Numerical simulation of acoustic attenuation coefficient in boiler with particulate matter

In thermal power systems, coal-fired boilers contain dense flue gas with high-concentrations of particulate matter. Their acoustic attenuation characteristics directly determine the measurement accuracy of acoustic monitoring equipment. Systematic investigations on boundary layer attenuation caused by nonlinear acoustic effects under high-concentration conditions is still insufficient. This study establishes a two-dimensional numerical model of acoustic attenuation in particle-laden flue gas based on nonlinear acoustic theory and thermoviscous boundary layer mechanism. The influences of particle radius, volume fraction, particle distribution, and acoustic frequency on the attenuation coefficient are quantitatively analyzed under ambient temperature and atmospheric pressure. The simulation results in the particle-free medium are highly consistent with the Stokes-Kirchhoff theoretical solution. In particle-laden media, particle surface viscous dissipation is the main attenuation mechanism. The attenuation coefficient increases significantly with particle radius and volume fraction, increasing sharply below 1000 Hz and following the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> scaling law above 5000 Hz. The boundary layer overlapping effect under 1 % volume fraction further enhances energy dissipation. This model can improve the theoretical system of sound propagation in high-concentration suspensions, and provide a solid theoretical foundation for the design and optimization of acoustic monitoring devices in practical furnace environments.