Abstract
When a narrow duct(=regenerator) is installed in a tube while the temperature ratio is higher than some critical value at both ends of the regenerator, the gas inside starts self-excited oscillation. These days, study on thermoacoustic engines applying thermoacoustic phenomena is being actively conducted. While most waste heat ranges from 400 K to 600 K, critical onset temperature of a thermoacoustic engine is higher, ranging from 600 K to 1000 K. In order to solve this problem, a multistage thermoacoustic engine that can lower the critical onset temperature was suggested recently. It has been reported that critical onset temperature was successfully lowered with multistage amplification. However, a multistage type that realizes low-temperature oscillation also has a point at issue. A multistage thermoacoustic engine with multiple regenerators needs regenerators installed not only at the peak of acoustic impedance distribution in real part, and therefore is generally inefficient. In this report, we suggest a composition of a multistage thermoacoustic engine by numerical calculation, so that high acoustic impedance and traveling-wave are realized at all regenerator positions, and traveling-wave with acoustic impedance pc is realized at positions other than the regenerators. Within the suggested composition, the viscous dissipation of the resonators is extremely small. Also, thermal efficiency of 33% has been achieved with each regenerator when the temperature of the heat exchanger is 600 K. Our result suggests that the use of multistage type enables thermoacoustic engines to have such a composition that both low-temperature drive and high efficiency are realized.
