bluuebunny/crossref_metadata_2025 huggingface dataset:
The Selection Process and Comparative Air Filter Performance Testing for Combustion Turbine Inlet Air Filters
Authors: Gidley Dave , Fritz Frederick M. , Yu Henry H. S.
Published: February 2015

Designers, OEM’s and Users have available to them a variety of standard air filter performance tests that can be used and currently are being used to specify inlet air filters for combustion turbines. These standard tests for the most part have been developed for the heating, ventilating and air conditioning industry using developed synthetic dust that simulates an air composition comprised of mostly recirculated air blended with outdoor make-up air. Other available standard tests and standard test dusts have been developed for diesel and gasoline powered engines. To our knowledge no standard air filter test method has been developed for filters to be used on combustion turbine air intakes using typical outdoor air. In our opinion, a standard test relating to 100% outdoor air, pressure drop rise over time, particle size and the particle size distribution most commonly recorded at combustion turbine installation sites would be beneficial in specifying and selecting the “best” filter for todays’ combustion turbine applications.

This paper will review and compare the various air filter tests currently used for combustion turbine inlet filtration selection and recommend an all-inclusive test standard that could be used in the future.
Predicting the Ultimate Performance of Advanced Power Cycles Based on Very High Temperature Gas Turbine Engines
Authors: Chiesa Paolo , Consonni Stefano , Lozza Giovanni , Macchi Ennio
Published: February 2015

It is well known that the history of gas turbine engines has been characterized by a very clear trend toward higher and higher operating temperatures, a growth which in the past 40 years has progressed at the impressive pace of approximately 13°C/year. Expected improvements in blade cooling techniques and advancements in materials indicate that this tendency is going to last for long time, leading to firing temperatures of over 1500°C within the next two decades.

This paper investigates the impact of such temperature increase on optimal cycle arrangements and on ultimate performance improvements achievable by future advanced gas/steam cycles for large-scale power generation.

Performance predictions have been carried out by a modified, improved version of a computer code originally devised and calibrated for “1990 state-of-the-art” gas/steam cycles. The range of performances to be expected in the next decades has been delimited by considering various scenarios of cooling technology and materials, including the extreme situations of adiabatic expansion and stoichiometric combustion.

The results of parametric thermodynamic analyses of several cycle configurations are presented for a number of technological scenarios, including cycles with intercooling and reheat. A specific section discusses how the optimum configuration of the bottoming steam cycle changes to keep up with exhaust gas temperature increases.

Calculations show that, under plausible assumptions on future technology advancements, within two decades the proper selection of plant configuration and operating parameters can yield net efficiencies of over 60%.
Large Combined Cycle HRSG Units Impact of Operating Considerations
Authors: Davis James S. , Steffen Mark , Thompson Anthony T.
Published: February 2015

Combustion turbine combined cycle plants continue to increase their role in worldwide power generation. Advanced combined cycle plants provide:

• high efficiency, often in excess of 50%

• short project schedules

• reasonable cost with minimum environmental considerations

For reliable operation of these facilities, it is essential the Heat Recovery Steam Generator (HRSG) design adequately address issues to include:

• required load rangeability

• transient operation, particularly start-up and shutdown

• low life cycle costs through high availability

This paper will address the more detailed aspects of the design configuration of large HRSG units.
Novel Approaches to the Repair of Vane Segments
Authors: Liburdi J. , Ellison K. A. , Chitty J. , Nevin D.
Published: February 2015

Thermal fatigue and craze cracks in a set of industrial vane segments were successfully repaired using an advanced LPM™ powder metallurgy process. Unlike conventional braze repair processes that rely solely on chemical cleaning to reduce the oxides, the LPM™ approach will physically remove the cracked or damaged areas in a manner similar to weld repairs. Consequently, large areas in the fillet radius, airfoils, and shrouds were mechanically prepared using conventional hand tools and then replaced with matching or alternate alloys in a powder metallurgy form. In this application, it was decided to use a stronger nickel-based IN738 alloy to repair the cobalt-based X-45 vanes. The patented LPM™ process uses conventional vacuum furnace heat treatments to produce dense, wide gap repairs that are well bonded to the parent metal. The results of the metallurgical and mechanical tests are presented, along with the observations during final inspection of the parts.
Overview of the WR-21 Intercooled Recuperated Gas Turbine Engine System: A Modern Engine for a Modern Fleet
Authors: Crisalli Anthony J. , Parker Michael L.
Published: February 2015

An overview description of the WR-21 Intercooled Recuperated Gas Turbine Engine System (ICR), currently being designed, built and tested for the U.S. Navy Surface Fleet is presented. The paper describes a development program which reduces development risk and results in a modem, affordable engine that reduces propulsion fuel costs by 30 percent. Major system components and their functions are outlined. Environmental and performance requirements are discussed together with trade-offs which lead to the current configuration as the best combination of cost, performance, reliability, maintainability and other attributes. Then the configuration design is presented. A key to the low-risk design is commonality with the commercial RB211 aircraft engine family. Inherited from the RB211 modular engine are the flexible ICR maintenance features. Modularity also allows mixing and matching to achieve a variety of engines ranging up to 37.3 MW (50,000 bhp). Finally, the ship integration aspects of the WR-21 are discussed.
The Effects of Scale Factor on the Aero-Thermodynamic and Infrared Radiation Performance of Naval Gas Turbine Exhaust System With Infrared Signature Suppression Device
Authors: Zhong Fangyuan , Dai Yu
Published: February 2015

On the basis of scale model tests in two different dimensions of marine gas turbine exhaust system with infrared signature suppression device, and in the light of similarity analysis and simplified numerical calculation, this paper discusses the effects of scale factor on the flow (flow resistance), temperature (of air-flow and tube wall), and infrared radiant (of exhaust plumes and exhaust uptake inner wall) fields of the exhaust system, and accordingly estimates the corresponding parameters of real ship exhaust systems as well as presents the magnitude of scale factor impacts and the recommended values for selecting the scale factor.
Impeller Rotating Stall as a Trigger for the Transition From Mild to Deep Surge in a Subsonic Centrifugal Compressor
Authors: Ribi Beat , Gyarmathy Georg
Published: February 2015

The present paper concerns the transition from mild to deep surge in a single stage centrifugal compressor using a vaned diffuser. Time-resolved measurements of the mass flow rate and the static pressures at various locations of the compressor were analyzed for different diffuser geometries and different operating points in the compressor map.

When the throttle valve was gradually closed at an impeller tip Mach number (Mu) above 0.4, the compressor showed first mild and then deep surge whereas at Mu=0.4 rotating stall was the dominant instability. This single-cell rotating stall was identified to be caused by the impeller.

During mild surge at higher Mach numbers the instantaneous flow and pressure traces showed that the overall flow at the stage inlet intermittently dropped below the critical value associated with the occurence of impeller rotating stall. Rotating stall appeared for a while but vanished as soon as the flow increased again. With further throttling, however, a threshold was reached at which rotating stall triggered deep surge. The results show that triggering only occurred if the flow deficiency causing rotating stall persisted long enough to permit the stall cell to make at least one or two revolutions.
Highly Loaded Tandem Compressor Cascade With Variable Camber and Stagger
Authors: Sachmann Johann , Fottner Leonhard
Published: February 2015

Highly loaded compressors, resulting from high pressure ratios and as few compressor stages as possible, need not only stators with variable stagger but furthermore with variable camber. By this means the blading can be adapted to the velocity triangles at off-design engine power setting leading to less sacrifice of the cycle efficiency and thus better engine power and improved fuel consumption.

Stators with variable stagger and camber can be accomplished by a tandem stator design where both stator blades can be adjusted independently from each other. In this investigation the usable range of such a tandem arrangement is measured and it is shown how the interference between the two blades can decrease losses in comparison with the two single blades of the tandem arrangement. Furthermore an inviscid flow calculation with a 2D-Euler-code shows the influence of this interference on the whole flow field.
Computational Structural Reliability Analysis of a Turbine Blade
Authors: Millwater H. R. , Wu Y.-T.
Published: February 2015

A system reliability methodology has recently been developed to determine accurately and efficiently the reliability of structures with multiple failure modes. This paper explores the computational implementation and application of the methodology through the structural system reliability calculation of a turbine blade subject to randomness in material properties. Failure due to creep, stress overload, and vibration is considered.

The methodology consists of a probabilistic system reliability analysis methodology integrated with finite element methods. The failure paths and failure modes are organized using a fault tree. An efficient method for assessing the reliability of a single failure mode, i.e., component reliability, is implemented as well as an efficient adaptive importance sampling method to assess the system reliability. A probabilistic structural analysis program, NESSUS, is used for the calculations.
Assessment of Remaining Life of a Control Stage Blade With Solid Particle Erosion Damage
Authors: Lam Tony C.-T. , McCloskey Thomas H. , Dewey Robert P. , Wawrzynek Paul
Published: February 2015

Unscheduled replacement of HP control stage blades due to solid particle erosion can be avoided if the structural integrity of the eroded blade has not been compromised, and the risk of an in-service failure is shown to be minimal. An analytical approach is presented which was used to evaluate whether blades with SPE damage could remain in service until the next convenient outage, in order to provide the plant engineers with specifications to assist them in determining the need for replacement based on further observed erosion damage. A three-dimensional fracture mechanics model was applied to study the propagation of cracks caused by erosion, and to assess when rupture was likely to occur. The results of the study are presented as a model for plant operators to use in scheduling the repair or replacement of HP blades.
Mechanical Design and Development of the RB211 Dry Low Emissions Engine
Authors: Summerfield Alan H. , Pritchard David , Tuson Dave W. , Owen David A.
Published: February 2015

To meet current and proposed worldwide emissions regulations without recourse to steam or water injection, the Industrial RB211 is being upgraded with a premix lean burn series staged combustion system. To incorporate this system a reverse flow cannular concept was adopted. This design retains the inherent proven modular construction and is suitable for retrofit.

This paper discusses the mechanical design analysis undertaken to ensure integration of the chosen solution into the RB211. Theoretical studies, combustion laboratory tests, aerodynamic scale and full size laboratory tests, together with extensive computer modelling were used to ensure the timely achievement of this design study.

To verify the design analyses a detailed full power test programme is in place, which is to be followed by field trials with a pre-production engine during 1993.
Repair Joints in Nickel-Based Superalloys With Improved Hot Corrosion Resistance
Authors: Ellison K. A. , Lowden P. , Liburdi J. , Boone D. H.
Published: February 2015

Sample repair joints in the nickel-base superalloys Inconel IN-713 and IN-738 were tested in the laboratory for Type I high temperature hot corrosion (HTHC) resistance at 900°C. The joints were produced using a conventional “wide-gap” brazing process, having a composition similar to IN-718, and a novel powder metallurgy repair technique LPM™ which in this study had a composition similar to alloy IN-738. Metallographic analysis of the resulting structures showed that the IN-718 based repairs, with and without simple aluminide coatings, had suffered extensive intergranular attack of the braze joints. However, the HTHC resistance of cast IN-718 was found to be excellent under identical test conditions. A comparison of the uncoated LPM™ repair joints and cast IN-738 revealed only subtle differences in the morphology of the corrosion products; the maximum depths of attack were similar in each case. Silicon modified aluminide coatings provided a slight reduction in the rate of attack for the IN-738 alloy, while simple aluminide coatings were less resistant to HTHC than the base alloy. Similar results were found for the LPM™ joints, however localized coating penetration was observed in the vicinity of boride particles embedded in the coatings. These differences in behaviour were interpreted with reference to the chemical and structural changes brought about by the use of varying levels of boron as a melting point depressant in the repair layers.
Turbine Lube Oil Mists: An Approach to the Generation Mechanism and an Investigation of Elimination Systems
Authors: Moliere M. , Gerome Y. , Truong L. S. , Tyack R.
Published: February 2015

Although valuable data now exists concerning lube oil mists, there seemingly lacked a global approach to (i) the basic processes that generate these mists, (ii) the real contribution of the oil vapors and (iii) the possible impacts on the lubricant in service. This paper discusses these aspects and also reports the findings of comparative elimination tests, which confirm the high performance of the glass microfiber technology.
Rotating Stall Acoustic Signature in a Low Speed Centrifugal Compressor: Part 2 — Vaned Diffuser
Authors: Lawless Patrick B. , Fleeter Sanford
Published: February 2015

An experimental study is performed to identify spatially coherent pressure waves which would serve as precursors to the development of an instability in the Purdue Low Speed Centrifugal Research Compressor when configured with a vaned diffuser. To achieve this, sensitive electret microphones were uniformly distributed around the circumference in the inlet and diffuser sections of the compressor. Fourier analysis of simultaneously sampled data from these microphone arrays was employed to identify the development of dominant spatial modes in the pressure field in the compressor. Three different diffuser geometries were investigated, resulting in three different instability pathologies. The rotating stall patterns observed in the compressor demonstrated propagation rates near impeller speed, and from one to four cells. These instabilities would classically be described as impeller stall, although the conditions appeared to arise simultaneously in the diffuser and impeller and were typically of similar magnitude in both locations. The excitation of the pressure waves, as indicated by spatial Fourier analysis, occurred five to fifteen impeller revolutions before small changes were evident in the raw microphone signals, and fifteen to twenty-five revolutions before the stall condition could be considered fully developed.
Piezoelectric Actuator-Active Vibration Control of the Shaft Line for a Gas Turbine Engine Test Stand
Authors: Palazzolo A. B. , Jagannathan S. , Kascak A. F. , Griffin T. , Giriunas J. , Montague G. T.
Published: February 2015

The Active Vibration Control (AVC) actuators which are discussed in the literature include piezoelectric, electromagnetic (contacting and non-contacting) and hydraulic. This paper presents results of an application of rotating machinery active vibration control (AVC) utilizing piezoelectric actuators. The paper gives actual test data on an aircraft engine test stand-shaft line, unlike the majority of related papers which are entirely theoretical or provide test results only on small, laboratory rotors. The AVC significantly suppresses vibration through two critical speeds of the shaft line.
A Dangerous Blade Vibration Phenomenon due to Unsteady Flow in Centrifugal Compressors
Authors: Jin D. , Hasemann H. , Haupt U. , Rautenberg M.
Published: February 2015

Dangerous blade excitation caused by unsteady flow in a high pressure/high mass flow compressor running in a low mass flow region has been investigated. Experiments were carried out for compressors with two different types of vaned diffusers. Blade vibration was measured with strain gages while simultaneous unsteady pressure was measured with fast response dynamic transducers. All measured results were analysed in detail so that an in-depth understanding of blade excitation mechanism can be obtained. Firstly, the compressor with a straight-channel vane diffuser at reduced rotational speed of 12,300 rpm in an unstable operation region was considered. The analysis of blade vibration and unsteady pressure showed an unusual excitation phenomenon. Besides a strong blade vibration frequency component near the first blade mode frequency excited by the rotating stall cells existed another dangerous resonance excitation with first blade mode component which dominated the blade vibration spectrum. A detailed pressure signal analysis indicated that this blade vibration was excited by a broad band pressure fluctuation due to a strong reverse flow occurring simultaneously with the rotating stall. Further reducing the compressor mass flow to the operation point shortly before surge, the rotating stall was significantly weakened while the reverse flow kept its intensity until surge occurred. In this operation region blades suffered throughout a violent excitation of resonance because of the strong reverse flow. These blade excitation phenomena were also found in the next experiment for the compressor with a cambered vane diffuser at higher rotational speeds of nred = 13,500 and 14,000 rpm. The maximum strain values of blade vibration were obtained to quantitavely estimate the danger of blade vibration caused by this excitation.
A Method of Digital Simulation for a Power Plant of Parallel Compound Dual Fluid Cycle Gas Turbine
Authors: Sun Yufeng , Wang Guoxe , Wang Qing , Lin Feng
Published: February 2015

This paper presented a set of mathematical models of the powerplant of parallel compound dual fluid cycle gas turbine, including the gas turbine and the heat recovery steam generator models in steady states and transient states. The authors did some simulating calculation and experimental works on this kind of power plant and obtained some useful results which were given in the paper. The results showed that this simulating method and this set of mathematical models could be used for designs and analyses of this kind of powerplant.
Endwall Effects at Two Tip Clearances in a Multistage Axial Flow Compressor With Controlled Diffusion Blading
Authors: Howard M. A. , Ivey P. C. , Barton J. P. , Young K. F.
Published: February 2015

Effects of tip clearance, secondary flow, skew and corner stall on the performance of a multi-stage compressor with controlled diffusion blading have been studied experimentally. Measurements between 1% and 99% annulus height were carried out in both the first and the third stages of a four-stage low-speed compressor with repeating-stage blading.

Measurements were obtained at a datum rotor tip clearance and at a more aerodynamically desirable lower clearance. The consequence of the modified rotor tip clearance on both rotor and stator performance are examined in terms of loss coefficient and gas exit angle. Stator losses close to the casing are found to increase significantly when the clearance of an upstream rotor is increased. These increased stator losses cause 30% of the stage efficiency reduction which arises with increased rotor tip clearance.

The deviation angles due to tip clearance from the multi-stage measurements are found to be similar to data from single stage machines with conventional blading which suggests that the unsteady flow phenomena associated with the multi-stage environment do not dominate the physics of the flow.
Computer-Aided FT8® RAM Analysis With On Condition Maintenance
Authors: Gaudette T. L. , Fraser Larry , Della Villa S. A.
Published: February 2015

Product reliability is influenced by both design and operating and maintenance practices. This means both the equipment manufacturer and the equipment’s operator have an impact on the systems’ achievable level of availability. Many variables such as application (utility or cogeneration) or service or duty cycle (peaking, cycling, or continuous duty), influence the expected availability/reliability of any unit. These variables and an understanding of the expected “economic demand” the unit must fill are important elements for a realistic and accurate reliability assessment. These variables also affect the expected maintenance costs associated with the unit.

Both the equipment manufacturer and the equipment operator have a vested interest in understanding and influencing this process. If the expected level of reliability/availability is a major requirement of the equipment owner/operator, then there must be an accurate understanding of how the reliability of the unit will be protected over the long term. Thus the unit first cost and life cycle cost can be estimated in a meaningful way.

The objective of this paper is to provide an assessment of proved design reliability along with the application of on condition maintenance of Turbo Power and Marine Systems’ (Turbo Power) most recent product introduction, the FT8. A computer-aided reliability analysis was made by Turbo Power with the support of Strategic Power Systems, Inc. (SPS), to demonstrate and support the suitability of the FT8 for both peaking and continuous duty applications utilizing on condition maintenance concepts. Consequently, the presentation of the RAM analysis is organized to assist in developing a complete and comprehensive understanding of the evolution of the product and to develop realistic RAM (Reliability, Availability, and Maintainability) and life cycle cost expectations.
Numerical Simulation of Tip Clearance Effects in Turbomachinery
Authors: Basson A. , Lakshminarayana B.
Published: February 2015

The numerical formulation developed here includes an efficient grid generation scheme, particularly suited to computational grids for the analysis of turbulent turbomachinery flows and tip clearance flows, and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, and is applicable to both viscous and inviscid flows. The values of these artificial dissipation is optimized to achieve accuracy and convergency in the solution. The numerical model is used to investigate the structure of tip clearance flows in a turbine nozzle. The structure of leakage flow is captured accurately, including blade-to-blade variation of all three velocity components, pitch and yaw angles, losses and blade static pressures in the tip clearance region. The simulation also includes evaluation of such quantities of leakage mass flow, vortex strength, losses, dominant leakage flow regions and the spanwise extent affected by the leakage flow. It is demonstrated, through optimization of grid size and artificial dissipation, that the tip clearance flow field can be captured accurately.
Ceramic Composite Attachments for Transmission of High Torque Loads
Authors: Brockmeyer Jerry W. , Straub Andreas C. , Krieg Eric J.
Published: February 2015

The use of fiber-reinforced ceramic matrix composites (FRCMC) for advanced turbopump (T/P) hot-section components offers a number of potential advantages relative to the use of ‘conventional’ materials. Among these advantages are reduced weight, enhanced life with reduced maintenance and improved performance achievable by increasing the turbine inlet temperature. FRCMC are, however, emerging materials, and their design and analysis present unique challenges. These composites have relatively low thermal expansion coefficients and low strain-to-failure characteristics, and they have nonlinear, anisotropic properties. These characteristics particularly complicate the design of attachments to mating metallic components within a T/P.

In an ongoing program*, an FRCMC stator and rotor for a rocket engine T/P are being developed for eventual ground test demonstration. The rotor attachment is designed to transmit high torque loads and provides an example of a design methodology which is compatible with current analytical capabilities. The approach used and described herein applies an empirically derived materials properties data base in combination with macromechanical analysis to reach a solution to this design challenge. This example demonstrates both the capabilities and the limitations of current design and analysis practices and provides direction for future development. A curvic coupling was chosen to meet the specific design goals and will be fabricated and tested to verify the design.
Detailed Heat Transfer Coefficient Measurements and Thermal Analysis at Engine Conditions of a Pedestal With Fillet Radii
Authors: Wang Zuolan , Ireland Peter T. , Jones Terry V.
Published: February 2015

The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modelled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution is compared to that calculated using an area averaged heat transfer coefficient. Metal temperature differences of 90K are predicted across the blade wall.
Transient Dynamics of Gas Turbine Engines
Authors: Ganji A. R. , Khadem M. , Khandani S. M. H.
Published: February 2015

Transient response of gas turbine engines depends on several parameters including engine type, components’ characteristics, and operational condition. This paper briefly describes the general methodology and approach for transient sensitivity analysis of various gas turbine engines, and the results of a computer program for analysis of the transient behavior of a single spool turbojet. Based on the method of intercomponent volumes, the general methodology applicable to transient analysis of any gas turbine based system has been developed. The method results in a set of stiff, time dependent non-linear ordinary differential equations (ODE) which can be solved by an appropriate ODE solver. The coefficients of the differential equations depend on the design and operational condition of the components represented by the component maps. The initial conditions of the ODE can be any steady state operating point of the engine. A steady state engine model provides these initial conditions. The program has the capability to match the components, and obtain a steady state operating point for the engine, accept a fuel protocol and predict the transient behavior of the engine. The program has produced satisfactory results for step, ramp and sinusoidal fuel inputs, as well as ramp variation in nozzle exit area.
Analytical Investigation of the Unsteady Aerodynamic Environments in Space Shuttle Main Engine (SSME) Turbines
Authors: Griffin Lisa W. , Rowey Richard J.
Published: February 2015

Unsteady computational fluid dynamics (CFD) analyses of the SSME alternate turbopump development (ATD) high pressure fuel turbopump (HPFTP) and high pressure oxidizer turbopump (HPOTP) turbine first stage blades are presented. Modal analyses of the first stage blades of each turbine indicated possible resonance problems in crucial operating ranges of the turbopumps. Unsteady aerodynamic simulations were conducted for each turbine to support further investigations of dynamic responses of the first stage blades. To appropriately characterize the aerodynamic environments in the turbines, unsteady, multistage, and multiblade calculations were required. Within this set of requirements, two approaches were taken. The first approach was to apply a two-dimensional (2D) Navier-Stokes code at each turbine midspan. Because the unsteady interactions were believed to be dominated by wake effects, this viscous approach was considered to be the more accurate. However, unsteady Navier-Stokes calculations have been shown to be computer intensive. Therefore, a second, quicker approach was undertaken. This approach was to apply, at each turbine midspan, an Euler code modified with a shear stress model that was calibrated with a set of turbine test data. Comparisons of time-averaged and transient pressure distributions, axial and tangential loads, and entropy contours calculated by each approach are presented. Discrepancies between results are noted and the relative merits of each approach are discussed.
Role of Predeformation in the Modification of Crack Tip Oxidation Resistance
Authors: Zheng D. , Rosenberger A. H. , Ghonem H.
Published: February 2015

The effects of predeformation on the high temperature, low frequency crack growth rate of wrought Alloy 718 is investigated. A series of crack growth experiments were carried out on specimens with different levels of deformation, in addition to specimens in the as received conditions. The experiments included continuous measurements of the crack length and its near field crack tip displacements, fractographic analysis of fracture surface facets and qualitative estimation of the slip density in the crack tip region. Furthermore the thickness of surface oxide layers formed during the fracture process was determined using Auger Spectroscopy. Results of this study show that predeformation enhances the crack tip resistance to environmental effects. This result has been analyzed on the basis of the concept that the deformation-associated slip line density controls the chromium oxide build up taking place along the effected grain boundaries in the crack tip region.
Fouling and Air Bleed Extracted Flow Influence on Compressor Performance
Authors: Cerri G. , Salvini C. , Procacci R. , Rispoli F.
Published: February 2015

Compressor performance deterioration with operating time has been analyzed and a method for the description of actual scaled map curves is discussed. These curves are obtained from actual operating point data from the monitoring system. Suitable scaling functions have been introduced. An inverse stage stacking technique solution has been adopted to obtain reference quantities to be used with generalized curves. In order to account for machine peculiar real phenomena, shape factors have been introduced for best fitting of given data.

An example is presented to discuss the deteriorated compressor map and the influence of mass flows extracted from bleeds.
ERCOFTAC: A European Research Network on Flow, Turbulence and Combustion
Authors: Hirsch Charles
Published: February 2015

The ERCOFTAC Association is formed by research groups from Academic, Governmental or Industrial institutions and Industry, actively engaged in the advancement of knowledge and applications of Flow, Turbulence and Combustion. The research activities are based on a double network structure, formed by the Pilot Centres (PC) and the Special Interest Groups (SIG). The PC’s are regional networks, generally of federative nature, formed by research and industrial groups within a geographical defined region. The SIG’s, on the other hand, are based on specific, well defined scientific topics. A Scientific Program Committee ensures coordination and guidelines. Several examples of activities and benefits of the ERCOFTAC framework are described in this presentation.
The Handling of a Variable Cycle Engine: The Selective Bleed Turbofan
Authors: Ulizar Inaki , Pilidis Pericles
Published: February 2015

The selective bleed turbofan is a two shaft, three compressor, variable cycle aircraft engine. At subsonic flight speeds it operates as a medium bypass turbofan. It becomes a low bypass turbofan when flying faster and is capable of supersonic cruise in the dry mode.

The aim of this paper is to indicate the limits of operation of this power plant and to suggest control schemes that will allow satisfactory handling throughout the flight envelope.

The performance benefits of the engine have been described in previous publications. Here its limits of operation are shown for two critical conditions, both at an altitude of 11km. The resulting scheduling requirements of the appropriate engine control variables are indicated. These are the low pressure compressor variable stators, the nozzle areas and the fuel flow. These parameters have to be controlled independently by a sophisticated system. The control strategies simulated indicate satisfactory engine handling over a wide flight envelope.
GETRAN: A Generic, Modularly Structured Computer Code for Simulation of Dynamic Behavior of Aero- and Power Generation Gas Turbine Engines
Authors: Schobeiri T. , Abouelkheir M. , Lippke C.
Published: February 2015

The design concept, the theoretical background essential for the development of the modularly structured simulation code GETRAN, and several critical simulation cases are presented in this paper. The code being developed under contract with NASA Lewis Research Center is capable of simulating the nonlinear dynamic behavior of single- and multi-spool core engines, turbofan engines, and power generation gas turbine engines under adverse dynamic operating conditions. The modules implemented into GETRAN correspond to components of existing and new generation aero- and stationary gas turbine engines with arbitrary configuration and arrangement. For precise simulation of turbine and compressor components, row-by-row diabatic and adiabatic calculation procedures are implemented that account for the specific turbine and compressor cascade, blade geometry, and characteristics. The nonlinear, dynamic behavior of the subject engine is calculated solving a number of systems of partial differential equations, which describe the unsteady behavior of each component individually. To unambiguously identify each differential equation system, special attention is paid to the addressing of each component. The code is capable of executing the simulation procedure at four levels which increase with the degree of complexity of the system and dynamic event. As representative simulations, four different transient cases with single- and multi-spool thrust and power generation engines were simulated. These transient cases vary from throttling the exit nozzle area, operation with fuel schedule, rotor speed control, to rotating stall and surge.
Development of a Dry Low NOx Combustor for 1.5 MW Gas Turbines
Authors: Kajita S. , Ohga S. , Kitajima J. , Kimura T. , Sasaki T.
Published: February 2015

To meet strict NOx regulations, Kawasaki Heavy Industries, Ltd. has been conducting a development program of dry, low-NOx combustion system since 1989. In a first step of the development program, a multi-burner type, can combustor has been developed. The test engine, with an output of 1.5 MW, demonstrated NOx emissions below 42 ppm at 15% O2. Following the engine performance tests, a 500 cycle endurance test and a 300 hour test at full load have been conducted to assess the reliability of the combustion system developed. During these tests, no mechanical durability issues arose.
Transonic Compressor Rotor Cascade With Boundary-Layer Separation: Experimental and Theoretical Results
Authors: Fuchs R. , Steinert W. , Starken H.
Published: February 2015

A transonic compressor rotor cascade designed for an inlet Mach number of 1.09 and 14 degrees of flow turning has been redesigned for higher loading by an increased pitch-to-chord ratio. Test results, showing the influence of inlet Mach number and flow angle on cascade performance are presented and compared to data of the basic design. Loss-levels of both, the original and the redesigned higher loaded blade were identical at design condition, but the new design achieved even lower losses at lower inlet Mach numbers.

The computational design and analysis has been performed by a fast inviscid time-dependent code coupled to a viscous direct/inverse integral boundary-layer code. Good agreement was achieved between measured and predicted surface Mach number distributions as well as exit-flow angles.

A boundary-layer visualization method has been used to detect laminar separation bubbles and turbulent separation regions. Quantitative results of measured bubble positions are presented and compared to calculated results.
Axial Compressor Fouling Evaluation at High Speed Settings Using an Aerothermodynamic Model
Authors: Haq Inam Ul , Saravanamuttoo H. I. H.
Published: February 2015

An aerothermodynamic model for a widely used industrial gas turbine engine compressor has been developed for studying in-situ compressor deterioration due to atmospheric fouling at high power settings. The model is developed using available geometrical dimensions of the compressor annulus. It is based on a mean line stage stacking method utilizing the basic turbomachinery equations. The model requires minimum inputs (mass flow, compressor speed, ambient conditions) from the instrument sensors and derives all the necessary information (compressor discharge temperature and pressure, isentropic efficiency, and power) that defines overall performance. The validity of the model was confirmed by comparing the results with the field tests and excellent agreement was achieved. The model is very economical in operation and is fully capable of detecting small changes that occur in the compressor due to fouling.
Combined Cycle HRSGs: Evaluation of Start-Up at Bottled-Up Conditions
Authors: Jolly Sanjeev , Gurevich Arkadiy , Pasha Akber
Published: February 2015

The prediction of boiler performance during start-up is critical, yet very little work has been done on this topic. The objective of this paper is to study the parameters characterizing the HRSG performance during start-up. These parameters are the rise of metal temperatures, steam pressure and water level in the drum. The extreme case was analyzed by assuming that all the openings were closed and there were no leakages. The heat transfer mechanism is discussed. The resulting governing equations were solved numerically. The results were then plotted as a function of time to illustrate the boiler performance. It is found that during the full-load condition of the gas turbine, the rise of metal temperatures, steam pressure and drum water level may be very high and thus subject the pressure parts to high thermal and pressure stresses.
Combined-Cycle Power Plants From Gas Turbines and Geothermal Source Integration
Authors: Bettocchi R. , Cantore G. , Negri di Montenegro G. , Peretto A. , Gadda E.
Published: February 2015

Geothermal power plants have difficulties due to the low conversion efficiencies achievable.

Geothermal integrated combined cycle proposed and analyzed in this paper is a way to achieve high efficiency.

In the proposed cycle the geothermal fluid energy is added, through suitable heat ecxhangers, to that of exhaust gases for generating a steam cycle.

The proposed cycle maintains the geothermal fluid segregated from ambient and this can be positive on the environmental point of view.

Many systems configurations, based on this possibility, can be taken into account to get the best thermodynamic result.

The perfomed analysis examines different possible sharings between the heat coming from geothermal and exhaust gases, and gives the resulting system efficiencies.

Various pressures of the geothermal steam and water dominated sources are also taken into account.

As a result the analysis shows that the integrated plant power output is largely greater than the total power obtained by summing the gas turbine and the traditional geothermal plant power output, considered separately.
Steam-Injected Gas Turbine Analysis: Part III — Steam-Regenerated Heat
Authors: Rice Ivan G.
Published: February 2015

Part III of this three-part paper examines steam ReGenerated Heat (RGH) (the residual steam sensible heat in the exhaust) for full (100%) steam-injected cycles. Parts I and II deal with Steam Rates and Steam-Cycle Efficiency respectively for a finite amount of steam injection. The following RGH analysis is based on the same approach used for large-utility steam turbines where one pound of throttle steam is passed through the steam system, and where enthalpy points are determined along the steam path. Accurate analysis of heat input, partial pressure expansion and heat-rejection enthalpy points are computed with steam-table software.
Probabilistic Analyses of Industrial Gas Turbine Durability
Authors: McClung R. Craig , Bernstein Henry L. , Buckingham Janet P. , Allen James M. , Touchton George L.
Published: February 2015

Probabilistic analyses of component durability have been developed for first stage buckets and nozzles in General Electric MS7001B and MS7001E industrial gas turbine engines. The analyses illustrate two different approaches to the development of probabilistic durability algorithms. The bucket algorithm is built around an existing thermal-mechanical fatigue life model which predicts average fatigue life as a function of local strains, dwell times, and constants in the fatigue model derived from laboratory testing. The fatigue model is linked to a fast probability integration method which calculates the uncertainty or variability in the response variable (life or damage) resulting from uncertainties or variabilities in the physical input variables. The nozzle cracking algorithm, in contrast, is built around a large data base of crack length sums for each vane on seven different nozzles from the field. The crack length sums on nozzles with similar numbers of fired starts were described with standard normal distributions. Extreme value distributions were then calculated analytically to describe the crack length sums on the single most heavily cracked vane per nozzle for different probability levels.
Thermodynamic Design Considerations for Steam-Injected Gas Turbines
Authors: Noymer Peter D. , Wilson David Gordon
Published: February 2015

Steam injection in gas turbines (steam raised from the energy of the exhaust and injected into one or more of the turbine stages) is an attractive option for cogeneration applications. From a thermodynamic point of view, however, there is little information available about methods for optimizing the use of the steam for injection into a gas turbine.

A computer model for an aeroderivative gas turbine is used to analyze the effect of steam injection on net power output and overall efficiency. The effects of varying the quantity of steam injected, the stations at which the steam is injected, and the temperature of the steam that is injected are assessed on a normalized basis, with the turbine-inlet temperature maintained from the simple-cycle design point.

The energy balance between the exhaust of the gas turbine and the flow of steam to be injected is the final constraint in selecting a steam-injected design point to maximize performance. For the engine in this study, increases of over 64% in net power output and 23% in overall efficiency can be achieved with roughly 16% steam/inlet air by mass, which represents all of the steam that can be produced by the exhaust stream for the given conditions.
Loss Mechanisms in Turbomachines
Authors: Denton J. D.
Published: February 2015

The origins and effects of loss in turbomachines are discussed with the emphasis on trying to understand the physical origins of loss rather than on reviewing the available prediction methods. Loss is defined in terms of entropy increase and the relationship of this to the more familiar loss coefficients is derived and discussed. The sources of entropy are in general: Viscous effects in boundary layers, viscous effects in mixing processes, shock waves and heat transfer across temperature differences. These are first discussed in general and then the results are applied to turbomachinery flows. Understanding of the loss due to heat transfer requires some discussion of cycle thermodynamics. Sections are devoted to discussing: Blade boundary layer and trailing edge loss, tip leakage loss, endwall loss, effects of heat transfer and miscellaneous losses. The loss arising from boundary layer separation is particularly difficult to quantify. Most of the discussion is based on axial flow machines but a separate section is devoted to the special problems of radial flow machines.

In some cases, eg attached blade boundary layers, the loss mechanisms are well understood, but even so the loss can seldom be predicted with great accuracy. In many other cases, eg endwall loss, the loss mechanisms are still not clearly understood and prediction methods remain very dependent on correlations. The paper emphasises that the use of correlations should not be a substitute for trying to understand the origins of loss and suggests that a good physical understanding of the latter may be more valuable than a quantitative prediction.
Optimization approaches to volumetric modulated arc therapy planning
Authors: Unkelbach Jan , Bortfeld Thomas , Craft David , Alber Markus , Bangert Mark , Bokrantz Rasmus , Chen Danny , Li Ruijiang , Xing Lei , Men Chunhua , Nill Simeon , Papp Dávid , Romeijn Edwin , Salari Ehsan
Published: February 2015

Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity‐modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state‐of‐the‐art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for improvements are discussed.