Visualization of the Effect of a Shroud on Entrainment of Fluidized Solids into a Gas Jet

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Craig Hulet ◽  
Jennifer McMillan ◽  
Cedric Briens ◽  
Franco Berruti ◽  
Edward W Chan
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Rectangular Cross Section ◽  
Surrounding Medium ◽  
Flow Patterns ◽  
Transparent Plate ◽  
Significant Difference ◽  
Fundamental Understanding ◽  
Expansion Angle ◽  
Inner Diameter

Submerged gas jets issuing into fluidized beds are used in many different industries and it is important to have a fundamental understanding of how the gas and surrounding medium interact – to understand the flow patterns and how the solids behave in the vicinity of the nozzle jet. Following the discussions of Bohnet and Teifke (1985) and Idelchek (1994) it was decided to qualitatively investigate the effects of altering the region surrounding the contact between the jet and the fluidized bed. Alteration of the flow pattern was accomplished using a semi-cylindrical shroud (0.035 m i.d. and 0.043 m long) that formed a physical barrier around the nozzle tip. The nozzle inner diameter was 0.0016 m i.d. and the motive gas flow rate was supersonic. Videos were recorded of the solids and gas flow patterns via a special transparent plate on the wall of the fluidized bed for a half-jet with and without a shroud at a superficial fluidization gas velocity of 0.11 m/s. Presented below are the original videos and observations derived from the two simple experiments in a fluidized bed with a rectangular cross-section (0.10 by 1.20 m and 2.0 m high). There was a significant difference in the flow patterns of the solids in the vicinity of the nozzle tip when the shroud was present. Furthermore, the jet expansion angle and penetration were observed to decrease by approximately 50% and 43%, respectively.

The Effect of Geometry on the Aerodynamics of a Prototype Gas Turbine Combustor

2010 ◽  
Author(s):  
Bassam Mohammad ◽  
San-Mou Jeng
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Flow Structure ◽  
Strong Influence ◽  
Swirling Flow ◽  
Rectangular Cross Section ◽  
Low Velocity ◽  
Significant Difference ◽  
Expansion Angle ◽  
The Asymmetry

The method of admission of the swirling flow to the combustion chamber has a strong influence on the flow field structure in Gas Turbine Combustors (GTC). Two different exit configurations are studied. The first configuration is that of a swirl cup that ends only with a splash plate such that there is a sudden unguided expansion as the flow emanates from the swirl cup. The second is a swirl cup that ends with a splash plate and an asymmetric combustion dome. Laser Doppler Velocimetry (LDV) measurements are conducted in the horizontal plane (X-Y), for both configurations, 5mm from the flare exit. Also, LDV measurements are conducted in two vertical planes passing by the combustor centerline (X-Z and Y-Z). The results reveal a significant difference in the flow structure for both configurations. The combustion dome appears to reduce the turbulence activities close to the exit of the swirl cup. In addition, the presence of the combustion dome eliminates the corner recirculation zone and the low velocity region close to the combustor walls. It is interesting to see that the asymmetry of the combustion dome (9° difference in the expansion angle on both sides) results in a significant asymmetry in the velocity magnitude as well as the turbulence activities. Moreover, the asymmetry in the combustion dome results in a tilting of the CRZ toward the surface with the higher expansion angle. The results highlight the importance of the proper and careful design of the GTC front section. The experiments are conducted in a dump combustor (rectangular cross section). To study the effect of the chamber geometry on the flow field, the base configuration is installed in an annular combustor sector and LDV measurements are conducted in the axial radial plane (X-Z). The flow field as well as the shape of the CRZ are significantly different in both cases. The CRZ height reduced by 40% with the swirl cup installed to the SAC sector. The results emphasize the strong influence of the confinement on the flow structure.

scholarly journals Cyclic fatigue resistance of 2Shape, Twisted File and EndoSequence Xpress nickel-titanium rotary files at intracanal temperature

2018 ◽  
Vol 12 (4) ◽  
pp. 283-287 ◽  
Author(s):  
Gülşah Uslu ◽  
Taha Özyürek ◽  
Mustafa Gündoğar ◽  
Koray Yılmaz
Keyword(s):  
Fatigue Resistance ◽  
Statistical Significance ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Bonferroni Correction ◽  
Significant Difference ◽  
Inner Diameter ◽  
The Difference ◽  
Number Of Cycles ◽  
Analyze Data

Background. The aim of this study was to compare the cyclic fatigue resistance of 2Shape, Twisted File (TF) and EndoSequence Xpress (ESX) nickel-titanium rotary files at intracanal temperature (35°C). Methods. Twenty 2Shape TS1 (25/.04), 20 TF (25/.04) and 20 ESX (25/.04) files were tested for cyclic fatigue at intracanal temperature (35°C). All the instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 60° angle of curvature and a radius curvature of 5 mm until fracture occurred; the time to fracture was recorded in seconds using a digital chronometer and the number of cycles to fracture (NCF) for each file was calculated. Kruskal-Wallis test with Bonferroni correction was performed to statistically analyze data using SPSS 21.0. Statistical significance was set at P<0.05. Results. NCF values revealed that the 2Shape had significantly the highest cyclic fatigue resistance, followed by TF and ESX at intracanal temperature (P<0.05). The difference was significant between the TF and ESX groups (P<0.05). There was no significant difference among the 2Shape, TF and ESX files with respect to the lengths of the fractured file fragments (P>.05). Conclusion. Within the limitations of present study, it was concluded that the cyclic fatigue resistance of 2Shape files at the intracanal temperature is higher than that of TF and ESX files.

Gas flow in a pressurized fluidized-bed combustor

1988 ◽  
Vol 56 (3) ◽  
pp. 157-163 ◽  
Author(s):  
J. Thýn ◽  
Z. Kolar ◽  
W. Martens ◽  
A. Korving
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Fluidized Bed Combustor

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.

The Pyrocarbon Deposition Techniques of Mechanical Heart Valve Prostheses

2011 ◽  
Vol 464 ◽  
pp. 749-752 ◽  
Author(s):  
Jian Hui Zhang ◽  
Xin Chen
Keyword(s):  
Fluidized Bed ◽  
Heart Valve ◽  
Gas Flow ◽  
Mechanical Heart Valve ◽  
Carbon Matrix ◽  
Artificial Heart Valve ◽  
Bed Temperature ◽  
Wide Range ◽  
Isotropic Carbon ◽  
Deposition Conditions

The structure and property of pyrocarbon varies widely with different deposition conditions. The isotropic carbon which can only been deposited in the bed of fluidized particles is very important in biomedical fields, for instance, it is often used as the coating of artificial heart valve components. The deposition of isotropic pyrocarbon containing silicon is experimented in fluidized bed over a wide range of deposition conditions. The results show that bed temperature influences strongly average coating rate, coating density, silicon content and coating micro-hardness. Propane concentration has a much effect on coating density, carbon matrix density and isotropic characteristics. Total gas flow rate and inlet dimension of fluidized bed affect the formation of fluidized bed.

Solids Flow Pattern in the Bottom Zone of a Rectangular Cross-Section Circulating Fluidized Bed

2003 ◽  
Author(s):  
Hong-Shun Li ◽  
Yi-Jun Wang ◽  
Shi-Ping Jin
Keyword(s):  
Flow Pattern ◽  
Fluidized Bed ◽  
Cross Section ◽  
Quartz Sand ◽  
Circulating Fluidized Bed ◽  
Rectangular Cross Section ◽  
Temperature Response ◽  
Cold Model ◽  
Hot Particles ◽  
Bottom Zone

Solids flow pattern in the bottom zone of a rectangular cross-section CFB was investigated by using hot particles as the tracer. The experiments were carried out in a cold model circulating fluidized bed. The riser has an inner cross-section of 0.3 m by 0.5 m and a height of 5.8 m. The solids were returned into the riser at a height of 0.75 m above the air distributor within an angle of about 40 degree. Quartz sand was used as the bed material. The hot particles were also quartz sand but with a little smaller size. Specially designed miniature electrically heating devices were installed flush with the inner bed wall or inside the bed. At each run, about 10–15 cm3 hot particles were slowly pulled into the bed. The temperature response around the device was measured with four copper-constantan thermocouples. Based on the experimental results, a 3-D core-annulus model describing the solids flow pattern in the bottom zone of the CFB riser is proposed.

CFD-DEM Modeling of CO2 Capture using Alkali Metal-Based Sorbents in a Bubbling Fluidized Bed

2014 ◽  
Vol 12 (1) ◽  
pp. 441-449 ◽  
Author(s):  
Zhonglin Zhang ◽  
Daoyin Liu ◽  
Yaming Zhuang ◽  
Qingmin Meng ◽  
Xiaoping Chen
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Fluidized Bed Reactors ◽  
Solid Sorbents ◽  
Bubbling Fluidized Bed ◽  
Shrinking Core ◽  
Simulation And Experiment ◽  
Kinetics Simulation ◽  
Reaction Processes ◽  
Back Mixing

Abstract This paper describes a CFD-DEM modeling of CO2 capture using K2CO3 solid sorbents in a bubbling fluidized bed, which takes into heat transfer, hydrodynamics, and chemical reactions. Shrinking core model is applied in reaction kinetics. Simulation and experiment results of bed pressure drop and CO2 concentration in the reactor exit agree well. Instantaneous dynamics as well as time-averaged profiles indicate detailed characteristics of gas flow, particle motion, and chemical reaction processes. The simulation results show an obvious core-annular flow and strong back-mixing flow pattern. CO2 concentration decreases gradually along the bed height, while regards on the lateral distribution CO2 concentration near the wall is lower than that in the middle zone where gas passes through faster. The effect of bubbles on CO2 reaction is two-sided: it can promote mixing which strengthens reaction, while it can be a short pass of gas which is not beneficial to reaction. The simulation is helpful for further understanding and optimal design of fluidized bed reactors of CO2 capture.

scholarly journals NMR Analysis Method of Gas Flow Pattern in the Process of Shale Gas Depletion Development

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-7
Author(s):  
Rui Shen ◽  
Zhiming Hu ◽  
Xianggang Duan ◽  
Wei Sun ◽  
Wei Xiong ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Pore Pressure ◽  
Shale Gas ◽  
Gas Flow ◽  
Continuous Medium ◽  
Slip Flow ◽  
Flow Patterns ◽  
Transitional Flow ◽  
Analysis Method ◽  
Adsorbed Gas

Shale gas reservoirs have pores of various sizes, in which gas flows in different patterns. The coexistence of multiple gas flow patterns is common. In order to quantitatively characterize the flow pattern in the process of shale gas depletion development, a physical simulation experiment of shale gas depletion development was designed, and a high-pressure on-line NMR analysis method of gas flow pattern in this process was proposed. The signal amplitudes of methane in pores of various sizes at different pressure levels were calculated according to the conversion relationship between the NMR T 2 relaxation time and pore radius, and then, the flow patterns of methane in pores of various sizes under different pore pressure conditions were analyzed as per the flow pattern determination criteria. It is found that there are three flow patterns in the process of shale gas depletion development, i.e., continuous medium flow, slip flow, and transitional flow, which account for 73.5%, 25.8%, and 0.7% of total gas flow, respectively. When the pore pressure is high, the continuous medium flow is dominant. With the gas production in shale reservoir, the pore pressure decreases, the Knudsen number increases, and the pore size range of slip flow zone and transitional flow zone expands. When the reservoir pressure is higher than the critical desorption pressure, the adsorbed gas is not desorbed intensively, and the produced gas is mainly free gas. When the reservoir pressure is lower than the critical desorption pressure, the adsorbed gas is gradually desorbed, and the proportion of desorbed gas in the produced gas gradually increases.

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