Ignition of turbulent swirling n-heptane spray flames using single and multiple sparks

Marchione, Teresa; Ahmed, Samer F.; Mastorakos, Epaminondas

doi:10.1016/j.combustflame.2008.10.003

Cited by 119 publications

(57 citation statements)

References 57 publications

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“…From locations with positive axial velocity, the kernel may get convected downstream, but if the flame grows enough in the radial direction to get inside the recirculation zone, then the flame has a good chance of growing fully. The movement of the flame upstream is key to successful ignition, consistent with previous work with nonpremixed [21] and spray [3] laboratory flames and single-sector gas turbine combustors [24,25].…”

Section: Ignition Visualisationsupporting

confidence: 73%

“…In recent years, new insights have been developed into the fundamentals of spark ignition processes in non-premixed and spray systems [1,3]. In both experiments and modelling the key finding is that the kernels from the spark must grow and also be advected by the flow towards the anchoring points of the flame for the overall burner ignition to be successful.…”

Section: Introductionmentioning

confidence: 99%

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Simulations and experiments on the ignition probability in turbulent premixed bluff-body flames

Sitte

Bach

Kariuki

et al. 2016

Combustion Theory and Modelling

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The ignition characteristics of a premixed bluff-body burner under lean conditions were investigated experimentally and numerically with a physical model focusing on ignition probability. Visualisation of the flame with a 5 kHz OH* chemiluminescence camera confirmed that successful ignitions were those associated with the movement of the kernel upstream, consistent with previous work on non-premixed systems. Performing many separate ignition trials at the same spark position and flow conditions resulted in a quantification of the ignition probability P ign , which was found to decrease with increasing distance downstream of the bluff body and a decrease in equivalence ratio. Flows corresponding to flames close to the blow-off limit could not be ignited, although such flames were stable if reached from a richer already ignited condition. A detailed comparison with the local Karlovitz number and the mean velocity showed that regions of high P ign are associated with low Ka and negative bulk velocity (i.e. towards the bluff body), although a direct correlation was not possible. A modelling effort that takes convection and localised flame quenching into account by tracking stochastic virtual flame particles, previously validated for non-premixed and spray ignition, was used to estimate the ignition probability. The applicability of this approach to premixed flows was first evaluated by investigating the model's flame propagation mechanism in a uniform turbulence field, which showed that the model reproduces the bending behaviour of the S T -versus-u curve. Then ignition simulations of the bluff-body burner were carried out. The ignition probability map was computed and it was found that the model reproduces all main trends found in the experimental study.

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Section: Ignition Visualisationsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Simulations and experiments on the ignition probability in turbulent premixed bluff-body flames

Sitte

Bach

Kariuki

et al. 2016

Combustion Theory and Modelling

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“…This turbulent mixing process later affects the probability of ignition. The spark ignition has been studied experimentally and numerically by a few researchers (Birch et al, 1981;Ahmed et al, 2007;Marchione, Ahmed, & Mastorakos, 2009;Mastorakos, 2009;Oldenhof et al, 2010Oldenhof et al, , 2011 and still needs more attention. A tungsten electrode was used by Ahmed et al (2006Ahmed et al ( , 2007 as an ignition rod for the spark ignition because it can withstand up to 3200 K. They studied electrode diameters of 1.0 mm, 0.7 mm, and 0.5 mm for ignition probability and found that the ignition probability was increased with the decrease of the electrode diameter and increase in spark energy.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Recirculation Zone and Ignition Position of Non-Premixed Bluff-Body for Biogas MILD Combustion

Noor¹,

Wandel²,

Yusaf³

2013

Int J Automot Mech Eng

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Combustion ignition study is important due to the combustion process becoming more lean and efficient. This paper studied the recirculation zone and ignition location for the bluff-body non-premixed MILD burner with biogas used as fuel. The location of the ignition was critical to ensure that the spark energy supply during the ignition process can successfully ignite the mixture of air and fuel. The numerical calculations were done using the commercial code ANSYS-Fluent to simulate the furnace with a bluffbody burner to determine the recirculation zone. The turbulence model used was the realizable k-ε model. The inner recirculation zone between the air and fuel nozzle is the best location for the ignition point, since the low velocity of air and fuel mixing will assist the ignition process. This is because the ignition energy will have time to ignite the mixture in the low speed turbulent swirl flow. The most suitable location with the highest possibility of ignition is the center of the recirculation zone.

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“…Indeed, turbulence, flow velocity, droplet size and velocity, and fuel vapour repartition are parameters governing the ignition mechanisms. Several studies on spray ignition [1][2][3] have been carried out. Studies on spray ignition in industrial configurations are still scarce although some pioneer experiments and simulations in linear [4,5] and annular combustors [6,7] have been done.…”

Section: Introductionmentioning

confidence: 99%

Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

Santiago

Verdier

Vandel³

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Laser ignition was investigated in the swirled, confined CORIA Rouen Spray Burner under ultra-lean conditions (=0.61) with n-heptane as the liquid fuel. Ignition probability was calculated for different spark locations and compared to the non-ignited local flow properties. Mean velocity components of the carrier flow were measured by PDA under spray presence and without spray, and are compared to mean values from PIV. PIV measurements provide information on the instantaneous airflow and the total strain rate. Fuel droplet size-velocity data was measured by PDA. Toluene-PLIF images were acquired to provide information on the local equivalence ratio and the flammability factor. Results show that the outer recirculation zone (ORZ) has a flammability factor close to 1 and the highest ignition probability (~80%). These results have a high correlation with the air velocity field and turbulent kinetic energy. Instantaneous equivalence ratio images and shear rate-velocity fields give important information on local segregation of the flow properties that help to understand the ignition process. The present work provides a useful database for numerical simulations and industry, plus new insight on spray ignition. KeywordsSpray ignition, PDA, PIV, Toluene PLIF, Ignition probability, Local flow properties. IntroductionThe ignition process in gas turbines involves a wide range of parameters which makes it a multi-physical complex problem. New aeronautical burner designs demand a better knowledge of the mechanisms here involved to assure, for instance, re-ignition in high altitude of lean-combustion engines. Real combustors work with two-phase flows with strongly varying local properties. Indeed, turbulence, flow velocity, droplet size and velocity, and fuel vapour repartition are parameters governing the ignition mechanisms. Several studies on spray ignition [1-3] have been carried out. Studies on spray ignition in industrial configurations are still scarce although some pioneer experiments and simulations in linear [4,5] and annular combustors [6,7] have been done. Investigations on the influence of parameters such as turbulence [8, 9] also exist. The knowledge is still not sufficient to identify and understand the real mechanisms of ignition. More experiments are also needed to validate numerical simulations. Ignition in aeronautical engines can be divided into four steps: (i) energy deposition through a spark and its evolution into a flame kernel; (ii) kernel propagation; (iii) flame stabilisation on one injector; (iv) injector-to-injector propagation of the flame. Sometimes one of these phases is not successful and leads to a missed ignition. Even with a sufficient energy supply at phase (i), phase (ii) appears to be a critical step, namely in lean conditions. During its propagation in the chamber, the flame kernel will be exposed to varying local properties of the flow that may be adverse for its survival. This depends on both, the initial location of the kernel (spark location) and on its subsequent trajectory...

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Ignition of turbulent swirling n-heptane spray flames using single and multiple sparks

Cited by 119 publications

References 57 publications

Simulations and experiments on the ignition probability in turbulent premixed bluff-body flames

Simulations and experiments on the ignition probability in turbulent premixed bluff-body flames

Analysis of Recirculation Zone and Ignition Position of Non-Premixed Bluff-Body for Biogas MILD Combustion

Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

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