Thermally-tunable acoustic power amplification and efficiency enhancement in thermoacoustic amplifier

Thermoacoustic amplifiers (TAAs) exploit temperature gradients to modulate acoustic power flow, yet the internal mechanisms governing power amplification and the trade-off between acoustic gain and conversion efficiency remain poorly understood. This study develops a numerical framework coupling CFD with linear thermoacoustic theory to investigate how temperature gradients regulate acoustic power under traveling-wave conditions. For the baseline case (298–673 K), the CFD-predicted gain is G = 1 . 95 , within 2.5% of the linear theory prediction. Acoustic power amplification is shown to arise from two concurrent effects: a density-driven increase in volume flow rate as the mean density decreases along the propagation direction, and a progressive shift in the pressure–velocity phase difference toward the traveling-wave condition. Reversing the gradient direction switches the thermoacoustic core (TAC) into an attenuation mode ( G = 0 . 43 ). The local gain follows the scaling law G TAC ≈ T 2 / T 1 , and a decoupling between gain and efficiency emerges at high temperature ratios owing to rapidly growing parasitic heat losses. A He–Xe working-fluid mixture balances coupling strength and heat leakage suppression through light–heavy atom pairing. Geometric optimization reveals that the dimensionless hydraulic radius and TAC length, respectively, govern the thermal-relaxation/viscous-dissipation and power-density/efficiency trade-offs; extending the TAC reduces parasitic heat losses and raises the system efficiency above 40%. These results provide quantitative guidance for TAA design and optimization.