bluuebunny/crossref_metadata_2025 huggingface dataset:
Lift Force of Delta Wings
Authors: Lee Mario , Ho Chih-Ming
Published: March 2013

On a delta wing, the separation vorticies can be stationary due to the balance of the vorticity surface flux and the axial convection along the swept leading edge. These stationary vortices keep the wing from losing lift. A highly swept delta wing reaches the maximum lift at an angle of attack of about 40°, which is more than twice as high as that of a two-dimensional airfoil. In this paper, the experimental results of lift forces for delta wings are reviewed from the perspective of fundamental vorticity balance. The effects of different operational and geometrical parameters on the performance of delta wings are surveyed.
Inverse Design and Active Control Concepts in Strong Unsteady Heat Conduction
Authors: Dulikravich George S.
Published: March 2013

A summary of recent research in the field of inverse design and optimization of coolant flow passages in the internally cooled configurations is presented. The methodology allows design engineers to prescribe desired surface temperature and heat flux distributions and to fix portions of the multiply connected realistically shaped configurations. The shapes of the resulting coolant flow passages can be arbitrarily or circularly shaped with a capability to maintain certain manufacturing geometric constraints. Unsteady cooling of organs and tissues in bioengineering is demonstrated by determining optimal time variation of thermal boundary conditions on the walls of the cooling container while maintaining the geometry and size of the configuration. Another concept suggests that components subjected to strong unsteady cooling or heating can be optimized for the desired time dependent overspecified surface thermal conditions by determining the corresponding instantaneous temperatures of the coolant flow passages. This effect can be achieved by applying optimal control of distributed coolant flow rates in each flow passage.
Measured Characteristics of a Journal Bearing Oil Film
Authors: Parkins D. W.
Published: March 2013

This paper presents the results obtained from two experimental methods of measuring the nonlinear characteristics of the eight coefficients which specify the lateral flexibility of a hydrodynamic journal bearing. Measured coefficients are given for both positive and negative discursion of the relevant journal center velocity or displacement from the static equilibrium position which occupied a range of eccentricity ratios. Coefficients are expressed in terms of a “zero” value and linear gradient. No difference was established between displacement coefficients deduced from the two experimental techniques. All zero velocity coefficients were found to be invariant with eccentricity ratio within 0.779 to 0.87, but to vary inversely with vibration/rotation frequency ratio. Eccentricity ratio was found to affect only zero displacement coefficients associated with vertical discussion, when greater than 0.87. Displacement coefficient gradients are shown to be only influenced by eccentricity ratio when the same is greater than 0.78. When possible, comparisons are made with other published results.
Temperature Gradients Through EHD Films and Molecular Alignment Evidenced By Infrared Spectroscopy
Authors: King V. W. , Lauer J. L.
Published: March 2013

Partial and complete emission band reversals have been observed in the infrared emission spectra from portions of operating sliding contacts. An elementary analysis has been carried out to show that partial reversals are due to temperature gradients in the fluid film—the film acts both as a radiation-emitter and absorber, and that total reversals—an emission spectrum appears as an absorption spectrum—are likely to be due to a continuum source, such as hot solid asperities. The total energy radiated under the latter conditions exceeds that under the others. A decrease in gap width with increased load was accompanied by a dramatic spectral change in the case of 5P4E polyphenyl ether, which is indicative of molecular alignment.
The Rotational Accuracy Characteristics of the Preloaded Hollow Roller Bearing
Authors: Bhateja C. P. , Pine R. D.
Published: March 2013

The rotational characteristics of the cageless, hollow roller radial bearing are investigated. The preloading of the hollow rolling elements in the annular space between the inner and the outer races in such a bearing provides a well controlled and consistent shaft rotational pattern. This pattern is determined by the dimensional and geometrical features of the rollers’ external and internal diameters and roundnesses, the outer and inner ring raceway roundnesses and the eccentricity of the inner race with respect to the shaft axis. The various patterns of shaft runout associated with these causes are identified and the sensitivity of the shaft runout to these factors is examined qualitatively and quantitively. The shaft runout in the present context is not merely the initial static offset of the shaft axis, but is a dynamic, cyclic pattern consisting of certain frequencies resulting from the geometrical features of the bearing components. The somewhat elusive, complex and dynamic nature of this apparent shaft runout makes it difficult to be measured. In addition, the importance of the need to control the circumferential clearance to a minimum is demonstrated. It is thus shown that through the proper control of the component geometry and certain design parameters, the hollow roller bearing can provide an extremely accurate bearing for precision applications.
The Role of Elastic Tangential Compliance in Oblique Impact
Authors: Maw N. , Barber J. R. , Fawcett J. N.
Published: March 2013

An extension of the Hertz theory of impact to the oblique impact of elastic bodies with circular contact is outlined. The tangential compliance of the contact surface under the action of Coulomb friction is shown to have a significant effect on the rebound angles, if the local angle of incidence does not greatly exceed the angle of friction. Experiments are described in which the trajectory of a moving body is measured before and after impact with a fixed block of similar material. Results obtained using both steel and rubber show good agreement with the theoretical values.
A Model of Lubrication Filtration
Authors: Tichy J. A.
Published: March 2013

Despite its obvious economic importance, the filtration process has seldom, if ever, been scientifically studied from the perspective of tribology. It is not well known among tribologists that a theory of filtration has been developed over some 50 years and is currently used with success in environmental engineering for the filtration of water and aerosols. This approach forms the basis for the present work. The filter porous medium is modeled as an array of spherical “collectors.” Forces and moments are balanced on a contaminant particle suspended in the fluid flowing through the array. Solution of the resulting equations yields the particle trajectories. Filtration capture efficiency is then the fraction of particles entering the filter which ultimately collide with a collector. For tribology applications, forces and moments on a particle are due to viscous fluid friction and van-der-Waals effects, the latter providing the final adhesive capture forces. Efficiency is predicted as a function of filter depth, porosity, and grain size; fluid viscosity; and particle size. Results agree qualitatively with the known behavior of filters. As opposed to existing empirical models, the effect of variable changes can be predicted, and the proposed model does not depend on a particular particle size distribution.
Friction—The Present State of Our Understanding
Authors: Tabor David
Published: March 2013

This paper presents a general critical picture of our present understanding of the frictional process. In particular it emphasizes the three main elements involved, namely the true area of contact, the nature and strength of the inerfacial bonds formed at the regions of contact, and the way in which the material around the contacting regions is sheared and ruptured during sliding. Most of the paper deals with metals but reference is also made to ceramics, lamellar solids, polymers, and elastomers. The paper concludes with a discussion of areas where further progress is desirable.
The Behavior of Adhered Fragments Interposed Between Sliding Surfaces and the Formation Process of Wear Particles
Authors: Sasada Tadashi , Norose Susumu , Mishina Hiroshi
Published: March 2013

To study the behavior of adhered fragments on rubbing surfaces, the transverse movement of a slider is measured and recorded during the wear process. The gap between the mating surfaces is enlarged gradually through the origin and growth of a transfer particle adhering to the slider and then closed suddenly by the removal of the particle. The removal process of wear particles can be observed by an optical microscope. Furthermore, an X-ray microanalysis is made on the cut section of the rubbing system just before the removal of the particle. The particle is press-slide flattened in shape and has a hair line mixed structure containing metals of both mating surfaces. The maximum lift of the slider is nearly equal to the size of the produced particle. These observations show that the adhered fragments are piling up and are being press-slide flattened between the mating surfaces until their final removal as wear particles.
Frictional Properties of a Surface Covered With a Soft Metal Film—Part 1: Experiments on Friction Between a Single Protuberance and a Surface
Authors: Kato S. , Yamaguchi K. , Marui E. , Tachi K.
Published: March 2013

Frictional properties in the contact between a hard protuberance and a metal surface covered by a soft thin metal film are examined experimentally. The protuberance used in the experiment is a hard steel ball which simulates asperities on many engineering surfaces. The load dependency of the coefficient of friction and the effects of thickness and hardness of the film on the friction are clarified. The simple empirical expression of friction, which represents the effect of the film properties, is presented, considering the deformation mechanism of the surface film.
Contact Temperature in Dry Bearings. Three Dimensional Theory and Verification
Authors: Floquet A. , Play D.
Published: March 2013

Boundary conditions were arbitrarily specified in an earlier two dimensional (2D) analysis of contact temperature. In this new work a general three dimensional (3D) Fourier transform solution is obtained from which for specific cases, the boundary conditions can be estimated. Further, experimental verification of 3D analysis was performed using infra-red technique.
Antiwear Mechanism of ZDDP in the Presence of Calcium Sulfonate Detergent
Authors: Kapsa Ph. , Martin J. M. , Blanc C. , Georges J. M.
Published: March 2013

Interactions between zinc dithiophosphate (ZDDP) antiwear additive and commercial calcium sulfonate detergent are studied using a plane/plane contact configuration friction machine lubricated under boundary conditions. Comparative tests have allowed us to envisage three types of interactions, respectively, due to, — first: chemical interaction between both additives in the oil phase leading to an effective ZDDP concentration decrease. — second: detergent effect due to the presence of the calcium sulfonate surfactant molecule, preventing basal materials from agglomerating during running. — third: specific role due to the overbasing agent, considered as a colloidal dispersion. When an overbased detergent is used, the two latter contributions are predominant. This study suggests that a new approach in boundary lubrication should be envisaged in relation to the evolution of the interface products which must be regarded as a highly concentrated colloidal system.
Failure of Thin Film Lubrication—An Expedient for the Characterization of Lubricants
Authors: Tabor B. J.
Published: March 2013

A method has been developed to characterize lubricants, starting from the failure of thin film lubrication in sliding concentrated steel contacts. For a number of lubricants, differing in viscosity and chemical composition, the collapse of the partial EHD film is taken as a criterion of the lubrication behavior. The contribution of viscosity and chemical composition of lubricants to the load carrying capacity of the partial EHD film at a speed of 1 m/s (P1) can be separated. This is achieved by plotting the value P1 as a function of the logarithm of the bulk viscosity (η). The following linear empirical relation P1 = β log η + α is found to be valid within the viscosity range of 2–200 • 10−3 Pa.s. Lubricants with the same chemical composition have an equal value of α.
Analysis Method for Both Internal Stresses and Microstructural Effect Under Pure Rolling Fatigue Conditions
Authors: Dudragne G. , Fougeres R. , Theolier M.
Published: March 2013

For pure rolling fatigue conditions, the effect of microstructural changes and internal stresses due to grinding and fatigue processes itself was studied. Using Sachs’ method, the field of internal stresses was determined and it has been shown that its evolution is correlated with microstructural changes. These microstructural changes lead to changes in mechanical properties, especially to the reversible strain limit stress (R.S.L.S.) which has been determined in each point of the subsurface contact. Assuming a given relation between R.S.L.S. and fatigue limit, and using fatigue criterion which includes R.S.L.S., the effect of internal stresses, microstructural evolution, and Hertz stresses was analyzed. It has been found that the grinding internal stresses have no significant effect. On the contrary, the R.S.L.S. value was strongly reduced by grinding thermal effect in subsurface region, and was also strongly changed by the fatigue process. Finally, this analysis method was used to determine the best field of internal stresses necessary to minimize the fatigue damage.
Fluid-Film Journal Bearings Operating in a Hybrid Mode: Part II—Experimental Investigation
Authors: Koshal D. , Rowe W. B.
Published: March 2013

An extensive experimental program was carried out to test the theoretical predictions discussed in Part I of this paper. The design of the bearing test rig is described. Line-source plain hybrid journal bearings have been investigated and results are presented for bearings at the optimum and higher speeds. Such parameters as load, eccentricity, oil-film pressure, speed, inlet and outlet temperatures, friction torque, oil flow-rate, and attitude angle have been measured. A description of the appropriate instrumentation is also included. Whereas close agreement was found between theory and experiment, there was a tendency for measured loads to be slightly higher than predicted, particularly as the eccentricity ratio approached a value of unity. It was also found that at high values of power ratio corresponding to higher temperature rise conditions, frictional torque was lower than predicted.
Externally Pressurized Two Layer Film Bearing—Gas Bearing With Liquid Layer
Authors: Nakahara T. , Kurisu T. , Aoki H.
Published: March 2013

A new type of gas lubricated externally pressurized thrust bearing was developed. The bearing consists of a central hole for feeding the gas and a row of 24 small holes located circumferencially at a constant radius for supplying a small amount of liquid which, by the combined wetting action and the gas flows, forms a thin liquid layer adhering onto one of the surfaces. The pattern of the liquid film was observed experimentally, and the bearing performance influenced by the thin liquid film was determined. The load capacity and film stiffness were found to increase approximately 2 and 6 times respectively.
Dynamic Response to Rotating-Seat Runout in Noncontacting Face Seals
Authors: Etsion I.
Published: March 2013

The dynamic response of a flexibly-mounted ring to runout of the rotating seat in mechanical face seal is analyzed assuming small perturbations. It is found that tracking ability of the stator depends only on its dynamic characteristics and operating conditions and is not affected by the amount of runout. Three different modes of dynamic response are shown and the condition for parallel tracking is presented. The present analysis is limited to flat-faced seals with no secondary seal damping. Nevertheless it provides a good insight into the dynamic behavior of noncontacting face seals.
Elastic-Plastic Analysis of a Radially Loaded Spherical
Shell
Authors: Brooks G. N. , Leung C.-P.
Published: March 2013

An elastic-plastic analysis of a spherical shell loaded radially through a rigid inclusion is performed. The sphere is modeled as a shallow shell of infinite extent. The Tresca yield condition is used to derive the elastic-plastic moment-curvature relationship in a simple form. This is used to develop a computationally efficient solution method.
Rupture Hardware Minimization in Pressurized Water Reactor
Piping
Authors: Mukherjee S. K. , Szy Slow Ski J. J. , Chexal V. , Norris D. M. , Goldstein N. A. , Beaudoin B. F. , Quiñones D. F. , Server W. L.
Published: March 2013

For much of the high-energy piping in light water reactor systems, fracture mechanics calculations can be used to assure pipe failure resistance, thus allowing the elimination of excessive rupture restraint hardware both inside and outside containment. These calculations use the concept of leak-before-break (LBB) and include part-through-wall flaw fatigue crack propagation, through-wall flaw detectable leakage, and through-wall flaw stability analyses. Performing these analyses not only reduces initial construction, future maintenance, and radiation exposure costs, but also improves the overall safety and integrity of the plant since much more is known about the piping and its capabilities than would be the case had the analyses not been performed. This paper presents the LBB methodology applied at Beaver Valley Power Station—Unit 2 (BVPS-2); the application for two specific lines, one inside containment (stainless steel) and the other outside containment (ferritic steel), is shown in a generic sense using a simple parametric matrix. The overall results for BVPS-2 indicate that pipe rupture hardware is not necessary for stainless steel lines inside containment greater than or equal to 6-in. (152-mm) nominal pipe size that have passed a screening criteria designed to eliminate potential problem systems (such as the feedwater system). Similarly, some ferritic steel line as small as 3-in. (76-mm) diameter (outside containment) can qualify for pipe rupture hardware elimination.
Damage Assessment Analysis of Composite Pressure Vessels Subjected to
Random Impact Loading
Authors: Yener M. , Wolcott E.
Published: March 2013

At the present time, advanced composites have been widely accepted as engineering materials. Analysis techniques for the response of composite materials and structures to static loads are reasonably well established. Because of their light weight, high modulus, high strength, and good fatigue resistance, carbon fiber composites have been used successfully in the aircraft industry and rocket motor cases. However, composite materials are very susceptible to low velocity and low energy impact damage. Recently, the damage inflicted by such impact has been a subject of great interest. This paper primarily illustrates that it is possible to quantitatively assess damage due to any type of unexpected loading, including impact, using progressive failure finite element analysis.
Local Effects and Defect Criticality in Homogeneous and Laminated
Structures
Authors: Pindera J. T.
Published: March 2013

The paper presents a theoretical framework of a more comprehensive methodology of analysis of behavior of homogeneous and composite materials and structures. The behavior of bolted flanged connections is taken as an illustrative example. Particular attention is given to the local effects. The term “local effects” denotes the actual, pronounced local three-dimensional stress states which exist in particular regions of the actual, weakly three-dimensional, stress fields occurring in plates and shells. Presented examples show that the local effects can be one of the major causes of failures of homogeneous or composite laminated structures. Within the chosen theoretical framework, an outline of new analytical/experimental methods is presented, called isodyne methods. It is demonstrated that the isodyne methods allow the determination of the normal and shear components of the stress states in plates and beams, including the three-dimensional stress states at the crack tips, tips of local disbounds or defects, or in the lamination planes.
Effect of Shear Deformation on Bending of Laminated Composite
Beams
Authors: Gordaninejad F. , Ghazavi A.
Published: March 2013

A higher-order shear deformation beam theory is utilized to analyze the bending of thick laminated composite beams. This theory accounts for parabolic distribution of shear strain through the thickness of the beam. The predicted displacements show improvement over the Bresse-Timoshenko beam theory. Mixed finite element results are obtained for those cases where closed-form solutions are not available. The finite element and exact solutions are in close agreement. Numerical results are presented for single, two and three-layer beams under uniform and sinusoidal distributed transverse loadings.
Dynamic Behavior of an Orthotropic Material Containing a Central
Crack
Authors: Tsai Y. M.
Published: March 2013

The dynamic response of a central crack in an orthotropic material is investigated. The crack is situated along one of the principal axes of the material. The load is harmonic in time and normally applied to the crack surface. The Fourier transform is used to solve the dynamic fracture problem, and the results are simplified through a complete contour integration. The dynamic stress intensity factor is obtained in an exact expression in terms of the frequency factor and the material constants. The frequency factor is defined as the product of the wave frequency and the half-crack length, divided by the shear wave speed. Glass/epoxy and graphite/epoxy composite materials are used as example materials in calculating the numerical values of the stress intensity factors. The maximum values of the stress intensity factors are shown to be dependent on the value of the nondimensional frequency factor and the material anisotropy. The motion of the crack surface is also investigated. The crack surface distortion from the associated static crack shape also depends on the wave frequency and the orthotropic material constants.
On the Micromechanical Characterization of the Creep Response of a
Class of Composite Systems
Authors: Haddad Y. M. , Tanary S.
Published: March 2013

The temperature-dependent creep of a class of composite systems is considered with the inclusion of the microstructure. The material system is regarded as a three-dimensional viscoelastic matrix which is reinforced with randomly oriented, short viscoelastic fiber-bundles. The nonlinear creep response of the composite matrix is modeled within the considered temperature range, using a modified form of the hereditary constitutive equation in linear viscoelasticity. The time-dependent behavior of the individual fiber-bundle is formulated as a combination of a viscoelastic matrix substance within the bundle and an ensemble of unidirectional, elastic fibers. The macroscopic behavior of the randomly oriented, fiber-composite is determined, with the inclusion of the microstructure, using the laminate analogy which assumes that the random fiber-composite may be treated as a laminated “quasi-isotropic” material. The presented approach is illustrated numerically for the case of the creep of SMC-R50 composite system within a temperature range of 28° to 76°C. The theoretical model is presented in a generalized manner and could be applicable to a large class of composite systems.
Three-Dimensional Axisymmetric Elastic Stresses in Intersections of
Hollow Sphere and Cylinders (Torsion, Tension and Internal
Pressure)
Authors: Kishida M. , Sasaki K. , Kawano M.
Published: March 2013

The three-dimensional axisymmetric elastic stresses in the intersections of hollow sphere and cylinders, subjected to torsion, tension and internal pressure, is analyzed easily and accurately by use of the indirect fictitious-boundary integral method. As a result, the influence of configuration parameters (e.g., the mean diameter ratio and the thickness ratio of hollow sphere and cylinder, and the roundness of a corner of intersection) on stress concentration is made clear. Furthermore, the other results, such as one obtained by photoelastic experiment, are evaluated by the present results.
A Simple Specimen for the Determination of Elastic-Plastic Fracture
Mechanics Parameters on Hollow Cylinders
Authors: Roos E.
Published: March 2013

Functions have been derived for a linear-elastic fracture mechanics specimen of an arc-shape, which because of this shape, can be removed relatively easily from pipes or cylindrical components. These specimens can be used for determining crack resistance curves using the J-integral so that, even for thinner components, it is relatively simple to obtain crack growth laws with crack propagation direction over the wall thickness. The ductile fracture mechanics characteristics determined on arc-shaped specimens corresponds well with the values determined on side-grooved CT-25 specimens.
Behavior of Pressure-Induced Discontinuity Stresses at Elevated
Temperature
Authors: Becht C.
Published: March 2013

Conventional wisdom has been that discontinuity bending stresses at temperatures within the creep regime are self-limiting, and therefore secondary. A series of creep relaxation analyses were performed on typical discontinuities (junctions). The analyses show that, in general, discontinuity bending moment and stress due to pressure do not relax, but remain more or less constant with time. These stresses should therefore be evaluated as primary. A creep follow-up mechanism was identified that sustains the discontinuity stresses. The implications for design are discussed.
An Evaluation of Material Weight and Contained Fluid Volume for
Eccentric Intersecting Cylinders of Arbitrary Size
Authors: Chao Y. J. , Sutton M. A.
Published: March 2013

Engineering personnel in industries which use pressurized containment vessels having attached nozzles are required not only to design portions of the lifting mechanism, but also to estimate the fluid volume which the vessel and nozzles will contain; most designers use simplified formulas for computing the quantities of interest. Typically, these formulas are valid approximations when the nozzle diameter is much smaller than the vessel diameter. The enclosed work develops three single-integral expressions which can be programmed and numerically integrated to obtain accurate estimates for both the material volume and also the containment volume present in a pair of eccentrically, or concentrically, intersecting thin-walled cylinders of arbitrary diameters. A table of such values is presented for a wide range of values of the standard nozzle pipe diameter and vessel diameter, for the special case of a concentric nozzle. In addition, an example is presented which compares the numerically integrated values for both the material volume and the containment volume to simplified upper and lower-bound estimates.
Design, Assembly, and Inspection of Advanced U-Bend/Antivibration Bar
Configurations for PWR Steam Generators
Authors: Langford P. J.
Published: March 2013

Tube vibration and wear potential in the U-bend region of pressurized water reactor (PWR) steam generators is reduced by enhanced design bases and fabrication procedures. Applicable vibration mechanisms are described and related to field experience to focus the development program which led to the enhancements. Technical bases were developed from flow-induced vibration tests and shaker tests in which the tube/antivibration bar (AVB) wear-producing forces and motions were characterized in terms of work rate. Fixtures to control weld shrinkage and instruments to measure tube/AVB fit-up were developed for fabrication. Assembly and application experience, including measurement of fabricated tube bundle/AVB fit-up, is summarized for several advanced steam generators. Implications for enhanced operating experience relative to conventional design configurations are noted.
Determination of the Fluid-Elastic Stability Threshold in the
Presence of Turbulence: A Theoretical Study
Authors: Lever J. H. , Rzentkowski G.
Published: March 2013

A model has been developed to examine the effect of the superposition of turbulent buffeting and fluid-elastic excitation on the response of a single flexible tube in an array exposed to cross-flow. The modeled response curves for a 1.375-pitch ratio parallel triangular array are compared with corresponding experimental data for the same array; reasonably good qualitative agreement is seen. Turbulence is shown to have a significant effect on the determination of the stability threshold for the array, with increasing turbulent buffeting causing a reduction in the apparent critical velocity. The dependence of turbulence response on mass ratio is also found to yield a slight independence between mass and damping parameters on stability threshold estimates, which may account for similar experimental findings. Different stability criteria are compared, and an attempt is made to provide some guidance in the interpretation of response curves from actual tests.
Boundary Element Method for Fluid-Structure Interaction Problems in
Liquid Storage Tanks
Authors: Hwang I.-T. , Ting K.
Published: March 2013

The dynamic response of liquid storage tank, including the hydrodynamic interactions, subjected to earthquake excitations is studied by the combinations of boundary element method and finite element procedure in this paper. The tank wall and inviscid fluid domain are treated as two substructures of the total system-coupled through the hydrodynamic pressures. The boundary element method is employed to determine the hydrodynamic pressures associated with small amplitude excitations and negligible surface wave effects in fluid domain which are expressed as the frequency-dependent terms related with the natural vibration modes of elastic tank alone. These terms are incorporated into the finite element formulation of elastic tank in frequency domain and the generalized displacements are computed by synthesizing their complex frequency response using Fast-Fourier Transform procedure. Thus, the hydrodynamic interactions between the elastic flexible tank wall and the fluid are then solved. To demonstrate the accuracy and validity of the solution procedure developed herein, numerical examples are analyzed. Good correlations between the computed results with the referenced solutions in literature can be noted. The effects of fluid compressibility and tank flexibility are also evaluated in this work. Finally, the dynamic response of liquid storage tank due to seismic excitations is also analyzed.
Shellside Waterflow-Induced Tube Vibration in Heat Exchanger
Configurations With Tube Pitch-to-Diameter Ratio of 1.42
Authors: Halle H. , Chenoweth J. M. , Wambsganss M. W.
Published: March 2013

The pitch-to-diameter ratio (P/D) of the tube layout in shell-and-tube heat exchangers is one of the major parameters with which the designer may control heat transfer and pressure drop and facilitate mechanical cleaning. As part of a comprehensive investigation of waterflow-induced tube vibration in an industrial-size research heat exchanger, various configurations characterized by different design parameters, including P/D ratio, had been investigated. To provide a comparison with previous data obtained with P/D = 1.25, this paper presents the results of a study of eight different tube bundle configurations with P/D = 1.42. Four equilaterally spaced tube layout patterns and two baffle edge orientations were investigated. The results indicate that the greater flow area of the P/D = 1.42 configuration increases flow penetration into the bundle, reduces the tube-to-tube vibration coupling and generally provides less well-defined, even though sometimes improved, fluidelastic instability thresholds.
Vibration of Tube Bundles in Two-Phase Cross-Flow: Part
2—Fluid-Elastic Instability
Authors: Pettigrew M. J. , Tromp J. H. , Taylor C. E. , Kim B. S.
Published: March 2013

An extensive experimental program was carried out to study the vibration behavior of tube bundles subjected to two-phase cross-flow. Fluid-elastic instability is discussed in Part 2 of this series of three papers. Four tube bundle configurations were subjected to increasing flow up to the onset of fluid-elastic instability. The tests were done on bundles with all-flexible tubes and on bundles with one flexible tube surrounded by rigid tubes. Fluid-elastic instabilities have been observed for all tube bundles and all flow conditions. The critical flow velocity for fluid-elastic instability is significantly lower for the all-flexible tube bundles. The fluid-elastic instability behavior is different for intermittent flows than for continuous flow regimes such as bubbly or froth flows. For continuous flows, the observed instabilities satisfy the relationship V/fd = K(2πζm/ρd2)0.5 in which the minimum instability factor K was found to be around 4 for bundles of p/d = 1.47 and significantly less for p/d = 1.32. Design guidelines are recommended to avoid fluid-elastic instabilities in two-phase cross-flows.
Optimum Design of Water Jet Pumps
Authors: Cairns J. R. , Na T. Y.
Published: March 2013

A summary of an extensive program of experimental and analytical work leading to a procedure for obtaining optimized performance of water jet-pump systems is presented. The procedure is extended to include systems involving n, series-staged ejector components operating in an optimal manner as a complete pump, pipeline, ejector unit. The theoretical, limiting performance of ejectors is established and several examples involving different design situations are shown.
An Approximate Solution for the Thermal Performance of a Stirling-Engine Regenerator
Authors: Qvale E. B. , Smith J. L.
Published: March 2013

An approximate closed-form solution for the thermal performance of a Stirling-engine regenerator is derived. The solution is for sinusoidal mass flow rate and sinusoidal pressure variation with a phase angle relative to the mass flow. The solution provides the net enthalpy flux along the regenerator and the change of phase between the mass flow and the pressure. The method is similar to the one developed by Rea [1], and the results agree well with his experimental data.
Advancing Boiler Steam Conditions
Authors: Horn G. , Street P. J.
Published: March 2013

Factors preventing the advancement of steam temperature in power plant are discussed. The construction of a coal-fired pilot plant designed to superheat steam to 760 deg C (1400 deg F) is described and the results of corrosion trials analyzed. Conclusions are drawn from the experiments relating to possible advances in design.
Optimization of Heater Design Conditions in Power Plant Cycles
Authors: Salisbury J. Kenneth
Published: March 2013

This paper presents a method of tailoring the regenerative feedwater-heating system in a nuclear plant to the availability of extraction openings on the main turbine. This is accomplished by optimizing the heater design conditions of each individual heater, in conformance with the peculiarities of the particular cycle being used, and the evaluation parameters that are applicable. It is shown by example that for a typical six-heater, reheat nuclear plant the evaluation is improved. The results show that such “total optimization” in an 880 Mwe plant will accomplish: 1 - An improvement of 27 Btu/kwhr in heat rate, 2 - An increase of 2500 kw in net output (at constant reactor thermal power), 3 - An increase of about 18.5 percent in heater surface, in the reference cycle, for the selected values of the heat rate and incremental kw evaluation parameters, and heater surface cost of $10/sq ft. However, if an incremental heater cost is used, say $6/sq ft, optimum evaluation yields: 1 - An improvement of 45.3 Btu/kwhr in heat rate, 2 - An increase of 4200 kw in net output (at constant reactor thermal power), 3 - An increase of about 42 percent in heater surface. For this set of conditions, there is an improvement in evaluation of about $300,000 for the 880 Mwe plant.
Heat Transfer in the Oscillating Turbulent Boundary Layer
Authors: Miller James A.
Published: March 2013

Measurements of local heat-transfer coefficients in the fully established oscillating turbulent boundary layer over a flat plate are reported. In the range of frequencies from 0.1 to 200 cps and amplitudes from 8 to 92 percent of the freestream mean velocity, increases in local Nusselt numbers of 3 to 5 percent were found. It is concluded that substantial increases in local coefficients, sometimes reported in oscillating flows of low standing wave ratio, may be traced to reduced transition Reynolds numbers.
Gear Design and Laboratory Experience—Marine Gas Turbine Propulsion
Authors: Gugliuzza T. A. , Hargett W. H.
Published: March 2013

A study of marine reduction gear design over the past 15 years and an indication of future development of marine propulsion gearing for gas tubine plants are presented. Emphasis is placed on those design considerations that relate to gas turbine installation: gearing arrangement, reversing mechanisms, and use and location of clutches and brakes. Comparison tabulations include weight analyses and gear rating influencing factors. Also included is a study of the marine gear-rating method and adaption to gas turbine operating characteristics with service factor chart for river craft, merchant and naval ships.
Effects of New International Formulation on Turbine-Generator Performance Calculations
Authors: Cotton K. C. , Deming N. R. , Garbinski E. H.
Published: March 2013

For the pressure-temperature range of steam turbine operation the new International Formulation properties differ from those in Keenan and Keyes Steam Tables primarily in the values of enthalpy and entropy around 1000 deg F. The deviation is significant at pressures above 2400 psi and diminishes as temperature is both increased and decreased. This paper presents the effect of this deviation in steam properties on steam turbine-generator heat rate and high pressure turbine efficiency. Some test data is presented which indicates the new Formulation is more correct at 1000 deg F.
Performance Testing of 580-MW Joliet Units No. 7 and No. 8
Authors: Basinski L. R. , McKinley D. E.
Published: March 2013

This paper emphasizes the point that performance testing of large steam turbines in accordance with the provisions of ASME Power Test Code No. 6–1964 requires extensive coordination between turbine manufacturer and the operating utility. This paper outlines the procedures followed in preparing for, conducting, and analyzing the results of performance tests conducted on two, duplicate, 580-MW cross-compound steam turbines installed in the Joliet Station of the Commonwealth Edison Company. Selection of test instrumentation and methods of calculating the test performance are discussed. Application of on-line and off-line digital computers for calculation of test results is reviewed. Problems encountered during the tests which affected accuracy of calculated results are outlined.
Thermodynamic Optimization of Rankine Cycle Space Power Systems
Authors: Huffman G. D. , Buxton O. E.
Published: March 2013

The design of a space power system yielding maximum performance is a laborious task requiring implicit knowledge of many criteria. The labor involved with previous techniques is not conducive to the analysis of systems employing novel fluids. To circumvent these problems, a new method of analysis of saturated and superheated Rankine cycles is presented. The approach employed equates maximum performance with the minimum radiating area which can then be linked to a particular cycle through thermodynamic relationships. The analysis is concluded by utilizing a semiempirical technique to determine turbine efficiencies. The new approach which is applicable to all fluids is then used to evaluate three typical cycles.
Quasi Two-Dimensional Flows Through a Cascade
Authors: Mani R. , Acosta A. J.
Published: March 2013

A thin airfoil theory is developed for airfoils spanning a slowly diverging or converging channel, the motivation being to predict, theoretically, the effect of varying axial velocity on the cascade performance of axial flow compressor rows.
Reynolds Number Effects in Axial Compressors
Authors: Wassell A. B.
Published: March 2013

The influence of variations in flow Reynolds number on the performance of axial compressors has been studied (changes in Reynolds number being, for the most part, achieved by changes in the inlet total pressure at or near the design speed). The measured results, so achieved, have been correlated to show how the main compressor performance parameters vary with Reynolds number. Reference has been made to cascade data to assist in choosing the form of the correlation, which is essentially empirical. A good correlation of the measured performance changes on component tests has been obtained. The method described, therefore, appears to be satisfactory for predicting trends for project assessments and avoids considering the detailed flow changes that occur within the machine as the Reynolds number is varied.
Heat Transfer With Film Cooling Near Nontangential Injection Slots
Authors: Metzger D. E. , Carper H. J. , Swank L. R.
Published: March 2013

A study of the effect of secondary fluid injection through single nontangential slots on the surface heat transfer in regions near the injection site is presented. The nondimensional parameters governing the heat transfer are obtained from the pertinent differential equations, and experimental results were obtained which cover the range of interest of these parameters for many situations encountered in film cooling applications. The experimental heat transfer rates were obtained from a novel transient test facility, and are presented as ratios of the heat transfer obtained with film injection to the heat transfer obtained with only the single mainstream.
The Effects of Variations in Municipal Refuse on Some Incinerator Design Parameters
Authors: Kalika P. W.
Published: March 2013

The variability of municipal refuse can have a marked effect on the performance of an incinerator during test, as compared to design expectations. A computer program has been developed which can assess this variability in terms of its effect on incinerator design parameters, such as gas, air, and quench water flows and temperatures. The results of calculations for several refuse compositions in the range of 4000 to 8000 Btu/lb (HHV) are presented in the form of tables and graphs and their significance with respect to incinerator design and testing is discussed. Tentative plans for further work involving influence coefficients and correction factors are outlined.
Von Karman Hydraulic Vortexes Cause Stay Vane Cracking on Propeller Turbines at the Little Long Generating Station of Ontario Hydro
Authors: Goldwag E. , Berry D. G.
Published: March 2013

Little Long Generating Station is situated about 500 miles north of Toronto and is one of four plants located close together on the Mattagami River which flows into Hudson Bay. Some 500 MW of power is transmitted at 500 kv to Sudbury and Toronto (Fig. 1). There are two turbines at Little Long Generating Station. Almost immediately from the time when the first unit was being commissioned and operated under load, field reports referred to what was said to be an abnormally high level of noise and vibration. When the second unit came into service, similar findings were reported. About six months after commissioning, the units were unwatered and a detailed inspection indicated that the stay vanes forming the speed ring contained numerous and serious fatigue cracks. The final diagnosis indicated the damage to be a result of what is now usually referred to as von Karman hydraulic vortexes. Because immediate repairs were required and in order to insure the future structural adequacy of the speed ring, it was decided to change the stay vane profile at the same time, in an attempt to eliminate the excitation due to von Karman vortexes, hoping thereby to avoid further damage of the stay ring after the repairs. Recent inspections of both units show that both the modifications and the final repairs were completely successful.
A Photographic Study of the Three-Dimensional Flow in a Radial Compressor
Authors: Senoo Y. , Yamaguchi M. , Nishi M.
Published: March 2013

In order to visualize the three-dimensional flow in the impeller and the vaneless diffuser of a centrifugal compressor, water is used as the working fluid and streak lines of colored water are photographed and examined. The test is made at an extremely low speed so that streak lines do not diffuse due to turbulent mixing. The streak lines clearly demonstrate several types of secondary flow, some of which agree with what have been speculated to exist in actual compressors. Most of observed secondary flow patterns are qualitatively understandable with existing theories.
A Correlation of End Wall Losses in Plane Compressor Cascades
Authors: Hanley W. T.
Published: March 2013

Consideration of parameters suggested by the momentum integral equations has lead to a successful correlation relating (a) the change of the free stream component of the end wall boundary layer displacement thickness to chord ratio, and (b) a profile parameter as functions of free stream loading. For the range of investigation, both correlations were found to be insensitive to gap-chord ratio, camber, stagger, incidence, and airfoil shape. Maximum permissible loading limits for operation without excessive end wall loss are shown to decrease with increasing inlet displacement thickness to chord ratio.
Qualification of Gas Turbine Engines for U. S. Navy Shipboard Use
Authors: Carleton R. S.
Published: March 2013

The author emphasizes the need for thorough proof testing of gas turbine engines prior to shipboard use. He describes some of the gas turbine testing programs in which the U. S. Navy has been involved and the type of testing that will be required in the future.
Evaluation of Heat-Resistant Alloys for Marine Gas Turbine Applications
Authors: Fiedler L. J. , Pelloux R. M. N.
Published: March 2013

Materials for the turbine and combustor sections of gas turbine engines were evaluated for their resistance to sulfidation corrosion. The basic evaluation was conducted in a test facility by exposing the materials to a combustion gas atmosphere which simulates conditions of gas composition, corrosive combustion residue, gas velocity, and temperature that are encountered while operating a gas turbine engine in a marine environment. The influence of alloy composition, protective coatings, salt ingestion rates, and fuel sulfur content is discussed in relation to the degree of sulfidation corrosion. The mechanism of sulfidation corrosion attack, as determined by electron microprobe analyses and X-ray diffraction studies of corroded materials, is also discussed.
Long-Life Base Load Service at 1600 F Turbine Inlet Temperature
Authors: Starkey N. E.
Published: March 2013

Design considerations required for base load long-life service at turbine inlet temperature above 1600 F are discussed. These include control of combustion profile, air cooling of the first-stage nozzle, long-shank turbine buckets, accurate air and fuel distribution, and accurate temperature control.