Experimental study of lean premixed CH4/N2/O2 flames under low-frequency alternating-current electric fields

Duan, Hao; Wu, Xiaomin; Hou, Juncai; Zhang, Cong; Gao, Zhongquan

doi:10.1016/j.fuel.2016.05.008

Cited by 6 publications

(4 citation statements)

References 25 publications

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“…Previous studies [30,31,38] have verified that our electrode arrangement could only produce an approximately uniform electric field between the ignition and the mesh electrode, and a u was about 0.7 in the main study zone for −2.5 kV and −5 kV electric field.…”

Section: Governing Equationssupporting

confidence: 55%

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Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

et al. 2016

Energies

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This paper compares numerical simulations with experiments to study the deformation of lean premixed spherically expanding flames under a negative direct current (DC) electric field. The experiments, including the flame deformation and the ionic distribution on the flame surface were investigated in a mesh to mesh electric field. Besides, a numerical model of adding an electric body force to the positive ions on the flame surface was also established to perform a relevant simulation. Results show that the spherical flame will acquire an elliptical shape with a marked flame stretch in the horizontal direction and a slight inhibition in the vertical direction under a negative DC electric field. Meanwhile, a non-uniform ionic distribution on the flame surface was also detected by the Langmuir probe. The simulation results from the numerical model show good agreement with experimental data. According to the velocity field analysis in simulation, it was found the particular motion of positive ions and neutral molecules on the flame surface should be responsible for the special flame deformation. When a negative DC electric field was applied, the majority of positive ions and colliding neutral molecules will form an ionic flow along the flame surface by a superposition of the electric field force and the aerodynamic drag. The ionic flow was not uniform and mainly formed on the upper and lower sides, so it will lead to a non-uniform ionic distribution along the flame surface. What's more, this ionic flow will also induce two vortexes both inside and outside of the flame surface due to viscosity effects. The external vortexes could produce an entraining effect on the premixed gas and take away the heat from the flame surface by forced convection, and then suppress the flame propagation in the vertical direction, while, the inner vortexes would scroll the burned zones and induce an inward flow at the horizontal center, which could be the reason for the pitted structure at the horizontal center when a high voltage was applied.

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Section: Governing Equationssupporting

confidence: 55%

“…The external systems for the two experiments were the same as what was used in the past [27,30,31], and consisted of six parts, including a constant-volume combustion chamber system, a fuel supply, an ignition control circle, an optical Schlieren system, a high-speed camera and a high-voltage supply system, as shown in Figure 1.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

et al. 2016

Energies

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“…The appearance of the ionic wind effect makes the flame surface unstable due to fluid dynamics. Fang et al and Duan et al used similar experimental devices to study the combustion under an electric field with the spherical flame method [26][27]. Experimental studies have found that the application of voltage can increase the stretching and burning rate of the flame.…”

Section: Spherical Flame Propagation Methodsmentioning

confidence: 99%

A Comprehensive Review of the Influence of Electric Field on Flame Characteristics

Yin¹,

Li²,

Yan³

et al. 2020

Preprint

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Electric field assisted combustion is an important means to improve fuel combustion efficiency. This paper conducts extensive research on flame characteristics under different forms and different application methods of electric fields, emission of soot particles and simulation status. Different flame parameter measurement methods will lead to different degrees of error, and perfect numerical simulation can make simple predictions on experimental data. Most of the current numerical simulations are in two dimensions, and it is necessary to develop a complete and accurate three-dimensional model to simulate and predict the characteristics of the flame under an electric field. The emission of soot particles is also affected by the electric field, and reasonable electric field parameters can greatly reduce the emission of soot particles. It is recommended to conduct centralized measurement of different fuels under the electric field under high pressure and temperature conditions, so as to be able to develop a wider and more accurate flame dynamics and chemical model under the electric field.

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“…Up to now, most studies on microwave-or electric field-assisted ignition in CVCC were more concentrated on the overall combustion characteristics, e.g., heat release, based on the pressure measurements during the combustion period [17,18,21], whereas scant attention was paid to the effects of energy absorption and microwave-induced flow during the initial flame development. It was only mentioned in [17] that microwave-induced wrinkles on the flame kernel surface were conducive to the flame kernel development.…”

Section: Introductionmentioning

confidence: 99%

Effect of Microwave Pulses on the Morphology and Development of Spark-Ignited Flame Kernel

et al. 2021

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Microwave-assisted spark ignition (MAI) is a promising way to enhance the ignition performance of engines under lean conditions. To understand the effect of microwave-induced flow during MAI, the development and morphology of spark-ignited methane-air flame kernel under various microwave pulse parameters are experimentally studied. Experiments are conducted in a constant volume combustion chamber, and flame development is recorded through a high-speed shadowgraph method. Flame area and deformation index are adopted to evaluate the flame characteristic. Results show that increasing the microwave pulse energy from 0 to 150 mJ exhibits a threshold process for expanding the flame kernel area under 0.2 MPa ambient pressure. When the pulse energy is below the threshold of 90 mJ, the microwave enhancing efficiency is much lower than that beyond the threshold. Increasing microwave pulse repetition frequency (PRF) changes the flow on flame surface and raises the absorption efficiency for microwave energy, and thus helps to improve the MAI performance under higher pressures. Hence, 1 kHz pulses cause more obvious flame deformation than those with higher PRF pulses under 0.2 MPa, while this tendency is reversed as the ambient pressure increases to 0.6 MPa. Besides, microwave pulses of different repetition frequencies lead to different flame kernel morphology, implying the various regimes behind the interaction between a microwave and spark kernel.

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Experimental study of lean premixed CH4/N2/O2 flames under low-frequency alternating-current electric fields

Cited by 6 publications

References 25 publications

Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

Deformation Study of Lean Methane-Air Premixed Spherically Expanding Flames under a Negative Direct Current Electric Field

A Comprehensive Review of the Influence of Electric Field on Flame Characteristics

Effect of Microwave Pulses on the Morphology and Development of Spark-Ignited Flame Kernel

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