Influence of scalar dissipation on flame success in turbulent sprays with spark ignition

Wandel, Andrew P.

doi:10.1016/j.combustflame.2014.04.006

Cited by 50 publications

(104 citation statements)

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“…The experimental data by Ahmed and Mastorakos (2006) demonstrated that an increase in mean velocity in jets also leads to a deterioration of ignition performance, which was quantified by a reduction in ignition probability. The detrimental effects of turbulent velocity fluctuation have also been reported for localized ignition of droplet-laden mixtures (Wandel, 2013(Wandel, , 2014Wandel et al, 2009).…”

Section: Introductionmentioning

confidence: 85%

“…where s indicates the mass of oxidizer consumed per unit mass of fuel consumption under stoichiometric conditions and the fuel reaction rate is given by an Arrhenius-type expression (Chakraborty et al, 2007Chakraborty and Mastorakos, 2008;Mastorakos et al, 1997;Tarrazo et al, 2006;Wandel, 2013Wandel, , 2014Wandel et al, 2009):…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…(6) is assumed to follow a Gaussian distribution in the radial direction from the center of the ignitor (Chakraborty et al, 2007;Chakraborty and Mastorakos, 2008;Espi andLiñán, 2001, 2002;Neophytou et al, 2010;Patel and Chakraborty, 2014;Wandel, 2013Wandel, , 2014Wandel et al, 2009) and is expressed in the following manner:…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…The parameter b sp for optimum spark duration varies between 0:2 < b sp < 0:4 (Ballal and Lefebvre, 1977b) and b sp ¼ 0:2 has been taken for the current analysis following previous studies (Chakraborty et al, 2007;Chakraborty and Mastorakos, 2008;Patel and Chakraborty, 2014;Wandel, 2013Wandel, , 2014Wandel et al, 2009). The details of spark formation (momentum modification contribution, plasma formation, and shock wave) are kept beyond the scope of the present analysis in order to keep this study computationally feasible.…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…The initial magnitudes of the normalized rms value of turbulent velocity u 0 =S b ϕ¼1 ð Þ , rms value of equivalence ratio ϕ 0 , and normalized Taylor micro-scale of equivalence ratio variation l ϕ =l f are listed in Table 1. The ratio of longitudinal integral length scale to flame thickness is considered to be L 11 =l f ¼ 3:36 for all turbulent cases following previous analyses (Chakraborty et al, 2007;Chakraborty and Mastorakos, 2008;Neophytou et al, 2010;Patel and Chakraborty, 2014;Wandel, 2013Wandel, , 2014Wandel et al, 2009). The case names are chosen in such a manner so that G and B stand for initial Gaussian and bi-modal equivalence ratio ϕ distributions; T0, T4, and T6 indicate increasing turbulence intensity u 0 =S b ϕ¼1 A compressible 3D DNS code SENGA (Chakraborty et al, 2007;Chakraborty and Mastorakos, 2008;Neophytou et al, 2010;Patel and Chakraborty, 2014, Wandel, 2013, 2014Wandel et al, 2009) was used to carry out the simulations in a domain of size 33l f Â 33l f Â 33l f , which ensures that about 10 integral eddies are retained on each side of the domain.…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

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Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Patel

Chakraborty

2016

Combustion Science and Technology

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The influences of initial mixture distribution on localized forced ignition of globally stoichiometric stratified mixtures have been analyzed using three-dimensional compressible direct numerical simulations. The globally stoichiometric mixtures (i.e., hϕi ¼ 1:0) for different root-meansquare (rms) values of equivalence ratio (i.e., ϕ 0 = 0.2, 0.4, and 0.6) and the Taylor micro-scale lϕ of equivalence ratio ϕ variation (i.e., lϕ=l f ¼ 2.1, 5.5, and 8.3 with l f being the Zel'dovich flame thickness of stoichiometric mixture) have been analyzed for different initial rms values of turbulent velocity u 0 . The equivalence ratio variation is initialized following both Gaussian and bi-modal distributions for a given set of values of ϕ 0 and lϕ=l f in order to analyze the effects of mixture distribution. The localized forced ignition is accounted for by considering a source term in the energy conservation equation that deposits energy for a stipulated time interval. It has been demonstrated that the initial equivalence ratio distribution has significant effects on the extent of burning of stratified mixtures following successful localized forced ignition. It has been found that an increase in u 0 =S b ϕ¼1 ð Þ (ϕ 0 ) has adverse effects on the burned gas mass, whereas the effects of lϕ=l f on the extent of burning are nonmonotonic and dependent on ϕ 0 for initial bi-modal mixture distribution. The initial Gaussian mixture distribution exhibits an increase in burned gas mass with decreasing lϕ=l f , but these cases are more prone to flame extinction for high values of u 0 than the corresponding bi-modal distribution cases. Detailed physical explanations have been provided for the observed mixture distribution, ϕ 0 , u 0 , and lϕ=l f dependences on the extent of burning following localized forced ignition of stratified mixtures. ARTICLE HISTORY

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