Acoustical power amplification and damping by temperature gradients |
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Authors: | Biwa Tetsushi Komatsu Ryo Yazaki Taichi |
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Institution: | Department of Mechanical Systems and Design, Tohoku University, Sendai, Miyagi 980-8579, Japan. biwa@amsd.mech.tohoku.ac.jp |
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Abstract: | Ceperley proposed a concept of a traveling wave heat engine "A pistonless Stirling engine-The traveling wave heat engine," J. Acoust. Soc. Am. 66, 1508-1513 (1979).] that provided a starting point of thermoacoustics today. This paper verifies experimentally his idea through observation of amplification and strong damping of a plane acoustic traveling wave as it passes through axial temperature gradients. The acoustic power gain is shown to obey a universal curve specified by a dimensionless parameter ωτα; ω is the angular frequency and τα is the relaxation time for the gas to thermally equilibrate with channel walls. As an application of his idea, a three-stage acoustic power amplifier is developed, which attains the gain up to 10 with a moderate temperature ratio of 2.3. |
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