bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Application of a Multistage Navier-Stokes Solver: Part I — Multistage Modeling Using Bodyforces and Deterministic Stresses
Authors: Rhie Chae M. , Gleixner Aaron J. , Spear David A. , Fischberg Craig J. , Zacharias Robert M.
Published: February 2015

A novel multistage compressor performance analysis method based on the three-dimensional Reynolds averaged Navier-Stokes equations is presented in this paper. This approach is a “continuous interface plane approach” where deterministic stresses are used to ensure continuous physical properties across interface planes. The average unsteady effects due to neighboring blades and/or vanes are approximated using deterministic stresses along with the application of bodyforces. Bodyforces are used to account for the “potential” interaction between closely coupled (staged) rows. Deterministic stresses account for the “average” wake blockage and mixing effects both axially and radially. The attempt here is to implement an approximate technique for incorporating periodic unsteady flow physics that provides for a robust multistage design procedure incorporating reasonable computational efficiency. The present paper gives the theoretical development of the stress/bodyforce models incorporated in the code, and demonstrates the usefulness of these models in practical compressor applications. Compressor performance prediction capability is then established through a rigorous code/model validation effort using the power of networked workstations. The numerical results are compared with experimental data in terms of one-dimensional performance parameters such as total pressure ratio and circumferentially averaged radial profiles deemed critical to compressor design. This methodology allows the designer to design from hub to tip with a high level of confidence in the procedure.
Development and Application of a Multistage Navier-Stokes Flow Solver: Part II — Application to a High Pressure Compressor Design
Authors: LeJambre C. R. , Zacharias R. M. , Biederman B. P. , Gleixner A. J. , Yetka C. J.
Published: February 2015

Two versions of a three dimensional multistage Navier-Stokes code were used to optimize the design of an eleven stage high pressure compressor. The first version of the code utilized a “mixing plane” approach to compute the flow through multistage machines. The effects due to tip clearances and flowpath cavities were not modeled. This code was used to minimize the regions of separation on airfoil and endwall surfaces for the compressor. The resulting compressor contained bowed stators and rotor airfoils with contoured endwalls. Experimental data acquired for the HPC showed that it achieved 2% higher efficiency than a baseline machine, but it had 14% lower stall margin. Increased stall margin of the HPC was achieved by modifying the stator airfoils without compromising the gain in efficiency as demonstrated in subsequent rig and engine tests. The modifications to the stators were defined by using the second version of the multistage Navier-Stokes code, which models the effects of tip clearance and endwall flowpath cavities, as well as the effects of adjacent airfoil rows through the use of “bodyforces” and “deterministic stresses”. The application of the Navier-Stokes code was assessed to yield up to 50% reduction in the compressor development time and cost.
Dynamic Simulation of the FT8-2™ Gas Turbine
Authors: Metzger Alan
Published: February 2015

With the approach of the 1990 Clean Air Act compliance limits, the race is on to produce a functional, low-emission gas turbine. While most prototype Dry Low NOx (DLN) gas turbines are based on existing designs, the leap in technology required to meet NOx abatement levels is significant. To meet these goals, significant testing is required before low-emission turbines are ready for commercial production.

This paper describes the test procedure that was used to verify control system and modulating valve technology for Turbo Power & Marine’s FT8-2™ Dry Low NOx prototype turbine. In particular, dynamic turbine simulation before the actual engine test will be discussed. The method and benefits of this test procedure will be presented.
Rapid Design, Integration and Test of Improved Digital Fuel Control for the LM2500 Gas Turbine Engine
Authors: Howell Max , Hartshorn Bill
Published: February 2015

This paper describes how Martin Marietta performed rapid design, integration, and test of a Digital Fuel Control (DFC) system for control of shipboard GE LM2500 Gas Turbine Engines. This phase was performed in Orlando, Florida and included real time hardware in the loop (HWTL) testing of the DFC with a simulated engine and test cell. With this approach, all of the DFC hardware and software could be validated before performing control of a real engine. Therefore risk was minimized and the schedule did not depend on availability of an LM2500 engine. The engine and test cell were simulated using the Integrated Systems, Inc. (ISI) AC100 Real Time Controller, which is easily transportable from site to site. The next phase will involve testing the DFC and AC100 with a real LM2500 engine and test cell.

The AC100 incorporates parallel digital signal processing and various input/output (I/O) options such as analog to digital (A/D) converters, digital to analog (D/A) converters, logical inputs and outputs, resolver to digital converters, pulse width modulation output, etc. Programs and I/O connections are made using extensive software on a workstation which produces code which is downloaded to the AC100 via Ethernet The programs are developed using a user-friendly, menu-driven graphical language called System Build. An autocode generator converts the system model to C or Ada, which is compiled and downloaded to the AC100 for real time execution.
A Combined Experimental/Computational Study of Flow in Turbine Blade Cooling Passage: Part I — Experimental Study
Authors: Tse D. G. N. , McGrath D. B.
Published: February 2015

A combined experimental/computational study has been performed for flow in a rotating serpentine passage which approximates the internal cooling passage for turbine blades. Experimental results are presented in Part I and computational results, in Part II. Benchmark quality velocity measurements were acquired by laser-Doppler velocimetry at Reynolds number of 25,000 and Rotation number of 0.24. The results were used to assess the influence of the Coriolis force on the velocity characteristics and to explain the heat transfer phenomena observed in Wagner et al (1991). The results showed an increase in streamwise velocity on the high pressure side and a decrease in streamwise velocity on the low pressure due to Coriolis effect. Cross-stream, tangential and rms velocities indicated the presence of swirl, strong secondary flow and large turbulent fluctuations in the vicinity of the turns.
A Method of Balancing Large-Scale Flexible Rotors Without Test Runs
Authors: Zhu Xiao-dong , Wang Xi-xuan
Published: February 2015

In all methods of balancing flexible rotors currently in use, test masses and test runs are required for the calculation of correction masses. In this paper, a method of identifying the unbalances is derived by main-shaft-section transfer matrix, which is based on the measured responses of the rotor. So, the unbalance can be identified without test runs.
Influence of Powder Manufacturing Process on TBC Lifetime
Authors: Froning Marc J. , Sahoo Purush
Published: February 2015

Thermal barrier coatings (TBC) have been used extensively in aircraft engines to protect the gas turbines’ hot section from mechanical and enviromental degradation as well as to improve thermodynamic efficiency. Because TBC’s enhance operating temperature and service life, they are expected to play and increasingly important role in protecting both flight and land based industrial turbine engines. This investigation examines the functionality of air plasma sprayed two-layer TBC systems with a MCrAlY bond coat and a yttria partially stabilized zirconia (YSZ) top coat.

Qualitative X-ray diffraction (XRD) analyses were conducted on several commercially produced YSZ powders and the coatings produced from the powders. Thermal cycle lifetime studies were carried out at 2040°F. Phase structures of the coatings were evaluated before and after testing. An attempt was then made to correlate those results to thermal cycle life. It was found that the powder manufacturing process appears to have an influence on coating characteristics and on thermal shock lifetime.
The Development of a Multi-Stage Compressor for Heavy Duty Industrial Gas Turbines
Authors: Meindl T. , Farkas F. , Klussmann W.
Published: February 2015

ABB has developed a new type of industrial gas turbine, the GT24 and GT26, in order to meet the increasing market requirement for a high efficiency in both simple cycle and combined cycle modes. The new engines are characterized by an increased pressure-ratio, a sequential combustion system and top component efficiencies. One of the most demanding tasks has been the development of the new high pressure ratio compressor, designed with controlled diffusion airfoils and 3 variable vane rows. In order to verify the aerodynamic design and the mechanical integrity, the first 15 stages of the compressor have been modeled and tested in an extensively instrumented rig. Both the aerodynamic behavior and the blade stresses have been measured during start-up, off-design, and nominal-speed operation, mapping the entire compressor performance field. The experimental results agree well with the predicted design data.
Application of an Industrial Gas Turbine for Cogeneration and Process Services
Authors: Ehlers Gary A.
Published: February 2015

The gas turbine is not limited to single service applications such as power generation or mechanical drive service. An application has been developed recently to use an industrial gas turbine to drive an electric generator for power while at the same time contributing to the heat balance of a refinery unit. Specifically, a G. E. Frame 5 gas turbine installed with a hydrogen reformer furnace can significantly reduce the overall heat input required by capturing the waste heat in the exhaust gas to preheat the feed to the furnace and to generate high pressure steam for the owner’s refinery steam system.

The gas turbine selected for the projects described in this paper is the G.E. Frame 5, model “R” (5271 RA). The model “R” was originally described as a “single shaft mechanical drive” turbine but easily adapted to generator drive. The design is some 30 years old as it was developed in the 1960’s. The term “single shaft mechanical drive” is somewhat strange to us in the process industries as we’re more accustomed to mechanical drive gas turbines designed with two shafts for speed control purposes. Many of the design / construction features of this model make it ideally suited for this application.

The higher cost of fuels, and electrical power contribute significantly to making the economics attractive. First of all the heat of the turbine exhaust gas will reduce the fuel required for firing to heat the feed to the furnace. The steam generated in the heat recovery section then contributes to generating power in the steam side in the steam turbine. The results are fuel savings and electric power purchase savings.

The steam turbine portion of the cycle is designed to vary with the owner’s steam system and balance. For that reason the steam turbine includes a high pressure inlet, medium pressure steam chest for extraction, a low pressure steam chest designed for induction or extraction and a surface condenser to condense the steam passed through.

Fuel flexibility is a major consideration of the unit design. Natural gas or methane rich gas is a base fuel that the gas turbine will fire most of the time. Alternate fuels however, such as propane or butane are commonly available in a refinery and could be fired in the gas turbine as currently configured.
Micromechanical Crack Propagation in Nicalon Fiber Toughened Composites
Authors: Preetam Nagoor , Larson Michael C.
Published: February 2015

Increasing the toughness of brittle ceramics with fibers has received much attention in the last five years. Many models have been put forth to describe the various facets of cracking in these materials. The intent here is to evaluate how well a relatively simple computational representation of the crack openings for a fracture in a fibrous material predicts the crack openings actually measured in an experimental specimen. The cracks are modeled as distributions of discontinuities within a surface integral representation. The influence of the fibers are accounted for through closing tractions applied at the fracture surfaces. Experimental specimens were loaded using a tensile substage mounted in a scanning electron microscope in visually monitor the crack and damage development. Some of the physical processes associated with matrix crack-fiber interactions were also evident.
Interstage Disk-Cavity/Brush Seal Numerical Flow Visualization Study
Authors: Kudriavtsev V. V. , Braun M. J.
Published: February 2015

This paper presents work-in-progress results and model developments that are directed towards the computational fluid dynamics simulation of the secondary flow system in a gas turbine engine. Numerical flow visualization results of the 2-D axisymmetric rotational fluid flow (Re=105) in a generic cross section of an interstage turbine cavity are displayed. The core flow is driven by an imposed pressure drop along the vane row of the main flow path. Three interconnected disk cavities separated by a brush seal are located along the secondary flow path. A new computational algorithm was developed in order to predict the flow patterns and leakages for different seal and cavity configurations. The code is based on the numerical solution of the transient laminar Navier-Stokes equations, written in primitive variables and approximated on a nonuniform rectangular collocated grid. The program uses a mass and momentum conservative formulation as well as a set of boundary conditions for pressure and conservation of mass. The pressure solution uses the Poisson equation under a direct implementation procedure. A time dependent Alternating Direction Implicit (ADI) method is also used for the solution of all primitive variables. This integrated computational approach allows the simulation of the rotating disk cavity vortex flow periodic features, as well as their impact on leakage flow and sealing effectiveness. In the present study this approach is used to numerically investigate the flow through the brush. The main purpose of this study is to present an integrated brush seal/disk cavity flow model, to demonstrate the effectiveness of this approach, and to emphasize the necessity for further work in this direction.
Reduction of Compressor Stator Endwall Losses Through the Use of Bowed Stators
Authors: Weingold Harris D. , Neubert Robert J. , Behlke Roy F. , Potter Glen E.
Published: February 2015

The growth of suction surface corner separation in multistage compressor stators is shown to limit the pressure rise capability of core flow stator sections, which would otherwise remain unseparated at the same incident flow. Three dimensional CFD modeling of the stator flowfield has led to the development of “bowed” stator shapes which are predicted to substantially delay the onset of suction surface corner separation. Experimental testing of the bowed stator concept in the exit stator of a three–stage research compressor has confirmed the elimination of suction surface corer separation, the resulting reduction of the endwall loss, and the increase in pressure rise capability of the stator core sections due to the elimination of the radial growth of the corner separation region. Application of bowed stators in all three stator rows of the research compressor has provided more robust characteristics and substantially improved efficiency over the entire flow range.
Use of Knowledge-Based Engineering in Compressor Rotor Design
Authors: Marra John
Published: February 2015

Competitive pressures are forcing manufacturers of turbine engines to reduce product development times, minimize design iterations, and react rapidly to changing markets and customers. Concurrent Engineering replaces the traditional sequential design process with parallel efforts in multiple disciplines, increasing product quality while reducing leadtime. Knowledge-Based Engineering captures product and process knowledge contained in the “corporate memory” to enhance and accelerate the design process. Linking the two together provides a wide variety of synergistic effects not separately available.

In this paper a general description of the process used to create a Knowledge Based Engineering (KBE) System capable of Concurrent Engineering (CE) will be presented, along with selected results. The summary discusses use of the system created to pursue real world design problems.
Oxide-Oxide Continuous Fiber Ceramic Composites for Gas Turbine Applications
Authors: Goettler Richard W. , Hindman Donald L. , DeBellis Crispin L. , Edwards Michael J.
Published: February 2015

Oxide-oxide continuous fiber ceramic composites (CFCCs) are being developed by Babcock & Wilcox (B&W) for a number of industrial applications including gas turbine components. Funding for this work is from the U.S. DoE’s CFCC, Ceramic Stationary Gas Turbine (CSGT) and Advanced Turbine Systems (ATS) Programs. A description of the oxide-oxide CFCCs being developed by B&W and their applicability to gas turbine combustor liners will be presented. Results of thermal and stress analyses performed for a combustion rig test at Solar Turbines as part of the CSGT Program and for a preliminary applications assessment for Allison Engine Company as part of the ATS Program will be presented.
An Evaluation of Indentation and Finishing Properties of Bearing Grade Silicon Nitrides
Authors: Dill James F. , Gardos Michael N. , Hardisty Robert G.
Published: February 2015

This paper describes the results of studies of the machining performance and the indentation hardness and fracture toughness of different silicon nitride materials as part of an effort to better define the optimum machining conditions for bearing components. This work builds on prior efforts by two of the authors, Gardos and Hardisty (1993) who formulated a simple relationship between diamond grinding performance of silicon nitride bearing balls and a wear equation first detailed by Evans and Wilshaw (1976).

The goal of this present work was to determine the general applicability of such a relationship, i.e. could simple indentation studies be used to define finishing conditions for different silicon nitride materials. The availability of such a simple test would reduce the time required for developing an acceptable process when a supplier changes his formulation, or when a new material becomes available. Quicker development of optimum finishing conditions would eventually result in a lower-cost product for users.

The initial study by Gardos and Hardisty (1993) was based on limited data taken at a fixed set of conditions. This study expanded the range of conditions evaluated and the number of ceramic materials studied in an effort to define the universality of the relationship between grinding wear, hardness and toughness.

This study has shown that no simple relationship like that first envisioned by the authors exists. The results showed that the grinding wear of the individual silicon nitride materials increased at different rates as a function of load. Because of the differences found in the load dependence of grinding rates, no simple relationship between hardness, fracture toughness and grinding rate could be found which fit the data over the range of conditions studied. This work is part of an ARPA funded effort to provide a tribological performance database on ceramic bearing materials, including their grinding and finishing properties, and their interaction with standard bearing steels.
Key Issues in the General Design of Motor-Vehicle Gas-Turbine Engines
Authors: Pfahnl Andreas Carl , Wilson David Gordon
Published: February 2015

Ideas and concepts are suggested for producing a motor-vehicle gas-turbine engine able to compete in performance and most likely in cost with similarly rated motor-vehicle spark-ignition and compression-ignition engines. Several of these ideas are discussed qualitatively, while others arc shown through simple performance analyses. Results predict the possibility of thermal efficiencies of over 50% and marked increases in the fuel economy (over 90%) if the gas-turbine engine is used, for instance, as a direct replacement for a standard motor-vehicle engine. The latter calculations were based on Federal-Test-Procedure driving cycles.
Modeling and Simulation Methods for MDOF Structures and Rotating Machinery With Impact Dampers
Authors: McElhaney John M. , Palazzolo A. , Kascak A.
Published: February 2015

Previously published work on applied impact damping typically relates to SDOF models or simple MDOF models such as the classical cantilever beam. Structural models often require an extremely large number of DOF with mode shapes that are generally very complex. Dynamics simulation of these typically becomes both complicated and time consuming as well. The non-linear behavior of impact dampers further complicates such simulation in that standard linear solutions are not possible.

The primary objective in this research extends previous work by applying impact dampers to MDOF structures that are modeled with general 3-D ‘beam’ finite elements. Modal based models of the MDOF systems and efficient impact damper tracking algorithms were also developed which significantly reduced CPU time for simulation.

Significant among the objectives was obtaining an impact damper design for the MDOF casing structure of the Space Shuttle Main Engine (SSME), High Pressure Oxygen Turbo-Pump (HPOTP), subject to pump rotor shaft unbalance. Impact damper performance is based on suppression of vibration at casing critical frequencies for rotor speed ranges, at rotor full speed, and very high unbalance to simulate a defect such as loosing an impeller blade fragment or a cracked bearing[6]. Simulations show significant reductions in vibration at the casing critical frequencies and very high unbalance levels while little or no improvement was observed off resonance.

Additionally, the previous work with an experimental rotor bearing system (RBS) and impact damper was modeled using the developed modal based methods. Simulation of the resulting model response shows remarkable agreement with the experimental.

Finally, both the RBS and the HPOTP were modeled and simulated as unstable systems with attached impact dampers. The simulations predict that the impact damper is an excellent stabilizing mechanism for a range of instability driver values.

Simulation of the models in this research with the developed modal based algorithms were accomplished with excellent efficiency, and accurate results.
Measured Force/Current Relations in Solid Magnetic Thrust Bearings
Authors: Allaire P. E. , Fittro R. L. , Maslen E. H. , Wakefield W. C.
Published: February 2015

When magnetic bearings are employed in a pump, compressor, turbine or other rotating machine, measurement of the current in the bearing coils provides knowledge of the forces imposed on the bearings. This can be a significant indicator of machine problems. Additionally, magnetic bearings can be utilized as a load cell for measuring impeller forces in test rigs. The forces supported by magnetic bearings are directly related to the currents, air gaps and other parameters in the bearings. This paper discusses the current/force relation for magnetic thrust bearings.

Force vs. current measurements were made on a particular magnetic bearing in a test rig as the bearing coil currents were cycled at various time rates of change. The quasi-static force vs. current relations were measured for a variety of air gaps and currents. The thrust bearing exhibits a hysteresis effect which creates a significant difference between the measured force when the current is increasing as compared to that when the current is decreasing. For design current loops, 0.95 A to 2.55 A, at the time rate of change of 0.1 A/sec, the difference between increasing and decreasing current curves due to hysteresis ranged from 4% to 8%. If the bearing is operated in small trajectories about a fixed (non-zero) operation point on the F/I (force/current) curve, the scatter in the measurement error could be expected to be on the order of 4 percent.

A quasi-static non-linear current/force equation was developed to model the data and curve Fit parameters established for the measured data. The effect of coercive force and iron reluctance, obtained from conventional magnetic materials tests, were included to improve the model but theoretically calculated values from simple magnetic circuit theory do not produce accurate results. Magnetic fringing, leakage and other effects must be included.

A sinusoidal perturbation current was also imposed on the thrust bearing. Force/current magnitude and phase angle values vs. frequency were obtained for the bearing. The magnitude was relatively constant up to 2 Hz but then decreased with frequency. The phase lag was determined to increase with frequency with value of 16 degrees at 40 Hz. This effect is due to eddy currents which are induced in the solid thrust bearing components.
Dry Ultra-Low NOx ‘Green Thumb’ Combustor for Allison’s 501-K Series Industrial Engines
Authors: Puri Rahul , Stansel David M. , Smith Duane A. , Razdan Mohan K.
Published: February 2015

This paper describes the progress made in developing an external ultra-low oxides of nitrogen (NOx) ‘Green Thumb’ combustor for the Allison Engine Company’s 501-K series engines. A lean premixed approach is being pursued to meet the emissions goals of 9 ppm NOx, 50 ppm carbon monoxide (CO), and 10 ppm unburned hydrocarbon (UHC). Several lean premixed (LPM) module configurations were identified computationally for the best NOx-CO trade-off by varying the location of fuel injection and the swirl angle of the module. These configurations were fabricated and screened under atmospheric conditions by direct visualization through a quartz liner; measurement of the stoichiometry at lean blow out (LBO); measurement of the fuel/air mixing efficiency at the module exit; and emissions measurements at the combustor exit, as well as velocity measurements. The influence of liner residence time on emissions was also examined.

An LPM module featuring a radial inflow swirler demonstrated efficient fuel-air mixing and subsequent low NOx and CO production in extensive atmospheric bench and simulated engine testing. Measurements show the fuel concentration distribution at the module exit impacts the trade-off between NOx and CO emissions. The effect of varying the swirl angle of the module also has a similar effect with the gains in NOx emissions reduction being traded for increased CO emissions. A uniform fuel-air mixture (± 2.5% azimuthal variation) at the exit of the module yields low NOx (5–10 ppm) at inlet conditions of 1 MPa (∼10 atmospheres) and temperatures as high as 616 K (650°F). The combustion efficiency at the above conditions was also good (> 99.9%) with CO and UHC emissions below 76 ppm and 39 ppm, respectively. This LPM module was resistant to flashback, and stability was good as LBO was observed below ϕ = 0.50. Tests with multiple modules in a single liner indicate a strong intermodule interaction and show lower NOx and CO emissions. The close proximity of adjacent modules and lower confinement in the liner most likely reduces the size of the recirculation zone associated with each module, thereby reducing the NOx formed therein. The CO emissions are probably lowered due to the reduced cool liner surface area per module resulting when several modules feed into the same liner.
The Enhanced TF40B Engine
Authors: DiGiovanni Robert , Sehra A. , House Edward M.
Published: February 2015

The AlliedSignal TF40B engine is currently used on the U.S. Navy’s Landing Craft Air Cushion for main propulsion. Through years of LCAC modifications, the net weight of the craft has increased which created a demand for more propulsion power at high ambient temperatures. The enhanced TF40B engine will incorporate compressor and turbine modifications designed to increase airflow by 17%. This will result in a 22% power increase to 5000 SHP and an 8% improvement in specific fuel consumption. The engine will have the capability to supply bleed air at approximately 2 lbm/sec and still maintain the present TF40B rating.
Conversion of Liquid to Gaseous Fuels for Lean Premixed Combustion
Authors: Stoffel B. , Reh L.
Published: February 2015

The lean premixed combustion of gaseous fuels is an attractive technology to attain very low NOx emission levels in gas turbine engines. If liquid fuels are converted to gaseous fuels by vaporization, they also can be used in premix gas burners and similar low NOx emissions are achievable. Experiments were carried out in a test rig in which the three main process steps of liquid fuel combustion (vaporization of fuel, mixing of air and fuel vapor and combustion reaction) can be performed successively in three separate devices and examined independently.

A wide range of liquid fuels (methanol, ethanol, heptane, gasoline, rape oil methyl ester and two diesel oil qualities) was vaporized in an externally heated tube in the presence of superheated steam. These fuel vapors were led to a Pyrocore® radiant burner operating in fully premixed mode at atmosperic pressure. For all fuels without bound nitrogen, NOx levels below 15 mg/m3 at 3% O2 in the dry exhaust gas (2.5 ppm at 15% O2) were measured at lean combustion conditions.

However, the nitrogen particularly bound in higher boiling fuels like diesel oil was converted completely to NOx under these conditions. The fuel bound nitrogen (FBN) proved to be the major source of NOx when burning vaporized diesel oil.
Application of Taguchi Optimization Techniques to the Combustor Design Process
Authors: Cooner M. L. , Reynolds R. S. , Srinivasan R.
Published: February 2015

This paper describes the application of Taguchi design of experiments (DOE) methods to the initial development of the T800-LHT-801 growth engine combustor design. The performance of a gas turbine combustor is strongly influenced by the primary zone aerodynamics and stoichiometry. The interactions between fuel spray and airflows through swirlers, primary jets, and dome surface cooling dominate the primary zone characteristics. Development of a robust combustor design requires a good knowledge of the relative sensitivities of these interactions. In this application, the Taguchi DOE method was used to efficiently determine the design parameters driving the combustor performance, while minimizing the number of tests. The improved design configuration resulted in 60 percent reduction in Lean Blow Out (LBO), 140°C reduction in peak wall temperature, and elimination of carbon formation potential at severe operating conditions.
Computational Methods for Modelling Port Flows in Gas-Turbine Combustors
Authors: McGuirk James J. , Spencer Adrian
Published: February 2015

The objective of the present paper is to describe a computational technique which has been developed to allow the detailed geometry of the air-admission ports to be included in computational fluid dynamic studies of gas-turbine combustors. As CFD modelling of combustors continues to improve, it is likely that it will become commonplace to consider complete geometry descriptions of combustors (i.e. external as well as internal) in associated flow calculations, rather than carry out separate calculations, as is more usual currently. It will therefore be both necessary and desirable to include in the calculation the various geometrical features used in port design to control air admission and overall flow splits, (e.g. radiused/plunged/chuted holes, splitter plates, etc.). This requires modifications to standard mesh generation practices which are outlined and demonstrated here. As an illustration of the success and capabilities of the current method, flow field calculations are presented which contrast the changes in flow-split (as a consequence of discharge coefficient changes) and flow-patterns which are predicted when port geometry is varied from a plain hole to a plunged/chuted hole typical of some current designs.
Blading Vibration and Failures in Gas Turbines: Part B — Compressor and Turbine Airfoil Distress
Authors: Meher-Homji Cyrus B.
Published: February 2015

With blades accounting for as many as 42% of failures in gas turbines, there is a pressing need for a unified treatment of their causes, failure modes and practical troubleshooting. In this paper, the significant causes of problems relating to axial compressors and turbine blading are covered. Case studies are provided pertaining to blading vibration, aerodynamic instability, and blade environment related problems.
Blading Vibration and Failures in Gas Turbines: Part C — Detection and Troubleshooting
Authors: Meher-Homji Cyrus B.
Published: February 2015

Blade failures account for as many as 42% of failures in gas turbines. This paper covers approaches to detect and avoid blade failures by direct and indirect measurement techniques. Direct measurements involve the use of special sensors or methods that measure blading vibration or condition. Indirect techniques do not quantitatively measure blade conditions but provide qualitative information that help in avoiding blade problems. Metallurgical tests of hot section blades to determine microstructure changes are also covered. A blade failure troubleshooting chart is furnished to assist users in diagnosing common failure modes.
Blading Vibration and Failures in Gas Turbines: Part D — Case Studies
Authors: Meher-Homji Cyrus B.
Published: February 2015

The investigation of gas turbine blade failures requires an interdisciplinary approach calling for expertise in gas turbine design, operation and metallurgy. The object of this paper is to show, in the context of blading problems, the interrelationship between design, operation, maintenance, and the operational envelope. This paper presents case studies dealing with a variety of failure modes. The treatment focuses on practical troubleshooting of blading problems augmented, in some cases, by the use of analytical tools.
Feasibility of Extending Current Allowable Weld Repairs for a Compressor Impeller
Authors: Miglietti W. , Jacobs F.
Published: February 2015

This research study was undertaken to evaluate whether gas tungsten arc welding (GTAW) could be utilised to extend the limits of an existing repair scheme. The compressor impeller of the GTC 85-71 suffers from such severe sand erosion to the leading edges, that the damage exceeds the manufacturers specification. The impeller is manufactured from Ti-6Al-4V. The study entailed performing a series of welding trials and post-weld heat treatments. After metallographic examination of the weld microstructure, mechanical property assessments (i.e. tensile and fatigue tests) were undertaken. The results demonstrated that the welds after the 550 °C/8 hr post-weld heat treatment had equivalent properties to those of the parent metal. The stress distribution determined by finite element analysis showed the weld to be in an area of low stress. The results achieved herein and the stress analysis showed that the GTAW process is feasible for extending the repair limits for restoration of the leading edges of the compressor impeller.
Problems in Military Propulsion Engines of the South African Air Force
Authors: Benson J. , Miglietti W. , Glass S. J. , Getliffe K.
Published: February 2015

The Nimonic 105 first stage turbine blade of the Rolls Royce Viper 22/1 engine has a design life of 2400 hrs. Over the years, these blades have prematurely failed (1 200–1 800 hrs), necessitating a service limit of 1 000 hrs. Initial investigations thought the cause of failure to be linked with higher than desired lead content but the final cause of failure was attributed to an incorrect heat treatment, forming continuous grain boundary carbides, resulting in embrittlement of the blade. A rejuvenation heat treatment was then developed.

The IN-713 and IN-X-40 first stage vanes of the Allison T56 engine suffer thermal fatigue cracking. The IN-713 vanes suffer narrow, fine but long cracks, whereas the X-40 vanes suffer severe cracking (cracks as wide as 3 mm) and excessive oxidation due to overheating. The X-40 alloy is protected by a Cr2O3 scale compared with Al3O3 on the IN-713 alloy. Above 1 000 °C the Cr2O3 breaks down and excessive oxidation results. A braze repair was developed for the X-40 vanes.
New Method for Turbine Blade Internal Cleaning
Authors: Irvine Jeffrey D. , Hampson Leonard M. , Rogers Steven T.
Published: February 2015

A program was undertaken to develop an improved internal cleaning procedure for high pressure turbine blades. HP turbine blades, such as JT8D and JT9D 1st stage blades, experience a build up of Si-Ca rich dirt/debris during engine service that inhibits the flow of cooling air creating localized “hot spots”. These “hot spots” lead to accelerated internal corrosion that may cause through-wall material failure. Autoclave processes, utilizing heated, pressurized caustic, are ineffective at removing large amounts of internal debris. A new process, called the TURBO-CLEAN℠ process (patent pending), effectively removes large deposits of internal debris in as few as 2 hours. This process involves pumping heated caustic at pressures approaching 400psi through the internal cavities of turbine blades. The increased caustic flow from this process, compared to autoclave processes, improves cleaning effectiveness. This new process does not harm the parent material or damage protective aluminide coatings. The development of this process has led to reduced repair costs for JT8D 1st blades by improving part yield during repair.
Tanker Fleet Upgrade: Gas Turbine and Propulsion Control Systems Retrofit
Authors: Kemp Stephen , Cozzetta Marc , Harclerode Scott
Published: February 2015

Many gas turbines commissioned in the late 1960’s and early 1970’s employ “first generation” electronic control systems. Usually a combination of analog-digital fuel and temperature control circuits and electromechanical relay sequencers, these systems (and the gas turbines they were designed to control) inevitably experience diminished performance as they age.

This paper describes the project to design, construct, install, and commission replacements for the control systems on the main and auxiliary gas turbines and the propulsion controls for Chevron Shipping Company’s domestic tanker fleet. Since replacing the main gas turbine control system and propulsion controls on the oil tanker Chevron Colorado in the spring of 1993, both the main and auxiliary turbine and propulsion controls have been replaced on each of the other four (4) tankers.

Triple modular redundant (TMR) digital systems were selected 10 replace the original analog-digital control systems on the main and auxiliary gas turbines (MGT & AGT). Required American Bureau of Shipping and US Coast Guard certification tests, as well as dock and sea trials for the new control systems are discussed. Economic results including maintenance repair action rates, start percentages, availabilities, and fuel savings are detailed.
U.S. Navy MK 105 Minesweeping System Upgrade Program: Installation of Pratt & Whitney Canada ST6L-813 Turbine
Authors: Levine Sheldon , Jarvis David G. , Lehman J. Michael
Published: February 2015

The U.S. Navy has in its arsenal a helicopter-towed magnetic minesweeping system for the task of sweeping seas of underwater magnetic influence mines. The EDO MK 105 Airborne Minesweeping System is a helicopter-towed, unmanned hydrofoil platform which operates at high speed in varied ocean environments with minimum risk to personnel and equipment. A gas turbine engine-generator set aboard the platform provides electrical power solely for the minesweeping operation.

Based on a need to improve its supportability, as well as reliability and maintainability, the U.S. Navy decided to update the present operational system. This decision necessitated the re-engining of the existing power plant Accordingly, the Pratt & Whitney Canada PT6 aircraft gas turbine engine was selected as the replacement prime mover. This paper discusses the gas turbine engine, the system design that was developed to integrate an aircraft turbine into this unusual Naval craft and the successful test program. The turbine was designated Model ST6L-813 for this marine application.
Blade Loss Simulation of Multi Mass Rotor Model With Nonlinear Tilt Pad Journal Bearings
Authors: Gadangi R. K. , Palazzolo A. B.
Published: February 2015

Prediction of rotor vibrations due to large imbalance requires nonlinear solution of the supporting bearings. This paper presents a methodology and results for the effects of large, sudden imbalance on the response of a multi mass rotor model supported on tilt pad journal bearings. For a given imbalance, response is obtained for rotor speeds below, above and at the rotor natural frequency. The maximum peak to peak amplitude is larger at the critical speed than at a speed above or below the critical. The imbalance response is compared with two other methods used for predicting the transient response of a rotor bearing system. The rigid rotor and nonlinear bearing model shows a response similar in shape to that obtained with a flexible rotor and nonlinear bearing model, but the magnitude is different, which reached a limiting value as the imbalance was increased. The flexible rotor and linearized bearing model predicts a similar trend as the flexible rotor and nonlinear bearing model, with increasing speed for a given imbalance, but the shape and magnitude of the orbit is completely different. The motion of rotor to static equilibrium location for the flexible rotor and nonlinear bearing model showed oscillations which diminished with time, while the rigid rotor and nonlinear bearing model does not show any oscillations.
Experimental Study of the Unsteady Boundary Layer Behavior on a Turbine Cascade
Authors: Schobeiri M. T. , Pappu K. , Wright L.
Published: February 2015

The unsteady boundary layer behavior on a turbine cascade is experimentally investigated and the results are presented in this paper. To perform a detailed study on unsteady cascade aerodynamics and heat transfer, a new large-scale, high-subsonic research facility for simulating the periodic unsteady flow has been developed. It is capable of sequentially generating up to four different unsteady inlet flow conditions that lead to four different passing frequencies, wake structures, and freestream turbulence intensities. For a given Reynolds number, three different unsteady wake formations are utilized. Detailed unsteady boundary layer velocity, turbulence intensity, and pressure measurements are performed along the suction and pressure surfaces of one blade. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity.
The Influence of Blade Negative Curving on the Endwall and Blade Surface Flows
Authors: Wang Zhongqi , Han Wanjin
Published: February 2015

In order to explore the mechanism reducing the energy losses by use of negative curved blades, an experiment was carried out on turbine rectangular cascades with straight and negative curved blades of high turning angle and low aspect ratio. Ink trace technology was employed to show the flows on the endwalls and blade surfaces. The pressures were measured in detail with static pressure taps on the endwalls and blade surfaces. Experimental results indicate that when negative curved blades are used, a separating saddle of inlet boundary layers goes forward into the passage and approaches the pressure surface, as the streamwise adverse pressure gradient on the cascade inlet endwall becomes lower, compared with that of straight blade cascade. In addition, the static pressure contours are almost parallel lines perpendicular to the endwall on the front part of the suction surface and the curves which internal normals with the positive slopes near the endwall direct to the midspan from high pressure to lower pressure on the middle, this leads to the separation of free vortex sheet pattern on the suction surface. As a result, it is delayed that the separation lines converge towards midspan.
Development of an Oilless, Gearless, and Bleedable Under Armor Auxiliary Power Unit
Authors: Nims Robert
Published: February 2015

The oilless, gearless and bleedable under armor auxiliary power unit (UAAPU) development program is providing the United States Army with a technically advanced auxiliary power unit (APU) for military tracked vehicles. Fully functional prototypes in two configurations are being demonstrated in both laboratory and field tests. The APU power output is 32 kw (43 shp) with 10 to 20 kw supplied as electrical power and the balance of power delivered as elevated pressure bleed air for use in conjunction with the vehicle nuclear, biological, and chemical (NBC) filtration and environmental control system (ECS).

The design of the UAAPU incorporates air bearings and a shaft-speed permanent-magnet starter/generator with electronic power conditioning to eliminate completely the need for oil lubrication and an auxiliary gearbox. This significantly simplifies the mechanical design of the APU with resulting reliability, durability, and maintainability improvements. Over 600 hours of laboratory system development test time has been logged and 90 hours in field tests on an M1A1 main battle tank. Operations in the field have included both gunnery and simulated warfare training exercises.
Current Status of 300 kW Industrial Gas Turbine R&D in Japan
Authors: Murayama Takumi , Nagata Kunihiro , Abe Hiroyuki , Ogiyama Hisao
Published: February 2015

The Ceramic Gas Turbine (CGT) has great advantages in terms of energy efficiency, environmental protection, and fuel-diversification. In Japan, R&D on the 300 kW CGT has been carried out as one of the national projects entitled “New Sunshine Program”, which are promoted by the New Sunshine Project Promotion Headquarters, Agency of Industrial Science and Technology (AIST), Ministry of International Trade and Industry (MITI).

R&D on the CGT has progressed faithfully and now the operation of prototype CGTs (Turbine Inlet Temperature (TIT) of 1200 °C) is focused.

In the paper, the overall status of the R&D activities on the 300 kW CGT will be reviewed with the test results to-date, problems awaiting solution, and perspective for the prototype and pilot CGTs.