Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis of unsteady forces acting on a slender cylinder

100%

Ziółkowski P. J. , Witkowski W. , Sobczyk B.

Transactions of the Institute of Fluid-Flow Machinery

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2018

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tom nr 140

23--38

EN

Developments in construction engineering (new materials, construction techniques) facilitate the design of very flexible, light structures with low damping which unfortunately results in higher susceptibility of these structures to wind action. It is therefore necessary to use more accurate scientific tools in the engineering phase of these structures. Analytical methods for considering wind effects on structures encounter difficulties with respect to mathematical formulations of aerodynamic forces. In this paper a 2D numerical model has been described which considers the fluid domain with respect to a cylindrical obstacle. This 2D model has been discretized using the finite volume method, and numerical simulations have been undertaken in order to describe the unsteady flow conditions within the analyzed domain. The simulations have been performed with boundary conditions characterizing the flow past a cylindrical obstacle. The results have been compared with the literature data from similar experiments. On the basis of the flow characteristics obtained, as well as the spatial distributions of the flow parameters, a model for further 3D analyses was selected. Next, a 3D numerical study of unsteady flow forces acting on a slender cylinder has been analyzed. Toward the end, a two-way fluid solid interaction approach has been utilized, which incorporates a computational fluid dynamics approach combined with computational solid dynamics.

2

Determination of turbulence and upper size limit in Jameson flotation cell by the use of computational fluid dynamic modelling

100%

Sahbaz O. , Ercetin U. , Oteyaka B.

Physicochemical Problems of Mineral Processing

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2012

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tom Vol. 48, iss. 2

533-544

EN

In the coarse particle flotation, turbulence which can be treated as energy dissipation rate, is one of the most significant parameters effecting the recovery and grade. Therefore, determination of energy dissipation rate is very beneficial for delineation of coarse particle flotation and determining the maximum floatable particle size in any cell. In this study, Computational Fluid Dynamic (CFD) modelling for the Jameson cell has been carried out to determine the high turbulent regions and the effect on the upper floatable size limit. The CFD modelling has been utilized for determining the flow characteristics and hydrodynamic behaviour of the Jameson flotation cell. In parallel with this purpose the turbulence map of the cell has been determined and energy dissipation rate determined by using the CFD modelling. According to the result acquired from the CFD modelling, there are two main turbulent regions which are mixing zone in the upper part of the downcomer and critical region at the separation tank. While the high turbulence at the mixing zone supplies fine bubbles and fast collection of particles, the turbulence at the separation tank causes the main detachment of the bubble-particle aggregate. Then, the increase in turbulence in the tank causes the decrease of the maximum floatable size of particles. In addition, the average energy dissipation rate in the critical region has been determined and used for estimation of the maximum floatable particle size in the Jameson cell. Moreover, the effect of hydrophobicity has been discussed.

3

Numerical Calculations of WR-40 Boiler Based on its Zero-Dimensional Model

100%

Hernik B.

Chemical and Process Engineering

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2014

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tom 35

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nr 2

173-180

EN

Generally, the temperature of flue gases at the furnace outlet is not measured. Therefore, a special computation procedure is needed to determine it. This paper presents a method for coordination of the numerical model of a pulverised fuel boiler furnace chamber with the measuring data in a situation when CFD calculations are made in regard to the furnace only. This paper recommends the use of the classical 0-dimensional balance model of a boiler, based on the use of measuring data. The average temperature of flue gases at the furnace outlet tk" obtained using the model may be considered as highly reliable. The numerical model has to show the same value of tk" . This paper presents calculations for WR-40 boiler. The CFD model was matched to the 0-dimensional tk" value by means of a selection of the furnace wall emissivity. As a result of CFD modelling, the flue gas temperature and the concentration of CO, CO2, O2 and NOx were obtained at the furnace chamber outlet. The results of numerical modelling of boiler combustion based on volumetric reactions and using the Finite-Rate/Eddy-Dissipation Model are presented.

4

Study of the Process of Hydraulic Mixing in Anaerobic Digester of Biogas Plant

100%

Karaeva J. V. , Khalitova G. R. , Kovalev D. A. , Trakhunova I. A.

Chemical and Process Engineering

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2015

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tom 36

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nr 1

101-112

EN

Two systems of hydraulic mixing in a vertical cylindrical anaerobic digester: standard and modernised are discussed in the paper. Numerical investigations that were carried out are focused on a study of hydrodynamic processes in an aerobic digester using two various systems of hydraulic mixing as well as on analysis of the efficiency of methane fermentation process accomplished under different geometric parameters of an anaerobic digester and systems of hydraulic mixing.

5

CFD analysis of mixing intensity in jet stirred reactors

100%

Gil I. , Mocek P.

Chemical and Process Engineering

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2012

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tom 33

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nr 3

397-410

EN

The homogeneous stirred reactor designed for kinetic studies of the combustion of hydrocarbons with intensive internal recirculation in high temperature combustion chamber is described. The originality of our reactor lies in its construction which allows to intensively mix fuel and flue gases, measure gas temperature as well as obtain samples which can be used to investigate diffusion flames. The cylindrical construction enables to use the reactor in laboratory cylindrical electrically heated ovens. The CFD analysis of the reactors, the mixing parameters (turbulent Peclet number and mixing level) and the volume average temperature in the reactors were elaborated on the basis of the typical dimensions of classical reactors to kinetics research as well as the own reactor design. The results of the analysis allow to reveal advantages of our construction.

6

CFD modelling of hydrogen starvation conditions in a planar Solid Oxide Fuel Cell

100%

Pianko-Oprych P. , Zinko T. , Jaworski Z.

Polish Journal of Chemical Technology

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2017

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tom Vol. 19, nr 2

16--25

EN

The aim of this study was to highlight the interest of using CFD technique as a diagnostic tool of a malfunctioning Solid Oxide Fuel Cells. Hydrogen starvation of a SOFC due to nitrogen dilution is one of the cell dysfunctions and can lead to its degradation. Identification of the starvation point allows to improve cell performance and establish the best conditions for degradation tests. To illustrate a potential of the CFD tool, several simulations of a single planar SOFC and its behaviour under hydrogen starvation were performed and analysed. The results showed that at lower cell voltage values of 0.3 and 0.5 V significant gradients in the electric current were noticed due to a local reduction in hydrogen concentration. The CFD analysis allowed defining desirable mass flow rate of hydrogen to SOFCs to avoid fuel starvation. The model constitutes a helpful tool for optimizing cell design and operational conditions.

7

Hydraulic Mixing Modelling in Reactor for Biogas Production

100%

Chmielewski A. G. , Berbeć A. , Zalewski M. , Dobrowolski A.

Chemical and Process Engineering

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2012

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tom 33

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nr 4

621-628

EN

Two-stage biogas production plant consists of two reactors: a hydrolyser and a fermentor. The bioreactor construction has to meet three requirements: low cost and simplicity of construction and good biomass mixing conditions with an application of appropriate method. This paper reports CFD modelling of hydraulic mixing in the tank to be applied in a two-stage industrial installation.

8

Wykorzystanie obliczeń CFD do powiększania skali precesu odsiarczania spalin na przykładzie wybranych instalacji wdrożonych w energetyce

100%

Mokrosz W.

Inżynieria i Aparatura Chemiczna

|

2010

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tom Nr 3

71-72

PL

W referacie zaprezentowano możliwości wykorzystania narzędzi CAD/ CAM w procesach powiększania skali oraz optymalizacji wdrożonych w energetyce instalacji odsiarczania spalin. Na przykładach mokrej i półsuchej technologii odsiarczania spalin omówiono proces powiększania skali począwszy od badań laboratoryjnych poprzez półtechnikę do wdrożenia i badań homologacyjnych. Wskazano sposoby i możliwości wykorzystania narzędzi CAD/CAM do powiększania skali oraz optymalizacji procesów oczyszczania spalin.

EN

The paper presents possibilities of CAD/CAM tools application for the scale-up and optimisation procedures in case of selected plants for flue gases desulphurisation, installed in power industry. Based on wet and semi-dry technologies of flue gases desulphurisation a scale-up procedure is described, starting from laboratory research, through a pilot plant scale research to implementation and certification of the plant. The methods and possible application of CAD/CAM tools for scale-up and optimisation of flue gases desulphurisation process are described.

9

Hydraulic Mixing Modelling in Reactor for Biogas Production

88%

Berbeć A. , Chmielewski A. G. , Zalewski M. , Dobrowolski A.

|

2012

|

nr 4

10

Study of the Process of Hydraulic Mixing in Anaerobic Digester of Biogas Plant

88%

Karaeva J. V. , Khalitova G. R. , Kovalev D. A. , Trakhunova I. A.

Chemical and Process Engineering

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2015

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nr 1

11

Modelling and Measurement of Bubble Formation and Growth in Electroflotation Processes

88%

Sarkar S. K. A. , Machniewski P. M. , Evans G. M.

Chemical and Process Engineering

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2013

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tom 34

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nr 3

327-336

EN

Electroflotation is used in the water treatment industry for the recovery of suspended particles. In this study the bubble formation and release of hydrogen bubbles generated electrolytically from a platinum cathode was investigated. Previously, it was found that both the growth rate and detachment diameter increased with increasing wire diameter. Conversely, current density had little effect on the released bubble size. It was also found that the detached bubbles rapidly increased in volume as they rose through the liquid as a result of decreasing hydrostatic pressure and high levels of dissolved hydrogen gas in the surrounding liquid. The experimental system was computationally modelled using a Lagrangian-Eulerian Discrete Particle approach. It was revealed that desorption of gaseous solutes from the electrolyte solution, other than hydrogen, may have a significant impact on the diameter variation of the formed bubbles. The simulation confirmed that liquid circulation, either forced or induced by the rising bubble plume, influences both the hydrogen supersaturation (concentration) in the neighbourhood of the electrode and the size of the resulting bubbles.

12

Numerical prediction of GTD-350 turboshaft engine combustor deterioration

88%

Chmielewski M. , Fulara S. , Gieras M.

Journal of KONES

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2017

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tom Vol. 24, No. 2

47--58

EN

The aim of this article is to describe the use of Computational Fluid Dynamics (CFD) model for turboshaft combustor chamber deterioration analysis. To show advantages of the proposed approach the test bench of GTD-350 turboshaft engine operating at the Institute of Heat Engineering, Warsaw University of Technology was used as an example. The CFD modelling of the reactive flow inside 40º sector of GTD-350 engine section was developed. Proposed modelling technique provides good correlations with experimental data and shows that the combustor front wall soot accumulation is clearly related to the fuel droplets residence time and the oxygen mass fraction. The temperature distribution inside the combustion chamber allows concluding on possible hot distress areas on the combustion chamber liner walls. Engine borescope inspection (BSI) of the compressor, combustion chamber, compressor turbine and power turbine is used to correlate model predictions with a real GTD-350 engine deterioration. Very good correlation of the engine BSI observations with the numerical predictions proves usefulness of the developed model. Finally, advantages and future applications of the developed model are discussed.

13

Wykorzystanie modelowania cfd do optymalizacji układów powietrza osłonowego chroniących kotły energetyczne przed korozją niskotlenową

75%

Wejkowski R.

Rynek Energii

|

2010

|

tom nr 3

143-146

PL

W pracy przedstawiono badania numeryczne układów powietrza osłonowego, służących do ochrony ekranów komór kotłów energetycznych przed korozją niskotlenową, nasilającą się zwłaszcza podczas obniżania emisji tlenków azotu przy użyciu metod pierwotnych. Opisane zostały różne systemy powietrza osłonowego stosowane w Polsce. Przedstawiono badania numeryczne istniejących rozwiązań układów powietrza osłonowego, próbę ich optymalizacji poprzez modyfikację kształtu dysz wylotowych, ich ilości i kątów wypływu powietrza osłonowego.

EN

The paper presents a numerical study of protection air systems against high temperature corrosion of waterwalls used in pulverized fuel boilers. Various air protection systems applied in Poland are described. CFD models of existing and new designs of air protection systems are presented, being an attempt to optimize the effectiveness of such systems.

14

Development of a coupled numerical and experimental approach to hydrodynamic noise estimation

75%

Felicjancik J. , Gatz M. , Badur J.

Transactions of the Institute of Fluid-Flow Machinery

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2017

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tom nr 138

89--105

EN

The hydroacoustic signatures of ship propellers can be identiﬁed experimentally through measurements of cavitation-induced pressure ﬂuctuations and the accompanying noise distribution at model scale. These measurements have to be performed in a cavitation tunnel at the propellers operating conditions and with suﬃcient accuracy. In comparison, the numerical approach can be used to present a good general idea of the predicted results. Numerical methods can provide highly accurate tools for noise level and propagation prediction, as well as giving insight into the ﬂow ﬁeld and other key aspects. They are also not inﬂuenced by signal conditioning or disturbance sources present in a physical environment. So we trade scope and precision of the results for time and cost reduction. In this paper, we described both experimental and numerical methods currently in use and present advantages and limitations of the practical application of both.

15

Selected problems of heat exchange modelling in pipe channels with ball turbulisers

75%

Badur J. , Charun H.

Archives of Thermodynamics

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2007

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tom Vol. 28, no. 1

65-88

EN

The paper presents selected problems of numerical modelling of intensification cases of the convective heat transfer in pipe channels with turbulisers. The example of water flow with ball shaped turbulisers through a vertical, copper pipe, externally heated by water vapour condensation heat, is used to present the rules and guidelines for a numerical model construction in the manner existing in the state-of-art CFD codes. This model, its implementation and numerical results has been verified against an experimental data with satisfactory agreement. /

16

Analiza numeryczna pracy ekspandera krzywkowego zasilanego sprężonym powietrzem

75%

Kurkus-Gruszecka M. , Krawczyk P. , Badyda K.

Rynek Energii

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2018

|

tom Nr 4

85--90

PL

W artykule przedstawiono analizę numeryczną pracy krzywkowego ekspandera zasilanego sprężonym powietrzem. Ekspandery krzywkowe są powszechnie stosowane, jako silniki w strefach zagrożonych wybuchem. Charakteryzują się niższymi kosztami aplikacji w porównaniu do silników turbinowych dla porównywalnych parametrów pracy (moc). W ramach przeprowadzonych prac przygotowano model matematyczny procesów cieplno – przepływowych zachodzących w ekspanderze, który następnie został zaimplementowany w środowisku numerycznym - ANSYS CFX. Podczas implementacji modelu matematycznego szczególną uwagę poświęcono wykorzystaniu ruchomej siatki obliczeniowej. Z wykorzystaniem przygotowanego modelu przeprowadzono szereg symulacji pracy ekspandera dla różnych warunków. Uzyskane wyniki pozwalają wnioskować na temat wpływu parametrów operacyjnych na osiągi ekspandera.

EN

The article covers a numerical analysis of the work of a rotary lobe expander powered by compressed air. Rotary lobe expanders are widely used as motors in potentially explosive environments. They are characterized by lower costs of application compared to turbine engines for comparable operating parameters (power). As part of the work presented in the article, a mathematical model of thermal and flow processes taking place in the expander was prepared, which was then implemented in a numerical environment - ANSYS CFX. During the implementation of the mathematical model, attention was paid to the moving grid. Series of simulations of the expander operation were carried out for various conditions. The obtained results allow to conclude on the influence of operational parameters on the expander's performance.

17

Computer modeling of destructive fire hazards dynamics

75%

Michaylov D.

Teka Komisji Motoryzacji i Energetyki Rolnictwa

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2013

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tom 13

|

nr 3

18

Weryfikacja teoretycznego modelu instalacji obiektów retencyjnych

75%

Pochwat K. , Słyś D.

Proceedings of ECOpole

|

2018

|

tom Vol. 12, No. 2

551--560

PL

Ścieki deszczowe transportowane w systemach odwodnieniowych charakteryzują się niekorzystnymi parametrami fizykochemicznymi. W konsekwencji tego do odbiorników trafiają ścieki, które istotnie pogarszają ich stan jakościowy. Na jego poprawę można w znaczny sposób wpłynąć m.in. poprzez stosowanie zbiorników retencyjnych, które pozwalają na zredukowanie kierowanego do odbiornika strumienia objętości ścieków. Przy wyborze konkretnego rozwiązania zbiornika retencyjnego należy kierować się wieloma kryteriami, wśród których najistotniejszymi są nakłady inwestycyjne ponoszone na ich budowę oraz parametry hydrauliczne ich działania. W następstwie tego powstało wiele rozwiązań zbiorników retencyjnych, które pozwalają ograniczyć koszty związane z ich budową, a także takich, które maksymalizują efektywność hydrauliczną ich funkcjonowania. Przykładem takiego rozwiązania jest instalacja obiektów retencyjnych, której wykorzystanie pozwala na zmaksymalizowanie efektywności hydraulicznej dowolnego obiektu retencyjnego. Celem artykułu jest weryfikacja funkcjonowania przykładowego zbiornika retencyjnego wyposażonego w przedmiotową instalację obiektów retencyjnych w zakresie rozkładu strugi cieczy w poszczególnych fazach jego działania. Analiza została wykonana z wykorzystaniem programu do numerycznej dynamiki płynów Autodesk Simulation CFD. Oprogramowanie to, bazując na metodzie elementów skończonych i równaniach opisujących przepływ turbulentny, pozwala na odzwierciedlenie zjawisk przepływowych w obiektach o skomplikowanej geometrii. Uzyskane wyniki badań pozwolą na ocenę zasadności stosowania rozpatrywanego rozwiązania oraz mogą stanowić podstawę do dalszych analiz z punktu widzenia stanu jakościowego odbiorników.

EN

Stormwater runoffs which are transport in drainage systems are characterized by unfavorable physicochemical parameters. As a consequence of this, to the receivers are directed sewage, which can significantly worsen them quality. It can be improved by using of storage reservoirs (underground tank), which would allow to significantly reduce the volume of inflow of the sewage to the rivers. The choice of solution of the storage reservoir (underground tank) is addicted to many aspects. The most important are investment costs and hydraulic parameters of their functioning. Following this, it arose many solutions of storage reservoirs (underground tank) which allow to reducing the costs associated with their construction, as well as those that allow maximizing the hydraulic effectiveness of their functioning. An example of this is installation of retention facilities. The use of this installation allows maximizing the hydraulic efficiency of any retention facilities. The aim of the paper is to verify the functioning of the storage reservoir (underground tank) equipped with the installations of retention facilities in terms of distribution of stream liquids in different phases of its operation. The analysis was performed using Computational Fluid Dynamics (CFD) analysis. This software, based on the finite element method and the equations describing turbulent flow, allows describing of phenomena of flow in objects with complex geometry. Results obtained in research will allow for an evaluation of the legitimacy of use of this installation. Additionally they can form the basis for further Analyses done from the standpoint of the quality of receivers.

19

Flow forces acting on the spool of directional control valve

75%

Rajda J. , Lisowski E.

Czasopismo Techniczne. Mechanika

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2013

|

tom R. 110, z. 1-M

349--356

EN

This paper presents a method with the use of CFD analysis for calculating the forces acting on the spool during the flow of working liquid stream through the electro-hydraulic pilot operated directional control valve. The liquid stream flowing through the directional valve causes hydrodynamic response according to the principle of conservation of momentum. Liquid pressure acting on the spool surface affects the forces balance of valve spool as well. An object of the research is the pilot operated directional control valve WEH22 type with flow rate up to 450 dm3/min. For the analysis ANSYS/Fluent software was used.

PL

W artykule przedstawiono metodę obliczania sił powstających na skutek oddziaływania strumienia przepływającej cieczy na suwak rozdzielacza z wykorzystaniem analizy CFD. Obiektem badań jest rozdzielacz hydrauliczny sterowany pośrednio elektrohydraulicznie. Struga przepływająca przez rozdzielacz hydrauliczny zgodnie z zasadą zachowania pędu wywołuje reakcję hydrodynamiczną. Również ciśnienie cieczy, działając na powierzchnię suwaka wpływa na bilans sił działających na suwak rozdzielacza. W artykule przedstawiono analizę sił związanych z przepływem dla rozdzielacza hydraulicznego typu WEH22 dla przepływu w zakresie do 450 dm3/min. Do analizy zastosowano program ANSYS/FLUENT.

20

CFD modelling and analytical calculations of thermal transmittance of multi-layer glazing with ultrathin internal glass partitions

75%

Lechowska A. , Schnotale J.

Czasopismo Techniczne. Budownictwo

|

2014

|

tom R. 111, z. 3-B

265--272

EN

In recent times, there has been a demand for developing new technologies for glazing with superior thermal performance, good optical quality and of the lowest possible weight. In the paper, CFD modeling and analytical calculation of the thermal performance of multi-layer glazing with ultrathin internal glass partitions is presented.

PL

Obecnie istnieje potrzeba rozwoju technologii okien z bardzo niskimi wartościami współczynników przenikania ciepła i jednocześnie posiadających dobre walory optyczne, a także niską wagę. W artykule zaprezentowano wyniki symulacji CFD wieloszybowego oszklenia z ultracienkimi wewnętrznymi szybami, które następnie porównano z wynikami obliczeń analitycznych wykonanymi zgodnie ze stosowną normą.