Noise Generation by Open Turbulent Flames

Abstract

In order to provide fundamental data on the acoustic energy released by combustion processes, measurements were made of the aerodynamic sound generated by premixed open turbulent flames. Studies are described that relate the characteristics of the noise to the various geometric and flow parameters defining the flame, and it is shown that the sound radiated may be considered to arise from a statistical distribution of monopole sources throughout the zone of combustion. Examination of the combustion-noise spectra indicated that their peak frequencies may be expressed by a constant value of a Strouhal number, in terms of the burner-port diameter, the mixture flow velocity, and the flame speed. The acoustic power radiated by a turbulent flame was found to be related to the flow parameters by the expression per P ∝ (ρU4D2/c)(Ub/U)2. This relationship is shown to be similar to the basic equation for the acoustic-power output of a monopole source.

Acoustic radiation from weakly wrinkled premixed flames

“…As noted above, the figure shows nearly omnidirectional sound radiation with slightly stronger radiation in the forward (φ 0 = 0 • -90 • ) than rearward (φ 0 = 90 • -180 • ) direction. The latter result is very consistent with measurements [22]. …”

A Model for Turbulent Combustion Noise

“…There its mathematical description emerged as aby-product of the analysis of aerodynamically generated noise which most of the early theoretical and experimental work wasfocused on [2,3]. Almost adecade later the first studies on combustion generated noise were published [4,5,6]. While most authors in the field of combustion noise agree that the coherent heat release structures postulated by Strahle [5] determine the overall noise emission of the investigated flames the spectral behavior washardly considered [6,5,7,8].…”

Sound Pressure Level Analysis of a Liquid-Fueled Lean Premixed Swirl Burner with Various Quarls

“…Power plants and airports that were built outside of major cities a couple of decades ago belong to suburban regions now [15]. Therefore, operational noise has to be minimized [16,17]. In the case of aviation engines, the contribution of combustion noise is notable at full thrust during takeoff [18,19].…”