Experimental and Numerical Study of Cold Gas-Solid Flow Regimes in a Fluidized Bed Gasifier

2017 ◽  
Author(s):  
Anton Pylypenko ◽  
Yevgenii Rastigejev ◽  
Lijun Wang ◽  
Abolghasem Shahbazi
Keyword(s):  
Fluidized Bed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Silica Sand ◽  
State University ◽  
Solid Flow ◽  
Fluidized Bed Gasifier ◽  
Isothermal Gas ◽  
Cold Gas

The objective of this work is to analyze the dynamics and regimes of cold gas-solid flow in a biomass gasifier that is built at North Carolina Agricultural and Technical State University and to identify its corresponding ranges of operating conditions. The value of the minimum fluidization velocity Umf ≈ 8 cm/s has been found experimentally in a series of measurements of a pressure drop in the fluidized bed filled with Gledart type-B silica sand for the range of superficial gas velocities between 0 and 40 cm/s. To complement the experimental results, a set of three-dimensional numerical simulations of the isothermal gas-solid flow based on Eulerian-Eulerian approach has been performed. The analysis of the fluidization characteristics such as axial void fraction distributions has allowed us to evaluate the dependence of the bed expansion ratios from the flow superficial velocity. Good agreement between experimental and numerical results for the considered operating conditions of the gasifier has been observed.

Numerical Simulation of Gas Flow and Heat Transfer in Cross-Wavy Primary Surface Channel for Microtubine Recuperators

2005 ◽  
Author(s):  
H. X. Liang ◽  
Q. W. Wang ◽  
L. Q. Luo ◽  
Z. P. Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Gas Turbine ◽  
Numerical Study ◽  
High Reliability ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Cross

Three-dimensional numerical simulation was conducted to investigate the flow field and heat transfer performance of the Cross-Wavy Primary Surface (CWPS) recuperators for microturbines. Using high-effective compact recuperators to achieve high thermal efficiency is one of the key techniques in the development of microturbine in recent years. Recuperators need to have minimum volume and weight, high reliability and durability. Most important of all, they need to have high thermal-effectiveness and low pressure-losses so that the gas turbine system can achieve high thermal performances. These requirements have attracted some research efforts in designing and implementing low-cost and compact recuperators for gas turbine engines recently. One of the promising techniques to achieve this goal is the so-called primary surface channels with small hydraulic dimensions. In this paper, we conducted a three-dimensional numerical study of flow and heat transfer for the Cross-Wavy Primary Surface (CWPS) channels with two different geometries. In the CWPS configurations the secondary flow is created by means of curved and interrupted surfaces, which may disturb the thermal boundary layers and thus improve the thermal performances of the channels. To facilitate comparison, we chose the identical hydraulic diameters for the above four CWPS channels. Since our experiments on real recuperators showed that the Reynolds number ranges from 150 to 500 under the operating conditions, we implemented all the simulations under laminar flow situations. By analyzing the correlations of Nusselt numbers and friction factors vs. Reynolds numbers of the four CWPS channels, we found that the CWPS channels have superior and comprehensive thermal performance with high compactness, i.e., high heat transfer area to volume ratio, indicating excellent commercialized application in the compact recuperators.

EFFECTS OF OPERATING CONDITIONS ON THE DEPOSITION OF GaAs IN A VERTICAL CVD REACTOR

2008 ◽  
Vol 15 (01n02) ◽  
pp. 111-116 ◽  
Author(s):  
JAE-SANG BAEK ◽  
JIN-HYO BOO ◽  
YOUN-JEA KIM
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Rotation Velocity ◽  
Operating Conditions ◽  
Deposition Condition ◽  
Three Dimensional Model ◽  
Trimethyl Gallium ◽  
Vertical Cvd Reactor

A numerical study is needed to gain insight into the growth mechanism and improve the reactor design or optimize the deposition condition in chemical vapor deposition (CVD). In this study, we have performed a numerical analysis of the deposition of gallium arsenide ( GaAs ) from trimethyl gallium (TMG) and arsine in a vertical CVD reactor. The effects of operating parameters, such as the rotation velocity of susceptor, inlet velocity, and inlet TMG fraction, are investigated and presented. The three-dimensional model which is used in this investigation includes complete coupling between the thermal-fluid transport and species transport with chemical reaction.

Experimental and Numerical Study of Stall Flutter in a Transonic Low-Aspect Ratio Fan Blisk

2003 ◽  
Author(s):  
A. J. Sanders ◽  
K. K. Hassan ◽  
D. C. Rabe
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Strain Gages ◽  
Pressure Transducers ◽  
Low Aspect Ratio ◽  
Benchmark Data

Experiments are performed on a modern design transonic shroudless low-aspect ratio fan blisk that experienced both subsonic/transonic and supersonic stall-side flutter. High-response flush mounted miniature pressure transducers are utilized to measure the unsteady aerodynamic loading distribution in the tip region of the fan for both flutter regimes, with strain gages utilized to measure the vibratory response at incipient and deep flutter operating conditions. Numerical simulations are performed and compared with the benchmark data using an unsteady three-dimensional nonlinear viscous computational fluid dynamic (CFD) analysis, with the effects of tip clearance, vibration amplitude, and the number of time steps-per-cycle investigated. The benchmark data are used to guide the validation of the code and establish best practices that ensure accurate flutter predictions.

Validation and Application of Computational Modeling to Reduce Erosion in a Circulating Fluidized Bed Boiler

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Peter J. Blaser ◽  
Giorgio Corina
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Palm Kernel ◽  
Operational Experience ◽  
Solid Flow ◽  
Internal Surfaces ◽  
And Performance ◽  
Palm Kernel Shells

Abstract The 40 MW Strongoli power plant, located in the Calabria region of Italy, produces power from 100% biomass sources. The combustion of wood biomass, exhausted olive residues and palm kernel shells, occurs in a sand-filled, Circulating Fluidized Bed (CFB) combustor. Operational experience with the unit dates back to 2003. This paper describes the optimization of the boiler in order to minimize erosion on internal surfaces and structures. Detailed three-dimensional, transient, multiphase gas-solid flow fields were computed and are presented. Details of the complex geometry include the combustion chamber, cyclone, cyclone dipleg, seal pot, fluidized bed heat exchanger and cyclone outlet structures including suspension tubes. The gas-solid flow was computed using the commercially-available software package Barracuda, a CFD software based on a unique Eulerian-Lagrangian formulation that was essential to the success of the subject work. Both instantaneous and time-averaged results were obtained. Results were validated against operational erosion experience. The validated model, in turn, was utilized to redesign various components of the boiler, optimizing both erosion characteristics and performance behaviour of the system. The redesigned unit was commissioned in early 2012.

Predicting cold gas-solid flow in a pilot-scale dual-circulating fluidized bed: Validation of computational particle fluid dynamics model

2021 ◽  
Vol 381 ◽  
pp. 25-43
Author(s):  
Frederik Zafiryadis ◽  
Anker Degn Jensen ◽  
Yashasvi Laxminarayan ◽  
Weigang Lin ◽  
Elisabeth Akoh Hove ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Pilot Scale ◽  
Dynamics Model ◽  
Solid Flow ◽  
Cold Gas

A Computational Investigation of Nonpremixed Combustion of Natural Gas Injected Into Mixture of Argon and Oxygen

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Martia Shahsavan ◽  
Mohammadrasool Morovatiyan ◽  
J. Hunter Mack
Keyword(s):  
Natural Gas ◽  
Internal Combustion Engines ◽  
Numerical Study ◽  
Direct Injection ◽  
Three Dimensional ◽  
Dynamic Structure ◽  
Operating Conditions ◽  
Working Fluid ◽  
Thermodynamic Efficiency ◽  
Transient Model

Natural gas is traditionally considered as a promising fuel in comparison with gasoline due to the potential of lower emissions and significant domestic reserves. These emissions can be further diminished by using noble gases, such as argon, instead of nitrogen as the working fluid in internal combustion engines. Furthermore, the use of argon as the working fluid can increase the thermodynamic efficiency due to its higher specific heat ratio. In comparison with premixed operation, the direct injection of natural gas enables the engine to reach higher compression ratios while avoiding knock. Using argon as the working fluid increases the in-cylinder temperature at top dead center (TDC) and enables the compression ignition (CI) of natural gas. In this numerical study, the combustion quality and ignition behavior of methane injected into a mixture of oxygen and argon have been investigated using a three-dimensional transient model of a constant volume combustion chamber (CVCC). A dynamic structure large eddy simulation (LES) model has been utilized to capture the behavior of the nonpremixed turbulent gaseous jet. A reduced mechanism consists of 22-species, and 104-reactions were coupled with the CFD solver. The simulation results show that the methane jet ignites at engine-relevant conditions when nitrogen is replaced by argon as the working fluid. Ignition delay times are compared across a variety of operating conditions to show how mixing affects jet development and flame characteristics.

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