title: Acoustical power amplification and damping by temperature gradients.
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.
authors.affiliation: Department of Mechanical Systems and Design, Tohoku University, Sendai, Miyagi 980-8579, Japan. biwa@amsd.mech.tohoku.ac.jp
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Biwa
authors.forename: Ryo
authors.initials: R
authors.lastname: Komatsu
authors.forename: Taichi
authors.initials: T
authors.lastname: Yazaki
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D000669:Amplifiers, Electronic; D004867:Equipment Design; D005740:Gases; D008962:Models, Theoretical; D009038:Motion; D011312:Pressure; D015203:Reproducibility of Results; D013016:Sound; D013696:Temperature; D013814:Thermal Conductivity; D013816:Thermodynamics; D014160:Transducers, Pressure
chemical_list: D005740:Gases