A transient method for measuring the gas volume fraction in a mixed gas-liquid flow using acoustic resonance spectroscopy

Abstract

In this paper, the feasibility of measuring the gas volume fraction in a mixed gas-liquid flow by using an acoustic resonant spectroscopy (ARS) method in a transient way is studied theoretically and experimentally. Firstly, the effects of sizes and locations of a single air bubble in a cylindrical cavity with two open ends on resonant frequencies are investigated numerically. Then, a transient measurement system for ARS is established, and the trends of the resonant frequencies (RFs) and resonant amplitudes (RAs) in the cylindrical cavity with gas flux inside are investigated experimentally. The measurement results by the proposed transient method are compared with those by steady-state ones and numerical ones. The numerical results show that the RFs of the cavity are highly sensitive to the volume of the single air bubble. A tiny bubble volume perturbation may cause a prominent RF shift even though the volume of the air bubble is smaller than 0.1% of that of the cavity. When the small air bubble moves, the RF shift will change and reach its maximum value as it is located at the middle of the cavity. As the gas volume fraction of the two-phase flow is low, both the RFs and RAs from the measurement results decrease dramatically with the increasing gas volume, and this decreasing trend gradually becomes even as the gas volume fraction increases further. These experimental results agree with the theoretical ones qualitatively. In addition, the transient method for ARS is more suitable for measuring the gas volume fraction with randomness and instantaneity than the steady-state one, because the latter could not reflect the random and instant characteristics of the mixed fluid due to the time consumption for frequency sweeping. This study will play a very important role in the quantitative measurement of the gas volume fraction of multiphase flows. acoustic resonance spectroscopy, mixed gas-liquid flow, gas volume fraction, transient method PACS: 43.58.+z, 47.55.Ca, 89.20.Bb,

Theoretical and Experimental Studies of Acoustic Reflection of Bubbly Liquid in Multilayer Media

“…There are several places where bubbly liquids exist in nature and industrial settings, including near-bottom and subsurface media in the ocean, mixed oil-gas-water media in petroleum reservoirs, and even within the human body, such as bubble-containing blood when divers experience decompression sickness [1][2][3][4]. Trace bubbles in liquids can lead to dramatic changes in the propagation characteristics of acoustic waves, and thus acoustic methods have the applicable potential for bubble detection, especially when the gas content is relatively tiny [5,6]. When using acoustic methods to detect the bubbles of decompression sickness, human tissues can also be approximated as a stratified medium if the acoustic wavelength is small enough.…”