热扩散效应在热声分离中的作用机理

在充满二元混合气体的声波谐振管中,振荡的气体会在径向上建立振荡的温度梯度,径向的温度梯度会引起两种组分的分子沿着不同方向进行扩散,在这种热扩散效应和热声效应的共同作用下,声波能够把混合气体中的两种组分分别带向谐振腔的速度节点和压力节点,使得混合气体在声波传播方向上逐渐分离。为了研究热声分离过程的机理,本文对一个半波长的声波谐振管进行了二维的建模,并基于可压缩的SIMPLE算法,通过求解He-Ar混合气体的速度场、温度场和一种组分的浓度场,对谐振腔内的传热传质过程进行了详细的数值模拟研究。数值模拟结果与文献的理论计算值进行了比较,结果符合良好。随后,通过研究一个周期内径向上的温度、速度和Ar的摩尔分数分布,揭示了径向上的热扩散过程,以及中间气体与边界层内气体之间的热质交换过程,完整地解释了热声分离过程的发生机理。

The Mechanism of Thermal Diffusion Effect on Thermacoustic Mixture Separation

In a resonator filled with binary mixtures,the oscillation of acoustic waves will create oscillating temperature gradient in the radial direction.The radial temperature gradient will lead to diffusion of the light and heavy components along the opposite directions.Based on the thermal diffusion effect and the thermoacoustic effect,the two components can be pumped to the velocity node and the pressure node respectively,which results in separation of the mixture along the propagation direction of sound wave.In order to study the mechanism of thermoacoustic mixture separation,a two-dimensional numerical model has been developed in a half-wavelength resonator.Then a numerical method based on the compressible SIMPLE algorithm is proposed to solve the velocity field,temperature field and the concentration field of a certain component.It is found that the numerical results are in good agreement with theoretical predictions from literature.Then the temperature,velocity,and concentration distributions of the mixture along the radial direction have been studied to investigate the thermal diffusion process and the mass and heat transfer process along the radial direction. This work provides insight into how the mixture can be separated along the wave-propagation direction.