Acoustic connection between thermoacoustic engine and impulse turbine

In this study, we studied how to connect a thermoacoustic engine (TAE) and an impulse turbine to construct a thermoacoustic generator for converting thermal energy into electric power. The thermoacoustic generator was separated into two sub-systems: (1) system A, which consisted of a looped-tube TAE and a branch tube, and (2) system B, which consisted of an impulse turbine loop and a branch tube. The sub-systems were evaluated individually using an acoustic driver to determine the driving conditions such as branch length, driving frequency, and temperature for the connected system. In system A, which included the TAE, the change in specific acoustic impedance was small with respect to the velocity amplitude. However, in system B, which included the impulse turbine, the change in specific acoustic impedance with respect to the velocity amplitude was nonlinear. The sub-systems were connected by branch pipes, whose lengths were determined from the individual sub-system evaluation results, and the device was confirmed to self-oscillate at the driving temperature. When the device was operated at the driving conditions, the frequency, velocity amplitude, and specific acoustic impedance with self-oscillation were the same as those of the individual sub-systems. This also confirms the validity of evaluating the TAE and impulse turbine separately.