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The erosive wear encountered in some industrial processes results in economic loss and even disastrous consequences. Hitherto, the mechanism of the erosive wear is not clear, especially when the erosive wear is caused by large particles (>3.0 mm) carried by a flowing liquid. Current approaches of predicting erosive wear need improvement, and the optimization of relevant equipment and systems lacks a sound guidance. It is of significance to further explore such a subject based on the relevant literature. The present review commences with a theoretical analysis of the dynamics of large particles and the fundamental mechanism of erosion. Then the characteristics of the erosion of various equipment are explicated. Effects of influential factors such as particle size and properties of the target material are analyzed. Subsequently, commonly used erosion models, measurement techniques, and numerical methods are described and discussed. Based on established knowledge and the studies reported, some expectations for future work are proposed. [ABSTRACT FROM AUTHOR]

This paper takes the power source (gas–solid injector) of the large-sized particle pneumatic conveying system as the design object, builds the pure gas flow field experiment bed and particle pneumatic injection experiment bed, and establishes the dataset of the large-sized particle gas–solid injector of the injection experimental results. Constructed the simulation model of gas–solid injectors based on CFD-DEM coupling, and established the dataset of pure gas flow field injection and gas–solid injection simulation results under multiple evaluation indexes. These datasets are valuable for engineers and designers, providing a reference for designing gas–solid injectors and other pneumatic conveying devices.

Fouling is one of the barriers to developing more efficient and near-zero emission internal combustion engines. The micron-sized particulate matter is one of the roots of this fouling phenomenon in exhaust gas recirculation (EGR) coolers. This fouling is inadequately evaluated quantitatively, and its deposition mechanism is unknown. To investigate the effect of gravity on the deposition of micron-sized particles, an original nondestructive sampling fouling method and experiment apparatus have been developed to effectively obtain the upper and lower bottom fouling in the cooler in the direction of airflow, and the area proportion, count, and diameter of large particles in the fouling using image processing software. It was found that (i) the area proportion of large particles in the lower bottom fouling was almost 2.5 times higher than the upper bottom fouling; (ii) the count of large particles in the lower bottom fouling was higher, and the maximum diameter was larger, up to 639mm; (iii) the mass of the lower bottom fouling was 1.5 times higher than the upper bottom fouling; (iv) gravity can significantly promote the deposition of micron-sized particles and should be considered in the design and arrangement of the EGR cooler to prevent fouling. [ABSTRACT FROM AUTHOR]

The preparation of large particles of cerium oxide with ammonium bicarbonate solution as precipitator was studied. The effects of reaction temperature, mass concentration of feed liquid, adding time of precipitator, amount of crystal seed, aging time and stirring speed on particle size and dispersion of cerium oxide were investigated. The heating rate and temperature of cerium carbonate were determined. The particle size and dispersion of cerium oxide were used as evaluation indexes to optimize the process conditions by orthogonal test. The results show that the particle size of cerium oxide prepared under suitable conditions is in the range of 25~55 µm, the dispersion is uniform and the quality is stable. [ABSTRACT FROM AUTHOR]

To solve the wear problem of stamping dies in high-speed machining，cathodic multi-arc ion plating is often used to improve surface properties，and the surface quality of cathode multi-arc ion plated coating is one of main factors affecting the life of stamping dies.In this paper，the effects of the DC bias voltage，flow rate of nitrogen and arc current on the surface quality of CrAlN coating were studied by the orthogonal experiments.The significance of the effects of DC bias voltage，flow rate of nitrogen and arc current on the surface quality of the CrAlN coating was analyzed by the extreme-range method and variance method.Results showed that the surface quality of the CrAlN coating was affected most significantly by the flow rate of nitrogen，and the DC bias voltage also influenced the number of large particles on the surface of the CrAlN coating.When the DC bias voltage was 160 V，the nitrogen flow rate was 1 600 mL/min，and the arc source current was 120 A，the as-prepared coating possessed the minimum number of large particles on the surface (42.5 per 10，000 μm2) and the optimal surface quality.

The Atkinson equation along with its friction factor is commonly used to estimate pressure requirement in mine ventilation. However, friction factor correlation of flow through broken rock, typically found in blasted stope, gob, rock pit or block caving rock deposits, etc., is currently unavailable. Also, it is impractical to conduct direct measurements of flow resistance in an inaccessible broken rock zone. This paper aims to develop a new friction factor correlation of flow through broken rock that can be used directly in Atkinson equation. The proposed correlation is valid for broken rocks with diameter between 0.04 and 1.2 m and porosity ranging from 0.23 to 0.7.

Sandy cobble strata with large granular particles are typically traversed by shield tunnels, leading to high tool wear and excessive surface settlement. Soil conditioning in the laboratory removes large particles owing to test device limitations and may not reflect field tunneling involving large cobbles and boulders. This study proposes a hybrid experiment/theory method for soil conditioning in sandy cobble strata having large particles. Viscosity, stirring, and slump tests are conducted to obtain suitable parameter ranges of different soil conditioning agents for soil samples (< 30 mm). To consider large particles, the average liquid bridge force per unit length F / d and the liquid flow velocity u in the foam's Plateau border are chosen to represent the static and motive characteristics of the samples. The calculation method for the liquid flow velocity in the Plateau border is determined, and a relationship between the particle clearance and the soil sample porosity ratio is proposed. Finally, the suitable parameter range for soil conditioning is revised by the theoretical part considering particles larger than 30 mm. The hybrid method was applied to two shield construction cases in Chengdu and Lanzhou, China. The results indicate that the bentonite injection ratio I b and the foam injection ratio I f should be increased by 42.7% and 60.6% on average for the two cases, respectively. The proposed soil conditioning hybrid approach provides a beneficial effect in the form of stable construction parameters while improving cutting tool life and can be used to guide soil conditioning in sandy cobble strata. [ABSTRACT FROM AUTHOR]

The gas-solid injector is the power source of the particle pneumatic conveying system. The injector structural parameters have a large impact on the pneumatic conveying system. To obtain the optimal structural parameters of the injector for large particles, the injection ratio in the pure flow field experiment (PFFE), the average static pressure of stable conveying (pressure index) and the particle transport time (time index) in the particle injection experiment (PIE) are used as the performance indexes. The influence of the structural factors on the injection performance in the PFFE and the PIE are obtained by the multi-index orthogonal test scheme. The optimal structural parameters of the injector in the PFFE and the PIE are compared and verified, providing significant guidance for practical applications and an experimental basis for the large particle pneumatic conveying system. Unlabelled Image • The injection ratio is used to evaluate the injection performance in the PFFE. • The pressure and time are used to evaluate the injection performance in the PIE. • Nozzle length has the most significant influence on the injection performance. • The influence of structure to injection performance in PFFE and PIE are obtained. • The optimal structure of the injector in the PFFE and the PIE are obtained. [ABSTRACT FROM AUTHOR]

• A novel louver has higher particle separation efficiency with lower pressure drop was developed. • When inlet air velocity was 2.8 m/s, compared with the commercial louver, the pressure drop of louver was reduced by 89.5 %, the large particle separation efficiency was increased by 158.6 %. • With the increase of inlet air velocity from 2.3 m/s to 2.8 m/s, the separation efficiency of the novel louver was decreased from 80.3 % to 57.3 %, and the pressure drop of the louver was increased from 11. 1 Pa to 13.9 Pa. Due to the inadequate separation efficiency of current louver used in industrial, commercial, and residential buildings in separating large particle, leading to clogging of subsequent high-efficiency filters and increased fan energy consumption. Therefore, it is essential to increase separation efficiency of large particle for fresh air intake to reduce the burden on the filter. In this study, a novel louver has higher large particle separation efficiency with lower pressure drop was developed based on experiments and computational fluid dynamics (CFD) model. The effect of different structural parameters (number, length and location of dustproof hooks) and inlet air velocity on separation efficiency and pressure drop was evaluated. Results showed that mentioned factors could pose important impacts on pressure drop and separation efficiency. With the increase of inlet air velocity from 2.3 m/s to 2.8 m/s, the separation efficiency of the louver was decreased from 80.3 % to 57.3 %, while the pressure drop of the louver was increased from 11.1 Pa to 13.9 Pa. In addition, when inlet air velocity was 2.8 m/s, compared with the commercial louver, the pressure drop of louver was reduced by 89.5 %, the large particle separation efficiency was increased by 158.6 %. [ABSTRACT FROM AUTHOR]

In the process of hydraulic lifting of solid mineral particles on the seabed, the two-phase flow in the pipeline causes wall wear, which reduces the reliability of the hydraulic lifting system. In this research, based on the coupled computational fluid dynamics (CFD) and discrete element method (DEM), the numerical simulation of large particle solid–liquid two-phase flow and wall wear in a bend pipe with different wall shapes was conducted to provide solutions for reducing wall wear. By adding bumps to the bend pipe wall to change the shape of its inner wall, under the working conditions of particle concentrations of 1–10% and particle sizes of 1–3 mm, wear experiments and calculations for the bend pipe with bumps at different positions were performed. With comparative analysis, it was found that the location of the bump in the bend pipe had an important influence on the maximum wear rate. When the bump was located near the location where the particles collided with the prototype bend pipe for the first time, the maximum wear rate decreased the most significantly. The particle mass flow rate will also affect the wear reduction effect of the bump on the bend pipe wall.

Characterization of flow through packed bed of spheres with large particle diameters (O ~ m) is important in industrial applications, such as mining, geothermal, oil and gas, and construction industries. In this study, a three-dimensional pore-scale mathematical model of packed bed of spheres with large particle diameters considering uniform and non-uniform particle size distributions is developed and validated against experimental data. It was found that the available correlations fail to predict flow behavior in packed bed with larger particle sizes. Hence, Ergun and Forchheimer theories along with pore-scale mathematical model are utilized to simulate and develop permeability (Carman-Kozeny) and inertial resistance (Forchheimer) correlations which are valid for flow through packed bed of spheres with large particle sizes, i.e. sphere diameter from 0.04 to 1.2 m and porosity between 0.2 and 0.7. The developed correlation can be used in either analytical or volume-averaged computational models which is useful for industrial/practical. Unlabelled Image • Pore-scale model of flow through packed bed of spheres with large particle diameters. • Model is validated with experimental data. • Available correlations fail to predict flow behavior in packed bed with larger particles. • New correlation is proposed for Ergun and Forchheimer parameters; valid for particle size 0.04–1.2 m, porosity 0.2–0.7. • Permeability and inertial resistance are functions of porosity and particle size. [ABSTRACT FROM AUTHOR]

Fine and large particles flowing through a bend in a pipe move differently and therefore erode the pipe differently. This paper simulates solid–liquid two-phase flow containing large particles in a bend and analyses the relationship between the wear formation and particle motion. Wear experiments are carried out using 3-mm glass bead particles at a mass concentration of 1–15%. At the same time, the flow field and the motion of the granular system are obtained in computational fluid dynamics–discrete element method simulation. The wear formation mechanism is revealed by comparing experiments with numerical simulations. The wear rate of the wall surface increases with the mass concentration, while the marginal growth rate decreases as the mass concentration increases. As the mass concentration increases to a certain value, the degree of wear reaches a maximum and remains unchanged subsequently because of the formation of a particle barrier along the bend wall. The particles near the wall region will bounce forward because of the periodic disturbance flow around particles. The impact of mass bouncing particles causes the formation of the erosion ripple on the test sheet.

Airborne coal dust generated during mining can deposit and accumulate on mine surfaces, presenting a dust explosion hazard. When assessing dust hazard mitigation strategies for airborne dust reduction, sampling is done in high-velocity ventilation air, which is used to purge the mining face and gallery tunnel. In this environment, the sampler inlet velocity should be matched to the air stream velocity (isokinetic sampling) to prevent oversampling of coarse dust at low sampler-to-air velocity ratios. Low velocity ratios are often encountered when using low flow rate, personal sampling pumps commonly used in underground mines. In this study, with a goal of employing mine-ready equipment, a personal sampler was adapted for area sampling of coarse coal dust in high-velocity ventilation air. This was done by adapting an isokinetic nozzle to the inlet of an Institute of Occupational Medicine (Edinburgh, Scotland) sampling cassette (IOM). Collected dust masses were compared for the modified IOM isokinetic sampler (IOM-MOD), the IOM without the isokinetic nozzle, and a conventional dust sampling cassette without the cyclone on the inlet. All samplers were operated at a flow rate typical of personal sampling pumps: 2 L/min. To ensure differences between collected masses that could be attributed to sampler design and were not influenced by artifacts from dust concentration gradients, relatively uniform and repeatable dust concentrations were demonstrated in the sampling zone of the National Institute for Occupational Safety and Health experimental mine gallery. Consistent with isokinetic theory, greater differences between isokinetic and non-isokinetic sampled masses were found for larger dust volume-size distributions and higher ventilation air velocities. Since isokinetic sampling is conventionally used to determine total dust concentration, and isokinetic sampling made a difference in collected masses, the results suggest when sampling for coarse coal dust the IOM-MOD may improve airborne coarse dust assessments over “off-the-shelf” sampling cassettes. [ABSTRACT FROM PUBLISHER]

Improving transport efficiency is one of the core issues in the field of deep-sea mining. Slip velocities have strong effects on the transport efficiency of deep-sea mineral nodules in the hydraulic conveying process. The present work proposes a probability model for predicting the transport velocity and efficiency, which can reflect the influence of different particle size distribution of large particles. By comparing with a numerical simulation, experimental data and empirical models, the proposed model is well verified and demonstrates advantages in accuracy. To acquire further knowledge of the optimal transport efficiency and the predominant factors, such as the volumetric concentration, the pipe diameter and the mixture velocity, effects of various parameters are explored in detail through the present model, including the medium particle diameter, the average dry solid production, the operating power, the particle density, and the fluid density. Furthermore, four general-purpose optimization algorithms, including the global search (GS), the MultiStart (MS), the pattern search (PS) and the genetic algorithm (GA), are combined to obtain the optimal transport efficiency and compared in an application study. The proposed model provides an efficient tool to fast optimize the transport efficiency of mineral nodules in hydraulic conveying pipes. [Display omitted] • Probability model to predict velocity considering particle size distribution • Complete procedure to obtain optimal efficiency and corresponding variables • Four general-purpose optimization algorithms compared for hydraulic conveying • Superior prediction accuracy validated by experimental data and empirical models • Efficient tool to fast optimize transport efficiency of conveying mineral nodules [ABSTRACT FROM AUTHOR]

Aerosol droplets or particles produced from infected respiratory secretions have the potential to infect another host through inhalation. These respiratory particles can be polydisperse and range from 0.05 to 500 µm in diameter. Animal models of infection are generally established to facilitate the potential licensure of candidate prophylactics and/or therapeutics. Consequently, aerosol-based animal infection models are needed to properly study and counter airborne infections. Ideally, experimental aerosol exposure should reliably result in animal disease that faithfully reproduces the modeled human disease. Few studies have been performed to explore the relationship between exposure particle size and induced disease course for infectious aerosol particles. The center flow tangential aerosol generator (CenTAG™) produces large-particle aerosols capable of safely delivering a variety of infectious aerosols to non-human primates (NHPs) within a Class III Biological Safety Cabinet (BSC) for establishment or refinement of NHP infectious disease models. Here, we report the adaptation of this technology to the Animal Biosafety Level 4 (ABSL-4) environment for the future study of high-consequence viral pathogens and the characterization of CenTAG™-created sham (no animal, no virus) aerosols using a variety of viral growth media and media supplements. [ABSTRACT FROM AUTHOR]

• The extent of secondary reaction was determined by both temperature and particle size. • Product distribution revealed two distinctive steps of intraparticle secondary reactions. • The initial decomposition step was transport-controlled and sensitive to particle size. • The further recombination step was jointly controlled by kinetics and transport. Thermochemical conversion provides promising approaches for utilization of agroforestry residues as energy sources in rural areas, such as decentralized biomass combustion and gasification. Understanding of the pyrolysis characteristics are crucial for the design of reactors and optimization of working conditions, but in these scenarios, utilization of centimeter-sized large fuel particles will bring challenges in predicting the evolution of pyrolytic products owing to the intraparticle secondary reactions. In this work, the product distribution of biomass pyrolysis was investigated in wide ranges of temperatures and particle sizes, and special attention was paid to the pyrolysis of centimeter-sized fuel particles under medium to high temperatures (500 °C – 900 °C). The yields of solid/liquid/gas-phase products were quantified, and the composition of tar and gas products were qualitatively and quantitatively evaluated, aiming at illustrating the effects of intraparticle secondary reactions. The results have shown that the differences between the product distribution of sawdust (<1 mm) and centimeter-sized wood cubes were significant over the whole temperature range, but the differences between wood cubes with varying sizes (1 cm, 1.5 cm and 2 cm) were dependent with the external temperature, indicating that the extent of intraparticle secondary reactions was simultaneously determined by external temperature and particle size. The evolution of tar composition indicated that the intraparticle secondary reactions could be divided into two distinctive steps. Increasing the particle size would firstly result in fast consumption of primary tar species and emergence of secondary tar species, while the second step would lead to the formation of simple phenols and aromatics, and large quantities of PAHs were released for centimeter-sized fuel particle under high temperatures (≥800 °C). Kinetic analysis further revealed that the first step was mainly transport controlled and sensitive to particle size, while the second step was jointly controlled by kinetics and transport, which appeared to be significant only if the particle size was large and simultaneously the temperature was sufficiently high. [ABSTRACT FROM AUTHOR]

Aerosol and inhalational studies of high-consequence pathogens allow researchers to study the disease course and effects of biologicals transmitted through aerosol in a laboratory-controlled environment. Inhalational studies involving Nipah virus with small (1-3 μm), intermediate (6-8 μm), and large particles (10-14 μm) were explored in African green nonhuman primates to determine if the subsequent disease course more closely recapitulated what is observed in Nipah virus human disease. The aerosol procedures outlined describe the different equipment/techniques used to generate the three particle sizes and control the site of particle deposition within this animal model., (© 2023. Springer Science+Business Media, LLC, part of Springer Nature.)