Diesel Engine Simulations with Multi-Dimensional Conditional Moment Closure

Paola, G. De; Mastorakos, Epaminondas; Wright, Yuri M.; Boulouchos, Konstantinos

doi:10.1080/00102200801894273

Cited by 71 publications

(26 citation statements)

References 26 publications

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“…Ignition can be expected to take place at the 'most reactive' mixture fraction, ξ MR , [55]. As shown in [33,34], values in the range of 0.08 to 0.1 were evaluated for auto-ignition calculations with homogeneous CMC at diesel engine conditions, which is sufficiently close to this high resolution region. However the exact value of ξ MR is dependent on the configuration, e.g.…”

Section: Methodsmentioning

confidence: 99%

“…air and fuel temperatures, scalar dissipation rate and the chemical mechanism considered. The allocation of the CFD nodes to the CMC grid uses a fully automated procedure for which the methodology is discussed in detail in [34,44]. The spatial resolution of the CMC grid is 40 and 23 nodes in the radial and axial direction respectively.…”

Section: Methodsmentioning

confidence: 99%

“…In [33], the influence of background air turbulence was further investigated for the same experimental data and the importance of the conditional transport terms during all three phases of spray combustion were demonstrated. The first demonstration to engines of an elliptic CMC code which is fully coupled to a CFD solver has been presented in [34]. The formulation allows for dynamic adjustment of the grid to the changing engine geometry and good agreement was shown for experimental pressure traces from [35] at two operating conditions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experiments and Simulations of n-Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions

Wright

Margari

Boulouchos

et al. 2009

Flow Turbulence Combust

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Auto-igniting n-heptane sprays have been studied experimentally in a high pressure, high temperature constant volume combustion chamber with optical access. Ignition delay and the total pressure increase due to combustion are highly 50 Flow Turbulence Combust (2010) 84:49-78 repeatable whereas the ignition location shows substantial fluctuations. Simulations have subsequently been performed by means of a first-order fully elliptic Conditional Moment Closure (CMC) code. Overall, the simulations are in good agreement with the experiment in terms of spray evolution, ignition delay and the pressure development. The sensitivity of the predictions with respect to the measured initial conditions, the spray modelling options as well as the chemical mechanism employed have been analysed. Strong sensitivity on the chemical mechanism and to the initial temperature on the predicted ignition delay is reported. The primary atomisation model did not affect strongly the predicted auto-ignition time, but a strong influence was found on the ignition location prediction.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experiments and Simulations of n-Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions

Wright

Margari

Boulouchos

et al. 2009

Flow Turbulence Combust

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“…5 excluding the conditional chemical source term ω α | η. To include the convective heat loss effects from solid walls in the sub-grid CMC model, the following term is introduced into the RHS of Q h equation only for CMC cells adjacent to a wall [48,49] …”

Section: Les and Cmc Modelsmentioning

confidence: 99%

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Zhang

Mastorakos

2015

Flow Turbulence Combust

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The Large Eddy Simulation (LES)/three-dimensional Conditional Moment Closure (CMC) model with detailed chemistry is applied to predict the operating condition and dynamics of complete extinction (blow-off) in swirling non-premixed methane flames. Using model constants previously selected to provide relatively accurate predictions of the degree of local extinction in the piloted jet flames Sandia D−F, the error in the blow-off air velocity predicted by LES/3D-CMC in short, recirculating flames with strong swirl for a range of fuel flow rates is within 25 % of the experimental value, which is considered a new and promising result for combustion LES that has not been applied before for the prediction of the whole blow-off curve in complex geometries. The results also show that during the blow-off transient, the total heat release gradually decreases over a duration that agrees well with experiment. The evolution of localized extinction, reactive scalars and scalar dissipation rate is analyzed. It has been observed that a consistent symptom for flames approaching blow-off is the appearance of high-frequency and high-magnitude fluctuations of the conditionally filtered stoichiometric scalar dissipation rate, resulting in an increased fraction of local extinction over the stoichiometric mixture fraction iso-surfaces. It is also shown that the blow-off time changes with the different blow-off conditions.

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“…In some reacting flow models such as the flamelet approach [1,2,3] and the conditional moment closure approach [4,5], these parameters are explicitly used to calculate filtered quantities. In other reacting flow models such as transported density function approaches [6], the importance of the variance and dissipation rate is embedded in model variables such as mixing coefficients [7].…”

Section: Introductionmentioning

confidence: 99%

Modeling scalar dissipation and scalar variance in large eddy simulation: Algebraic and transport equation closures

et al. 2012

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The scalar dissipation rate and the scalar variance are important modeling parameters in large eddy simulations (LES) of reacting flows. Approaches ranging from constant coefficient algebraic equations to transport equations with complex closure models have been proposed to describe these parameters. While currently available approaches capture many of the physics behind the dissipation and variance, their modeling remains challenging. Here, two direct numerical simulations (DNS) are used to analyze LES dissipation rate and variance models, and to propose a new model for the dissipation rate that is based on a transport equation. The first DNS that is considered is a non-premixed auto-igniting C 2 H 4 jet flame simulation performed by Yoo et al. (Proc. Comb. Inst., 2010). An LES of this case is run using algebraic models for the dissipation rate and variance. It is shown that the algebraic models do not accurately reproduce the subfilter DNS fields. This motivates the introduction of a transport equation model for the LES dissipation rate. Closure of the equation is addressed by formulating a new adapted dynamic approach. This approach borrows dynamically computed information from LES quantities that, unlike the dissipation rate, do not reside on the smallest flow length scales. The adapted dynamic closure is analyzed by considering a second DNS of scalar mixing in homogeneous isotropic turbulence. Data from this second DNS is used to confirm that the adapted dynamic procedure successfully closes the dissipation rate equation over a wide range of LES filter widths. The first reacting jet case is then returned to and used to test the LES transport equation models. These models are shown to predict the dissipation rate and variance fields more accurately than the the algebraic LES models.

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Diesel Engine Simulations with Multi-Dimensional Conditional Moment Closure

Cited by 71 publications

References 26 publications

Experiments and Simulations of n-Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions

Experiments and Simulations of n-Heptane Spray Auto-Ignition in a Closed Combustion Chamber at Diesel Engine Conditions

Prediction of Global Extinction Conditions and Dynamics in Swirling Non-premixed Flames Using LES/CMC Modelling

Modeling scalar dissipation and scalar variance in large eddy simulation: Algebraic and transport equation closures

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