bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsteady Flow Field due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part I — Rotor Passage Flow Field
Authors: Zaccaria Michael A. , Lakshminarayana Budugur
Published: February 2015

The flow field in turbine rotor passages is complex with unsteadiness caused by the aerodynamic interaction of the nozzle and rotor flow fields. The two-dimensional steady and unsteady flow field at midspan in an axial flow turbine rotor has been investigated experimentally using an LDV with emphasis on the interaction of the nozzle wake with the rotor flow field. The flow field in the rotor passage is presented in Part I, while the flow field downstream of the rotor is presented in Part II. Measurements were acquired at 37 axial locations from just upstream of the rotor to one chord downstream of the rotor. The time average flow field and the unsteadiness caused by the wake has been captured. As the nozzle wake travels through the rotor flow field, the nozzle wake becomes distorted with the region of the nozzle wake near the rotor suction surface moving faster than the region near the rotor pressure surface, resulting in a highly distorted wake. The wake is found to be spread out along the rotor pressure surface, as it convects downstream of midchord. The magnitude of the nozzle wake velocity defect grows until close to midchord, after which it decreases. High values of unresolved unsteadiness were observed at the rotor leading edge. This is due to the large flow gradients near the leading edge and the interaction of the nozzle wake with the rotor leading edge. High values of unresolved unsteadiness were also observed near the rotor pressure surface. This increase in unresolved unsteadiness is caused by the interaction of the nozzle wake with the flow near the rotor pressure surface.
Unsteady Flow Field due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part II — Rotor Exit Flow Field
Authors: Zaccaria Michael A. , Lakshminarayana Budugur
Published: February 2015

The two-dimensional steady and unsteady flow field at midspan in a turbine rotor has been investigated experimentally using an LDV with an emphasis on the interaction of the nozzle wake with the rotor flow field. The velocity measurements are decomposed into a time-averaged velocity, a periodic velocity component and an unresolved velocity component. The results in the rotor passage were presented in Part I. The flow field downstream of the rotor is presented in this paper.

The rotor wake profiles and their decay characteristics were analyzed. Correlations are presented which match the decay of the various wake properties. The rotor wake velocity defect decays rapidly in the trailing edge region, becoming less rapid in the near and far wake regions. The rotor wake semi-wake width increases rapidly in the trailing edge region and then grows more gradually in the near and far wake regions. The decay of the maximum unresolved unsteadiness and maximum unresolved velocity cross correlations are very rapid in the trailing edge region and this trend slows in the far wake region. In the trailing edge region, the maximum periodic velocity correlations are much larger than the maximum unresolved velocity correlations. But the periodic velocity correlations decay much faster than the unresolved velocity correlations. The interaction of the nozzle and rotor wakes are also studied. While the interaction of the nozzle wake with the rotor wake does not influence the decay rate of the various wake properties, it does change the magnitude of the properties. These and other results will be presented in this paper.
Assessment of Two- and Three-Scale k-ε Models for Rotating Cavity Flows
Authors: Guo Zhou , Rhode David L.
Published: February 2015

A three-scale k-ε turbulence model was recently developed for complex flows such as the rotor-rotor and rotor-stator cavities found in gas turbine engines. The three-scale model is a logical extension of the previous two-scale k-ε model of Ko and Rhode (1990). Both multi-scale turbulence models are presented and assessed via comparison with measurements for possible adoption in future cavity computations. A single computer code solving the 2-D axisymmetric Navier-Stokes equations with a “switch” for selecting among the various turbulence models being compared was used. It was found for both cavity cases that the three-scale model gives a marginal improvement over the two-scale model. Further, both multi-scale models give a substantial improvement over the standard k-ε model for the rotor-stator case, especially in the near-wall region where different eddy sizes are found. However, the feasibility of using a multi-scale model for the rotor-rotor case is unclear since it gives improved values over the standard high-Re model in some regions but worse values in other regions.

In addition, the solutions provide enhanced insight concerning the large changes in flow pattern previously photographed in the rotor-rotor case as rotation increases. In particular, it is shown how: (a) the number of recirculation zones increase with increasing rotation rate and (b) the recirculation zones decrease in size with a decreasing G ratio.
Effect of Cyclic Loading on the Creep Performance of Silicon Nitride
Authors: Wereszczak Andrew A. , Ferber Mattison K. , Kirkland Timothy P. , Lin Chih-Kuang J.
Published: February 2015

Tension-tension cyclic fatigue tests (triangular waveform, σmax = 100 MPa, R = 0.1) were conducted on hot isostatically pressed (HIPed) silicon nitride at frequencies spanning several orders of magnitude (5.6×10−6 to 0.1 Hz or 10−3 MPa/s to 18 MPa/s) at 1370°C in air. The amount of cyclic creep strain was found to be a function of the frequency or stressing rate with greater strains to failure observed as the frequency or stressing rate decreased. The total strain was viewed as the sum of elastic, anelastic (or transient recoverable), and plastic (viscous or non-recoverable) strain contributions, after the empirical Pao and Marin model. The plastic strain was found to be the dominant component of the total creep and was unsatisfactorily represented by the Pao and Marin model. To circumvent this, a time exponent was introduced in the plastic strain term in the Pao and Marin model. This modification resulted in good correlation between model and experiment at the slower frequencies examined but over-predicted the cyclic creep strain at the faster frequencies. The utility of using the modified Pao and Marin model to predict cyclic creep response from static creep and strain relaxation tests is described.
Benefits of Compressor Inlet Air Cooling for Gas Turbine Cogeneration Plants
Authors: De Lucia Maurizio , Lanfranchi Carlo , Boggio Vanni
Published: February 2015

Compressor inlet air cooling is an effective method for enhancing the performance of gas turbine plants. This paper presents a comparative analysis of different solutions for cooling the compressor inlet air for the LM6000 gas turbine in a cogeneration plant operated in base load. Absorption and evaporative cooling systems are considered and their performance and economic benefits compared for the dry low-NOx LM6000 version. Reference is made to two sites in Northern and Southern Italy, whose climatic data series for modeling the variations in ambient temperature during the single day were used, to account for the effects of climate in the simulation. The results confirmed the advantages of inlet air cooling systems. In particular, evaporative cooling proved to be cost-effective, though capable of supplying only moderate cooling, while absorption systems have a higher cost but are also more versatile and powerful in base load operation. An integration of the two systems proved to be able to give both maximum performance enhancement and net economic benefit.
Design Development and Implementation of a Compact 5000 SHP Gas Turbine Package for an Electromagnetic Gun System
Authors: Meher-Homji Feroze J. , Herrera Gustavo , Rech Ben
Published: February 2015

The Center for Electromechanics at the University of Texas in Austin, has developed a 9 Megajoule Electromagnetic gun system which will fire projectiles at hypervelocities of Mach 8. The compulsator (compensated pulsed alternator) is powered by a 5000 HP GE LM 500 aeroderivative gas turbine. This turbine and a 650 SHP Pratt and Whitney APU are mounted on a compact power skid. The APU drives lubrication pumps and the main variable displacement hydraulic pump for the starter and hydraulically operated heat exchanger cooling fans. The skid is a compact 12 ft by 12 ft by 2 ft deep aluminum and stainless steel structure. The fuel, lube and hydraulic tanks are rubber cells mounted inside compartments in the skid. The two turbines are mounted on top of the skid. The LM 500 turbine drives the pulsed alternator through a speed increaser gearbox. This paper details the innovative packaging designs and hardware and control system requirements. The design concepts used are different from the traditional approach because of severe constraints on weight, dimensions and abnormal performance requirements. Results of tests conducted are also provided.
Combustor Flame Sensor With High Temperature Electronics
Authors: Glasheen Wm. Michael , Cusack Deidre E. , Steglich Helmar R.
Published: February 2015

A high temperature solid state turbine flame sensor has been developed and is being tested for eventual use as a combustor performance sensor. It directly senses only the flame deep ultraviolet without any response to hot component infrared energy (> 700 nanometers); the dynamic range is large; and the response time is fast enough for combustor control, i.e., less than 200 milliseconds.

The sensor electronics operate up to 250°C and some detector performance data has been taken as high as 540°C as described by Cusack et al (1994). The design uses recently available SiC electronic components, other components specially tested for the application, and proprietary techniques of electronic component packaging. Specific experience in packaging turbine engine optical and temperature sensors is necessary for this unique high temperature electronic technology.

A test program for discrete components indicates what elements are available for this temperature range and prototype sensor data from both laboratory qualification tests and engine performance tests verify the design.
Enhanced Mixing of 2D Lobed Nozzles
Authors: Liu Huo-Xing , Wu Shou-Sheng
Published: February 2015

The jet axial velocity decay and velocity distributions of two 2D Lobed Nozzles (2DLN), and three baseline nozzles, one circular and two rectangular with different aspect ratios (AR), were measured and compared at low velocity (M0 <0.35) and ambient temperature conditions. The five nozzles have the same exit area. Test results show:

1) The jet axial velocity decay of the 2DLN may be characterized by three distinct regions; i.e., “potential core region”, where the jet axial velocity almost remains constant; “rapid decay region”, where streamwise and normal vortices play major roles for enhanced mixing; and, “smooth-down decay region”, where the mixing process is dominated by viscous shear layer spreading and small-scale turbulence.

2) The jet potential core length of the two 2DLN tested is only half to one-third that of the baseline rectangular nozzle (AR=4.37), and about one-fourth to one-sixth compared with the baseline circular nozzle. The length, in which the jet mixed with surrounding air is nearly uniform, is one to two times that of the 2DLN equivalent exit diameter, and depends on lobe design.
An Advanced Control System for Turbofan Engine: Multivariable Control and Fuzzy Logic (Application to the M88-2 Engine)
Authors: Garassino Alain
Published: February 2015

The search for better performance of present and future turbofan engine involves an increase on the number of variable geometries and thus of control loops.

As we can not or do not want to disregard the interaction between loops any more, the future control systems will therefore be multivariable. The aim of the architecture of multivariable control presented here is to optimize a performance index during transients.

This architecture consists of an inner loop which optimizes the performance index taking in account the limitations, an outer loop which brings the nominal steady-state offsets to zero and a trajectory which allows to take into account the topping schedule limitation.

This basic architecture can be improved by fuzzy supervisor.

Indeed, two control outputs are generated according to the description above:

- the first one optimizes the thrust and does not care very much about LP stall margin limitation,

- the second one optimizes again the thrust and strongly takes low pressure stall margin limitation into account.

The fuzzy logic then allows to do a compromise between these two control outputs according to the engine state.

Simulation results showing the efficiency of the method are given.
Integrated Turbine-Compressor Controls Retrofit for an Olefins Unit
Authors: Gaston John R. , Piercy W. Brian , Harclerode C. Scott
Published: February 2015

The Olefins Unit that is the subject of this case study has been operating for 25 years. Recently, the unit initiated a control system retrofit program to increase availability, save energy, and improve access to operating information. New control systems were installed on the ethylene, propylene and furnace gas compressor trains. The gas compression equipment consists of single and multi-case compressor trains driven by steam and gas turbines and electric motors.

Significant control system improvements were made to the turbine/compressor speed/load regulation and temperature limiting. The systems also execute “safety system” logic for process and machinery protection. In addition to integrated turbine compressor control, the strategy that incorporates all control functions for the entire compresor train, a new anti-surge algorithm is included. To meet more stringent availability requirements imposed by integration, a triple modular redundant (TMR) system structure is employed. The surge algorithm described in this paper accurately predicts where surge occurs, regardless of changes in gas composition and conditions (e.g., molecular weight, temperature, etc.), and allows the integrated controls to compensate accordingly. A PC workstation-based operator display is provided for enhanced operator awareness of machinery conditions. This paper describes the requirements and implementation of this new approach to control.
Endwall Heat Transfer and Aerodynamic Measurements in an Annular Cascade of Nozzle Guide Vanes
Authors: Spencer M. C. , Lock G. D. , Jones T. V. , Harvey N. W.
Published: February 2015

Aerodynamic and heat transfer measurements have been made on the hub and casing endwalls of an annular cascade of high pressure nozzle guide vanes. The measurements have been made over a range of engine representative Mach and Reynolds numbers and with large levels of freestream turbulence intensity.

The transient liquid crystal technique has been employed, which has the advantage of yielding full surface maps of heat transfer coefficient. Computational predictions and aerodynamic measurements of Mach number distributions on the endwall surfaces are also presented, along with surface-shear flow visualisation using oil and dye techniques. The heat transfer results are discussed and interpreted in terms of the secondary flow and Mach number patterns.
Enhancing Performance of Silicon-Modified Slurry Aluminides on Turbine Components Operating in Marine Environments
Authors: Berry David , Meelu Mehar Chand , McMordie Bruce G. , Kircher Thomas A.
Published: February 2015

A variety of coatings have been designed to protect turbine components from corrosion due to the combined effects of environmental contaminants, fuel impurities and elevated temperatures. The most effective of these systems rely upon formation of a protective alumina scale to act as a barrier between the gas path environment and the component.

Protection offered by these alumina-forming high temperature coatings is increased by a number of additive elements, including platinum and chromium, but silicon (Si) is found to be especially beneficial in coatings exposed to high concentrations of sulfur in marine environments. Silicon-modified slurry aluminides are shown to resist to both high temperature and low temperature hot corrosion on both nickel and cobalt alloys in marine service.

Laboratory tests show this corrosion resistance can be further enhanced by redistributing critical elements (particularly silicon) within the microstructure of the silicon-modified aluminide. The benefits of these changes are demonstrated in field engine trials.
High Temperature Strength of Large Size SC and DS Buckets for Industrial Gas Turbines
Authors: Sato M. , Kobayashi Y. , Matsuzaki H. , Tamaki H. , Yoshinari A. , Iijima K. , Fukui Y. , Kodama H. , Wada K.
Published: February 2015

This paper describes successful results of trial manufacturing of single crystal (SC) buckets, 235mm long, for industrial gas turbines. The bypass method was adopted for casting of the SC buckets. Directionally solidified (DS) buckets, whose size is the same as SC buckets, were cast without grain boundary cracking. The materials for the buckets are CMSX-4 for the SC buckets and CM186LC for the DS buckets. Applicability of these buckets was mainly evaluated by creep rupture tests. The degradation due to casting defects is negligible for both SC and DS buckets which achieve the aimed creep rupture strength for the 1500°C class industrial gas turbines, because these creep rupture strengths are similar to the cast to size (CTS) specimens. The other properties such as tensile strength, hot corrosion resistance, oxidation resistance and low cycle fatigue (LCF) were also obtained from the CTS specimens.
Advances in Laser Drilling of Turbine Engine Components
Authors: VanderWert Terry L.
Published: February 2015

The application of laser systems for drilling turbine engine components has continued to grow. New designs for components are being made as understanding of the process has increased and as capability of laser systems has grown.

Advances in process control have led to higher throughput and quality in automatic production. Greater understanding of the laser drilling process has led to improved methods for controlling the spatter and remelt that are characteristic of laser processing. Availability of high speed. PC based controls has facilitated high speed sensing of the component location for precise and repeatable positioning of laser drilled features.

This paper describes recent advances in laser drilling turbine engine components. Current capabilities of laser drilling are summarized.
Cascade Vortical Gust Response Including Steady Loading Effects
Authors: Henderson Gregory H. , Fleeter Sanford
Published: February 2015

A series of experiments are performed to investigate the effect of steady loading and separated flow on the unsteady vortical gust response of both low and high solidity blade rows, including the effects of airfoil camber. This is accomplished utilizing a unique single stage turbomachine research facility in which the flow is not generated by the blading but rather by an additional fan. This provides the ability to quantify the steady or mean performance of the stator row over a range of steady loading levels both with and without unsteady flow effects. In particular, for a particular mean stator angle-of-attack, the steady and mean aerodynamic performance are determined in a steady flow and also in an unsteady flow generated by a rotor composed of perforated plates at the same mean operating condition. This enables the stator vane row dynamic stall conditions to be identified. The unsteady aerodynamic response of both symmetric and cambered stator vanes configured as low and high solidity stator vane rows is then investigated over a range of mean angle-of-attack values, including attached and separated flows with dynamic stall.
Technology Benefits Estimation (T/BEST) for Aerospace Engine Technology Propulsion Systems: Life and Maintenance
Authors: Generazio Edward R. , Chamis Christos C.
Published: February 2015

A Technology Benefit Estimator (T/BEST) system has been developed to provide a formal method to assess advanced technologies and quantify the benefit contributions for prioritization. T/BEST may be used to provide guidelines to identify and prioritize high payoff research areas, help manage research and limited resources, show the link between advanced concepts and the bottom line, i.e., accrued benefit and value, and to credibly communicate the benefits of research. An open-ended, modular approach is used to allow for modification and addition of both key and advanced technology modules. T/BEST has a hierarchical framework that yields varying levels of benefit estimation accuracy that are dependent on the degree of input detail available. This hierarchical feature permits rapid estimation of technology benefits even when the technology is at the conceptual stage. T/BEST’s software framework, status, novice-to-expert operation, interface architecture, analysis module addition, key analysis modules are discussed. Representative example of T/BEST benefit analyses for life and maintenance is described in some detail.
An On-Line System for Heterogeneous Distributed Computing and Advanced Visualization of Test Cell Data
Authors: Clark David A.
Published: February 2015

In most turbine engine testing facilities, the tools and techniques of computational fluid dynamics (CFD) and advanced visualization have never been applied to facilitate (near) real-time analysis of the test hardware. New computer software technology has now been applied which allows server-to-client remote procedure calls (RPC), enabling supercomputers to be called from within the online test scanning program. Coupled with advanced visualization software and graphics workstations, it is possible to view the inside of a test while it is being conducted. Such capability can be as valuable to researchers in steering tests as X-rays are to doctors in diagnosing health.

This report presents results from a library of software for on-line visualization. Using this system, a full turbomachine (compressor) has been visually analyzed by interpolating pressure instrument rakes to give a full flow field view of the engine (compressor). All data values at each grid cross-section are non-dimensionalized and viewed at varying ranges of iso-distortion surfaces. Regions of low or high energy can be seen as they proceed through the compressor stages. A full range of capabilities are displayed for both pressure and temperature using computer animation techniques recorded to video. Such views are unique and may provide extra information to help understand flow phenomena such as inlet distortion and how it relates, for example, to stall margin.

CFD efforts are also described in conjunction with the use of RPC to supercomputers. A stream function meridional, 2D/quasi-3D solution to five blade rows is shown in context with rotating blade rows and shown on video. The value of the computer work is all generic and can be applied in almost any scientific area where on-line computer systems are used.
Ceramic Composites for Industrial Gas Turbine Engine Applications: DOE CFCC Phase 1 Evaluations
Authors: Corman Gregory S. , Heinen Jeffrey T. , Goetze Raymond H.
Published: February 2015

Conceptual design evaluations of the use of continuous fiber ceramic composite (CFCC) turbine shrouds and combustor liners in an industrial gas turbine engine were performed under Phase 1 of the DOE CFCC program. Significant engine performance improvements were predicted with the use of CFCC components. Five composite systems were evaluated for use as shrouds and combustor liners, the results of which are discussed with particular reference to Toughened Silcomp. Several current CFCC materials were judged to be relatively close to meeting the short term performance requirements of such a system. However, additional CFCC property data are required for significant component design optimization and life prediction, two key design steps that must be completed before ceramic composites can be utilized in large gas turbines.
F117–PW–100 Hybrid Ball Bearing Ceramic Technology Insertion
Authors: Miner J. R. , Dell J. , Galbato A. T. , Ragen M. A.
Published: February 2015

Results of an Advanced Research Projects Agency (ARPA) sponsored project to demonstrate the operational benefits of incorporating advanced structural ceramic ball elements into the F117–PW–100 aircraft gas turbine engine high rotor thrust bearings is described. This program consists of design, fabrication and experimental evaluation of candidate hybrid ball bearing designs in Pratt & Whitney and MRC Bearings test facilities. The bearing design criteria and development test conditions utilized for the project are compatible with the requirements of the F117–PW–100 engine system application. Two hybrid bearing designs were produced by analytically varying internal geometry features such as M–50 race curvatures and contact angles to optimize for the modulus of elasticity of the ceramic balls. One–and–one–eighth inch size CERBEC grade NBD 200 silicon nitride ceramic balls demonstrated integrity and a quadruple rolling contact fatigue life improvement versus state–of–the–art M–50 steel balls in single ball test rigs. Thermal performance data obtained in full scale bearing rig performance testing with one–hundred–seventy–eight millimeter size hybrid and all–steel baseline bearings shows comparable characteristics. The hybrid bearing displayed a distinct survivability benefit in bearing liquid lubricant starvation testing. Two dozen hybrid bearings will be fabricated for full–scale bearing rig endurance tests to be conducted in 1995–1996 as a prerequisite to validation in operating F117–PW–100 engines in 1996–1997.
Hybrid Ceramic Bearings for Difficult Applications
Authors: Dezzani Michael M. , Pearson Philip K.
Published: February 2015

The Torrington Company under contract from the Advanced Research Projects Agency (ARPA) has developed a hybrid bearing with improved properties for difficult applications. M50 and M50 NiL steel rings were nitrided to produce rolling contact raceway surfaces with hardnesses near Rockwell C 70. Rings were assembled with NBD-200 silicon nitride balls. Full scale bearing tests were run under conditions that included 150°C temperature, surface flaws created by hard particle contamination, partial EHD lubrication, and the sliding action of balls running under thrust loading. The hybrid bearings had longer life than all steel bearings and demonstrated resistance to the surface peeling mode of failure initiation. Higher strength of the rolling contact surfaces, high residual compressive stresses in the nitrided layers, and a more favorable action in ceramic to steel rolling contact are discussed as the reasons for improved performance of the hybrid over all steel bearings.
Predicting Steady State Temperature, Life, Skid and Film Thickness in a Greased Preloaded Hybrid Ball Bearing
Authors: Poplawski Joseph V. , Atwell David R. , Lubas Michael J. , Odessky Vladimir
Published: February 2015

This paper describes the use of the SHABERTH computer program supplemented with experimental temperature and skid data to quantify steady state bearing operation. Parametric studies on ball diameter and number, contact angle, curvature, grease type and preload are presented with their influence on contact stress, fatigue life, skid load, film thickness and inner and outer race temperatures. These results are compared for a steel vs. hybrid bearing set in a DB and DFSL mounting. The method presented can be applied to the design of other steel and hybrid ball thrust bearing systems.
“Snapping” Torsional Response of an Anisotropic Radially Loaded Rotor
Authors: Bently Donald E. , Goldman Paul , Muszynska Agnes
Published: February 2015

A rotor system with two orthogonal lateral and two angular (torsional) degrees of freedom is considered. The rotor has asymmetry of the lateral stiffness and is laterally loaded with a constant radial force and a rotating unbalance. Constant driving and load torques are applied to the rotor. The important part of the research includes an analysis of “snapping” action, when, during rotation, the rotor experiences a peak of torsional acceleration. This occurs when the “strong stiffness” axis of the anisotropic rotor passes under the axis of the sideload. The numerical simulation of the analytical model exhibits a “snapping” (accelerated) torsional response of the rotor at twice synchronous frequency (2 ×), and it is especially pronounced at 1 × and 2 × torsional resonances. The “snapping” response can initiate a rotor crack in the area of stress concentration, can stimulate existing crack propagation, and can be a cause of the coupling failure. The analytical results are obtained by the Averaging Method application. They confirm the numerical results and show the possibility of combination resonance occurrences. The synchronous dynamic stiffness for the frequency range around 1 × lateral resonance is analytically obtained. The specific shape of the quadrature dynamic stiffness component can serve as a shaft crack indicator and can be used for early detection of a lateral crack on the rotor.
Specification, Development, and Testing of the FT8-2 Dry Low NOx Control System
Authors: Bell Russell C. , Prete Thomas W. , Stewart Jeffery T.
Published: February 2015

This paper describes the specification, development and testing of the FT8-2 Dry Low NOx control system, and how the lean bum process requires an integration of the control system and combustion hardware. The FT8-2 digital fuel control system was developed to achieve the precise multi-zone fuel metering of both gas and liquid fuels, the calculation of combustor air flow necessary to achieve Dry Low NOx and the traditional governing/limiting control loops necessary for safe, stable engine operation.

The achievement of the system design goals was accomplished by the concurrent development of software Based fuel metering algorithms and fuel metering hardware. The fuel metering hardware utilizes an all electronic valve positioner, employing a combination of feedback and software to achieve closed loop control of actual fuel flow. Extensive testing under actual gas flow conditions and closed loop bench testing using a real time engine model and fuel system model was conducted to prove system operation and develop system transient response prior to Installation on the test engine. The setup and results of the flow testing and dosed loop testing are described.

The paper describes the control scheme used to apportion the gas fuel between combustion zones and how external conditions such as ambient temperature and fuel gas composition effect the apportionment.

The paper concludes with a description of the control system installation in the engine test cell and a review of engine test results.
Affordable Nacelle Technologies for Future Turbofans
Authors: Smith C. J.
Published: February 2015

Costs are playing an ever increasing role in determining what the next generation of aircraft and engines will be. In addition to deciding to what extent wing/engine integration or drag reducing laminar flow technologies can be employed etc, the economic impact on both aircraft operation and engines launch and development costs must be evaluated. SFC or fuel burn advantages are no longer dominant to the extent they used to be and for some apparently promising technology concepts the cost disadvantages out weight the aerodynamic advantages when both effects are transposed into aircraft direct operating costs. In addition, a simple metric has been evolved to rank different technology concepts and prioritize them in order to help determine the most deserving technologies for scarce development funds.
Nondestructive Evaluation of Thermally Shocked Silicon Carbide by Impact-Acoustic Resonance
Authors: Bemis Robert A. , Shiloh Klara , Ellingson William A.
Published: February 2015

Monolithic ceramics are under consideration as structural components for hot stage sections of gas fired turbine engines. In addition to manufacturing quality control, other important aspects for this application include life prediction modeling and time between engine overhauls. One non-destructive evaluation (NDE) method that provides information about material condition involves an analysis of resonant vibrations. In previous work by this general approach, changes in modal parameters have been related to bulk defect mechanisms such as microcracking due to thermal shock damage. In this work resonant vibrations from monolithic ceramic specimens were excited by an instrumented impact hammer and detected by a non-contact acoustic microphone over frequencies up to 100kHz. Computer based analysis of vibration signatures from test specimens allowed extraction of modal frequencies and damping constants. Downward shifts in detected resonant frequencies and increases in internal friction or (specific) damping capacity measurements were obtained from SiC cylindrical rings, and these measurements were shown to relate to thermal shock severity. This NDE method not only provides measurable parameters that could be used as an accept-reject criteria for inline process inspection, it also provides a means for tracking the mechanical integrity of in-service engine components to support life prediction modeling.
Final Report of the Key Technology Development Program for a Next Generation High Temperature Gas Turbine
Authors: Sato M. , Kobayashi Y. , Matsuzaki H. , Aoki S. , Tsukuda Y. , Akita E.
Published: February 2015

There is a strong demand for efficient and clean power generating systems to meet recent energy saving requirements and environmental regulations. A combined cycle power plant is one of the best solutions to the above.

Tohoku Electric Power Co., Inc. and Mitsubishi Heavy Industries, Ltd. have jointly developed three key technologies for a next generation 1,500°C class gas turbine. The three key technologies consist of (1) high temperature low NOx combustion system, (2) row I turbine vane and blade with advanced cooling schemes, and (3) advanced heat resistant materials, verified by HTDU (High Temperature Demonstration Unit).

This paper describes the results of the above mentioned 6 year joint development.
Installation of a Gas-Turbine/Electric Propulsion System in a 65 Foot Patrol Boat
Authors: Brown J. B. , Martino Nicholas F. , Stavenger William S. , Lee C. M.
Published: February 2015

This paper presents a descriptive summary of the significant features of a gas-turbine/electrical propulsion system as installed in a 65 foot patrol boat for test purposes.
Development of the Taurus 70 Industrial Gas Turbine
Authors: Rocha George , Saadatmand Mohammad , Bolander Gary
Published: February 2015

Solar Turbines Incorporated has developed the Taurus 70 gas turbine in response to growing market demands in the 7 MW size range. The simple cycle, two shaft engine is rated for 7.1 MW and 34% thermal efficiency at the ISO inlet condition. The product development strategy adopted for the Taurus 70 was to incorporate proven technology that has been demonstrated with the existing Taurus 60 and Mars engines. The final design configuration was influenced by the use of an uprated Taunts 60 compressor assembly to achieve thermodynamic cycle parameters similar to the Mars engines. The standard engine configuration also includes a dry, lean-premix, combustion system to provide a gas turbine with the lowest emission and highest simple cycle efficiency in its size class.

This paper describes the proven product technology, basic engine configuration and development test strategy involved in the development of the new Taurus 70 gas Turbine.
PEMS: Monitoring NOx Emissions From Gas Turbines
Authors: Hung Wilfred S. Y. , Langenbacher Fritz
Published: February 2015

Predictive Emission Monitoring System (PEMS) was developed in 1990 to provide continuous monitoring of NOx emissions from stationary gas turbines with minimum maintenance. This system will meet the Enhanced Monitoring requirements under Title V of the Clean Air Act Amendments of 1990 when these requirements are finalized. The PEMS has been well received by various United States federal, state and local environmental agencies. It has been certified in the state of Colorado, and accepted in Pennsylvania and Texas.

This paper reviews the Enhanced Monitoring requirements for gas turbine NOx emissions monitoring and discusses the technical background of the PEMS. The PEMS design is described, including inputs, outputs and operator interface. Experiences with some of the installed systems are presented.

The PEMS predicts NOx emissions from turbine control system inputs and measurements of ambient air conditions. The prediction algorithms are based upon a time tested NOx emission model for gas turbines. This model has successfully predicted all measured NOx emission phenomena from gas turbines since 1974. The PEMS has been proven to be accurate within the 20% relative accuracy required for certification.

The PEMS operates unattended, with extremely low maintenance and high reliability. Record keeping and report generation are automated. The PEMS is typically integrated into the turbine control and condition monitoring system. The PEMS meets regulatory requirements with a much lower cost than a conventional Continuous Emission Monitoring System (CEMS).
The Basic Performance of Combined Cycles and Their Optimum Gas Turbine Pressure Ratios
Authors: Cai Ruixian
Published: February 2015

Based on the idea of the Comparison Method proposed by the author in 80’s, the expressions for efficiencies and power ratios between gas turbine and steam turbine of various typical combined cycles such as pressurized fluidized bed type, fully fired type and pure heat recovery types are derived. These expressions are very simple, physically clear and accurate enough. In addition, the values of optimum gas turbine pressure ratios for efficiency of these combined cycles are derived or discussed also. It is found that the optimum gas turbine pressure ratio for efficiency of pressurized fluidized bed type combined cycle can be expressed as the same as the optimum pressure ratio for specific output of the simple cycle gas turbine, and the optimum pressure ratios for efficiency of other combined cycles are only a little bit higher than the optimum pressure ratio for specific output of the simple cycle gas turbine.
Blading Vibration and Failures in Gas Turbines: Part A — Blading Dynamics and the Operating Environment
Authors: Meher-Homji Cyrus B.
Published: February 2015

Blades account for as much as 42% of failures in gas turbines. This paper provides a practical treatment of the subject taking into account the complex nature of blading problems, influence of the operating environment, design factors and maintenance practices. Blading failure modes such as fatigue, environmental attack, creep, erosion, and embrittlement are addressed along with a synopsis of design tools to review blade reliability. Peripheral issues affecting blade integrity such as fuel and blade quality control are addressed. The Appendix provides applicable tools and formula that can be used by gas turbine users for design review and troubleshooting.
Advantages of Non-Metallics in Satisfying Criteria for Combined Cycle Expansion Joints
Authors: Brown Thomas R.
Published: February 2015

Increased worldwide power demand, coupled with clean air requirements, has created a worldwide surge in single cycle and combined cycle Gas Turbine installations. These new Gas Turbines are often large megawatt facilities installed as base load units, which increases the need for component reliability. Today, high reliability in Expansion Joints can be achieved as a result of design criteria developed from new product components and in-service experience.
A New Technique to Repair Localised Coating Defects for Gas Turbines Blades and Vanes
Authors: Guerreschi U. , Rebora E. , Gandini E.
Published: February 2015

The protection against corrosion and oxidation of the blades and vanes of gas turbines has been successfully obtained by depositing overlay coatings of MCrAlY with vacuum plasma spray (VPS) technique. However it is necessary to qualify repair processes, even for localised coating defects produced during the manufacturing process or after service.

Ansaldo and Atla have developed a technique to repair such localised defects.

This process consists in:

• localised stripping with two different techniques,

• depositing new coating on the removed zone by plasma spray with special device,

• diffusing of the new coating with vacuum thermal treatment,

• non destructive evaluating to examine the repaired zone.

This process guarantee good quality with economical advantages comparing with the traditional method which removes all the coating and repeats the VPS process.
GE LM2500 Gas Turbine Enters Commercial Marine Service in Aquastrada Class Ships
Authors: Vincent Charles T. , Weber Rolf
Published: February 2015

This paper reviews the highlights of the first two seasons of commercial operation of GE LM2500 gas turbines installed in the Aquastrada class of fast ferries. The ships’ total propulsion systems were supplied and packaged by MTU-Friedrichshafen for this first commercial marine application of the LM2500 gas turbine. Problems encountered and lessons learned are presented as part of the paper.
ICR Gas Turbine Update
Authors: Harmeyer Jerome E.
Published: February 2015

The Intercooled, Recuperated (ICR) marine gas turbine development program is a U.S. Navy program to design, develop, and qualify an engine for propulsion of future surface ships. This paper provides a brief description of the program objectives, technical requirements, design overview, and status of development program and the test program currently underway. The engine system being developed is designated the WR-21 and is being designed in accordance with a detailed technical specification issued by the U.S. Navy.
Theory Versus Experiment for the Rotordynamic Coefficients of an Interlocking Labyrinth Gas Seal
Authors: Elrod David A. , Pelletti Joseph M. , Childs Dara W.
Published: February 2015

Experimental results for the rotordynamic coefficients of an interlocking, compressible flow, labyrinth seal are presented. Tests were conducted at supply pressures out to 18.3 bars and rotor speeds out to 16,000 rpm. Seal back pressure was controlled to provide four pressure ratios at all supply pressures. Inlet guide vanes were used to provide fluid prerotation at the seal inlet. The experimental results are compared to the predictions of the bulk-flow, turbulent, one-control-volume, perturbation analysis of Scharrer (1988). The results show that the direct stiffness is negative but small, and is predicted well by theory. At high rotor speeds, the experimental cross-coupled stiffness is negative (stabilizing for forward whirl) for all values of fluid prerotation. Theory predicts positive (destabilizing for forward whirl) cross-coupled stiffness for high fluid prerotation, and overpredicts the direct damping of the seal. In general, the net stabilizing effect of the seal, as indicated by the whirl frequency ratio, is predicted well.
Inlet Guide Vane Wakes, Including Rotor Effects
Authors: Johnston Robert T. , Fleeter Sanford
Published: February 2015

A series of fundamental experiments are directed at the acquisition and analysis of data defining forcing functions generated by an inlet guide vane (IGV) row, including interactions with the downstream rotor, for application to turbomachine forced response design systems. The research fan facility is comprised of an IGV row upstream of a rotor. IGV-rotor axial spacing is variable, with the IGV row able to be indexed circumferentially, thereby allowing measurements to be made across several IGV wakes. With an IGV relative Mach number of 0.29, measurements include the IGV wake pressure and velocity fields for three IGV-rotor axial spacings. The decay characteristics of the IGV wakes are compared to the Majjigi and Gliebe empirical correlations. After Fourier decomposition, a vortical-potential gust splitting analysis is implemented to determine the vortical and potential harmonic wake gust forcing functions both upstream and downstream of the rotor. Higher harmonics of the vortical gust component of the IGV wakes are found to decay at a uniform rate due to viscous diffusion.
Color Response Modification of Encapsulated Liquid Crystals Used in Rotating Disk Heat Transfer Studies
Authors: Camci Cengiz , Glezer Boris
Published: February 2015

The liquid crystal thermography can be successfully used in both transient and steady-state heat transfer experiments with excellent spatial resolution and good accuracy. Although most of the past liquid crystal based heat transfer studies are reported in the stationary frame, measurements from the rotating frame of turbomachinery systems exist The main objective of the present investigation is to determine the influence of rotation on the color calibration of encapsulated liquid crystals sprayed on the flat surface of a rotating aluminum disk. The investigation is performed for a rotational speed range from 0 rpm to 7500 rpm using three different liquid crystal coatings displaying red at 30, 35 and 45° C, under stationary conditions. An immediate observation from the present study is that the color response of liquid crystals is strongly modified by the centrifugal acceleration of the rotating environment. It is consistently and repeatedly observed that the hue versus temperature curve is continuously shifted toward lower temperatures by increasing rotational speed. The relative shift of the display temperature of the green can be as high as 7°C at 7500 rpm when compared to the temperature of the green observed under stationary conditions. The present study shows that relative shift of the liquid crystal color has a well-defined functional dependency to rotational speed. The shift is linearly proportional to the centrifugal acceleration. It is interesting to note that the individual shift curves of the green for all three liquid crystal coatings collapse into a single curve when they are normalized with respect to their own stationary green values. When the color attribute is selected as “intensity” instead of “hue”, very similar shifts of the temperature corresponding to the intensity maximum value appearing around green is observed. An interpretation of the observed color shift is made from a thermodynamics energy balance point of view.
Compressor Blade Boundary Layers in the Presence of Wakes
Authors: Cumpsty N. A. , Dong Y. , Li Y. S.
Published: February 2015

Transition on compressor blades is strongly affected by the wakes from upstream blade rows and by the strong adverse pressure gradients which tend to make the laminar flow to separate. This paper outlines the processes involved and illustrates them with measurements on two different types of blade. Of particular importance is the calmed region which follows any turbulent patch created by a wake; the calmed region resists transition from other disturbances and is able to overcome strong adverse pressure gradients without separation.
An Adaptive Perturbation Scheme for the Analysis of Mistuned Bladed Disks
Authors: Lin Chung-Chih , Mignolet Marc P.
Published: February 2015

In this paper, a novel perturbation technique is introduced for the determination of the forced vibration response of mistimed bladed disks. The proposed technique is adaptive in the sense that the level of approximation can be varied at will to accommodate any specificities of the tuned system and/or of the existing mistuning. This versatility of the proposed approach not only guarantees the reliability of the computed response but also leads to an excellent compromise between accuracy and computational effort. Numerical results are presented that demonstrate both the reliability of the computed response and the computational saving obtained by relying on the suggested perturbation technique as opposed to a straightforward steady state analysis.