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Local flame structure analysis in turbulent CH4/air flames with multi-regime characteristics

Butz, D. and Hartl, S. and Popp, S. and Walther, S. and Barlow, R. S. and Hasse, C. and Dreizler, A. and Geyer, D. (2019):
Local flame structure analysis in turbulent CH4/air flames with multi-regime characteristics.
In: Combustion and Flame, Elsevier, pp. 426 - 438, 210, ISSN 0010-2180,
DOI: 10.1016/j.combustflame.2019.08.032,
[Online-Edition: https://doi.org/10.1016/j.combustflame.2019.08.032],
[Article]

Abstract

In practical applications, partial premixing of fuel and oxidizer, as well as recirculation of combustion products, result in complex combustion scenarios where multi-regime effects arise and a numerical representation of local reaction zones by purely premixed or purely non-premixed flame structures may not hold. Here, a novel burner system is introduced to investigate the fundamental characteristics of multi-regime combustion and to provide a basis for validating numerical models. This multi-regime burner (MRB) is specifically designed to produce flames with multi-regime characteristics while maintaining well-defined boundary conditions. Thermochemical data from Raman/Rayleigh/CO-LIF scattering experiments are provided for two selected operating conditions. The experimental investigation focuses on the overall flame structure by examining radial profiles of temperature and mixture fraction, as well as scatter plots of temperature, CH4, and CO versus mixture fraction. In order to assess the relative importance of different flame regimes, the gradient-free regime identification (GFRI) approach is extended to allow for an automated classification of local reaction zone structures. Classification criteria are defined, based on the ratio of local heat release rate peaks associated with premixed and non-premixed reaction zones located in close spatial proximity, and an automated process is implemented to classify 1D Raman/Rayleigh sample lines as premixed, dominantly premixed, multi-regime, dominantly non-premixed, or non-premixed flame zones. The importance of different flame zones, indicated by their population fractions, are found to evolve with downstream distance and show distinct differences between the two selected flames. Further, a prior analysis is used to test the applicability of 1D flame structure assumptions for the underlying combustion regime.

Item Type: Article
Erschienen: 2019
Creators: Butz, D. and Hartl, S. and Popp, S. and Walther, S. and Barlow, R. S. and Hasse, C. and Dreizler, A. and Geyer, D.
Title: Local flame structure analysis in turbulent CH4/air flames with multi-regime characteristics
Language: English
Abstract:

In practical applications, partial premixing of fuel and oxidizer, as well as recirculation of combustion products, result in complex combustion scenarios where multi-regime effects arise and a numerical representation of local reaction zones by purely premixed or purely non-premixed flame structures may not hold. Here, a novel burner system is introduced to investigate the fundamental characteristics of multi-regime combustion and to provide a basis for validating numerical models. This multi-regime burner (MRB) is specifically designed to produce flames with multi-regime characteristics while maintaining well-defined boundary conditions. Thermochemical data from Raman/Rayleigh/CO-LIF scattering experiments are provided for two selected operating conditions. The experimental investigation focuses on the overall flame structure by examining radial profiles of temperature and mixture fraction, as well as scatter plots of temperature, CH4, and CO versus mixture fraction. In order to assess the relative importance of different flame regimes, the gradient-free regime identification (GFRI) approach is extended to allow for an automated classification of local reaction zone structures. Classification criteria are defined, based on the ratio of local heat release rate peaks associated with premixed and non-premixed reaction zones located in close spatial proximity, and an automated process is implemented to classify 1D Raman/Rayleigh sample lines as premixed, dominantly premixed, multi-regime, dominantly non-premixed, or non-premixed flame zones. The importance of different flame zones, indicated by their population fractions, are found to evolve with downstream distance and show distinct differences between the two selected flames. Further, a prior analysis is used to test the applicability of 1D flame structure assumptions for the underlying combustion regime.

Journal or Publication Title: Combustion and Flame
Volume: 210
Publisher: Elsevier
Uncontrolled Keywords: Raman/Rayleigh, Multi-regime, Local flame structure, Tabulated chemistry
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Simulation of reactive Thermo-Fluid Systems (STFS)
16 Department of Mechanical Engineering > Institute of Reactive Flows and Diagnostics (RSM)
Date Deposited: 30 Sep 2019 07:36
DOI: 10.1016/j.combustflame.2019.08.032
Official URL: https://doi.org/10.1016/j.combustflame.2019.08.032
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