scholarly journals Dynamically structured bubbling in vibrated gas-fluidized granular materials

2021 ◽  
Vol 118 (35) ◽  
pp. e2108647118
Author(s):  
Qiang Guo ◽  
Yuxuan Zhang ◽  
Azin Padash ◽  
Kenan Xi ◽  
Thomas M. Kovar ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Granular Materials ◽  
Fluidized Beds ◽  
Gas Flow ◽  
Scale Up ◽  
Clean Energy ◽  
System Size ◽  
Optimal Operation ◽  
Constitutive Relationship ◽  
Energy Processes

The dynamics of granular materials are critical to many natural and industrial processes; granular motion is often strikingly similar to flow in conventional liquids. Food, pharmaceutical, and clean energy processes utilize bubbling fluidized beds, systems in which gas is flowed upward through granular particles, suspending the particles in a liquid-like state through which gas voids or bubbles rise. Here, we demonstrate that vibrating these systems at a resonant frequency can transform the normally chaotic motion of these bubbles into a dynamically structured configuration, creating reproducible, controlled motion of particles and gas. The resonant frequency is independent of particle properties and system size, and a simple harmonic oscillator model captures this frequency. Discrete particle simulations show that bubble structuring forms because of rapid, local transitions between solid-like and fluid-like behavior in the grains induced by vibration. Existing continuum models for gas–solid flows struggle to capture these fluid–solid transitions and thus cannot predict the bubble structuring. We propose a constitutive relationship for solids stress that predicts fluid–solid transitions and hence captures the experimental structured bubbling patterns. Similar structuring has been observed by oscillating gas flow in bubbling fluidized beds. We show that vibrating bubbling fluidized beds can produce a more ordered structure, particularly as system size is increased. The scalable structure and continuum model proposed here provide the potential to address major issues with scale-up and optimal operation, which currently limit the use of bubbling fluidized beds in existing and emerging technologies.

Gas and solids motion around deformed and interacting bubbles in fluidized beds

1972 ◽  
Vol 51 (1) ◽  
pp. 187-205 ◽  
Author(s):  
R. Clift ◽  
J. R. Grace ◽  
L. Cheung ◽  
T. H. Do
Keyword(s):  
Particle Motion ◽  
Fluidized Beds ◽  
Gas Flow ◽  
Theoretical Models ◽  
Flow Patterns

Previous analyses of gas and particle motion around bubbles in fluidized beds have concentrated on idealized isolated bubbles. In this paper three non-idealities are considered using the theoretical models of Davidson and Murray. Gas flow patterns are derived for indented and elongated bubbles and for pairs of interacting bubbles. Cloud boundaries are predicted for these situations and some effects on gas-solid contacting are discussed.

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.

Scale-up effects of the flow structure in bubbling and turbulent fluidized beds

2021 ◽  
Vol 379 ◽  
pp. 223-230
Author(s):  
Xiaoyang Wei ◽  
Jiangshan Liu ◽  
Jesse Zhu
Keyword(s):  
Flow Structure ◽  
Fluidized Beds ◽  
Scale Up

Phenomenological Modeling of Combustion in Pre-Chamber and the Pilot Flame for Natural Gas Engines

2019 ◽  
Author(s):  
Long Liu ◽  
Xia Wen ◽  
Qian Xiong ◽  
Xiuzhen Ma
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Alternative Fuels ◽  
Gas Flow ◽  
Combustion Process ◽  
Clean Energy ◽  
Combustion Model ◽  
Flame Surface ◽  
Flow Process ◽  
Natural Gas Engines

Abstract With energy shortages and increasing environmental problems, natural gas, as a clean energy, has the advantages of cheap price and large reserves and has become one of the main alternative fuels for marine diesel engines. For large bore natural gas engines, pre-chamber spark plug ignition can be used to increase engine efficiency. The engine mainly relies on the flame ejected from the pre-chamber to ignite the mixture of natural gas and air in the main combustion chamber. The ignition flame in the main combustion chamber is the main factor affecting the combustion process. Although the pre-chamber natural gas engines have been extensively studied, the characteristics of combustion in the pre-chamber and the development of ignition flame in the main combustion chamber have not been fully understood. In this study, a two-zone phenomenological combustion model of pre-chamber spark-ignition natural gas engines is established based on the exchange of mass and energy of the gas flow process in the pre-chamber and the main combustion chamber. The basic characteristics of the developed model are: a spherical flame surface is used to describe the combustion state in the pre-chamber, and according to the turbulent jet theory, the influence of turbulence on the state of the pilot flame is considered based on the Reynolds number. According to the phenomenological model, the time when the flame starts to be injected from the pre-chamber to the main combustion chamber, and the parameters such as the length of the pilot flame are analyzed. The model was verified by experimental data, and the results showed that the calculated values were in good agreement with the experimental values. It provides an effective tool for mastering the law of flame development and supporting the optimization of combustion efficiency.

Optimal Operation of Multireservoir Systems by Enhanced Water Cycle Algorithm

2019 ◽  
Vol 7 (1) ◽  
pp. 27-43
Author(s):  
Yanjun Kong ◽  
Yadong Mei ◽  
Weinan Li ◽  
Ben Yue ◽  
Xianxun Wang
Keyword(s):  
Water Cycle ◽  
Water System ◽  
System Size ◽  
Optimal Operation ◽  
Test Functions ◽  
Water Cycle Algorithm ◽  
Adaptive Parameter ◽  
Fitness Value ◽  
Better Than

In this article, an enhanced water cycle algorithm (EWCA) is proposed and applied to optimize the operation of multireservoir systems. Three improvements have been made to the water cycle algorithm (WCA). They refer to high-quality initial solutions obtained by the chaos-based method, balancing of exploration of streams using a dynamic adaptive parameter, and dynamic variation of sub-water system size using the fitness value of rivers. For the purpose of verifying the improvements, three typical benchmark functions were selected as test functions. It has shown that EWCA performs better than WCA and water cycle algorithm with evaporation rate (ER-WCA). And then these three algorithms were also applied to optimize the operation of a multireservoir system with complex constrains as the case study. By comparing the results, it is found that the EWCA has higher ability to find a feasible solution in a narrow searching space. The effectiveness of the improvements is confirmed.

scholarly journals Optimal Operation for Integrated Electricity–Heat System with Improved Heat Pump and Storage Model to Enhance Local Energy Utilization

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6729
Author(s):  
Yang Chen ◽  
Yao Zhang ◽  
Jianxue Wang ◽  
Zelong Lu
Keyword(s):  
Variable Mass ◽  
Clean Energy ◽  
Heat Pumps ◽  
Optimal Operation ◽  
Energy Utilization ◽  
Water Tank ◽  
Heat Network ◽  
Heat System ◽  
Guarantee System ◽  
Electricity Network

As the need for clean energy increases, massive distributed energy resources are deployed, strengthening the interdependence of multi-carrier energy systems. This has raised concerns on the electricity-heat system’s co-operation for lower operation costs, higher energy efficiency, and higher flexibility. This paper discusses the co-operation of integrated electricity–heat system. In the proposed model, network constraints in both systems are considered to guarantee system operations’ security: the branch flow model is utilized to describe the electricity network, while a convexified model considering variable mass flow and temperature dynamics is adopted to describe the heat network. Additionally, novel models for heat pumps and the stratified water tank are proposed to represent the physical system more accurately. Finally, to preserve the information privacy of separate systems, a distributed algorithm is proposed based on the alternating direction method of multipliers (ADMM). Numerical studies show that the co-operation could provide a more economical and reliable solution than the decoupled operation of the heat network and electricity network. Moreover, the ADMM-based algorithm could derive solutions very close to the optimum provided by centralized optimization.

scholarly journals Modelling size segregation of granular materials: the roles of segregation, advection and diffusion

2014 ◽  
Vol 741 ◽  
pp. 252-279 ◽  
Author(s):  
Yi Fan ◽  
Conor P. Schlick ◽  
Paul B. Umbanhowar ◽  
Julio M. Ottino ◽  
Richard M. Lueptow
Keyword(s):  
Granular Materials ◽  
Dimensionless Parameter ◽  
System Size ◽  
Quantitative Agreement ◽  
Particle Sizes ◽  
Control Parameters ◽  
Size Segregation ◽  
Particle Segregation ◽  
Kinematic Measures ◽  
And Diffusion

AbstractPredicting segregation of granular materials composed of different-sized particles is a challenging problem. In this paper, we develop and implement a theoretical model that captures the interplay between advection, segregation and diffusion in size bidisperse granular materials. The fluxes associated with these three driving factors depend on the underlying kinematics, whose characteristics play key roles in determining particle segregation configurations. Unlike previous models for segregation, our model uses parameters based on kinematic measures from discrete element method simulations instead of arbitrarily adjustable fitting parameters, and it achieves excellent quantitative agreement with both experimental and simulation results when applied to quasi-two-dimensional bounded heaps. The model yields two dimensionless control parameters, both of which are only functions of control parameters (feed rate, particle sizes, and system size) and kinematic parameters (diffusion coefficient, flowing layer depth, and percolation velocity). The Péclet number, $\mathit{Pe}$, captures the interplay of advection and diffusion, and the second dimensionless parameter, $\Lambda $, describes the interplay between segregation and advection. A parametric study of $\Lambda $ and $\mathit{Pe}$ demonstrates how the particle segregation configuration depends on the interplay of advection, segregation and diffusion. The model can be readily adapted to other flow geometries.

Scale-up of bottom-bed dynamics and axial solids-distribution in circulating fluidized beds of Geldart-B particles

1999 ◽  
Vol 54 (13-14) ◽  
pp. 2103-2112 ◽  
Author(s):  
Jaap C. Schouten ◽  
Robert C. Zijerveld ◽  
Cor M.van den Bleek
Keyword(s):  
Fluidized Beds ◽  
Scale Up ◽  
Circulating Fluidized Beds
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