Characteristic-based non-linear simulation of large-scale standing-wave thermoacoustic engine

Area of Science:

• Acoustics
• Thermodynamics
• Computational Fluid Dynamics

Background:

• Existing linear theories and low-Mach number models inadequately predict the behavior of standing-wave thermoacoustic engines with significant temperature gradients.
• There is a lack of simulation results for practical thermoacoustic engines experiencing large-amplitude oscillations.

Purpose of the Study:

• To develop and present a one-dimensional non-linear numerical simulation for standing-wave thermoacoustic engines.
• To accurately predict the dynamic pressure response and harmonic content of practical thermoacoustic engines.

Main Methods:

• Utilized the method of characteristics to solve unsteady compressible Euler equations.
• Implemented explicit time integration with deduced friction coefficients and Stanton numbers for oscillating flow.
• Applied appropriate boundary conditions for circular ducts.

Main Results:

• Successfully captured self-induced pressure oscillations in the time domain.
• Transferred pressure signals to the frequency domain, identifying fundamental and harmonic responses.
• Demonstrated accurate prediction of non-linear dynamic pressure response.

Conclusions:

• The developed non-linear simulation provides accurate predictions for thermoacoustic engine behavior, especially under non-linear conditions.
• Results show improved agreement with experimental data compared to existing linear theories.
• The simulation is applicable to various working gases like Helium, Helium-Argon mixtures, and Neon.