Numerical Study on Layout of Refractory Belt and Fouling Deposition in Tangentially Fired Boiler

2016 ◽  
Author(s):  
Qiongliang Zha ◽  
Kai Chen ◽  
Jianwen Zhang ◽  
Jiangtao Li ◽  
Chang’an Wang ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Numerical Investigation ◽  
Numerical Study ◽  
High Surface ◽  
Three Dimensional ◽  
Furnace Wall ◽  
Combustion Stability ◽  
Particle Capture ◽  
Dimensional Simulation ◽  
Ignition And Combustion

The refractory belt installed in primary combustion zone provides simplest and most effective solution to suppress ignition delay and enhance combustion stability for low volatile anthracite and lean coal. The fouling deposition generally formed on radiative refractory lined wall of the boiler due to a high surface temperature. The growth of deposition thickness is mainly dependent on the parcile impact on the surface of water wall. A particle capture submodel was used to determine whether a particle was captured to form deposition or not when it reached the furnace wall, and the particle capture criterion was based on the particle’s viscosity and the temperature of the furnace wall. A reduced fouling deposition model was implemented in a three dimensional simulation of a tangentially fired boiler. The numerical investigation was conducted to assess the performance of different layouts of refractory belt. Furnace temperature, surface temperature of refractory belt, and deposition distributions on the furnace wall should be taken into account when layouts of refractory belt are optimized. Based on this, three layouts of refractory belt were proposed for tangentially fired boilers. A numerical investigation was conducted to assess the performance of different layouts of refractory belt and the results showed that the temperature in furnace was increased, and the ignition and combustion processes were stabilized when refractory belts were installed. The reasonable arrangement of refractory belt could reduce the possibility of fouling deposition in furnace.

Investigation of Three-Dimensional Flow in Microchannels With Patterned Surfaces

2007 ◽  
Author(s):  
Auro Ashish Saha ◽  
Sushanta K. Mitra
Keyword(s):  
Surface Tension ◽  
Flow Instability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Bottom Wall ◽  
Surface Tension Effect ◽  
Hydrophobic Region ◽  
Side Walls ◽  
Dimensional Simulation

A three-dimensional numerical simulation of flow in patterned microchannel with alternate layers of hydrophilic and hydrophobic surfaces at the bottom wall is studied here. Surface characteristics of the microchannel are accounted by specifying the contact angle and the surface tension of the fluid. Meniscus profiles with varying amplitude and shapes are obtained under the different specified surface conditions. Flow instability increases as the fluid at the bottom wall traverses alternately from hydrophilic region to hydrophobic region. To understand the surface tension effect of the side walls, a two-dimensional numerical study has also been carried out for the microchannel and the results are compared with three-dimensional simulation. The surface tension effect of the side walls enhances the capillary effect for three-dimensional case.

Numerical Anaysis of a Thermopneumatic Micropump

2010 ◽  
Author(s):  
S. Shahsavari ◽  
M. B. Shafii ◽  
M. H. Saidi
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Working Fluid ◽  
Structure Interaction ◽  
Positive Displacement ◽  
Dimensional Simulation ◽  
Center Deflection ◽  
Bidirectional Flow ◽  
Secondary Fluid

Thermopneumatic micropump is one type of positive displacement micropump, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet channels of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which contains the secondary fluid, and the main chamber through which the working fluid is passing. The temperature distribution, the pressure variations, and the center deflection of the diaphragm are obtained. In order to validate the model, the numerical results are compared with some experimental data, which shows fair consistency. According to the results of the three dimensional simulation, the rectification efficiency for the nozzle and diffuser channels depends on the frequency.

Buoyancy Induced Convection in a Narrow Open-Ended Annulus

1997 ◽  
Vol 119 (3) ◽  
pp. 483-494 ◽  
Author(s):  
K. Vafai ◽  
C. P. Desai ◽  
S. V. Iyer ◽  
M. P. Dyko
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Axial Length ◽  
Numerical Study ◽  
Fluid Motion ◽  
Three Dimensional ◽  
Transfer Coefficients ◽  
State Equations ◽  
Element Analysis ◽  
Gap Width

Results from a combined experimental and numerical investigation of buoyancy driven flow and heat transfer in a narrow annular gap between co-axial, horizontal cylinders are presented in this work. The annulus is open at both ends through which the ambient fluid can interact with the fluid inside the gap. In the experimental study, a constant heat flux was utilized to simulate buoyancy induced convection in an open ended annular cavity with a low gap to inner cylinder radius ratio; local surface temperature measurements were made to determine heat transfer characteristics of the convective flow. The heat transfer results are correlated by Nu = 0.134(Ra*)0.264 for the range of Rayleigh numbers considered (7.09 ×108 ≤ Ra* ≤ 4.76 × 109) in the experiments. In the numerical investigation, solutions to the three-dimensional time-averaged (Reynolds) steady-state equations of fluid motion and heat transfer were obtained using a finite element analysis. Results of the conjugate study including the local temperature distributions, heat transfer coefficients, and the flow field showing the interactions between the ambient and cavity flow fields agree favorably with experimental results. An investigation was also carried out to study the effect of axial length and the gap width of the annulus. A correlation for the average Nusselt number as a function of Rayleigh number, axial length and gap width has been obtained. The present work provides, for the first time, an experimental and numerical study of turbulent buoyancy induced flows in a narrow open-ended annulus.

scholarly journals A Numerical Study of the effect of Bolt Thread Geometry on the Load Distribution of Continuous Threads

2021 ◽  
Author(s):  
Abdulla Sherif Mahmoud Fathalla ◽  
◽  
Ali Akhavan Farid ◽  
Reza Moezzi ◽  
Seyed Saeid Rahimian Koloor ◽  
...  
Keyword(s):  
Load Distribution ◽  
Numerical Study ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Reliable Performance ◽  
Dimensional Simulation ◽  
Three Dimensional Finite Element ◽  
Distribution Behaviour

Load distribution has been studied extensively for ISO thread, but the load distribution on power screw threads, specifically ACME and Square threads, has not been studied yet. In this article, axisymmetric two-dimensional and three-dimensional Finite Element Analysis have been conducted on bolts with different sizes and thread geometries to examine the effect of the thread geometry on the load distribution. The thread geometries were studied with ISO, ACME, and Square threads attention. The sizes used are from the ISO coarse series. In order to investigate on the effect of bolt thread geometry, several simulations have been performed. The two-dimensional simulation results have shown reliable performance in determining the load distribution behaviour when the thread geometry is modified. Moreover, the results agreed with the three-dimensional simulation outcomes regarding the load distribution behaviour when the size is varied.

scholarly journals Numerical study on aerothermal performance of shroud movement in the vivinity of turbine tips

2020 ◽  
pp. 321-321
Author(s):  
Yunsong Zhang ◽  
Yongbao Liu ◽  
Yujie Li ◽  
Qijie Li
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Flow Structure ◽  
Numerical Study ◽  
Three Dimensional ◽  
Breakdown Point ◽  
Axial Direction ◽  
Suction Surface ◽  
Initial Location ◽  
Dimensional Simulation

In this paper, the effects of shroud movement on transonic flow and heat transfer in the vicinity of turbine tip was studied by using three-dimensional simulation of GE-E3 first-stage HPT. Aerothermal performance and flow structure were analyzed with and without turbine shroud moving, respectively. Based on the distribution of limiting streamlines and the vortex structures, the influential characteristics between the leakage flow and the secondary flow generated by shroud movement were studied. Moreover, the coefficient of heat transfer at the wall were investigated. Results show that the flow structure is changing with the movement of turbine shroud, and the location of the separation line changes significantly by the influence of the secondary flow. The leakage vortex initial location delayed in axial direction and its breakdown point located at 65% cross section. This accelerates the mixing loss and increase the perturbation. In addition, it is observed that the coefficient of average heat transfer is increased obviously by 54.8% in the region of shroud surface. However, this coefficient in the region of suction surface decreased by 11.9%.

Numerical Study of Large Diameter Butterfly Valve on Flow Characteristics

2011 ◽  
Vol 236-238 ◽  
pp. 1653-1657 ◽  
Author(s):  
Xiao Dong Wang ◽  
Jing Liang Dong ◽  
Tian Wang
Keyword(s):  
Pressure Drop ◽  
Flow Resistance ◽  
Numerical Study ◽  
Large Diameter ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Numerical Approach ◽  
Resistance Coefficient ◽  
Butterfly Valve ◽  
Dimensional Simulation

A numerical approach was used to investigate the flow characteristics around a butterfly valve with the diameter of 2108 mm by the commercial computational fluid dynamics (CFD) code FLUENT6.3. The simulation was carried out to predict flow field structure, flow resistance coefficient, hydrodynamics torque and so on, when the large diameter butterfly valve operated at various opening degrees. The three-dimensional simulation results shown that there are vortexes presented near valve back region as the opening degree smaller than 40 degree; the flow resistance coefficient reduces rapidly with the increasing of opening degree and the resistance coefficient is quite small as the angle larger than 50 degree; the hydrodynamic torque reduces with the increasing of opening degree and the hydrodynamic torque is smaller than 20% of maximum torque; the torque ratio and the pressure drop ratio are reduce with the increasing of opening degree, the pressure drop ratio reduces rapidly as the opening degree is smaller than 50 degree.

scholarly journals Numerical Study on Erosion Wear and Strength of Main Gas Pipelines Bends

2021 ◽  
Vol 71 (1) ◽  
pp. 27-40
Author(s):  
Doroshenko Yaroslav ◽  
Kogut Galyna ◽  
Doroshenko Yuliia ◽  
Tarayevs’kyy Oleh ◽  
Pyrig Taras
Keyword(s):  
Stress State ◽  
Numerical Study ◽  
Three Dimensional ◽  
Wall Stress ◽  
Internal Cavity ◽  
Erosion Wear ◽  
Gas Pipelines ◽  
Wear Process ◽  
Simulation Based ◽  
Dimensional Simulation

Abstract The purpose of this work is to ensuring the strength of main gas pipelines bends by studying the peculiarities of single-phase and multiphase flows movement through the internal cavity, the processes of erosion wear and the wall stress state. The problem of synergistic influence of gas-dynamic processes (uneven pressure distribution in the internal cavity), temperature difference and erosion wear on the stress state of the bends of main gas pipelines was solved by numerical simulation. Based on the results of simulation the processes of bends erosion wear, an algorithm for three-dimensional simulation of bend walls erosion defects was developed. The complex three-dimensional geometric shape of the erosion defects of the bend wall varied according to the rate of erosion wear process. This algorithm made it possible to determine the regularities for the influence of the bend erosion defects magnitude on bends stress state. It was established that considering the maximum depth of bend erosion defects 9.6 mm, 10.5 mm and 11.9 mm, the equivalent stresses in the deepest places of the erosion defect were greater than on the concave side of the bend and in straight sections of the pipeline.

An Effect of Swept Vane in Hydrogen-Fueled Combustion Turbine

2010 ◽  
Author(s):  
Hironori Honda ◽  
Masaya Suzuki ◽  
Makoto Yamamoto
Keyword(s):  
Surface Temperature ◽  
High Surface ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Hydrogen Combustion ◽  
Hydrogen Gas ◽  
Propulsion System ◽  
The Other ◽  
Other Hand ◽  
Turbine Vane

A lot of environmental problems such as global warning, air pollution and exhaustion of fossil fuels have been discussed frequently. Many researches have been underway in several countries to develop a propulsion system for an advanced aircraft to achieve low environmental loading. On the other hand, with the recent development of an aircraft, the propulsion system is required to have lighter weight, higher power and lower emissions. To satisfy these requirements, we have supposed a new cycle concept for advanced propulsion system, in which the combustion camber is eliminated; hydrogen gas is directly injected from turbine vane surfaces and combusted within turbine vane passages. However, to apply the cycle to practical use, there are problems of extremely high surface temperature and aerodynamic performance decrease by hydrogen combustion. It is well known that three-dimensional design approaches such as sweep, lean and twist decrease the secondary flow loss. However, there is no knowledge how these three-dimensional designs affect on the flow characteristics of the hydrogen-fueled turbine. In the present study, we focus on sweep. To clarify the sweep effect on the surface temperature and performance of the hydrogen-combustion turbine, three-dimensional numerical simulations based on RANS are carried out. We find that the swept vanes with positive sweep give the aerodynamic performance. On the other hand, the swept vanes with negative sweep suppress the vane surface temperature.

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