Acoustic attenuation in three-component gas mixtures—Theory

Abstract

Vibrational relaxation accounts for absorption and dispersion of acoustic waves in gases that can be significantly greater than the classical absorption mechanisms related to shear viscosity and heat conduction. This vibrational relaxation results from retarded energy exchange between translational and intramolecular vibrational degrees of freedom. Theoretical calculation of the vibrational relaxation time of gases based on the theory of Landau and Teller [Phys. Z. Sovjetunion 10, 34 (1936); 1, 88 (1932): 2, 46 (1932)] and Schwartz et al. [J. Chem. Phys. 20, 1591 (1952)] has been applied at room temperature to ternary mixtures of polyatomic gases containing nitrogen, water vapor, and methane. Due to vibrational-translational and vibrational-vibrational coupling between all three components in ternary mixtures, multiple relaxation processes produce effective relaxation frequencies affecting the attenuation of sound. The dependence of effective relaxation frequencies and the attenuation on mole fractions of the constituents was investigated. The acoustic attenuation in a mixture that is primarily nitrogen is strongly dependent on the concentrations of methane and water vapor that are present. However, the attenuation in a mixture that is primarily methane is only weakly dependent on the concentrations of nitrogen and water vapor. The theory developed in this paper is applicable to other multicomponent mixtures.

Measurement of methane Ccontent in upgraded biogas using pulse-echo ultrasound

“…Both of these are frequency dependent. They depend on the details of underlying physics [3], [4], [9], [10]. Good physical models are crucial for the understanding of the problem, so that proper instrumentation can be designed.…”

“…Previous work shows that the composition of a gas mixture significantly affects the acoustic wave propagation through the gas [3], [4]. Some work has also suggested how to extract these effects from experimental data using multivariate statistical tools, see [5], [6] and references therein.…”

Gas Composition Recognition Based on Analyzing Acoustic Relaxation Absorption Spectra: Wavelet Decomposition and Support Vector Machine Classifier

“…As a key of acoustic gas sensing, acoustic properties of different gas mixtures should be acquired comprehensively and accurately [2,3]. Lueptow et al inherited and accomplished gas probing by measuring sound velocity, which has been widely adopted for gas detection [3].…”

Ultrasonic measurement of molar fractions in gas mixtures by orthogonal signal correction

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“…Hence, both these parameters can help to monitor changes in experimental conditions. This has recently been studied in both theory and experiments by Dain and Lueptow [4], [5], Martinsson [6], and Townsend and Meador [7].…”