bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuum Theory of Ductile Rupture by Void Nucleation and Growth: Part I—Yield Criteria and Flow Rules for Porous Ductile Media
Authors: Gurson A. L.
Published: November 2010

Widely used constitutive laws for engineering materials assume plastic incompressibility, and no effect on yield of the hydrostatic component of stress. However, void nucleation and growth (and thus bulk dilatancy) are commonly observed is some processes which are characterized by large local plastic flow, such as ductile fracture. The purpose of this work is to develop approximate yield criteria and flow rules for porous (dilatant) ductile materials, showing the role of hydrostatic stress in plastic yield and void growth. Other elements of a constitutive theory for porous ductile materials, such as void nucleation, plastic flow and hardening behavior, and a criterion for ductile fracture will be discussed in Part II of this series. The yield criteria are approximated through an upper bound approach. Simplified physical models for ductile porous materials (aggregates of voids and ductile matrix) are employed, with the matrix material idealized as rigid-perfectly plastic and obeying the von Mises yield criterion. Velocity fields are developed for the matrix which conform to the macroscopic flow behavior of the bulk material. Using a distribution of macroscopic flow fields and working through a dissipation integral, upper bounds to the macroscopic stress fields required for yield are calculated. Their locus in stress space forms the yield locus. It is shown that normality holds for this yield locus, so a flow rule results. Approximate functional forms for the yield loci are developed.
Analysis of Fatigue Fracture of Ball Joint Sockets by Indentation Hardness and Transmission Electron Microscopy
Authors: Felbeck D. K.
Published: November 2010

An accident involving a 3-wheeled vehicle resulted in personal injury and property damage. Analysis of the failure by direct observation, optical microscopy, transmission electron microscopy, and techniques involving mutual indentation hardness shows that the accident resulted from fatigue fracture in a ball-joint socket at one end of a strut connecting the frame to the rear axle. Absence of a suspension system in the vehicle was the most likely single cause of the fatigue fracture.
Failure of a Welded Blower Fan Assembly
Authors: Smith Charles O.
Published: November 2010

This is an account of a welded blower fan assembly which failed in operation with a large detached portion killing the owner. The circumstances, method of fabrication, and mode of operation are discussed. Failure was due to a combination of a design defect and a worn shaft.
Effect of Hydrothermal Environments on the Erosion of Castable Refractories
Authors: Wiederhorn S. M. , Fuller E. R. , Bukowski J. M. , Robbins C. R.
Published: November 2010

Hydrothermal environments are expected to adversely affect the erosive resistance of castable refractories intended for use in high wear areas of coal gasification plants. The erosive wear behavior of two grades of refractories proposed for such use was studied at room temperature after exposure of the refractories to high-pressure steam. Wear occurs primarily in the cement phase that bonds the more wear-resistant aggregate. The wear resistance of the refractories depended on chemical interactions between the cement and the high pressure steam. Although chemical changes were observed to occur in both refractories, the wear resistance was found to decrease only in those cases for which the strength of the cement phase was substantially reduced.
The Tensile Ductility of Austenitic Steels in Air and Hydrogen
Authors: Capeletti T. L. , Louthan M. R.
Published: November 2010

An empirical correlation of yield strength with reduction-in-area at fracture was demonstrated for austenitic stainless steel. The correlation is consistent with an existing fracture model that involves microvoid nucleation at isolated inclusions. Hydrogen effects on tensile ductility are also consistent with this model, if one assumes that hydrogen is transported by glide dislocations and that localized hydrogen accumulations lower the stress necessary to initiate fracture at particle-matrix interfaces. Smooth-bar tensile specimens of fourteen austenitic stainless steels were tested at room temperature in air, in 69-M Pa He, and in 69-M Pa H2. Macroscopic reductions-in-area at fracture varied between 12 and 82 percent, and yield strengths were between 179 and 1069 MN/m2. The resulting empirical correlation suggests that the ductility of austenitic stainless steels is limited by the interfacial stress required for microvoid nucleation and coalescence. For low strength steels, the required interfacial stress is reached only after extensive plastic deformation. However, as steel strength is increased, fracture occurs at lower strains.
Development of Random Fatigue Data for Adhesively Bonded and Weldbonded Structures Subjected to Dynamic Excitation
Authors: Wentz K. R. , Wolfe H. F.
Published: November 2010

Prediction methods are being developed to determine the sonic fatigue life of various weldbonded and adhesively bonded aircraft structures when exposed to high intensity acoustic excitation. This paper describes the results of the experimental investigations performed by the AF Flight Dynamics Laboratory to obtain the factors that affect the random fatigue life of typical aircraft structural joint configurations. The structures tested included full-scale components, simple beam sections, and acoustic panel configurations. A variety of aluminum skin thicknesses, stiffener configurations, and bond systems have been tested under dynamic excitation. The bond systems tested begin with the weldbond systems developed in the early 1970s up to the present bond systems. Random flexural fatigue curves for two modes of failure have been developed: adhesive bond system failure and metal fatigue failure. These curves are part of the design criteria needed to predict the sonic fatigue life of weldbonded and adhesively bonded structures.
The Effect of Material Constitutive Models on Stress Wave Propagation Calculations
Authors: Herrmann W. , Lawrence R. J.
Published: November 2010

Material models which have been successfully used for describing experimental observations of stress wave propagation in metals, polymers, composites, and porous materials are used in a series of one-dimensional finite-difference calculations of stress pulses propagating in a semi-infinite medium. These calculations show the effect of the material model on pulse attenuation. Parametric variations indicate the sensitivity of the attenuation to the parameters of each model. A simple conceptual description based on the hysteretic energy loss experienced by the material in a loading-unloading cycle is used to explain the results. Relevance of the results to the prediction of damage in specific engineering design calculations is developed. The results and conceptual description should aid the stress analyst in assessing which effects to include in the material model used in specific multidimensional calculations.
Crack Growth Resistance at Low Stress Intensities
Authors: Wilhem D. P. , Ratwani M. M.
Published: November 2010

A detailed examination of the early stage of slow tear in thin section aluminum, under increasing load, is reported in this study. The relationship between plane strain fracture toughness and crack growth resistance is shown as a point on the crack growth resistance curve. The confirmation of this behavior for thin sections leads to a better understanding of the early stage of crack growth resistance. A crack line wedge loaded (CLWL) specimen was loaded in both tension and wedge loading. Good correlation was obtained between the early stage crack growth resistance for each loading mode.
Helium Blistering in Metals
Authors: St-Jacques R. G. , Terreault B. , Martel J. G. , L’Ecuyer J.
Published: November 2010

In a fusion reactor, various parts will be exposed to an important flux of helium atoms. Under certain conditions this will cause blistering resulting in surface erosion and plasma contamination. We discuss measurements of the following blister parameters: blister skin structure and thickness, helium depth distribution, and swelling. These data refer mainly to 10-20 ke V He blistering of Nb and Cu where the blister skin is apparently two times thicker than in the “gas pressure” model. However, the observation of a depletion at the center of the helium distribution, of bubbles in the skin, and of ∼ 40 percent swelling allow us to conclude that this model is still valid.
Corrosion Performance of Austenitic Alloys in Automobile Exhaust Environments
Authors: Chart J. E. , Michels H. T.
Published: November 2010

The performance of several austenitic alloys ranging from low alloy content stainless steels to nickel-base alloys has been evaluated at temperatures from 704–1093°C (1300–2000°F) in cyclic air + 10 percent water vapor and from 704–982°C (1300–1800°F) in gasoline engine exhaust. The gasoline engine exhaust was found to be the more aggresive of the two test environments. A general trend of increasing performance with increasing nickel content was observed. At the highest test temperatures in both tests, the nickel-base alloys clearly displayed superior performance.
Sodium Vapor Deposition in Inert Enclosures
Authors: Sutherland J. D. , Markley R. A. , McKinney J. L.
Published: November 2010

Sodium vapor deposition is acknowledged to be a potential problem in several activities associated with Liquid Metal Fast Breeder Reactors (LMFBRs). Attempts were made to predict sodium evaporation rates using the empirical expression Nu = 0.643 (GrSc)0.25 developed for the evaporation of water. Small scale experiments were performed which indicate the general validity of this expression for sodium evaporation. The experiments also demonstrated that deposition of sodium within inert gas filled enclosures can be substantially reduced by circulating and filtering the atmosphere of the enclosure.
A Thermodynamic Analysis for Detonation-Free Engine Performance
Authors: Powell C. K. , Alford R. N. , Chen T. N. , Kevorkian V.
Published: November 2010

A method of thermodynamic analysis of power cycles incorporating more complete expansion and turbocharging with after-cooling is presented; it predicts the performance of constant volume combustion engines under detonation-free conditions. The analysis involves expressing the detonation limit in terms of the firing pressure and a theoretical adiabatic end-gas temperature. Expressing the detonation limit in this form, the performance map for any constant volume combustion engine can be predicted. The map yields detonation-free operation over a wide range of bmep and bsfc by identifying the required combinations of fuel-air ratio, compression ratio, expansion ratio, and blower pressure ratio. The analysis requires information on the combustion characteristics of the specific engine, namely, the deviations of the thermal efficiency and the firing pressure from those derived from the equivalent fuel-air cycle. Analysis showed that a significant gain of engine output can be realized without detonation occurring by employing higher blower pressure ratio and firing pressure. The lower limit of fuel consumption is determined directly by the performance of the turbocharger and indirectly by the heating of the inlet air and the detonation limit. Tests performed on a 17-in-bore single cylinder gas engine at two different expansion ratios verified the analytical prediction of detonation-free operation over a wide range of bmep, from 135 to 346 psi. The type of performance map resulting from this analysis is useful in the selection of engine performance and engine parameters for the development of new engines.
Off-Design Performance of Multistage Turbines
Authors: Kroon R. P. , Tobiasz H. J.
Published: November 2010

Nondimensional equations are developed for the performance of a multistage axial flow turbine operating at conditions which differ from those for which the turbine is designed. The effect of variations in inlet temperature, inlet pressure, exit pressure, and turbine speed is explored. Typical cases are evaluated. The method presented is thought to be useful particularly for preliminary design.
Analysis of a Combined Gas Turbine and Absorption-Refrigeration Cycle
Authors: Nagib M. M.
Published: November 2010

An appreciable improvement in the performance of gas turbines operating with ambient temperatures above 90 deg F could be achieved by combining an absorption-refrigeration unit to the power cycle. The thermal energy in the exhaust gases from the turbine is used to operate the refrigeration unit, which in turn cools the air prior to entering the compressor. This reduction in compressor-inlet temperature results an average improvement of about 7–9 points in the thermal efficiency of the combined cycle as well as an increase in the specific output. The analysis includes the effect of different cycle parameters such as compressor pressure ratio, maximum cycle temperature, and regeneration.
Acceleration Performance Analysis of a Gas Turbine Destroyer Escort
Authors: Bodnaruk A. , Rubis C. J.
Published: November 2010

The dynamic acceleration performance of a single screw destroyer escort driven by two FT4A-2 gas turbine engines through a reversing reduction gear was analyzed. The analysis was carried out on a digital computer using a new method of a second modified advance coefficient to represent propeller thrust and torque coefficients. Quantitative results for all the major ship and propulsion plant parameters are given for the ship in a calm sea with no turning motions during fuel scheduled acceleration in the base and base-plus-boost operating modes. Control of fuel flow rates using fuel ramps with varying time bases was found to be effective in limiting engine overtorque conditions during acceleration. Other conclusions on transient thrust, acceleration time, and head reach are also presented.
Laboratory Procedures for Evaluating High-Temperature Corrosion Resistance of Gas Turbine Alloys
Authors: Lee S. Y. , DeCorso S. M. , Young W. E.
Published: November 2010

With an increasing interest in the burning of heavy fuels in gas turbines there is also concern with the precise determination of the corrosive effects which may arise from the use of these fuels. Of particular interest is a class of fuels known as ASTM Specification No. 3-GT which has a low level of metal contaminant, nominally up to 5 ppm alkali metal and 2 ppm vanadium. In this paper we describe experimental laboratory equipment and the program with which we determine the extent of corrosion to be expected when such fuels are burned in gas turbines. The results using several pieces of experimental apparatus are presented, and their correlation with available field experience is considered. In general, the amount of deposit which collects on the blade surface and precedes corrosive attack is proportional to the amount of contaminant in the gas stream. There is a significant influence of stream velocity and/or pressure on hot corrosion which must be considered in applying the results from low-velocity low-pressure rigs to operating gas turbines. According to the data obtained in a pressurized passage which realistically simulates the actual gas turbine, fuel containing 5 ppm Na and 2 ppm V is too corrosive to use in the gas turbine at a 1500 deg F metal temperature.
An Approximate Analysis of Gaseous Film Cooling With Constant Fluid Properties
Authors: Gaddis J. L. , Lamb J. P.
Published: November 2010

Presented herein is an analysis of the velocity and temperature fields for a constant-property turbulent flow downstream of a step-type injection slot. The flow field is considered to be in a developing condition and is quantitatively described with a two-layer model in which the outer region is dominated by large-scale turbulence typical of free shear layers. An approximate solution for the outer region is appropriately joined to an inner profile determined by the usual “law of the wall” so that one obtains both the correct profile shape for the complete viscous layer and the proper spatial positioning of velocity and temperature profiles. The latter are obtained from a linearized energy equation with unit turbulent Prandtl number and are employed, along with the velocity profiles, in an energy balance to determine the longitudinal variation of the effectiveness. A successful calculation technique is discussed and typical results are compared with existing experimental data. The analysis is shown to be competitive in accuracy with available correlation expressions while also yielding considerable insight into the interaction of various design parameters.
Measurements of Secondary Flows in a Rotating Duct
Authors: Wagner R. E. , Velkoff H. R.
Published: November 2010

The paper presents a review of analytical and experimental work which has been done on flows in rotating ducts. It presents the results of an experimental study to measure the secondary flows predicted by the previous analytical work. A duct of approximately 3 ft in length with a cross section of 2 × 5 in. was rotated up to speeds of 300 rpm. Air was used as the working fluid. Static pressures, total pressures, and yaw angles were measured at selected points along the channel. The flow regime examined was the developing flow from the entrance to the exit of the channel. Examination of the data revealed the presence of two longitudinal vortices which extended the length of the channel. Pressure distribution across the height of the channel and across the width of the channel was obtained. The magnitude of the cross-flow velocities in the channel were determined and mapped. It was found that the data for various rotational speeds could be collapsed upon a single curve by dividing all data by the rotational speeds. The results of the experimental study provide solid verification for the hypothesis of longitudinal vortices in rotating ducts.
Perspectives for Waste Heat Recovery by Means of Organic Fluid Cycles
Authors: Angelino G. , Moroni V.
Published: November 2010

Organic compounds, employed as working fluids for low temperature heat recovery, are shown to exhibit a performance better than that of steam cycles. The potential influence on efficiency and specific work of organic fluid power recovery applied to existing open cycle gas turbine, diesel and gas engines is illustrated on the base of a statistical documentation. The basic characteristics of a typical combined cycle layout are analyzed with respect to fuel economy, air consumption and heat exchange surface requirements. The possibility of improving the performance of closed cycle (helium) gas turbines by means of an organic fluid heat recovery cycle is then examined. The potential benefits deriving from the use of the power turbine of the organic fluid cycle as a direct driver for the compressor of a refrigerating cycle or heat pump employing the same working fluid are discussed. The basic results of a test program aiming to determine the decomposition rates and the corrosion characteristics of some organic working media are presented.
Review of Compressible Flow Theories for Airfoil Cascades
Authors: Gostelow J. P.
Published: November 2010

Solutions to the direct problem of subsonic flow calculation for cascades are first reviewed and the existing techniques are classified into series, iterative, matrix, and streamline curvature solutions. Most techniques appear to be successful when the peak velocity remains subsonic. Some solutions to the design problem are reviewed but results from these require further verification. Purely supersonic cascade flows, although rare, offer no particular difficulties but the regime of greatest current activity involves transonic or mixed flows. Where both subsonic and supersonic flows exist various new techniques offer great promise.
The Containment of Disk Burst Fragments by Cylindrical Shells
Authors: Hagg A. C. , Sankey G. O.
Published: November 2010

Tests and analysis show that containment of missile-like steel disk fragments by a steel cylindrical shell is a sequential two-stage process. Stage 1 involves inelastic impact and transfer of momentum to include an effective target mass. For nonperforation, the energy dissipated in plastic compression and shear strain at the local impact area must be sufficient to accommodate the loss in kinetic energy of the system. With nonperforation, the process enters stage 2, which involves dissipation of energy in plastic tension strain over extended volumes of shell material. For containment, the energy dissipated in plastic strain in stage 2 must accommodate the residual kinetic energy of the system. Criteria for nonperforation and containment are given which are in satisfactory agreement with test results.
High-Temperature Corrosion in Gas Turbines and Steam Boilers by Fuel Impurities: IV—Evaluation of Silicon and Magnesium-Silicon as Corrosion Inhibitors
Authors: May W. R. , Zetlmeisl M. J. , Annand R. R.
Published: November 2010

The corrosion rates of Udimet™ 500 in a variety of sodium sulfate-silica-vanadium pentoxide and sodium sulfate-magnesium sulfate-silica-vanadium pentoxide slag compositions were measured electrochemically at temperatures up to 950 deg. The weight ratios of the elements, sodium, silicon, and magnesium to vanadium were defined for acceptable corrosion rates. A simple burner test for slag evaluation is described. Characteristics of slags produced by magnesium, silicon, and magnesium-silicon in conjunction with sodium sulfate and vanadium pentoxide are discussed. Results indicate that the magnesium-silicon combination produces a slag which is equally as low as magnesium in corrosivity and superior in slag characteristics.
Power Reduction in Air Conditioning by Means of Off-Peak Operation and Coolness Storage
Authors: Dudley J. C. , Freedman S. I.
Published: November 2010

An original air-conditioning system was developed which requires considerably less power than conventional systems while providing identical cooling and dehumidification. The 50 percent (depending on application) power reduction is accomplished by off-peak compressor operation and storage of chilled water. The full cooling and dehumidification is accomplished by means of a new thermodynamic cycle involving two evaporators with an intermediate condenser operating with the stored chilled water. The system was built, instrumented, and operated reliably. Evaluation of performance data confirmed the theory and verified the power reduction, cooling, and dehumidification performance calculations.
Conversion of Fuel Nitrogen to NOx in a Compact Combustor
Authors: Hazard H. R.
Published: November 2010

A low-nitrogen fuel, ASTM Jet A aviation kerosene, was doped with increasing amounts of pyridine as a means of increasing the content of chemically bound nitrogen, then burned at a rate of 50 lb/hr in a compact combustor incorporating staged air admission with a rich primary zone, and water cooling of the walls. Each increase in fuel nitrogen content resulted in a significant increase in NOx in the combustion products, and it is estimated that as much as 90 percent of the fuel nitrogen was converted to NOx at very low nitrogen levels, decreasing to 55 percent conversion at higher levels. These results are consistent with data reported for large steam boilers and for small residential boilers. It appears that emission standards requiring very low levels of NOx emission will require use of fuels with very low nitrogen content.
Vibrations and Stability of Turbine Blades at Stall
Authors: Pigott R. , Abel J. M.
Published: November 2010

A method is given for analyzing the vibrations of turbine blades subjected to flows at high negative incidence angles. The conditions for the existence of self-excited vibrations and the stability of these vibrations are derived for free-standing or grouped blades which are of tapered and twisted form. The technique given extends the analysis of Sisto [1] to the case in which any mode of vibration may be considered and in which the aerodynamic forces and moments taken on a quasi-steady basis are functions of Mach number as well as instantaneous angle of attack. Results are given for a group of four lashed blades and some experimentally observed behavior is reported.
The Correlation Between Droplet Steam Structure and Steam Turbine Blading Erosion
Authors: Krzyz˙anowski J.
Published: November 2010

A theoretical study of the correlation between droplet stream structure and steam turbine blading erosion is presented. To this end a simplified description of the motion of the individual droplet within the axial gap of a turbine stage has been used. It’s validity has been checked in an earlier paper [1]. The structure of the droplet stream has been defined by a distribution function assumed to depend, at a given gas velocity, on the droplet radius only. The family of these functions has been established by some experimental data; more knowledge in this field, however, is needed. The formulas for the mean values of some selected parameters of droplet impact have been developed, and some results of numerical calculations for two typical rotor blade profiles are discussed.
Heat Transfer and Film Cooling Following Normal Injection Through a Round Hole
Authors: Eriksen V. L. , Goldstein R. J.
Published: November 2010

Heat transfer is measured downstream of perpendicular injection of an air jet through a single hole into a turbulent mainstream boundary layer. The heat transfer coefficient, calculated from wall temperature measurements with a constant heat flux from the test surface, is determined with injection of both heated and unheated jets. The heat transfer coefficient near the hole is as much as 45 percent larger than the value without injection for a blowing rate (mass flux ratio) of 2.0. Even far downstream, the heat transfer coefficient is 10–15 percent greater than the flat plate value for blowing rates greater than 0.2. The increased value of the heat transfer coefficient near the point of injection is due to the high turbulence levels that arise from interaction between the jet and main flow near the point of injection. Significant variations of the heat transfer coefficient with Reynolds number or wall heat flux are not observed.
The M.I.T. Blowdown Compressor Facility
Authors: Kerrebrock J. L. , Epstein A. H. , Haines D. M. , Thompkins W. T.
Published: November 2010

A Blowdown Compressor Test Facility has been developed which allows time resolved aerodynamic testing of full-scale transonic compressor rotors at low cost. The rotor is brought to speed in vacuum, a diaphragm is opened, and the test gas allowed to flow for a time of the order of one tenth sec, during which the rotor is driven by its own inertia. Both “steady-state” performance evaluation and detailed time resolution of the flow on the blade-passing time scale have been demonstrated for a two-ft dia transonic rotor with tangential Mach number of 1.2 and nominal pressure ratio of 1.6. The steady-state performance as determined in the experiments includes an efficiency of 0.92 and a pressure ratio of 1.55 at design speed. The time resolved measurements include the combination tone structure in the upstream flow field, resolved both axially and radially, and the wake structure downstream of the rotor, also resolved both radially and axially. The radial and axial variations of the rms amplitude of a dominant combination tone are found to agree well with duct mode theory, the axial dependence indicating a standing wave. From the wake measurements, preliminary estimates are given of wake spreading and decay rates, in rotor-exit flow fields.
Rejection of Waste Heat From Power Plants Through Phased-Cooling
Authors: MacFarlane J. A. , Goodling J. S. , Maples G.
Published: November 2010

Because of the disadvantages associated with present power plant cooling systems, a new concept in waste heat dissipation, called “phased-cooling”, is introduced. Heated condenser cooling water is held in a storage pond during certain hours of the day, to be cooled at a later time by traveling across a cooling surface. A thermodynamic analysis of the system is performed, and the equations of heat transfer from a water surface are presented. The developed model is then used for prediction of system performance. The optimum number of storage hours is shown to be dependent upon the size of the system, the season, and meteorological conditions. Phased-cooling evaporation losses are approximately 40 percent less than those of cooling towers and cooling ponds. Condenser inlet temperatures are significantly lower than those of cooling ponds of similar size.
Rotor Design to Attenuate Flow Distortion—Part I: A Semiactuator Disk Analysis
Authors: Savell C. T. , Wells W. R.
Published: November 2010

The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady semiactuator disk cascade theory. This method models the blade cascade as one-dimensional wave guides and describes the transmission characteristics of a rotor to be a function of the distortion wave length and the length of the rotor chord, as well as the normal design parameters. Two parametric studies on the response of a loaded rotor to inlet distortions are done for a single rotor operating at off design conditions and a number of rotors operating at their design points. Fourier series representations of arbitrary distortion wave shapes are used for comparison with experimental data.
Effects of Inlet Temperature Gradients on Turbomachinery Performance
Authors: Lakshminarayana B.
Published: November 2010

An analysis is carried out to predict the nature and magnitude of secondary flows induced by temperature gradients in turbomachinery stator and rotor. The effect of this thermal driven secondary flow is severe in gas turbines, due to large temperature gradients that exist at the outlet of the combustion chamber. Secondary flows change the temperature profiles at the exit of the blade row and generate thermal wakes. A method of incorporating these effects into the calculation of gas, blade and casing temperatures in a turbine is demonstrated through an example.
Secondary Flow Effects on Gas Exit Angles in Rectilinear Cascades
Authors: Bardon M. F. , Moffatt W. C. , Randall J. L.
Published: November 2010

This paper considers the problem of secondary flow generation in a blade passage resulting from the presence of end-wall boundary layers at the passage inlet. These boundary layers are represented by a vorticity normal to the inlet flow, which takes on a streamwise component as the fluid is turned in the passage. Finite-difference solutions for this streamwise vorticity at the passage exit are found for steady, inviscid, incompressible flow about thin, circular arc blades of moderate turning. From these, the secondary flow stream functions, and subsequently outlet angle changes due to secondary flow are computed. Calculations were made for a wide range of blade spacings, chords and lengths, inlet boundary layer thicknesses and gas inlet and leaving angles. A careful study of these results led to the development of a simple but remarkably consistent correlation between outlet angle change due to secondary flows and the cascade geometry. While somewhat limited in its applicability, the correlation gives the axial turbomachine designer a very simple method of assessing the spanwise variation of gas leaving angles resulting from secondary flows at the blade exit.
Influence of Liquid Properties on Airblast Atomizer Spray Characteristics
Authors: Rizkalla A. A. , Lefebvre A. H.
Published: November 2010

A series of tests has been carried out on a specially designed airblast atomizer in which the liquid is first spread into a thin sheet and then subjected on both sides to the atomizing action of high velocity air. The primary aim of the invesitgation was to examine the influence on mean drop size of liquid viscosity, surface tension and density. The liquids employed represented a range of values of surface tension from 26 to 73 dynes/cm, while viscosity and density were varied between 1.3 and 124 centipoise and 0.8 and 1.8 gm / cm3, respectively. Atomizing air velocities covered the range of practical interest to the designers of continuous combustion systems and varied between 60 and 125 m/sec. Analysis of the experimental data showed that they could be described to a reasonable order of accuracy by the following empirical expression: SMD=521Va−1·σ0.5·ρ0.75(1+WlWa)+0.037η0.85(σρ)1.2(1+WlWa)2
A Method of Predicting the Behavior of a Turbulent Boundary Layer With Discrete Transpiration Jets
Authors: Herring H. J.
Published: November 2010

A method is proposed for predicting the behavior of a turbulent boundary layer with heat transfer under the influence of transpiration with discrete jets. The boundary layer is treated as a laterally averaged flow and the effects of nonuniformity are introduced through additional momentum and energy source terms in the equations of motion. These nonuniformity interaction terms are obtained using solutions of a set of ordinary differential equations governing the trajectory of jets. The effects of interaction between the jet and boundary layer turbulence structure are also treated. The predictions of the theory are shown to compare well with available discrete jet-boundary layer data.
Analysis of Power Plant Safety and Relief Valve Vent Stacks
Authors: Liao G. S.
Published: November 2010

Power plant safety and relief value vent stacks have generally been sized according to the methods and design criteria published by Max W. Benjamin in the 1940s. Although the method might have been satisfactory at that time utilizing basic flow dynamics, it not only requires laborious calculations, but also contains some inadequate approaches which may contradict the theory of compressible fluid mechanics available today. This paper presents a complete analysis of steam conditions and its properties from power plant safety/relief valve inlet through its vent stack to the atmosphere. The analysis is based on the theory of compressible fluid flow under irreversible adiabatic process to establish a method and criterion for vent stack design. The method developed herein is applicable to both choking and nonchoking conditions at the valve exit and/or vent stack outlet, and greatly reduces complex trial-and-error solution. Furthermore, an accurate determination of fluid conditions will facilitate the calculation of reaction forces on safety/relief valve and its stack. This paper also presents the results of sensitivity analyses to verify the validity of applying perfect gas equations to steam.
Theoretically Estimating the Performance of Gas Turbines Under Varying Atmospheric Conditions
Authors: Ushiyama I.
Published: November 2010

It is well known that the performance of internal combustion engines is affected by varying atmospheric conditions, namely by the atmospheric temperature, pressure, and humidity. However, except for variable-speed gas turbines, performance correction formulas have not been established for gas turbines as they have for reciprocating engines. Although performance correction formulas, based on dimensional analysis, have been proposed for variable-speed gas turbines, these formulas are not applicable to the constant-speed gas turbines which are commonly used to drive generators. The correction quantities of gas turbines must be obtained experimentally. But, in general, a gas turbine, compared to a reciprocating engines, consumes such a large amount of air that conducting experiments at various atmospheric conditions in an environmental laboratory is hardly feasible. Therefore it is necessary to establish highly accurate performance correction formulas theoretically. The purpose of this paper, as a basic study in the development of correction formulas, is to analyze theoretically the effects of atmospheric conditions on the performance of gas turbines. For the purpose of analysis, the following concepts are introduced: (1) the use of moist air in place of dry air as the working medium, thus enabling one to estimate the effects of humidity; (2) the idea of “the specific output per unit volume” in addition to the specific output per unit mass and the thermal efficiency; (3) the effect of air temperature on the pressure ratio and the efficiency of the compressor. In the performance analysis, the following two methods are adopted: first, the changes in the efficiencies of the components are neglected while varying atmospheric conditions; second, as a more precise method, the changes in the efficiencies of the components are also considered. Finally, in order to confirm the validity of the assumptions and the calculation methods, the theoretical values obtained are compared with actual gas turbine data. As the result of this paper, the effects of varying atmospheric conditions on the performance of gas turbines are described quantitatively, so that the resultant change in performance can be estimated without experiment.
Missile Firing Tests at Stationary Targets in Support of Blade Containment Design
Authors: Goatham J. I. , Stewart R. M.
Published: November 2010

Compressor and turbine blades of aircraft engines are liable to failure from a number of causes. Their subsequent containment within the immediate confines of the engine has long posed problems for the designer aiming for minimum weight designs. To assist the understanding of the dynamics of the containment problem, a series of small scale model tests have been conducted. The particular tests reported, deal with the failure mechanism at the point of impact. A theoretical analysis in support of the results obtained is developed. Fairly good agreement is obtained between tests and theory and the read-across to full scale containment tests indicates that the containment problem is capable of scaling if linear velocities are kept constant. A discontinuity in the behavior of materials with respect to their just contained energy capacity has been identified. While several contributory factors can be suggested, a fully satisfactory explanation is not found.
A Family of Surface Velocity Distributions for Axial Compressor Blading and Their Theoretical Performance
Authors: Walker G. J.
Published: November 2010

The influence of free stream disturbances on transition is discussed and it is noted that significant regions of laminar flow may exist on axial turbomachine blades despite the high level of disturbance to which they are subjected. A family of surface velocity distributions giving unseparated flow on the suction surface of an axial compressor blade is derived using data from detailed boundary layer measurements on the blading of a single-stage machine. The distributions are broadly similar to those adopted by Wortmann in designing high performance isolated aerofoil sections for operation at much higher Reynolds numbers. The theoretical performance of blades having the specified surface velocity distributions is computed for a wide range of conditions, and the effects of varying Reynolds number and other design parameters are analyzed. The results suggest the possibility of obtaining useful improvements in performance over that of conventional compressor blade sections. The computed performance values show an almost unique relation between the blade losses and the suction surface diffusion ratio. However the correlation of losses with the equivalent diffusion ratio is found to break down at high values of the latter parameter.
Spatial Supersonic Flow Through Annular Cascades
Authors: Fruehauf H. H.
Published: November 2010

The spatial supersonic flow through rotating and stationary annular cascades is analyzed by means of a nonlinear three-dimensional method of characteristics. Three-dimensional corrections for flow quantities referred to a quasi-three-dimensional approximation method are determined depending on geometric and gas dynamical parameters. Characteristic properties of spatial supersonic flow through annular cascades are analyzed, leading to guiding principles for practical design purposes.
Treatment of the Annulus Wall Boundary Layer Using a Secondary Flow Hypothesis
Authors: Railly J. W. , Sharma P. B.
Published: November 2010

Hitherto, theories of annulus wall boundary layer development in axial compressors have assumed an axially-symmetric flow in which the blade action has been replaced by a force field. A more rigorous treatment of the momentum equations in the annulus boundary layer by Mellor and Wood demonstrated the presence of certain terms, after the equations had been averaged in the pitch-wise direction, which arise from the truly three-dimensional character of the flow. These terms, which may be described as the gradients of apparent stresses, were not regarded by them (apart from a discussion of tip clearance) as having importance for the problem. In the present work a second equation of the annulus wall boundary layer is obtained by consideration of the work of these apparent stresses. By integration of the system of equations over a single blade row, two equations are obtained relating various integral quantities at inlet to and exit from the row. Each equation contains terms which depend upon apparent stresses connected with the relative velocity field at the exit plane. An experiment is described in which the six turbulent stresses in the stationary frame downstream of a single rotor, determined by means of a multiple hot wire array, are used to evaluate each term of the aforementioned equations. The integral quantities thus determined are shown to be reasonably consistent with the predictions from the two equations, in particular, for the case of the hub boundary layer. Theoretical solutions of the two integral equations require a secondary flow hypothesis so that the departure from collateral flow at blade row exit is determined by the solution.
Catalysts for Gas Turbine Combustors—Experimental Test Results
Authors: DeCorso S. M. , Mumford S. , Carrubba R. V. , Heck R.
Published: November 2010

This paper describes experimental test runs utilizing catalytically supported thermal combustion for gas turbine application. Test fuels were No. 2 distillate oil and low Btu synthetic coal gas. The tests were carried out over a range of pressure, temperature, and mass flow conditions. Analysis of these results are presented and the implications for future combustor design are discussed. Catalytically supported thermal combustion demonstrated the potential for very low emission performance.
Performance Analysis of a Pancake Absorber-Helical Heat Exchanger for a Solar Concentrator
Authors: Duff W. S.
Published: November 2010

This paper presents an analysis of the performance of a pancake absorber with a helical heat exchanger for use with point focus solar concentrating collectors. The principal difference between this type of absorber and most other concentrating solar collector absorbers is that the intensity of concentrated radiation monotonically increases from the inlet to the outlet of the heat exchanger tube. A performance expression for this absorber type and radiation distribution is derived and used to calculate thermal performance for several different absorber designs. Thermal performance for these designs is then calculated using a performance analysis based on the simplifying assumption that the heat exchanger tube is uniformly irradiated and the two performances are compared. The comparison indicates that the different radiation distribution assumptions lead to different absorber design choices. In particular, the simplifying assumption overstates thermal losses for increases in absorber size.
Structural and Cooling Aspects of the Aden Nonaxisymmetric Exhaust Nozzle
Authors: Nash D. O. , Wakeman T. G. , Palcza J. L.
Published: November 2010

The initial development of a nonaxisymmetric vectoring exhaust nozzle has been completed for the U. S. Navy by the General Electric Company. This exhaust system, called ADEN (Augmented Deflector Exhaust Nozzle), has been tested at GE’s Peebles, Ohio test facility using a YJ101 engine as the gas producer. This paper reviews the structural and cooling design of the ADEN nonaxisymmetric nozzle. Temperature and pressure data from the test series are compared to design intent for the nozzle operating in normal cruise and deflected (vectored) modes.
Structural and Mechanical Design of Tokamaks
Authors: Young W. C. , Sviatoslavsky I. N.
Published: November 2010

The UWMAK series of reactor studies have assessed the technological problems associated with the design and construction of a working power reactor. A procedure has been developed to evaluate the quality of magnet design by a comparison to a minimum mass system established by the virial theorem. Failure and fault analyses and material selection for the many diverse environments are critical for long term reliability. Overall structural compatibility and multipurpose use of structural components are also emphasized.
Tokamak Reactors
Authors: Mills R. G.
Published: November 2010

The physical properties of nuclear fusion reactions govern the fuel choice and the selection of the operating plasma temperature. Scientific feasibility, or energy break-even, is one objective of the current research program. Engineering and economic feasibilities will depend on achievable plasma densities at thermonuclear temperatures and on technological questions of achievable magnetic field, effects of radiation damage, and mechanical design problems. A pure fusion reactor will have stringent requirements on its performance parameters. If achieved, it should provide clean, safe, abundant economic power, but from rather large central stations. Hybrid fission/fusion systems put far less stringent requirements on the plasma performance. They simplify the fission lattice design. They may provide a superior method for burning the vast reserves of uranium-238.
DNB Oscillatory Temperature and Thermal Stress Responses for Evaporator Tubes Based on Rivulet Model
Authors: Chu C. L. , Roberts J. M. , Dalcher A. W.
Published: November 2010

Experiment evidence and observations have shown that the DNB oscillation phenomena can best be characterized by water rivulets motion with temperature variation in the circumferential direction. This paper presents the rivulet thermal model that directly corresponds to these observations. Finite element computer codes were used to evaluate temperature and thermal stress behavior of the steam tube under the condition where water rivulets appear and disappear along the tube inside circumference. An inherently complicated three-dimensional problem can reasonably be reduced to a two-dimensional analysis with relative simplicity.
The Influence of Droplet Size on the Turbine Blading Erosion Hazard
Authors: Krzyzanowski J. , Szprengiel Z.
Published: November 2010

A new version of the erosion threat criterion [1], taking into account the effect of the size of droplets impinging on the unit rotor blade surface element, has been presented in the paper. A manner of evaluation of the rotor blade lifetime basing on the modified erosion threat criterion τF′ = f(UEMD (η), erosion state) and a method of determination of the depth of material loss have been described.
The Effects of Ambient Conditions on Gas Turbine Emissions—Generalized Correction Factors
Authors: Donovan P. , Cackette T.
Published: November 2010

A set of factors which reduces the variability due to ambient conditions of the hydrocarbon, carbon monoxide, and oxides of nitrogen emission indices has been developed. These factors can be used to correct an emission index to reference day ambient conditions. The correction factors, which vary with engine rated pressure ratio for NOx and idle pressure ratio for HC and CO, can be applied to a wide range of current technology gas turbine engines. The factors are a function of only the combustor inlet temperature and ambient humidity.