bluuebunny/crossref_metadata_2025 huggingface dataset:
A Theoretical Investigation of the Jet-Flap Compressor Cascade in Incompressible Flow
Authors: Stark U.
Published: November 2010

The use of jet flaps gives a new possibility of achieving high turning cascades. In this paper a new theory for unstaggered cascades with jet flaps, developed under simplifying assumptions, is described. With the help of this theory, besides turning angles and lift coefficients, for the first time pressure distributions on, and jet slope distributions behind, the blades were calculated. The effect of stagger angle on the turning angles and lift coefficients is determined with the help of the Schlichting method, using the concept of the equivalent flat plate cascade. Sample calculations illustrate the theory and, at the same time, give an insight into the behavior of cascades with jet flaps in inviscid flow. Results of previously published experiments on cascades with jet flaps, where they fulfill the conditions of the theory, are compared with the theoretical results and demonstrate satisfactory agreement.
Effect of Rotor Design Tip Speed on Aerodynamic Performance of a Model VTOL Lift Fan Under Static and Crossflow Conditions
Authors: Stockman N. O. , Loeffler I. J. , Lieblein S.
Published: November 2010

Results are presented for a wind tunnel investigation of three single VTOL lift fan stages designed for the same overall total pressure ratio at different rotor tip speeds. The stages were tested in a model lift fan installed in a wing pod. The three stages had essentially the same aerodynamic performance along the operating line. However, differences in stage thrust characteristics were obtained when a variation in back pressure was imposed on the stages by crossflow effects and thrust-vectoring louvers.
Calculation of Compressible Subsonic Flow in Cascades With Varying Blade Height
Authors: Van den Braembussche R. A.
Published: November 2010

This paper deals with a singularity method to calculate the subsonic compressible flow in compressor and turbine cascades, with constant or varying blade height. The method is an extension of an incompressible flow method by means of the Janzen-Rayleigh theorem, using an exact relation between pressure and density. Theoretical results are compared with experimental data. A further extension of this method to rotational flow in plane cascades obtained from the transformation of the blade to blade surface of a mixed flow machine is also discussed.
Ash in Gas Turbines Burning Magnesium-Treated Residual Fuel
Authors: Lay K. W.
Published: November 2010

The equilibrium ash composition in a magnesium treated residual fuel-fired gas turbine is considered in detail. The stability of the condensed phases of interest—MgO, MgSO4, and the magnesium vanadates are shown to be determined by the temperature and the equilibrium SO3 pressure at the deposit. The ash present will depend on these parameters as well as the Mg : V ratio in the ash. A thermodynamic treatment of the ternary MgO-V2O5-SO3 system is presented and experimental measurements of the stability limits of Mg3V2O8 and Mg2V2O7 are presented. A simple graphical method is described for representing the condensed phases present in ash for any Mg : V ratio and for temperatures and equilibrium SO3 pressures of interest in gas turbines.
Investigation Into the Likelihood of Thermal Fatigue Damage to Furnace and Superheater Tubes Caused by On-Load Water Deslagging
Authors: Ellery A. R. , Johnson T. R. , Newton J. D.
Published: November 2010

Boilers operating on brown coal from the Morwell Open Cut in Victoria require frequent off-load cleaning outages because of severe ash deposition on heating surfaces. The problem has been alleviated by the use of on-load water deslaggers in the furnace, and consideration has been given to a similar application in superheaters. Water deslagging in superheaters has been studied by: (a) plant tests to determine cleaning effectiveness and metal temperatures during operation, and (b) laboratory tests where tubes and test specimens have been subjected to repeated water quenching to investigate the initiation and propagation of thermal fatigue cracking. A similar study into the effects of water deslagging of furnace tubes is in progress. Results have shown that cracking will occur in superheater tube steels when the metal temperature is above 500 deg C. Tests on plain carbon steel furnace tubes at 450 deg C have produced cracking, but no significant cracking was found after 64,000 cycles of quenching from 325 deg C.
Supersonic Unstalled Flutter In Fan Rotors; Analytical and Experimental Results
Authors: Snyder L. E. , Commerford G. L.
Published: November 2010

Supersonic unstalled flutter is predicted using an unsteady supersonic cascade analysis, a cascade wind tunnel and a high speed fan rotor. Since the unsteady analysis assumes thin flat plate airfoils, the effect of thickness and blade shape was examined experimentally by flutter testing two sets of supersonic blading in a cascade wind tunnel. The effects of changes in Mach number, reduced frequency, stagger angle and interblade phase angle were examined from the analysis and tests. Results show that the trends are in agreement, but that blade shape has an effect on the level of reduced velocity at the incipient flutter point. The unsteady aerodynamic analysis is applied to two transonic fan stages. The first rotor was designed as a supersonic flutter test vehicle while the second was designed to be flutter free. Results of the fan tests show that the analysis correctly predicts the susceptibility to flutter of each rotor.
Ensuring Stable Circuit Conditions of Direct Cycle Helium Gas Turbine System
Authors: Frutschi H. U.
Published: November 2010

The choice of compressor characteristics of turbogroups is of decisive importance for the stable behavior of circuits during transients. It is shown how compressor surge at dangerous speeds during rapid shutdown can be suppressed by combining a compressor having a steep characteristic and low reaction with a compressor having a flat characteristic and high reaction. This combination is also well suited with respect to loss of load and startup. In addition, very favourable properties are obtained during positive load steps executed for the purpose of frequency support. Beside providing a machine design with inherent safety, a control system must be supplied which is not only redundant but exhibits inherent safety from malfunction and failures which could endanger the power plant. Because of the importance of these problems, the design and operation of such a control system are presented in this paper.
A Proposed Mechanism for Ash Fouling Burning Northern Great Plains Lignite
Authors: Tufte P. H. , Beckering W.
Published: November 2010

Fouling of boiler heat transfer surfaces by lignite ash continues to be a problem that reduces boiler efficiency and availability. The present study evaluates the fouling mechanism in a microscopic sense. It endeavors to establish a relationship between the identity and mode of occurrence of mineral matter in lignite and the resultant ash deposits. Severe fouling conditions are believed caused by the formation of a melted phase binding material within the deposit. Sodium, volatilized from coal and reacted in the flue gas to form sulfate or carbonate, reacts with a fly ash subspecies (termed matrix parent) to form the integrative matrix within ash deposits. The reactive subspecies (matrix parent) is derived from the inherent ash present in each burning coal particle. However, only inherent ash having elemental compositions lying within a given range is fluxable by sodium to form a sticky, deposit-integrating material. The major elements comprising the matrix are Na, Ca, Al, and Si. A chemical solution to the lignite fouling problem must alter the fluxing sodium or the fluxable matrix parent.
Performance Curves for Mechanical Draft Cooling Towers
Authors: Hallett G. F.
Published: November 2010

This paper presents cooling tower theory and methods for analytical verification of manufacturers’ guaranteed performance curves for mechanical draft cooling towers. Both ASME PTC-23 and Cooling Tower Institute Bulletin ATP-105 are being revised and both test codes have historically used performance curves as a means of evaluating cooling tower capacity. Techniques and methods are given for calculating performance curves for both counterflow and crossflow type cooling towers. These procedures can be used during bid evaluation to assess and predict tower performance at various operating conditions other than the design point.
Recirculation Effects in Gas Turbine Combustors
Authors: Kollrack R. , Aceto L. D.
Published: November 2010

An evaluation of the effects caused by recirculation of hot final combustion products into unburned or partially burned fuel/air mixtures indicates that the thermal effect predominates the combustion activity. Dilution and the introduction of active radicals produce lesser results. Internal recirculation, such as produced by swirl or bluff body stabilization, differs from external recirculation by the temperature levels of the recirculant and its composition. The net effect of recirculation is to simulate a longer residence time and/or an effective higher inlet temperature. As a general result, the end products are closer to equilibrium, specifically the CO levels are lower and the NO levels higher.
“C” Evaluation—Differences Between “Mathematical” and “Physical” Possibilities
Authors: Halmi D.
Published: November 2010

A review of the pertaining ASME literature shows that so far all ASME efforts to assign “uncalibrated” tolerances to ASME devices (orifice plates, ASME nozzles, PTC-6 throat tap nozzles) failed when tested against a newer set of calibration data. The paper shows that the cause of failure may have been the use of statistical methods and/or mathematical generalizations without physical scrutinization of the calibration data and the device under investigation. The purpose of the paper, therefore, is to help to map out the “physical road” to reliable “C” evaluation work. Another purpose of the paper is to uncover some hidden obstacles that have retarded progress in this area and would assure failure for future investigators, unless recognized and handled properly.
Modeling of Turbine Blade Tip Contact
Authors: Burton R. A. , Kilaparti S. R. , Heckmann S. R.
Published: November 2010

A mathematical model is developed for the condition where turbine blade/shroud contact occurs at discrete patches on the shroud. The contact patch is treated as having uniform time-mean contact pressure; and several components of relative displacement are identified, these having to sum to zero in the contact patch to assure an unbroken interface in the patch. Operating conditions which meet this requirement permit the postulated patchlike contact to exist. Operating conditions which do not meet it will not be associated with such patches. The components of relative displacement are almost independent of one another and are treated as linearly additive. These are: (1) thermal expansion of the shroud material in the patch, (2) elastic indentation of the shroud by the blade tip, (3) wear of the shroud material, (4) wear of the blade tip, (5) dynamic displacement of the blade tip, (6) dynamic displacement of the shroud, (7) elastic compression of the thinned blade tip portion. Using these components and applying the foregoing condition for full contact, the speed at which the contact patch traverses along the shroud surface is solved for, and the factors which determine the width of the contact patch are determined.
Effect of Streamline Curvature on Film Cooling
Authors: Mayle R. E. , Kopper F. C. , Blair M. F. , Bailey D. A.
Published: November 2010

The effects of streamline curvature on film cooling effectiveness are discussed. Experiments for air discharged through a slot and into a turbulent boundary layer along a flat, convex, and concave surface are described. Adiabatic wall effectiveness measurements on each surface for several blowing rates are presented. Boundary-layer velocity and temperature measurements are also presented for one of the blowing rates. Compared to the results for the flat surface, convex curvature is found to increase the adiabatic wall effectiveness whereas concave curvature is found to be detrimental.
A New Approach to the Experimental Study of Turbomachinery Flow Phenomena
Authors: Gostelow J. P.
Published: November 2010

Measurements of the unsteady flow field over a rotor and within its wake are needed in the development of most turbomachines. The technique advocated is that of data acquisition by on-line computer, using the periodic passing of a blade as a phase reference. The phase-lock averaging process is described as is its use in reducing the noise of raw data traces. Measurements of the unsteady flow over a cascade and of the resulting boundary layer behavior are presented. The approach was used in interpreting the unsteady flow field of an axial-flow compressor rotor and the static pressure distribution over the rotor tip. Finally the application to centrifugal pumps is discussed, enabling the designer to obtain information on the suction pressures and the extent of any separated region.
Optical Determination of Rotating Fan Blade Deflections
Authors: Stargardter H.
Published: November 2010

Measurement of flutter motion for rotating fan and compressor blades is necessary to verify mode shape analysis and assure an accurate description of the deflection and twist distribution required for stability prediction. The static deflection of blades caused by centrifugal and gas loads also needs to be measured to improve the accuracy of performance analysis. This paper presents a new technique for making these measurements with small blade-mounted mirrors that reflect laser light once per revolution. For steady operation, in the absence of blade vibration, each mirror reflects a light beam to project a repeating spot on a display screen, once for every revolution of the rotor. However, when the blades are fluttering the reflected light moves from its stationary position and during successive revolutions describes the blade motion as a lissajous pattern. Vibration amplitude, phase, and frequency are discussed and related to analysis. Limits in accuracy and the importance of precise mode shape description for flutter analysis are presented.
Heat Exchanger Design Considerations for Gas Turbine HTGR Power Plant
Authors: McDonald C. F. , Van Hagan T. , Vepa K.
Published: November 2010

The Gas Turbine High Temperature Gas Cooled Reactor (GT-HTGR) power plant combines the existing design HTGR core with a closed-cycle helium gas turbine power conversion system directly in the reactor primary circuit. Unlike open-cycle gas turbines where the recuperative heat exchanger is an optional component, the high cycle efficiency of the nuclear closed-cycle gas turbine is attributable to a high degree to the incorporation of the recuperator (helium-to-helium) and precooler (helium-to-water) exchangers in the power conversion loop. For the integrated plant configuration, a nonintercooled cycle with a high degree of heat recuperation was selected on the basis of performance and economic optimization studies. A recuperator of high effectiveness was chosen because it significantly reduces the optimum pressure ratio (for maximum cycle efficiency), and thus reduces the number of compressor and turbine stages for the low molecular weight, high specific heat, helium working fluid. Heat rejection from the primary system is effected by a helium-to-water precooler, which cools the gas to a low level prior to compression. The fact that the rejection heat is derived from the sensible rather than the latent heat of the cycle working fluid results in dissipation over a wide band of temperature, the high average rejection temperature being advantageous for either direct air cooling or for generation of power in a waste heat cycle. The high heat transfer rates in the recuperator (3100 MWt) and precooler (1895 MWt), combined with the envelope restraints associated with heat exchanger integration in the prestressed concrete reactor vessel, require the use of more compact surface geometries than in contemporary power plant steam generators. Various aspects of surface geometry, flow configuration, mechanical design, fabrication, and integration of the heat exchangers are discussed for a plant in the 1100 MWe class. The influence of cycle parameters on the relative sizes of the recuperator and precooler are also presented. While the preliminary designs included are not meant to represent final solutions, they do embody features that satisfy many of the performance, structural, safety, and economic requirements.
Fracture Strength and Thermal Shock Resistance of Thick And Thin-Wall Magnesium-Aluminum-Silicate Ceramic Heat Regenerators
Authors: Cleveland J. J. , Fritsch C. W. , Kleiner R. N.
Published: November 2010

Thin-wall regenerator cores offer the potential for higher effectiveness than comparable thick-wall cores. The fracture strength of magnesium-aluminum-silicate (MAS) ceramic heat-exchanger cores with wall thickness of 0.083 mm (0.003 in.) and 0.160 mm (0.006 in.) are compared. Thermal shock resistance calculations for these cores are also presented.
Flow Field Coupling Between Compression System Components in Asymmetric Flow
Authors: Greitzer E. M. , Mazzawy R. S. , Fulkerson D. A.
Published: November 2010

The coupling between an axial compressor in an inlet distortion and downstream compression system components is studied analytically and experimentally. The analysis is based on a nonlinear multisegment parallel compressor model coupled to a calculation procedure for the asymmetric flowfield downstream of the compressor. It is shown that in the presence of circumferentially nonuniform flow (distortion) there can be a strong interaction between the compressor and its overall environment. The response of the compressor to an inlet total pressure distortion can therefore depend not only on the compressor, as has sometimes been assumed, but also on the other components in the compression system. Further, the alteration in the response as a result of the interaction can be either beneficial or detrimental, depending on the nature of the component. Experiments investigating this coupling have been carried out on a three stage compressor. The experiments, which involved operating the compressor with three quite different downstream components, show clearly the differences that can exist in compressor response to distortion due to the compressor-component coupling. The analytical predictions of these effects are found to be in good agreement with the experimental results.
Development of a Hybrid Catalytic Combustor
Authors: Siminski V. J. , Shaw H.
Published: November 2010

The pollution problems associated with unburned hydrocarbons and carbon monoxide in the idle mode, and NOx and smoke production in the power mode of aircraft gas turbine operation can be minimized using hybrid catalytic combustion. A hybrid catalytic combustor (HCC) consists of a fuel-rich precombustor, secondary air quenching zone, and monolithic catalyst stage which rapidly oxidizes CO and UHC produced in the precombustor. The concentration of thermally produced NOx in the precombustor is very low because of the lack of oxygen. However, the formation of NOx precursors such as HCN and NH3 produced under fuel rich conditions must be considered. Data showed that nitrogenous species produced in the rich precombustion zone were efficiently converted to NOx by catalysts under very lean mixture conditions. The equivalence ratio in the precombustor was varied from 0.5 to 1.5, while the overall mixture, after secondary air injection, was in the range of 01–0.3. The noble metal catalysts on various monolithic support geometries and compositions were found to be the most active materials for CO and UHC oxidation in the temperature range of 700–1200 K. The HCC combustion efficiency of JP-4 which contained 535-ppm sulfur was determined to be 99.8 percent under realistic conditions. The combustor pressure drop was less than 6 percent. The average emission indices of CO, UHC, and NOx leaving the HCC were on the order of 0.95, 0.43, and 1.8 g/kg of fuel, respectively, for metal supported Pt catalyst. This catalyst was effective in reducing CO by 86 percent and UHC by 94 percent, and increasing NOx by 68 percent. Using approximate methods for calculating EPA emission parameters, it was estimated that the HCC can meet the 1979 new aircraft emission standards but fails to meet the 1981 new aircraft emission standards because UHC are slightly too high.
High-Temperature Potential of Uncooled Radial Turbines
Authors: Arnold D. J. , Balje O. E.
Published: November 2010

Radial turbines are used predominantly for turbo-charges where the geometry is frequently compromised to favor low fabrications costs. Theoretical as well as experimental investigations have shown that the efficiency potential of radial turbines is as high as the efficiency potential of high reaction axial turbines. Structural and heat transfer studies on radial turbines show that the highest stresses in “deep scalloped” radial rotors occur at locations where the metal temperature is considerably lower than at rotor inlet. Thus the maximum allowable gas inlet temperature for radial turbines is several hundred degrees higher than for high-reaction axial turbines. This difference tends to increase with increasing expansion ratios, at least up to expansion ratios of 10:1. Since the thermal efficiency of typical gas turbine cycles increases with increasing gas temperatures and increasing expansion ratios, it results that the application of uncooled radial turbines will yield cycle efficiencies which are not obtainable with uncooled axial turbines.
Special Engineering Problems of TFTR
Authors: Lee D. E.
Published: November 2010

Design of the TFTR presents special engineering problems as a result of constraints posed by the physics requirements of the fusion experiments. The ratio of plasma major and minor radii and the associated magnetic field strength required to achieve desired plasma conditions, the required confinement time, the two-component plasma concept, the complications of providing shielding from the 14 MeV neutrons and the necessity to control the inventory of tritium fuel, all constitute problems which, often, in actuality, must be approached as materials problems. The complex, precision structures must satisfy various criteria, for example, low magnetic permeability, high electrical resistivity, resistance to neutron activation and high damage tolerance. Another constraint in the engineering design of TFTR is the requirement to optimize access to machine components for maintenance and repair. Many of the problems associated with accessibility have been resolved: the vacuum vessel has been designed as a ten-segment vessel; the igloo shielding of the machine is composed of interlocking blocks of boron-loaded concrete; the center column is designed in three segments. Current engineering emphasis is on finalizing design of the toroidal field coils, lower poloidal field coils, vacuum vessel liners and limiters, and peripheral systems such as the vacuum pumping system and arrangement of diagnostics.
Measurement of Nonsteady Forces in Three Turbine Stage Geometries Using the Hydraulic Analogy
Authors: Rieger N. F. , Wicks A. L.
Published: November 2010

Experimental results for the nonsteady forces and nonsteady torques acting at the e.g. of an instrumented moving turbine blade have been obtained. Three different turbine stage geometries have been tested in this manner. The data described was obtained using a rotating model turbine stage consisting of a row of stationary inlet nozzles and a rotating blade row. The hydraulic analogy was used to stimulate the two-dimensional gasdynamic flow through the three stage geometries in turn. The free-surface horizontal flow of water across the rotating water table then represents the gas flow through the stage. Results for the nonsteady forces and torques in the tangential, axial, and torsional directions are presented as dimensionless force ratios or dimensionless torque ratios in each instance. Charts of results are presented for various stage pressure ratios, for practical ranges of stage velocity ratios. Typical results and observed trends are discussed in detail, and a summary table of observed nonsteady excitation values is presented.
Approximation of Fundamental Equations for Finite-Dimensional Modeling of Thermo-Fluid Processes
Authors: Ray A.
Published: November 2010

Finite-dimensional lumped models of thermo-fluid processes are usually formulated from fundamental conservation equations. In dynamic modeling and system simulation, internal energy is often replaced by enthalpy in the energy conservation equation without considering the work term (p/ρ). For compressible fluids, this leads to a significant dynamic error, although the steady-state results are unchanged. A more exact formulation, presented here, can be easily implemented. A numerical example is given for a typical case.
Jet Cooling at the Rim of a Rotating Disk
Authors: Metzger D. E. , Mathis W. J. , Grochowsky L. D.
Published: November 2010

Results are presented from an experimental study conducted to measure heat transfer rates at the rim of a rotating disk convectively cooled by impinging jets. The disk face contour radially inward from the rim is varied to simulate the geometric conditions found on gas turbine engine rotors. Heat transfer rates are found to be relatively unaffected by impingement for jet flowrates less than the order of one-tenth the disk pumping flow. Disk pumping flows are evaluated through the use of an analysis which accounts for the presence of the disk hub. At larger jet flowrates, heat transfer rates increase strongly with increasing jet flow, reaching two to three times the no-impingement values at jet flowrates approximately equal to the pumped flow. All the heat transfer results, both with and without jet impingement, are essentially unaffected by changes in the disk face contour.
The Reliability of Gas Turbine Powered Compressor Units
Authors: Harrison R. A. , Weatherilt P. F.
Published: November 2010

This paper describes British Gas Corporation (BGC) experience of the operating reliability of aircraft gas turbine powered compressor units utilized in the gas transmission system. The complex nature of the system has led to the design of computer based simulation models to identify the relationship between operating reliability and spare unit provisioning. The need to achieve particular reliability levels has led to the specification in contracts of quantified reliability criteria which are both measurable and achievable. There seems a clear need for national or international standards for reliability specification. BGC is introducing operational and defect data collection systems to identify areas of weakness in current plant and to provide a feedback to the manufacturer.
Development of an Inlet for a Tilt Nacelle Subsonic V/STOL Aircraft
Authors: Potonides H. C.
Published: November 2010

A fixed geometry inlet capable of efficient operation to very high angles-of-attack has been developed by the Grumman Aerospace Corporation for a tilt nacelle subsonic V/STOL airplane. The inlet, sized to fit a 5.5-in. (13.97 cm) diameter fan, has been extensively tested and demonstrated very high pressure recoveries and low distortions at higher angles-of-attack than any of the published inlet data to date, including an inlet with the very high contraction ratio of 1.78 on the windward lip. This inlet capability has been achieved by judicious selection of the inlet design parameters affecting flow separation. The substantial angle-of-attack capability of the inlet provides the opportunity for trading off some of the margin at low speed to reduce nacelle maximum diameter, hence weight, and to increase the estimated drag divergence Mach number of 0.75 to higher than Mach 0.80. Tests with lower lip contraction ratio show that this may be possible and investigations exploring this possibility are now in progress at NASA/Lewis.
Combustion of Pulverized, Solvent-Refined Coal
Authors: McCann C. R. , Demeter J. J. , Bienstock D.
Published: November 2010

The handling, pulverizing, combustion, and fouling characteristics of solvent-refined coal (SRC) were studied in a multiburner, water-wall furnace designed to burn pulverized, bituminous coal at a rate of 500 lb/hr. The products from two SRC plants, Southern Services, Inc., at Wilsonville, Alabama, and ERDA’s plant at Fort Lewis, Washington, were included in the study. SRC obtained from the Southern Services, Inc. plant had a fluid temperature less than 300°F while the product obtained from Fort Lewis had a fluid temperature of about 430°F. When operating at secondary air temperatures of 500–600°F it was necessary to water-cool the primary air-coal passages and burner nozzle to prevent melting and subsequent fouling. In addition, secondary air swirl adjustments were made to optimize recirculation and flame shape to overcome burner fouling. Flame temperatures obtained with SRC were several hundred degrees (°F) higher than those measured with bituminous coal, however, NOx emissions were considerably lower than those obtained with coal fired through the more conventional burners originally used in the combustion system. Sulfur oxides emissions of 0.8–1.0 lb SO2/106 Btu would meet emissions regulations in most air regions in the U. S. Carbon conversion values were similar to those obtained when firing bituminous coal. To provide a basis for comparison, combustion tests were also conducted on a Pittsburgh seam coal, and an Illinois No. 6 coal, the parent coal for the SRC produced at the Wilsonville plant.
Chemical Cleaning of Coal
Authors: Friedman Sidney , Warzinski R. P.
Published: November 2010

Between the expensive coal conversion processes and the relatively inexpensive flotation and magnetic methods for pyrite removal are the chemical methods for desulfurizing coal. Chemical cleaning removes more sulfur than physical separations, less than coal conversion, at costs and investment which are intermediate. Fuel value losses are small for chemical methods, comparable with the best of the physical separation procedures. In addition, certain chemical treatment methods effect useful changes in coal composition and properties. The principal chemical desulfurization methods involve treatment, at elevated temperature, with either basic media or oxidizing systems. Aqueous sodium hydroxide, at 225°C, removes almost all of the pyrite from coal, while subsequent washing with dilute acid removes most of the remaining mineral matter. At 300°C, similar treatment can remove, in addition, up to 40 percent of the organic sulfur from coals and also destroy caking properties. Oxidative desulfurization, using steam and air, also removes most of the pyritic sulfur and 20–40 percent of the organic sulfur, under milder conditions than those required for alkali treatment. The steam-air desulfurization process is presently the simplest and cheapest concept for removing organic sulfur from coal, making much eastern and midwestern coal environmentally acceptable as boiler fuel at realistic cost.
Corrosion and Deposits From Combustion of Solid Waste—Part V: Firing of Refuse With High-Sulfur Coal
Authors: Krause H. H. , Vaughan D. A. , Cover P. W. , Boyd W. K. , Oberacker D. A.
Published: November 2010

The utilization of municipal refuse as a supplementary fuel in a coal-fired power-generating plant has been investigated. The preparation of the solid waste consisted of shredding, ferrous metal separation, and air classification. Probes inserted in the superheater section of the stoker-fired boiler were used to collect deposits and to measure the extent of corrosion. The corrosion rates found for refuse–coal mixtures containing up to 42 weight percent refuse approximated those found with the coals and were about an order of magnitude less than those found with refuse alone. The flue gas temperatures were found to be important factors in corrosion. Sulfur oxide emissions of the high-sulfur coal were reduced both by dilution with the refuse and by the action of the alkaline components of the refuse.
Real-Time Test Techniques for Sea-Salt Aerosol-Separator Evaluation
Authors: Mihalek E. W. , Shen C. N.
Published: November 2010

Gas turbine power plants are increasingly finding use as prime movers in Naval and commercial vessels, at-sea drilling platforms, and land-based power generating stations. With this rise in usage, the life of the machine becomes a consideration when operation in a marine environment is necessary. Limited data are available on the subject of marine aerosols and even less information can be found on the necessary requirements for effective separators for the ship-encountered marine environment. In order to specify the inlet system performance required by the new classes of gas turbine powered U.S. Navy ships, the Naval Ship Engineering Center (NAVSEC) has funded a gas turbine engine inlet separator test program to be performed at the Naval Air Propulsion Test Center (NAPTC) as one phase of a total inlet development program. This paper discusses the NAPTC sea-salt aerosol test facility and the real-time test techniques and instrumentation utilized.
A Calculation Method for Incompressible Viscous, Blade-to-Blade Flow through Radial Turbomachines with Log-Spiral Blade Surfaces
Authors: Bosman C. , Chan K. C. , Hatton A. P.
Published: November 2010

A finite difference method of blade-to-blade calculation for incompressible turbulent, viscous flow through radial turbomachines having log-spiral blades lying entirely in the r-θ plane is presented. A Newtonian stress system is incorporated into the calculation which employs a slip model for flow close to the blade surfaces. The effects of turbulence are simulated by use of an enhanced molecular viscosity. This problem is of a higher mathematical order than the usual free slip, inviscid calculation commonly applied in the design and analysis of these machines and raises interesting considerations of understanding with respect to mathematical closure and boundary conditions. Experimental results for flow through an actual machine of similar geometry to that analyzed are available and comparison of streamlines and velocity profiles are made.
Velocity Distributions and Turbulence Intensities at Tubesheets in a Two-Pass Condenser Model
Authors: March P. A.
Published: November 2010

A 1:7.8 scale hydraulic model was used to determine flow patterns, velocity distributions, and turbulence intensities within the inlet/outlet waterbox and reversing waterbox of a two-pass condenser for a nuclear generating station currently under construction. A laser doppler anemometer with an acousto-optical frequency shifter was used to measure the velocity components perpendicular to the tubesheets and the turbulence intensities associated with these components. Test results were discussed in terms of their implications for tubesheet and condenser tube erosion.
Development of Sprayed Ceramic Seal System for Turbine Gas Path Sealing
Authors: Shiembob L. T. , Stewart O. L. , Bill R. C.
Published: November 2010

Analytical and experimental research was conducted to evaluate a ceramic seal system for a high-pressure turbine employing plasma-sprayed graded metallic ceramic, yttria-stabilized zirconium oxide (YSZ). The performance characteristics of several YSZ configurations were determined through rig testing for thermal shock resistance, abradability and erosion resistance. Results and test data acquired from this work indicate that this type of sealing system offers the potential to meet the operating requirements of future gas-turbine engines. However, continued development and refinement of this technology, particularly in the area of improving cyclic thermal stress tolerance, is necessary.
On the Dynamics of Electrostatically Precipitated Fly Ash
Authors: Juricic D. , Herrmann G.
Published: November 2010

One of the factors influencing the efficiency of modern electrostatic precipitators is the proper cleaning of dust collecting plates, which is usually done by a periodic rapping. The rapping blow excites the plates, which in turn dislodge the accumulated dust layer. The paper analyzes the response of a deposited dust layer to an arbitrary out-of-plane motion of the plate to which it is held by the action of molecular and electrostatic adhesive forces. A simplified one-dimensional model of the precipitated dust-layer is assumed to have viscoelastic properties of the Kelvin solid. The results indicate that—in addition to the acceleration level—the frequency of excitation as well as the adhesive-force arrangement are decisive in defining how and when the dust layer will break off the plate.
A Stress Gradient Theory of Rock Fracture In Drilling
Authors: Swanson S. R.
Published: November 2010

It seems likely that improvements in drilling mechanics will result from an understanding of the stress and strain fields in the rock. Along with this an understanding of rock fracture under the appropriate conditions is required. The stress fields in drilling are characterized by high spatial gradients of stress, and the stress gradients are known to interact with rock fracture properties. The present investigation is concerned with quantifying the stress gradient effect on fracture. Laboratory tests were performed on a variety of specimen configurations for three brittle rocks. A very strong effect of stress gradient was found, indicating an apparent elevation of fracture strength with increasing stress gradient. A correlation was shown with a critically stressed distance concept.
On Pipeline Bending at the Seabed
Authors: Mousselli A. H.
Published: November 2010

Analysis is presented on stresses in a pipeline caused by bottom irregularities during installation and by trenching operations. The governing equations are described in non-dimensional forms, and results of the computer solutions are presented in terms of general dimensionless graphs, so they may be applied directly to various problems. It is found that the magnitude of the maximum stress is substantially different when the pipe span end conditions are changed. Further, the inclusion of axial tension considerably alters stresses in the pipe spans. This becomes particularly significant in some pipe installations where elevated bottom tensions are required.
Velocity Field Induced by Singularities in a Reaction Turbine Fluid Filament of Varying Thickness Approximated by Hyperbolic Law
Authors: Khan M. N. , Swaroop Adarsh , Rao Y. V. N.
Published: November 2010

The flow in a hydraulic reaction turbine can be analyzed by considering the blade surfaces to be surfaces of discontinuity. For such an analysis the velocity field induced by a system of distributed singularities (sources and vortices) is to be determined. In this paper the runner space is divided into elementary runners, assuming the absolute flow in the runner to be irrotational and the stream surfaces to be surfaces of revolution. The axisymmetric fluid filament thus obtained is then conformally mapped on to a plane. The variable thickness of the resulting plane filament is approximated by hyperbolic law. The velocity field due to a singularity is obtained by solving the governing differential equation in a closed form. The solution is extended for a chain of singularities.
Calculation of Interacting Turbulent Shear Layers: Duct Flow
Authors: Bradshaw P. , Dean R. B. , McEligot D. M.
Published: November 2010

The boundary-layer calculation method of Bradshaw, Ferriss, and Atwell has been adapted to deal with the interaction between two shear layers with a change of sign of shear stress. Good agreement with experiments in symmetrical duct flow is found, using the same empirical input as in a boundary layer and assuming that the turbulence fields on either side of the duct can be superposed. The restriction to symmetrical flow is temporary and is a numerical rather than a physical simplification. In free jet flows, which have higher turbulence levels than ducts, small changes in empirical input are required to treat the interaction.
An Investigation of Pressure Transients in a System Containing a Liquid Capable of Air Absorption
Authors: Driels M. R.
Published: November 2010

The object of the paper is to describe the formulation and use of a computer model which will predict the mode of flow in hydraulic systems with rapidly changing boundary conditions. The analysis takes into account the possibility of air absorbtion, its release, and a mathematical representation of the subsequent separated flow. The model’s performance is compared to that of an experimental rig and the results and discrepancies are discussed at the end of the paper.
A Finite Difference Solution of the Two and Three-Dimensional Incompressible Turbulent Boundary Layer Equations
Authors: Klinksiek W. F. , Pierce F. J.
Published: November 2010

A modified Crank-Nicholson implicit finite difference formulation is presented for two and three-dimensional turbulent boundary layers. The turbulent stresses are treated after Prandtl’s early mixing length model. “Boundary layer like” assumptions result in only the streamwise and transverse stresses remaining. The specific empirical input is the Maise and McDonald mixing length model. Excellent agreement with two independent experiments is obtained for mean velocity field data. Both experiments included a plane of symmetry to provide a transverse coordinate initial condition.
The Dynamic Behavior and Compliance of a Stream of Cavitating Bubbles
Authors: Brennen C.
Published: November 2010

The role played by turbopump cavitation in the POGO instability of liquid rockets motivates the present study on the dynamic response of streams of cavitating bubbles to imposed pressure fluctuations. Both quasistatic and more general linearized dynamic analyses are made of the perturbations to a cavitating flow through a region of reduced pressure in which the bubbles first grow and then collapse. The results when coupled with typical bubble number density distribution functions yield compliances which compare favorably with the existing measurements. Since the fluids involved are frequently cryogenic, a careful examination was made of the thermal effects both on the mean flow and on the perturbations. As a result the discrepancy between theory and experiment for particular engines could be qualitatively ascribed to reductions in the compliance caused either by these thermal effects or by relatively high reduced frequencies.
Nozzle Discharge Coefficients—Compressible Flow
Authors: Olson A. T.
Published: November 2010

Using Walz’s approximation method for boundary layer calculation, along with a one-dimensional treatment of the compressible inviscid core flow, discharge coefficients for small nozzle to pipe diameter ratios have been calculated. Discharge co-efficients calculated for the ASME long radius nozzle agree with those recommended by the ASME Power Test Code. In addition, experimental confirmation of an indicated Mach number effect has been achieved in a nozzle modified to minimize two-dimensional effects.
A Modern Laboratory for Hydraulic Turbine and Pump/Turbine Model Performance Testing
Authors: Frey G. R. , Rohrbaugh R. L. , Whippen W. G.
Published: November 2010

Increased demands for higher performance, reliability, and versatility from hydraulic turbines and pump/turbines have dictated that manufacturers improve their model testing facilities to thoroughly evaluate individual designs as required by customer specifications. Advances in supporting technology, particularly electronic instrumentation, data acquisition, and motor/generator control, have significantly improved performance data and have reduced testing time to a minimum. This paper discusses a new laboratory design, incorporated by the Hydro-Turbine Division of Allis-Chalmers Corporation for model testing, including the building, the flexible test circuits, the data acquisition system, the power generation system, and the model test stand.
Impact of Liquid Jets at Velocities Approaching Liquid Sound Speed
Authors: Neusen K. F. , LaBrush E. C.
Published: November 2010

Experiments were performed to obtain information concerning the action of high velocity liquid jets impacting at velocities that erode the target surface (1000–4000 fps, 305–1200 mps). Nozzle pressure, impact force and target temperature data were obtained using a quasisteady flow system at pressures up to 146,000 psi (1007 MN/m2). Under no-flow conditions, the system was used to determine liquid compressibility for a diester synthetic hydraulic fluid. The jet flow data are compared to results from a calculational model for quasisteady flow.
Experiments on the Resistance Law for Non-Darcy Compressible Gas Flows in Porous Media
Authors: Masha B. A. , Beavers G. S. , Sparrow E. M.
Published: November 2010

Experiments were performed to examine the resistance law for non-Darcy compressible gas flow through a porous material. A particular objective of the investigation was to determine whether a resistance law deduced from incompressible flow experiments could be applied to flows with significant density changes. To this end, the coefficients appearing in the Forchheimer resistance law were first determined from experiments in the incompressible flow regime. These values were then used in an analytical model employing the Forchheimer resistance law to predict streamwise pressure distributions for subsonic compressible flow through the porous material. Corresponding experimental pressure distributions were measured for flow Reynolds numbers up to 81.6. At the highest Reynolds number of the tests the density changed by about a factor of two along the length of the porous medium. The greatest discrepancy between experimental and predicted pressures at any Reynolds number was 2 percent. This agreement lends strong support to the validity of using the incompressible Forchheimer resistance law for subsonic flows in which density changes are significant.
Shock-Excited Pulsations of Large Air Bubbles in Water
Authors: Jensen F. B.
Published: November 2010

The interaction between an air bubble in water (d0 = 10–30 mm) and a shock wave generated by a small detonator (0.8 g) is studied. On the basis of direct pressure measurements inside pulsating bubbles and simultaneous photographic recording of the diameter variations, the overall thermal behavior of the gas in the bubbles is determined. It is found that the pulsation process is nearly adiabatic for the bubble sizes considered. The measured maximum pressures inside pulsating bubbles are given as a function of bubble size and distance from the explosion. From these results, the total energy absorbed by a bubble is calculated as a measure of the attenuation effect of a single bubble on a shock wave.
Solid Particle Demixing in a Suspension Flow of Viscous Gas
Authors: Hamed A. , Tabakoff W.
Published: November 2010

The motion of a medium consisting of an incompressible viscous fluid and suspended solid particles was analyzed from the standpoint of continuum mechanics. It was assumed that the particles’ translational and rotational velocities were different from those of the fluid. A numerical scheme was used to determine the non-equilibrium particulate flow properties as well as their equilibrium and frozen values. The results are presented for the case of particulate flow due to the impulsive motion of an infinite flat plate in a suspension. A demixed region, with no particles present, was found to develop near the plate due to particle migration away from the wall. Similar demixed particle regions were noticed in the experimental data of particulate flows in pipes and channels.