scholarly journals Mechanism of primary fragmentation of coal in fluidized bed

2016 ◽  
Vol 20 (suppl. 1) ◽  
pp. 125-132 ◽  
Author(s):  
Milijana Paprika ◽  
Mirko Komatina ◽  
Milica Mladenovic ◽  
Goran Zivkovic ◽  
Dragoljub Dakic
Keyword(s):  
Tangential Stress ◽  
Radial Stress ◽  
Particle Surface ◽  
Surface Region ◽  
Temporal Analysis ◽  
Fragmentation Model ◽  
Fuel Particle ◽  
Gaseous Products ◽  
Particle Center ◽  
Primary Fragmentation

In order to lay a foundation of a credible primary fragmentation model, a theoretical analysis of the thermo-mechanical processes in a devolatilizing solid fuel particle was carried out. The devolatilization model comprises heat transfer, chemical processes of generation of gaseous products of combustion (volatiles), volatile transfer, and solid mechanic processes. A spatial and temporal analysis of the stresses within the particle showed that the radial stress is caused primarily by the pressure of generated volatiles. This stress monotonously decreases from the particle center towards the particle surface, without changing its sign. The tangential stress is caused primarily by the thermal shock. Close to the surface, it changes its sign. In the particle cross-section, the radial stress prevails close to the particle center, whilst the tangential stress is dominant in the surface region. At the points where these stresses exceed the particle tensile strength, cracks occur. Cracks extend tangentially close to the surface, and radially close to the center of the particle.

Predicting the ignition of crown fuels above a spreading surface fire. Part II: model evaluation

2006 ◽  
Vol 15 (1) ◽  
pp. 61 ◽  
Author(s):  
Miguel G. Cruz ◽  
Bret W. Butler ◽  
Martin E. Alexander
Keyword(s):  
Particle Surface ◽  
Lower Boundary ◽  
Ground Surface ◽  
Volume Ratio ◽  
Fuel Particle ◽  
Particle Surface Area ◽  
Surface Fire ◽  
Fuel Layer ◽  
Model Predictions ◽  
A Minor

A crown fuel ignition model (CFIM) describing the temperature rise and subsequent ignition of the lower portion of tree crowns above a spreading surface fire was evaluated through a sensitivity analysis, comparison against other models, and testing against experimental fire data. Results indicate that the primary factors influencing crown fuel ignition are those determining the depth of the surface fire burning zone and the vertical distance between the ground/surface fuel strata and the lower boundary of the crown fuel layer. Intrinsic crown fuel properties such as fuel particle surface area-to-volume ratio and foliar moisture content were found to have a minor influence on the process of crown fuel ignition. Comparison of model predictions against data collected in high-intensity experimental fires and predictions from other models gave encouraging results relative to the validity of the model system.

A carbon microtube array with a multihole cross profile: releasing the stress and boosting long-cycling and high-rate potassium ion storage

2019 ◽  
Vol 7 (45) ◽  
pp. 25845-25852 ◽  
Author(s):  
Bo Wang ◽  
Fei Yuan ◽  
Wei (Alex) Wang ◽  
Di Zhang ◽  
Huilan Sun ◽  
...  
Keyword(s):  
Tangential Stress ◽  
Porous Carbon ◽  
Radial Stress ◽  
Potassium Ion ◽  
Cycling Stability ◽  
High Rate ◽  
Ion Storage ◽  
Excellent Cycling Stability ◽  
Microtube Array

As an advanced anode for potassium-ion batteries (PIBs), the porous carbon microtube can reduce the radial stress and tangential stress during cycling, resulting in excellent cycling stability.

scholarly journals A New Unified Solution for Deep Tunnels in Water-Rich Areas considering Pore Water Pressure

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hao Fan ◽  
Lianguo Wang ◽  
Shuai Wang ◽  
Chongyang Jiang
Keyword(s):  
Principal Stress ◽  
Tangential Stress ◽  
Pore Water ◽  
Radial Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Surface Displacement ◽  
Intermediate Principal Stress ◽  
Maximum Tangential Stress ◽  
Coulomb Criterion

Pore water pressure has an important influence on the stresses and deformation of the surrounding rock of deep tunnels in water-rich areas. In this study, a mechanical model for deep tunnels subjected to a nonuniform stress field in water-rich areas is developed. Considering the pore water pressure, a new unified solution for the stresses, postpeak zone radii, and surface displacement is derived based on a strain-softening model and the Mogi-Coulomb criterion. Through a case study, the effects of pore water pressure, intermediate principal stress, and residual cohesion on the stress distribution, postpeak zone radii, and surface displacement are also discussed. Results show that the tangential stresses are always larger than the radial stress. The radial stress presents a gradually increasing trend, while the tangential stress presents a trend of first increasing and then decreasing, and the maximum tangential stress appears at the interface between the elastic and plastic zones. As the pore water pressure increases, the postpeak zone radii and surface displacement increase. Because of the neglect of the intermediate principal stress in the Mohr-Coulomb criterion, the postpeak zone radii, surface displacement, and maximum tangential stress solved by the Mohr-Coulomb criterion are all larger than those solved by the Mogi-Coulomb criterion. Tunnels surrounded by rock masses with a higher residual cohesion experience lower postpeak zone radii and surface displacement. Data presented in this study provide an important theoretical basis for supporting the tunnels in water-rich areas.

scholarly journals 2D Semimodel of Full-Section Anchorage in Thick Soft Rock Roadway

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xianzhou Lyu ◽  
Zenghui Zhao ◽  
Qing Ma ◽  
Xiaojie Wang ◽  
Xiaojie Gao
Keyword(s):  
Tangential Stress ◽  
Radial Stress ◽  
Coupling Effect ◽  
Superposition Principle ◽  
Soft Rock ◽  
Surrounding Rock ◽  
Stress Release ◽  
Full Face ◽  
Soft Rock Roadway ◽  
Rock Roadway

This paper focuses on the reinforcement effect of full-face anchorage in thick soft rock roadway. A 2D semimodel of full-face anchorage in roadway with thick surrounding soft rock was proposed firstly by transforming the confinement effect of the excavation face in the longitudinal direction as the virtual internal support force at the circumferential surface. Then, based on the theory of elasticity, the theoretical model of the coupling effect between surrounding rock and anchoring system was established, and the analytical solutions of stress and displacement were obtained employing superposition principle. Finally, the theoretical solution was verified by numerical simulation, and the distribution laws of stress release-anchor stock-surrounding rock coupling were analyzed in detail considering stress release. Results demonstrated that the stress field of the surrounding rock diverse widely with different stress release coefficients. With the increasing of stress release coefficient, the radial stress of the surrounding rock decreases, while the tangential stress increases. The supporting role of the bolt is mainly reflected in improving the radial stress of the anchorage zone. However, it has little effect on the tangential stress. What is more, the anchoring effect is more significant to soft rock stress than hard rock. In addition, the prestress of rock bolt has a certain matching relation with the bolt parameters, the surrounding rock parameters, and the initial stress. This study laid a theoretical foundation for further analysis of the interaction between surrounding rock and bolt supporting in plastic zone.

Effect of a Concentric Reinforcing Ring on Stiffness and Strength of a Circular Plate

1948 ◽  
Vol 15 (1) ◽  
pp. 25-29
Author(s):  
W. A. Nash
Keyword(s):  
Tangential Stress ◽  
Circular Plate ◽  
Radial Stress ◽  
Normal Pressure ◽  
Pressure Vessels ◽  
Maximum Tangential Stress ◽  
Vertical Deflection ◽  
Concentric Ring ◽  
Thin Walled

Abstract In this study of a fixed-edge circular plate subjected to uniform normal pressure (such as is commonly used on ends of thin-walled cylindrical pressure vessels), it is shown that the maximum vertical deflection, the maximum radial stress, and the maximum tangential stress may all be reduced by reinforcing the plate with a concentric ring.

Influence of Speed-up and Speed-down on Internal Stresses of Wound Rolls in Web Handling Process

2012 ◽  
Vol 452-453 ◽  
pp. 1262-1266
Author(s):  
Mongkolwongrojn Mongkol ◽  
Jeenkour Puttha
Keyword(s):  
Tangential Stress ◽  
Friction Force ◽  
Radial Stress ◽  
Research Work ◽  
Air Entrainment ◽  
Internal Stresses ◽  
Web Handling ◽  
Wound Rolls ◽  
Speed Up ◽  
Air Film

In web winding process, the effects of speed-up and speed-down on internal stresses of wound roll have been investigated. The air-entrainment can be obtained theoretically using the modified nonlinear Hakiel model. In this research work, air-entrainment model established by Hamrock and Dowson was applied to estimate the initial air film layers into a wound roll in the winding system with a nip-roller. Moreover, the characteristics of a wound roll were examined under varying tension and varying speed conditions. The numerical results showed the radial stress, tangential stress, and friction force distributions at central inside a wound roll under the condition for a wound roll without wrinkle and slippage phenomena.

A technique to prepare cross-sectional TEM specimens of semiconducting devices

1986 ◽  
Vol 44 ◽  
pp. 742-743
Author(s):  
A. K. Rai ◽  
P. P. Pronko
Keyword(s):  
Thin Films ◽  
Surface Region ◽  
Sample Surface ◽  
Specific Region ◽  
Cross Sectional ◽  
Thin Sections ◽  
The Past ◽  
Device Structures ◽  
Ion Implanted

Several techniques have been reported in the past to prepare cross(x)-sectional TEM specimen. These methods are applicable when the sample surface is uniform. Examples of samples having uniform surfaces are ion implanted samples, thin films deposited on substrates and epilayers grown on substrates. Once device structures are fabricated on the surfaces of appropriate materials these surfaces will no longer remain uniform. For samples with uniform surfaces it does not matter which part of the surface region remains in the thin sections of the x-sectional TEM specimen since it is similar everywhere. However, in order to study a specific region of a device employing x-sectional TEM, one has to make sure that the desired region is thinned. In the present work a simple way to obtain thin sections of desired device region is described.

Preparation of cross-sectional samples for near-surface TEM studies

1987 ◽  
Vol 45 ◽  
pp. 380-381
Author(s):  
R.C. Dickenson ◽  
K.R. Lawless
Keyword(s):  
Standard Sample ◽  
Surface Region ◽  
Specimen Preparation ◽  
Thick Sheet ◽  
Drill Bit ◽  
Sample Holder ◽  
Metal Interface ◽  
Cross Sectional ◽  
Near Surface ◽  
Cold Worked

In thermal oxidation studies, the structure of the oxide-metal interface and the near-surface region is of great importance. A technique has been developed for constructing cross-sectional samples of oxidized aluminum alloys, which reveal these regions. The specimen preparation procedure is as follows: An ultra-sonic drill is used to cut a 3mm diameter disc from a 1.0mm thick sheet of the material. The disc is mounted on a brass block with low-melting wax, and a 1.0mm hole is drilled in the disc using a #60 drill bit. The drill is positioned so that the edge of the hole is tangent to the center of the disc (Fig. 1) . The disc is removed from the mount and cleaned with acetone to remove any traces of wax. To remove the cold-worked layer from the surface of the hole, the disc is placed in a standard sample holder for a Tenupol electropolisher so that the hole is in the center of the area to be polished.

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