bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-Dimensional Optimization of Turbomachinery Bladings Using Sensitivity Analysis
Authors: Ka¨mmerer S. , Mayer J. F. , Paffrath M. , Wever U. , Jung A. R.
Published: February 2009

This paper presents an approach to optimize the geometry of turbomachinery blades utilizing an automated optimization loop. Optimization examples of turbomachinery blade geometries with selected objective functions and a set of design variables are introduced. The presented optimization examples are performed for a 1.5-stage turbine test case. The blade geometries are fully parameterized, enabling three-dimensional changes to the blade shape during the optimization. Therefore various non-physical and physical parameters such as stacking line or stagger angle can be selected as design variables. Three-dimensional steady-state numerical flow simulations and a sensitivity equation method are part of the optimization process. The design sensitivities used within the optimization are obtained by numerically solving the analytical sensitivity equations. This optimization scheme uses the same numerical method for the flow simulation and for the computation of the sensitivity equation. A Navier-Stokes flow solver, which has especially been designed for turbomachinery applications was used for the implementation of the sensitivity equation method. The focus of this paper is on the application of the described optimization strategy to turbomachinery flows. The presented optimization examples are used to demonstrate and to discuss the capabilities of this approach.
Vibration Analysis of Rotor With Transverse Surface Cracks
Authors: Guo Dan , Chu Fu-Lei , He Yong-Yong
Published: February 2009

The vibration of cracked rotor is investigated by numerical method. The FEM is used to model the rotor with cracks. Six degrees of freedom are considered in each elemental node. Full 6×6 flexibility matrix is deduced by Papadopoulos and Dimarogonas’ method, and 12×12 stiffness matrix of cracked element is derived. The influence of one or more cracks on the natural frequencies and different modals (including bending modal, torsion modal and longitudinal modal) of cracked rotor is explored. Vibration responses of rotor with open cracks or breathing crack loading by eccentric force and rotor gravity force are obtained and analyzed by numerical integer method and spectral technology. The coupling of lateral, longitudinal and torsion vibrations due to transverse surface crack is studied. It is concluded that the above research is useful in detecting crack in rotor.
Unique Challenges for Bolted Joint Design in High-Bypass Turbofan Engines
Authors: Czachor Robert P.
Published: February 2009

Bolted joints are used at numerous locations in the rotors and carcass structure of modern aircraft turbine engines. This application makes the design criteria and process substantially different from that used for other types of machinery. Specifically, in addition to providing engine alignment and high-pressure gas sealing, aircraft engine structural joints can operate at high temperatures and may be required to survive very large applied loads which can result from structural failures within the engine, such as the loss of a fan blade. As engine bypass ratios have increased in order to improve specific fuel consumption, these so-called “Ultimate” loads increasingly dominate the design of bolted joints in aircraft engines. This paper deals with the sizing and design of both bolts and lever flanges to meet these demanding requirements. Novel empirical methods, derived from both component test results and correlated analysis have been developed to perform strength evaluation of both flanges and bolts. Discussion of analytical techniques in use includes application of the LS-DYNA™ code for modeling of high-speed blade impact events as related to bolted joint behavior.
Probabilistic Methodology for Combustor Airflow Surrogate Development
Authors: Shah Minesh , Arar Malath I.
Published: February 2009

Operability of Dry-Low-NOx (DLN) combustors in heavy-duty gas turbines is dependent in part on satisfying boundaries or constraints associated with lean blow out (LBO), NOx, and combustion dynamics. To satisfy each of these boundaries or constraints, the determination of combustor airflow is critical. Since combustor airflow is difficult to measure directly, a surrogate or an estimator of combustor airflow that can be implemented in the control system is required. Presented in this paper is a methodology for determining the combustor airflow surrogate based on measurable parameters. The approach relies on developing a nonlinear equation of combustor airflow based on cycle simulations over a wide range of ambient (temperature, pressure and humidity) and parameter (e.g., inlet guide vane and load) variations. To understand the robustness of the combustor airflow estimate, sensitivity analysis with regard to sensor uncertainty, machine degradation, and machine-to-machine variation is presented. In each of these cases, the uncertainty/parameter variation is investigated via Monte Carlo simulations to quantify performance in terms of mean shift (i.e, bias) and standard deviation. It is shown that the resulting surrogate, which is comprised of compressor discharge pressure, compressor discharge temperature and specific humidity, is capable of addressing the variations listed above and is capable of representing a compressor map at different IGV settings via a simple relationship.
Specifying Manufacturing Tolerances for a Given Amplification Factor: A Nonparametric Probabilistic Methodology
Authors: Capiez-Lernout Evange´line , Soize Christian
Published: February 2009

It is known that the forced response of mistuned bladed disks can strongly be amplified in comparison with the forced response of the tuned system. The random character of mistuning thus requires the construction of probabilistics models of random uncertainties. This paper presents a nonparametric probabilistic model of random uncertainties which is adapted to the problematics of the blade mistuning. This nonparametric approach allows all the uncertainties yielding mistuning (manufacturing tolerances, dispersion of materials) to be taken into account and includes also the uncertainties due to the modeling errors. This new probabilistic model takes into account both the mistuning of the blade eigenfrequencies and the blade modal shapes. The first point concerns the construction of this nonparametric approach in order to perform a mistuning analysis. The second part is devoted to the inverse problem associated with the manufacturing tolerances. A relationship between the manufacturing tolerances and the level of mistuning is also constructed.
The Oxidation of Metal Alloy Foils in the Presence of Water Vapor
Authors: Rakowski James M.
Published: February 2009

Water vapor can be detrimental to the elevated temperature oxidation resistance of alloys that rely on the formation of a protective chromium oxide layer. The resulting degradation can be significant, particularly when such alloys are in the form of light gauge sheet and strip. Long term test results will be presented for commercially available wrought austenitic stainless steels and for the nickel-base superalloys 625 and HX exposed at 1300°F and 1400°F in environments containing various levels of water vapor.
Experimental Demonstration of Maximum Mistuned Bladed Disk Forced Response
Authors: Kenyon J. A. , Griffin J. H.
Published: February 2009

A theory was previously developed for predicting robust maximum forced response in mistuned bladed disks from distortion of a structural mode. This paper describes an experiment to demonstrate the theory. A bladed disk is designed to be sufficiently sensitive to mistuning to obtain maximum response. The maximum amplitude magnification from mistuning is predicted using the theory, 1.918. The bladed disk is intentionally mistuned to obtain the maximum response, and the response to an engine order traveling wave excitation is measured. The measured amplitude magnification is in close agreement with the theory. The robustness of the maximum response is demonstrated.
Procedure for Determining 1-D Flow Distributions in Arbitrarily Connected Passages Without the Influence of Pumping
Authors: Meitner Peter L.
Published: February 2009

A calculation procedure is presented which allows the 1–D determination of flow distributions in arbitrarily connected (branching) flow passages having multiple inlets and exits. The procedure uses an adaptation of the finite element technique, iteratively coupled with an accurate 1–D flow solver. The procedure eliminates the usual restrictions inherent with finite element flow calculations. Unlike existing 1–D methods, which require simplifications to the flow equations (uncoupling the momentum and energy equations), to allow for arbitrary branching and multiple inlets and exits, the only limitation of the described methodology is that, at present, it can only accommodate non-rotating configurations (no pumping effects). The calculation procedure is robust, and will always converge for physically possible flow. The procedure is described, and its use is illustrated by an example.
Modelling and Simulation of Transient Performance of the Semi-Closed O2/CO2 Gas Turbine Cycle for CO2-Capture
Authors: Ulfsnes Ragnhild E. , Bolland Olav , Jordal Kristin
Published: February 2009

One of the concepts proposed for capture of CO2 in power production from gaseous fossil fuels is the semi-closed O2/CO2 gas turbine cycle. The semi-closed O2/CO2 gas turbine cycle has a near to stoichiometric combustion with oxygen, producing CO2 and water vapor as the combustion products. The water vapor is condensed and removed from the process, the remaining gas, primarily CO2, is mainly recycled to keep turbine inlet temperature at a permissible level. A model for predicting transient behavior of the semi-closed O2/CO2 gas turbine cycle is presented. The model is implemented in the simulation tool gPROMS (Process System Enterprise Ltd.), and simulations are performed to investigate two different issues. The first issue is to see how different cycle performance variables interact during transient behavior; the second is to investigate how cycle calculations are affected when including the gas constant and the specific heat ratio in compressor characteristics. The simulations show that the near to stoichiometric combustion and the working fluid recycle introduce a high interaction between the different cycle components and variables. This makes it very difficult to analytically predict the cycle performance during a transient event, i.e. simulations are necessary. It is also found that, except for the shaft speed calculation, the introduction of gas constant and specific heat ratio dependence on the compressor performance map will have only a minor influence on the process performance.
Artificial Neural Network Model for a Biomass-Fueled Boiler
Authors: Arriagada Jaime , Costantini Mattia , Olausson Pernilla , Assadi Mohsen , Torisson Tord
Published: February 2009

In order to operate plants fueled with biomass in an optimum manner, it is important to create thermodynamic models of the same. However, these kind of plants are hard to model by “traditional” methods such as heat and mass balance programs. Some difficulties are the large inertia of some sub-systems, as well as the fact that many important parameters are not constant nor unequivocally determined. For this reason, Artificial Neural Networks (ANNs), a technique within the field of Artificial Intelligence (AI), have been chosen as the main candidates to build an adequate model of these kind of plants. Data from an existing plant is used to train, validate and test the ANNs. More specifically, an ANN-based model of the biomass-fired boiler of the plant is implemented which is able to catch the non-linear behavior of the system at different operational conditions with a satisfying accuracy. A conclusion of this work is that ANNs can be considered as a useful tool to model the biomass-fueled boiler. Several sensitivity analyses and pruning of unnecessary inputs were carried out. For instance, some input parameters revealed themselves to not have significant influence on the accuracy of the ANN-model, while in physical modeling they are to be considered as essentials. One possible outcome of ANN modeling is to gain insight about which sensors could be excluded from the existing sensor configuration without lowering the reliability of the plant. A good plant model will supply the personnel in the control room with information necessary to make reliable predictions and arrive at correct decisions. This can lead to a considerable reduction of operational and maintenance costs and improved performance of the plant.
Gas Turbine Operation Offshore: On-Line Compressor Wash at Peak Load
Authors: Syverud Elisabet , Bakken Lars E. , Langnes Kyrre , Bjo̸rna˚s Frode
Published: February 2009

On-line compressor wash is discussed for a RB211 compressor driver running at peak load at the Statoil Heidrun offshore platform. The oil field’s economy is directly linked to oil production; however, the production rate is limited by driver and gas compressor capacity. From this perspective, the power output and gas turbine uptime become decisive economic factors. The economic potentials related to successful on-line washing are given. This work is based on a series of trials with on-line compressor washing over a two-year period. Results include effect of different on-line washing procedures and washing fluids. The field test campaign has shown no significant improvements with on-line compressor washing at peak load. Understanding the gas turbine performance deterioration is of vital importance. Trending of its deviation from the engine baseline (datum maps) facilitates load-independent monitoring of the gas turbine’s condition. Peak load turbine response to compressor deterioration is analyzed. Instrument resolution and repeatability are key factors that sometimes are more important than absolute accuracy in condition trending. As a result of these analyses, a set of monitoring parameters is suggested for effective diagnostics of compressor degradation in peak load operation. Avenues for further research and development are suggested as our understanding of the deterioration mechanisms at peak load remains incomplete.
Prognostics/Diagnostics for Gas Turbine Engine Bearings
Authors: Orsagh Rolf F. , Sheldon Jeremy , Klenke Christopher J.
Published: February 2009

Development of robust in-flight prognostics or diagnostics for oil wetted gas turbine engine components will play a critical role in improving aircraft engine reliability and maintainability. Real-time algorithms for predicting and detecting bearing and gear failures are currently being developed in parallel with emerging flight-capable sensor technologies including in-line oil debris/condition monitors, and vibration analysis MEMS. These advanced prognostic/diagnostic algorithms utilize intelligent data fusion architectures to optimally combine sensor data, with probabilistic component models to achieve the best decisions on the overall health of oil-wetted components. By utilizing a combination of health monitoring data and model-based techniques, a comprehensive component prognostic capability can be achieved throughout a components life, using model-based estimates when no diagnostic indicators are present and monitored features such as oil debris and vibration at later stages when failure indications are detectable. Implementation of these oil-wetted component prognostic modules will be illustrated in this paper using bearing and gearbox test stand run-to-failure data.
Influence of Loading Distribution on the Performance of Transonic HP Turbine Blades
Authors: Corriveau D. , Sjolander S. A.
Published: February 2009

Midspan measurements were made in a transonic wind tunnel for three HP turbine blade cascades at design incidence. The baseline profile is the midspan section of a HP turbine blade of fairly recent design. It is considered mid-loaded. To gain a better understanding of blade loading limits and the influence of loading distributions, the profile of the baseline airfoil was modified to create two new airfoils having aft-loaded and front-loaded pressure distributions. Tests were performed for exit Mach numbers between 0.6 and 1.2. In addition, measurements were made for an extended range of Reynolds numbers for constant Mach numbers of 0.6, 0.85, 0.95 and 1.05. At the design exit Mach number of 1.05, the aft-loaded airfoil showed a reduction of almost 20% in the total pressure losses compared with the baseline airfoil. However, it was also found that for Mach numbers higher than the design value the performance of the aft-loaded blade deteriorated rapidly. The front-loaded airfoil showed generally inferior performance compared with the baseline airfoil.
Development and In Service Introduction of a Rolls-Royce Spey SM1C Digital Control System
Authors: Charman N. , Rand M. J.
Published: February 2009

The first part of this paper will briefly detail the requirement for and the development of a Digital Fuel Control System (DCS) for the Spey SM1C gas turbines fitted in the latest Royal Netherlands Navy (RNLN) class of ships the Luchtverdedigings en Commando Fregat (LCF). The middle section will cover the shore trials, customer acceptance demonstrations and first sea trials of the DCS where the correlation between simulation and a real engine was seen to diverge drastically. This section will also detail the SM1C control system, the DCS controls philosophy, signal sampling and Human Machine Interface (HMI). The final part of the paper will deal with the investigations into the problems encountered, the simulation of faults, the validation of the SM1C simulations, outstanding problems and the successful in-service performance of the resulting software modifications.
Laminar Flow Theory as a Guide to Compact Recuperator Design
Authors: Chapman William I.
Published: February 2009

A small gas turbine needs a good recuperator to achieve high efficiency. It is desirable that this recuperator be small in size, light in weight, and low cost. Laminar flow theory is used to show the effect of heat transfer surface selection, passage size, and flow length. A comparative study was then made of counterflow recuperators using heat transfer test data from published sources to show how these variables apply to a typical design. One group of surfaces with simple flow passages, smooth, straight, and constant cross-section, followed laminar flow theory quite closely. A second group of more complicated surfaces deviated considerably from laminar flow theory. For a given performance, both groups show that as flow length is reduced, along with the corresponding passage size, the flow volume and surface area decreases. The corresponding material weight and cost also decrease. There are practical limitations on how far this can go.
Effect of Exhaust Cleanup Systems on Gas Turbine Combustor Selection
Authors: DeCorso Mario , Moen David L. , Pillsbury Paul W.
Published: February 2009

Diffusion flame combustors have served the gas turbine industry well since the invention of jet engines in the 1930’s. They provided fuel flexibility and the diffusion flame process gave the designer many options. Recently for heavy-duty land gas turbines, the need to reduce NOx emissions has led to the introduction of premixed combustor designs (Dry Low NOx - DLN) that have reduced fuel flexibility, operating range and reliability. With the increasing use and availability of Exhaust Cleanup Systems (EXCLUS) such as SCR and CO reduction catalysts, new gas turbine plant schemes that use diffusion flame combustors are back in the picture. This paper proposes a number of technique combinations that could achieve low NOx targets using diffusion flame combustors.
An Experimental Investigation on Different Radial Loading Distribution and Patterns of Stall Inception in a Single-Stage Low-Speed Axial Compressor
Authors: Nie Chaoqun
Published: February 2009

Recent research efforts have focused on the aerodynamic mechanism, identifications, and advanced capturing methods of stall inception. Making use of active control and intelligent casing treatment, all the efforts aim at expanding operational ranges of compressors and at improving their operational stability. It is widely known that the dynamic behavior of stall inception is strongly influenced by occurrence of inlet distortion, radial loading distribution, tip-clearance flow, stage matching, and downstream oscillation from combustion chambers. Therefore, experimental research is imperative to study the interconnection between radial loading distribution of rotor and patterns of stall inception. The following is the main experimental results: 1) With two sets of different pre-whirl order of inlet guide vanes (IGV), the incidences along blade height are modified, which provide different radial loading distribution. 2) It is discovered that spiky stall inception corresponds to high loading distribution near the tip of rotor blade. However modal stall inception is related to low loading distributed near the tip. 3) The different loading conditions near the hub of the rotor do not apparently change the pattern of stall inception. 4) It is also found that adjusting the stagger angles of IGVs can change the steady characteristics and stall inception pattern.
Computer Simulation and Optimization of Heat Recovery Steam Generator (HRSG)
Authors: Kumar Rajeev , Singh Onkar
Published: February 2009

Heat recovery steam generators are successfully used in combined cycle power plants and many more applications. In a gas / steam combined cycle power plant the performance of bottoming cycle depends largely upon the effectiveness of HRSG. For a good HRSG in combined cycle power plants the heat exchange effectiveness should be as high as possible for maximum waste heat utilization and loss in the pressure of hot gases passing through HRSG should be small. In this paper, the computer simulation of HRSG has been carried out based on its thermodynamic study. An exhaustive generic computer code has been developed in C++ language for getting the critical information such as surface area required, number of tubes required, pressure loss, steam generation rate, effectiveness etc. for a single pressure & multi pressure HRSG. Results obtained using the code have been analyzed for varying operating thermodynamic conditions and different arrangements in HRSG. Preferable HRSG configuration and its thermodynamic analysis have been made using the computer code. Optimization of the HRSG design is carried out in respect to cost of HRSG using genetic algorithm.
Thermodynamic Evaluation of Advanced Combined Cycle Using Latest Gas Turbine
Authors: Sanjay  , Singh Onkar , Prasad B. N.
Published: February 2009

The present work deals with the thermodynamic evaluation of combined cycle with re-heat in gas turbine using the latest gas turbines namely ABB GT26 gas turbine (advanced) in which reheat is used and the blade cooling is done by air bled from compressor. The same turbine is subjected to closed loop steam cooling. Parametric study has been performed on plant efficiency and specific work for various independent parameters such as turbine inlet temperature, compressor pressure ratio, reheating pressure ratio, reheater inlet temperature, blade temperature, etc.. It has been observed that due to higher compressor pressure ratio involved in reheat gas turbine combined cycle and higher temperature of exhaust, the plant efficiency and specific work are higher with the advanced reheat gas/steam combined cycle over the simple combined cycle. Steam cooling offers better performance over aircooling.
Theoretical and Experimental Evaluation of a Plate Heat Exchanger Aftercooler in an Evaporative Gas Turbine Cycle
Authors: Thern Marcus , Lindquist Torbjo¨rn , Torisson Tord
Published: February 2009

The evaporative gas turbine pilot plant (EvGT) has been in operation at Lund Institute of Technology in Sweden since 1997. This article presents the experimental and theoretical results of the latest process modifications made, i.e. the effect of the installation of an aftercooler. The purpose of the aftercooler is to increase the performance of the cycle by utilizing more low-level heat in the humidification tower. The chosen aftercooler is of plate heat exchanger type, which is very compact, has high thermal efficiency and low pressure drop. The installation of an aftercooler lowers the temperature of the air entering the humidification tower. This also lowers the temperature of the circulating humidification water, which facilitates the extraction of more low-level heat from the economizer. This low-level heat can be utilized to evaporate more water in the humidification tower and thus increase the gas flow in the expander. The pilot plant has been operated at different loads and the measured results has been evaluated and compared with theoretical models. The performance of a plate heat exchanger in power plant applications has also been evaluated. Experience from the measurements has then been used for the potential cycle calculations. It has been shown that the aftercooler lowers the flue gas temperature in the pilot plant to 93°C, the rate of humidification was increased from 13 wt% to 14.5 wt%, and the pressure drop on the airside in the aftercooler is 1.6%. The electrical efficiency for the pilot plant was increased by 0.4%. The increase in electrical efficiency for a more advanced EvGT cycle with an intercooler, aftercooler and economizer will be around 3.5 percentage units in comparison with a cycle without an aftercooler. The plate heat exchanger showed very good performance in terms of cost, size, pressure drop and thermal efficiency. An alternative to the chosen heat exchanger is the tubular one, but it is 10 times heavier, has a higher pressure drop and is more expensive. The aftercooler increases the electrical efficiency significantly by lowering the flue gas temperature and increasing the expander work.
Suppression of Instabilities in Gaseous Fuel High-Pressure Combustor Using Non-Coherent Oscillatory Fuel Injection
Authors: Shcherbik D. , Lubarsky E. , Neumeier Y. , Zinn B. T. , McManus K. , Fric T. F. , Srinivasan S.
Published: February 2009

This paper describes the application of active, open loop, control in effective damping of severe combustion instabilities in a high pressure (i.e., around 520 psi) gas turbine combustor simulator. Active control was applied by harmonic modulation of the fuel injection rate into the combustor. The open-loop active control system consisted of a pressure sensor and a fast response actuating valve. To determine the dependence of the performance of the active control system upon the frequency, the fuel injection modulation frequency was varied between 300 and 420 Hz while the frequency of instability was around 375 Hz. These tests showed that the amplitude of the combustor pressure oscillations strongly depended upon the frequency of the open loop control. In fact, the amplitude of the combustor pressure oscillations varied ten fold over the range of investigated frequencies, indicating that applying the investigated open loop control approach at the appropriate frequency could effectively damp detrimental combustion instabilities. This was confirmed in subsequent tests in which initiation of open loop modulation of the fuel injection rate at a non resonant frequency of 300Hz during unstable operation with peak to peak instability amplitude of 114 psi and a frequency of 375Hz suppressed the instability to a level of 12 psi within approximately 0.2 sec (i.e., 75 periods). Analysis of the time dependence of the spectra of the pressure oscillations during suppression of the instability strongly suggested that the open loop fuel injection rate modulation effectively damped the instability by “breaking up” (or preventing the establishment of) the feedback loop between the reaction rate and combustor oscillations that drove the instability.
Thermodynamic and Economic Assessment of Two Semi-Closed CO2 Cycles for Emission Abatement and Power Augmentation at Compressor Stations
Authors: Botros K. K. , Sennhauser D. , Siarkowski L.
Published: February 2009

Concerns about the effects of greenhouse gas emissions on the Earth’s climate have lead to a considerable focus by the public and governments on the levels of emissions that are generated by industrial activities. In Canada, it has been recognized that gas transmission systems are rated second in overall CO2 production in the Natural Gas Industry (next to gas processing). Most of the gas transmission systems are powered by gas turbines at compressor stations resulting in significant CO2 emissions (at the rate of ∼ 6 kilo tonnes/ per MW-year). This can be reduced if the CO2 can be separated from the gas turbine exhaust stream and directed for reuse or sequestration. This paper presents results of techno-thermodynamic assessment of two power cycle adjustments to increase CO2 concentrations in the exhaust gas from turbines. The working fluid in the two semi-closed cycles are made rich in CO2, thus making it easy to capture the CO2 from the flue gas by means of physical absorption techniques rather than by the conventional expensive amine adsorption methods. Additionally, the CO2 rich working fluid is shown to give rise to a higher exhaust gas temperature from the gas turbine semi-closed cycles, allowing a steam bottom cycle to be effective in augmenting the power delivered by the entire system by 50%, hence contributing to reducing emission by increasing the overall thermal efficiency of the system.
Comparison of High-Efficiency Distributed Cogeneration and Large Combined-Cycle Power Generation
Authors: Martin John R.
Published: February 2009

The fundamental conclusion of this paper is that high-efficiency distributed cogeneration is substantially more energy efficient and economical than large, remote, combined-cycle power plants. The cogeneration case produces lower emission levels, consumes less water, and distributes these impacts over a wider geographic area. The siting of large electric power generating facilities is commonly focused on locations that are distant from energy load centers. The choice of distant locations can be explained by the NIMBY “not in my backyard” mentality. New facilities are usually located at the intersection of high-voltage electric power transmission lines and natural gas pipelines to supply fuel and to deliver energy to the grid. Unfortunately, developers do not always understand the load-carrying capacity of electric transmission systems and the cost and schedule requirements to expand them. The siting process normally does not consider the overall efficiency of delivered energy, embedded costs including infrastructure expansions, marginal air emissions, and marginal water consumption. Siting high-efficiency distributed cogeneration facilities at major load centers produces significant energy efficiencies and fuel cost savings and can reduce the high cost of major transmission improvements. Modern cogeneration facilities are usually difficult for the public to identify within the boundaries of a large industrial plant and have environmental impacts that, in many cases, are positive (e.g., reducing local air emissions). This can help diminish the public’s NIMBY reaction. In this paper, the efficiency, delivered cost of energy, marginal air emissions, and water consumption of a modern combined cycle power plant are compared to those of a high-efficiency distributed cogeneration facility.
Probabilistic Analysis of a Turbine Cooling Air Supply System: The Effect on Airfoil Oxidation Life
Authors: Sidwell Vince , Darmofal David
Published: February 2009

This paper analyzes the variability of turbine airfoil oxidation life due to variability in the turbine cooling air portion of the auxiliary air system of a commercial turbofan engine. The variability imposed on the system results from both aerothermal variability in the main gaspath and geometric variability, such as seal clearance and blade effective flow area, within the turbine cooling air system. The probabilistic analysis of the oxidation life is compared to documented lives for in-service turbine blades for two airlines operating the same engine model. Probabilistic results are similar to the field experience for the airline operating in a hotter environment. Historical calibration factors within the lifing system which can potentially cause the probabilistic results to be too conservative are discussed. To demonstrate the importance of including all the blades in an analysis, a model with a single “lumped” blade with an effective area equivalent to all the blades in a turbine stage is shown to over predict the oxidation life of an engine. In addition, regression analysis is used to identify input variables for which a decrease in tolerance would provide a significant increase in life. For the more severe operator, a 10% decrease in the tolerance of the effective flow area of the blade leading edge cooling passage can more than double the minimum oxidation life (5% failed) of a fleet of engines. To offset the economic impact of tightened tolerances, the regression analysis also identifies input variables whose tolerances can be loosened with little impact on blade life.
Large-Eddy Simulations of Heat Transfer in a Ribbed Channel for Internal Cooling of Turbine Blades
Authors: Tafti D. K.
Published: February 2009

Large-Eddy Simulations (LES) are performed in a ribbed square channel with rib height to hydraulic diameter ratio of 0.1, and rib pitch to rib height ratio of 10. The calculations are performed for a nominal bulk Reynolds number of 20,000. Hydrodynamic and thermal fully-developed conditions are assumed. Results from two mesh resolutions, 963 and 1283 are presented and compared to available data in the literature. Time evolution, mean, and turbulent quantities are presented, together with the heat transfer. Both calculations capture the mean flow structures with precision and compare well with experimental data. Turbulent rms quantities also agree extremely well with available measurements. The finer mesh resolves the separated shear layer with greater precision and differences of 10–15% are observed between the two calculations. Similar differences are observed in the predictions of friction factors and Nusselt numbers between the two meshes. The friction factor and Nusselt number are underpredicted when compared to measurements in the literature.
Investigation of an Inversely Designed Centrifugal Compressor Stage: Part 2 — Experimental Investigations
Authors: Schleer M. , Hong S. S. , Zangeneh M. , Roduner C. , Ribi B. , Plo̸ger F. , Abhari R. S.
Published: February 2009

This paper presents an experimental investigation of two centrifugal compressor stage configurations. The baseline configuration has been designed using conventional design engineering tools. The second configuration was designed using advanced inverse design rules as described in part 1 (Zangeneh et al. 2003). It is designed to match the choke flow as well as the best point of the conventionally designed stage. The experimental investigation is conducted in the industry-scale centrifugal compressor facility at the Turbomachinery Laboratory of the Swiss Federal Institute of Technology. Performance maps for both configurations at several speed-lines are presented. These plots show the overall behavior of the stages designed using the different design approaches and their operating range. Time resolved measurements show details of the unsteady flow field within the diffuser close to the impeller exit. The time resolved data has been analyzed to assist the explanation of changes in the characteristics and associated efficiency penalties and gains. The processed data shows the benefits of the new inverse design method with respect to an improvement of the compressor efficiency and the operating range. It is seen that the application of an inverse design method results in a more uniform flow into the diffuser.
Unsteady, 3-Dimensional Flow Measurement Using a Miniature Virtual 4 Sensor Fast Response Aerodynamic Probe (FRAP)
Authors: Pfau A. , Schlienger J. , Kalfas A. I. , Abhari R. S.
Published: February 2009

This paper introduces the new fast response aerodynamic probe, which was recently developed at the ETH Zurich. The technique provides time-resolved, three-dimensional flow measurements using the virtual four sensor technique. The concept and the evaluation of the virtual four sensor probe is discussed in detail. The basic results consist of yaw and pitch flow angles as well as the total and static pressure. They combine to form the unsteady, three dimensional flow vector. The outer diameter of the cylindrical probe head was miniaturized to 0.84mm, hence probe blockage effects as well as dynamic lift effects are reduced. The shape of the probe head was optimized in view of the manufacturing process as well as aerodynamic considerations. The optimum geometry for pitch sensitivity was found to be a cylindrical surface with the axis perpendicular to the probe shaft. The internal design of the probes led to a sensor cavity eigenfrequency of 44kHz for the yaw sensitive and 34kHz for the pitch sensitive probe. Data acquisition is done with a fully automated traversing system, which moves the probe within the test rig and samples the signal with a PC-based A/D-board. An error analysis implemented into the data reduction routines revealed acceptable accuracy for flow angles as well as pressures for many turbomachinery flows. Depending on the dynamic head of the application the yaw angle is accurate within ±0.35° and pitch angle within ±0.7°. In the final section, a comparison of time averaged results to five hole probe measurements is discussed. The advantages of the new probe, beside its unique smallness, are the complete unsteady kinematic information and the improved recording of unsteady total pressure measurement as it is pointed out in a comparison against a 2D virtual three sensor probe.
Rich-Catalytic Lean-Burn Combustion for Low-Single-Digit NOx Gas Turbines
Authors: Smith Lance L. , Karim Hasan , Castaldi Marco J. , Etemad Shahrokh , Pfefferle William C. , Khanna Vivek K. , Smith Kenneth O.
Published: February 2009

A new Rich-Catalytic Lean-burn combustion concept (trademarked by PCI as RCL) was tested at industrial gas turbine conditions, in Solar Turbines’ high-pressure (17 atm) combustion rig and in a modified Solar Turbines engine, demonstrating ultra-low emissions of NOx < 2 ppm and CO < 10 ppm for natural gas fuel. For the single-injector rig tests, an RCL catalytic reactor replaced a single swirler/injector. NOx < 3 ppm and CO < 10 ppm were achieved over a 110 C operating range in flame temperature, including NOx < 1 ppm at about 1350 C flame temperature. Combustion noise was less than 0.15% peak-to-peak. Four RCL catalytic reactors were then installed in a modified (single can combustor) engine. NOx emissions averaged 2.1 ppm over the allowable operating range for this modified engine, with CO < 10 ppm and without combustion noise (less than 0.15% peak-to-peak).
Numerical Optimization of a Gas Turbine Cogeneration Plant
Authors: Teixeira Jose´ C. F. , Teixeira Senhorinha F. C. F. , Silva Aˆngela M. E.
Published: February 2009

Amongst the various alternatives for the combined production of heat and power, the systems based on a gas turbine are becoming increasingly attractive. In addition to the high thermal efficiency, they can also operate on a wide variety of fuels. The basic configuration of a simple cogeneration system consisting of a gas turbine and a heat recovery steam generator has been used to illustrate the application of nonlinear optimization numerical methods as a tool to evaluate and optimize complex energy systems. The problem was formulated as the minimization of costs as the objective function, subject to the constraints imposed by the physical and thermodynamic quantities. Two numerical nonlinear optimization methods with constraints have been tested using a Fortran code and the MATLAB® environment. The model has been evaluated on a real cogeneration plant consisting of a gas turbine heat recovery system of a local textile factory.
Development of a Torque Limiting Device to Provide a Measure Against Grid Blackout in Gas Turbine Power Generating Plants
Authors: Toyoda Mituso , Matsumoto Gaisa , Kokubu Kunihiro , Koga Shonosuke , Takahashi Yoshihiro , Maesono Akira , Sakumi Teruo , Nakamura Hideki , Abe Tatsuro
Published: February 2009

Gas turbine power generating plants are generally equipped with shear pins to protect the turbine shaft from excessive torque caused by grid blackout, etc. As a substitute for the shear pins, a torque limiting device has been developed. This torque limiting device is an application of the wet process multi-plate clutch. When the generator is subjected to excessive torque, the device slips instantly and protects the turbine shaft. Moreover, if the excessive torque is dissipated, the device connects automatically. Employing this device, it becomes easily possible to take an automatic measure against grid blackout without performing special operations such as parts exchange, and thus the effect of a blackout can be limited to a minimum. As a result of test demonstrations, it has been clearly shown that this torque limiting device can be applied to an aero-derivative gas turbine in addition to an industrial one.
Maximum Unbalance Responses of a Gear-Coupled Two-Shaft Rotor-Bearing System
Authors: Lee An Sung , Ha Jin Woong
Published: February 2009

A general method is presented for obtaining the unbalance response orbit of a gear-coupled two-shaft rotor-bearing system, based on the finite element approach. Specifically, analytical solutions of the maximum and minimum radii of the orbit are proposed. The method has been applied to the unbalance response analysis of a 600 kW turbo-chiller rotor-bearing system, having a bull-pinion speed increasing gear. Bumps in the unbalance responses have been observed at the first torsional natural frequency because of the coupling between the lateral and torsional dynamics due to gear meshing. In addition, the analytical solutions have been validated with results obtained by a full numerical approach. The proposed method can be generally applied to an analysis of the unbalance response orbits of dual-shaft rotor-bearing systems coupled by bearings as well, which are often found in aerospace gas turbine engines.
Fuzzy Approaches for Searching Optimal Component Matching Point in Gas Turbine Performance Simulation
Authors: Kong Changduk , Ki Jayoung , Kang Myoungcheol
Published: February 2009

In performance simulation of gas turbine, some iteration processes for searching the operating point, which should be matched through gas path components, would be needed. Therefore if the engine is very complicated, the efficiency of convergence is getting lower due to increasing the number of routines and iterations for matching procedure. Furthermore there may be some problems in numerical calculation such as the tendency of divergence, instability and increase of calculation time. In the traditional matching methods, after some variable parameters are initially assumed and then calculated, the calculation is iterated to converge within an appropriate error range by expressing the new variables with the previous calculation error function. Even though these traditional methods show comparatively reasonable results in performance simulation, there may be some unsatisfied results in particular cases. Moreover in this case it can be more difficult in more precise calculation due to simplification by using various assumptions. Therefore in order to search the optimal matching point in performance simulation of gas turbine efficiently and quickly, the fuzzy approaches were applied. In performance simulation using the fuzzy logic, it was found that more effective engine operating points were found and calculation time was considerably reduced less than the traditional methods. Furthermore the MATLAB was used to apply the fuzzy logic easily as well as to make user-friendly circumstance in performance analysis.
Centrifugal Compressor of a 100 kW Microturbine: Part 3 — Optimization of Diffuser Apparatus
Authors: Benini E. , Toffolo A.
Published: February 2009

This is the last part of a three-part paper regarding performance analysis and optimization of a centrifugal compressor used in a 100 kW microturbine. This part deals with the numerical constrained optimization of the diffuser apparatus (i.e. the radial and deswirl cascades) for maximum aerodynamic efficiency and pressure recovery. The optimization is accomplished through the application of a multiobjective Pareto evolutionary algorithm which is interfaced to a parametric code, that generates the geometries to be analyzed, and a Computational Fluid Dynamics code that measures the fitness of the candidate solutions. The variables of the optimization include the main dimensions of diffuser (with a constraint on the overall radial and axial size) and the profiles’ shape. The set of optimized configurations is illustrated and compared to the original one; the reason of improved performance are finally discussed.
Fluid Flow and Heat Transfer Features at a Cross-Flow of Dimpled Tubes in a Confined Space
Authors: Kovalenko G. V. , Khalatov A. A.
Published: February 2009

This paper provides the primary results of an experimental study into the fluid flow and heat transfer features at a cross-flow of a dimpled tube in a rectangular-shaped duct between two adjacent dimpled tubes. The cylindrical dimples were engraved on each tube surface both in the staggered and in-line mode; altogether nine dimpled tubes were tested in the range of the Reynolds number Re from 8,000 to 115,000. The first group (four samples) represents tubes structured with symmetrical dimples drilled in the radial direction, while the second group (five samples) is tubes with asymmetrical dimples. In the latter case each dimple was made in such a way that its axis is parallel to the tube diameter with a certain clearance between axes. For comparisons a row of smooth tubes of the same configuration was tested under identical fluid boundary conditions. Three factors primarily influencing heat transfer are under consideration in this paper: a) increase in a heat exchange surface due to a tube dimpling, b) variations in the flow pattern, c) interaction between boundary layer and main flow. Behind a smooth tube in confined space the reverse flow zone grows initially to Re = 37,000 however decreases at larger Reynolds numbers. Unlike this, behind a dimpled tube in confined space the reverse flow zone reduces at low Reynolds numbers to reach minimum magnitude at Re = 10,000–28,000, and increases afterwards to become approximately constant at Reynolds numbers over 45,000. It has been found, the reverse flow length depends on the Reynolds number, dimple parameters and configuration. The frequency spectrum of the dimpled tube is different from that occurring for a smooth tube. A few frequency ‘picks’ with corresponding the Strouhal numbers were registered including those typical to a single dimple on a flat plate. The heat transfer enhancement rates of around 45%–55% compared with a smooth tube in confined space were obtained depending on dimple parameters and flow regimes. Increase in the heat transfer enhancement rate for tubes with shallow dimples exceeds growth of heat exchange surface due to a dimpling. Increases in a pressure drop at the tube bundle caused by dimpling do not exceed 14%.