bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Analysis of Spray Dispersion, Evaporation and Combustion in a Single Gas Turbine Combustor
Authors: Chrigui M. , Sadiki A. , Janicka J.
Published: August 2009

Spray dispersion, evaporation and combustion have been numerically studied in a complex industrial configuration, which consists in a single annular combustor that was experimentally measured by Rolls-Royce-Deutschland Company. Simulations have been achieved using the Eulerian-Lagrangian approach. The computations of the continuous phase have been performed by means of RANS simulations. Though the k-ε as well as the Reynolds Stress model (Jones-Musonge) have been used for turbulence modeling. The 3D-computations have been performed in a fully two-way coupling. The effects of turbulence on droplets distribution are accounted for using the Markov sequence dispersion model. The equilibrium as well as the non-equilibrium evaporation model have been applied. In order to account for the combustion, the diffusion flame model is chosen. It relies on the computation of the mixture fraction that has been affected by the presence of vapor source terms. For the interaction of the turbulence with the chemistry, the mixture fraction variance has also been solved. For that purpose a presumed beta-PDF function has been considered. The equilibrium and the flamelet chemistry approaches have been used for the generation of the chemistry tables. The performed simulations have also been compared to commercial CFD-codes. From there one observes, that the obtained results using the mentioned sub-models combination agree most favorably with experimental measurements. One noted that the Reynolds Stress model provided smoother temperature distribution compared to k-ε. The flamelet model has been performed using three different scalar dissipation rates. One observes that differences are mainly located at the nozzle exit, where the scalar dissipation rate has got the highest value. Although the comparison between the numerical results and the experimental data was possible only at the combustor exit, due to the limitation on the measurement techniques, one can reiterate that the combination of the following sub-models: thermodynamically consistent model for the turbulence modulation, Langmuir-Knudsen non-equilibrium model for the evaporation, Reynolds Stress Model for the turbulence and flamelet model for the chemistry establish a reliable complete model that seems to allows a better description of reactive multi-phase flow studied in the frame of this work.
Experimental Characterization of a Hydrogen Fuelled Combustor With Reduced NOx Emissions for a 10 MW Class Gas Turbine
Authors: Cocchi Stefano , Provenzale Michele , Cinti Valerio , Carrai Luciano , Sigali Stefano , Cappetti Davide
Published: August 2009

In the frame of a research project launched in 2006 (partly funded by Regione Veneto, a local institution in the North-East of Italy), ENEL and Nuovo Pignone are developing an innovative “zero emission” gas turbine cycle suitable for power generation. The gas turbine, a GE10-1 model, is manufactured by Nuovo Pignone and will be installed at ENEL’s coal-fired Fusina power plant, near Venice. The turbine, rated for 11 MWe, is equipped with a diffusive flame combustor and is suitable for operation with 100% hydrogen as main fuel over the entire load range. Hydrogen is available at Fusina site as by-product of petrochemical plants. Natural gas will be used as start-up and back-up fuel, and NOx emission abatement will be achieved by means of steam injection. Load operation will be possible with hydrogen only, with methane or hydrogen-methane mixtures (in case of reduced availability of hydrogen) and with or without steam injection. In order to support the combustion system’s design, experimental activities have been carried over a prototypical combustor, installed on a combustion test rig at ENEL’s experimental facility, located in Sesta (Tuscany). The test rig has been upgraded in order to permit full-scale combustor operation. Tests have been planned with the aim of providing a complete screening of combustion system’s sensitivity to minor hardware modification (three different burners and two different liners, designed for diffusive combustion, have been available) and operating conditions (sensitivity to cycle parameters and effect of steam injection). Special instrumentations have been installed for a detailed monitoring of hot parts’ metal temperature, combustion-driven pressure oscillations and pollutant emissions. A water-cooled camera has been installed for direct flame visualization. The experimental campaign is still on-going and only the default combustor configuration has been tested so far. However, collected results indicate safe combustor operation in both hydrogen and methane combustion mode: metal temperatures have never exceeded warning limits and pressure pulsation have been extremely quiet. NOx emission during hydrogen operation in dry combustion mode have been proven to be roughly 3 times higher than in dry methane combustion mode. Steam injection has been proven to be effective in reducing NOx emissions down to contractual values. Additional efforts are in progress to obtain a further reduction of emission level. Finally, experimental results have been processed in order to set up a simple NOx emissions’ model, accounting for NOx production in any possible operating mode.
Conjugate Heat Transfer Study of a Spin Pit Rig: Application to the Lifing of HP Turbine Disc Firtrees
Authors: Gopinathrao N. , Mabilat C. , Alizadeh S. , Jackson D. , Clarkson R.
Published: August 2009

Structural life and durability of gas turbine engine discs and blade firtree has always been a key design issue for designers and technologists. This is particularly important for gas turbine components which operate at elevated temperatures under high loads. The testing for these components need to be undertaken at operating conditions, particularly when Low Cycle Fatigue (LCF) lives of components are evaluated. The spin pit and biaxial rig tests, the former of which is the concern of this study, are used in the aero gas turbine industry for the lifing analysis of these critical engine parts. In this study a three dimensional conjugate heat transfer analysis of the spin pit rig with the HP turbine disc and blade assembly for a large turbofan engine has been performed. The scope of the Computational Fluid Dynamics (CFD) analysis has allowed a detailed understanding of the flow and thermal field within the domain to be obtained. Flow within the rig was found to be complex, with multiple flow mechanisms simultaneously at play in several distinct areas of the solution domain. All heat transfer processes, radiation, convection and conduction were found to be important in the overall heat. Radiation heat transfer was found to be dominant in terms of temperature levels achieved in components, whilst convection heat transfer majorly influenced temperature gradients in solids. The appropriate capturing of flow leakages in the rig proved to have a significant impact on rig performance and component thermal fields. The component temperatures predicted by the tuned CFD model compared well against thermocouple measurements and predictions of the conjugate CFD analyses were directly used as boundary conditions in follow-on stress analyses for lifing purposes. The methodology adopted has resulted in a very satisfactory outcome on declared disk life. It is understood that this is the first time where a full conjugate heat transfer CFD study of the spin pit rig without any separate thermal analyses, has been applied directly to the lifing of HP disc firtree and the eventual engine certification, in the aero gas turbine industry.
Mixing Planes Revisited: A Steady Mixing Plane Approach Designed to Combine High Levels of Conservation and Robustness
Authors: Holmes D. Graham
Published: August 2009

The use of “mixing planes” for steady multistage turbomachinery calculations has been common for some time. The basic idea is simple: in order to perform quasi-steady multistage turbomachinery calculations, the exchange of information at an interface between stationary and rotating blade rows must involve a pitchwise averaging process. This pitchwise averaging implies a mixing process of some sort, which may or may not have a physical analog. This paper revisits the mixing plane idea, and describes an attempt to produce a novel mixing plane algorithm that achieves several key goals, including complete flux conservation at the interface, robustness, indifference to local flow direction and non-reflectivity. The key elements of the algorithm are described, along with some examples of its application.
Laboratory Investigations of Low-Swirl Injectors Operating With Syngases
Authors: Littlejohn David , Cheng Robert K. , Noble D. R. , Lieuwen Tim
Published: August 2009

The low-swirl injector (LSI) is a lean premixed combustion technology that has the potential for adaptation to fuel-flexible gas turbines operating on a variety of fuels. The objective of this study is to gain a fundamental understanding of the effect of syngas on the LSI flame behavior, the emissions and the flowfield characteristics for its adaptation to the combustion turbines in IGCC clean coal power plants. The experiments were conducted in two facilities. Open laboratory flames generated by a full size (6.35 cm) LSI were used to investigate the lean-blow off limits, emissions, and the flowfield characteristics. Verification of syngas operation at elevated temperatures and pressures were performed with a reduced scale (2.54 cm) LSI in a small pressurized combustion channel. The results show that the basic LSI design is amenable to burning syngases with up to 60% H2. Syngases with high H2 concentration have lower lean blow-off limits. From PIV measurements, the flowfield similarity behavior and the turbulent flame speeds of syngases flames are consistent with those observed in hydrocarbon and pure or diluted hydrogen flames. The NOx emissions from syngas flames show log-linear dependency on the adiabatic flame temperature and are comparable to those reported for the gaseous fuels reported previously. Successful firing of the reduced-scale LSI at 330 < T < 446° F and 8 atm verified the operability of this concept at gas turbine conditions.
Smart Turbomachines Using Active Magnetic Bearings
Authors: Larsonneur R. , Richard P.
Published: August 2009

Due to the convergence of several key technologies, direct driven (i.e. gearless) turbomachines have become established solutions for specific applications. Magnetic bearings are a key element enabling such machine topologies, which has led to increased interest and also understanding of manufacturers and end customers of this technology. Whereas the key benefit of magnetic bearings — contactless levitation — is well known, the fact that using magnetic bearings turns a classic turbomachine into a state-of-the-art mechatronic system with a host of additional possibilities is still not widely accepted. This paper presents the applications, advantages and benefits of enhancing a basic magnetic bearing system by a measurement function that makes full use of magnetic bearings’ built-in instrumentation.
Numerical and Experimental Study of Spray Produced by an Airblast Atomizer Under Elevated Pressure Conditions
Authors: Chrigui M. , Sadiki A. , Batarseh Feras Z. , Roisman I. , Tropea C.
Published: August 2009

This work has two-fold contributions. First, a detailed experimental database that allows an understanding of important aspects of the spray generated by an airblast atomizer, including atomization and spray propagation, at various ambient pressures is provided. Second, as the control, design or optimization tasks are repetitive and costly, the ability of a recently developed numerical spray module (Sadiki et al. 2005) based on a Euler-Lagrangian method to well capture spray properties under elevated pressure is evaluated. Such a module should help to provide early detailed information at moderate costs of processes under study. The experiments have been performed in a pressure chamber equipped with transparent windows allowing optical access to the spray. By means of PIV technique and Phase Doppler instrument the spray properties have been characterized at various ambient pressures (between 1 and 18 bars). Especially three average velocity components and droplet diameters of the spray have been measured. Numerical studies of the spray transport have been achieved by using advanced URANS-based models. An overall agreement between experimental data and numerical simulation points out the accuracy of the evaluation techniques used for the measurement treatment and demonstrated the prediction ability of the mathematical spray model.
Simulation and Production of Wound Impellers
Authors: Eyler Allen , Mu¨ller Norbert
Published: August 2009

The wound composite impeller, developed at Michigan State University, is a new way of manufacturing turbomachine impellers with a wide range of potential applications, even including use in gas turbines. The production can be rapid, inexpensive, and utilize commercially available winding machines. This work focuses on the modeling of the Wound Impeller for computer simulation and optimization processes, and for automation of the production process.
PIV Investigation of a High Speed Centrifugal Compressor Diffuser: Spanwise and Loading Variations
Authors: Cukurel Beni , Lawless Patrick B. , Fleeter Sanford
Published: August 2009

An efficient diffuser is essential to a modern compressor stage, due to its significance in stage performance, durability and operability. To address the need for data that describe the complex, unsteady flow field in a vaned diffuser, Particle Image Velocity is utilized to characterize the spanwise and circumferential variations of the flow features in the vaned diffuser passage of a transonic centrifugal compressor. The spanwise variation in the diffuser flow field is further investigated by comparison of 3 different operating conditions representative of low, nominal and high loading. These data demonstrate that not only the diffuser flow field is highly dependent on the operation conditions, e.g. hub-to-shroud variation increases with loading, but also the circumferential periodicity, created by the highly three dimensional impeller discharge flow, generates a larger unsteadiness towards the hub region of the vaned diffuser.
Heat Transfer and Pressure Measurements in a Lattice-Cooled Trailing Edge of a Turbine Airfoil
Authors: Saha Krishnendu , Guo Shengmin , Acharya Sumanta , Nakamata Chiyuki
Published: August 2009

An experimental study of the heat transfer distribution and pressure drop through a converging lattice-matrix structure has been performed. This structure represents a gas turbine blade trailing-edge cooling passage. Stationary tests were performed on a scaled up model under three Reynolds numbers (24000<Re<60000). To obtain the wall temperature, the narrow band liquid crystal technique was used, and the heat transfer coefficient value was obtained using the transient method. It’s found that the Nusselt number ratio (Nu/Nu0) is around 4–5, comparing to the channel flow of similar hydraulic diameter and Re, for the whole lattice-matrix structure. Under the impingement and turning areas, the ratio can be as high as 7–8. Pressure data are taken throughout the lattice structure following the flow direction. The pressure drop increases with Reynolds number and as a result there is a decrease in the thermal performance factor at higher Reynolds number. In the present study thermal performance factor is found to be around 1–1.2. For comparison, pin fin based trailing edge configuration has a typical thermal performance factor of 0.7 to 0.85 under the same Reynolds numbers.
Introduction of the Taurus™ 65 Industrial Gas Turbine for Power Generation
Authors: Rocha George , Reynolds Simon , Brown Theresa
Published: August 2009

Solar Turbines Incorporated has combined proven technology and product experience to develop the new Taurus 65 gas turbine for industrial power generation applications. The single-shaft engine is designed to produce 6.3 megawatts of electrical power with a 33% thermal efficiency at ISO operating conditions. Selection of the final engine operating cycle was based on extensive aerodynamic-cycle studies to achieve optimum output performance with increased exhaust heat capacity for combined heat and power installations. The basic engine configuration features an enhanced version of the robust Centaur®50 air compressor coupled to a newly designed three-stage turbine similar to the Taurus 70 turbine design. Advanced cooling technology and materials are used in the dry, lean-premix annular combustor, consistent with Solar’s proven SoLoNOx™ combustion technology, capable of reducing pollutant emissions while operating on standard natural gas or diesel liquid fuels. Like the Titan™ 130 and Taurus 70 products, a traditional design philosophy has been applied in development of the Taurus 65 gas turbine by utilizing existing components, common technology and product experience to minimize risk, lower cost and maximize durability. A comprehensive factory test plan and extended field evaluation program was used to validate the design integrity and demonstrate product durability prior to full market introduction.
Environmental Degradation of Heat-Resistant Alloys During Exposure to Simulated and Actual Gas Turbine Recuperator Environments
Authors: Rakowski James M. , Stinner Charles P. , Lipschutz Mark , Montague J. Preston
Published: August 2009

Primary surface recuperators (PSR’s) for land-based industrial gas turbines are typically constructed from heat-resistant alloys such as nickel-base superalloys or highly-alloyed austenitic stainless steels. The water vapor present in gas turbine exhaust has been shown to increase the rate of chromium oxide volatility, which in turn can cause rapid oxidation of the underlying metal. As PSR’s are generally fabricated from thin foil materials, excessive degradation can cause perforation, leading to failure of components. The results of a field test program will be summarized, based on analysis of recuperator stand-in components which were exposed to a full-flow exhaust stream during gas turbine operation for times ranging from 500 hours to 21,500 hours. A significant effect of service on the materials of construction was observed, with near-surface chromium depletion and microstructural instability evident after the longest exposures. These results will be combined with those from an extensive laboratory test program to evaluate the performance of heat-resistant alloys during recuperator service, outlining the different modes of degradation and means for their mitigation.
Adiabatic Effectiveness on the Suction Side of a Turbine Vane and the Effects of Curvature at the Point of Film Injection
Authors: Davidson Frederick T. , Bruce-Black Joshua E. , Bogard David G. , Johns David R.
Published: August 2009

The effects on film cooling performance due to the use of angled slots with impinging cylindrical holes were studied on the suction side of a scaled-up turbine vane. Various configurations were explored to fully characterize the effects of varying the depth of the slot and the pitch between the impinging feed holes within the slot. Experiments were also conducted to evaluate the effect of local curvature at the point of coolant injection. Each test was conducted with and without an upstream boundary layer trip to determine the effects of changing the approach boundary layer. Rows of discrete round and shaped holes were tested for comparison with the slots. The study of varying slot geometries showed that increasing the depth of the slot and decreasing the pitch between the impinging cylindrical holes enhanced film cooling effectiveness. The optimum slot configuration was found to have comparable adiabatic effectiveness with the better shaped holes configuration at lower blowing ratios, and superior performance at higher blowing ratios. The results pertaining to the local curvature and approach flow showed a significant effect on the round hole performance, but had negligible effect on the angled slot and shaped hole configurations.
Wave Rotor Design Procedure for Gas Turbine Enhancement
Authors: Pohorˇelsky´ Ludeˇk , Sane´ Pranav , Rozsas Tomas , Mu¨ller Norbert
Published: August 2009

This paper presents an analytical design procedure for pressure wave machines, also known as wave rotors, to enhance gas turbines and internal combustion (IC) engines in a topping or bottoming cycle. The advantage of using a wave rotor for improving the performance of gas turbines or internal combustion engines is that it uses a pressure and enthalpy exchange process. Employing pressure or even shockwaves for the energy transfer, no mechanical parts like pistons or blades are necessary inside the chamber (channel) that houses the process, which increases the air pressure delivered to the combustor of a gas turbine or cylinder of an internal combustion (IC) engine. The wave rotor has found fair success in its application to IC engines. Research and development continues for both, applications in IC engines and its originally envisioned application in gas turbines. Here an analytical 1-D algebraic wave model is realized by utilizing shockwave theory and linear gas dynamic principles to model the process in a 4-port wave rotor, with five wave reflections in the low pressure part for better gas scavenging. Using this analytical model, a comprehensive design space has been investigated and documented in performance maps. From this, conclusions and recommendations are drawn for performance and geometry optimization. The analytical algorithm has been validated using a 1-D commercial code GT-POWER and 2-D CFD code FLUENT. While here the interest is mainly in steady state operation, the analytical algorithm also models transient processes.
Vibratory Response Characterization of a Radial Turbine Wheel for Automotive Turbocharger Application
Authors: Kulkarni Avadhoot , LaRue Gerry
Published: August 2009

One of the major challenges in the design and development of a turbine wheel for automotive turbochargers is high cycle fatigue (HCF) due to blade resonant vibrations. This is a result of the design trend towards higher blade loading, thinner blades and higher tip speeds which has led to wheel designs and manufacturing techniques which further accentuate the HCF risk. This paper is directed at investigating the resonant response of a variable geometry radial turbine wheel. Wheel resonant response due to vane count excitation was captured by measuring blade tip timing using the Non-intrusive Stress Measurement System (NSMS). Blade deflections in second mode were measured at various turbine inlet pressures and at various inlet vane openings to study their sensitivity. Time dependent 3D CFD calculations were performed to accurately predict the flow field and hence the blade loading at various operating conditions. A finite element (FE) model of the wheel was created in ANSYS and blade loadings calculated from CFD were transferred to the FE mesh to predict blade vibratory strains. Trends of predicted strains were successfully compared against the blade deflection measurements at different turbine inlet pressures and at different vane openings.
Manufacturing Optimization for Bondcoat/Thermal Barrier Coating Systems
Authors: Bossmann Hans-Peter , Bachegowda Sharath , Schnell Alexander
Published: August 2009

A reliable lifetime prediction rule for bondcoat/thermal barrier coating (BC/TBC) coated parts in gas turbine operation is necessary to determine remnant service life. The specimens investigated were coated with MCrAlY plus Yttria partially stabilized Zirconia (7YSZ) applied by vacuum plasma spraying (VPS) and atmospheric plasma spraying (APS) processes respectively. The performances of these laboratory specimens were statistically assessed, combining long term oxidation testing with thermal cycling, thus superimposing thermo-mechanical loading on the lab specimens to more accurately represent engine conditions. A design of experiment (DOE) approach was used for manufacturing optimization of the BC/TBC system. The life of the coating system is influenced by several manufacturing parameters such as BC thickness, BC roughness, TBC thickness, TBC porosity and TBC stiffness. Specimens with a suitable variation of these parameters were produced to ensure a balanced test matrix of fractional factorial DOE. Based on results derived from lab testing the specifically tailored parts, first and second order effects of manufacturing parameters on lifetime were quantified. The findings revealed that the second order effects (the interaction of manufacturing parameters) were more important on the lifetime of the BC/TBC system than the corresponding first order effect (single parameter). For instance, the variation of BC thickness or BC roughness led to a scatter of lifetime of 10% and 60% respectively, whereas their interaction resulted in a scatter of lifetime of 150% for the same range of coating parameters. Further examples of such pairings are also demonstrated. Finally, a lifetime prediction for 3 quality classes (high, medium and low quality) has been demonstrated. The difference in achievable lifetime highlights the importance of manufacturing parameters in determining the life of the BC/TCB system.
Heavy Duty Gas Turbines Fuel Flexibility
Authors: Campbell Anthony , Goldmeer Jeffrey , Healy Tim , Washam Roy , Molie`re Michel , Citeno Joseph
Published: August 2009

Gas Turbine fuel flexibility is becoming an increasingly important global issue. The global power sector is being driven by a complex assembly of customer economics, environmental concerns and global political uncertainties to look at cost-effective gas and liquid fuel alternatives without sacrificing plant efficiency and emissions characteristics. In this climate, fuel flexibility includes natural gas, but also expands to non-traditional fuels. GE’s extensive experience with natural gas, industrial and syngas fuels, as well as biofuels segments are surveyed.
Performance and Short Length-Scale Disturbance Generation in an Axial Compressor With Non-Uniform Tip Clearance
Authors: Morris Scott C. , Cameron Joshua D. , Bennington Matthew A. , McNulty G. Scott , Wadia Aspi
Published: August 2009

The performance, efficiency, and stall inception of an axial compressor was investigated experimentally with small levels of rotor centerline offset. The measurements were acquired using a high-speed, single-stage compressor. The rotor was levitated magnetically during operation which allowed precise positioning of the rotor centerline within the circular casing. The offset magnitude used in this study was 0.23% of the rotor tip chord, equivalent to approximately 24% of the nominal gap value. The resulting asymmetry in the tip gap resulted in circumferential and radial variations in the measured stagnation pressure and stagnation temperature downstream of the stage. However, the spatially averaged performance of the compressor was not measurably different from that obtained with a concentric rotor. An array of unsteady (Kulite) pressure transducers was used to investigate the flow field during stall inception. These measurements were recorded during transient throttle movements which quickly decreased the mass flow in the compressor until the onset of rotating stall. A second set of measurements was acquired during quasi-transient throttling starting from a mass flow about 1% larger than the stalling mass flow. In both the symmetric and offset cases the flow breakdown was consistent with spike type inception. The measurements with offset indicated that the asymmetries in the local compressor flow field produced significant changes in the number of short-length scale rotating disturbances observed during throttling to stall. These disturbances appeared in the region of the annulus where the local flow coefficient was lowest and usually decayed upon rotating to the higher flow region. In this way, the addition of very small amounts of rotor offset tended to fix the disturbance generation location in the stationary reference frame. This was in contrast to the symmetric tip clearance case where the location of spike generation appeared stochastic.
Numerical Investigation on the Effects of Self-Excited Tip Flow Unsteadiness and Blade Row Interactions on the Performance of a Low Speed Compressor Rotor
Authors: Lee Daniel , Orkwis Paul D. , Tsung Fu-Lin , Magnuszewski William , Noll Christopher , McNulty G. Scott
Published: August 2009

A numerical investigation has been conducted to determine the effects of self-excited tip-leakage flow unsteadiness, upstream stator wakes, and downstream blade row interactions on the performance prediction of a low speed research compressor rotor. Calculations included a single blade-row rotor configuration as well as two multi-blade row configurations: one where the rotor was modeled with an upstream stator and a second where the rotor was modeled with a downstream stator. Steady-state and time accurate calculations were performed using a RANS solver and the results were compared with detailed experimental data at operating conditions corresponding to the compressor design point, near stall and a mid-point between the two. Differences in the performance predictions between the three configurations were then used to determine the effect of the upstream stator wakes and the downstream blade row interactions. Results obtained show that for this compressor with rather large tip clearance, time-accurate calculations are a vast improvement over steady-state calculations, but the upstream stator wakes and the downstream blade row interactions have only a small effect on the numerical solution. In this paper, changes in the rotor flow field due to the upstream and downstream stators are investigated and discussed to explain the limited impact of the stator wakes and downstream blade row interactions on this tip dominated flow. In addition, the unsteady nature of the rotor tip vortex at near stall conditions is discussed to explain the improvement of time accurate analysis over steady state computations.
Transient Response and Thermal Performance of a Variable Displacement Vane Pump-Based Actuation System for Turbo Jet and Turbofan Aircraft Engines
Authors: Paluszewski Paul J. , Desai Mihir C.
Published: August 2009

The Goodrich Variable Displacement Vane Pump (VDVP) has been described in earlier proceedings (GT2007-27948) as a potential solution to thermally constrained aircraft fuel systems. Higher fueldraulic system pressures and flow requirements have placed severe demands on fuel system thermal management techniques. Furthermore, larger heat loads from a variety of sources are constantly increasing the temperatures at which modern aircraft fuel systems are required to operate. The ongoing objective for the development of the VDVP and VDVP-based fuel systems is to minimize the waste heat returned to bulk fuel, which in turn can reduce or eliminate heat exchangers and/or increase aircraft mission capability. The earlier noted reference also describes how a twin-element pumping system can provide superior thermal and transient response when in a closed-loop pressure compensating regulation mode; one example of this is VDVP coupled to a Fixed Displacement Vane Pump (FDVP). These claims were substantiated analytically by several trade studies and performance predictions that have been performed throughout the development cycle. Since these performance predictions have been made, the aforementioned twin VDVP/FDVP pumping and control system has undergone extensive testing and development. This paper discusses the thermal and transient performance predictions and test data of the twin-element pumping system, and summarizes the development of the pumps and controls. For a given hypothetical mission cycle, the VDVP/FDVP fueldraulic system with quantified performance can be compared analytically to other pumping solutions operating in the same environment.
Integrating Optical Sensors in Fuel Injectors for Combustion Control
Authors: Myhre Doug , Aadland Timothy , Cornwell Michael , Goeke Jerry
Published: August 2009

As the industry pushes the envelope to run turbine engines as lean as possible, combustion can become very unstable, risking engine damage, or combustion extinction. The challenge is to find solutions that will allow engines to run leaner while eliminating these risks. Active Combustion Control Systems (ACCS) are becoming a viable way to control unwanted instabilities in turbine engines. Many areas of investigation are under way by several companies and institutions to develop ACCS. One of these systems utilizes sensors to detect abnormalities in the engine operation and provides a means of feeding back the corrective action in real time using fuel pulsation. Two technologies have been competing as the primary feedback sensor, optical and acoustic. Acoustics measures the secondary effect of combustion instabilities, namely the pressure pulses. Optics measures the primary source of the pressure fluctuations, namely the flame intensity variation. This paper describes a unique optical method for viewing the flame with sensors at the flame front. The flame is viewed at its source, the fuel injector. Optical rods are integrated into the injector to view the flame in the axial direction. Different fields of view are possible using simple methods to view different parts of the flame. Also, issues associated with fouled optics are discussed along with a proven approach to keep the viewing window clean. Other advantages of optical flame viewing and the additional intelligence that can be gained are also discussed. Some of these advantages are possible emissions determination, lean blow-out onset, fuel/air mixture ratio, and flame temperature. One of the unique ways in which optical flame detection is able to add intelligence to the control system is its ability to differentiate between types of instabilities (helical and longitudinal) and this may be useful in the application of countermeasures. Testing has indicated that direct sensing of the flame using optical sensors appears to be the fastest way to predict the onset of an instability or lean blowout. When using fuel control pulsations to quell instabilities, both the amplitude and frequency of the instability are needed. Testing has shown that the combination of acoustic and optical sensors provides the best signals for feedback to the fuel control system.
Comparison of RANS Turbulence Models for Prediction of Film Cooling Performance
Authors: Harrison Katharine L. , Bogard David G.
Published: August 2009

The realizable k-ε, standard k-ω, and RSM turbulence models were used to simulate flat plate film cooling experiments that are commonly described in literature. Adiabatic effectiveness simulations revealed that using the standard k-ω model resulted in the closest agreement with experimentally determined laterally averaged adiabatic effectiveness, but the worst agreement with centerline adiabatic effectiveness. Conversely, the realizable k-ε model agreed worst with experimental laterally averaged adiabatic effectiveness values and best with centerline values. Use of the anisotropic RSM model was not found to predict more realistic coolant spreading than the other models. Simulations to find heat transfer coefficients without film cooling showed good agreement with correlations for all three models, and the closest agreement resulted from using the realizable k-ε model. Heat transfer coefficient augmentation was also examined for two configurations: unit density ratio with and without upstream heating. Laterally averaged heat transfer coefficient augmentation simulations using all three turbulence models agreed well with experiments. However, the spanwise variation in heat transfer coefficient augmentation in all cases was greater than is typically seen experimentally.
Use of the Adiabatic Wall Temperature in Film Cooling to Predict Wall Heat Flux and Temperature
Authors: Harrison Katharine L. , Bogard David G.
Published: August 2009

The adiabatic wall temperature is generally assumed to be the driving temperature for heat transfer into conducting gas turbine airfoils. This assumption was analyzed through a series of FLUENT simulations using the standard k-ω turbulence model. Adiabatic effectiveness and heat transfer experiments commonly documented in literature were mimicked computationally. The results were then used to predict both the heat flux and temperature distributions on a conducting flat plate wall and the predictions were compared to the heat flux and temperature distributions found through a flat plate conjugate heat transfer simulation. The heat flux analysis was compared to previously published work using the realizable k-ε turbulence model. The same conclusions could be drawn for both turbulence models despite differences in simulated adiabatic effectiveness and heat transfer coefficient distributions. Agreement between heat flux predictions and the heat flux from the conjugate simulations correlated well with how closely the adiabatic wall temperature approximated the over-riding gas driving temperature for heat transfer into the wall. In general, the driving temperature for heat transfer was represented well by the adiabatic wall temperature and the heat flux was well predicted. However, in some locations, the heat flux was over-predicted by up to 300%. Since wall temperature is ultimately the parameter of interest for industrial gas turbine design, the conducting flat plate temperature distribution was also predicted. This was done by using the adiabatic effectiveness and heat transfer coefficients found with the standard k-ω turbulence model as boundary conditions in a three dimensional solid conduction simulation. Then metal temperatures predicted in the solid conduction simulation were compared to those found through conjugate analysis. Despite deviations in predicted heat flux and the conjugate model heat flux of up to 300%, deviations in the predicted and the conjugate model non-dimensional metal temperatures were less than 10%. Thus, use of the adiabatic wall temperature as the driving temperature for heat transfer to predict temperature on the surface of a conducting wall results in relatively small errors.
Integration of Thermal Stress and Lifetime Supervision System of Steam Turbine Rotors
Authors: Carnero P. Antonio , Serrano R. Lui´s , Nebradt G. Jesu´s , Leyva M. Lui´s
Published: August 2009

The turbine rotors experience high-thermo mechanical stresses caused by requirements of their operation. These cause mechanical damage (fatigue) that is accumulated according to the frequency with which the different ways of operation (cold, warm or hot starts) of the turbine happens. On the other hand, the greater efficiency of combined-cycle utilities with respect to conventional utilities is reflected in a greater production cost of the electrical energy, which has forced to that conventional units of generation to be designed to operate with base load, nowadays they are used in variable and peak load regime to satisfy the demand during the hours of greater demand. As mentioned earlier, repercussions in a greater frequency of operations of stops and hot starts of turbines, it is the reason of why the fatigue damage will be increased when it changes its regime of operation. In Mexico, turbines that have been in operation between 15 or 20 years and that were designed for base load operation and that have changed their operation to variable and peak load, still they do not have a supervisor of thermal stresses and lifetime consumption. For that reason is essential to equip them with a supervisor to limit the stresses during the stops and starts and reduce its consumption of lifetime. The paper deals about the integration of a system supervisor of thermal stresses, which from the parameters of operation of the turbine (temperature pressure, rpm, etc), determines the gradient of temperature in the zone of the control stage of the rotor. After that, it calculates the thermal and mechanical stresses and finally it apply the fatigue concept to assess the consumption of lifetime by each cycle of operation (stop – start).
Rotating Stall Inception From Spike and Rotating Instability in a Variable-Pitch Axial-Flow Fan
Authors: Nishioka Takahiro , Kanno Toshio , Hayami Hiroshi
Published: August 2009

End wall flow fields at the two stagger-angle settings for the rotor blades in the low-speed axial-flow fan are experimentally and numerically investigated to elucidate the mechanism of stall inception. Rotating instability is confirmed near the maximum pressure-rise point at both design and large stagger-angle settings. This instability is induced by the interaction between the incoming flow, tip leakage flow, and backflow from the trailing edge. The stall-inception pattern, however, differs at the two stagger-angle settings. The stall inception from a spike is observed at the design stagger-angle setting, and the stall inception without the spike and modal disturbance is observed at the large stagger-angle setting. The rotating instability seems to influence the formation of stall cell at the large stagger-angle setting. Tip-leakage vortex breakdown occurs at both design and large stagger angle settings. This breakdown induces the three-dimensional separation on the suction surface of the rotor blade at the tip. Three-dimensional separation at the design stagger-angle setting is stronger than that at the large stagger-angle setting. The strong separation grows into a three-dimensional separation vortex, which crosses the blade passage near the trailing edge. This separation vortex seems to be one of the conditions for spike initiation.
Simulation of Performance Deterioration of a Microturbine and Application of Neural Network to Its Performance Diagnosis
Authors: Yoon Jae Eun , Lee Jong Joon , Kim Tong Seop , Sohn Jeong Lak
Published: August 2009

This study aims to simulate performance deterioration of a microturbine and apply artificial neural network to its performance diagnosis. As it is hard to obtain test data with degraded component performance, the degraded engine data have been acquired through simulation. Artificial neural network is adopted as the diagnosis tool. First, the microturbine has been tested to get reference operation data, assumed to be degradation free. Then, a simulation program was set up to regenerate the performance test data. Deterioration of each component (compressor, turbine and recuperator) was modeled by changes in the component characteristic parameters such as compressor and turbine efficiency, their flow capacities and recuperator effectiveness and pressure drop. Single and double faults (deterioration of single and two components) were simulated to generate fault data. The neural network was trained with majority of the data sets. Then, the remaining data sets were used to check the predictability of the neural network. Given measurable performance parameters (power, temperatures, pressures) as inputs to the neural network, characteristic parameters of each component were predicted as outputs and compared with original data. The neural network produced sufficiently accurate prediction. Reducing the number of input data decreased prediction accuracy. However, excluding up to a couple of input data still produced acceptable accuracy.
Combustion Performance of Biodiesel and Diesel-Vegetable Oil Blends in a Simulated Gas Turbine Burner
Authors: Panchasara Heena V. , Simmons Benjamin M. , Agrawal Ajay K. , Spear Scott K. , Daly Daniel T.
Published: August 2009

Recent increases in fuel costs, concerns for global warming, and limited supplies of fossil fuels have prompted wide spread research on renewable liquid biofuels produced domestically from agricultural feedstock. In this study, two types of biodiesels and vegetable oil (VO) are investigated as potential fuels for gas turbines to generate power. Biodiesels produced from VO and animal fat were considered in this study. The problems of high viscosity and poor volatility of VO (soybean oil) were addressed by using diesel-VO blends with up to 30% VO by volume. Gas chromatography/mass spectrometry, thermogravimetric analysis, and density, kinematic viscosity, surface tension and water content measurements were used to characterize the fuel properties. The combustion performance of different fuels was compared experimentally in an atmospheric pressure burner with an air assist injector and swirling primary air around it. For different fuels, the effect of the atomizing airflow rate on Sauter mean diameter was determined from a correlation for air-assist atomizers. Profiles of nitric oxides (NOx) and carbon monoxide (CO) emissions were obtained for different atomizing airflow rates, while the total airflow rate was kept constant. Results show that despite the compositional differences, the physical properties and emissions of the two biodiesel fuels are similar. Diesel-VO fuel blends resulted in slightly higher CO emissions compared to diesel, while the NOx emissions correlated well with the flame temperature. Results show that the CO and NOx emissions are determined mainly by fuel atomization and fuel/air mixing processes, and that the fuel composition effects are of secondary importance for fuels and operating conditions of the present study.
High Temperature Static and Dynamic Pressure Transducer for Combustion Instability Control Using Acoustic Low-Pass Filter Structures
Authors: Hurst Adam M. , Kurtz Anthony D. , Kochman Boaz
Published: August 2009

There is a need to measure static and dynamic conditions in many gas turbine applications, in particular for combustion instabilities, such as those in the afterburner. The DC and low frequency components are typically used for conventional engine control, while the high frequency data is essential for acoustic screech and rumble diagnostics and control. This paper presents a static-dynamic piezoresistive pressure transducer that measures low amplitude, dynamic pressure perturbations superimposed on top of a high pressure through the implementation of low pass mechanical structures. The transducer, which is capable of operating at ultra-high temperatures and in harsh environments, consists of a static piezoresistive pressure transducer, which measures the large pressures on the order of 200psi and greater, and an ultrasensitive, dynamic piezoresistive pressure transducer which captures small, high frequency pressure oscillations on the order of a few psi. The heightened sensitivity in high pressure environments is achieved by filtering the measured pressure of high frequency content through an innovative low pass mechanical filter structure. The large static pressures passed by the low-pass mechanical filter structures are routed to the backside of the dynamic pressure sensor, which results in both the front and the back of the dynamic sensor being exposed to the large pressures within the environment. Therefore, the large static pressures cancel out, and the dynamic sensor only senses the low magnitude, high frequency pressure perturbations. This dual sensor, static-dynamic pressure transducer reproduces pressure signals with sensitivity far higher than any single high pressure transducer available today. The dual sensor, static-dynamic transducer meets the pressure sensing specification of numerous applications including, but not limited to, the following: the optimization of turbine operation, turbine design and testing, the detection of the onset of rotating stall and surge in turbine compressors, and combustion instabilities. This paper describes a six element model of the static-dynamic transducer’s low-pass mechanical filtering structures. The paradigm is derived from first-principles of fluid motion in acoustic ducts with viscous dissipation. A dynamic pressure source is used to verify the model and its operation. Finally, a transfer function characterization of a fully operational static-dynamic pressure transducer over a wide bandwidth is presented. Based upon the analytical and experimental results, the static-dynamic pressure transducer will make it possible for turbine users and manufacturers to implement ultra-sensitive pressure monitoring to reduce compressor and combustion instabilities [1] [2].