1. Analytical, numerical and experimental performance prediction of a model-sized wind turbineMatej Fike, Andrej Predin, Gorazd Hren, Marko Pezdevšek, 2024, original scientific article Abstract: The present work focuses on the comparison of the capabilities of Blade Element Momentum Theory, with and without the high induction factor value model and Computational Fluid Dynamics modelling in relation to experimental measurements of the power coefficient for a model-sized horizontal axial wind turbine. Initially, an analytical investigation was performed to obtain the power coefficient curve. Furthermore, three-dimensional numerical simulations were performed, where a lot of effort was devoted to the preparation of a low y+ structured mesh. Analytical and numerical results of the power coefficient were compared with experimental results, which were obtained with our own conducted experiments in the wind tunnel. The most significant conclusions are that the classic BEM method deviates from measured data in the entire range of tip speed ratios, the BEM method with Spera correction predicts a significantly better agreement with experimental measurements compared to the classic BEM method, especially the part where the power coefficient decreases and finally that CFD computations can accurately predict the performance of wind turbines and compute the flow around an aerofoil of the blade.
Keywords: BEM method, CFD, measurements, wind turbine
Published in DKUM: 06.11.2025; Views: 0; Downloads: 1
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2. Improving electricity generation during the product reaction loop and the use of exhaust gas for co-product production using polyethylene waste and flue gas or woodAnita Kovač Kralj, 2022, original scientific article Abstract: More energy-efficient industries could reduce the problems of pollution, global warming,
energy security, and fossil fuel depletion, including processing waste into raw materials and more
efficient energy cogeneration. This research project considers the novelties of the upgraded electricity
cogeneration technique, including one open gas turbine during the high-pressure product reaction
loop and a second turbine during the exhaust gas for co-product production with only one compressor.
The upgraded electricity cogeneration was carried out in two steps and based on the productive use of
otherwise useless polyethylene waste, flue gas, and wood. The first step can simulate the simulation
model from the existing product production with well-known technology and process units using
the Aspen Plus® simulator. The maximum available electricity cogeneration can previously be
determined from the thermodynamics of the products and co-products, and an existing energy unit’s
characteristic capacity. In the second step, conventional natural gas can be replaced with waste
as the raw materials by using the same simulated model from the first step, including electricity
cogeneration using the gas turbines during the high-pressure reaction loop, and the exhaust gas as the
co-product with only one compressor. This research on electricity generation is based on processes
that include the pressure drop during the product reaction loop. This approach is illustrated using an
existing methanol production process, using wastes as sustainable raw materials, including electricity
cogeneration during the reaction loop and exhaust gas, generating a possible increase in annual profit
of 7.28 MEUR/a.
Keywords: waste recovery, cogeneration, exothermic reactor, gas turbine, exhaust gas, combined compressor
Published in DKUM: 15.05.2025; Views: 0; Downloads: 6
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3. Theoretical and experimental investigations of a water hammer in Sava river Kaplan turbine hydropower plantsAnton Bergant, Jernej Mazij, Jošt Pekolj, 2024, original scientific article Abstract: This paper deals with critical flow regimes that may induce an unacceptable water hammer in the Sava River Kaplan turbine hydropower plants. The rigid water hammer model is introduced first. The computational results are then compared with the results of measurements in two distinct hydropower plants (HPP): (i) The refurbished and upgraded Medvode HPP, and (ii) The newest Brežice HPP. Comparisons of the computed and measured results are examined for normal operating regimes. The water hammer in the two power plants is controlled by appropriate adjustment of the wicket gates and runner blades closing/opening manoeuvres. The agreement between the computed and measured results is reasonable.
Keywords: hydropower plant, Kaplan turbine, Sava River, water hammer, validation
Published in DKUM: 11.04.2025; Views: 0; Downloads: 40
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4. Vetrne elektrarne na Goliču : diplomsko deloJan Nečemer, 2024, undergraduate thesis Abstract: Diplomsko delo predstavlja projekt vetrne elektrarne na območju Goliča. V začetnih poglavjih je opisano samo delovanje vetrnih elektrarn ter razlike med vetrnimi elektrarnami moči 3,45 MW ter 6,2 MW. V nadaljevanju sledi podroben opis predlaganih variant postavitve ter posamezne analize na tem območju.
Keywords: Vetrna elektrarna, vetrne turbine moči 3, 45 MV, 6, 2 MV, daljnovod, obnovljivi viri energije.
Published in DKUM: 13.02.2025; Views: 0; Downloads: 41
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5. Numerical analysis of a wind turbine blade with different softwareGorazd Hren, 2019, original scientific article Abstract: The development of wind power generation technology recognises the wind turbine blade design and manufacturing as crucial for its performance. The laboratory size wind turbine blade was analysed, considering the 3D printing plastic material for blades. Applying the structural dynamic equations of blades, the aero-elastic model of the rotating rotor and the numerical simulation method of the deflections are presented under the aerodynamic loads and centrifugal forces. Based on the parameters of aerofoil and the geometrical parameters of blade, 3D model of the blade was established with the modelling software. Then the model was introduced into computational flow dynamics software to carry out the loads on the blade and further into numerical structural analysis. The analysis was performed in two different software packages. Design of wind turbine blades depends on high precision, reliable and robust numerical predictions of performance where the plug-in software is found to be inadequate for nontrivial problems.
Keywords: computational fluid dynamics, numerical analysis, structural analysis, wind turbine blade
Published in DKUM: 22.02.2024; Views: 332; Downloads: 70
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6. Experimental and Numerical Research of Micro Wind Turbine for Low Wind SpeedsMatej Fike, Marko Pezdevšek, Andrej Predin, Gorazd Hren, 2019, published scientific conference contribution Abstract: In this paper, experimental and numerical study of micro wind turbine for low wind speeds is presented. Numerical simulations were performed for two turbines with different blades at various wind speeds. The first geometry was NTNU turbine and the second was modified NTNU turbine with shorter blades. Results from the numerical study showed that more efficient with higher power coefficient is turbine with modified blades.
Keywords: wind turbine, NREL S826, CFD, power coefficient, structured mesh
Published in DKUM: 04.12.2023; Views: 301; Downloads: 48
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7. Reversible pump-turbines - a study of pumping mode off-design conditionsUroš Ješe, Aleš Skoták, 2020, original scientific article Abstract: The role of pumped storage power plants (PSP) in electrical grid systems has been changing in recent years. Demands for switching from pumping to generating mode are becoming increasingly frequent. Moreover, the operating ranges of the reversible pump-turbines used in PSP systems are becoming wider in order to use the PSP as a regulator and a stabilizer of the electrical grid. The primary challenges in the development of pump-turbines are the hydraulic instabilities that occur in pumping and generating modes. The present paper focuses on partial load pumping mode instabilities, such as cavitation and rotating stall. Modern tools, such as CFD, are used for the analysis of the phenomena along with conventional experimental approaches. Rotating stall has been investigated in hydraulic laboratory experimentally and reproduced numerically using commercial CFD code. Three rotating stall cells with a rotational frequency of 2.5% of nominal pump-turbine frequency have been identified. Cavitating vortices related to rotating stall were found in the guide vanes region. Both phenomena indicate highly unstable and potentially dangerous operating conditions that need to be investigated in detail. Understanding the causes for the instabilities will lead to an improved pump-turbine design that will enable safer, more flexible and more reliable operating with fewer unwanted instabilities.
Keywords: pump-turbine, rotating stall, cavitation, Pumping mode instabilities
Published in DKUM: 01.12.2023; Views: 392; Downloads: 23
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8. Off-design flow analysis of cogeneration steam turbine with real process dataDušan Strušnik, Igor Kuštrin, Jurij Avsec, 2022, original scientific article Abstract: This paper presents the concept of reconstruction of the existing coal-fired combined heat and power plant to comply with new European environmental policies. The existing coal-fired boiler will be replaced by two new dual pressure heat recovery steam generators, which will utilize the exhaust gas heat from two new gas turbines. The steam from the heat recovery steam generators will be fed to the existing steam turbine. After the reconstruction, the nominal turbine inlet steam mass-flow of 40 kg/s will be reduced to 30 kg/s. During periods of low heat demand, only one gas turbine and one heat recovery steam generator will be in operation and the live steam mass-flow may drop even to 12 kg/s. Prior to the reconstruction, dedicated tests of the existing steam turbine were carried out using the steam from the existing coal-fired boiler. The goal of the test was to verify the viability of operation with such an extremely low mass-flow. The results of tests show that such operation is possible but inefficient from a power generation point of view. Besides this, the turbine control algorithm needs to be accommodated to this extreme operating regime and additional measures like displacement of the extraction points and steam cooling will be required to control the temperature of the steam extractions. The novelty of this paper is using real prereconstruction process data for the assessment of feasibility and efficiency of the post-reconstruction operation of a combined heat and power turbine.
Keywords: cogeneration, control valves, exhaust gas, heat recovery, steam turbine
Published in DKUM: 30.10.2023; Views: 248; Downloads: 26
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9. Obratovalne karakteristike modela vetrne turbine v cevi in v prostem toku : diplomsko deloKlementina Cifer, 2022, undergraduate thesis Abstract: Diplomska naloga »Obratovalne karakteristike modela vetrne turbine v cevi in v prostem toku« je zasnovana na ideji, da meritve karakteristik modelov vetrnih turbin v cevi ne dajejo verodostojnih rezultatov, ker hitrostni in tlačni profil v cevi vplivata na karakteristiko.
Meritve so opravljene pod kontroliranimi pogoji v laboratoriju. Z ventilatorjem se je ustvaril veter, ki se mu je z meritvami določila hitrost ter izračunala moč. Električna moč se je določila prek meritev toka in napetosti ter vrtljajev turbine. Mehanska moč se je določila z napetostmi na merilnih trakovih ter z izkustvenimi enačbami.
Rezultati so pokazali, da se modeli v prostem toku obnašajo zelo drugače kot v cevi.
Keywords: vetrne turbine, obratovalne karakteristike, izkoristki, energija vetra, meritve v cevi in v prostem toku, obnovljivi viri energije
Published in DKUM: 29.09.2022; Views: 465; Downloads: 76
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10. Primerjava karakteristik alternativnih vodnih turbin za malo HESimon Trupi, 2019, undergraduate thesis Abstract: Namen diplomskega dela je primerjava karakteristik alternativnih vodnih turbin s karakteristikami klasičnih vodnih turbin za malo hidroelektrarno. Male vodne hidroelektrarne so specifične, predvsem v padcu in pretoku vode, ki jo lahko izkoristimo za proizvodnjo električne energije. V diplomskem delu na konkretnem primeru ugotavljamo učinkovitost in rentabilnost alternativnih vodnih turbin, in ugotavljamo katera je v danem primeru najprimernejša. Ugotovili smo, da je izbrana alternativna turbina ugodna zamenjava za klasično vodno turbino.
Keywords: alternativne vodne turbine, mala hidroelektrarna, obnovljivi viri energije
Published in DKUM: 18.07.2019; Views: 3063; Downloads: 171
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