bluuebunny/crossref_metadata_2025 huggingface dataset:
Explosions in Gas Turbine Lube Oil Reservoir Result in Installation of Dry Gas Seal System
Authors: Ferrill Lawrence R. , Ronsky N. Daryl , Harris Tim A.
Published: March 2015

Mechanical dry gas seal systems were retrofitted into two centrifugal natural gas compressors which are located offshore in the Norwegian sector of the North Sea.

The project was initiated after a fire and several gas explosions had occurred in the gas turbine lube oil reservoir. These incidents were a result of gas leaking from the compressor’s seal oil system and then migrating via the lube oil lines into the reservoir.

The dry gas seal systems have eliminated gas leakage into the turbine lube oil reservoir, eliminating the hazard of gas explosion. The retrofits have also provided additional benefits including reductions in space and weight, reduced power usage, reduced maintenance, and elimination of seal oil consumption which had been up to 440 gal./day (2000 liters/day).
Revaluation of Researches on the Free Rotating Vaneless Diffusor
Authors: Ribaud Yves , Fradin Christian
Published: March 2015

After eighteen years, an attempt is now being made to revaluate the studies performed by RODGERS-MNEW and RIBAUD-FRADIN on the rotating vaneless diffuser. These two studies are complementary. The first deals with a high speed rotating vaneless diffusor fed by a swirl generating nozzle and giving high Mach numbers. The second concerns a real compressor comprising a low speed rotor followed by a rotating vaneless diffuser. The free rotation of the vaneless diffusor reduces the friction losses by about 70%. The high speed, mechanical design of the rotating vaneless diffusor is a success. The structure of the flow at the rotor outlet seems to have an important effect on the efficiency of the rotating vaneless diffusor. New types of rotating vaneless diffusors should be experimented and new comparative experiments attempted. The application of the rotating vaneless diffusor concept to low specific speeds compressors is also proposed.
Design of a 500 KW Turboexpander
Authors: Simms James S.
Published: March 2015

The design and development of a new generation of an economical 500 kW turboexpander/generator is presented. This paper briefly discusses current pressure reduction power recovery applications and describes in detail major steps in the development of this new 500 kW turboexpander/generator.
Experience From Expansion of On-Board Maintenance for Marine Gas Turbines
Authors: Thompson Bruce D. , Badgley Robert H. , Hartranft John J.
Published: March 2015

Extensive fleet operational experience now exists for the LM2500 marine gas turbine engine. Based upon this experience, this engine is susceptible to a number of wear-out modes caused by excessive operational stresses. It has been found that the principal factors responsible are engine power profile, aero-dynamic disturbances and self-generated vibration. The failures involve both external and internal engine components. External components which fail can readily be replaced or repaired. Rapid replacement or repair has had a positive impact on engine availability. For failed internal engine components, however, depot repair was originally planned. High repair costs and operational impact from depletion of rotable pool spares accelerated the need for in-place repairs. A number of such repairs have been developed and validated, resulting in substantial cost savings and increased engine availability. Special repairs have also been developed to reduce the operational stresses themselves.
Industrial Centrifugal Compressors: The Influence of the Impeller Diffusion on the Stage Performance
Authors: Lüdtke Klaus
Published: March 2015

The meridional convergence of an unshrouded inducer type impeller with 30° backward leaning blades was modified by reducing the exit width by 22%. The vaneless diffuser was changed accordingly, whereas the impeller eye opening was kept constant. Performance curves show that the lower diffusion leads to enhanced surge limit, lower head at increased efficiency. Choke point remains unchanged and the extension of the rotating stall range is reduced. The range of tip speed Machnumbers tested was 0.6 to 1.17.

Test value analysis, broken down into components, is based on the two-zone model impeller exit evaluation procedure detecting clearly the causes of performance map changes.
Braze Repair of MA754 Aero Gas Turbine Engine Nozzles
Authors: Elder J. E. , Thamburaj R. , Patnaik P. C.
Published: March 2015

MA754, an oxide-dispersion strengthened nickel-base superalloy, is the vane material being used in the High Pressure Turbine (HPT) Nozzle of the F404-400 turbofan engine. Thermal fatigue cracks are known to develop in the nozzle vanes during service and the component replacement costs can, in general, be very high. Attempts to demonstrate the feasiblity for braze repair of MA754 have thus far yielded little success.

An experimental program aimed at developing a braze repair procedure for healing cracks in MA754 HPT nozzles is described. Thirteen different braze compositions, using two different brazing times and gap widths, are evaluated. Experimental results are described detailing the microstructure, degree of oxide agglomeration and porosity in the region of the brazed joints. The feasibility of applying a braze repair procedure to the nozzle component is discussed.
Experimental Investigations of Pressure Drop in the Combustion Chamber of Gas Turbine
Authors: Dzida Marek , Kosowski Krzysztof
Published: March 2015

In bibliography we can find many methods of determining pressure drop in the combustion chambers of gas turbines, but there is only very few data of experimental results.

This article presents the experimental investigations of pressure drop in the combustion chamber over a wide range of part-load performances (from minimal power up to take-off power). Our research was carried out on an aircraft gas turbine of small output. The experimental results have proved that relative pressure drop changes with respect to fuel flow over the whole range of operating conditions. The results were then compared with theoretical methods.
Development of Silicon Nitride Engine Components for Advanced Gas Turbine Applications
Authors: Busovne B. J. , Pollinger J. P.
Published: March 2015

The development and fabrication of reliable high temperature-high strength silicon nitride components by Garrett Ceramic Components Division for the Advanced Turbine Technology Applications Project (ATTAP) is discussed. Garrett Ceramic Components’ advanced turbine component process development philosophy and practices will be presented, including implementation of statistically designed experiments, in-process controls, extensive NDE, and mechanical properties characterization. The current status of material, process, and part properties of specific components being developed by Garrett Ceramic Components are compared with the properties required for their implementation and the successful operation of advanced gas turbines with ceramic components at 1370°C.
Influence of Fuel Chemical Properties on Soot Emissions From Gas Turbine Combustors
Authors: Chin J. S. , Lefebvre A. H.
Published: March 2015

The influence of fuel composition on soot emissions from continuous flow combustors is examined. A study of the combustion characteristics of a wide range of present and potential aviation fuels suggests that smoke point provides a better indication of sooting tendency than does hydrogen content. It is concluded from this study that the best empirical relationship between fuel chemical composition and soot emissions is one which combines two fuel composition parameters — smoke point and naphthalene content — into a single parameter which is shown to correlate successfully soot emissions data acquired from several different fuels burning in a variety of gas turbine and model combustors.
Studies on Influence of Liquid Film Wave on Atomization and Wave Measurement
Authors: Xiaohua Gan , Qishou Zhao
Published: March 2015

In the present paper, two-phase interaction inside pre filming airblast atomizer and its influence on atomization are studied. Liquid film wave inside the atomizer is measured with techniques called resistance method and optics method, which are also developed herein. By the means of laser pulse micrography, high speed photography and laser particle sizer, disintegration and fluctuation of liquid wave are picturized and spray size SMD and size distribution parameter N are measured. Experiments show that liquid wave inside atomizer has important influence on spray characteristics.
Experimental Evaluation of a Liquid-Fueled, Lean-Premixed Gas Turbine Combustor
Authors: Smith K. O. , Cowell L. H.
Published: March 2015

Rig testing of a lean-premixed, liquid-fueled corabustor was conducted to establish the feasibility of achieving ultra-low NOx emissions at typical gas turbine operating conditions. Two different filming fuel injector concepts were evaluated.

The majority of combustor testing was conducted using No. 2 diesel. The test results showed 12 and 20 ppm NOx at 6 and 9 atm, respectively. Corresponding CO levels were 50 ppm in both cases.
Performance Testing of a Low Emissions, Natural-Gas Fired, Small Gas Turbine Combustor
Authors: Smith K. O. , Wade G. W. , Samii M. H. , Mak H. K.
Published: March 2015

The initial development of a lean-premixed, natural gas-fired combustor for a 200 kw gas turbine is described. The development effort included both rig testing and on-engine testing of the combustor. The combustor demonstrated an ultra-low NOx emissions capability in both test environments.
Resonant Stress Determination of a Turbine Blade With Modal Damping as a Function of Rotor Speed and Vibrational Amplitude
Authors: Rao J. S. , Vyas N. S.
Published: March 2015

An iterative procedure is proposed to determine the resonant stresses of turbomachinery blading using the damping coefficient as a function of not only the rotating speed but also of vibrational amplitude. The results obtained are compared with previous analytical results obtained by ‘average’ damping values and experimental results. Significant improvement has been shown with the proposed procedure.
Heat Transfer in Rotating Passages With Smooth Walls and Radial Outward Flow
Authors: Wagner J. H. , Johnson B. V. , Hajek T. J.
Published: March 2015

Experiments were conducted to determine the effects of rotation on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a smooth wall, large scale heat transfer model. The objective was to obtain the heat transfer data base required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. An analysis of the governing equations showed that four parameters influence the heat transfer in rotating passages (coolant density ratio, Rossby number, Reynolds number and radius ratio). These four parameters were varied over ranges which exceed the ranges of current open literature results, but which are typical of current and advanced gas turbine engine operating conditions. Rotation affected the heat transfer coefficients differently for different locations in the coolant passage. For example, heat transfer at some locations increased with rotation, but decreased and then increased again at other locations. Heat transfer coefficients varied by as much as a factor of 5 between the leading and trailing surfaces for the same test condition and streamwise location. Comparisons with previous results are presented.
Surface Injection Effect on Mass Transfer From a Cylinder in Crossflow: A Simulation of Film Cooling in the Leading Edge Region of a Turbine Blade
Authors: Karni J. , Goldstein R. J.
Published: March 2015

A naphthalene sublimation technique is used to study the effect of surface injection on the mass (heat) transfer from a circular cylinder in crossflow. Using a heat/mass transfer analogy the results can be used to predict film cooling effects in the leading edge region of a turbine blade. Air injection through one row of circular holes is employed in the stagnation region of the cylinder. Streamwise and spanwise injection inclinations are studied separately, and the effects of blowing rate and injection location relative to the cylinder front stagnation line are investigated. Streamwise injection produces significant mass transfer increases downstream of the injection holes, but a relatively small increase is observed between holes, normal to the injection direction. The mass transfer distribution, measured with spanwise injection through holes located near the cylinder front stagnation line, is extremely sensitive to small changes in the injection hole location relative to stagnation. When the centers of the spanwise injection holes are located 5° or more from the stagnation line, the holes lay entirely on one side of the stagnation line and the injection affects the mass transfer only on that side of the cylinder, approaching the pattern observed with streamwise injection.
The Trailing Edge Loss of Transonic Turbine Blades
Authors: Denton J. D. , Xu L.
Published: March 2015

Trailing edge loss is one of the main sources of loss for transonic turbine blades, contributing typically 1/3 of their total loss. Transonic trailing edge flow is extremely complex, the basic flow pattern is understood but methods of predicting the loss are currently based on empirical correlations for the base pressure. These correlations are of limited accuracy. Recent findings that the base pressure and loss can be reasonably well predicted by inviscid Euler calculations are justified and explained in this paper. For unstaggered choked blading it is shown that there is is a unique relationship between the back pressure and the base pressure and any calculation that conserves mass, energy and momentum should predict this relationship and the associated loss exactly. For realistic staggered blading which operates choked but with subsonic axial velocity there is also a unique relationship between the back pressure and the base pressure (and hence loss) but the relationship cannot be quantified without knowing a further relationship between the base pressure and the average suction surface pressure downstream of the throat. Any calculation that conserves mass, energy and momentum and also predicts this average suction surface pressure correctly will again predict the base pressure and loss. Two dimensional Euler solutions do not predict the suction surface pressure exactly because of shock smearing but nevertheless seem to give reasonably accurate results.
Parametric Trends in the Flutter of Advanced Turboprops
Authors: Crawley Edward F. , Ducharme Eric H.
Published: March 2015

The parametric trends in the aeroelastic behavior of an advanced turboprop were experimentally investigated using a sub-velocity scaled testing procedure. A two ft. diameter sub-velocity scaled model was constructed and its flutter behavior was favorably correlated to that of a full-velocity scaled UnDucted Fan™ model for which a flutter point had been documented. With the validity of the sub-velocity scaled procedure established, the inherent versatility was exploited through the construction and flutter testing of models which allowed for the parametric variation of sweep, mass distribution, and solidity. The correlation between an analytic model developed and the experiment is favorable for variation in mass distribution and sweep. As is typical of moderate mass ratio wings and blades, the flutter was found to be of a coalescence type, the onset of which is determined by a critical relative velocity with a slight dependence on loading and cascade effects.
An Experimental Assessment of the Influence of Downstream Conditions on the Performance of a Transonic Turbine Nozzle of High Turning
Authors: Schaub U. W. , Williamson R. G. , Huot J.-P. , Moustapha S. H.
Published: March 2015

The present work was conducted to extend information derived in a previous study where it was found that the performance of a transonic turbine nozzle of high turning angle was significantly affected by the design and operation of the downstream rotor and the detailed characteristics of the nozzle flow field. Measurements obtained in an operating stage environment were compared with information from simplified test arrangements. In particular, it was possible to make direct comparisons of static pressure distributions at the vane root as affected by downstream conditions. Detailed exit flow surveys indicated areas susceptible to the influence of rotor presence. Probe interaction effects were also assessed in a special series of tests conducted over a representative range of Mach numbers. Finally, experiments were performed with a perforated plate simulating rotor presence, in an attempt to determine the limitations of such simplified test arrangements in the generation of pertinent data. The results shed further light on a complex subject, and have been aimed at practical validation of test arrangements and techniques.
Transient Liquid Crystal Measurement of Local Heat Transfer on a Rotating Disk With Jet Impingement
Authors: Metzger D. E. , Bunker R. S. , Bosch G.
Published: March 2015

All experimental technique has been developed for measurement of local convection heat transfer characteristics on rotating surfaces, utilizing thin liquid crystal surface coatings in a thermal transient test procedure. The encapsulated liquid crystal coatings used are sprayed directly on the test surface and their response is observed and processed during the transient with automated computer vision and data acquisition systems. Heat transfer coefficients are calculated from the thermal transient response of the test surface, as determined from the color indication from the thin coating. A significant advantage of the method, especially for convection in disk/shroud cavities that may contain recirculating fluid regions, is that appropriate thermal boundary conditions are naturally imposed on all of the boundary surfaces. The method is also relatively fast and inexpensive, and allows the geometry of the disk and stator surfaces to be changed easily, without the expenses of mounting discrete heat flux and temperature sensors and equipment to transfer information to a stationary frame of reference. Application of the experimental technique is demonstrated with detailed radially local surface Nusselt number distributions acquired for cases involving jet impingement onto a plane smooth disk, rotating in close proximity to a parallel plane stator disk. A single circular jet, with nozzle exit flush mounted in the stator, is oriented normal to the disk surface at various radii and flowrates. Local Nusselt numbers are presented nondimensionally as functions of both disk and flow Reynolds numbers. The results indicate that the local radial heat transfer distribution can be controlled by varying the impingement radius, but maximum radially averaged heat transfer is obtained with impingement at the disk center.
The Influence of Dilution Hole Geometry on Jet Mixing
Authors: Carrotte J. F. , Stevens S. J.
Published: March 2015

Measurements have been made on a fully annular test facility, downstream of a row of heated dilution jets injected normally into a confined cross-flow at a momentum flux ratio of 4. The investigation concentrated on the consistency of mixing between the jets, as indicated by the regularity of the temperature pattern around the cross-flow annulus. When the heated air was supplied from a representative feed annulus, the exit velocity profile across each plunged hole was significantly altered and caused a distortion of the temperature distribution in the ensuing jet. The degree of distortion varies in a random manner, so that each jet has its own mixing characteristics thereby producing irregularity of the temperature pattern around the annulus. With the same approach and operating conditions some of the plunged dilution holes were modified, and tests on this modified sector indicated a significant improvement in the circumferential regularity of the temperature pattern. Further tests showed these modifications to the dilution holes had a negligible effect on the values of the discharge coefficients.
Blade Vibration With Nonlinear Tip Constraint: Model Development
Authors: Wagner L. F. , Griffin J. H.
Published: March 2015

Turbine blades having integrally-machined tip shrouds, with associated gaps between adjacent shrouds, often exhibit unusual vibratory responses with significant differences between the amplitudes and frequencies of individual blades on the same stage. These differences result from unavoidable variations in the shroud gaps causing, for large enough excitation, nonlinear constraint at the blade tips which varies from blade to blade. This study shows that the blade stresses cannot be adequately represented by the type of single degree-of-freedom models that are often used for dynamic impact studies, but require the participation of higher frequency beam-type modes. The extension of the resulting beam model to multi-degree-of-freedom systems will allow the study of the “gap mistuning” phenomenon for practical bladed disks.
Inlet Distortion Generated Periodic Aerodynamic Rotor Response
Authors: Manwaring Steven R. , Fleeter Sanford
Published: March 2015

Fundamental inlet distortion generated rotor blade row unsteady aerodynamics, including the effects of both the detailed aerodynamic forcing function for the first time and steady loading are experimentally investigated in an extensively instrumented axial flow research compressor. A two-per-rev forcing function with three gust amplitude ratios is generated. On the rotor blade pressure surface, the unsteady pressure nondimensionalization compresses the magnitude data with mean flow incidence angle. This is not the case on the higher camber suction surface. Also, these pressure surface unsteady data are primarily affected by the steady loading level whereas the suction surface unsteady data are a function of the steady loading level and distribution as well as the gust amplitude ratio. In addition, a design inlet distortion blade surface unsteady pressure correlation is considered.
Turbine Blade Tip-Shroud Wear Characteristics Monitored by Surface Layer Activation
Authors: Kuo Peter S. , Blatchley Charles C.
Published: March 2015

An on-line investigation into turbine shroud gap control and optimization was recently conducted at Textron Lycoming Division. The Surface Layer Activation (SLA) technique was used (for the first time in turbine blades) to determine shroud wear rates during operation and to detect related blade motions in the shrouded assembly. Surface losses from shroud tip faces, which were activated by a particle accelerator, were detected by gamma spectrometry. Engine testing deliberately used “tight” and “loose” shroud assemblies to evaluate the effect of total gap on wear. Tests were run at speed ranges known to include blade-disc system modes, with over 30 hours of running time for each shroud configuration. On-line wear monitoring and total accumulated wear for each blade both indicated a faster wear rate in the “loose” shroud wheel than in the “tight” assembly, with most wear occurring in the high engine speed range. The experimental measurements provide a further understanding of design parameters for the optimization of turbine blade tip shrouds.
Determining Redundancy Requirements for a Fault Tolerant Control System
Authors: Lockner Paul A. , Hancock Paul D.
Published: March 2015

The key element in all fault tolerant controls is redundancy [1], but it can be difficult to determine how much redundancy is necessary to achieve the desired level of control system availability. Through examples, this paper examines reliability effects of various elements used in real turbo control systems, including the input sensors, control channels and output stages. The paper then shows that with module reliability and repair rate information, we can determine the redundancy necessary to achieve the desired level of control system availability.
Ceramics-to-Metal Joining Technology for Gas Turbine Rotors
Authors: Sakamoto T. , Horinouchi H. , Maeda T.
Published: March 2015

The joining technology of a ceramic wheel and a metal shaft for a ceramic turbocharger rotor was reviewed. The braze-bonded cup-joint method which has established for the ceramic turbocharger rotors was revealed to be effective for the gas turbine applications, in which the temperature of a joining reached to 700°C at turbine inlet temperature of 1371°C.

Slip resistance and bend strength of ceramic shaft was completed by selecting the metal sleeve and braze materials and design with FEM.

The reliability and the durability of the joining was confirmed by cyclic exposure test between 150°C and 700°C for 1000 cycles and 200 hour oxidation test.
Influence of the Continuous and Dispersed Phases on the Symmetry of a Gas Turbine Air-Blast Atomizer
Authors: McDonell V. G. , Samuelsen G. S.
Published: March 2015

Current trends in liquid-fueled practical combustion systems are leaving less tolerance for fuel injection deficiencies such as poor spray field symmetry. The present paper evaluates the symmetry of the flowfield produced by a practical air-blast atomizer. Specifically, the influence of both the continuous phase and dispersed phase on the sprayfield symmetry is assessed. In the present case, asymmetry in volume flux is associated principally with disparities in the injection of the dispersed phase, which is manifested by a maldistribution of larger drops. Asymmetries observed in the continuous phase without the dispersed phase are reduced in magnitude by the presence of the dispersed phase, but still contribute to asymmetry in radial spread of the dispersed phase.
Propulsion Systems for Supersonic V/STOL Aircraft
Authors: Lewis W. J.
Published: March 2015

A number of different powerplant systems have been and are being considered for supersonic V/STOL aircraft. Some of the main features of these different powerplants are described. As a result of studying the results of operation of successful and unsuccessful V/STOL aircraft in the powered lift condition, a number of real requirements for practical and flexible operation can be identified. These requirements may have a profound impact on the design and configuration of the powered lift powerplant. Some of these are discussed and conclusions reached.
Comments on Compressor Efficiency Scaling With Reynolds Number and Relative Roughness
Authors: Wright Terry
Published: March 2015

The background and literature on scaling of model test results to predict the performance of large scale turbomachines are presented and discussed in the context of both industry restrictions and recent improvements in analytical rigor and accuracy of scaling algorithms. The variety and disparity of methods developed before about 1970 is illustrated and plausible explanation is offered to account for the broad differences. The more recent literature is considered and the older exponential algorithms for scaling are reconciled with the current methods based on friction factor correlations. A simpler form is developed in terms of either exponential or friction factor formulations which includes the influence of Reynolds Number, relative roughness and fixed, friction-independent losses. This method is compared to the recently developed algorithms and to experimental data taken from the literature.
Composite Materials for Future Aeroengines
Authors: Kirk G. E.
Published: March 2015

Aeroengines will only satisfy the future market requirement if advances are made in material and manufacturing technology. Current aeroengine materials are reaching the limits of their development but composite materials have the potential to meet the increased requirements. The use of resin composites has increased and with further improvements could be used more extensively. Metal and ceramics composites are being considered where higher temperature capability is required. However there are a number of problems which are being addressed so that these newer composites can be so used to their full potential with confidence.
Near Net Shape Manufacturing of Composite Engine Components by 3-D Fiber Architecture
Authors: Pastore Christopher M. , Ko Frank K.
Published: March 2015

Responding to the need for a higher level of through thickness strength, higher damage tolerance, and near net shape manufacturing in structural engine components, there is a worldwide revival in the interest in 3-D fabric preforms. Recent advances in computer aided design, analysis and manufacturing of fully integrated 2-D and 3-D woven, knitted, and braided fibrous structures promises to lead to major advances in composite technology. Through thickness strength imparted to composites by virtue of such integrated reinforcement will open new applications for composites that could not be considered previously, primarily due to the poor transverse strength and interlaminar shear properties of traditional laminated composites. The ability of these structures to conform to shape or assume near net structural shapes promises to simplify manufacturing processes, reduce costs, and enhance design flexibility.
Introduction and Application of Modular Turbine Engine Performance Analyses System Within KLM Royal Dutch Airlines
Authors: Schröder Willem J. , Lanser Harmen
Published: March 2015

KLM Royal Dutch Airlines has successfully been using the General Electric Ground-based Engine Monitoring (GEM) system for overall monitoring of on-wing engines for several years.

GEM provides a function for the modular analysis of engines with the Turbine Engine Modular Performance Estimation Routine (TEMPER).

This paper describes the introduction and first applications of the Test Cell TEMPER routine within KLM for the CF6-50 and CF6-80 engines.

The subjects to be discussed include a short description, the installation and the evaluation of the Test Cell TEMPER function. Furthermore, KLM’s first experience with Test Cell TEMPER and KLM’s plans with TEMPER for the near future are discussed.
Methods and Procedures for Trim Balancing the LM2500 Marine Gas Turbine in the Test Cell and Aboard Ship
Authors: Thompson Bruce D. , Badgley Robert H. , Raczkowski Richard
Published: March 2015

Extensive fleet experience with LM2500 marine gas turbines shows that engines with higher than normal vibration are more likely to show early wear. Gas generator rotor unbalance has been identified as the main cause of high vibration. Rotor rebalancing reduces vibration to acceptable levels, at the same time reducing or eliminating many wearout modes. Initially, the only rebalance option was to remove the gas generator from the ship and send it to the depot. The high cost of this option led to a search for alternatives, and the successful development of a procedure for rebalancing the gas generator rotor aboard ship. The method adopted was the well known influence coefficient procedure, developed by the National Aeronautics and Space Administration (NASA) in the late 1960’s. This method is well suited for implementation on portable computers, and fits readily into a practical procedure for use by trained technicians. The NASA program originally included a procedure to minimize peak residual vibration. Navy engineers added an improved optimizing procedure and a method to account for engine nonlinearities. Rebalancing involves mounting four external accelerometers on the engine, along with a tachometer to give a one-per-rev signal for phase angle measurement. Baseline vibration measurements, together with stored influence coefficients for the LM2500 engine series, permit first shot multi-plane, multi-speed trim correction weights to be calculated. The compressor case is readily opened and the weights installed without disturbing the engine. Application of this procedure has been highly successful: vibration levels of less than 0.001 inch peak-to-peak over the entire speed range have been achieved. The avoided cost of removal, replacement and repair of an LM2500 is estimated to be about $500,000.
An Off-Design Loss and Deviation Prediction Study for Transonic Axial Compressors
Authors: Çetin M. , Üçer A. Ş. , Hirsch Ch. , Serovy G. K.
Published: March 2015

A study on the design and off-design loss and deviation correlations was performed in which transonic compressor test data of 1970’s was used. Losses are considered as a whole and expressed by a total pressure loss coefficient with design and off-design parts identified separately. A modified version of NASA-2D minimum loss incidence correlation is proposed for DCA and MCA blades. Koch and Smith design loss correlation was found to be most satisfactory. For DCA and MCA blade profiles new off-design loss correlations were formulated. A correction is proposed to the Carter’s design deviation angle prediction method. For off-design deviation prediction Creveling’s correlation is easy to apply and gives most consistent and successful results.
Cycle Analysis for Helicopter Gas Turbine Engines
Authors: Bewley A. D.
Published: March 2015

Over the years there have been steady improvements in helicopter engine performance — higher specific powers (power/unit air flow), lower specific fuel consumptions and improved power/weight ratios. The gains have been the result of improving materials and cooling technologies and better aerodynamic design methods. These advances have allowed higher combustor temperatures and component efficiencies, with direct benefit to both specific power and specific fuel consumption (sfc), and higher turbomachinery stage loadings. These higher loadings have mainly been exploited as a means of reducing stage numbers, leading to improved reliability and maintainability and lower acquisition cost — always particularly strong goals in the helicopter field.
Metal Ceramic Guide Vanes New Design Concept
Authors: Krüger W. , Hüther W.
Published: March 2015

With the aim of achieving a considerable reduction in the cooling air requirement of HPT nozzles of jet engines, a new guide vane concept which utilizes the high service temperature capability (≈1900 K) of sintered silicon carbide was proposed. In this concept, the load bearing structure of the vane is formed by the metallic shrouds and metallic core. The uncooled vane shell in SSiC, which floats in recesses in the shrouds, surrounds the vane core and projects the major metallic areas from direct contact with the hot gas. Straight cascades with 4 vanes of metal-ceramic construction were designed, manufactured and successfully rig-tested at 1800 and 1900 K.
A Proposal for Optimized Design of Multistage Compressors
Authors: Tuccillo Raffaele
Published: March 2015

The aim of the paper is to provide a methodology for optimum design of axial flow multistage compressors derived from a flow model, previously defined by the author, that takes into account the effects of several geometrical parameters on blade losses and on the growth of end-wall boundary layers and secondary vorticities. The optimization is performed by means of a “Quasi-Newton” algorithm that controls an “Augmented Lagrangian Function” with the objective of maximizing efficiency for assigned values of total to total head. The paper outlines the theoretical approach and the main practical feature of the methodology, the latter consisting of a performance optimization by imposing even slight variations to the geometry of an existing compressor.
A Theory for Wake-Induced Transition
Authors: Mayle R. E. , Dullenkopf K.
Published: March 2015

A theory for transition from laminar to turbulent flow as the result of unsteady, periodic passing of turbulent wakes in the free stream is developed using Emmons’ transition model. Comparisons made to flat plate boundary layer measurements and airfoil heat transfer measurements confirm the theory.
Optimum Design of a Low Pressure, Double Inflow, Radial Steam Turbine for Open-Cycle Ocean Thermal Energy Conversion
Authors: Schobeiri T.
Published: March 2015

This paper describes the thermo-fluid design concept of a low pressure, radial inflow steam turbine for the Open-Cycle Ocean Thermal Energy Conversion (OTEC). For the optimum design consideration, the necessary theoretical tools are developed. The design concept permits the utilization of single-stage and multi-stage configuration for small and medium power range, respectively.
Effects of Endwall Suction and Blowing on Compressor Stability Enhancement
Authors: Lee N. K. W. , Greitzer E. M.
Published: March 2015

An experimental investigation was carried out to examine the effects on stall margin of flow injection into, and flow removal out of, the endwall region of an axial compressor blade row. A primary objective of the investigation was clarification of the mechanism by which casing treatment (which involves both removal and injection) suppresses stall in turbomachines. To simulate the relative motion between blade and treatment, the injection and removal took place through a slotted hub rotating beneath a cantilevered stator row. Overall performance data and detailed (time-averaged) flowfield measurements were obtained.

Flow injection and removal both increased the stalling pressure rise, but neither was as effective as the wall treatment. Removal of high blockage flow is thus not the sole reason for the observed stall margin improvement in casing or hub treatment, as injection can also contribute significantly to stall suppression. The results also indicate that the increase in stall pressure rise with injection is linked to the streamwise momentum of the injected flow, and it is suggested that this should be the focus of further studies.
Inlet Skew and the Growth of Secondary Losses and Vorticity in a Turbine Cascade
Authors: Walsh J. A. , Gregory-Smith D. G.
Published: March 2015

This paper presents results of an experimental investigation into the effects of inlet skew on the flowfield of a large scale axial flow turbine cascade. The results are presented in terms of the development of the streamwise vorticity since, in classical terms, the streamwise vorticity generates the transverse velocity components that cause the generation of the secondary losses. Inlet skew is shown to have a profound effect on the distribution and magnitude of the generated losses. A number of correlations for the secondary losses are compared with the measured values and it is shown that the correlations are not adequate for accurate loss prediction purposes.
Application of Low-Solidity Cascade Diffuser to Transonic Centrifugal Compressor
Authors: Hayami H. , Senoo Y. , Utsunomiya K.
Published: March 2015

Low-solidity circular cascades, conformally transformed from high-stagger linear cascades of double-circular-arc vanes with solidity 0.69, were used as a part of the diffuser system of a transonic centrifugal compressor. Performance test results were compared with data of the same compressor with a vaneless diffuser. Good compressor performance, a wider flow range as well as a higher pressure ratio and a higher efficiency, superior to those with a vaneless diffuser, where the flow range was limited by choke of the impeller, were demonstrated. The test circular cascade diffusers demonstrated a good pressure recovery over a wide range of flow angles, even when the inflow Mach number to the cascade was over unity.
Small Diameter Film Cooling Hole Heat Transfer: The Influence of the Number of Holes
Authors: Andrews G. E. , Bazdidi-Tehrani F.
Published: March 2015

The overall surface averaged heat transfer was determined for air passing through arras of small diameter holes drilled at 90 through thin metal walls. The influence of the number of holes and hence of the pitch to diameter ratio, X/D, was investigated over the range 4.7 to 21 for a fixed hole size of 1.4 mm and hole L/D of 4.5. A transient cooling technique was used to determine the overall heat transfer coefficient for the cooling due to the air passage through the wall. It was shown that the dominant heat transfer was that on the hole approach surface area due to flow acceleration into the hole. The hole approach surface area was used in the heat transfer correlation. The results of the authors were combined with previous results for the variation of X/D at constant X to give a heat transfer correlation, independent of L/D.
Three-Dimensional Separated Flow Field in the Endwall Region of an Annular Compressor Cascade in the Presence of Rotor-Stator Interaction: Part I — Quasi-Steady Flow Field and Comparison With Steady-State Data
Authors: Schulz H. D. , Gallus H. E. , Lakshminarayana B.
Published: March 2015

An experimental study of three-dimensional flow field in an annular compressor cascade with an upstream rotor has been carried out at four different incidences to the stator blade. Blade boundary layers and the three-dimensional flow field at the exit are surveyed using a hot wire sensor and a five hole probe, respectively. The data on the blade boundary layer, passage flow and separated corner flow is presented. The upstream rotor wake has a major influence on the transition, laminar separation bubble, extent of wall/corner flow separation, aerodynamic losses, secondary flow and three-dimensional flow inside the passage. Detailed interpretation of the effects of upstream wakes on the entire passage flow is presented and compared with the data in the absence of a rotor.
Comparison of Steady and Unsteady Secondary Flows in a Turbine Stator Cascade
Authors: Hebert Gregory J. , Tiederman William G.
Published: March 2015

The effect of periodic rotor wakes on the secondary flow structure in a turbine stator cascade was investigated. A mechanism simulated the wakes shed from rotor blades bypassing cylindrical rods across the inlet to a linear cascade installed in a recirculating water flow loop. Velocity measurements showed a passage vortex, similar to that seen in steady flow, during the time associated with undisturbed fluid. However, as the rotor wake passed through the blade row, a large crossflow toward the suction surface was observed in the midspan region. This caused the development of two large areas of circulation between the midspan and endwall regions, significantly distorting and weakening the passage vortices.
Vibration Analysis for Immediate Assessment of Battle-Damaged Gas Turbine Engines
Authors: Badgley Robert H. , Shade Wayne A.
Published: March 2015

Operation of aircraft in hostile combat areas exposes the aircraft to risks of substantial damage or loss. Engine damage can occur as a result of impact or penetration by projectiles or fragments, or by ingestion of impact debris. The risk level depends upon threat, aircraft type, and mission. Historical evidence indicates that damage is often survivable. Aircraft can often be repaired and returned to service. The damaged engine may still be able to operate. Normal action is to remove and replace a damaged engine, but replacement engines may not be available. A procedure is needed at the operational unit level to immediately assess the exact nature and extent of engine damage, as well as rapid (perhaps nonstandard) engine repair procedures for use at forward locations. Such repairs can include reblading of compressors and turbines, replacement of cracked or broken gear cases or gears, and replacement or repair of accessories. Without repairs, the aircraft fleet may quickly lose its effectiveness. Performance indicators, gas path and oil debris quantity and size, and vibration levels can help identify the location and extent of damage. Vibration analysis with portable, computerized equipment can identify damage in the engine’s compressor and turbine rotating components, as well as cracked, broken, or otherwise damaged accessory drive gearboxes and accessories. Vibration analysis either provides an immediate indication that all vibration indicators are within limits, or localizes the damage to specific components for immediate replacement or repair at the operating unit location.
Direct Coal Firing for Large Combustion Turbines: What Do Economic Projections and Subscale Combustor Tests Show?
Authors: Pillsbury P. W. , Bannister R. L. , Diehl R. C. , Loftus P. J.
Published: March 2015

Westinghouse Electric Corporation and Avco Research Lab/TEXTRON have been working for three years on a Department of Energy program to establish the technology required for commercially viable direct coal-fueled utility-size gas turbine combined cycles. These plants are to meet the EPA’s New Source Performance Standards for coal-fired steam generators and to generate power at a favorable cost-of-electricity relative to steam plants with flue gas desulfurization. Economic projections indicate that the latter goal is achievable by a method of approach which uses inexpensive utility-grade coal, and removes the resulting sulfur and ash through use of a slagging combustor in the gas turbine cycle. High pressure, subscale slagging combustor tests have been underway for several months at Avco Research Laboratory and are encouraging. Experimental highlights are shown here.
Performance of Hot Gas Clean-Up Devices Tested at the NYU DOE-PFBC Facility
Authors: Zakkay V. , Gbordzoe E. A. M. , Sellakumar K. M. , Lu C. Q.
Published: March 2015

Three hot gas clean up units namely, the Screenless Granular Bed Filter (GBF), Ceramic Cross-flow Filter (CXF) and High Temperature, High Pressure Electrostatic Precipitator (ESP) designed for PFBC combined cycle power applications were tested at the New York University (NYU) DOE-PFBC facility located at Westbury, New York using a 780 mm ID pressurized fluidized bed combustor. The combustor was operated up to 10 atma and 870 °C.

With the exception of the ESP whose performance was hampered by persistent electrode bushing failure, the particulate capturing efficiencies of the GBF and the CXF were predominantly in the upper 90 % range. The dust loading leaving the filters was consistently lower than the NSPS particulate emission limit. The results also indicate that the filter exit gas stream may meet the gas turbine particulate tolerance limit.

None of the three high temperature, high pressure (HTHP) gas clean up units tested emerges as a favorite for use in cleaning PFBC exhaust stream because, each has mechanical design as well as operational flaws which could be corrected. The Cross-flow filter suffered from filter element cracking or delamination or gasket failure during its short test program. The backpulse cleaning system also needs to be optimized. The GBF is susceptible to media bubbling and granule flow problems through its lower seal leg. The Electrostatic Precipitator tested at NYU failed because its electrode bushings cracked due to overheating and could not hold their designed voltage.

Further HTHP filter testing at the sub-pilot plant scale is necessary to optimize filter design and develop effective operational procedures for the hot gas clean up systems that will make them viable for commercial PFBC application.
Effect of Acceleration on the Heat Transfer Coefficient on a Film Cooled Surface
Authors: Ammari H. D. , Hay N. , Lampard D.
Published: March 2015

Results are presented of an experimental investigation into the influence of mainstream acceleration on the heat transfer coefficient downstream of injection through a row of 35° holes in a flat plate. A mass transfer analogue technique was used, with two uniform acceleration parameters, K (=ν(du∞/dx)/u∞2), of 1.9 × 10−6 and 5.0 × 10−6 in addition to the zero acceleration base-line case.

Two injectants, air and carbon dioxide, were employed to give coolant to mainstream density ratios of 1.0 and 1.52 respectively. The blowing rate varied from 0.5 to 2.0.

The heat transfer coefficient beneath the film reduced progressively as the acceleration increased, with maximum reductions from the zero acceleration datum case of about 27%. In the presence of acceleration, the heat transfer coefficient at a given blowing rate was dependent on the density ratio, an increase in the density ratio leading to a decrease in the heat transfer coefficient. An empirical correlation of the data over most of the range of densities and blowing rates of the experiments has been developed.