel–air mixtures to the flame stretch, the trajectory of the flame centroid was tracked until the flame front touched the piston surface. The results showed that the end centroid for the lean mixture deviated from the start point more than those of the rich and stoichiometric mixtures because the lean mixture had a higher flame stretch and lower flame speed. Furthermore, comparing the flame stretch at three different engine speeds revealed that increasing the engine speed increased the flame stretch, especially during the early flame development period. According to previous studies which discussed flame stretch as a flame extinguishment mechanism, the probability of flame extinction is higher when the engine speed is higher. Also, uncertainty analysis was conducted to determine the effect of camera setting on the flame stretch. Results showed that a maximum relative uncertainty of 4.5% occurred during the early flame development.

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Section: Image Processing and Calculation Of Flame Propertiesmentioning

confidence: 99%

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

Afkhami

Wang

Miers

et al. 2019

International Journal of Engine Research

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“…Equation (5) has been tested against methane/air S T data at high-pressure gas engine conditions [26], while Equations (1)- (4) have not yet done so. To see how well these five correlations, Equations (1)-(5), could be applicable to SI engines for S T prediction, an uncertainty comparison is performed by accessing the accuracy of these correlations based on the MAPE value which is calculated using the following equation [23].…”

Section: Introductionmentioning

confidence: 99%

General Correlations of Iso-octane Turbulent Burning Velocities Relevant to Spark Ignition Engines

Nguyen

Chen

et al. 2019

Energies

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A better understanding of turbulent premixed flame propagation is the key for improving the efficiency of fuel consumption and reducing the emissions of spark ignition gasoline engines. In this study, we measure turbulent burning velocities (ST) of pre-vaporized iso-octane/air mixtures over wide ranges of the equivalence ratio (φ = 0.9–1.25, Le ≈ 2.94–0.93), the root-mean-square (r.m.s.) turbulent fluctuating velocity (u′ = 0–4.2 m/s), pressure p = 1–5 atm at T = 358 K and p = 0.5–3 atm at T = 373 K, where Le is the effective Lewis number. Results show that at any fixed p, T and u′, Le < 1 flames propagate faster than Le > 1 flames, of which the normalized iso-octane ST/SL data versus u′/SL are very scattering, where SL is the laminar burning velocity. But when the effect of Le is properly considered in some scaling parameters used in previous correlations, these large scattering iso-octane ST/SL data can be collapsed onto single curves by several modified general correlations, regardless of different φ, Le, T, p, and u′, showing self-similar propagation of turbulent spherical flames. The uncertainty analysis of these modified general correlations is also discussed.

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“…Several numerical studies have been realized to examine the influence of the pressure on premixed methane flames. − Ratzke et al examined the pressure effect for the internal combustion engines both experimentally and numerically. They have tested several turbulent flame speed correlations at high pressures, up to 7 MPa.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Turbulent Lean Premixed Methane–Air Flame Statistics at Elevated Pressures

Yılmaz

Gökalp

2017

Energy Fuels

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Combustion takes place within turbulent environments and under pressurized conditions in most industrial applications, for instance, gas turbines and internal combustion engines. The mixing of fuel and oxidizer is enhanced by turbulence, so that combustion will be more efficient. In addition, during combustion, heat is released; therefore, it causes flow instability as a result of gas expansion and high gradients of temperature. The interaction of turbulence and combustion under pressurized conditions may lead to modifications and even disruption of the flame. There are still ongoing studies on the prediction of flame and flow statistics, which are crucial for the stable operation of high-pressure combustion systems. In the present study, the aim is to investigate the influence of elevated pressures on the structure of turbulent premixed methane−air flames, within the range from atmospheric to 0.9 MPa, by numerical modeling and experimental validation. The computations are performed initially for the cold flow field and then for the reactive flow statistics using the Fluent software. For the cold flow case results, it is found that the velocity potential core region extends until three diameters downstream from the burner exit and the decay rate decreases with increasing pressure. However, in the reactive case simulations, the decay in the velocity profiles is not observed as a result of gas expansion through the flame front, similar to the experiments. The turbulent flame front statistics in terms of the flame front location, the flame brush thickness, and the flame surface density (FSD) have been computed. The flame tip location and flame brush thickness are found more downstream and thicker at elevated pressures, respectively. Moreover, both the profiles and peak values of FSD are well-captured for various pressure conditions in computations compared to the measurements.

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Validation of turbulent flame speed models for methane–air-mixtures at high pressure gas engine conditions

Cited by 25 publications

References 31 publications

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

Experimental determination of flame speed and flame stretch using an optically accessible, spark-ignition engine

General Correlations of Iso-octane Turbulent Burning Velocities Relevant to Spark Ignition Engines

Analysis of Turbulent Lean Premixed Methane–Air Flame Statistics at Elevated Pressures

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