bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite Element Analysis of Thermomechanical Contact of an Elastomeric O-Ring Seal
Authors: Lin Baojiu , Nicholson David W.
Published: December 2014

This study concerns the development of a finite element model to support design improvements in elastomeric seals subject to high temperature and pressure, such as in aircraft engines. Existing finite element codes familiar to the authors do not couple thermal and mechanical fields, nor do they implement thermomechanical contact models suitable for highly deformable materials. Recently, the authors have introduced a thermohyperelastic constitutive model for near-incompressible elastomers. In two subsequent studies, using the constitutive model, a method has been introduced for finite element analysis of coupled thermomechanical response, including boundary contributions due to large deformation and variable contact. A new thermomechanical contact model has also been introduced to accommodate the softness of elastomers. The method has been implemented in a special purpose code which concerns a seal compressed into a well. Several computations are used to validate the code. Simulations of a seal in an idealized geometry indicate rapid pressure increase with increasing compression and temperature.
Quantification of Thermal-Structural Uncertainties in Engine Combustor Composite Liners
Authors: Pai Shantaram S. , Chamis Christos C.
Published: December 2014

A typical hot structural component within an engine such as composite combustor liner is computationally simulated and probabilistically evaluated in view of the numerous uncertainties associated with the structural, material, and thermo-mechanical load variables (primitive variables) that describe the combustor. The combustor is evaluated for local stresses. Results show that the scatter in the combined stress near the support is significantly dependent upon the uncertainties in the through thickness thermal gradients, the liner material thickness, the coefficient of thermal expansion, and the axial and both the axial and shear moduli.
The Design of Fabricated Ducts to Avoid Gas Induced High Cycle Fatigue
Authors: Eaton R. , Platt J. , Gallimore S.
Published: December 2014

The design and fatigue life analysis of many fabricated sheet metal components which operate in a hot gas path environment is made uncertain by the difficulty in predicting the gas dynamic forces to which the component will be subjected. This is particularly true for ducts which are exposed to minimal static loading such as inter-turbine ducts, which have little pressure drop across them but are subjected to highly non-uniform flow from the upstream turbine exit. Finite element analysis and static testing has revealed — that certain modal frequencies respond much more significantly than others and where these coincide with gas dynamic frequencies a resonance is set up and rapid and catastrophic failure will occur.

Through a combination of analysis and engine testing it has been possible to identify the damaging gas dynamics and modal frequencies. This has enabled rules to be developed which assist in the design of such ducts to avoid high cycle fatigue failure.

This paper describes the development of the design process and by means of a typical example shows its application and effect on the design of an inter-turbine duct.
Evaluation of Gas Turbine Reliability Effects Using the Sustainable Capacity Methodology
Authors: Chmilar W. S.
Published: December 2014

The reliability of gas turbine driven compressor units is a major factor in the ability of a pipeline system to satisfy delivery or service requirements. However, despite it’s importance, unit reliability is not typically considered in design or operations. At Nova Gas Transmission Ltd (NGTL), a reliability evaluation methodology, referred to as Sustainable Capacity, has been developed to quantify service expectations through the explicit consideration of the effects of gas turbine reliability. The methodology, which has been adapted from one widely used in the electric power industry, is based on the representation of the load and capacity processes with statistical models. Time-series representing simultaneous load and capacity profiles are generated and evaluated to determine reliability expectations. A cost-benefit methodology which recognizes the variation in the value attributed to pipeline reliability by individual customers is also used to assess the economic efficiency of any proposed system modification. Although developed as a system design tool, the Sustainable Capacity methodology can also be used to quantify the value of gas turbine maintenance strategies provided the effect on unit reliability can be quantified.
Nonlinear Dynamic Simulation of an Active Magnetic Bearing System With Non-Symmetric Coordinate Coupling Forces
Authors: Ecker Horst , Knight Josiah D. , Wu Lan
Published: December 2014

Equations of motion are presented for a two degree of freedom system representing a rotor suspended with an active magnetic bearing. The rotor is subjected to both a rotating unbalance force and a steady load, which is balanced by differential bias in the vertical magnet pair. A coupling between the coordinate directions resulting from the spatial arrangement of magnets is included in the equations of motion, which renders them nonlinear even though the closed loop control on each axis is linear. Results of a path-following analysis of the equations show that the addition of a steady load has several effects. Compared with previous results for an unloaded system, the response is now asymmetric due to unequal stiffnesses, and the region of unacceptable high amplitude response extends over a larger frequency range. In addition, the frequency ranges over which multiple stable solutions coexist is expanded. New results for the unloaded case are also presented that show domains of attraction to large amplitude stable response due to an applied impulse. There is a strong dependence of the domains of attraction on the timing of the impulse.
The Maximum Transient Resonance Response of Rotating Blades With Regard to Centrifugal Force and Non-Linear Damping Effects
Authors: Irretier Horst D.
Published: December 2014

During the operation process in many types of fluid flow machines the rotating blades pass through various resonances e.g. during run-up or run-down or other transient conditions. Therefore, for the high cycle fatigue problem of the blades it might be important to consider the transient vibratory response of the blades during these passages through resonance and to get knowledge about the occuring maximum vibratory stresses.

In the paper, approximate formulas are presented which allow the estimation of the maximum transient response of the blades. Thereby, the influence of the change of the natural frequencies due to the increasing or decreasing centrifugal force field during the run-up or run-down, respectively, is taken into consideration. Basically, the approximate formulas are based on a linear change of the natural frequencies versus time and on a linear viscous type of damping. Extensions to account for parabolic changes which are more realistic for centrifugal effects and for non-linear damping models e.g. friction damping or turbulence damping are discussed.
A New Model for Free-Stream Turbulence Effects on Boundary Layers
Authors: Volino Ralph J.
Published: December 2014

A model has been developed to incorporate more of the physics of free-stream turbulence effects into boundary layer calculations. The transport in the boundary layer is modeled using three terms: 1) the molecular viscosity, ν; 2) the turbulent eddy viscosity, εT, as used in existing turbulence models; and 3) a new free-stream induced eddy viscosity, εf. The three terms are added to give an effective total viscosity. The free-stream induced viscosity is modeled algebraically with guidance from experimental data. It scales on the rms fluctuating velocity in the free-stream, the distance from the wall, and the boundary layer thickness. The model assumes a direct tie between boundary layer and free-stream fluctuations, and a distinctly different mechanism than the diffusion of turbulence from the free-stream to the boundary layer assumed in existing higher order turbulence models. The new model can be used in combination with any existing turbulence model. It is tested here in conjunction with a simple mixing length model and a parabolic boundary layer solver. Comparisons to experimental data are presented for flows with free-stream turbulence intensities ranging from 1 to 8% and for both zero and non-zero streamwise pressure gradient cases. Comparisons are good. Enhanced heat transfer in higher turbulence cases is correctly predicted. The effect of the free-stream turbulence on mean velocity and temperature profiles is also well predicted. In turbulent flow, the log region in the inner part of the boundary layer is preserved, while the wake is suppressed. The new model provides a simple and effective improvement for boundary layer prediction.
Dual Brayton Cycle Gas Turbine Pressurized Fluidized Bed Combustion Power Plant Concept
Authors: Yan Xing L. , Lidsky Lawrence M.
Published: December 2014

High generating efficiency has compelling economic and environmental benefits for electric power plants. There are particular incentives to develop more efficient and cleaner coal-fired power plants, to permit use of the world’s most abundant and secure energy source. This paper presents a newly-conceived power plant design, the Dual Brayton Cycle Gas Turbine PFBC, that yields 45% net generating efficiency and fires on a wide range of fuels with minimum pollution, of which coal is a particularly intriguing target for its first application. The DBC-GT design allows power plants based on the state-of-the-art PFBC technology to achieve substantially higher generating efficiencies while simultaneously providing modern gas turbine and related heat exchanger technologies access to the large coal power generation market.
A Three-Dimensional Turbine Engine Analysis Compressor Code (TEACC) for Steady-State Inlet Distortion
Authors: Hale Alan , O’Brien Walter
Published: December 2014

The direct approach of modeling the flow between all blade passages for each blade row in the compressor is too computationally intensive for practical design and analysis investigations with inlet distortion. Therefore a new simulation tool called the Turbine Engine Analysis Compressor Code (TEACC) has been developed. TEACC solves the compressible, time-dependent, 3D Euler equations modified to include turbomachinery source terms which represent the effect of the blades. The source terms are calculated for each blade row by the application of a streamline curvature code. TEACC was validated against experimental data from the transonic NASA rotor, Rotor 1B, for a clean inlet and for an inlet distortion produced by a 90-deg, one-per-revolution distortion screen. TEACC revealed that strong swirl produced by the rotor caused the compressor to increase in loading in the direction of rotor rotation through the distorted region and decrease in loading circumferentially away from the distorted region.
Design of a Semiclosed Cycle Gas Turbine With Carbon Dioxide-Argon as Working Fluid
Authors: Ulizar Inaki , Pilidis Pericles
Published: December 2014

The main performance features of a semiclosed cycle gas turbine with carbon dioxide-argon working fluid are described here. This machine is designed to employ coal synthetic gas fuel and to produce no emissions.

The present paper outlines three tasks carried out. Firstly the selection of main engine variables, mainly pressure and temperature ratios. Then a sizing exercise is carried out where many details of its physical appearance are outlined. Finally the off-design performance of the engine is predicted.

This two spool gas turbine is purpose built for the working fluid, so its physical characteristics reflect this requirement. The cycle is designed with a turbine entry temperature of 1650 K and the optimum pressure ratio is found to be around 60. Two major alternatives are examined, the simple and the precooled cycle.

A large amount of nitrogen is produced by the air separation plant associated with this gas turbine and the coal gasifier. An investigation has been made on how to use this nitrogen to improve the performance of the engine by precooling the compressor, cooling the turbine nozzle guide vanes and using it to cool the delivery of the low pressure compressor.

The efficiencies of the whole plant have been computed, taking into account the energy requirements of the gasifier and the need to dispose of the excess carbon dioxide. Hence the overall efficiencies indicated here are of the order of 40 percent. This is a low efficiency by current standards, but the fuel employed is coal and no emissions are produced.
The GE Rich-Quench-Lean Gas Turbine Combustor
Authors: Feitelberg Alan S. , Lacey Michael A.
Published: December 2014

The General Electric Company has developed and successfully tested a full-scale, ‘F’ class (2550°F combustor exit temperature), rich-quench-lean (RQL) gas turbine combustor, designated RQL2, for low heating value (LHV) fuel and integrated gasification combined cycle applications. Although the primary objective of this effort was to develop an RQL combustor with lower conversion of fuel bound nitrogen to NOx than a conventional gas turbine combustor, the RQL2 design can be readily adapted to natural gas and liquid fuel combustion.

RQL2 is the culmination of a 5 year research and development effort that began with natural gas tests of a 2″ diameter perforated plate combustor and included LHV fuel tests of RQL1, a reduced scale (6″ diameter) gas turbine combustor. The RQL2 combustor includes a 14″ diameter converging rich stage liner, an impingement cooled 7″ diameter radially-stratified-quench stage, and a backward facing step at the entrance to a 10″ diameter film cooled lean stage. The rich stage combustor liner has a novel double-walled structure with narrow circumferential cooling channels to maintain metal wall temperatures within design limits. Provisions were made to allow independent control of the air supplied to the rich and quench/lean stages.

RQL2 has been fired for almost 100 hours with LHV fuel supplied by a pilot scale coal gasification and high temperature desulfurization system. At the optimum rich stage equivalence ratio NOx emissions were about 50 ppmv (on a dry, 15% O2 basis), more than a factor of 3 lower than expected from a conventional diffusion flame combustor burning the same fuel. With 4600 ppmv NH3 in the LHV fuel, this corresponds to a conversion of NH3 to NOx of about 5%. As conditions were shifted away from the optimum, RQL2 NOx emissions gradually increased until they were comparable to a standard combustor. A chemical kinetic model of RQL2, constructed from a series of ideal chemical reactors, matched the measured NOx emissions fairly well. The CO emissions were between 5 and 30 ppmv (on a dry, 15% O2 basis) under all conditions.
Effect of Squealer Tip on Rotor Heat Transfer and Efficiency
Authors: Ameri A. A. , Steinthorsson E. , Rigby David L.
Published: December 2014

Calculations were performed to simulate the tip flow and heat transfer on the GE-E3 first stage turbine, which represents a modern gas turbine blade geometry. Cases considered were a smooth tip, 2% recess, and 3% recess. In addition a two-dimensional cavity problem was calculated. Good agreement with experimental results was obtained for the cavity calculations, demonstrating that the k-ω turbulence model used is capable of representing flows of the present type. In the rotor calculations, two dominant flow structures were shown to exist within the recess. Also areas of large heat transfer rate were identified on the blade tip and the mechanisms of heat transfer enhancement were discussed. No significant difference in adiabatic efficiency was observed for the three tip treatments investigated.
The Effect of Bulk Flow Pulsations on Film Cooling From Two Rows of Holes
Authors: Sohn Dong Kee , Lee Joon Sik
Published: December 2014

Effect of bulk flow pulsations on film cooling from two rows of holes with inline and staggered arrangements is experimentally investigated. As a baseline study, a single row injection is also tested. Two-row injection is important because the phase lag between the two rows may cause changes in the film coolant coverage. Potential flow pulsations are generated by the rotating shutter mechanism attached downstream of the test section. Free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033–0.33, and the amplitude of the phase-averaged freestream velocity due to static pressure variation about 10–20% Both the time-averaged and phase-averaged temperature distributions in the cross-sectional plane of the boundary layer are presented for four different pulsation frequencies of 0, 4, 20 and 40 Hz. Film cooling effectiveness is evaluated from the adiabatic wall temperature distributions, with time-averaged temperature measurements showing rapid diffusion of the injectant due to the free-stream pulsations. Effect of the phase lag between two rows is evidenced from the phase-averaged measurements, particularly in the case of staggered hole arrangement. All film cooling effectiveness distributions are reduced compared to no-pulsation case. Effect of pulsations appears dominantly in the case of the two-row staggered arrangement which shows more than 35% reduction in the film cooling effectiveness.
Effect of Passive and Active Air-Jet Turbulence on Turbine Blade Heat Transfer
Authors: Welsh Sean T. , Barlow D. Neal , Butler Robert J. , Van Treuren Kenneth W. , Byerley Aaron R. , Baughn James W. , Rivir Richard B.
Published: December 2014

The heat transfer distribution on a turbine blade shape has been measured in a linear cascade wind tunnel for turbulence levels between 0.5% and 15%. The measurements were conducted at a low Reynolds number (80,000). This is typical of low pressure turbine stages at high altitude where unpredicted losses, attributed to transition and separation, have been observed. The heat transfer distributions provide insight into the transition and separation behavior. Turbulence levels from 5% to 10% were generated with a passive biplane lattice grid, while turbulence levels from 10% to 15% were generated by an active air-jet grid. As turbulence levels increased, stagnation heat transfer increased and the location of the boundary layer transition advanced toward the leading edge on the suction side of the blade. The stagnation Nu/Re0.5 increased by 18.6% when going from a clean tunnel turbulence of 0.5% to 15% turbulence. The heat transfer was measured using a uniform heat flux liquid crystal technique. At turbulence intensities of 0.5% stream wise streaks of varying heat transfer were recorded on the concave pressure side of the turbine blade characteristic of Görtler vortices. At higher levels of turbulence these streaks disappeared. Turbulence decay rates, along with micro and macro length scales, are reported for both active and passive grid test conditions.
Heat Transfer in a Rotating Cavity With a Peripheral Inflow and Outflow of Cooling Air
Authors: Mirzaee Iraj , Gan Xiaopeng , Wilson Michael , Owen J. Michael
Published: December 2014

This paper describes a combined computational and experimental study of the heat transfer in a rotating cavity with a peripheral inflow and outflow of cooling air for a range of rotational speeds and flow rates. Measurements are made in a purpose-built rig, with one of the two rotating discs heated, and computations are conducted using an axisymmetric elliptic solver incorporating the Launder-Sharma low-Reynolds-number k-ε turbulence model. Measured values of the tangential component of velocity, Vϕ, exhibit Rankine-vortex behaviour which is not accurately modelled by the computations. Both computed and measured values of the radial component of velocity, Vr, confirm the recirculating nature of the flow. In the outflow region, agreement between computed and measured values of Vr is mainly good, but in the inflow region the computations exhibit a “peaky” distribution which is not shown by the measurements. The measured and computed Nusselt numbers show that Nu increases as the magnitudes of the flow rate and the rotational speed increase. The computed Nusselt numbers (allowing for the effects of conduction through and radiation to the unhealed disc) reproduce the measured trends but tend to underestimate the experimental values at the larger radii.
Failure to Achieve Hot Section Component Service Intervals: Why and What to Do About it
Authors: Lefton Steven A. , Burnett Thomas D. , Kuntz Todd A. , Paterson Steve R.
Published: December 2014

Recent work done by Aptech Engineering Services, Inc. (APTECH) has demonstrated that many hot section gas turbine components are not achieving their intended service lives and/or maintenance intervals, falling short by a factor of as much as ten. As summarized in (Makansi, 1996), this observation has been confirmed by numerous industry and literature reports of failures, degradation, reduced availability and increased maintenance for a wide variety of turbines and manufacturers.

This paper focuses on hot corrosion damage as one common mechanism that is frequently the cause of failure to reach expected service intervals. In general, attempts are made to limit hot corrosion damage by specifying impurity limits for fuel oil, combustion air, NOx reduction injection water and compressor washing water. Strict adherence to manufacturers recommended impurity limits is often very difficult to achieve, particularly if the machine is frequently cycled through harsh (but not uncommon) operating transients. A discussion of various manufacturer specifications and their implications will be presented, followed by two case studies which demonstrate that extensive hot corrosion damage can result even when manufacturers specifications for fuel, air and water purity are (apparently) being met. A proposed modification of traditional impurity limit specifications is offered, which would include guidelines for acceptable corrosion rate limits. Practical recommendations for reducing the potential for hot corrosion are also offered.
Low Frequency Noise Considerations for Combustion Turbine Projects
Authors: Beeson Lisa A. , Schott George A.
Published: December 2014

Combustion turbine projects have become a popular choice for providing a clean and efficient source of electricity. However, since combustion turbines generally produce low frequency sound energy, special siting considerations should be evaluated to minimize the potential for impacts on sensitive receptors, such as residences, churches, hospitals, and schools.

For successful siting of combustion turbine projects near sensitive receptors, it is necessary to incorporate noise control features into plant designs to reduce not only audible noise but also noise at frequencies which are even lower than the human ear can perceive. These extremely low frequencies can rattle walls and windows, causing pressure pulsations which may be perceived by some people, or vibration of small objects inside houses and other structures.

Even “quiet” plants which include extensive noise control features may still result in perceptible low frequency noise due to the relative difficulty of attenuating low frequency sound energy. Noise attenuation options are discussed, including active, passive, and reactive technologies, along with the impacts associated with each type of design.

Guidelines for siting combustion turbine power generation facilities near sensitive receptors are presented, to enable development of projects which not only meet applicable noise requirements, but also reduce the potential for community complaints.
A Numerical Study of Chemically Reactive Flow of Hot Combustion Gases in a First-Stage Turbine Nozzle
Authors: Godin Th. , Harvey S. , Stouffs P.
Published: December 2014

Current progress in gas turbine performance is achieved mainly by increasing the turbine inlet temperature. At high temperature levels (>2000K), the hot combustion gases can no longer be considered as chemically inert, and it becomes important to account for dissociation and recombination reactions occurring not only in the combustion chamber but also within the expanding gas stream in the turbine. In this paper, the authors present a two-dimensional numerical study of chemically reactive flow of hot combustion gases through the first guide vane of a gas turbine. For this initial study, simplified boundary conditions are assumed: blade cooling air mixing is neglected, the blade wall temperature is assigned a fixed value, and uniform inlet conditions are assumed. This study investigates the effect of turbulence on chemical reaction kinetics and presents pollutant emission levels at the nozzle exit. Particular attention is also focussed on chemical reactivity near the pressure and suction sides of the turbine guide vane blades.
Experimental and Theoretical Study of Droplet Vaporization in a High Pressure Environment
Authors: Stengele Jörg , Willmann Michael , Wittig Sigmar
Published: December 2014

Due to the continuous increase of pressure ratios in modern gas turbine engines the understanding of high pressure effects on the droplet evaporation process gained significant importance. The precise prediction of the evaporation time and the movement of the droplets is crucial for optimum design and performance of modern gas turbine combustion chambers. Numerous experimental and numerical investigations have been done already in order to understand the evaporation process of droplets in high pressure environments. But until now, all high pressure experiments were carried out with droplets attached to a thin fiber resulting in the impairment of the droplet evaporation process due to the suspension unit.

In the present study, a new experimental set up is introduced where the evaporation of free falling droplets is investigated. Monodisperse droplets are generated in the upper part of the test rig and fall through the stagnant high pressure gas inside the pressure chamber. Due to the relative velocity between droplet and gas, convective effects have to be considered in this study which are taken into account by experimental correlations. The droplet diameter and the droplet velocity are measured simultaneously by means of video technique and a stroboscope lamp. Detailed measurements with heptane droplets are presented for different pressures (p = 20 bar, 30 bar and 40 bar), gas temperatures (T = 550 K and 650 K) and initial diameters (d0 = 680 μm, 780 μm and 840 μm). The experiments were carried out with single component droplets.

The experimental results are compared with numerical calculations. For this a theoretical model was developed based on the Conduction Limit model and the Uniform Temperature model. Good agreement for all conditions investigated is observed when using the Conduction Limit model. The Uniform Temperature model predicts incorrectly the evaporation process of the droplet.
Testing of a Full Scale, Low Emissions, Ceramic Gas Turbine Combustor
Authors: Smith K. , Fahme A.
Published: December 2014

The design and development testing of a full scale, low emissions, ceramic combustor for a 5500 HP industrial gas turbine are described. The combustor was developed under a joint program conducted by the U.S. DOE and Solar Turbines.

The ceramic combustor is designed to replace the production Centaur 50S SoLoNOx burner which uses lean-premixed combustion to limit NOx and CO to 25 and 50 ppm, respectively. Both the ceramic and production combustors are annular in shape and employ twelve premixing, natural gas fuel injectors. The ceramic combustor design effort involved the integration of two CFCC cylinders (76.2 cm [30 in.] and 35.56 cm [14 in.] diameters) into the combustor primary zone.

The ceramic combustor was evaluated at Solar in full scale test rigs and a test engine. Performance of the combustor was excellent with high combustion efficiency and extremely low NOx and CO emissions. The hot walls of the ceramic combustor played a significant role in reducing CO emissions. This suggests that liner cooling air injected through the metal production liner contributes to CO emissions by reaction quenching at the liner walls. It appears that ceramics can serve to improve combustion efficiency near the combustor lean limit which, in turn, would allow further reductions in NOx emissions.

Approximately 50 hours of operation have been accumulated using the ceramic combustor. No significant deterioration in the CFCC liners has been observed. A 4000 hour field test of the combustion system is planned to begin in 1997 as a durability assessment.
Experiment on Water Spraying Internal Cooling Within the Compressor of Gas Turbine
Authors: Qun Zheng , Guoxue Wang , Yufeng Sun , Shunlong Liu , Shuying Li , Zhengyi Zhang
Published: December 2014

Experiment on internal cooling effect of water spraying within compressor of S1A-02 gas turbine plant is carried out. The experimental results are represented in this paper. The water spraying particle diameter and distribution are measured by Laser Beam Diffraction Method. In addition, the relationship of evaporative time of water particle with its diameter and relative humidity are discussed. The design and mechanism of compressed air blowing type water sprayer nozzle are also analyzed in this paper.
Velocity Measurements and Local Heat Transfer in a Rotating Ribbed Two-Pass Square Channel With Uneven Wall Heat Flux
Authors: Hsieh Shou-Shing , Chiang Ming-Hung , Chen Ping-Ju
Published: December 2014

The influence of rotation and uneven wall heat flux effect on the local velocity distribution as well as local heat transfer coefficient in a rotating, two pass rib roughened (rib height e/DH = 0.20; rib pitch p/e = 5) square channel were studied for Reynolds numbers from 5000 to 10000 and rotation numbers from 0 to 0.1602 (≤ 300 rpm). The measured mean velocity under different wall heat flux condition for the specified rib configuration at ReH = 5000 and 10000, ReH = 0, 267, 534 and 801 are presented. Regionally averaged Nusselt number variations with rotation (≤ 800 rpm)along the duct have been determined over the trailing and leading surfaces for a two pass channel. Moreover, LDV measurements with heating were examined. It was found that the Coriolis force as well as centrifugal buoyancy is significant as the rotational speed increases.
Heat Transfer Predictions for Rotating U-Shaped Coolant Channels With Skewed Ribs and With Smooth Walls
Authors: Bonhoff Bernhard , Tomm Uwe , Johnson Bruce V. , Jennions Ian
Published: December 2014

A computational study was performed for the flow and heat transfer in rotating coolant passages with two legs connected with a U-bend. The dimensionless flow conditions and the rotational speed were typical of those in the internal cooling passages of turbine blades. The calculations were performed for two geometries and flow conditions for which experimental heat transfer data were obtained under the NASA HOST project. The first model had smooth surfaces on all walls. The second model had opposing ribs staggered and angled at 45 deg. to the main flow direction on two walls of the legs, corresponding to the coolant passage surfaces adjacent to the pressure and suction surfaces of a turbine airfoil. Results from these calculations were compared with the previous measurements as well as with previous calculations for the nonrotating models at a Reynolds number of 25,000 and a rotation number of 0.24. At these conditions, the predicted heat transfer is known to be strongly influenced by the turbulence and wall models. The differential Reynolds-stress model (RSM) was used for the calculation. Local heat transfer results are presented as well as results averaged over wall segments. The averaged heat transfer predictions were close to the experimental results in the first leg of the channel, while the heat transfer in the second leg was overestimated by RSM. The flow field results showed a large amount of secondary flow in the channels with rotational velocities as large as 90 percent of the mean value. These secondary flows were attributed to the buoyancy effects, the Coriolis forces, the curvature of the bend and the orientation of the skewed ribs. Details of the flow field are discussed. Both the magnitude and the change of the heat transfer were captured well with the calculations for the rotating cases.
An On-Line Materials Database for the Design of Gas Turbine Components
Authors: Piearcey Barry J. , Bullough Chris K.
Published: December 2014

In this paper the objectives and implementation of the company Materials Database at European Gas Turbines (EGT) are described. In the initial stages, a materials audit identified the existing functional requirements for materials information, the properties required by each function, and the flow of information. The main requirement of the database is to provide materials design data. Related, but separate databases for bibliographic and test data were also created. Technical procedures are necessary to define and control the content, use and maintenance of the Database, with an example being the creation, review and approval of materials property sets. Written procedures were also prepared to describe the flow of data resulting in relationships between a unique material specification, the ‘design data’ and its source, and the applications of the material for EGTs engines.

The database and technical procedures developed by EGT may be used as a model for other manufacturers developing their own computerised systems. It is shown that data may be represented in several ways, and it is argued that the structure of the data evolves during the implementation stage. Current standards and key publications (eg. Newton, 1993, and Buttner and Kröckel, 1989) which define how to build a materials database do not, so far, define the information content for gas turbine materials. With increasing electronic exchange of data amongst turbine manufacturers, and with their material suppliers and external test houses, there is an urgent need for standardisation of exchange methods. It is concluded that new standards for formatting and exchange of material property data will be of general benefit to the gas turbine industry.
Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Startup/Shutdown Cost
Authors: Yokoyama Ryohei , Ito Koichi
Published: December 2014

A rational method of determining the operational strategy of energy supply plants in consideration of equipment startup/shutdown cost is proposed. The operational planning problem is formulated as a large-scale mixed-integer linear programming one, in which on/off status and energy flow rates of equipment are determined so as to minimize the sum of energy supply and startup/shutdown costs over the period considered. By utilizing a special structure of the problem, an algorithm of solving the problem efficiently is proposed. Through a numerical study on the daily operational planning of a gas turbine cogeneration plant for district heating and cooling, the effectiveness of the proposed algorithm is ascertained in terms of computation time, and the influence of equipment startup/shutdown cost on the operational strategy and cost is clarified.
Thermoeconomic Analysis and Optimization of a Gas Turbine Plant Combined With an Absorption Unit
Authors: De Lucia Maurizio , Carcasci Carlo , Matucci Antonio
Published: December 2014

The aim of the paper is to study the performance of a power plant for the combined production of electrical, thermal and cooling thermal energy.

The exergy analysis was developed from the system’s operating conditions measured in a previous experimental phase, and allowed description and quantification of causes of efficiency loss in the plant.

The following thermoeconomic analysis, based on the exergy balance, allowed appraisal of the actual costs of each component and possible optimization of the plant for higher efficiency and cost saving.

The thermoeconomic results lead to a better understanding of the influence of off-design operating conditions on the performance of the whole plant and on this basis further improvements and modifications are envisaged.

Three modifications of the plant layout are described and discussed, in greater detail for the most promising of them, i.e., compressor inlet air cooling with absorber excess cooling power production.

Results show that this solution is particularly effective in the present case, not only from the energetic point of view, but, as is not always the case, also form the economic one.

The application of thermoeconomic analysis to the pharmaceutical factory under study has the aim of identifying those components which have the highest cost quantifying losses in cost terms.
Energy System Sensitivity Parameter
Authors: Negri di Montenegro G. , Peretto A.
Published: December 2014

In this paper, sensitivity analysis of energy systems was developed. This analysis was performed by using a quantity called sensitivity parameter, suitable for this purpose.

The parameter establishes the relative influence of input variables on the calculation results.

The sensitivity parameter evaluation was carried out by using a numerical procedure. This procedure is very convenient because it permits the employment of computational commercial codes.

A Brayton cycle gas turbine power plant was the considered energy system.

Sensitivity analysis was developed relatively to conversion efficiency and power output delivered by the system.

Three gas turbine typologies were examined: heavy duty, small size and aeroderivative gas turbines.

For these gas turbine typologies, in steady state working conditions, the verification case was analyzed and the corresponding input variables assumed.

It resulted that the sensitivity parameter values relative to performance are very different according to the input variable considered. Furthermore, the sensitivity parameter values, for an assigned variable, are different for each of the three examined typologies of gas turbines.

It was verified that percentage power output and conversion efficiency variations versus percentage variation of each variable is substantially linear for all the variables analyzed. This permits the employment of the sensitivity parameter for evaluating the percentage performance variations for assigned percentage variations of input variables.

It also resulted that many of the considered variables have the same sensitivity parameter value if it is relative to power or conversion efficiency. This is important because it simplifies the sensitivity parameter calculation, particularly for the complex energy systems.

Moreover, the sensitivity parameter trend versus the input variable value, is substantially the same for the three gas turbine typologies considered.

In conclusion, the sensitivity parameter evaluation is interesting since it establishes how much the numerical value of a quantity resulting from the calculation is affected by a quantity assumed as input and by its numerical value.
Back Fitting Maintainability Into a Gas Turbine Generator Set
Authors: Russom Dennis M. , Masincup William E.
Published: December 2014

The Allison Model AG9130 Ship Service Gas Turbine Generator Set was designed to meet specifications for the DDG 51 Class destroyer of the U.S. Navy. The specifications called for a “turnkey” unit which required only fluid and electrical interfaces with the ship to operate. The fitting of all of the controls, voltage regulating and ancillary equipment on to a single foundation resulted in a cluttered and difficult to maintain set. This paper discusses the program initiated by the Navy to improve the maintainability of the AG9130. It details the changes which have already been made and those currently proposed. It also provides some insight into possible future modifications.
The Performance of a Centrifugal Compressor With High Inlet Prewhirl
Authors: Whitfield A. , Abdullah A. H.
Published: December 2014

The performance requirements of centrifugal compressors usually include a broad operating range between surge and choke. This becomes increasingly difficult to achieve as increased pressure ratio is demanded. In order to suppress the tendency to surge and extend the operating range at low flow rates inlet swirl is often considered through the application of inlet guide vanes. To generate high inlet swirl angles efficiently an inlet volute has been applied as the swirl generator, and a variable geometry design developed in order to provide zero swirl. The variable geometry approach can be applied to progressively increase the swirl or to switch rapidly from zero swirl to maximum swirl. The variable geometry volute and the swirl conditions generated are described.

The performance of a small centrifugal compressor is presented for a wide range of inlet swirl angles. In addition to the basic performance characteristics of the compressor the onset of flow reversals at impeller inlet are presented, together with the development of pressure pulsations, in the inlet and discharge ducts, through to full surge. The flow rate at which surge occurred was shown, by the shift of the peak pressure condition and by the measurement of the pressure pulsations, to be reduced by over 40%.
Numerical Flow Analysis in a Subsonic Vaned Radial Diffuser With Leading Edge Redesign
Authors: Casartelli E. , Saxer A. P. , Gyarmathy G.
Published: December 2014

The flow field in a subsonic vaned radial diffuser of a single stage centrifugal compressor is numerically investigated using a 3D Navier-Stokes solver (TASCflow) and a 2D analysis & inverse-design software package (MISES). The vane geometry is modified in the leading edge area (2D blade shaping) using MISES, without changing the diffuser throughflow characteristics. An analysis of the 2D and 3D effects of two redesigns on the flow in each of the diffuser subcomponents is performed in terms of static pressure recovery, total pressure loss production and secondary flow reduction. The computed characteristic lines are compared with measurements, which confirm the improvement obtained by the leading edge redesign in terms of increased pressure rise and operating range.
A Coupled Mode Analysis of Unsteady Multistage Flows in Turbomachinery
Authors: Silkowski Peter D. , Hall Kenneth C.
Published: December 2014

A computational method is presented for predicting the unsteady aerodynamic response of a vibrating blade row which is part of a multistage turbomachine. Most current unsteady aerodynamic theories model a single blade row isolated in an infinitely long duct. This assumption neglects the potentially important influence of neighboring blade rows. The present ‘coupled mode’ analysis is an elegant and computationally efficient method for modelling neighboring blade row effects. Using this approach, the coupling between blade rows is modelled using a subset of the so-called spinning modes, i.e. pressure, vorticity, and entropy waves which propagate between the blade rows. The blade rows themselves are represented by reflection and transmission coefficients. These coefficients describe how spinning modes interact with, and are scattered by, a given blade row. The coefficients can be calculated using any standard isolated blade row model; here we use a linearized full potential flow model together with rapid distortion theory to account for incident vortical gusts. The isolated blade row reflection and transmission coefficients, inter-row coupling relationships, and appropriate boundary conditions are all assembled into a small sparse linear system of equations which describes the unsteady multistage flow. A number of numerical examples are presented to validate the method and to demonstrate the profound influence of neighboring blade rows on the aerodynamic damping of a cascade of vibrating airfoils.
Turbulent Computations of Internal Flows Using an Anisotropic Diffusivity Model
Authors: Laroche E.
Published: December 2014

The Reynolds analogy is known to give inadequate results for strongly anisotropic turbulence. The use of an anisotropic diffusivity, through the Generalized Gradient Diffusion Hypothesis (GGDH), can partially overcome these deficiencies.

The quality of the heat transfer prediction then relies on the accuracy of the Reynolds stresses estimation, which requires a second order closure. The article presents applications of an Algebraic Stress Model (ASM) coupled with a GGDH to the computations of various internal flows. The computations were done using the NS3D MATHILDA code, developed at ONERA, and largely used in the French aerospace industry.

The study compares the ASM+GGDH results with experimental measurements for heated configurations such as a pipe, a rotor/stator cavity and a channel with ribs, ie covering a wide spectrum of turbine gas internal flows.

The ASM+GGDH model leads to major improvements for the latter case, where the wall fluxes were largely underestimated in a standard k-ε calculation. The difference is due to an overestimation of the turbulent Prandtl number, closer to 0.5 for a mixing layer. The ASM+GGDH model also gives a correct hierarchy of the turbulent heat fluxes for pipe flows, contrary to a standard isotropic model. Concerning the rotor/stator cavity the results are in good agreement with the measurements provided by Owen et al [1].
Multiple Brush Seals in Series
Authors: O’Neill Aideen T. , Hogg Simon I. , Withers Peter A. , Turner Mike T. , Jones Terry V.
Published: December 2014

Rolls-Royce has identified phenomena associated with aeroelastic instability of brush seal bristles, when multiple seals are operated in series at high pressure loading. This paper gives a general overview of test experience to date. A brush seal test facility commissioned by Rolls-Royce at Oxford University is described, along with results from double and triple brush seal tests carried out using the facility. The effect of bristle pack instability on sealing performance is clearly identified in the paper. A design modification aimed at suppressing the instability is described. Results from the Oxford University tests show that the device significantly increases the operating range of multiple seal arrangements.
Some Problems Associated With Design for a Combustion Chamber Provided With Working Air Tube Radiation Screens
Authors: Golinski Joseph A.
Published: December 2014

Indirect fired multistage combined/cogeneration turbine system, fed with pulverized coal, has been considered. Net electric power of the system amounts to about 46 MW. Such a system has already been considered in former paper of the author, No 95-CTP-60, except that water/steam tube radiation screens were discussed. In this paper, on the other hand, a course of calculation as well as an example of air tube radiation screen is presented. The radiation screen supplys heat to the working air for the high-pressure turbine. The middle- and low-pressure turbines are fed with air heated in two convective hot-heat-exchangers placed just behind the combustion chamber.