| 1. |
- Akbari, Keramatollah, 1961-
(författare)
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Simulation of Indoor Radon and Energy Recovery Ventilation Systems in Residential Buildings
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study aims to investigate the effects of ventilation rate, indoor air temperature, humidity and using a heat recovery ventilation system on indoor radon concentration and distribution.Methods employed include energy dynamic and computational fluid dynamics simulation, experimental measurement and analytical investigations. Experimental investigations primarily utilize a continuous radon meter and a detached house equipped with a recovery heat exchanger unit.The results of the dynamic simulation show that the heat recovery unit is cost-effective for the cold Swedish climate and an energy saving of about 30 kWh per floor area per year is possible, while it can be also used to lower radon level.The numerical results showed that ventilation rate and ventilation location have significant impacts on both radon content and distribution, whereas indoor air temperature only has a small effect on radon level and distribution and humidity has no impact on radon level but has a small impact on its distribution.
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| 2. |
- Andrinopoulos, Nikolaos
(författare)
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Development of a test facility for experimental investigation of fluid-structure interaction
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)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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| 3. |
- Aslanidou, Ioanna, et al.
(författare)
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Introduction of a Smartphone Application in an Aeroengine Technology Course
- 2020
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Ingår i: Proceedings of the ASME Turbo Expo 2020, Sep 21-25. - 9780791884157
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Konferensbidrag (refereegranskat)abstract
- The main goal of an engineering course is for the students to achieve the defined educational goals, enhance their problem- solving capabilities and develop the essential engineering mindset. The continuous improvement of a course is essential to maintain its challenging nature while improving the course quality. Adapting the teaching methods used to new types of students can provide a significant improvement in student learning. In that context, a digital tool is employed in an advanced course in Aeroengine Technology. A smartphone application that calculates gas turbine performance is introduced in the course to help students understand some of the key concepts. The purpose of the application is to provide the students with an interactive tool to understand the gas turbine thermodynamic cycle. An exercise regarding this application is assigned to note the performance of different engine technologies used in aircraft propulsion through the years. The assignment with the application is combined with a larger assignment on gas turbine performance. The application is also employed in the final exams of the course. The purpose of this paper is to present the use of the application in the course and to address any challenges that arise in the implementation of the app in the learning process. The employed teaching methods received positive feedback from the students who indicated that the app assignment helped them understand some of the key concepts in the course. After all, the main aim of the use of novel teaching methods should be to make learning more interesting, so that students get more involved in a course.
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| 4. |
- Aslanidou, Ioanna, et al.
(författare)
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Reforming heat and power technology course structure using student feedback to enhance learning experience
- 2021
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Ingår i: International Journal of Mechanical Engineering Education. - : SAGE Publications. - 0306-4190 .- 2050-4586. ; 49:4, s. 410-434
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Tidskriftsartikel (refereegranskat)abstract
- The main outcomes of an engineering course should be for the students to achieve the educational goals, enhance their problem solving capabilities and develop essential skills for their future career. In that context, it is important to understand what motivates the students and what helps them develop an engineering mindset. This paper discusses the improvement of a course with the use of student feedback to motivate students and help them develop essential skills. The purpose of the paper is to provide insight into how different aspects of the course are linked to the students’ growth. Different activities have been integrated in the course over the past years. The effect these have on the student motivation to follow the course and develop skills, knowledge and interest in the subject is discussed through the analysis of student performance, student feedback and the experience of the lecturers. The improvements in the course based on the student feedback were received positively by the students, whose learning experience improved, even though the workload of the course was high. Their motivation to successfully complete the course has also increased through the changes in the delivery of the course and the support by the teachers. The combination of student feedback and teacher experience is key for the improvement of a course, while ensuring that the students develop their engineering knowledge. Therefore, the teachers should strike a balance between helping the students find the solution and encouraging them to think on their own in order to develop essential skills.
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| 5. |
- Gkoutzamanis, Vasilis G., et al.
(författare)
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Conceptual Design and Energy Storage Positioning Aspects for a Hybrid-Electric Light Aircraft
- 2021
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 143:9
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Tidskriftsartikel (refereegranskat)abstract
- This work is a feasibility study of a 19-passenger hybrid-electric aircraft, to serve the short-haul segment within the 200-600 nautical miles. Its ambition is to answer some dominating research questions, during the evaluation and design of aircraft based on alternative propulsion architectures. The potential entry into service (EIS) is foreseen beyond 2030. A literature review is performed to identify similar concepts under research and development. After the requirements' definition, the first level of conceptual design is employed. The objective of design selections is driven by the need to reduce CO2 emissions and accommodate aircraft electrification with boundary layer ingestion engines. Based on a set of assumptions, a methodology for the sizing of the hybrid-electric aircraft is described to explore the basis of the design space, incorporating a parametric analysis for the consideration of boundary layer ingestion effects. Additionally, a methodology for the energy storage positioning is provided to highlight the multidisciplinary aspects between the sizing of an aircraft, the selected architecture (series/ parallel partial hybrid), and the storage characteristics. The results show that it is not possible to fulfill the initial design requirements (600 nmi) with a fully-electric aircraft configuration, due to the farfetched battery necessities. It is also highlighted that compliance with airworthiness standards is favored by switching to hybrid-electric aircraft configurations and relaxing the design requirements (targeted range, payload, battery technology). Finally, the lower degree of hybridization (40%) is observed to have a higher energy efficiency (-12% energy consumption) compared to the higher degree of hybridization (50%) and greater CO2 reduction, with respect to the conventional configuration.
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| 6. |
- Gkoutzamanis, Vasilis, et al.
(författare)
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Thermal energy storage for gas turbine power augmentation
- 2019
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Ingår i: Journal of the Global Power and Propulsion Society. - : Global Power and Propulsion Society. - 2515-3080. ; 3, s. 592-608
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Tidskriftsartikel (refereegranskat)abstract
- This work is concerned with the investigation of thermal energy storage (TES) in relation to gas turbine inlet air cooling. The utilization of such techniques in simple gas turbine or combined cycle plants leads to improvement of flexibility and overall performance. Its scope is to review the various methods used to provide gas turbine power augmentation through inlet cooling and focus on the rising opportunities when these are combined with thermal energy storage. The results show that there is great potential in such systems due to their capability to provide intake conditioning of the gas turbine, decoupled from the ambient conditions. Moreover, latent heat TES have the strongest potential (compared to sensible heat TES) towards integrated inlet conditioning systems, making them a comparable solution to the more conventional cooling methods and uniquely suitable for energy production applications where stabilization of GT air inlet temperature is a requisite. Considering the system’s thermos-physical, environmental and economic characteristics, employing TES leads to more than 10% power augmentation.
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| 7. |
- Kavvalos, Mavroudis, et al.
(författare)
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A Modelling Approach of Variable Geometry for Low Pressure Ratio Fans
- 2019
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Ingår i: International Symposium on Air Breathing Engines, ISABE 2019, Canberra, Australia, 23 - 27 September 2019 Paper No. ISABE-2019-24382.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the development and application of a modelling approach of variable geometry conceptsfor low pressure ratio fans; namely Variable Area Nozzle and Variable Pitch Fan. An enhanced approachfor Outlet Guide Vane pressure loss predictions and an aerothermodynamic analysis of variable pitchconcept are developed and integrated into a multi-disciplinary conceptual engine design framework. Astreamline curvature algorithm is deployed for the derivation of the off-design fan performance map,alleviating scaling issues from higher pressure ratio fan designs. Correction deltas are derived through thevariable pitch analysis for calculating the re-shaped off-design fan performance map. The aforementionedvariable geometry concepts are evaluated in terms of surge margin at engine and aircraft level for a lowpressure ratio aft-fan of a hybrid-electric configuration. Performance assessments carried out suggest thata +8° closing of fan blade cascades leads to a 33% surge margin improvement (with reference being thesurge margin without variable geometry) compared to a 25% improvement achieved by +20% opening thenozzle area at end of runway take-off conditions. Although weight and complexity implications of variablegeometry are not considered, the integrated modelling approach is shown to be able to assess and comparesuch novel engine technologies for low pressure ratio fans in terms of operability.
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| 8. |
- Kladovasilakis, Nikolaos, et al.
(författare)
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Rotor Blade Design of an Axial Turbine using Non-Ideal Gases with Low Real-Flow Effects
- 2017
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 142, s. 1127-1132
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to describe a design methodology for supersonic rotor blade geometry, depending on the working fluid, for a low enthalpy Organic Rankine Cycle (ORC) system. Thus, the working fluid is a non-ideal gas with low impact of real flow effects. An innovate algorithm was developed, in order to generate the two-dimensional geometry of the rotor blade, for various working media. A design method, based on the principle of vortex flow field, was used for the blading design and, for the design of supersonic blades, the method of characteristics was selected as the most optimum. The geometry was tested using a commercial simulation software that uses a pressure-based solving algorithm named SIMPLE (Semi-implicit Method for Pressure-Linked Equations). Key advantages of this procedure are both its simplicity and precision of the results.The above procedure was applied for three working fluids, indicatively isobutane (R-600a), tetrafluroethane (R134a) and a mixture of 15% isobutane – 85% isopentane. Considering the ratio of specific heat capacities as constant, which is a realistic assumption for the operating conditions of these systems, the algorithm produces three different blade geometries. Results comparison indicates that every working fluid, for the same operating conditions and for the same design options, has a significantly differentiated geometry of the two-dimensional blade. Finally, the calculated total to total isentropic efficiency, for these rotor blades, is almost 92%.
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| 9. |
- Kyprianidis, Konstantinos, et al.
(författare)
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Dynamic performance investigations of a turbojet engine using a cross-application visual oriented platform
- 2008
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Ingår i: Aeronautical Journal. - 0001-9240. ; 112:1129, s. 161-169
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Kyprianidis, Konstantinos G., et al.
(författare)
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EVA : A Tool for EnVironmental Assessment of Novel Propulsion Cycles
- 2008
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Ingår i: <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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Konferensbidrag (refereegranskat)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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