bluuebunny/crossref_metadata_2025 huggingface dataset:
Void Growth and Local Necking in Biaxially Stretched Sheets
Authors: Needleman A. , Triantafyllidis N.
Published: November 2010

The role of void growth in triggering local necking in biaxially stretched sheets is investigated. A recently proposed constitutive equation for porous plastic materials is employed in conjunction with the model of localized necking introduced by Marciniak and Kuczynski. An increased initial volume concentration of voids within the incipient neck plays the role of the imperfection. The predictions of this analysis are compared with corresponding predictions based on classical plasticity theory with various types of initial inhomogeneities. It is found that the porous plastic material model predicts forming limit diagrams qualitatively in accord with experimental results. However, the results also show that any microstructural inhomogeneity that gives rise to a continually decreasing rate of hardening in the neck would be expected to predict qualitatively similar forming limit diagrams. It is also found that the hypothesis of an equivalent thickness imperfection is not necessarily appropriate for high hardening materials.
Combined Mode Fracture Toughness Measurement by the Disk Test
Authors: Awaji Hideo , Sato Sennosuke
Published: November 2010

The disk test in which a circular specimen with an internal crack is subjected to diametral compression is used to investigate combined mode I and mode II fracture. The stress intensity factors in the disk test are calculated numerically by means of the boundary collocation procedure and the dislocation method. Special care was taken to analyze the effect of the compression anvils. This method has the advantage, of allowing successive measurement of mode I, mode II and the combined mode fracture toughness under the same conditions. Some kinds of graphite, plaster and marble are examined to obtain the fracture toughness values, KIC, KIIC and the combined mode fracture criterion.
Cryogenic Tensile, Fatigue, and Fracture Parameters for a Solution-Annealed 18 Percent Nickel Maraging Steel
Authors: Tobler R. L. , Reed R. P. , Schramm R. E.
Published: November 2010

The mechanical properties of an eighteen percent nickel, solution-annealed 300-grade maraging steel were measured to assist in the evaluation of this material for low-temperature structural applications. Tensile, fatigue-crack growth rate, and fracture toughness tests were perfromed in ambient air (295 K), liquid nitrogen (76 K), and liquid helium (4 K), with the following results: (1) the yield strength of this material increases from 831 MPa at room temperature to 1596 MP a at 4 K; (2) the tensile ductility is moderate with elongation decreasing from 15.5 to 6.7 percent for this temperature region; (3) the estimated values of fracture toughness (KIc) decrease from 165 MPa·m1/2 at room temperature to 83 MPa·m1/2 at 4 K; and (4) the fatigue-crack propagation resistance at intermediate stress intensity ranges is relatively insensitive to temperature. These results are compared with similar data for other cryogenic alloys.
Further Developments in Anisotropic Plasticity
Authors: Shih C. F. , Lee D.
Published: November 2010

A simple extension of Hill’s formulation for anisotropic plasticity which accounts for the distortion of the yield surface, Mij, the strength differential between tension and compression, αi and the effective size of the loading surface, k, has been proposed. These material parameters, Mij, αi, and k, define the initial state of the material and vary with plastic deformation. The parameters describing the anisotropic state are determined from uniaxial tension and compression tests along the principal axes. It is shown that the yield stresses in tension and compression along the three principal axes are related by a constraint equation when the condition of incompressibility is imposed. Experimental data obtained from several anisotropic materials are reasonably consistent with the constraint equation. The anisotropic plasticity formulation is also shown to describe the yield surface of different HCP metals more closely than the Hill’s theory. Based on the proposed formulation, finite element calculations have been made for the notched and the three-point bend specimens. The calculated load-deflection relationships are in good agreement with the experimental results.
On Time-Temperature Parameters for Correlation of Creep-Rupture Data in Stainless Steel Weldments
Authors: White W. E. , Le May Iain
Published: November 2010

The Manson-Haferd, Larson-Miller, and Orr-Sherby-Dorn time-temperature parameters were applied to creep-rupture data obtained from testing two batches of austenitic stainless steel weldments. It was found that none of these correlated the data satisfactorily. A new parameter, based on a modification of one proposed originally by Manson and by Goldhoff and Sherby, was found to adequately correlate the data. The Minimum-Commitment, Station-Function Approach of Manson and Ensign was also applied, the results of which supported those obtained from the analysis made using the parameters listed above. Finally, from the relationship between rupture-time and secondary creep-rate, it is suggested that the form of the rupture data may be useful in predicting the physical basis for creep.
An Analysis of High Temperature Metal Creep—Part II: A Constitutive Formulation and Verification
Authors: Laflen J. H. , Stouffer D. C.
Published: November 2010

A phenomenological development of a constitutive equation is presented for the high temperature viscoplastic flow of a metal. The development rests on a viscoelasticity foundation but incorporates several features of a classical metals theory. The one dimension representation is developed using the creep response, strain rate response, and stress rate response of wrought Udimet 700 at 926.7°C (1700°F). The strain response to several cyclic stress histories is successfully predicted using the model. A three dimensional theory is proposed.
Near-Threshold Fatigue Crack Propagation in Ultra-High Strength Steel: Influence of Load Ratio and Cyclic Strength
Authors: Ritchie R. O.
Published: November 2010

Fatigue crack propagation behavior of an ultra-high strength steel (300-M) has been investigated in humid air over a very wide spectrum of growth rates from 10−8 to 10−1 mm/cycle. Particular emphasis has been devoted to the influence of mean stress (or load ratio R = Kmin/Kmax) and microstructure on fatigue crack growth near the threshold stress intensity for crack propagation, ΔK0. Increasing the load ratio from R = 0.05 to 0.70 was found to lead to increased near-threshold growth rates, and a decrease in the threshold stress intensity. Similarly, increasing material strength, by varying the microstructure through quench and tempering and isothermal transformation, resulted in higher near-threshold growth rates, and a marked reduction of ΔK0. These effects are contrasted with behavior at higher growth rates. The influence of strength on ΔK0 is rationalized in terms of the cyclic hardening or softening response of the material, and hence it is shown that cyclic softening can be beneficial to fatigue crack propagation resistance at very low growth rates. The results are discussed in the light of crack closure and environmental contributions to fatigue crack growth at low stress intensities.
Thermoeconomics and the Design of Heat Systems
Authors: El-Sayed Y. M. , Evans R. B.
Published: November 2010

This paper formulates the interactions between thermodynamics and economics for complex systems in a manner which assures a wise use of nonrenewable energy resources. The concept of “essergy” (generalized potential work) is used to reduce all thermodynamic processes to a common basis of evaluation and comparison. The concept of “internal economy” is used as a means of estimating the economic value of essergy, thus permitting a designer to trade essergy dissipation against capital expenditure in the main dissipative zones of a thermodynamic system. This approach extends the classical optimization problem of balancing running expenses against fixed charges of single-zone, single-degree-of-freedom systems to stagewise as well as interconnected multi-zone multidegrees-of-freedom systems. A companion paper discusses some detailed applications.
Heat Transfer by a Square Array of Round Air Jets Impinging Perpendicular to a Flat Surface Including the Effect of Spent Air
Authors: Kercher D. M. , Tabakoff W.
Published: November 2010

The results of an experimental investigation on the average surface heat transfer co-efficients under a perforated plate of multiple, square array, round impinging air jets are presented. Correlation of the heat transfer performance in a semi-enclosed environment is presented. The correlation includes the effects of the jet “spent air” flowing perpendicular to the jets; the effects of the jet diameter, jet spacing, and jet-to-surface distance. The data cover a range of jet diameter Reynolds number from 3 × 102 to 3 × 104, jet spacing from 3.1 to 12.5 dia, and plate-to-surface distance of 1.0 to 4.8 dia. The results are compared with previously reported investigations with reasonable agreement. Correlation is in the form NuD,x = φ1φ2ReDm(Zn/D)0.091Pr1/3 where φ1 and m are functions of the jet spacing parameter, Xn/D, and Reynolds number, and φ2 is the heat transfer coefficient degradation factor due to “spent air”. φ1, φ2 and m are presented in graphical form as a function of important dimensionless parameters.
Engine Prime Mover Automation
Authors: McCune M. K.
Published: November 2010

“Full range” automation control of engine prime movers makes possible the direct conversion of primary fuel sources of liquid or gaseous types to prime mover power with the labor savings advantages of unattended automated operation. This paper outlines the development of the “full range” automation program control with related “slave” control devices as required for the overall automated system, and reviews some requirements for a successful engine automation program.
SO2 Pickup by Limestone and Dolomite Particles in Flue Gas
Authors: Coutant R. W. , Barrett R. E. , Lougher E. H.
Published: November 2010

An investigation was made of the reaction between SO2 and limestone and dolomite particles in flue gas. Reaction data were generated by exposing the particles to flue gas in a dispersed-phase reactor that simulates localized boiler-furnace conditions. Variables included in the study were residence time, temperature, particle size, SO2 concentration, and chemical state of the stone. A model is hypothesized for the SO2- particle reaction that is consistent with the experimental data. The hypothesis states that the initial reaction products are sulfites, and that as the particle temperature rises above about 1400 deg F, SO2 is lost by thermal decomposition of the sulfite. Concurrently the sulfite can oxidize and/or disproportionate to form sulfate.
Electrical Measurement of Flow Rate of Pulverized Coal Suspension
Authors: Cheng L. , Tung S. K. , Soo S. L.
Published: November 2010

Electrostatic probes for indicating instantaneous flow rate of pulverized coal suspension in a pipe were devised and tested. Experiments were performed on flow systems consisting of 2 and 5-in-ID pipes with mass flow ratios up to 0.66 lb of coal/lb of air at up to 115 fps air velocity. Calibrations were made with a differential isokinetic sampling technique. With accurate control of probe potential, consistent indication of electrostatic ball probes (1/4 to 1/2-in. dia) was at the 10−7 amp level and at 10−8 amp level with cylindrical probes (0.2-in. ID). Accuracy within 1 percent was demonstrated to be feasible. Since the probe output is an electrical signal, this device makes integrated control system including the coal line feasible. Further, instantaneous and accurate fuel adjustment into furnaces facilitates air-pollution control.
Loss and Flow Path Studies on Centrifugal Compressors—Part II
Authors: Balje´ O. E.
Published: November 2010

The flow conditions in a mixed flow rotor are investigated for a “pressure balanced” flow path design. Boundary layer arguments are applied to calculate the losses in the rotor as well as in the subsequent diffuser section. The resulting efficiency data imply a comparatively high efficiency potential for mixed flow compressors with multiple cascaded components, designed on the premise of a “pressure balanced” rotor flow path.
Fabrication Stresses in Graphite-Resin Composites
Authors: Novak R. C. , DeCrescente M. A.
Published: November 2010

Residual thermal stresses are present in cross-plied graphite-epoxy composites due to the anisotropic thermal and mechanical properties of the individual layers. Experimental measurements and analytical calculations of the thermal stress induced in two different cross-plied composites during fabrication are presented and shown to be in good agreement. The occurrence of cracking in certain composites is explained in terms of the transverse tensile strength of the unidirectional composite layers and the stress developed during fabrication. Two approaches are presented to avoid cracking during fabrication.
A Unified Procedure for the Calculation of Off-Design Performance of Radial Turbomachinery
Authors: Davis R. C. , Dussourd J. L.
Published: November 2010

An analytical technique is presented which permits calculating the off-design performance of radial, or mixed, flow centrifugal compressers and pumps. The method is based on the variation of blade loading diagrams as they are affected by the operating conditions of the machine. The influence of the changes of blade loading is expressed in terms of changes in the boundary layer momentum thickness in the internal flow passages. In turn the boundary layer thicknesses are expressed as a loss and as a flow acceleration in the critical passages such as the throat and the exit. The method makes use of no external arbitrary inputs except one relating to the development of the boundary layer thickness with the amount of fluid deceleration. The method was computerized and checked against five impellers and three diffusers. Acceptable agreement is found in the calculation of the shape of the characteristics and the location of the surge and choke points.
Unbalance Response of an Elastic Rotor in Damped Flexible Bearings at Supercritical Speeds
Authors: Rieger Neville F.
Published: November 2010

The unbalance response of a uniform flexible rotor in fluid-film bearings has been analyzed for speeds up to 20 times the lowest rigid-bearing critical speed. Rotor mass and elasticity are distributed uniformly along the length of the rotor. A single radial speed-dependent force is used to represent the rotor unbalance. The rotor is assumed to operate in stable plain cylindrical bearings which are represented by direct and cross-coupled spring and damping forces. The influence of rotor speed, bearing operating eccentricity, relative stiffness of rotor and bearings, and unbalance location along rotor on the performance of the rotor-bearing system has been determined. Results are presented as charts of rotor maximum whirl amplitude and of bearing maximum whirl transmitted force for wide ranges of the foregoing parameters. Mode shapes at critical speeds are also included.
A Survey of Nitrogen-Oxides Control Technology and the Development of a Low NOx Emissions Combustor
Authors: Tomany J. P. , Koppang R. R. , Burge H. L.
Published: November 2010

The problem of NOx emissions reduction is gaining increased attention from those concerned with air pollution control activities. HEW proposes to issue criteria for the control of nitrogen oxides within the year. The Los Angeles Air Pollution Control District (LAAPCD) has already published regulations which limit emissions from combustion sources to a fixed rate of 140 lb/hr NOx. This is equivalent to an allowable emission concentration of about 20 ppm for a 500 MW power station. Two of the major contributors to oxides of nitrogen air pollution in the United States are Industrial Processes and Stationary Combustion Sources, both being responsible for over 50 percent of the total NOx emissions. Motor vehicles contribute the remainder for a total of 20 million tons per year. Although some advances have been made in the development of commercial control equipment for Industrial Process emissions, there is very little well-developed technology available for NOx emissions control from Stationary Combustion Sources. Two of the most promising areas being investigated are: • Stoichiometric variations of the air-fuel feed and partial recycling of the combustion products. • Advanced design of combustion equipment. The former system of control, in a test program with 17 commercial boilers, has been responsible for the reduction of NOx emissions from about 350–150 ppm. An advanced design combustor, operated at a heat release level of 105 Btu/hr, has produced NOx emission values of about 150 ppm. When coupled with simulated combustion gas recycle, the emissions were further reduced to 100 ppm. Although both the “stoichiometric” and “combustor” approach to the problem of NOx emissions represent a good beginning, greater efforts must be expended on these and other promising control techniques in preparation for future regulations.
Experimental Investigation of Methods for Improving the Dynamic Response of a Twin-Spool Turbojet Engine
Authors: Fawke A. J. , Saravanamuttoo H. I. H.
Published: November 2010

This paper describes experimental tests carried out on a twin-spool turbojet to confirm earlier simulator predictions of methods of improving the dynamic response. The engine was controlled by a digital computer, permitting ready changes of control schedules. It was verified that dynamic response could be improved by trading HP surge margin for LP surge margin by suitable variation of the nozzle area. Operating trajectories were obtained on both compressor characteristics during both accelerations and decelerations and excellent agreement with simulator results was obtained.
The Interaction of Air Motion, Fuel Spray, and Combustion in the Diesel Combustion Process
Authors: Melton R. B. , Rogowski A. R.
Published: November 2010

This paper is pertinent mainly to combustion in open-chamber diesel engines employing air swirl. It is shown how an increase in air swirl rate can cause a marked loss of combustion efficiency unless fuel spray penetration is increased. High swirl reduces radial fuel spray penetration with central injection and the resulting excess fuel in the central area may be trapped by buoyancy forces following ignition, becoming isolated for as much as a tenth of a second in a chamber of four in. diameter. A brief explanation of fuel injection in terms of the mechanics of fluid jets is given and circumstances described in which buoyancy forces assist fuel-air mixing following ignition.
New Particle Size Measuring Probe—Application to Aerosol Collector and Emissions Evaluations
Authors: Downs W. , Strom S. S.
Published: November 2010

A basic parameter needed for judicious design, selection, and regulation of industrial gas cleanup equipment is particle size distribution of gas-borne emissions. Despite the importance of this parameter, a cloud of uncertainty about the validity of present methods used for particle size distribution measurements has produced a technological gap. This paper describes an apparatus and method which is capable of bridging this gap. Particle size distribution data obtained, particularly in the near micron and submicron range, can provide means for determining grade efficiencies of dust collectors, expected opacity of stack emissions, and dispersion characteristics of plumes. The apparatus described was developed for manual sampling and size distribution determination of aerosols within industrial flues and stacks. The entire apparatus is contained within a sampling probe. The principal component is a cylindrical cascade impactor. Design of the probe eliminates most of the technical difficulties associated with previous attempts at implementing cascade impactors to this task. This probe has been used successfully for sampling gases up to 450 F.
Pollutants From Methane Fueled Gas Turbine Combustion
Authors: Parikh P. G. , Sawyer R. F. , London A. L.
Published: November 2010

In view of the greater flexibility of a gas turbine combustion system design as compared to that for a piston engine, control of NOx emissions even while keeping the CO and hydrocarbon emissions at very low levels appears feasible. Factors influencing the production of these pollutants in a methane fueled gas turbine type combustor are studied in this investigation by analyzing the gas samples taken at various locations within the combustor. Increasing the homogeneity of the primary zone gas composition by using gaseous or prevaporized liquid fuels is found to be an effective way to reduced NOx emissions.
Some Comparisons of Simultaneous Stack Gas Particulate Determinations Using the ASME and EPA Methods
Authors: Selle S. J. , Gronhovd G. H.
Published: November 2010

Simultaneous determinations of particulate concentrations were made by the ASME and EPA methods on flue gas from a test furnace burning about 75 lb/hr of low-sulfur North Dakota lignite. Comparisons were made at dust concentration levels of about 0.5 and 0.01 grain per standard cu ft. At the higher dust concentration the two methods checked within about 5 percent and the impinger residues were not significant. At the low dust concentration the EPA complete train generally gave values from 50 to 200 percent greater than the ASME method and the impinger residues constituted a substantial part of the total weight. Attempts were made to identify the various residues from the EPA impinger train.
Low Emission Variable Area Combustor for Vehicular Gas Turbines
Authors: White D. J. , Roberts P. B. , Compton W. A.
Published: November 2010

In recent years automotive engine emissions have become subject to stringent Federal legislation. The most severe of these regulations pertains to the 1976 Emission Standards as defined by the Advanced Automotive Power Systems (AAPS) Division of the Environmental Protection Agency (EPA). A unique combustor concept has been developed by Solar which has demonstrated the feasibility of meeting these emission requirements. The integrated emissions of a typical regenerative gas turbine engine employing this combustor type were each below one half of the levels specified by the Federal 1976 Standards, when tested over a simulated federal driving cycle. The success of the feasibility tests for this combustor concept has lead to more fundamental studies and the planned development of a prototype combustor for demonstration on the EPA-AAPS baseline gas turbine engine. The prototype combustor for the baseline engine is described together with its variable area port mechanisms, which has been demonstrated as necessary for emission control.
Small Turbomachinery Compressor and Fan Aerodynamics
Authors: Pampreen R. C.
Published: November 2010

This paper discusses aerodynamic considerations in the design of small turbomachinery axial and centrifugal compressors and fans. Test results are presented to show the effect of scaling on compressor performance. Correlations are presented which relate compressor efficiency to Reynolds Number and clearance. It is shown that clearance effects are more prominent when scaling designs, and Reynolds Number effects are more prominent as density is lowered.
Hydrodynamic Stability and Thermal Performance Test of a 1-MWt Sodium-Heated Once-Through Steam Generator Model
Authors: Waszink R. P. , Efferding L. E.
Published: November 2010

The 1-MWt Heat Transfer Model (HTM-1) test program was directed to the development of techniques to predict, and thereby avoid, water-side instabilities in sodium-heated once-through and recirculating steam generators. Water-side performance instabilities in steam generators have been an underlying problem through decades of experience. This subject is of particular concern to sodium-heated units due to the severe performance deterioration that can result from such instability. The 1-WMt test model contains nine 0.50 in. OD 130 ft long serpentine tubes. Thermocouples and low-pressure-drop orifice flow meters were installed at the feedwater inlet end of each of the three active tubes to disclose instabilities. These measurements were recorded on a high-speed oscillograph. Instabilities were deliberately induced in order to determine the inception condition of instability. The model was dynamically stable for a range of operating conditions. The model was statically stable (uniform static feedwater flow distribution) at all steam outlet conditions tested. The model was generally more stable than predicted especially at higher loads.
Torsional Stability Analysis of a Gas-Turbine Powered Helicopter Drive System
Authors: Darlow M. S. , Vance J. M.
Published: November 2010

The torsional stability of a closed-loop dynamic system is evaluated. The system is a typical transport helicopter speed governor, gas-turbine engine and drive train. This is compared with the stability of a similar system in which a nonlinear coupling is included in the drive train, to determine if the coupling will increase the torsional stability of the system [1]. This nonlinear coupling is designed to isolate torsional vibrations in the rotor. The two systems are first linearized, using a decoupled rotor model for the ZTS coupling, and expressed in the form of Laplace transfer functions. Then a Bode Analysis is conducted and gain and phase margins are compared for the two systems. The nonlinear systems are numerically simulated to determine the time response and frequency response to excitation. The ZTS coupling design considered is found to be effective in stabilizing the previously unstable helicopter drive system.
A Generalized Discharge Coefficient for Differential Pressure Type Fluid Meters
Authors: Benedict R. P. , Wyler J. S.
Published: November 2010

A generalized rational equation is derived for the discharge coefficient of differential pressure-type fluid meters. Its factors are particularized for throat tap meters, pipe wall tap nozzles, and for orifice-type flow meters. Comparisons are made with available theories and with current Fluid Meter practices, and these support the new formulation. Because of its rational basis, the generalized equation may be useful for extrapolations to Reynolds numbers which lie beyond the capabilities of calibration laboratories.
Experimental Investigation of Film Cooling With Ejection From a Row of Holes for the Application to Gas Turbine Blades
Authors: Liess C.
Published: November 2010

The adiabatic wall effectiveness and the heat transfer coefficient is determined experimentally on a flat plate downstream of a row of inclined circular ejection holes. The measuring technique provides local values in downstream direction and averaged values in lateral direction. The ejection geometry is kept constant, i.e., ejection angle β = 35 deg, spacing to diameter ratio of ejection holes s/d = 3. The range of flow parameters corresponds closely to the conditions encountered on gas turbine blades. The main flow Mach number varies from 0.3 to 0.9, the mass velocity ratio from 0.1 to 2.0. Two favorable pressure gradients in the main flow are applied and several ratios of main flow boundary layer displacement thickness to ejection hole diameter. The main flow boundary layer upstream of the ejection is laminar and turbulent.
Parameter Selection for Multiple Fault Diagnostics of Gas Turbine Engines
Authors: Urban L. A.
Published: November 2010

An introduction to the fundamentals of turbine engine multiple fault diagnosis and its relationship to engine parameter selection and measurement requirements is presented. The influence of the type (thermodynamic cycle) of the engine to be diagnosed, and the nature of its expected problems, on the required parameters and the attendant measurement repeatability requirements are discussed.
Comparison of Test Results Obtained on Plane and Annular, Fixed or Rotating Supersonic Blade Cascades
Authors: Paulon J. , Reboux J. , Sovrano R.
Published: November 2010

Results of an experimental research on the comparison of flow patterns in linear and annular, fixed and rotating supersonic blade cascades are presented. The fixed plane cascade and the fixed annular cascade give very similar results at low back pressure and the flow configuration (Schlieren pictures) and the pressure distributions are those given by theoretical calculations. In the rotating cascade the fully started supersonic regime was not obtained. At high back pressure, sidewall flow separation perturbates the flow pattern in the plane cascade. In the annular setups, the flow configuration with suction side flow separation is correctly predicted by the theory.
Instantaneous Measurements in the Jet-Wake Discharge Flow of a Centrifugal Compressor Impeller
Authors: Eckardt D.
Published: November 2010

One of the critical problems in centrifugal compressor design is the diffuser-impeller interaction. Up to now, theoretical models, which describe one of the salient features of this problem, the impeller discharge mixing process, appear to be proved experimentally only at low tip speeds. In the present study investigations on this subject were accomplished in the vaneless diffuser of a low-pressure ratio centrifugal compressor, running at tip speeds of 300 m/s. Detailed, instantaneous measurements in the impeller discharge mixing zone were performed by high-frequency measuring systems. Relative velocity distributions at the exit of impeller blade channels show pronounced jet/wake-patterns. The radial extension of flow distortions in the vaneless diffuser entry region, caused by rotating wakes, reached up to higher radius ratios than predicted by theoretical models.
Fluidelastic Tube Vibration in a Heat Exchanger Designed for Sodium-to-Air Operation
Authors: Halle H. , Boers B. L. , Wambsganss M. W.
Published: November 2010

Analysis and testing were performed to evaluate the potential for flow induced vibrations of the finned U-tubes of a sodium-to-air dump heat exchanger of the Fast Flux Test Facility (FFTF). The analysis showed that fluidelastic vibration of the U-bend sections, caused by a displacement-dependent mechanism, could be experienced. Consequently, model tests, with prototypic tubing and stagnant water simulating the sodium mass on the tubeside, were performed. The tests consisted of subjecting the overhanging U-bends of a bank of five U-tubes to a range of air flow velocities at room temperature. Test results showed that, for a given support and restraint condition, a critical flow velocity exists above which large vibration amplitudes are induced. Characterization of the critical flow velocity was investigated. Supplementary single tube experiments determined vortex shedding frequencies, U-tube natural frequencies, damping, and, separately, the effect of internal water flow.
The Effect of Edge Sharpness on the Discharge Coefficient of an Orifice
Authors: Benedict R. P. , Wyler J. S. , Brandt G. B.
Published: November 2010

The effect of inlet edge roundness on the discharge coefficient of an orifice plate is studied experimentally. Several methods for measuring edge roundness are discussed and applied. An optical method in particular is shown to provide reliable measurements of edge roundness. Flow results are summarized in terms of radius of curvature by the empirical equation ΔCD/CD = 0.85 ln (rk/d × 103) + 1.74.
A Variational Formulation of the Compressible Throughflow Problem
Authors: Oates G. C. , Knight C. J. , Carey G. F.
Published: November 2010

A variational formulation of the compressible throughflow problem is developed. The method is suitable for the calculation of throughflow flow fields in which large rotational effects, large compressibility effects and large variations in hub and tip radii may exist. The formulation requires the absence of viscous forces between the blade rows, though the effects of losses within the blade rows may be included through the variation of entropy across stream surfaces. The meridional Mach number is restricted to be less than unity, though the complete flow Mach number may be much in excess of unity. The variational formulation represents a complete statement of the problem in that the boundary conditions, far upstream and far downstream conditions, and matching conditions at all actuator disks are all natural conditions of the variational formulation. Furthermore, terms involving density variations vanish. The variational problem is posed in terms of the streamline position and the density. A finite element approximation produces a coupled nonlinear algebraic problem for numerical solution. Example calculations of flows with highly-loaded actuator disks, existing in annuli with large variations in hub and tip radii, are given.
Accelerated Diffusion Bonding Using Induced Forces
Authors: Morin T. J.
Published: November 2010

Classical diffusion bonding has always connoted nonproduction-like conditions such as extremely high pressures for long times, protective environments, and excessive cleanliness requirements. The attractive characteristics are that diffusion bonds are normally produced at comparatively low temperatures and they have parent metal properties. This paper presents a technique whereby high pressures are selectively applied to the interfacial region of the two parts being joined at temperatures approximately 90–95 percent of the parent metal melt range. The parts to be joined are heated rapidly using “induction heating” techniques. The mating surfaces and the areas immediately adjacent to them are the only portions of the parts that are significantly heated in most applications. As soon as the proper temperature range has been reached, the heating current is shut off and an intense magnetic field is forced or driven through the parts. The orientation and direction of this moving magnetic field is such that a large pulsed current is caused to flow on both sides of and parallel to the interface. These large currents attract each other and give rise to substantial pressures normal to the interface, thereby producing intimate contact on a microscopic scale, allowing for rapid diffusion. There is also some preferential super heating in the interfacial zone for a few milliseconds only but greatly enhancing diffusion conditions. Results of the application of this technique to several material combinations are discussed along with photomicrographs of joined sections.
Surge and Rotating Stall in Axial Flow Compressors—Part I: Theoretical Compression System Model
Authors: Greitzer E. M.
Published: November 2010

This paper reports a theoretical study of axial compressor surge. A nonlinear model is developed to predict the transient response of a compression system subsequent to a perturbation from steady operating conditions. It is found that for the system investigated there is an important nondimensional parameter on which this response depends. Whether this parameter is above or below a critical value determines which mode of compressor instability, rotating stall or surge, will be encountered at the stall line. For values above the critical, the system will exhibit the large amplitude oscillatory behavior characteristic of surge; while for values below the critical it will move toward operation in rotating stall, at a substantially reduced flow rate and pressure ratio. Numerical results are presented to show the motion of the compression system operating point during these two basic modes of instability, and a physical explanation is given for the mechanism associated with the generation of surge cycle oscillations.
Coal Firing and Industrial Boiler Design—The Modern Approach
Authors: Smith V. L.
Published: November 2010

Coal is becoming increasingly more favorable as a fuel due to petroleum becoming too valuable to be used as one. The technology of firing coal has advanced tremendously as a result of new coal source discoveries and higher pressure and temperature steam generation. This paper defines the modern classifications of the different coals found in the United States and presents the respective design parameters for each classification. The varying design parameters in conjunction with the coal classifications are then related to modern industrial boiler design.
Corrosion and Deposits From Combustion of Solid Waste—Part IV: Combined Firing of Refuse and Coal
Authors: Krause H. H. , Vaughan D. A. , Boyd W. K.
Published: November 2010

Combined firing of processed municipal refuse with coal has been investigated in a stoker-fired boiler. The refuse preparation consisted of shredding, magnetic separation of metals, and air classification. The nature of the deposits and the extent of corrosion of simulated boiler tube surfaces was determined by inserting probes into the boiler. For amounts of refuse up to 35 percent on a heating value basis, the corrosion rate of carbon steels was reduced substantially below that found from previous measurements for refuse alone, and below that calculated on the basis of dilution by the coal. The temperature of the boiler flue gases also was found to be an important factor in corrosion. The emissions of sulfur oxides from high sulfur coal were reduced by the action of the alkaline components of the refuse.
Film Cooling With Injection Through Slots
Authors: Mukherjee D. K.
Published: November 2010

This work deals with film cooling of a surface with injection through slots. From the vast number of literatures surveyed, the cooling effectiveness for an ideal geometry—a flat plate with no pressure gradient having tangential blowing from a slot with no lip thickness—could be found by using a suitable blowing parameter for three different regions. The influence of blowing angle and lip geometry has been investigated and defined, each separately.
Defects and Fracture Strength of Large Rotor Forgings for Steam Turbines
Authors: Kumeno K. , Nishimura M. , Mitsuda K. , Iwasaki T.
Published: November 2010

Engineering criterion for brittle fracture of turbine rotors has been established based on the fracture mechanics and test results of fracture toughness and crack growth rate. From two typical large rotor forgings which contain defects in the region of center bore, the reliable KIC data and crack growth rate data were obtained by various types of test specimens. The strength evaluation method of the rotor in the presence of defects has been completed as a form of allowable flaw size diagrams considering the loading conditions in service life of steam turbines.
On the “In-Situ” Control of Acoustic Liner Attenuation
Authors: Dean P. D.
Published: November 2010

In this paper a concept is presented which enables the attenuation of sound in a lined duct to be controlled via the control of the fundamental liner characteristic (the acoustic impedance). The concept is described and modeled by a semiempirical analysis. The feasibility is demonstrated by means of measurements of attenuation and local impedance in a small scale flow duct test facility.
Measurement of the Three-Dimensional Flow Field Behind an Axial Compressor Stage
Authors: Hirsch Ch. , Kool P.
Published: November 2010

Hot wire instrumentation and a periodic sampling and averaging technique have been used in order to measure the three-dimensional flow field behind a rotor of an axial compressor stage. A single slanted rotating wire allows the determination of the three components of the blade-to-blade velocity distribution together with informations on the turbulence level. A description is given of the measurement technique, and typical experimental results are presented.
An Investigation on the Diffusion of Momentum and Mass of Fuel in a Diesel Fuel Spray
Authors: Vara Prasad C. M. , Kar Subir
Published: November 2010

An investigation on the diesel fuel spray injected into stagnant ambient air in a chamber is reported in this paper. The objective of the investigation was to analyze the processes of diffusion of mass and velocity of the fuel in the fuel spray. The distribution of velocity and mass of the fuel showed similarity in the zone of established flow. Gaussian normal probability distribution for free jet was assumed by earlier workers, starting with Albertson, et al., for analyzing such a situation. However, it has been found that diesel fuel spray in a chamber necessitates modification of the model described and a modified model has been proposed herein. The Abramovich model is also compared with the experimental data. The ratio of εm/εm0 varied from 1.24 to 1.45 for the change of injection pressure from 100 to 200 atm. It is conclusively shown that mass diffuses faster than the momentum, the rate of diffusion increasing with the increase in the injection pressure. The proposed model gives good agreement with experimental results. The various parameters of the equations for depicting the fuel spray as a jet have been evaluated and tabulated.
Experimentally Determined Stability Parameters of a Subsonic Cascade Oscillating Near Stall
Authors: Carta F. O. , St. Hilaire A. O.
Published: November 2010

Tests were performed on a linear cascade of airfoils oscillating in pitch about their midchords at frequencies up to 17 cps, at free-stream velocities up to 200 ft/s, and at interblade phase angles of 0 deg and 45 deg, under conditions of high aerodynamic loading. The measured data included unsteady time histories from chordwise pressure transducers and from chordwise hot films. Unsteady normal force coefficient, moment coefficient, and aerodynamic work per cycle of oscillation were obtained from integrals of the pressure data, and indications of the nature and extent of the separation phenomenon were obtained from an analysis of the hot-film response data. The most significant finding of this investigation is that a change in interblade phase angle from 0 deg to 45 deg radically alters the character of the unsteady blade loading (which governs its motion in a free system) from stable to unstable. Furthermore, the stability or instability is governed primarily by the phase angle of the pressure distribution (relative to the blade motion) over the forward 10–15 percent of the blade chord. Reduced frequency and mean incidence angle changes were found to have a relatively minor effect on stability for the range of parameters tested.
Aerodynamic Design and Verification of a Two-Stage Turbine With a Supersonic First Stage
Authors: Binsley R. L. , Boynton J. L.
Published: November 2010

The detailed aerodynamic design and test verification of a 6000-hp (4474-kW) turbine with a supersonic first stage for an airborne application is described. The 12.3-in. (312.4-mm) pitch diameter turbine is driven by products of hydrazine decomposition at 700 psia (4.826 MPa) and 2110 R (1172 K) with an overall pressure ratio of 41.2. The design of the supersonic nozzles and rotor incorporated improved concepts compared to previously reported designs. Test results show that the predicted performance was verified. The supersonic design concepts described are applicable to other high-pressure ratio designs where maximum efficiency is required.
An Investigation of the Influence of Back Pressure on the Diffusion of Mass and Momentum of Fuel in Diesel Spray
Authors: Vara Prasad C. M. , Kar Subir
Published: November 2010

The influence of the back pressure on the diffusion of mass and momentum of the fuel in the diesel spray is investigated and reported in this paper. Analytical models were proposed to depict the similarity profiles for the distribution of velocity and mass of the fuel in the diesel spray injected into stagnant atmosphere maintained at different back pressures and ambient temperature. It is conclusively shown that the proposed models are superior to Abramovich and Albertson models so far as the spray situation is concerned. The Schmidt number, σf, varied from 0.806 to 0.430 when the injection pressure was varied from 100 to 200 atm and the back pressure from 1 to 10 atm. It is confirmed that mass diffuses faster than the momentum, the rate of diffusion increasing with the increase in injection pressure and the back pressure.
A Method for Testing Cascades with Converging Sidewalls
Authors: Meauze´ G.
Published: November 2010

Cascade tests on a set-up equipped with converging lateral walls are more representative of the flow in a section of actual turbomachine than in those with two-dimensional-flow. The experiment is carried out at mid-span, where it is necessary to know the local area contraction evolution in order to get more representative data: for this purpose, a simple computation method has been developed and successfully applied, as shown by the comparison with experimental data. By means of successive approaches, the side wall shape can be defined so that a given area contraction evolution can be obtained at the center.
The Effects of Aircraft Engine Pollutant Emission Measurement Variability on Engine Certification Policy
Authors: Wassell A. B. , Dryburgh D. C.
Published: November 2010

Emission measurements on a sample of nominally similar aero-gas-turbines—a single engine type—exhibit scatter as a result of assembly and manufacturing tolerances and of instrumentation and sampling errors. For some pollutant species, the standard deviation can be a quarter of the mean. The paper shows how to obtain an estimate of the value below ehich, say, 95 percent of the population will lie, by fitting an appropriate statistical distribution to the data. When the amount of data is small so that the precision of such estimates is not good, it is not meaningful to predict a limit which contains more than about 95 percent of the population. On entering service, each new engine type will require a certificate, similar to an Airworthiness Certificate, recognizing compliance with the emissions regulations. The authors show that, despite the large variability in the measurements, it is possible to devise a certification procedure which requires a test on only one engine. It would have to demonstrate emissions levels rather better than the maximum permitted and the results would have to be supported by additional information on the variability of related standards of engine, obtained perhaps during the development program. Some engine results available to the authors have been analyzed for variability and the paper recommends values of the parameter σ/mean to be used in setting certification standards for the different species of pollutant.
Significance of Disk Flexing in Viscous-Damped Jet Engine Dynamics
Authors: Klompas N.
Published: November 2010

A new method of analyzing multishaft jet engine critical speeds and unbalance response is derived to account for flexible bladed disks, asymmetric mounting, and squeeze film bearing damping. The resulting elliptical shaft whirling drives traveling waves in disks at speeds equal to the sum and the difference of the rotating speed and the whirling speed. To illustrate a possible problem that cannot be predicted by current methods, a sample calculation shows a simplified model representing possible engine parameters tuned so that a critical speed associated with backward whirling is lowered into the operating range by reduction in disk stiffness. In contradiction to the current literature, the rotor is shown highly responsive to unbalance at this critical speed.
Propagation of Inlet Flow Distortions through an Axial Compressor Stage
Authors: Colpin J.
Published: November 2010

This contribution will present an original calculation method predicting the development of an inlet flow distortion through a compressor stage. A finite difference technique is used to treat the flow equations outside the blade rows. That flow is two-dimensional, compressible and nonviscous. The blade rows are modelized using a quasi actuator disk approach, but include the unsteady transfer terms due to the rotor relative motion in a non uniform inlet flow. A set of experimental data, measured on a one stage axial compressor, submitted to a rectangular inlet total pressure distortion will be discussed and will serve as basis for a comparison between theory and experiments.