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1
Content available Modelling the throttle effect in a mine drift
Hansen Rickard
Journal of Sustainable Mining
|
2021
|
Vol. 20, iss. 4
277--295
EN
The throttle effect is a phenomenon, which may occur during a fire underground, causing unforeseen smoke spread. This paper focuses on the modelling of the throttle effect in a mine drift, using a CFD software. The aim of the paper is to investigate whether the CFD tool is able to predict and reproduce the throttle effect for fire scenarios underground. Experimental data from fire experiments in a model-scale mine drift and modelling results from a CFD model were used during the analysis. It was found that the CFD model was not able to fully reproduce the throttle effect for fire scenarios in a mine drift. The inability was due to the under prediction of the fire gas temperature at the ceiling level and the over prediction of the temperatures at the lower levels. The difficulties occurred foremost during transient periods with high fire growth rates. Given the difficulties in modelling the thermal stratification and the throttle effect, the use of CFD models should be mainly for qualitative analysis. Qualitative analysis could possibly be performed for non-transient and low intensity fires.
2
Content available remote Influence of Printer Head Velocity on FDM Deposited Path Deformations
Wzorek A., Bajkowski J. M.
Machine Dynamics Research
|
2018
|
Vol. 42, No. 1
117--127
EN
Fused deposition modeling is a technology, which uses print head’s nozzle that is moved in three dimensions, during extraction of the filament material. The common issue is the fact, that the quality parameters of the deposited model are significantly influenced by the actual material’s flow rate. Although highest accuracy of the model should be obtained when the mass flow rate is directly proportional to an actual velocity of the printer’s head, the discrepancy between expected and real flow rate causes deformations and inaccuracies of the printed path. This phenomena is especially visible during acceleration and deceleration of the printhead. Development of commercially efficient measurement method may be used in software calibration of the material mass flow. In perspective, direct feedback control of material flow rate could increase correlation of quality and print time of deposited models that can lead to an FDM printing process enhancements and refinements in an efficient manner. The influence of the 3D printer’s head velocity on the width of the deposited path is studied using visual methods.
3
Content available Example of flow modelling characteristics in diesel engine nozzle
Kolaric D., Kolaric M.
Zeszyty Naukowe. Transport / Politechnika Śląska
|
2016
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z. 90
123--135
EN
Modern transport is still based on vehicles powered by internal combustion engines. Due to stricter ecological requirements, the designers of engines are continually challenged to develop more environmentally friendly engines with the same power and performance. Unfortunately, there are not any significant novelties and innovations available at present which could significantly change the current direction of the development of this type of propulsion machines. That is why the existing ones should be continually developed and improved or optimized their performance. By optimizing, we tend to minimize fuel consumption and lower exhaust emissions in order to meet the norms defined by standards (i.e. Euro standards). Those propulsion engines are actually developed to such extent that our current thinking will not be able to change their basic functionality, but possible opportunities for improvement, especially the improvement of individual components, could be introduced. The latter is possible by computational fluid dynamics (CFD) which can relatively quickly and inexpensively produce calculations prior to prototyping and implementation of accurate measurements on the prototype. This is especially useful in early stages of development or at optimization of dimensional small parts of the object where the physical execution of measurements is impossible or very difficult. With advances of computational fluid dynamics, the studies on the nozzles and outlet channel injectors have been relieved. Recently, the observation and better understanding of the flow in nozzles at large pressure and high velocity is recently being possible. This is very important because the injection process, especially the dispersion of jet fuel, is crucial for the combustion process in the cylinder and consequently for the composition of exhaust gases. And finally, the chemical composition of the fuel has a strong impact on the formation of dangerous emissions, too. The research presents the influence of various volume mesh types on flow characteristics inside a fuel injector nozzle. Our work is based upon the creating of two meshes in the CFD software package. Each of them was used two times. First, a time-dependent mass flow rate was defined at the inlet region and pressure was defined at the outlet. The same mesh was later used to perform a simulation with a defined needle lift curve (and hereby the mesh movement) and inlet and outlet pressure. In next few steps we investigated which approach offered better results and would thus be most suitable for engineering usage.
4
Content available Simulation of Diffusion Flows in Two-Phase Multilayered Stochastically Nonhomogeneous Bodies with Non-Uniform Distribution of Inclusions
Chaplya Y., Chernukha O., Davydok A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2015
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Vol. 19, No 3
321--351
EN
Admixture diffusion flows are investigated in two-phase randomly nonhomogeneous multilayered strips with non-uniform distributions of inclusions. Cases where the most probable disposition of layered inclusions is located near the body boundary on which the mass source acts in the neighborhood of another boundary and in the middle of the body are considered. The initial-boundary value problem is formulated for the function of random mass flow under conditions of a constant flow on the upper surface and zero concentration of the admixture on the lower surface. Calculation formulae are obtained for the diffusion flow averaged over the ensemble of phase configurations in the particular cases of beta-distribution at zero and nonzero initial concentrations. The dependences of the averaged admixture flows on medium characteristics are established. It is shown that if the admixture diffusion coefficient in inclusions is greater than in the matrix, consolidation of inclusions in the middle of the body leads to an increasing diffusion flow. Simulation of the averaged diffusion flows of the admixture in the multilayered strip is performed for different model variants of a probable disposition of phases in the body and their comparative analysis is carried out.
5
Content available Mathematical Modeling of Random Diffusion Flows in Two-Phase Multilayered Stochastically Nonhomogeneous Bodies
Chaplya Y., Chernukha O., Davydok A.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
|
2015
|
Vol. 19, No 3
297--320
EN
An approach for studying stochastical diffusion flows of admixture particles in bodies of multiphase randomly nonhomogeneous structures is proposed, according to which initialboundary value problems of diffusion are formulated for flow functions and methods of solution construction are adapted for the formulated problems. By this approach the admixture diffusion flow is investigated in a two-phase multilayered strip for the uniform distribution of phases under conditions of constant flow on the upper surface and zero concentration of admixture on the lower surface. An integro-differential equation equivalent to the original initial-boundary value problem is constructed. Its solution is found in terms of the Neumann series. Calculation formulae are obtained for the diffusion flow averaged over the ensemble of phase configurations under both zero and constant nonzero initial concentrations. Software is developed, a dependence of averaged diffusion flows on the medium characteristics is studied and general regularities of this process are established.
6
Content available remote Metodyka doboru przepływomierzy próbkujących z czujnikami powierzchniowymi prostokątnymi umieszczonymi w średnicy rurociągu
Krieser W.
Napędy i Sterowanie
|
2015
|
R. 17, nr 5
90--95
PL
Pomiary przepływu są bardzo ważne w przemyśle. Przepływomierze próbkujące to urządzenia, których można użyć do pomiaru przepływu w sytuacji, gdy nie ma możliwości użycia całoprzewodowych, uwzględniając techniczne i ekonomiczne warunki. W przypadku, gdy używamy matematycznych modeli czujnika oraz matematycznych modeli obiektu, istnieje możliwość teoretycznej analizy optymalnego położenia czujnika w rurociągu.
EN
Flow-rate measurements have very important meanings in industry. The sampling flowmeters are devices which can be used for measuring the flow-rate in situations where full-bore flowmeters cannot be used for technical or economical reasons. When we use a mathematical model of a sensor and a mathematical model of an object, we can theoretically optimize the position of the sensor in the pipe.
7
Content available remote Badania teoretyczne i konstrukcja łożyskowania gazowego wrzeciona szlifierskiego
Oryński F., Kawczyński S.
Mechanik
|
2015
|
R. 88, nr 8-9CD1
244--249
PL
W artykule zaprezentowano nową konstrukcję łożyska gazostatycznego. Łożysko powstało na podstawie analizy istniejących konstrukcji, jednak ma prostszą budowę. W drugiej części artykułu zaprezentowano metodę obliczeń i wyniki analizy matematycznej łożyska.
EN
The article presents a new gasostatic bearing design. Bearing was established on the basis of existing structures, but has a simpler design. In the second part of the article the calculation method and the results of mathematical analysis have been presented.
8
Content available Experimental research on the influence of the pulse injector control parameters on its flow rate
Czarnigowski J.
Combustion Engines
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2015
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R. 54, nr 4
15--20
EN
The paper presents the results of the impact of the control parameters on the fuel mass flow from the injector. The control parameters examined in the paper were: frequency and pulse width modulation of the modulated control signal (the second part of the injector control signal). The analysis covers 6 injector types of different design of the valve element and the coil. The experiments have shown that the frequency of the signal does not affect the injector performance, contrary to pulse modulation affecting the injector performance significantly.
PL
W artykule przedstawiono wyniki badań stanowiskowych wpływu parametrów sterowania na wydatek wtryskiwacza. Jako parametry sterowania rozumiano wypełnienie oraz częstotliwość sygnału modulowanego, czyli drugiej części sygnału sterowania wtryskiwaczem. Przedstawiono wyniki badań stanowiskowych 6 typów wtryskiwaczy różniących się konstrukcją zarówno elementu zaworowego, jak i cewki elektromagnetycznej. Wykazano, że częstotliwość sygnału prawie nie wpływa na wydajność wtryskiwaczy, w przeciwieństwie do wypełnienia, które wpływa znacznie.
9
Content available remote Badania przepływu ciepła i masy w przegrodzie hybrydowej z izolacją transparentną
Wilk-Słomka B.
Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska
|
2010
|
z.57[271], nr 4
565-572
PL
Przedstawiono wybrane parametry cieplne przegrody hybrydowej z izolacją transparentną. Analiza została przeprowadzona na podstawie pomiarów gęstości strumienia cieplnego, natężenia całkowitego promieniowania słonecznego oraz odpowiednich temperatur: powietrza wewnętrznego i zewnętrznego, na wewnętrznej i zewnętrznej powierzchni przegrody uzyskanych na stanowisku badawczym Katedry Budownictwa Ogólnego i Fizyki Budowli.
EN
Collected measurement data during researches in Department of Building and Building Physics are the base for trial of selected thermal parameters of hybrid wall with transparent insulation description. This kind of insulation is one of the alternative for energy-saving buildings.
10
Content available Studia nad przepływem masy w suszarniach o przepływie mieszanym
Kocsis L., Meszaros C., Farkas I.
Problemy Inżynierii Rolniczej
|
2009
|
R. 17, nr 4
83-92
PL
Suszenie jest jednym z ważniejszych i najbardziej niezbędnych zabiegów w produkcji rolnej. Około 30% ziarna po zbiorze wymaga suszenia. Proces suszenia jest jednak bardzo energochłonny, a w wielu przypadkach nieprzyjazny dla środowiska ze względu na spalanie paliw kopalnych w celu uzyskania niezbędnej energii cieplnej. Chociaż suszarnie o przepływie mieszanym są szeroko stosowane, wciąż istnieje potrzeba optymalizacji wielu procesów cząstkowych. Na przykład, występują duże różnice w prędkości pionowej partii ziarna, co powoduje różnice w czasie ich ekspozycji. W rezultacie mamy do czynienia z nierównomiernym wysychaniem, a w konsekwencji z niedosuszaniem lub przesuszaniem poszczególnych partii materiału. Przeprowadzone badania miały na celu określenie oddziaływania ścianek komory suszenia oraz daszkowych kanałów powietrznych, na rozkład prędkości masy ziarna. Opracowanie przedstawia wyniki doświadczeń z przepływem ziarna. W przyszłych działaniach przewiduje się opracowanie modelu PFC dla przepływu masy ziarna, co umożliwi doskonalsze prognozowanie przebiegu procesu suszenia.
EN
Drying is one of the most important and most significant operations in agricultural business. Approximately 30% of the grain must be dry after harvesting. The energy consumption of the drying process is extremely high and in many cases it is not environment friendly because of the combustion of fossil fuels to produce the required heat energy. Although the mixed-flow dryers are widely used it is still necessary to optimize many segment processes. For example there are big differences in the vertical grain particle velocity causing differences in the residence time. As a result, uneven drying occurs and, hence, under-drying or over-drying of single grain portions. To investigate the influences of the dryer walls and the air ducts on the particle velocity distribution experiments have been carried out. Hereby this work submits the results of the grain-flow experiments. In a future work a PFC model for the grain mass flow will be developed enabling improvements in the prediction of the drying process.
11
Określanie strumienia masy wody chłodzącej skraplacze turbin w bloku energetycznym
Andruszkiewicz A., Godlejewski T., Górecki J., Kubas K.
Systems : journal of transdisciplinary systems science
|
2008
|
Vol. 13, spec. iss. 1/2
96--102
EN
The parameter that decides about the correction of energy unit activity in power plant could be the capacitor cooling water flux. This parameter is not defined by professional polish power plants. Authors of publications have processed and accustomed the system of bringing a measurement result to the steer point of the unit. This signal is proportional to the above mentioned water flux. In this paper two alternative methods were used to measure the water mass flow: either by application the flux dynamic pressure averaging probes or by using flux inertial power in elbow flow meters case. It helps to optimize the power unit running through fitting it to current energetic needs of the power unit.
12
Content available remote Analysis of Velocity Distribution in Vaneless Diffuser of the Radial Compressor
Dembski G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2005
|
nr 128, vol. 1
139-146
EN
In the article the flow phenomena in the blower with impellers dia. D²= 800m is presented. Thermoanometric reserch of aerodynamic trail and its comparison with numeric calcualtion is shown. Distribution of velocity vectors behind the impeller is presented for impellers with different blade angles.
13
Content available remote A New Value to 3D Shape Optimisation of LP Turbine Stages Operating in Wet Steam
Dykas S., Lampart P.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2005
|
nr 128, vol. 1
155-166
EN
3D blading for the exit stage of a large power steam turbine was optimised based on direct constrained optimisation on coarse grids using a simplex method and a RANS solver with the Baldwin-Lomax turbulence model and state equation for perfect gas. The process of optimisation yielded new designs with changed 3D stacking lines of stator blades, including compound lean and sweep of stator blades. The results of optimisation are validated in this paper by 3D RANS computations on refined grids with the κ-ω SST turbulence model and perfect gas equation, or alternatively the real gas model without or with condensation. The paper concentrates on differences in flow fields and stage characteristics obtained from both gas models to estimate the quality of coarse-grid perfect-gas optimisation.
14
Content available The Numerical solution for the problem of heat and mass flow in the soil heated with warm air
Bożek B., Kurpaska S.
Archives of Hydro-Engineering and Environmental Mechanics
|
2000
|
Vol. 47, nr 1-4
75-96
EN
In this paper a difference method of solving the system of differential equations is presented for differential equations, describing the distribution of temperature and water content in the greenhouse substrate heated with a system of heating pipes. The algorithm of solving the proposed method (explicite-implicite difference scheme) is presented. In addition, the effects of temperature and water content changes obtained from the solution of proposed the model as well as the model where the thermal diffusion of mass was included were compared.
15
Content available remote Analysis of compression/expansion processes in zero-emission power carbon dioxide cycle based on non-ideal gas model
Górski J., Chmielniak T., Yantovski E.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
1999
|
nr 115
159--166
PL
The new high performance and no releasing pollutants CO2 power MATHIANT cycle, operates within the pressure range 1 - 300 bar (4). The paper is concerned with some aspects of CO2 compression/expansion processes. The thermodynamic and flow processes in high-pressure units of CO2 compressor and turbine are strongly affected by real gas phenomena, especially in the supercritical region. For the assumed pressure ratios, polytropic efficiencies, cooling and mass flows in each stage it is possible to obtain the final state parameters, compression/expansion work and other performance characteristics based on the real gas model CO2 properties obtained from Altunin's virial EOS.
16
Content available remote Application of Korteweg's capillary stress tensor in momentum balance for flashing flow
Badur J., Banaszkiewicz M.
Archives of Thermodynamics
|
1998
|
Vol. 19, no 1/2
61-85
EN
This paper presents a modification to the Gizburg-Landau model by means of a new definition of stress tensor for liquid-vapour mixture. The proposed modification takes into account stresses arising in response to density gradients that models the contribution of interfacial areas in the homogeneous Ginzburg-Landau model. The additional capillary stress is derived from the constitutive equation postulated by Korteweg. The modified model has beentested on classical experiments of water-steam flows, such as Moby Dick and BNL. It seems that the inclusion of capillary stresses brings about a significant improvement both in the mass flow rate and pressure distribution predictions. These facts promise the possibility of better description of phenomena occurring in choked two-phase flows.
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