A-Priori Validation of Scalar Dissipation Rate Models for Turbulent Non-Premixed Flames

Sitte, Michael Philip; Turquand, d'Auzay; Giusti, Andrea; Mastorakos, Epaminondas; Chakraborty, Nilanjan

doi:10.1007/s10494-020-00218-x

Cited by 7 publications

(6 citation statements)

References 55 publications

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“…, where C N = 42 [49,50], µ sgs is the sub-grid scale viscosity and ∆ is the filter width estimated as the cube root of the LES cell volume. The molecular diffusivity was calculated from the kinematic viscosity of the mixture using a constant Schmidt number (Sc = 0.7).…”

Section: Investigated Premixer and Cfd Analysismentioning

confidence: 99%

Quantification of Autoignition Risk in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor and Surrogate Modeling

Iavarone

Gkantonas

Jella

et al. 2022

Journal of Engineering for Gas Turbines and Power

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The design and operation of premixers for gas turbines must deal with the possibility of relatively rare events causing dangerous autoignition. Rare autoignition events may occur in the presence of fluctuations of operational parameters, such as temperature and fuel composition, and must be understood and predicted. This work presents a methodology based on Incompletely Stirred Reactor (ISR) and surrogate modelling to increase efficiency and feasibility in premixer design optimisation for rare events. For a representative premixer, a space-filling design is used to sample the variability of three influential operational parameters. An ISR is then reconstructed and solved in a post-processing fashion for each sample, leveraging a well-resolved CFD solution of the non-reacting flow inside the premixer. Via detailed chemistry and reduced computational costs, the evolution of autoignition precursors and temperature, conditioned on a mixture fraction, is tracked, and accurate surrogate models are trained on all samples. The final quantification of the autoignition probability is achieved by querying the surrogate models via Monte Carlo sampling of the random parameters. The approach is fast and reliable so that user-controllable, independent variables can be optimised to maximise system performance while observing a constraint on the allowable probability of autoignition.

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Section: Investigated Premixer and Cfd Analysismentioning

confidence: 99%

Quantification of Autoignition Risk in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor and Surrogate Modeling

Iavarone

Gkantonas

Jella

et al. 2022

Journal of Engineering for Gas Turbines and Power

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“… N ~ is the mixture fraction scalar dissipation rate which consists of contributions from both the resolved and sub-grid scales: N ~ = D normal∇ ξ ~ ⋅ normal∇ ξ ~ + 0.5 C N μ s g s ξ ″ 2 ~ / false( ρ false¯ Δ 2 false), where D is the molecular diffusivity, μ s g s is the sub-grid scale turbulent viscosity, ρ false¯ is the filtered density and C N is a model constant taken equal to 42.0. 37,28,38 The conditionally filtered chemical source term, ω α | η ~, is closed with a first order approximation. The ARM2 mechanism 39 (19 species and 15 reactions) is used.…”

Section: Methodsmentioning

confidence: 99%

Numerical investigation of the response of turbulent swirl non-premixed flames to air flow oscillations

Giusti

Zhang

Kypraiou

et al. 2022

International Journal of Spray and Combustion Dynamics

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The response of swirl non-premixed flames to air flow oscillations is studied using Large-Eddy Simulation (LES) and the Conditional Moment Closure (CMC) combustion model, focusing on the physical mechanisms leading to the heat release rate oscillations observed in a parallel experimental study. Cases relatively close to blow-off and characterized by different amplitude of the flow oscillations are considered. Numerical results are in good agreement with the experiment in terms of both mean flame shape and heat release rate response. Simulations show that the oscillation of the air flow leads to an axial movement and fragmentation of the flame that are more pronounced with increasing amplitude of the forcing. The flame response is characterized by fluctuations of the flame area, time-varying local extinction and lift-off from the fuel injection point. LES-CMC, due to the inherent capability to capture burning state transitions, predicts properly the flame transfer function as a function of the amplitude of the air flow oscillations. This suggests that the response mechanism for this flame is not only due to time-varying flame area, but also local extinction and re-ignition. This study demonstrates that LES-CMC is a useful tool for the analysis of the response of flames of technical interest to large velocity oscillations and for the prediction of the flame transfer function in conditions close to blow-off.

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“…, where C N = 42 [33,34], µ sgs the sub-grid scale viscosity and ∆ the filter width estimated as the cube root of the LES cell volume. The molecular diffusivity was calculated from the kinematic viscosity of the mixture using a constant Schmidt number (Sc = 0.7).…”

Section: Investigated Premixer and Cfd Analysismentioning

confidence: 99%

Estimation of Autoignition Propensity in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor Network Modeling

Gkantonas

Jella

Iavarone

et al. 2022

Journal of Engineering for Gas Turbines and Power

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The study of autoignition propensity in premixers for gas turbines is critical for their safe operation and design. Although premixers can be analysed using reacting Computational Fluid Dynamics (CFD) coupled with detailed autoignition chemical kinetics, it is essential to also develop methods with lower computational cost to be able to explore more geometries and operating conditions during the design process. This paper presents such an approach based on Incompletely Stirred Reactor Network (ISRN) modelling. This method uses a CFD solution of a non-reacting flow and subsequently estimates the spatial evolution of reacting scalars such as autoignition precursors and temperature conditioned on the mixture fraction, which are used to quantify autoignition propensity. The approach is intended as a "post-processing" step, enabling the use of very complex chemical mechanisms and the study of many operating conditions. For a representative premixer of an aeroderivative gas turbine, results show that autoignition propensity can be reproduced with ISRN at highly reactive operating conditions featuring multi-stage autoignition of a dual fuel mixture. The ISRN computations are consequently analysed to explore the evolution of reacting scalars and propose some autoignition metrics that combine mixing and chemical reaction to assist the design of premixers.

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A-Priori Validation of Scalar Dissipation Rate Models for Turbulent Non-Premixed Flames

Cited by 7 publications

References 55 publications

Quantification of Autoignition Risk in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor and Surrogate Modeling

Quantification of Autoignition Risk in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor and Surrogate Modeling

Numerical investigation of the response of turbulent swirl non-premixed flames to air flow oscillations

Estimation of Autoignition Propensity in Aeroderivative Gas Turbine Premixers Using Incompletely Stirred Reactor Network Modeling

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