Abstract
This paper experimentally analyzes a looped thermoacoustic engine with liquid pistons. The engine consists of three identical unit sections, each of which contains a liquid column and a gas column. The gas column region includes a regenerator, hot and cold heat exchangers and a thermal buffer tube. The critical temperature ratio at both ends of the regenerator is found to be 1.34 and the engine starts to operate with a frequency of 4.5 Hz. From simultaneous measurements of pressure and axial velocity of the gas column, we determine the complex acoustic impedance to show that the thermodynamic cycle equivalent to the Stirling thermodynamic cycle is executed. The magnitude of the acoustic impedance is found to be as high as more than 20 times the characteristic impedance of the working fluid. The pressure amplitude in the gas column increases with the temperature ratio, but its growth stops at a certain level of the pressure amplitude. This phenomenon is discussed on the basis of the acceleration of the liquid column motion and gravitational acceleration.
