bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of an Exhaust Gas Recirculation Distribution Prediction Method Using Three-Dimensional Flow Analysis and Its Application
Authors: Yoshizawa K. , Mori K. , Matayoshi Y. , Kimura S.
Published: November 2003

A multidimensional computational fluid dynamics (CFD) method has been used to improve the exhaust gas recirculation (EGR) distribution in the intake manifold. Since gas flow in the intake system is affected by intake pulsation caused by the gas exchange process, a pulsation flow simulation is used. A one-dimensional gas exchange calculation is combined with three-dimensional intake gas flow calculation to simulate pulsation flow. This pulsation flow simulation makes it possible to predict the EGR distribution. The gas flow in the intake system was analyzed in detail. It was found that a reverse flow region formed downstream of the throttle valve. The size and shape of the reverse flow region greatly depend on the engine operating conditions. With a conventional EGR system, it is difficult to distribute EGR uniformly under various engine operating conditions. A new EGR system that uses a spiral flow to mix the fresh air and EGR gas has been developed to obtain a uniform EGR distribution. As a result of adopting this system, a uniform EGR distribution is obtained regardless of the engine operating conditions. This spiral flow EGR system was applied to a low-emission vehicle (LEV) put on the Japanese market.
Active Combustion Instability Control With Spinning Valve Actuator
Authors: Barooah P. , Anderson T. J. , Cohen J. M.
Published: November 2003

Active combustion control has been accomplished in many laboratory and real-world combustion systems by fuel modulation as the control input. The modulation is commonly achieved using reciprocating flow control devices. These demonstrations have been successful because the instabilities have been at relatively low frequencies (∼200 Hz) or the scale of demonstration has been small enough to require very small levels of modulation. A number of real-world instabilities in gas turbine engines involve higher frequencies (200–500 Hz) and attenuation requires the modulation of large fractions of the engine fuel flow rate (hundreds of pounds per hour). A spinning drum valve was built to modulate fuel for these applications. Tests showed that this device provided more than 30% flow modulation up to 800 Hz for liquid fuel flows of greater than 400 lbm/hr. This paper describes the performance of the valve in flow bench tests, open-loop forcing, and closed-loop instability control tests. The closed-loop tests were done on a single-nozzle combustor rig which exhibited a limit-cycling instability at a frequency of ∼280 Hz with an amplitude of ∼7 psi. It also encounters an instability at 575 Hz under a different set up of the rig, though active control on that instability has not been investigated so far. The test results show that the spinning valve could be effectively used for active instability control, though the control algorithms need to be developed which will deal with or account for actuator phase drift/error.
Low NOx Combustion for Liquid Fuels: Atmospheric Pressure Experiments Using a Staged Prevaporizer-Premixer
Authors: Lee J. C. Y. , Malte P. C. , Benjamin M. A.
Published: November 2003

Low emissions of NOx are obtained for a wide range of liquid fuels by using a staged prevaporizing-premixing injector. The injector relies on two stages of air temperature and fires into a laboratory jet-stirred reactor operated at atmospheric pressure and nominal ϕ of 0.6. The liquid fuels burned are methanol, normal alkanes from pentane to hexadecane, benzene, toluene, two grades of light naphtha, and four grades of No. 2 diesel fuel. Additionally, natural gas, ethane, and industrial propane are burned. For experiments conducted for 1790 K combustion temperature and 2.3±0.1 ms combustion residence time, the NOx (adjusted to 15% O2 dry) varies from a low of 3.5 ppmv for methanol to a high of 11.5 ppmv for No. 2 diesel fuel. For the most part, the NOx and CO are positively correlated with the fuel carbon to hydrogen ratio (C/H). Chemical kinetic modeling suggests the increase in NOx with C/H ratio is caused in significant part by the increasing superequilibrium concentrations of O-atom created by the increasing levels of CO burning in the jet-stirred reactor. Fuel bound nitrogen also contributes NOx for the burning of the diesel fuel. This paper describes the staged prevaporizing-premixing injector, the examination of the injector, and the NOx and CO measurements and their interpretation. Optical measurements, using beams of He-Ne laser radiation passed across the outlet stream of the injector, indicate complete vaporization and a small variation in the cross-stream averaged fuel/air ratio. The latter is determined by measuring the standard deviation and mean of the transmission of the laser beam passed through the stream. Additional measurements and inspections indicate no pressure oscillations within the injector and no gum and carbon deposition. Thus, the NOx and CO measurements are obtained for fully vaporized, well premixed conditions devoid of preflame reactions within the injector.
Contact Stresses in Dovetail Attachments: Alleviation via Precision Crowning
Authors: Sinclair G. B. , Cormier N. G.
Published: November 2003

Previous studies of contact stresses in dovetail attachments provide verified finite element stresses as well as some simple physical models of such stresses. Generally there is good agreement between the finite element analysis and the simple physical models. Together the two identify a pinching mechanism as leading to large fluctuations in hoop stresses at the edges of contact. These fluctuating hoop stresses can be expected to be a major contributor to the fatigue of dovetail attachments. The present study investigates a method of alleviating the fluctuating hoop stresses. This method entails crowning of the contacting flat on a blade. Such crowning is in two orthogonal directions on the blade flat. Two-dimensional finite element analyses are made in both directions. These analyses indicate that significant reductions in fluctuating hoop stresses can be achieved by the method, provided the crowning is controlled sufficiently precisely.
Investigation of the Response of an Air Blast Atomizer Combustion Chamber Configuration on Forced Modulation of Air Feed at Realistic Operating Conditions
Authors: Hassa C. , Heinze J. , Stursberg K.
Published: November 2003

DLR investigated forced combustion oscillations of two liquid fuel burners in a research combustion chamber at elevated pressures simulating idle conditions of aircraft engine combustors. The work was performed in collaboration with MTU Munich. An existing combustion chamber with optical access, capable to operate up to 20 bar, was upgraded with an air flow pulsator, that bypasses air from the combustor plenum to the exhaust with a sinusoidal massflow variation up to 700 Hz. Pressure transducers in the plenum and the flame tube monitored the forced disturbances. A photomultiplier recorded the OH* chemiluminescence of the flame. For the agreed operating conditions frequency scans of these values were registered. Additionally images of the OH* chemiluminescence were taken at selected frequencies and evaluated in a statistical manner, to separate turbulent and periodic behavior. From the analysis of the pressure data, it can be concluded, that serious thermoacoustic feedback was not observed for both burners. However, burner 2 with the flame detached from the wall exhibited a higher fluctuation level as burner 1 with the wall attached flame. A resonant behavior was observed near the characteristic frequency of the sound room comprised of plenum, flame tube, and burner nozzle as connecting passage. The chemiluminescence images show different modes of spatial fluctuation for the burners and for burner 2 they also vary with the operating condition.
Disintegration of Oil Films Emerging From Radial Holes in a Rotating Cylinder
Authors: Glahn A. , Blair M. F. , Allard K. L. , Busam S. , Scha¨fer O. , Wittig S.
Published: November 2003

A fundamental study has been performed to examine the disintegration of oil films emerging from radial holes in a rotating hollow cylinder. The configuration investigated is an abstraction of one of the droplet generation sources in an aeroengine bearing compartment; similar configurations may also occur inside gearboxes. The paper aims to contribute to both the determination of directly applicable droplet characteristics and the establishment of a database that can be used for the development of droplet generation models. Similar to a prior paper on droplet generation processes at the rim of a rotating disk (Glahn, A. et al., 2000, “Droplet Generation by Disintegration of Oil Films at the Rim of a Rotating Disk,” ASME Paper No. 2000-GT-0279.) the near-term objectives of the study are (i) to determine droplet sizes under relevant aeroengine bearing compartment operating conditions, and (ii) to measure individual droplet diameter/velocity relationships. The long-term objective is to incorporate this information into advanced CFD-based design tools. Therefore, special emphasis has been directed towards a correlation of test results that enables determination of boundary conditions for a two-phase (oil droplets/air) simulation of lubrication system components. Based on the results of the present paper, droplet flow boundary conditions in terms of mean diameter, standard deviation of the diameter distribution, starting velocity, and flow angle are available for oil droplets generated by disintegration of oil films emerging from rotating radial holes and rotating disks.
Off-Design Performance Analysis of a Hybrid System Based on an Existing Molten Fuel Cell Stack
Authors: Bedont P. , Grillo O. , Massardo A. F.
Published: November 2003

This paper addresses the off-design analysis of a hybrid system (HS) based on the coupling of an existing Ansaldo Fuel Cells (formerly Ansaldo Ricerche) molten carbonate fuel cell (MCFC) stack (100 kW) and a micro gas turbine. The MCFC stack model at fixed design conditions has previously been presented by the authors. The present work refers to an off-design stack model, taking into account the influence of the reactor layout, current density, air and fuel utilization factor, CO2 recycle loop, cell operating temperature, etc. Finally, the design and off-design model of the whole hybrid system is presented. Efficiency at part load condition is presented and discussed, taking into account all the constraints for the stack and the micro gas turbine, with particular emphasis on CO2 recycle control.
The Recuperative-Auto Thermal Reforming and the Recuperative-Reforming Gas Turbine Power Cycles With CO2 Removal—Part I: The Recuperative-Auto Thermal Reforming Cycle
Authors: Fiaschi D. , Lombardi L. , Tapinassi L.
Published: November 2003

The relatively innovative gas turbine based power cycles R-ATR and R-REF (Recuperative–Auto Thermal Reforming GT cycle and Recuperative–Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO2 removal by the way of natural gas fuel reforming. The power unit is a gas turbine (GT), fueled with reformed and CO2 cleaned syngas produced by adding some basic sections to the simple GT cycle: • auto thermal reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H2,CO2,H2O, and CH4; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel CH4, exhausts and steam. • water gas shift reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO2 and H2 by the addition of water. • water condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). • CO2 removal unit for the CO2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT cycle recuperator, compressor intercooler, and steam injection in combustion chamber. The CO2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44–46%. High specific work levels have also been observed (around 450–550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however, partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the thermal load per kg of removed CO2.
Thermoeconomic Analysis of Gas Turbine Plants With Fuel Decarbonization and Carbon Dioxide Sequestration
Authors: Bozzolo M. , Brandani M. , Traverso A. , Massardo A. F.
Published: November 2003

In this paper the thermoeconomic analysis of gas turbine plants with fuel decarbonization and carbon dioxide sequestration is presented. The study focuses on the amine (MEA) decarbonization plant layout and design, also providing economic data about the total capital investment costs of the plant. The system is fuelled with methane that is chemically treated through a partial oxidation and a water-gas shift reactor. CO2 is captured from the resulting gas mixture, using an absorbing solution of water and MEA that is continuously recirculated through an absorption tower and a regeneration tower: the decarbonized fuel gas is afterwards burned in the gas turbine. The heat required by CO2 sequestration is mainly recovered from the gas turbine exhausts and partially from the fuel treatment section. The reduction in efficiency and the increase in energy production costs due to fuel amine decarbonization is evaluated and discussed for different gas turbine sizes and technologies (microturbine, small size regenerated, aeroderivative, heavy duty). The necessary level of carbon tax for a conventional plant without a fuel decarbonization section is calculated and a comparison with the carbon exergy tax procedure is carried out, showing the good agreement of the results.
Design Formulas for Oscillatory Heat Transport in Open-Ended Tubes
Authors: Furukawa Masao
Published: November 2003

Modified Watson's functions dependent on the Womersley Number, concerning a forced oscillatory pipe flow, are introduced to mathematically simply express the effective thermal conductivity, the tidal displacement, and the tidal work of fluid. Those three are developed into algebraic expressions giving the required electrical oscillating power and the necessary number of capillary tubes. The relative conductivity increase, the specific shaker driving power, and the specific tube bundle size are graphically shown in the figures for several fluids of interest to contribute to designing a heaterless liquid warmer.
A Natural Convection Model for the Rate of Salt Deposition From
Near-Supercritical, Aqueous Solutions
Authors: Hodes Marc , Smith Kenneth A. , Griffith Peter
Published: November 2003

A model is developed for the rate of salt deposition by natural convection from aqueous salt solutions onto a horizontal cylinder heated beyond the solubility temperature for the dissolved salt. The model accounts for the deposition rate at the salt layer-solution interface (SLSI) formed on the cylinder, but it does not account for deposition which may occur inside the porous salt layer (PSL). Dissolved salt is transported to the SLSI by molecular diffusion (with advection) and subsequently nucleates heterogeneously there. The model is applied to the experimental deposition rate data acquired by Hodes et al. (1998, 2002) at conditions pertinent to Supercritical Water Oxidation (SWCO). The ratio of the predicted deposition rate to the measured one ranges from roughly 0.5 to 2 indicating that deposition inside the PSL can be considerable.
An Experimental Study of Miniature-Scale Pool Boiling
Authors: Chen Tailian , Chung Jacob N.
Published: November 2003

By generating single bubbles on a micro-heater at different wall superheats, an experimental study of miniature-scale pool boiling heat transfer has been performed to provide a fundamental understanding of the heater size effect. In this study, the constant-temperature microheater is set at different temperatures by an electronic feedback control system. The heat transfer history during the lifetime of a single bubble which includes nucleation, growth, detachment and departure has been measured. The boiling curve obtained from the microheater is composed of two regimes which are separated by a peak heat flux. It is suggested that in the lower superheat regime, the boiling is dominated by liquid rewetting and micro-layer evaporation, while in the higher superheat regime, conduction through the vapor film and micro-convection plays the key heat transfer role as the heater is covered by vapor all the time. In general, boiling on microheaters is characterized by larger bubble departure sizes, smaller bubble growth rates due to the dryout of microlayer as the bubble grows, and higher bubble incipience superheat. As the heater size decreases, the boiling curve shifts towards higher heat fluxes with corresponding higher superheats.
Inverse Determination of the Local Heat Transfer Coefficients for Nucleate Boiling on a Horizontal Cylinder
Authors: Louahlia-Gualous H. , Panday P. K. , Artioukhine E. A.
Published: November 2003

This article treats the local heat transfer for nucleate pool boiling around the cylinder using the inverse heat conduction analysis. The physical model considers a half section of a cylinder with unknown surface temperature and heat flux density. The iterative regularization and the conjugate gradient methods are used for solving the inverse analysis. The local Nusselt number profiles for nucleate pool boiling are presented and analyzed for different electric heat. The mean Nusselt number estimated by IHCP is closed with the measured values. The results of IHCP are compared to those of Cornewell and Houston (1994), Stephan and Abdelsalam (1980) and Memory et al. (1995). The influence of the error of the measured temperatures and the error in placement of the thermocouples are studied.
An Experimental Study on Heat/Mass Transfer From a Rectangular
Cylinder
Authors: Yoo Seong-Yeon , Park Jong-Hark , Chung Chang-Hwan , Chung Moon-Ki
Published: November 2003

Local and average mass transfer rates from a rectangular cylinder having various width to height ratios are measured using naphthalene sublimation technique, and influence of flow characteristics on mass transfer is investigated. The experimental apparatus comprises a wind tunnel, a naphthalene casting facility and a sublimation depth measurement system. Mass transfer data are compared with those of heat transfer which are obtained using thermocouples in the constant heat flux boundary condition, and analogy between heat and mass transfer is examined. The reasons for discrepancy in both transport values are explained in detail.
Mechanical Surface Treatment Technologies for Gas Turbine Engine Components
Authors: Zhuang W. , Wicks B.
Published: November 2003

Various mechanical surface treatment technologies have been invented and developed to induce a protective layer of compressive residual stress at the surface of gas turbine engine components where the operating loads are tensile dominated. The benefits of these surface treatments are to prevent crack initiation, to retard propagation of small cracks, and even to resist corrosion and wear damage. In this paper the literature on these technologies and their effects on component reliability and durability is reviewed, with an emphasis on shot peening (SP), laser shock peening (LSP), and low plasticity burnishing (LPB). The relative advantages of these three surface treatment technologies, as well as their limitations, are identified and evaluated. The most important issues for these three technologies, and the relative merits of the resultant residual stress fields, are presented and discussed with a view to enhancing gas turbine engine component operating lives.
Numerical Study of Lean-Direct Injection Combustor With Discrete-Jet Swirlers Using Reynolds Stress Model
Authors: Yang S. L. , Siow Y. K. , Teo C. Y. , Tacina R. R. , Iannetti A. C. , Penko P. F.
Published: November 2003

The flowfield in a lean-direct injection (LDI) combustor with discrete-jet swirlers is described and analyzed using a computational fluid dynamics (CFD) code with a Reynolds stress turbulence model (RSTM). The results from the RSTM are compared to time-averaged laser-Doppler velocimetry (LDV) data, as well as results from the National Combustion Code (NCC) that has a cubic nonlinear κ-ε turbulence model, and from the KIVA code using the standard κ-ε model. The comparisons of results indicate that the RSTM accurately describes the flow details and resolves recirculation zones and high velocity gradients while the κ-ε models are unable to capture most flow structures. This confirms that, within the Reynolds averaging approach, the higher-order RSTM is preferred for simulating complex flowfields where separations, strong anisotropy, and high swirl are present.
A New Scaling Method for Component Maps of Gas Turbine Using System Identification
Authors: Kong C. , Ki J. , Kang M.
Published: November 2003

A scaling method for characteristics of gas turbine components using experimental data or partially given data from engine manufacturers was newly proposed. In case of currently used traditional scaling methods, the predicted performance around the on-design point may be well agreed with the real engine performance, but the simulated performance at off-design points far away from the on-design point may not be well agreed with the real engine performance generally. It would be caused that component scaling factors, which were obtained at on-design point, is also used at all other operating points and components’ maps are derived from different known engine components. Therefore to minimize the analyzed performance error in the this study, first components’ maps are constructed by identifying performances given by engine manufacturers at some operating conditions, then the simulated performance using the identified maps is compared with performances using currently used scaling methods. In comparison, the analyzed performance by the currently used traditional scaling method was well agreed with the real engine performance at on-design point but had maximum 22% error at off design points within the flight envelope of a study turboprop engine. However, the performance result by the newly proposed scaling method in this study had maximum 6% reasonable error even at all flight envelope.
Energy and Exergy Analyses of the Pulse Detonation Engine
Authors: Hutchins T. E. , Metghalchi M.
Published: November 2003

Energy and exergy analyses have been performed on a pulse detonation engine. A pulse detonation engine is a promising new engine, which uses a detonation wave instead of a deflagration wave for the combustion process. The high-speed supersonic combustion wave reduces overall combustion duration resulting in an nearly constant volume energy release process compared to the constant pressure process of gas turbine engines. Gas mixture in a pulse detonation engine has been modeled to execute the Humphrey cycle. The cycle includes four processes: isentropic compression, constant volume combustion, isentropic expansion, and isobaric compression. Working fluid is a fuel-air mixture for unburned gases and products of combustion for burned gases. Different fuels such as methane and JP10 have been used. It is assumed that burned gases are in chemical equilibrium states. Both thermal efficiency and effectiveness (exergetic efficiency) have been calculated for the pulse detonation engine and simple gas turbine engine. Comparison shows that for the same pressure ratio pulse detonation engine has better efficiency and effectiveness than the gas turbine system.
Unified Model for Gas-Liquid Pipe Flow via Slug Dynamics—Part 1: Model Development
Authors: Zhang Hong-Quan , Wang Qian , Sarica Cem , Brill James P.
Published: November 2003

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at all inclination angles from −90° to 90° from horizontal. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.
Steady and Dynamic Performance and Emissions of a Variable Geometry Combustor in a Gas Turbine Engine
Authors: Li Y. G. , Hales R. L.
Published: November 2003

One of the remedies to reduce the major emissions production of nitric oxide NOx, carbon monoxide (CO), and unburned hydrocarbon (UHC) from conventional gas turbine engine combustors at both high and low operating conditions without losing performance and stability is to use variable geometry combustors. This type of combustor configuration provides the possibility of dynamically controlling the airflow distribution of the combustor based on its operating conditions and therefore controlling the combustion in certain lean burn conditions. Two control schemes are described and analyzed in this paper: Both are based on airflow control with variable geometry, the second including fuel staging. A model two-spool turbofan engine is chosen in this study to test the effectiveness of the variable geometry combustor and control schemes. The steady and dynamic performance of the turbofan engine is simulated and analyzed using an engine transient performance analysis code implemented with the variable geometry combustor. Empirical correlations for NOx, CO, and UHC are used for the estimation of emissions. Some conclusions are obtained from this study: (1) with variable geometry combustors significant reduction of NOx emissions at high operating conditions and CO and UHC at low operating condition is possible; (2) combustion efficiency and stability can be improved at low operating conditions, which is symbolized by the higher flame temperature in the variable geometry combustor; (3) the introduced correlation between nondimensional fuel flow rate and air flow ratio to the primary zone is effective and simple in the control of flame temperature; (4) circumferential fuel staging can reduce the range of air splitter movement in most of the operating conditions from idle to maximum power and have the great potential to reduce the inlet distortion to the combustor and improve the combustion efficiency; and (5) during transient processes, the maximum moving rate of the hydraulic driven system may delay the air splitter movement but this effect on engine combustor performance is not significant.
Unified Model for Gas-Liquid Pipe Flow via Slug Dynamics—Part 2: Model Validation
Authors: Zhang Hong-Quan , Wang Qian , Sarica Cem , Brill James P.
Published: November 2003

In Zhang et al. [1], a unified hydrodynamic model is developed for prediction of gas-liquid (co-current) pipe flow behavior based on slug dynamics. In this study, the new model is validated with extensive experimental data acquired with different pipe diameters, inclination angles, fluid physical properties, gas-liquid flow rates and flow patterns. Good agreement is observed in every aspect of the two-phase pipe flow.
Low-Liquid Loading Multiphase Flow in Natural Gas Pipelines
Authors: Ayala Luis F. , Adewumi Michael A.
Published: November 2003

Pressure and temperature variations of natural gas flows in a pipeline may cause partial gas condensation. Fluid phase behavior and prevailing conditions often make liquid appearance inevitable, which subjects the pipe flow to a higher pressure loss. This study focuses on the hydrodynamic behavior of the common scenarios that may occur in natural gas pipelines. For this purpose, a two-fluid model is used. The expected flow patterns as well as their transitions are modeled with emphasis on the low-liquid loading character of such systems. In addition, the work re-examines previous implementations of two-flow model for gas-condensate flow.
Finite Element Stress Analysis of Composite Sucker Rods
Authors: Woldesenbet Eyassu
Published: November 2003

Analysis of polymer-matrix composite sucker rod systems using finite element methods is performed. Composite sucker rods used in oil production fail mainly due to fatigue loading. In majority of cases, the failure is in the region of the joint where the composite rod and the steel endfitting meet. 2D and 3D Finite Element Analysis and experimental tests are carried out in order to observe the stress distribution and to find the regions of stress concentrations inside the endfitting. The causes of failure of the composite sucker rods are identified as high transverse compressive stress caused by overloading that results in the crushing of the rod, and high stress concentrations present at the grooves of the endfitting that initiate premature cracks. Based on the result of this study, enhanced design of the composite sucker rod system can be accomplished.
Thermal Processing of Materials: From Basic Research to Engineering
Authors: Jaluria Yogesh
Published: November 2003

This paper reviews the active and growing field of thermal processing of materials, with a particular emphasis on the linking of basic research with engineering aspects. In order to meet the challenges posed by new applications arising in electronics, telecommunications, aerospace, transportation, and other areas, extensive work has been done on the development of new materials and processing techniques in recent years. Among the materials that have seen intense interest and research activity over the last two decades are semiconductor and optical materials, composites, ceramics, biomaterials, advanced polymers, and specialized alloys. New processing techniques have been developed to improve product quality, reduce cost, and control material properties. However, it is necessary to couple research efforts directed at the fundamental mechanisms that govern materials processing with engineering issues that arise in the process, such as system design and optimization, process feasibility, and selection of operating conditions to achieve desired product characteristics. Many traditional and emerging materials processing applications involve thermal transport, which plays a critical role in the determination of the quality and characteristics of the final product and in the operation, control, and design of the system. This review is directed at the heat and mass transfer phenomena underlying a wide variety of materials processing operations, such as optical fiber manufacture, casting, thin film manufacture, and polymer processing, and at the engineering aspects that arise in actual practical systems. The review outlines the basic and applied considerations in thermal materials processing, available solution techniques, and the effect of the transport on the process, the product and the system. The complexities that are inherent in materials processing, such as large material property changes, complicated and multiple regions, combined heat and mass transfer mechanisms, and complex boundary conditions, are discussed. The governing equations for typical processes, along with important parameters, common simplifications and specialized methods employed to study these processes are outlined. The field of thermal materials processing is quite extensive and only a few important techniques employed for materials processing are considered in detail. The effect of heat and mass transfer on the final product, the nature of the basic problems involved, solution strategies, and engineering issues involved in the area are brought out. The current status and future trends are discussed, along with critical research needs in the area. The coupling between the research on the basic aspects of materials processing and the engineering concerns in practical processes and systems is discussed in detail.
Direct Numerical Simulation of Turbulent Heat Transfer Across a
Mobile, Sheared Gas-Liquid Interface
Authors: Lakehal D. , Fulgosi M. , Yadigaroglu G. , Banerjee S.
Published: November 2003

The impact of interfacial dynamics on turbulent heat transfer at a deformable, sheared gas-liquid interface is studied using Direct Numerical Simulation (DNS). The flow system comprises a gas and a liquid phase flowing in opposite directions. The governing equations for the two fluids are alternately solved in separate domains and then coupled at the interface by imposing continuity of velocity and stress. The deformations of the interface fall in the range of capillary waves of waveslope ak=0.01 (wave amplitude a times wavenumber k), and very small phase speed-to-friction velocity ratio, c/u*. The influence of low-to-moderate molecular Prandtl numbers Pr on the transport in the immediate vicinity of the interface is examined for the gas phase, and results are compared to existing wall-bounded flow data. The shear-based Reynolds number Re* is 171 and Prandtl numbers of 1, 5, and 10 were studied. The effects induced by changes in Pr in both wall-bounded flow and over a gas-liquid interface were analyzed by comparing the relevant statistical flow properties, including the budgets for the temperature variance and the turbulent heat fluxes. Overall, Pr was found to affect the results in very much the same way as in most of the available wall flow data. The intensity of the averaged normal heat flux at high Prandtl numbers is found to be slightly greater near the interface than at the wall. Similar to what is observed in wall flows, for Pr=1 the turbulent viscosity and diffusivity are found to asymptote with z+3, where z+ is the distance to the interface, and with z+n, where n>3 for Pr=5 and 10. This implies that the gas phase perceives deformable interfaces as impermeable walls for small amplitude waves with wavelengths much larger than the diffusive sublayers. Moreover, high-frequency fluctuating fields are shown to play a minor role in transferring heat across the interface, with a marked filtering effect of Pr. A new scaling law for the normalized heat transfer coefficient, K+ has been derived with the help of the DNS data. This law, which could be used in the range of Pr=1 to 10 for similar flow conditions, suggests an approximate Pr−3/5 relationship, lying between the Pr−1/2 dependence for free surfaces and the Pr−2/3 law for immobile interfaces and much higher Prandtl numbers. A close inspection of the transfer rates reveals a strong and consistent relationship between K+, the frequency of sweeps impacting the interface, the interfacial velocity streaks, and the interfacial shear stress.
Radiative Heat Transfer Properties of Electro-Controllable Fluids
Authors: Hargrove Jeffrey B. , Lloyd John R. , Radcliffe Clark J.
Published: November 2003

Active control of radiation heat transfer in liquids can be accomplished with the use of a class of fluids referred to here as electro-controllable (EC) fluids. EC fluids in general consist of a colloidal suspension of polarizable, micron-size particles dispersed in a carrier fluid with an appropriate dielectric constant. When an electric field is applied, the particles redistribute in the fluid, changing from a uniformly dispersed configuration to a tightly organized chain formation that follows the lines of the electric field, thus causing a change in the thermal radiation transport. In an example application, experiments are conducted and models are developed for thermal radiation transmittance through a composite window featuring a central layer of EC fluid. The specific EC fluids of this study are made of micron-sized Zeolite particles suspended in a light Silicone oil carrier fluid of appropriate dielectric strength. The incident thermal radiation ranged in wavelength between 500 nm and 800 nm, and the strength of the applied electric field ranged from 100 V/mm to 500 V/mm. The models are applicable for both the dispersed organizational state and the field induced chained state. Absorption was demonstrated to be the fundamental radiation transport property enabling the control process. The EC fluid transmittance predicted by these models are compared to the data obtained by experimental measurement demonstrate very good agreement.
Heat Transfer Characteristics of a Pair of Impinging Rectangular
Flame Jets
Authors: Dong L. L. , Leung C. W. , Cheung C. S.
Published: November 2003

Experiments were carried out to study the heat transfer characteristics of a pair of premixed, laminar, rectangular, butane/air flame jets impinging vertically upon a water-cooled flat plate. The effects of jet-to-jet spacing and the nozzle-to-plate distance on heat transfer were examined. The Reynolds number of the exit flow was 800. The non-dimensional jet-to-jet spacing ranged from 0.9 to 4.1, while the non-dimensional nozzle-to-plate distance varied from 1 to 6. The between-jet interference decreased with increasing jet-to-jet spacing and nozzle-to-plate distance. Both the maximum local and average heat flux occurred at a moderate jet-to-jet spacing of twice effective nozzle diameter, and when the nozzle-to-plate distance was equal to the effective diameter of the nozzle. The heat flux decreased faster along the shorter sides of the slot jets than the longer sides.
Spectral Radiation Properties of Partially Premixed Turbulent Flames
Authors: Zheng Yuan , Barlow R. S. , Gore Jay P.
Published: November 2003

Instantaneous spectral radiation intensities of three standard turbulent jet flames were measured and simulated in this study. In the simulation, a recently developed technique was adapted to reconstruct the local integral time and length scales in the flames. The simulated radiation properties, including mean, root mean square, probability density function, power spectral density and autocorrelation coefficient, were generally within 10% of the measurements. The macro time and length scales were found to increase with increasing distance from the axis and the radial averages of these scales were found to increase with down stream distance but decrease with Reynolds number.
Round Turbulent Thermals, Puffs, Starting Plumes and Starting Jets in
Uniform Crossflow
Authors: Diez F. J. , Bernal L. P. , Faeth G. M.
Published: November 2003

The self-preserving properties of round turbulent thermals, puffs, starting plumes and starting jets, in unstratified and uniform crossflow, were investigated experimentally. The experiments involved dye-containing fresh water (for nonbuoyant flows) and salt water (for buoyant flows) sources injected vertically downward into crossflowing fresh water within a water channel. Time-resolved video images of the flows were obtained using CCD cameras. Experimental conditions were as follows: source exit diameters of 3.2 and 6.4 mm, source Reynolds numbers of 2,500–16,000, source/ambient velocity ratios of 4–35, source/ambient density ratios (for buoyant flows) of 1.073 and 1.150, volumes of injected source fluid (for thermals and puffs) comprising 16–318 source diameters, streamwise (vertical) penetration distances of 0–200 source diameters and 0–13 Morton length scales (for buoyant flows) and crosstream (horizontal) penetration distances of 0–620 source diameters. Near-source behavior varied significantly with source properties and distance from the source but the flows generally became turbulent for streamwise distances within 5 source diameters from the source and became self-preserving for streamwise distances from the source greater than 40–50 source diameters. Crosstream motion satisfied the no-slip convection approximation. Streamwise motion for self-preserving conditions satisfied the behavior of corresponding self-preserving flows in still fluids: round thermals and puffs in still fluids for round thermals and puffs in crossflow and two-dimensional line thermals and puffs in still fluids for round starting plumes and jets in crossflow. The no-slip convection approximation for crossflow motion combined with self-preserving approximations for streamwise motion were also effective for predicting flow trajectories at self-preserving conditions for steady round turbulent plumes and jets in crossflow.
Experimental Study of Low Liquid Loading Gas-Liquid Flow in Near-Horizontal Pipes
Authors: Olive Nicolas R. , Zhang Hong-Quan , Wang Qian , Redus Clifford L. , Brill James P.
Published: November 2003

Gas-liquid two-phase flow exists extensively in the transportation of hydrocarbon fluids. A more precise prediction of liquid holdup in near-horizontal, wet-gas pipelines is needed in order to better predict pressure drop and size downstream processing facilities. The most important parameters are pipe geometry (pipe diameter and orientation), physical properties of the gas and liquid (density, viscosity and surface tension) and flow conditions (velocity, temperature and pressure). Stratified flow and annular flow are the two flow patterns observed most often in near-horizontal pipelines under low liquid loading conditions. Low liquid loading is commonly referred to as cases in which liquid loading is less than 1,100m3/MMm3 (200 bbl/MMscf). Low liquid loading gas-liquid two-phase flow at −1° downward pipe was studied for air-water flow in the present study. The measured parameters included gas flow rate, liquid flow rate, pressure, differential pressure, temperature, liquid holdup, pipe wetted perimeter, liquid film flow rate, droplet entrainment fraction and droplet deposition rate. A new phenomenon was observed with air-water flow at low superficial velocities and with a liquid loading larger than 600m3/MMm3. The liquid holdup increased as gas superficial velocity increased. In order to investigate the effects of the liquid properties on flow characteristics, the experimental results for air-water flow are compared with the results for air-oil flow provided by Meng. (1999, “Low Liquid Loading Gas-Liquid Two-Phase Flow In Near-Horizontal Pipes,” Ph.D. Dissertation, U. of Tulsa.)
Application of Distributed Sensor Arrays for Monitoring Multiphase Processes
Authors: Jaworski Artur J. , Dyakowski Tomasz , Davies Graham A.
Published: November 2003

This paper presents a novel approach to designing sensors and instrumentation for monitoring and controlling multiphase processes. It is based on the use of distributed sensor arrays, embedded within vital plant components, which provides an enhanced method of monitoring multiphase phenomena in both the spatial and temporal sense. This can be of particular importance for a more efficient extraction of fossil fuels and improved energy management in manufacturing sector. Two case studies are provided. First example shows the use of the concept in the separation processes in oil and gas extraction sector, while the second relates to nylon polymerization in the chemical industry.
Improved Green Fluorescent Protein Reporter Gene-BasedMicroplate Screening for Antituberculosis Compounds by Utilizing anAcetamidasePromoter
Authors: Changsen Chartchai , Franzblau Scott G. , Palittapongarnpim Prasit
Published: November 2003

The
green fluorescent protein (GFP) gene offers many advantages as a
viability reporter for high-throughput antimicrobial drug screening.
However, screening for antituberculosis compounds by using GFP driven
by the heat shock promoter,
hsp60
, has been of limited utility
due to the low signal-to-noise ratio. Therefore, an alternative
promoter was evaluated for its enhanced fluorescence during
microplate-based culture and its response to 18 established
antimicrobial agents by using a green fluorescent protein microplate
assay (GFPMA).
Mycobacterium tuberculosis
strains H37Rv, H37Ra, and Erdman were transformed with pFPCA1, which
contains a red-shifted
gfp
gene driven by the acetamidase
promoter of
M. smegmatis
mc
2
155. The pFPCA1
transformants achieved higher levels of GFP-mediated fluorescence than
those carrying the
hsp60
construct, with signal-to-noise
ratios of 20.6 to 27.8 and 3.8 to 4.5, respectively. The MICs of 18
established antimicrobial agents for all strains carrying pFPCA1 in the
GFPMA were within 1 to 2 twofold dilutions of those determined by
either the fluorometric or the visual microplate Alamar Blue assay
(MABA). No significant differences in MICs were observed between
wild-type and pFPCA1 transformants by MABA. The optimized GFPMA is
sufficiently simple, robust, and inexpensive (no reagent costs) to be
used for routine high-throughput screening for antituberculosis
compounds.
Treatment of Intra-Abdominal Abscesses Caused byCandida albicanswith Antifungal Agents and Recombinant MurineGranulocyte Colony-StimulatingFactor
Authors: Vonk Alieke G. , Netea Mihai G. , van Krieken Johan H. , Verweij Paul E. , van der Meer Jos W. M. , Kullberg Bart Jan
Published: November 2003

The aim of the present study was to assess the influence of immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (rmG-CSF) on intra-abdominal abscesses caused byCandida albicans. Mice received prophylaxis or therapy with 1 μg of rmG-CSF/day in the presence or absence of antifungal treatment consisting of amphotericin B (0.75 mg/kg of body weight/day) or fluconazole (50 mg/kg/day). The number ofCandidaCFU in abscesses was significantly reduced (P< 0.05) in mice receiving rmG-CSF prophylaxis (day −1 or day −1 through 2) compared with controls on day 8 of infection. Administration of rmG-CSF therapy alone (for 5 days starting on day 4 of infection) had no influence on the number ofCandidaCFU in abscesses. Amphotericin B treatment was significantly more effective than fluconazole treatment (3.41 log CFU/abscesses; 95% confidence interval [CI], 3.17 log CFU/abscesses; 3.65 versus 3.90 log CFU/abscesses; 95% CI, 3.66 log CFU/abscesses, 4.16 log CFU/abscesses;P< 0.05). Therapeutic administration of rmG-CSF in conjunction with an antifungal agent showed a tendency towards a further reduction ofCandidaCFU in abscesses than antifungal treatment only. In conclusion, in this experimental model of intra-abdominalCandidaabscesses, rmG-CSF administration did not have a detrimental influence on the course of infection. Amphotericin B treatment was most effective, and additional rmG-CSF therapy did not antagonize the effect of antifungal treatment. In contrast, addition of rmG-CSF therapy to antifungal treatment might further enhance the beneficial effect of the antifungal agent.