bluuebunny/crossref_metadata_2025 huggingface dataset:
Blade Excitation by Circumferentially Asymmetric Rotating Stall in Centrifugal Compressors
Authors: Jin D. , Haupt U. , Hasemann H. , Rautenberg M.
Published: March 2015

The excitation of blade vibration by circumferentially asymmetric rotating stall in a high pressure ratio, high mass flow centrifugal compressor with radial impeller and vaned diffusers has been investigated. This was accomplished experimentally by means of blade vibration measurements with strain gages mounted on the blades and simultaneous unsteady pressure measurements with fast response dynamic transducers. The earlier results showed rotating stall effects as the monofrequent excitation of blade vibration. However a more detailed analyses of blade vibration by very strong rotating stall in the speed range of 13,000–14,500 rpm displayed multiple frequency components of blade vibration besides the main excitation frequency caused by rotating stall. The frequency values were found to be related to frequencies of shaft rotation and rotating stall. The detailed analyses of the pressure signals of rotating stall obtained from dynamic transducers located at different circumferential positions on the shroud wall showed a different pressure pattern amplitude due to rotating stall. The circumferentially asymmetric amplitude profile of the rotating stall was an additional excitation of blade vibration. By aid of two-dimensioal Fourier analysis for the pressure pattern of rotating stall, a calculation method for blade vibration frequencies by circumferentially asymmetric rotating stall was developed. The predicted blade vibration frequencies corresponded to the frequency components on the blade vibration spectrum obtained from the strain gages.
Calculations on the Time-Dependent Potential Flow in a Centrifugal Pump
Authors: Badie R. , Jonker J. B. , van Essen T. G.
Published: March 2015

In this paper a finite element based method is presented for the calculation of two-dimensional time-dependent potential flows through a rotor/stator configuration. An algorithm was developed that numerically evaluates the time derivative of all relevant field quantities. For that purpose the computational domain was split into a region containing the rotor and one containing the stationary parts, each region being treated in a different coordinate system. The corresponding finite element grids are matched by an interface consisting of connect-elements which move in time. The pressure field was then obtained from the unsteady Bernoulli equation. The Kutta condition was imposed by a method using the linear property of the operators. The algorithm was in particular applied to calculate the two-dimensional quasi-steady flow through a volute laboratory pump which made an experimental verification possible. For various mass flows the lateral fluid forces, the axial moment, the total head of the pump were computed and analyzed. The agreement with the experimental data, with respect to the quantities in the volute, was reasonable. The deviation was quantitatively greatest at low mass flow, the maximum deviation in the velocity being 10%. The overall behavior of the pump could be well predicted.
Profile Losses of an Annular Turbine Cascade in Unsteady Periodic Flow
Authors: Lisal M. , Soch P. , Vratny J.
Published: March 2015

The paper deals with an experimental study of aerodynamic characterizations of an annular turbine cascade in an unsteady flow with the constant mean value i.e. characteristic flow of turbomachinery. The experimental research was done in an annular measure area of the CKD-VZLU low speed tunnel with a time control running of pressure fluctuations. These fluctuations were generated by the wakes behind rotating row of prismatic blades with speed up to 100 m/s and frequency up to 3500 Hz. The results of measurements of steady profile losses in the axial annular turbine cascade Tu-2 which is used in Czechoslovak aircraft industry are reported in this paper for incidences in the range from −10 deg. to 20 deg. and for Reynolds numbers from 60 000 to 150 000. These results are also compared with the ones of Kacker and Okapuu method. Measurements of unsteady profile losses in turbine cascade i.e. measurements with upstream rotating rotor of prismatic blades were taken at nearly identical conditions as those in the case without the rotor. Comparison of the profile losses in the unsteady flow with the profile losses in the steady flow is presented.
Comparison Between Experiment and Prediction for a Subsonic Turbulent Separated Boundary Layer
Authors: Bohn D. , Dibelius G. H. , Sucharski Z.
Published: March 2015

Experimental and theoretical investigations were conducted for examining the effects of high free-stream turbulence at a high adverse pressure gradient and of periodically unsteady perturbations on the turbulent boundary layer development along the suction side of a turbine blade.

As part of the experimental test rig the blade suction side is represented by a flat plate of 550 mm length. A pressure distribution typical for a turbine blade channel is generated by a curved wall opposite to this plate. The separated region towards the trailing end of the plate is 25 % of its total length. For simulating the unsteady effect of wakes being shed from the previous blade row, a wake generator is installed in the inlet cross section of the test rig. The turbulence level is raised by a turbulence grid just ahead of the wake generator. An LDV with high spatial resolution is used for measuring averaged and fluctuating components of the velocity and turbulence related quantities in the boundary layer. New correlations for the measured velocity profiles and other flow quantities especially for the separated near wall region are presented.

Two separated turbulent boundary layers in a steady stream i.e. the forementioned and that measured by Simpson as well as an unseparated unsteady turbulent boundary layer have been theoretically examined. The solutions were obtained with a finite-difference boundary layer computer code and as well as with a fully elliptic finite-volume calculation procedure. The Cebeci-Smith algebraic, the Johnson-King nonequilibrium algebraic and two variants of the k-ε turbulence models were used in these calculations. The results of the various turbulence models for these flows are compared with the experimental data.
Effect of Tangential Torque on the Stability of Rotors Supported by Hydrodynamic Bearings
Authors: Han Dong-Chul
Published: March 2015

The effect of tangential torque on the stability of a rotor supported by various hydrodynamic journal bearings is investigated by the free vibration and transient response analyses. It is shown that the stability region of the rotational speed is bounded by both upper and lower rotational speeds. The parametric study of this investigation has been carried out in terms of the dimensionless bearing characteristics, shaft flexibility and tangential torque. It is shown that the use of hydrodynamic journal bearing can eliminate the instability due to tangential torque except for the case of light bearing loads and high shaft flexibilities.
An Analysis System for Blade Forced Response
Authors: Chiang Hsiao-Wei D. , Kielb Robert E.
Published: March 2015

A frequent cause of turbomachinery blade failure is excessive resonant response. The most common excitation source is the nonuniform flow field generated by inlet distortion, wakes, and/or pressure disturbances from adjacent blade rows. The standard method for dealing with this problem is to avoid resonant conditions using a Campbell diagram. Unfortunately, it is impossible to avoid all resonant conditions. Therefore, judgements based on past experience are used to determine the acceptability of a blade design.

A new analysis system has been developed to predict blade forced response. The system provides a design tool, over and above the standard Campbell diagram approach, for predicting potential forced response problems. The incoming excitation sources are modeled using a semi-empirical rotor wake/vortex model for wake excitation, measured data for inlet distortion, and a quasi-3D Euler code for pressure disturbances. Using these aerodynamic stimuli, and the blade’s natural frequencies and mode shapes from a finite element model, the unsteady aerodynamic modal forces and the aerodynamic damping are calculated. A modal response solution is then performed.

This system has been applied to current engine designs. A recent investigation involved fan blade response due to inlet distortion. An aeromechanical test had been run with two different distortion screens. The resulting distortion entering the fan was measured. With this as input data, the predicted response agreed almost exactly with the measured response. In another application, the response of the LPT blades of a counter-rotating supersonic turbine was determined. In this case the blades were excited by both a wake and a shock wave. The shock response was predicted to be three times larger than that of the wake. Thus, the system identified a new forcing function mechanism for supersonic turbines.

This paper provides a basic description of the system, which includes: 1) models for the wake excitation, inlet distortion, and pressure disturbance; 2) a kernel function solution technique for unsteady aerodynamics; and 3) a modal aeroelastic solution using strip theory. Also, results of the two applications are presented.
A Study of the Influence of Bearing Clearance on Lateral Coupled Shaft/Disk Rotordynamics
Authors: Flowers George T. , Wu Fang Sheng
Published: March 2015

This study examines the influence of bearing clearance on the dynamical behavior of a rotating, flexible disk/shaft system. Most previous work in nonlinear rotordynamics has tended to concentrate separately on shaft vibration or on bladed disk vibration, neglecting the coupling dynamics between them. The current work examines the important rotordynamical behavior of coupled disk/shaft dynamics. A simplified nonlinear model is developed for lateral vibration of a rotor system with a bearing clearance nonlinearity. The steady-state dynamical behavior of this system is explored using numerical simulation and limit cycle analysis. It is demonstrated that bearing clearance effects can produce superharmonic vibration that may serve to excite high amplitude disk vibration. Such vibration could lead to significantly increased bearing loads and catastrophic failure of blades and disks. In addition, multi-valued responses and aperiodic behavior was observed.
Discharge Coefficients of Holes Angled to the Flow Direction
Authors: Hay N. , Henshall S. E. , Manning A.
Published: March 2015

In the cooling passages of gas turbine blades, branches are often angled to the direction of the internal flow. This is particularly the case with film cooling holes. Accurate knowledge of the discharge coefficient of such holes at the design stage is vital so that the holes are correctly sized thus avoiding wastage of coolant and the formation of hot spots on the blade.

This paper describes an experimental investigation to determine the discharge coefficient of 30° inclined holes with various degrees of inlet radiusing and with the axis of the hole at various orientation angles to the direction of the flow. Results are given for nominal main flow Mach numbers of 0, 0.15 and 0.3.

The effects of radiusing, orientation and cross flow Mach number are quantified in the paper, the general trends are described, and the criteria for optimum performance are identified.
An Experimental Study of Heat Transfer in a Large-Scale Turbine Rotor Passage
Authors: Blair Michael F.
Published: March 2015

An experimental study of the heat transfer distribution in a turbine rotor passage was conducted in a large–scale, ambient temperature, rotating turbine model. Meat transfer was measured for both the full–span suction and pressure surfaces of the airfoil as well as for the hub endwall surface. The objective of this program was to document the effects of flow three–dimensionality on the heat transfer in a rotating blade row (vs. a stationary cascade). Of particular interest were the effects of the hub and tip secondary flows, tip leakage and the leading–edge horseshoe vortexsystem. The effect of surface roughness on the passage heat transfer was also investigated. Midspan results are compared with both smooth–wall and rough–wall finite–difference two dimensional heat transfer predictions. Contour maps of Stanton number for both the rotor airfoil and endwall surfaces revealed numerous regions of high heat transfer produced by the three dimensional flows within the rotor passage. Of particular importance are regions of local enhancement (as much as 100% over midspan values) produced on the airfoil suction surface by the secondary flows and tip–leakage vortices and on the hub endwall by the leading–edge horseshoe vortex system.
Interactions Between Embedded Vortices and Injectant From Film Cooling Holes With Compound Angle Orientations in a Turbulent Boundary Layer
Authors: Ligrani P. M. , Mitchell S. W.
Published: March 2015

Experimental results are presented which describe the effects of embedded, longitudinal vortices on heat transfer and film injectant downstream of two staggered rows of film cooling holes with compound angle orientations. Holes are oriented so that their angles with respect to the test surface are 30 degrees in a spanwise/normal plane projection, and 35 degrees in a streamwise/normal plane projection. A blowing ratio of 0.5, non-dimensional injection temperature parameter θ of about 1.5, and freestream velocity of 10 m/s are employed. Injection hole diameter is 0.945 cm to give a ratio of vortex core diameter to hole diameter of 1.6–1.67 just downstream of the injection holes (x/d=10.2). At the same location, vortex circulation magnitudes range from 0.15 m2/s to 0.18 m2/s. By changing the sign of the angle of attack of the half-delta wings used to generate the vortices, vortices are produced which rotate either clockwise or counter-clockwise when viewed looking downstream in spanwise/normal planes.

The most important conclusion is that local heat transfer and injectant distributions are strongly affected by the longitudinal embedded vortices, including their directions of rotation and their spanwise positions with respect to film injection holes. Differences resulting from vortex rotation are due to secondary flow vectors, especially beneath vortex cores, which are in different directions with respect to the spanwise velocity components of injectant after it exits the holes. When secondary flow vectors near the wall are in the same direction as the spanwise components of the injectant velocity (clockwise rotating vortices R0-R4), the film injectant is more readily swept beneath vortex cores and into vortex upwash regions than for the opposite situation in which near-wall secondary flow vectors are opposite to the spanwise components of the injectant velocity (counter-clockwise rotating vortices L0-L4). Consequently, higher St/Sto are present over larger portions of the test surface with vortices R0-R4 than with vortices L0-L4. These disruptions to the injectant and heat transfer from the vortices are different from the disruptions which result when similar vortices interact with injectant from holes with simple angle orientations. Surveys of streamwise mean velocity, secondary flow vectors, total pressure, and streamwise mean vorticity are also presented which further substantiate these findings.
Experimental and Computational Investigation of the NASA Low-Speed Centrifugal Compressor Flow Field
Authors: Hathaway M. D. , Chriss R. M. , Wood J. R. , Strazisar A. J.
Published: March 2015

An experimental and computational investigation of the NASA Low-Speed Centrifugal Compressor (LSCC) flow field has been conducted using laser anemometry and Dawes’ 3D viscous code. The experimental configuration consists of a backswept impeller followed by a vaneless diffuser. Measurements of the three–dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational analysis, and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the rotor as well as surface flow visualization along the impeller blade surfaces provide independent confirmation of the laser measurement technique.
Experimental Study on the Three Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part I — Velocity and Pressure Fields
Authors: Kang Shun , Hirsch Ch.
Published: March 2015

Experimental results from a study of the 3-D flow in a linear compressor cascade with stationary endwall at design conditions are presented for tip clearance levels of 1.0, 2.0 and 3.3 percent of chord, compared with the no clearance case. In addition to five-hole probe measurements, extensive surface flow visualizations are conducted. It is observed that for the smaller clearance cases a weak horseshoe vortex forms in the front of the blade leading edge. At all the tip gap cases, a multiple tip vortex structure with three discrete vortices around the midchord is found. The tip leakage vortex core is well defined after the midchord but does not cover a significantly great area in traverse planes. The presence of the tip leakage vortex results in the passage vortex moving close to the endwall and to the suction side.
Advanced Ducted Engines: Impact of Unsteady Aerodynamics on Fan Vibration Properties
Authors: Klose Arno H.
Published: March 2015

Fans of Advanced Ducted Engines (ADE) will be built from light-weight materials such as carbon-fibre-reinforced plastics (CFRP). Due to their low density, the aeroelastic behaviour of these fan blades is significantly different from that of conventional titanium fan blading. Calculations performed during the design of ADE fan bladings show that self-induced aerodynamic loads can significantly alter the resonant frequencies; furthermore, aerodynamic coupling of the different in-vacuo eigenmodes can occur. This is not the case for conventional titanium fan blading, where the vibration properties are largely unaffected by unsteady aerodynamic forces. It is concluded that for light-weight fan blading, it is necessary to take into account aerodynamic stiffening and aerodynamic mode coupling when computing eigenfrequencies and aeroelastic stability.
Application of Digital Video Interactive Technology for Operation and Maintenance of Industrial Gas Turbines
Authors: Golas K. , Mutter S. , Smalley A. J. , Quentin G.
Published: March 2015

The operation and maintenance of large combustion turbines for electric power generation can be enhanced by training plant operators and maintenance technicians using Digital Video Interactive (DVI®) technology.

DVI® is an all digital format for generating motion video, audio, animation, and graphics and still images. Using DVI® for visual information display provides effective training that encompasses both functional and diagnostic training, and can be augmented by on-line access to gas turbine documentation. The success of DVI® as a training vehicle is expected to be patterned after the success of interactive videodisc with the added advantage of an all digital format. DVI® is being integrated with other advanced technologies including expert systems and intelligent tutoring to form a complete informational resource for diagnostic training, visual data bases, and post disturbance analysis and blade inspection.

These informational resources can be applied to on-site training using a new low-cost portable delivery system combining powerful microcomputers, dual visual displays, and large disk storage media. This portable information system is an outgrowth of the EPRI research into field troubleshooting based upon the SA*VANT® system. SA*VANT® is a portable computer-based expert system advisor to aid technicians in troubleshooting the Westinghouse 501 during fail-to-start situations.
An Improved Boundary Layer Transition Correlation
Authors: Fasihfar Ahmad , Johnson Mark W.
Published: March 2015

The influence of pressure gradient and freestream turbulence level on boundary layer transition has been studied experimentally using hot wire instrumentation and digital signal processing and analysis. An established transition correlation and recent transition model were found to give acceptable prediction of the experimental results. The digital system was used to conditionally sample the transitional boundary layer data and hence to determine the mean and fluctuating velocity profiles for the laminar and turbulent parts of the boundary layer separately. The turbulent portions were found to correlate well with fully developed turbulent boundary layer profiles, but the laminar portion profiles deviated considerably from those typical of a laminar boundary layer.
Conceptual Design of Turbo-Accelerator for HST Combined Cycle Engine
Authors: Yanagi R. , Morita M. , Watanabe Y. , Itahara H. , Sasaki Y. , Aoki T.
Published: March 2015

Hypersonic Transport Propulsion System Research (HYPR) Project was started in 1900 to develop technologies for the propulsion system of a Mach 5 Hypersonic Civil Transport, which could be environmentally acceptable and economically viable. The engine being studied is the methane fueled combined cycle engine composed of a turbo-accelerator for low speed range and a ramjet engine for high speed range. what is called a turbo/ramjet engine. The turbo-accelerator is required to meet the low noise regulations at take-off and achieve high specific thrust at high speed flight like the second generation SST (Supersonic Transport) engine. The single bypass turbofan engine (SBE) with variable cycle concept was selected as the turbo-accelerator engine to meet the above requirements in one engine. The engine was conceived to have variable geometry in compressor stator, low pressure turbine stator, fan bypass flow nozzle aren and exhaust nozzle area for low jet velocity at take-off and high jet velocity at altitude high speed and be equipped with a mixer ejector in the exhaust nozzle for further noise reduction.

This paper describes the cycle study and conceptual design of the demonstrator of a turbo-accelerator engine being planned to be tested in 1903.
Peaking Gas Turbine Capacity Enhancement Using Ice Storage for Compressor Inlet Air Cooling
Authors: Ebeling Jerry A. , Halil Rick , Bantam Doug , Bakenhus Byron , Schreiber Henry , Wendland Ron
Published: March 2015

Combustion turbine peaking units provide power for short time periods when hot, humid weather creates summer demand peaks. These same weather conditions degrade combustion turbine capacity and heat rate. Cooling combustion turbine inlet air increases its density and improves combustion turbine performance. A full size retrofit air chilling system for a G.E. MS7001B engine was installed by Lincoln Electric System, in Lincoln, Nebraska (U.S.A.), in an EPRI and American Public Power Associated supported and co-funded demonstration project. Detailed design and construction documents for the project were developed by Burns & McDonnell Engineering Company.
Evaluation of Gas Turbine Transitions After 20,000 and 37,000 Hours of Service
Authors: Swaminathan V. P. , Owens H. B. , Hicks N.
Published: March 2015

A metallurgical investigation was conducted on transitions from two land-based 105 MW gas turbines. One transition suffered catastrophic failure, and two transitions had cracking at the top panel. Two alloys, IN-617 and a modified IN-617, were used in these transitions. The investigation consisted of thickness measurements, optical and scanning electron microscope fractographic studies, metallography, EDS and Auger analysis of precipitates, chemical analysis, and hardness measurements. In both units, heavy oxidation of the top panel on the hot gas side (inside) occurred. Oxide intrusion along the grain boundaries and exfoliation of the oxide layer occurred. This caused thinning of the panel with a resultant loss of about 50% of the panel thickness. Bulk creep cavitation along the grain boundaries and multiple discontinuous creep cracks were present. Crack origins were located at the outer surface of the top panels. Creep cracks and cavities, carbide precipitates, agglomeration of grain boundary carbides, and aluminum nitride were present in the microstructure. The primary cause of cracking was the increase in net section stress, which exceeded the creep strength of the panel. The effect of microstructural changes on the formation of cracks was secondary in nature. Cracks were not associated with welds.
On Aerodynamic Loading of Linear Compressor Cascades
Authors: Citavý Jan
Published: March 2015

A study is presented concerning a high loading of the pressure surface of a blade in a linear compressor cascade. Assuming the two–dimensional incompressible flow, two cascades denoted as RK3 and VD17 have been designed using an inverse method developed previously at SVÚSS. Both cascades have similar aerodynamic loading over the blade suction surface, but the cascade RK3 has lower minimum velocity (i.e. higher loading) on the pressure surface than the cascade VD17. Both cascades have been tested at the design as well as at the off–design incidence angles in a low-speed windtunnel. The results have been used for definition of the maximum permissible aerodynamic loading on both suction and pressure surfaces.
A Simulation of Secondary Flow in Centrifugal Impeller Channel by a Stationary Three-Dimensional Curved Duct
Authors: Mizuki Shimpei , Tsujita Hoshio
Published: March 2015

A duct with three-dimensional curvatures was employed in order to investigate the complex secondary flow patterns similar to those within centrifugal impellers. The curvature within a pair of co-cylindrical surfaces of the duct simulates that within the meridional plane of an impeller, and the curvature within the other pair of co-cylindrical surfaces perpendicular to the above-mentioned surfaces simulates the effect of the Coriolis force within the blade-to-blade surface. The computed and the measured results showed the qualitative similarity of the secondary flow patterns to those within centrifugal impellers except the effects of pressure rise by the centrifugal force generated by the impeller rotation and the tip leakage flow.
Transition Prediction in Attached and Separated Shear Layers Using an Integral Method
Authors: Leoutsakos G. , Papailiou K. D.
Published: March 2015

Calculation of the aerodynamic parameters of axial turbomachinery blades, and an accurate assessment of the flow over the blade surfaces under today’s increasingly demanding requirements for higher efficiencies and optimized blade shapes, at both design and off-design conditions, impose a need for accurate prediction methods able to compute through two sensitive but highly critical phenomena: separation and transition. The present study describes work done on the modelling and prediction of transitional regions, such as those appearing on turbomachinery blading, covering both attached and separated flows. The concept of an engineering method, cheap to run and avoiding complex CFD and turbulence model formulations was always kept in mind. Results include comparisons of integral quantities and velocity profiles in zero, favourable or adverse pressure gradient attached flows, and velocity distributions including points of separation, transition and reattachment in separated airfoil flows, obtained either from a straightforward shear layer calculation or from a viscous-inviscid interaction procedure.
Unsteady Boundary-Layer Transition in Flow Periodically Disturbed by Wakes
Authors: Orth U.
Published: March 2015

Boundary layers on turbomachinery blades develop in a flow which is periodically disturbed by the wakes of upstream blade cascades. These wakes have a significant effect upon laminar-turbulent boundary-layer transition. In order to study these effects, detailed velocity measurements using hot-wire probes were performed within the boundary-layer of a plate in flow periodically disturbed by wakes produced by bars moving transversal to the flow. The measurements were evaluated using the ensemble-averaging technique. The results show how the wake disturbance enters the boundary-layer and leads to a turbulent patch, which grows and is carried downstream. In favorable pressure gradients, transition due to wake turbulence occured much earlier than predicted by linear stability theory. Between two wakes, laminar becalmed regions were observed far beyond the point at which the undisturbed boundary-layer was already turbulent.
Progress on the Advanced Turbine Technology Applications Project (ATTAP), and Automotive Gas Turbine Outlook
Authors: Haley Philip J.
Published: March 2015

Of the four key technology areas attendant to the automotive gas turbine (ACT), structural ceramic components are the prime focus of the Department of Energy (DOE)-sponsored, NASA-managed ATTAP. The General Motors (GM) ATTAP team first focused on the ceramic gasifier turbine rotor, and in 1990 achieved full design temperature (2500°F TIT) at 100%N1 (gasifier speed). Four generations of axial-rotor design have led to such success, which also includes demonstrated resistance to foreign object impact; functionality after impact and minor damage; survivability in high-speed tip rub; and a 1000-hour durability demonstration. The ceramic gasifier turbine static structure, comprising scroll and vaneset (plus other support components), has also been successfully demonstrated at full (2500°F) design conditions, including successful completion of a 100-hour durability test of an all-ceramic gasifier stage. This major contractual milestone was completed during 1991. These successes represent fundamental technology progress, not only in the GM designs, but in the materials and processes implemented by the Kyocera Corporation, Norton/TRW Ceramics, and GTE Labs.

Heat management (regenerator system and thermal insulation) and combustion are other key AGT technologies. Ceramic regenerator disk efforts with Corning focus on developing extrusion technology in concert with evaluation of four ceramic material systems, to provide a disk with the requisite geometry, strength, survivability, and cost characteristics. Insulation activities with Manville target developing a ceramic refractory fiber-based system, which is wet injection molded directly in-place, and has the required thermal, adhesion, durability, and erosion properties. During 1991 a turbine engine component was successfully injection molded with this system. Some ATTAP effort has been directed toward design of a prevaporizing/premixing combustor to meet the California 0.2 gm/mile NOx standard.
A Simple Method for Estimating Secondary Losses in Turbines at the Preliminary Design Stage
Authors: Okan M. B. , Gregory-Smith D. G.
Published: March 2015

Reasonably accurate estimation of losses at an early design stage plays an important part in the success of a turbine design. Although various computational methods exist for estimating the profile loss, for secondary losses which are equally important, designers still rely on emprical estimates. A method has been developed for estimating the secondary flow and secondary losses within an axial turbine cascade. It is assumed that the inlet boundary layer is convected into a loss core within the blade passage while extra loss has been generated due to the secondary kinetic energy and a new boundary layer that is developing on the end wall. The method has been applied to various test cases and the results show that the basic approach is reliable.
The Role of Laminar-Turbulent Transition in Gas Turbine Engines: A Discussion
Authors: Walker G. J.
Published: March 2015

An extended discussion of Mayle’s (1991) critical study of transition phenomena in gas turbine engines is presented. Attention is focussed on transition in decelerating flow regions which are the major sources of loss production for axial turbomachine blades.

The following points are examined in detail:

(a) the physics of transition and its implications for the correlation of various transition phenomena;

(b) the relative importance of pressure gradient and free-stream turbulence in controlling transition;

(c) the influence of pressure gradient on periodic-unsteady transition;

(d) the correlation of transition length under conditions of arbitrary pressure gradient and free-stream turbulence level; and

(e) transition behavior in laminar separation bubbles.

The discussion examines various differences in philosophy concerning the above phenomena and corrects some areas of misinterpretation in the subject review paper. It concludes with further suggestions for transition research which may assist in resolving the issues raised.
The Transfer of Heat by Self-Induced Flow in a Rotating Tube
Authors: Gilham S. , Ivey P. C. , Owen J. M.
Published: March 2015

This paper provides a review of recently published research on self-induced flow and heat transfer in a rotating tube, together with additional theoretical work on heat transfer to the cylindrical wall of the tube. Earlier work has shown that self-induced flow can occur when a tube, with one end open and the other sealed, is rotated about its axis: fluid flows along the axis towards the sealed end and returns in an annular layer on the cylindrical wall. The flow and heat transfer on the end wall are similar to those associated with the so-called free disc, and measured velocity distributions in the tube and Nusselt numbers for the end wall are in good agreement with those computed from numerical solutions of the Navier-Stokes and energy equations. The Reynolds analogy is used in this paper to provide a correlation for the computed Nusselt numbers for the cylindrical wall, and design correlations are provided to enable the results to be applied to anti-icing systems for the nose bullets of aero-engines.
An Investigation of Turbulence Modelling in Transonic Fans Including a Novel Implementation of an Implicit κ–ϵ Turbulence Model
Authors: Turner Mark G. , Jennions Ian K.
Published: March 2015

An explicit Navier-Stokes solver has been written with the option of using one of two types of turbulence models. One is the Baldwin-Lomax algebraic model and the other is an implicit k-ϵ model which has been coupled with the explicit Navier-Stokes solver in a novel way. This type of coupling, which uses two different solution methods, is unique and combines the overall robustness of the implicit k-ϵ solver with the simplicity of the explicit solver. The resulting code has been applied to the solution of the flow in a transonic fan rotor which has been experimentally investigated by Wennerstrom. Five separate solutions, each identical except for the turbulence modelling details, have been obtained and compared with the experimental results. The five different turbulence models run were: the standard Baldwin-Lomax model both with and without wall functions, the Baldwin-Lomax model with modified constants and wall functions, a standard k-ϵ model and an extended k-ϵ model which accounts for multiple time scales by adding an extra term to the dissipation equation. In general, as the model includes more of the physics, the computed shock position becomes closer to the experimental results.
Ceramic Matrix Composite Applications in Advanced Liquid Fuel Rocket Engine Turbomachinery
Authors: Brockmeyer Jerry W.
Published: March 2015

Hot gas path components of current generation, liquid fuel rocket engine turbopumps (T/P) are exposed to severe thermal shock, extremely high heat fluxes, corrosive atmospheres and erosive flows. These conditions, combined with high operating stresses, are severely degradative to conventional materials. Advanced turbomachinery (T/M) applications will impose harsher demands on the turbine materials. These demands include higher turbine inlet temperature for improved performance and efficiency, lighter weight for improved thrust-to-weight ratio, and longer life for reduced maintenance of re-usable engines.

Conventional materials are not expected to meet these demands, and fiber-reinforced ceramic matrix composites (FRCMC) have been identified as candidate materials for these applications. This paper summarizes rocket engine T/M needs, reviews the properties and capabilities of FRCMC, identifies candidate FRCMC materials and assesses their potential benefits, and summarizes the status of FRCMC component development with respect to advanced liquid fuel rocket engine T/M applications.
Second-Generation Low-Emission Combustors for ABB Gas Turbines: Field Measurements With GT11N-EV
Authors: Aigner M. , Müller G.
Published: March 2015

In February 1991 a type GT11N gas turbine (Midland U.S.A.) was retrofitted with ABB’s new EV-Silo-Combustor. Tests were then carried out to examine the operation concept, to demonstrate the technical reliability and to confirm the low emission performance of this new technology. This paper will describe:

1.) The combustor design:

- one single silo combustor mounted on the turbine and equipped with 37 EV-burners.

2.) The results of the extensive field measurements:

The operation concept (lean premix combustion without any pilot diffusion flames, 7 burner groups) is simple and reliable:

- The emission targets

NOx < 25 ppmv (15% O2, natural gas)

CO < 8 ppmv

UHC < 5 ppmv

were reached. NOx-values are even lower than 15 ppmv at base load.

- The NOx-predictions for the GT11N-EV, based on the results of high pressure tests in Cologne (ASME PAPER 90-GT-308), compare very well with the results of field measurements.
A Summary of Allison Gas Turbine’s Marine Experience
Authors: Weisert J. S.
Published: March 2015

Allison Gas Turbine Division of General Motors Corporation has manufactured industrial gas turbines for nearly 30 years and marine gas turbines for nearly 20 years. Allison marine gas turbines have been produced in both the 501-K and 570/571-K engine product lines. Each Allison marine application provided unique challenges to a successful installation. This paper will describe the major Allison marine propulsion and power generation installations, and will discuss the challenges presented by, and solutions for, each project.
Advanced Blading for Last Stages of Heavy Duty Gas Turbines: A Joint German Action
Authors: Pickert U. , Keienburg K. H. , Bürgel R. , Schneider K.
Published: March 2015

Large stationary gas turbine blades are highly stressed by static and dynamic loads. In 1986, ABB and Siemens/KWU initiated an R&D-program to develop large blades of Ni-base superalloys with higher operating capability. The aim of the program is to develop with main suppliers new manufacturing routes and non-destructive testing methods for measuring residual stresses as well as to generate with institutes the relevant material/component property data. So far — scheduled end of the program in mid 1993 — new manufacturing routes are established which allow a higher stressing of blades. The current status and future outlook will be highlighted.
The Comparison of Different Simplified Mathematical Models of the Gas Turbine Combustion Chamber as an Object of Temperature and Pressure Control
Authors: Dzida Marek
Published: March 2015

The paper presents the mathematical model of the combustion chamber as an object of temperature and pressure control. Using the step function characteristics and the frequency method (in the range of low frequency f<20Hz), the theoretical models with different degrees of simplifications were compared with the results of the experimental investigations.

The proposed theoretical model may turn out very useful in the research of the gas turbine dynamics.
Magnetic Particle Inspection of Turbine Blades in Power Generating Plants
Authors: Imbert Clement , Rampersad Krishna
Published: March 2015

Modern societies expect and depend on regular, relatively uninterrupted, supply of electric power. Preventive maintenance is therefore vital for power generating plants. Non-Destructive Evaluation (NDE) is a significant element of the maintenance programme of power plants. Power plants use a wide variety of steam and gas turbines. Turbine failure can occur without warning and with disastrous results. Such failures are invariably caused by cracks. Such defects are readily detected by NDE techniques such as Magnetic Particle Inspection (MPI) if they are on or near the surface and accessible.

This paper reports on the use of MPI in the examination of martensitic stainless steel turbine blades in power plants in Trinidad and Tobago so as to quantify the testing parameters and determine field strength in relation to defect detectability. Specific recommendations are made regarding the configuration and optimum placement of magnetizing coils for turbine blade inspection insitu and detached.
Coal Gas Cleaning and Purification With Inorganic Membranes
Authors: Fain Douglas E. , Roettger George E.
Published: March 2015

The economic viability of coal gasification could depend on the ability to clean and purify the coal gases at elevated temperatures. Inorganic membranes have the potential for being used for that purpose. Efforts have been undertaken at the Oak Ridge K-25 Site to develop membranes that would be useful for separating hydrogen from the coal gas at the high operating temperatures. This paper will give a brief review of some fundamentals of gas separation with membranes. Also, a brief discussion of the theory derived to guide the development process will be given. The theory can be used to indicate the pore size needed to achieve good separation. In addition, some experimental results that have been obtained with some of the membranes that have been fabricated will be discussed.
Models for Predicting the Performance of Brayton-Cycle Engines
Authors: Korakianitis Theodosios , Wilson David Gordon
Published: March 2015

The performance of gas-turbine engines is the result of choices of type of cycle for the application, cycle temperature ratio, pressure ratio, cooling flows and component losses. The output is usually given as efficiency versus specific power. The type of efficiency of interest (thermal, propulsive, specific thrust, overall efficiency) must be specified. This paper presents a set of computer programs for the performance prediction of shaft-power and jet-propulsion cycles, such as simple, regenerative, intercooled-regenerative, turbojet and turbofan cycles. Each cycle is constructed using individual component modules. Realistic default assumptions are made by the programs, or other values can be specified by the user for component efficiencies as functions of pressure ratio, cooling mass-flow rate as a function of cooling technology levels, and various other cycle losses. The programs can be used to predict design point and off-design point operation using appropriate component efficiencies. The effect of various cycle choices on overall performance are discussed.
The Extension of a Solution-Adaptive 3D Navier-Stokes Solver Towards Geometries of Arbitrary Complexity
Authors: Dawes W. N.
Published: March 2015

This paper describes recent developments to a three dimensional, unstructured mesh, solution-adaptive Navier-Stokes solver. By adopting a simple, pragmatic but systematic approach to mesh generation, the range of simulations which can be attempted is extended towards arbitrary geometries. The combined benefits of the approach result in a powerful analytical ability. Solutions for a wide range of flows are presented including a transonic compressor rotor, a centrifugal impellor, a steam turbine nozzle guide vane with casing extraction belt, the internal coolant passage of a radial inflow turbine and a turbine disc-cavity flow.
HVOF Spraying and Laser Processing of Waspaloy Thick Films
Authors: Adamski A. , Bamola R. , Hultman L.
Published: March 2015

Waspaloy is used extensively in gas turbine engines. Although several techniques exist for depositing Waspaloy claddings or coatings such as gas tungsten arc welding (GTAW) or low pressure plasma spray (LPPS), little work has been performed on laser cladding or high velocity oxygen fuel (HVOF) spraying of this material. Advantages of these techniques include penetration to the substrate and thinner (250–500 micrometers) deposits. This study involved characterizing the microstructure and properties of Waspaloy coatings deposited using laser cladding and HVOF spraying. It was found that totally dense, metallurgically bonded coatings having properties similar to the base metal could be formed. Proper control of process parameters avoids thermal damage to the Waspaloy base. It is felt that such coatings can offer viable restoration schemes on worn or mis-machined components.
Massive Steam Injection on an MS6001B Gas Turbine in Cogeneration Service
Authors: Elward Kevin M. , Flodman David A. , Symonds Richard A.
Published: March 2015

A recent field test has completed the qualification of the MS6001B combustion system for operation on gas fuel with steam injection for NOx control to 25 ppmvd. Recently, dry operation on gas fuel at 25 ppmvd has been achieved on the MS6001. To meet the immediate need for running at the 25 ppmvd NOx level, increased steam injection was investigated. Laboratory testing on a single MS6001 combustor indicated the potential for achieving NOx levels as low as 25 ppmvd through the use of steam injection. This paper describes the lab testing and the field test of the MS6001B, and includes data on emissions, steam flow requirements, and dynamic pressure levels. The MS6001B is now available at 25 ppmvd NOx with steam injection on gas wherever this level is required. This system provides an easy retrofit to those gas fired, steam injected units where installation of the dry 25 ppmvd NOx system is not immediately feasible.
Mechanical Design of Free Standing Exhaust Stacks for Offshore Applications
Authors: Allison I. M. , Steel A. C.
Published: March 2015

This paper describes the methods developed to optimize the mechanical design of a free standing exhaust stack and its supporting structure. These particular methods have been used for the design of three gas turbine exhaust systems on a UK sector offshore platform currently under construction. The driving force behind the choice of a free standing stack was to save weight and therefore cost. The move towards the development of marginal fields in deeper waters will only increase the need for lighter, and therefore more cost effective design solutions.

Although national standards which cover the basic design philosophy are available, these have serious limitations when applied to this type of structure. The aim of this paper is to demonstrate how the limitations may be overcome by undertaking fundamental design analysis, and also to indicate those critical areas which demand special consideration. The detailed design analysis presented here considers the possibility of failure due to local instability, the effect on the dynamic response of the flexible foundation provided by the platform, and the determination of thermal stresses at critical locations.

Although this design has been developed for offshore use, the techniques utilized can be applied equally to onshore applications.
Ceramic Matrix Composites for Rocket Engine Turbine Applications
Authors: Herbell Thomas P. , Eckel Andrew J.
Published: March 2015

A program to establish the potential for introducing fiber reinforced ceramic matrix composites (FRCMC) in future rocket engine turbopumps was instituted in 1987. A brief summary of the overall program (both contract and in-house research) is presented. Tests at NASA Lewis include thermal upshocks in a hydrogen/oxygen test rig capable of generating heating rates up to 2500 °C/sec. Post thermal upshock exposure evaluation includes the measurement of residual strength and failure analysis. Test results for monolithic ceramics and several FRCMC are presented. Hydrogen compatibility was assessed by isothermal exposure of monolithic ceramics in high temperature gaseous hydrogen plus water vapor.