Basic study for practical application of thermoacoustic power generation system—A loop tube thermoacoustic prime mover with branches

This study basically examined the effects of the length and connection position of the branches (straight resonator tubes) in a loop-tube thermoacoustic prime mover on the onset temperature and oscillation frequency, aiming at application to thermoacoustic power generation systems. This system is composed of a 3.3-m-long loop tube combined with straight resonator tubes (branches) using atmospheric air and a 600 CPSI ceramic stack. The length of the resonator tube and its connection position to the loop tube were systematically varied, and the onset temperature and oscillation frequency were evaluated from both stability analysis and experimental measurements. As a result, introducing the branch significantly reduced the onset temperature, with the lowest onset temperature of 500K recorded when the resonator length was 150 mm. Regarding the oscillation frequency, experimental and analytical values closely matched across the entire length range, confirming the reliability of the analytical model. These findings indicate that the branches configuration is effective in reducing the onset temperature and that analytical methods are also effective for frequency prediction. Future work will proceed with demonstrations of power conversion by installing linear generators or speaker-type generators at the tip of the branches (straight resonator tubes).