Interferometric Investigation of the Thermoacoustics in a Swirl Stabilized Methane Flame

Abstract

In this work, an atmospheric model combustion chamber was characterized employing Laser Vibrometry, chemiluminescence and Particle Image Velocimetry. The test object was a variable geometry burner enclosed with a liner, with the flame optically accessible through four fused silica windows. In this burner with adjustable flame conditions the cavity of the atmospheric model combustion chamber was excited at a frequency around 200Hz. Resonant and non-resonant flame conditions were investigated and compared by laser vibrometer interferometry, schlieren visualization and OH*/CH* chemiluminescence. Additionally, the velocity field was recorded with Particle Image Velocimetry, while the aerodynamics of the burner plenum was analyzed with Computational Fluid Dynamics.

Analysis of chemiluminescence, density and heat release rate fluctuations in acoustically perturbed laminar premixed flames

“…These perturbations are inferred here with a Laser interferometric vibrometer (LIV). This technique was already successfully used to determine density fluctuations in turbulent non reacting flows [42,43] as well as in perturbed reacting flows [25,26,44].…”

“…Using the transport equation for the mass fraction Y k of each species k: ρ dY k dt =ω k − ∇ · j k (25) …”

“…A novel approach yielding line-of-sight integrated data was recently examined by exploiting the link between heat release rate fluctuations and density disturbances in acoustically perturbed laminar premixed flames [3] and turbulent swirling flames [25,26]. The following relation is exploited: (1) where ρ andq denote density and heat release rate (per unit volume) perturbations, respectively, c corresponds to the speed of sound and γ indicates the specific heat capacity ratio of gases.…”

“…In a recent analysis of the response of turbulent premixed swirling flames to acoustic forcing [25,26], differences between heat release rate disturbances deduced from chemiluminescence emission measurements and exploitation of Eq. (1) were also found due to a series of contributions to density fluctuations which were not linked to heat release rate perturbations.…”

Numerical Steady and Transient Evaluation of a Confined Swirl Stabilized Burner

“…One of the most common method used for the measurement of heat release concerns the analysis of OH* radical chemiluminescence in the flame [3,4]. A large amount of research [5][6][7][8] has been carried out to provide an overview of different techniques applied to analyze the flame dynamics.…”