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A flamelet/progress variable approach for modeling coal particle ignition

Vascellari, M. and Tufano, G. L. and Stein, O. T. and Kronenburg, A. and Kempf, A. M. and Scholtissek, A. and Hasse, C. (2017):
A flamelet/progress variable approach for modeling coal particle ignition.
In: Fuel, Elsevier, pp. 29-38, 201, ISSN 0016-2361,
DOI: 10.1016/j.fuel.2016.09.005,
[Online-Edition: http://dx.doi.org/10.1016/j.fuel.2016.09.005],
[Article]

Abstract

Abstract In this work an extended flamelet/progress variable (FPV) approach is presented with the aim of simulating the homogeneous auto-ignition of single coal particles during devolatilization. The {FPV} approach allows chemistry to be decoupled from the solution of the flow field, using a pre-computed strained flamelet look-up table. In this way, the complex chemistry governing coal particle ignition can be accurately accounted for. In particular, one-dimensional unsteady laminar diffusion flamelet (ULDF) simulations are used to generate the table, considering different values of the mixture fraction and the scalar dissipation rate on the particle surface. A new analytical formulation for the scalar dissipation rate is used to solve the diffusion flamelet equations in mixture fraction space, characterized by maximum values on the particle side, rapidly decreasing to zero towards the oxidizer. The time of the {ULDF} simulations is mapped to progress variable to characterize the ignition process. The {FPV} approach is then used in laminar resolved {CFD} simulations of the reactive boundary layer around a single coal particle. The flamelet table look-up is performed using the cell values of the mixture fraction and progress variable along with the particle surface values of the mixture fraction and scalar dissipation rate. Results from the new approach are finally compared with results from a simulation fully resolving transport processes and the detailed chemistry by means of a priori and a posteriori analyses. The results show that the {FPV} method is able to correctly reproduce the flame structure before and during the ignition process.

Item Type: Article
Erschienen: 2017
Creators: Vascellari, M. and Tufano, G. L. and Stein, O. T. and Kronenburg, A. and Kempf, A. M. and Scholtissek, A. and Hasse, C.
Title: A flamelet/progress variable approach for modeling coal particle ignition
Language: English
Abstract:

Abstract In this work an extended flamelet/progress variable (FPV) approach is presented with the aim of simulating the homogeneous auto-ignition of single coal particles during devolatilization. The {FPV} approach allows chemistry to be decoupled from the solution of the flow field, using a pre-computed strained flamelet look-up table. In this way, the complex chemistry governing coal particle ignition can be accurately accounted for. In particular, one-dimensional unsteady laminar diffusion flamelet (ULDF) simulations are used to generate the table, considering different values of the mixture fraction and the scalar dissipation rate on the particle surface. A new analytical formulation for the scalar dissipation rate is used to solve the diffusion flamelet equations in mixture fraction space, characterized by maximum values on the particle side, rapidly decreasing to zero towards the oxidizer. The time of the {ULDF} simulations is mapped to progress variable to characterize the ignition process. The {FPV} approach is then used in laminar resolved {CFD} simulations of the reactive boundary layer around a single coal particle. The flamelet table look-up is performed using the cell values of the mixture fraction and progress variable along with the particle surface values of the mixture fraction and scalar dissipation rate. Results from the new approach are finally compared with results from a simulation fully resolving transport processes and the detailed chemistry by means of a priori and a posteriori analyses. The results show that the {FPV} method is able to correctly reproduce the flame structure before and during the ignition process.

Journal or Publication Title: Fuel
Volume: 201
Publisher: Elsevier
Uncontrolled Keywords: Coal, Flamelet, Flamelet progress variable, Ignition, CFD, Pyrolysis
Divisions: 16 Department of Mechanical Engineering > Simulation of reactive Thermo-Fluid Systems (STFS)
16 Department of Mechanical Engineering
Date Deposited: 15 Nov 2017 08:35
DOI: 10.1016/j.fuel.2016.09.005
Official URL: http://dx.doi.org/10.1016/j.fuel.2016.09.005
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