bluuebunny/crossref_metadata_2025 huggingface dataset:
Grid Aspects of Screw Compressor Flow Calculations
Authors: Kovacevic Ahmed , Stosic Nikola , Smith Ian K.
Published: November 2021

Dynamic flow losses and leakage decrease screw compressor adiabatic efficiency, thereby increasing power consumption. These effects can be determined more precisely by use of Computational Fluid Dynamics analyses to estimate the flow and pressure distribution within them based on 3-D flow patterns. Numerical grids of the suction, compression and discharge chambers were generated by application of a 2-D transfinite interpolation combined with a layer meshing technique in an independent stand-alone CAD-CFD interface program developed by the authors. Flow calculations were then obtained by use of Comet, a commercial CCM solver.
Application of the Small-Scale Combined Heat and Power Installations in the District Heating Systems
Authors: Zwierzchowski Ryszard , Dzierzgowski Mieczysław
Published: November 2021

This paper is concerned with the application of the Small-Scale Combined Heat and Power (SSCHP) installations as a perspective way of the District Heating System (DHS) modernization programs in Poland. The small-scale installations analyzed hereto, mean the installations with an overall capacity (heat plus power generation) of less than 30 MW.

For the purpose of selection of appropriate type and capacity of the SSCHP installation, operational analysis of the DHS and investigation of possible implementation of the Thermal Energy Storage (TES) systems were performed. Also, the criteria for application of the SSCHP installations in the District Heating Plant (DHP) assuring continuous and efficient operation were presented.

Operational analysis of the DHS covered supply and demand side of the annual heat generation and electricity consumption by the DHP and heat consumption by the consumers. Detailed heat consumption analysis during summer season was carried out in order to increase operational time for the SSCHP installations and for investigation of TES systems application in the DHS.

Heat storage in the DHS and its influence on capacity and operation of the SSCHP was also investigated. Heat accumulation by the District Heating Network (DHN) and by the vertical, stratified TES systems were analyzed. Additionally, heat accumulation by the non-pressure TES system was proposed as an alternative to the vertical, stratified TES system.

Finally, results of calculation of the required capacity of the TES systems assuring continuous and efficient operation of the SSCHP installation in the DHS, especially during summer season were shown. Some advantages of the TES system implementation in the DHS in case where the SSCHP installation is applied in the DHP were presented as well.
Heat Transfer in the Regenerator of a Liquid Air Energy Storage System
Authors: Araki Hidefumi , Kitoh Kazuaki , Chino Kooichi
Published: November 2021

An energy storage system that stores energy in the form of liquid air has been studied. In this system, the thermal storage regenerator recovers cold heat from liquid air during the daytime, and it is utilized to produce the liquid air during the nighttime. The energy storage efficiency is greatly improved by the regenerator that consists of steel pipes inserted in a concrete medium. A computer code, that simulates unsteady-state heat transfer between air and a concrete medium, was developed. The calculation results showed the good agreement with the experimental results. The required volume of the concrete regenerator was less than 1/100 of that of reservoirs for a pumped-hydro power station.
Thermodynamic Model of the Loss Factor Applied to Steam Turbines
Authors: Zaleta Alejandro , Vega Luis F. , Gallegos Armando , Hernandez Abel
Published: November 2021

Erosion, roughness, steam path damage, etc., are factors that reduce power capacity in a steam turbine. Any power loss occurring locally in intermediate stages of a steam turbine results in more available energy in the downstream stages, this effect is well-known as the Loss Factor (Salisbury, 1974; Stodola, 1927; Husain, 1984). Currently, the Loss Factor is been calculated by graphical methods (Cotton, 1996). In this work a new thermodynamic expression for the Loss Factor (LF) is introduced, in order to improve applications to evaluate malfunctions in the first and intermediate stages of steam turbines. The new thermodynamic expression for the Loss Factor, is based on Second Law Analysis; and concepts like the internal parameter θ, and the dissipation temperature Td; (Royo, 1992). An Example of a steam turbine in a conventional power plant of 158 MW is analyzed by comparing a classical graphical method (ASME/ANSI PTC-6, 1970; and Cotton, 1993), and the proposed expression of the Loss Factor (LF). Special emphasis is made on the thermoeconomical deviations that could arise by an imprecise application of the Loss Factor Method, during an energy audit of the steam turbine internal parts.
Water and Thermal Management of an Indirect Methanol Fuel Cell System for Automotive Applications
Authors: Eggert Anthony , Badrinarayanan P. , Friedman David , Cunningham Joshua
Published: November 2021

Proton exchange membrane (PEM) fuel cell systems using steam-reformed methanol are currently under consideration for first generation commercial fuel cell vehicles. Proper water and heat management of such a system is critical in achieving high overall efficiency and maintaining water self-sufficiency.

The first part of the paper briefly describes the key aspects of the water and thermal management (WTM) model developed as part of the Fuel Cell Vehicle Modeling Program (FCVMP) at the University of California – Davis. The main purpose of this model was to determine the water self-sufficiency and temperature management requirements of the indirect methanol fuel cell system and to evaluate the associated parasitic losses. This model has imbedded in it the main components of the fuel cell system, such as the fuel cell stack, air compressor, and fuel processor as seen by the WTM system.

The second half of the paper discusses the results obtained from the model and their implications. We find that the cooling and humidification of the anode and cathode inlet streams can be accomplished with water injection and therefore, a separate heat exchanger is not needed for additional cooling. Additionally we find that the instantaneous and cumulative excess water is determined by factors such as air supply characteristics, condenser efficiency, ambient air humidity, and stack attributes. We find that these factors can affect the ability of the vehicle to achieve true water self-sufficiency.
The Full-Spectrum Correlated-K Distribution and Its Relationship to the Weighted-Sum-of-Gray-Gases Method
Authors: Modest Michael F. , Zhang Hongmei
Published: November 2021

A new Full-Spectrum correlated-k distribution has been developed, which provides an efficient means for accurate radiative transfer calculations in absorbing/emitting molecular gases. The Full-Spectrum correlated-k distribution can be used together with any desired solution method to solve gray-medium radiative transfer equations for a small number of gray absorption coefficients, followed by numerical quadrature. It is shown that the Weighted-Sum-of-Gray-Gases model is effectively only a crude implementation of the Full-Spectrum correlated-k distribution approach.

Within the limits of the Full-Spectrum correlated-k distribution model (i.e., an absorption coefficient obeying the so-called “scaling approximation”), the method is exact. This is demonstrated by comparison with line-by-line calculations for a one-dimensional CO2-N2 gas mixture with varying temperature and concentration fields.
An Upwinding Procedure for Numerical Radiation Heat Transfer
Authors: Rousse Daniel R. , Gautier Guillaume , Sacadura Jean-François
Published: November 2021

This paper presents a skewed upwinding procedure for application to the Control Volume Finite Element Method (CVFEM) in the context of radiation heat transfer problems involving participating media. The proposed first order scheme is stable, economical, accurate and it inherently precludes the possibility of computing negative coefficients in the discretized algebraic equations while accounting for the direction of radiant propagation. The suggested first-order skew positive coefficients upwind scheme (SPCUS) is validated by application to several basic test problems, acknowledged by the radiative heat transfer community: its performance has proven to be excellent.
Numerical Modeling of Microporosity Formation in Aluminum-Rich Aluminum-Copper Alloys in Microgravity Conditions
Authors: Xiong M. , Kuznetsov A. V.
Published: November 2021

The microporosity formation in a vertical unidirectionally solidifying Al-4.1%Cu alloy casting is modeled in both microgravity and standard gravity as well as in the conditions of decreased (Moon, Mars) and increased (Jupiter) gravity. Due to the unique opportunities offered by a low-gravity environment (absence of metallostatic pressure and of natural convection in the solidifying alloy) future microgravity experiments will significantly contribute to attaining a better physical understanding of the mechanisms of microporosity formation. One of the aims of the present theoretical investigation is to predict what microporosity patterns will look like in microgravity in order to help plan a future microgravity experiment. To perform these simulations, the authors suggest a novel three-phase model of solidification that accounts for the solid, liquid, and gas phases in the mushy zone. This model accounts for heat transfer, fluid flow, macrosegregation, and microporosity formation in the solidifying alloy. Special attention is given to the investigation of the influence of microporosity formation on the inverse segregation. Parametric analyses for different initial hydrogen concentrations and different gravity conditions are carried out.
Analysis and Design of Soldering Splice in Superconducting Magnets
Authors: Tong Wei , Zhuo Zhang Qing
Published: November 2021

In superconducting magnets, soldering splices are used to connect superconducting cables for providing electrical current paths. One of the main considerations in the splice design is the splice electrical resistance across the joint. High joint resistance can increase the Joule heat generation and thus result in conductor instability.

A finite element analysis has been performed to determine the key parameters affecting soldering splice resistance for superconductors with high purity aluminum stabilizers. The parameters investigated include: high purity aluminum RRR value, copper RRR value, solder layer thickness, magnetic field, splice configuration, and operating temperature. The results obtained from this work can benefit splice cooling and the design optimization.
A Helium II Heat Transfer Level Meter
Authors: Zhang T. , Smith M. R. , Van Sciver S. W.
Published: November 2021

This paper presents the design and measurement techniques for a new type of liquid helium level meter. The measurement principle is given by the change of heat transfer rate with the liquid level. Detailed heat transfer analysis has been done to show the anticipated behavior and accuracy of the meter.

To verify our design, a prototype level meter was fabricated and tested in saturated He II bath with temperature from 1.7 K to 2.0 K. With the experiment, we obtained the relationship between overall heater power and liquid level. The data indicate that the device can measure liquid level with the uncertainty of ±1 mm in a practical system.
A Study of Three-Dimensional Mixed Convective Heat Transfer From Short Vertical Cylinders in a Horizontal Forced Flow
Authors: Scott David A. , Oosthuizen P. H.
Published: November 2021

Heat transfer from relatively short vertical isothermal cylinders in a horizontal forced fluid flow has been considered. The flow conditions are such that the buoyancy forces resulting from the temperature differences in the flow are in general significant despite of the presence of a horizontal forced flow of air, that is, mixed convective flow exists. Because the cylinders are short and the buoyancy forces act normal to the forced flow, three-dimensional flow exists. The experiments were performed in a low velocity, open jet wind tunnel. The study involved the experimental determination of the mean heat transfer coefficient and a comparison of the results with a previous numerical analysis. Mean heat transfer rates were determined using the ‘lumped capacity’ method. The mean Nusselt number has the Reynolds number, Grashof number and the height to diameter ratio of the cylinders as parameters. The results have been used to determine the conditions under which the flow departs from purely forced convection and enters the mixed convection regime, i.e., determining the conditions for which the buoyancy effects should be included in convective heat transfer calculations for short cylinders.
Experimental Investigation of Contact Resistance Across Pressed Lead and Aluminum Contact in Vacuum
Authors: Ma Xiao , Khan Jamil A. , Rhodes Curtis A. , Smith Allen , Hamm L. Larry
Published: November 2021

In a proposed nuclear application (production of Tritium using an accelerator, Accelerator Production of Tritium (APT)) lead is proposed to be used as a shield in the blanket module. This lead will be encased in aluminum cladding. The energy transfer rate from the lead to the cooling water will be a function of the thermal contact resistance (TCR) between lead and aluminum. Presently, data for contact resistance for this application does not exists in the literature. An experimental investigation has been conducted to determine the thermal contact resistance between lead and aluminum in vacuum. In this study we investigate the effect of pressure, surface roughness and interface temperature on the contact resistance.

The experimentally determined range of contact resistance was found to be from 3.74×10−4K-m2/W to 11.45×10−4K-m2/W at 100°C∼200°C under 120∼370psi (0.827∼2.551MPa). The contact resistance increases to 168×10−4K-m2/W at small external pressure of 2.0∼3.9psi (0.013∼0.027MPa). The contact resistance decreases with increasing in contact pressure. Interface temperature and surface roughness do not affect the contact resistance significantly. There is a slight increase in contact conductance with increasing temperature. The experimental results provide contact resistance data, which should be a good reference for the APT design evaluation.
Liquid Crystal Imaging of Surface-Tension-Driven Convection
Authors: Dutton T. W. , Pate L. R. , Hollingsworth D. K.
Published: November 2021

Surface tension forces can drive fluid motion within thin liquid layers with a free surface. Spatial variations in the temperature of the free surface create surface tractions that drive cellular motions. The cells are most commonly hexagonal in shape and they scale on the thickness of the fluid layer. This investigation documents the formation of cells in the liquid film in the presence of a uniform-heat-flux lower boundary condition. Liquid crystal thermography was used to image the cells and measure the temperature distribution on the lower surface of the liquid layer.

A 1.1-mm deep pool of silicone oil was supported on a 50-μm-thick electrically heated metal foil. The oil was retained inside an independently heated acrylic ring mounted on the top surface of the foil, and a dry-ice cooling plate served as the low-temperature sink above the free surface of the oil. Color images of hexagonal convection cells were captured using liquid crystal thermography and a digital image acquisition and processing system. The temperature distribution inside a typical cell was measured using thermographic image analysis. Experimental issues such as the use of an independently heated retaining ring to control the height of the liquid film, and the utility of a flux-based Marangoni number are discussed.
Heat Transfer on a Film Cooled Inlet Guide Vane
Authors: Holmer Marie-Louise , Eriksson Lars-Erik , Sundén Bengt
Published: November 2021

The steady flow and temperature fields around a film cooled inlet guide vane are determined numerically by a CFD method. In particular the outer surface temperatures and heat transfer coefficient distributions are calculated. Static pressure distributions are also presented. The film cooling is achieved by 10 rows of film cooling holes. The computed results are compared with experimental data.

The governing equations are solved by a 3D finite-volume Navier-Stokes solver. The low Reynolds number version of the k-ω turbulence model by Wilcox is implemented to enable calculations of turbulent flow cases. A realizability constraint is applied to reduce the generation of unphysical turbulent kinetic energy, particularly close to the leading edge.

To handle the film cooling process a special procedure is used. An injection model was implemented in the computer code. This injection model adds the mass flow rate passing through the film cooling holes to the main flow as source terms in the equations for mass, momentum, energy and turbulent kinetic energy.

The grid used in the calculations is block-structured, and the total number of grid points is around 250,000.

In a related investigation for the same vane geometry but considering pure convective heat transfer, the authors have investigated the importance of the wall thermal boundary condition. Based on this a conjugate heat transfer approach was applied in this paper. The conjugate heat transfer condition means that the heat transfer coefficient distribution is prescribed on the inner surface of the vane and also the wall thickness and thermal conductivity of the vane material are prescribed. The vane outer surface temperature is then found as part of the numerical solution.

Some essential parameters in the injection model were varied and the calculated results for the vane outer surface temperature were found to compare favourably with measurements. The static pressure distribution on the vane surface agrees well with experiments. The Mach number distribution provides information of the flow field.
A Real-Time Neural Network Estimator for Workpiece Thermal Expansion Errors
Authors: Yoder A. D. , Smith R. N.
Published: November 2021

The importance of predicting and reducing thermal expansion errors in workpieces is becoming greater as better precision machining processes are developed. An artificial neural network model to estimate the workpiece thermal expansion errors in real-time during precision machining operations is developed and compared with experimental results. A finite element model of workpiece thermal expansion has been created to predict expansions in a thin cylinder undergoing a turning process. The neural network has been trained using finite element model solutions over a range of conditions to allow for changing machining parameters. To realize “on-line” capability, the measurable values of heat flux into the workpiece, surface heat transfer coefficient, and tool location are used as inputs and the expansion as the output for the neural network. The estimations of the network are compared with experimental results from a turning process on a large diameter aluminum cylinder. There is reasonable agreement between measured and estimated expansions with an average error of 18%. The neural network has not been trained at the cutting conditions used during the experiment. The speed of the neural network estimation is much greater than the solution to the finite element model. The finite element model required over 15 minutes to solve on a Pentium 133Mhz computer. The neural network calculated the expansions easily at 1 Hz during the experiment on the same computer. With real-time estimation using measurable data, compensation can be made in the tool path to correct for these errors. The application of this method to precision machining processes has the capability of greatly reducing the error caused by workpiece thermal expansions.
Modeling of Interphase Formation on Unsized Fibers in Thermosetting Composites
Authors: Yang Fuzheng , Pitchumani Ranga
Published: November 2021

The interphase is the region between the fiber and matrix whose properties strongly influence the overall composite behavior in terms of mechanical strength, chemical and thermal durability. The composition and thickness of the interphase region is governed by the processing conditions, in addition to the fiber surface treatments and other characteristics of the fiber and the resin materials. One of the strong contributing mechanisms to interphase formation is the preferential adsorption of matrix components onto the fiber surface, which takes place on the order of molecular scales. Chemical reaction in the matrix also happens simultaneously with the adsorption process. In this paper, a multi-layer adsorption-desorption-reaction model for a binary fluid mixture in contact with a solid surface is implemented to study the kinetics of interphase formation near bare fiber surfaces in thermosetting composite systems. Composition and thickness evolution of the interphase are predicted as functions of time. Conditions that lead to interphase formation upon vitrification are identified. Parametric studies are presented to investigate the effects of various nondimensional groups on the interphase region development.
Splashing of a Small Droplet Impinging on a Solid Surface at High Velocity
Authors: Mehdizadeh N. Z. , Chandra S. , Mostaghimi J.
Published: November 2021

We photographed water droplets (550 μm diameter) as they impacted on a stainless steel surface. We varied droplet impact velocity (10–40 m/s) and the average surface roughness (0.03–0.23 μm) of the steel plates used as test surfaces in our experiments. A piezoelectric droplet generator was used to produce water droplets. The stainless steel substrate was mounted on the end of a rotating arm, giving linear velocities of up to 40 m/s. A CCD video camera was used to photograph droplets impinging on the substrate. By synchronizing the ejection of a single droplet with the position of the rotating arm and triggering of the camera, different stages of droplet impact were photographed. From these photographs we measured the size of droplets as they spread. It was observed that as the impact velocity increased, finger-shape perturbations around the spreading droplet became longer and narrower. At sufficiently high velocities the tips of these fingers detached, producing satellite droplets. Increasing surface roughness was found to promote splashing and reduce the velocity at which splashing was first observed. By increasing surface roughness, both the number of fingers and the maximum extent of spreading were decreased. At high impact velocities the spreading liquid film became so thin that it ruptured in several places.
Saturated Pool Boiling Mechanisms During Single Bubble Heat Transfer: Comparison at Two Wall Superheats
Authors: Kim Jungho , Demiray Fatih , Yaddanapudi Nagaraja
Published: November 2021

A study of single bubbles growing on a microscale heater array kept at nominally constant temperature was performed. The behavior of bubbles nucleating at a single site at two different temperatures (22.5 K and 27.5 K superheat) is compared for saturated pool boiling of FC-72 at 1 atm. It is concluded that energy is transferred from the surface through similar heat transfer mechanisms at both superheats. Microlayer evaporation was observed to play a minor role in the overall heat transfer, with microconvection/transient conduction being the dominant mechanism. Evaluation of various heat transfer models are made.
Numerical Solution of Thermal and Fluid Flow With Phase Change by VOF Method
Authors: Shirakawa Hidemi , Takata Yasuyuki , Ito Takehiro , Satonaka Shinobu
Published: November 2021

Numerical method for thermal and fluid flow with free surface and phase change has been developed. The calculation result of one-dimensional solidification problem agrees with Neumann’s theoretical value. We applied it to a bubble growth in superheated liquid and obtained the result that a bubble grows with spherical shape. The present method can be applicable to various phase change problems.
Numerical Investigation of Marangoni Convection Around a Vapor Bubble in Aqueous Surfactant Solutions
Authors: Wasekar Vivek M. , Manglik Raj M. , Jog Milind A.
Published: November 2021

The effect of surfactant concentration on the Marangoni convection around vapor bubbles has been numerically investigated. The model consists of an adiabatic, hemispherical bubble on a downward facing constant temperature heated wall, in a fluid pool with an initial uniform temperature gradient. The time-dependent liquid mass, momentum, energy, surfactant bulk and surface transport, and adsorption kinetic rate equations are solved simultaneously. Conditions for bubble sizes varying from boiling nuclei to growing bubbles, and different surfactant bulk concentrations and wall heat flux levels are represented by a range of Marangoni and Rayleigh numbers: 100 ≤ MaT ≤ 6000, 0 ≤ MaS ≤ 2.2×106, 0 ≤ Ra ≤ 2.2. In the early transients, liquid motion is found to be induced by the temperature non-uniformity over the bubble surface, which along with self-diffusion, transports surfactant molecules from the bulk liquid towards the bubble surface. Consequently, the surface excess concentration is higher at the bubble base and decreases along the interface towards the bubble crown. The resulting concentration gradients promote diffusocapillary flows, which act in the same direction as the temperature-gradient induced thermocapillary flows, thereby enhancing the convection significantly. Also, for conditions representing boiling nuclei (in both partially and fully developed boiling regimes), the initial time transients appear to be heat flux independent.
Buoyancy-Induced Convection in Metal Foam and Finned Metal Foam Heat Sinks©
Authors: Bhattacharya A. , Mahajan Roop L.
Published: November 2021

In this paper, we present our recent experimental results on buoyancy induced convection in metal foams of different pore densities (corresponding to 5, 10, 20 and 40 pores per inch) and porosities (0.89–0.96). The results show that compared to a hot surface facing up, the heat transfer coefficients in these heat sinks are 5 to 6 times higher. However, when compared to commercially available heat sinks of similar dimensions, the enhancement is found to be marginal. The experimental results also show that for a given pore size, the heat transfer rate increases with porosity suggesting the dominant role played by conduction in enhancing heat transfer. On the other hand, if the porosity is held constant, the heat transfer rate is found to be lower at higher pore densities. This can be attributed to the higher permeability with the larger pores, which allows higher entrainment of air through the porous medium. An empirical correlation, developed for the estimation of Nusselt number in terms of Rayleigh and Darcy numbers, is found to be in good agreement with the experimental data with a maximum error of 10%.

We also report our results on novel finned metal foam heat sinks© in natural convection. Experiments were conducted on aluminum foams of 90% porosity with 5 and 20 PPI (pores per inch) with one, two, and four aluminum fins inserted in the foam. All these heat sinks were fabricated in-house. The results show that the finned metal foam heat sinks© are superior in thermal performance compared to the normal metal foam and conventional finned heat sinks. The heat transfer increases with increase in the number of fins. However, the relative enhancement is found to decrease with each additional fin. The indication is that there exists an optimum number of fins beyond which the enhancement in heat transfer due to increased surface area is offset by the retarding effect of overlapping thermal boundary layers. Similar to normal metal foams, the 5 PPI samples are found to give higher values of the heat transfer coefficient compared to the 20 PPI samples due to higher permeability of the porous medium. Future work is planned to arrive at the optimal heat sink configuration for even larger enhancement in heat transfer.
Cooling of Thermal Enhanced BGA Package Using Foam Metal Heat Sinks
Authors: Hwang Jenn-Jiang , Chao Chung-Hsing
Published: November 2021

This study reported thermal performance of a thermally enhanced plastic ball grid array (PBGA), namely T2-BGA™ which incorporates a heat slug in package, with a foam-metal heat sink on the top of this package. Experimental measurement of junction-to-ambient thermal resistance is performed in accordance with the SEMI standards of G38-0996 and G42-0996 for thermal characterization of BGA packages. Allowable power dissipation is subject to the constraint of junction temperature (Tj) at 95°C and ambient temperature (Ta) in chassis at 35 °C under free and forced air (0 ∼ 3 m/s) conditions. Based on this constraint, allowable power dissipation of a regular PBGA with a commercial pin fin heat sink under free and 3 m/s forced air is 5.45 W and 9.17 W compared with those of T2-BGA with a foam heat sink of 6.80 W and 19.6 W respectively. This results show that T2-BGA™ with a foam heat sink offers enormous potential to high power package applications.
Numerical Investigation of the Steady State Operation of a Cylindrical Capillary Pumped Loop Evaporator
Authors: Yan Y. H. , Ochterbeck J. M.
Published: November 2021

A two-dimensional numerical model was established to study the behavior of a cylindrical capillary pumped loop evaporator under steady-state operations. The influence of heat load, liquid subcooling and effective thermal conductivity of the wick structure on the evaporator performance were studied. It was found that increasing the applied heat flux and degree of liquid subcooling resulted in a decrease the temperature in the liquid core. This helped to prevent the vapor from generating in the liquid core and decreased the length of the two phase region in the wick structure. Decreasing the effective thermal conductivity also decreases the temperature in the liquid core as related to the back wick condition. It was observed that for a given liquid subcooling, a minimum heat flux exists below which vapor will generate in the liquid core and render the evaporator non-operational. It was also observed that for a given heat flux, a minimum required liquid subcooling exists. Vapor may form in the liquid core when the liquid subcooling is less than the minimum value.
Numerical Modeling of Steam Injection Into Saturated Porous Media
Authors: Kaslusky Scott F. , Udell Kent S. , McCreery Glenn E.
Published: November 2021

The Steam Enhanced Extraction (SEE) process is being considered for removal of volatile organic contaminants contained in the fractured basalt rocks which lie above the Snake River aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL). In this work the computer code M2NOTS (Multiphase Multi-component Non-isothermal Organic Transport Simulator) was used to simulate an experiment which tracked the movement of a steam condensation front through glass blocks separated by glass beads. The experiment was designed to represent steam injection into highly fractured basalt. For grid spacing equal to the block size heat transfer from the fractures to the blocks was severely under predicted, resulting in an over prediction of the condensation front velocity. A method was developed to accurately simulate the propagation of a steam condensation front through a fractured porous media using grid spacing equal to the block dimension. The method accounts for non-equilibrium conduction within a grid node, allowing the grid spacing to be increased well beyond the local equilibrium restriction. Simulation results compare well with the experimental results, validating the non-equilibrium model, and also indicating that M2NOTs can be effectively used to model the steam enhanced extraction process in fractured porous media.
Optimum Design of Chills in the Sand Casting Process
Authors: Manzari M. T. , Gethin D. T. , Lewis R. W.
Published: November 2021

A re-meshing free algorithm is presented for optimizing the size and shape of chills in a sand casting process. The heat conduction in each chill is assumed to be one-dimensional normal to its contact surface. The chill is removed from the casting layout and replaced with heat fluxes applied on the associated mould and casting interfaces. The change in size and shape of the chill is modeled by moving the borders of the interface contact regions. A change in thickness of the chill is also included using a parameter which controls the magnitude of the interface heat fluxes and implies the thermal capacity of the chill. The model is linked to an optimization tool to search for the optimum set of dimensions of the chill that produces a prescribed directional cooling in the casting. A test case is solved to demonstrate the capability of the proposed algorithm in optimizing chill design in complex geometries.
New Finite Element Modeling Strategy for Large-Scale Industrial Problems in Structural Acoustics
Authors: Dey Saikat , Couchman Luise S.
Published: November 2021

A simple scheme to model and mesh stiffened shell-like structures is presented. Combined with a high-order finite/infinite element based infrastructure, it enables the solution of complex structural acoustics problems at high wave numbers. Numerical examples are presented to show the applicability of the method at high wave-numbers.
Modeling the Space-Time Correlations in the Wake Region of a Turbulent Boundary Layer
Authors: Gavin Joseph R. , Lauchle Gerald C.
Published: November 2021

An empirical turbulence model has been developed for boundary layer flows. The goal is to simulate the statistical behavior of turbulent velocity fluctuations in both space and time using the two-point correlation field.

The new model is based on physical concepts from earlier measurements and flow visualizations. In particular, it is useful to think of packets of turbulent fluid that are angled to towards the wall and convect with a velocity similar to the local mean. However, the actual behaviors which exist are complicated and sometimes quite subtle (but physically important). For instance, measurements show that the correlation field is only strongly peaked at zero time delay. This is interpreted in wavenumber space as a rapid decorrelation of the small scale eddies, and is modeled in a way that captures the transition.

The new turbulence model has been calibrated using recent measurements and is now available for general studies. Efforts are underway to refine the model, improve its theoretical basis, and confirm its application to high Reynolds number flows.
Acousto-Optic Sensors for Real-Time, Wide-Area Inspection of Advanced Materials and Components
Authors: Sincebaugh Patrick J. , Sandhu Jaswinder S. , Wang Honghui , Popek Witold J.
Published: November 2021

The objective of this paper is to provide details on the development of a novel acousto-optic sensor that can be utilized to nondestructively evaluate materials and components in near real-time. The acousto-optic sensor, which is the basis for Acoustography, provides wide-area, near real-time ultrasonic attenuation maps that can be analyzed to detect anomalies such as cracks, delaminations, and porosity. Details on applying Acoustography to inspect complex shaped parts will be provided. Future work in the area of Acoustography will also be presented.
Chlorination in Combustion Systems
Authors: Tsang Wing , Babushok Valeri
Published: November 2021

This paper is concerned with the formation of polychorinated organics in the gas phase in combustion systems. The results are derived from simulation studies with inputs from the fundamental kinetics of single step thermal gas phase reactions. Attention is focussed on the case where initial chlorine loading is low. It is shown that in a well mixed system high degrees of chlorination are difficult to attain due to the decrease in thermal stability with chlorination. A hypothesis for their formation as a consequence of chlorine formation during lean combustion followed by chlorination of organics as a result of the mixing and quenching of the products from rich combustion is tested. Under such conditions the competition between oxidation and chlorination of intermediates governs the final product distribution. The stability of propargyl radicals (C3H3) to oxidation makes chlorination of its products a preferred mode and results have been obtained where more highly chlorinated compounds are found in the products. Since this radical is a known precursor to benzene formation, this provides a direct route for the formation of polychlorinated benzenes. The scenario presented here extends regions for possible gas phase chlorination into the exhaust system of combustors.
CFD Modeling of NOx Reduction Technologies in Utility Boilers
Authors: Cremer Marc A. , Adams Bradley R. , Wang David H. , Heap Michael P.
Published: November 2021

This paper discusses the development and application of CFD modeling tools that have been utilized to assess and design NOx reduction systems that are currently being evaluated by the electric utility industry. Stringent limits on NOx emissions have been imposed by the Clean Air Act Amendments, and a number of NOx reduction technologies are available to help meet these limits including selective noncatalytic reduction (SNCR) and reburning, as well as various combinations of these. This paper discusses the development and implementation of global and reduced chemical mechanisms for NOx formation/destruction into a comprehensive CFD code so that these various options for NOx control can be evaluated. Also, some examples showing the application of these tools to full-scale utility boilers utilizing low-NOx burners, air staging, and SNCR are presented.
Simulations of Transonic Diffuser-Volute System Using Hybrid Unstructured CFD
Authors: Hosangadi A. , Ahuja V. , Lee Y. T.
Published: November 2021

Simulations for a vaneless diffuser-volute configuration at transonic flow conditions are presented using a multi-element unstructured CFD code CRUNCH. The unstructured framework permits the generation of a contiguous grid without internal boundaries between the diffuser-volute interface, and also provides good local resolution around the cut-water region. The increased numerical stability resulting from these factors coupled with the parallel solution framework yields an efficient solution procedure. Numerical results indicate good comparison with experimental data for the baseline geometry where the measured performance was below the design prediction.
A Numerical Investigation on the Volute/Diffuser Interaction due to the Axial Distortion at Impeller Exit
Authors: Gu Fahua , Engeda Abraham , Cave Mike , Di Liberti Jean-Luc
Published: November 2021

A numerical simulation is performed on a single stage centrifugal compressor using the commercially available CFD software, CFX-TASCflow. The steady flow is obtained by circumferentially averaging the exit fluxes of the impeller. Three runs are made at design condition and off-design conditions. The predicted performance is in agreement with experimental data. The flow details inside the stationary components are investigated, resulting in a flow model describing the volute/diffuser interaction at design and off-design conditions. The recirculation and twin vortex structure are found to explain the volute loss increase at lower and higher mass flows, respectively.
Mesoscale Analysis of Porous Shape Memory Alloys
Authors: DeGiorgi Virginia G. , Qidwai Muhammad A.
Published: November 2021

Shape memory alloys are frequently used in smart materials and structures as the active component. Their ability to provide high force and large displacements has been used to the advantage in many applications. The majority of applications to date utilize solid shape memory alloy materials in quasi-static loading conditions. Recent work has proposed the use of porous SMAs as an energy absorbing material under dynamic loading conditions. The use of porous SMAs under dynamic loading will require advancements in the understanding of SMA behavior both in the dense or solid form and in the porous form. The current work examines the quasi-static behavior of porous SMA as a first step. The material behavior is modeled on a mesoscale level allowing for the examination of pore size and shape variation effects. Bulk material response is estimated and compared with micromechanical periodic unit cell predictions.
Wind-Tunnel Determination of Aeroelastic Response of Piezoelectric and Aileron Controlled 3-D Wing
Authors: Suleman Afzal , Crawford Curran A. , Costa António P.
Published: November 2021

This paper presents the results of wind tunnel testing performed on a true three dimensional adaptive wing structure. The focus of this study was to test the aeroelastic response and control of a wing built with conventional stressed skins. The aeroelastic performance of the wing using traditional aerodynamic surface control methods is compared to the results obtained using piezoelectric actuators on the skins of the wing. Results are presented for the system identification, free stream vibration and buffeting tests performed in the wind tunnel. The design of the adaptive wing and control interface is discussed in addition to the experimental setup.
Study of Microstructure in 0.9PMNTa-0.1PT Ceramics
Authors: Wang Jin T. , Tang Feng
Published: November 2021

Ta-Doping effect on the microstructure of lead magnesium niobate-lead titanate crystalline solutions 0.9PbMg1/3(Nb(1−x)Tax)2/3O3-0.1PbTiO3(PMN-PT) have been firstly investigated in this paper. Scanning Electron Micrographs (SEM) were taken from fractured surfaces of the samples with different additives of x = 0.0, 0.1, 0.2, 0.3 and 1.0 by Hitachi F-2460N microscope operating at an accelerating voltage of 25kV. The chemical content analysis for the synthesized samples performed on JEOL Super Prob733 Energy Perspective Spectrum. The x-ray diffraction was carried out with a Siemens D5000 Dual Diffraction Meter. It is clearly evident that doping Ta in PMNTa-PT can affect the grain size and density of the compounds. Smaller grain size (3.1μm) is formed in the specimens with the additives of x = 0.1, 0.2 and 0.3 in comparison with those of the specimens without doping (6.6μm) or over doping (6.4μm). The porosity at grain intersections increase with increasing of additive tantalum for niobium site in 0.9PMNTa-0.1PT. Larger grain size (6.4μm), greater non-uniformity and more inter-granular voids are found in the compound, if tantalum completely substitutes niobium (x = 1). No non-reacted starting regents were observed in any of the compositions mentioned above.
Damage Detection Using Piezoelectrics Modal Analysis and PSD Technique
Authors: Liberatore Sauro , Carman Gregory P.
Published: November 2021

A damage detection method has been implemented on a simply supported beam structure. The method is developed with both a theoretical model and experimental results. The simply supported beam contains one piezoelectric actuator and one piezoelectric sensor. The theoretical model was obtained from an energy formulation and a Rayleigh-Ritz approach. Matrices were composed in a State Space model to reproduce the input-output system between actuator and sensor. The damage was modeled with material properties variations. The experimental set up consisted of an aluminum beam with damage introduced by adding different weights in various locations. The dynamic changes produced were investigated and compared with theoretical prediction with reasonable agreement obtained. In order to quantify the size of damage, Power Spectral Density approach was used. To locate damage, frequency changes were used.
Autonomous Vibration Suppression Using On-Line Pole-Zero Identification
Authors: McEver Mark , Leo Donald J.
Published: November 2021

An on-line identification and control algorithm is developed based on the properties of collocated sensing and actuation. The feedback control law consists of second-order compensators that achieve equivalent damping in both the filter dynamics and resonant structural dynamics, thus maximizing the damping in the structure and controller. Optimal design of the feedback compensator is obtained using a pole placement algorithm applied to a single, undamped resonant mode. Numerical analysis indicates that multiple modes and structural damping do not appreciably change the damping achieved using the optimal parameters. The pole placement analysis demonstrates that only the pole-zero spacing and DC gain of the collocated transfer function are required to choose the optimal parameters. An on-line identification procedure is developed that sequentially determines the DC gain and pole-zero spacing and automatically designs the feedback compensator. This forms the basis for the autonomous control algorithm. Experimental results on a flexible beam demonstrate that the procedure can accurately identify the pole-zero spacing and automatically design the feedback compensator. A fivefold increase in damping is achieved in the first mode and a twofold increase in damping is achieved in the second mode. Discrepancies between predicted and measured damping are attributed to phase lags due to signal conditioning and low-pass filtering of the sensor signal.
Piezoceramic Hysteresis in the Adaptive Structural Vibration Control Problem
Authors: Lee Soon-Hong , Ozer M. Bulent , Royston Thomas J.
Published: November 2021

Structural vibration control via passive electrical shunting and active (hybrid) actuation of a piezoceramic wafer bonded onto the surface of a simply supported beam is investigated with emphasis on modeling and understanding the effect of piezoceramic nonlinearity on system performance. A nonlinear rate-independent hysteresis model, the Maxwell resistive-capacitor (MRC) model, is experimentally identified for the PZT wafer by itself and then integrated into the coupled dynamic equations of the overall system consisting of the beam and electrically shunted PZT wafer. Experimental studies of the system validate the theoretical model. This model is then used to investigate the impact of PZT hysteresis on its vibration control performance in passive and hybrid scenarios that have been optimized based on a linear system assumption. A multi-term describing function representation of the MRC hysteresis model is formulated to aid in computational studies.
Workpiece Quality Estimation in Turning by Quasi-Sensor Fusion
Authors: Shiraishi Masatake , Kikuchi Makoto , Sumiya Hideyasu
Published: November 2021

Two types of sensor fusion approaches are reported for quality assurance based on the decision making process via the sensor fusion technique: quasi-sensor fusion with several data-processed signals from a single sensor and general sensor fusion using multiple sensors. The former method may be expected to provide new information about an object to be measured from a single sensor, i.e., a strain gauge in this study. The latter method with a tool dynamometer and a strain gauge is, on the other hand, important on a practical production floor for real in-process measurement. Experimental results show the effectiveness of both techniques.
Application of the Radial Return Method to Compute Stress Increments From Mroz’s Hardening Rule
Authors: Tang Sing C. , Xia Z. Cedric , Ren Feng
Published: November 2021

It is well known in the literature that the isotropic hardening rule in plasticity is not realistic for handling plastic deformation in a simulation of a full sheet metal forming process including springback. An anisotropic hardening rule proposed by Mroz is more realistic. For an accurate computation of the stress increment for a given strain increment by using Mroz’s rule, the conventional sub-interval integration takes excessive computing time. This paper proposes the radial return method to compute such stress increment for saving computing time. Two numerical examples show the efficiency of the proposed method. Even for a sheet model with more than 10000 thin shell elements, the radial return method takes only 40% of the overall computing time by the sub-interval integration.