Numerical investigations on energy conversion performances in twin standing-wave thermoacoustic engines with various geometric and operational conditions

The present work considers the heat-driven acoustic characteristics and dynamic thermal-fluid flow fields in a twin standing-wave thermoacoustic engine (TSWTAE). Emphasis is placed on enhancing its acoustic power output performances for efficiently driving thermoacoustic refrigerators by varying operating conditions and geometric shapes. For this, a time-domain 2D twin TAE model is developed to analyze the TSWTAE in the presence of different working gases and various operating pressures first. It is then applied to examine the geometry effect on the thermo-acoustics energy conversion performances of the twin SWTAE. The model is validated by comparing with those results obtained from DeltaEC (Design Environment for Low-amplitude ThermoAcoustic Energy Conversion) software and experimental data available in the literature. The results indicate that the acoustic oscillation pressure and sound pressure level are increased with the charge pressure and the molecular weight of the working gases, while the acoustic power and thermo-acoustics energy conversion efficiency of the different working gases remain roughly constant. Considering the comprehensive acoustic characteristics, the optimal engine performance is achieved with a 0.6 MPa charge pressure, as helium is applied. Furthermore, the implementation of the tapered conical resonator demonstrates a substantial enhancement in oscillation pressure and thermal efficiency, yielding improvements of 82.03% and 32.60% respectively compared to the utilization of a cylindrical narrow resonator in the experimental setup. The present study provides a design tool for predicting and optimizing twin SWTAE performances.