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A Study of Vertical Gas Jets in a Bubbling Fluidized Bed

Description: A detailed experimental study of a vertical gas jet impinging a fluidized bed of particles has been conducted with the help of Laser Doppler Velocimetry measurements. Mean and fluctuating velocity profiles of the two phases have been presented and analyzed for different fluidization states of the emulsion. The results of this work would be greatly helpful in understanding the complex two-phase mixing phenomenon that occurs in bubbling beds, such as in coal and biomass gasification, and also in building more fundamental gas-solid Eulerian/Lagrangian models which can be incorporated into existing CFD codes. Relevant simulations to supplement the experimental findings have also been conducted using the Department of Energy’s open source code MFIX. The goal of these simulations was two-fold. One was to check the two-dimensional nature of the experimental results. The other was an attempt to improve the existing dense phase Eulerian framework through validation with the experimental results. In particular the sensitivity of existing frictional models in predicting the flow was investigated. The simulation results provide insight on wall-bounded turbulent jets and the effect frictional models have on gas-solid bubbling flows. Additionally, some empirical minimum fluidization correlations were validated for non-spherical particles with the idea of extending the present study to non-spherical particles which are more common in industries.
Date: January 18, 2011
Creator: Ceccio, Steven & Curtis, Jennifer
Partner: UNT Libraries Government Documents Department

Commercialization of Turbulent Combustion Code CREBCOM for Chemical Industry Safety

Description: This program developed the Kurchatov Institute’s CREBCOM (CRiteria and Experimentally Based COMbustion) code to the point where it could be commercialized and marketed for the special applications described above, as well as for general purpose combustion calculations. The CREBCOM code uses a different approach to model the explosion phenomenon. The code models, with full 3D gas dynamics, the development of an explosion in three characteristics regimes: a) slow flames, b) fast flames, and c) detonation. The transition from one regime to another is governed by a set of empirical criteria and correlations. As part of the commercialization, the code was validated with the use of experimental data. The experimental data covered a range of thermodynamic initial conditions and apparatus scale. Proprietary experimental data were provided to the Kurchatov Institute by the DuPont for this purpose. The flame acceleration and detonation data was obtained from experiments in methane and oxygen enriched air mixtures carried out in two vessels with diameters of 20 and 27 cm. The experimental data covers a wide spectrum of initial temperature (20-525C) and pressure (1-3 atm). As part of this program, the Kurchatov Institute performed experiments in a 52 cm vessel in mixtures of methane-air at room temperature and pressure to be used in the validation of the code. The objective of these tests was to obtain frame acceleration data at a scale close to that found in actual industrial processes. BNL was responsible for managing the DOE/IPP portion of the program, and for satisfying DOE reporting requirements. BNL also participated in an independent assessment of the CREBOM code. DuPont provided proprietary experimental data to the Kurchatov Institute on flame acceleration and detonation in high temperature methane and oxygen enriched air mixtures in addition to the matching fund. In addition, DuPont also supplied to KI instrumentation for ...
Date: June 30, 2007
Creator: Rohatgi, Upendra
Partner: UNT Libraries Government Documents Department


Description: Low-cycle fatigue tests were conducted by tension-compression until rupture, on a 2024-T3 aluminum alloy sheet. Initial crack sizes and orientations in the fatigue specimens were found to be randomly distributed. Acoustic emission was continuously monitored during the tests. Every few hundred cycles, the acoustic signal having the highest peak-amplitude, was recorded as an extremal event for the elapsed period. This high peak-amplitude is related to a fast crack propagation rate through a phenomenological relationship. The extremal peakamplitudes are shown by an ordered statistics treatment, to be extremally distributed. The statistical treatment enables the prediction of the number of cycles left until failure. Predictions performed a-posteriori based on results gained early in each fatigue test are in good agreement with actual fatigue lives. The amplitude distribution analysis of the acoustic signals emitted during cyclic stress appears to be a promising nondestructive method of predicting fatigue life.
Date: May 1, 1980
Creator: Baram, J. & Rosen, M.
Partner: UNT Libraries Government Documents Department

Quarterly Summary Report April-June 1978 Process for Cleaning and Removal of Sulfur Compounds From Low Btu Gases

Description: In this phase of work the Process Development Unit (PDU) is to be remodeled by incorporation of appropriate subsystems to permit operation in continuous process mode. The PDU will be operated for a period of time sufficient to demonstrate process viability.
Date: July 1, 1978
Partner: UNT Libraries Government Documents Department

Wave transmission and mooring-force characteristics of pipe-tire floating breakwaters

Description: The results are presented of a series of prototype scale tests of a floating breakwater that incorporates massive cylindrical members (steel or concrete pipes, telephone poles, etc.) in a matrix of scrap truck or automobile tires, referred to as the Pipe-Tire Breakwater (PT-Breakwater). Tests were conducted in the large wave tank at the US Army Coastal Engineering Research Center (CERC). Breakwater modules were preassembled at SUNY in Buffalo, New York, and then transported to CERC by truck, where final assembly on location was again performed by SUNY personnel. Wave-tank tests were conducted jointly by CERC and SUNY personnel. A series of wave-tank experiments and mooring system load-deflection tests were performed, and are described. Wave-transmission and mooring-load characteristics, based on 402 separate tests, were established and are reported. (LCL)
Date: October 1, 1980
Creator: Harms, Volker W. & Westerink, Joannes J.
Partner: UNT Libraries Government Documents Department

Integrated Advanced Reciprocating Internal Combustion Engine System for Increased Utilization of Gaseous Opportunity Fuels

Description: The project is addressing barriers to or opportunities for increasing distributed generation (DG)/combined heat and power (CHP) use in industrial applications using renewable/opportunity fuels. This project brings together novel gas quality sensor (GQS) technology with engine management for opportunity fuels such as landfill gas, digester gas and coal bed methane. By providing the capability for near real-time monitoring of the composition of these opportunity fuels, the GQS output can be used to improve the performance, increase efficiency, raise system reliability, and provide improved project economics and reduced emissions for engines used in distributed generation and combined heat and power.
Date: August 31, 2013
Creator: Pratapas, John; Zelepouga, Serguei; Gnatenko, Vitaliy; Saveliev, Alexei; Jangale, Vilas; Li, Hailin et al.
Partner: UNT Libraries Government Documents Department

Investigation of Gas Solid Fluidized Bed Dynamics with Non-Spherical Particles

Description: One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed height for ...
Date: June 30, 2013
Creator: Choudhuri, Ahsan
Partner: UNT Libraries Government Documents Department


Description: A turbulent reacting shear layer in a premixed propane/air flow has been studied in a two dimensional combustor, with the flame stabilized behind a rearward facing streamlined step. Spark shadowgraphs show that in the range of velocities (7.5 to 22.5 m/sec corresponding to Reynolds numbers of .5 x 10{sup 4} cm{sup -1} to 1. 5 x 10{sup 4} cm{sup -1} ) and equivalence ratios (0.4 to 0.7) studied, the mixing layer is dominated by Brown~ Roshko type large coherent structures in both reacting and nonreacting flows. High speed schlieren movies show that these eddies are convected downstream and increase their size and spacing by combustion and coalescence with neighboring eddies. Tracing individual eddies shows, in the reacting shear layer, that, on the average, eddies accelerate as they move downstream with the highest acceleration close to the origin of the shear layer. Combustion is confined to these large structures which develop as a result of vortical action of the shear flow. On the average, the reacting eddies have a lower growth rate than nonreacting eddies. A turbulent boundary layer created by means of a tripping wire upstream of the edge of the step virtually eliminates the large coherent structures in the shear layer, while for the case in which the wire could not trigger the transition to turbulence, the large coherent structures dominated the reacting and nonreacting flows.
Date: April 1, 1980
Creator: Ganji, A.R. & Sawyer, R.F.
Partner: UNT Libraries Government Documents Department


Description: The velocity of thermal repulsion of large aerosol particles has been calculated by others by equating the thermal force on a stationary partlcle to the Stokes-Cunningham viscous force. This procedure is theoretically unsound because the boundary conditions employed in the viscous force equation are erroneous when the particle moves in a thermal gradient. In the current study these difficulties have been circumvented by rederiving the thermal force equation, allowing for a relative velocity between the particle and the gas stream. The velocity of motion is then calculated by setting the net force on the particle equal to zero. The velocity obtained by this more realistic approach agrees with that calculated by the former method, which is surprising in view of the incorrect boundary conditions employed in the former method. Investigation of the drag force equation shows that the thermal force and the viscous force are exerted independently of each other, which explains this unexpected agreement, The range of applicability of the analysis is explored by comparison with available experimental data,
Date: November 1, 1965
Creator: Postma, A. K.
Partner: UNT Libraries Government Documents Department


Description: The windstorm of January 11 caused a minor amount of damage to the Hanford Reservation and Hanford vicinity. Damage sustained to Hanford Reservation structures (roofing, flashing, fences, windows) was approximately $20,000. One building did receive structural damage to roof members. Evidence that wind pressures did not reach 30 lb/ft{sup 2} during the January 11 windstorm was provided in the fact that specially designed exterior wall panels did not fail. These panels were designed and carefully proof-tested to insure that they would fail at a loading of 30 lb/ft{sup 2} as a requirement of structural safety in the original design-construction program in 1952-1954. There was one power outage on the Hanford Reservation due to the January 11 windstorm (Rattlesnake Mountain Observatory). Damage to power lines and electrical facilities amounted to about $1600. Damage to structures in the Hanford vicinity (excluding the Hanford Reservation) from the January 11 windstorm was estimated to cost $13,000. This does not include damage to private residences, etc., which has been estimated by others to be near $250,000. Power line damage in the Hanford vicinity amounted to about $80,000, of which $60,000 was accounted for in the loss of four transmission towers in the tie-line between Priest Rapids and Wanapum Dams. The January 21 windstorm, which struck Toppenish, Washington, was a straight-wind of the catabatic foehn type and not a tornado-type wind as described in newspaper accounts. No funnel cloud was associated with this windstorm. The maximum gust was about 85 mph at 30 ft above the ground. Cost estimates of damage in Toppenish were not available. There were no power outages or structural damage on the Hanford Reservation from the January 21 windstorm. Total damage to the Hanford Reservation from the two windstorms was estimated to be about $22,500.
Date: June 1, 1972
Creator: Henager, C. H. & Fuquay, J. J.
Partner: UNT Libraries Government Documents Department

Computational fluid dynamic modeling of fluidized-bed polymerization reactors

Description: Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.
Date: November 2, 2012
Creator: Rokkam, Ram
Partner: UNT Libraries Government Documents Department