bluuebunny/crossref_metadata_2025 huggingface dataset:
Status of Centrifugal Impeller Internal Aerodynamics—Part II: Experiments and Influence of Viscosity
Authors: Adler D.
Published: October 2009

Recent developments in internal viscous aerodynamics of centrifugal impellers and related flows are critically reviewed. The overall picture which emerges provides the reader with a state-of-the-art perspective on the subject. Gaps in understanding are identified to stimulate future research. Topics included in this review are: experimental work carried out in the last decade, the structure of turbulence in curved rotating passages and solution of viscous flow problems in impellers.
Compressor Rotating Stall in Uniform and Nonuniform Flow
Authors: Cossar B. F. J. , Moffatt W. C. , Peacock R. E.
Published: October 2009

Rotating stall in axial compressors consists of regions or cells of retarded flow moving around the annulus relative to the blades. Planar symmetry is destroyed, resulting in stalled blades in part of the annulus and unstalled blades in the remainder. The stall cell moves in the direction opposite to the rotor, relative to the blades, but since the relative speed of propagation is usually less than the rotor speed, the cell is seen to move in the same direction as the rotor from an absolute reference frame. The presence of the stall cells results in a deterioration of compressor performance since the maximum pressure ratio is not achieved in regions of retarded flow. Furthermore, since this self-induced distortion is periodic, the forced frequencies generated may coincide with the natural harmonics of the blading, tending to cause structural damage. This paper describes a series of experiments in which a single-stage, lightly loaded compressor operated under stall-free conditions and with rotating stall, both with uniform inlet flow and with distortions generated by an upstream screen of uniform porosity. Not only was the overall compressor performance determined in the traditional manner, but the distribution of static pressure over the rotor suction and pressure surfaces was measured with high response instrumentation. The rotor pressure profiles measured in both undistorted and distorted flow are presented for operation before and after the onset of rotating stall and the latter are compared with the steady flow results. It is observed that two distinctly different types of rotating stall exist depending upon whether or not an inlet flow distortion is present. These cells differ not only in macroscopic properties—rotational speed, circumferential extent, mass-averaged flow conditions, etc.—but also in detailed flow characteristics as evidenced by the rotor blade static pressure distributions. It is further observed that not all inlet distortion geometries lead to the development of rotating stall.
Optimum Design of Axial Flow Gas Turbine Stage—Part I: Formulation and Analysis of Optimization Problem
Authors: Rao S. S. , Gupta R. S.
Published: October 2009

The problem of stage design of axial flow gas turbines has been formulated as a nonlinear mathematical programming problem with the objective of minimizing aerodynamic losses and mass of the stage. The aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem is presented in Part I of this paper. The optimization problem is solved by using the interior penalty function method in which the Davidon-Fletcher-Powell variable metric unconstrained minimization technique with cubic interpolation method of one-dimensional minimization is employed. Problems involving the optimization of efficiency and/or mass of the stage have been solved numerically in Part II of the paper. The results of a sensitivity analysis conducted about the optimum point have also been reported.
Optimum Design of Axial Flow Gas Turbine Stage—Part II: Solution of the Optimization Problem and Numerical Results
Authors: Rao S. S. , Gupta R. S.
Published: October 2009

The problem of stage design of axial flow gas turbines has been formulated as a nonlinear mathematical programming problem with the objective of minimizing aerodynamic losses and mass of the stage. The aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem is presented in Part I of this paper. The optimization problem is solved by using the interior penalty function method in which the Davidon-Fletcher-Powell variable metric unconstrained minimization technique with cubic interpolation method of one dimensional minimization is employed. Problems involving the optimization of efficiency and/or mass of the stage have been solved numerically in Part II of the paper. The results of sensitivity analysis conducted about the optimum point have also been reported.
An Instrument for Spray Droplet Size and Velocity Measurements
Authors: Bachalo W. D. , Hess C. F. , Hartwell C. A.
Published: October 2009

Laser light scattering techniques that measure the size of single droplets at a time have experienced difficulties when applied to high number density sprays. This problem has been alleviated by developing the particle sizing interferometric method for the off-axis detection of scattered light. The method has the advantages of being insensitive to the absolute intensity of the light scattered and light absorbed by the droplet and measures the droplet size and velocity simultaneously. A theoretical description of the technique is given along with experimental verifications of the results. The experiments showed that the method can produce accurate in situ measurements of typical nozzle sprays when large off-axis light collection angles are used.
Analysis of Heat Transfer Surface Geometries for Dry Cooling Tower Applications
Authors: Montakhab Ali
Published: October 2009

An analysis of heat exchanger surface geometries for the purpose of reducing dry cooling tower cost is presented. Two sets of results are derived. The first set can be used to evaluate heat transfer surface geometries in an attempt to select those most suitable for dry cooling tower applications. The second set of results can be used to direct research and development efforts toward developing better geometries for dry cooling tower applications. The first set of results is general and is applicable to all heat exchanger surface geometries. The second set is valid only for helical round or continuous fins having smooth, serrated, or cut fins and for staggered and in-line tube arrangements. The methods developed in this paper are not restricted to dry cooling towers per se, but are valid for other applications of fin tube heat exchangers as well.
Short Pipe Manifold Design for Four-Stroke Engines: Part II
Authors: Vorum P. C.
Published: October 2009

Continued study has gone on examining a discrete modal model of intake and exhaust breathing of four-stroke engines. By matching a Helmholtz defined pressure excursion to specific average flow velocities, maximum ram supercharge on intake and scavenging on exhaust are possible. Inclusion of all engine parameters allows for a quick, accurate design of an intake/exhaust pair. Trends are noted easily and errors can be corrected quickly. The intake and exhaust systems can be designed to compliment the additional power possible when a turbocharger, Roots blower, or some other supercharger system is added to the engine. Improved performance, economy, and emissions characteristics are possible with the careful matching of the manifolds to the operating conditions.
The Effect of Percent Hydrogen in Fuel on Smoke Emissions of a Compression-Ignition Engine
Authors: Voorhies A. , Daniel L. R. , Long L.
Published: October 2009

Six diesel fuels, varying in percent hydrogen from 12.36 to 14.38 percent and in cetane number from 37.5 to 55.5, were evaluated for percent opacity as a function of fuel-air ratio—both at 800 and 1000 rpm—in a Waukesha CFR diesel engine. In both cases, at a given fuel-air ratio, the smoke emissions (measured by percent opacity) decreased with increasing percent hydrogen in the fuel. In these studies, percent hydrogen was both a satisfactory and a unique parameter, since neither cetane number nor volatility of the various fuels could be correlated with smoke emissions. In these studies, percent hydrogen is apparently the essential index of diesel fuel quality for satisfactory smoke emissions.
Cavitation Erosion Damage in Engine Bearings: Theory and Practice
Authors: Garner D. R. , James R. D. , Warriner J. F.
Published: October 2009

Cavitation erosion damage in engine bearings has assumed increasing importance during the past 5–10 years, probably as a result of the design trends towards higher rotational speeds, and, in some cases, higher rates of change of cylinder pressure rise. In many instances the damage is merely cosmetically undesirable, and of only minor functional significance; this is particularly so when the bearing is overlay plated. In more extreme cases extensive loss of lining material will result, and the consequential adverse effects on oil film conditions will reduce reliability and life of the bearings and associated parts. This paper presents a general background to cavitation erosion damage and examples of specific forms of this type of damage in plain bearings are given. A number of commonly applied palliatives and their effectiveness, based on engine experience, are discussed. A description of computer-based methods for predicting crankshaft journal locus, oil film pressure profile, and film extent is provided. An attempt has been made to rationalize several typical forms of cavitation damage on the basis of the theoretical model. An ultrasonic vibratory test facility used by the authors to determine the relative erosion resistance of the more commonly used bearing materials is described, and results presented.
Recuperators for the HHT-Demonstration Plant
Authors: Nordstroem L.-A. , Fischli H. , Naegelin R.
Published: October 2009

Recuperators of closed cycle gas turbine plants are characterized by large heat transfer areas accommodated in rather small volumes. Clean gas conditions, moderate operating temperatures and modest requirements with respect to tightness have resulted in generally good operational records. In the case of recuperators for direct cycle high temperature reactors, more stringent boundary conditions are being imposed than for conventional plants. In this paper studies and experiments performed for the recuperator of the HHT demonstration plant (670 MWe) are described. Five different design concepts are discussed and mutually compared. All designs use straight tubes. The main concept is a proposal with longitudinal flow on the shell side, but also the proven cross-counterflow concept has its merits. Special subjects are sensitivity to temperature streaks and optimum subdivision into modules.
Crossflows in a Turbine Cascade Passage
Authors: Langston L. S.
Published: October 2009

Measurements of the subsonic flow in a large scale plane turbine cascade, that were given in an earlier paper, are examined in more detail from the standpoint of the endwall boundary layer. Representative data are presented in terms of normal and streamwise velocities, flow angle deviations, and polar plots, that can be used to substantiate analytical models of the endwall flow. The qualitative behavior of the endwall crossflow was found to be correlated by a relatively simple expression, based on the flow angle deviation.
High-Speed Noncontacting Instrumentation for Jet Engine Testing
Authors: Scotto M. J. , Eismeier M. E.
Published: October 2009

This paper discusses high-speed, noncontacting instrumentation systems for measuring the operating characteristics of jet engines. The discussion includes optical pyrometers for measuring blade surface temperatures, capacitance clearanceometers for measuring blade tip clearance and vibration, and optoelectronic systems for measuring blade flex and torsion. In addition, engine characteristics that mandate the use of such unique instrumentation are pointed out as well as the shortcomings of conventional noncontacting devices. Experimental data taken during engine testing are presented and recommendations for future development discussed.
The Perbury Transmission
Authors: de B. Perry F. G.
Published: October 2009

The Perbury transmission is a form of toroidal traction drive. This descriptive paper presents a brief overall view of its principles, background, present status of development, applications and future development areas.
Full Coverage Film-Cooled Blading in High Temperature Gas Turbines: Cooling Effectiveness, Profile Loss and Thermal Efficiency
Authors: Hempel H. , Friedrich R. , Wittig S.
Published: October 2009

Extending data obtained from hot gas cascade measurements on the cooling effectiveness and profile loss coefficients of full coverage film-cooled blading, use is made of similarity considerations to determine the heat transfer characteristics under actual engine conditions. Of primary interest are stationary gas turbines. Calculations are made for a four-stage single shaft gas turbine with air preheat and common component efficiencies. As a representative result it is found that for a pressure ratio of π = 10 a relative cooling air flow of approximately 8 percent will be required in rising the temperature from 1173 to 1573 K. The resulting relative improvement of the thermal efficiency is 24 percent and that of the specific work about 70 percent.
Investigations of an Axial Flow Compressor with Tandem Cascades
Authors: Bammert K. , Beelte H.
Published: October 2009

In axial flow compressors with high degrees of reaction the transfer of energy can be increased by using suitable tandem cascade arrangements. The application of multistage tandem cascade systems therefore allows savings in constructional length and blading and thus a very compact compressor design. Therefore a four-stage tandem cascade compressor with 100 percent reaction was built. To determine the operating behavior of the machine, the compressor characteristic on speed control was measured. For optimization and further development of this compressor the characteristics on adjustment of all stator blade rows and speed control were measured. To allow the behavior of the stator blade rows and tandem cascade wheels to be assessed, the channel flow in the axial gaps behind selected wheels was measured. The tandem cascade compressor, its layout and the results of experimental investigations are presented and discussed.
Measurements of the Boundary Layer Development along a Turbine Blade with Rough Surfaces
Authors: Bammert K. , Sandstede H.
Published: October 2009

During the operation of turbines the surfaces of the blades are roughened by corrosion, erosion and deposits. The generated roughness is usually greater than that produced by manufacture. The quality of the blade surfaces determines the losses of energy conversion in turbine cascades to a great extent. The loss coefficient can be found theoretically by a boundary layer calculation. For rough surfaces there are no boundary layer measurements along the profiles of a turbine cascade. Therefore in a cascade wind tunnel measurements of the boundary layer development were carried out. The chord length of the blades was 175 mm. The cascade represented a section through the stator blades of a 50 percent reaction gas turbine. For smooth surfaces and three different roughnesses up to 3.3 · 10−3 (equivalent sand roughness related to chord length) the boundary layers were measured. The momentum thickness is up to three times as great as that on smooth surfaces. Especially in regions with decelerated flow the effects of roughness are high. A rough surface causes a rise of the friction factor and a shift of the transition of laminar to turbulent flow. The results of the measurements are shown. Correction factors are worked out to get good agreement between measurement and calculation according to the Truckenbrodt theory.
Arrays of Impinging Jets with Spent Fluid Removal through Vent Holes on the Target Surface—Part 1: Average Heat Transfer
Authors: Hollworth B. R. , Dagan L.
Published: October 2009

Measurements of average convective heat transfer are reported for square arrays of impinging air jets. The target plate on which the jets impinge is perforated so that spent air is withdrawn through the plate rather than at one or more edges of the array, as is usually the case in such investigations. Jet holes and vent holes had the same diameters, but the spacing of the jet holes was twice that of the vent holes. This information is especially relevent to the design of hybrid cooling configurations, in which a surface is cooled by the combined mechanisms of impingement and transpiration. Tests were conducted for both inline arrangements (with a vent hole opposite each jet orifice) and for staggered arrangements; and the latter always yielded higher average heat transfer. The degradation of performance of inline arrays was most pronounced when the clearance between the jet orifice plate and the target plate was small. Under these conditions, a significant portion of each jet flows directly out through the opposing vent without “scrubbing” the target surface. Arrays with staggered vent holes yield heat transfer rates consistently higher (sometimes by as much as 35 percent) than the same jet array with edge venting. The authors attribute the superior performance of the former geometry to high local heat transfer due to boundary layer suction in the vicinities of the vent holes.
Demonstration of a Unified Approach to the Balancing of Flexible Rotors
Authors: Darlow M. S. , Smalley A. J. , Parkinson A. G.
Published: October 2009

A flexible rotor balancing procedure, which incorporates the advantages and eliminates the disadvantages of the modal and influence coefficient procedures, has been developed and implemented. This new procedure, referred to as the Unified Balancing Approach, has been demonstrated on a supercritical power transmission shaft test rig. The test rig was successfully balanced through four flexural critical speeds with a substantial reduction in effort as compared with the effort required in modal and influence coefficient balancing procedures. A brief discussion of the Unified Balancing Approach and its relationship to the modal and influence coefficient methods is presented. A series of tests which were performed to evaluate the effectiveness of various balancing techniques are described. The results of the Unified Balancing Approach tests are presented and discussed. These results confirm the superiority of this balancing procedure for the supercritical shaft test rig in particular and for multiple-mode balancing in general.
Influence of Acceleration on the Critical Speed of a Jeffcott Rotor
Authors: Hassenpflug H. L. , Flack R. D. , Gunter E. J.
Published: October 2009

The effects of angular acceleration on a Jeffcott rotor have been examined both theoretically and experimentally. The equations of motion were solved via numerical integration. The rotor’s response to unbalance was predicted for a number of cases of acceleration and damping. Both amplitude and phase responses were studied. In addition, techniques were developed for identifying system damping from data taken during accelerated runs. The results of the analysis indicate that for high acceleration rates the amplitude response at the critical speed may be reduced by a factor of four or more. The speed at which the peak response occurs can also be shifted by 20 percent or more. Experimentally, a small lightly damped rotor (ζ = 0.0088) was run for several acceleration rates. The peak responses typically agree within 6 percent of theoretical predictions. Also, a beat frequency was observed both theoretically and experimentally after the rotor had passed through the critical speed.
Some Effects of Using Water as a Test Fluid in Fuel Nozzle Spray Analysis
Authors: Simmons H. C. , Harding C. F.
Published: October 2009

A systematic investigation was made of the differences in atomizing performance between water and kerosene fuel for six simplex fuel nozzles of small flow capacity. A large number of tests was run using two methods of spray analysis, to determine the effect of nozzle liquid pressure drop (ΔPF) on Sauter Mean Diameter (SMD). It was found that there is a clearly-defined relationship dependent on both the relative values of surface tension and also on a Weber Number calculated for conditions in the liquid film at the nozzle discharge orifice. It is concluded that large errors in estimating SMD for modeling programs are possible if results observed with water are assumed to be representative of behavior with kerosene fuel.
Structure and Decay Characteristics of Turbulence in the Near and Far-Wake of a Moderately Loaded Compressor Rotor-Blade
Authors: Ravindranath A. , Lakshminarayana B.
Published: October 2009

The wake of a turbomachinery rotor-blade is turbulent, highly three-dimensional, and nonisotropic with appreciable curvature in the trailing-edge and near-wake regions. The characteristics of the turbulence vary considerably with radius, blade loading, free-stream turbulence, Reynolds number, and the rotor-blade geometry. This paper is concerned with the turbulence properties of a moderately loaded compressor blade, particularly near the blade trailing-edge. The tangential variation of the axial, tangential and radial intensities and stresses across the wake, as well as their decay characteristics were measured with a tri-axial hot-wire probe in the rotor frame of reference. The decay of intensities and stresses were found to be very rapid in the trailing-edge and near-wake regions and slow in the far-wake region. The effects of inlet-guide-vane and the hub-wall boundary layers on the rotor wake turbulence spectra are also discussed. Similarity rules for the three components of intensity are also derived and presented in this paper.
Low-Pressure Plasma-Spray Coatings for Hot-Corrosion Resistance
Authors: Smith R. W. , Schilling W. F. , Fox H. M.
Published: October 2009

The hot corrosion of low-pressure plasma-sprayed coating, GT-29 (Co-29Cr-6Al-1Y) on a γ′-strengthened nickel base superalloy, IN-738, was characterized at both 871 °C and 983 °C in a simulated gas turbine environment. The test results show that at 871 °C the dense, defect-free, low-pressure, plasma-sprayed GT-29 coatings provide good corrosion protection up to 8000 hr. The mechanism of protection was the formation of a dense, adherent Al2O3 scale underneath a mixed oxide scale; scale was maintained by a uniformly dispersed Al rich β(CoAl) reservoir. At 982 °C, the coating corrosion protection exceeded 5000 hours and also utilized a protective Al2O3 scale. Due to the higher test temperature, interdiffusion of O, S, Al, Co, and Cr was higher and internal sulfidation/oxidation of the coating occurred; however, the rates were much lower than uncoated IN-738. Field tests were run (13051 and 19842 hr) to evaluate the low-pressure, plasma-sprayed GT-29 coatings’ corrosion resistance on turbine buckets. Metallographic inspection of the field-tested coatings verified the simulated burner-rig test results and demonstrated that the low-pressure plasma process provides an attractive alternative to other coating processes for producing hot-corrosion resistant coatings.
The Control of Hot Corrosion in Marine Gas Turbines
Authors: Conde´ J. F. G. , McCreath C. G.
Published: October 2009

Ingestion of sea salt and sulphur from fuel can lead to aggressive environments in gas turbines operating in marine conditions resulting in corrosion damage to hot end components, even in well-filtered engines. The nature of the environment in the engine and the factors which influence this are indicated. The chemistry of salt contaminant particles in the engine and combustion environments and temperature levels prevailing in naval engines are described in relation to the normal operating profile and the incidence of corrosion effects in relation to temperature. Results of rig evaluation of materials and coatings are given. Erosion resistance, the combined effects of erosion/corrosion and the mechanisms of hot corrosion are discussed together with the effects of material composition and the use of inhibition as a control procedure. The effects of a salt environment on the creep and stress-rupture behavior of superalloys are covered briefly.
Gas Turbine Engine Disk Retirement-for-Cause: An Application of Fracture Mechanics and NDE
Authors: Annis C. G. , VanWanderham M. C. , Harris J. A. , Sims D. L.
Published: October 2009

Historically, gas turbine engine disks are retired when they accrue an analytically determined lifetime where the first fatigue crack per 1000 disks could be expected. By definition then, 99.9 percent of these components are being retired prematurely. Retirement-for-cause (RFC) is a procedure, based on fracture mechanics, which would allow safe utilization of the full life capacities of each individual disk. Since gas turbine disks are among the most costly of engine components, adopting a RFC philosophy could result in substantial systems life cycle cost savings. These would accrue from reduced replacement costs, conservation of strategic materials such as cobalt, and energy savings.
Nonaxisymmetric Blade Row Interaction in Axial Turbomachines
Authors: Mitchell N. A.
Published: October 2009

A three-dimensional nonaxisymmetric theory is presented to analyze the interaction effects due to wakes between two blade rows in an axial turbomachine. The relative importance of potential and wake interaction with varying row separations and the contribution to the flow of shed radial and shed streamwise vorticity from the first row are examined. Numerical calculations of turbine and compressor stages are presented to illustrate the theory.
Investigations of an Axial Compressor End-Wall Boundary Layer Prediction Method
Authors: De Ruyck J. , Hirsch C.
Published: October 2009

A previously developed axial compressor end-wall boundary layer calculation method which requires the introduction of three-dimensional velocity profile models is summarized. In this method the classical three-dimensional velocity profile models were shown to present inherent limitations at stall limit, with regard to the range of transverse boundary layer thicknesses they are able to represent. A corrected profile model is presented which contains no more limitations without affecting the previous found overall results. Stall limit is predicted by limiting values of shape factor and/or diffusion factor. The new profile model containing also compressibility effects allows the calculation of boundary layers in machines with shrouded blades, by simulating the jump between rotating and non rotating parts of the walls. A corrected version of a force defect correlation is presented which is shown to give better agreement at high incidences. Some results on high and low speed machines are discussed. The model is applied to obtain an end-wall blockage correlation depending on geometry, flow coefficient, AVR, aspect ratio, solidity, diffusion factor, Reynolds number, axial blade spacing, tip clearance and inlet boundary layer thickness. A quantitative estimation of the losses associated with the end-wall boundary layers can be obtained using this analysis and therefore can be a useful tool in the design of an axial compressor stage.
Boundary Layer Studies on Highly Loaded Cascades using Heated Thin Films and a Traversing Probe
Authors: Oldfield M. L. G. , Kiock R. , Holmes A. T. , Graham C. G.
Published: October 2009

In the continuing quest for increased turbine efficiency, the part played by blade profile shape remains crucial. Three turbine vanes with successively increased aerodynamic loading were tested in the High Speed Cascade Wind Tunnel at DFVLR Braunschweig. In addition to wake traverses, measurements of the boundary layer behavior were made. These consisted of (1) use of a constant temperature anemometer to measure the fluctuating heat transfer rate on an array of thin film platinum thermometers deposited on the vanes and (2) a flattened, traversing pitot probe held against the vane surface. Transition measurement by these techniques is described.
The Combined Effect of Axial Velocity Density Ratio and Aspect Ratio on Compressor Cascade Performance
Authors: Stark U. , Hoheisel H.
Published: October 2009

The paper describes theoretical and experimental investigations on the combined effect of axial velocity density ratio (AVDR) and aspect ratio (AR) on compressor cascade performance in incompressible and compressible flow. The results presented demonstrate that it is the aspect ratio that defines the axial velocity distribution through the cascade at a given wall shape and contraction ratio. It is further shown that it is, in turn, the axial velocity distribution that decisively determines the local values of pressure distributions as well as the cascade overall parameters like turning angles and loss coefficients.
A Detailed Transient Model of an OTEC Evaporator
Authors: Chapman M. C. , Heydt G. T.
Published: October 2009

Ocean thermal energy conversion (OTEC) is a process in which a working fluid is alternately evaporated and condensed in heat exchangers fed by shallow and deep ocean water, respectively. The expansion of the working fluid permits extraction of useful work in a low pressure turbine. Models of the OTEC cycle often consider the evaporator and condenser units simply as having sufficient capacity (steady-state model) or with simple linear low-order models. In this paper, the evaporator is modeled in detail including the nonlinearities of two phase boiling, enthalpy-temperature relationship, and mixed phase fluid flow and heat exchange. The evaporator considered is of the cross-flow type using propane as the working fluid, however, the technique is valid for any channel configuration and working fluid provided that vertical flow exists in the working fluid. The model is used for transient studies in a wide range of working states.
An Assessment of Deposition in PFBC Power Plant Turbines
Authors: Wenglarz R. A.
Published: October 2009

Using turbine deposition models and data from PFBC (pressurized fluidized bed combustion) pilot plant/cascade experiments, deposit buildup rates and turbine maintenance intervals to remove deposits are projected for a PFBC power plant system. The power plant consists of a 10 atmosphere PFB boiler with a matching 10:1 pressure ratio turbine and a gas cleanup system to remove particulates from combustor product gases before entering the turbine. The effects on turbine deposition of three alternative particle cleanup systems are evaluated. Turbine deposit removal intervals to prevent excessive power drops due to deposition are found for the alternative gas cleanup systems.
Water Tempered Cleaning Medium for Sootblowers
Authors: Shenker J. D. , White A. R. , Ziels B. D.
Published: October 2009

Injection of relatively small amounts of water into the air or steam blowing medium of long retractable sootblowers can result in many benefits in initial cost, operational cost, and functional operation of sootblower systems. This paper explores the possibilities that this method of sootblowing presents, and includes experimental data on the operation of test systems. Thermal shock tests have been performed on superheater and waterwall tubes, and boiler tube samples have been analyzed after long term operation with combined air and water mist sootblowing.
Separation Efficiency of a Cyclone Separator with a Turbulence-Suppressing Rotating-Insert
Authors: Razgaitis R. , Guenther D. A.
Published: October 2009

This paper presents further experimental investigations with a cyclone separator. Specifically, an altered wall boundary condition, that of an internal rotating insert, as a technique which not only enhances the separating field, but, more importantly, diminishes the turbulence level within the cyclone is discussed. The data presented clearly illustrate that the proposed geometry is both turbulence suppressing and separation enhancing. Additional data presented for the efficiency with the insert show more than 10 percentage point improvement even for modest rotation rates. This improvement in the cyclone separator efficiency is significant and increases the potential of the cyclone as an air pollution control device.
NOx Removal Process by Injection of NH3 and H2O2 in Gas Turbine Exhaust Gas
Authors: Hishinuma Y. , Akimoto H. , Azuhata S. , Nakajima F. , Matsuda S. , Uchiyama Y. , Oshima R. , Kato M.
Published: October 2009

For the removal of NOx in a gas turbine exhaust gas, the reduction of NOx with NH3 and H2O2 was studied. It was found that the addition of H2O2 very effectively lowered the reduction temperature of NO with NH3 and that more than 90 percent NOx reduction could be attained at 550°C in the absence of O2. However, the NOx reduction rate decreased with increases in the concentration of O2 and NOx reduction was about 40 to 60 percent under gas turbine exhaust gas condition (15 percent O2). In order to attain a high rate of reduction of NOx, a combined reduction process, which consisted of the homogeneous gas phase and the catalytic heterogeneous reactions, was also developed. The efficiency of the new process was proved in a pilot plant using half a size model of a 25-MW gas turbine combustor.
Once-Through Cooling Potential of the Middle and Lower Mississippi River During Low Flow Conditions
Authors: Giaquinta A. R.
Published: October 2009

The once-through cooling potential of the Middle and Lower Mississippi River has been computed for the seven-day, ten-year low flow by the steady-state Iowa Thermal Regime Model. Longitudinal temperature distributions are shown with existing power plants and future power plants proposed through 1995. Permissible future plant additions based on current thermal standards also are determined. It is shown that even if thermal standards were based on low flow conditions, no existing or proposed future power plants will violate present thermal standards, and the total permissible future fossil-fueled power plant capacity along the study reach ranges from about 70,000 to 90,000 MW depending on the temperature base used. It also is shown that the total consumptive water use for existing and proposed future plants should cause no problems even during periods of low flow.
EBR-II Metallic Driver Fuel—A Live Option
Authors: Seidel B. R. , Walters L. C.
Published: October 2009

The exceptional performance of metallic driver fuel has been demonstrated by the irradiation of a large number of Experimental Breeder Reactor II (EBR-II) driver-fuel elements of uranium-5 wt percent fissium clad in austenitic stainless steel. High burnup with high reliability has been achieved by a close coupling of element design and materials selection. The irradiation performance has been improved by decreasing the fuel smear density, increasing the plenum volume, increasing the cladding thickness, and selecting a higher-strength, lower-swelling cladding alloy which exhibits less fuel-cladding chemical interaction. Quantification of reliability has allowed full utilization of the element lifetime. Lifetimes much greater than 10 at. percent could be achieved by a design change of the restrainer, which currently limits life. Use of U-Pu-Zr fuel alloy with current cladding material would provide higher-temperature capability, as demonstrated by test elements. Metallic fuel systems with their inherently superior breeding and irradiation performance are capable and attractive next-generation power systems.
Creep Relaxation of Fuel Pin Bending and Ovalling Stresses
Authors: Chan D. P. , Jackson R. J.
Published: October 2009

Analytical methods for calculating fuel pin cladding bending and ovalling stresses due to pin bundle-duct mechanical interaction taking into account nonlinear creep are presented. Calculated results are in close agreement with finite element results by MARC-CDC program. The methods are used to investigate the effect of creep on the FTR fuel cladding bending and ovalling stresses. It is concluded that the cladding of 316 SS 20 percent CW and reference design has high creep rates in the FTR core region to keep the bending and ovalling stresses to acceptable levels.
Effects of Coolant Air Inlet Conditions on Turbulent Flow Between a Turbine Disk and its Casing
Authors: Uzkan T.
Published: October 2009

An integral method to predict the performance of the incompressible, turbulent flow between a rotating disk and a parallel stationary wall, when there is radial outflow of ventilation air, is presented. Using this method, the effects of the inlet conditions of the ventilation air on the core rotation, on the radial velocity profile development, on the radial inflow rates, on the separation streamlines between outflow and inflow regions and on the disk torque coefficient are calculated and presented. The method is general enough to calculate other effects. The important conclusions are: (a) that inlet radial velocity profile should be skewed toward the stationary wall, to reduce radial inflow, and (b) that disk friction can be decreased by increasing the rotation of the ventilation air.
Development of a Large-Scale Wind Tunnel for the Simulation of Turbomachinery Airfoil Boundary Layers
Authors: Blair M. F. , Bailey D. A. , Schlinker R. H.
Published: October 2009

The procedures employed for the design of a closed-circuit, boundary layer wind tunnel are described. The tunnel was designed for the generation of large-scale, two-dimensional boundary layers on a heated flat surface with Reynolds numbers, pressure gradients, and free-stream turbulence levels typical of turbomachinery airfoils. The results of a series of detailed tests to evaluate the tunnel performance are also described. Testing was conducted for zero pressure gradient flow with natural boundary layer transition. Heat transfer data and boundary layer profiles are presented for a flow with 0.25 percent free-stream turbulence. The flow in the tunnel test-section was shown to be highly uniform and two-dimensional. Test boundary layer profile and convective heat transfer data were self-consistent and in excellent agreement with classic correlations. Test-section free-stream total pressure, multi-component turbulence intensity, longitudinal integral scale, and spectral distributions are presented for grid-generated turbulence levels ranging from 1 to 7 percent. The test-section free-stream turbulence was shown to be both homogeneous and nearly isotropic. Anticipated applications of the facility include studies of the heat transfer and aerodynamics for conditions typical of those existing on gas turbine airfoils.
A Study on Centrifugal Impeller and Diffuser Flow
Authors: Krain H.
Published: October 2009

The flow field development within a centrifugal compressor stage was analyzed using an advanced laser velocimetry [4]. A splitter blade impeller coupled with a vaned and vaneless diffuser has been found to have similar internal flow patterns for both the vaneless and vaned diffuser design. Different velocity profiles have been analyzed for adjacent channels behind the splitter blade leading edge. A considerable wake flow was observed near the impeller exit. Detailed optical measurements within the vaned diffuser entrance region gave evidence of a periodically fluctuating, highly distorted diffuser inlet flow. Unsteady flow angle deviations of 13 degrees have been discovered within the diffuser throat. Maximum flow angle differences up to 27 degrees occurred from hub to shroud.
The CIVIC—A Concept in Vortex Induced Combustion, Part II
Authors: Shekleton J. R.
Published: October 2009

Turbomach, A Division of Solar Turbines International, An Operating Group of International Harvester, manufactures the small 10kW Gemini gas turbine. The very small size of the combustor precluded the use of conventional gas turbine combustor design techniques. A novel solution was arrived at based primarily on an amalgam of design practices used in furnaces and reciprocating engines. Use was made of the centrifugal force effects of swirl flow (Rayleigh Instability Criteria) both as a method of fuel evaporation and as a method of control of the rate of flame propagation. Substantial advantage can be obtained by this design technique provided that a fine and accurately located fuel spray is achieved. Various applications of this method of combustor design are outlined with emphasis on aerodynamics and fuel atomization and volatility rather than reaction rate criteria as the dominant influences.
Efficiency Prediction for Axial-Flow Turbines Operating with Nonconventional Fluids
Authors: Macchi E. , Perdichizzi A.
Published: October 2009

The need for a simple and reliable method for predicting the efficiency of a turbine stage without carrying out a detailed aerodynamic design is enhanced. The results of an optimization study carried on a large number of turbine stages are presented. The turbine stage efficiency is found to be a function of three main parameters: the expansion ratio, defined as the specific volume variation across the turbine in an isentropic process; the dimensional parameter V˙out/Δhis1/4, which accounts for actual turbine dimensions, and the specific speed. The presented method is believed to be useful mainly for nonconventional turbine stages, the efficiency of which cannot be anticipated on previous machines experience.
The Development of a Substitute Bird Model
Authors: Wilbeck James S. , Rand James L.
Published: October 2009

A comprehensive program was conducted to develop a model synthetic bird for use in engine blade impact testing. A hydrodynamic theory of the impact event was used to aid in determining the bird properties which had to be duplicated in the model. Of the two candidate models studied extensively, it was determined that a projectile fabricated from commercial gelatin impregnated with phenolic mircoballoons most nearly duplicated the impact loading history of real birds.
Superhybrid Composite Blade Impact Studies
Authors: Chamis C. C. , Lark R. F. , Sinclair J. H.
Published: October 2009

An investigation was conducted to determine the feasibility of superhybrid composite blades for meeting the mechanical design and impact resistance requirements of large fan blades for aircraft turbine engine applications. Two design concepts were evaluated: (1) leading edge spar (TiCom) and (2) center spar (TiCore), both with superhybrid composite shells. The investigation was both analytical and experimental. The results obtained show promise that superhybrid composites can be used to make light-weight, high-quality, large fan blades with good structural integrity. The blades tested successfully demonstrated their ability to meet steady-state operating conditions, overspeed, and small bird impact requirements.
Pattern Factor Improvement in the F-100 Primary Combustion System
Authors: Cox G. B. , Tiller A. R. , LeTourneau J. J. , Ogg J. S.
Published: October 2009

Causes of exit temperature nonuniformity in the primary combustion system of the F100 augmented turbofan engine have been identified and investigated in a comprehensive test program. This test program involved a combination of instrumented full engine, annular combustor rig, and subscale component rig tests. Modifications to the fuel nozzle, which provide significant improvements in combustor exit temperature uniformity, are now being incorporated into the production version of the engine. Modifications to the combustor configuration are being incorporated into growth versions of the engine.
An Exploratory Study of Soot Sample Integrity and Probe Perturbation in a Swirl-Stabilized Combustor
Authors: Hack R. L. , Samuelsen G. S. , Poon C. C. , Bachalo W. D.
Published: October 2009

In-flame measurements of soot particulate using conventional extractive and nonintrusive optical probes are compared for a swirl-stabilized combustor. Except for large (∼5μm) particulate present in the extracted samples, the soot particle size compares favorably with optically measured values, and the soot particle morphology reflects that formed in gas turbine combustors. Two, nonflame sources for the large particulate are suggested by the optical data: particles formed or elongated during transport subsequent to extraction, and particles attrited from upstream carbon deposits on a solid surface. The extractive probe produces a change in the local particle number density which varies from little change to a 70-fold suppression in reacting flow and a 200-fold increase in cold seeded flow depending on the location within the combustor of the optical sampling volume, the location of the extractive probe relative to the optical sampling volume, and the combustor operating conditions.
The Vibration Isolating Properties of Uncentralized Squeeze-Film Damper Bearings Supporting a Flexible Rotor
Authors: Cookson R. A. , Kossa S. S.
Published: October 2009

The ability of an uncentralized squeeze-film damper bearing to inhibit the effects of vibration in a flexible rotor-bearing system, has been assessed in terms of non-dimensional system parameters. This analytical approach has shown that a correctly designed squeeze-film damper bearing is a very effective means of reducing both the amplitude of motion of the rotor and the force transmitted to the bearing support structure. However, the analysis has also indicated that a poorly designed squeeze-film damper bearing can produce amplitudes and forces greater than those which would arise if the bearing support remained rigid. An experimental programme has supported the validity of the above analytical technique by showing that the measured motion orbits of the journal and disk centers as the rotor passes through the critical speed, are very similar to those predicted theoretically. Also, the response curves for specific groups of system parameters show very similar trends in practice, to those which result from the analytical approach. Some indication of the ability of a squeeze-film damper bearing to reduce the effect of much greater unbalance than normal is also reported.
Performance and Air Pollutant Emissions of an Experimental Water/Residual Oil Emulsion Burner in a Commercial Boiler
Authors: Beard J. Taylor , Hall R. E.
Published: October 2009

The performance and air pollution emissions of an experimental water/oil emulsion burner are presented. The burner was fired with two residual oils at selected emulsion water fractions. In addition, various stoichiometric ratios and two load conditions were used to determine how operational parameters influenced the results. Particulate mass emissions and particle size distributions are presented. Examples show that, even though particulate mass may decrease, the total amount of fine particulate emissions may increase by using water/oil emulsions. The performance of the boiler is reduced when large fractions of water are used in the emulsion due to latent heat losses. This performance loss may be only slightly recovered by operating at a reduced stoichiometric ratio corresponding to a smoke limit. NOx and CO emissions data are also presented for various test conditions, but neither were affected significantly by use of water/oil emulsions.
Compound Hybrid Geothermal-Fossil Power Plants: Thermodynamic Analyses and Site-Specific Applications
Authors: DiPippo Ronald , DiPippo Eileen A. , Kestin Joseph , Khalifa H. E.
Published: October 2009

In this paper, we extend the analysis of hybrid fossil-geothermal power plants to compound systems which combine the features of the two previously analyzed hybrid plants, the geothermal preheat and the fossil superheat systems. Compound systems of the one- and two-stage type are considered. A complete summary of formulae to assess the performance of the plants is included for completeness. From the viewpoint of thermodynamics, compound hybrid plants are superior to individual all-geothermal and all-fossil plants, and have certain advantages over basic geothermal-preheat and fossil-superheat hybrid plants. The flexibility of compound hybrid systems is illustrated by showing how such plants might be used at several geothermal sites in the western United States.