Wyniki wyszukiwania - Biblioteka Nauki

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Modelowanie procesów cieplno – przepływowych w akumulatorze ciepła z materiałem zmiennofazowym

100%

Smykowski D.

Rynek Energii

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2017

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tom Nr 5

23--28

PL

Alternatywą dla akumulacji energii w cieple jawnym (woda) jest akumulacja ciepła w przemianie fazowej. Rozwiązanie to polega na wykorzystaniu zjawiska przemiany fazowej ciało stałe – ciecz, którego entalpia (ciepło utajone) jest znacznie większa niż ciepło jawne. Kolejną zaletą są szerokie możliwości pod względem temperatury pracy akumulatora ograniczone jedynie właściwościami materiału zmiennofazowego. Technologia akumulacji ciepła w przemianie fazowej nie jest jednak wolna od wad. Podstawową wadą jest niska przewodność cieplna wielu materiałów zmiennofazowych, wynosząca np. 0,2 W/m.K dla parafin i 0,5 – 0,7 W/m.K dla soli nieorganicznych. Analiza procesu wymiany ciepła pomiędzy płynem dostarczającym ciepło, materiałem zmiennofazowym oraz płynem odbierającym ciepło umożliwia dobór konstrukcji akumulatora zapewniającej odpowiednio skuteczny transport ciepła. W ramach przedstawionej pracy przeprowadzono symulacje cieplno – przepływowe dla wybranego wariantu konstrukcji akumulatora z materiałem PCM (Phase Change Material).

EN

An alternative for energy storage in sensible heat (water) is the heat storage in phase change. This solution takes advantage of the solid – liquid phase change process, which is characterized by significantly larger enthalpy comparing to sensible heat. Another advantage of heat storage in phase change is the accumulator operation temperature range, limited only by phase change material properties. However, latent heat storage technology has several drawbacks. The main limitation is the low thermal conductivity of most phase change materials, which ranges from 0.2 W/m.K in case of paraffins up to 0.5 – 0.7 W/m.K for inorganic salts. The analysis of heat transfer between the hot fluid and the phase change material as well as between the phase change material and cold fluid allows to adjust the construction of the heat accumulator in order to ensure efficient heat transport. Within presented study, the heat transfer for a selected geometry variant of heat accumulator was investigated using computational fluid dynamics simulations.

2

Turbina wiatrowa o poziomej osi obrotu z elementami silnika turbowentylatorowego

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Jureczko M. , Błędowski P.

Modelowanie Inżynierskie

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2017

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tom T. 31, nr 62

37--42

PL

Ideą badań przedstawionych w artykule było zwiększenie wydajności turbiny wiatrowej o poziomej osi obrotu poprzez zmodernizowanie jej konstrukcji. W tym celu zastosowano elementy konstrukcyjne turbowentylatorowego silnika odrzutowego firmy Rolls-Royce serii Trent XWB oraz innych elementów stosowanych w General Aviation. Następnie przeprowadzono numeryczną analizę opływu zmodernizowanej turbiny w celu sprawdzenia jej wydajności. Uzyskane wyniki pozwalają stwierdzić, iż przyjęto właściwy trend w modernizacji turbin wiatrowych typu HAWT.

EN

The idea behind the research presented in the article was to maximize efficiency of wind turbine with horizontal rotation axis through construction changes. For this purpose, there were used construction elements of RollsRoyce’s turbo fan jet engine from line Trent XWB, and some other parts used in General Aviation. Next proceeded numerical analysis of flow around modernized turbine to check its efficiency. The results allow to state that proper trend in modernization process HAWT wind turbines has been adopted.

3

A Temperature Error Correction Method for a Thermometer Screen

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Yang J. , Liu Q.

Acta Physica Polonica A

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2017

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tom 132

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nr 4

1301-1305

EN

Due to solar radiation exposure, air flowing inside a thermometer screen may produce a measurement error of 0.8°C or higher. To improve the air temperature observation accuracy, a temperature error correction method is proposed. The correction method is based on a computational fluid dynamics method and a genetic algorithm method. The computational fluid dynamics method is implemented to analyze and calculate the temperature errors of a screen under various environmental conditions. Then, a temperature error correction equation is obtained by fitting the computational fluid dynamics results using the genetic algorithm method. To verify the performance of the correction equation the screen and an aspirated temperature measurement platform are characterized in the same environment to conduct the intercomparison. The aspirated temperature measurement platform serves as an air temperature reference. The mean temperature error given by measurements is 0.77°C, and the mean temperature error given by correction equation is 0.79°C. This correction equation allows the temperature error to be reduced by approximately 97.5%.

4

A CFD Study of the Aerodynamic Characteristics of Twardowsky and FOK Rockets

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Sahbon N. , Murpani S. , Michałów M. , Miedziński D. , Sochacki M.

Transactions on Aerospace Research

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2022

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tom Nr 1 (266)

35--58

EN

Stability and performance are crucial characteristics for aerospace vehicles. The ability to investigate the aerodynamics and performance of rockets gives an insight into their stability before flight and the potential for design and performance enhancements. For the past 13 years, the Rocketry Division within the students’ Space Association of Warsaw University of Technology has been developing sounding rockets of different designs and mission profiles. Two rockets have been chosen for the CFD (Computational Fluid Dynamics) campaigns, FOK and Twardowsky. This paper describes the mathematical model of aerodynamic loads used by the Division for sounding rocket simulation, followed by CFD campaigns for the two rockets. The results of the CFD analysis are then used to calculate the rockets’ aerodynamic derivatives according to a previously defined mathematical model.

5

Effect of Electrode Induction Melting Gas Atomization Process on Fine Powder Yields: Continuous Metal Melt Flow

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Wu J. , Xia M. , Wang J. , Ge C.

Archives of Metallurgy and Materials

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2023

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tom Vol. 68, iss. 3

839--849

EN

Electrode induction melting gas atomization (EIGA) is a newly developed method for preparing ultra-clean metal powders, and is a completely crucible-free melting and atomization process. Based on conducted several atomization experiments, we found that the fine powder yields obtained during the EIGA process were greatly affected by the status of metal melt flow. While, continuous metal melt flow was beneficial for the yield of fine powders, it was in conflict with the principle described for the vacuum induction melting inert gas atomization (VIGA) process. To understand the critical role of continuous metal melt flow in the EIGA process, a computational fluid dynamics (CFD) approach was developed to simulate the gas atomization process. The D50 particle size of powder prepared by atomization under continuous liquid metal flow was about 70 μm, while that obtained by atomization under non-continuous liquid metal flow was about 100 μm. The diameter distribution results of numerical simulations agreed well with the experimental measurements, which demonstrated the accuracy of our simulation method. This study provides theoretical support for understanding the critical role of continuous metal melt flow and improving fine powder yields in the EIGA process.

6

Robust generation method of a signed distance function for preprocessing of cartesian-grid-based CFD

100%

Takeda Y. , Ueno K. , Takahashi Y. , Matsubara K.

Journal of Theoretical and Applied Mechanics

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2023

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tom Vol. 61 nr 3

453--463

EN

In practical computational fluid dynamics simulations around industrial products with com- plex surface shapes, the robustness of preprocessing to “dirty” geometry is an important issue. The dirty STL (Standard Triangle Language) data contains errors such as gaps be- tween facets, overlapping of facets, and flipping of normal vectors. These errors in the STL data are difficult to avoid in 3D modeling of complex geometry. Using a Cartesian grid is advantageous to the boundary-fitted grid in the aspect of preprocessing for dirty STL files. In this study, a robust and automatic generation method of a signed distance function for the preprocessing of Cartesian grid solvers is proposed. To ensure robustness to the complex and dirty STL data, the proposed method uses information of all STL facets to determine each grid point. The proposed preprocessing method is verified by numerical simulation of the flow around the NASA common research model.

7

Study of the influence of the lack of contact in platefin and tube heat exchanger on heat transfer

100%

Andrzejewski D. , Łęcki M. , Gutkowski A.

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8

Study on the effect of the descent rate of a helicopter in the Vortex Ring conditions

100%

Surmacz K. , Kowaleczko G.

Journal of KONES

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2016

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tom Vol. 23, No. 1

345--352

EN

One of the limiting factors for a helicopter operation is the Vortex Ring State (VRS). This aerodynamic phenomenon, known as the VRS or “Settling with Power”, is characterized by the formation of circulating air stream moving along a ring shaped track around the main rotor of a helicopter. Conditions, conducive to development of the vortex ring state, occur in the vertical or nearly vertical descent. This leads to decrease in thrust and thus rapidly increasing the rate of descent. This phenomenon occurs for an appropriate combination of induced velocity and the velocity of the stream of airflow from the bottom to the rotor. The rates of change of velocities delimit dangerous areas of flight. The objective of this work was to investigate the influence of the descent rate of a helicopter on the vortex ring formation process and determinants of the occurrence of vortex rings. For better understanding of the nature of this state, a computational method was applied. Series of three-dimensional (3D) unsteady analysis was carried out using Computational Fluid Dynamics tools (CFD). Simulations were realized using geometry and performance of the W-3 “Sokol” helicopter. The paper presents results of a helicopter operation in axial and non-axial descent conditions. Three calculation cases of vertical flight of a helicopter with different rates of velocity changes were considered. A simulation of non-axial descent was based on the measured flight test data for the W-3 helicopter. The results provide information about the changing nature of the flow in the course of the movement of a helicopter and show the influence of the rate of descent during initiation on the development of VRS. Results of the calculations provide guidelines for helicopter pilots.

9

Computational Fluid Dynamics calculation of a planar solid oxide fuel cell design running on syngas

100%

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

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10

Numerical analysis of the steam flow past the turbine blade stage

100%

Rogowski K. , Pawlicki J.

Journal of Machine Engineering

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2017

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tom Vol. 17, No. 2

102--110

EN

The steam flow past a last stage (the eleventh stage) of the high pressure part of the TK120 steam turbine was investigated using computational fluid dynamics (CFD). The simulations are performed using the unsteady compressible Navier-Stokes equations. Viscous steam flow has been analyzed using the Spalart-Allmaras turbulence model. The paper presents distributions of instantaneous flow parameters around turbine blades as well as instantaneous aerodynamic blade loads. Flow parameters such as: velocity and static pressure are presented as contour maps whereas aerodynamic loads, axial and circumferential, are given as functions of time. Theoretical power of the examined turbine stage is 4.11 MW. Based on the numerical investigations the power of the analyzed stage is evaluated to be 3.5 MW. All presented in this paper results have been performed using the ANSYS Fluent solver.

11

On general-purpose turbulence models in CFD

100%

Pozorski J.

Transactions of the Institute of Fluid-Flow Machinery

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2015

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tom nr 127

45--62

EN

The computational fluid dynamics (CFD) tools for various flow problems have become widespread nowadays, yet their use still needs attention and care. In particular, turbulence models are often a crucial part of flow computations undertaken with various software packages, either commercial, open-source or in-house. In the paper, an overview of available model categories is provided, together with some discussion of their advantages or drawbacks with respect to flow cases of interest.

12

Evaluation of pressure losses reduction possibility for WEH22 directional control valve by internal geometry correction

100%

Lisowski E. , Rajda J.

Technical Transactions

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2017

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tom Vol. 7(114)

157--164

EN

The article presents the evaluation of possibility of pressure losses reduction at the flow through a WEH22 hydraulic directional control valve. For this purpose, 3D models of flow paths were built using the Creo Parametric software. Then the models were used in the ANSYS/Fluent software to calculate pressure losses. The results of the analysis have allowed for determination of possibilities of pressure losses reduction without changing overall dimensions of the valve body.

PL

W artykule przedstawiono ocenę możliwości obniżenia strat ciśnienia przy przepływie przez rozdzielacz hydrauliczny WEH22. W tym celu zbudowano modele 3D dróg przepływowych, które wygenerowano za pomocą programu CREO Parametric, a następnie te modele wykorzystano w programie ANSYS/Fluent do obliczenia strat ciśnienia. Uzyskane wyniki analiz pozwoliły na określenie możliwości obniżenia strat ciśnienia bez zmian wymiarów gabarytowych korpusu rozdzielacza.

13

Analysis and optimization of radiant cooling panel with wave-type embedded pipes

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Prasanna R. , Moorthy P. , Krishnan A. , Balakrishnan V.

Engineering Transactions

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2020

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tom Vol. 68, iss. 1

47--67

EN

In this study, the radiant cooling panel with wave-type pattern pipes is analyzed and optimized through Taguchi’s design of experiments methods and grey relation method for better performance. Radiant cooling panel’s bottom surface temperature and temperature non-uniformity index are considered as the quality objective functions. Control parameters such as pipe length, the spacing between the pipes, radiant panel thickness, pipe bent radius, pipe diameter, insulation layer thickness, pipe material, panel material, insulation material, and mass flow rate of water entering the pipe are included as the control parameters of the optimization study. The performance of radiant cooling panels is analyzed through numerical simulation technique- computation fluid dynamic (CFD) method. The numerical simulation is carried out in the Fluent software, and the CFD code is checked for grid independence and validation. Through single and multi-objective optimization, the best design of the radiant cooling panel is identified, and a confirmation test is also conducted. Finally, an analysis of variance (ANOVA) calculation is made and it is found that the mass flow rate of water entering the pipe is the most influencing parameter on the performance of the radiant cooling panel.

14

Experimental and numerical study on the classification of a cyclonic field in a flotation column

100%

Li X. , Li X. , Yan X. , Wang L. , Zhang H.

Physicochemical Problems of Mineral Processing

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2020

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tom Vol. 56, iss. 3

421--431

EN

The cyclonic-static micro-bubble flotation column (FCSMC) performs well in fine mineral flotation. Compared to traditional flotation columns, its design innovatively introduces a cyclonic structure. The separation of middling and tailing occurs in the cyclonic flow field induced by a cyclonic reversal cone. In this study, the particle size distribution analysis and computational fluid dynamics (CFD) simulations were conducted to reveal the particle distribution law and the classification mechanism in cyclonic flow fields under different circulation pressures. The results showed that particle size showed the same distribution tendency as tangential velocity in the radial direction: both increase from the center and decrease around the wall. As circulation flux increased, the tangential velocity increased, and the particle size differences in the radial direction also increased. The position of the largest particles will move to outside as the largest value of tangential velocity migrates the outward in the radial direction. According to the particle size distribution of the feed, it can be adjusted to the flow field to change the particle distribution, thereby improving the efficiency of separation. This study has an important guiding significance for column design and adjustment of the operating parameters of the flotation process.

15

Steady and unsteady analysis of NACA 0018 airfoil in vertical-axis wind turbine

100%

Rogowski K. , Hansen M. O. L. , Maroński R.

Journal of Theoretical and Applied Mechanics

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2018

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tom Vol. 56 nr 1

203--212

EN

Numerical results are presented for aerodynamic unsteady and steady airfoil characteristics of the NACA 0018 airfoil of a two-dimensional vertical-axis wind turbine. A geometrical model of the Darrieus-type wind turbine and the rotor operating parameters used for numerical simulation are taken from the literature. Airfoil characteristics are investigated using the same mesh distribution around the airfoil edges and two turbulence models: the RNG k-ε and the SST Transition. Computed results for the SST Transition model are in good agreement with the experiment, especially for static airfoil characteristics.

16

Metodyka przeprowadzania symulacji przepływu płynów w programie Autodesk CFD

100%

Warchulski M. , Warchulski J. , Jatczak I.

Przegląd Mechaniczny

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2021

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tom nr 6

25--34

PL

W artykule przedstawiono metodykę przeprowadzania symulacji przepływu płynów w programie Autodesk CFD. Omówiono problematykę numerycznej mechaniki płynów w zakresie analizy zewnętrznego przepływu ściśliwego.

EN

This paper presents the methodology for fluid flow simulation in Autodesk CFD software. Computational fluid dynamics issues relating to analysis of external compressible flow are discussed.

17

Computational and Experimental Investigation of Inert Gas Flow Field in Direct Metal Laser Melting Printer Build Chambe

100%

Czekałowski P. , Stryczniewicz W. , Żuk P. , Panna K. , Borkowski P. , Bujak M. , Iglewski T.

Advances in Science and Technology. Research Journal

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2023

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tom Vol. 17, no 6

378--387

EN

Additive manufacturing methods are becoming more and more popular in today’s production market. These methods became a useful and flexible alternative to traditional manufacturing approach. One of the most popular methods in this family is Direct Metal Laser Melting. It can achieve high quality prints, however, numerous parameters need to be established, to achieve a good quality product. One of the aspects of printing process is inert gas flow. The goal of presented study is to quantitatively assess inert gas flow field using both experimental and numerical methods. Flow field parameters have been measured with anemometry and Particle Image Velocimetry. Additionally Computational Fluid Dynamics tools were used to investigate flow phenomena occurring inside the build chamber. PIV measurements give good insight into the flow field, but they are costly and require significant time for preparation. For this reason, CFD analysis is widely used as a design tool, giving reasonable turnaround time. In addition, every design tool to be reliable need to be validated against test data. In this study the team was able to collect both experimental and numerical data and finally conduct the validation. Work allowed to determine the most suitable approach for predictions in given problem. Different turbulence models have been tested. Simulation results were validated against collected experimental data.

18

Computational fluid dynamics (CFD) aided design of a multi-rotor flying robot for locating sources of particulate matter pollution

100%

Suchanek G. , Filipek R.

Applied Computer Science

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2022

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tom Vol. 18, no 3

86--104

EN

The use of flying robots for various environmental protection issues is a very important and current research topic. Designing a dedicated multi-rotor flying robot is necessary for the efficient and automated localization of sources of air pollution, especially solid particles. In particular, one of the most important requirements that must be met by such a robot is its appropriate impact on the measurement process, i.e., increasing the sensitivity of sensors or reducing the interference. This is particularly difficult because its rotating rotors introduce significant disturbances to the surrounding fluid. In these studies, the design process is supported by the creation of a mathematical flow model and a series of analyzes to optimize the PM measurement system. The model is built using the finite-volume method in ANSYS Fluent software and steady-state RANS averaging. First, a flow field model with one propeller was modeled and its parameters identified by comparison with the results from the dedicated original dynamometer stand -- characteristics of the propeller performance. On the basis of the simulations and measurement of one rotor, subsequent systems of the highest practical importance are built. The effect of that design process was the preparation and testing of a functional robot prototype. The field parameter distributions resulting from the analyzes, in particular the turbulence intensity, allow one to propose a criterion on the basis of which both the best rotor configuration and localization of sensors are selected.

19

Computational prediction of the resistance of the the floatplane at various trim angles

100%

Sulisetyono A. , Fadhlurrohman I. , Ali B. , Zubaydi A.

Journal of Theoretical and Applied Mechanics

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2022

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tom Vol. 60 nr 2

267--278

EN

The prediction of the total resistance occurred during operation of a floatplane on the water surface is an important aspect in developing the floater as well as the engine power required. Theoretically, the trim angle of the floater may affect the total resistance. This paper intends to find the optimal trim angle for the take-off operation using the computational fluid dynamics (CFD) software. The floater set up under a fixed trim angle includes 2◦, 5◦ and 10◦ taken in simulation at five different speeds between 9.21 m/s and 15.87 m/s. In one case of 2◦ trim angle, the floater model test has been carried out in a tow tank laboratory to validate the accuracy of the numerical result. Comparison of both results has a good fit with an average error of 2.27%. In the final simulation results, the optimum trim angle is 5◦, which produces the total resistance less than 2◦ and 10◦ of the trim angle with average differences of 9.21% and 50.46% for all speeds, respectively.

20

Computational fluid dynamics analysis of several designs of a Curtis wheel

100%

Koprowski A. , Rządkowski R.

Archives of Thermodynamics

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2021

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tom Vol. 42, no 3

197--208

EN

In small steam turbines, sometimes the efficiency is not as important as the cost of manufacturing the turbine. The Curtis wheel is a solution allowing to develop a low output turbine of compact size and with a low number of stages. This paper presents three fully dimensional computational fluid dynamics cases of a Curtis stage with full and partial admission. A 1 MW steam turbine with a Curtis stage have been designed. The fully admitted stage reaches a power of over 3 MW. In order to limit its output power to about 1 MW, the partial admission was applied. Five variants of the Curtis stage partial admission were analyzed. Theoretical relations were used to predict the partial admission losses which were compared with a three-dimensional simulations. An analysis of the flow and forces acting on rotor blades was also performed.