Abstract
A thermoacoustic power converter consists of a thermoacoustic engine driving a linear alternator connected to a matched electric load. Accordingly, linear alternators are essential parts of thermoacoustic power converters. However, integration of a linear alternator in a thermoacoustic power converter is complicated since it requires acoustic matching with the thermoacoustic engine as well as electrical matching with the off-grid electric load connected to it and fast protection against piston over-stroking. In order to simplify the integration process, an experimental setup is designed and built in which the acoustic power generated by a thermoacoustic engine is simulated by an acoustic driver. This setup provides a platform to test and evaluate the performance of a linear alternator in a controlled environment in isolation of thermoacoustic engines and allows identification and resolution of potential problems in a linear alternator separately. A control circuit is designed and built to protect the alternator's piston against over-stroking. A non-linear electric load is connected to the alternator to provide a stable operating point of the complete system. In this setup, instrumentation are used to monitor the main variables (input and output currents, input and output voltages, dynamic gas pressure at exit of acoustic driver and inlet of linear alternator, acoustic driver stroke, linear alternator stroke, air and coil temperatures). The setup allows use of different resonators to simulate the effects of different front volumes on the performance of linear alternators and allows alterations in the enclosure volumes housing the acoustic driver and/ or alternator to control their resonance frequencies. Results showing the performance of a given linear alternator under different operating frequencies are presented and discussed