Suspension Design, Modeling, and Testing of a Thermo-Acoustic-Driven Linear Alternator

C.m Johnson ,Chinmoy Saha ,Paul H Riley ,Robert Jinks

doi:10.1115/1.4038270

Abstract

The Score-Stove™ generates electricity from a wood-burning cooking stove using a thermo-acoustic engine (TAE) that converts heat to sound through a linear alternator (LA). This paper introduces a prototype hemitoroidal suspension that was refined into a segmented trapezoidal shape that gave a higher cyclic life for the LA and includes a critical evaluation that compares a theoretical analysis with experimental results. The results show an improvement from the 40% efficiency of a standard loudspeaker used in reverse as an LA to 70–80% efficiency with the new suspension and a double Halbach array magnetic topology.

Highlights

There has been growing interest in the thermo-acoustic technology over the last few years, little until very recently has been done on its application
Implementation of the Trapezoidal semi-circular shape Linear Alternator (LA) suspension To design the alternator suspension to achieve sufficient excursion from the driving force of the thermosacoustic engine without hitting an end-stop, so the hemi-toroidal concept was modified to a trapezoidal semicircular shape using sixteen segments as shown in fig
The hemi-toroidal and trapezoidal semicircular shape suspension of the linear alternator are presented in this paper

Summary

Introduction

There has been growing interest in the thermo-acoustic technology over the last few years, little until very recently has been done on its application. A more suitable alternative is moving coil technology found in the construction of commercial loud-speakers that can be used in reverse as a LA [8] These devices are less efficient when used as a LA (This is typically 40%, and their suspension possesses limited mechanical stability [9]) due to the higher damping in their suspension; a necessary feature for hi-fidelity audio that is unimportant when used as an electrical generator. Parameters Coil resistance (Ω) Force factor – Bl (T-m) Suspension outer diameter (mm) Suspension thickness (mm) Moving mass (g) Resonant frequency (Hz). The experimental results of the stainless steel design showed high hoop stress, failed after 10 minutes operation and was significantly stiffer than expected so is not suited to a large coil excursions

Theoretical analysis of the semi-circular cantilever theory

Implementation of the Trapezoidal semi-circular shape LA suspension

Findings

Conclusions