Numerical investigation of the effect of pressure on heat release rate in iso-octane premixed turbulent flames under conditions relevant to SI engines

Savard, Bruno; Lapointe, Simon; Teodorczyk, A.

doi:10.1016/j.proci.2016.07.056

Cited by 23 publications

(14 citation statements)

References 37 publications

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“…The HRR in convex regions is significantly enhanced even for Case φ = 0.6. Moreover, the peak HRR happens in low curvature regions, which is due to the effects of the Markstein number [48]. Comparing the ordinate values of the two set plots, it is found that the gap is decreasing with increasing equivalence ratio.…”

Section: Characteristics Of Turbulent Reaction Zonesmentioning

confidence: 90%

“…However, the Reynolds number is higher when the equivalence ratio is increased. To save computational resources, the ratio lt/δL, is kept unity, which is also used in other DNS studies [48][49][50]. Figure 2 shows that the three cases are located in the distributed reaction zone with high ' u /SL ratio, which is more relevant to combustion in real combustors.…”

Section: Simulation Parametersmentioning

confidence: 99%

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Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm

Wang

Jin

Luo

2019

International Journal of Hydrogen Energy

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Reaction layer thickness Δx Grid resolution κ Mean curvature v Kinematic viscosity v'kj Forward stoichiometric coefficient for species k in reaction j v''kj Reverse stoichiometric coefficient for species k in reaction j φ Equivalence ratio of the fresh mixture φL Local equivalence ratio ω  Species reaction rate Ai Pre-exponential factor of Arrhenius equation c Progress variable Ei Activation energy of a reaction Ka Karlovitz number Kf Forward reaction rate constant Kr Reverse reaction rate constant K0 Limit of low-pressure reaction rate constant K∞ Limit of high-pressure reaction rate constant Kci Equilibrium constant t l Integral length scale [M] Overall contribution of different species in Three-body reactions Re Reynolds number SL Laminar flame speed Syz Cross-section area T Local temperature Tu Temperature of unburnt gas Tb Temperature of burnt gas ' u Root-mean-square turbulent velocity fluctuation Vrec Reaction zone volume Xk Molar concentration of species k , f k Y Local mass fraction of species k

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Section: Characteristics Of Turbulent Reaction Zonesmentioning

confidence: 90%

Section: Simulation Parametersmentioning

confidence: 99%

Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm

Wang

Jin

Luo

2019

International Journal of Hydrogen Energy

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“…in hydrocarbon-air mixtures) decrease with increasing pressure and thus flame resolution for a fixed geometry (as in this work) becomes a real challenge for high pressure DNS and nearly impossible in the context of detailed chemistry and transport. Often DNS studies are done for statistically planar flames in a box and the computational domain shrinks with increasing pressure [57]. In this sense the present configuration is a relatively complex geometry for highpressure combustion.…”

Section: Numerical Implementationmentioning

confidence: 99%

Evolution of Flame Curvature in Turbulent Premixed Bunsen Flames at Different Pressure Levels

Alquallaf

Klein

Dopazo

et al. 2019

Flow Turbulence Combust

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The physical mechanisms underlying the curvature evolution in turbulent premixed Bunsen flames at different thermodynamic pressures are investigated using a three-dimensional Direct Numerical Simulation database. It is found that, due to the occurrence of the Darrieus-Landau instability, the high-pressure flame exhibits higher probability than the low-pressure cases of developing large negative curvature values and saddle concave topologies. The terms in the curvature transport equation due to normal strain rate gradients and curl of vorticity arising from both turbulent flow and flame normal propagation play pivotal roles in the curvature evolution. The mean value of the net contribution of the flame propagation terms dominates over the net contributions arising from the background fluid motion. The net contribution of the source/sink terms tries to reduce the convexity of the flame surface in the positively curved locations. By contrast, the net contribution of the source/sink terms promotes concavity of the flame surface towards the reactants in the negatively curved regions and this effect is particularly strong for the high pressure flame, where the effects of the Darrieus-Landau instability are prominent. This also gives rise to large negative skewness of the probability density functions of curvature in the high-pressure flame with the Darrieus-Landau instability.

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“…Previous homogeneous flame kernel development DNS analyses showed that differential diffusion tends to increase the flame speed and accelerate the overall flame expansion [8]. Furthermore, flame curvature dynamics was shown to be sensitive to Lewis number [9], in particular at low pressures [10]. On the other hand, flame kernel ignition dynamics have been shown to be strongly influenced by the fuel Lewis number, even in inhomogeneous mixtures [11].…”

Section: Introductionmentioning

confidence: 99%

Effects of differential diffusion and stratification characteristic length-scale on the propagation of a spherical methane-air flame kernel

Er-Raiy

Boukharfane

Parsani

2021

AIAA Scitech 2021 Forum

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Early flame kernel development and propagation in globally lean stratified fuel-air mixtures is of importance in various practical devices such as internal combustion engines. In this work, three-dimensional direct numerical simulation (DNS) is used to study the influence of the differential diffusion effects in a globally lean methane-air mixtures in presence of mixture heterogeneities with the goal of understanding the flame kernel behavior in such conditions. The DNS typical configuration corresponds to a homogeneous isotropic flow with an expanding spherical flame kernel. The local forced ignition of the kernel is performed by appending as source term in the sensible enthalpy transport equation that emulates spark ignition by energy deposit for a prescribed duration. The combustion chemistry is described with a skeletal methane-air mechanism, which i) features 14 species and 38 reactions, and ii) uses a multicomponent approach to evaluate transport coefficients. To assess the joint effects of differential diffusion and the stratification characteristic length-scale Φ on the flame kernel development, we considered cases with constant (unitary) and variable fuel Lewis number, both with different values for Φ .

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Numerical investigation of the effect of pressure on heat release rate in iso-octane premixed turbulent flames under conditions relevant to SI engines

Cited by 23 publications

References 37 publications

Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm

Response of heat release to equivalence ratio variations in high Karlovitz premixed H2/air flames at 20 atm

Evolution of Flame Curvature in Turbulent Premixed Bunsen Flames at Different Pressure Levels

Effects of differential diffusion and stratification characteristic length-scale on the propagation of a spherical methane-air flame kernel

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