The Prediction of Wear in Fluidized Beds

1995 ◽  
Vol 117 (2) ◽  
pp. 142-149 ◽  
Author(s):  
W. A. Rogers
Keyword(s):  
Fluidized Bed ◽  
Single Particle ◽  
Fluidized Beds ◽  
Tube Bundle ◽  
Optimization Procedure ◽  
Quantitative Agreement ◽  
Particle Collisions ◽  
Wear Model ◽  
Wear Rates ◽  
Fluidized Particles

A procedure is formulated to model impact and abrasion wear of surfaces exposed to a fluidized bed. A methodology adapting a single-particle wear model and the kinetic theory of gases to granular flows is used to develop a model accounting for impact wear from all possible particle collisions. Abrasive wear is modeled using a single-particle abrasion model adapted to describe the effects of many abrading particles. Parameters describing granular flow are necessary for evaluation of the resulting wear expressions. They are determined by numerical solution of the conservation equations describing fluidized-bed hydrodynamics. Additional parameters appear in the wear expressions which describe the contact between individual fluidized particles and the wearing surface. These are determined by an optimization procedure which minimizes error between predicted and measured wear rates. The modeling procedure was used to analyze several bubbling and turbulent fluidized bed experiments with single-tube and tube bundle configurations. Quantitative agreement between the measured and predicted wear rates was found, with some exceptions for local wear predictions. This work demonstrates a methodology for wear predication in fluidized beds.

Expulsion of particles from a buoyant blob in a fluidized bed

1994 ◽  
Vol 278 ◽  
pp. 63-81 ◽  
Author(s):  
G. K. Batchelor ◽  
J. M. Nitsche
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Particle Concentration ◽  
Small Concentration ◽  
Numerical Calculations ◽  
Significant Feature ◽  
Average Particle ◽  
Remarkable Property ◽  
Gas Fluidized Beds ◽  
Secondary Instabilities

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.

Development of a Simulation Model to Investigate Tool Wear in Ti-6Al-4V Alloy Machining

2011 ◽  
Vol 223 ◽  
pp. 535-544 ◽  
Author(s):  
Volker Schulze ◽  
Frederik Zanger
Keyword(s):  
Tool Wear ◽  
High Strength ◽  
State Variables ◽  
Wear Model ◽  
Fem Model ◽  
Load Variations ◽  
Wear Rates ◽  
Simulation Results ◽  
Mechanical Machining ◽  
Very High

Titanium alloys like Ti‑6Al‑4V have a low density, a very high strength and are highly resistant to corrosion. However, the positive qualities in combination with the low heat conductivity have disadvantageous effects on mechanical machining and on cutting in particular. Ti‑6Al‑4V forms segmented chips for the whole range of cutting velocities which influences tool wear. Thus, optimization of the manufacturing process is difficult. To obtain this goal the chip segmentation process and the tool wear are studied numerically in this article. Therefore, a FEM model was developed which calculates the wear rates depending on state variables from the cutting simulation, using an empirical tool wear model. The segmentation leads to mechanical and thermal load variations, which are taken into consideration during the tool wear simulations. In order to evaluate the simulation results, they are compared with experimentally obtained results for different process parameters.

scholarly journals Influence of Induction Hardening on Wear Resistance in Case of Rolling Contact

2016 ◽  
Vol 66 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Michal Šofer ◽  
Rostislav Fajkoš ◽  
Radim Halama
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Induction Hardening ◽  
Rolling Contact ◽  
Isotropic Hardening ◽  
Wear Model ◽  
Wear Rates ◽  
C Programming Language ◽  
Hardening Rule ◽  
C Programming

AbstractThe main aim of the presented paper is to show how heat treatment, in our case the induction hardening, will affect the wear rates as well as the ratcheting evolution process beneath the contact surface in the field of line rolling contact. Used wear model is based on shear band cracking mechanism [1] and non-linear kinematic and isotropic hardening rule of Chaboche and Lemaitre. The entire numerical simulations have been realized in the C# programming language. Results from numerical simulations are subsequently compared with experimental data.

scholarly journals Study on Fluidization Characteristics of Magnetically Fluidized Beds for Microfine Particles

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 61
Author(s):  
Yakun Tian ◽  
Shulei Song ◽  
Xuan Xu ◽  
Xinyu Wei ◽  
Shanwen Yan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Fluidized Bed ◽  
Magnetic Field Strength ◽  
Fluidized Beds ◽  
Expansion Rate ◽  
Gas Velocity ◽  
Bed Height ◽  
Bed Expansion ◽  
The Magnetic Field

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with ‘adding magnetic field first’ shows a more stable fluidization state than ‘adding magnetic field later’. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal.

Scale Effects on Fluidized Bed Hydrodynamics

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Rachid Mabrouk ◽  
Ramin Radmanesh ◽  
Jamal Chaouki ◽  
Christophe Guy
Keyword(s):  
Fluidized Bed ◽  
Particle Tracking ◽  
Fluidized Beds ◽  
Fiber Optic ◽  
Scale Effects ◽  
Scale Up ◽  
Radial Profile ◽  
Radioactive Particle Tracking ◽  
Industrial History ◽  
Radioactive Particle

Industrial history is full of events related to scale-up challenges. Failure at the scale-up stage is no longer surprising. Engineers and scientists have been trying to gather all the key parameters for decades, but, unfortunately, there are still no exact and well-established rules ensuring an accurate transition from one scale to another. Even the minimum lab-scale fluidized bed is still undefined.In this work, the effect of bed diameter on gas-solid behavior is investigated in three fluidized beds, 152mm, 78mm, and 50mm in diameter, in which the conventional scale-up rules are respected. The experiments were carried out using sand and alumina particles.The results were obtained and confirmed using fiber optic techniques and radioactive particle tracking, respectively. The results show that radial solid hold-up behavior on a small bed diameter scale is completely different from that on the intermediate bed diameter scale. The radial profile of solid hold-up on a small and very small bed diameter indicates an increase from a low value near the wall to a high value at the center at different heights from the distributor. By contrast, the opposite profile is observed on the intermediate bed diameter, similar to what is usually reported in the literature.

Thermal Pyrolysis of Polyethylene in Fluidized Beds: Review of the Influence of Process Parameters on Product Distribution

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
K. Suresh Kumar Reddy ◽  
Pravin Kannan ◽  
Ahmed Al Shoaibi ◽  
C. Srinivasakannan
Keyword(s):  
Fluidized Bed ◽  
Process Parameters ◽  
Fluidized Beds ◽  
Pyrolysis Temperature ◽  
Liquid Product ◽  
Product Distribution ◽  
Major Influence ◽  
Process Conditions ◽  
Influence Of Process Parameters ◽  
Thermal Pyrolysis

The present work is an attempt to compile and analyze the most recent literature pertaining to thermal pyrolysis of plastic waste using fluidized bed reactors. The review is short owing to the small number of work reported in the open literature in particular to the fluidized beds. Although works on pyrolysis are reported in fixed beds, autoclaves, and fluidized beds, vast majority of them address to the utilization of fluidized bed due to their advantages and large scale adaptability. The pyrolysis temperature and the residence time are reported to have major influence on the product distribution, with the increase in pyrolysis temperature favoring gas production, with significant reduction in the wax and oil. The pyrolysis gas generally contains H2, CO, CO2, CH4, C2H4, C2H6 while liquid product comprises benzene, toluene, xylene, styrene, light oil, heavy oil, and gasoline with the variations depending on process conditions. The effects of other process parameters, namely fuel feed rate, fuel composition, and fluidizing medium have been reviewed and presented.

Calculation of Transient Flow in Circulating Fluidized Beds With Straight and Double Abrupt Outlet Configuration: Relation With the Inelasticity of the Particle-Particle Collisions

2001 ◽  
Author(s):  
Juray De Wilde ◽  
Jan Vierendeels ◽  
Geraldine J. Heynderickx ◽  
Erik Dick ◽  
Guy B. Marin
Keyword(s):  
Kinetic Theory ◽  
Gravity Waves ◽  
Granular Flow ◽  
Fluidized Beds ◽  
Transient Flow ◽  
Industrial Scale ◽  
Circulating Fluidized Beds ◽  
Restitution Coefficient ◽  
Particle Collisions ◽  
The Stability

Abstract Gas-solid flow in industrial scale Circulating Fluidized Beds (CFB’s) is calculated in 3D using the Eulerian-Eulerian approach and the Kinetic Theory of Granular Flow (KTGF). Two outlet configurations are used: a straight top outlet and a double abrupt T-outlet. The effect of the value of the restitution coefficient for particle-particle collisions on the stability of the flow is investigated. Oscillations appearing in CFB’s, are shown to be gravity waves.

Pollutants formation during single particle combustion of biomass under fluidized bed conditions: An experimental study

Fuel ◽  
2020 ◽  
Vol 278 ◽  
pp. 117958 ◽  
Author(s):  
Iliyana Naydenova ◽  
Ognyan Sandov ◽  
Florian Wesenauer ◽  
Thomas Laminger ◽  
Franz Winter
Keyword(s):  
Experimental Study ◽  
Fluidized Bed ◽  
Single Particle ◽  
Particle Combustion

scholarly journals Heat transfer in fluidized and fixed beds of adsorption chillers

2019 ◽  
Vol 128 ◽  
pp. 01003 ◽  
Author(s):  
Jaroslaw Krzywanski ◽  
Karolina Grabowska ◽  
Marcin Sosnowski ◽  
Anna Zylka ◽  
Anna Kulakowska ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Fixed Bed ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Innovative Idea ◽  
Fixed Beds

An innovative idea, shown in the paper constitutes in the use of the fluidized bed of sorbent, instead of the conventional, fixed-bed, commonly used in the adsorption chillers. Bed–to–wall heat transfer coefficients for fixed and fluidized beds of adsorbent are determined. Sorbent particles diameters and velocities of fluidizing gas are discussed in the study. The calculations confirmed, that the bed–to–wall heat transfer coefficient in the fluidized bed of adsorbent is muchhigher than that in a conventional bed.

A dynamic contact wear model of ball bearings without or with distributed defects

2020 ◽  
Vol 234 (24) ◽  
pp. 4827-4843
Author(s):  
Xi Zhang ◽  
Hua Xu ◽  
Wei Chang ◽  
Hui Xi ◽  
Shiyuan Pei ◽  
...  
Keyword(s):  
Dynamic Contact ◽  
Ball Bearings ◽  
Wear Model ◽  
Wear Rates ◽  
Contact Wear ◽  
Body Dynamics ◽  
Ball Diameter ◽  
Dynamic Wear ◽  
Multi Body ◽  
The Ideal

A dynamic contact wear model of ball bearings consisting of wear degree and position distribution is proposed by integrating the developed contact wear model, multi-body dynamics and raceway waviness or ball diameter differences. Subsequently, the dynamic wear characteristics, not only for the ideal bearing under different axial and radial loads, but also for the bearing with above defects are analysed. The influences of load, typical waviness orders and amplitude on the wear of each ball against both raceways are evaluated and qualitatively validated. Finally, the dynamic characteristics of ball bearings with one ball larger are discussed, and then vibration frequency and wear rates distinction are verified by the experiment with working-surface roughness measurement as a way for wear rate assessment.

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