Low temperature difference thermoacoustic prime mover with asymmetric multi-stage loop configuration

T Jin,R Yang,K Tang,Y Feng,Y Wang

doi:10.1038/s41598-017-08124-5

Abstract

Environmentally friendly and low-cost technologies to recover low-grade heat source into usable energy can contribute to ease the energy shortage. Thermoacoustic technology is expected as one promising approach in this ascendant field. In this work, the multi-stage looped thermoacoustic prime movers with asymmetric configuration, which can provide travelling-wave resonator and appropriate acoustic field for efficient regenerator, have been proposed and experimentally studied. The presented looped thermoacoustic prime movers can start to oscillate with quite low temperature difference along the regenerator. The lowest onset temperature difference obtained in the experiments is only 17 °C (the corresponding heating temperature is 29 °C), which can be achieved in both three-stage and four-stage looped thermoacoustic prime movers, with CO2 of 1 MPa or 1.5 MPa as the working fluid. An electric generator driven by a three-stage looped thermoacoustic prime mover with low heating temperature was tested to achieve the acoustic to electric conversion.

Highlights

Low-grade thermal energy, such as solar thermal energy, geothermal energy, ocean thermal energy and waste heat, is enormously reserved but not yet effectively utilized[1,2,3]
Simulation has been firstly conducted to verify whether appropriate acoustic field can be established or not in these four looped thermoacoustic prime movers (LTAPMs), with the help of DeltaEC (Design Environment for Low-amplitude Thermoacoustic Energy Conversion)[14]
The results show that the LTAPM can achieve a considerably high pressure ratio with a heating temperature much lower than that of a Stirling thermoacoustic engine, whose required heating temperature is typically above 600 °C to achieve a similar pressure ratio[6]

Summary

Introduction

Low-grade thermal energy, such as solar thermal energy, geothermal energy, ocean thermal energy and waste heat, is enormously reserved but not yet effectively utilized[1,2,3]. A traditional thermoacoustic prime mover generally requires high-temperature heat source to achieve effective acoustic power output, which is a huge barrier to utilizing the low-grade heat source. To reduce the onset and operating temperatures of a thermoacoustic engine is of great importance for its application in the field of low-grade heat source recovery. A looped travelling-wave thermoacoustic engine can theoretically execute a reversible thermodynamic cycle analogous to that in a Stirling engine. It was ever troubled with low acoustic impedance in the regenerator, which can cause severe viscous loss, when it was firstly proposed[9, 10]. A three-stage LTAPM has been used to drive a linear alternator, as an example, for preliminarily verifying its applicability to electric generation with low-grade heat source

Methods

Results

Conclusion