bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Approach to an Endwall Heat Transfer Analysis: A Linear Guide Vane and a Curved Duct
Authors: Khalatov A.
Published: December 2014

This paper consists of two sections. The first section of the paper illustrates successful application of the improved approach developed by author to the endwall heat transfer data analysis in a low speed linear guide vane and in a curved duct. Effects of a three dimensional turbulent flow, a horseshoe vortex, a passage vortex, as well as an entry boundary layer thickness have been considered in both passages and as a result the common experimental correlation on a local heat transfer have been derived for the H/t = 1.0 ratio. All affected factors are presented as a superposition of the linear correction functions in the basic experimental correlation for a flat plate heat transfer.

In the second section the common correlation is used as the reference correlation to establish effect of the span-to-pitch ratio on the endwall heat transfer in both passages. It was found that variation in the H/t ratio affects slightly the freestream velocity; the most important result which came from the heat transfer study is that in contrast to a curved duct a heat transfer rate in a blade passage is reduced while the H/t ratio decreases.

Comparison of the experimental data obtained by the author with results of the two-dimensional heat transfer prediction confirms that it is very important to take a three-dimensional heat transfer nature into account in design of the endwall convective cooling system. It has been demonstrated that distinction between the results of two- and three dimensional approach to the endwall heat transfer can achieve up to 70% at the passage’s inlet area.
Water Injection Into Navy Gas-Turbine Combustors to Reduce NOx Emissions
Authors: Urbach Herman B. , Knauss Donald T. , Wallace Balfour L. , Emory John , Frese John , Bishop Joseph W.
Published: December 2014

Land-based water injection into the combustor of gas turbines is a state-of-the-art technology, which is a low-risk, low-cost option for reduction of gas-turbine emissions. A controller for a water-injected combustor (WIC) system was designed for automatic control of water injection. Steady-state tests of the WIC system in an LM2500 propulsion-engine facility yielded basic engine-interactive data for the WIC’s unique automatic software logic. The steady-state tests demonstrated anticipated NOx reductions in conformity with proposed (but not implemented) California Air Resources Board (CARB) mandates. The controller automatically compensates for the effects of humidity, temperature and engine load.

This automatic response was expressly designed to deliver acceptable water rates even during the abrupt power excursions encountered in emergencies, including collision-avoidance crashback maneuvers. The transient test data indicated unacceptable flameout in the engine during engine deceleration to idle speed. Detailed analyses of the flameouts show that the controller can reduce water flow within two deciseconds of a change in power demand. However, the residence time of water in the manifolds can be about a second for some operating conditions. Several fixes for this problem are described.
Identification of the Intermittent Synchronous Instability in a High Performance Steam Turbine Rotor Due to Deteriorated Labyrinth Seals
Authors: Haq Inam U. , Kumar Chittineni V. , Al-Zaid Rayed M.
Published: December 2014

This paper reports the synchronous vibration instability problem (a rare phenomenon) experienced in a high pressure steam turbine rotor (19MW) driving synthesis gas compressor train in a large scale petrochemical complex. The turbine had about one year history of showing infrequently high vibration. Rotor vibrations appeared in an intermittent and irregular fashion and the perturbation frequency was the rotor operating speed of 10,135 rpm. The sealing steam system was found responsible for cropping the vibration. At a definite level of seal steam pressure (0.90 to 1.10 bar-gauge), operating speed and load, the rotor radial vibration response was reached at 4.5 mils as compared to the frequently smooth running level of less than 1.0 mil. Subsequently, the major overhauling of the turbine revealed severely worn and, virtually, non-functional high pressure end labyrinth seals. The paper also elaborates the steam turbine rotordynamics behaviors recorded during excessive levels of vibration.
Dry Low Emissions Combustor Development
Authors: Joshi Narendra D. , Mongia Hukam C. , Leonard Gary , Stegmaier Jim W. , Vickers Ed. C.
Published: December 2014

Lower Emissions have become key characteristics of most new gas turbine engines over the last several years. The ‘lean premixed’ approach has been used in the development of the Dry Low Emissions (DLE) technology. The LM6000 and the LM2500 combustors employ a triple dome design with staging of fuel and air flows to achieve lean-premixed operation from light-off to full power. This technology permits the operator to run with reduced emissions of NOx as well as CO and UHC over a wide load setting. Emissions goals of 25 ppm have been successfully met at site rating conditions for the entire family of LM DLE products. The DLE combustor operates on the mid dome at light-off, the inner and the outer domes are brought on progressively, as the engine is loaded. The combustor utilizes a small quantity of air for dome and liner cooling as most of the combustor air is mixed with fuel in the premixers. Backside cooling enhancements permit the reduction of film cooling, which can cause quenching of CO oxidation reactions. Combustion acoustics are controlled by the use of passive devices on the exterior of the engine as well as by fuel staging within premixers and by the use of a control system which senses and alters the combustor operation to limit acoustics. The DLE technology meets the emissions and reliability needs of the industry with limited package modifications. This paper describes the DLE technology, developed to meet the needs of the industry. Critical design features including the Double Annular Counter-Rotating Swirler (DACRS) premixer, the triple annular dome design, the heat shield design and the staging sequence are discussed, in addition to the field experience gained on the LM2500 and LM6000 DLE models.
Fugitive Methane Emission Reduction Using Gas Turbines
Authors: Parker Todd
Published: December 2014

Natural gas transmission systems have many sources of fugitive methane emissions that have been difficult to eliminate. This paper discusses an option for dealing with one such source for operations using turbo-compressor units fitted with dry gas seals. Dry seals rely on a small leakage of process gas to maintain the differential pressure of the process against the atmosphere. The seal leakage ultimately results in waste gas that is emitted to the atmosphere through the primary vent. A simple, cost effective, emission disposal mechanism for this application is to vent the seal gas into the gas turbine’s air intake. Explosion hazards are not created by the resultant ultra-lean fuel/air mixture, and once this mixture reaches the combustion chamber, where sufficient fuel is added to create a flammable mixture, significant oxidation of the seal vent gas is realized. Background of the relevant processes is discussed as well as a review of field test data. Similar applications have been reported [1] for the more generalized purpose of Volatile Organic Compound (VOC) destruction using specialized gas turbine combustor designs. As described herein, existing production gas turbine combustors are quite effective at fugitive methane destruction without specialized combustor designs.
Influence of Turbulence on the Dynamic Behaviour of Premixed Flames
Authors: Krüger Uwe , Hoffmann Stefan , Krebs Werner , Judith Hans , Bohn Dieter , Matouschek Gero
Published: December 2014

Environmental compatibility requires low emission burners for gas turbine power plants as well as for jet engines. In the past significant progress has been made developing low NOx and CO burners by introducing lean premixed techniques. Unfortunately these burners often have a more pronounced tendency than conventional burner designs to produce combustion driven oscillations. The oscillations may be excited to such an extent that strong pulsation may possibly occur; this is associated with a risk of engine failure and higher NOx emissions.

In order to describe the acoustical behaviour of the complete burner system the determination of the transfer function of the flame itself is crucial. Using a new method which was presented by Bohn, Deutsch and Krüger (1996) and Bohn, Li, Krüger and Matousckek (1997), the dynamic flame behaviour can be predicted by means of a full Navier-Stokes-simulation of the complex combustion process for the steady-state as well as for the transient situation.

This method has been successfully used by the authors to obtain the frequency response of turbulent diffusion flames and laminar premixed flames. For the application in modern gas turbines the influence of turbulence on the dynamic behaviour of premixed flames is of big interest.

Therefore, this paper presents numerical studies of a turbulent premixed flame configuration for which experimental data is available in the literature. Two different combustion models have been used for the steady-state as well as for the transient calculations. With the improved model, which takes into account the chemical kinetics and the interaction between turbulence and kinetics, good agreement has been found for the steady-state results and for the frequency response of the flame.
Thermo-Mechanical Characterizations of Coatings for HP Turbines
Authors: Boudot A. , Crabos F. , Fournier D. , Monceau D.
Published: December 2014

Three different coatings were studied in this work: vacuum plasma-sprayed NiCoCrAlYTa, electrolytically deposited NiCoCrAlYTa and Ni-Pt aluminide diffusion coatings. These three coatings were deposited on AM3 single crystal alloy. The tensile properties of coated single crystal test specimens were investigated. Ductile to Brittle Transition Temperatures (DBTT) were determined from tensile tests. All the coatings were examined before and after testing.

All the tested coatings induce a ductile/brittle transition. Strain rate has a great influence on the transition temperature. The comparison between plasma-sprayed deposition and electrodeposition illustrates the strong influence of coating microstructure. In every case, NiCoCrAlYTa coatings were more ductile, and then less detrimental, than aluminide coatings.
Three-Dimensional Flow Predictions in Axial-Flow Turbine Cascades
Authors: Niestroj O. , Came P. M.
Published: December 2014

Numerical investigations of the three-dimensional flowfields in a turbine linear cascade and in an annular, non-rotating turbine cascade have been carried out. Both cascades were the subjects of published experimental studies. In the experimental set-up for the annular cascade the hub wall upstream of the blades could be either stationary or rotating so that a collateral or a skewed inlet boundary layer could be achieved.

The results of the computations have been compared with the experimental data. Total pressure loss coefficients and exit flow angles have been studied and in both cascades the predicted secondary flow effects are in good agreement with the experimental results. Two-dimensional contour plots in the measurement planes and pitchwise-averaged flow angle comparisons illustrate the accuracy of the computations.
Prediction of Heat and Mass Transfer in a Rotating Ribbed Coolant Passage With a 180 Degree Turn
Authors: Rigby David L.
Published: December 2014

Numerical results are presented for flow in a rotating internal passage with a 180 degree turn and ribbed walls. Reynolds numbers ranging from 5200 to 7900, and Rotation numbers of 0.0 and 0.24 were considered. The straight sections of the channel have a square cross section, with square ribs spaced one hydraulic diameter (D) apart on two opposite sides. The ribs have a height of 0.1D and are not staggered from one side to the other. The full three dimensional Reynolds Averaged Navier-Stokes equations are solved combined with the Wilcox k-ω turbulence model. By solving an additional equation for mass transfer, it is possible to isolate the effect of buoyancy in the presence of rotation. That is, heat transfer induced buoyancy effects can be eliminated as in naphthalene sublimation experiments. Heat transfer, mass transfer and flow field results are presented with favorable agreement with available experimental data. It is shown that numerically predicting the reattachment between ribs is essential to achieving an accurate prediction of heat/mass transfer. For the low Reynolds numbers considered, the standard turbulence model did not produce reattachment between ribs. By modifying the wall boundary condition on ω, the turbulent specific dissipation rate, much better agreement with the flow structure and heat/mass transfer was achieved. It is beyond the scope of the present work to make a general recommendation on the ω wall boundary condition. However, the present results suggest that the ω boundary condition should take into account the proximity to abrupt changes in geometry.
Characteristics of Low Frequency Non-Synchronous Vibrations Induced by an Epicyclic Gearbox in Gas Turbogenerator Applications
Authors: Rakhit A. K. , Cornejo G. A. , Lack G. J.
Published: December 2014

Epicyclic gearboxes of star configuration running at partial loads were found to induce non-synchronous (not related to speed) low-frequency vibrations, besides low level sub-synchronous (speed related) which were transmitted to other parts of a turbogenerator power train. At certain loads, the amplitudes of the non-synchronous vibrations were high enough to cause potential damage to sleeve bearings used in the power train system if a generator set would run for any considerable length of time at these loads. It was also observed that a very small increase in load above a certain limit (about 18% of full load) resulted in almost total elimination of these vibrations. Analysis of test data showed the non-synchronous vibrations were due to ‘backward whirl’ motion of gearbox output shaft in its sleeve bearings. Higher damping in the bearings was considered to be one of the most effective methods to suppress backward whirl of a shaft and hence, the non-synchronous vibrations. Accordingly, a new set of gearbox output shaft sleeve bearings was designed for higher damping that would allow these types of generator sets to run at partial and full loads without any detrimental vibration.
LM2500 Gas Turbine Fuel Nozzle Design and Combustion Test Evaluation and Emission Results With Simulated Gasified Wood Product Fuels
Authors: Neilson Charles E. , Shafer Douglas G. , Carpentieri Eduardo
Published: December 2014

The Brazilian Wood Biomass Demonstration Project (WBP) Phase II was contracted with the United Nations Development Programme - PNUD, Setor Comerical Norte, Quadra 2 - BLOCO A, EDF.Corporation-7° Andar, Brasilia - DF Brasil 70712-900 and General Electric Marine & Industrial Engines to develop the gas turbine equipment necessary to utilize fuel produced by the gasification of wood products. The program included performance studies, control specification requirements, bleed and fuel valve specifications, a modified dual gas fuel nozzle for fuel delivery to the combustor and results of two (2) combustor component tests utilizing biomass simulated fuel. This paper will deal primarily with the fuel nozzle design elements, the setup and evaluation of the component combustor tests and resulting emissions produced by the simulated Biomass fuel. Details of the combustor test arrangement, facilities and special test equipment needed to complete the evaluation will be presented. In addition, background on the two types of combustor testing will be discussed.
Development of Hexaaluminate Catalysts for Combustion of Gasified Biomass in Gas Turbines
Authors: Johansson E. Magnus , Danielsson K. M. Jonny , Ersson Anders G. , Järås Sven G.
Published: December 2014

There is an increasing interest in catalytic combustors fuelled by low-heating value (LHV) gases, with a LHV of 5–7 MJ/Nm3. This is because catalytic combustion could be advantageous compared to flame combustion with respect to stable combustion of LHV-gases and low conversions of fuel-N (mainly NH3) to NOx. In the present project, funded by the EU Joule Programme, catalytic combustion of gasified wood for gas turbine applications is studied. A synthetic gas mixture of H2, CO, CO2, H2O, CH4, N2 and NH3, that resembles the output from a fluidized bed gasifier using biomass as raw material, is used. The gas mixture is mixed with air at atmospheric pressure and combusted over washcoated cordierite monoliths in a bench-scale laboratory quartz-reactor.

The objectives of the work described here are twofold. To begin with, improvement of the thermal stability of hexaaluminate washcoats by substitutions of rare earth or transition metal compounds is being studied. Secondly, catalytic combustion of gasified biomass over these washcoats has been studied in a bench-scale unit.

In this on-going project, obtained result show that it is possible to improve the surface area of hexaaluminate compounds up to 17 m2/g after careful synthesis and calcination up to 1400 °C for four hours. The selectivity of NH3-conversion to N2 is at present at 60 percent, but varies strongly with temperature. Fuel components such as H2, CO, C2H4 and NH3 ignite at temperatures close to compressor outlet temperatures. This means that a pilot-flame may not be needed for ignition of the fuel. A comparison between a Pd-impregnated lanthanum hexaaluminate and a Mn-substituted lanthanum hexaaluminate showed that the ignition temperature and the NOx-formation varied strongly over the two different catalysts.
Fuel Gas Cleanup Parameters in Air-Blown IGCC
Authors: Newby Richard A. , Yang Wen-Ching , Bannister Ronald L.
Published: December 2014

Fuel gas cleanup processing significantly influences overall performance and cost of IGCC power generation. The raw fuel gas properties (hearing value, sulfur content, alkali content, ammonia content, “tar” content, particulate content) and the fuel gas cleanup requirements (environmental and turbine protection) are key process parameters. Several IGCC power plant configurations and fuel gas cleanup technologies are being demonstrated or are under development. In this evaluation, air-blown, fluidized-bed gasification combined-cycle power plant thermal performance is estimated as a function of fuel type (coal and biomass fuels), extent of sulfur removal required, and the sulfur removal technique. Desulfurization in the fluid bed gasifier is combined with external hot fuel gas desulfurization, or, alternatively with conventional cold fuel gas desulfurization. The power plant simulations are built around the Westinghouse 501F combustion turbine in this evaluation.
Research and Development of Swirling Flow Combustor for Low NOx
Authors: Takahashi Shuroku , Arai Masashi , Kuyama Toshiyuki , Kawano Manabu
Published: December 2014

The development of a low NOx combustor is underway at the Advanced Material Gas-Generator Research Institute (AMG). To achieve low NOx emissions, a lean-premixed-prevaporized (LPP) swirling flow combustor was selected. There are two objectives for this combustor: a uniform fuel/air mixture coupled with well-atomized fuel for low NOx emissions, and a combustion stabilization of this new concept combustor. The spray characteristics test and the combustion test have carried out. This paper describes the evaluation of these results.
Effects of Fuel Nozzle Displacement on Pre-Filming Airblast Atomization
Authors: Han Yeoung Min , Seol Woo Seok , Lee Dae Sung , Yagodkin Victor I. , Jeung In Seuck
Published: December 2014

In gas turbine combustors, optimum arrangement between a fuel nozzle and a swirler/prefilmer module must be sought to achieve satisfactory ignition and stability characteristics in addition to reduced level of emissions. However, due to thermal expansion of the combustor or misalignment of the fuel nozzle, the location of a fuel nozzle may vary. Displacement of a fuel nozzle may change the amount of fuel injected to the pre-filming device (usually the inner swirler wall) and the location of attachment, which in turn affects the thickness of pre-filming liquid sheet on the wall. As a result, the spray structure formed by pre-filming airblast atomization may be significantly changed.

An experimental investigation is carried out to study the effects of fuel nozzle displacement on the structure of a spray formed by a dual orifice pressure atomizer and a counter-rotating dual swirler. The inner wall of the swirler is designed to be used as a pre-filming device. The behavior of droplets, the flow characteristics of the swirling air flow, and the interaction between droplets and the flow are studied. Optical diagnostic methods including a flow visualization and an Adaptive Phase/Doppler technique are used. Distributions of droplet size, number density, and liquid phase volume flux are presented for various fuel nozzle displacements, in addition to gas phase velocity.
Periodic Transition on an Axial Compressor Stator — Incidence and Clocking Effects: Part I — Experimental Data
Authors: Walker G. J. , Hughes J. D. , Solomon W. J.
Published: December 2014

Periodic wake-induced transition on the outlet stator of a 1.5 stage axial compressor is examined using hot-film arrays on both the suction and pressure surfaces. The time-mean surface pressure distribution is varied by changing the blade incidence, while the freestream disturbance field is altered by clocking of the stator relative to an inlet guide vane row.

Ensemble average plots of turbulent intermittency and relaxation factor (extent of calmed flow following the passage of a turbulent spot) are presented. These show the strength of periodic wake-induced transition phenomena to be significantly influenced by both incidence and clocking effects. The nature and extent of transition by other modes (natural, bypass and separated flow transition) are altered accordingly. Leading edge and mid-chord separation bubbles are affected in a characteristically different manner by changing freestream periodicity. There are noticeable differences between suction and pressure surface transition behavior, particularly as regards the strength and extent of calming.

In Part II of this paper, the transition onset observations from the compressor stator are used to evaluate the quasi-steady application of conventional transition correlations to predict unsteady transition onset on the blading of an embedded axial compressor stage.
Mach Number Effects on Turbine Blade Transition Length Prediction
Authors: Boyle R. J. , Simon F. F.
Published: December 2014

The effect of a Mach number correction on a model for predicting the length of transition was investigated. The transition length decreases as the turbulent spot production rate increases. Much of the data for predicting the spot production rate comes from low speed flow experiments. Recent data and analysis showed that the spot production rate is affected by Mach number. The degree of agreement between analysis and data for turbine blade heat transfer without film cooling is strongly dependent of accurately predicting the length of transition. Consequently, turbine blade heat transfer data sets were used to validate a transition length turbulence model. A method for modifying models for the length of transition to account for Mach number effects is presented. The modification was made to two transition length models. The modified models were incorporated into the two-dimensional Navier-Stokes code, RVCQ3D. Comparisons were made between predicted and measured midspan surface heat transfer for stator and rotor turbine blades. The results showed that accounting for Mach number effects significantly improved the agreement with the experimental data.
Acoustic Sensitivities of Lean-Premixed Fuel Injectors in a Single Nozzle Rig
Authors: Kendrick Donald W. , Anderson Torger J. , Sowa William A. , Snyder Timothy S.
Published: December 2014

An experimental and numerical investigation into the attenuation of combustion induced pressure oscillations in a single nozzle rig was undertaken at the United Technologies Research Center. Results from these investigations indicated a high combustor exit Mach number, similar to that used in a gas turbine engine, was required to correctly simulate the combustor dynamics and evaluate acoustic characteristics of lean premixed fuel injectors. Comparisons made between aerodynamically stabilized and bluff-body stabilized nozzles and the use of premixed and diffusion pilots showed that small levels of diffusion piloting behind a bluff-body yielded the best acoustic/emission performance. Their success is due to increased flame stabilization (superior anchoring ability) which reduced flame motion and thermal/acoustic coupling. For cases where diffusion piloting was not present, both designs exhibited similar dynamical behavior. Increases in the combustor exit Mach number and reductions in the inlet air temperature were shown to degrade acoustic performance of both nozzle designs. The bluff-body configuration with small levels of diffusion piloting, however, was found to be less sensitive to these changes when compared to its aerodynamic counterpart.
An Empirical Approach to the Preliminary Design of a Closed Cycle Gas Turbine
Authors: op het Veld R. P. , van Buijtenen J. P.
Published: December 2014

This paper investigates the layout and achievable efficiencies of rotating components of a Helium gas turbine. This is done by making a preliminary design of the compressor and turbine needed for the power conversion in a combined heat and power plant with a 40 MWth nuclear high temperature reactor as a heat source. State of the art efficiency values of air breathing gas turbines are used for the first calculations. The efficiency level is corrected by comparing various dimensionless data of the Helium turbomachine with an air gas turbine of similar dimensions.

A single shaft configuration with a high speed axial turbine will give highest performance and simple construction. If a generator has to be driven at a conventional speed, a free power turbine configuration must be chosen. The choice of the configuration depends among others on the cost and availability of the asynchrone generator and frequency convertor.
Development of Ceramic Components for Ceramic Gas Turbine Engine (CGT302)
Authors: Yoshida Makoto , Tanaka Koichi , Kubo Toshifumi , Terazono Hirofumi , Tsuruzono Sazo
Published: December 2014

The 300kW Industrial Ceramic Gas Turbine (CGT) Research and Development Project is going on as a part of New Sunshine project under the contract of Japanese Ministry of International Trade and Industry (MITI). The objective of this project is to achieve higher efficiency and lower pollutant emissions for small sized gas turbine engines used in co-generation systems.

Under this project, Kyocera has been developing various ceramic components for the CGT302 engine designed by Kawasaki Heavy Industries (KHI). This engine has set a thermal efficiency of over 42% at a turbine inlet temperature (TIT) of 1350°C as a final target. For such operations, we have developed the new silicon nitride materials, SN281 and SN282, which have excellent stress rupture strength and superior oxidation resistance at elevated temperatures up to 1500°C.

We have also developed improved fabrication technologies for the use of SN281 and SN282 as engine components. In 1997 fiscal year, all ceramic components for the CGT302 were successfully fabricated by using these new materials. Especially, the large sized monolithic power turbine (PT) rotor, which has a 192mm outer diameter, was manufactured by SN282, and exhibited fracture rotating speeds greater than 120% of the design rotating speed in cold spin tests.

This paper discusses the mechanical properties of these new materials and the results of ceramic components evaluated under engine test conditions.
Stress Relaxation of MCrAlY Bond Coat Alloys as a Function of Temperature and Strain
Authors: Wereszczak A. A. , Hemrick J. G. , Kirkland T. P. , Haynes J. A. , Fitzgerald T. J. , Junkin J. E.
Published: December 2014

The tensile stress relaxation behavior of two NiCoCrAlY bond coat alloys was examined at several temperatures between 25 and 899°C (1650°F) and at 0.1, 0.3, 0.5, and 0.8% strain. One alloy was made from Praxair’s CO211 powder and served as the reference alloy, while the other was a Westinghouse-developed, oxide-dispersion-strengthened alloy. The specimens were loaded to the desired tensile strain at a constant strain rate, and the elastic modulus, yield strength, and yield strain were determined as a function of temperature for the two alloys using the stress/strain information from this loading segment. There was not a statistically significant difference in the high temperature elastic properties between the two alloys, although the oxide-dispersion-strengthened alloy tended to exhibit larger yield strengths. The relaxation data for both alloys were reduced into a form in which instantaneous stressing rate during relaxation was examined as a function of stress and temperature using an Arrhenius power-law model. The oxide-dispersion-strengthened alloy exhibited a larger stress exponent and activation energy than the reference alloy between 677–899°C (1250–1650°F), and was generally more creep resistant. The results from this study demonstrate that bond coat relaxation should occur during engine operation. Bond coatings fabricated from the oxide-dispersion-strengthened alloy have the potential to reduce residual stresses in the TBC ceramic top coating.
Vibrational Response Analysis of Mistuned Bladed Disk System of Grouped Blades
Authors: Kaneko Y. , Mori K. , Ohyama H. , Watanabe E.
Published: December 2014

For the purpose of the efficient analysis of a mistuned bladed disk system, a new analysis method which applies the substructure synthesis method and the modal analysis method is proposed. Using the proposed method, the vibrational characteristics of the grouped blades structure are studied. From the results, it is found that the grouped blades structure is very sensitive to the mistuning. It is also found that the mixed grouped blades structure (a bladed disk system consisting of some different types of grouped blades relating to the number of blades contained) has an undesirable effect on the forced response. Moreover, by comparing the vibrational characteristics of the integral shroud blades (ISB) structure with those of the grouped blades structure, it is clarified that the reliability of the ISB structure is superior to other structures also from the viewpoint of the mistuning.
FT8 Phase II Reliability Improvement Program
Authors: Boley Warren M. , Prete Thomas W.
Published: December 2014

This paper describes the FT8 gas generator (GG8) development history, including required design modifications to the JT8D aircraft engine, initial field experience and the latest reliability improvements incorporated into the GG8. The modifications include improvements to bearing compartment operating temperature, bearing compartment seals, and increases to bearing life. Turbine durability improvements are also discussed.

The incorporation and control of a cold air buffer system to control bearing compartment oil coke formation is provided. Improvements to bearing compartment carbon seals are reviewed and the benefits of this design are discussed. Rotor system thrust bearing life improvements are achieved through the incorporation of modified compressor seals and turbine aerodynamics.
Gas Turbine Compressor Washing State of the Art — Field Experiences
Authors: Stalder Jean-Pierre
Published: December 2014

Technology development in gas turbine compressor washing over the last 10 years and today’s state of the art technology is presented in this paper. Based on various long term field tests and observations, correlation between rate of power degradation and atmospheric conditions can be established. Questions about compressor on line washing with water alone against the use of detergents, as well as washing frequencies are also addressed in this paper. Performance degradation behavior between gas turbines of different sizes and models can be explained with an index of sensitivity to fouling. The implementation of an optimised regime, of on line and off line washing in the preventive turbine maintenance program is important, it will improve the plant profitability by reducing the costs of energy production and contribute to a cleaner environment.
Genetic Algorithm Based Strategies for Radial Flow Impeller Design
Authors: Tuccillo Raffaele , Senatore Adolfo
Published: December 2014

The authors present a method for radial flow impeller design which pays attention to the set-up of optimal design strategies, the latter based upon the employment of a genetic algorithm which controls a Quasi-3D flow simulation of a radial flow impeller, with integral boundary layer calculation.

The design procedure develops through a number of steps, which are characterized by a progressive reduction in the search interval of each independent variable. In addition, a more accurate definition of the blade geometry and a more reliable flow analysis is obtained through a mesh refinement in the flow model, when the whole optimization process is close to convergence.

The results demonstrate the possibility of achieving an optimal choice of the impeller geometrical parameters by approaching, in a first phase, the design data, and then by proceeding with a number of refinement steps, as outlined above. In this way. the accuracy of the whole procedure is strongly increased, so that the typical effectiveness of the genetic algorithms in the preliminary selection steps is combined with a detailed investigation of the impeller blade features in the final steps of the optimized design. The effectiveness becomes, therefore, comparable with that of classical gradient based methods of optimization. At the same time, the genetic algorithm is capable of handling discontinuities in the objective function, thus overcoming the typical limits of numerical methods.

In order to emphasize the effectiveness of the proposed procedure, the results refer to a wide variety of design data. Both the impeller configurations and the flow distributions found demonstrate that the final solution is in agreement with the design target and constraints.
Numerical Calculation of Three-Dimensional Euler Flow Through a Transonic Test Turbine Stage
Authors: Paßrucker Harald , Sanz Wolfgang , Jericha Herbert
Published: December 2014

The objective of this work is the development of an implicit block-structured central-differencing scheme with implicit treatment of the boundary conditions for the calculation of three-dimensional inviscid compressible steady flow, primarily through transonic turbomachinery stages. The implicit boundary treatment is based on the mathematical theory of characteristics for hyperbolic systems of equations. Steady-state non-reflecting boundary conditions at the inflow and outflow boundaries and at the stator/rotor interface based on Fourier analysis applied to the linearized Euler equations are also used. Getting a monotonous resolution of shocks, a non-linear additive viscosity term of 2nd and 4th order with pressure-controlled factors is implemented. The three-dimensional blade geometry consists of Bézier-surfaces which are determined by two-dimensional blade profiles based on Bézier-curves. The grid for the flow calculation is obtained by parameterizing special Bézier-surfaces, respectively Bézier-volumes. Finally, the aerodynamic design of the one-stage highly loaded transonic test turbine of Institute of Thermal Turbomachinery and Machine Dynamics - Graz University of Technology) with these tools described above is illustrated with detailed presentation of the specific aerodynamic features, the design technology and the computational results.
A Comprehensive Model to Predict Simplex Atomizer Performance
Authors: Liao Y. , Sakman A. T. , Jeng S. M. , Jog M. A. , Benjamin M.
Published: December 2014

The performance of liquid fuel atomizer has direct effects on combustion efficiency, pollutant emission and stability. Pressure swirl atomizer, or simplex atomizer, is widely used in liquid fuel combustion devices in aircraft and power generation industry. A computational, experimental, and theoretical study is conducted to predict its performance. The Arbitrary-Lagrangian-Eulerian method with finite volume scheme is employed in the CFD model. Internal flow characteristics of the simplex atomizer as well as its performance parameters such as discharge coefficient, spray angle and film thickness are predicted. A temporal linear stability analysis is performed for cylindrical liquid sheets under 3-D disturbance. The model incorporates swirling velocity component, finite film thickness and radius which are essential features of conical liquid sheets emanating from simplex atomizers. It is observed that the relative velocity between liquid and gas phase, density ratio and surface curvature enhance the interfacial aerodynamic instability. As Weber number and density ratio increase, both the wave growth rate and the unstable wave number range increase. Combination of axial and swirling velocity components is more effective than single axial component for disintegration of liquid sheet. A breakup model for conical liquid sheet is proposed. Combining the breakup model with linear stability analysis, mean drop sizes are predicted. The theoretical results are compared with measurement data and agreement is very good.
Study on High Liquid Pressure Internal Mixing Prefilming Airblast Atomization
Authors: Chin Ju S. , Rizk Nader K. , Razdan Mohan K.
Published: December 2014

The objective of the present investigation is to provide better understanding of the hybrid atomization process in an effort to support the development of fuel injectors for future high performance / low emissions gas turbine combustors. A specially designed atomizer that incorporated two swirling air streams, and a prefilming device located upstream of the atomizer exit section was tested under a combined hybrid airblast and high liquid pressure mode. The experiments focused on evaluating the effects of several operating parameters, in particular the air / liquid ratio, on the atomization quality. The results demonstrated that, to accurately determine the role of the air / liquid ratio in the atomization process, the effects of liquid injection velocity and the relative air–liquid velocity need to be separated from that of the air / liquid ratio. Two approaches were used in the present investigation to deduce the actual effect of the air / liquid ratio: first, by reducing the air swirler flow areas, and second, by increasing the number of liquid injection holes. Both approaches enabled changing the air / liquid ratio without changing the air or liquid velocities. The atomization results indicate that changes in swirler flow area produce a stronger effect of the air / liquid ratio than that when liquid hole number was changed. For fixed air / liquid ratio, better atomization quality was achieved when both levels of air flow and liquid flow were high compared to when both flow rates were low. Also, the atomizer demonstrated a continuous improvement in atomization quality under very high air pressure drop, indicating a better utilization of the air kinetic energy over conventional airblast atomizers. The other important observation was that the dependency of the atomization process on air velocity was not constant, but rather changed with liquid pressure, air flow rate, and air pressure drop.
Power Generation Possibilities in the State of São Paulo, Brazil
Authors: Llagostera Jorge
Published: December 2014

São Paulo is the Brazilian state with the largest economic production, the largest population and the largest industrial park of the country, with a participation in GDP of 36.6% (population: 34 million; area: 248,600 km2; urbane population: 92,8%; illiteracy: 10%; infantile mortality: 26.2/1000). Great part of the industry from São Paulo concentrates in the metropolitan area of São Paulo. Nevertheless, in the interior several cities are becoming important in many industrial sectors. After 1930 São Paulo became the vanguard of the Brazilian modernization. Concurrently with the agricultural expansion the state had an extraordinary industrial development. Channeling the great flows of investments of the American and European multinationals and the great internal migratory currents, São Paulo increased its population vastly, it diversified its social structure and it consolidated its economic power. However, the poverty of a great part of its population is a severe social problem. The State of São Paulo, in 1995, consumed 82.9 TWh of electricity, with the consumption of the industrial sector of 39.6 TWh. In that same year Brazil consumed a total of 249.9 TWh, and of this total value, 118.0 TWh was consumed by the industrial sector. By analyzing the evolution tendencies of energy consumption in São Paulo in the last years, it is possible to identify important aspects of the energetic development of this State, particularly in relation to the perspectives of natural gas utilization in gas turbines for power generation.
Gas Turbine Spinning Reserve Operation to Support Frequency Drops in Small Grid
Authors: Brito Ismael , Dost Michael , von Rappard Axel W.
Published: December 2014

The use of gas turbines in relatively small grids is often connected with an additional requirement from the grid side. Such a requirement can be the increase of power production within seconds to support the stability of a grid. This topic was investigated thoroughly in 1985 for several types of power plants. In 1992 ABB received an order for a gas turbine power plant on the island of Puerto Rico where a fast loading response with 40% load increase within 3 seconds was required. Based on earlier investigations the order was accepted. The powerplant built a „Steam Enhanced Power (SEP) plant“, each consisting of three powertrains each with a gas turbine, a once through steam generator and an exhaust system with an SCR for emission control. This paper describes the control functions necessary to meet the requirements and the consequences for the operation of the plant. Results from the acceptance tests where the rapid loading from a standby mode at 60% load was simulated will be shown and discussed in detail.
On the Application of Transition Correlations in Turbomachinery Flow Calculation
Authors: Hu Jiasen , Fransson Torsten H.
Published: December 2014

Prediction of boundary-layer transition is important to turbomachine design. Various experimental correlations are still the most practical models used in engineering calculations. In an acceleration or deceleration flow field, however, the predictions depend on the free-stream turbulence intensity incorporated in the correlations. A numerical analysis is therefore presented in this paper to investigate how much the different implementations of the turbulence levels can affect the numerical results. The main emphasis is on the importance of such influence in engineering calculations in comparison with the importance of correlation and grid resolution effects. The analysis is performed using an industrial Reynolds-averaged Navier-Stokes solver with different transition correlations and models of free-stream turbulence intensity. Eight benchmark test cases, including basic incompressible flat-plate cases and more realistic transonic cascade cases, have been calculated. The study reveals that the effects of grid resolution and the choice of correlations on the transition results are relatively small. But a proper presentation of free-stream turbulence intensity in the correlations plays a vital role in this sort of calculation. The use of a computed local turbulence level with the correlations appears to be the most flexible choice among the approaches considered.
Dimensional Instability Studies in Machining of Inconel 718 Nickel Based Superalloys as Applied to Aerogas Turbine Components
Authors: Subhas B. K. , Bhat Ramaraja , Balakrishna H. K. , Ramachandra K.
Published: December 2014

Inconel 718 alloy is used extensively in aerogas turbines and this alloy is most difficult to machine and highly prone to dimensional instability after machining. Such detrimental phenomenon poses enormous problem in engine assembly and affect structural integrity. This paper highlights the systematic research work undertaken to study the plastic deformation characteristics of Inconel 718, effect of process variables on machined surface, subsurface and dimensional instability. Also illustrated the technique developed for simultaneous optimization of several process variables such as cutting speed, feed, depth of cut, rake angle and tool nose radius, to control the residual stresses and dimensional instability, within the acceptable tolerance band of the component. Prediction equations were developed for residual stress, dimensional instability, tool life, surface finish and material removal rate. Predicted data were validated experimentally. This paper also presents the qualitative and quantitative data on dimensional instability with specific case studies of jet engine components and clearly illustrates the approach followed to develop technique to control such detrimental effect.
Coating Life Prediction for Combustion Turbine Blades
Authors: Chan Kwai S. , Cheruvu N. Sastry , Leverant Gerald R.
Published: December 2014

A life prediction method for combustion turbine blade coatings has been developed by modeling coating degradation mechanisms including oxidation, spallation, and aluminum loss due to inward diffusion. Using this model, the influence of cycle time on coating life is predicted for GTD-111 coated with an MCrAlY, PtAl, or aluminide coating. The results are used to construct a coating life diagram that depicts failure and safe regions for the coating in a log-log plot of number of startup cycles versus cycle time. The regime where failure by oxidation, spallation, and inward diffusion dominates is identified and delineated from that dominated by oxidation and inward diffusion only. A procedure for predicting the remaining life of a coating is developed. The utility of the coating life diagram for predicting the failure and useful life of MCrAlY, aluminide, or PtAl coatings on the GTD-111 substrate is illustrated and compared against experimental data.
High Temperature Oxidation and Corrosion of Silicon-Based Nonoxide Ceramics
Authors: Klemm Hagen , Herrmann Mathias , Schubert Christian
Published: December 2014

The present study is focussed on the oxidation behavior of nonoxide silicon-based ceramics. Various Si3N4 and SiC ceramics were examined after long term oxidation tests (up to 5000 h) at 1500°C in ambient air. The damage mechanisms were discussed on the basis of a comprehensive chemical and microstructural analysis of the materials after the oxidation tests. The diffusion of oxygen into the material and its further reaction in the bulk of the material were found to be the most critical factors during long term oxidation treatment at elevated temperatures. However, the resulting damage in the microstructure of the materials can be significantly reduced by purposeful microstructural engineering. Using Si3N4/SiC and Si3N4/MoSi2 composite materials provides the possibility to improve the high temperature stability.