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Fu-sheng Wang - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of supersonic flow in new type externally pressurized spherical Air bearings
Journal of Central South University of Technology (English Edition), 2012Co-Authors: Fu-sheng WangAbstract:In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical Air bearings under large bearing clearance and high Air Supply Pressure, which could decrease their load carrying capacity and stability, a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible Air flow governing equations. The realizable k-epsilon model was used as a turbulent closure. The supersonic flow field near Air inlets was analyzed. The flow structures illustrate that the interaction exists between shock waves and boundary layer, and the flow separation is formed at the lower corner and the lower wall around the point of a maximum velocity. The numerical results show that the conversion from supersonic flow to subsonic flow in spherical Air bearing occurs through a shock region (pseudo-shock), and the viscous boundary layer results in the flow separation and reverse flow near the shock. The calculation results basically agree with the corresponding experimental data.
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Static characteristics of new type externally pressurized spherical Air bearings
Journal of Central South University of Technology, 2011Co-Authors: Fu-sheng Wang, Gang BaoAbstract:In order to provide some theoretical guideline for the structure design of the new type externally pressurized spherical Air bearings, the static characteristics and the factors affecting the static characteristics of the Air bearings were analyzed. A finite volume method was adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations, and a modified SIMPLE algorithm for compressible fluid was applied to solve the discretized governing equations. The Pressure field and velocity field of the Air bearings were obtained, and the factors and rules affecting the static characteristics were analyzed. The results show that the Pressure of near Air intakes can reach above 80% of Air Supply Pressure, and there is a Pressure steep fall around the Air intakes. When the film thickness is greater than 20 μm, the bearing capacity rapidly decreases as film thickness increases. As the Air Supply Pressure increases from 0.2 to 0.6 MPa, the maximum static stiffness increases by more than three times. The calculation method proposed well fits the general principle, which can be extended to the characteristic analysis of other Air bearings.
David Mills - One of the best experts on this subject based on the ideXlab platform.
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Case Study 2: A Coarse Material
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:In this case study a material is selected that has no low-velocity dense phase conveying capability and so all the scaling is in terms of relatively high-velocity dilute phase suspension flow conveying. The operating Pressure has been limited to 1 bar gauge and so it is applicable to one of the most common pneumatic conveying systems in industry, being the low-Pressure rotary valve as a feeding device and a Roots-type blower for the Air Supply. Other combinations, of course, are equally applicable, as well as vacuum or higher Pressure operation. Once again the scaling is from data obtained for the given material in a test facility and so involves scaling in terms of differences in pipeline bore, conveying distance, pipeline orientation, and number of bends. The specification is in terms of the Air Supply Pressure, pipeline bore, and Airflow rate required in order to achieve the given duty. The power required for the conveying system and the solids loading ratio at which the material will be conveyed are evaluated, as well as the specific cost of operating the system.
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Chapter 17 – Design Procedures
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:Logic diagrams are presented for the design of pneumatic conveying systems based on the use of both mathematical models and conveying data. Logic diagrams are also presented for checking the performance of an existing system, or for a potential change of duty, again based on the use of both models and data. There is rarely a single solution to the specification of a pneumatic conveying system for a given duty. As a consequence the logic diagrams include numerous checks so that optimum solutions are achieved in terms of either obtaining the minimum power requirement for a given duty, or achieving a maximum material flow rate for the given conveying parameters. To help in this process several series of design curves are included to illustrate the potential influence of the major system variables such as conveying distance, pipeline bore, and Air Supply Pressure, as well as the problematical issue of material type.
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First approximation design methods
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:For feasibility studies an approximate solution to a problem will often suffice in the first instance so that a reasonable order of magnitude of the variables involved can be obtained, particularly if a comparison is to be made with alternative mechanical means of conveying a material. This will give sufficient details of the pneumatic conveying system in terms of pipeline bores, Air Supply Pressures, and Airflow rates for a given duty, in terms of material flow rate and conveying distance required, so that capital cost estimates for plant items such as pipelines, compressors, feeding devices, and filtration plant can be made. Operating costs for the plant are also likely to be required and so with data on Airflow rate and Air Supply Pressure required, this is a straightforward procedure. As was shown in previous chapters, a given duty can generally be achieved with a range of Air Supply Pressure and pipeline bore combinations, and so this method of analysis will enable the best combination of conveying parameters to be achieved for the given duty.
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Case Study 1: A Fine Material
Pneumatic Conveying Design Guide, 2016Co-Authors: David MillsAbstract:In this chapter a case study is considered for a pneumatic conveying system required to convey cement. The design is based on the use of data for the cement obtained specifically from a pneumatic conveying test facility. The necessary scaling of the data obtained from the test facility, to that of the plant pipeline required, is outlined step by step with detailed explanations and calculations. A particular complexity with materials such as cement, that have good Air-retention properties, is that the value of the conveying-line inlet Air velocity, which is a critical design parameter, is a variable in the analysis to be undertaken. It is, therefore, essentially an iteration process and so guidance is provided on how to achieve convergence of the equations. Because pipelines are available in standard incremental sizes, precise answers are not achieved, but Air Supply Pressure can generally be varied quite easily and so compromise will generally provide a satisfactory solution. Both Airflow rate and power requirements are evaluated as part of the design process.
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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.
Pengfei Wang - One of the best experts on this subject based on the ideXlab platform.
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influence of Air Supply Pressure on atomization characteristics and dust suppression efficiency of internal mixing Air assisted atomizing nozzle
Powder Technology, 2019Co-Authors: Pengfei Wang, Kui Zhang, Ronghua LiuAbstract:Abstract In this study, the effect of Air Supply Pressure on atomization characteristics and dust-suppression efficiency of internal-mixing Air-assisted atomizing nozzle was investigated. Firstly, the FLUENT software was employed to simulate the flow field inside the nozzle and near the outlet of the nozzle under different Air Supply Pressures. The numerical simulation results showed that as the Air Supply Pressure increased, the Pressure and Air flow velocity inside the mixing chamber of the nozzle increased dramatically, while the water flow velocity at the water injection hole decreased. At the same time, with the increase of Air Supply Pressure, the fragmentation scale of the liquid jet was continuously shortened, thus the primary atomization of the liquid was more sufficient. Secondly, the custom-developed dust suppression experimental system via spraying was used to investigate the atomization characteristics of the nozzle. According to the experimental results, when the Air Supply Pressure increased, both the droplet size and the droplet volume fraction decreased, the Air flow rate increased exponentially, and the water flow rate decrease linearly. In addition, as the Air Supply Pressure increased, the atomization angle, the droplet velocity and the droplet number density first increased and then decreased. Finally, the dust-reduction experiment via spraying was performed under different Air Supply Pressures. The results showed that the dust-suppression efficiency of total dust and respirable dust had a trend of first increasing and then decreasing with the increase of the Air Supply Pressure. The classification efficiency of dust suppression via spraying first increased and then decreased with the increase in the dust particle diameter. Furthermore, as the droplet size decreased, the peak particle diameter decreased accordingly.
Ronghua Liu - One of the best experts on this subject based on the ideXlab platform.
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influence of Air Supply Pressure on atomization characteristics and dust suppression efficiency of internal mixing Air assisted atomizing nozzle
Powder Technology, 2019Co-Authors: Pengfei Wang, Kui Zhang, Ronghua LiuAbstract:Abstract In this study, the effect of Air Supply Pressure on atomization characteristics and dust-suppression efficiency of internal-mixing Air-assisted atomizing nozzle was investigated. Firstly, the FLUENT software was employed to simulate the flow field inside the nozzle and near the outlet of the nozzle under different Air Supply Pressures. The numerical simulation results showed that as the Air Supply Pressure increased, the Pressure and Air flow velocity inside the mixing chamber of the nozzle increased dramatically, while the water flow velocity at the water injection hole decreased. At the same time, with the increase of Air Supply Pressure, the fragmentation scale of the liquid jet was continuously shortened, thus the primary atomization of the liquid was more sufficient. Secondly, the custom-developed dust suppression experimental system via spraying was used to investigate the atomization characteristics of the nozzle. According to the experimental results, when the Air Supply Pressure increased, both the droplet size and the droplet volume fraction decreased, the Air flow rate increased exponentially, and the water flow rate decrease linearly. In addition, as the Air Supply Pressure increased, the atomization angle, the droplet velocity and the droplet number density first increased and then decreased. Finally, the dust-reduction experiment via spraying was performed under different Air Supply Pressures. The results showed that the dust-suppression efficiency of total dust and respirable dust had a trend of first increasing and then decreasing with the increase of the Air Supply Pressure. The classification efficiency of dust suppression via spraying first increased and then decreased with the increase in the dust particle diameter. Furthermore, as the droplet size decreased, the peak particle diameter decreased accordingly.
Gang Bao - One of the best experts on this subject based on the ideXlab platform.
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Static characteristics of new type externally pressurized spherical Air bearings
Journal of Central South University of Technology, 2011Co-Authors: Fu-sheng Wang, Gang BaoAbstract:In order to provide some theoretical guideline for the structure design of the new type externally pressurized spherical Air bearings, the static characteristics and the factors affecting the static characteristics of the Air bearings were analyzed. A finite volume method was adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations, and a modified SIMPLE algorithm for compressible fluid was applied to solve the discretized governing equations. The Pressure field and velocity field of the Air bearings were obtained, and the factors and rules affecting the static characteristics were analyzed. The results show that the Pressure of near Air intakes can reach above 80% of Air Supply Pressure, and there is a Pressure steep fall around the Air intakes. When the film thickness is greater than 20 μm, the bearing capacity rapidly decreases as film thickness increases. As the Air Supply Pressure increases from 0.2 to 0.6 MPa, the maximum static stiffness increases by more than three times. The calculation method proposed well fits the general principle, which can be extended to the characteristic analysis of other Air bearings.
