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To reveal the particle dynamic characteristic in the bend, high-speed particle image velocimetry (PIV) and wavelet transform were used to measure and analyze the particle velocity in a horizontal-vertical pneumatic conveying system. The pressure drop and particle velocity are analyzed to elucidate the macroscopic motion properties of particles in t...
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Citations
... A qualitative comparison between blind T and radius bending was made with specific material properties. Tu et al. [19] analyzed the pressure drop and particle velocity and clarified the macroscopic motion characteristics of particles under different bending-diameter ratios. Zhou et al. [20] studied the effects of wall wear, particle breakage, and pressure drop on the elbow using an orthogonal experimental design. ...
The pressure drop and conveying stability caused by the bend significantly affect the pneumatic conveying process of stiff shotcrete, which is the key to solving the problem of long-distance transportation. In this paper, the effects of different air velocities (32 m/s, 36 m/s, 40 m/s), water-cement ratios (0.1, 0.2, and 0.3), and bending-diameter ratios (4, 12, and 20) on the pressure drop of the elbow R1 and conveying stability R2 are studied using the response surface method. The conveying stability is characterized by the pressure variation coefficient (C.V). The response surface graph aids in the intuitive analysis of the effects of these variables. The results show that the impact of air velocity on R1 and R2 is exceptionally significant, and the interaction of each factor on the response value is analyzed. The response value and the quadratic polynomial regression equation between the various factors are obtained in addition to the flow characteristics of stiff shotcrete under different working conditions. The relationship established by the statistical processing of the experimental results can provide some reference for specifying the pressure loss model of stiff shotcrete.
... The results showed that the soft fins were effective in pipes with larger R/D. Yan et al. (2021) and Tu et al. (2021) studied the flow characteristics of particles in different curvature radius bends by using different analysis methods to dissect the flow pattern. Yilmaz and Levy (2001) investigated the particle velocity distribution downstream of the bend and discovered that the rope structure fragmented into big discontinuous clusters. ...
To examine the flow characteristics of particles in the vertical tube corresponding to different curvature radius bends, the particle velocity is measured at the Minimum Pressure Drop (MPD) using a high-speed Particle Image Velocimeter (PIV). This experiment explores the effects of particle flow characteristics at different curvature radius bends and their corresponding vertical tubes with pressure drop, power consumption, the intensity of particle fluctuation velocity, power spectrum and time-frequency characteristics. It is observed that the pressure drop and power consumption can be reduced with the help of a large curvature radius bend. Besides, the reduction of particle velocity in the large curvature radius bend and its corresponding vertical tube is less, and the particle possesses a larger intensity of fluctuation velocity in its corresponding vertical tube. The particles in the vertical tube corresponding to the large curvature radius bend lead to large peaks of the power spectrum in the low-frequency region, which is closely linked to the pressure drop. Eventually, the dynamics of particles in a vertical tube are revealed from the perspective of time-frequency analysis by using a continuous wavelet transform © 2022, Journal of Applied Fluid Mechanics.All Rights Reserved.
... In addition, some scholars have used fast Fourier transform , probability density function (Yan et al., 2019) and autocorrelation (Yan et al., 2017) to analyze the particle velocity. Nowadays, Tu et al. (2021) employed the wavelet transform to examine the dynamic properties of particles in three different curvature radius bends and discovered that in the fast-falling position, the particles move mostly on a tiny scale and increase in large scale motion at the entrance and exit of the bends. Using continuous wavelet transform and orthogonal wavelet multiresolution techniques, Zheng and Rinoshika (2018) investigated fluctuation velocities in accelerated and fully developed regions in pneumatic conveying systems using the wavelet technology. ...
In the pneumatic conveying process, particles move to the bend under the influence of inertia to form a particle rope, which will cause serious wear between the particles and the pipe wall, and then the dune model is designed and installed in the 90° bend to reduce energy consumption and wear in this study. Firstly, the minimum pressure drop velocity of particles transported by different size dune models was obtained through experimental study. Then the energy saving mechanism of the dune model is studied by CFD-DEM coupling. The experimental results show that the installation of the dune model reduces the minimum pressure drop velocity. The numerical simulation results show that the number of collisions between the particles and the tube wall in the vertical tube decreases after the installation of the dune model, which reduces the energy loss. Moreover, the increasing of tail size of the dune model is beneficial to the diffusion and acceleration of the particles in the vertical tube.
... Nowadays, Tu et al. (2021) employed the wavelet transform to examine the dynamic properties of particles in three different curvature radius bends and discovered that in the fast-falling position, the particles move mostly on a tiny scale and increase in large-scale motion at the entrance and exit of the bends. Using continuous wavelet transform and orthogonal wavelet multiresolution techniques, Zheng and Rinoshika (2018) investigated fluctuation velocities in accelerated and fully developed regions in pneumatic conveying systems using the wavelet technology. ...
To study the flow characteristics of particles in the vertical tube, the velocity is measured at the minimum pressure drop (MPD) by using a high-speed particle image velocimeter (PIV). Firstly, the pneumatic conveying system’s pressure drop and the particle velocity characteristics in the vertical tube were investigated. Then, for the axial fluctuation velocity of the particles, the continuous wavelet transform, and one-dimensional discrete orthogonal wavelet decomposition are used to reveal the dynamic characteristics of the particles based on the time-frequency characteristics, the contribution of wavelet levels to the energy of particle fluctuations, the auto-correlation of each wavelet level and the probability distribution of wavelet levels. The results demonstrate that large-scale movement dominates particle movement in the vertical tube, whereas small-scale movement increases as conveying height rises. The energy contribution of the low-frequency wavelet level is larger, and this contribution decreases with the acceleration of the particles along the tube. The high-frequency wavelet level’s auto-correlation coefficients decay more slowly and have a longer duration. At increasing wavelet levels, the skewness and kurtosis coefficients grow, and the departure of the Gaussian probability distribution becomes more obvious.
Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems.
