Wyniki wyszukiwania - BazTech

1

Sterowanie przepływem gazu w sieci na podstawie wyników symulacji przepływu

Szoplik Jolanta, Ciuksza Marta

Instal

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2020

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nr 4

17--21

PL

W pracy przedstawiono przykład zastosowania wyników symulacji przepływu mieszaniny gazu ziemnego i paliwa alternatywnego (wodoru lub biometanu) w sieci rurociągów niskiego ciśnienia do sterowania nadciśnieniem strumienia mieszaniny w zależności od wielkości strumienia gazu ziemnego w sieci. Na podstawie rzeczywistych danych o zapotrzebowaniu na energię w przyłączu sieci zaprezentowano metodykę wyznaczania dobowego oraz godzinowego zapotrzebowania na gaz o dowolnej wartości ciepła spalania w zależności od temperatury otoczenia. Dane te były następnie stosowane w symulacjach przepływu w sieci do opracowywania charakterystyki sieci w postaci rozkładów strumieni, prędkości oraz nadciśnienia mieszanin gazowych w rurociągach sieci w celu wyznaczenia minimalnej wartości nadciśnienia strumienia mieszaniny wprowadzanej do sieci.

EN

The paper presents an example of the application of the flow simulation results of a mixture of natural gas and alternative fuel (hydrogen or biomethane) in low pressure gas network pipelines to control the overpressure of the mixture stream depending on the size of the natural gas stream in the network. On the basis of actual data on energy demand at the network connections, the methodology for determining the daily and hourly demand for gas with any value of combustion heat depending on the ambient temperature was presented. These data were then used in network flow simulations to develop network characteristics in the form of stream distributions, velocities and overpressure of gas mixtures in network pipelines to determine the minimum overpressure value of the mixture stream entering the network.

2

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

Surmacz K., Kowaleczko G.

Journal of KONES

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2016

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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.

3

Determination of water collection on two- and three-dimensional aerodynamic surfaces in external two-phase flow in atmospheric conditions

Sznajder R.

Journal of KONES

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2016

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Vol. 23, No. 1

369--376

EN

Simulations of two-phase flow cases consisting of air and water dispersed in atmosphere were conducted using ANSYS FLUENT solver. The computational model was built with the aim of determination of zones of water droplets impinging on the investigated surface, which is a first step towards simulations of ice accretion in flow conditions where super cooled water is present as dispersed phase. It follows Eulerian approach, currently most effective approach for determination of distribution of water collection on two- and three-dimensional surfaces. Dispersed water is treated as continuous phase and its transport equations are being solved along with air flow equations in the whole computational domain. There are two specific factors of this two-phase flow problem. One of them is ratio of air and water density, which is a cause of existence of two time scales in obtaining a numerical solution of this problem: one for convergence of air flow solution and another for solution of flow of dispersed water in the computational domain. This required development of a specific strategy in obtaining a numerical solution in some circumstances important in aerodynamics, especially at high angle of attack with flow recirculation zones on the wing. The other factor is relatively low concentration of water droplets in conditions important for atmospheric icing. The consequence of this is possibility of uncoupling of solution for both phases and narrowing the solution of the phase of dispersed water to a small region of non-uniformity of velocities of the dispersed phase. Results for two objects: an airfoil and helicopter tail rotor blade, exploiting the developed computational strategy will be presented.

4

Analysis of effects of shape and location of micro-turbulators on unsteady shockwave-boundary layer interactions in transonic flow

Sznajder J., Kwiatkowski T.

Journal of KONES

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2016

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Vol. 23, No. 2

373--380

EN

Solutions for turbulisation of a part of laminar boundary layer upstream of shockwave on laminar airfoil in transonic flow were investigated by means of solution of Unsteady Reynolds-Averagd Navier-Stokes equations using as a closure the four-variable Transition SST turbulence model of ANSYS FLUENT solver. This turbulence model has the capability of resolving laminar-turbulent transition occurring in undisturbed flow as well as under the influence of flow-control devices. The aim of the work was to investigate possibilities of improvement of aerodynamic characteristics of laminar wing of a prospective transport aircraft in adverse conditions characterised by occurrence of a shockwave over a laminar-turbulent transition region with separation of laminar flow under the shockwave. The subject is important for application of laminar flow technology, offering economic and environmental advantages due to decreased friction drag, into civil transport aviation. Natural laminar-turbulent transition in the investigated conditions takes place with occurrence of “laminar separation bubble” under the foot of a shockwave and the resulting shockwave is intensive and prone to unsteady oscillations, the “buffet” phenomenon, limiting operational range of flight parameters. In order to counteract the harmful effects of natural laminar-turbulent transition in transonic flow two types of turbulators, placed upstream of the shockwave, were investigated. One of them consisted of delta-shaped vortex generators, producing chordwise-oriented vortices. The other consisted of rectangular micro-vanes, perpendicular to flow and to airfoil surface producing vortices of rotation axes oriented spanwise. Effectiveness of both types of turbulators was investigated for varying height and their location on airfoil chord. Both types of turbulators have proved their effectiveness in tripping laminar boundary layer. The specific effects of the tutbulators, different for each type occurred in the region where laminar separation takes place on clean airfoil. As a result, the changes of lift and drag were different for each type of turbulators.

5

Effects of turbulence induced by micro vortex generators on shockwave : boundary layer interactions

Sznajder J., Kwiatkowski T.

Journal of KONES

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2015

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Vol. 22, No. 2

241--248

EN

Interactions between viscous and transonic effects in air flow around a laminar wing were investigated computationally by means of the solution of unsteady Reynolds-averaged Navier-Stokes Equations. The subject is important from the point of view of applications of Natural Laminar Flow technology in modern, economically efficient passenger aircraft. The research was focused on simulations and analyses of influence of turbulence induced by micro vortex generators on intensity of harmful transonic phenomena like strong shock waves and buffet. Two ways of modelling of the effects of turbulators – the micro vortex generators were taken into consideration. The first way consisted in resolving the shape and inclination angle of the generator in the grid over airfoil and setting the non-slip wall boundary condition on the surface of the generator. The second way, taking advantage of the BAY model of vortex generator, was implemented on orthogonal grid without the need of resolving the shape of the vortex generator in the grid. Calibration of the BAY model was aimed at producing similar distribution of vorticity and velocity circulation behind the model of the vortex generator, as obtained for the grid-resolved model of the vortex generator. The calibration procedure resulted, however, in overestimated turbulisation of the boundary layer in the BAY model, compared to the effects of the grid-resolved vortex generator. The flow simulations indicated, however, that turbulisation of boundary layer induced by micro vortex generators can reduce or eliminate the oscillation of strong shock wave and buffet in off-design conditions and that further adjusting of the BAY model is an efficient strategy for modelling the interactions between viscous and transonic effects in air flow around a laminar wing.

6

Modelowanie numeryczne procesu napełniania cylindra silnika ZI

Paliszewski P., Szczygieł I.

Postępy Nauki i Techniki

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2012

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Nr 15

116-122

PL

W pracy przedstawiono model numeryczny procesu napełniania cylindra silnika ZI. Model został zbudowany z użyciem komercyjnego pakietu obliczeniowego Ansys Fluent, który jest narzędziem pozwalającym na modelowanie przepływów zarówno ciepła jak i masy. Możliwości pakietu obliczeniowego można szeroko wykorzystać w procesie projektowania, eksploatacji bądź modyfikacji silników. W pracy zwrócono szczególną uwagę na proces napełniania cylindra. Opracowany model umożliwia analizę wpływu takich czynników jak długość kolektora dolotowego czy kształt profili wzniosu zaworów na napełnienie cylindra.

EN

In the paper the numerical model of a cold flow simulation inside IC engine is presented. Model was build using commercial computational package Ansys Fluent, which is able to simulate heat and mass flows. Ability of computational package can be used in engine design, or modification process. Created model gives opportunity to analyse influence of such aspects like: intake manifold length or valve lift profile on cylinder fill rate. Using numerical model, it is also possible to analyse the impact of an intake manifold shape on air swirl inside cylinder. As a result of computations in cylinder contours of pressure, temperature, particle tracks and many more physical quantities are obtained.

7

Badania numeryczne wpływu stenozy w tętnicach kręgowych na przepływ w tętnicy podstawnej

Jóźwik K., Obidowski D., Kłosiński P.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2008

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nr 134

17-25

PL

Transport krwi do mózgu odbywa się poprzez tętnice szyjne oraz tętnice kręgowe. W wyniku połączenia się tętnic kręgowych powstaje tętnica podstawna. Za pomocą obrazowania TK stworzone zostały modele geometryczne odwzorowywujące układ tych tętnic dla badanych przypadków. Metody numeryczne umożliwiają odwzorowanie przepływów krwi w wygenerowanych modelach. Na podstawie wyników wykonanych obliczeń i symulacji zidentyfikowano wpływ zmian miażdżycowych na charakterystyczne parametry przepływu.

EN

Blood transportation to the brain takes place through carotid arteries and vertebral arteries. As a result of the natural junction of vertebral arteries a basilar artery is created. A computer tomography could be used to make images of these arteries for the investigated cases and then to generate their geometrical models. Numerical methods allow one to represent blood flows in the generated models. On the basis of the results of conducted calculations and simulations, an influence of atherosclerotic changes on characteristic flow parameters has been identified.