Acoustic power measurements of oscillating flames

Abstract

The acoustic power of an oscillating flame is measured. A turbulent premixed propane/air flame is situated near a pressure antinode of a standing wave in a laboratory combustion chamber. This standing wave is generated by a piston. The fluctuating heat release of the flame will supply acoustic power to the standing wave as postulated by Rayleigh. This flame acoustic power is obtained by setting up a power balance of the whole combustion chamber.Experiments proved that it is possible to measure quantitatively the acoustic power and the frequency change as a function of relevant parameters. This frequency change is a second phenomenon described by Rayleigh. The acoustic power of the flame as a function of the amplitude of the fluctuating component of the mixture flow velocity at different frequencies can be measured.Measurement techniques are described and results for frequencies ranging from 3 to 120 Hz are given.Address: M. Valk, Technische Hogeschool Twente,

Effect of Low Frequency Burner Vibrations on the Characteristics of Jet Diffusion Flames

“…1(c)]. Single point measurements are made following the work of Valk [26]. These entrainment velocity measurements are performed only in cold air jet flows in order to avoid placing the hotwire in the vicinity of flames.…”

Experimental and theoretical study of a premixed vibrating flame

“…The direct investigation of turbulent combustion waves remains a complex task, despite the advent of a new generation of computers and instrumentation, due to the random nature of the flows in which combustion takes place. Thus, in order to study some characteristics of the combustion-flow perturbations interaction, "simple" fundamental experiments involving the disturbance of a laminar flame have been conducted, in which the perturbation is considered to be well-known and well controlled: vibrating flames, (b1) stabilized upon a vibrating flame holder [4][5][6] (b2) subjected to a time sinusoidal velocity field [3][4][5][6][7] (b3) subjected to a time-space sinusoidal velocity field [6,8,9] In the first case (a), the experimental contributions deal with the impact of vortices from a laminar or turbulent Von Karman street, created behind a cylindrical rod placed in an unburned gas flow, on a V-shaped flame front. This interaction can be identified with an idealized two-dimensional turbulence, localized in a precise part of the front, since the perturbation spectrum is reduced to the Strouhal frequency of the vortex passage.…”

“…In the case (b2), the flame is placed into a tube and subjected to a sinusoidal time modulation of the unburned gas flow, by using the frequency of the vertical duct analogous to a Helmholtz resonator [3,7]. This problem becomes one of the interactive studies of the phenomena combining combustion and acoustics.…”

“…8 and 10. As a reminder, we also mention some experimental and theoretical studies that have more specifically taken up the acoustic/combustion coupling by using the combustion chamber as a Helmholtz resonator [11][12][13][14][15][16]. These studies are initially based on some observations made by Rayleigh about the response of a diffusive flame to some standing waves developed in tubes [11].…”