| 1. |
- Andrinopoulos, Nikolaos
(author)
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Development of a test facility for experimental investigation of fluid-structure interaction
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Fluid-structure interaction phenomena are strongly related to the loading appearing on many energy converting components introducing limitations for improving their efficiency. The term “fluid-structure interaction” includes many phenomena with the “shock wave – boundary layer interaction” being one of the most important. This interaction is commonly met in turbomachines where the flow can accelerate enough to become compressible and can cause separation of the boundary layer formed on the structural components of the machine. This results to fluctuating loading on the structure which can lead to its failure due to High Cycle Fatigue (HCF). A vibrating structure in compressible flow can become unstable depending on the sign of the aerodynamic damping that the flow has on the structure. Although the mechanism that causes a structure to become unstable is known, the limits of the stability region are not yet possible to predict with reasonable accuracy. It is therefore necessary to investigate the underlying mechanism of fluid-structure interaction by means of experimental and numerical studies for providing prediction tools regarding the stability change. The present work aims at developing an experimental facility to be used for investigating fluid-structure interaction. The experimental setup is based on the concept of a simplified aeroelastic test case bringing into focus the area of interaction between an oscillating shock wave and a turbulent boundary layer. This work is based on previous research campaigns using the same generic experimental concept but takes the investigation further to higher and so far unexplored reduced frequencies. The experimental setup has been validated regarding its suitability to meet the research objectives by running vibration tests at an initial stage without the effect of flow. The results from the experimental validation of the facility have shown that the design objectives are met. Specifically the vibration response of the test object concerning vibration amplitude and vibration mode shape is desirable; the vibration amplitude is in the range of 0.5mm and the mode shape remains below the 2nd throughout the targeted frequency range (0-250Hz). This makes the facility suitable for simplified investigation of fluid-structure interaction, bringing the shock foot region into focus. Having validated the facility performing vibration tests without flow, tests with flow is the next step to take place. Since the vibration response of the test object has been investigated in detail, tests with flow will reveal the influence of fluidstructure interaction on the dynamic response of the test object. Similarly, the influence of this interaction on the flow side can be assessed by monitoring the flow parameters. As a first step for performing this investigation, the design study and the validation results for the experimental setup are presented in this work.
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| 2. |
- Kyprianidis, Konstantinos, et al.
(author)
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Dynamic performance investigations of a turbojet engine using a cross-application visual oriented platform
- 2008
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In: Aeronautical Journal. - 0001-9240. ; 112:1129, s. 161-169
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Journal article (peer-reviewed)abstract
- This paper presents the development of visual oriented tools for the dynamic performance simulation of a turbojet engine using a cross-application approach. In particular, the study focuses on the feasibility of developing simulation models using different programming environments and linking them together using a popular spreadsheet program. As a result of this effort, a low fidelity cycle program has been created, capable of being integrated with other performance models. The amount of laboratory sessions required for student training during an educational procedure, for example for a course in gas turbine performance simulation, is greatly reduced due to the familiarity of most students with the spreadsheet software. The model results have been validated using commercially available gas turbine simulation software and experimental data from open literature. The most important finding of this study is the capability of the program to link to aircraft performance models and predict the transient working line of the engine for various initial conditions in order to dynamically simulate flight phases including take-off and landing.
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| 3. |
- Kyprianidis, Konstantinos G., et al.
(author)
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EVA : A Tool for EnVironmental Assessment of Novel Propulsion Cycles
- 2008
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In: <em><em></em></em>ASME Turbo Expo 2008: Power for Land, Sea, and AirVolume 2: Controls, Diagnostics and Instrumentation; Cycle Innovations; Electric PowerBerlin, Germany, June 9–13, 2008. - 9780791843123 - 0791838242 ; , s. 547-556
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Conference paper (peer-reviewed)abstract
- This paper presents the development of a tool for EnVironmental Assessment (EVA) of novel propulsion cycles implementing the Technoeconomical Environmental and Risk Analysis (TERA) approach. For nearly 3 decades emissions certification and legislation has been mainly focused on the landing and take-off cycle. Exhaust emissions measurements of NOx, CO and unburned hydrocarbons are taken at Sea Level Static (SLS) conditions for 4 different power settings (idle, descent, approach and take-off) and are consecutively used for calculating the total emissions during the ICAO landing and take-off cycle. With the global warming issue becoming ever more important, stringent emissions legislation is soon to follow, focusing on all flight phases of an aircraft. Unfortunately, emissions measurements at altitude are either extremely expensive, as in the case of altitude test facility measurements, or unrealistic, as in the case of direct in flight measurements. Compensating for these difficulties, various existing methods can be used to estimate emissions at altitude from ground measurements. Such methods, however, are of limited help when it comes to assessing novel propulsion cycles or existing engine configurations with no SLS measurements available. The authors are proposing a simple and fast method for the calculation of SLS emissions, mainly implementing ICAO exhaust emissions data, corrections for combustor inlet conditions and technology factors. With the SLS emissions estimated, existing methods may be implemented to calculate emissions at altitude. The tool developed couples emissions predictions and environmental models together with engine and aircraft performance models in order to estimate the total emissions and Global Warming Potential of novel engine designs during all flight phases (i.e. the whole flight cycle). The engine performance module stands in the center of all information exchange. In this study, EVA and the described emissions prediction methodology have been used for the preliminary design analysis of three spool high bypass ratio turbofan engines. The capability of EVA to radically explore the design space available in novel engine configurations, while accounting for fuel burn and global warming potential during the whole flight cycle of an aircraft, is illustrated.
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| 4. |
- Kyprianidis, Konstantinos G., et al.
(author)
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Thermo-Fluid Modelling for Gas Turbines-Part I: Theoretical Foundation and Uncertainty Analysis
- 2009
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In: ASME TURBO EXPO 2009 Proceedings, GT2009-60092.
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Conference paper (peer-reviewed)abstract
- In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.In Part I of this two-part publication, a comprehensiveanalysis of thermo-fluid modelling for gas turbines is presentedand the fluid models developed are discussed in detail.Common technical models, used for calculating caloricproperties, are compared while typical assumptions made influid modelling, and the uncertainties induced, are examined.Several analyses, which demonstrate the effects of composition,temperature and pressure on caloric properties of workingmediums for gas turbines, are presented. The working mediumsexamined include dry air and combustion products for variousfuels and H/C ratios. The errors induced by ignoringdissociation effects are also discussed.
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| 5. |
- Kyprianidis, Konstantinos G., et al.
(author)
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Thermo-Fluid Modelling for Gas Turbines-Part II : Impact on Performance Calculations and Emissions Predictions at Aircraft System Level
- 2009
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In: ASME TURBO EXPO 2009 Proceedings, GT-2009-60101. ; , s. 483-494
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Conference paper (peer-reviewed)abstract
- In this two-part publication, various aspects of thermo-fluidmodelling for gas turbines are described and their impact onperformance calculations and emissions predictions at aircraftsystem level is assessed. Accurate and reliable fluid modellingis essential for any gas turbine performance simulation softwareas it provides a robust foundation for building advanced multidisciplinarymodelling capabilities. Caloric properties forgeneric and semi-generic gas turbine performance simulationcodes can be calculated at various levels of fidelity; selection ofthe fidelity level is dependent upon the objectives of thesimulation and execution time constraints. However, rigorousfluid modelling may not necessarily improve performancesimulation accuracy unless all modelling assumptions andsources of uncertainty are aligned to the same level. Certainmodelling aspects such as the introduction of chemical kinetics,and dissociation effects, may reduce computational speed andthis is of significant importance for radical space explorationand novel propulsion cycle assessment.This paper describes and compares fluid models, based ondifferent levels of fidelity, which have been developed for anindustry standard gas turbine performance simulation code and an environmental assessment tool for novel propulsion cycles.The latter comprises the following modules: engineperformance, aircraft performance, emissions prediction, andenvironmental impact. The work presented aims to fill thecurrent literature gap by: (i) investigating the commonassumptions made in thermo-fluid modelling for gas turbinesand their effect on caloric properties and (ii) assessing theimpact of uncertainties on performance calculations andemissions predictions at aircraft system level.In Part II of this two-part publication, the uncertaintyinduced in performance calculations by common technicalmodels, used for calculating caloric properties, is discussed atengine level. The errors induced by ignoring dissociation areexamined at 3 different levels: i) component level, ii) enginelevel, and iii) aircraft system level. Essentially, an attempt ismade to shed light on the trade-off between improving theaccuracy of a fluid model and the accuracy of a multidisciplinarysimulation at aircraft system level, againstcomputational time penalties. The results obtained demonstratethat accurate modelling of the working fluid is not alwaysessential; the accuracy/uncertainty for an overall engine modelwill always be better than the mean accuracy/uncertainty of the individual component estimates as long as systematic errors arecarefully examined and reduced to acceptable levels to ensureerror propagation does not cause significant discrepancies.Computational time penalties induced by improving theaccuracy of the fluid model as well as the validity of the idealgas assumption for future turbofan engines and novelpropulsion cycles are discussed.
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| 6. |
- Terzis, Alexandros, et al.
(author)
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Comparative Performance Evaluation of a Multistage Axial Fan Assembly
- 2009
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In: XIX International Symposium on Air Breathing Engines (ISABE), (ISABE-2009-1187).
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Conference paper (peer-reviewed)abstract
- Small fans which are primarily axial machines induce the air movement of a relatively large mass flow within comparatively low velocities for reasons of thermal management. In the present investigation six axial fans of the same type were assessed for their structural (inactivity), geometrical and dynamic similarity. The results indicated that the fans including the stators and the rotors were operationally and dynamically similar. A series of experiments was conducted for a single stage, 2-stage and 3-stage fan configurations. The experimental data were used for the derivation of a linear algebraic model, as well as for calibrating a stage stacking model developed by Cranfield University for predicting the overall performance of multi-stage axial flow machines. The comparison between the computed values and the experimental data indicated very good agreement in the entire range of speed lines. The algebraic model can be used with high confidence for predicting the fan performance for rotational speeds where experimental data are not available. The validated stage stacking model can be used for predicting the performance of multi-stage lowvelocity axial fans when experimental data are only available for a single stage.
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