bluuebunny/crossref_metadata_2025 huggingface dataset:
Get the Most Out of Your Gas Turbine SCR NOx Abatement System
Authors: Collins Martin F. , DeCorso S. Mario , Moen David L.
Published: February 2009

Selective catalytic reduction (SCR) of NOx from turbine exhaust has been used successfully for at least 12 years. With this process, ammonia (NH3) is mixed with the exhaust gas before it passes through the SCR catalyst where the ammonia reacts selectively with the NOx, producing nitrogen and water. To make this simple reaction work properly over the life of the plant requires attention to issues during design and fabrication of the equipment, operation of the system, and quality control. There are a total of more than 25 issues involved. When all of these issues are recognized and addressed properly, the SCR catalytic system will produce the specified performance for the planned life of the catalyst. This paper identifies, describes, and discusses each of these issues. Most cases of unsatisfactory SCR turbine system performance can be traced to one or more of these issues being overlooked or not addressed properly in the design, construction, or operation of the catalytic system. The purpose of this paper is to make turbine system users aware of what must be done to get the most out of their SCR system.
Predictions of Cooling From Dirt Purge Holes Along the Tip of a Turbine Blade
Authors: Hohlfeld E. M. , Christophel J. R. , Couch E. L. , Thole K. A.
Published: February 2009

The clearance gap between the tip of a turbine blade and its associated shroud provides a flow path for leakage from the pressure side of the blade to the suction side. The tip region is one area that experiences high heat transfer and, as such, can be the determining factor for blade life. One method for reducing blade tip heat transfer is to use cooler fluid from the compressor, that exits from relatively large dirt purge holes placed in the tip, for cooling purposes. Dirt purge holes are typically manufactured in the blade tip to extract dirt from the coolant flow through centrifugal forces such that these dirt particles do not block smaller diameter film-cooling holes. This paper discusses the results of numerous computational simulations of cooling injection from dirt purge holes along the tip of a turbine blade. Some comparisons are also made to experimental results in which a properly scaled-up blade geometry (12X) was used to form a two-passage linear cascade. Computational results indicate that the cooling achieved through the dirt purge injection from the blade tip is dependent on the gap size as well as the blowing ratio. For a small tip gap (0.54% of the span) the flow exiting the dirt purge holes act as a blockage for the leakage flow across the gap. As the blowing ratio is increased for a large tip gap (1.63% of the span), the tip cooling increases only slightly while the cooling to the shroud increases significantly.
Computational Predictions of Endwall Film-Cooling for a First Stage Vane
Authors: Knost Daniel G. , Thole Karen A.
Published: February 2009

In gas turbine development, the direction has been higher turbine inlet temperatures to increase the work output and thermal efficiency. This extreme environment can significantly impact component life. One means of preventing component burnout in the turbine is to effectively use film-cooling whereby coolant is extracted from the compressor and injected through component surfaces. One such surface is the endwall of the first stage nozzle guide vane. This paper presents results from a computational study of two endwall film-cooling hole patterns combined with cooling from a flush slot that simulates leakage between the combustor and turbine sections. Results indicate reasonable agreement between predictions and measurements of the turbine endwall cooling for a flush slot alone. Effectiveness predictions showed an increase in film cooling flow was needed for both hole patterns to insure coolant was present near the pressure side of the vane. Results also indicated that superposition overpredicted the effectiveness levels along the endwall for the combined endwall film-cooling and slot cooling configurations.
Flow Field Computations of Combustor-Turbine Interactions Relevant to a Gas Turbine Engine
Authors: Stitzel Sarah , Thole Karen A.
Published: February 2009

The current demands for high performance gas turbine engines can be reached by raising combustion temperatures to increase power output. High combustion temperatures create a harsh environment that leads to the consideration of the durability of the combustor and turbine sections. This paper presents a computational study of a flow field that is representative of what occurs in a combustor and how that flow field convects through the first downstream stator vane. The results of this study indicate the development of the secondary flow field in the turbine is highly dependent on the incoming total pressure profile. The endwall heat transfer is found to also depend strongly on the secondary flow field.
Effects of Periodic Unsteadiness, Free-Stream Turbulence, and Flow Reynolds Number on Separation-Bubble Transition
Authors: Roberts S. K. , Yaras M. I.
Published: February 2009

This paper presents measurements of the combined effects of free-stream turbulence and periodic streamwise velocity variations on separation-bubble transition. The measurements were performed on a flat plate at two values of flow Reynolds number, with a streamwise pressure distribution similar to those encountered on the suction side of axial turbine blades. The experiment was designed to facilitate independent control of turbulence and periodic velocity fluctuations in the free-stream. The free-stream turbulence intensity was varied from 0.4% to 4.5%, and the periodic unsteadiness corresponded to Strouhal numbers of 0.0, 2.4 and 4.0. Based on the results, the relative importance of free-stream turbulence and periodic unsteadiness on the streamwise locations of separation, transition and reattachment points are quantified. Existing mathematical models for predicting separated-flow transition and reattachment are then evaluated in this context.
A Robust Design Methodology for High-Pressure Compressor Throughflow Optimization
Authors: Lecerf N. , Jeannel D. , Laude A.
Published: February 2009

Reducing costs and development times are two of the main challenges for aircraft engines manufacturers. Analysis shows that the main troubles encountered during the industrialization phase are due to choices made during the first steps, such as the preliminary design of the compressor throughflow (flowpath and velocity triangles). Therefore, constraints and needs from the later phases have to be taken into account as early as possible. A deterministic optimization method for automated compressor throughflow design has been developed to achieve these objectives, improving efficiency and surge margin while modifying the design parameters. Nevertheless, variability between the theoretical geometry and the actual one may occur because of the manufacturing process or the damages encountered during the engine life cycle. Depending on their magnitude, these differences can affect the engine performance. To consider these random phenomena from the design step, the deterministic optimization is coupled with a probabilistic approach, based on a robust design methodology which aims at guarantee the engine performance despite geometrical variability. This article deals with geometrical robustness. It presents a robust design methodology and introduces a capability function used to optimize the outputs of a compressor model while minimizing their standard deviation. The model has two kinds of inputs: the design factors, which are known by both designer and manufacturer, and the noise factors, that are just known by their mean value and their standard deviation. As robust design requires a large number of calculations, it is interesting to work with an approximated physical model such as a response surface, generated through the computation of a suitable design of experiments. This method has been successfully applied to the design of a Snecma Moteurs high-pressure compressor.
Investigation of Stator-Rotor Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Pneumatic Probes
Authors: Go¨ttlich E. , Neumayer F. , Woisetschla¨ger J. , Sanz W. , Heitmeir F.
Published: February 2009

The current paper presents steady and unsteady flow data of a transonic test turbine stage operating under flow conditions similar to modern highly loaded gas turbines. Measurements were performed between stator and rotor as well as downstream of the rotor in planes perpendicular to the rotor axis. Time resolved axial and tangential velocities were measured by a two-component Laser Doppler Velocimeter (LDV) to investigate unsteady phenomena, while time-averaged flow properties were measured by means of a pneumatic seven-hole probe for all three spatial directions. The time-resolved investigation done by LDV allows to present velocity fields, flow angles and turbulence data at different stator-rotor positions during one blade passing period. Averaging these results enabled comparison with the pneumatic multi-hole probe measurement. LDV data and stage geometry can be obtained per email request and used for CFD code verification.
Demonstration Plant and Expected Performance of an Externally Fired Micro Gas Turbine for Distributed Power Generation
Authors: Traverso Alberto , Magistri Loredana , Scarpellini Riccardo , Massardo Aristide
Published: February 2009

The paper presents the design and development of the first world-wide Externally Fired micro Gas Turbine (EFmGT) demonstration plant based on micro gas turbine technology. The system is particularly useful for exploitation of renewable resources for distributed power and heat generation. The plant has been designed by Ansaldo Ricerche (ARI) s.r.l. and Thermochemical Power Group (TPG) of University of Genoa using TPG in house codes such as TEMP (Thermoeconomic Modular Program) and TRANSEO (TRANSient analysis of energy systems). The plant is based on a recuperated 80 kW micro gas turbine (Elliott TA-80R), and it is under construction at ARI laboratory. The first goal of this plant is the demonstration of the EFmGT system at full and part load operations, mainly from the control point of view. The expected performance (50kW at 16% LHV efficiency) can be improved in the near future using high temperature heat exchangers (a field where ARI has a very long expertise), which should allow the system to operate at the actual micro gas turbine inlet temperature (900–950 °C). In the present paper the design point, off design performance, and part load control system are presented and analysed in depth: it is shown that there are no “forbidden” part load steady state operating points. In a companion paper, where transients of advanced cycles based on mGT technology are discussed, TPG presents the fast and slow transient operation of the EFmGT system.
Transient Analysis of and Control System for Advanced Cycles Based on Micro Gas Turbine Technology
Authors: Traverso Alberto , Calzolari Federico , Massardo Aristide
Published: February 2009

Microturbines have a less complex mechanical design than large-size gas turbines that should make it possible to fit them with a more straightforward control system. However, these systems have very low shaft mechanical inertia and a fast response to external disturbances, such as load trip, that make this very difficult to do. Furthermore, the presence of the recuperator requires smooth variations to the Turbine Outlet Temperature (TOT), when possible, to ensure reduced thermal stresses to the metallic matrix. This paper, after a brief overview of microturbine control systems and typical transients, presents the expected transient behavior of two advanced cycles: the Externally Fired micro Gas Turbine (EFmGT) cycle, where the aim is to develop a proper control system set-up to manage safe part-load operations at constant rotational speed, and a solar Closed Brayton Cycle (CBC), whose control system has to ensure the maximum efficiency at constant rotational speed and constant Turbine Inlet Temperature (TIT).
Effects of Labyrinth Seal Variation on Multistage Axial Turbine Flow
Authors: Schlienger J. , Pfau A. , Kalfas A. I. , Abhari R. S.
Published: February 2009

The need to increase overall turbine efficiency is always a driving force for redesigning a turbine stage. In particular, the labyrinth leakage flows in the endwall regions contribute to an increase of the overall loss generation. In order to asses this mechanism, a detailed study of the effects of labyrinth seal geometry variation on the blade performance is presented. Two different shroud seal geometries have been experimentally investigated in a two stage low speed turbine facility. The seal geometries differ in the size and shape of the re-entry cavity. The baseline seal is designed with a large rectangular re-entry cavity volume in order to dissipate the kinetic energy of the accelerated leakage flow after the seal gap. The re-entry cavity volume of the alternative seal design is reduced in size and a spline shaped contour is added to the endwall using annular inserts. This modification alters the gas path of the leakage jet and changes the incidence angles on the downstream blade rows. The measurements are performed with state of the art pneumatic and fast response pressure probes at various planes within the turbine stage. It is found that the inserts improved the flow profile uniformity at the endwalls. The measurements within the stator passage reveal the origin of the tip passage vortex formation at the blade suction side, already at the inlet to the stator passage. This result does not conform to the classical secondary flow theory, which suggests that the passage vortex migrates from the pressure to the suction side within the stator passage. The origin and formation of the secondary flow passage vortices at rotor hub and stator tip is described in a flow schematic. The generation of streamwise and tangential vorticity at the interaction area of leakage and main flow field also is studied and discussed. The measured overall polytropic turbine efficiency for the second seal configuration, relative to the baseline case, is reduced by 0.3%. The change in the re-entry flow angle of the leakage gas path reduces the negative incidence angle on the rotor hub and increases it at the stator tip leading edge. The secondary flow and mixing loss is reduced at the hub and increased at the tip in the second test case with the smaller cavity volume. Hence, the combination of small clearances and inserts in the re-entry cavities shows no beneficial effect on the overall turbine efficiency.
Studies on Effects of Periodic Wake Passing Upon a Blade Leading Edge Separation Bubble: Experimental Investigation Using a Simple Leading Edge Model
Authors: Funazaki K. , Yamada K. , Kato Y.
Published: February 2009

This paper describes experimental investigation on aerodynamic interaction between incoming periodic wakes and leading edge separation bubble on a compressor or turbine blade, using a scaled leading edge model. The studies aims at expanding the range of the test conditions from that of the previous study (Funazaki and Kato [15]) in order to deepen the knowledge on how and to what extent upstream wake passing suppresses the leading edge separation bubble. Special attention is paid to the transitional behaviors of the separated boundary layers, in particular, to the emergence of wake-induced turbulence spots. Hot-wire probe measurements are then executed under five different flow conditions. The test model has a simple structure consisting of a semi-circular leading edge and two flat-plates. Cylindrical bars of the wake generator generate the periodic wakes in front of the test model. Effects of Reynolds number, Strouhal number, direction of the bar movement and incidence of the test model against the incoming flow are examined in this paper. The measurements reveal that the wake moving over the separation bubble does not directly suppress the separation bubble. Instead, wake-induced turbulence spots and the subsequent calmed regions have dominant impacts on the separation bubble suppression for the all test cases. Distinct difference of the bubble suppressing effect by the wakes is also observed when the direction of the bar movement is altered.
Transition Modelling With the SST Turbulence Model and an Intermittency Transport Equation
Authors: Lodefier Koen , Merci Bart , De Langhe Chris , Dick Erik
Published: February 2009

A transition model for describing bypass transition is presented. It is based on a two-equations k–ω model and a dynamic equation for intermittency factor. The intermittency factor is a multiplier of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al. [1], the start of transition is computed based on local variables. The choice of the Shear-Stress Transport (SST) model instead of a k–ε model is explained. The quality of the transition model, developed on flat plate test cases, is illustrated for cascades.
Prediction of the Fatigue Life of Thermal Barrier Coatings in Gas Turbines: Modelling and Experimental Verification
Authors: Sjo¨stro¨m So¨ren , Brodin Ha˚kan , Jinnestrand Magnus
Published: February 2009

Models of oxidation, low-cycle fatigue and thermomechanical fatigue are studied in order to establish a life model of APS-TBC. An experimental programme to pinpoint the relevant mechanisms is run in parallel with macro- and micromechanical modelling, including also fracture-mechanical analysis of the BC/TC interface. Finally, the models are calibrated by further experiments.
Numerical Investigations About the Aerodynamic Performance of the Cascade in Unsteady Environment
Authors: Ji L. C. , Chen J. , Xu J. Z.
Published: February 2009

The paper presents detailed parametric simulations about the unsteady flow in the cascade passageways. The studies focus on two aspects of unsteady cascade flow. One is two dimensional (2D), which describes unsteady flow characteristics only in blade-to-blade surfaces. The other is three-dimensional (3D, a linear cascade), in which more attentions are paid to the stacking of the unsteady flow of 2D cascades along all spanwise positions. In the former aspect, two different types of unsteadiness are applied at the inlet. One is an azimuthal wave structure that processes through the cascade. The other unsteadiness is spatially uniform and oscillates in time. Using each type of unsteadiness, inflow oscillations of total pressure, total temperature and inflow angle are studied for one turbine and one compressor cascades. The emphasis is focused on the aerodynamic effects of the time-average value, the amplitude and the frequency of the unsteady flow. Results show that the unsteady cascade flow produces more losses than a steady one. Some potentials towards engineering applications are also described. Finally, unsteady flow in 3D linear cascade is studied. A design freedom that can not be used under steady flow frame, Edge-Matching, is put forward. It is essentially to match phase angle of unsteady flow along the whole span so that aerodynamic, aeroelastic, aeroacoustic and heat transfer performances of turbomachinery can be optimized and compromised. With a comprehensive viewpoint, case treatment, hot streak/blade interaction, clocking and even calming effects all belong to Edge-Matching technique. It may eventually promote the daily use of unsteady design.
Numerical Study on the Effects of Blade Leading Edge Shape to the Performance of Supersonic Rotor
Authors: Park Kicheol
Published: February 2009

Recently, it is required to design a fan and compressor with higher stage pressure ratio while maintaining adiabatic efficiency high also. To increase the stage pressure ratio, blade rotational speed or diffusion factor should be increased. In the case of increased rotational speed, relative speed of flow at blade leading edge is well supersonic. With supersonic rotor blade, total pressure loss is mainly due to leading edge shock waves and the thickness should be thin enough to minimize this. As a result, the blade is like to be week in terms of mechanical strength and the manufacturing cost would be increased because high-precision NC machining is required. Furthermore, it is one of the biggest hurdles to maintain proper level of thickness while one making small stages. In this paper, aerodynamic performance of supersonic rotor blades with different leading edge thickness and shapes are calculated using the finite volume method. The effects of blade leading edge shape and thickness to the performance are investigated especially in terms of total pressure loss and the already known loss correlations of leading edge thickness are examined. Subsequently this will be verified by performance test on rig.
Numerical Optimization of Turbomachinery Bladings
Authors: Burguburu S. , Toussaint C. , Bonhomme C. , Leroy G.
Published: February 2009

An optimization process is used to design bladings in turbomachinery. A gradient-based method is coupled to Navier-Stokes solvers and is applied to three different bladings. A new rotor blade of a transonic compressor is designed by using a Q3D approach, with a significant efficiency improvement at the design point. The off-design behavior of this new compressor is also checked afterwards. The same Q3D approach is used on a stator blade of a turbine, but the whole stage is computed in this case. The losses are locally reduced, proving the good sensitivity of the solver. Finally, a new three-dimensional rotor blade of a compressor is designed by applying deformation functions on the initial shape. The efficiency is improved over a wide range of mass flow. The whole results indicate that the optimization process can find improved design and can be integrated in a design procedure.
An Investigation of Turbomachinery Shrouded Rotor Blade Flutter
Authors: Chiang Hsiao-Wei D. , Chen Chi-Chin , Hsu Chih-Neng , Tsai Gwo-Chung , Koai Kwang-Lu
Published: February 2009

Turbomachinery shrouded rotor blade design has been widely used in fans, compressors, and turbines. By using shroud design, the blade structural damping can be increased to prevent blade flutter. However, the shrouded rotor blade design will cause the blade mode shapes to be complex, and in some cases both bending and torsion mode components can be present at the same time in a single mode. Therefore, a complex mode analysis was developed to predict shrouded rotor blade flutter with these bending and torsion combined system modes. Using the blade natural frequencies and mode shapes from a finite element model, and the blade aerodynamic flow-field, the unsteady aerodynamic forces of the system mode can be calculated. A complex mode flutter analysis was then performed using a modal solution to determine the stability of the system. The analysis system was applied to two shrouded rotor blade applications. The bending and torsion combined system mode was decomposed into a real mode component and an imaginary mode component. Bending-dominated or torsion-dominated mode shapes can be analyzed using single mode approach to obtain consistent flutter stability results. However, for the bending and torsion combined mode shape cases, the single mode analysis can be misleading, and the complex mode analysis can be a useful tool.
Discharge Coefficients of Rotating Short Orifices With Radiused and Chamfered Inlets
Authors: Dittmann M. , Dullenkopf K. , Wittig S.
Published: February 2009

The secondary air system of modern gas turbine engines consists of numerous stationary or rotating passages to transport the cooling air, taken from the compressor, to thermally high loaded components that need cooling. Thereby the cooling air has to be metered by orifices to control the mass flow rate. Especially the discharge behavior of rotating holes may vary in a wide range depending on the actual geometry and the operating point. The exact knowledge of the discharge coefficients of these orifices is essential during the design process in order to guarantee a well adapted distribution of the cooling air inside the engine. This is crucial not only for a safe and efficient operation but also fundamental to predict the component’s life and reliability. In this paper two different methods to correlate discharge coefficients of rotating orifices are described and compared, both in the stationary and rotating frame of reference. The benefits of defining the discharge coefficient in the relative frame of reference will be pointed out. Measurements were conducted for two different length-to-diameter ratios of the orifices with varying inlet geometries. The pressure ratio across the rotor was varied for rotational Reynolds numbers up to Reφ = 8:6 × 105. The results demonstrate the strong influence of rotation on the discharge coefficient. An analysis of the complete data shows significant optimising capabilities depending on the orifice geometry.
Design and Development of a Small Jet Engine Test Cell
Authors: Mathioudakis K. , Argyroupoulos P.
Published: February 2009

The process of designing a test cell for a small jet engine is described. The test cell was designed to support educational activities in the field of gas turbines. The design was undertaken by a student, as a part of his requirements for obtaining a Mechanical Engineering Degree. The requirements for the design are first laid out, according to the characteristics of the engine to be tested and the restrictions posed by the installation location. The phases of designing and construction are presented. Technical aspects of design choices for setting up the test chamber are presented. The choice of instrumentation and the way it is arranged is discussed. Results from the first tests conducted on the finished facility are presented, first, to check how design targets have been met and second, to show what kind of information can be provided to support gas turbine courses. The fact that a multidisciplinary knowledge is applied in the project is discussed. Educational benefits for the student that has undertaken the project are discussed, while particular choices made for a better suitability for subsequent educational use are highlighted.
Predictions of Temperature Redistribution in a Turning Duct and in High-Pressure Turbines
Authors: Praisner T. J. , Magowan J. W. , Clark J. P.
Published: February 2009

An ability to predict the redistribution of total enthalpy in a turbine is critical to assess heat loads on turbine surfaces and hence, to estimate component life. Here, a finite-volume, Reynolds-Averaged Navier Stokes (RANS) code was used to predict the redistribution of temperature in the 90-degree turning duct of Eckert and Irvine (1957). The duct was modeled as inviscid, laminar, and turbulent flow with both an algebraic and a two-equation model. The algebraic model was that of Baldwin and Lomax (1978), and the two-equation model was the k-ω formulation of Wilcox (1998). The results indicate that the average exit profile from the duct can be accurately modeled by all types of modeling considered, however, the two-dimensional exit distributions of temperature from the duct were most closely matched by the two-equation model. Subsequently, the lessons learned in the turning-duct study were applied to predict the redistribution of enthalpy in both single-stage and two-stage high-pressure turbines. The temperature redistribution within the two turbines considered was modeled with: a one-dimensional empirical code, an inviscid 3D solver as both steady and time-accurate k-ω RANS. The cooling flows were modeled with distributed and local mass-injection. The most consistent accuracy for both turbines was realized with the time-accurate, local mass-injection film-cooling k-ω simulations. The steady k-ω simulations with local mass-injection film cooling predicted normalized temperature profiles nearly as well as the time-accurate simulations.
Turbine Nozzle Endwall Inlet Film Cooling: The Effect of a Back-Facing Step
Authors: Zhang Luzeng , Moon Hee Koo
Published: February 2009

Film cooling effectiveness was measured on a contoured endwall surface using the pressure sensitive paint (PSP) technique. A double staggered row of holes was adopted to supply cooling air in front of the nozzle leading edges. To simulate realistic engine configuration, a back-facing step was built, which was located upstream from the film injection. Nitrogen gas was used to simulate film cooling flow as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to be from 0.5% to 3.0% of the mainstream mass flow. Film effectiveness distributions were measured on the endwall surface for both smooth (baseline) and back-facing step inlet configurations. For the smooth inlet case, film effectiveness increased nonlinearly with mass flow rate, indicating a strong interference between the cooling jets and the secondary flows. At lower mass flow ratios, the secondary flow dominated the near wall flow field, resulting in a low film effectiveness value. At higher mass flow ratios, the cooling jet momentum dominated the near wall flow field, resulting in a higher film effectiveness. For the back-facing step inlet configuration, the values of film effectiveness were reduced significantly, suggesting a stronger secondary flow interaction. In addition to the comparison between the smooth and back-facing step inlet configurations, comparison to previous data by the authors on a flat endwall was also made.
Turbocharger Unstable Operation Diagnosis Using Vibroacoustic Measurements
Authors: Aretakis N. , Mathioudakis K. , Kefalakis M. , Papailiou K.
Published: February 2009

The possibility to detect unstable operating condition (stall or surge) of an automotive turbocharger using vibration or acoustic measurements is studied. An experimental study is performed, in order to acquire and analyze test data, to find out whether vibration or acoustic measurements can be correlated to aerothermodynamic operating condition. An instrumentation set allowing the definition of the operating point on the map of the compressor of the turbocharger is used. Hot wires the compressor inlet serve as flow condition indicators and provide a clear indicator of the presence or not of instabilities, such as rotating stall or surge. Accelerometers are mounted on the casing and microphones are placed in the vicinity of the compressor casing, to measure vibration and sound emission. Data covering an extensive range of the compressor performance map have been collected and analyzed. Signal features from the different measuring instruments are discussed. Using such features, a bi-parametric criterion is established for determination of whether the compressor operates in the stable part of its performance characteristic or in the presence of unstable operation phenomena (rotating stall, surge). The possibility of generalizing the validity of observations is supported, by presenting results from testing a second turbocharger, which is shown to exhibit similar behavior.
Non-Conventional Turbines for Hydrogen Fueled Power Plants
Authors: Cerri G. , Battisti L. , Soraperra G.
Published: February 2009

A survey was carried out on CO2 & NOx emission-free hydrogen-fuelled power cycles, pinpointing characteristic points of steam turbine expansions. Innovative aspects arose for turbine design owing to unexplored steam thermodynamic states, severe operating conditions and lifetime issues. A Ljungstro¨m-type radial-flow turbine design was explored for such an application, investigating stress, cooling and thrust-balancing aspects. Massive cooling was recognized as a primary need to ensure safe turbine operation. To take technological and thermodynamic issues into account, an integrated procedure was set up for preliminary design. The final design is amply discussed.
Modal Strain Analyses of a Radial Turbine
Authors: Irwanto B. , Gier J. , Pawandenat D. , Hardtke H.-J.
Published: February 2009

Strain measurement on blade and the calculation of blade stress during test are critical to determine the actual stress and the life of blades. Since the dynamic loads acting on blades, such as gas pressures and load changes during operation, might not be known, the concept of strain amplification factor (SAF) can be used to estimate the maximum strain/stress of blade during resonance. The SAF is defined as a ratio between the maximum modal strain on blade from FE analysis and the measured strain or computed strain of a particular place on blade. In this paper, this concept is reviewed and further analysis is carried out. To verify the theoretical analysis, the experimental tests of a radial turbine (blisk) are performed in detail. However, only experiments in static condition are considered in this work, since a better experimental condition can be achieved. Moreover, the verification of rotating blades could be accomplished with the similar procedure. The FE method is chosen as a tool to provide theoretical results. Two computations by using FE method are performed to obtain the SAFs. The first computation considers the use of sector model of turbine, which is usually practiced in industry. In the second calculation, the complete tuned turbine is taken into account. The obtained results for both computations and the effect of mistuning on SAF are discussed. Furthermore, the computed SAFs are compared to the experimental results.
Evaluation of Alternative High Temperature Coatings to Improve Hot Corrosion Resistance in a Shipboard Environment
Authors: Shifler David A. , Russom Dennis M. , Rodman Bruce E.
Published: February 2009

501-K34 marine gas turbine engines serve as auxiliary power sources for the U.S. Navy’s DDG-51 Class. It is desired that 501-K34 marine gas turbine engines have a mean time between removal of 20K hours. While some engines have approached this goal, others have fallen significantly short. A primary reason for this shortfall is hot corrosion (Type I and Type II) damage in the turbine area (more specifically the first row turbine hardware) due to both intrusion of salts from the marine air and from sulfur in the gas turbine combustion fuels. In order to improve the durability of hot section components with more corrosion resistant coatings, low velocity, atmospheric-pressure burner-rig (LVBR) tests were conducted for up to 2000 hours to evaluate several alternative high-temperature coatings in both Type I and Type II hot corrosion environments. The objectives of this paper are to report the results of: (1) the hot corrosion performance of these alternative high temperature coating systems for the 1st stage vane of a given gas turbine engine; (2) compare the performance of these alternative coating systems to the current, baseline 1st stage vane coating and (3) downselect the best performing coating systems (in terms of their LVBR hot corrosion and thermal cycling resistance) to install as rainbow arrays into the first stage vanes of several engines for Fleet evaluation.
Computational and Experimental Investigation of Emissions in a Highly Humidified Premixed Flame
Authors: Hermann Fredrik , Klingmann Jens , Gabrielsson Rolf
Published: February 2009

Emission formation and flame stability were investigated, both experimentally and computationally, for premixed combustion with varying amounts of water vapor in the mixture. Emission measurements were made in a gas turbine combustor at atmospheric conditions, using Danish Natural Gas (NG) as fuel. The emissions were mapped as a function of humidity, inlet air temperature, equivalence ratio and aerodynamic load. Operating conditions were chosen to match what can be expected from e.g. an EvGT cycle for power generation. The inlet air temperature was slightly lower than the inlet temperatures that would be found in a recuperated cycle. The degree of humidity was varied from 0w% to 33w% of the airflow in the experiment, while the air inlet temperature was varied from 500K to 800K. Computations were made using a single Perfectly Stirred Reactor (PSR) model and a reaction scheme with 821 reactions and 69 species. It was found that the NOx emissions were strongly reduced by the addition of water. Most of this decrease vanishes in practical combustion since richer combustion is required to keep CO emissions (combustion efficiency) at a tolerable level. The maximum humidity was found to be dependent on inlet air temperature and aerodynamic load. In this experiment, the maximum humidity achieved was 33%.
Integration of High Heat Sink Fuels in Aircraft Thermal Management Systems
Authors: Glickstein Marvin R. , Van Griethuysen Valerie J. , Hodge Ernest S.
Published: February 2009

Efficient design of advanced military aircraft to satisfy defined mission roles requires designing the individual components and subsystems, and subsequently integrating all of these to yield the desired final product. This design process, to be efficient, must optimize the total integrated design to best attain its product goal. Attaining operational goals requires that two related requirements are satisfied, namely aircraft operation performance (i.e., the ability to operate over the desired flight profile with the desired range and payload), and the thermal control requirements (i.e., the ability to manage all of the thermal environments within the available resources). Development of future aircraft fuels with enhanced thermal stability provides the potential for greater heat sink capacity, thus expanding the thermal resources available for cooling. However, it is not immediately obvious how these additional resources should be integrated into the complex thermal control systems of future aircraft in order to fully capitalize on the potential cooling capability. This paper describes the results of a study addressing this question for an advanced strike fighter, with appropriate mission and thermal requirements, along with an evaluation of the effects of system integration architecture for a variety of system concepts. The methods of system analysis and the study results provide some general guidelines for thermal system design employing enhanced fuels and several types of overall system integration configurations.
Pressure and Flow Characteristics in a Rotating Two-Pass Square Duct With 45° Angled Ribs
Authors: Liou Tong-Miin , Dai Guang-Yuan
Published: February 2009

Measurements are presented of the local velocity and wall static-pressure distributions by using laser-Doppler velocimeter and pressure transducers, respectively, in a rotating two-pass square duct with ribs placed on the leading and trailing walls at an angle of 45° to the main stream. The ribs were square in cross-section and in a parallel mode of arrangement. The rib-height/duct-height ratio and the pitch/rib-height ratio were 0.136 and 10, respectively. The duct Reynolds number was 1×104 and rotation number Ro ranged from 0 to 0.2. Results are addressed in terms of the evolutions of both main flow and cross-stream secondary flow and the distributions of the pressure coefficient, which are lacking in the published literature for ducts ribbed with 45° ribs and under rotation. In addition, the relationships between the regional averaged Nusselt number, transverse and convective mean velocity component, and turbulent kinetic energy are documented. The 45° ribs are found to reduce the pressure loss to 60% of the 90° ribs for rotating duct under same operating conditions. For CFD reference, the fully developed flow condition is absent for the rotating ducts investigated. The measured evolution of complex secondary flow vortices is believed to be a challenge to numerical simulations.
Conceptual Design and Cooling Blade Development of 1700 °C-Class High-Temperature Gas Turbine
Authors: Ito Shoko , Saeki Hiroshi , Inomata Asako , Ootomo Fumio , Yamashita Katsuya , Fukuyama Yoshitaka , Koda Eiichi , Takahashi Toru , Sato Mikio , Koyama Miki , Ninomiya Toru
Published: February 2009

This paper describes the conceptual design and cooling blade development of a 1700 °C-class high-temperature gas turbine in the ACRO-GT-2000 (Advanced Carbon Dioxide Recovery System of Closed-Cycle Gas Turbine Aiming 2000K) project. In the ACRO-GT closed cycle power plant system, the thermal efficiency aimed at is more than 60% of higher heating value of fuel (HHV). Because of the high thermal efficiency requirement, the 1700 °C-class high-temperature gas turbine must be designed with the minimum amount of cooling and seal steam consumption. The hybrid cooling scheme, which is a combination of closed loop internal cooling and film ejection cooling, was chosen from among several cooling schemes. The elemental experiments and numerical studies, such as those on blade surface heat transfer, internal cooling channel heat transfer and pressure loss and rotor coolant passage distribution flow phenomena, were conducted and the results were applied to the conceptual design advancement. As a result, the cooling steam consumption in the first stage nozzle and blade was reduced by about 40% compared with the previous design that was performed in the WE-NET (World Energy Network) Phase-I.
A New Paradigm for Simulation of Turbulent Combustion in Realistic Gas Turbine Combustors Using LES
Authors: Constantinescu G. , Mahesh K. , Apte S. , Iaccarino G. , Ham F. , Moin P.
Published: February 2009

This paper presents a new paradigm for numerical simulation of turbulent combustion in realistic gas turbine combustors. Advanced CFD methods using Large Eddy Simulation (LES) turbulence models are central to this paradigm in fluid dynamics where engineers can apply the full predictive abilities of numerical simulations to the design of realistic gas turbine combustors. The use of LES models is motivated by their demonstrated superiority over RANS to predict turbulent mixing. The subgrid scale models incorporated in LES are based on the dynamic approach where the model coefficients are computed rather than prescribed by the user. This has provided unparalleled robustness to modern turbulent flow computations using LES. A new numerical algorithm was derived that is discretely energy conserving on hybrid unstructured grids, thus allowing numerical simulations at high Reynolds numbers corresponding to operating conditions without using artificial numerical dissipation. This paper deals specifically with the simulation of the gas phase flow through realistic gas turbine combustors and the implementation of combustion and spray models that are needed to predict and control the combustion phenomena in these geometries. Results from several simulations and comparison with experimental data are used to validate this approach. In particular, a complete simulation of the unsteady flow field in a realistic combustor geometry is carried out. Some preliminary results for reacting flow simulations in gas turbine combustors are also discussed. We discuss several challenges related to large-scale simulations of the flow in realistic combustors, including methods to further accelerate the algorithm’s convergence (e.g., use of multigrid techniques), improvement of the parallel performance of the flow solver for two-phase flow simulations (e.g., use of dynamic load balancing that accounts for the additional CPU time spent in the spray module when particles are present in the cells).
Stall Inception in a Vaneless Diffuser of a Centrifugal Compressor
Authors: Kang Jeong-Seek , Kang Shin-Hyoung
Published: February 2009

This paper presents an experimental and analytical investigation of a rotating stall inception in a vaneless diffuser of a centrifugal compressor. Eight fast-response pressure transducers are equally spaced around the circumference at the inlet and exit of a parallel vaneless diffuser. Instantaneous pressure data is measured near the stall inception point and characteristics of a rotating stall, a stall-initiating mechanism, a stall precursor and its warning schemes are discussed. It is found that one-cell, two-cell and three-cell structures of small amplitude wave grow and decay repeatedly before they are fully developed to a rotating stall, which is named as “pre-cell.” When it appears, the phase of spatial Fourier coefficient increases linearly and the traveling wave energy increases. The pre-cell travels at, or slightly lower than, the speed of the fully developed rotating stall. Its growing-decaying life span is about several decades of the impeller revolution. Pre-cells of one-cell, two-cell, and three-cell structures are found to interact frequently with their growing and decaying mechanism through transferring energy from one structure to another. Two stall warning schemes are used for the stall in the vaneless diffuser. The first scheme is to detect the linear increase region in the phase of the spatial Fourier coefficient from where the according warning time is about 0.3∼1.4 sec. (300∼700 impeller revs.) The second scheme is to detect the increase of traveling wave energy from where the according warning time is about 0.2∼2.3 sec. (200∼1200 impeller revs.) These warning schemes are useful because their warning time is long enough to be applied in active control of a compressor stall.
Gas Path Model Identification as an Instrument of Gas Turbine Diagnosing
Authors: Yepifanov S. V. , Loboda I. I.
Published: February 2009

This paper deals with a development of identification procedures of gaspath static and dynamic models and with their application for gas turbine diagnosing. The identification is important because the parameters estimated during this task aid to detect particular degraded components. The first purpose of our work was to develop and test the identification procedure of a nonlinear dynamic model. A statistical procedure testing on the model input data was applied to analyze diagnostic possibilities of the developed procedure. The second purpose was to present and generalize previous investigations related with static model identification and to give any common approach of both techniques application in gas turbine diagnostics.
Interaction of Rim Seal and Annulus Flows in an Axial Flow Turbine
Authors: Cao C. , Chew J. W. , Millington P. R. , Hogg S. I.
Published: February 2009

A combined computational fluid dynamics (CFD) and experimental study of interaction of main gas path and rim sealing flow is reported. The experiments were conducted on a two stage axial turbine and included pressure measurements for the cavity formed between the stage 2 rotor disc and the upstream diaphragm for two values of the diaphragm-to-rotor axial clearance. The pressure measurements indicate that ingestion of the highly swirling annulus flow leads to increased vortex strength within the cavity. This effect is particularly strong for the larger axial clearance. Results from a number of steady and unsteady CFD models have been compared to the measured results. Good agreement between measurement and calculation for time-averaged pressures was obtained using unsteady CFD models, which predicted previously unknown unsteady flow features. This led to fast response pressure transducer measurements being made on the rig, and these confirmed the CFD prediction.