Numerical investigation of a looped-tube travelling-wave thermoacoustic engine with a bypass pipe

Abstract

A new configuration ("a looped-tube with a bypass pipe") was recently proposed for low temperature travelling wave thermoacoustic engines and a prototype using atmospheric air as the working gas achieved an onset temperature difference as low as 65 °C. However, no further research has been reported about this new configuration to reveal its advantages and disadvantages. This paper aims to analyse this type of engine through a comprehensive numerical research. An engine of this type having dimensions similar to the reported prototype was firstly modelled. The calculated results were then qualitatively compared with the reported experimental data, showing a good agreement. The working principle of the engine was demonstrated and analysed. The research results show that an engine with such a bypass configuration essentially operates on the same thermodynamic principle as other travelling wave thermoacoustic engines, differing only in the design of the acoustic resonator.Both extremely short regenerators and a near-travelling wave resonator minimise the engine's acoustic losses, and thus significantly reduce its onset temperature difference. However, such short regenerators likely cause severe heat conduction losses, especially if the engine is applied to heat sources with higher temperatures. Furthermore, the acoustic power flowing back to the engine core is relatively low, while a large stream of acoustic power has to propagate within its resonator to maintain an acoustic resonance, potentially leading to low power density. The model was then applied to design an engine with a much longer regenerator and higher mean pressure to increase its power density. A thermoacoustic cooler was also added to the engine to utilise its acoustic power, allowing the evaluation of thermal efficiency. The pros and cons of the engine configuration are then discussed.

Thermoacoustic Stirling power generation from LNG cold energy and low-temperature waste heat

“…The parameters of pressure, volume flow rate, temperature, power, and the others are then numerically calculated after specifying the initial and boundary conditions. DeltaEC has now been widely used for predicting the performances and characteristics of various thermoacoustic systems[29][30][31][32][49][50][51][52].…”

Numerical analysis on a four-stage looped thermoacoustic Stirling power generator for low temperature waste heat

“…This new concept makes looped thermoacoustic engines more cost-effective and attractive for waste heat recoveries. Great attention has been drawn into looped thermoacoustic engines thereafter [28][29][30][31][32][33][34][35][36][37]. The onset characteristics, acoustic fields and performances of looped thermoacoustic engines have been investigated numerically and experimentally by many researchers [26,[31][32][33].…”