bluuebunny/crossref_metadata_2025 huggingface dataset:
The Development and Application of the Rolls-Royce MT30 Marine Gas Turbine
Authors: Pearson David , Newman Simon
Published: May 2012

The MT30 is the latest and most powerful gas turbine to enter the marine market. Recently entering US Navy service in USS Freedom, the first-of-class Littoral Combat Ship (LCS), MT30 has now been selected to be the prime power plant for two further classes of front-line warships; The Queen Elizabeth Class Aircraft Carriers for the Royal Navy, and the US Navy DDG-1000 Destroyers. This paper tracks the development of the MT30 from its well-established Rolls-Royce Aero Trent parent, discussing the changes necessary to adapt and harden the gas turbine for the marine application. The MT30 development program is described, including the rigorous testing undertaken to qualify the engine to American Bureau of Shipping (ABS) rules. Existing and future applications for the MT30 are described. Systems for achieving efficient hybrid propulsion utilising electric motors for cruise and the MT30 for boost are presented. The latest all-electric marine propulsion architectures as used on DDG-1000 and the Queen Elizabeth Class Carriers is discussed -in particular, the issue of maintaining the quality of power supply through transient load demands. The paper concludes with an insight into the latest MT30 package, which sees the system reaching class-beating power densities whilst ensuring maintainability through innovative design features.
Effect of GTL-Like Jet Fuel Composition on GT Engine Altitude Ignition Performance: Part I—Combustor Operability
Authors: Fyffe Darren , Moran John , Kannaiyan Kumaran , Sadr Reza , Al-Sharshani Ali
Published: May 2012

The current fuel used in aviation turbines is kerosene, and is tightly controlled to a well defined specification. The past 50 years of simultaneous development between the aviation turbine and kerosene jet fuel has led to the fuel specification. The design of the combustion system has also been developed with this fuel chemistry and specification. In the past 5 years, there has been a ground swell of interest in alternative fuels for aviation, where the fuels can be made from a variety of feedstocks and processes. The chemistry and composition of species within future alternative fuels will change from the current kerosene jet fuel specifications; therefore research has been carried out looking at the effects of some of the fundamental component species that will be found in potential future fuels. The gas turbine combustion ignition and stability characteristics were studied while fuelled by a series of gas-to-liquid (GTL) Synthetic Paraffinic Kerosene (SPK)-type fuels by measurement of the successful ignition and flame stability regimes at realistic altitude temperatures and pressures. The combustor under test was a multi-sector representation of an advanced gas turbine combustor and fuel injector. Tests were conducted on the Rolls-Royce plc TRL3 (Technology Readiness Level) sub-atmospheric altitude ignition facility in Derby, UK. The facility was operated at simulated altitude conditions of 6 and 8 psi combustor inlet pressure with corresponding air and fuel temperatures to represent combustor conditions following flame-out during high altitude cruise. The GTL SPK-type fuels were selected to generate a pseudo-Design of Experiments (DoE) matrix in which the iso- to normal-paraffin ratio, cyclic paraffin content, and carbon number range were varied to isolate the effects of each. Tests were conducted at combinations of air mass flow rate and fuel-air ratio necessary to map the regimes of successful ignition and flame stability. All fuels indicated little or no deterioration to the weak boundary of the ignition regime, nor the weak extinction limits, within the scatter of the experimental method. Evidence was found that a commercial GTL SPK, as well as one of the DoE blends, may have greater ignition performance at simulated altitude conditions. Further testing at higher TRL levels is recommended to confirm this finding. The test programme was supported by DLR, German Aerospace Centre, through high-speed diagnostic imaging of the ignition process, including OH* and CH* chemi-luminescence measurements, which is the subject of a separate complementary paper.
A Method to Estimate the Performance Map of a Centrifugal Compressor Stage
Authors: Casey Michael , Robinson Chris
Published: May 2012

A novel approach to calculate the performance map of a centrifugal compressor stage is presented. At the design point four non-dimensional parameters (the flow coefficient φ, the work coefficient λ, the tip-speed Mach number M and the efficiency η) characterize the performance. In the new method the performance of the whole map is also based on these four parameters through physically-based algebraic equations which require little prior knowledge of the detailed geometry. The variable empirical coefficients in the parameterized equations can be calibrated to match the performance maps of a wide range of stage types, including turbocharger and process compressor impellers with vaned and vaneless diffusers. The examples provided show that the efficiency and the pressure ratio performance maps of turbochargers with vaneless diffusers can be predicted to within ± 2% in this way. More uncertainty is present in the prediction of the surge line, as this is very variable from stage to stage. During the preliminary design the method provides a useful reference performance map based on earlier experience for comparison with objectives at different speeds and flows.
Tip Running Clearances Effects on Tip Vortices Induced Axial Compressor Rotor Flutter
Authors: Peng Caetano
Published: May 2012

The present study aimed at investigating numerically the effects of large blade tip running clearances on flutter stability of axial core multi-stage compressor rotor. During this study, the influences of aerodynamic boundary conditions, variable stator vane incidence and tip running clearances of upstream and downstream rotors on aerodynamic compressor flow and rotor flutter stability are thoroughly investigated. The simulations were carried out using an in-house 3-D aeroelasticity code. The steady-state-solution computations are performed on single-blade-passage-one-bladerow, stage-blocks and whole compressor models. These analyses included rotor blade models with nominal tip running clearances and artificially large tip clearances. Moreover, the effects of the variable stator vane incidences are assessed by performing steady-state-solution computations for nominal vane schedules and extreme vane malschedule. The first four flap and torsion vibration modes from finite element analyses are included in the unsteady flow computations and assessed for flutter stability. The results from the numerical investigations showed that the compressors with large rotor tip running clearances are susceptible to rotor tip flow induced flutter instability. The aerodynamic losses on the rotor with large tip clearances increase with other rotors having also large tip gaps. For the aerodynamic boundary conditions considered here, the simulations predicted flutter instability for the first flap vibration mode. The flutter instability predicted on the rotors with large tip clearances is driven by oscillating tip vortices on blade suction surface close to the blade tip leading edge. The flow in the rotor tip gap is mostly stalled and tip vortices oscillations are close to blade tip leading edge. The strength of these oscillating vortices appears to increase with increase in variable stator vane malschedule or negative incidence. Small changes in aerodynamic conditions can offset these instabilities. These studies indicate that the main ingredients for the occurrence of these phenomena are likely to be excessively large rotor tip running clearances combined with significant changes in flow incidence.
Aeroelastic Analysis of Blades Cascades Through Aerodynamic Reduced-Order Modeling
Authors: Finamore Davide , Nitzsche Fred , Gennaretti Massimo
Published: May 2012

An aerodynamic Reduced-Order Model (ROM) is introduced to describe the aeroelastic behavior of a blade cascade of a turbomachine. This is obtained coupling an aerodynamic model with a semi-rigid 2D model for the description of the structure dynamics. The advantages of using an aerodynamic reduced-order model concern the high computational efficiency compared to the direct use of a CFD code, and the applicability of control laws to reduce, for instance, blades vibrations. ROMs are identified from both an analytical aerodynamic model and a numerical CFD solver. The aeroelastic stability of a blade cascade is examined with the presence or not of mistuning.
Case Studies for Biomass/Coal Co-Gasification in IGCC Applications
Authors: Long Henry A. , Wang Ting
Published: May 2012

Employing biomass as a feedstock to generate fuels or power has the advantage of being carbon neutral or even becoming carbon negative, if carbon is captured and sequestrated. However, there are challenges facing the effective utilization of biomass wastes: (a) biomass supply is limited and varies with the seasons, (b) biomass density is low and expensive for long-distance transportation, and (c) due to a limited supply of feedstock, biomass plants are usually small, which results in higher capital and production costs. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal. This paper focuses on discussing issues associated with coal/biomass co-gasification as well as an investigation into the effect of adding different amounts of biomass up to 50% (wt.) on a 250MW IGCC plant’s performance, although a smaller plant of 75MW using 100% biomass is also included for comparison. The Siemens SGT6-6000G and Alstom GT8C2 gas turbines are used in the larger and smaller plants respectively. The results show the plant’s efficiency increases first as 10% biomass is added; then decreases as the biomass is increased to 30%; and increases again once the biomass reaches 50%. The variation of efficiency is minor, only within one percentage between 38% and 39%. The advantage of adding biomass can be seen from the almost proportional reductions of SOx, ash, energy for H2S removal, water for scrubber, and the effective CO2 emission. The effective CO2 is calculated by subtracting the neutral CO2 that is theoretically produced by burning the added biomass.
A Higher Turndown Flexibility on AE64.3A Gas Turbine: Design and Operating Experience
Authors: Bonzani Federico , Bozzi Luca , Bulli Alessia , Silingardi Andrea , Zito Domenico
Published: May 2012

Italian power generation market is living today a period of substantial changes due to the liberalization process, climate issues, natural gas price fluctuation and the uncertain future of nuclear and coal. In this framework, many gas turbine power plants, originally designed to operate mainly at base load, feel the necessity to be flexibly and profitably operated into the dispatch and ancillary energy service market. In particular, many operators ask for the possibility to operate their gas turbines intermittently, frequently cycling and quickly ramping up and down to satisfy energy demand. Such using drafts new trade off between profitability and maintenance cost. From this point of view it’s not unusual to shut down the engine when the power demand is low if the unit cannot be cost effectively parked at a suitable low load and then quickly ramped up to base load when the power demand is higher. The main barrier against lowering the minimum load of the gas turbines is the increase of the CO emission. When the engine operates close to its turndown load the compressor airflow is such that the heat released by the flame cannot properly support the conversion of CO into CO2. In such a condition, the power plant will not comply with the environmental legislation and must be operated at a higher load or, worse, shut down. An operating strategy has been devised to face up such problem. It is based on the adjustment of compressor IGV (Inlet Guide Vanes) and the optimisation of cooling air consumption in order to keep the proper amount of combustion air close to the turndown load. This paper shows the feasibility check, the installation and final field tests of the low load turndown upgrade on a AE64.3A gas turbine which allowed to operate the unit in a more cost effective way even when the power demand is low.
Correlations Hidden in Compressor Maps
Authors: Kurzke Joachim
Published: May 2012

Realistic compressor maps are the key to high quality gas turbine performance calculations. When modeling the performance of an existing engine then these maps are usually not known and must be approximated by adapting maps from literature to either measured data or to other available information. There are many publications describing map adaptation processes, simple ones and more sophisticated physically based scaling rules. There are also reports about using statistics, genetic algorithms, neural networks and even morphing techniques for re-engineering compressor maps. This type of methods does not consider the laws of physics and consequently the generated maps are valid at best in the region in which they have been calibrated. This region is frequently very narrow, especially in case of gas generator compressors which run in steady state always on a single operating line. This paper describes which physical phenomena influence the shape of speed and efficiency lines in compressor maps. For machines operating at comparatively low speeds (so that the flow into each stage is subsonic), there is usually considerable range between choke and stall corrected flow. As the speed of the machine is increased the range narrows. For high-speed stages with supersonic relative flow into the rotor the efficiency maximum is where the speed line turns over from vertical to lower than maximum corrected flow. At this operating condition the shock is about to detach from the leading edge of the blades. The flow at a certain speed can also be limited by choking in the compressor exit guide vanes. For high pressure ratio single stage centrifugal compressors this is a normal case, but it can also happen with low pressure ratio multistage boosters of turbofan engines, for example. If the compressor chokes at the exit, then the specific work remains constant along the speed line while the overall pressure ratio varies and that generates a very specific shape of the efficiency contour lines in the map. Also in other parts of the map, the efficiency varies along speed lines in a systematic manner. Peculiar shapes of specific work and corrected torque lines can reveal physically impossibilities that are difficult to see in the standard compressor map pictures. Compressor maps generated without considering the inherent physical phenomena can easily result in misleading performance calculations if used at operating conditions outside of the region where they have been calibrated. Whatever map adaptation method is used: the maps created in such a way should be checked thoroughly for violations of the underlying laws of compressor physics.
Integrated Preliminary Design Approach for Turbomachinery Design
Authors: Chaudhari Vinod , Moniz Thomas , NaikTari Chandrakant , Waslo Daniel , Kanase Mohan
Published: May 2012

Turbo machinery preliminary design is an iterative process that begins with an initial Cycle design and culminates with a cross-section of an engine that meets performance, weight and cost criteria. There is a need to have an integrated system that can allow designers to work seamlessly with the conceptual design process involving Cycle, aero and mechanical preliminary design methods. This becomes a huge challenge considering the minimal inputs available at the initial design stage, complexities of design requirements and the multi-disciplinary skills required to come up with accurate design concepts that can satisfy aero and mechanical design requirements. Also, it becomes a highly challenging task to assess the impact of design changes on the downstream design phase for realistic trade-offs. This paper focuses on providing an Integrated Design approach called IPD system (Integrated Preliminary Design) to reduce design cycle time (by 50% per design iteration) and improve fidelity of engine cross-sections at the preliminary design stage (weight & cost prediction improvement by 5%). The IPD system smoothly connects different multi-design disciplines including Cycle design, Flowpath design, nacelle aeroline design and system level mechanical and architectural design across all conceptual and preliminary design stages. Apart from system level design, the IPD system helps the designer to create components iteratively and update the system level model accordingly arriving at a solution that meets aero and mechanical design requirements. This design approach also provides a high fidelity system plan to optimize the system level design that can meet performance, weight and cost requirements.
Drag Management in High Bypass Turbofan Nozzles for Quiet Approach Applications
Authors: Shah P. , Robinson A. , Price A. , Spakovszky Z.
Published: May 2012

The feasibility of a drag management device that reduces engine thrust on approach by generating a swirling outflow from the fan (bypass) nozzle is assessed. Deployment of such “engine air-brakes” (EABs) can assist in achieving slower and/or steeper and/or aero-acoustically cleaner approach profiles. The current study extends previous work from a ram air-driven nacelle (a so-called “swirl tube”) to a “pumped” or “fan-driven” configuration, and also includes an assessment of a pylon modification to assist a row of vanes in generating a swirling outflow in a more realistic engine environment. Computational fluid dynamics (CFD) simulations and aero-acoustic measurements in an anechoic nozzle test facility are performed to assess the swirl-flow-drag-noise relationship for EAB designs integrated into two NASA high-bypass ratio (HBPR), dual-stream nozzles. Aerodynamic designs have been generated at two levels of complexity: (1) a periodically spaced row of swirl vanes in the fan flowpath (the “simple” case), and (2) an asymmetric row of swirl vanes in conjunction with a deflected trailing edge pylon in a more realistic engine geometry (the “installed” case). CFD predictions and experimental measurements reveal that swirl angle, drag, and jet noise increase monotonically, but approach noise simulations suggest that an optimal EAB deployment may be found by carefully trading any jet noise penalty with a trajectory or aerodynamic configuration change to reduce perceived noise on the ground. Constant speed, steep approach flyover noise predictions for a single-aisle, twin-engine tube-and-wing aircraft suggest a maximum reduction of 3 dB of peak tone-corrected perceived noise level (PNLT) and up to 1.8 dB effective perceived noise level (EPNL). Approximately 1 dB less maximum benefit on each metric is predicted for a next-generation hybrid wing/body aircraft in a similar scenario.
A Numerical Investigation of Moment Coefficient and Flow Structure in a Rotor-Stator Cavity With Rotor Mounted Bolts
Authors: Moghaddam Elham Roshani , Coren Daniel , Long Christopher , Sayma Abdulnaser
Published: May 2012

This paper presents a numerical study of the effect of rotor mounted bolts on the moment coefficient and flow structure within a rotor-stator cavity representative of modern gas turbine engine design. The CFD computations are performed using the commercial code FLUENT. The simulation methodology is first validated using experimental data from plain co-rotating disc and rotor-stator cavities from the open literature. Comparisons are then made with experimental data obtained from a test rig at the Thermo Fluid Mechanics Research Centre (TFMRC), University of Sussex. Computations were performed at Reφ = 6.8 × 106, Cw = 5929 (λT = 0.35) with different numbers of bolts (0 < N < 60), and also a continuous ring, at r/b = 0.9. The study has improved the current understanding of the effect on moment coefficient and flow structure that rotor mounted protrusions have in rotor-stator systems. It is seen that the contribution of skin friction to the moment coefficient reduces as the number of bolts is increased. The size and shape of the wake created by a rotating bolt also means that the pressure loss per bolt reduces with N but the overall effect is to increase the moment coefficient because there are more bolts.
Power Reserve Control for Gas Turbines in Combined Cycle Applications
Authors: Mu¨ller Eric A. , Wihler Andrew
Published: May 2012

In order to be able to optimally operate a combined cycle power plant in a liberalized electricity market, knowledge of the plant’s maximum exportable power generation capacity is vital. However, the maximum power output of a power plant is affected by numerous variable factors, such as the ambient conditions at the plant site. In addition, the allowable plant operating range might be narrowed by a compulsory reserve margin, if the power plant is participating in a frequency regulation program. In this paper, a power reserve controller is derived, which facilitates the optimal operation of a combined cycle gas turbine power plant subject to a reserve margin requirement. The power reserve controller bases on a mathematical description of the power plant and uses an adaptation mechanism to predict on a real-time basis the maximum allowable plant load limit. Based on tests on a single shaft combined cycle power plant, the operation of the power reserve controller is demonstrated and its performance is assessed. The test results prove that the controller predicts the maximum power output of the plant with high accuracy and that it is able to maintain a desired reserve capacity for frequency response as specified.
Integrated OGV Design for an Aggressive S-Shaped Compressor Transition Duct
Authors: Walker A. D. , Barker A. G. , Carrotte J. F. , Bolger J. J. , Green M. J.
Published: May 2012

Within gas turbines the ability to design shorter aggressive S-shaped ducts is advantageous from a performance and weight saving perspective. However, current design philosophies tend to treat the S-shaped duct as an isolated component, neglecting the potential advantages of integrating the design with the upstream or downstream components. In this paper such a design concept is numerically developed in which the upstream compressor outlet guide vanes are incorporated into the first bend of the S-shaped duct. Positioning the vane row within the first bend imparts a strong radial gradient to the pressure field within the vane passage. Tangential lean and axial sweep are employed such that the vane geometry is modified to exactly match the resulting inclined static pressure field. The integrated design is experimentally assessed and compared to a conventional non-integrated design on a fully annular low speed test facility incorporating a single stage axial compressor. Several traverse planes are used to gather five-hole probe data which allow the flow structure to be examined through the rotor, outlet guide vane and within the transition ducts. The two designs employ almost identical duct geometry, but integration of the vane row reduces the system length by 21%. Due to successful matching of the static pressure field, the upstream influence of the integrated vane row is minimal and the rotor performance is unchanged. Similarly the flow development within both S-shaped ducts is similar such that the circumferentially averaged profiles at duct exit are almost identical, and the operation of a downstream component would be unaffected. Overall system loss remains nominally unchanged despite the inclusion of lean and sweep and a reduction in system length. Finally, the numerical design predictions show good agreement with the experimental data thereby successfully validating the design process.
A Joined MBL-Zonal Method Technique for Evaluating Radiative Thermal Loads Into Combustion Chambers of Industrial Gas Turbines
Authors: Ottino Gabriele , Ratto Luca , Maritano Massimiliano
Published: May 2012

Thermal radiation is typically one of the most important phenomenon to be taken into account in the evaluation of combustor walls thermal loads due to the high temperatures reached into them. A classical approach is based on the so called Zonal Method, originally developed by Hottel and Sarofim (1967), and actually widely employed in the industrial environment. Even if its accuracy has been largely demonstrated, its efficiency is affected by computational costly solution of 4th – 6th fold integrals constituting the DEAs. A direct integration is usually employed, subsequently smoothing the results in order to obey the conservation constraints. The last decades have seen a growing interest on developing new techniques able to simplify these time consuming direct numerical integrations. Among them one of the most promising approaches has been recently introduced by Yuen (2008) which is based on the classic Mean Beam Length concept. The emittance (absorptance) coefficients of the radiating (receiving) gas volume zones of cubic shape are treated as those of a grey gas filled hemisphere. According to Yuen (2008), a correlative expression has been employed for evaluating the MBL corresponding to each single volume zone. In the present work its application has been extended to more complex zone shapes by means of an Artificial Neural Network trained on a properly selected geometry database. In this way the DEA integral folds can be all reduced to the 4th order, and, employing well known geometrical techniques (Walton, 2002), can be further decreased to lower order integrals. The proposed model has been compared with 3D benchmark test cases available in literature: the accuracy has been tested against the results of DTM, FVM and classical Zonal Method. Moreover an industrial application is shown. The geometry of the AE94.2 gas turbine combustion chamber has been considered; the gas mixture has been treated as a non-grey gas using the well known Weighted Sum of Gray Gases (WSGG) model. In comparison with the classical zonal method approach, the efficiency of the proposed one demonstrates the possibility of a zone refinement enabling a more accurate evaluation of radiative thermal loads at the same computational cost. Results are presented and discussed.
Effect of Mixing Quality on NOx Emissions in Reheat Combustion of GT24 and GT26 Engines
Authors: Du¨sing K. Michael , Ciani Andrea , Eroglu Adnan
Published: May 2012

Alstoms GT24 and GT26 engines feature a unique sequential combustion system [1, 2]. This system consists of a premixed combustor (called EV), which is followed by a high pressure turbine, a reheat combustor (called SEV) and a low pressure turbine (Figure 1). Recently improvements in NOx performance of the SEV have been demonstrated. Starting with relatively simple methods numerous design variants have been tested and down selected. Further down-selection has been done with methods of increased complexity. Overall a fast and cost effective development process has been assured. During the development process the variation coefficient and unmixedness measured and calculated for mixing only systems (CFD and water channel) has proven to be a reliable indicators for low NOx emissions for the real combustion system on atmospheric and high pressure test rigs. To demonstrate this a comparison of both quantities against NOx emissions is shown. The paper focuses on the NOx results achieved during this development and its relation to mixing quantities. Using this relation, together with a detailed understanding of the flow characteristic in the SEV burner, reductions in NOx emissions for GT24 and GT26 SEV burner and lance hardware can be reached using relatively simple methods.
Fluid-Structure Interaction Using a Modal Approach
Authors: Debrabandere F. , Tartinville B. , Hirsch Ch. , Coussement G.
Published: May 2012

A new method for Fluid-Structure Interaction (FSI) predictions is here introduced, based on a Reduced-Order Model (ROM) for the structure, described by its mode shapes and natural frequencies. A linear structure is assumed as well as Rayleigh damping. A two-way coupling between the fluid and the structure is ensured by a loosely-coupling staggered approach: the aerodynamic loads computed by the flow solver are used to determine the deformations from the modal equations, which are sent back to the flow solver. The method is firstly applied to a clamped beam oscillating under the effect of von Karman vortices. The results are compared to a full-order model. Then a flutter application is considered on the AGARD wing 445.6. Finally, the modal approach is applied to the aeroelastic behavior of an axial compressor stage. The influence of passing rotor blade wakes on the downstream stator blades is investigated.
Mechanical Design of Highly Loaded Large Steam Turbines
Authors: Lu¨ckemeyer N. , Almstedt H. , Kern T.-U. , Kirchner H.
Published: May 2012

There are no internationally recognized standards, such as the ASME Boiler and Pressure Vessel Code or European boiler and pipe codes, for the mechanical design of large steam turbine components in combined cycle power plants, steam power plants and nuclear power plants. One reason for this is that the mechanical design of steam turbines is very complex as the steam pressure is only one of many aspects which need to be taken into account. In more than one hundred years of steam turbine history the manufacturers have developed internal mechanical design philosophies based on both experience and research. As the design of steam turbines is pushed to its limits with greater lifetimes, efficiency improvements and higher operating flexibility requested by customers, the validity and accuracy of these design philosophies become more and more important. This paper describes an integral approach for the structural analysis of large steam turbines which combines external design codes, material tests, research on the material behavior in co-operation with universities and experience gained from the existing fleet to derive a substantiated design philosophy. The paper covers the main parameters that need to be taken into account such as pressure, rotational forces and thermal loads and displacements, and identifies the relevant failure mechanisms such as creep fatigue, ductile failure and creep fatigue crack growth. It describes the efforts taken to improve the accuracy for materials already used in power plants today and materials with possible future use such as advanced steels or nickel based alloys.
Hot-Acoustic-Testrig (HAT): A Unique Facility for Thermoacoustic Research
Authors: Knobloch Karsten , Lahiri Claus , Enghardt Lars , Bake Friedrich , Peitsch Dieter
Published: May 2012

A modular test facility for the investigation of thermoacoustic phenomena has been constructed in Berlin, which exhibits the accuracy of laboratory experiments with well defined boundary conditions. Moreover, the facility provides independent control of temperature, operating pressure and flow velocity up to a range relevant for real gas turbine applications. The unique facility is decribed in detail with an emphasis on instrumentation to be used for acoustic investigations and the data assessment procedure for the investigation of bias flow liner damping characteristics as the primary reasearch target for the initial operation. An outlook is given with respect to options und upgrades planned for the future.
The Simulation of an Axial Flow Fan Performance Curve at Low Flow Rates
Authors: van der Spuy S. J. , le Roux F. N. , von Backstro¨m T. W. , Kro¨ger D. G.
Published: May 2012

Simplified fan models are often used to simulate the effect of axial flow fans in large arrays of air-cooled condensers. The actuator disc method and its shortcomings are discussed and illustrated using computational fluid dynamics. A full 3-dimensional analysis of the fan is also performed at a single operating point to evaluate the flow conditions around the blade. This analysis confirms the results of the actuator disc method at the specific operating point. An adaptation of the actuator disc method, to improve its ability to model fan operation at low flow rates, is proposed. The effectiveness of the adaptation is evaluated by comparing the fan static pressure curve obtained from experimental results to the fan static pressure curve obtained from the simulations. The comparison shows that an analysis using the adapted actuator disc method produces results that correlate well with experimental values.
Mechanical Property Variability of Cast Ni-Base Superalloy IGT Components
Authors: Klein Cynthia , Kiesow Hans-Juergen , Gravett Phillip
Published: May 2012

Reliable life predictions are economically vital to the Industrial Gas Turbine (IGT) Original Equipment Manufacturer (OEM). Improper understanding of component life can lead to a shortened service life interval, or in the worst case, component failure and forced outage. To understand component life, and assure safe life operation, components are qualified by demonstrating that the predicted stresses do not exceed the material capabilities. Predicted stresses are typically calculated through the Finite Element Method (FEM), while allowable material capabilities are determined using materials properties from an engineering design materials database. The materials properties in the engineering design materials database are dependent on variables such as alloy chemistry and heat treatment, which are understood and included in allowable tolerances per qualification specification limits. The current approach for materials characterization to support IGT design is primarily with separately cast slab or bar material. This standardized material testing method is intended to encompass the properties for the multitude of components cast with that material. Whilst this approach tests the compositional properties, it does not take into account the significant influence of the material property dependence on dimension/geometry and position within a component. Since the quality of the design of a component is so closely related to the materials properties, it is imperative that the materials database data accurately represent the component material. In this paper, the sources and magnitude of variability found in a cast turbine blade is investigated by testing samples machined from production cast turbine blades. These blades are cast from a polycrystalline Nickel-base superalloy commonly used for hot gas path turbine components. In order to improve design criteria, and accurately determine component life, a broader understanding of variability effects is needed. As hypothesized, the engineering design materials database properties derived from cast slab/bar material are not necessarily representative of the local properties in critical regions of the components. Additionally, variations in local properties were discovered due to location in the component, and dimensions/geometry of the specimen. The understanding gained in this investigation enables the IGT OEM to more reliably design components through a better understanding of the properties in the life limiting locations of a component. Optimizing the manufacturing processes to enhance these properties at specific locations within the component provides an additional capability to improve overall component reliability. Overall, this understanding allows for improved reliability of the IGT design life and makes use of the full potential of the chosen material for maximum economic benefit.
Effects of Rotation on Jet Impingement Channel Heat Transfer
Authors: Lamont Justin A. , Ekkad Srinath V.
Published: May 2012

The effects of the Coriolis force and centrifugal buoyancy is investigated in rotating internal serpentine coolant channels in turbine blades. For complex flow in rotating channels, detailed measurements of the heat transfer over the channel surface will greatly enhance the blade designer’s ability to predict hot spots so coolant air may be distributed more effectively. The present study uses a novel transient liquid crystal technique to measure heat transfer in a rotating, radially outward channel with impingement jets. This is the beginning of a comprehensive study on rotational effects on jet impingement. A simple case with a single row of constant pitch impinging jets with crossflow effect is presented to demonstrate the novel liquid crystal technique and document the baseline effects for this type of geoemtry. The present study examines the differences in heat transfer distributions due to variations in jet Rotation number and jet orifice-to-target surface distance. Colder air below room temperature is passed through a room temperature test section to simulate the centrifugal buoyancy effect seen in a real engine environment. This ensures that buoyancy is acting in a similar direction as in actual turbine blades where walls are hotter than the coolant fluid. Three parameters were controlled in the testing: jet coolant-to-wall temperature ratio, average jet Reynolds number, and average jet Rotation number. Results show, like serpentine channels, the trailing side experiences an increase in heat transfer and the leading side experiences a decrease for all jet channel height to jet diameter ratios (H/dj). At a jet channel height to jet diameter ratio of 1, the cross-flow from upstream spent jets greatly affects impingement heat transfer behavior in the channel.
Oxidation Behaviour of Conventional and Nanocrystalline CoNiCrAlY Bond Coats Manufactured by Cold Spray
Authors: Richer P. , Yandouzi M. , Brochu M. , Zu´n˜iga A. , Corbeil A. , Jodoin B.
Published: May 2012

The purpose of the present study is to investigate and compare the oxidation behaviour of conventional and nanocrystalline CoNiCrAlY bond coats. The nanocrystalline feedstock powder is produced from the conventional feedstock powder using the cryogenic milling process. Conventional and nanocrystalline bond coats are produced using the Cold Spray (CS) process in order to avoid the onset of thermally induced grain growth and minimize the inclusion of oxides in the bond coat microstructure. The oxidation behaviour of free-standing CoNiCrAlY coating samples is determined by means of isothermal oxidation experiments consisting of heat treatments in air at 1000°C for various periods of time. Characterization of the feedstock powders and resulting CS coatings, as well as investigation of the oxide scale growth dynamics, is achieved by means of SEM, XRD and TEM analyses. Mass gain measurements were also carried out throughout the oxidation tests to evaluate oxide growth rates.
Dynamic-Stability Characteristics of Premixed Methane Oxy-Combustion
Authors: Shroll Andrew P. , Shanbhogue Santosh J. , Ghoniem Ahmed F.
Published: May 2012

This work explores the dynamic stability characteristics of premixed CH4/O2/CO2 mixtures in a 50kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different fractions of carbon dioxide used to control the flame temperature (Tad). For the highest Tad’s, the combustor is unstable at the five-quarter wave mode. As the temperature is reduced, the combustor jumps to the three quarter mode and then to the quarter wave before eventually reaching blowoff. Similar to the case of CH4/air mixtures, the transition from one mode to another is predominantly a function of the Tad of the reactive mixture, despite significant differences in laminar burning velocity and/or strained flame consumption speed between air and oxy-fuel mixtures for a given Tad. High speed images support this finding by revealing similar vortex breakdown modes and thus similar turbulent flame geometries that change as a function of flame temperature.
Flowfield Measurements in a Single Row of Low Aspect Ratio Pin-Fins
Authors: Ostanek Jason K. , Thole Karen A.
Published: May 2012

Pin-fin arrays are commonly used as compact heat exchangers for cooling the trailing edge of gas turbine airfoils. While much research has been devoted to the heat transfer characteristics of various pin-fin configurations, little work has been done to investigate the flowfield in pin-fin arrays. Such information may allow for further optimization of pin-fin configurations. A new pin-fin facility at large scale has been constructed to allow optical access for the use of non-intrusive measurement techniques such as laser Doppler velocimetry and time-resolved, digital particle image velocimetry. Using these techniques, the flow through a single row of pin-fins having a height-to-diameter ratio of 2 and span-to-diameter ratio of 2.5 was investigated. Results show that the length of the wake region decreases with increasing Reynolds number. At higher Reynolds numbers, Ka´rma´n vortices developed closer to the pin-fins than for single, infinitely long cylinders. Transverse fluctuations correlated well with endwall heat transfer indicating that the Ka´rma´n vortices play a key role in energy transport.
Numerical Investigations on Film Cooling Performances
Authors: Wang Jianhua , Zhu Yejun , Kuang Jian , Wang Xiaochun
Published: May 2012

This paper presents a numerical investigation on film cooling of gas turbine endwall using commercial CFD software. The cooling effect is widely estimated with adiabatic wall assumption. The adiabatic effectiveness largely depends on film hole geometry. In this paper, three geometries of film hole with the same inclined angle and expansion angle have been investigated with the adiabatic effectiveness. Firstly, a fanshaped hole with laidback and sharp-angle exit has been put forward to compare with traditional fanshaped hole with round exit and fanshaped hole with laidback and round exit on the cooling performance. Through numerical results obtained by the ideal adiabatic film effectiveness, the comparison suggests that the new design can provide larger and more uniform coolant coverage. Considering two coupled effects in film cooling process, i.e. hot mainstream mixing with cooling air, and heat exchange between fluid and solid, the practicality of ideal adiabatic effectiveness and real film cooling effectiveness based on the coupled effect of fluid with solid were analyzed by two materials, with one being steel wall and the other a thermal insulator. The analysis indicates that it is not reasonable to estimate film effect only through consideration of the mixing effect, i.e. fluid flow performances under adiabatic assumption. To describe the second effect, the heat exchange between fluid and solid, the influence of material’s property on the film cooling effectiveness was quantitatively discussed at a given mainstream and coolant flow condition using seven thermal conductivities, and the relation of the film cooling effectiveness with the Biot numbers was exhibited along the center line at five points (x = D, 5D, 10D, 15D, 20D) behind film hole. Through the discussion, it can be found that there is possibility to describe the film cooling effectiveness at the given mainstream and coolant flow conditions using an exponential expression, in which the Biot number is an independent variable. This approach using an expression to describe the second effect may be more practical than using two parameters, adiabatic film effectiveness and heat transfer coefficient.
Experimental Investigation of Thermoacoustic Instabilities for a Model Combustor With Varying Fuel Components
Authors: Zhang X. Y. , Zhang H. , Zhu M.
Published: May 2012

In this study, a combustion facility was constructed that includes a flexible fuel supply system to produce synthesis gas using a maximum of three components. The rig with lean premixed burner is able to operate at up to 5 bars. The length of the inlet plenum and the outlet boundary conditions of the combustion chamber are adjustable. Experiments were carried out under a broad range of conditions, with variations in fuel components including hydrogen, methane and carbon monoxide, equivalence ratios, thermal power and boundary conditions. The dynamic processes of self-excited combustion instabilities with variable fuel components were measured. The mechanisms of coupling between the system acoustic waves and unsteady heat release were investigated. The results show that instability modes and flame characteristics were significantly different with variations in fuel components. In addition, the results are expected to provide useful information for the design and operation of stable syngas combustion systems.
Impact of Mistuning on the Vibration Behaviour of the Last Stage in a Model Three Stage Low Pressure Steam Turbine
Authors: Heinz Christoph , Schatz Markus , Casey Michael V. , Stu¨er Heinrich
Published: May 2012

The last stages of a low-pressure steam turbine, with long freestanding blades, may experience forced response excitation during resonance crossing at start-up and shut-down and this can be responsible for blade failure. This paper presents an experimental investigation of the circumferential blade amplitude distribution at different operating conditions and for different mistuning configurations in a scale model of a state-of-the-art low pressure steam turbine. Five configurations are investigated; two with different intentionally mistuned frequency arrangements, where the blades are placed alternately in different high-low configurations and three randomly mistuned systems. For the randomly mistuned systems the standard deviation of the resonance frequencies of the last stage blades is varied. The maximum blade amplitude and the circumferential blade amplitude distribution of each mistuning configuration are compared at different operating points and at a repeatable rotational speed gradient. The behaviour of the blade amplitude distribution at different operating conditions shows that the vibration levels depend on both the mistuning configuration and the operating points.
Nonlinear Model-Based Predictor: Its Application to the Closed Loop Control of the Alstom GT11N2 Gas Turbine
Authors: Zhang Xiao-Yi
Published: May 2012

The market requirements with regard to transient operation capabilities of gas turbines (GT) in utility use are becoming stringent. Besides normal frequency support features, gas turbines in local electrical grids are often required to maintain the grid frequency under various situations, including emergencies, such as, loss of national grid connection or trip of a large consumer, etc. These requirements demand high performance and stability of GT control. On the other hand, the environmental aspects are becoming increasingly a public concern. In the past decades, remarkable progress has been made in combustion technologies of heavy-duty gas turbines. Lean premixing is a preferred technology for NOx emission reduction. Because of its flashback and extinction limits, a premix flame has usually a much narrower operation range compared to a diffusional one, adding tight constraint on GT control. This paper demonstrates a successful implementation of a model-based predictor, a proven control technique, in the closed loop control of the ALSTOM GT11N2 gas turbine. First, an online GT model, which is integrated into the GT control algorithm, was developed. By applying appropriate assumption and simplification, this model is capable of simulating the GT process over the whole load operation range with high dynamic accuracy. Secondly, a model-based predictor for accelerating slow measured signals was implemented. It dynamically compensates the system delays in the GT process and in the measuring instruments. Thirdly, the predictor was applied to the GT core control by replacing the measured signals with the accelerated signals. The original control structure was kept unchanged. In order to verify its performance and stability, the new control technique was validated on a real engine. Successful engine tests proved that the model-based predictor improves GT transient operation capabilities.