Effect of RC load on the performance of a three-stage looped thermoacoustic engine

Abstract

Thermoacoustic heat engine is a type of machine converting thermal energy into acoustic energy with the attracting characteristics of high reliability and environmental friendliness. This work proposed a three-stage looped thermoacoustic engine, where a compliance tube is utilized as the phase adjuster, to realize the high acoustic impedance and the near traveling-wave acoustic field in the regenerator, which is significant for effective thermoacoustic conversion. In order to investigate its performance with low-grade thermal energy, the output acoustic power of the engine is measured with the variable load method. It can be found that as the resistance decreases, the efficiency of the engine may rise, but the required heating temperature also rises. Thus, there exists a trade-off between the efficiency and the heating temperature, and the relative Carnot efficiency is adopted as a main index to evaluate the performance of the system. The maximum relative Carnot efficiency of 12.6% (the corresponding efficiency was 3.2%) was achieved in our experiments, when the heating temperatures of the three stages were 120 °C.