Wyniki wyszukiwania - BazTech

1

Sezonowe magazyny ciepła

Czekalski Rafał, Ksiądz Mateusz

Energetyka

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2023

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nr 2

77--87

PL

W artykule przedstawiono ideę sezonowego magazynowania ciepła w systemach ciepłowniczych. Dokonano przeglądu potencjalnych technologii długoterminowego magazynowania ciepła wraz z opisem przykładowych instalacji. Skupiono się na magazynach typu PTES współpracujących z kolektorami słonecznymi. Przedstawiono także autorski model układu ciepłowniczego wyposażonego w sezonowy magazyn ciepła, opracowany w programie TRNSYS.

EN

The article presents the concept of seasonal thermal energy storage in district heating systems. A review of potential long-term heat storage technologies is included and some examples of installations are described. The focus is on the technology of pit thermal energy storage (PTES) systems integrated with solar collectors. Moreover, the original model of a district heating system equipped with seasonal thermal energy storage developed using TRNSYS software is presented.

2

Numerical investigations of the thermal properties of window systems: a review

Sadko Karolina, Piotrowski Jerzy Zbigniew

Structure and Environment

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2022

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Vol. 14, no. 4

126--141

EN

Windows are an essential part of building envelopes since they enhance the appearance of the building, allow daylight and solar heat to come in, and allow people to observe outside. However, conventional windows tend to have poor U-values, which cause significant heat losses during the winter season and undesired heat gain in summer. Modern glazing technologies are therefore required to improve thermal resistance and comfort of the occupants, whilst mitigating the energy consumption of buildings. In the present work, a comprehensive review of the numerical investigations of the thermal properties of window systems and glazed buildings partitions is presented. However, the proposed models to predict the thermal performance most often concern only specific cases of window systems related to geometry and used material solutions, focused on specific physical processes, thus they contain a lot of simplifications, such as omitting the influence of radiation, temperature changes or velocity profiles.

PL

Istotnymi elementami budynków są okna, które wpływają na ich wygląd, umożliwiają dostęp światła dziennego i ciepła pochodzącego z promieniowania słonecznego, a także pozwalają na obserwowanie otoczenia. Jednakże w porównaniu do pozostałych przegród budowlanych konwencjonalne okna charakteryzują się zwykle gorszymi wartościami współczynnika przenikania ciepła U, generując znaczne straty ciepła w sezonie zimowym i niepożądane zyski ciepła w lecie. W związku z tym konieczne jest poszukiwanie nowoczesnych rozwiązań w technologii okiennej, które poprawią opór cieplny i komfort mieszkańców, jednocześnie zmniejszając zużycie energii przez budynki. W niniejszej pracy przedstawiono przegląd numerycznych metod określania właściwości cieplnych okien i przeszklonych przegród budowlanych. Analiza literatury pokazuje, że proponowane modele dotyczą jednak najczęściej tylko konkretnych przypadków systemów okiennych, związanych z określoną geometrią i zastosowanymi rozwiązaniami materiałowymi, w których uwzględnia się jedynie wybrane procesy fizyczne. Skutkiem tego jest przyjmowanie podczas modelowania wymiany ciepła szeregu uproszczeń, takich jak pomijanie wpływu promieniowania czy nieuwzględnianie zmian temperatury i prędkości.

3

The Use of the k-ω SST Turbulence Model for Mathematical Modeling of Jet Fire

Lewak Michał Wojciech, Tępiński Jarosław, Klapsa Wojciech

Safety & Fire Technology

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2022

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Vol. 59, iss. 1

28--40

EN

Aim: The purpose of this study is to verify the usability of the k-ω SST turbulence model for the description of the combustion process during a vertical propane jet fire. Simulating a jet fire using computational fluid mechanics involves an appropriate selection of a mathematical model to describe the turbulent flow. It is important as the variables from this model also describe the rate of the combustion reaction. As a result, they have an impact on the size and shape of the flame. The selection of an appropriate model should be preceded by preliminary simulations. Project and methods: For this purpose, a vertical jet fire in no wind conditions was selected for simulation. Consequently, it was possible to develop a two-dimensional axisymmetric geometry. A good numerical mesh can be applied to such axisymmetric geometry. Selected process conditions allowed to create an axisymmetric numerical grid. Its values, proving the quality, are shown in a chart demonstrating the distribution of the parameter quality depending on the number of elements from which the numerical grid was built. In the work, a two-stage model of the combustion reaction was selected in order to verify whether the area in which the mole fraction of carbon monoxide will have significant values is so large that the selected kinetic reaction model will have an impact on the flame length. Results: Three simulations of jet fire taking place in the direction opposite to the force of gravity were performed. The simulations performed allowed for setting the basic Lf parameter, which determines the flame length. Additionally, the length of the mixing path slift-off, needed to initiate the combustion reaction, was determined. The simulations performed allowed for comparing significant parameters characterizing the flame with the parameters calculated using correlations included in the literature on the subject. Due to this comparison, it was possible to define an interesting scope of research work, because the length of the gas mixing path determined from the CFD simulation differed significantly from the values calculated from the correlation. Conclusions: Interestingly, such large differences between CFD results and correlations were not observed for the Lf parameter. The correlations based on the Froude number give slightly higher values of the flame length than the results of the CFD simulation. On the other hand, the correlation based on the Reynolds number gives slightly lower values of the Lf parameter than the values obtained from the CFD calculations. This may indicate that the effects related to the inertia forces (Re number) better describe the simulation process conditions than the correlations based on the influence of inertia forces and gravity forces (Fr number).

PL

Cel: Celem tego opracowania jest sprawdzenie przydatności modelu k-ω SST do opisu procesu spalania podczas pionowego pożaru strumieniowego propanu. Symulacja pożaru strumieniowego przy pomocy obliczeniowej mechaniki płynów wiąże się z odpowiednim wyborem modelu matematycznego służącego do opisu przepływu burzliwego. Jest to o tyle ważne, że zmienne z tego modelu opisują również szybkość reakcji spalania, a więc mają wpływ na rozmiar i kształt płomienia. Dobór odpowiedniego modelu powinien być poprzedzony symulacjami wstępnymi. Projekt i metody: Do symulacji wybrano pionowy pożar strumieniowy w warunkach bezwietrznych. Dzięki temu opracowana została dwuwymiarowa osiowosymetryczna geometria, na którą możliwe jest nałożenie dobrej siatki numerycznej. Wybrane warunki procesowe pozwoliły na stworzenie osiowosymetrycznej siatki numerycznej, której wartości świadczące o jakości uwidoczniono na wykresie przedstawiającym rozkład jakości parametru w zależności od liczby elementów, z jakich zbudowano siatkę numeryczną. Na podstawie dwuetapowego modelu reakcji spalania sprawdzono, czy obszar, w którym ułamek molowy tlenku węgla będzie miał duże wartości wpłynie na długość płomienia w wybranym modelu kinetycznym reakcji. Wyniki: Wykonane zostały trzy symulacje pożaru strumieniowego odbywającego się w kierunku przeciwnym do działania sił grawitacji. Pozwoliły one na wyznaczenie podstawowego parametru Lf , który określa długość płomienia. Dodatkowo wyznaczona została długość drogi mieszania slift-off , która jest niezbędna do zapoczątkowania reakcji spalania. Wykonane symulacje pozwoliły na porównanie istotnych parametrów charakteryzujących płomień z parametrami obliczonymi przy pomocy korelacji zawartych w literaturze przedmiotu. Wnioski: Porównanie wyżej wymienionych parametrów umożliwiło określenie ciekawego zakresu pracy badawczej, ponieważ wyznaczona z symulacji CFD długość drogi mieszania gazu znacząco różniła się od wartości obliczonych z korelacji. Co ciekawe, tak dużych rozbieżności między wynikami CFD a korelacjami nie zaobserwowano dla parametru Lf . Przy czym korelacje oparte o liczbę Froude’a podają nieco większe wartości długości płomienia niż wyniki symulacji CFD. Natomiast korelacja oparta o liczbę Reynoldsa podaje nieco mniejsze wartości parametru Lf niż wartości otrzymane z obliczeń CFD. Może to świadczyć o tym, że efekty związane z siłami bezwładności (liczba Re) lepiej opisują warunki procesowe niż korelacje oparte o wpływ sił bezwładności i sił ciężkości (liczba Fr).

4

Modelowanie matematyczne pożarów strumieniowych za pomocą obliczeniowej mechaniki płynów CFD

Lewak Michał, Tępiński Jarosław, Lesiak Piotr

Przemysł Chemiczny

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2022

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T. 101, nr 5

324--329

PL

Przedstawiono modelowanie matematyczne pożaru strumieniowego metodą CFD na przykładzie pożaru propanu wydostającego się z dyszy. Pokazano wpływ masowego przepływu gazu na długość, szerokość i wysokość płomienia. Symulacje numeryczne przeprowadzono dla przepływów cieczy w zakresie liczby Macha poniżej 0,2. Pozwoliło to na prowadzenie symulacji w zakresie przepływu nieściśliwego. Otrzymane wyniki symulacji porównano z korelacjami opisanymi w literaturze.

EN

Math. modeling of a jet fire using the CFD method was presented on the example of a propane fire escaping from a nozzle. The effect of gas mass flow on the length, width and height of the flame was shown. Numerical simulations were performed for fluid flows in the Mach number range below 0.2. This allowed the process to be defined as an incompressible flow. The obtained simulation results were compared with the correlations described in the literature.

5

The mathematical modelling of transient processes in a three phase electric power system for a single phase short-circuit at the end of a long power supply line

Chaban Andriy, Lis Marek, Szafraniec Andrzej, Levoniuk Vitaliy

Przegląd Elektrotechniczny

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2022

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R. 98, nr 2

174--177

EN

A mathematical model of a three-phase power line loaded with a resistance and inductive receiver is developed in the paper. The power line is considered as a system with distributed electrical parameters with a calculated output voltage. This approach makes it possible to use the three-phase line model as a stand-alone, universal subsystem of the integrated electric power system. The results are presented of a computer simulation of transient processes as the line is switched on in the single-phase short-circuit mode at the end of the line.

PL

W pracy opracowano model matematyczny trójfazowej elektroenergetycznej linii zasilania obciążonej odbiornikiem o charakterze rezystancyjno-indukcyjnym. Linia elektroenergetyczna jest traktowana, jako układ o elektrycznych parametrach rozłożonych, w którym obliczono napięcie wyjściowe. Takie podejście umożliwiło opracowanie modelu linii trójfazowego, jako autonomicznego, uniwersalnego podsystemu scalonego układu analizowanej sieci elektrycznej. Przedstawiono wyniki symulacji komputerowej procesów nieustalonych w sieci elektrycznej w czasie włączania linii w tryb zwarcia jednofazowego na końcu linii.

6

The mathematical modelling of transient processes in a drive system including asynchronous and synchronous drives of susceptible motion transmission

Chaban Andriy, Lis Marek, Szafraniec Andrzej, Levoniuk Vitaliy

Przegląd Elektrotechniczny

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2022

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R. 98, nr 1

66--70

EN

A mathematical model is developed of an electric drive system including a power transformer, deep bar cage induction asynchronous motors, and long shaft synchronous drives of distributed mechanical parameters. The model of a deep bar cage induction asynchronous motor addresses the skin-effects across the rotor cage bars using the theory of electromagnetic field. The motion transmission of the drives is described with a mixed problem of the third type Poincaré boundary conditions. The general system of differential equations is given in the Cauchy form, integrated by means of the latent Euler method. Results of computer simulations are shown with graphics, which are analysed.

PL

W pracy niniejszej opracowano model matematyczny zespołu elektrycznego obciążenia, który zawiera transformator mocy, głębokożobkowe napędy asynchroniczne i napędy synchroniczne z długimi wałami o mechanicznych parametrach rozłożonych. Model głębokożłobkowych silników asynchronicznych uwzględnia zjawisko naskórkowości w prętach klatki wirników za pomocą teorii pola elektromagnetycznego. Transmisję ruchu napędów opisuje się za pomocą zadania mieszanego o warunkach brzegowych trzeciego rodzaju Poincaré. Ogólny układ równań różniczkowych podany jest w postaci Cauchy, który całkuje się za pomocą ukrytej metody Eulera. Wyniki symulacji komputerowej przedstawione są w postaci rysunków, które są analizowane.

7

Mathematical modelling by convection-diffusion with reaction of organic pollution in the wadi Mouillah stream, north-western Algeria

Benadda Lotfi, Djelita Belkheir, Chiboub-Fellah Abdelghani

Journal of Water and Land Development

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2022

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no. 54

26--37

EN

This work describes the behaviour of organic pollutants along the wadi Mouillah watercourse and its main tributaries and their impacts on the Hammam Boughrara dam, located in the NW of Algeria, in the Wilaya of Tlemcen. The use of a database relating to physico-chemical, biotic and hydrological variables, covering the period from January 2006 to December 2009, contributed to the understanding of the spatiotemporal evolution of each variable. The application of a mathematical model of the diffusion by convection-dispersion with a reaction on two characteristic parameters of organic pollution, the biochemical oxygen demand (BOD5) which records values above the norm, with peaks that can reach 614%, and total phosphorus (Ptot), which the concentration is always higher with maxima reaching 53 mg∙dm-3 favouring eutrophication; this made it possible with precision to synthesise the propagation of pollutants in the liquid mass. The results obtained on the waters of Wadi Mouillah are therefore of poor quality; there is a need to set up a rigorous water quality monitoring system, with water treatment and decontamination devices to preserve the water resources. This will allow to contribute to better management of water quality in terms of combating the spread of pollution. Therefore, they can be used to support decisions in the context of sustainable development.

8

Development of mathematical and numerical models for the analysis of overlap laser beam welding of dissimilar materials

Domański Tomasz, Piekarska Wiesława, Saternus Zbigniew, Kubiak Marcin

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 2

15--26

EN

The welding process of dissimilar materials causes a lot of technological issues related to different properties of materials of joined elements. Thermal conductivity is one of most important factors influencing the deformation of the weld. The change of thermal conductivity in the function of the temperature can produce various strains that cannot be predicted during construction design. Different structures of materials appear during joining of dissimilar materials as well as different characteristic zones of the joint and its mechanical properties. The most important is the proper identification of joint zones and the size of deformation at the production stage of welded construction. This work presents the numerical analysis of physical phenomena in overlap welding of two sheets made of S355 carbon steel and 304 austenitic steel using a laser beam. A three-dimensional discrete model is developed taking into account thermophysical properties changing with temperature. Temperature distribution and the shape of the welding pool is predicted on the basis of performer computer simulations. The influence of thermal load on the formation of stress and strain fields is determined.

9

Investigation of dynamics and power needs for container unloading from ship process

Janutėnienė Jolanta, Bogdevičius Marijonas, Jankūnas Valdas, Janutėnaitė-Bogdanienė Jūratė, Andziulis Arūnas, Kurmis Mindaugas, Drungilas Darius

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 1

89--99

EN

The operational problem of container unloading from the ship is analyzed in this paper. Dynamic “crane-cargo-ship” system was investigated, and a mathematical model was created. In the model, the gap between the container and the ship’s cargo hold, the mass of the cargo, the container’s center of the mass, and the frictional forces that may occur during lifting from the cargo hold were estimated. Numerical analysis of the system was performed. Results of numerical analysis were compared with experimental measurements of containers unloading process in port. Requirement of lifting power was modelled depending on mass of cargo. Additional power needs in case of contact forces between container and wall of the ship’s cargo hold were calculated. Rational lifting conditions could be deduced using a created mathematical model and the reliability of the container and cargo during lifting could be deduced.

10

Hybrid methodology using balancing optimization and vibration analysis to suppress vibrations in a double crank-rocker engine

Albaghdadi Anwr M., Baharom Masri, Sulaiman Shaharin

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 1

53--61

EN

This study aims to present mathematical modelling to evaluate and analyze double crankrocker engine performance. The study suggests the use of two methods to reduce system vibration through balancing optimization and vibrational analysis. The combination of both methods acts as a verification method; besides it can be used as a tool for further system design enhancement and condition monitoring. The derived mathematical model is then used for balancing optimization to identify system shaking forces and moments, while variable speed is considered as an added parameter to evolve the optimization process. This factor shows better enhancement in reducing system shaking forces and moments compared to constant speed balancing method. Next, the system characteristics were concluded in terms of mode shapes and natural frequencies using modal and frequency response analysis, which give clear clue for secure system operational ground. Finally, the reduction in system vibrations was translated into engine’s centre of mass velocity, which evaluates balancing process effectiveness and indicate if further enhancement should be conducted.

11

Dynamic modelling of bacteriophage production process

Konopacki Maciej, Grygorcewicz Bartłomiej, Gliźniewicz Marta, Miłek Dominika, Kordas Marian, Rakoczy Rafał

Chemical and Process Engineering

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2022

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Vol. 43, nr 4

471–-482

EN

Bacteriophages, viruses that can infect bacteria, are promising alternatives for antibiotic treatment caused by antibiotic-resistant bacteria strains. For that reason, the production of bacteriophages is extensively studied. Mathematical modelling can lead to the improvement of bioprocess by identification of critical process parameters and their impact on the demanded product. Dynamic modelling considers a system (i.e. bioreactor or bioprocess) as a dynamic object focusing on changes in the initial and final parameters (such as biomass concentration and product formation) in time, so-called signals and treats the studied system as a “black box” that processes signals. This work aimed to develop a mathematical model that describes bacteriophage production process. As result, we created a dynamic model that can estimate the number of bacteriophages released from cells as plaque-forming units at specific time points based on the changes in the bacteria host-cell concentration. Moreover, the proposed model allowed us to analyze the impact of the initial virus concentration given by multiplicity of infection (MOI) on the amount of produced bacteriophages.

12

Modeling the problem of sequencing projects in the contractor’s portfolio of orders

Jaśkowski Piotr, Biruk Sławomir, Krzemiński Michał

Archives of Civil Engineering

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2022

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Vol. 68, nr 3

307--322

EN

It is a usual practice for a contractor to deliver several projects at a time. Typically, the projects involve similar types of works and share the same pool of resources (i.e. construction crews). For this reason, the company’s portfolio of orders considered for a particular planning horizon can be modeled as a project with repeatable processes to be performed in heterogeneous units located in a number of construction sites. Its scheduling requires determining the best sequence of the resources’ moving from unit to unit while minding the due dates related with particular orders as well as resource continuity constraints. The authors present a model of this scheduling problem in the form of a mixed-integer linear program. The aim is to schedule a portfolio of projects in a way that minimizes the total of the resource idle time-related costs, the indirect costs, and the delay penalties. The model can be solved by means of a general-purpose solver. The model is applied to schedule a portfolio of multifamily housing projects.

PL

W artykule opracowano model matematyczny umożliwiający przydział brygad roboczych do realizacji poszczególnych procesów, spośród będących w dyspozycji przedsiębiorstwa w przyjętym horyzoncie planowania, a także na ustalenie harmonogramu ich pracy - terminów realizacji przydzielonych im procesów na wznoszonych obiektach. Model ma na celu zapewnienie redukcji łącznych kosztów pośrednich i przestojów w pracy brygad oraz kar umownych. Straty spowodowane przestojami w pracy każdej brygady są obliczane jako iloczyn czasu przestoju po wykonaniu procesu na działce roboczej oraz jednostkowych (dziennych) kosztów przestoju. Wysokość kar umownych jest obliczana jako iloczyn różnicy między czasem realizacji przedsięwzięcia a czasem dyrektywnym oraz jednostkowej kary. W przypadku ukończenia realizacji w czasie krótszym od dyrektywnego wykonawca nie zostanie obciążony karami finansowymi, przyjęto również, że nie uzyska za to bonusu. Zaproponowany sposób doboru zmiennych decyzyjnych oraz zapisu analitycznego ograniczeń problemu o charakterze permutacyjnym pozwolił na sformułowanie modelu w postaci modelu mieszanego całkowitoliczbowego, do którego rozwiązania można stosować dostępne na rynku solvery. Oczywiście dotyczy to modeli problemów o niewielkiej złożoności obliczeniowej, lecz stwarza możliwość opracowania bazy przykładów testowych i weryfikacji jakości tworzonych w przyszłości algorytmów dedykowanych. Zaproponowane podejście do modelowania i rozwiązania problemu szeregowania zleceń przedsiębiorstwa przedstawiono na przykładzie realizacji stanu surowego zamkniętego sześciu budynków wielorodzinnych wznoszonych w technologii monolitycznej (fundamenty, ściany i stropy żelbetowe monolityczne; stropodach z żelbetowych płyt prefabrykowanych z warstwami izolacyjnymi; ściany ocieplone z wykorzystaniem ETICS (External Thermal Inusulation Composite System). Realizacja każdego obiektu wymaga wykonania następujących procesów powierzanych do wykonania odrębnym brygadom branżowym: roboty ziemne i fundamentowe (stan zero), konstrukcja monolityczna żelbetowa (stan surowy), dach, elewacja. Realizacja tych obiektów stanowi portfel zleceń analizowanego przykładowego przedsiębiorstwa w okresie jednego roku.

13

Impact of cutting units’ design on biomass cutting resistance

Zastempowski Marcin, Bochat Andrzej, Janiec Maciej, Hujo Lubomir, Jablonicky Juraj

Acta Mechanica et Automatica

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2022

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Vol. 16, no. 3

159--265

EN

The paper presents mathematical models describing the moments of resistance to cutting on the cutting drum shafts in the biomass cutting process. The mathematical procedures described in the paper have been verified on a test stand developed and constructed by the authors, which reflects real conditions of the process of cutting plant material into pieces of specified lengths. Experimental verification proved that the developed mathematical models are adequate for drums of both cylindrical and conical constructions. The value of the average error did not exceed 13%. Following the mathematical elaboration and verification studies, the authors carried out calculations for machines currently available on the market that are equipped with drum cutting units. The calculations were carried out for the most commonly cut material, i.e. for maize, straw and green plant materials. The obtained results confirm the complexity of the problem arising from a wide range of numerical values of cutting resistance, which is contained in the range of 400–1,800 nm. The compiled database can be practically applied in the selection of machines for specific field works, and the mathematical models developed and verified in the study can be applied at the stage of designing new designs of cutting drums used in forage harvesters.

14

Self-preservation Effect of Gas Hydrates

Pavlenko Anatoliy

Rocznik Ochrona Środowiska

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2021

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Tom 23

346--355

EN

This work was performed to improve the storage and transportation technology of gas hydrates in nonequilibrium conditions. At atmospheric pressure and positive ambient temperature, they gradually dissociate into gas and water. Simulation of the gas hydrate dissociation will determine optimal conditions for their transportation and storage, as well as minimize gas loss. Thermodynamic parameters of adiabatic processes of forced preservation of pre-cooled gas hydrate blocks with ice layer were determined theoretically and experimentally. Physical and mathematical models of these processes were proposed. The scientific novelty is in establishing quantitative characteristics that describe the gas hydrates thermophysical parameters thermophysical characteristics influence on the heat transfer processes intensity on the interphase surface under conditions of gas hydrates dissociation. Based on the results of experimental studies, approximation dependences for determining the temperature in the depths of a dissociating gas hydrate array have been obtained. Gas hydrates dissociation mathematical model is presented.

15

The mathematical model of high voltage switch as an element of a power system

Czaban Andriy, Levoniyk Vitaliy, Figura Radosław

Przegląd Elektrotechniczny

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2021

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R. 97, nr 7

94--97

EN

In this work, on the basis of an interdisciplinary method of modelling, a mathematical model of a power system is presented, main element of which system is an gas switch. For modelling of non-mechanical part, a popular theorem on flickering centre of speed of rotation was used. For a mathematical model of an arc, when the resistance was of non-linear nature, a resistive-capacitive alternative diagram was used. The final system of differential equations was presented in a normal cauche form. Results of simulation were given as drawings and were analysed.

PL

W pracy na podstawie interdyscyplinarnej metody modelowania zaproponowano model matematyczny układu elektroenergetycznego, głównym elementem którego wyłącznik gazowo-elektryczny typu SF6. Dla modelowania części mechanicznej wyłącznika wykorzystano słynny teoremat o migowym centrum prędkości obracania. Dla modelu matematycznego luku wykorzystano rezystancyjno-pojemnościowy schemat zastępczy, gdy rezystancja rozpatrywała się jako funkcja nieliniowa. Końcowy układ równań różniczkowych przedstawiony w normalnej postaci Causze’go. Wyniki symulacji komputerowej podano w postaci rysunków, które analizują się.

16

Simulations of fuels consumption in the CHP system based on modernised GTD-350 turbine engine

Hryniewicz Marek, Roman Kamil

Journal of Water and Land Development

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2021

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no. 51

250--255

EN

There were done simulations of fuels consumption in the system of electrical energy and heat production based on modernised GTD-350 turbine engine with the use of OGLST programme. In intention the system based on GTD-350 engine could be multifuel system which utilise post-fying vegetable oil, micronised biomass, sludge, RDF and fossil fuels as backup fuels. These fuels have broad spectrum of LHV fuel value from 6 (106 J•kg-1 ) (e.g. for sludge) to 46 (106 J•kg-1) (for a fuel equivalent with similar LHV as propan) and were simulations scope. Simulation results showed non linear dependence in the form of power function between unitary fuel mass consumption of simulated engine GTD-350 needed to production of 1 kWh electrical energy and LHV fuel value (106 J•kg-1). In this dependence a constant 14.648 found in simulations was multiplied by LHV raised to power - 0.875. The R2 determination coefficient between data and determined function was 0.9985. Unitary fuel mass consumption varied from 2.911 (kg•10-3•W-1•h-1) for 6 (106 J•kg-1) LHV to 0.502 (kg•10-3 •W-1 •h-1) for 46 (106 J•kg-1) LHV. There was assumed 7,000 (h) work time per year and calculated fuels consumption for this time. Results varied from 4,311.19 (103 kg) for a fuel with 6 (106 J•kg-1) LHV to 743.46 (103 kg) for a fuel with 46 (106 J•kg-1) LHV. The system could use fuels mix and could be placed in containers and moved between biomass wastes storages placed in many different places located on rural areas or local communities.

17

Mathematical models use to yield prognosis of perennials on marginal land according to fertilisers doses

Hryniewicz Marek, Strzelczyk Maria, Helis Marek, Paszkiewicz-Jasińska Anna, Steinhoff-Wrzesniewska Aleksandra, Roman Kamil

Journal of Water and Land Development

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2021

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no. 51

233--242

EN

Models describe our beliefs about how the world functions. In mathematical modelling, we translate those beliefs into the language of mathematics. Mathematical models can yield prognose on the base of applied fertiliser dose. In this work results of finding yield mathematical model according to fertiliser (nitrogen) dose for perennials (willowleaf sunflower Helianthus salicifolious, cup plant Silphium perfoliatum and Jerusalem artichoke Helianthus tuberosus) on marginal land are presented. Models were described as normalised square equations for dependence between yield and fertiliser doses. Experiments were conducted in lisymeters and vases for willowleaf sunflower and cup plant. For Jerusalem artichoke experiments were done in vases only. All experiments have been doing during two years (2018 and 2019) for different fertilisers doses (45, 90 and 135 kg N∙ha-1) in three repetitions. From simulations maximal yield could be achieved for following fertiliser doses – willowleaf sunflower 104 kg N∙ha-1, cup plant 85 kg N∙ha-1 and Jerusalem artichoke 126 kg N∙ha-1.

18

Mathematical modelling of filtration processes in drainage systems with different depths of drainage

Havryliuk Volodymyr, Bomba Andrii, Pinchuk Oleg, Gerasimov Ievgenii, Klimov Serhii, Tkachuk Mykola, Turcheniuk Vasyl

Journal of Water and Land Development

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2021

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no. 50

74--78

EN

The article discusses the option for the application of the methodology for the solution of boundary value problems on the conformal mapping for the calculation of filtration process in the horizontal systematic drainage, provided that the drain is installed at a different depth. In particular, the case of methods combining fictitious areas and quasiconformal mappings for solving nonlinear boundary conditions problems for calculating filtration regimes in soils with free sections of boundaries (depression curves) and intervals of the “drainage” type. As an example, the authors designed a hydrodynamic flow grid, determined the values of the flows to the drain, established a section line and elicited other process characteristics. The algorithm for the numerical solution of model nonlinear boundary conditions problems of quasiconformal reflection in areas bounded by two equipotential lines and two flow lines, when for one of the sections, the boundary is an unknown (free) curve with fixed and free ends. The conducted numerical calculations prove that the problems and algorithms of their numerical solution, with a relatively small iterations number (k = 141) suggested in the paper, can be applied in the simulation of nonlinear filtration processes that arise in horizontal drainage systems. Total filtration flow obtained Q = 0.9 dm3∙s–1; flow for drains Q1 = 0.55 dm3∙s–1 and Q2 = 0.35 dm3∙s–1 are quite consistent with practically determined values.

19

Determination of the stress-strain state of rock mass and zone of inelastic deformation around underground mine excavation using modern methods of numerical modelling

Ignatiev Sergey A., Sudarikov Aleksandr E., Imashev Askar Zh.

Journal of Sustainable Mining

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2021

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Vol. 20, iss. 3

220--227

EN

The paper reviews methods and trends of numerical modelling of geomechanical processes around underground mine excavations. The most rational method of determining the additional stresses caused by the mine excavations is chosen. Mathematical modelling was performed for excavations of various cross sections and different strength of rocks. The dimensions of the inelastic deformation zone around the mine excavations have been identified. The area of the total fracture zone around the excavation, as well as the area of the roof fracture zone are calculated. The results of the fracture zone modelling are presented both as coordinates and in a graphical form. To simplify application of the modelling results, dependency plots of the obtained parameters were created and analytical dependencies of the fracture zone parameters were identified. The SURFER and KOMPAS software packages were used as the graphic tools to visualize the modelling results.

20

Optimal passive structural control under extreme earthquake excitations using a combined pendulum tuned mass damper

Kamel Abanoub G., Basily Remon M.

Journal of Applied Mathematics and Computational Mechanics

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2021

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Vol. 20, nr 4

51--64

EN

Many engineering applications utilize passive Tuned Mass Dampers (TMDs) in several engineering applications because of their simplicity, readiness, and their ability in attenuating structural vibrations exposed to mild or extreme earthquake excitations. The main aim of this work is to find the optimum values of the system parameters after attaching a three degree of freedom Combined Pendulum Tuned Mass Damper (3-DOF CPTMD) to the main structure to investigate if the proposed solution will assist in reducing the amplitudę of the vibration. Three optimization search techniques are utilized, and the best optimum method is determined. Moreover, the structural system was modelled mathematically to get the governing motion equations, and the system was put into state-space format before being simulated using a homemade MATLAB© code. Additionally, it is found that the proposed 3-DOF CPTMD is very effective in dampening the structural vibrations under various earthquake excitations (including extreme conditions)