Study On The Model Of Acoustic Wave Propagation Velocity In Gas-Solid Two-Phase Flow

Acoustic measurement has been widely used in industry and scientific research due to its non-intrusive,real-time,and convenience etc.An accurate and reliable gassolid two-phase sound velocity model forms the base and key to the measurement of gas-solid two-phase flow,e.g.pulverized coal concentration by using the sonic method.However,the mechanism affecting the gas-solid two-phase sound velocity is quite complex.In order to consider the influence of particle in the fluid on the velocity of sound propagation,models on gas-solid sound velocity established in different modes were studied and compared.And comparatively,a novel sound velocity model was established.Related simulation research and experimental verification of these models in gas-solid two-phase flow were carried out.A new sound velocity model considering particle slip correspondingly in the low frequency range is established under the Stokes two-phase flow condition.Relevantly,different literature sound velocity models considering the two-phase interaction were analyzed,and a numerical simulation comparative analysis was carried out on the changes of different sound velocity models with particle concentration,size,and sound frequency.Based on that,experimental study was performed for a validation.Firstly,COMSOL software was used to simulate the gravity settlement law of particles.Then,the sound velocity measurement system of air-pulverized coal settling flow was built to measure the sound velocity in the two-phase flow under different concentrations and frequencies,so as to verify the reliability of the sound velocity model proposed in this paper,and the two-phase flow sound velocity model in the literature as well.At the same time,a gas-solid two-phase flow concentration measurement method based on pressure difference was proposed in the experiment study,and the particle sedimentation and weighing method were used to verify it.The study reached the following main conclusions:(1)Compared with the traditional quasi-homogeneous sound velocity model(by Urick et al.),the improved Ament model based on the quasi-homogeneous model,the Soo model based on interphase coupling,and the Qian Zuwen model based on particle scattering turned out to be obviously closer to the experimentally measured sound velocity in gas-solid two-phase flow,which reflects the reasonability of the related improved models.(2)Experiment results show that,compared with other models,the sound velocity model on the Stokes two-phase flow proposed in this paper is more agreeable to the experimental values at lower acoustic frequencies with the variation of dispersion concentration and sound frequency.Combined with numerical simulation comparison,the reliability of the new sound velocity model of two-phase flow proposed in this paper was verified,which combines with the traditional Urick quasi-homogeneous model.(3)In a broader frequency range,with the increase of concentration,the Soo model is closer to the sound attenuation data in literature,relative to other models.It shows that Soo attenuation model is more suitable to act as the theoretical basis of acoustic concentration measurement than other attenuation models.(4)The pressure difference method for volumetric concentration measurement obtained by the differential pressure gauge falls in good agreement with the weighing method-volume concentration obtained by the powder feeding metering system.The pressure difference showed a linear changing law with the concentration.The feasibility of the proposed method for measuring the concentration of two-phase flow based on differential pressure was demonstrated.