bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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%.
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].
Investigation of Tip Leakage Effects in Transonic Flow Using a Parallel Unstructured Navier-Stokes Code
Authors: Hustad C-W. , Bölcs A. , Wehner M. 
Published: December 2014

Calculated results for tip flow around two different blade configurations are presented and compared with experimental data. The first configuration (case number 1) is a flat-plate profile tested in a linear transonic tunnel — the profile is an idealized representation of the aft-section of some highly curved turbine blades. The second configuration (case number 2) originates from the outer profile on the last-stage-blade of a steam turbine, however it is also reminiscient of a section from a turbine blade with supersonic exit flow. This configuration was tested in an annular cascade at Mach numbers representative of engine operating conditions.
The computed results were obtained using a parallel 3D unstructured Navier-Stokes code. The code runs on a work-station cluster, as well as being optimized for the 256 processor Cray T3D at EPFL: the code is capable of gigaflop performance using more than 3 million cells — adaptive mesh refinement thus allows enhanced resolution within the tip gap region.
For each configuration we have calculated two Runs. In both cases, Run-1 is similar to the experimental conditions, so that direct comparison between measured and calculated results is possible. With case number 1/Run-2 we re-calculated the flow without imposing a prescribed inflow boundary-layer along the sidewall. Comparison between the two runs helped reveal how free-stream total pressure can establish itself within the tip gap region. For the second configuration — in the annular cascade — we were interested in observing the influence of relative movement between the blade tip and adjacent sidewall. Hence for case number 2/Run-2 we imposed a circumferential velocity on the adjacent sidewall. This modified the effective sidewall boundary-layer and had a noticeable influence on the development of the tip-leakage flow.
Measurement and Prediction of Tip Leakage Losses in an Axial-Flow Transonic Turbine
Authors: Wehner M. , Bütikofer J. , Hustad C-W. , Bölcs A. 
Published: December 2014

This paper presents a simple method for predicting tip leakage losses in transonic axial-flow turbines. The method is based upon experimental work conducted on a flat plate at 5° incidence and with isentropic exit Mach number of 1.26. The tip gap height was varied from zero up to 15% of chord. Measurements were made (using Laser-2-Focus) of velocity vectors around the tip gap region. These revealed a strong shear layer emerging from the gap onto the suction side of the plate. The relative angle between the leakage flow and the freestream was identified as a key parameter determining the subsequent mixing and overall loss generation. The proposed model applies two-dimensional potential flow analysis to estimate the flow angle as a function of tip gap height and the angle of incidence.
Subsequently, comparisons were made with experimental results obtained in an annular cascade on the outer profile of the last-stage blade of a steam turbine. The predicted tip leakage losses compare favourably with the measured values.
A Prediction Method for the Frictional Torque of a Rotating Disk in a Stationary Housing With Superimposed Radial Outflow
Authors: Gärtner W. 
Published: December 2014

Experimental data from various sources for the frictional torque of a rotating disk in a stationary housing under the influence of a superimposed radial outflow were correlated.
Existing correlations were found to overpredict the frictional torque when the superimposed flow exceeds the pumped flow of the rotating disk. Therefore a new correlation is established for this case to improve the agreement with experimental results. Since the governing equation is an integral which can only be solved numerically the method is installed in a PC-based spread sheet programme for convenient use in the engineering practice.
For throughflow rates less or equal than the pumped flow of the rotating disk an existing correlation is modified to take account of the effect on the frictional torque of the axial distance between the disk and the stationary housing.
Effect of Main Flow Pressure Asymmetry on Seal Characteristics of a Gas Turbine Rotor-Stator System
Authors: Ishida K. , Hamabe K. 
Published: December 2014

The effect of circumferential pressure asymmetry of the main flow on sealing characteristics of a shrouded rotor-stator system has been studied.
Local distribution of seal efficiency was measured using a tracer gas method. Blocks of various height were placed in the main flow path to generate circumferential pressure asymmetry. The range of main flow static pressure asymmetry (the ratio of difference between maximum and minimum pressure to main flow dynamic pressure) was 2% to 38%.
The test results showed that pressure asymmetry of main flow has a dominant effect on seal efficiency, and local distribution of seal efficiency is strongly correlated with pressure asymmetry. An experimental correlation of mean seal efficiency and pressure asymmetry was obtained.
Investigation of the Solidity and the Blade Vibration Behaviour of Unshrouded Centrifugal Compressor Impellers With Different Aerodynamic Design
Authors: Hasemann H. , Weser G. , Hagelstein D. , Rautenberg M. 
Published: December 2014

The efficiency and the characteristics of unshrouded centrifugal compressors depend on the thermodynamic and aerodynamic design of the stage and especially of the impeller. Both, the efficiency and the characteristics, can strongly be influenced by a variation of the geometry of the blade structure.
The design of the leading edge depends on the given inlet flow angle distribution and the outlet part of the blade is fixed by the desired outlet angle distribution. Due to the manufacturing process, the selected material, the solidity and the blade vibration, the restrictions and limitations have to be taken into consideration during the aerodynamic optimization process of the blade geometry.
By means of Finite Element Code computations of the solidity and the vibration behaviour the possibilities, the restrictions and the limits of a modern aerodynamic design especially in the inlet and outlet part of the impeller blades were investigated.
The results of this work could demonstrate the importance of integrating the Finite Element Code computation in the design process — not only to see the limits, but also to try and realize new ideas of design optimization.
Turbine Engine Installed Performance Optimisation With a Multi-Axis Thrust Vectoring Nozzle
Authors: Ulizar Iñaki 
Published: December 2014

Advanced fighter aircraft engine performance improvements associated with the nozzle can represent important thrust gains as well as reductions in fuel consumption, with the consequent mission range extension and superior acceleration capability.
ITP is currently developing a multi-axis Thrust Vectoring Nozzle concept with the necessary exit area independent control capability to allow the engine to operate close enough to its optimum condition over the complete flight envelope and at different power settings. This variation is achieved with an innovative system, instead of using the conventional double actuation system already developed.
In this paper both installed and uninstalled thrust losses have been evaluated for a conventional mono-parametric axi-symmetric nozzle fitted on a low bypass ratio turbofan. The optimum exit to throat area ratio schedules are determined for the complete operating range at Max-Dry and Max-Reheat conditions. Several geometric and Fluid-Dynamic constraints have been considered during the optimisation.
Two axi-symmetric schedules have been identified for the multi-axis Thrust Vectoring Nozzle, resulting in two different exits to throat area ratio independent control ranges. The performance improvements in terms of thrust are presented for both cases, showing that at almost every condition the optimum schedule is achievable.
The computer code developed for nozzle performance has been validated with conventional axi-symmetric Con-Di nozzles showing an excellent agreement between measured and calculated thrust.