bluuebunny/crossref_metadata_2025 huggingface dataset:
Modal and Aeroelastic Analysis of a Compressor Blisk Considering Mistuning
Authors: Nipkau Jens , Ku¨hhorn Arnold , Beirow Bernd
Published: May 2012

Focussing on three basic blade modes the effect of the flow’s influence on the forced response of a mistuned HPC-blisk is studied using a surrogate lumped mass model called equivalent blisk model (EBM). Both measured and intentionally allowed mistuning is considered to find out in principle if the flow contributes to a slowdown of blade displacements with increasing mistuning. In a first step the mechanical properties of the EBM are adjusted to a finite element model and known mistuning distributions given in terms of blade frequencies and damping. Taking into account the flow structure interaction CFD-computations are carried out in order to derive aerodynamic influence coefficients (AIC) which are used to describe the aerodynamic forces coming along with the motion of each blade in the flow. These aerodynamic forces can be included directly in the EBM equations of motion or alternatively be used to calculate aeroelastic eigenvalues from which additional equivalent aerodynamic elements representing the co-vibrating air mass as well as aerodynamic stiffening and damping effects are derived. Both kinds of EBM are applied to study the forced response at least in a qualitative manner aiming to demonstrate some basic effects at low computing time.
Optimized Global Mechanisms for CFD Analysis of Swirl-Stabilized Syngas Burner for Gas Turbines
Authors: Abou-Taouk Abdallah , Eriksson Lars-Erik
Published: May 2012

A 3-step global reaction mechanism for a methane-air mixture is optimized against a detailed reference mechanism for perfectly stirred reactor (PSR) calculations. The global mechanism consists of three reactions corresponding to the fuel oxidation into CO and H2O, and the CO–CO2 equilibrium reaction. To ensure good agreement for rich conditions, correction functions that are dependent on the local equivalence ratio are introduced into the global mechanism. In a comparison of the optimized 3-step global reaction mechanism with the reference detailed reaction mechanism, GRI Mech 3.0, the results show that the gas temperature and emissions are reasonably well predicted for lean and rich conditions. The optimized 3-step global reaction scheme is adapted in the Computational Fluid Dynamics (CFD) analysis of a swirl-stabilized syngas burner, designed by Siemens Industrial Turbomachinery (SIT syngas burner) for gas turbines. The burner consists of a main premixed flame, a partially premixed pilot flame and a confined rich premixed lean flame which produces radicals that support both the pilot and the main flame. The CFD results are compared with experimental results obtained in an atmospheric version of the burner test rig at Lund University. Both steady-state Reynolds Averaged Navier Stokes (RANS) and hybrid Unsteady RANS/Large Eddy Simulation (URANS/LES) results were computed. The CFD results with the 3-step global reaction mechanism show good agreement with the experimental data on gas analysis and flame visualization, while the Westbrook Dryer 2-step (WD2) [2] and Meredith et al. [3] 3-step global reaction mechanisms failed in their predictions of the CO emissions downstream in the burner.
A New Approach for Compressor Endwall Contouring
Authors: Hergt Alexander , Meyer Robert , Liesner Karsten , Nicke Eberhard
Published: May 2012

Against the background of the high development status of modern axial compressors, a further performance enhancement is linked with the extension of the design space in the development process and the concentration on the essential loss mechanisms in the compressor. The performance of a compressor cascade is considerably influenced by secondary flow effects in the near endwall region, since up to 50 percent (for low aspect ratio) of the losses in the bladed channel of a turbomachinery are linked to the endwalls. In this context the application of non-axisymmetric profiled endwalls provides a potential for compressor improvement. The paper presents the detailed experimental and numerical investigation of controlling the endwall cross flow in a compressor cascade. The general approach is based on a boundary layer fence arrangement, whose application on the compressor endwall works as a non-axisymmetric endwall contour. This non-axisymmetric endwall modification constrains the interaction of the endwall cross flow with the suction side boundary layer, thus the onset of the corner separation is delayed and a significant loss reduction of 8 percent is achieved. The experiments were carried out in a linear compressor cascade at the high-speed cascade wind tunnel of the DLR in Berlin at peak efficiency (design point) and off-design of the cascade at Mach number M = 0.67. Furthermore, high fidelity 3D-RANS flow simulations were performed in order to analyze the complex blade and endwall boundary layer interaction. The combined consideration of experimental and numerical flow pattern allows a detailed interpretation and description of the resulting flow phenomena.
Numerical Investigations of a Swirl-Stabilized Premixed Flame at Ultra-Wet Conditions
Authors: Kru¨ger Oliver , Go¨ckeler Katharina , Go¨ke Sebastian , Paschereit Christian Oliver , Duwig Christophe , Fuchs Laszlo
Published: May 2012

The present study focuses on the numerical investigation of a generic swirl-stabilized burner operated with methane at ultra-wet conditions. The burner is fed with a preheated homogeneous mixture formed by steam and air. As a set of operating conditions atmospheric pressure, inlet temperature of 673K, equivalence ratio of 0.85 and a steam content of 30% is applied. Large eddy simulations have been performed to investigate the flow features. In a first step the non-reacting flow field was investigated with water as working medium. Comparison with Particle Image Velocimetry (PIV) and Laser-Doppler Velocimetry (LDV) measurements conducted in a water tunnel facility showed that an excellent agreement within the experimental uncertainty is obtained for the flow field. A dominant frequency in the turbulent energy spectrum was identified, which corresponds to the motion associated with a precessing vortex core (PVC). In order to investigate the reactive flow in a second step, a customized solver for handling low Mach number reacting flows based on an implicit LES approach was developed. As reaction mechanism a reduced 4 steps / 7 species global scheme was used. To compare the simulations qualitatively with a wet flame, OH chemiluminescence pictures serve as a reference. The simulations showed a more compact flame compared to the OH pictures. Nevertheless, the prolongation and position of the flame were found to be reasonable. The reduced mechanism captures the main effects, such as the reduction of the peak and mean temperatures. Furthermore, the presence of a PVC in the reacting flow could be determined and was not suppressed by heat-release.
Multiscale Partially Averaged Navier Stokes Approach for the Prediction of Flow in Linear Compressor Cascade With Moving Casing
Authors: Borello Domenico , Delibra Giovanni , Rispoli Franco
Published: May 2012

In this paper we present an innovative Partially Averaged Navier Stokes (PANS) approach for the simulation of turbomachinery flows. The elliptic relaxation k-ε-ζ-f model was used as baseline Unsteady Reynolds Averaged Navier Stokes (URANS) model for the derivation of the PANS formulation. The well established T-FlowS unstructured finite volume in-house code was used for the computations. A preliminary assessment of the developed formulation was carried out on a 2D hill flow that represents a very demanding test case for turbulence models. The turbomachinery flow here investigated reproduces the experimental campaign carried out at Virginia Tech on a linear compressor cascade with tip leakage. Their measurements were used for comparisons with numerical results. The predictive capabilities of the model were assessed through the analysis of the flow field. Then an investigation of the blade passage, where experiments were not available, was carried out to detect the main loss sources.
Temporal and Convective Inertia Effects in Plain Journal Bearings With Eccentricity, Velocity and Acceleration
Authors: Dousti Saeid , Cao Jianming , Younan Amir , Allaire Paul , Dimond Tim
Published: May 2012

Fluid film bearings are commonly analyzed with the conventional Reynolds equation, without any temporal inertia effects, developed for oil or other high viscosity lubricants. In applications with rapidly time varying external loads, e.g. ships on wavy oceans, temporal inertia effect should be taken into account. As rotating speeds increase in industrial machines and the reduced Reynolds number increases above the turbulent threshold, a form of linearized turbulence model is often used to increase the effective viscosity to take the turbulence into account. Other than the turbulence effect, with high reduced Reynolds number, convective inertia effect gains importance. Water or other low viscosity fluid film bearings used in subsea machines and compressors are potential applications with a highly reduced Reynolds number.” This paper extends the theory originally developed by Tichy [1] for impulsive loads to high reduced Reynolds number lubrication in different bearing configurations. Both fluid shear and pressure gradient terms are included in the velocity profiles across the lubricant film. The incompressible continuity equation and Navier Stokes equations, including the temporal inertia term, are simplified using an averaged velocity approach to obtain an extended form of Reynolds equation which applies to both laminar and turbulent flow. All terms in the Navier Stokes equation, including both the convective and temporal inertia terms are included in the analysis. The inclusion of the temporal inertia term creates a fluid acceleration term in the extended Reynolds equation. A primary advantage of this formulation is that fluid film bearings lubricated with low viscosity lubricants which are subject to high force slew rates can be analyzed with this extended Reynolds equation. A short bearing form of the extended Reynolds equation is developed with appropriate boundary conditions. A full kinematic analysis of the short journal bearing is developed including time derivatives up to and including shaft accelerations. Linearized stiffness, damping and mass coefficients are developed for a plain short journal bearing. A time transient solution is developed for the pressure and bearing loads in plain journal bearings supporting a symmetric rigid rotor when the rotor is subjected to rapidly applied large forces. The change in the rotor displacements when subjected to unbalance forces is explored. Several comparisons between conventional Reynolds equation solutions and the extended Reynolds number form with temporal inertia effects will be presented and discussed.
Experimental Determination of Flame Transfer Function Using Random Velocity Perturbations
Authors: Cuquel Alexis , Durox Daniel , Schuller Thierry
Published: May 2012

This study focus on the experimental determination of the Flame Transfer Function (FTF) which can be used to analyze acoustic induced combustion instabilities. In the present work random non-harmonic velocity signals are generated to perturb the flame. This method enables to rapidly determine the FTF compared to other techniques and improves the frequency resolution. A System Identification (SI) technique is applied to model the frequency response of different components of the test bench. It is firstly used to impose a white noise velocity signal at the burner exit, with a tunable perturbation level. SI tools and spectral analysis are used to reconstruct the FTF of a laminar conical flame. Experiments are conducted for different operating conditions and forcing levels. Results are compared with those obtained by harmonic modulations of the flow. They closely match over a large frequency range for small perturbation levels. The limits of the technique are examined when the modulation amplitude is increased.
Validation of a 3D Linearized Method for Turbomachinery Tone Noise Analysis
Authors: Pinelli Lorenzo , Poli Francesco , Marconcini Michele , Arnone Andrea , Spano Ennio , Torzo Davide
Published: May 2012

A fully three-dimensional noise propagation analysis method accounting for 3D radial modes was developed in order to predict the tone noise emissions of a multistage low-pressure turbine. This propagation procedure employs a time-linearized aeroacoustic solver with 3D non-reflecting boundary conditions to compute the acoustic response of each single row and allows the acoustic waves to propagate across adjacent rows up to the turbine exit, where such perturbations radiate to the far field. This method follows the evolution of the acoustic modes within the machine, taking into account both circumferential and radial mode orders. The overall turbine exit sound power level, due to specific rotor-stator interactions, may thus be evaluated. Some numerical results are compared with experimental data measured in an acoustic two-stage test rig which is representative of the last stages of a low-pressure turbine in terms of row geometry, blade loading and flow deflection.
Characterization of the As Manufactured Variability in a CVI SiC/SiC Woven Composite
Authors: Bonacuse Peter J. , Mital Subodh , Goldberg Robert
Published: May 2012

The microstructure of a 2D woven ceramic matrix composite displays significant variability and irregularity. For example, a chemical vapor infiltrated (CVI) SiC/SiC composite exhibits significant amount of porosity arranged in irregular patterns. Furthermore, the fiber tows within a ply frequently have irregular shape and spacing, and the stacked plies are often misaligned and nested within each other. The goal of an ongoing project at NASA Glenn is to investigate the effects of the complex microstructure and its variability on the properties and the durability of the material. One key requirement for this effort is the development of methods to characterize the distribution in as-fabricated ceramic matrix composite (CMC) microstructures with the objective of correlating microstructural distribution parameters with mechanical performance. An initial task in this effort was to perform quantitative image analysis of polished cross sections of CVI SiC/SiC composite specimens. This analysis provided sample distributions of various microstructural composite features, including: inter-tow pore sizes and shapes, transverse sectioned tow sizes and shapes, and within ply tow spacing. This information can then be used to quantify the effect of extreme values of these features on the local stress state with the goal of determining the likelihood of matrix cracking at a given external load.
Coal Ash Deposition on Nozzle Guide Vanes: Part I—Experimental Characteristics of Four Coal Ash Types
Authors: Webb J. , Casaday B. , Barker B. , Bons J. P. , Gledhill A. D. , Padture N. P.
Published: May 2012

An accelerated deposition test facility was operated with three different coal ash species to study the effect of ash composition on deposition rate and spatial distribution. The facility seeds a combusting (natural gas) flow with 10–20 micron mass mean diameter coal ash particulate. The particulate-laden combustor exhaust is accelerated through a rectangular-to-annular transition duct and expands to ambient pressure through a nozzle guide vane annular sector. For the present study, the annular cascade consisted of two CFM56 aero-engine vane doublets; comprising three full passages and two half passages of flow. The inlet Mach number (0.1) and gas temperature (1100°C) are representative of operating turbines. Ash samples were tested from the three major coal ranks: lignite, subbituminous, and bituminous. Investigations over a range of inlet gas temperatures from 900°C to 1120°C showed that deposition increased with temperature, though the threshold for deposition varied with ash type. Deposition levels varied with coal rank, with lignite producing the largest deposits at the lowest temperature. Regions of heightened deposition were noted; the leading edge and pressure surface being particularly implicated. Scanning electron microscopy was used to identify deposit structure. For a limited subset of tests, film cooling was employed at nominal design operating conditions but provided minimal protection in cases of severe deposition.
Experiments on Aft-Disk Cavity Ingestion in a Model 1.5-Stage Axial-Flow Turbine
Authors: Balasubramanian J. , Junnarkar N. , Zhou D. W. , Roy R. P. , Kim Y. W. , Moon H. K.
Published: May 2012

Experiments were carried out in a model 1.5-stage (vane-blade-vane) axial-flow air turbine to investigate the ingestion of main-stream air into the aft disk cavity. This cavity features rotor and stator rim seals with radial clearance and axial overlap, and an inner labyrinth seal. Results are reported for two main air flow rates, two rotor speeds, and three purge (secondary) air flow rates. The initial step at each experimental condition was the measurement of time-average static pressure distribution in the turbine stage to ensure that a nominally steady run condition had been achieved. Subsequently, tracer gas concentration and particle image velocimetry (PIV) techniques were employed to measure, respectively, the main gas ingestion into the disk cavity (rim and inner parts) and the fluid velocity field in the rim cavity. Finally, the egress trajectory of the purge air into the main-stream air was mapped in the axial-radial plane by PIV at multiple circumferential positions within one aft vane pitch. The purge air egress trajectory and velocity field are important because the interaction of this air with the main gas stream has aerodynamic, stage performance, and downstream vane/endwall heat transfer implications.
Ethanol and Distillate Blends—A Thermodynamic Approach to Miscibility Issues: Part 2—The Influence of Water
Authors: Privat Romain , Jaubert Jean-Noe¨l , Molie`re Michel
Published: May 2012

In recent years, the quest for sustainable primary energies has increased the potential interest of biogenic/fossil fuels mixes. As an example, ethanol is used as a gasoline extender to both partly substitute hydrocarbons and increase octane number while improving vehicle emissions. In a previous paper (GT2010-22126), it has been shown that ethanol and gasoil are able to blend and form homogeneous solutions only in limited proportion ranges, due to their markedly different physical and chemical properties. However the incorporation of small amounts of water in ethanol dramatically decreases this already narrow miscibility domain. Indeed, in function of the temperature, such ternary mixtures often give rise to liquid-liquid equilibria i.e. to two separated phases that are respectively lipophilic and hydrophilic. A key parameter is thus the Minimum Miscibility Temperature, i.e. the temperature above which ethanol, water and gasoil become completely miscible. On another hand, commercial gasoils do not constitute a single product but display worldwide a large range of compositions that influence the stability of these ternary blends. In this context, an investigation program intended to characterize and predict the stability of ternary ethanol + water + gasoil blends has been carried out by the LRGP laboratory (Laboratoire Re´actions et Ge´nie des Proce´de´s). The approach is based on a thermodynamical, theoretical calculation of the liquid-liquid phase diagrams formed by ethanol, water and a mixture of various hydrocarbons representative of the diesel oil pool using the group-contribution concept. The basic idea is that whereas there are thousands of chemical compounds, the number of functional groups that constitute these compounds is much smaller. The work relies on the experimentally verified theory that a physical property of a fluid can be expressed as the sum of contributions made by molecule’s functional groups, which allows correlating the properties of a very large number of substances in terms of a much smaller number of parameters that represent the contributions of individual groups. This work shows the huge influence exerted by the water content of ethanol on the shape of the liquid-liquid phase diagram and on the value of the Minimum Miscibility Temperature (MMT). As seen in our previous paper, the paraffinic, aromatic or naphthenic character of the fossil fraction, also considerably influences the value of the MMT. Calculations were performed with a water content varying between 1 and 10%. This study concludes that the MMT expressed in kelvins is generally multiplied by two when the water content rises from 1 to 10%.
Influence of Coolant Flow Rate on Aero-Thermal Performance of a Rotor Blade Cascade With Endwall Film Cooling
Authors: Barigozzi G. , Fontaneto F. , Franchini G. , Perdichizzi A. , Maritano M. , Abram R.
Published: May 2012

This paper investigates the influence of coolant injection on the aerodynamic and thermal performance of a rotor blade cascade with endwall film cooling. A 7 blade cascade of a high-pressure-rotor stage of a real gas turbine has been tested in a low speed wind tunnel for linear cascades. Coolant is injected through ten cylindrical holes distributed along the blade pressure side. Tests have been preliminarily carried out at low Mach number (Ma2is = 0.3). Coolant-to-mainstream mass flow ratio has been varied in a range of values corresponding to inlet blowing ratios M1 = 0–4.0. Secondary flows have been surveyed by traversing a 5-hole miniaturized aerodynamic probe in two downstream planes. Local and overall mixed-out secondary loss coefficient and vorticity distributions have been calculated from measured data. The thermal behaviour has been also analysed by using Thermochromic Liquid Crystals technique, so to obtain film cooling effectiveness distributions. All this information, including overall loss production for variable injection conditions, allow to draw a comprehensive picture of the aero-thermal flow field in the endwall region of a high pressure rotor blade cascade.
Application of a Miniature Telemetry System in a Small Gas Turbine Engine
Authors: Long Stephen A. , Reiger Patrick A. , Elliott Michael W. , Edney Stephen L. , Knabe Frank , Bernhard Dieter
Published: May 2012

For the purpose of assessing combustion effects in a small gas turbine engine, there was a requirement to evaluate the rotating temperature and dynamic characteristics of the power turbine rotor module. This assessment required measurements be taken within the engine, during operation up to maximum power, using rotor mounted thermocouples and strain gages. The acquisition of this data necessitated the use of a telemetry system that could be integrated into the existing engine architecture without affecting performance. Due to space constraints, housing of the telemetry module was limited to placement in a hot section. In order to tolerate the high temperature environment, a cooling system was developed as part of the integration effort to maintain telemetry module temperatures within the limit allowed by the electronics. Finite element thermal analysis was used to guide the design of the cooling system. This was to ensure that sufficient airflow was introduced and appropriately distributed to cool the telemetry cavity, and hence electronics, without affecting the performance of the engine. Presented herein is a discussion of the telemetry system, instrumentation design philosophy, cooling system design and verification, and sample of the results acquired through successful execution of the full engine test program.
Full Authority Digital Control (FADC) Local Operating Panels (LOCOPs)…The Foundation for Improvement
Authors: Corso Christopher , Bigley Andrew , Connery Brian , Nichols Jeremy
Published: May 2012

Full Authority Digital Control systems are the premier control system. The applications are limitless (motorcycles to power plants and everything in between). Over the past 15 years, the US Navy has worked successfully with Woodward Governor Co. to develop and implement FADC LOCOPs for use in a number of applications including DDG and CG class ships gas turbine generators. The FADC LOCOPs provide closed loop control features as did the old analog control systems. But the FADC LOCOPs add the ease and speed of control improvements via software change, constant data monitoring/recording and network connectivity. The network connectivity advantage is still early in development; however this key feature of the control system opens up many doors. Distance support can be taken to an entirely new level via the network. Imagine a setup where if the control detects an abnormality…an email containing control system data gets sent to the blackberry of the In Service Engineering Agent (ISEA) so immediate action can be taken to maintain system reliability and reduce overall system cost. This future can help save money and avoid expensive catastrophic failure via condition based maintenance. In this future, it is possible that eventually the ISEA suggestions can be prompted right back to the FADC LOCOP so the sailors onboard can communicate with the ISEA via the FADC LOCOP. Essentially, every ship could have the ISEA (or an ISEA representative)onboard 24 hours a day seven days a week via FADC LOCOP communicating over a network. The system is not this evolved yet. However, several Navy Programs are working in conjunction towards a similar future including DDG Modernization and Integrated Condition Assessment System (ICAS) via Maintenance Engineering Library Server (MELS) and Integrated Performance Analysis Reports (IPAR). FADC LOCOPs are the foundation upon which these improvements rely to be implemented…thus the premier control system.
Characterizing the Effect of Radial Vane Height on Flame Migration in an Ultra Compact Combustor
Authors: LeBay Kenneth D. , Polanka Marc D. , Branam Richard D.
Published: May 2012

The Ultra Compact Combustor (UCC) has shown viable merit for significantly improving gas turbine combustor performance. UCC models for small engines can provide centrifugal loading up to 4,000 gs. However, as the scale of the combustor increases, the g-load will necessarily decrease and the radial vane height will increase. Thus, the importance of understanding flame migration over increasing radial vane heights is pivotal to the applicability of this design to larger engine diameters. The Air Force Institute of Technology’s Combustion Optimization and Analysis Laser laboratory studied this effect with a sectional UCC model using three different vane heights. By varying the mass flow rates of the circumferential UCC section, the g-loading was varied from 500–2,000 gs. Two-line Planar Laser Induced Fluorescence at 10Hz was used for 2D temperature profiles. High-speed video at 2kHz was also used for qualitative flame migration characterization. Several cases were studied varying the radial vane height, the circumferential g-load, and the UCC/core mass flow ratio but specifically focusing on the interaction between matching the core mass flow and the core freestream velocity among the different vane heights. Finally, the decreased core flow velocity for the same mass flow weakened the shear layer between the main and cavity flows and this allowed deeper flame migration into the core flow from the UCC. Control of the overall flame migration is the key to produce desirable combustor exit temperature profiles. Increased spans lead to higher velocity gradients and increased flame injection angles at the same mass flow rates. However, at the same core flow velocities and UCC to core flow velocity ratios the flame injection angle was relatively independent of the radial vane height and almost entirely dependent on the core flow velocity alone.
Influence of Shock Wave on Turbine Vane Suction Side Film Cooling With Compound-Angle Shaped Holes
Authors: Liu K. , Narzary D. P. , Han J. C. , Mirzamoghadam A. V. , Riahi A.
Published: May 2012

This paper studies the effect of shock wave on turbine vane suction side film cooling using a conduction-free Pressure Sensitive Paint (PSP) technique. Tests were performed in a five-vane annular cascade with a blow-down flow loop facility. The exit Mach numbers are controlled to be 0.7, 1.1, and 1.3, from subsonic to transonic flow conditions. Two foreign gases N2 and CO2 are selected to study the effects of two coolant-to-mainstream density ratios, 1.0 and 1.5, on film cooling. Four averaged coolant blowing ratios in the range, 0.4 to 1.6 are investigated. The test vane features 3 rows of radial-angle cylindrical holes around the leading edge, and 2 rows of compound-angle shaped holes on the suction side. Results suggest that the PSP is an accurate technique capable of producing clear and detailed film cooling effectiveness contours at transonic flow conditions. At lower blowing ratio, film cooling effectiveness decreases with increasing exit Mach number. On the other hand, an opposite trend is observed at high blowing ratio. In transonic flow, the rapid rise in pressure caused by shock benefits film-cooling by deflecting the coolant jet toward the vane surface at higher blowing ratio. Results show that denser coolant performs better, typically at higher blowing ratio in transonic flow. Results also show that the optimum momentum flux ratio decreases with density ratio at subsonic condition. In transonic flow, however, the trend is reversed and the peak effectiveness values plateau over a long range of momentum flux ratio.
Experimental Study of Blade Vibration in Centrifugal Compressors
Authors: Lerche Andrew H. , Moore J. Jeffrey , Allison Timothy C.
Published: May 2012

Blade vibration in turbomachinery is a common problem that can lead to blade failure by high cycle fatigue. Although much research has been performed on axial flow turbomachinery, little has been published for radial flow machines such as centrifugal compressors and radial inflow turbines. This work develops a test rig that measures the resonant vibration of centrifugal compressor blades. The blade vibrations are caused by the wakes coming from the inlet guide vanes. These vibrations are measured using blade mounted strain gauges during a rotating test. The total damping of the blade response from the rotating test is compared to the damping from the modal testing performed on the impeller. The mode shapes of the response and possible effects of mistuning are also discussed. The results show that mistuning can affect the phase cancellation which one would expect to see on a system with perfect cyclic symmetry.
Two-Dimensional Nonlinear Finite Element Analysis of CMC Microstructures
Authors: Mital Subodh K. , Goldberg Robert K. , Bonacuse Peter J.
Published: May 2012

Detailed two-dimensional finite element analyses of the cross-sections of a model CVI (chemical vapor infiltrated) SiC/SiC (silicon carbide fiber in a silicon carbide matrix) ceramic matrix composites are performed. High resolution images of the cross-section of this composite material are generated using serial sectioning of the test specimens. These images are then used to develop very detailed finite element models of the cross-sections using the public domain software OOF2 (Object Oriented Analysis of Material Microstructures). Examination of these images shows that these microstructures have significant variability and irregularity. How these variabilities manifest themselves in the variability in effective properties as well as the stress distribution, damage initiation and damage progression is the overall objective of this work. Results indicate that even though the macroscopic stress-strain behavior of various sections analyzed is very similar, each section has a very distinct damage pattern when subjected to inplane tensile loads and this damage pattern seems to follow the unique architectural and microstructural details of the analyzed sections.
E-Class DLN Technology Advancements, DLN1+
Authors: Thomas Larry L. , Simons Derrick W. , Popovic Predrag , Romoser Carey E. , Vandale Daniel D. , Citeno Joseph V.
Published: May 2012

In the 1990s, GE’s Dry Low NOx (DLN) technology helped E-class industrial gas turbines with the DLN1 combustor achieve single-digit NOx emissions. Today more than 730 DLN1 systems are installed worldwide. Recent advances in the technology achieve ultra-low single-digit NOx emissions well below 5 ppm. This paper summarizes the development history of DLN1, the operating experience of DLN1 and the recent technical advancements made to enable DLN1+ to achieve low single digit NOx emissions on 7E and 6B engines. Field validation performance results of the systems in commercial operation will be shared as well as a summary of fuel-flexibility results for the DLN1 and DLN1+ systems.
A Revised Equation for Heat Flux Reduction in Film Cooling Studies and Discussion of Its Applications
Authors: Wang Ting , Zhao Lei
Published: May 2012

In film cooling experimental studies, due to the difficulty in measuring the surface heat flux variation, a Heat Flux Ratio (HFR) equation originally derived by Mick and Mayle [1], has been widely employed to calculate the surface heat flux distribution using the measured adiabatic film effectiveness and surface temperature. A close examination of the derivation process and applications of the HFR equation reveals two issues of concern. First, an implicit assumption was introduced by letting the wall surface temperature of the system without-film be the same as that which would occur with a film-cooled condition. A revised equation is then derived by removing this implicit assumption and incorporating the wall temperature change due to film cooling Secondly, a uniform value of the non-dimensional metal temperature φ (or film cooling effectiveness) has been used in all the previous applications of the HFR equation. This practice implicitly implies that a uniform wall temperature is distributed throughout the entire surface under film cooling, which is usually not the case in real conditions. A series of computational experiments are conducted to verify the revised HFR equation under different conditions as well as examine the validity of using a constant surface temperature in the HFR equation. Results reveal that using a constant value of φ (0.5 ∼ 0.7) to calculate surface heat flux may result in a negative HFR in some simulated cases showing the commonly adopted value φ = 0.5∼0.7. This could induce errors and give false HFR. The error is reduced in 3D cases because the streamwise wall temperature becomes more uniform than 2D cases. The difference between the old and new equations can reach about 20%. A conjugate wall cooling simulation shows negative HFR is possible in the region close to the film hole due to the heat conduction from the downstream hotter region into the cooler region near the film hole. Using the actual wall temperature as the φ-value, the newly revised HFR equation produces the exact heat flux as calculated by CFD including the correct calculation of negative heat flux caused by the conjugate wall.
Aerodynamic and Aerothermal Investigation of the Flow Around an HPT Rotor Shroud: Heat Transfer and Cooling Effectiveness
Authors: Lehmann Knut , Kanjirakkad Vasudevan , Hodson Howard
Published: May 2012

An experimental study has been conducted to investigate the aerothermal performance of a shrouded high pressure turbine blade in a large scale rotating rig. The rotor blade and the associated shroud and casing geometry have been modelled in a large scale low speed turbine rig that was designed to investigate a novel passive shroud cooling methodology. The objective of the present paper is to describe the aerothermal performance of a passive shroud cooling strategy using measured heat transfer and adiabatic cooling effectiveness data. Improved physical understanding of the shroud aerodynamics as reported in the companion paper Lehmann et al. [1] will be used here to support the analysis. Highly resolved experimental heat transfer data was acquired on the shroud, the fins and on the shroud underside with the thin heater film method. The distribution of the adiabatic cooling effectiveness on the rotor shroud was measured with a combination of the Ammonia-Diazo and a foreign gas sampling technique. The measurements are complemented by steady numerical computations of the turbine stage. Due to the impact of vortical flow structures in the over shroud cavities, the Nusselt numbers on the shroud top surfaces were found to be of the same order as on the shroud underside. The passive shroud cooling concept was found to provide quite efficient and uniform cooling to the over-shroud surfaces while the distribution of coolant on the shroud underside was significantly affected by the rotor secondary flow.
Development of Centrifugal Type Fuel Gas Compressor Package for FPSO
Authors: Lee Sangmyeong , Hwang Yeongsoo , In Beaseog
Published: May 2012

Fuel gas compressors are required to supply fuel gas to the gas turbine engines for compressor trains or generation sets, especially those used for offshore application such as FPSO (Floating Production, Storage & Off-loading) or FSRU (Floating Storage Re-gasification Unit). These gas turbine engines driven package are increasing in number to meet the LNG (Liquefied Natural Gas) market demand. Thus a significant number of fuel gas compressors are required to meet these demands. In this study the centrifugal type fuel gas compressor has been researched to compete against existing screw or reciprocation type compressors for offshore application and is the first developed in the world. The natural gas being pumped consisted of methane with more than 85% from 5.2barG to 58barG with a 42°C inlet temperature of each stage. The impeller type chosen is open as the result of structural analysis. A dry gas seal is selected to tandem type. The core parts consist of 3 stages, bull gear, pinion gears, bearings and dry gas seals. Package layout is designed considering compactness and rational placement.
New Alstom Monitoring Tools Leveraging Artificial Neural Network Technologies
Authors: Palme´ Thomas , Breuhaus Peter , Assadi Mohsen , Klein Albert , Kim Minkyo
Published: May 2012

This study presents a methodology to improve monitoring of gas turbines (GTs) while not having the specific engine characteristics available by applying a nonparametric statistical modeling based on operational data. The goal is to quantify the relationship between the operational conditions and the GT performance parameters during normal operation. In this study, the Multi-Layer Perceptron (MLP) Neural Network (NN) model is used to develop so called baseline models of the GTs. To verify the generic applicability, two different GTs and several units for each GT type are evaluated. A methodology to both, selecting the appropriate models with regard to input and output parameters as well as validating the selection of the parameters is reported. The key result can be summarized as: MLPs can be used for statistical modeling of GTs with very high accuracy, which permits an accurate prediction of the performance parameters during different operational conditions. It is also shown that under certain conditions, a developed NN model can be transferred to a similar GT. In summary, this study shows that NN can be used to improve on-line monitoring of a GT, making it possible to detect trends in the measured data indicating a change in the health status of the engine, requiring operational data only for model development.
Early Warning of Gas Turbine Failure by Nonlinear Feature Extraction Using an Auto-Associative Neural Network Approach
Authors: Palme´ Thomas , Breuhaus Peter , Assadi Mohsen , Klein Albert , Kim Minkyo
Published: May 2012

This study investigates the application of nonlinear Principal Component Analysis (PCA), implemented through the use of Auto-Associative Neural Network (AANN), for early warning of impending gas turbine failure. The study is based on a real operational data set that includes a compressor failure. The analyzed data set consists of measured operational parameters whose identity are unknown, hence this study presents a purely data driven approach to the problem of early warning. In this case study, the use of AANNs for early detection of abnormal engine behavior could have provided the operator with a warning a few days prior to the fully developed failure, which resulted in a forced shut-down and extensive maintenance. Furthermore, a comparison is made between the nonlinear PCA by AANNs and the standard PCA model, which is an inherently linear method. The result shows that the AANN provides a more reliable detection of the failure by a higher residual generation during failure mode as well as fewer false indications prior to the failure. Consequently, this study shows that nonlinear PCA as performed with AANNs can be a valuable data driven tool for early warning of gas turbine failure.
The Whole Annulus Computations of Particulate Flow and Erosion in an Axial Fan
Authors: Yang Hong , Boulanger Joan
Published: May 2012

Gas turbine engines operating in a hostile environment, polluted with sand or dust particles, are susceptible to the erosion damage, mostly at front axial fans and compressors. To accurately predict the erosion pattern and rate due to sand ingestion is one of the big challenges faced by the transportation and power industries. Maintenance costs are scrutinized and intensive research efforts are currently deployed in predictive life assessment tools to minimize the overhaul down time. The conventional prediction methods were usually based on steady-state simulations of gas-phase flows through a single blade passage per blade row to reduce computational cost. However, the multi-stage turbomachinery flows are intrinsically subject to unsteadiness, especially due to statorrotor interactions which may affect sand particle trajectories even if a one-way coupling method is considered. Furthermore, an unsteady stator-rotor interaction asks for a whole-annulus model at great computational cost to avoid simplifications of geometries or flow physics. To study the effects of the stator-rotor interaction on sand particle trajectories and erosion, an axial fan with inlet guide vanes is investigated based on the whole annulus computations of both steady and unsteady gasphase flows, each of which is then followed by a Lagrangian particle tracking step. A numerical algorithm for tracking particles driven by unsteady gas-phase flow is presented. The comparison of the numerical predictions with the experimental data confirms the validity and necessity of the unsteady CFD model in providing adequate predictions of sand erosion in the axial fan.
Turbomachinery Thermal Analysis Using Coupled Two- and Three Dimensional Models and Reduced Order Fluid Models
Authors: Contreras Jesus , Corral Roque , Pastor Guillermo
Published: May 2012

A methodology to couple two- and three dimensional thermal models is described. The method uses reduced order fluid models as a mechanism to transfer heat fluxes and average temperatures at the interface. In particular the concept of a duct-void is introduced to ease the coupling of different types of models. A new edge-based thermal solver, which is used in this process, is briefly described. A realistic case, corresponding to a two-stage turbine, is used to illustrate the usefulness of the method. It is concluded that the temperature difference between a fully coupled a approach and a simpler unidirectional method (in which a two-dimensional global model is first computed and, then, the temperatures at the interface are transferred to three-dimensional sub-components) may be large enough to affect engineering decisions.
Effect of Narrow Jet Spacing on Impinging Flow and Heat Transfer
Authors: Guo L. , Yan Y. Y. , Zu Y. Q.
Published: May 2012

Limited by the structures of the engineering components, sometimes the narrow gap impingement with limited jet-to-target spacing is required in the practical situations. In order to obtain an improved understanding upon the effects of narrow gap impingement on surface heat transfer and to fill gaps in the limited literatures, experiments of multi-jet impingement have been carried out using different jet-to-target distance (0.5D and 1D). Different configurations of jet-array are adopted and the transient thermochromic liquid crystal (TLC) is applied for the acquisition of the heat transfer data. Reynolds number of the jet flow ranges from 2.43×104 to 5.39×104. It shows that the impingement using 90° attack angle with a jet-to-target distance of 0.5D leads to non-uniform distributions of the Nusselt number, especially for the upstream jet-region. According to the experimental results, the jets with the non-orthogonal attack angle and staggered array perform better than the normal ones. Under the same experimental conditions, the staggered jets with 75° attack angle can give higher average Nusselt numbers with fewer fluctuations in the jet region.
Numerical Investigation of Different Casing Treatments on Performance of a High Speed Centrifugal Compressor Stage
Authors: Ma Yan , Xi Guang , Wu Guangkuan
Published: May 2012

In this paper, two different casing treatment devices—one adopting inlet recirculation at the shroud side of the impeller inlet and the other adopting circumferential casing grooves at the shroud side of the vaneless space, are designed for a high speed centrifugal compressor stage. The effects of different casing treatments to the flow range and performance of the centrifugal compressor stage are studied numerically. The results indicate that traditional inlet recirculation at impeller inlet does not extend the stall margin of the stage and the performance deteriorates due to the adding of the extra device. The study also shows that, when the location of the bleed slot moves downstream, the performance of the stage deteriorates due to the longer flow path. Moreover, the 2mm depth circumferential casing grooves extend the stall margin by about 12.05%. By contrast, the 6mm depth and 10mm depth grooves extend the stall margin by 3% and 2.4% respectively.
Dynamic Analysis of a Wind Energy Storage System in Remote Offshore Areas
Authors: Zhao Pan , Dai Yiping , Wang Jiangfeng , Xie Danmei
Published: May 2012

Due to the increasing oil and gas demand, the shortage of fossil fuel resources, serious global greenhouse effect and extremely environmental deterioration, the renewable energy sources are more and more attractive. The energy storage is a vital problem for the intermittent and seasonal renewable energy sources. In this paper, a wind energy storage system consideration of chlorine production which is located in remote offshore area is proposed. The detailed dynamic models are established and simulations are also carried out. The proposed system stores the surplus energy generated from wind farm as a form of hydrogen via the electrolyzer array, and uses the stored hydrogen to generated electrical energy at poor wind condition through a PEM fuel cell array. The simulation results show that the proposed system could not only absorb the wind power maximally, but also produce sufficient electric energy to meet the load power demands. Moreover, the proposed system could tolerate the frequently impulses because of the variations of wind energy on the small stand-alone power system effectively.