Abstract
A thermoacoustic power converter consists of a thermoacoustic heat engine and a linear alternator. Integration of linear alternators into thermoacoustic power converters is complicated since it requires acoustic matching with the thermoacoustic engine and matching with the load connected to it. In order to fully understand this process, this work presents an experimental setup designed and built to test linear alternators under different thermoacoustic-power-conversion conditions. The setup supplies the acoustic power to the linear alternator in a controllable and stable form, using an acoustic driver. Results indicate that introduction of a low-resistance in parallel to the linear alternator can provide over-stroke protection on a time scale of few milliseconds. Results on how the key performance indices (mechanical stroke, acoustic-to-electrical conversion efficiency, mechanical-motion loss, fluid-seal loss and Ohmic loss) of the linear alternator are affected by the operating frequency, the mean gas pressure and the working gas mixture composition are presented and discussed. Under the conditions employed, the proportionality constant between the mechanical stroke and the generated voltage is found to increase linearly with the operating frequency (even across the mechanical resonance frequency point) and to decreases linearly with the mean gas pressure and to be almost independent on the gas mixture composition. The effects of the acoustic gas impedance at different mean gas pressures and different gas mixture compositions on the acoustic matching between the acoustic power supplied and the linear alternator are quantified.