Development of a CFD model for simulation of a traveling-wave thermoacoustic engine using an impedance matching boundary condition

Abstract

Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical modeling of complex thermoacoustic phenomena. The basic problem concerning a CFD simulation of a complete system is the computational cost. To overcome this problem, a CFD simulation tool using an impedance matching boundary (IMB) condition has been developed to analyze the characterization of the flow field in a looped-tube traveling-wave thermoacoustic engine. The thermodynamic processes were simulated using a two-dimensional numerical solution for the compressible Navier–Stokes equations. By imposing an impedance matching boundary condition, flow fields around the regenerator and heat-exchanger plates were simulated. The boundary condition being defined as an acoustic load which was derived from experimental data. From the simulations, features of the flow field such as nonlinear vortex generation around the regenerator and heat-exchanger plates were observed that were not present in the analytical solutions. Furthermore, the temperature oscillations were obtained around regenerator plates, and the operating mechanism of a looped-tube traveling-wave thermoacoustic engine was characterized both qualitatively and quantitatively. The CFD tool was validated by obtaining good agreement when comparing results with those from experimental data and analytical solutions. As a result, it was concluded that CFD simulations with this impedance matching boundary condition are effective in predicting actual flow behaviors in a traveling-wave thermoacoustic engine.