Particle Deposition Characteristics Research Articles

Effect of gas-solid flow parameters and fracture structure parameter on particle deposition characteristics in the mining-induced fracture

The particle deposition in mining-induced fracture is an important reason for the sudden drop in gas drainage flow. In this study, particle deposition characteristics in fracture were investigated. The results showed that the particle deposition bed had prominent regional distribution characteristics along the axial direction of the fracture, and a humped distribution of the particle deposition height was observed along the radial direction of the fracture. In addition, the mechanism of the influence of the operating parameters of the gas-solid flow and the fracture shrinkage ratio factors on the particle deposition scale in the fracture differed fundamentally. The operating parameters of gas-solid flow mainly affected the deposition range of the transitional deposition bed. In contrast, the fracture shrinkage ratio mainly affected the deposition range of the local and transitional deposition beds. The results can provide guidance for understanding the particle deposition characteristics in fractures with a fracture shrinkage structure.

A CFD Study of Particulate Deposition on Dimple-Type Flue Walls of Coal-Fired Power Plants

The study of particle deposition in bends is always a continuous challenge in various engineering and industrial applications. New types of channels with special microstructures on the surfaces can be effective in modifying the flow field structure as well as particle deposition in channels. In this study, a 90° circular bend with a convex dimple structure was used, and the flow field and the deposition of particles in the channel were analyzed; the Stokes numbers (St) used were 0.016, 0.355 and 1.397. The reliability of the model was ensured by mesh-independence validation as well as speed validation. In a 90° bend channel with convex dimples, the temperature distribution, particle deposition distribution, flow structure and secondary flow were examined. The effects of the number of convex dimples and St in the bend on the flow field structure and particle deposition characteristics were analyzed. The results show that the main factors affecting the deposition characteristics of particles in bends are St, gravitational deposition, thermophoretic force, turbulent vortex clusters and secondary flow distribution. The effect of St is more pronounced, with the deposition rate increasing as the St increases, and the deposition location of the particles is mainly clustered on the outside of the bend structure of the elbow.

Study on the Particle Deposition Characteristics of Transpiration Cooling Structures with Sintered Wire Mesh.

Transpiration cooling based on a porous structure has an ultra-high cooling efficiency, which is expected to be one solution to improve the cooling technology of aero-engine turbine blades. However, particulate impurities in the gas flow channel continue to deposit on the surface of turbine components, blocking cooling holes, which causes great harm to the cooling of turbine blades. In this study, a sintered metal mesh plate was selected as the transpiration cooling structure, and the evolution of particle deposition quality and deposition thickness on the transpiration cooling surface with time, as well as spatial distributions of particle deposition thickness at different times, were explored through experimental and simulation methods. The results showed that, with the increase in spray time, deposition quality and maximum deposition thickness of the transpiration cooling surface gradually increased. Along the main-stream direction, when spray time was short, deposition thickness was higher in a narrow range upstream of the experimental specimen. With the increase in spray time, deposition thickness gradually decreased along the direction of the transpiration cooling mainstream. In the spanwise direction, when spray time was very short, deposition thickness in the spanwise direction was more consistent and, after spray time increased further, the deposition thickness distribution began to tend to a "∩"-type distribution. It can be seen from the simulation results of the metal wire mesh particle deposition that particles were easily deposited on the windward side of the metal wire in the main-stream direction, which agreed with the experimental distribution characteristics of the metal wire mesh deposition. Moreover, the increase in blowing ratio reduced the deposition of particles on the wall of the metal wire mesh.

Analysis of the correlation between mechanical and physicochemical properties of particles based on a diesel oxidation catalytic system

The mechanical and physicochemical properties of diesel engine exhaust particles before and after diesel oxidation catalyst (DOC) treatment are analyzed. It is considered important to explore the interrelationships between these attributes in order to understand their relevance. Understanding of these properties provides insights into the deposition characteristics of particles within the system and the evolution of the particles after the DOC treatment, which may help the selection of appropriate aftertreatment strategies. In this paper, particle samples were collected before and after the DOC to explore the variations in the mechanical and physicochemical properties of the particles under different operating conditions. Atomic force microscopy, thermogravimetric analysis, transmission electron microscopy, and Raman spectroscopy were employed to investigate the attraction force, adhesion force, adhesion energy, oxidative reactivity, primary particle size, nanostructure, and graphitization degree of the particles. The results indicated that under post-injection conditions, the attraction force, adhesion force, and adhesion energy of the particles increased significantly. However, when the particles passed through the DOC, these properties decreased to varying degrees. By analyzing the combination of physicochemical properties, it was determined that the attraction force of the particles was primarily influenced by the primary particle size and the particle's graphite structure. The adhesion force was found to be closely related to the content of soluble organic matter. Additionally, the soluble organic matter affected the degree of particle agglomeration by altering the adhesion energy of the particles.

Numerical study on particle deposition characteristics of turbine blade with cooling film

The aircrafts face the serious issue of particle deposition on blade surface when inevitably working in the dust environment. A simplified C3X turbine blade within film holes is selected to investigate the particle deposition characteristics on blade surface. The EI-Batsh deposition model is applied to observe the particle deposition process and the dynamic grid method is used to rebuild the surface morphology of deposit layer. It is found that the particle deposition rate rises with the increasing particle size due to the increasing impacting frequency of particles. But the deposition rate gradually decreased when the particle diameter increasing to the constant value (15 μm). The particle density has a little influence on particle deposition in comparison to the particle size, especially when particle density increases to 1700 kg/m3, density no longer affects the deposition rate. Besides, the deposit layer on blade surface leads to the increase of particle deposition rate due to the increasing roughness when St < 1.

Effect of particle size distribution on the transmission efficiency of atomized water to the tracheal tube

Ultrasonic atomization is a widely used technology. As the atomization device, lead zirconate titanate (PZT) and lithium niobate (LN) are comparatively investigated through experimental and numerical schemes. However, knowledge on a profitable scheme by which to efficiently deliver the atomized particles into the tracheal tube remains unclear. In this study, the physical difference of the transmission efficiency of water particles atomized by PZT and LN devices was measured. The water particles atomized by PZT and LN were injected into a human airway model including a nasal cavity and bronchial tube. The distribution of the amount of transmitted particles deposited at each of the monitoring positions was then estimated using the results of image analysis of color intensity. As a result, the atomized particles of the PZT device, which produced larger particles than the LN device, were more strongly affected by inertia and tended to be deposited at the area closer to the entrance of the nasal cavity. In contrast, the particles produced by the LN device tended to be transmitted deeper into the trachea. The experimental results indicated that the particle size distribution of PZT and LN, which have quite different maximum sizes of particles, largely influences the spatial distribution characteristics of particle deposition along the airway from the nasal cavity to the trachea.

Numerical simulations on film cooling performance of turbine blade before and after particles deposition

In the present study, a C3X turbine blade with film holes is selected to investigate the effect of blowing ratio on particle deposition and heat transfer characteristics on the blade surface. The deposition characteristics of the blade surface are obtained based on the EI⁃Batsh particle deposition model, and the surface morphology of the deposited layer is reproduced using the dynamic mesh model. The results show that the particle deposition mainly occurs at the leading edge and pressure surface of the blade, but the large-size particles will be deposited on the suction surface due to rebound. The effect of blowing ratio on large-size particles is more obvious, and the deposition rate tends to decrease and then increase with the increase of blowing ratio. Within the range of blowing ratios in this paper, particle deposition leads to an improvement in the cooling efficiency of the air film in the pressure surface along the flow direction near the air film hole region, but a significant decrease in the cooling efficiency near the trailing edge region. Overall, particle deposition caused an increase in overall blade temperature.

Numerical study on transport and deposition characteristics of particles associated with heat setting process in opposed jet flow field

The transport and deposition of particles accompanying the heat setting process in the opposed jet air supply system have a significant impact on the equipment safety. This paper used the Realizable k–ε model to simulate the flow field distribution of the impinging jet and the Lagrange method to track the trajectory of particles, by considering factors, such as jet velocity (7–13 m/s), oven temperature (413–473 K), and particle size (1–30 μ m ) changes, the instantaneous force process of particles was analyzed and their deposition mechanism was revealed. The numerical results have been well validated, with the root mean square error of within 10%. The results indicate that the flow field form of the opposed jet significantly affects particle placement on the surface of the air duct, the maximum turbulent vortex structure appears at the inlet of the air duct on both sides of the protruding nozzle, enhancing the capture of particles. Under the influence of gravity, the lower surface of the air duct becomes the main deposition surface, this phenomenon becomes more pronounced as the particle size increases and the maximum deposition rate difference between the upper and lower layers is 37%. The number of particles deposited on the rear end of the air duct is greater than that on the front end, and the deposition rate decreases with the increase in jet velocity. In the initial stage, a temperature gradient appeared in the machine room, which provided upward lift for the particles, resulting in more small diameter particles ( d p < 10 μ m ) depositing on the upper surface of the air duct. The results can provide theoretical support for the fire prevention and pollutant purification of equipment, such as heat setting machines.

Hybrid manipulation of inkjet-printing deposition pattern of high particle concentration droplet by means of thermal and binary solvent effects

Inkjet-printing of functional material is a well-known drop-on-demand technology used in a wide range of modern applications, such as flexible electronics, biomedical testing, etc. It enables to deliver small amount of materials as ink to the specific location on target substrates. However, it is challenging to precisely manipulate the particle deposition characteristics which is crucial to the quality of the fabricated device. Unlike the traditional passive methods by manipulating the nanoparticle, solvent or substrate surface condition, we propose a passive-active hybrid manipulation method by employing a binary mixture solvent and heating substrate. In this paper, the effects of the solvent mixing ratio, the substrate temperature, the substrate thermal properties on the deposition characteristics of high concentration ITO nano-ink were investigated. Interestingly, we have observed a transition of the classic slim coffee-ring to a fat coffee-ring with a large ring width. A dimensionless number was developed to predict the transition boundary from fat-ring pattern to slim-ring pattern. Finally, the phase diagrams of deposition patterns on three substrates were developed, which were convenient for deposition pattern manipulation in real applications.

The CPFD approach was used to investigate the particle flow characteristics and auxiliary air inlet in an ash transfer pipe

Numerical simulations for the air-solid two-phase flow in a horizontal pipe with a diameter of 125 mm and a length of 10 m were carried out using the Computational Particle Fluid Dynamics (CPFD) method. The deposition characteristics of particles in the pipe were investigated at various inlet flow rates and velocities, and the effect of the auxiliary inlet with different structural parameters on the evacuation of particles in the pipe after the auxiliary inlet was added to the horizontal pipe was compared. The results show that when the volume fraction of particles in the tube is less than 0.6, the flow of particles is relatively stable, and when the volume fraction of particles is greater than 0.8, the particles are seriously deposited and easily form a blockage; the auxiliary air inlet speed is proportional to the effect at the same tilt angle; when the air inlet speed is constant, the auxiliary air inlet angle increases from 35° to 55°, the effect of auxiliary air inlet increases and then decreases, and the effect of auxiliary air inlet reaches its peak at around 45°. The study's findings have implications for long-distance particle transport in horizontal pipelines.

Effects of water-based SiO2 nanofluids on the wettability of coal dust and particle deposition characteristics

Coal wettability plays a crucial role in the prevention of coal mine dust and associated disasters such as coal and gas outbursts. Water-based SiO2 nanofluids have emerged as promising wetting agents because of their sustainable wetting effects on coal. However, the current research on the wetting characteristics of nanofluids has predominantly focused on small coal fragments, with limited studies on coal dust. This study aims to investigate the influence of water-based SiO2 nanofluids with varying particle concentrations on the wettability of coal dust via physical experiments. The findings revealed that the modification by nanofluids significantly reduced the contact angles of the coal dust particles with the particle size ranges of 60–80, 80–100, and 100–150 mesh, compared to the initial contact angles. Moreover, higher particle concentrations resulted in smaller contact angles. Notably, the wetting effects of the nanofluid modification on coal dust were particularly prominent for larger particles. Furthermore, compared with water immersion, nanofluid modification demonstrated a significantly more positive impact on the wettability of coal dust. Notably, the SiO2 nanoparticles exhibited a wide distribution and substantial adsorption capacity on the coal surface, enabling the formation of a hydrophilic structure coverage. This study contributes to a comprehensive understanding of the wetting behavior of coal dust when exposed to water-based SiO2 nanofluids. These findings underscore the potential of nanofluids to enhance coal dust prevention and control, and provide valuable insights for future research in this field.

Hydrate deposition characteristics analysis and structural optimization design of reduced-diameter pipe based on an improved model

High-pressure and low-temperature conditions in deep-water development are probably going to cause serious hydrate deposition problems. Current studies on hydrate migration and deposition are mainly centered on through-diameter conditions, and relatively few studies have been carried out for reduced-diameter conditions. Meanwhile, the effect of heat transfer between the particle-fluid-wall in the pipe on hydrate particle deposition is usually neglected, resulting in discrepancies between results and reality. Here, an improved hydrate deposition-stripping model is developed based on hydrate particle adhesion and rebound as well as deposition and stripping criteria, and combined with the inter-phase heat transfer characteristics. The effects of several important parameters, such as thermophoretic force and pipeline structure, on the deposition characteristics of micron-sized hydrate particles were investigated, and the deposition mechanism of hydrate in special pipelines was revealed. Also, the combination of calculation results provides new ideas for the design of oil and gas pipes. Based on the enhanced mechanism of hydrate particle deposition in the reduced-diameter pipe proposed in this paper, a new parameter of hydrate particle deposition enhancement rate (ξh) is defined to characterize the integrated enhancement effect of reduction structure and heat transfer in the pipe on hydrate particle deposition, and a new correlation calculation method is provided for it. The results can provide a valuable reference for efficient and accurate calculation of hydrates.

Mechanism study on particle deposition and clogging characteristics in film cooling hole

The present study is focused on the problems of gas–solid two-phase flow transport in the film cooling hole that cause film flow obstruction and cooling failure. To study the unsteady development process of the deposition layer in the film hole, a simulation method combining computational fluid dynamics and the discrete element method was used, and a film hole flow model was established. The effect of gas phase and solid phase characteristics on clogging and deposition in the film hole was studied. The following conclusions are drawn: The inlet/outlet pressure ratio is inversely proportional to the clogging degree of the film hole. The inlet/outlet pressure determines the deposition behavior by affecting the initial momentum and drag force of particles. In the Stokes number range of 1.58–14.26, the deposition in the film hole first increases and then decreases. There is a Stokes number with the most severe clogging. The Stokes number determines the deposition pattern by affecting the relative magnitudes of the drag force and interaction forces of particles. The particle surface energy is positively correlated with film hole clogging. The particle surface energy determines the stability of the deposition layer by influencing the strength of the force chain network.

Experimental Study of Particle Transport and Deposition Distribution over Complex Terrains Based on Spherical Alumina

The transport and deposition of atmospheric particulate matter have attracted significant attention recently due to the increasing frequency of extreme disaster events, such as dust storms, volcanic eruptions, and extensive forest fires. The size distribution of the transported material and the conditions of the land–air interface are dominant factors in comprehending the detrimental potential of atmospheric particulate matter. However, it is still a challenge to understand the mechanism of dust deposition, especially over complex terrain. In an effort to investigate the deposition characteristics of particles over complex terrain, a series of experiments were conducted in a multifunctional environmental wind tunnel. The results show that the wind speed directly above the top of the mild slope model is significantly greater than that in the steep slope model, which indicates that a steep slope has a greater blocking effect on wind fields. At low wind speeds, the average wind speed at the top of the mild slope model is 17.8% higher than that at the top of the steep slope model, and at high wind speeds the average wind speed at the top of the mild slope model is 8.6% higher than that at the top of the steep slope model. The influence trend of the steep slope model and the combination model is basically the same, with both decreasing first and then increasing with the direction of wind velocity. The amount of surface deposition is greatly affected by the location of the feeding point and the microscale characteristics of the surface. In the steep slope model, the deposition is mainly distributed on the windward side, while the leeward side has a small amount of deposition. In the mild slope model, particles are deposited not only on the windward side, but also on the leeward side. The average rate of decline in deposition flux in the steep slope model is 88.4% and 75.1% in the mild slope model. The use of the combination model reduces the particle concentration at the back end compared with the single model. In three different models, the deposition on the windward side was shown to be significantly greater than that on the leeward side of the model. Our work increases understanding of the deposition of coarse dust particles over complex terrain and provides basic data for improving the accuracy of large-region particle transport and deposition simulations.

Thermophoretic particle deposition on double-diffusive Ree-Eyring fluid flow across two deformable rotating disks with Hall current and Ion slip

This work emphasizes the characteristics of thermophoretic particle deposition on Ree-Eyring fluid flow with Hall current and Ion slip effects between two deformable spinning disks. The novelty of the envisioned model is strengthened by considering generalized Fourier and Fick laws with thermal source/sink. The proposed model is optimized by taking multiple slip boundary constraints at the surface. The equations that govern the flow are simplified with the use of the proper transformations. The numerical solution is obtained using the boundary value problem of fourth order (bvp4c) method. Graphical representations of the emerging parameters are presented. Numerical values of skin friction coefficient, local Nusselt, and Stanton number are highlighted in tabular form. The velocity field depicts a deteriorating behavior on incrementing the Reynold number. For augmented values of Hall and ion slip parameters fluid velocity elevates. An upsurge is noticed in the axial and radial velocities on amplifying the rotation parameter. On augmenting the thermophoretic parameter the particle deposition at the interface of the upper disk diminishes. Growing values of rotation parameter, Weissenberg, and Reynold numbers imply an additional resistance to the fluid flow that ultimately reinforced the surface drag force causing a decline in the fluid velocity. The rate of heat transmission accelerates on enhancing the Reynold number, however, heat flux exhibits a decay on augmenting the thermal slip parameter. On augmenting the thermophoretic parameter particle deposition deteriorates at the interface of the upper disk. An excellent concordance is noticed when the outcomes are contrasted with the previous literature. For the value of the rotation parameter β=-1 and β=-8 the percentage error of the present analysis with Imtiaz et al. [68] are 0.00001 and 0.00002.

Experimental study of particle deposition characteristics in a gasifier: Effect of slag wall temperature

Based on the visualization system, the particle tracking method was used to study the influence of slag wall temperature on the deposition characteristics of coal particles under gasification conditions. The results show that particle deposition can be divided into five types: rebound, rebound after blocking for a distance, crushing, rolling, and adhesion. When slag wall temperature is lower than the deformation temperature, the probability of rebound is over 70%. With the increase of slag wall temperature, the global coefficient of restitution remains constant and then decreases with 1100 °C as the dividing line and the tangential coefficient of restitution concentrates around 0.65. It is proved that the fusion characteristics of slag wall are the main cause of the change in particle deposition on the wall. The collision theory is introducted in the study of deposition characteristics of particles. The collision process is classified into “elastic-plastic collision” and “wet collision”.

Operando investigation of deposition characteristics of submicron particles in electric-flow coupled fields combined with object detection

Submicron particle is a harmful air pollutant due to size effect, gathering characteristic and biological activity, which not only causes a serious threat to human health and public sanitary security, but also is difficult to capture with lowest removal efficiency. Here, Operando investigation system is constructed to explore deposition characteristics of submicron particles in electric-flow coupled fields through combining microfluidic technology for forming micro electric field on the lab-on-a-chip with micro-visualization technology for capturing dynamic deposition process. Besides, based on object detection and deep learning, an image processing method is developed which can realize automatic object detection and rapid extraction of required information. Results show that particle chain grows preferentially from the convex position to prove the influence of electrode surface roughness on the growth site. The global electric field has a positive effect on keeping particle chain growing up at upright direction, and the growth process of particle chain is proposed: forming growth site stage, grow fast stage and fluctuation stage. Particle velocity in the airflow direction presents a decrease trend during the process particle migrates towards to electrode surface, which proves the direct influence of boundary layer effect on the ultimate height of particle chain.

Understanding the effects of inhaler resistance on particle deposition behaviour – A computational modelling study

Background and objectiveUnderstanding the impact of inhaler resistance on particle transport and deposition in the human upper airway is essential for optimizing inhaler designs, thereby contributing to the enhancement of the therapeutic efficacy of inhaled drug delivery. This study demonstrates the potential effects of inhaler resistance on particle deposition characteristics in an anatomically realistic human oropharynx and the United States Pharmacopeia (USP) throat using computational fluid dynamics (CFD). MethodMagnetic resonance (MR) imaging was performed on a healthy volunteer biting on a small mockup inhaler mouthpiece. Three-dimensional geometry of the oropharynx and mouthpiece were reconstructed from the MR images. CFD simulations coupled with discrete phase modelling were conducted. Inhaled polydisperse particles under two different transient flow profiles with peak inspiratory flow rates (PIFR) of 30 L/min and 60 L/min were investigated. The effect of inhaler mouthpiece resistance was modelled as a porous medium by varying the initial resistance (Ri) and viscous resistance (Rv). Three resistance values, 0.02 kPa0.5minL−1, 0.035 kPa0.5minL−1 and 0.05 kPa0.5 minL−1, were simulated. The inhaler outlet velocity was set to be consistent across all models for both flow rate conditions to enable a meaningful comparison of models with different inhaler resistances. ResultThe results from this study demonstrate that investigating the effect of inhaler resistance by solely relying on the USP throat model may yield misleading results. For the geometrically realistic oropharyngeal model, both the pressure and kinetic energy profiles at the mid-sagittal plane of the airway change dramatically when connected to a higher-resistance inhaler. In addition, the geometrically realistic oropharyngeal model appears to have a resistance threshold. When this threshold is surpassed, significant changes in flow dynamics become evident, which is not observed in the USP throat model. Furthermore, this study also reveals that the impact of inhaler resistance in a geometrically realistic throat model extends beyond the oral cavity and affects particle deposition downstream of the oral cavity, including the oropharynx region. ConclusionResults from this study suggest that key mechanisms underpinning the working principles of inhaler resistance are intricately connected to their complex interaction with the pharynx geometry, which affects the local pressure, local variation in velocity and kinetic energy profile in the airway.

Study on particle deposition performance in liquid lead-bismuth eutectic and supercritical CO2 heat exchanger

Lead-bismuth eutectic (LBE) and supercritical CO2 (SCO2) heat exchangers are highly recommended and designed due to their compactness and high thermal efficiency. During heat exchanger operation, however, undesired particle impurities are generated, which deposit on the surface and degrade heat transfer. To predict the deposition distribution, a tube-shell heat exchanger was proposed with LBE as the heat source and SCO2 as the cool source. Based on this proposal, a three-dimensional model was established, and particle deposition characteristics were studied numerically. The results indicated that the inlet section had a high concentration and deposition rate. At the inlet, the deposition rate in LBE was higher than SCO2. Specifically, particle deposition in LBE was concentrated mainly in the inlet section, while it occurred throughout the entire channel in SCO2. An increase of particle diameter and concentration contributed to deposition on both sides. The average deposition rates of LBE and SCO2 showed an increase of 1.04 times and 2.76 times, respectively, when the particle diameter was varied from 2 μm to 6 μm. Similarly, an increase in concentration from 1 % to 2.5 % resulted in an increase of deposition rates of LBE and SCO2 by 3.75 times and 3.68 times, respectively. This implied that the concentration had a stronger impact on deposition. The deposition characteristics of particle species differed in LBE and SCO2. As the particle density increased, the deposition rate decreased in LBE but increased in SCO2. The particle deposition mechanism in LBE and SCO2 was revealed by analyzing the forces acting on particles.

Particle Deposition Characteristics on Turbine Blade Surface Based on Critical Velocity Model

Based on the critical velocity model of EI-Batsh, this paper further considered the particle deposition-bounce and the secondary collision deposition after the bounced, which improved the original particle deposition model. Then the particle deposition mass per unit of time and area (PDM) was proposed to characterize the particle deposition on the turbine blade surface. The effects of different rows of cooling film holes, blowing ratios, particle diameters and diameters of cooling film holes on the particle deposition characteristics of the blade surface were then investigated. The results show that the deposition amount of the single cooling film holes opening with radial inclination facing the leading edge is the smallest, and the deposition amount gradually increases when the inclination angle is shifted toward the pressure and suction surface. As the blowing ratio increases from 0.3 to 1.5, the amount of particle deposition tends to decrease and then increase, and reaches a minimum value when the blowing ratio is about 0.5. The deposition increases with increasing particle diameters in the range of 2-10 μm and gradually increases when the diameter of cooling film holes is from 0.99 mm to 1.5 mm.