A Fundamental Model for Flame Kernel Formation in S. I. Engines

Herweg, R.; Maly, R.

doi:10.4271/922243

Cited by 193 publications

(93 citation statements)

References 85 publications

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“…It has an initial high value due to the spark boosted combustion, followed by a minimum value that occurs between 200 and 500 ls, and then a fairly steady increase until the end of the investigated period. Such a trend shows good agreement with the computational model of Herweg and Maly [42] for flame kernel formation in spark ignition engines. Considering the very different engine geometries, ignition modes and fuel mixing methods, the result is surprisingly well matched.…”

Section: Resultssupporting

confidence: 71%

Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine

Ihracska

Korakianitis

Ruiz

et al. 2014

Combustion and Flame

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a b s t r a c tPremixed fuel-air flame propagation is investigated in a single-cylinder, spark-ignited, four-stroke optical test engine using high-speed imaging. Circles and ellipses are fitted onto image projections of visible light emitted by the flames. The images are subsequently analysed to statistically evaluate: flame area; flame speed; centroid; perimeter; and various flame-shape descriptors. Results are presented for gasoline, isooctane, E85 and M85. The experiments were conducted at stoichiometric conditions for each fuel, at two engine speeds of 1200 rpm (rpm) and 1500 rpm, which are at 40% and 50% of rated engine speed. Furthermore, different fuel and speed sets were investigated under two compression ratios (CR: 5.00 and 8.14). Statistical tools were used to analyse the large number of data obtained, and it was found that flame speed distribution showed agreement with the normal distribution. Comparison of results assuming spherical and non-isotropic propagation of flames indicate non-isotropic flame propagation should be considered for the description of in-cylinder processes with higher accuracy. The high temporal resolution of the sequence of images allowed observation of the spark-ignition delay process. The results indicate that gasoline and isooctane have somewhat similar flame propagation behaviour. Additional differences between these fuels and E85 and M85 were also recorded and identified.

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Section: Resultssupporting

confidence: 71%

Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine

Ihracska

Korakianitis

Ruiz

et al. 2014

Combustion and Flame

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“…The lowest bound of this length is experienced as the quenching distance, and it is a property of the mixture [11][12][13].The minimum ignition energy decreases with an increasing gap size until the gap size reaches the critical value, and, beyond this quenching distance, the minimum ignition energy remains nearly constant over a considerable range of the gap size [5,7,8,14]. The size of the spark kernel at which the rate of heat loss at its surface is precisely balanced by the rate of heat release throughout its volume [15][16][17].A larger spark gap requires greater voltage to go down the gap, an increase in gap width results in increased arc length more current is made along the spark to hold an almost constant voltage across it [6,7].…”

Section: Resultsmentioning

confidence: 99%

Application of Schlieren Optical Visualization System in External Combustion and Internal Combustion Engine: A Review

Samsudin

Othman

Manshoor

et al. 2015

AMM

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Schlieren optical visualization technique system is the unique technique due to the ability in producing a neutral image easily-interpretable image of refractive-index-gradient areas. The Schlieren system provides a method for viewing the flow through the transparent media and the most using this technique is to photograph the flow. This paper presents the review of the application of the Schlieren optical visualization system external and internal combustion engine in order to observe the fuel-air mixing and flame development during the burning process. The basic technique of Schlieren system, especially for Z-type and two mirror Schlieren system provide a powerful and clearly image to visualize the changes of the density in a transparent medium. This method can capture spray evaporation, spray interference and mixture formation clearly with real images. Analysis of optical image visualization observations reveals that the mixture formation of fuel and air exhibits the influence of the ignition and flame development. Thus, the observation of systematic control of the creation of a mixture of experimental apparatus allows us to achieve significant progress in the combustion process and will present the information to understanding the basic terms of reduced fuel consumption and exhaust emissions. IntroductionThe first Schlieren system was invented by Robert Hook in the 17th century and Schlieren technique developed in the 19th century by Toepler [1]. The Schlieren technique is an optical technique that detects density gradients occurring in a fluid flow in its simplest from light a slit is collimated by a lens and focused onto a knife-edge by a second lens, the flow pattern is placed between these two lenses and the diffraction pattern that results on a screen or photographic film placed behind the knife-edge is observed. The schlieren technique is often used to investigate heat and mass transfer process in gases and liquid [1][2][3]. Referable to the three dimensionality of the investigated processes, it's virtually inconceivable to get quantitative result about the density gradient from the schlieren image [1,2].The primary reasons why Schlieren technique difficult to produce quantitative results because when the geometry is known or simple like sphere, cylinder or other it is possible to calculate the density gradient. Thither are many types of Schlieren technique, setup, but all the setup are based using the same principle [3][4][5][6].

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“…Our primary goal for this model was to examine the effects of flow through the spark gap on the subsequent ignition and flame propagation processes. Flow through the spark gap is of interest because Herweg and Maly (1992) found that the efficiency of electrical-to-thermal energy conversion depends upon the bulk flow through the gap for both arc and glow. This initial version of the 3D model used a simple progress variable to simulate flame growth and did not include the dynamic response of the ignition circuit.…”

Section: 3c 3d Spark Ignition Modelmentioning

confidence: 99%

Railplug Ignition System for Enhanced Engine Performance and Reduced Maintenance

Ezekoye¹,

Hall²,

Matthews³

2005

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This Final Technical Report discusses the progress that was made on the experimental and numerical tasks over the duration of this project. The primary objectives of the project were to 1) develop an improved understanding of the spark ignition process, and 2) develop the railplug as an improved ignitor for large bore stationary natural gas engines.We performed fundamental experiments on the physical processes occurring during spark ignition and used the results from these experiments to aid our development of the most complete model of the spark ignition process ever devised. The elements in this model include 1) the dynamic response of the ignition circuit, 2) a chemical kinetics mechanism that is suitable for the reactions that occur in the plasma, 3) conventional flame propagation kinetics, and 4) a multi-dimensional formulation so that bulk flow through the spark gap can be incorporated. This model (i.e., a Fortran code that can be used as a subroutine within an engine modeling code such as KIVA) can be obtained from Prof. Ron Matthews at rdmatt@mail.utexas.edu or Prof. DK Ezekoye at dezekoye@mail.utexas.edu.Fundamental experiments, engine experiments, and modeling tasks were used to help develop the railplug as a new ignitor for large bore natural gas engines. As the result of these studies, we developed a railplug that could extend the Lean Stability Limit (LSL) of an engine operating at full load on natural gas from φ = 0.59 for operation on spark plugs down to φ = 0.53 using railplugs with the same delivered energy (0.7 J). However, this delivered energy would rapidly wear out the spark plug. For a conventional delivered energy (<0.05 J), the LSL is φ = 0.63 for a spark plug. Further, using a permanent magnet to aid the plasma movement, the LSL was extended to φ = 0.54 for a railplug with a delivered energy of only 0.15 J/shot, a typical discharge energy for commercial capacitive discharge ignition systems. Here, it should be noted that railplugs and the associated ignition circuit should not cost much more than a conventional spark ignition system. Additionally, it is believed that the railplug performance can be further improved via continued research and development.iii TABLE OF CONTENTS Abstract iii EXECUTIVE SUMMARYThis Final Technical Report discusses the progress that was made on the experimental and numerical tasks over the duration of this project. The primary objectives of the project were to 1) develop an improved understanding of the spark ignition process, and 2) develop the railplug as an improved ignitor for large bore stationary natural gas engines.Due to these two objectives, the experimental subtasks involved 1) detailed measurements regarding the physical processes occurring during spark ignition, and 2) measurements of the factors that affect railplug performance. Similarly, the modeling subtasks involved developing an improved model for the conventional spark ignition process and developing a model for railplug performance and ignition.The four phases of spark ignition are ...

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A Fundamental Model for Flame Kernel Formation in S. I. Engines

Cited by 193 publications

References 85 publications

Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine

Assessment of elliptic flame front propagation characteristics of iso-octane, gasoline, M85 and E85 in an optical engine

Application of Schlieren Optical Visualization System in External Combustion and Internal Combustion Engine: A Review

Railplug Ignition System for Enhanced Engine Performance and Reduced Maintenance

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