Electromagnetically induced motion of spark ignition kernels

Bradley, D.; Critchley, Ian

doi:10.1016/s0010-2180(74)80001-5

Cited by 21 publications

(5 citation statements)

References 11 publications

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“…Many investigators have also performed experimental studies on visualizing spark discharge and ignition using optical and laser techniques. Experiments have been done to visualize the fluid mechanics of the evolving spark and ignition kernels using shadowgraph and schlieren visualization [4,[17][18][19][20][21][22][23][24][25] and interferometry [4,26]. Laser diagnostics, such as laser-induced fluorescence (LIF) [12,23,27] and spectroscopy [23,27], have also been implemented to measure characteristics of the spark kernel such as temperature and magnitude of OH radicals.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the effect of electrode geometry on spark ignition

Bane

Ziegler

Shepherd

2015

Combustion and Flame

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High-speed schlieren visualization and numerical simulations are used to study the fluid mechanics following a spark discharge and the effect on the ignition process in a hydrogen-air mixture. A two-dimensional axisymmetric model of spark discharge in air and spark ignition was developed using the non-reactive and reactive Navier-Stokes equations including mass and heat diffusion. The numerical method employs structured adaptive mesh refinement software to produce highly-resolved simulations, which is critical for accurate resolution of all the physical scales of the complex fluid mechanics and chemistry. The simulations were performed with three different electrode geometries to investigate the effect of the geometry on the fluid mechanics of the evolving spark kernel and on flame formation. The computational results were compared with high-speed schlieren visualization of spark and ignition kernels. It was shown that the spark channel emits a blast wave that is spherical near the electrode surfaces and cylindrical near the center of the spark gap, and thus is highly influenced by the electrode geometry. The ensuing competition between spherical and cylindrical expansion in the spark $ Full-length article submitted to Combustion and Flame.

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Section: Introductionmentioning

confidence: 99%

Investigation of the effect of electrode geometry on spark ignition

Bane

Ziegler

Shepherd

2015

Combustion and Flame

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“…Tilston [26] has shown that, following ignition, the small flame kernel can be convected over relatively large distances within a gas turbine combustor before it undergoes significant growth. In addition, Bradley and Critchley [27] proposed the presence of a force, generated electromagnetically during breakdown, that tends to propel the ignition kernel away from the surface of the SDI. In contrast to the results for Site 1, laser ignition at Site 2 resulted in an approximately 33% increase in the range of combustor mass flows at which 75% ignition probability could be achieved when compared to the SDI, Figure 10.…”

Section: Resultsmentioning

confidence: 99%

Investigation of Ignition Probability in a Gas Turbine Combustor Using Laser Ignition

Hicks¹,

Wilson²,

Sheppard

et al. 1999

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

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For an aircraft gas turbine engine, the ignition performance is usually expressed in terms of the range of flight conditions over which stable combustion can be established. At present, the size of an aircraft’s gas turbine combustor is governed predominately by its altitude relight performance and is principally derived from existing empirical design rules. These indicate the volume required to give adequate primary zone airodynamic loading to achieve the desired relight performance. A possible means of improving altitude relight performance is to relocate the point of ignition away from the combustor wall to a more favourable location within the combustion chamber. One way of achieving this is through the use of laser ignition. Reported in the paper is an initial programme of work in which the possibility of using laser ignition has been investigated in a gas turbine research combustor operating at several inlet conditions. Comparative results show that, when sited at the same location, laser ignition gave no noticeable improvement in ignition performance when compared to a standard surface discharge igniter (SDI). However, by using laser ignition to locate the ignition site away from the combustor wall, the range of combustor mass flow and AFR at which ≥75% ignition probability could be achieved was increased by approximately 33%. In conjunction with the experimental study, an ignition probability model, based on the local magnitude of a Karlovitz stretch factor, has been developed to identify suitable regions within the combustor in which to apply laser ignition. The Karlovitz parameter gives an indication as to whether or not a flame kernel will propagate successfully and has been used in conjunction with flow field and scalar distributions generated by Computational Fluid Dynamics (CFD) to yield a 2D map of ignition probability. However, the sensitivity shown by the model to the accuracy of the CFD predictions meant that reliable estimates of optimum ignition sites could only be obtained using experimental fuel and turbulence intensity distributions.

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“…Thus, for a railplug, the combined effects of electromagnetic and thermodynamic forces drive the plasma into the combustion chamber. Other designs for electromagnetically enhanced plasmas have been studied (Tozzi and Dabora 1982;Fitzgerald 1976;and Bradley and Crichley 1974), but in general they do not provide a significant electromagnetic driving force (Hall et al 1991). The electromagnetic principle governing the operation of the railplug is similar to that of the rail accelerator proposed by Harrison and Weinberg (1974), who use an external rather than self-induced magnetic field to accelerate the arc.…”

Section: Introductionmentioning

confidence: 99%

Computational and experimental study of a railplug igniter

Ellzey

Hall

Zhao

1993

Experiments in Fluids

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The plasma plume generated by a new type of high energy igniter known as the railplug is examined. The railplug is a miniaturized railgun that has the potential for improving ignition characteristics of combustible mixtures in engines. The objective of the study is to gain an understanding of the characteristics of the plasma created by a transparent railplug and to validate a multidimensional computer simulation of the plasma and shock fronts. The nature of the plume emitted by the railplug was examined for three levels of electrical energy while firing into air at a pressure of 1 atm. The computer model is to be used to predict trends in railplug performance for various railplug designs, energies, and ambient conditions. The velocity of the plasma movement inside a transparent railplug was measured, as well as the velocity of the plume ejected from the cavity. A shock is produced at the initiation point of the arc and propagates down the cavity, eventually exiting the plug. The velocity of the shock was both measured experimentally and simulated by the model. The computer simulation produces a mushroom-shaped plasma plume at the railplug exit similar to that observed in the shadowgraph photos. The simulation also reproduced the toroidal circulation observed at the plug exit in the shadowgraphs, the radial expansion, and the penetration depth of the plume. The trend of linearly increasing plasma kinetic energy with stored electrical energy predicted by the simulation was verified by shadowgraph photos. The agreement between the experiments and the simulations suggests that the multidimensional model holds promise as a predictive design tool.

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Electromagnetically induced motion of spark ignition kernels

Cited by 21 publications

References 11 publications

Investigation of the effect of electrode geometry on spark ignition

Investigation of the effect of electrode geometry on spark ignition

Investigation of Ignition Probability in a Gas Turbine Combustor Using Laser Ignition

Computational and experimental study of a railplug igniter

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