Influence of Strouhal number on pulsating methane–air coflow jet diffusion flames

Sánchez–Sanz, Mario; Bennett, Beth Anne V.; Smooke, Mitchell D.; Liñán, A.

doi:10.1080/13647830.2010.490048

Cited by 10 publications

(8 citation statements)

References 56 publications

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“…The key parameter that affects the time to solution is the number of linear solver iterations, which also provides an approximate measure of the number of nonlinear residual function evaluations, since the Jacobian-free method requires one such evaluation for every linear solver iteration. The correlation between the number of function evaluations and the time to solution would be expected for calculations with detailed chemistry models, as in this case the expense of computing the chemical production rates and We now turn our attention to the flame with the 50% amplitude perturbation (henceforth, "the 50% flame"), which is the one that has received the most attention in the literature [7,22,29,56,59,70]. The 30% flame has also been computed previously [8,29]; to our knowledge, the other two (70% and 90%) have not, but we refrain from any real discussion of these other three flames until results with a detailed chemistry model are available.…”

Section: Resultsmentioning

confidence: 99%

“…In the laboratory, the forcing frequency was chosen to be a multiple of the 10 Hz frequency of the laser, and 20 Hz was settled on since it yielded the most interesting flame dynamics. This may be because of a near-resonance effect with some natural frequency of the steady flame [70]. The average axial velocity in the fuel tube W F avg and the constant axial velocity in the oxidizer tube W O are both set to 35 cm/s.…”

Section: Resultsmentioning

confidence: 99%

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A Fully Implicit, Compact Finite Difference Method for the Numerical Solution of Unsteady Laminar Flames

Dobbins

Smooke

2010

Flow Turbulence Combust

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Forced laminar diffusion flames form an important class of problems that can help to bridge the significant gap between steady laminar flames in simple burner configurations and the turbulent flames found in many practical combustors. Such flames offer a much wider range of interactions between convection, diffusion, and chemical reaction than can be examined under steady-state conditions, and yet detailed simulations of them should be feasible without having to resort to "modeling" any of the relevant physics, above all without having prematurely to reduce the large kinetic mechanisms typical of hydrocarbon fuels. Nevertheless, the computation of time-dependent laminar diffusion flames with conventional numerical methods is hindered by technical challenges that, while not new, are more troublesome to surmount than in the calculation of otherwise similar, unforced flames. First, the intricate spatiotemporal coupling between fluid dynamics and combustion thermochemistry ensures that spurious numerical diffusion or spatial under-resolution of the mixing process at any stage of the computation can lead to inaccurate prediction of flame characteristics for the remainder thereof. Second, relatively long simulated flow times and extremely short chemical time scales make many standard time integration algorithms impractical on all but the largest parallel computer clusters. This paper introduces a new numerical approach for time-varying laminar flames that addresses these challenges through the use of high order compact finite difference schemes within a robust, fully implicit solver based on a Jacobianfree Newton-Krylov method. The capabilities of this implicit-compact solver are demonstrated on a periodically forced axisymmetric laminar jet diffusion flame 764 Flow Turbulence Combust (2010) 85:763-799 with one-step Arrhenius chemistry, and the results are compared to those of a conventional low order finite difference solver.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A Fully Implicit, Compact Finite Difference Method for the Numerical Solution of Unsteady Laminar Flames

Dobbins

Smooke

2010

Flow Turbulence Combust

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“…Because it can ensure mass conservation on non-staggered grids while maintaining the second-order ellipticity of the governing equations, the modified vorticity-velocity formulation is particularly suitable for flame simulations and has been applied to a broad spectrum of flow and flame problems (e.g. [34,[41][42][43]). At the same time, since an incomplete Laplacian operator is employed in one of Downloaded by [Universite Laval] at 07: 39 29 September 2015 its governing equations, the modified vorticity-velocity formulation has a relatively limited ability to ensure the smoothness of the velocity field.…”

Section: Introductionmentioning

confidence: 99%

“…[8,9,[19][20][21][22][23][24][25][26][27]). Of particular relevance to the current work is the successful extension of the Poisson approach, first by Ern and Smooke [33] and then by Dworkin, Bennett and Smooke [34], to chemically reactive flow problems such as chemical vapour deposition [35], steady flames [28,34,[36][37][38][39] and time-dependent flames [40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

MC-Smooth: A mass-conserving, smooth vorticity–velocity formulation for multi-dimensional flows

Cao

Bennett

Smooke

2015

Combustion Theory and Modelling

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A novel vorticity-velocity formulation of the Navier-Stokes equations -the MassConserving, Smooth (MC-Smooth) vorticity-velocity formulation -is developed in this work. The governing equations of the MC-Smooth formulation include a new secondorder Poisson-like elliptic velocity equation, along with the vorticity transport equation, the energy conservation equation, and N spec species mass balance equations. In this study, the MC-Smooth formulation is compared to two pre-existing vorticity-velocity formulations by applying each formulation to confined and unconfined axisymmetric laminar diffusion flame problems. For both applications, very good to excellent agreement for the simulation results of the three formulations has been obtained. The MC-Smooth formulation requires the least CPU time and can overcome the limitations of the other two pre-existing vorticity-velocity formulations by ensuring mass conservation and solution smoothness over a broader range of flow conditions. In addition to these benefits, other important features of the MC-Smooth formulation include: (1) it does not require the use of a staggered grid, and (2) it does not require excessive grid refinement to ensure mass conservation. The MC-Smooth formulation is a computationally attractive approach that can effectively extend the applicability of the vorticity-velocity formulation.

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“…Representative of the evolution of the reacting flow are the timescales associated with the forcing acoustic cycle and the timescales describing the evaporation and the fluid mechanical response of the flow. An important contribution to the study of forced flames response is the work done by Sánchez-Sanz et al [10]. They computed and analysed the effects of several regimes of Strouhal number on the chemistry and temperature of methane-air diffusion flames.…”

Section: Introductionmentioning

confidence: 99%

Ethanol turbulent spray flame response to gas velocity modulation

Fratalocchi

Kok

2017

Combustion Theory and Modelling

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A numerical investigation of the interaction between a spray flame and an acoustic forcing of the velocity field is presented in this paper. In combustion systems, a thermoacoustic instability is the result of a process of coupling between oscillations in heat released and acoustic waves. When liquid fuels are used, the atomisation and the evaporation process also undergo the effects of such instabilities, and the computational fluid dynamics of these complex phenomena becomes a challenging task. In this paper, an acoustic perturbation is applied to the mass flow of the gas phase at the inlet and its effect on the evaporating fuel spray and on the flame front is investigated with unsteady Reynolds averaged Navier-Stokes numerical simulations. Two flames are simulated: a partially premixed ethanol/air spray flame and a premixed pre-vaporised ethanol/air flame, with and without acoustic forcing. The frequencies used to perturb the flames are 200 and 2500 Hz, which are representative for two different regimes. Those regimes are classified based on the Strouhal number St = (D/U)f f : at 200 Hz, St = 0.07, and at 2500 Hz, St = 0.8. The exposure of the flame to a 200 Hz signal results in a stretching of the flame which causes gas field fluctuations, a delay of the evaporation and an increase of the reaction rate. The coupling between the flame and the flow excitation is such that the flame breaks up periodically. At 2500 Hz, the evaporation rate increases but the response of the gas field is weak and the flame is more stable. The presence of droplets does not play a crucial role at 2500 Hz, as shown by a comparison of the discrete flame function in the case of spray and pre-vaporised flame. At low Strouhal number, the forced response of the pre-vaporised flame is much higher compared to that of the spray flame.

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Influence of Strouhal number on pulsating methane–air coflow jet diffusion flames

Cited by 10 publications

References 56 publications

A Fully Implicit, Compact Finite Difference Method for the Numerical Solution of Unsteady Laminar Flames

A Fully Implicit, Compact Finite Difference Method for the Numerical Solution of Unsteady Laminar Flames

MC-Smooth: A mass-conserving, smooth vorticity–velocity formulation for multi-dimensional flows

Ethanol turbulent spray flame response to gas velocity modulation

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