The Experts below are selected from a list of 2421 Experts worldwide ranked by ideXlab platform
David Mills - One of the best experts on this subject based on the ideXlab platform.
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Pipeline Feeding Devices
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:The choice of feeding device for a pneumatic Conveying system is one of the key decisions to be made for a pneumatic Conveying system. The first is probably whether to use pressure or vacuum and to what value. There is a wide selection from which to choose and the decision must take account of the properties of the material to be conveyed such as friability, abrasiveness, particle size, and cohesivity. A steady feed rate is important and particularly so for dilute phase Conveying, as Conveying Air velocities are relatively high and small changes will result in a rapid change in Conveying-line pressure drop. The potential importance of being able to control the feed rate should also be considered, particularly if the quality of the material is likely to change or if the pipeline is required to convey the material over a range of distances.
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Troubleshooting and Material Flow Problems
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:By the very nature of the problems associated with the design of pneumatic Conveying systems, it is not the least surprising that a multitude of problems can arise when it comes to their operation. The main problem is that it is not always possible to identify the source of any particular problem. Problems that arise during commissioning may well be attributed to fundamental design errors, but faults that occur after a period of time can be more difficult to identify. It may sound a little silly, but the performance can even be influenced by the weather. In the winter, with lower prevailing temperatures, there is the possibility of Conveying Air velocities being a little too low because the density of the Air will increase. In the rainy season and with rapid changes of temperature, moisture and condensation can be a problem. With abrasive materials, gradual wear of plant will occur and this can affect the performance of material feeding devices and compressors over a period of time. A change in the source or quality of the material to be conveyed is always a potential candidate.
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Multiple Use Systems
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:All pneumatic Conveying systems are not dedicated to the Conveying of a single material over just one distance. In many cases, several materials have to be conveyed to a number of different reception points. In a manufacturing process, a single pipeline is used to convey a diverse range of materials from a number of supply hoppers to a single delivery point for blending. In many industries, such as glass and food, a wide variety of materials have to be conveyed by a common system, since there is a requirement to deliver a given menu for a particular process. In ship off-loading, a single line may be used to unload several different materials and to convey them to separate locations. In all of these cases, it is essential that each material should be conveyed successfully. However, each material may have different Conveying characteristics and as a consequence, the Air requirements for the Conveying of different materials and the material flow rates achieved can vary significantly. Conveying distance can also have a significant influence on Conveying performance. Some of the materials to be transported may be capable of being conveyed in dense phase, and hence at low velocity, while others may have no dense phase capability and will have to be conveyed in dilute phase with a high Conveying Air velocity. The Conveying performance of different grades of the same material can also widely differ.
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Chapter 12 – Conveying Capability
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:Detailed data on the pneumatic Conveying of a wide range of materials is presented in this chapter to further illustrate the differences in the performance and capability of materials having a wide range of properties in terms of size, size distribution, and density. In the previous chapter low-velocity dense phase Conveying was illustrated with materials having good Air retention properties and in this chapter, this is extended to materials having very good permeability. Various comparative plots of data are also provided to illustrate the potential range of Conveying limits for materials, the influence of Airflow rate on Conveying capability, and the potential range of minimum Airflow rates and hence minimum values of Conveying Air velocity. As mentioned before, virtually anything can be conveyed pneumatically and the bulk particulate materials included here have a mean particle size range from about 10 micron to 10 millimeters and material bulk densities range from 100 to 2380 kg/m3.
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Chapter 18 – Stepped Pipelines
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:The use of stepped pipelines are to be recommended in any positive-pressure pneumatic Conveying system where the Air supply pressure is above about 0.8 bar gauge and in any vacuum Conveying system where the operating vacuum is below about 0.4 bar. It can almost be guaranteed that a stepped pipeline will convey material at a higher rate than the equivalent single-bore line and this applies to vacuum Conveying systems as well as positive pressure. In some of the cases reported here, the improvement in Conveying performance has been of the order of 100%. Significant reductions in Conveying Air velocity values can be achieved and this of particular advantage if the conveyed material is either abrasive or friable. Reference is also made to alternative Air-extraction systems, which are generally applied to single-bore pipelines, and it is shown that an improvement in Conveying performance can be achieved even when more than half of the original Conveying Air is discharged before the end of the pipeline.
Jens Denecke - One of the best experts on this subject based on the ideXlab platform.
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Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media
Chemical Engineering & Technology, 2010Co-Authors: Mira Sturm, Siegmar Wirtz, Viktor Scherer, Jens DeneckeAbstract:A DEM-CFD coupling for the simulation of gas-solid flows was successfully implemented and simulations were performed for the application to industrial-scale pneumatic Conveying. Therefore, all particle collisions and phase interactions were considered and porosity determination was optimized. The aim of this work is to show the applicability of the presented simulation model to the different regimes of pneumatic Conveying systems. As a first test case a dense vertical pneumatic Conveying system was chosen and an individual plug was investigated in detail. Variations of the Conveying Air velocity were also considered. As a second test case dilute Conveying in a horizontal-to-vertical pipe bend was simulated. The occurrence of roping and the reduction of particle velocity is of high interest for the design of specific pneumatic systems. It is shown that both regimes can be captured reasonably well and the results are rich in details.
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Coupled Discrete Element (DEM)–Continuous Fluid (CFD) Method for the Application of Pneumatic Conveyed Granular Media
Volume 4: Fluid-Structure Interaction, 2009Co-Authors: Mira Sturm, Siegmar Wirtz, Viktor Scherer, Jens DeneckeAbstract:A Coupled Discrete Element - Continuous Fluid Method is developed, which allows the numerical simulation of the behaviour of pneumatic conveyed granular media. While the fluid is simulated by computational fluid dynamics, the soft-sphere discrete element approach is used for the particle system. A “four-way coupling” is implemented to account for phase interaction on both sides and for the collisions among particles and with the pipe walls. The purpose of this work is to show the applicability of the presented simulation model to dense pneumatic Conveying systems. Unfortunately, only few complete experimental data are available in this field. In this work a pneumatic Conveying system for dense phase regime with a vertical pipe of 2 m height and a diameter of 50 mm is investigated. Periodic conditions are applied to both phases, the fluid and the particle system. The particles, which leave the pipe at one end, are inserted back at the other end of the pipe, so that a much larger simulation domain is represented. After an initial set up and some intermediate time steps a stable mode is reached and one single plug forms, which is then investigated in detail. The pressure distribution along the plug which coincides with the porosity distribution, the length of the plug and its velocity are important parameters which are examined and compared to experimental investigations. Variations of the Conveying Air velocity and their influence are also considered.Copyright © 2009 by ASME
Akira Rinoshika - One of the best experts on this subject based on the ideXlab platform.
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Self-excited pneumatic Conveying through vertical curved 90° bends
Powder Technology, 2019Co-Authors: Lin Dong, Akira RinoshikaAbstract:Abstract The effect of self-excited soft fins on a pneumatic Conveying with different vertical curved 90° bends was experimentally studied to reduce pressure drop, power consumption and Conveying Air velocity. The distributions of particle velocity and particle fluctuating velocity near and in the first bend were measured based on the high-speed PIV. The polyethylene particles with a diameter of 2.3 mm were used as Conveying materials. The superficial Air velocity was varied from 10 to 14 m/s, and the stable mass flow rate was fixed at 0.45 kg/s. Compared to the non-fin pneumatic Conveying, the pressure drop, the minimum pressure drop (MPD) velocity, power consumption, and additional pressure drop can be reduced by using soft fins for two bends of different radii (R/D = 3.2 and 4.4) in lower Air velocity range. The maximum reduction rates of the MPD velocity and power consumption by using soft fins is about 8.2% and 8%, respectively. At the upstream of the bend, the particle velocity of the soft fins is higher than that of the non-fin. The effect of soft fins on the particle velocity and its fluctuating energy remains in the bend. The particle velocity and fluctuating energy of particle velocity of the soft fins are higher than that of the non-fin in the first vertical bend. At the downstream of the bend, the fluctuating energy of particle velocity of the soft fins is higher than that of non-fin in the large radius bendon the top part of the pipe.
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Self-excited pneumatic Conveying of granular particles in various horizontal curved 90° bends
Experimental Thermal and Fluid Science, 2015Co-Authors: Akira RinoshikaAbstract:Abstract The effect of using the soft fins on a horizontal pneumatic Conveying of granular particles in various curved 90° bends was studied in this paper, in order to reduce pressure drop and Conveying Air velocity. Experimental measurements were performed in terms of the pressure drop, Conveying Air velocity, power consumption and additional pressure drop. The distributions of particle velocity near and in the curved 90° bend were measured by high-speed PIV. The test pipeline consisted of a 4.5 m-long horizontal straight acrylic tube, a curved 90° acrylic bend and a 1.5 m-long horizontal straight acrylic tube, having an inside diameter of 80 mm. The polyethylene particles with diameter of 2.3 mm were used as Conveying materials. The superficial Air velocity was varied from 10 to 14 m/s, and the solid mass flow rate was fixed at 0.45 kg/s. Comparing with the dilute phase pneumatic Conveying, the pressure drop, the minimum pressure drop (MPD) velocity, power consumption and additional pressure drop can be reduced by using soft fins for various bends in lower Air velocity range. The reduction becomes more evident with increasing the radius ratio of bend. The maximum reduction rates of the MPD velocity and power consumption by using soft fins is about 8.2% and 11.7%, respectively. At the upstream of bend, the particle velocity of the soft fins is evidently higher than that of the dilute phase in the bottom part of pipe for all bends. The effect of soft fins on the particle velocity and its fluctuating energy still remains in the bend and the downstream of bend, and the fluctuating energy of particle velocity gradually decreases through the bend. At the downstream of bend, the fluctuating energy of particle velocity decreases with increasing the radius ratio of bend.
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Dilute pneumatic Conveying of a horizontal curved 90° bend with soft fins or dune model
Powder Technology, 2014Co-Authors: Akira RinoshikaAbstract:Abstract In order to reduce pressure drop and Conveying Air velocity, the paper studied the effect of the dune model and soft fins in horizontal pneumatic Conveying involving a 90° bend. Experimental measurements were performed in terms of the pressure drop, Conveying Air velocity and additional pressure drop. The distributions of particle velocity near and in the curved 90° bend were measured by high-speed PIV. The test pipeline consisted of a 4.5 m-long horizontal straight acrylic tube, a curved 90° acrylic bend (mean radius of curvature 250 mm) and a 1.5 m-long horizontal straight acrylic tube, having an inside diameter of 80 mm. The polyethylene particles with diameter of 2.3 mm were used as Conveying materials. The superficial Air velocity was varied from 10 to 14 m/s, and the solid mass flow rate was fixed at 0.45 kg/s. Comparing with the conventional pneumatic Conveying, the pressure drop, the minimum pressure drop (MPD) velocity and additional pressure drop can be reduced by using soft fins in lower Air velocity range. The reduction rates of the MPD velocity by using soft fins and dune model were about 4.1% and 8.3%, respectively. At the upstream of bend and in the bend, the particle velocity of using the dune model is evidently higher than that of the conventional pneumatic Conveying and using soft fins. However, the effect of soft fins and dune model on the particle velocity is maintained downstream of the bend.
Mira Sturm - One of the best experts on this subject based on the ideXlab platform.
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Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media
Chemical Engineering & Technology, 2010Co-Authors: Mira Sturm, Siegmar Wirtz, Viktor Scherer, Jens DeneckeAbstract:A DEM-CFD coupling for the simulation of gas-solid flows was successfully implemented and simulations were performed for the application to industrial-scale pneumatic Conveying. Therefore, all particle collisions and phase interactions were considered and porosity determination was optimized. The aim of this work is to show the applicability of the presented simulation model to the different regimes of pneumatic Conveying systems. As a first test case a dense vertical pneumatic Conveying system was chosen and an individual plug was investigated in detail. Variations of the Conveying Air velocity were also considered. As a second test case dilute Conveying in a horizontal-to-vertical pipe bend was simulated. The occurrence of roping and the reduction of particle velocity is of high interest for the design of specific pneumatic systems. It is shown that both regimes can be captured reasonably well and the results are rich in details.
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Coupled Discrete Element (DEM)–Continuous Fluid (CFD) Method for the Application of Pneumatic Conveyed Granular Media
Volume 4: Fluid-Structure Interaction, 2009Co-Authors: Mira Sturm, Siegmar Wirtz, Viktor Scherer, Jens DeneckeAbstract:A Coupled Discrete Element - Continuous Fluid Method is developed, which allows the numerical simulation of the behaviour of pneumatic conveyed granular media. While the fluid is simulated by computational fluid dynamics, the soft-sphere discrete element approach is used for the particle system. A “four-way coupling” is implemented to account for phase interaction on both sides and for the collisions among particles and with the pipe walls. The purpose of this work is to show the applicability of the presented simulation model to dense pneumatic Conveying systems. Unfortunately, only few complete experimental data are available in this field. In this work a pneumatic Conveying system for dense phase regime with a vertical pipe of 2 m height and a diameter of 50 mm is investigated. Periodic conditions are applied to both phases, the fluid and the particle system. The particles, which leave the pipe at one end, are inserted back at the other end of the pipe, so that a much larger simulation domain is represented. After an initial set up and some intermediate time steps a stable mode is reached and one single plug forms, which is then investigated in detail. The pressure distribution along the plug which coincides with the porosity distribution, the length of the plug and its velocity are important parameters which are examined and compared to experimental investigations. Variations of the Conveying Air velocity and their influence are also considered.Copyright © 2009 by ASME
J.g. Švec - One of the best experts on this subject based on the ideXlab platform.
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AEROELASTIC MODEL OF VOCAL-FOLD-SHAPED VIBRATING ELEMENT FOR STUDYING THE PHONATION THRESHOLD
Journal of Fluids and Structures, 2002Co-Authors: Jaromír Horáček, J.g. ŠvecAbstract:An original theoretical model for vibration onset of the vocal folds in the Air-flow coming from the human subglottal tract is designed, which allows studying the influence of the physical properties of the vocal folds (e.g., geometrical shape, mass, viscosity) on their vibration characteristics (such as the natural frequencies, mode shapes of vibration and the thresholds of instability). The mathematical model of the vocal fold is designed as a simplified dynamic system of two degrees of freedom (rotation and translation) vibrating on an elastic foundation in the wall of a channel Conveying Air. An approximate unsteady one-dimensional flow theory for the inviscid incompressible fluid is presented for the phonatory Air-flow. A generally defined shape of the vocal-fold surface is considered for expressing the unsteady aerodynamic forces in the glottis. The parameters of the mechanical part of the model, i.e., the mass, stiffness and damping matrices, are related to the geometry and material density of the vocal folds as well as to the fundamental natural frequency and damping known from experiments. The coupled numerical solution yields the vibration characteristics (natural frequencies, damping and mode shapes of vibration), including the instability thresholds of the aeroelastic system. The vibration characteristics obtained from the coupled numerical solution of the system appear to be in reasonable qualitative agreement with the physiological data and clinical observations. The model is particularly suitable for studying the phonation threshold, i.e., the onset of vibration of the vocal folds.