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    Wyświetlanie 1-7 z 7
    Tytuł:
    CFD simulation on wind turbine blades with leading edge erosion
    Autorzy:
    Wang, Yan
    Wang, Liang
    Duan, Chenglin
    Zheng, Jian
    Liu, Zhe
    Ma, Gaosheng
    Powiązania:
    https://bibliotekanauki.pl/articles/2055055.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    wind turbine
    leading edge erosion
    flow field structure
    aerodynamic performance
    Opis:
    Deep understanding on the impacts of leading edge erosion on the performance and flow characteristics of wind turbines is significant for the blade design and wind farms manage- ment. Pitting erosion and three levels of delamination are considered in the present study. The results show that the degrees of leading edge erosion have great influence on the flow separation, tangential force coefficient, normal force coefficient as well as the power output of the wind turbine. Leading edge erosion has the greatest impact on aerodynamics of the wind turbine at 15m/s, where the maximum loss in the power output can reach up to 73.26%.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2021, 59, 4; 579--593
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study on the behavior of streamwise vortices formed between leading edge tubercles in a compressor cascade
    Autorzy:
    Zheng, Tan
    Qiang, Xiao-Qing
    Teng, Jin-Fang
    Feng, Jin-Zhang
    Powiązania:
    https://bibliotekanauki.pl/articles/281149.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    compressor cascade
    flow separation
    leading edge tubercles
    streamwise vortices
    formation mechanism
    Opis:
    A study has been carried out to investigate the formation mechanism and development of streamwise vortices induced by leading edge tubercles in a high speed compressor cascade. The preliminary assessment of the cascade performance in terms of the total pressure loss coefficient shows that the loss reduction is achieved at high incidence angles. A smaller wavelength leads to higher additional losses at the design point, but gives rise to a greater loss reduction at high incidence angles. The modified cascade with a tubercle wavelength of 4% chord achieves the maximum loss reduction of 36.1% at i = 10◦ , as well as the stall angle improvement of 27.6%. The formation mechanism of streamwise vortices is elaborated on the basis of the streamwise vorticity equation, in which the streamwise turning terms may be responsible for the generation of streamwise vortices. Slices of streamwise vorticity at various streamwise locations, combined with vorticity strength distributions, have been presented to study the development of streamwise vortices. The counter-rotating vortices are divided into the crest-induced streamwise vortices (CSVs) and trough-induced streamwise vortices (TSVs). A streamwise vortex pair formed from a part of the CSV sheets behind troughs, is gradually entrained by the TSV pair along the streamwise direction. In addition, the tubercles with a smaller wavelength result in higher streamwise vorticity strength with which the streamwise vortices interact with the flow separation more sufficiently and delay the separation to a greater extent.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2019, 57, 3; 617-629
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical loss analysis in a compressor cascade with leading edge tubercles
    Autorzy:
    Zheng, T.
    Qiang, X.-Q.
    Teng, J.-F.
    Teng, J.-Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/280966.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    compressor cascade
    flow separation
    passive flow control
    leading edge tubercles
    streamwise vortices
    loss analysis
    Opis:
    A numerical analysis of loss has been carried out to explore the loss mechanism of leading edge tubercles in a high speed compressor cascade. Taking the lead from flippers of the humpback whale, tubercles are passive structures of a blade for flow control. Evaluation of the overall performance in terms of entropy increase shows that the loss reduction is achieved both at high negative and high positive incidence angles, while a rise in the loss is obtained near the design point. And a smaller wave number as well as a smaller amplitude results in lower additional losses at the design point. Spanwise and streamwise distributions of pitchwise-averaged entropy increase combined with flow details have been presented to survey the loss development and, subsequently, to interpret the loss mechanism. The tubercle geometry results in the deflection flow and the consequent spanwise pressure gradient. This pressure gradient induces formation of counter-rotating streamwise vortices, transports away the low-momentum fluid near wall from crests towards troughs and leads to local high loss regions behind troughs as well as loss reduction behind the crests in comparison to the baseline. The interaction between these vortices and flow separation by momentum transfer leads to separation delay and the consequent loss reduction at the outlet.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2018, 56, 4; 1083-1095
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Technologia wykonania noska łopaty wirnika nośnego, porównanie trzech technologii
    Technology made the leading edge of the blade carrier, comparison of three technologies
    Autorzy:
    Szymański, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/212665.pdf
    Data publikacji:
    2016
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Lotnictwa
    Tematy:
    preimpregnat
    technologia kompozytowa
    infuzja
    technologia „na mokro"
    krawędź natarcia
    prepreg
    composite technology
    infusion
    wet technology
    leading edge
    Opis:
    Artykuł zawiera opis rodzajów i parametrów materiałów kompozytowych stosowanych w przemyśle lotniczym. Przedstawiono również rozwój technologiczny kompozytów pod kątem ich zastosowania w najbardziej ważnych elementach konstrukcji lotniczych, takich jak kompozytowe łopaty do śmigłowców, poddawane dużym obciążeniom podczas pracy. Porównano trzy główne technologie wykonywania kompozytów: ręczne laminowanie „na mokro" z zastosowaniem worka próżniowego, infuzyjne oraz preimpregnatowe, użyte do wykonania krawędzi natarcia łopaty nośnej. Opisano sposob wykonania struktur lotniczych, w celu minimalizacji porowatości kompozytu w całej objętości. Wymieniono niezbędną aparaturę stosowaną podczas wykonania kompozytów, odpowiedniej dla danej technologii. Przedstawiono rodzaje zastosowanych mieszanek sycących oraz dobór czasu i temperatury w procesie utwardzania w celu odpowiedniego połączenia warstw laminatu podczas jego utwardzania. Wymieniono rowniez główne wady i zalety poszczególnych technologii oraz przedstawiono tendencje rozwoju kompozytów.
    The article contains the types and parameters of composite materials used in the aerospace industry. It also presents technological development of composites for their use in the most important elements of aircraft structures, such as composite blades for helicopters, subjected to high loads during operation. Three major technologies of composites manufacturing were compared: hand layup "wet" using a vacuum bag, infusion and prepregs, used to make the leading edge of the main rotor blade. The method of minimizing the porosity of the composite aircraft structures was explained. The necessary apparatus used during the execution of composites, appropriate for the technology was listed. Different types of resin matrices and optimal selection of time and temperature curing process in order to properly bond the laminate layers during final polymerization are presented. The paper also lists the main pros and cons of each technology and presents trends in the development of composites.
    Źródło:
    Prace Instytutu Lotnictwa; 2016, 3 (244); 153-164
    0509-6669
    2300-5408
    Pojawia się w:
    Prace Instytutu Lotnictwa
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Shape optimization of a hydrofoil with leadingedge protuberances using full factorial sweep sampling and an RBF surrogate model
    Autorzy:
    Nazemian, Amin
    Ghadimi, Parviz
    Powiązania:
    https://bibliotekanauki.pl/articles/135182.pdf
    Data publikacji:
    2020
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    humpback whale flippers
    leading-edge protuberances
    free-form deformation (FFD)
    surrogate model
    CFD
    lift-to-drag ratio (L/D)
    Opis:
    This paper investigates improving the leading-edge of a hydrofoil with sinusoidal protuberances based on its hydrodynamic performance. The original hydrofoil geometry was inspired by the leading edge of the flipper of a humpback whale. A multi-step optimization process was performed for a 634-021 hydrofoil. The free-form deformation technique defined the shape parameters as a variable design, and these parameters included the amplitude of the leading-edge protuberances, which ranged from 0 to 20% of the chord length, and the corrugate span, with 3 and 4 crests. The flow characteristics of a parametric hydrofoil were examined using a CFD solver, and the lift, drag, and lift-to-drag ratio (L/D) were computed as responses to the optimization cycle. To accomplish this, two design study methods were sequentially applied at different angles of attack. A full factorial design sweep tool was applied that went through all parameter value combinations, and an RBF-based surrogate model was constructed to investigate the system behavior. The results indicated the existence of an optimum design point, and the highest L/D ratio was determined to be 10.726 at a 12° angle of attack.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2020, 62 (134); 116-123
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Review of peak signal detection methods in nanosecond pulses monitoring
    Autorzy:
    Achtenberg, Krzysztof
    Mikołajczyk, Janusz
    Szabra, Dariusz
    Prokopiuk, Artur
    Bielecki, Zbigniew
    Powiązania:
    https://bibliotekanauki.pl/articles/221035.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    peak detection
    pulse amplitude
    free space optics
    constant fraction discriminator
    leading edge discriminator
    sample and hold
    ADC
    fast acquisition
    Opis:
    The paper is a review of analog and digital electronics dedicated to monitor nanosecond pulses. Choosing the optimal peak detector construction depends on many factors for example precision, complexity, or costs. The work shows some virtues and limitations of selected peak detection methods, for example standard peak detector with rectifier, sample and hold circuit with triggering units and ADC fast acquisition. However, the main attention is paid to problems of results from effective triggering signal for sample and hold operation. The obtained results allow for designing a peak detector construction as an alternative for costly and very complex fast acquisition systems based on ADC and FPGA technologies.
    Źródło:
    Metrology and Measurement Systems; 2020, 27, 2; 203-218
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Novel analytic-numerical model of free convection: with leading edge considered
    Autorzy:
    Leble, S.
    Lewandowski, W. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1954434.pdf
    Data publikacji:
    2022-02-01
    Wydawca:
    Politechnika Gdańska
    Tematy:
    Navier-Stokes equations
    Fourier-Kirchhoff equations
    free convection
    heat transfer
    isothermal surface
    boundary layer
    vertical plate
    leading edge
    Równania Naviera-Stokesa
    równanie Fouriera-Kirchhoffa
    przenikanie ciepła
    izoterma powierzchni
    warstwa graniczna
    płyty pionowe
    Opis:
    A novel solution of the free convection boundary problem is represent ed in analytical form for velocity and temperature for an isothermal vertical plate, as an example. These fields are built as a Taylor Series in the x coordinate with coefficients as functions of the vertical coordinate (y). We restrict ourselves by cubic approximation for both functions. The basic Navier-Stokes and Fourier-Kirchhoff equations and boundary conditions give links between coefficients and connected with free convection heat transfer phenomen on which define the analytical form of the solution as a function of the Grashof number only. In t he solution the non zero velocity of a fluid flow through a leading edge of the plate is take n into account. The solution in the form of velocity and temperature profiles is numerically evaluated and illustrated for air.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2014, 18, 2; 167--185
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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