Mathematical modeling of methane combustion

The paper presents the process of the creation of the mathematical model of methane turbulent combustion using ANSYS FLUENT 13.0 software. The decommissioned mathematical model for species transfer with chemical reaction is described, where burning is based on stoichiometric equations of perfect combustion. Work also analyzes the appropriateness of models dealing with the kinetics of burning and describes their mutual comparison

Matematické modelování proudění spalin včetně přestupu tepla ve spirálovém výměníku tepla

The paper presents the numerical solution of gas flow in a spiral heat exchanger, which flowing water is heated. Gaseous combustion products are derived from the combustion of natural gas in micro-turbine, which reaches tens of power [kW]. The paper defines a mathematical model of gas flow in the exchanger, including consideration of heat transfer through the conductive spiral heat exchanger. Conductive heat exchanger areas are different wall and the insulation layer that surrounds the heat exchanger itself. Inlet boundary conditions for gas and water were got from the experimental measurements. Then defined mathematical model was solved numerically in programming software ANSYS Fluent13. The results of numerical simulations are presented in the basic distribution of current values in the individual sections of exchanger. Subsequently, variables are evaluated to determine the energy analysis of the heat exchanger.Příspěvek prezentuje numerické řešení proudění spalin ve spirálovém výměníku tepla, kterým se ohřívá proudící voda. Plynné spaliny jsou získány ze spalování zemního plynu V mikroturbíně, která dosahuje výkonu řádově desítky [kW]. V příspěvku je definován matematický model proudění spalin ve výměníku včetně uvažování přestupu tepla skrz vodivé oblasti spirálového výměníku. Vodivými oblastmi výměníku tepla jsou jednotlivé stěny a vrstva izolace, která obklopuje samotný výměník. Vstupní okrajové podmínky pro spaliny a vodu byly získány na základě experimentálního měření. Definovaný matematický model byl následně řešen numericky V programovém prostředí ANSYS Fluent13. Výsledky numerické simulace jsou prezentovány rozložením základních proudových veličin V jednotlivých řezech výměníkem. Následně jsou vyhodnoceny veličiny K stanovení energetické analýze výměníku tepla

Flow of oil and water through the nozzle and cavitation

Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a convergent-divergent nozzle of circular cross-section. Cavitation depends on the physical properties of the flowing medium as a function of temperature. Usually, cavitation in water is defined by a two-phase flow of water and vapor, but the air contained in the water significantly affects cavitation. There is usually no vapor cavitation in the oil. Far more often, cavitation in oil is caused by the air it contains. For comparison, cavitation in water and oil was generated in experiments with an identical nozzle. The measurement was used to define boundary conditions in mathematical models and to verify simulations. The problem of cavitation was solved by three variants of multiphase flow, single-phase flow (water, oil), two-phase flow (water-vapor, oil-air) and three-phase flow (water-vapor-air, oil-vapor-air). A turbulent model with cavitation was used for all variants. The verification of simulations shows that for water cavitation it is necessary to use a three-phase model (water, vapor, air) and for oil cavitation a two-phase model (oil, air) is sufficient. The measurement results confirm the importance of the air phase in modeling cavitation in both water and oil.Web of Science911art. no. 193

Methods of CFD modelling of twin-screw pumps for non-newtonian materials

The twin-screw pump is designed for pumping highly viscous materials in the food industry. Rheological characteristics of materials are important in the specification of design parameters of screw pumps. Analysis of flow in the twin-screw pumps with definition of non-newtonian materials can be made by numerical modelling. CFD generally oriented software ANSYS Fluent and ANSYS Polyflow has been used for modelling. In this study those software's (ANSYS Fluent and ANSYS Polyflow) were defined for solution of flow in the twin-screw pumps. Results were compared for the same boundary conditions on the inlet and outlet of the 3D model. For definition of the viscosity were used the Nonnewtonian power law. Parameters as consistency coefficient and flow exponent for Nonnewtonian power law were analysed by software ANSYS Fluent and ANSYS Polyflow. Postprocessing form ANSYS Fluent and ANSYS Polyflow were made by contours of field and by graphs.Web of Science20215372536

Rozšíření měřicího rozsahu pádové trubky na výzkumném energetickém centru

Better understanding of combustion process in large scale pulverized coal boilers can help with increasing of coal combustion efficiency and decreasing of pollutant emissions, such as nitrogen oxides and arguable carbon dioxide. This improvement cannot be performed without testing in labor-atory conditions. For this purpose, a new testing facility called the drop tube has been built in the Energy Research Center (ERC) of VSB-Technical University of Ostrava. This paper describes the methodology of pulverized coal thermo-kinetic properties determination with the use of the Drop Tube Test Facility and the first steps in improvement of this methodology. There is a new design of the sampling probe, an improved one, gas-tight double-wall design, implemented into the methodolo-gy lately. The intermediate space is vacuumed for the purpose of better isolating properties of the probe. Further, the probe is newly supplemented with a cryogenic control valve for smooth regulation of small flow rates of cooling media - liquid nitrogen. These innovations bring cooling media sav-ings, especially thanks to increased efficiency of this media’s cooling potential. Furthermore, smoother regulation allows a sample cooling in an accurately defined point.Lepší pochopení spalovacího procesu ve velkých práškových uhelných kotlích může pomoci se zvyšováním efektivity spalování uhlí a snížením emisí znečišťujících látek jako jsou oxidy dusíku a diskutabilní oxid uhličitý. Tato zlepšení není možné provést bez laboratorního zkoušení. Pro tento účel bylo na Výzkumném energetickém centru VŠB-Technické univerzity Ostrava postaveno nové testovací zařízení nazvané pádová trubka. Tento článek popisuje metodiku stanovení termo-kinetických vlastností uhelného prášku s použitím pilotního testovacího zařízení pádové trubky a popisuje první kroky ke zlepšení této metodiky. Do metodiky je nově začleněna druhá vylepšená verze odběrové chladící sondy, která je vyhotovena v plynotěsném dvouplášťovém provedení. Mezi-prostor je pro zlepšení izolačních vlastností sondy evakuován. Dále je sonda nově doplněna kryogenním regulačním ventilem pro jemně nastavitelné dávkování chladícího média – tekutého dusíku. Tyto inovace přináší úspory ve spotřebě chladícího media zejména díky zvýšení účinnosti chladícího potenciálu tohoto media. Dále plynulejší regulace umožňuje zchlazení vzorku v přesně definovaném místě

Multiphase fluid models to deal with fluid flow dynamics

When dealing with dynamic issues, we often encounter problems of hydraulic shock (water hammer) and cavitation causing distortion of the surrounding material, destruction of material, accompanied by sounds and vibrations. These dynamic behavior of the liquids is due to the presence of gases in the liquid, especially air, vapor and possibly other gases in smaller quantities. The density of such a liquid is assumed to be a function of a liquid elastic modulus depending on pressure or it is defined as the density of a multiphase mixture of incompressible liquid and compressible gases (vapour, air) depending on pressure too. The article is focused on specification of mathematical models of multiphase flow for piping (one dimensional) hydraulic systems and spatial (three dimensional) hydraulic elements and systems. The electrohydraulic analogue (Matlab-SimHydraulics) method and finite volume method (Ansys-Fluent) are used for illustrative fluid dynamics tasks.Web of Science20192896289

Computational fluid dynamics could enable individualized surgical treatment of nasal obstruction (a preliminary study)

Passage of nasal airflow during breathing is crucial in achieving accurate diagnosis and optimal therapy for patients with nasal disorders. Computational fluid dynamics (CFD) is the dominant method for simulating and studying airflow. The present study aimed to create a CFD nasal airflow model to determine the major routes of airflow through the nasal cavity and thus help with individualization of surgical treatment of nasal disorders. The three-dimensional nasal cavity model was based on computed tomography scans of the nasal cavity of an adult patient without nasal breathing problems. The model showed the main routes of airflow in the inferior meatus and inferior part of the common meatus, but also surprisingly in the middle meatus and in the middle part of the common nasal meatus. It indicates that the lower meatus and the lower part of the common meatus should not be the only consideration in case of surgery for nasal obstruction in our patient. CFD surgical planning could enable individualized precise surgical treatment of nasal disorders. It could be beneficial mainly in challenging cases such as patients with persistent nasal obstruction after surgery, patients with empty nose syndrome, and patients with a significant discrepancy between the clinical findings and subjective complaints.Web of Science1211art. no. 264

Matematický model nízkoteplotní oxidace uhlí v uhelných skládkách a odvarech

Article define mathematical model of the low-temperature oxidation of coal, when it is spontaneously combustion. Process of spontaneously combustion can be initialization inside the coal stockpile by specific atmospheric conditions by reason of air flow through store of coal. Problem of lowtemperature oxidation of coal is defined as wall surface reactions of adsorbed carbon in porous zone, which is presented as store of coal. Influence of water vapour product is neglected in definition of reaction mechanism and in stoichiometric equation of combustion. Thus defined mathematical model is applied on the simple geometry as porous zone. Then software FLUENT 12 is used for numerical simulation.Tento příspěvek definuje matematický model nízkoteplotní oxidace uhlí, kdy dochází k tzv. samovzněcování. K samovzněcování uhlí v uhelných skládek může docházet za určitých atmosférických podmínek v důsledků účinku proudícího vzduchu skrz uhelnou hromadu. Problematika nízkoteplotní oxidace uhlí je definována jako povrchové spalování adsorbovaného uhlíku v porézní oblasti, která představuje uhelnou hromadu. V definicí reakčního mechanismu a stechiometrické rovnice je zanedbán vliv produkce vodní páry v důsledků spalování. Takto nadefinovány matematický model je aplikován na jednoduchou geometrii porézní oblasti. Následně k numerické simulací je použit software FLUENT 12

Numerická optimalizace proudění plynů v dnových dmyšnách tepelného agregátu

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojní. Katedra (338) hydromechaniky a hydraulických zařízen

Matematické modelování průtoku plynných médií dmyšnými systémy do kyslíkového konvertoru

Import 23/11/2006Prezenční338 - Katedra hydromechaniky a hydraulických zařízen