Abstract
To what extent can we lower the onset temperature ratio (OTR) to start a thermoacoustic engine? We tried to answer this question by installing a secondary regenerator in a travelling wave engine consisting of a looped tube and a branch resonator. Factors governing the OTR were studied experimentally through measurements of the quality factor at various temperature ratios. Installation of the secondary regenerator at a suitable position drastically enhanced thermoacoustic effects while introducing a slight damping to the system. As a result, the OTR of the present thermoacoustic engine was decreased from 1.76 to 1.19, when the regenerators were increased to five.
