Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Development and validation study of a 1D analytical model for the response of reheat flames to entropy waves
Authors: Gant, Francesco
Gruber, Andrea
Bothien, Mirko
et. al: No
DOI: 10.1016/j.combustflame.2020.09.005
Published in: Combustion and Flame
Volume(Issue): 222
Page(s): 305
Pages to: 316
Issue Date: 2020
Publisher / Ed. Institution: Elsevier
ISSN: 0010-2180
Language: English
Subjects: Flame transfer function; Non-linear flame response; Entropy waves; Reheat combustion; Autoignition flames
Subject (DDC): 621.04: Energy engineering
Abstract: Numerical simulations of laminar premixed flames burning hydrogen and methane in spontaneous ignition mode are performed by harmonically exciting the reactants’ temperature at the domain inlet. The results are compared to an analytical model representing the same reactive flow configuration. The model provides a simplified but nevertheless accurate representation of reheat combustion taking place in sequential gas turbine combustors. An analytic expression for autoignition flames transfer functions to entropy waves is derived and used to extend transfer function models from the literature. For validation purposes, results from fully compressible Direct Numerical Simulations (DNS), including a complete representation of the fluctuating acoustic and entropic fields of the reactive flow, are analyzed and compared to incompressible Unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations that only take into account the fluctuating entropic field. Methane flames are found to be more sensitive to entropic forcing than hydrogen flames, featuring nonlinear phenomena even for low excitation amplitudes. In the linear regime, all flames behave as predicted by the analytical model and the URANS simulations are found to correctly predict the fluctuating entropic field. The transition from linear to nonlinear flame response is described in detail and its physical mechanisms are explained. Comparisons with results available in the literature show good prediction capabilities, both in terms of flame describing function and integrated heat release rate. Limitations of the proposed analytical model with respect to real combustion systems are discussed and a simple correction is proposed.
URI: https://digitalcollection.zhaw.ch/handle/11475/22516
Fulltext version: Published version
License (according to publishing contract): Licence according to publishing contract
Departement: School of Engineering
Organisational Unit: Institute of Energy Systems and Fluid Engineering (IEFE)
Appears in collections:Publikationen School of Engineering

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