Analytical modelling of flame transfer functions for technically premixed flames

IF 1.4 4区工程技术 Q3 ENGINEERING, MECHANICAL

International Journal of Spray and Combustion Dynamics Pub Date : 2022-03-01 DOI:10.1177/17568277221094403

F. Biagioli, A. Innocenti, Ammar Lamraoui, K. Syed

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引用次数: 0

Abstract

The linear response to harmonic acoustic excitation of the total heat release rate in technically premixed flames (Flame Transfer Function, FTF) is studied in case of an ideal swirl burner. The analysis is based on the linearization of the production rate for the mean reaction progress variable modelled with a turbulent flame speed closure. Three main components of the FTF are identified which are generated by: I) direct fluctuations in the fuel mixture fraction (formation enthalpy contribution), II) direct fluctuations in the turbulent flame speed and III) flame surface area fluctuations driven by velocity and turbulent flame speed fluctuations. The velocity fluctuation is separated into an irrotational acoustic displacement and a rotational convective component. The effect of the rotational velocity component on the FTF is modelled here in a semi-empirical way, related to swirl number fluctuations at the flame base due to the phase shift between convected tangential velocity fluctuations and acoustically propagating axial velocity fluctuations. It is finally shown that fuel mixture fraction fluctuations can be generated not only by air mass flow rate fluctuations but also by fuel flow rate fluctuations which depend upon the air side impedance at the fuel injection location. It is shown that this impedance changes with the geometry of the plenum placed upstream the burner affecting in this way also the FTF.

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技术预混火焰传递函数的分析建模

研究了在理想旋流燃烧器条件下，技术预混火焰总放热率对谐波声激励的线性响应(火焰传递函数，FTF)。分析是基于用湍流火焰速度关闭模型对平均反应过程变量的产率进行线性化。确定了FTF的三个主要组成部分:1)燃料混合物分数的直接波动(形成焓贡献)，2)湍流火焰速度的直接波动和3)由速度和湍流火焰速度波动驱动的火焰表面积波动。速度波动分为非旋转声位移分量和旋转对流分量。这里以半经验的方式模拟了旋转速度分量对FTF的影响，这与火焰底部由于切向速度波动和声传播轴向速度波动之间的相移而产生的旋流数波动有关。结果表明，混合气分数波动不仅是由空气质量流量波动引起的，而且是由燃油流量波动引起的，而燃油流量波动取决于喷油位置的空气侧阻抗。结果表明，该阻抗随放置在燃烧器上游的静压室的几何形状而变化，以这种方式也影响了FTF。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Spray and Combustion Dynamics THERMODYNAMICS-ENGINEERING, MECHANICAL

CiteScore

2.20

自引率

12.50%

发文量

审稿时长

>12 weeks

期刊介绍： International Journal of Spray and Combustion Dynamics is a peer-reviewed open access journal on fundamental and applied research in combustion and spray dynamics. Fundamental topics include advances in understanding unsteady combustion, combustion instability and noise, flame-acoustic interaction and its active and passive control, duct acoustics...