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EN
Efficiency is a crucial parameter for an airplane to reduce both cost of operations and emission of pollutants. There are several airplane concepts that potentially allow for increasing the efficiency. A few of them were not investigated thoroughly enough yet. The inverted joined wing configuration, with the upper wing in front of the lower one is an example of such concept. Therefore, a project consisting of development of an experimental scaled demonstrator, and its wind tunnel and flight testing, was undertaken by consortium: Institute of Aviation, Warsaw University of Technology, Air Force Institute of Technology and a MSP company. Results led to a conclusion, that the inverted joined wing configuration allows to build an airplane with excellent performance, but its advantage against the conventional airplane is marginal because of large trimming drag of the configuration with relatively high position of the thrust vector in pusher configuration. It was applied because the demonstrator was a flying model of manned airplane and the tractor configuration would affect the pilot’s field of observation. However, in case of the UAV, this reason becomes insignificant. Therefore two configurations of tractor propulsion were tested to see, if their performance is better than the performance of original design.
PL
Doskonałość jest kluczowym parametrem samolotu decydującym o redukcji kosztów operacyjnych i ilości emitowanych zanieczyszczeń. Istnieje kilka układów samolotu, które potencjalnie pozwalają na zwiększenie doskonałości. Kilku z nich nie przebadano dotychczas dogłębnie. Konfiguracja odwróconego płata zespolonego, gdzie przednie skrzydło w układzie górnopłata łączy się z tylnym w układzie dolnopłata, jest dobrym przykładem takiej koncepcji. Stąd, projekt mający na celu zbudowanie skalowanego demonstratora oraz przetestowanie w tunelu aerodynamicznym i w locie, został wykonany przez powołane do tego celu konsorcjum w składzie: Instytut Lotnictwa, Politechnika Warszawska, Instytut Techniczny Wojsk Lotniczych i firma MSP. Rezultaty dowiodły, że zastosowanie odwróconej konfiguracji połączonych skrzydeł pozwala na zbudowanie samolotu o doskonałych osiągach. Jego przewaga nad samolotami konwencjonalnymi jest jednak marginalna ze względu na duży opór konfiguracji w warunkach równowagi. Wynika on z konieczności zrównoważenia momentu od relatywnie wysoko położonego napędu. Napęd tak umiejscowiono ze względu na to, że demonstrator był modelem zdalnie sterowanym samolotu załogowego, w którym przedni napęd znacząco ograniczałby pole widzenia załogi. W przypadku bezzałogowca argument ten traci na istotności. Dlatego wybrano i przebadano obliczeniowo dwie konfiguracje napędu ciągnącego, sprawdzając, czy ich osiągi poprawią się względem oryginalnej konstrukcji.
EN
In this work a multilevel CFD analysis have been applied for the design of an engine exhaust system include manifold and muffler with improved characteristics of noise reduction and fluid dynamic response. The approaches developed and applied for the optimization process range from the 1D to fully 3D CFD simulation, exploring hybrid approaches based on the integration of a 1D model and 3D tools. Once the best configuration has been defined, the 1D-3D approach has been adopted to confirm the prediction carried out by means of the simplified approach, studying also the impact of the new configuration on the engine performances.
3
Content available remote Impact of coronary tortuosity on the artery hemodynamics
EN
The presence of tortuosity in coronary artery (CA) affects the local wall shear stress (WSS) which is an influencing hemodynamic descriptor (HD) for the development of atherosclerotic sites. To conduct a morphological parametric study in coronary arteries (CAs), several idealized tortuous artery models were obtained by varying three morphological indices namely, curvature radius (CR), distance between two bends (DBB) and the angle of bend (AoB). Computational fluid dynamics methodology with multiphase mixture theory is used to explore the effect of coronary tortuosity on various WSS based hemodynamic descriptors (HDs) namely, time-averaged WSS, oscillatory shear index, time-averaged WSS gradient, endothelial cell activation potential and the relative residence time that are used to determine the vulnerable locations for the onset of thrombosis and atherosclerosis. Our findings suggest that all the tortuosity morphological indices, CR, DBB and AoB have significant influence on the distributions of various HDs and hemodynamics. It is also observed that atherosclerosis prone sites were witnessed at the inner artery wall at downstream regions of the bend section 1 and bend section 2 in all the tortuous artery models studied and found to increase as the CR and DBB were reduced however, found to increase as the AoB is increased. Hence, severe coronary tortuosity in CAs with small CR, small DBB and higher AoB may have lower WSS zones at inner bend sections which promote atherosclerosis plaque progression. The analysis obtained from this multiphase blood flow study can be employed potentially in the clinical assessment on the severity of atherosclerosis lesions as well as in understanding the underlying mechanisms of localization and formation of atherosclerotic plaques.
EN
Literature review on flow acoustic methods and materials of an automotive muffler. A car is judged comfortable also depending on the acoustic level transmitted inside, and a thorough knowledge of acoustics of ducts and mufflers is needed for the design of efficient muffler configurations. Unstable exhaust gas at high temperature flowing from internal combustion engine manifold may cause of noise and vibrations conflicting with the high standard of acoustic comfort requested by this kind of vehicle. The basic gaols are to define most important methods to identify noise occur from the motion of fluid in case of turbulent model. Materials properties like velocity, temperature, thermal conductivity and density have been technical presented in this work.
EN
The flat tubes are necessary apparatus to design the modern heat exchangers. In this context, a CFD (computational fluid dynamics) study has been achieved to explore the influence of the flat tube size on the heat transfer characteristics in cross-flow over flat tube banks. The calculations are performed with the help of the computer software (Fluent) which is based on the finite volume method to solve the continuity, momentum and energy equations. The numerical investigations are achieved for laminar flow (Reynolds numbers changing from 50 to 800), two dimensional flows and incompressible fluids. Some predicted results are compared with available experimental data of the literature and a satisfactory agreement is observed. The obtained results show a decrease in the heat transfer coefficient with increased size of the flat tube. A new valuable empirical correlation is suggested for the prediction of heat transfer coefficients over a flat tube bank. The proposed correlation may be useful for engineers to predict the heat transfer rates in such devices without requirements of experimental measurements.
EN
Inhalants, such as bronchodilators, are often used to treat asthma. Numerical simulation can be applied to quantitatively evaluate the transport and deposition of medicinal particulates in the respiratory tract. In this study, numerical simulation of an airflow including particles in a tracheobronchial model was conducted based on a computed tomography (CT) image of a human respiratory tract, and then the anatomical factors of the airway that influence the volume flow rate and the number of particles arriving at each bronchus were investigated. The oral cavity, pharynx, larynx, trachea, and intra-thoracic central airways of up to seven generations were modeled from the CT image. The airflow was simulated by large eddy simulation using OpenFOAM ver. 2.3.1. The particle transport was calculated in a Lagrangian manner. Statistical analysis was performed on the results of computational fluid dynamics simulation. It was found that the cross-sectional area of the outlet boundary, the total distance of the center line of the respiratory tract between the carina and the outlet boundary, and the angles between each bronchus and the trachea have large influences on the volume flow rate at each outlet. These influences increase almost linearly as the inhalation flow rate increases. The outlet area and the total angle markedly influenced the number of arriving particles. Larger particles are more likely to be influenced by the angle at which the direction of the particle is deflected. As the inhalation flow rate increases, the influence of the total angle increases and that of the outlet area decreases in all particle conditions.
EN
In this work, an indirect solar dryer integrated thermal storage for drying figs. (Ficuscarica) is studied numerically. Unsteady turbulent airflow and heat transfer through a two-dimensional model is carried out for a typical day of August under the climatic conditions of Tlemcen (Algeria). Effects of air inlet size and thickness of the packed bed on the dynamic and thermal behaviors of the dryer with and without packed bed have been discussed. The study shows that: (1) Increase the inlet size from 0.04 m to 0.10 m can accelerate the extraction of air by about 13% and reduce the maximum crops temperature by about 14%. (2) The packed bed can reduce the mass flow rate extracted by 22% and the fluctuations of air temperature by 1.3%. (3) A packed bed with a thickness of 0.15 m can extend the operating time of the dryer up to 23%.
8
Content available remote A software tool for automatic geometry generation of a micro turbine
EN
Heat recovery plays an important role in increasing the efficiency of renewable energy facilities like biomass furnaces, solar power plants or biofuel combustion engines. As the overall efficiency of the facilities can be increased by recovering the energy. The available waste heat can be converted directly into mechanical energy, pressure or subsequently converted into electrical energy by coupling the expansions machine with a generator. The waste heat can be converted by Organic Rankine Cycle (ORC). Therefore, an expansion machine, e.g. a turbine is required. Also small amounts of waste heat can be recovered, if so-called micro turbines are used. Design and construction of such micro turbines always follow fixed rules. Aim of this work is to explain the rules how to design a micro turbine. Furthermore, our workflow and a software tool which follows these rules should be presented.
9
Content available remote Modelowanie procesu napełniania przy użyciu obliczeniowej mechaniki płynów
PL
Celem pracy było przeprowadzenie symulacji procesu napełniania pojemników cieczami pieniącymi się o różnych właściwościach reologicznych oraz określenie wpływu tych właściwości na ułamek objętościowy powietrza w cieczy. Wykazano, że zgodnie z przewidywaniami największy wpływ ma lepkość oraz napięcie powierzchniowe płynu. Im niższa wartość napięcia powierzchniowego tym powstawała większa liczba pęcherzyków powietrza podczas procesu napełniania. Dla cieczy o dużej lepkości proces przebiegał odmiennie - zatrzymane powietrze w cieczy w trakcie procesu dużo wolniej zanika niż przy nalewaniu cieczy o małej lepkości.
EN
The aim of this work is to simulate the process of filling containers with foaming liquids with different rheological properties and to determ ine the effect of these properties on the volume fraction of air in the liquid. It has been shown that, as predicted, viscosity and surface tension of the fluid have the greatest influence. The lower the surface tension, the greater the number of air bubbles during the filling process. For viscous liquids the process is different - the air retained in the liquid during the process disappears much slower than when pouring Iow viscosity liquids.
PL
Praca przedstawia numeryczną analizę pracy konwekcyjnego ogrzewacza pomieszczeń opalanego paliwem gazowym w warunkach równowagi cieplnej dla układu z naturalną grawitacją. Uzyskano informacje na temat sprawności cieplnej urządzenia oraz jego bilans masowy. Pokazano rozkład temperatury na powierzchni urządzenia i w jego wnętrzu. Podano również zalety stosowania metod numerycznych do optymalizacji geometrii urządzenia. Obliczenia numeryczne CFD przeprowadzono z wykorzystaniem komercyjnego kodu ANSYS Workbench 17.0 - program FLUENT.
EN
This paper presents a numerical investigation of the independent gas-fired convection heater work in thermal equilibrium for natural gravity system. Tested convection gas heater was connected to air/flue duct. In this paper information about thermal efficiency, mass and fluid flow and contours of temperature on the surface of the device and in his interior are given. The advantages of using numerical methods to optimize the geometry of the device were also presented. Numerical calculation were performed using commercial code ANSYS Workbench 17.0 - Fluent program.
EN
Heat exchangers are widely employed in numerous industrial applications to serve the heat recovery and cooling purpose. This work reports a performance analysis of a tube in tube heat exchanger for different flow configuration under variable operating conditions. The experimental investigation was performed on a U-shaped double pipe heat exchanger set up whereas Commercial Computational Fluid Dynamics code FLUENT along with k-ε turbulence modeling scheme was implemented for the simulation study. The flow solution was achieved by implementing k-ε turbulence modeling scheme and the simulation findings were compared with the experimental results. The experimental findings were in good agreement with the simulation results. The counter-flow configuration was found to be 29.4% more effective than the cocurrent one at low fluid flow rate. Direct relationship between heat transfer rate and flow rate is observed while effectiveness and LMTD showed inverse relationship with it. The significance of inlet temperature of hot and cold stream has been evaluated, they play crucial role in heat exchange process.
EN
The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work.The multi-phase Euler-Lagrange model with standard k- ϵ turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented.The simulation findings show good agreement with the published findings.
EN
The authors developed a simple and efficient method, called the Coupled Displacement method, to study the linear free vibration behavior of the moderately thick rectangular plates in which a single-term trigonometric/algebraic admissible displacement, such as total rotations, are assumed for one of the variables (in both X,Y directions), and the other displacement field, such as transverse displacement, is derived by making use of the coupling equations. The coupled displacement method makes the energy formulation to contain half the number of unknown independent coefficients in the case of a moderately thick plate, contrary to the conventional Rayleigh-Ritz method. The smaller number of undetermined coefficients significantly simplifies the vibration problem. The closed form expression in the form of fundamental frequency parameter is derived for all edges of simply supported moderately thick rectangular plate resting on Pasternak foundation. The results obtained by the present coupled displacement method are compared with existing open literature values wherever possible for various plate boundary conditions such as all edges simply supported, clamped and two opposite edges simply supported and clamped and the agreement found is good.
EN
An important phenomenon of delta wing is the mechanism of vortex core, which indicates the increase in lifting force until the occurrence of the vortex breakdown. The computational fluid dynamics (CFD) is very helpful in visualizing and providing analysis of the detailed data. The use of turbulent models will affect the quality of results in obtaining the vortex breakdown phenomenon. This study used several models of turbulence to capture the occurrence of vortex breakdown and compare it with experiments using water tunnel test facility. The results show that all turbulence models give good results at a low angle of attack (AoA), but at a high AoA the DES model gives the results closest to experimental ones with Cl error value of about 1 %. Taking into account the time required and the acceptable level of accuracy, the use of SST and k-ω models is an alternative option for use in the detection of vortex breakdown.
PL
W artykule przedstawiono sposoby modelowania dwuwirnikowej turbiny wiatrowej z wykorzystaniem technik Obliczeniowej Mechaniki Płynów. Omówiono uproszczone metody modelowania Actuator Disc i Actuator Line Method oraz aspekty związane z dokładnym odwzorowaniem turbiny na siatce obliczeniowej. Zaprezentowano przykładowe wyniki obliczeń turbiny dwuwirnikowej złożonej z wirników NREL o mocy nominalnej 5 MW każdy. Do wykonania badań symulacyjnych wykorzystano metodę Actuator Line Method. Zaprezentowane wyniki symulacji potwierdziły zwiększenie wartości współczynnika wykorzystania energii wiatru dla rozpatrywanej konstrukcji turbiny wiatrowej.
EN
In the paper modeling and simulating methods applicable for the Counter Rotating Wind Turbine have been presented. The methods described in paper are based on Computational Fluid Dynamics techniques. An actuator methods, namely Actuator Line (ALM) and Actuator Disk (ADM) have been introduced. These methods do not require to explicitly represent the rotor. Beside of that calculated aerodynamic forces are projected onto computational domain in actuator points distributed on line (ALM) or disk surface (ADM). Aspects regarding direct rotor modeling e.g. rotor-fitted grid have been discussed as well. Case study of ALM use has been performed. Studied CRWT consisted of NREL 5MW rotors located half a diameter from each other. Rotors were exactly counter rotating with angular velocity of 9,115 rpm. Calculation were performed in OpenFOAM CDF solver. The LES code solved the incompressible Navier-Stokes equations over grid with 11,6 mln elements. The simulation was performed in unsteady conditions with 0,03 s time step and total time of 210 s. In comparison purposes simulation of SRWT was performed as well. Obtained results confirmed that CRWT is more efficient than SRWT and about 20% of additional power can be extracted from a wind energy.
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.
EN
An analysis of heat transfer in a low power line-start permanent magnet synchronous motor is presented. A three-dimensional numerical model together with its experimental verification are reported. The model takes into account the mixed convection and heat conduction inside the motor. Radiative heat transfer is assumed to be negligible due to relatively low temperature difference between the motor’s surface and the environment. The analysis was performed for steady state operation conditions at rated load. To determine the loss density distribution in the motor, electromagnetic calculations were performed. The temperature distribution on the surface of the frame in a steady state calculated numerically was compared with pictures taken with an infrared camera. To verify the thermal images four thermocouples placed on the frame were used. Furthermore, the surface temperature of the rotor was measured using pyrometers.
PL
W pracy opisano analizę wymiany ciepła w silniku synchronicznym małej mocy o rozruchu bezpośrednim i jego otoczeniu. Zaprezentowano trójwymiarowy numeryczny model cieplny obiektu oraz jego weryfikację doświadczalną. Model uwzglednia konwekcję naturalna i wymuszoną oraz przewodzenie ciepła wewnątrz silnika. Oddawanie ciepła przez promieniowanie pominięto, jako nieznaczące ze względu na zbyt niską róźnicę temperatur powierzchni i otoczenia. Analizę przeprowadzono w stanie ustalonym podczas pracy silnika ze znamionowym obciążeniem. W celu wyznaczenia rozkładu gęstości strat w silniku wykonano obliczenia na modelu elektromagnetycznym. Rozkład temperatury na powierzchni korpusu w stanie ustalonym obliczony metodą numeryczną i porównano ze zdjęciami wykonanymi kamerą termowizyjną. Do weryfikacji termogramów uzyskanych przy pomocy kamery termowizyjnej wykorzystano cztery termopary umieszczone w korpusie. Ponadto zmierzono temperaturę powierzchni czołowej wirnika wykorzystujac pirometry.
18
EN
The presented paper contains an analysis of heat transfer in a low power electric motor. A numerical model is presented together with its empirical verification. The model includes mixed convection as well as heat diffusion in motor’s frame. Steady-state conditions at constant rated load were investigated. Frame surface temperature distribution obtained using CFD was compared with measurements conducted using thermocouples. Comparison between measured and calculated temperatures allows for an assessment of accuracy of the presented numerical model.
PL
Artykuł zawiera analizę wymiany ciepła w silniku synchronicznym wzbudzonym magnesami trwałymi i rozruchem bezpośrednim małej mocy. Zaprezentowano model numeryczny oraz jego weryfikacją eksperymentalną. W obliczeniach uwzględniono konwekcję mieszaną oraz dyfuzję ciepła wewnątrz maszyny. Wyniki obliczeń temperatury na powierzchni silnika porównano z pomiarami wykonanymi przy pomocy termopar. Porównanie wyników pomiarów i obliczeń pozwala na ocenę dokładności modelu numerycznego.
19
Content available remote Turbina wiatrowa o poziomej osi obrotu z elementami silnika turbowentylatorowego
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.
20
Content available Air flow analysis around the autogyro fuselage
EN
The paper presents the results of the simulation of the air flow around the gyroplane without the influence of the rotor and pusher propellers. Three-dimensional calculations were performed using ANSYS Fluent software. Based on the calculations, the values of the drag force and the lift force on each component of the rotorcraft were determined. Based on the results obtained, the effect of angle of attack on the aerodynamic forces was obtained.
PL
W pracy przedstawiono wyniki symulacji opływu modelu wiatrakowca bez wpływu wirnika nośnego oraz śmigła pchającego. Trójwymiarowe obliczenia wykonano za pomocą programu ANSYS Fluent. Na podstawie przeprowadzonych obliczeń wyznaczono wartości siły oporu oraz siły nośnej działające na poszczególne części składowe statku powietrznego. W oparciu o uzyskane wyniki otrzymano wpływ kąta natarcia na siły aerodynamiczne.
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