Effects of ground and velocity profiles on aerodynamic performances of small-scale vertical-axis wind turbines

The past few decades have been marked by an immense interest of the scientific community in making better use of renewable energy sources, particularly wind energy. One of the suggestions is to increase the number of small-scale vertical-axis wind turbines in urban environment. However, given that they mostly operate in adverse conditions (irregular wind speeds, Earth's boundary layer, vortex trail of surrounding objects), it is necessary to pay special attention to the numerical and experimental estimation of their performances. The conceptual design of small-scale wind turbines usually begins with detailed simulations of the encompassing flow field. Considered medium-solidity wind turbine rotor comprises three straight blades. Its aerodynamic analysis is complex since blades undergo a wide range of angles-of-attack during every rotation. This induces numerous flow instabilities, separation and interaction between the oncoming blade and the vortex trail detached from the previous. Those are some of the main reasons for the decreased efficiency of this type of wind turbines. On the other hand, their main advantages include: structural simplicity, omnidirectional operability as well as operability in "dirty" winds. Three-dimensional numerical simulations of fluid flow around a small-scale vertical-axis wind turbine have been completed for ten different working regimes. Transient computations of incompressible, viscous flow have been performed by finite volume method. Aerodynamic performances of the investigated rotor in idealized, uniform velocity stream and a power-law profile (corresponding to Earth's boundary layer) have also been compared. Computed values of power coefficient indicate that a performance reduction of 1-4 % can be expected in real working conditions

Performance analysis of wind turbines with different characteristics

Growing concerns about global warming, environmental pollution and the rise in the price of fossil fuels have led to an interest in developing renewable and environmentally friendly energy sources, such as wind, solar, geothermal, hydrogen and biomass as a replacement for fossil fuels. Therefore, the research of renewable energy, and wind energy in particular, is in constant expansion. Wind energy can provide appropriate solutions to the global climate and energy crisis. The use of wind energy basically eliminates the emission of harmful gases such as CO2, SO2 as in traditional coal-fired power stations or radioactive material waste in nuclear power plants. There has been a tremendous increase in wind energy worldwide over the last three decades. In 2009, the global yearly installed wind power reached 37 GW, bringing the total wind capacity to 158 GW. As the most promising renewable, clean and most reliable source of clean energy, it is expected to occupy a much larger part in electricity distribution all over the world. Wind turbines are types of power plants that use renewable energy, wind, to generate electricity. The purpose of this paper is to analyze wind turbine with vertical axis - VAWT, that have two or three blades. Two methods were used for preliminary aerodynamic studies and they are BEM - Blade Element Momentum and DMS - Double Multiple Streamtube, usually adopted for early turbine design and rating. The program used in this work is QBlade. Obtained results enable the comparison of computed power curves of different geometries

Analiza performansi vetroturbina različitih aeroprofila

Rastuća zabrinutost zbog globalnog zagrevanja, zagađenja životne sredine i poskupljenja fosilnih goriva doveli su do interesovanja za razvoj obnovljivih i ekološki prihvatljivih izvora energije. Stoga istraživanja u oblasti obnovljivih izvora, posebno energije vetra, postaju izuzetno aktuelna. U radu je izvršena aerodinamička analiza vetroturbina sa vertikalnom osom obrtanja - VAWT, koje imaju različite aeroprofile. Korišćene su dve metode BEM - Blade Element Momentum i DMS - Double Multiple Streamtube, obično usvojene za rani dizajn i ocenu turbina. U radu je korišćen program Qblade, a dobijeni rezultati snage u zavisnosti od brzine vetra omogućuvaju upoređivanje performansi vetroturbine

Određivanje modifikovanog profila brzine pomoću proračuna opstrujavanja i veštačkih neuronskih mreža

Efikasno iskorišćenje energije vetra (kao jednog od najzastupljenijih obnovljivih izvora energije) je danas veoma aktuelna tema. Mnogo se radi na poboljšanju aerodinamičkih performansi vetroturbina u urbanim sredinama gde je raspoloživi prostor ograničen i postoji mnogo okolnih objekata koji mogu lokalno da unaprede ili unazade nadolazeći profil brzine. Iz tog razloga, često se postavljaju pomoćne geometrije (koncentratori) koje treba da usmere ili povećaju brzinu kroz rotor. Rad prikazuje olakšano određivanje takvog modifikovanog (ubrzanog) profila brzine pomoću sprege numeričkih simulacija opstrujavanja koncentratora i veštačkih neuronskih mreža. Geometrija koncentratora je parametrizovana da bi se postiglo najveće moguće ubrzanje za uslove na određenoj lokaciji

Optimizacija koncentratora vazduha vetroturbina sa vertikalnom osom obrtanja

Neki od osnovnih problema savremenog društva su klimatske promene, globalno zagrevanje, zagađenje i sl. Većom eksploatacijom obnovljivih izvora energije, a naročito energije vetra, moguće je donekle smanjiti negativne efekte povećanja energetskih potreba. Jedan od mogućih načina boljeg iskorišćenja resursa vetra je postavljanje povećanog broja vetroturbina u urbane sredine. Međutim, kako one tada funkcionišu u nepovoljnim radnim uslovima (neravnomernoj i promenljivoj brzini, Zemljinom graničnom sloju, vrtložnom tragu okolnih objekata), potrebno je paralelno razvijati elemente kojima je moguće lokalno povećati brzinu neporemećenog, nadolazećeg strujnog polja. U tu svrhu, moguće je instalirati koncentrator vazduha, posebno projektovan za vetroturbine sa vertikalnom osom obrtanja. Predloženi koncentrator je koničnog oblika. Njegove geometrijske karakteristike moguće je dodatno optimizovati u zavisnosti od same vetroturbine ali i uslova na lokaciji na koju se postavlja. Odlikuju ga jednostavnost i operabilnost u svim pravcima duvanja vetra. Rad opisuje izvršene ravanske numeričke simulacije strujnog polja oko koncentratora vazduha sa ciljem definisanja njegovog optimalnog oblika, a u zavisnosti od zadatog prečnika i visine vetroturbine kao i nominalne vrednosti neporemećene brzine vetra. Proračuni su izvršeni metodom konačnih zapremina uz pretpostavke nestišljivog, viskoznog fluida. Rezultati su dati u obliku raspodela brzine kao i brojnih vizuelizacija strujnog polja. Optimizacija nekoliko osnovnih geometrijskih karakteristika koncentratora izvršena je na osnovu proračunatih aerodinamičkih performansi kao i ravnomernosti rezultujućih profila brzine

The usage of 3D printing in the analysis of the product design: Case: Electronic enclosure of compact pressure transmitter

Aditivna proizvodnja uključuje izradu proizvoda složene geometrije u relativno malim količinama, kao i izradu alata i kalupa za masovnu proizvodnju. Aditivnom proizvodnjom realizuju se modeli prema digitalnom prikazu, a primena je ogromna u različitim industrijskim sektorima. U poređenju sa tradicionalnom proizvodnjom, glavni parametri u odabiru aditivne tehnologije su: ušteda energije, smanjenje otpada, smanjenje upotrebe većeg broja alata, kao i optimizacija dizajna. Aditivna proizvodnja ili tehnologija 3D štampe rade na principu dodavanja materijala u slojevima, tj. model se formira od slojeva rastopljenog materijala koji se odmah hladi i očvršćava. 3D štampa omogućava čestu i jednostavnu modifikaciju modela na zahtev kupca, a pre ulaska modela u samu proizvodnju. Ovo čini komunikaciju na relaciji proizvođač-kupac dosta jednostavnom. Polazni materijal za izradu modela je polilaktična kiselina (PLA). To je ekološki termoplastični poliester koji se prirodno razgrađuje u prirodi. Na mehaničke karakteristike realizovanog modela od PLA značajno utiču različite tehnološke promenljive kao što su: prečnik brizgaljke, debljina definisanog sloja, procentualna vrednost ispune, veličina uzorka koji se puni, brzina punjenja i temperatura proizvodnje. Cilj ovog rada je da se prikaže postupak realizacije kutije elektronike za malogabaritni transmiter pritiska na 3D štampaču. Time se projektantu daje mogućnost da ispravi postojeće greške, modifikuje proizvod prema zahtevima krajnjih korisnika i na kraju daje polazna osnova za realizaciju prototipa novog proizvoda.Additive manufacturing involves manufacturing of products with complex geometry in relatively small quantities, as well as the tools and molds manufacturing for mass production. With additive manufacturing, digital models are being realized and implementation is huge in various industrial sectors. Compared to traditional manufacturing, the main parameters in the choice of additive technology are: energy savings, waste reduction, reduced use of more tools and optimization of design. Additive manufacturing or 3D printing technology works on the principle of adding material in layers, i.e. the model is formed from layers of molten material that is immediately cooled and solidified. 3D printing allows to work with customers to solve design problems before embarking on a launch production. The starting material for the model is polyactic acid (PLA). It is an eco-friendly thermoplastic polyester, that breaks down naturally. The mechanical characteristics of the realized PLA model are significantly influenced by various technological variables, such as following: nozzle diameter, thickness of defined layer, percentage of fill, sample size to be filled, filling rate and production temperature. The aim of this paper is to present the process of realization of an electronics enclosure for a compact pressure transmitter on a 3D printer. This gives the designer the possibility to correct existing errors, modify the product according to the wishes of the end users and finally provides a starting point for the prototype of new product

The usage of 3D printing in the analysis of the product design: Case – Electronic enclosure of compact pressure transmitter

Aditivna proizvodnja uključuje izradu proizvoda složene geometrije u relativno malim količinama, kao i izradu alata i kalupa za masovnu proizvodnju. Aditivnom proizovnjom realizuju se modeli prema digitalnom prikazu, a primena je ogromna u različitim industrijskim sektorima. U poređenju sa tradicionalnom proizvodnjom, glavni parametri u odabiru aditivne tehnologije su: ušteda energije, smanjenje otpada, smanjenje upotrebe većeg broja alata, kao i optimizacija dizajna. Aditivna proizvodnja ili tehnologija 3D štampe rade na principu dodavanja materijala u slojevima, tj. model se formira od slojeva rastopljenog materijala koji se odmah hladi i očvršćava. 3D štampa omogućava čestu i jednostavnu modifikaciju modela na zahtev kupca, a pre ulaska modela u samu proizvodnju. Ovo čini komunikaciju na relaciji proizvođač-kupac dosta jednostavnom. Polazni materijal za izradu modela je polilaktična kiselina (PLA). To je ekološki termoplastični poliester koji se prirodno razgrađuje u prirodi. Na mehaničke karakteristike realizovanog modela od PLA značajno utiču različite tehnološke promenljive kao što su: prečnik brizgaljke, debljina definisanog sloja, procentualna vrednost ispune, veličina uzorka koji se puni, brzina punjenja i temperatura proizvodnje. Cilj ovog rada je da se prikaže postupak realizacije kutije elektronike za malogabaritni transmiter pritiska na 3D štampaču. Time se projektantu daje mogućnost da ispravi postojeće greške, modifikuje proizvod prema zahterima krajnjih korisnika i na kraju daje polazna osnova za realizaciju prototipa novog proizvoda.Additive manufacturing involves manufacturing of products with complex geometry in relatively small quantities, as well as the tools and molds manufacturing for mass production. With additive manufacturing, digital models are being realized and implementation is huge in various industrial sectors. Compared to traditional manufacturing, the main parameters in the choice of additive technology are: energy savings, waste reduction, reduced use of more tools and optimization of design. Additive manufacturing or 3D printing technology works on the principle of adding material in layers, i.e. the model is formed from layers of molten material that is immediately cooled and solidified. 3D printing allows to work with customers to solve design problems before embarking on a launch production. The starting material for the model is polyactic acid (PLA). It is an eco-friendly thermoplastic polyester, that breaks down naturally. The mechanical characteristics of the realized PLA model are significantly influenced by various technological variables, such as following: nozzle diameter, thickness of defined layer, percentage of fill, sample size to be filled, filling rate and production temperature. The aim of this paper is to present the process of realization of an electronics enclosure for a compact pressure transmitter on a 3D printer. This gives the designer the possibility to correct existing errors, modify the product according to the wishes of the end users and finally provides a starting point for the prototype of new product

Computational aerodynamic analysis of a small wind turbine

The growing climate change issues and the ongoing energy crisis stipulate further exploitation of renewable energy sources and the development of systems capable to efficiently generate clean energy. Among the most promising are wind turbines, that come in different shapes and sizes. Small-scale wind turbines are economic and particularly suitable for small consumers and rural areas. They are not too common, and further research into their performance is necessary. This paper focuses on the design and aerodynamic performance of a small horizontal-axis wind turbine. Its rotor geometry is described while its basic aerodynamic coefficients, power and thrust coefficients, are computed by finite volume method in ANSYS Fluent. Flow is assumed as incompressible and viscous, while Reynolds-averaged Navier-Stokes (RANS) equations are closed by different turbulence models. Wind turbine aerodynamic performance is estimated, and different flow visualizations are provided, particularly focusing on the wind turbine wake

Simulating transitional and turbulent flow around airfoils at medium angles-of-attack

Investigated topic of the presented research is transitional and turbulent flow around smallscale propeller blade airfoils that are characterized by small chords, low speeds and therefore, low Reynolds numbers. Here, an airfoil of medium relative thickness designed for nominal operating conditions of 0.3 MRe is considered. Prior studies by simpler computational models (including panel methods and 2D CFD simulations) have demonstrated that best lift-to-drag ratio (that is the desired working regime) ranging from 60 to 80 can be achieved at angles-of-attack 4-6°. Here, that observation is checked by more advanced turbulence models that incorporate the resolution of at least a portion of turbulence spectrum, in particular transition SST scale-adaptive simulation (SAS). Such complex turbulence models require 3D models and quite refined computational grids. Furthermore, the necessary computational effort is truly enormous due to small time-steps and slow convergence. The conducted computational process is presented and explained. Various obtained results, both quantitative and qualitative, are provided. In the end, it can be concluded that the choice of turbulence modeling (and/or resolving) greatly affects the final output, even at medium angles-of-attack where laminar, attached flow dominates. Distinctive flow phenomena still exist, and in order to be adequately simulated, a comprehensive modeling approach should be adopted