Taking the input and reflected waves into account, the relationship between the acoustic impedance at the end and the input of a system were theoretically analyzed. Closed and open acoustic configurations that influence the pressure, volumetric velocity, impedance and acoustic work were compared in detail. Based on the above investigation, an open-air traveling-wave thermoacoustic generator was designed and fabricated. It is composed of a looped tube, a resonator open at one end, a regenerator, and hot and cold heat exchangers. It is a small scale and simple configuration. The resonant frequency is 74 Hz at 1 bar in air. The maximum acoustic pressures at the open end and 0.5 m far away from the open end are 133.4 dB and 101 dB from a reference value of 20 μPa when the heating power was 210 W, respectively. Acoustic pressure is reasonable for practical application as a low-frequency acoustic source. In further work, we believe that the acoustic pressure at the open end can achieve 150 dB, which could be a solution to problems in existing acoustic generators. These problems include low acoustic pressure and system complexity. It can be used as a basic acoustic source for low frequency and long-range noise experiments, and as a supply for high acoustic pressures necessary for industrial sources.
open-air, traveling-wave, thermoacoustic generator
Citation:Xie X J, Gao G, Zhou G, et al. Open-air traveling-wave thermoacoustic generator. Chinese Sci Bull, 2011Bull, , 56: 2167Bull, −2173Bull, , doi: 10.1007 The thermoacoustic principle [1] is a thermodynamic effect that occurs between compressible gases (the first medium) and solids (the second medium) in an acoustic field. It results in a time-averaged heat flow and a time-averaged work flow along (against) the sound propagation direction at penetration depths that are far from the solid boundaries. The conversion of heat to work is called thermal to acoustic effect, and the opposing process is called the acoustic to thermal effect. Based on these two effects, thermoacoustic systems can be classified as thermoacoustic engines and thermoacoustic refrigerators. A regenerator in an acoustic field can bring standing-waves [2,3], traveling-waves [4][5][6] and standing-traveling waves [7,8] into being. In the latest two decades, engineering applications in thermoacoustic refrigeration and thermoacoustic electricity have been rapidly developed. In 1990, thermoacoustic engines first re-
