bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbogroup Spare Part Optimization by Availability Centered Maintenance Methodology: An Application to LTSA Contract
Authors: Cheschini Giuseppe Fabio , Carlevaro Fausto , Racioppi Giuseppe , Masi Andrea
Published: February 2009

Most Oil&Gas companies that currently outsource both maintenance and related engineering activities, by establishing Long Terms Service Agreements (LTSA) with engine manufacturers, base their contracts on several clauses. A minimum level of overall Plant Availability is usually to be guaranteed by the maintenance services supplier. Both parts agree upon this availability threshold and Bonus/Penalty clauses are based on this value. The Availability of a system is a non-linear function of: • Reliability, in terms of components life, system functional configuration and scheduled maintenance frequencies; • Maintainability, in terms of time to repair/restore, duration of scheduled maintenance tasks and special maintenance tools on site; • Logistics. Concerning Logistics, the problem is to define both the set and levels of spare parts in a warehouse for one or more installations (pooling) and the location of the warehouse itself. In this paper a solution for this problem is presented, based on RBD (Reliability Block Diagram) Monte Carlo simulation techniques and an associated What-If analysis. One of the deliverables of this optimisation process is the ranking of all the system components in terms of their influence on the availability of the whole system. This spare part list optimisation is one of the major deliverables of the discipline called ACM “Availability Centered Maintenance”, currently developed in Nuovo Pignone.
Numerical Study of the Unsteady Blade Row Interaction in a Three-Stage Low Pressure Turbine
Authors: Nayeri Christian , Ho¨hn Wolfgang
Published: February 2009

The focus of this paper is on the one hand the quantitative optimization of the unsteady numerical simulations compared to experiments, and on the other hand to gain a better insight into the underlying mechanisms when an upstream wake of a stator interacts with the flow-field of the next stator. This was achieved by optimizing the numerical turbulence parameters used in the turbulence and transition models. Using steady calculations an optimal initial solution for the unsteady calculation was found. Also, the computational mesh was refined. For the numerical computations a time accurate Reynolds averaged Navier-Stokes solver is applied. Turbulence is modeled using the Spalart-Allmaras one equation turbulence model. The integration of the governing equations in time is performed by an implicit time integration for the steady calculations, and by an implicit dual time stepping scheme for the unsteady calculations. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. The results show that by adjusting the turbulence parameters in the turbulence and transition models, a better qualitative and quantitative agreement between experiments and numerical results can be achieved. Steady and unsteady quantities are shown, e.g. the surface pressure distribution and the wall shear stress. The unsteady simulations of two different azimuthal positions of the first and third stator reveal different evolutions of the boundary layers of the second and third stators due to the influence of the wake of the upstream stators. These differences are better captured through the above mentioned improvements, i.e. reduction of sheared cells in the computational mesh and optimization of turbulence and transition parameters in the allowable range of the models.
Performance Analysis of Regenerative Steam Injection Gas Turbine (RSTIG) Systems
Authors: Nishida Kousuke , Takagi Toshimi , Kinoshita Shinichi
Published: February 2009

There is a demand for developments of a distributed energy system using a small scale gas turbine. The steam injection configurations can improve the performances of the simple and regenerative gas turbine cycles. In this study, the thermal efficiency and exergy loss of two types of regenerative steam injection gas turbine (RSTIG) system are analyzed, and the performances of them are compared with those of the regenerative, water injection and STIG systems. It is noted that the optimum pressure ratio of the RSTIG systems becomes relatively low. The thermal efficiency of the RSTIG systems is higher than that of the water injection and STIG systems. The specific power of them is larger than that of the regenerative cycle. The steam injection configurations can be applied to the flexible heat and power generation system. The total efficiency of the heat and power generation of the RSTIG systems reaches more than 70% (HHV).
Fretting Fatigue Modeling and Repair Evaluation for Generator Rotors
Authors: Akkaram Srikanth , Chati Mandar , Sundaram Sairam , Barnes Gary
Published: February 2009

Generator Rotor Tooth Cracks have been recently observed on some long service generator rotors. The purpose of this paper is to document the root cause analysis as well as a repair methodology that was developed in support of one of these cracked units. The paper discusses the development of a finite element model to understand the operating modes and failure mechanisms that caused the initiation of these cracks. The results of the analysis agreed very well with field observations on cracked units and with some limited repair options that have been successfully used in the past. An experimental fretting fatigue testing program is currently underway to substantiate and extend the results reported in this paper.
Experimental Response of Simple Gas Hybrid Bearings for Oil-Free Turbomachinery
Authors: Wilde Deborah A. , San Andre´s Luis
Published: February 2009

Gas film bearings offer unique advantages enabling successful deployment of high-speed micro-turbomachinery (< 0.4 MW). Current applications encompass micro power generators, air cycle machines and turbo expanders. Mechanically complex gas foil bearings are in use; however, their excessive cost and lack of calibrated predictive tools deter their application to mass-produced systems. The present investigation provides experimental results for the rotordynamic performance of a small rotor supported on simple and inexpensive hybrid gas bearings with static and dynamic force characteristics desirable in high-speed turbomachinery. These characteristics are adequate load support, stiffness and damping coefficients, low friction and wear during rotor startup and shutdown, and most importantly, enhanced rotordynamic stability. The test results evidence the paramount effect of feed pressure on early rotor lift off and substantially higher threshold speeds of rotordynamic instability. Higher supply pressures also determine larger bearing direct stiffnesses, and thus bring an increase in the rotor-bearing system critical speed albeit with a reduction in damping ratio.
Effect of Elevated Free-Stream Turbulence on Transitional Heat Transfer Over Dual-Scaled Rough Surfaces
Authors: Wang Ting , Rice Matthew C.
Published: February 2009

The surface roughness over a serviced turbine airfoil is usually multi-scaled with varying features that are difficult to be universally characterized. However, it was previously discovered in low freestream turbulence conditions that the height of larger roughness produces separation and vortex shedding, which trigger early transition and exert a dominant effect on flow pattern and heat transfer. The geometry of the roughness and smaller roughness scales played secondary roles. This paper extends the previous study to elevated turbulence conditions with free-stream turbulence intensity ranging from 0.2–6.0 percent. A simplified test condition on a flat plate is conducted with two discrete regions having different surface roughness. The leading edge roughness is comprised of a sandpaper strip or a single cylinder. The downstream surface is either smooth or covered with sandpaper of grit sizes ranging from 100 ∼ 40 (Ra = 37 ∼ 119 μm). Hot wire measurements are conducted in the boundary layer to study the flow structure. The results of this study verify that the height of the largest-scale roughness triggers an earlier transition even under elevated turbulence conditions and exerts a more dominant effect on flow and heat transfer than does the geometry of the roughness. Heat transfer enhancements of about 30 ∼ 40 percent over the entire test surface are observed. The vortical motion, generated by the backward facing step at the joint of two roughness regions, is believed to significantly increase momentum transport across the boundary layer and bring the elevated turbulence from the freestream towards the wall. No such long-lasting heat transfer phenomenon is observed in low FSTI cases even though vortex shedding also exists in the low turbulence cases. The heat transfer enhancement decreases, instead of increases, as the downstream roughness height increases.
Cogeneration System Simulation and Control to Meet Simultaneous Power, Heating and Cooling Demands
Authors: Sancho-Bastos Francisco , Perez-Blanco Horacio
Published: February 2009

Gas turbines are projected to meet increasing power demand throughout the world. Cogeneration plants hold the promise of increased efficiency at acceptable cost. In a general case, a cogen plant could be able to meet power, heating and cooling demands. Yet those demands are normally uncoupled. Control and storage strategies need to be explored to ensure that each independent demand will be met continuously. A dynamic model of a mid-capacity system was developed, including gas and steam turbines, two heat recovery steam generators (HRSG) and an absorption-cooling machine. Controllers were designed using linear quadratic regulators (LQR) to control two turbines and a HRSG with some novelty. It was found that the power required could be generated exclusively with exhaust gases, without a duct burner in the high-pressure HRSG. The strategy called for fuel and steam flow rate modulation for each turbine. The stability of the controlled system and its performance were studied and simulations for different demand cases were performed.
Better Power Generation From Gas Turbine Along With Improved Heat Rate
Authors: Patel Pankaj , Prajapati Vishnu , Modi Amit
Published: February 2009

Performance of a Gas Turbine is largely dependent on inlet air temperature. Gas Turbines are constant volume machines. At a given shaft speed they always move the same volume of air. But the power output of a turbine depends on the flow of mass through it. This is precisely the reason why on hot days, when air is less dense, power output falls off. A rise of one degree Centigrade temperature of Inlet air decreases the power output by 1% and at the same time heat rate of the turbine also goes up. This is a matter of great concern to power producers. Many techniques have been developed to cool Inlet air to Gas Turbine. Traditionally, Gas Turbine inlet air has been cooled by either mechanical chillers or media type evaporative coolers. It is also important to note that power consumption to cool inlet air is also of concern since it decreases the net power output of a Gas Turbine. In mechanical Chiller auxiliary power consumption is very high compared to media type evaporative coolers. Efficiency of evaporative cooler largely depends on moisture present in the air. Higher the moisture in the air lesser the advantage from it. Use of Geo exchange Systems can provide energy-efficient cooling by using underground pipes, filled with water solution because the underground temperature is quite low than ambient temperature and relatively constant round the year. Circulation of water in closed loop pipe system will extract heat from the inlet air to Gas Turbine and disperse the same into the earth. This will reduce sensible heat from the inlet air, which gives more benefit. After reduction in dry bulb temperature we can take advantage from Fog system /Evaporative Cooler. Using a combination we can get much more benefit. This will not only improve power output but also improve the heat rate of the Gas Turbine.
Side Air-Jet Modulation for Control of Heat Release and Pattern Factor
Authors: Tuncer Onur , Acharya Sumanta , Cohen Jeff , Banaszuk Andrzej
Published: February 2009

The effect of a forced dilution air jet introduced through the combustor shell, on the air-fuel mixing in the combustion chamber has been investigated. Thermocouple based temperature measurements have been made at a number of forcing frequencies in the range of 100–1100Hz and blowing ratios in the range of 10–15. The open-loop integral flame response to forcing has also been acquired by recording pressure and heat release spectra. A CH-radical imaging technique is used to provide spatially- and temporally-resolved information about the heat release behavior. The results exhibit that the mean temperature field inside the main reaction zone can significantly be altered as a consequence of air jet modulation. The most significant effects are observed by forcing at vertical locations that are close to the dump plane. Enhancements in temperature of the order of 100–200 degrees C, and reduction in pattern factor of the order of 10% (e.g., from 1.13 to 1.03) were observed, with the lowest pattern factors achieved at the lowest forcing frequency of 100 Hz.
Performance of a WC Coated Mechanical Seal Prototype With Integral Micro Heat Exchanger
Authors: Johns Gina M. , Stephens L. Scott , Hayden Matthew A.
Published: February 2009

Temperature induced failures are among the most frequent for end face mechanical seals. Recently, a new approach to cooling has been proposed that uses a micro heat exchanger fabricated integrally with the stationary mechanical seal ring. This paper presents experimental results for a WC coated, air-cooled mechanical seal with integral micro heat exchanger in dry-running and water-lubricated conditions at 2400 RPM and various PV values. The micro heat exchanger is a pin fin design and is fabricated from nickel using a modified LIGA process. The heat exchanger has a surface area to volume ratio of 10,500 m2/m3 and fin pitch of 315 μm. Testing is performed using a thrust washer rotary tribometer. The results show that the micro heat exchanger has the potential to alleviate temperature related failures associated with mechanical seals and, in particular, with seals that use low friction hard coatings.
Numerical Predictions of Film Cooled NGV Blades
Authors: Adami P. , Martelli F. , Chana K. S. , Montomoli F.
Published: February 2009

Film-cooling is commonly used in modern gas turbines to increase inlet temperatures without compromising the mechanical strength of the hot components. The main objective of the study reported here is the critical evaluation of the capability of CFD, to predict film-cooling on three-dimensional engine realistic turbine aerofoil geometries. To achieve this aim two different film-cooling systems for NGV aerofoils are predicted and compared against experiments. The application concerns the following turbine vanes: • the AGTB-B1 blade investigated by the “Institut fur Strahlantriebe of the Universitat der Bundeswehr Munchen (Germany)”; • the MT1 HP NGV investigated by QinetiQ (ex DERA, UK). In the first test case the application mainly focuses on the interaction between the main flow and the coolant jets on the leading edge of the cooled aerofoil. In the second case, vane heat transfer rate is predicted with the film-cooling system made of six rows of cylindrical holes in single and staggered configuration.
Millimeter-Scale, MEMS Gas Turbine Engines
Authors: Epstein Alan H.
Published: February 2009

The confluence of market demand for greatly improved compact power sources for portable electronics with the rapidly expanding capability of micromachining technology has made feasible the development of gas turbines in the millimeter-size range. With airfoil spans measured in 100’s of microns rather than meters, these “microengines” have about 1 millionth the air flow of large gas turbines and thus should produce about 1 millionth the power, 10–100 W. Based on semiconductor industry-derived processing of materials such as silicon and silicon carbide to submicron accuracy, such devices are known as micro-electro-mechanical systems (MEMS). Current millimeter-scale designs use centrifugal turbomachinery with pressure ratios in the range of 2:1 to 4:1 and turbine inlet temperatures of 1200–1600 K. The projected performance of these engines are on a par with gas turbines of the 1940’s. The thermodynamics of MEMS gas turbines are the same as those for large engines but the mechanics differ due to scaling considerations and manufacturing constraints. The principal challenge is to arrive at a design which meets the thermodynamic and component functional requirements while staying within the realm of realizable micromachining technology. This paper reviews the state-of-the-art of millimeter-size gas turbine engines, including system design and integration, manufacturing, materials, component design, accessories, applications, and economics. It discusses the underlying technical issues, reviews current design approaches, and discusses future development and applications.
Fully Clocking Effect in a Two-Stage Compressor
Authors: Huang Hongyan , Yang HaiTao , Feng GuoTai , Wang Zhongqi
Published: February 2009

Turbomachines have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. The important part of the unsteady effects results from the rotor-stator interaction. The main sources of unsteadiness in the rotor-stator interaction are potential flow interaction and wake interaction. Since the distribution of the potential flow and wake in the flow passage depends much on the relative position of blade row, variation in the relative circumferential position (clocking effect) of stator or rotor will change the distribution and consequently result in different multistage performance. The current study presents the experimental result of stator clocking effect in low-speed axial compressor, and performs numerical simulation to investigate the effects of fully (stator & rotor) clocking. In the test, time averaged data were collected. The result of time accurate flow calculation for stator clocking was in good qualitative agreement with experimental data. During the clocking of rotor, the stator was indexed to a position corresponding to maximum efficiency, and 8 clocking positions are compared for each clocking.
High Temperature Characterization of a Radial Magnetic Bearing for Turbomachinery
Authors: Provenza Andrew J. , Montague Gerald T. , Jansen Mark J. , Palazzolo Alan B. , Jansen Ralph H.
Published: February 2009

Open loop, experimental force and power measurements of a radial, redundant-axis, magnetic bearing at temperatures to 1000°F (538°C) and rotor speeds to 15,000 RPM along with theoretical temperature and force models are presented in this paper. The experimentally measured force produced by a single C-core circuit using 22 A was 600 lb. (2.67 kN) at room temperature and 380 lb. (1.69 kN) at 538°C. These values were compared with force predictions based on a 1D magnetic circuit analysis and a thermal analysis of gap growth as a function of temperature. The analysis showed that the reduction of force at high temperature is mostly due to an increase in radial gap due to test conditions, rather that to reduced core permeability. Tests under rotating conditions showed that rotor speed has a negligible effect on the bearing’s static force capacity. One C-core required approximately 340 W of power to generate 190 lb. (845 N) of magnetic force at 538°C, however the magnetic air gap was much larger than at room temperature. The data presented is after bearing operation for eleven total hours at 538°C and six thermal cycles.
Experimental Investigation of Airfoil Wake Clocking Impacts on Aerodynamic Performance in a Two Stage Turbine Test Rig
Authors: Jouini D. B. M. , Little D. , Bancalari E. , Dunn M. , Haldeman C. , Johnson P. D.
Published: February 2009

This paper presents experimental findings on the effects of circumferential clocking of vanes and blades in a turbine test rig, based on a 1/3 scale model of the first two stages of the four stage Advanced Turbine System (ATS) turbine. The investigation was a collaborative effort among Siemens Westinghouse Power Corporation, The Ohio State University, and Florida Turbine Technologies, Inc. The objective of this experimental program was to investigate the effects of airfoil wake clocking and to explore ways to evaluate clocking feasibility during the design phase. Measurements obtained included inlet and exit total pressures and temperatures, turbine mass flow and shaft speed, airfoil leading edge temperatures, and inter-row endwall and airfoil surface static pressures and heat fluxes. Results presented herein focus primarily on the measured turbine performance based on inlet and exit pressures and temperatures. Results from the heat transfer measurements and analyses are not presented in this paper, but are the focus of another paper. Supporting aerodynamic analyses were conducted and results compared to the experimental results to confirm operating boundary conditions and provide input to uncertainty analyses. The results of these experiments and analyses validate the use of one and two-dimensional aerodynamic design approaches coupled with wake tracking to produce a “clockable” turbine; followed by the use of steady and unsteady 3D computational fluid dynamics (CFD) and experimental investigation to verify the 3D wake position, quantify the benefits, and further understand the flow physics.
High Temperature Hydro Corrosion Resistance of Silica Based Oxide Ceramics
Authors: Ueno Shunkichi , Kondo Naoki , Jayaseelan D. Doni , Ohji Tatsuki , Kanzaki Shuzo
Published: February 2009

Water vapor corrosion behavior of Ln2Si2O7 (Ln = Nd, Er, Lu), mullite, CaYb4Si3O13 and Al2O3 were investigated at 1500°C. In Ln2Si2O7 phases, Ln = Nd and Er samples were completely dissolved in water vapor environment. CaYb4Si3O13 phase underwent decomposition during the corrosion test. Lu2Si2O7 and mullite showed excellent water vapor corrosion protection. In the case of mullite, Al2O3 rich phase was formed on the surface and the corrosion progression was successfully protected. In the case of Lu2Si2O7 phase, phase transition occurred and the grain boundaries of surface layer were slightly corroded by the corrosion test.
Evaluation of Zero Compressor Wash Routine in RN Service
Authors: Fielder James
Published: February 2009

In order to maintain engine performance and prevent the build up of airborne particles within compressor systems, the Royal Navy (RN) has traditionally employed a compressor cleaning routine on all marine gas turbines. This routine consists of turning the engine using the starter motor whilst spraying the cleaning medium (water or water and detergent) into the intake. The cleaning medium is driven through the engine, cleaning the compressor as it goes. The wash effluent is then drained away via the engine drains. Although most gas turbine users use similar routines, the harsh, salt laden marine environment presents a unique challenge to the Naval operator. In order to evaluate the current level of compressor washing, ascertain effects on performance and corrosion and investigate potential cost savings, the RN initiated a trial whereby 2 Rolls-Royce SM1C marine Spey’s were subject to a zero wash routine. The two ships involved, HMS Richmond & HMS Northumberland, accumulated approximately 750 and 1500 unwashed operating hours respectively. As the Original Equipment Manufacturer (OEM), Rolls-Royce was closely involved with the project and inspected the engines throughout the trial. The trial concluded that significant operational benefits could be gained by modifying the existing wash routine, adopting a new cleaning medium and extending the wash periodicity. In addition, the report concluded that engine performance and cleanliness would not be affected by altering the wash routine. The paper will discuss the background to the trial, explain the methodology used, explore the conclusions and discuss the benefits derived from the trial, including applicability to other marine gas turbines.
Improvement of H-Type Grid for Compressor Cascade Flow Calculation
Authors: Zhou Zheng-Gui
Published: February 2009

For high speed flow through compressor passages, due to very small radii of the blades or the sharp leading and trailing edges, it is proper to adopt H-type grid for the flow field calculation. In this paper, a new kind of H-type grid generation method was proposed, by which the generated grid lines orthogonally intersect at blade surfaces. The method was successfully applied to grid generation of several types of compressor cascade flow fields. It was also proposed that in blade wake region the grid node distribution along the cascade tangent direction should gradually tends to uniformity, to adapt to flow parameter variation in the region. To analyze influence of grid line intersection angle at the wall on calculated results, expression of discrete errors of the flow parameter derivatives in relation to the angle was deduced. Numerical calculation of a plate turbulent boundary layer and cascade flows were performed. The investigation demonstrates that the intersection angles of grid lines at solid walls have significantly influence on the predicted results in the boundary layer regions; but nearly have no evident influence on the results in the potential regions.
CHP Based on an Internally Integrated SOFC/GT Hybrid System: A Hospital Under Spanish Legislation
Authors: Garcia Gaston F. , Pilidis P. , Hales R. , Diacakis M.
Published: February 2009

Combined Heat and Power plants, with their inherent advantages and high efficiencies can offer attractive solutions on the small-scale stationary power generation industry. Gas Turbines are widely used as prime movers for small-medium size co-generation systems producing electricity and useful heat on-site. Fuel Cells appear as a promising technology for power generation showing considerably higher efficiencies than conventional heat engines. Fuel Cells operating at high temperatures are especially suitable to be matched with Gas Turbines leading to further reduction of emissions and enhanced overall cycle efficiency. The present study deals with the Internal Integration of a Solid Oxide Fuel Cell into a simple Cycle GT. In such integration the SOFC replaces the combustion chamber of the conventional GT. The benefits of a CHP based on an Internally Integrated SOFC/GT Hybrid System are analysed for the case of a medium size hospital. In order to assess the feasibility of such a CHP plant, a conventional co-generation plant based on a simple Cycle Gas Turbine is analysed as well. Then, both CHP plants are compared in respect of both performance and economical. Government policies which strongly influence the overall performance of such schemes have been taken into account with the introduction of the Spanish legislation concerning co-generation, electricity tariffs and Natural Gas prices.
CFD Model of a Narrowbody Aircraft Elliptical Inlet
Authors: Wiegmann R. Thomas , Pilidis Pericles , Tourlidakis Antonios
Published: February 2009

The objective of this paper will be to determine if the “elliptical inlet” on the lower lip of a popular narrowbody aircraft engine nacelle is capable of handling inlet distortion and lip separation. Ground clearances considerations on this aircraft required an elliptical lower lip on the inlet. A grid of the nacelle incorporating this elliptical inlet will be built in order to utilize computational fluid dynamics (CFD) as an analysis tool. In addition, another grid will be created for a nacelle with a normally circular inlet as the only difference in the nacelle. This will serve as the baseline for the analysis. Preliminary results indicate that the high bypass ratio turbofan intake with the “elliptical inlet” does seem capable of delivering a clean, undistorted stream of air with a total pressure recovery to the fan face and subsequently the engine core, when a 20 deg angle of attack at Takeoff (T/O) is considered the design requirement. The CFD results also give evidence of the presence of a lip separation bubble on the lower lip as the incidence angle increases. This can be seen quite clearly in the CFD results, where there are lower pressure regions manifested in the shape of a small bubble on the inside of the lower lip towards the edge. This phenomenon intensifies as the incidence angle increases.
Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels With Four Heated Walls and Film Coolant Extraction
Authors: Parsons James A. , Han Je-Chin , Lee C. Pang
Published: February 2009

The effect of orthogonal channel rotation on jet impingement cooling by arrays of circular jets in two channels was studied. Impinging jet flows on smooth target walls were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. Spent air exited the channels through extraction holes in each target wall which eliminates cross flow on other jets. Heat transfer results for these target walls, for the jet walls containing the jet producing orifices, and for the connecting sidewalls show as the jet rotation number increases to 0.0028, these wall Nusselt numbers decrease to 35, 25 and 30%, respectively, below the corresponding non-rotating values. Jet rotation number is a correlating parameter and as wall-to-jet temperature difference ratio increases to 0.129 the wall Nusselt numbers vary up to 10%. Comparisons are made with previous rotating results for target wall heating only and for the radially outward cross flow exit configuration.
Heat Transfer Coefficients on the Squealer Tip and Near Tip Regions of a Gas Turbine Blade With Single or Double Squealer
Authors: Kwak Jae Su , Ahn Jaeyong , Han Je-Chin , Lee C. Pang , Boyle Robert , Gaugler Raymond , Bunker Ronald S.
Published: February 2009

Detailed heat transfer coefficient distributions on a gas turbine squealer tip blade were measured using a hue detection based transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Squealer rims were located along (a) the camber line, (b) the pressure side, (c) the suction side, (d) the pressure and suction sides, (e) the camber line and the pressure side, and (f) the camber line and the suction side, respectively. Tests were performed on a five-bladed linear cascade with a blow down facility. The Reynolds number based on the cascade exit velocity and the axial chord length of a blade was 1.1×106 and the overall pressure ratio was 1.2. Heat transfer measurements were taken at the three tip gap clearances of 1.0%, 1.5% and 2.5% of blade span. Results show that the heat transfer coefficients on the blade tip and the shroud were significantly reduced by using a squealer tip blade. Results also showed that a different squealer geometry arrangement changed the leakage flow path and resulted in different heat transfer coefficient distributions. The suction side squealer tip provided the lowest heat transfer coefficient on the blade tip and near tip regions compared to the other squealer geometry arrangements.
Development of the Advanced Cycle Low-Power Gas Turbine Alternator (ACL GTA)
Authors: McCallum N. R. , English C. R.
Published: February 2009

The Royal Navy (RN) is pursuing the ‘All Electric’ ship under its Marine Engineering Development Strategy (MEDS). This strategy envisages the use of long life, fuel efficient, advanced cycle marine gas turbine alternator sets in an Integrated Electric Propulsion (IEP) system, which includes the wide scale electrification of auxiliary systems. In 2000 the UK Ministry of Defence (MoD) placed a contract on Turbomeca Limited, France, for the development of a 1.8MW advanced cycle gas turbine driving a high speed alternator, providing 800V dc output. The basic details of this 1.8MW Gas Turbine Alternator (GTA), known as the ACL GTA, have been provided at papers presented at ASME 2001 and 2002. This paper will briefly reiterate the basic engine design including the recuperator, and provide details of the recently selected directly coupled High Speed Alternator (HSA). Progress with the overall programme and meeting project aims will be reviewed. Issues surrounding the power output, self sustainability and power system stability when operating in parallel with large GTAs will be discussed. Reference will be made to the GTA’s ability to compete in a highly competitive market dominated by diesel driven alternators.
Turbine Tip and Shroud Heat Transfer and Loading: Part B — Comparisons Between Prediction and Experiment Including Unsteady Effects
Authors: Polanka M. D. , Clark J. P. , White A. L. , Meininger M. , Praisner T. J.
Published: February 2009

Flowfield predictions in the tip regions of turbine blades have recently increased in fidelity, but additional data and greater collaboration between numerical and physical experimenters is required to make further improvements. This is particularly true as one moves to experiments and predictions of the full annulus, rotating conditions found in actual turbomachines. Toward this end, a recent set of experimental measurements obtained in a single-stage high pressure turbine at the US Air Force Turbine Research Facility (TRF) was complemented with true predictions of the tip flowfield undertaken at Pratt & Whitney. The TRF is a full scale rotating rig that operates at flow conditions that are non-dimensionally consistent with the true turbine environment. Both heat transfer and surface pressure measurements were obtained on the tip of the blade, along the shroud, and at 96.5% of the blade span providing significantly detailed information on the flowfield in the tip region. The experimental data was obtained at frequencies up to 100 kHz so that multiple data samples per vane and/or blade passing event were recorded. These measurements were complemented and extended with 3-D, Reynolds-Averaged Navier-Stokes (RANS) predictions that together revealed the true flow pattern and the overall heat load to the airfoil. Because of the greater spatial resolution of the predictions, they also revealed additional flowfield physics that was not captured by the experiment. Both steady state and time-resolved comparisons were then made between the predictions and the data to reveal the complex nature of the flowfield in the turbine tip-gap region. These comparisons will help to elucidate the fundamental physics involved in this highly complicated region of the turbine.
On the Physics of the Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions
Authors: Schobeiri Meinhard T. , O¨ztu¨rk Burak , Ashpis David E.
Published: February 2009

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05°, which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re = 50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.
Strength and Toughness of Interface Between EBC and Ceramic Substrates at Elevated Temperature
Authors: Nair Shanti , Sun Ellen Y.
Published: February 2009

In a previous study, the strength of the interface between an environmental barrier coating (EBC) and the substrate was measured at ambient temperature using a unique compression test methodology. In this study, the method was extended for elevated temperature characterization of the strength of this interface. The extension of the method also allowed for the characterization of the elevated temperature toughness ofthe EBC/substrate interface. An essential component of measuring elevated temperature interface strength and toughness was characterization of the elevated temperature elastic modulus of the EBC coating layers. The elastic moduli of EBC layers were characterized at both ambient and at elevated temperature. The results point to a substantial decrease in the moduli of the EBC coating layers at elevated temperature. Preliminary results also indicate a decrease in both the strength and toughness of the EBC/substrate interface at elevated temperatures compared to ambient temperature.
Experimental Investigation on a Newly Designed Combustor for LCV Gas
Authors: Adouane Belkacem , van der Wel Marco C. , de Jong Wiebren , van Buijtenen Jos. P.
Published: February 2009

Air blown gasification of biomass is one of the most promising and efficient ways to use alternative energy sources like organic matters from waste and biomass for producing LCV (Low Calorific Value) gas. This fuel is best used in highly efficient gas turbines (or combined cycles). The section Thermal Power Engineering of Delft University of Technology operates a 1.5 MW pressurized fluidized bed gasification rig, including a hot gas cleaning unit with the ability to test pressurized combustors designed and optimized for LCV gas combustion. In this paper, the results of six combustion experiments with the 1 MW non-swirling TUD (Technical University Delft) combustor are presented and compared with the results of experiments performed with a 1.0 MW swirling combustor designed by ALSTOM Power UK. The primary and cooling airflow of the TUD combustor can be altered independently for optimization purposes. The experiments were performed at 3.5 and 5.0 bara and stable combustion was accomplished with gas of heating values (HHV) ranging from 2.7 to 3.8 MJ/m3n. Combustion efficiencies of the TUD combustor were well above 99.9% and emissions of CO were within the EU standards, except for one experiment where Minphyl as catalyst was added to the gasifier fuel. A high percentage of primary air was used in this experiment. Emissions of NO were outside the EU standards (100 ppm) for four of the six experiments because of the high fuel bound nitrogen (FBN) concentrations in the fuel gas. The FBN conversion rate ranged from 98% to 39% for FBN concentrations ranging from 238 to 2238 ppm.
Development of Detailed Chemical Kinetic Mechanisms for Ignition/Oxidation of JP-8/Jet-A/JP-7 Fuels
Authors: Mawid M. A. , Park T. W. , Sekar B. , Arana C. A.
Published: February 2009

Progress on development and validation of detailed chemical kinetic mechanisms for the U.S. Air Force JP-8 and JP-7 fuels [1] is reported in this article. Two JP-8 surrogate fuel blends were considered. The first JP-8 surrogate blend contained 12 pure hydrocarbon components, which were 15% n-C10H22, 20% n-C12H26, 15% n-C14H30, 10% n-C16H34, 5% i-C8H18, 5% C7H14, 5% C8H16, 5% C8H10, 5% C10H14, 5% C9H12, 5% C10H12 and 5% C11H10 by weight. The second JP-8 surrogate blend contained 4 components, which were 45% n-C12H26, 20% n-C10H22, 25% C10H14, and 10% C7H14 by weight. A five-component surrogate blend for JP-7 was also considered. The JP-7 surrogate blend components were 30% n-C10H22, 30% n-C12H26, 30% C10H20, 5% i-C8H18, and 5% C7H8 by weight. The current status of the JP-8 and JP-7 mechanisms is that they consist of 221 species and 1483 reactions and 205 species and 1438 reactions respectively. Both JP-8 and JP-7 mechanisms were evaluated using a lean fuel-air mixture, over a temperature range of 900–1050 K and for atmospheric pressure conditions by predicting autoignition delay times and comparing them to the available experimental data for Jet-A fuel. The comparisons demonstrated the ability of the 12-component JP-8 surrogate fuel blend to predict the autoignition delay times over a wider range of temperatures than the 4-component JP-8 surrogate fuel blend. The 5-component JP-7 surrogate blend predicted autoignition delay times lower than those of JP-8 blends and Jet-A fuel. The JP-8 and JP-7 mechanisms predictions, however, showed less agreement with the measurements towards the lower end of the temperature range (i.e., less than 900 K). Therefore, low temperature oxidation reactions and the sensitivities of the autoignition delays to reaction rate constants are still needed.
Micro-Scale Radial-Flow Compressor Impeller Made of Silicon Nitride: Manufacturing and Performance
Authors: Kang Sangkyun , Johnston James P. , Arima Toshiyuki , Matsunaga Minoru , Tsuru Hideaki , Prinz Fritz B.
Published: February 2009

A micro-scale, high-speed compressor impeller (12mm diameter, 800,000 rpm) was tested for feasibility in regard to aerodynamic performance. The compressor was designed for application in a fist-sized gas-turbine-generator. To survive high stresses at such high temperatures, the rotor was manufactured as a single turbine/compressor/shaft unit in silicon nitride, by the Mold SDM process. Performance testing was conducted in a cold-flow rig at reduced speed of 420,000 rpm. Results from a CFD code compared favorably to measured data at this speed. Extrapolation from test conditions to full design speed was accomplished by application of CFD applied at both speeds.
Unsteady Turbine Blade Wake Characteristics
Authors: Sieverding Claus H. , Ottolia Davide , Bagnera Carlo , Cimadoro Andrea , Desse Jean-Michel
Published: February 2009

The paper presents an experimental investigation of large coherent structures, commonly referred to as “von Karman vortex street”, in the wake of a turbine blade at high subsonic Mach number (M2,is = 0.79) and high Reynolds number (RE = 2.8×106 and their effect on the steady and unsteady pressure and temperature distribution in the wake. Ultra short smoke visualizations and two interferometric measurement techniques, holographic interferometry and white light differential interferometry provide insight into the vortex formation and shedding process. In addition, the interferometric measurement provides quantitative information on the stream wise evolution of the minimum density associated with the vortices and on their lateral spreading. Wake traverses are performed with a four-head fork probe carrying a Kiel probe and a fast response Kulite pressure probe for pressure measurements and a thermo-couple probe and a cold wire resistance probe for temperature measurements. The results confirm the observation of energy separation in the wake as found by other researchers. The experimental data are a unique source for the validation of unsteady Navier-Stokes codes.
Comparison of Trip-Strip/Impingement/Dimple Cooling Concepts at High Reynolds Numbers
Authors: Kim Yong W. , Arellano Leonel , Vardakas Mark , Moon Hee-Koo , Smith Kenneth O.
Published: February 2009

Modern industrial combustor liners employ various cooling schemes such as, but not limited to, impingement arrays, trip-strips, and film cooling. With an increasing demand for a higher turbine inlet temperatures and lower emissions, there is less air available to cool the combustor liner. To ensure the required liner durability without compromising engine performance more innovative cooling schemes are required. In the present work, three different cooling concepts, i.e., strip-strips, jet array impingement and dimples, operating at unusually high flow conditions were investigated. There is very little data available in the open literature for the aforementioned cooling schemes in the indicated Reynolds Number range (ReDh>60,000). The wall flow friction characteristics as well as the local heat transfer were measured. The heat transfer coefficients were obtained using a transient liquid crystal technique. The test configurations consisted of a 90° trip-strip surface (only one side turbulated), a fixed staggered array with varying impingement hole sizes, and a fixed staggered dimple pattern. For the Reynolds numbers investigated (26,000< ReDh <360,000), the jet-impingement cooling provided the highest average heat transfer enhancement followed by the trip-strip channel, and then by the dimpled channel. In terms of the overall thermal performance, the dimpled channel tends to stand out as the most effective cooling scheme. This is consistent with findings from other investigators at lower Reynolds numbers.
Flexible Spacers Compressor Stator Blades for Heavy Industrial Gas Turbines Model 7EA
Authors: Ingistov Steve
Published: February 2009

This paper describes efforts to upgrade the mechanical integrity of axial compressor stator blades. The blades under discussion are part of an axial compressor of a heavy duty industrial Combustion Gas Turbine (CGT) made by GE, frame No. 7, model EA. The axial compressor stator blades, in the later stages of compression, are kept in required position by spacers or shims shaped to match the root profile of the blades. These spacers/shims may be as thick as 1/4 of an inch and as thin as 1/32 of an inch. These spacers/shims tend to wiggle out of the slots and eventually liberate themselves from the stator. This paper introduces a proposed solution to minimize liberation of the spacer/shims by introduction of flexible spacers/shims. This paper also describes field experience with loss of the stator blades in the last stage of compression, due to aerodynamic disturbances.
Propulsion Systems and the MT30 Marine Gas Turbine: The Quest for Power
Authors: Tooke Roger W. , Bricknell David
Published: February 2009

Both naval and commercial marine propulsion systems are increasingly seeking more power from fewer prime movers. In naval systems, the move to electric propulsion for larger escorts and the introduction of single boost gas turbines for smaller escorts has allowed the reduction in number of installed prime movers, while retaining the required redundancy. To meet this power demand, Rolls-Royce has marinised the Trent 800 aero gas turbine to produce the MT30 a 36MW simple cycle marine gas turbine. With first packaged engine deliveries available in early 2004, this paper introduces the MT30, outlines the marinisation process and announces the performance confirmed though the two demonstration engines. Completion of endurance testing, leading to preliminary certification of the engine is programmed for June 2003. In addition, this paper looks at the potential applications, (both mechanical and genset) of the MT30 and the propulsion system benefits made possible through the engine’s introduction.