Using a side-branched volume to tune the acoustic field in a looped-tube travelling-wave thermoacoustic engine with a RC load

Highlights: • A new passive phase tuning method (i.e., a side-branched volume) has been proposed. • It can adjust the acoustic field within looped-tube thermoacoustic engines. • The working principle has been demonstrated though simulations. • The effectiveness of this phase tuning method has been proven experimentally. - Abstract: Travelling-wave thermoacoustic engine utilises a compact acoustic network to obtain a right time-phasing between the acoustic velocity and pressure oscillations within the regenerator to force gas parcels to experience a Stirling-like thermodynamic cycle. As such, thermal energy can be converted to mechanical work (i.e., high-intensity pressure waves). It is therefore crucial to control the time-phasing carefully to improve the performance of thermoacoustic engines. Various ways have been proposed and demonstrated for adjusting time-phasing, including both passive and active methods. The aim of this study is to introduce a new passive phase tuning method (i.e., a side-branched acoustic volume) to tune the time-phasing within a looped-tube travelling wave thermoacoustic engine. The proposed concept has been investigated both numerically and experimentally in this research. An experimental rig was simulated and designed using DeltaEC software (Design Environment for Low-amplitude ThermoAcoustic Energy Conversion). It was then constructed according to the obtained theoretical model. The result of this study showed a qualitative agreement between experimental measurement and numerical simulations, demonstrating that the proposed technique can effectively adjust the phase angle between the acoustic velocity and pressure oscillations within the loop-tube thermoacoustic engines, and improve its performance.