The influence of particle shape on flow modes in pneumatic conveying

CFD-DEM model of plugging in flow with cohesive particles

Plugging in flows with cohesive particles is crucial in many industrial and real-life applications such as hemodynamics, water distribution, and petroleum flow assurance. Although probabilistic models for plugging risk estimation are presented in the literature, multiple details of the process remain unclear. In this paper, we present a CFD-DEM model of plugging validated against several experimental benchmarks. Using the simulations, we consider the process of plugging in a slurry of ice in decane, focusing on inter-particle collisions and plugging dynamics. We conduct a parametric study altering the Reynolds number (3000...9000), particle concentration (1.6...7.3%), and surface energy (21...541 mJ/m[Formula: see text]). We note the process possesses complex non-linear behaviour for the cases where particle-wall adhesion reduces by more than 20% relative to inter-particle cohesion. Finally, we demonstrate how the simulation results match the flow maps based on the third-party experiments.

Development and evaluation of an innovative grain cart with a pneumatic conveyor

In line with the requirements of the Egyptian government to find a solution for wheat transportation during the peak harvesting season, an innovative design for a grain cart with a capacity of 8 tons supplemented with a grain hopper, a lifting double-action pneumatic conveyor, and a built-in digital scale was tested and evaluated to facilitate the transport of wheat crops from farmers' fields to storage sites. The cart was manufactured in the workshop of a local industrial company. It was tested under varying operational conditions in different wheat production areas in terms of working performance, efficiency of the grain loading and unloading mechanism, precision of the grain weighing mechanism, and cost/ton. The cart will enable wheat farmers and traders to transport and deliver their crops easily to storage sites with minimal losses and maximum working efficiency. It will also increase farmers' profit because transportation cost by using this grain cart is less than that of the current conventional method. Moreover, the developed cart can secure wheat supply in government storage sites without any interruption during the peak wheat harvesting season.

On the drag force closures for multiphase flow modeling

Drag force models are one of the most important factors that can affect TFM and CFD-DEM simulation results of two-phase systems. This article investigates the accuracies, implementation issues and limitations of the majority of the drag models for spherical, non-spherical and systems with size distribution and evaluates their performance in various simulations. Around 1888 data points were collected from 19 different sources to evaluate the drag force closures on mono-dispersed spherical particles. The Reynolds number and fluid volume fraction ranges were between 0.01 and 10,000 and between 0.33 and 1, respectively. In addition, 776 data points were collected from seven different sources to evaluate the drag force closures on poly-dispersed spherical particles. The Reynolds numbers were between 0.01 and 500, fluid volume fractions between 0.33 and 0.9, and diameter ratios up to 10. A comprehensive discussion on the accuracy and application of these models is given in the article.

A new method of flow blockage collapsing in the horizontal pipe: the pipe-rotation mechanism

In dense pneumatic conveying, flow blockage is a severe problem in the horizontal pipe, so accelerating the collapse velocity of blockage can improve the efficiency of powder transportation. In this paper, we offered a new method of the pipe-rotation mechanism and focused on the effect of this method on blockage collapse from collapse velocity, mass flow rate, and the change of the particle region. The physical model developed is horizontal pipe-rotation geometry at a uniform rotational speed of 0, 150, 300, 450, and 600 rpm, respectively. Then we used a computational fluid dynamics and discrete element method (CFD-DEM) model to investigate a single slug of particles passing through these geometries. The results show that collapse velocity and the mass flow rate increase with increasing rotational speed, which proves that the pipe-rotation mechanism can accelerate the collapse of flow blockage evidently. Moreover, the pipe-rotation mechanism changes the particle region significantly, which is polarized in the lower half of the pipe. It is trusted that the findings reported in this paper well serve as a helping source for further studies toward dense pneumatic conveying.

Inhaled mucoactive particles with tailored architecture for enhanced aerodynamicity, stability and efficacy

In respiratory and genetic disorders such as asthma, chronic obstructive pulmonary disease (COPD), chronic bronchitis and cystic fibrosis (CF), the lungs produce excess mucus, resulting in a thickened mass, which clogs up the airways and reduces airflow. Consequently, breathing becomes more difficult. Medications that break down the structure of mucus will be especially useful in managing the early symptoms of these diseases and preventing their progression into the more severe forms. This work therefore seeks to develop an inhaled mucoactive dry powder formulation that is efficacious on multiple fronts. As an innovative step, sodium chloride was used to tailor the surface architecture of ambroxol hydrochloride particles, such that the resulting angular features on the surfaces contributed to the creation of corrugated particles with enhanced aerodynamicity. The optimized spray-dried powder particles were of respirable-size (d₅₀ of 2.85 ± 0.15 μm) and moderately corrugated. When the crystalline powder was dispersed via an Aerolizer® inhaler at 60 L/min, it gave a fine particle fraction (FPF) of ~31%, which was a ten-fold improvement over the unmodified species (i.e. ambroxol hydrochloride alone). Tests on artificial sputum medium (ASM) showed that the optimized formulation was potentially useful in liquefying the mucus, which favorably pointed towards the effectiveness of the formulation. In addition, the formulation was also stable to moisture ingress (up to ~60% RH) and had good flowability. Hence, the advent of angular adjuvant sodium chloride particles in a mucoactive formulation conferred a three-fold benefit to the product: (1) Improved aerodynamicity and flowability, (2) Enhanced moisture stability and (3) Synergistic mucolytic properties.

Frictional Fluid Dynamics and Plug Formation in Multiphase Millifluidic Flow

We study experimentally the flow and patterning of a granular suspension displaced by air inside a narrow tube. The invading air-liquid interface accumulates a plug of granular material that clogs the tube due to friction with the confining walls. The gas percolates through the static plug once the gas pressure exceeds the pore capillary entry pressure of the packed grains, and a moving accumulation front is reestablished at the far side of the plug. The process repeats, such that the advancing interface leaves a trail of plugs in its wake. Further, we show that the system undergoes a fluidization transition-and complete evacuation of the granular suspension-when the liquid withdrawal rate increases beyond a critical value. An analytical model of the stability condition for the granular accumulation predicts the flow regime.