bluuebunny/crossref_metadata_2025 huggingface dataset:
The Cracking of Ti-6Al-4V Alloys Under Sustained Load in Ambient Air
Authors: Yoder G. R. , Griffis C. A. , Crooker T. W.
Published: November 2010

This study reveals that degradation in load-carrying capacity owing to sustained-load cracking (SLC) can occur in alloys of the Ti-6Al-4V family. Each of eight alloys tested with fatigue-precracked specimens in ambient room air exhibited the phenomenon, with degradations ranging from 11 to 35 percent. The degree of susceptibility to SLC was seen to be dependent upon crack orientation in rolled plate materials. The threshold stress-intensity factor below which SLC failures will not occur in these alloys, KIt, appears to represent a more conservative fracture-safe design parameter than the plane-strain fracture toughness KIc, which cannot account for time-delayed failures owing to SLC.
Subsequent Yield Surfaces for Annealed Mild Steel Under Servo-Controlled Strain and Load Histories: Aging, Normality, Convexity, Corners, Bauschinger and Cross Effects
Authors: Michno M. J. , Findley W. N.
Published: November 2010

Initial-yield results on SAE 1017 steel are presented for: four different specimens under combined axial load and twisting moment for servo controlled loading; and six different specimens under various combinations of servo controlled axial strain and shear strain. Subsequent yield curves determined by small strain offset multiple probes on a given specimen are presented covering all four quadrants of axial stress-shear stress space. The resulting families of subsequent yield curves allows conclusions to be drawn concerning the effects of plastic strain and strain aging. All curves were found to be convex and normality of the plastic strain increment vector was obeyed. The response to plastic straining allowed discussion of corner formation, translation, rotation, Bauschinger and cross effects of subsequent yield curves and formation of a limit curve. A comparison is made between the experiments and the Prager kinematic hardening model and the Ziegler modification.
Flow Stresses in Sheet Material Formed Into Nearly Spherical Shapes
Authors: Hsu T. C. , Shang H. M. , Lee T. C. , Lee S. Y.
Published: November 2010

The relationship between the geometry and the membrane stresses of a thin shell under internal or external pressure is analyzed through the concept of prolateness. Prolateness is a quantitative measure of the local deviation from the spherical surface and it varies in a complex manner throughout a thin shell formed by hydraulic pressure. It is found that for the metals tested the surface is locally a sphere only at the pole and at an annular ring; elsewhere, it is oblate or prolate. The stress distributions in the shell being formed are also determined. Their variation as the forming progresses reveals that the material deforms quite differently at the beginning and at the end of the process.
On the Speeds of Instability of a Rotating Hollow, Anisotropic
Cylinder
Authors: Lenard J. G.
Published: November 2010

Hill's theory of plastic anisotropy is used to investigate the effect of the parameters of anisotropy on the speeds at which long, hollow cylinders rotating about their longitudinal axes reach their maximum load carrying ability. Taking the principal axes of anisotropy to coincide with the principal stress directions and considering true stresses and logarithmic strains a relationship between the tangential strain at the bore and the rotational speed is derived and the rotational speed at which fracture due to instability may begin is noted. It is found that decreasing yield strength in the axial direction results in increased load carrying capacity.
A Case History of Cracking Failures in Deformed Austenitic Alloy Pipe Operating in the Temperature Range of 1000-1300 Deg F (538-705 Deg C)
Authors: Kohut G. B.
Published: November 2010

The results of several cracking failures in fabricated austenitic alloy pipe are reported in detail. These failures were a result of cracking which occurred at the operating temperature in zones which exhibited deformation. The failure analysis included metallography, mechanical and stress rupture tests, electron microscopy and electron microprobe scanning. Although a firm conclusion on the cause of cracking could not be reached, it was obvious that the deformation induced in the pipe during fabrication played a significant role in the failure and in the loss of rupture tensile ductility.
Static and Dynamic Collapse Characteristics of Scale Model Corrugated Tubular Sections
Authors: Thornton P. H.
Published: November 2010

The collapse load of a series of scale model, corrugated tubular sections was determined, both by quasi-static and by dynamic testing. Provided that the material from which the models are made is identical to that of the full size component, then the scaling laws for structures undergoing complex deformation processes will be obeyed. The dynamic collapse response, which occurred by the operation of a plastic hinge mechanism, is governed by the strain rate sensitivity of the material; structural rate effects do not affect the collapse process.
Deformation Mechanism Maps: Their Use in Predicting Creep Behavior
Authors: Mohamed F. A. , Langdon T. G.
Published: November 2010

A simple form of deformation mechanism map is presented which graphically illustrates the behavior of materials under steady-state creep conditions. Examples are given of maps for deformation mechanisms occurring both independently and sequentially. The use of deformation mechanism maps in the prediction of creep behavior is reviewed in detail, and an improved method is presented for estimating the total strain experienced after long-term exposure to stress and temperature.
Analysis of Deep-Drawing Over a Tractrix Die
Authors: Woo D. M.
Published: November 2010

An analysis is given of the deep-drawing of a circular blank into a cylindrical shell over a tractrix die. Comparison is made between the theoretical and the experimental results of the drawing of aluminum blanks of 122 mm dia and 1.6 mm thickness into 51 mm dia cups. The correlation appears satisfactory.
Influence of Interstage Annealing on the Stretch-Formability of Sheet-Metal Laminates
Authors: Beese J. G.
Published: November 2010

The interstage annealing of sheet-metal laminates is studied. A method of predicting the stretch-formability, as measured by the maximum possible uniform strain in simple tension, is proposed. Practical composite systems of potential commercial interest are examined. It is suggested that for certain sheet-metal laminates improved stretch-formability can be achieved as a consequence of a low-temperature, low-cost heat-treatment.
The Fracture Toughness of Cast High-Strength Steels
Authors: Floreen S.
Published: November 2010

The mechanical properties of four cast high-strength steels, 4340, 15-5 PII stainless steel, and two maraging steels were examined. To provide a direct comparison with wrought steels split heats were prepared in which part of each heat was sand cast and the balance was forged and hot-rolled to plate. The KIc properties of the castings were comparable to the plate properties. Limited tests indicated that the cast steels also had reasonably good fatigue and stress corrosion cracking resistance. The castings showed surprisingly low Charpy values, which was attributed to notch acuity due to the more heterogeneous nature of the fractures in the cast structures. The overall results suggest that cast high-strength steels had satisfactory toughness and could be used in many applications.
Effect of J3 on Creep and Relaxation in a Plate With a Central Hole
Authors: Goel R. P.
Published: November 2010

Mises type of creep equations have been used widely to study creep and relaxation phenomena. In a study by Murakami and Yamada [1] inclusion of J3, the third invariant of the deviatoric stress tensor, in the Mises type creep theories helped explain the deviations between experimental and theoretical results of a thick-walled cylinder creeping under an internal pressure. Similarly, the present study investigates the effects of including J3 in the creep constitutive equations on creep and relaxation in a circular plate with a central hole. The results show that inclusion of J3 in the creep equations tends to predict higher values of Σθ (tangential stress) in the creep problem and lower values of Σθ and Σr in the relaxation problem. Lower value of Σr in the relaxation problem implies a lower contact force at the interface of a press-fitted joint.
Fatigue Crack Propagation in 8- and 22-Layer 7075-T6 Aluminum Alloy Laminates
Authors: Pfeiffer N. J. , Alic J. A.
Published: November 2010

Rates of fatigue crack propagation have been determined for adhesively bonded 7075-T6 laminates having a crack divider geometry. Two lamina thicknesses were used, the resulting laminates having either 8 or 22 layers. Crack growth rates were generally within the same range as for monolithic 7076-T6 alloy, and were somewhat slower in the 22-layer laminates than in those with 8 layers. Instances of decreasing crack propagation rate with increasing stress intensity amplitude, as well as of crack arrest, were observed. These are interpreted in terms of interactions between the layers during the progressive transition from a flat mode of crack growth to a slant mode.
A Parametric Study of Fatigue Crack Growth Behavior in Adhesively Bonded Metallic Structures
Authors: Ratwani M. M.
Published: November 2010

Problems of adherend cracks inadhesively bonded structures are considered in this paper. Two different methods of analysis, namely the finite element method and the integral equation approach, are used to obtain the stress intensity factors, which are compared with those obtained experimentally. The results of fatigue crack growth tests on two-ply, adhesively bonded panels with a width of 300 mm and 150 mm, a crack at a hole, and a cracked plate with a bonded stiffener are discussed. Fatigue crack growth behavior predictions based on the analytical stress intensity factors are correlated with those obtained from experiments for a variety of test geometries. The influence of adhesive type, adhesive thickness, and stiffener thickness on crack growth behavior are discussed for the case of a cracked plate with a bonded stiffener.
Spectrum Crack Growth in Adhesively Bonded Structure
Authors: Johnson W. S. , Rister W. C. , Spamer T.
Published: November 2010

A method is presented by which crack growth of damage tolerance type flaws can be predicted in adhesively bonded structure subjected to spectrum loading. The method accounts for a laminate stress intensity correction factor, induced bending and axial load transfer between plies, as well as a crack growth analysis procedure to predict the crack growth retardation behavior under spectrum load. Analytical predictions are compared to several test results to show the applicability of the prediction method presented.
General Yielding of Charpy V-Notch and Precracked Charpy Specimens
Authors: Server W. L.
Published: November 2010

By applying a slip-line fields solution for general yielding, which includes the tup indenter for Charpy V-notch and precracked Charpy tests, estimates of high loading-rate yield stress values can be obtained. These values of yield stress are of particular interest for loading-rate sensitive materials such as low strength steels. Normal tensile tests are not performed at strain-rates indicative of impact tests; dynamic fracture toughness tests require the knowledge of dynamic yield stresses for the determination of validity limits for the fracture toughness measurements. This paper reviews the calculation of yield stresses from static and dynamic three-point bend tests and presents data for a nuclear pressure vessel steel which shows good agreement with high rate and conventional tensile test data.
Factors Affecting the Notch Toughness of Carbon and Low-Alloy Steel Forgings for Pressure Vessel and Piping Applications
Authors: Nisbett E. G.
Published: November 2010

When notch toughness is required in a forging for pressure vessel or piping application, many phases of the manufacturing process are involved. Some significant aspects including the role of the material specification, chemistry balance, mechanical test locations, forging practice and heat treatment are reviewed. A variant of the heat treatment process is described which utilizes quenching from the intercritical temperature range as a means of enhancing notch toughness.
Fatigue Lives of Metals up to Crack Initiation
Authors: Ihara Chiaki , Tsurui Akira , Igarashi Akito
Published: November 2010

Recently a stochastic model for fatigue of metals has been proposed by two of the present authors. In this paper some parameters adopted in that model are related to the material properties obtained from the static true stress-strain tension test. On this basis, the probability density functions of lives up to crack initiation and their mean values are estimated.
A Modified Tension Test
Authors: Thomsen E. G. , Shabaik A. H. , Sohrabpour S.
Published: November 2010

The present paper deals with a modified tension test with experimental results for SAE 1020, SAE 1215, and OFHC Cu of standard 12.8 mm (0.505 in.) dia test bars. The tension test was interrupted at predetermined intervals in order to remove excess material from the gage sections after necking had commenced, or to subject the gage sections to a drawing operation in order to keep the difference between the neck diameters and the gage section diameter as small as possible for the purpose of reducing the triaxiality of the stresses in the necked region. The tests showed that the triaxiality could be reduced for SAE 1215 and OFHC Cu by machining the gage section. However, as expected and shown for one series of tests with ETPC Cu, the drawing operations were more effective because of work hardening of the gage sections.
Application of the Thermoeconomic Approach to the Analysis and Optimization of a Vapor-Compression Desalting System
Authors: El-Sayed Y. M. , Aplenc Andre J.
Published: November 2010

A conventional vapor-compression desalting system is analyzed thermodynamically and economically by the concepts of essergy and internal economy. Thermodynamic analysis using the concept of essergy reveals that the low thermodynamic efficiency is inherent to the process even when the pieces of equipment have individual high thermodynamic efficiencies. Economic analysis using the concept of internal economy shows that the decomposition of the system into zones is not totally arbitrary. A closer engineering understanding of the economic effects of the various design variables is permitted. Optimum results, in general, reveal that for the usual rates of electrical energy costs, optimum conditions favor a high thermodynamic efficiency for each of the compressor, evaporator condenser, and main exchanger. Optimum tube diameter, tube length and allowable pressure drops for the main exchanger as a shell-and-tube type may differ appreciably from conventional values. The optimum design depends upon economic factors, which vary from one locality to another. Therefore the specific numerical results given herein may not be applicable to a specific installation but the methods are quite general.
Trials of Additives for Sulfur-Dioxide Removal in Industrial Plants
Authors: Land G. W.
Published: November 2010

Trials of additives for the removal of sulfur dioxide from combustion gases have been made by several investigative groups. Three of these—an industry and local government cooperative group in Chicago, and two industry groups—are discussed in this paper. Materials tested include limestones, dolomites, red mud, and nahcolite.
Laminar Flow Gas Turbine Regenerators—The Influence of Manufacturing Tolerances
Authors: London A. L.
Published: November 2010

Several current designs for high effectiveness gas turbine regenerators involve low Reynolds number fully developed, laminar flow type surfaces. Such surfaces consist of cylindrical flow passages, of small hydraulic radius, in parallel. The cylinder geometry may, as examples, be triangular, as in some glass-ceramic surfaces, or rectangular, as in deepfold metal foil surfaces. This presentation demonstrates that manufacturing tolerances of several thousandths of an in. in passage dimension have a significant influence on the overall heat transfer and flow friction behavior. The analysis is also useful in rationalizing the difference between theory and test results for the basic heat transfer (j factor) and friction (f factor) characteristics as a function of Reynolds number for various surfaces of the laminar flow type.
Flow Through Cascades of Slotted Compressor Blades
Authors: Mikolajczak A. A. , Weingold H. D. , Nikkanen J. P.
Published: November 2010

The performance of axial flow compressors can be improved when it becomes possible to achieve higher loading per stage than currently attainable. The major obstacles to attaining this objective are the limitations on loading in the end wall region and the limited range of operating incidence of compressor blades. A possible method of achieving a wide range of operating incidence is the use of slotted or multibody airfoils. An incompressible, two-dimensional, potential flow analysis for thick, highly cambered multibodies in cascade is presented. The analysis is extended to include compressibility. A boundary-layer calculation, including a wake model, is described and used to predict cascade losses. Theoretical predictions are compared against slotted and unslotted cascade and compressor stator experimental results and adequate agreement obtained. The slotted blade concept is shown to offer performance benefits, provided that end-wall loading limitations can be overcome.
An Analytical and Experimental Evaluation of the Pressure-Drop Losses in the Stirling Cycle
Authors: Rios P. A. , Smith J. L.
Published: November 2010

An analysis of the effects of pressure drop in the heat-exchange components of a Stirling cycle has been made and successfully applied to an experimental refrigerator. Data are presented for the indicated work per cycle for each cylinder of the machine. Two successive approximations to the real cycle are used. The first approximation is a Stirling cycle with two adiabatic cylinders and is used to compute the mass flow rates at each location. The second approximation uses these flow rates to obtain the pressure-drop losses in the heat-exchange components. The correlation between measured and calculated pressure-drop losses and individual cylinder work substantiates the validity of the analysis.
Glass-Ceramic Surfaces, Straight Triangular Passages—Heat Transfer and Flow Friction Characteristics
Authors: London A. L. , Young M. B. O. , Stang J. H.
Published: November 2010

Basic heat transfer and flow friction design data are presented for three straight, triangular passage, glass-ceramic heat exchanger surfaces. These surfaces have heat transfer area density ratios ranging from 1300–2400 ft2/ft3, corresponding to a passage count of 526–2215 passages per sq in. Glass-ceramic heat exchangers are of importance to vehicular gas turbine technology as they give promise of allowing low mass-production costs for the high effectiveness rotary regenerator required in most of the vehicular turbine engine concepts now under development. The present data are compared to previously available conflicting information and are recommended for design purposes, with stipulated specification relating to the uniformity of passages. Additionally, some limited information is provided relating to the low fouling characteristics of glass ceramic surfaces in the rotary regenerator application.
Performance Prediction for High Turning Low Aspect Ratio Stator Cascades in the Transonic Regime
Authors: Griepentrog H. F. L.
Published: November 2010

This paper describes a method for the prediction of the transonic flow field in a high solidity, high turning cascade, suitable for use as stator of a shock-in-rotor supersonic compressor stage. Effects of shock boundary layer interaction is taken into account by empirical correlation, valid for blade aspect ratios below unity. Use of partial slots for reduction of the secondary flows is briefly discussed and a correlation on slot efficiency is presented.
A Method for Predicting Compressor Cascade Total Pressure Losses When the Inlet Relative Mach Number Is Greater Than Unity
Authors: Balzer R. L.
Published: November 2010

During the last few years, considerable progress has been made in predicting the total pressure losses from viscous effects for axial-flow compressor cascades. With the advent of the transonic and the supersonic stage, another pressure loss generating mechanism was introduced—the shock wave. Various methods have been published over the past few years accounting for the pressure losses associated with the shock formation, but of those reviewed by this author, none of them has been consistently successful for predicting the losses at other than design conditions. This paper develops a method which has given consistent success at all flow conditions for compressors with subsonic axial and supersonic relative velocities.
A Traversing-Thermocouple Technique for the Rapid Measurement of Thermal Conductivity in the Range 300 to 1200 K
Authors: Eggers Philip E. , Best Ralph E.
Published: November 2010

A thermal conductivity measurement technique has been developed based on a novel design employing an ultrafine (0.02 cm dia) “traversing” thermocouple. This technique features the rapid determination of thermal conductivity as a function of temperature for specimens operating in the range from 300 up to 1200 K. In contrast to conventional “comparative” methods of thermal conductivity measurement, the present approach requires only one equilibrium condition, viz., the condition in which the specimen is maintained between the two temperature extremes of interest. The traversing-thermocouple measurement technique also permits the accommodation of a wide range of specimen sizes (e.g., 0.25 to 1.3 cm in diameter and 0.7 to 3.0 cm in length) and measurements accurate to within 5 to 7 percent. Although initially developed for use with semiconductors, the measurement technique is equally well suited to semimetals, metals, and insulators.
Discrete Frequency Noise From Lifting Fans
Authors: Abdelhamid A. N.
Published: November 2010

Discrete frequency noise characteristics of a research lifting fan is investigated analytically. Based on steady aerodynamic data of the fan, unsteady aerodynamic forces acting on the rotor and stator blades were calculated using the results of previous investigators and an analysis which determines the effect of fluctuating velocity disturbance parallel to blade chord on the unsteady lift of cambered thin airfoils. The calculated unsteady forces were then used to determine the characteristics of discrete frequency noise emission from the fan. For the fan under consideration it is shown that the rotor interaction noise dominates the fan noise. Comparison between the predicted sound pressure levels and experimental observations shows good agreement. Based on the calculated detailed contributions of the different force harmonics acting on the blades to the fan noise, possible means of reducing lifting fan noise are discussed.
Heat Transfer to an Airfoil in Oscillating Flow
Authors: Miller J. A. , Pucci P. F.
Published: November 2010

Local heat transfer coefficients to an airfoil in an oscillating stream have been measured for a range of frequencies and oscillation amplitudes. Results at moderate angles of attack are in agreement with previously reported findings. However, at large angles of attack, including those associated with stall in steady flow, a strong periodic starting vortex shed from the leading edge leads to a dramatic reattachment of the flow and consequent increase in local Nusselt Numbers of as much as five-fold. These effects are shown to be amplified by increasing oscillation frequency and amplitude.
Performance of Compressor Blade Rows in a Sloping Flowpath
Authors: Harmon H. A. , Mikolajczak A. A. , Marchant D.
Published: November 2010

In an effort to reduce engine length and weight it is desirable in some applications, such as high bypass ratio turbofan engines, to introduce compressor stages into a downward sloping flowpath. In this “mixed flow” compressor the airfoil orientation with respect to the flowpath becomes important to ensure good performance. The performance of cascades and compressor stages with sloping walls is presented. Three methods of introducing blading into the flowpath were evaluated. It is shown that by canting the blading to be normal to the flow direction, no penalty in performance is incurred compared to the performance of a typical axial compressor with cylindrical flowpath. Test results are compared with predictions based on intrablade analysis and a wall boundary layer calculation. Qualitatively good agreement is obtained except for the case when the blading is swept with respect to the flow direction. Need for further investigtion of three dimensional internal viscous flows is indicated.
Heat Transfer Characteristics of a Liquid-Metal Filled Closed Thermosyphon
Authors: Pucci P. F. , Gerretsen J. C. R.
Published: November 2010

Experimentally determined heat transfer characteristics are presented for two geometrically similar, closed thermosyphons. Results using water, mercury, and the sodium-potassium eutectic, NaK 56/44, were obtained for two hot wall boundary conditions, namely, constant wall temperature and uniform heat flux. The water filled thermosyphon data were correlated over a range of td = GrdPr (d/Lh) from 5 × 104 to 1.3 × 107, which agrees with and extends existing data. The liquid-metal filled thermosyphon data were correlated over a range of GrdPr2 from 3. × 102 to 2. × 105.
Lift and Pressure Fluctuations of a Cambered Airfoil Under Periodic Gusts and Applications in Turbomachinery
Authors: Naumann H. , Yeh H.
Published: November 2010

Previous authors have considered the unsteady lift of a flat-plate (zero-cambered) airfoil travelling through sinusoidal gusts. The present paper extends the analysis to cambered airfoils with angle of attack moving through both longitudinal and transverse gusts. Closed-form analytical solutions are obtained. The results are used to calculate the unsteady lift on a blade moving through periodic wakes in an axial-flow turbomachine. Knowledge gained by this analysis clearly indicates design trends to obtain minimum lift fluctuations. Since the interference effects of neighboring blades are ignored in this analysis, the conclusions on turbomachinery are strictly valid only for cascades with low solidity.
Corrosion and Deposits From Combustion of Solid Waste
Authors: Krause H. H. , Vaughan D. A. , Miller P. D.
Published: November 2010

Combustion of solid waste in municipal incinerators has resulted in fouling and corrosion on heat transfer surfaces. The nature of these deposits and the extent of the corrosion has been investigated in a combined field and laboratory study. In addition to the elements normally found in boiler deposits, chlorine, lead, and zinc appeared in significant quantities in the incinerator deposits. Twenty specific compounds have been identified in the deposits. The presence of potassium, sulfur, chlorine, lead, and zinc in the corrosion product scale at the metal-deposit interface has been demonstrated. Corrosion resulting from the action of flue gases and accumulated deposits has been measured by means of probes exposed in large municipal incinerators. Mechanisms for the corrosion processes are suggested, and possible remedies are discussed.
An Experimental Correlation of Oxides of Nitrogen Emissions From Power Boilers Based on Field Data
Authors: Rawdon A. H. , Sadowski R. S.
Published: November 2010

A brief review of the kinetic formation of oxides of nitrogen is presented. Distinction is made between thermal NOx and fuel nitrogen NOx. The correlation of results is based both on data from literature and field data from Riley Stoker’s Air Pollution Study Program. The emission of NOx is shown to be capable of correlation based on fuel nitrogen, excess air, fuel, burning area heat release, combustion air temperature, furnace wall deposits, and furnace type. The results correlate to a standard deviation of 60 ppm.
A Contribution to the Theoretical and Experimental Examination of the Flow Through Plane Supersonic Deceleration Cascades and Supersonic Compressor Rotors
Authors: Simon H.
Published: November 2010

The results of the experimental investigations of plane supersonic deceleration cascades (tandem cascades) conducted in recent years at the Institut fu¨r Strahlantriebe und Turboarbeitsmaschinen der Technischen Hochschule Aachen (Institute for Jet Propulsion and Turbine Machines of the Aachen Technical University) are summarized. The flow through a supersonic compressor rotor is determined by means of a suitably enlarged method of characteristics. A division of the blade channel into two sets of stream surfaces permits an iterative calculation of the three-dimensional flow. To determine the flow values in the subsonic range, 5-hole-probes featuring a semi-spherical head are used in front of the rotor. The supersonic flow is determined by means of 5-hole-probes of the conical type arranged at varying distances behind the rotor. To determine the efficiencies, all probes were equipped with two NTC-elements each, for temperature measurement. These measurements were carried out at different rotational speeds and throttle positions and supplied rotor characteristics as well as information on the course of the flow behind the rotor. With unthrottled flow, a total pressure ratio of 3.9 resulted, with a total isentropic efficiency of 89 percent. The measurement of wall pressures on hub and tip furnishes additional information on the course of flow. The test values measured show a satisfactory agreement with the calculated design values.
Reduction of Nitrogen Oxide Emissions From a Gas Turbine Combustor by Fuel Modifications
Authors: Shaw H.
Published: November 2010

A broad experimental program was undertaken to assess the feasibility of reducing NOx from aircraft gas turbine engines by fuel modifications (additives and/or treatments). The modifications were selected without regard to practical limitations in order not to obscure potentially useful approaches. The Esso high pressure cannular combustor was used to simulate the characteristic emissions of gas turbines. Approximately 70 fuel modifications were tested using Jet A as the base fuel. These fell into 7 general categories: (a) soluble organometallic additives which become heterogeneous reduction or decomposition catalysts, (b) additives that scavenge or recombine oxygen atoms, (c) additives that reduce peak temperatures, (d) additives that delay ignition, (e) additives that change spray fluid-dynamics, (f) additives that decompose NO or inhibit the NO producing chain reactions, (g) combinations of the foregoing for synergistic effects. Only category a proved to be effective in reducing NOx emissions. Transition metals added to the Jet A fuel as organometallic compounds reduced NOx by as much as 30 percent. Other additives, some not containing metals, reduced NOx by up to 15 percent. None of the investigated additives was fully acceptable because of the relatively low NOx reduction that was obtained even with high additive treat rates. The experimental work was carried out at an overall air to fuel ratio of around 50 and at a pressure of 48 psig. The exhaust gas composition was typical of the latest aircraft turbine engines with the exception of the carbon monoxide levels which were too high. A statistical analysis of results with unmodified Jet A fuel indicated that variation of air inlet moisture from 0.00025 to 0.0025 lb of water per lb of air, and pressure variations between 45 and 60 psig had an insignificant effect on NOx production over the range of the experimental work.
Fluid Pressure Drop Testing on Once-Through Boilers
Authors: Brummel K. D. , Buchanan A. S.
Published: November 2010

Boiler pressure drop testing has become a useful tool in evaluating the internal waterwall tube deposition on two once-through supercritical pressure boilers. This paper presents the results of five years of testing and describes test procedures, instrumentation requirements, and analysis techniques. The result of this test program has been the minimizing of unit forced outages due to waterwall tube failures.
Thermal-Hydraulic Performance of a 2 MWt Sodium-Heated, Forced Recirculation Steam Generator Model
Authors: Hunsbedt A. , Roberts J. M.
Published: November 2010

The results of LMFBR (Liquid Metal Fast Breeder Reactor) steam generator model tests conducted in a 2 MWt sodium-heated test facility at prototypical Breeder Reactor Demonstration Plant conditions are presented. This includes heat transfer performance data and a sodium-side heat transfer correlation for a seven-tube bayonet tube forced recirculation evaporator with identical tube geometry to a proposed LMFBR Demonstration Plant evaporator. The departure from nucleate boiling characteristic of the bayonet tubes employing swirl flow generators and the steam-side heat transfer coefficients in the transition boiling regime were measured. The steam-side boiling stability characteristics of the evaporator were evaluated and a summary of the results are presented. The results also include heat transfer performance data for a helical coil superheater containing two active tubes and one inactive tube. Sodium temperature distribution data for the evaporator measured at various load conditions indicating steep axial temperature gradients in the sodium inlet plenum region are presented along with sodium temperature distribution data for the superheater. Finally, sodium-side instability data associated with series operation of the models, both containing cover gas spaces, are presented along with sodium temperature fluctuation data measured in the inlet plenum of the evaporator.
A Probabilistic Approach to Safety System Testing and Maintenance
Authors: Chay S. C. , Loftus W. D. , Mazumdar M.
Published: November 2010

This paper presents a method to quantify in terms of probabilistic availability the effects of testing and maintenance schedule on the performance of a standby safety system and it describes the mathematical rationale which lies behind it. The purpose of periodic testing and maintenance is to detect any unannounced failures in the system, repair them, and thus ensure the readiness or availability of the equipment. A scheme is given to model generally any complex system in terms of easily visualized equivalent block diagrams such that the formulas developed in this paper or similarly developed formulas can be easily applied. Also presented is a method for incorporating the field failure data to refine a´ priori assumed failure rates which were used in the initial computations.
Protection of Boiler Feed Pump Against Transient Suction Pressure Decay
Authors: Liao G. S.
Published: November 2010

In a previous paper [1], the analysis of pump suction pressure decay utilizing the varying condensate temperature approach was first introduced. Although the paper provided power plant engineers with an accurate analytical method for determining the magnitude of feedwater pump suction pressure decay, no protective method to prevent or alleviate the pressure decay under instant turbine load rejection was mentioned. As unit size has rapidly increased in recent years, the power plant deaerator requires not only a larger storage capacity but also must be elevated higher to protect the boiler feed pumps against suction pressure decay under load rejection. Since this trend is expected to continue, the cost of supporting the power plant deaerator may soon become prohibitive. Several protective methods have been previously introduced. However, the evaluation of the methods was invariably based on the constant-condensate-temperature approach, which is not suitable for central station regenerative cycle units. This paper reevaluates those methods in general and recommends the on-off type deaerator bypass system as the most effective and economical method. The use of this protective method will not only reduce deaerator storage capacity to the absolute minimum as required solely for surge, but will also largely preclude the provision of additional static head for instant load reduction. As a result, enormous savings can be expected both from the deaerator itself and its supporting structures. The magnitude of savings in supporting structures alone may amount to more than a half million dollars for a 750 MW fossile unit. Based on the varying condensate temperature approach, mathematical equations expressing the deaerator pressure decay as well as design parameters required for designing the protective system have been derived. The paper also presents a detailed description of the recommended protective system and discusses some advantages of this system over the others. Finally, a few engineering examples are included to illustrate the application in system design.
A Two-Temperature, Gas-Particle Suspension in MHD Power Generation
Authors: Helfritch D. J. , Gustafson W. A.
Published: November 2010

A feasibility study has been made of the use of a two-temperature, gas-particle suspension as the conducting medium in MHD generators. Large gas-particle temperature differences following nozzle expansions have been calculated, and the power generated by the use of these suspensions in MHD generator ducts has been investigated. Although relatively low gas temperatures have been considered, high electrical conductivities can be achieved by means of thermionic emission of electrons from high temperature particles. It is shown that total output power increases as gas temperature is decreased by means of continued nozzle expansion. Output power is also increased through the use of relatively large particles.
A Three-Dimensional Theory for Calculating Circulation in Axial Turbomachines (Direct Problems)
Authors: Lumsdaine E. , Fathy A.
Published: November 2010

In this work the steady-state spanwise circulation distribution of thin, slightly cambered radial blades of finite length is calculated using the method of singularities. The analysis extends the method of Scholz [1] for two-dimensional cascades to the three-dimensional case of radial blades of finite length. The effect of the casing enclosing the cascade is introduced by the method of images. The present analysis uses the generalized cylindrical coordinates without the restriction of the Prandtl lifting line theory. Comparisons show that for large hub-tip ratios, the use of the lifting line approximation will result in large errors. For small tip clearance or large length-chord ratio the present results reduce to the two-dimensional cascade solution.
Operational Limits for Gas Turbine Compressors During Transient Conditions in a Helium Cooled Reactor
Authors: Tiberini A.
Published: November 2010

The use of gas turbines in Gas Cooled Fast Reactors requires an accurate analysis of the loss of pressure accident induced by the rupture of a main helium pipe. In this paper a multiloop design is considered. The loop in which the pipe rupture occurs is assumed to be out of operation. The results presented show under which conditions the turbogroups of the nondamaged loops are capable to maintain forced convection, thus ensuring the after heat removal even if a very small quantity of coolant gas is left in the reactor system. In particular the influence of the flow restrictors at the reactor inlet and outlet, the total helium mass, the final containment pressure, the pony motors and the scram delay on the proper functioning of the helium compressors is investigated.
Two-Dimensional Compressor Cascades With Optimum Velocity Distribution Over the Blade
Authors: Citavy´ J.
Published: November 2010

Results are presented of a research on an optimum cascade problem in two-dimensional subsonic flow at SVUSS (National Research Institute for Machine Design, Bechovice). The optimisation is based on a determination of the optimum velocity distribution (OVD) and on the solution of the inverse cascade problem. The OVD has been ascertained from a variational problem formulated by Sˇpacˇek as follows: to find such a velocity distribution on the suction surface for which the momentum thickness at the trailing edge has a minimum value. The problem was solved by Ru˚zˇicˇka using a simplified boundary layer method. Inverse cascade problem due to Pola´sˇek was employed to calculate the cascade geometry for a given optimum velocity distribution and the given stagger angle and the space chord ratio. Series of compressor cascades having the optimum velocity distributions has been designed by means of a digital computer. Some cascades of the series were tested in the low-speed windtunnel as well as at the high subsonic speeds. Reasonable agreement between the predicted and the experimental pressure distributions, flow deflection and loss coefficient has been achieved.
Ceramic Rotating Blades: Some Critical Design Parameters for Gas Turbine Applications
Authors: Schaller R. J. , Visser C. , Lien S.
Published: November 2010

A three-dimensional analysis of a ceramic rotating blade is presented. The analysis reveals that under a centrifugal force load the maximum stress occurs in the root of the blade. The root, a critical area for this blade, is then analyzed in detail in an effort to reduce this stress. This requires a study which considers the effect of friction, contact area, and root geometry on root stresses. This paper is the first step in a feasibility study to ascertain if ceramics are applicable to rotating blades for heavy duty gas turbines. The next step will be to determine the transient thermal and vibratory stresses in the ceramic blade during a turbine operating cycle.
Theoretical Solution of High Subsonic Flow Past Two-Dimensional Cascades of Airfoils
Authors: Lakomy´ C.
Published: November 2010

The paper presents an entirely novel theoretical solution of inviscid flow past two-dimensional cascades of aerofoils at high subsonic velocities. The solution is carried out in the physical plane by the help of transformation equations derived for streamline coordinates. The transformation equations define the dependence between the flow fields in the regions of incompressible and compressible flows past the cascade. Knowing the incompressible flow, one can calculate the velocity distribution on an aerofoil and the outlet flow angle of the cascade in a comparatively simple way. The method makes it possible to determine the critical Mach number of the cascade with ease. The requisite computer time is relatively short. The results obtained by the new method show a very good agreement with those of other authors and with experiments.
Parametric Study of a Gas Turbine
Authors: Boyce M. P. , Hanawa D. A.
Published: November 2010

The evaluation of a gas turbine starts out with the basic cycle analysis and ends up with developing techniques for field performance evaluation and maintenance scheduling. This paper outlines the various cycles available to the user and the performance of each of these cycles. It also outlines techniques and equations which may be used in the field to get a fast and relatively accurate check on the performance of these units. Also some significant parameters and their sensitiveness on the calculations are indicated. The paper also investigates the way exhaust temperature readings may be utilized as an effective maintenance tool.
High-Temperature Corrosion in Gas Turbines and Steam Boilers by Fuel Impurities—Part V: Lead Containing Slags
Authors: Zetlmeisl M. J. , May W. R. , Annand R. R.
Published: November 2010

The effect of lead on the corrosivity and friability of slags containing various ratios of sodium, vanadium, magnesium, and silicon has been evaluated. The application of the linear polarization technique was demonstrated. Lead produces very corrosive melts and tenacious slags. Magnesium will inhibit corrosion to acceptable levels and produce friable slags at 800 °C with a 4 to 1 ratio of additive to vanadium plus lead and a sodium to vanadium plus lead ratio no greater than 0.1. To produce friable slags at 900°, sodium must first be reduced to a sodium to vanadium plus lead ratio of 0.01. Second, a magnesium-silicon additive must be used at a 6 to 1 ratio of additive to vanadium plus lead. The corrosion rates of lead containing melts increases rapidly with sodium level.
Experimental and Analytical Sonic Nozzle Discharge Coefficients for Reynolds Numbers up to 8×106
Authors: Szaniszlo A. J.
Published: November 2010

Sonic discharge coefficients are presented for two different geometry flow nozzles using nitrogen gas at high pressures (100 atm (100 × 105N/m2)) where real-gas corrections are significant. Throat Reynolds number range extended up to 8 × 106. Experimentally obtained coefficients for a nozzle with a continuous and finite radius of curvature agreed with those obtained analytically to within 0.2 percent. Experimental coefficients for a long-radius ASME nozzle agreed to within 1/4 percent to an empirical equation representing the most probable subsonic discharge coefficient.
Effect of Solid Particles on Turbine Performance
Authors: Tabakoff W. , Hosny W. , Hamed A.
Published: November 2010

A theoretical method was developed for predicting the pressure distribution over a blade in cascade for a compressible flow with solid particles. Experimental results were obtained from a cascade wind tunnel equipped with a solid particle injection system. Good agreement was noted between the theoretical and experimental pressure distribution. The change in pressure due to the particles gives reduction in the force on the blades. The presence of solid particles in air-breathing engine gas flow changes the turbine performance. The overall turbine efficiency decreases as a result of the introduction of solid particles. The performance experiment was performed on a two-stage velocity-compounded turbine.
A Theory of Concentrators of Solar Energy on a Central Receiver for Electric Power Generation
Authors: Riaz M. R.
Published: November 2010

The modeling of the performance of large-area solar concentrators for central receiver power plants is formulated using a continuum field representation of ideal heliostat arrays that accounts for two governing factors: the law of reflection of light rays imposes steering constraints on mirror orientations; the proximity of mirrors creates shadow effects by blocking the incident and/or reflected solar radiation. The results of a steering analysis which develops the space-time characteristics of heliostats and of a shadow analysis which determines the local effectiveness of mirrors in reflecting solar energy to a central point are combined to obtain in closed analytical form the global characteristics of circular concentrators. These characteristics which appear as time profiles for mirror orientations, for effective concentration areas (i.e., reflected solar flux), and for concentration ratios, establish theoretical limits of performance against which actual or realistic solar power systems can be compared and assessed.
Techniques for Noise Exposure Control in Existing Power Plants
Authors: Popeck R. A.
Published: November 2010

The control of noise exposure in existing power plants is a horrendous task. Among the difficulties encountered in a noise control program are: (1) identification of sources of high sound levels; (2) identification of personnel exposure; and (3) identification of feasible means to control sound levels. In addition, there is the ever-present problem of implementing a personal hearing protection program for those areas which cannot feasibly be quieted and, during the feasibility study and implementation period, for those areas which can be feasibly quieted. This paper describes procedures and equipment which can be used to control noise exposure in existing power plants.