bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric Analysis of Small Scale Recuperated SOFC/Gas Turbine Cycles
Authors: Campanari Stefano
Published: November 2008

High temperature fuel cells are experiencing an increasing amount of attention thanks to the operation of several prototype plants, including an integrated Solid Oxide Fuel Cell (SOFC) and gas turbine power plant. Several authors estimate that the projected performances of such cycle have the potential of exceeding those of combined cycles, even at a small-scale size and with an extremely low environmental impact. However, performance estimates generally cover a very wide range, with predicted net electric efficiency spanning between 55 and 70%. The reasons for this excessive variety of results is generally hidden into the different quality assumptions which are made for the simulation of cycle components, as well as in the different level of detail considered for the design of the cycle layout. Starting with the detailed analysis of a 55% efficient plant layout proposed by a manufacturer, this paper investigates the effects of the most significant component quality features (efficiencies, losses) on small scale recuperated SOFC hybrid cycles performances, by mean of a sensitivity assessment. The work provides a comprehensive list of cycle components performance assumptions, frequently lacking in the available literature, easily allowing a future comparison with the work of other researchers. The aim of the work is to better focus the real performance potential of such cycles and to evidence the way to achieve the highest projected efficiencies; as a result of the simulations performed, two “advanced scenario” plant configurations are presented and discussed, based also on a second law analysis. The analysis includes a discussion of the effects of different pressure ratios on cycle optimization. Results show the possibility of exceeding 65% (LHV) cycle efficiency, depending on the quality level of cycle components.
Aerodynamic Design and Test Result Analysis of a Three Stage Research Compressor
Authors: Touyeras Armel , Villain Michel
Published: November 2008

The present paper describes the aerodynamic design and the test result analysis of a three-stage research compressor designed by Snecma Moteurs and tested at Ecole Centrale de Lyon, France. Firstly, the CREATE compressor, representative of the median or rear stages of modern high-pressure compressors, is presented. Particular emphasis is put on the CFD process employed in its design, which was based largely on three-dimensional Navier-Stokes multistage simulations. A brief description of the stage-by-stage matching achieved on the compressor is also presented. Test results available from traversal probes and laser velocimetry are compared with CFD simulation for overall compressor performance, stage-by-stage matching, and secondary flow effects. Prediction of the design and off-design compressor performance with 3D multistage tools is discussed. Finally, the prospects of new developments concerning the CFD tools and the evolution of the experimental compressor are also mentioned.
A CFD Investigation of IGV Flow Vectoring by Counter Flow Blowing
Authors: Harff Michael R. , Wolff J. Mitch , Copenhaver William W.
Published: November 2008

This paper describes a CFD analysis conducted to examine the impact of counter-flow blowing (CFB) on a row of uncambered, circulation-controlled (CC) inlet guide vanes (IGVs). In addition to a Coanda jet blown over the rounded trailing edge of the IGV blade, a second slot was placed on the pressure surface near the trailing edge to inject air upstream, i.e., in a counter-flow direction. Two blade shapes were modeled, each with four basic combinations of Coanda blowing and CFB, and the results were compared to flow turning and loss as modeled for a typical flapped IGV. The Advanced Ducted Propfan Analysis Code (ADPAC) was used to perform the 2-D simulations. While neither of the modified IGVs matched the 39-degree flow turning capability of the flapped IGV, CFB was predicted to augment flow turning by up to 5.3 degrees on the first geometry and up to 2.6 degrees on the second geometry. Cascade losses for the modified IGVs were more than twice as high as the flapped IGV, with the only exception being equivalent losses generated for Coanda-only blowing.
Thermoacoustic Stability of Quasi-One-Dimensional Flows: Part II — Application to Basic Flows
Authors: Prasad Dilip , Feng Jinzhang
Published: November 2008

In this paper, applications of a previously developed numerical formulation (Prasad and Feng 2004) for the stability analysis of spatially varying one-dimensional flows are investigated. The results are interpreted with the aid of a generalized acoustic energy equation, which shows that the stability of a flow system depends not only on the nature of the unsteady heat, mass and momentum sources but also on the mean flow gradients and on the inlet and exit boundary conditions. Specifically, it is found that subsonic diffusing flows with strongly reflecting boundary conditions are unstable, whereas flows with a favorable pressure gradient are not. Transonic flows are also investigated, including those that feature acceleration through the sonic condition and those in which a normal shock is present. In both cases, it is found that the natural modes are stable. Finally, we study a simplified ducted flame configuration. It is found that the length scale of the mean heat addition affects system stability so that the thin-flame model commonly used in studies of combustion stability may not always be applicable.
Redundant Networked Controls for Industrial Turbines
Authors: Schulke William W.
Published: November 2008

Increasing market pressure for industrial turbine controls that reduce cost of installation, increase availability, and reduce overall installation and commissioning time have driven systems in a new direction. This direction is away from complex and expensive triplex or TMR (Triple Modular Redundant) systems and towards dual redundant and networked control systems. Woodward’s core fuel and combustion control is currently being used in a networked system for GE’s LM2500 aeroderivative gas turbine packages. This networked control system utilizes redundant high-speed communications from the sequencer to fuel control. Packaging I/O is also distributed over redundant communications to localize wiring. The fuel control communicates to the gas metering valves and gas turbine variable geometry servo-valves to reduce wiring and installation time. This control system utilizes simplex CPU’s to save cost and duplex hardware and communications for availability. Expansion of this to full redundant CPU processing capabilities can also be achieved to add availability with some cost tradeoff. Woodward has also applied this full redundancy concept in the commercial marine GE LM2500 package applications. In addition to using network communications the core fuel control system is in itself networked, being “package” mounted. Mounting the fuel control on the package reduces the number of field installation wire terminations and the total length of wire used between the gas turbine and the fuel control. Having the main fuel control system mounted on the package allows the control to be wired and tested at the factory rather than at site. The use of network communications in gas turbine control applications has many advantages. Reduction in overall system cost, installation and commissioning time are the main advantages to using networked controls for gas turbines. System expandability and distributed processing are other advantages. Expanding this with hardware redundancy improves availability.
Experimental Investigation of Airflow and Spray Stability in an Air-Blast Injector of an Industrial Gas Turbine
Authors: Secareanu Andrei , Stankovic Dragan , Fuchs Laszlo , Milosavljevic Vladimir , Holmborn Jonas
Published: November 2008

The airflow field and spray characteristics from an air blast type of injector in an industrial gas turbine (GT) combustor geometry have been investigated experimentally and numerically. The flame in the current combustor is stabilized by a highly swirling flow. The stabilization of the flame is strongly dependent on the stability of the flow field out from the injector and into the combustor. Liquid fuel spray formation in the current type of injector is highly dependent on the airflow from the internal swirler, which supplies the shear to break the liquid film, and form the spray. Experiments were performed in a Perspex model of a 12° sector of the combustor with airflow scaled to atmospheric conditions. The geometry was comprised of the air section including the full primary zone, injector, combustor swirler, front panel and primary air jets. The flow field was visualized using particles that were illuminated by a laser sheet. Quantitative characterization was done using LDA. The airflow field was characterized by the mean flow pattern covering the full cross-section of the flow field and additional long time measurements at a number of locations in order to capture frequency content of the flow. Isothermal spray measurements were performed in an unconfined geometry including the injector, swirl generator and front panel. The spray uniformity was qualitatively investigated using video camera and quantitatively characterized by PDA. The studies of the flow field and fuel atomization (droplet size and density) under different conditions are summarized below.
CM 939 Weldable® Alloy
Authors: Harris Ken , Wahl Jacqueline B.
Published: November 2008

IN 939 alloy, developed by the International Nickel Co. in the late 1960s, is a unique 22% Cr hot corrosion resistant γ′ strengthened, cast nickel-base superalloy. It is widely used in industrial gas turbines for equiaxed vanes, vane segments and burner nozzles and is of interest to the aero turbine industry for LP and PT integral nozzles (vane rings) and high temperature turbine casings. However, IN 939 is considered difficult to weld repair without parent metal microcracking and can exhibit marginal ductility in heavy section castings. Cannon-Muskegon has developed a proprietary chemistry modified version of IN 939 alloy designated CM 939 Weldable®. Emphasis has been directed on optimizing aim chemistry and ultra high purity manufacture using CM-developed single crystal superalloy melting and raw material technology and subsequently on obtaining superior casting microstructure for improved weldability and mechanical properties. Alloy purity and heat cleanliness will be discussed, along with a simplified two-step heat treatment cycle, resulting in attractive microstructure, mechanical properties and repair weldability. Significant market interest has resulted in extensive vacuum casting experience throughout the gas turbine industry. Excellent results in terms of fluidity, casting cleanliness and minimal microporosity have been obtained without any hot tearing or hot cracking problems.
Engine Test and Post Engine Test Characterization of Self-Sealing Ceramic Matrix Composites for Nozzle Applications in Gas Turbine Engines
Authors: Bouillon Eric P. , Spriet Patrick C. , Habarou Georges , Louchet Caroline , Arnold Thibault , Ojard Greg C. , Feindel David T. , Logan Charles P. , Rogers Kimberly , Stetson Doug P.
Published: November 2008

The advancement of self-sealing ceramic matrix composites offers durability improvements in hot section components of gas turbine engines. These durability improvements come with no need for internal cooling and with reduced weight. Building on past material efforts, ceramic matrix composites based on either a carbon fiber or a SiC fiber with a sequenced self-sealing matrix have been developed for gas turbine applications. The specific application being pursued on this effort is an F100-PW-229 nozzle seal. Full design life ground engine testing has been accomplished with both material systems. The ground testing has demonstrated a significant durability improvement from the baseline metal design. Residual properties are being determined for both systems by extracting tensile and microstructural coupons from the ceramic matrix composite seal. Nondestructive interrogation showed no material degradation and was used as a guide in setting cutting diagrams. The results from this effort will be presented along with documentation from flight test efforts.
Thermoacoustic Modeling of a Gas Turbine Combustor Equipped With Acoustic Dampers
Authors: Bellucci Valter , Schuermans Bruno , Nowak Dariusz , Flohr Peter , Paschereit Christian Oliver
Published: November 2008

In this work, the TA3 thermoacoustic network is presented and used to simulate acoustic pulsations occurring in a heavy-duty ALSTOM gas turbine. In our approach, the combustion system is represented as a network of acoustic elements corresponding to hood, burners, flames and combustor. The multi-burner arrangement is modeled by describing hood and combustor as Multiple Input Multiple Output (MIMO) acoustic elements. The MIMO transfer function (linking acoustic pressures and acoustic velocities at burner locations) is obtained by a three-dimensional modal analysis performed with a Finite Element Method. Burner and flame analytical models are fitted to transfer function measurements. In particular, the flame transfer function model is based on the time-lag concept, where the phase shift between heat release and acoustic pressure depends on the time necessary for the mixture fraction (formed at the injector location) to be convected to the flame. By using a state-space approach, the time domain solution of the acoustic field is obtained. The nonlinearity limiting the pulsation amplitude growth is provided by a fuel saturation term. Furthermore, Helmholtz dampers applied to the gas turbine combustor are acoustically modeled and included in the TA3 model. Finally, the predicted noise reduction is compared to that achieved in the engine.
Fuzzy Logic Estimation Applied to Newton Methods for Gas Turbines
Authors: Martis Dan
Published: November 2008

This method, based on fuzzy logic principles, is intended to find the most likely solution of an over-determined system, in specific conditions. The method addresses typical problems encountered in gas turbine performance analysis and, more specifically, to the alignment of a synthesis model with measured data. Generally speaking, the relatively low accuracy of measurements introduces a random noise around the true value of a performance parameter and distorts any deteministic solution of a square matrix-based linear system. The Fuzzy Logic Estimator (FLE) is able to get very close to the real solution by using additional (pseudoredundant) parameters and by building the most likely solution based on each of the measurement accuracies. The accuracy — or “quality” — of a measurement is encapsulated within an extra dimension which is defined as fuzzy and which encompasses the whole range of values, between 0 (false) and 1 (true). The value of the method is shown in two examples. The first simulates compressor fouling, the other deals with actual engine test data following a hardware modification. Both examples experience noisy measurements. The method is stable and effective even at high level of noise. The results are within the close vicinity of the expected levels (within 0.2% accuracy) and the accuracy is about ten times lower than the noise level.
Local, Near-Field Mixing Augmentation Using Square Coaxial Jets
Authors: Bonnafous Samuel , Piffaut Victor , Choy Wai-Ho , Nikitopoulos Dimitris E.
Published: November 2008

Results from un-forced experiments in flows ensuing from circular and equivalent square coaxial nozzles with parallel sides are presented in this paper. The nozzles are contoured and are designed so that the hydraulic diameters of the internal flow passages are identical for both geometries. The flow experiments were conducted at a co-flow-jet Reynolds number of Re = 16,000 and inner-to-outer jet nominal velocity ratios of λ = 0, 0.5, 1.5. Axis switching, a phenomenon readily observed in single non-axisymmetric nozzles, is shown for the first time to occur in the square coaxial nozzles as well. Comparisons of the mixing regions of the flows from both geometries are made to examine mixing advantages when using square nozzle configurations. Comparisons of stream wise mean velocity fields measured on a center plane parallel to the square nozzle sides, on a diagonal plane of the square nozzle and the center plane of the corresponding circular nozzle, are presented and discussed. Axis switching is shown to be evident in the near-field shear regions for all velocity ratios, resulting in considerable mixing advantages. The spreading rates (and therefore mixing rates) of the outer mixing region of the square nozzles clearly exceed the spreading rate observed in the circular case on the central plane. Axis switching and improved mixing is also observed in the inner mixing region of the square nozzle. This work is relevant to coaxial nozzles for gas turbine combustor applications, although the study has been carried out in a scaled up geometry with respect to this application.
Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios
Authors: Saha A. K. , Acharya Sumanta
Published: November 2008

The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) of 1:1, 4:1, and 1:4 are numerically studied through the solution of the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The URANS procedure can resolve large-scale bulk unsteadiness, and utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The computations are carried out for a fixed Reynolds number of 25000 and density ratio of 0.13 while the Rotation number has been varied between 0.12–0.50. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers with multiple rolls in the secondary flow structures near the leading wall. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. At high rotation number, both the 1:1 and 4:1 AR cases exhibit loss of axial periodicity over one inter-rib module. The friction factor reveals an increase with the rotation number for all aspect ratio ducts, and shows a sudden jump in its value at a critical rotation number because of either loss of spatial periodicity or the onset of backflow.
Open Loop Control of Combustion Instability With a High-Momentum Air-Jet
Authors: Uhm Jong Ho , Acharya Sumanta
Published: November 2008

A new strategy for open-loop control of combustion oscillations using a high-momentum air-jet modulated at low frequencies is presented in this paper. The oscillations in the swirl-stabilized spray combustor of interest are dominated by an acoustic mode (235 Hz) with a low frequency (13 Hz) bulkmode (of the upstream cavity) oscillation superimposed. The most effective strategy for control is shown to be achieved through the use of a new concept which utilizes a high-momentum air-jet injected directly into the region of flame dynamics. It is shown that with a low frequency modulation (15 Hz) of the high momentum air-jet, the pressure oscillations can be reduced significantly (by a factor of nearly 10). Square wave modulation is shown to be considerably more effective than sine-wave modulation. These results are extremely promising since high bandwidth actuation is not required for effective control.
Real Time Flutter Monitoring System for Turbomachinery
Authors: Dhadwal Harbans S. , Radzikowski Marc , Strukov Dmitri , Kurkov Anatole
Published: November 2008

A fiber optic laser probe based system is described for real time monitoring of flutter in rotating turbomachinery. The digital flutter monitoring system is designed for continuous processing of blade tip timing data at a rate of 10 MB/s. A USB2.0 interface provides un-interrupted real time processing of the data. The blade tip arrival times are measured with a 50 MHz bscillator and a 24-bit pipelined counter architecture. A graphical user interface provides on-line interrogation of any blade tip from any light probe sensor. Alternatively, data from all blades can be superimposed into a single composite scatter plot displaying the vibration amplitude of each blade. A hardware platform was developed to simulate a seventy two bladed turbine operating at 15,000 rpm. Blade tip responses from three light probes were generated in an infinite loop, providing reproducible and controlled conditions for testing the vibration monitoring system. Time interval measurements were consistently made with a single count error in a 24-bit count vector. Real time testing was done using a two blade rotor mounted in an evacuated chamber at the Spin Rig Facility at the NASA Glen Research Center. The shaft in this facility was suspended by two radial magnetic bearings and the nonsynchronous vibration was communicated to the blades through the magnetic bearing. The shaft motion was much smaller than the blade vibratory amplitude, realistically simulating flutter vibrations. Nonsynchronous vibratory amplitudes for the first mode were of the order of twenty mils and for the second mode of the order of a few mils.
High Pressure Spray Diagnostics Facility for Development and Evaluation of Aero-Engine Atomizer and Swirler Assemblies
Authors: Lai Mark K. , Freeman William G. , Yankowich Paul R. , Bryant Joe D. , Walterscheid Peter
Published: November 2008

Recently, Honeywell has developed an unique industry capability of a high-pressure spray diagnostics facility to characterize 3D spray structures. Capability unique to Honeywell is highlighted. Major issues in measurement procedures under laser, industrial, and high-pressure environments and in acquisition and post-processing of 3D imaging are discussed. To characterize 3D spray, methodologies are described to quantitatively analyze vertical and horizontal spray images and to develop correlations of atomizer performances with engine (or rig) test data. Applications of this facility for a dual-orifice atomizer with an air shroud, a piloted airblast atomizer, and an assembly of a Lean-Direct Injection (LDI) atomizer with premixed swirlers are presented. The results indicate that, to have good correlations of atomizer performance with engine (or rig) test data, atomizers must be tested under high-pressure conditions and characterized three-dimensionally. Capabilities are shown to provide critical information for design and development of combustion systems.
An Augmented Multipoint Estimation Technique for Gas Path Analysis Model Generation
Authors: Sko¨lde Patrik , Wallin Markus , Gro¨nstedt Tomas
Published: November 2008

A generic gas turbine simulation tool has been used for the development of a gas path analysis model for the PW100 engine. The suggested method estimates the performance parameters of an individual engine model based on overhaul test cell acceptance data of a well-serviced engine. The method makes simultaneous use of data from readings collected at three different power levels, by selecting a preliminary design model, which gives optimal off-design agreement with the recorded data. Measured thermodynamic data has been augmented with the use of low pressure and power turbine areas to maximise the use of available information. Nine performance parameters are estimated from, in total, 32 thermodynamic and geometric data recorded at the three different power levels. The resulting model is subsequently used for fault detection for the same engine. The method was tested on two data sets, representing a well serviced and a faulty condition. The known low-pressure turbine nozzle fault was successfully detected based on the output from the gas path analysis tool. The analysis was repeated for the three single power settings. Analysis based on all three operating points produced a marginal improvement in diagnostic capability, compared to the best single point case and substantially better than the worst single point case.
Adiabatic and Overall Effectiveness for a Film Cooled Blade
Authors: Albert Jason E. , Bogard David G. , Cunha Frank
Published: November 2008

Laboratory studies of film cooling performance for turbine section airfoils typically quantify adiabatic effectiveness and occasionally the heat transfer coefficient for the film cooling configuration. In this study the normalized airfoil metal surface temperatures are obtained directly by using a test model that has a material conductivity scaled to the external and internal heat transfer coefficients so that the Biot number for the model is similar to that for the actual airfoil. These results provide an experimental test case of the conjugate heat transfer involved in turbine airfoil cooling. In this study, conventional adiabatic effectiveness and the overall cooling effectiveness (normalized surface temperature for the matched Biot model) were measured for a generic blade leading edge using three rows of shaped holes. Distinct differences were found between the adiabatic effectiveness and overall cooling effectiveness. Also included is a practical application of this experimental method for which the degradation of overall cooling effectiveness due to a plugged cooling hole is examined.
Modeling Soot Formation in a Stirred Reactor
Authors: Colket Meredith B. , Hall Robert J. , Stouffer Scott D.
Published: November 2008

The formation of carbonaceous particulate matter and polycyclic aromatic hydrocarbons has recently been studied (Stouffer, et al, 2002 and Reich, et al, 2003) in a toroidal well-stirred reactor using ethylene as the fuel, with and without the additive ethanol. In the later work, modeling of the gas-phase species was performed and compared to the experimental trends. In the present study, a modified version of the CHEMKIN-based code for ‘perfectly stirred reactors’ has been used to model soot particle formation, including computations of particle mass and smoke number. Detailed soot formation routines have been extracted from Hall and coworkers (1997), who modeled soot formation in flames. Experimental trends are accurately modeled by the code with quantitative accuracies generally within 50%. The importance of accurate knowledge and control of reactor temperature is discussed. In fact, scatter in the original experimental study can be largely attributed to inadequate temperature control. Speculation for differences between the model and experiment are offered while additive effects and the well known ‘soot bell’ are discussed. For the initial experiments examined by Stouffer et al, the effect of the additive is largely due to temperature differences.
Gas Turbine and Generator Test Experience in Support of the Advanced Hull Form Inshore Demonstrator (AHFID)
Authors: Carr Roger J. , Lison Denis , Willett Fred T.
Published: November 2008

This paper describes a test program designed to assess the suitability of a TF40-based gas turbine genset for use in the Advanced Hull Form Inshore Demonstrator (AHFID). An overall description of the test program and its objectives is given. Test results are presented. The relevance of the test to the greater program goal of demonstrating the viability of rimdriven propulsion technology is discussed. The genset demonstration test was successfully completed in 2003. The package performed as designed and met all test objectives.
Integrated Process for CFD Modeling and Optimization of Gas Turbine Combustors
Authors: Dudebout Rudolph , Reynolds Bob , Molla-Hosseini Khosro
Published: November 2008

Honeywell Engines, Systems & Services has developed the Advanced Combustion Tool (ACT) CFD process to rapidly analyze the performance of a combustor configuration from a given fuel injector, CAD geometry and engine cycle information. ACT integrates and streamlines the traditional steps of generating and specifying geometry, mesh, physical models, boundary conditions, initial conditions, convergence criteria and post-processing. Notably, ACT utilizes several key features to reduce cycle time and improve fidelity in the CFD analysis process: a high-pressure spray diagnostic facility to obtain fuel droplet boundary conditions, feature-based macros to parametrically automate geometry and mesh generation, preprocessors to simplify and standardize boundary condition and physical model specification, and post-processors to provide graphical and analytical responses. This integrated process for CFD modeling and optimization is the subject of this paper. A demonstration of this process is the numerical prediction of the TFE731-60 combustor flowfield on a 30 degree sector model compared to experimentally measured results.
An Evaluation of Advanced Humid Air Turbine System With Water Recovery
Authors: Hatamiya Shigeo , Araki Hidefumi , Higuchi Shin’ichi
Published: November 2008

The AHAT (Advanced HAT) system can be used for single shaft gas turbines without redesigning them and it gives a similar effect as intercooling by using suction air atomization. In this paper, two basic experiments with a spray nozzle, simplified humidifier and water recovery were carried out. A compact heat exchanger for humidified gas turbines could be realized by using the spray nozzle without significant pressure loss. In addition, a big effect was found in the efficiency improvement when water atomization into the compressor was combined with the regenerative cycle. The AHAT system had high efficiency, 5% higher compared with the mid-size combined cycle.
Life-Refurbishment of Service-Degraded Gas Turbine Buckets
Authors: Yoshioka Yomei , Saito Daizo , Ishibashi Kazutoshi , Ishii Junji , Izumi Atsuhiko , Aburatani Yasuhiro , Itou Akihiro , Kagiya Yukio , Watanabe Hirotaka , Hyakudome Seiichi
Published: November 2008

Various methods have been developed, and used in practice, to reduce the maintenance cost of gas turbine hot parts by extending the replacement life. The life-refurbishment process by Hot Isostatic Pressing (HIP) is one of our accomplishments for the buckets retired due to the scheduled life and was confirmed to rejuvenate the microstructures and the tensile, Charpy impact, creep and low cycle fatigue properties to a condition equivalent to or even better than the new ones under the development program. According to above mentioned accomplishments, a number of HIP refurbished buckets were reinstalled in a Chubu Electric Power Co. Inc. (CEPCO) 1100°C-class gas turbine rotor on December 1999 and operated successfully for 2 years under the joint program. Those buckets also served for destructive and non-destructive evaluations after operation. From those tests, we reconfirmed the reliability of the HIP refurbished buckets and also validated that the life-consumption rate was the same as new ones.
Numerical Study of the Effect of Blowing Angle on Cooling Effectiveness of an Effusion Cooling
Authors: Hu Yaping , Ji Honghu
Published: November 2008

The paper numerically investigates the influences of the blowing angle α of coolant flow on the cooling effectiveness of effusion cooling of a plate. Nine cases were studied which cover three blowing angles of α = 30°, 60°, 90° and for each angle three blowing ratios of M = 0.5, 1.0, 2.0 are calculated, respectively. The results show that with the increase of α the cooling effectiveness reduces for all the calculated cases. For the cases of α = 30° and 60° the distribution of cooling effectiveness η along the whole plate are very similar for any given blowing ratio, especially when M = 1.0 and 2.0. Whereas for the cases of α = 90°, the distributions of cooling effectiveness are quite different from other two blowing angles for a given blowing ratio, especially for M = 1.0 and in the trailing region of the plate. Although the cooling effectiveness of the cases with α = 90° for any given blowing ratio is the worst one among the three angles (α = 30°, 60°, and 90°) stated, its absolute value is still quite high comparing to the conventional film cooling.
Advances in Thermal Barrier and Abradable Ceramic Coatings by Chemically Bonded Composite Sol-Gel Technology
Authors: Fu Junlong , Yang Quanzu , Troczynski Tom
Published: November 2008

The novel technology of chemically bonded composite sol-gel (CB-CSG) coatings has been developed at UBCeram. This essentially “ceramic paint” technology operates with CSG slurries formulated to contain a sol-gel “glue”, e.g. hydrated alumina sol, and inert filler, e.g. alpha alumina or yttria stabilized zirconia (YSZ), suspended in water or other solvent. The CSG is spray-deposited on metallic surfaces, and heat-treated at about 300°C to partially dehydrate the gel-derived hydroxides. CSG film is subsequently chemically bonded (CB) through reaction of the gel-derived active alumina with metal phosphates, such as aluminum phosphate. Effectively, the microstructure of such coating includes a porous network of refractory phosphate bonded alumina and/or YSZ. The vol% of porosity can be easily controlled in 5–60% range by adjusting spray conditions. Structural integrity (e.g. hardness and “abradability”) of the coatings can be controlled through the degree of chemical bonding treatment given. The spray-heat treat operations can be repeated to build porous films in excess of 1 mm thickness. The paper reviews the basics of CB-CSG technology. This research has focused on achieving the unique, strain-tolerant columnar microstructure of the coatings, somewhat resembling that of TBC by EB-PVD. Explanation of the process parameters controlling development of the columnar microstructure of the coatings is attempted.
Clocking Effects in a 1.5-Stage Axial Turbine: Boundary Layer Behaviour at Midspan
Authors: Ko¨nig Sven , Heidecke Axel , Stoffel Bernd , Fiala Andreas , Engel Karl
Published: November 2008

This paper presents an experimental and numerical investigation on the influence of clocking on the boundary layer behaviour of the second stator in a 1.5-stage axial low pressure turbine. Surface mounted hot-film sensors were used to measure the quasi shear stress on the second stator and static pressure tappings to obtain the pressure distribution. All experiments were carried out at midspan for different clocking positions. The supporting numerical calculations were conducted with a two-dimensional Navier-Stokes solver using a finite volume discretization scheme and the v′2f turbulence model.
Optimization Combines the Genetic Algorithms With Augmented Lagrange Multiplier Method for Rotor-Bearing Systems Under Dynamic Behavior Constraints
Authors: Shiau T. N. , Kang C. H. , Liu D. S.
Published: November 2008

A new optimization strategy for the design of rotor-bearing system was investigated in this study. For most optimization methods applied to rotor-bearing system, it need to select a set of better initial values for design variables to get good results. This trial-and-error process is time consuming and even affects the results. To overcome this difficulty, Genetic Algorithms is applied to provide the set of initial values for design variables and Augmented Lagrange Multiplier Method is employed to determine the optimum results. Furthermore, the hybrid method is applied to minimize, individually or simultaneously, the weight of the shaft and the transmitted forces at the bearings. The results shows that the hybrid method can effectively search the better initial values set for design variables, and further, it can find the superior results to reduce both the shaft weight and the bearing transmitted forces under critical speed constraints.
A Numerical Method for 3D Turbomachinery Aeroelasticity
Authors: Cinnella Paola , Cappiello Emanuele , De Palma Pietro , Napolitano Michele , Pascazio Giuseppe
Published: November 2008

This work provides an extension to 3D aeroelastic problems of a recently developed numerical method for turbomachinery aeroelasticity. The unsteady Euler or Reynolds-averaged Navier-Stokes (RANS) equations are solved in integral form, the blade passages being discretised using a deforming grid. The grid is regenerated at each time step using a novel methodology, that automatically avoids grid lines overlapping and guarantees the smoothness of the regenerated mesh. Firstly, the method has been validated versus the 2D 4th Aeroelastic Turbine Standard Configuration. Both inviscid and viscous turbulent computations have been performed, and the results previously obtained usind a different moving grid strategy have been recovered. In order to prove the robustness of the proposed deforming grid methodology, the same case has also been computed with the blade under-going large torsion displacements, the regenerated grid always preserving a good smoothness. Then, the methodology has been validated versus the 3D 4th Standard Aeroelastic Configuration, that involves a rigid body blade motion. Finally, a more severe 3D configuration, involving a clamped-beam-like blade deformation, has been considered.
Multilevel Optimization of the Geared Rotor-Bearing System for Multi-Objectives With Critical Speed Constraints
Authors: Shiau T. N. , Chang J. R. , Lu W. B.
Published: November 2008

This paper presents the multi-objective optimization of a geared rotor-bearing system with the critical speeds constraints by using an efficient multilevel algorithm. The weight of each rotor shaft, the unbalance response, and the response due to the transmission error are minimized simultaneously under the critical speed constraints. The design variables are the inner radii of the shaft, the stiffness of bearings, and the gear mesh stiffness. The finite element method (FEM) is employed to analyze the dynamic characteristics and the method of feasible direction (MFD) is applied in the optimization of the single objective stage. Based on the sensitivity analysis that gear mesh stiffness has almost no influences on the critical speeds of the uncoupled modes of two shafts, an efficient multilevel algorithm composed of system and subsystem levels is developed. In the cycle of iteration, the minimization of the shaft weight is performed in the subsystem level with the critical speed constraints of only uncoupled modes of two shafts and the unbalance response and the transmission error response are reduced in the system level with the critical speed constraints of only coupled modes. It is indicated from the numerical results that the shaft weight, the unbalance response, and the transmission error response via the multilevel technique (ML) are all reduced much more than those via the weighting method (WM) and the goal programming method (GPM).
Aero-Thermodynamic Aspects of Film Cooling in Regions of Separated Flow on the Pressure Side of a High-Lift HPT Blade
Authors: Homeier Lars , Lutum Ewald , Janke Erik , Haselbach Frank
Published: November 2008

Due to the ever increasing demand for cost-optimised designs, modern engine design concepts lead to more and more highly loaded HP turbine blades. In order to achieve the high lift required, turbine airfoils will have to cope with main flow diffusion up to separation both on suction and pressure side. Thus, for film cooled HP turbine blades and vanes, the possible aerodynamic and aero-thermal interaction of highly loaded blade rows and film cooling needs to be addressed. The first results to be presented from this ongoing work within the European 5th Frame-Work-Project AITEB jointly comprises experimental high-speed cascade wind-tunnel as well as numerical investigations with state-of-the-art 3D-RANS CFD. Steady and unsteady experimental results detailing the row characteristic of the highly-loaded T120 HP-turbine cascade set the stage for detailed numerical investigations with and without coolant injection from rows of holes on the pressure side surface as well as comparative numerical calculations with different codes and turbulence models. Despite the current focus of the experimental work on aerodynamic topics, the numerical results to be presented comprise thermodynamic investigations and detailed studies on optimised coolant injection geometries as well.
An Economic Assessment Method of Gas Turbine Power Cycles by Means of Genetic Algorithms
Authors: Codeceira Neto Alcides , Pilidis Pericles , Kalfas Anestis I.
Published: November 2008

The Performance assessment of power plants involves a large number of equations with many variables taking part in the whole calculation. The assessment method described here takes into account a process for optimising a conventional gas turbine combined cycle power plant from the point of view of power plant performance calculations and economic analysis. The process requires optimisation of the whole thermal power plant based on cost considerations. The performance assessment of power plants uses the exergy method and considers the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within plant components, and it is of particular interest in this investigation. Generally, the optimisation procedure to determine an optimal solution for a problem considers constraints imposed to some variables and requires the use of an optimisation technique. This paper is precisely concerned with the use of Genetic Algorithms (GAs) as a recommended tool for applying the optimisation process of the whole power plant based on minimising costs of products. Genetic Algorithms (GAs) are adaptive methods which may be used to solve search and optimisation problems. They are based on the genetic processes of biological organisms and do not require complicated mathematical calculations like the evaluation of derivatives necessary to be considered in conventional optimisation techniques.
The Influence of In Situ Reheat on Turbine-Combustor Performance
Authors: Chambers Steven , Flitan Horia , Cizmas Paul , Bachovchin Dennis , Lippert Thomas , Little David
Published: November 2008

This paper presents a numerical and experimental investigation of the in situ reheat necessary for the development of a turbine-combustor. The flow and combustion are modeled by the Reynolds-averaged Navier-Stokes equations coupled with the species conservation equations. The chemistry model used herein is a two-step, global, finite rate combustion model for methane and combustion gases. A numerical simulation has been used to investigate the validity of the combustion model by comparing the numerical results against experimental data obtained for an isolated vane with fuel injection at its trailing edge. The numerical investigation has then been used to explore the unsteady transport phenomena in a four-stage turbine-combustor. In situ reheat simulations investigated the influence of various fuel injection parameters on power increase, airfoil temperature variation and turbine blade loading.
Stagger Angle and Pitch-Chord Ratio Effects on Secondary Flows Downstream of a Turbine Cascade at Several Off-Design Conditions
Authors: Dossena V. , D’Ippolito G. , Pesatori E.
Published: November 2008

The paper presents the results of an extensive measurement program addressed to investigate the influence of a large number of parameters on the development of secondary flows downstream of linear turbine cascades. Tests have been performed on linear cascades manufactured in order to obtain a large performances database referred to new 50 per cent reaction steam turbine stages. Measurements have been carried out for three different incidence angles (I = −24, 0, +24 degrees), for three pitch-chord ratios (S/C = 0.6, 0.8, 1.0) and for six values of the isentropic downstream Mach number (M2is = 0.3, 0.5, 0.65, 0.8, 0.9, 1.0). The paper also presents the analysis about the influence of the contemporary variation of the abovementioned parameters on the downstream flow features. Moreover, particular attention is addressed to the role of stagger angle variation by considering two different conditions: Δγ = −4 and Δγ = +2 degrees, measured from the design value. Experiments have been obtained by traversing a miniaturized five holes probe in a plane located at 50 per cent of the axial chord downstream of the trailing edge. Results show that pitch-chord ratio is the parameter mostly influencing the profile aerodynamic efficiency, but also incidence strongly influences the spanwise distribution of discharge angle and secondary losses. Besides, the expansion ratio throughout the cascade has a sensitive influence on secondary flows only when the combination of other test parameters already evidences strong secondary effects. Measurements point out that also a small change in stagger angle may surprisingly affect blade performances and 3D flow field.
Analysis of Gas-Steam Combined Cycles With Natural Gas Reforming and CO2 Capture
Authors: Corradetti Alessandro , Desideri Umberto
Published: November 2008

In the last years greenhouse gas emissions, and in particular carbon dioxide emissions, have become a major concern in the power generation industry and a large amount of research work has been dedicated to this subject. Among the possible technologies to reduce CO2 emissions from power plants, the pre-treatment of the fossil fuels to separate carbon from hydrogen before the combustion process is one of the least energy consuming way to facilitate CO2 capture and removal from the power plant. In this paper several power plant schemes with reduced CO2 emissions were simulated. All the configurations were based on the following characteristics: (1) syngas production via natural gas reforming; (2) two reactors for CO-shift; (3) “pre-combustion” decarbonization of the fuel by CO2 absorption with amine solutions; (4) combustion of hydrogen rich fuel in a commercially available gas turbine; (5) combined cycle with three pressure levels, to achieve a net power output in the range of 400 MW. The base reactor employed for syngas generation is the ATR (Auto Thermal Reformer). The attention was focused on the optimization of the main parameters of this reactor and its interaction with the power section. In particular the simulation evaluated the benefits deriving from the post-combustion of exhaust gas and from the introduction of a gas-gas heat exchanger. All the components of the plants were simulated using Aspen Plus software, and fixing a reduction of CO2 emissions of at least 90%. The best configuration showed a thermal efficiency of approximately 48% and CO2 specific emissions of 0.04 kg/kWh.
Investigation of the Effectiveness of Various Types of Boundary Layer Transition Elements of Low Reynolds Number Turbine Bladings
Authors: Sieverding Claus H. , Bagnera Carlo , Boege A. C. , Anto`n Juan A. Cordero , Lue`re Vincent
Published: November 2008

The paper describes an experimental investigation of the use of different types of boundary layer transition elements for the control of boundary layer separation at low Reynolds numbers. The tests are carried out in a low speed cascade tunnel for Reynolds numbers between 30000 and 200000. For convenience the author used an existing HP turbine guide vane with ∼63 degree turning. To obtain representative adverse pressure gradients as those existing on the rear suction side of highly loaded LP blades the tests are run at a pitch-to-chord ratio of 1. The transition elements include tripwires, single and double rows of spherical roughness elements, balloon type transition elements and a metal sheet actuated by shape memory alloy springs. The optimum position and height of the transition elements are obtained with systematic tests with the trip wire. All other elements are placed at the same position and have approximately the same height. As expected, the transition elements are very beneficial at low Re numbers but deteriorate the performance at high Re numbers. The advantages and drawbacks of the various configurations are discussed and suggestions for real turbine applications are made.