Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

Abstract

This paper presents an experimental study on the dynamics of a ducted, conical, laminar premixed flame subjected to low amplitude acoustic excitation from upstream. The heat release response of the flame to velocity disturbances is investigated through measurement of the so called 'flame transfer function' for a wide range of forcing frequencies. The results are compared with those predicted by the existing linear kinematic theories. It is observed that these theories are in general agreement with the experiment, although there exist some disparities. A detailed comparison of the experimental data with the kinematic theories shows that the phase speed of flame disturbances has an essential influence upon the level of agreement between the theory and experiment. The data set presented in this work complements that reported in an earlier study. In keeping with others, visualisation of the excited flames clearly shows that the flame response includes waves on the flame front which are formed at the base and then convect along the flame.

Chaos in an imperfectly premixed model combustor

“…Individual contribution of the two has been investigated by studying the response of premixed and partially premixed flames to velocity and equivalence ratio fluctuations. [8][9][10][11][12][13] As often, the direct and indirect mechanisms of flame response are inherently coupled; it has been difficult to isolate individual contributions. However, such investigations have provided critical understanding on the dynamics of flame response.…”

“…The experiment is repeated for a wide range of forcing frequencies to evaluate the flame frequency response. 11 The resultant transfer function can be included in a network model of system acoustics to develop a predictive thermoacoustic model of the combustor. 13,14 This model can then be used to predict the stability of the thermoacoustic system.…”

Generation of Adverse Pressure Gradient in the Circumferential Flashback of a Premixed Flame

“…This, in turn, introduces further difficulties [2,6]. Variations in fuel properties can cause operational problems such as thermoacoustic instabilities [7] and flame flashback [6]. The latter is, particularly, problematic in premixed combustion of hydrogen containing fuels [8][9][10].…”

Entropy and flame transfer function analysis of a hydrogen-fueled diffusion flame in a longitudinal combustor

“…Numerous researchers have performed FTF/FDF studies [33,34]. For example, Balachandran et al [31] studied the ethylene-air premixed experimentally and also measured the flame transfer function.…”

“…Durox et al [32] measured the flame transfer functions of different flame geometries experimentally. Karimi [33] also measured the flame transfer function through experiments in which a laminar premixed flame was studied under low amplitude acoustic excitation. Sabatino et al [34] experimentally investigated the effect of acoustic pressure on the response of methane-air and propane-air swirl flames via determining the flame transfer functions (FTF).…”