Abstract: The research on a thermoacoustic engine micro-cycle is of great importance to understand the thermodynamic performance of thermoacoustic engine. An actual thermoacoustic engine micro-cycle ideal model which expressed as an ellipse in pressure-volume diagram is established in terms of the feature of thermoacoustic non-constant entropy oscillation. And the deflection angle of the ellipse depends mainly on the phase displacement between pressure oscillation and volume oscillation. The demarcation points of endothermic processes and exothermic processes in the micro-cycle are found. The expressions of the dimensionless acoustic work output and the thermal efficiency are derived with considering the influence of heat leakage and factor of irreversible degree. The relationship between the work output and the thermal efficiency are investigated by numerical calculation. It is a willow-shaped curve, which is identical with that of a classical Carnot cycle, and in which there are a maximum work output and a maximum thermal efficiency. The region between the maximum work output and the maximum thermal efficiency is the optimal operation conditions of a thermoacoustic engine. In addition, the phase displacement and the irreversible factor have a significant effect on the work output and the thermal efficiency. The results obtained will be helpful for optimal design of thermoacoustic engine.

Key words: Micro-cycle, Thermal efficiency, Thermoacoustic engine, Work output