Development of a novel flamelet-based model to include preferential diffusion effects in autoignition of CH4/H2 flames

Abtahizadeh, Ebrahim; Goey, de Lph Philip; Oijen, J.A. van

doi:10.1016/j.combustflame.2015.06.015

Cited by 39 publications

(34 citation statements)

References 29 publications

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“…An IML is the simplest physical representation of an igniting non-premixed combustion system [19,[28][29][30]. The IML configuration as considered here has an exponentially decaying scalar dissipation field and thereby incorporates the simultaneous reactive and diffusive processes on ignition.…”

Section: Methodsmentioning

confidence: 99%

“…where χ is the scalar dissipation rate. It is clear from (19) that the accurate reproduction of the time integral ofω Y from detailed chemistry simulation is critical for an accurate reproduction of ignition delay in a-posteriori simulation of IML using FGM. For convenience of representation, the time integral ofω Y till ignition can be denoted as the change Y from unburnt state Y u till ignition Y ig although it is not exact due to the transport terms in the scalar conservation equation.…”

Section: New Optimisation Approachmentioning

confidence: 99%

“…For computational simulation of MILD combustion, ignition has a crucial role in flame stabilisation as found in detailed numerical and experimental studies [16][17][18]. Unsteady flamelet models based on igniting flamelets have been used in LES simulations of lifted JHC flames [19,20], which capture the flame lift-off heights in the vitiated coflow burner of Cabra et al [21] and the Delft JHC burner [22]. In methods based on non-premixed flamelets, the mixture fraction Z serves as a primary controlling variable that represents laminar mixing in a two-stream problem or equivalence ratio in case of partially premixed flamelets.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A novel method to automate FGM progress variable with application to igniting combustion systems

Vasavan

Goey

Oijen

2019

Combustion Theory and Modelling

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This paper introduces a new method to formulate reaction progress variables for the application of FGM in combustion systems. The method involves a multiobjective optimisation to find a reaction progress variable that accurately reproduces complex reactive phenomenon of interest. In our current research, the method is applied to igniting non-premixed flames. The optimised progress variable combinations are evaluated for their accuracy in reproducing detailed chemistry results for the ignition of hydrocarbon fuels. Comparisons are made against conventional progress variable formulations used in the literature. The current approach takes into consideration the table resolution and error reduction for the application of FGM in combustion problems. Methods that rely on maximising the smoothness of the manifold or ensuring monotonic increase in progress variables alone are shown to be insufficient to capture ignition. The possibility of optimising the progress variable with emphasis on accurately resolving a particular zone or phase of combustion, such as ignition, while maintaining minimum data loss is demonstrated. Through its application in a number of igniting counterflow flames, the effectiveness of the current method is verified. Progress variables optimised using specific flame databases are shown to accurately reproduce the ignition delays even with moderate variations in boundary conditions of the respective flames.

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Section: Methodsmentioning

confidence: 99%

Section: New Optimisation Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A novel method to automate FGM progress variable with application to igniting combustion systems

Vasavan

Goey

Oijen

2019

Combustion Theory and Modelling

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“…These computations were conducted using CHEM1D [25], which is a 1D flame simulation tool developed at Eindhoven University of Technology. Igniting mixing layers (IML), which were shown to be successful in modeling JHC conditions [17], was selected as the flamelet type. In IML; the fuel and oxidizer are initially placed side by side, mix through molecular diffusion, and react in time.…”

Section: Numerical Methods and Simulation Setupmentioning

confidence: 99%

“…Y is generally chosen as a combination of mass fractions of reactants and/or products [13,14,16,17], because they are either consumed or produced throughout all combustion stages. However, Medwell et al [18] found that in an autoigniting MILD system, initially a preignition stage takes place in which precursors form, but reactants or products do not vary much.…”

Section: Introductionmentioning

confidence: 99%

Modeling MILD combustion using a novel multistage FGM method

Goktolga

Oijen

Goey

2017

Proceedings of the Combustion Institute

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Moderate or intense low-oxygen dilution (MILD) combustion is a promising concept to reduce emissions and increase efficiency. It requires high levels of dilution and preheating of reactants, which is realized by mixing reactants with products. In order to extend the application areas of MILD combustion, adequate computational models must be developed. In this study, one of the candidate models, flamelet generated manifolds (FGM), has been assessed in terms of applicability to MILD combustion. Based on the results of this assessment, a novel multistage (MuSt) FGM method has been developed. The need for developing such a method mainly stems from the existence of different combustion stages in the MILD regime, which cannot be represented by a single progress variable. In the MuSt-FGM approach, each stage of combustion is modeled using a different progress variable, without increasing the dimension of the lookup table. The MuSt-FGM approach has been tested by conducting a priori study, and simulating both 1D laminar and 2D turbulent flames. Proving successful in all three tests, the MuSt-FGM method emerges as a promising tool for modeling not only MILD combustion, but also other systems where combustion is characterized by different stages.Keywords: Multistage flamelet generated manifolds (FGM), Moderate or intense low-oxygen dilution (MILD), Non-premixed combustion, Autoignition, Jet in hot coflow (JHC).2

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On the Definition of Reaction Progress Variable in Exhaust Gas Recirculation Type Turbulent MILD Combustion of Methane and n-Heptane

Abo-Amsha,

Awad,

Ahmed

et al. 2024

Flow Turbulence Combust

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Three-dimensional Direct Numerical Simulations of Exhaust Gas Recirculation (EGR)-type Moderate or Intense Low Oxygen Dilution (MILD) combustion of homogeneous mixtures of methane- and n-heptane–air have been conducted with skeletal chemical mechanisms. The suitability of different choices of reaction progress variable (which is supposed to increase monotonically from zero in the unburned gas to one in fully burned products) based on the mass fractions of different major species and non-dimensional temperature have been analysed in detail. It has been found that reaction progress variable definitions based on oxygen mass fraction, and linear combination of CO, CO2, H2 and H2O mass fractions (i.e. $${c}_{O2}$$ c O 2 and $${c}_{c}$$ c c ) capture all the extreme values of the major species in the range between zero and one under MILD conditions. A reaction progress variable based on fuel mass fraction is found to be unsuitable for heavy hydrocarbons, such as n-heptane, since the fuel breaks down to smaller molecules before the major reactants (products) are completely consumed (formed). Moreover, it has been found that the reaction rates of $${c}_{O2}$$ c O 2 and $${c}_{c}$$ c c exhibit approximate linear behaviours with the heat release rate in both methane and n-heptane MILD combustion. The interdependence of different mass fractions in the EGR-type homogeneous mixture combustion is considerably different from the corresponding 1D unstretched premixed flames. The current findings indicate that the tabulated chemistry approach based on premixed laminar flames may need to be modified to account for EGR-type MILD combustion. Furthermore, both the reaction rate and scalar dissipation rate of $${c}_{O2}$$ c O 2 and $${c}_{c}$$ c c are found to be non-linearly related in both methane and n-heptane MILD combustion cases but the qualitative nature of this correlation for n-heptane is different from that in methane. This suggests that the range of validity of SDR-based turbulent combustion models can be different for homogeneous MILD combustion of different fuels.

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Development of a novel flamelet-based model to include preferential diffusion effects in autoignition of CH4/H2 flames

Abstract: Original citation & hyperlink:Abtahizadeh, E. , de Goey, P. and van Oijen, J.

Cited by 39 publications

References 29 publications

A novel method to automate FGM progress variable with application to igniting combustion systems

A novel method to automate FGM progress variable with application to igniting combustion systems

Modeling MILD combustion using a novel multistage FGM method

On the Definition of Reaction Progress Variable in Exhaust Gas Recirculation Type Turbulent MILD Combustion of Methane and n-Heptane

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