bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Cyclic Operation of Heat Recovery Steam Generators — A Practical Approach
Authors: Douglas Lewis R. , Schroeder Joseph E. , Eriksen Vernon L.
Published: August 2014

In the past, power plants for the most part did not operate in cyclic service. Today the demand for dispatchable operations is a common requirement for many new facilities. In this report practical considerations for evaluating and accommodating high cyclic operations of Heat Recover Stream Generators, (HRSG), are discussed. A general understanding of the difference between Low Cycle and High Cycle Fatigue is provided, how fatigue causes damage is discussed and the operating parameters that are most influential are identified. Non-analytical methods that can be used to minimize the effects of fatigue and how these options can greatly decrease damage are discussed. Typical HRSG operating cycles that should be considered in life evaluation are defined. Finally, a practical approach to evaluating the fitness of the equipment for high cyclic operations is presented along with an example of how this method can be used.
A Steady State Calculation Model for Gas Turbine Thermal Enclosures
Authors: Desideri Umberto , Di Maria Francesco
Published: August 2014

Heavy duty and aeroderivative gas turbines for power generation and mechanical drive are installed inside an enclosure that is thermally and acoustically insulated and is equipped with fire extinguishing systems.

The enclosure is bolted on the gas turbine basement and is made of a steel frame that supports removable side panels, doors and roof sections.

All the fire extinguishing systems, lubricating oil pipes and electrical systems are fitted inside the enclosure and release, together with the gas turbine, a large amount of heat that has to be dissipated to avoid overheating of the gas turbine itself and its auxiliaries. Overheating of the enclosures is one of the main reasons for gas turbine unplanned stops.

For avoiding high internal temperatures, the enclosure is equipped with a cooling system consisting of pipes and fans, that extracts heat from the enclosure and limits the internal temperature increase.

This paper presents a calculation model developed for the study of the enclosure cooling system. Results are compared with experimental data measured on an aeroderivative gas turbine used as mechanical drive for a natural gas compression station, and acceptable correspondence is achieved.
Water Mist Fire-Fighting System in the Marine LM2500 Gas Turbine Module
Authors: McAndrews Glenn , Gameiro Victor M. , Shirriff Tom
Published: August 2014

Gas turbine packagers and end users find themselves today faced with the problem of identifying optimal gas turbine enclosure fire-fighting systems in an era of evolving technology. Research over the last several years has identified water mist as one of the most promising candidates for marine gas turbine enclosures. This paper will discuss the background and implementation of such a system in a military marine gas turbine enclosure.
Fracture Toughness Properties of a Modern Ni-Mo-Cr High Temperature Alloy
Authors: Seeley R. R. , Klarstrom D. L.
Published: August 2014

The Ni-Mo-Cr alloy (HAYNES® 242™) is an age-hardenable alloy that can be significantly strengthened by a simple aging heat treatment at 650°C (1200°F). Long-term thermal exposures at moderate temperatures increase the strength and decrease the ductility and Charpy V-notch impact toughness. Tensile ductility and Charpy impact toughness have traditionally been used to study the effect of long-term thermal exposure on mechanical properties. However, there has been little or no work reported on the effect of long-term thermal exposures on the fracture toughness of nickel-base alloys. The room temperature fracture toughness (KJc) properties have been evaluated for Ni-Mo-Cr plate material in the annealed, annealed and aged, and annealed plus long-term thermal exposed condition. The microstructural and fracture mode characteristics of this alloy were examined as well. The tensile ductility, impact toughness and fracture conditions of the toughness properties were decreased by a long-term thermal exposure at 650°C (1200°F). The fracture toughness test data revealed the crack extension during the KJc tests to be stable throughout the test. The mechanical property data suggest a strong relationship between fracture toughness and tensile ductility. The microstructures and fracture surface morphologies for three metallurgical conditions of the Ni-Mo-Cr alloy are presented.
Component-Mode-Based Reduced Order Modeling Techniques for Mistuned Bladed Disks: Part II — Application
Authors: Bladh Ronnie , Castanier Matthew P. , Pierre Christophe
Published: August 2014

In this paper, the component-mode-based methods formulated in the companion paper (Part I: Theoretical Models) are applied to the dynamic analysis of two example finite element models of bladed disks. Free and forced responses for both tuned and mistuned rotors are considered. Comprehensive comparisons are made among the techniques using full system finite element solutions as a benchmark. The accurate capture of eigenfrequency veering regions is of critical importance for obtaining high-fidelity predictions of the rotor’s sensitivity to mistuning. Therefore, particular attention is devoted to this subject. It is shown that the Craig-Bampton component mode synthesis (CMS) technique is robust and yields highly reliable results. However, this is achieved at considerable computational cost due to the retained component interface degrees of freedom (DOF). It is demonstrated that this problem is alleviated by a secondary modal analysis reduction technique (SMART). In addition, a non-CMS mistuning projection method is considered. Although this method is elegant and accurate, it is seen that it lacks the versatility and efficiency of the CMS-based SMART. Overall, this work shows that significant improvements on the accuracy and efficiency of current reduced order modeling methods are possible.
On the Application of Powder Shear Damping to a Structural Element
Authors: Swanson Erik E. , Xu David S. , Russell Thomas E. , Walton James , Heshmat Hooshang
Published: August 2014

With the increasing demands placed on modern gas turbine components, improvements in high temperature compatible damping technology are required. The areas of application include turbine airfoils, struts, guide vanes, exhaust ducts, and similar components. The need for improved damping elements is especially acute for integrally bladed disks (“blisks”). Constrained powder shear dampers, using thin pockets of high temperature compatible powders meets these needs. With damping performance comparable to current visco-elastic elements, shear powder damping elements add the capability of high temperature operation, compatibility with blade heat treatments, good high frequency damping characteristics, and minimal degradation predicted for high centrifugal loads. Building on previous fundamental work, this paper discusses a proof of concept application of powder shear damping to a thin beam. Both cantilever and free-free configurations are examined. Comparisons between experimental measurements of undamped, constrained layer visco-elastic damping, and powder shear damped beams are presented. FEA results for the cantilever configuration are also shown to correlate well with the experimental data.
Experimental Determination of Powder Film Shear and Damping Characteristics
Authors: Heshmat Hooshang
Published: August 2014

Thin powder films are proposed as a damping medium to overcome the temperature and creep limitations associated with viscoelastic dampers. Its basis is the established quasi-continuum model for fine powders successfully applied to such devices as bearings, piston rings, conventional dampers and others. In developing this technology over the past ten years it has been shown that satisfactory performance with respect to levels of load capacity, friction, etc. can be achieved with powder films which operate in a quasi-viscous mode much as fluid films do. Direct measurements have demonstrated that high levels of damping are possible at high frequencies even with extremely small excitational amplitudes, and that the achieved stiffness and damping are insensitive to temperature. Apart from its physical characteristics, measured stiffness and damping of powder films were shown to be related to powder compaction pressure, relative velocity, film thickness and imposed shear stress. With its Theological characteristics established thin powder layers should then be applicable as dampers in such devices as turbine airfoils, struts, guide vanes, exhaust ducts and similar systems subject to high frequency vibrations and high temperatures.
Prediction of Low Engine Order Inlet Distortion Driven Resonance in a Low Aspect Ratio Fan
Authors: Marshall J. G. , Xu L. , Denton J. , Chew J. W.
Published: August 2014

This paper presents a forced response prediction of 3 resonances in a low aspect ratio modern fan rotor and compares with other worker’s experimental data. The incoming disturbances are due to low engine-order inlet distortion from upstream screens. The resonances occur in the running range at 3 and 8 engine orders which cross low modes (flap, torsion and stripe) of the blade. The fan was tested with on-blade instrumentation at both on- and off-resonant conditions to establish the unsteady pressures due to known distortion patterns.

The resulting steady and unsteady flow in the fan blade passages has been predicted by three methods, all three-dimensional. The first is a linearised unsteady Euler method; the second is a non-linear unsteady Navier-Stokes method; the third method uses a similar level of aerodynamic modelling as the second but also includes a coupled model of the structural dynamics. The predictions for the 3 methods are presented against the test data, and further insight into the problem is obtained through post-processing of the data. Predictions of the blade vibration response are also obtained. Overall the level of agreement between calculations and measurements is considered encouraging although further research is needed.
Application of Model Order Reduction to Compressor Aeroelastic Models
Authors: Willcox Karen , Peraire Jaime , Paduano James D.
Published: August 2014

A model order reduction technique that yields low-order models of blade row unsteady aerodyamics is introduced. The technique is applied to linearized unsteady Euler CFD solutions in such a way that the resulting blade row models can be linked to their surroundings through their boundary conditions. The technique is applied to a transonic compressor aeroelastic analysis, in which the high-fidelity CFD forced-response results are better captured than with models that use single-frequency influence coefficients. A low-speed compressor stage is also modeled to demonstrate the multistage capability of the method. These examples demonstrate how model order reduction can be used to systematically improve the versatility, fidelity, and range of applicability of the low-order aerodynamic models typically used for incorporation of CFD results into aeroelastic analyses.
Parametric Study of the Pressure Stability on an Oscillating Airfoil From Stable to Stalled Flow Conditions
Authors: Svensdotter S. , Johansson U. , Fransson T.
Published: August 2014

This paper presents investigations on the suction side of an oscillation blade at an inlet Mach number of 0.5, with oscillation frequencies from 60 to 210Hz, mean incidence angles from 0° to 10° and with blade amplitudes up to 4.2° (for 60Hz). The time-dependent pressures show that the aerodynamic loads are not linear for the stall region. It was found that an increased mean incidence caused a higher excitation of the blade from the aerodynamic forces, while the effects of varying the blade amplitudes and frequencies were more difficult to determine. At 6° mean incidence, and below, increased blade amplitude for a constant frequency caused the blade suction surface to experience an increased excitation, while for the 7° incidence, and above, the opposite was shown. The fact that the blade amplitude dependence changes when the mean incidence increases above the steady state stall angle is explained by the increased portion of the oscillation cycle spent at stalled conditions. A shift in phase was seen for the highest investigated frequency, which might be due to a phase lag between the blade motion and the leading edge vortex, increasing with increasing frequency.
Dynamic Coefficients of Labyrinth Gas Seals: A Comparison of Experimental Results and Numerical Calculations
Authors: Kwanka K. , Sobotzik J. , Nordmann R.
Published: August 2014

Non-contacting labyrinth seals are still the most common constructive elements used to minimize leakage losses in turbomachinery between areas with high pressure and areas with low pressure. Unfortunately, the leakage flow through the labyrinth seal generates forces which can have a great impact on the dynamics of the turborotor. Particularly in cases of instability, the turbomachinery is restricted in its power or rotating speed because of violent self-excited vibrations of the rotor.

The occurrence of self-excited rotor vibrations due to lateral forces must definitely be excluded. To consider the labyrinth forces in Finite-Element prediction, a set of preferably exact dynamic coefficients is required. Numerical approaches used to calculate the coefficients are based on Navier-Stokes equations. A comparison with experimental data is essential for a validation of the calculation. The experimental identification is difficult, because of the littleness of the forces to be measured in gas seals. Especially the non-conservative coefficients, cross-coupled stiffness and direct damping, show a good agreement in both magnitude and trend depending on the entry swirl of the seal.
A Probabilistically-Based Damage Tolerance Analysis Computer Program for Hard Alpha Anomalies in Titanium Rotors
Authors: Millwater Harry R. , Fitch Simeon H. K. , Wu Y.-T. (Justin) , Riha David S. , Enright Michael P. , Leverant Gerry R. , McClung R. Craig , Kuhlman Chris J. , Chell G. Graham , Lee Yi-Der
Published: August 2014

A probabilistically-based damage tolerance analysis computer program for engine rotors has been developed under Federal Aviation Administration (FAA) funding to augment the traditional safe-life approach. The computer program, in its current form, is designed to quantify the risk of rotor failure due to fatigue cracks initiated at hard alpha anomalies in titanium. The software, DARWIN™ (Design Assessment of Reliability With Inspection), integrates a graphical user interface, finite element stress analysis results, fracture-mechanics-based life assessment for low-cycle fatigue, material anomaly data, probability of anomaly detection, and inspection schedules to determine the probability-of-fracture of a rotor disk as a function of operating cycles with and without inspections. The program also indicates the relative likelihood of failure of the disk regions. Work is underway to enhance the software to handle anomalies in cast/wrought and powder nickel disks, and manufacturing and maintenance-induced surface anomalies in all disk materials.
Effects of Hot Streak Shape on Rotor Heating in a High-Subsonic Single-Stage Turbine
Authors: Dorney Daniel J. , Gundy-Burlet Karen L.
Published: August 2014

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location (clocking) of the hot streak relative to the first-stage vane airfoils can be used to minimize the adverse effects of the hot streak. The effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have also been evaluated. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine operating in high subsonic flow. In addition to a simulation of the baseline turbine, simulations have been performed for circular and elliptical hot streaks of varying sizes in an effort to represent different combustor designs. The predicted results for the baseline simulation show good agreement with the available experimental data. The results of the hot streak simulations indicate: that a) elliptical hot streaks mix more rapidly than circular hot streaks, b) for small hot streak surface area the average rotor temperature is not a strong function of hot streak temperature ratio or shape, and c) hot streaks with larger surface area interact with the secondary flows at the rotor hub endwall, generating an additional high temperature region.
Direct Numerical Simulation of Rotating Stall and Stall Induced in Centrifugal Vaneless Diffusers
Authors: Kinoshita Yoshifumi , Matsumura Takashi
Published: August 2014

A direct numerical simulation (DNS) method is proposed to evaluate the general incompressible flow behaviors in the centrifugal vaneless diffusers. This method is then applied to three kinds of centrifugal vaneless diffusers. In this way, it is confirmed that the flow pattern predicted based on the present DNS method agrees with experiments not only under the rotating stall condition but also under the diffuser stall condition. In addition, the predictions for rotating stall limit are shown to agree with the authors’ previously proposed criterion for rotating stall limit. Finally, it is clarified both experimentally and numerically that the authors’ previously proposed criterion for diffuser stall is correct; that is, when the zone of inward swirl flow reaches the exit of the diffuser, diffuser stall begins.
Direct Method for Optimization of a Centrifugal Compressor Vaneless Diffuser
Authors: Lee Yu-Tai , Luo Lin , Bein Thomas W.
Published: August 2014

A Direct Method for Optimization (DMO) is developed for investigating pressure rise and energy loss in a vaneless diffuser of a generic compressor used in shipboard air-conditioning systems. The scheme uses Reynolds Averaged Navier-Stokes (RANS) results and evaluates gradients of a predetermined objective function. The current Direct Method for Optimization differs from the popular Inverse Design Method in the process of obtaining final configurations and in the final configurations obtained. The Direct Method for Optimization achieves a final shape from maximizing/minimizing a nonlinear function; i.e., the objective function. Both gradient and non-gradient Direct Methods for Optimization are compared with respect to accuracy and efficiency.

The coupled DMO/RANS optimization code is benchmarked using a plane turbulent diffuser also investigated by Zhang et al. using an adjoint method. The benchmark indicates that if a global optimum exists, the result should be independent of the methodologies or design parameters used.

The DMO/RANS method is applied to redesign a 3-D centrifugal vaneless diffuser used in a modern generic compressor. The objective function is a composite function of the diffuser’s pressure rise and total energy loss. The new optimum diffuser has a minimum width at a location far beyond the conventional diffuser pinch point. The new diffuser also provides an efficient section for pressure recovery, which takes place after the minimum width location. Test data for the new diffuser validates the current approach at the design condition. Furthermore, improved performance is also recorded experimentally at off-design conditions for the optimized diffuser.
Suppression of Rotating Stall by Wall Roughness Control in Vaneless Diffusers of Centrifugal Blowers
Authors: Ishida Masahiro , Sakaguchi Daisaku , Ueki Hironobu
Published: August 2014

By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1%. This is based on the fact that the local reverse flow occurs firstly in the hub side in most centrifugal blowers with the backswept blade impeller. The 3-D boundary layer calculation shows that the increase in wall shear component normal to the main-flow direction decreases markedly the skewed angle of the 3-D boundary layer, and results in suppression of the 3-D separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = 1.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the 3-D boundary layer, supports the adverse pressure gradient.
A Numerical Study on Performances of Centrifugal Compressor Stages With Different Radial Gaps
Authors: Sato K. , He L.
Published: August 2014

A numerical study of 3D unsteady flows in centrifugal compressor stages solving the Navier-Stokes equations is presented. The emphasis is on the effect of the radial gap between blade rows on the aerodynamic performance. In the numerical tests, Krain’s centrifugal impeller was combined with a DCA (Double Circular Arc) type radial vaned diffuser. The compressor stages with three settings of radial gap ranging from 5 to 15 percent of the impeller trailing edge radius are configured and unsteady flow simulations are carried out to compare the time-averaged efficiencies.

The performance predictions show that the efficiency is deteriorated if the radial gap between blade rows is reduced with intensified blade row interaction, which is in contradiction to the general trend for axial compressor stages. In the centrifugal compressors tested, wake chopping by diffuser vanes, which usually benefits efficiency in axial compressor stages, causes unfavourable wake compression through the diffuser passages to deteriorate the efficiency.
Computational and Experimental Comparison of Different Volute Geometries in a Radial Compressor
Authors: Reunanen Arttu , Pitkänen Harri , Siikonen Timo , Heiska Harri , Larjola Jaakko , Esa Hannu , Sallinen Petri
Published: August 2014

Two different volute geometries of a radial compressor at three different operating points have been analyzed using Computational Fluid Dynamics and detailed laboratory measurements. The performance of the volutes were compared using steady-state CFD-analysis, where the volute and the impeller with diffuser were modeled separately. In addition, a time dependent simulation of the complete compressor using the sliding mesh technique was performed for one operation point. Both volutes were manufactured and the overall performance of the compressor, the pressure distribution in the volute and the flow field in the volute inlet were measured with the respective volute geometries. The results obtained from steady, quasi-steady and time-accurate simulations are compared with experimental data.
Influence of Endwall Contouring in Axial Gaps on the Flow Field in a Four-Stage Turbine
Authors: Bohn Dieter E. , Kusterer Karsten , Sürken Norbert , Kreitmeier Franz
Published: August 2014

Secondary flows and leakage flows are leading to complex vortex structures in the 3-D flow field of a turbine blading. Aerodynamic losses are the consequence. Reducing the aerodynamic losses related to tip leakage flows by endwall contouring is subject of an actual numerical investigation of the flow field in a 4-stage test turbine with repeating stages. The 3-D flow field for various geometric configurations with endwall contouring is calculated by application of a 3-D Navier-Stokes code. Here, the numerical results of configurations with arc-like and wave-like contours (bumps) at the shaft and the casing with a maximum deviation from the reference contour in the axial gap between stator and rotor are presented. Furthermore, the results are compared to the experimental and numerical data of the test turbine with a reference contour without endwall contouring.

The results show a significant influence of the bumps on the radial velocity distribution in the flow field and the static pressure field. By application of a subtraction method where the reference flow field is subtracted from the flow fields of the bump-configurations, it can be shown that the leakage flows are reduced. A detailed flow analysis shows the presence of a leakage vortex.

For a measure of the flow field inhomogeneity and for reducing the complex 3-D data to 2-D and 1-D values a balance-based averaging method is used. The method is based on a hypothetical equilibration process between two infinitesimal neighbouring control surfaces. During this physically based averaging process, equilibration coefficients can be derived which are a measure for the flow inhomogeneity. It can be shown that arc-like and wave-like endwall contouring has a positive influence on the homogeneity of the flow field. Thus, this effect leads to higher aerodynamic stage efficiencies for repeating stages.
Aerodynamic Performance of a Transonic Turbine Cascade at Off-Design Conditions
Authors: Jouini D. B. M. , Sjolander S. A. , Moustapha S. H.
Published: August 2014

The paper presents detailed measurements of the midspan aerodynamic performance of a transonic turbine cascade at off-design conditions. The measurements were conducted for exit Mach numbers ranging from 0.5 to 1.2 and for Reynolds numbers from 4×105 to 106. The profile losses were measured for incidence values of +14.5°, +10°, +4.5°, 0°, and −10° relative to design. To aid in understanding the loss behaviour and to provide other insights into the flow physics, measurements of blade loading, exit flow angles, trailing-edge base pressures, and the Axial Velocity Density Ratio (AVDR) were also made. It was found that the profile losses at transonic Mach numbers can be closely related to the base pressure behaviour. The losses were also affected by the AVDR.
Numerical and Experimental Investigation of an Aerodynamically High-Loaded Axial Boiler Fan
Authors: Reischke A. , Jung M. , Breuhaus P. , Molin J. , Hess S.
Published: August 2014

In a common project ABB Fläkt Industri AB, Sweden, and ABB Turbo Systems Ltd., Switzerland, developed a Q3D design system for low Mach number axial fans. In order to validate the Q3D-calculations and the customized loss correlation, the flow field of an industrial high-pressure boiler fan was investigated experimentally.

The examined single stage fan is equipped with hydraulically adjustable rotor blades, non-profiled guide vanes and an annular diffuser. Varying the stagger angle between 34° and 76° allows operating the fan over a wide range of volume flows. Experiments and calculations cover the entire stable operating range.

Flow field traverses by means of hot film anemometry and pneumatic total pressure Kiel probes at different sections within the rotor/vane configuration, combined with axially and tangentially distributed static pressures tabs and fix mounted Kiel probes, allowed a deep insight in the flow behavior. The fast response capability of the hot film anemometry was used to measure the flow field downstream of the rotor in detail. Additionally, flow field visualizations inside the guide vane channel based upon a TiO4/Oil-paint technique completed the experimental fan investigation.

The Q3D system is based on coupling the Euler codes MISES (S1) and MTFlow (S2), both developed at MIT. Loss models were implemented to account for profile losses, leakage losses and endwall losses. Near wall viscous effects are considered by boundary layer modeling.

The investigations show that the S1/S2 Euler solvers behave well even in case of Mach numbers below 0.03. S1 convergence problems arise for off-design cases because of unfavorable incidence angles. The fully automated Q3D systems allows calculating fan performance charts with low turnaround time in good agreement with the measurement.
Quantitative Influence of the Steady Non-Reflecting Boundary Conditions on Blade-to-Blade Computations
Authors: Contreras Jesus , Corral Roque
Published: August 2014

The initial purpose of this work was to implement steady non-reflecting boundary conditions on an unstructured code to improve the quality of turbomachinery simulations in general and in particular about LPT blades. One of the distinctive characteristics of this type of configurations is the fact that inflow and outflow boundary conditions are located extremely close to the blade and a potential distortion of the flowfield due to the effect of the boundary conditions is expected. It is shown that the improvement due to the use of exact, non-reflecting boundary conditions, although clearly seen in the flowfield, is negligible in practice on the blade and that in subsonic flows its effect is of second order compared to the sensitivity of the solution to small changes on the mesh for distances from the blade to the boundary conditions of about 0.25 chords or larger.
Optimization of Multistage Turbines Using a Through-Flow Code
Authors: Petrovic Milan V. , Dulikravich George S. , Martin Thomas J.
Published: August 2014

Very fast and accurate flow calculation and performance prediction of multistage axial flow turbines at design and off-design conditions was performed using a compressible steady state inviscid through-flow code with high fidelity loss and mixing models. The code is based on a stream function model and a finite element solution procedure. A new design system has been developed which optimizes hub and shroud geometry and inlet and exit flow-field parameters for each blade row of a multistage axial flow turbine. Optimization was performed using our hybrid constrained optimization code that includes the following modules: genetic algorithm, simulated annealing, modified simplex method, sequential quadratic programming, and a gradient search algorithm. Switching among the modules was performed automatically. By varying a relatively small number of geometric variables per each turbine stage it is possible to find an optimal radial distribution of flow parameters at the inlet and outlet of every blade row. Thus, an optimized meridional flow path can be found that is defined by the optimized shape of the hub and shroud. The multistage design optimization system has been demonstrated using an actual two-stage axial gas turbine as an example. The comparison of computed performance of an already very high efficiency initial design and its optimized design demonstrates more than one percent improvement in the turbine efficiency at design and significant off-design conditions. The entire design optimization process is feasible on a typical single-processor computer workstation or a personal computer.
Control of Combustor Instabilities Using an Artificial Neural Network
Authors: Vaudrey Michael A. , Saunders William R.
Published: August 2014

It is well-known that phase-shifting controllers used for active combustion control must be manually adjusted in order to maintain control over a broad range of operating combustor operating conditions. If one assumes that the thermoacoustic instabilities are linearly stabilizable, then what is needed is a method to determine, and ultimately predict, the frequency response of the plant for any range of operating conditions, so the controller design can be automatically updated to track the changing plant gain/phase relationships that are observed with changing heat release. A unique test-based, design process has been proposed to predict the gain/phase characteristics required of a proportional, phase-shifting controller that can stabilize the thermoacoustic instabilities. In this paper, that process is used to automate the design of a fixed-gain feedback controller that limits the amplitudes of any feedback induced instabilities (to some pre-specified level) while providing the best control of the targeted limit cycling pressure oscillations.

The paper describes how a neural network was trained, using the suggested design process, to predict the frequency response of the thermoacoustics in a tube combustor at frequencies adjacent to the limit cycle frequency using certain operating conditions that included a sparsely-sampled temperature profile, total air/fuel flow rate, and equivalence ratio. The neural net training was performed using complex valued, open-loop frequency response function data as the desired signal with the previously mentioned operating conditions as the input signals. (The open loop data was collected for a narrow frequency range surrounding the limit cycle instability by performing a sine dwell at discrete frequencies). Once the neural network was trained, it was used to predict the approximate phase and gain margins as a function of temperature and flow conditions. The margins were then used to automatically update and design a fixed shape feedback controller having the proper phase and magnitude to ensure stability and control in the face of changing operating conditions. A companion paper describes the methodology that underlies the automated design of the feedback controller gain and phase delay.
Development and Evaluation of Ceramic Components for Small Gas Turbine Engine
Authors: Tanaka Koichi , Yoshida Makoto , Kubo Toshifumi , Terazono Hirofumi , Tsuruzono Sazo
Published: August 2014

The 300kW class CGT project in Japan administered by the New Energy and Industrial Technology Development Organization (NEDO) under the sponsorship of the Ministry of International Trade and Industry (MITI) was completed in March, 1999 after 11 years. The purposes of the project were energy conservation and environmental protection. The CGT302 group of the CGT project, in cooperation with Kawasaki Heavy Industries, Ltd. (KHI), achieved all of the project targets. The targets included the turbine inlet temperature (TIT) of 1350°C, a thermal efficiency of 42%, emissions below 70ppm, and a 1000hr engine durability test carried out at 1200°C1).

To achieve such targets Kyocera has been developing various ceramic components such as large-sized stationary components, monolithic rotors and ceramic shrouds with abradable seal. These components have been successfully fabricated with SN281 and SN282. Damage was caused as a result of contact between the turbine blades and the shrouds. In order to reduce such damages, the shroud has been modified to incorporate an abradable material newly developed for this application, and an engine test has been carried out successfully with no damage.

For practical use, the greatest concern is the durability of ceramic components. The ceramic components were evaluated in a 1000hr long term durability test. There were, however, some troubles for the GGT rotors and the engines were broken when the durability tests were carried out. Finally, only the combustor survived the 1000hr engine test at 1200°C. The material characteristics of the survived combustor along with other broken components were analyzed after the long-term engine tests. The test results revealed no obvious change in mechanical properties nor in blade shape.

In this paper, the development of selected components is presented along with the evaluation results of components exposed to the long-term engine tests.
Ceramic Turbine Engine Demonstration Project — A Summary Report
Authors: Schenk Bjoern
Published: August 2014

Honeywell Engines & Systems has successfully addressed critical concerns that are slowing commercialization of structural ceramics in gas turbines. The U.S. Department of Energy (DoE) sponsored Ceramic Turbine Engine Demonstration Project (CTEDP) had the mission of advancing ceramic gas turbine component technology toward commercialization. The thrust of the program was to “bridge the gap” between ceramics in the laboratory and near-term commercial heat engine applications. Most of this mission has been achieved. The 331-200[CT] auxiliary power unit (APU) test bed featured ceramic first-stage nozzles and blades. Fabrication of ceramic components provided manufacturing process demonstration scale-up to the minimum levels needed for commercial viability. Through this program, design methods refinement and the development of new design methods unique to ceramic turbine components have been supported and validated in rig and development engine testing. Over 6800 hours of on-site endurance tests demonstrated component reliability. Additional field testing in APUs onboard commercial aircraft and stationary industrial engines has been initiated and will continue beyond completion of this program.
Ultra High Efficiency Hybrid Direct Fuel Cell / Turbine Power Plant
Authors: Leo Anthony J. , Ghezel-Ayagh Hossein , Sanderson Robert
Published: August 2014

FuelCell Energy, Inc has developed a design for a hybrid powerplant which combines the company’s carbonate Direct Fuel Cell (DFC) with a gas turbine cycle in an ultra high efficiency system. Under a recently completed program supported by the U.S. Department of Energy through the Federal Energy Technology Center (FETC, Morgantown WV), the system design was optimized to eliminate high-temperature developmental components and reduce the overall complexity of the cycle. Modeling studies indicate that the system is capable of operating with fuel-to-electrical LHV efficiencies in the low 70’s with near term fuel cell performance levels. Longer term fuel cell performance gains may provide system efficiencies near 80 percent.
Effects of Gap Leakage on Fluid Flow in a Contoured Turbine Nozzle Guide Vane
Authors: Lin Y.-L. , Shih T. I-P. , Chyu M. K. , Bunker R. S.
Published: August 2014

Computations were performed to study the three-dimensional flow in a nozzle guide vane with leakage issuing from a narrow gap with a backward-facing step located upstream of the airfoil on each endwall. The nozzle guide vane investigated has one flat and one contoured endwall. For the contoured endwall, two configurations of the same contouring profile were investigated with and without gap leakage. In one configuration, all contouring is upstream of the airfoil passage. In the other, the contouring starts upstream of the airfoil passage and continues through it.

Results obtained show that when there is gap leakage, secondary flows are reduced at all endwalls for both nozzle configurations investigated. Without gap leakage, secondary flows are reduced only on the contoured endwall in which the contouring started upstream of the airfoil passage and continued through it. When all of the contouring is located upstream of the airfoil passage, there is considerable hot gas ingestion into the gap at both endwalls. When the contouring starts upstream of the airfoil passage and continues throught it, hot gas ingestion was minimal at the contoured endwall and greatly reduced at the flat endwall.

This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence were modeled by the low Reynolds number shear-stress transport k-ω model. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters and multigrid acceleration of a diagonalized ADI scheme with local time stepping on patched structured grids.
Brush Seals for the No. 3 Bearing of a Model 7EA Gas Turbine
Authors: Ingistov Steve , Meredith Gary , Sulda Erik
Published: August 2014

Gas Turbines in power generation are frequently of the single rotor type. The rotor is directly connected to the electrical generator. The rotor may be supported by two journal bearings or in some cases there is an additional journal bearing situated between the axial compressor discharge and the gas turbine intake. This third bearing serves to provide the rotor with additional support required to reduce rotor dynamic instabilities. The third bearing is, therefore, inside the machine housing and a significant amount of maintenance work is necessary to inspect it. The third bearing is also exposed to elevated temperatures by, essentially, being surrounded by compressor discharge air. A certain amount of compressor discharge air leaks through the seals into the cylindrical space around the third bearing housing and from there, due to significant pressure gradients, into the third bearing. Labyrinth seals are provided to impede air leakage from the pressurized cylindrical space into the bearing cavity. The air that leaks into the bearing housing mixes with a buffer air stream. This buffer air stream serves to cool the bearing cavity and to prevent leakage of hot, high-pressure air into the bearing cavity. Two dry air streams are then routed into the atmosphere via the coaxial space formed by two cylindrical surfaces. The portion of the buffer air stream contacting the bearing lubricating oil is de-misted in a special de-mister vessel. The de-misted air is exhausted into the atmosphere and the separated oil is returned to the gas turbine lubricating oil reservoir. This Paper discusses the introduction of brush seals into the No. 3 bearing housing as an additional element in retarding the high pressure, high temperature air infiltration into the No. 3 bearing housing.
Experimental Investigation of Stall in a Two Stage Compressor
Authors: Nurzia F. , Palomba C. , Puddu P.
Published: August 2014

This paper is concerned with the experimental characterisation of the unstable behaviour exhibited by a two stage axial flow compressor with variable geometry inlet guide vanes. The characterisation includes performance assessment stall transient and determination of three dimensional flow during one cell operation. The three flow components have been measured with a single slanted hot wire ensemble phase averaging technique based on several cell passages. This technique, already successfully applied for stall in an isolated rotor, is now tried on the more complex two stage compressor.
The Engineering Doctorate — An ‘Enhanced’ Doctoral Programme for Engineers Incorporating Business Decision-Making Skills: A Gas-Turbine Engineering Perspective
Authors: Ivey Paul C. , Sanderson Michael L. , Morris Vivien , Ferguson Derek G.
Published: August 2014

This paper describes a new UK initiative in the post graduate education of Engineers. The new ‘enhanced’ degree of Engineering Doctorate educates graduate Engineers in their respective technical disciplines whilst at the same time integrating the world of commerce and business into the technical decision making process.

The paper describes the initial candidate selection methodology, project selection, course structure, assessment, thesis structure and outputs. The advantages of this enhanced postgraduate training are demonstrated, as are the objectives for the UK in adopting such a scheme.

An example is presented from a joint Rolls Royce / Cranfield case study of the Design, Development and Product launch of a new type of Gas Turbine Instrumentation. This is set in a Gas Turbine Engineering perspective, in particular the consideration of active control of compressor surge to benefit aircraft engine fuel burn and increased flight range.
Introduction of Project Based Learning for Designing a Heat and Power Plant Into the Last Year Curriculum
Authors: Svensdotter Susanne , Almqvist Per , Fransson Torsten H.
Published: August 2014

Teaching the curriculum in heat and power technology in the classical way consists of giving lectures and exams to the students. A few laboratory exercises might highlight some details, but in general the students have problems with understanding the relevance of the lectures to real engineering subjects. The Division of Heat and Power Technology at the Royal Institute of Technology (KTH) in Sweden has started to give part of the curriculum as a project to design a complete heat and power plant. The objectives were to increase the interest and understanding of the heat and power technology by the students, encourage them to actively search for information in the subject on their own, work in teams and to make oral and written reports. Connecting external experts to the project gave the students a link to the industry. Several written and oral presentations were included in the project, which gave the students a good training in presentation techniques. The results show that the students had achieved a better knowledge of the investigated techniques than did the students at earlier years, when the course was given in the classical way. The disadvantages were mainly the extra amount of time needed for the teachers and the external experts for discussions with the students.
Experience With a Fast Track Power Generation Project
Authors: Mayer Albrecht H. , Lively Noel W.
Published: August 2014

To meet peaking power demands the E.W. Brown Station, owned and operated by Kentucky Utilities Company, was extended by two GT24 gas turbines. The project had to meet a 9-month engineering, construction and commissioning schedule. The conceptual design is based on ABB ALSTOM POWER’S reference plant design for combined cycle application. It was adjusted to the requirements of a simple cycle operation.

Special plant features such as evaporative cooling of the inlet air, system design of the evaporative cooling system, performance and experience will be discussed in detail. The plant has an aggressive running and starting reliability goal; the approach to meet the required plant reliability will be discussed below. The initial operational feedback will be addressed as well as an outlook on how to meet all project goals.
A Recuperated Gas Turbine Incorporating External Heat Sources in the Combined Gas-Steam Cycle
Authors: Chodkiewicz Ryszard , Krysinski Jan , Porochnicki Jerzy
Published: August 2014

The recuperation by means of external waste heat sources, as opposed to the recuperation of the turbine exhaust gases (to preheat the compressed air), allows one to utilize the hot exhaust gases of the gas turbine in the bottoming steam cycle to produce steam in order to generate additional power. Such a combined gas/steam energy system, closely integrated with the industrial process, can produce electric power (and useful heat) with high efficiency and very low atmospheric air pollution. In the present paper two examples of applications of this new technology have been analyzed from the economic and ecological viewpoint.
Alabama Electric Cooperative Compressed Air Energy Storage (CAES) Plant Improvements
Authors: Holden Paul , Moen David , DeCorso Mario , Howard John
Published: August 2014

This paper presents a review of recent developments that were made to improve the reliability and maintenance costs associated with operation of the AEC CAES plant in McIntosh, Alabama. The combustor, fuel injector, and igniter of the LP expander were redesigned by Power Tech Associates, Inc., (PTA) of Media, Pennsylvania to improve durability, facilitate maintenance as required, and reduce cost. The modified combustor system was fitted with special instrumentation, installed and tested through an in-situ development program. Test data shows significant improvement in liner metal temperatures, transition gas temperature profile and pattern factor. Combustor system dynamics and emissions were maintained at acceptable levels.
Understanding and Minimizing the Vibratory Response of LM2500 Gas Turbine
Authors: Thompson Bruce D. , Wainscott Ben , Mulcahy Jim
Published: August 2014

Since the introduction of the LM2500 in USN marine use, significant efforts have been made to address vibration issues. From a programmatic standpoint, the main goal has been to reduce vibration levels to prolong engine operating life. These have resulted in the reduction of vibration limits for new engine acceptance, the development of LM2500 trim balance, and engine design changes. From an in-service standpoint, operational use and in-place repairs have resulted in conditions that have exacerbated vibration problems. Developments within the USN gas turbine program to address these issues are presented, including the continuing efforts to understand and minimize both synchronous and non-synchronous vibration. These include optimizing trim balance techniques by understanding structural and bearing considerations, the impact of engine modal response and how engine non-linearities effect the trim balance procedure, and the reduction of non-synchronous factors which include rotating stalls.