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    Wyświetlanie 1-9 z 9
    Tytuł:
    A Numerical Study of The Heat Transfer Intensification Using High Amplitude Acoustic Waves
    Autorzy:
    Rulik, S.
    Wróblewski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/177492.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cavity noise
    sound wave cooling
    flow over a cavity
    transient cooling
    blade cooling intensification
    Opis:
    The current practice in the efforts aiming to improve cooling conditions is to place emphasis on the application of non-stationary flow effects, such as the unsteady jet heat transfer or the heat transfer intensification by means of a high-amplitude oscillatory motion. The research presented in this paper follows this direction. A new concept is put forward to intensify the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by a properly shaped fixed cavity or group of cavities. The sound generated by the cavity is a phenomenon analysed in various publications focused on the methods of its reduction. The phenomenon is related to the feedback mechanism between the vortices flowing from the leading edge and the acoustic waves generated within the cavity. The acoustic waves are generated by the interaction between the vortices and the cavity walls. Strong instabilities can be observed within a certain range of the free flow velocities. The investigations presented in this paper are oriented towards the use of the phenomenon for the purposes of the heat transfer process intensification. The first part of the work presents the numerical model used in the analysis, as well as its validation and comparison with empirical relations. The numerical model is constructed using the commercial CFD Ansys CFX-16.0 commercial program. The next part includes determining of the relationship between the amplitude of the acoustic oscillations and the cooling conditions within the cavity. The calculations are performed for various flow conditions.
    Źródło:
    Archives of Acoustics; 2018, 43, 1; 31-47
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Numerical Study of the Relation Between the Acoustic Generator Geometry and the Heat Transfer Conditions
    Autorzy:
    Rulik, S.
    Wróblewski, W.
    Rusin, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/140076.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cavity noise
    cavity cooling
    new cooling techniques
    acoustic cooling
    acoustic waves
    heat transfer in cavities
    thermoacoustics
    szum aerodynamiczny
    chłodzenie zewnętrzne
    nowe techniki chłodzenia
    chłodzenie akustyczne
    fale akustyczne
    przepływ ciepła
    termoakustyka
    Opis:
    Modern gas turbine systems operate in temperatures ranging from 1200°C to even 1500°C, which creates bigger problems related to the blade material thermal strength. In order to ensure appropriate protection of the turbine blades, a sophisticated cooling system is used. Current emphasis is placed on the application of non-stationary flow effects to improve cooling conditions, e.g., the unsteady-jet heat transfer or the heat transfer enhancement using high-amplitude oscillatory motion. The presented research follows a similar direction. A new concept is proposed of intensification of the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by an appropriately shaped fixed cavity or group of cavities. The phenomenon is related to the coupling mechanism between the vortex shedding generated at the leading edge and the acoustic waves generated within the cavity area. Strong instabilities can be observed within a certain range of the free flow velocities. The presented study includes determination of the relationship between the amplitude of acoustic oscillations and the cooling conditions within the cavity. Different geometries of the acoustic generator are investigated. Calculations are also performed for variable flow conditions. The research presented in this paper is based on a numerical model prepared using the Ansys CFX-17.0 commercial CFD code.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 1; 5-26
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metamodel-Based Optimization of the Labyrinth Seal
    Autorzy:
    Rulik, S.
    Wróblewski, W.
    Frączek, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/140287.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    labyrinth seal
    metamodel optimization
    neural network
    genetic algorithm
    evolutionary algorithm
    CFD optimization
    uszczelnienie labiryntowe
    optymalizacja oparta na metamodelu
    sieć neuronowa
    algorytm genetyczny
    algorytm ewolucyjny
    optymalizacja CFD
    Opis:
    The presented paper concerns CFD optimization of the straight-through labyrinth seal with a smooth land. The aim of the process was to reduce the leakage flow through a labyrinth seal with two fins. Due to the complexity of the problem and for the sake of the computation time, a decision was made to modify the standard evolutionary optimization algorithm by adding an approach based on a metamodel. Five basic geometrical parameters of the labyrinth seal were taken into account: the angles of the seal’s two fins, and the fin width, height and pitch. Other parameters were constrained, including the clearance over the fins. The CFD calculations were carried out using the ANSYS-CFX commercial code. The in-house optimization algorithm was prepared in the Matlab environment. The presented metamodel was built using a Multi-Layer Perceptron Neural Network which was trained using the Levenberg-Marquardt algorithm. The Neural Network training and validation were carried out based on the data from the CFD analysis performed for different geometrical configurations of the labyrinth seal. The initial response surface was built based on the design of the experiment (DOE). The novelty of the proposed methodology is the steady improvement in the response surface goodness of fit. The accuracy of the response surface is increased by CFD calculations of the labyrinth seal additional geometrical configurations. These configurations are created based on the evolutionary algorithm operators such as selection, crossover and mutation. The created metamodel makes it possible to run a fast optimization process using a previously prepared response surface. The metamodel solution is validated against CFD calculations. It then complements the next generation of the evolutionary algorithm.
    Źródło:
    Archive of Mechanical Engineering; 2017, LXIV, 1; 75-91
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analiza sprawności obiegu cieplnego ultra-nadkrytycznego bloku kondensacyjnego dla szeregowej konfiguracji skraplaczy
    The influence of application of a serial condenser for the ultra-critical power unit
    Autorzy:
    Wróblewski, W.
    Łukowicz, H.
    Rulik, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/173112.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    obieg cieplny
    ultra-nadkrytyczny blok kondensacyjny
    skraplacz
    thermal cycle
    ultra-supercritical condensing unit
    condenser
    Opis:
    Przedmiotem niniejszej analizy jest dobór parametrów oraz konfiguracji układu chłodzenia dla bloku ultra-nadkrytycznego o mocy 900 MW. Analizę pracy skraplacza oparto o amerykańską normę Heat Exchange Institute. Przedstawione badania obejmują porównanie dwóch wariantów układu chłodzenia, które dotyczą konfiguracji równoległej oraz szeregowej pracy skraplacza. Układ równoległy jest powszechnie stosowany, a rozdzielenie strumienia wody chłodzącej na poszczególne skraplacze bądź sekcje skraplacza daje w nich jednakowe warunki kondensacji. W przypadku konfiguracji szeregowej całkowity strumień wody chłodzącej przepływa szeregowo przez skraplacz pierwszy, a następnie trafia do skraplacza drugiego. Takie rozwiązanie w stosunku do układu równoległego powoduje wzrost sprawności obiegu wynikający z obniżenia całkowitego ciśnienia w skraplaczu. Konfiguracja szeregowa powoduje, że obniżeniu ciśnienia w pierwszej sekcji skraplacza towarzyszy nieznaczny wzrost ciśnienia w drugiej sekcji skraplacza. Stąd też pole powierzchni wymiany ciepła drugiej sekcji skraplacza jest często zwiększone w celu poprawy warunków kondensacji. Niniejsza praca stanowi uzupełnienie oraz rozszerzenie przedstawionych w literaturze analiz. Dotyczy to w szczególności dokładnego uwzględnienia wpływu straty wylotowej turbiny niskoprężnej na wartość uzyskiwanych przyrostów sprawności obiegu cieplnego w przypadku konfiguracji szeregowej pracy skraplacza.
    The aim of this paper is the selection of parameters and configuration of the cooling system of 900 MW ultra-supercritical power unit. The performed analysis of the condenser was based on the Heat Exchange Institute standard. The presented studies include comparison of two variants of cooling water system. Both, the parallel and serial configuration of the condenser was investigated. Parallel cooling water system is widely used, and the separation of the cooling water stream into individual sections of the condenser or condensers give equal conditions of condensation. In the case of a serial configuration, the total flow of cooling water flows through the first condenser and then it goes to the second condenser. This causes the decrease of pressure in the first and increase of pressure in the second condenser. Hence, the heat exchange surface area of the second condenser is often increased to improve the conditions of condensation. This paper extends the analyzes presented in the literature. It particularly concerns the investigation of influence of the exhaust loss for obtained efficiency gains in case of the serial configuration of condenser.
    Źródło:
    Archiwum Energetyki; 2013, 43, 1/2; 117-127
    0066-684X
    Pojawia się w:
    Archiwum Energetyki
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    What-if analysis of the labyrinth seal of the gas turbine rotor tip
    Autorzy:
    Wróblewski, W.
    Bochon, K.
    Borzęcki, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/175228.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    gas turbine
    labyrinth seal
    honeycomb
    CFD
    Opis:
    This paper presents a preliminary, numerical what-if analysis of selected geometrical parameters of the tip seal of the last stage of an aircraft engine turbine and the impact of the parameters on the leakage mass ow. The analysis is a part of the task of improving the rotor tip seal conguration in aircraft turbines. Calculations were carried out using the commercial computational uid dynamics code. A straight-through seal with two leaning ns and a honeycomb land was analysed. The computational model was prepared based on some simplications introduced to improve the eciency of the calculations. The rotor entire blade-to-blade channel was analysed, while the seal pitch was reduced to the dimensions of two honeycomb cells. The geometry of the ns themselves was simplied too. In the original variant, the n tips had caps to protect them from wear (shape deformation) due to rubbing. In the simplied model, the caps were omitted. The simplications did not change the leakage mass ow signicantly. Several variants of changes in the basic geometrical parameters of the seal were analysed to assess their eect on the leakage mass ow for altered ow conditions. Parameters such as the n thickness, the n inclination angle and the position of the ns and of the entire labyrinth were analysed. The best seal variant was selected, the ow phenomena were commented on and some points in the design of this type of the labyrinth seal were discussed.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2017, 136; 3-21
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Models for water steam condensing flows
    Autorzy:
    Wróblewski, W.
    Dykas, S.
    Chmielniak, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/240446.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    dysza Lavala
    kondensacyjne modele przepływu
    para wylotowa
    condensing flow models
    Laval nozzle
    wet steam
    Opis:
    Abstract The paper presents a description of selected models dedicated to steam condensing flow modelling. The models are implemented into an in-house computational fluid dynamics code that has been successfully applied to wet steam flow calculation for many years now. All models use the same condensation model that has been validated against the majority of available experimental data. The state equations for vapour and liquid water, the physical model as well as the numerical techniques of solution to flow governing equations have been presented. For the single-fluid model, the Reynolds-averaged Navier-Stokes equations for vapour/liquid mixture are solved, whereas the two-fluid model solves separate flow governing equations for the compressible, viscous and turbulent vapour phase and for the compressible and inviscid liquid phase. All described models have been compared with relation to the flow through the Laval nozzle.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 1; 67-86
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Method for Modeling of Acoustic Waves Propagation
    Autorzy:
    Dykas, S.
    Wróblewski, W.
    Rulik, S.
    Chmielniak, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/177994.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    acoustic wave
    fluctuations
    aerodynamic noise
    Euler equations
    Opis:
    In this paper, numerical results of modeling of acoustic waves propagation are presented. For calculation of the acoustic fluctuations, a solution of the full non-linear Euler equation is used. The Euler equations are solved with the use of a numerical scheme of third-order accuracy in space and time. The paper shows a validation process of the described method. This method is suitable also for an aerodynamic noise assessment on the basis of unsteady mean flow field data obtained from a CFD calculations. In such case this method is called a hybrid CFD/CAA method. The proposed method is numerically decoupled with CFD solution, therefore the information about the mean unsteady flow field can be obtained using an arbitrary CFD method (solver). The accuracy of the acoustic field assessment depends on the quality of the CFD solutions. This decomposition reduces considerably the computational cost in comparison with direct noise calculations. The presented Euler acoustic postprocessor (EAP) has been used for modeling of the acoustic waves propagation in a cavity and in the flow field around a cylinder and an aerodynamic profile.
    Źródło:
    Archives of Acoustics; 2010, 35, 1; 35-48
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Transient expression assay for optimization of direct gene transfer into cucumber meristem protoplasts by electroporation
    Autorzy:
    Burza, W
    Wochniak, P.
    Wroblewski, T.
    Malepszy, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2048135.pdf
    Data publikacji:
    1995
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    electroporation
    gene transfer
    protoplast
    transient expression
    cucumber
    Cucumis sativus
    Opis:
    The paper presents a new way of obtaining viable and very homogeneous cucumber protoplasts. Protoplasts from cells formed in the shoot tip meristem culture were isolated from suspension. Plasmid pBI121 was introduced using impulse electric field. Effectiveness of transformation process was determined by the transient expression of ß-glucuronidase (GUS) gene, controlled by promotor 35S. The activity of ß-glucuronidase enzyme as a product of GUS reporter gene was estimated by fluorimetric method (JEFFERSON 1987). Parameters of electroporation process were optimized. The transient expression of GUS gene was measured 24 h after electroporation. The highest effectiveness of transformation process was achieved using three electric impulses at the initial voltage of 250-350 V at 10-sec. intervals as a result of discharging a 140 µF capacitor and 50-70 µg × cm⁻³ plasmid DNA in the presence of 50 µg × cm⁻³ carrier DNA. The system presented is an effective method of exogenic DNA transfer, which is indicated by a high transient expression of the reporter gene. In comparison to Agrobacterium tumefaciens and A. rhizogenes, this alternative method of gene transfer can be used for obtaining transgenic cucumber plants.
    Źródło:
    Journal of Applied Genetics; 1995, 36, 1; 1-10
    1234-1983
    Pojawia się w:
    Journal of Applied Genetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Radial fan controlled with impeller movable blades – CFD investigations
    Autorzy:
    Jóźwik, K.
    Papierski, A.
    Sobczak, K.
    Obidowski, D.
    Kryłłowicz, W.
    Marciniak, E.
    Wróbel, G.
    Marciniak, A.
    Wróblewski, P.
    Kobierska, A.
    Frącczak, Ł.
    Podsędkowski, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/175168.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    radial fan control systems
    CFD methods
    radial fan performance
    partial load
    Opis:
    Modern classical power generation systems, based on power plants in Poland, where coal (hard bituminous coal or lignite) is the primary energy source, operate under variable loading conditions. Thus, all machines working in the technological system of the power generation unit are required to be adapted to variable loading, and, consequently, to operate beyond the design point of their performance characteristics. High efficiency of the process requires the efficiency of individual devices to be high, beyond the design point, as well. For both air and exhaust gases fans, an effective control system is needed to attain a high level of efficiency. As a result of cooperation between two institutes from the Faculty of Mechanical Engineering, Lodz University of Technology, and the Vibroson company, a new design of the radial fan with impeller movable blades, which allows for controlling the device operation within a wide range, has been developed. This new design and determination the performance characteristics for two geometrical variants of blades with computational fluid dynamics methods are presented. The obtained results have been compared to the results of the measurements of fan performance curves conducted on the test stand.
    Źródło:
    Transactions of the Institute of Fluid-Flow Machinery; 2016, 131; 17-40
    0079-3205
    Pojawia się w:
    Transactions of the Institute of Fluid-Flow Machinery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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