Temat: gas dynamics - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Global existence for a one-dimensional model in gas dynamics
Autorzy:: Njamkepo, Serge
Tematy:: capillarity
Navier-Stokes equations
gas dynamics; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Matematyczny PAN
Powiązania:: https://bibliotekanauki.pl/articles/1339279.pdf Link otwiera się w nowym oknie
Opis:: We prove the existence of a global solution for a one-dimensio- nal Navier-Stokes system for a gas with internal capillarity.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: The Gas dynamics of the exhaust diffusers: computational aspects
Autorzy:: Solodov, V. G.
Tematy:: gas dynamics
diffusers
exhaust devices
CFD
computational fluid dynamics CFD; Pokaż więcej
Wydawca:: Politechnika Gdańska
Powiązania:: https://bibliotekanauki.pl/articles/1967649.pdf Link otwiera się w nowym oknie
Opis:: Some recent advances in computational gas dynamics of exhaust diffusers are presented. The compressor/turbine axial-radial exhaust diffusers and outlet devices of compressor/turbine units, exhaust hoods for power steam turbines are considered. The peculiarities of gas dynamics of the above mentioned devices are discussed. The formulations of problems for CFD analysis of these devices are discussed including the coupling procedure for joint operation of the last stage and exhaust hood. The numerical method and the implementation of a differential turbulence model are described. The new approach to the description of computational domain and parallel numerical solution of transport equations based on the unstructured set of structured grid blocks is also presented.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Influence of engine load on piston ring pack operation of a marine two - stroke engine
Autorzy:: Wolff, A.
Tematy:: marine engines
piston rings
gas dynamics
hydrodynamic lubrication
mixed friction; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/246695.pdf Link otwiera się w nowym oknie
Opis:: A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall. Many physical phenomena are associated with the operation of the system piston-ring-cylinder (PRC), such as: inter-ring gas dynamics for the labyrinth seal, hydrodynamic lubrication and mixed friction in gaps between the rings and cylinder liner, oil flow and distribution of lubricant along the liner, twist motion of rings, liner temperature influence on the oil viscosity. A complex model of the PRC system has been developed by the author. Among own models it includes several sub-models taken from literature, like: a model of viscous oil flow between rough gap surfaces formulated by Patir and Cheng and an elastic contact model of Greenwood and Tripp. The main parts of the mathematical model and software have been experimentally verified abroad by the author at the marine engine-designing centre. A relatively good qualitative and quantitative compatibility between the experimental measurements and calculated results has been achieved. In contrast to the previous papers of the author, new calculation results for a marine two-stroke engine have been presented. These results concern influence of engine load on piston ring pack operation of the analysed engine. They include basic physical quantities associated with gas and oil flow in the piston-ring-cylinder system of the engine. The developed model can be utilized for: evaluation of gas leakage through the sealing ring set, prediction of lubrication conditions of piston rings and oil consumption, defining areas of the possible cylinder liner wear and profile changes of piston rings sliding surfaces, and thus can be useful for optimization of the PRC system design.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: A data assimilation approach for estimating strength of steel pipes reinforced with composite sleeves under unsteady pressure-flow conditions
Autorzy:: Witek, Maciej
Uilhoorn, Ferdinand
Tematy:: pipe wall metal loss
composite sleeve
pipe fracture
gas dynamics
data assimilation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1845453.pdf Link otwiera się w nowym oknie
Opis:: The aim of this paper is twofold: to estimate the unsteady pressure-flow variations in gas transmission pipelines using the ensemblebased data assimilation approach and to analyse the strength of steel tubes reinforced with composite sleeves containing localized part-wall thickness loss caused by corrosion while taking into consideration a safe operating pressure of the pipeline. For a steel thin-walled cylinder containing a partwall metal loss, a flexible wrap of fibreglass as well as carbon glass with epoxy resin are determined. The strength of the repaired pipeline with two kinds of materials for sleeves is investigated taking into consideration the internal pressure at the defect location. For the case study, a section of the Yamal transit pipeline on the Polish territory is selected. The results enable pipeline operators to evaluate the strength of corroded steel pipelines and develop optimal repair activities, which are of vital importance for the maintenance and operation of underground steel networks.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: A data assimilation approach for estimating strength of steel pipes reinforced with composite sleeves under unsteady pressure-flow conditions
Autorzy:: Witek, Maciej
Uilhoorn, Ferdinand
Tematy:: pipe wall metal loss
composite sleeve
pipe fracture
gas dynamics
data assimilation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1845456.pdf Link otwiera się w nowym oknie
Opis:: The aim of this paper is twofold: to estimate the unsteady pressure-flow variations in gas transmission pipelines using the ensemblebased data assimilation approach and to analyse the strength of steel tubes reinforced with composite sleeves containing localized part-wall thickness loss caused by corrosion while taking into consideration a safe operating pressure of the pipeline. For a steel thin-walled cylinder containing a partwall metal loss, a flexible wrap of fibreglass as well as carbon glass with epoxy resin are determined. The strength of the repaired pipeline with two kinds of materials for sleeves is investigated taking into consideration the internal pressure at the defect location. For the case study, a section of the Yamal transit pipeline on the Polish territory is selected. The results enable pipeline operators to evaluate the strength of corroded steel pipelines and develop optimal repair activities, which are of vital importance for the maintenance and operation of underground steel networks.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Dispersion of Methane in Closed Enclosures
Dyspersja metanu w zamkniętych obudowach
Autorzy:: Cioclea, Doru
Ianc, Nicolae
Boanta, Corneliu
Matei, Adrian
Dragoescu, Razvan
Tematy:: explosive gas
methane
dispersion
gas dynamics
closed spaces
gaz wybuchowy
metan
dyspersja
dynamika gazu
zamknięte obudowy; Pokaż więcej
Wydawca:: Polskie Towarzystwo Przeróbki Kopalin
Powiązania:: https://bibliotekanauki.pl/articles/59114856.pdf Link otwiera się w nowym oknie
Opis:: The increase of the population also involve the increase of the consumption of raw materials. This requires the diversification and development of industrial processes in semi-enclosed or open spaces. The carrying out of human activities of an industrial nature involves the accidental use, handling or presence of explosive substances such as methane. The presence of this gas in closed or semi-closed spaces can generate explosion phenomena. The accumulation of methane in narrow spaces is well studied and known, but the dispersion and especially the dispersion dynamics of methane released from a source considered infinite is less known. Knowing how methane disperses into the air is very important for establishing preventive measures. The paper presents the experiment on the dynamics of methane dispersion in a closed enclosure.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: A mathematical model for evaluation the efficiency of gas-main pipelines in transient operational modes
Autorzy:: Chekurin, V.
Ponomaryov, Yu.
Khymko, O.
Tematy:: gas-main pipeline
transient modes of operation
models of gas dynamics
control by transient process
efficiency of gas transportation
duration of transient process; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Oddział w Lublinie PAN
Powiązania:: https://bibliotekanauki.pl/articles/410871.pdf Link otwiera się w nowym oknie
Opis:: A mathematical model for control by transient modes of gas flows in the long-distance gas pipeline is considered in the paper. The long-distance pipeline is considered in the model as the system of Line segments serially connected via compressor stations. Gas motion in such system is described by the non-linear system of equations of gas dynamics. In the frame of this model the integral parameters which determine the expenditure of energy and durations of the transient mode are introduced. These parameters can be used for formulation the problems for optimal control steady-state and transient modes of operation of main-gas pipelines.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Influence of piston ring pack configuration on blowby and friction losses in a marine two-stroke engine
Autorzy:: Wolff, A.
Tematy:: marine engines
piston rings
gas dynamics
hydrodynamic lubrication
mixed friction
silnik okrętowy
pierścień tłokowy
dynamika gazów
smarowanie hydrodynamiczne
tarcie mieszane; Pokaż więcej
Wydawca:: Polskie Towarzystwo Naukowe Silników Spalinowych
Powiązania:: https://bibliotekanauki.pl/articles/134100.pdf Link otwiera się w nowym oknie
Opis:: In the paper a comprehensive model of a piston ring pack motion on an oil film has been presented. The local thickness of the oil film can be compared to height of the combined surface roughness of a cylinder liner and piston rings. Equations describing the mixed lubrication problem based on the empirical mathematical model formulated in works of Patir, Cheng and Greenwood, Tripp have been combined and used in this paper. In addition a model of gas flow through the labyrinth seal of piston rings has been developed. The main parts of the model and software have been experimentally verified abroad by the author at the marine engine designing centre. For the selected two-stroke marine engine, the influence of the number of piston rings used and the type of the top ring lock (straight or overlapped) on blowby to piston underside and on friction losses of the piston-ring-cylinder (PRC) system have been investigated. The developed model and software can be useful for optimization of the PRC system design.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: An approach to coupling the gas flow dynamics and thermodynamics of hydrogen solubility in L485ME steel grade for estimation of fracture toughness
Autorzy:: Witek, Maciej
Uilhoorn, Ferdinand
Tematy:: gas flow dynamics
hydrogen embrittlement
fracture toughness
hydrogen
solubility
L485ME steel grade; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/59112037.pdf Link otwiera się w nowym oknie
Opis:: The paper presents the problem of coupling the gas flow dynamics in pipelines with the thermodynamics of hydrogen solubility in steel for the estimation of the fracture toughness. In particular, the influence of hydrogen blended natural gas transmission on hydrogen solubility and, consequently, on fracture toughness is investigated with a focus on the L485ME low-alloy steel grade. Hydraulic simulations are conducted to obtain the pressure and temperature conditions in the pipeline. The hydrogen content is calculated from Sievert’s law and, as a consequence, the fracture toughness of the base metal and heat-affected zone is estimated. Experimental data is used to define hydrogen-assisted crack size propagation in steel as well as to a plane strain fracture toughness. The simulations are conducted for a real natural gas transmission system and compared against the threshold stress intensity factor. The results showed that the computed fracture toughness for the heat-affected zone significantly decreases for all natural gas and hydrogen blends. The applied methodology allows for identification of the hydrogen-induced embrittlement susceptibility of pipelines constructed from thermomechanically rolled tubes worldwide most commonly used for gas transmission networks in the last few decades.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The influence of parameters of an undisturbed air on the blast wave characteristics
Wpływ parametrów niezaburzonego powietrza na charakterystyki powybuchowych fal uderzeniowych
Autorzy:: Łęgowski, Z.
Tematy:: mechanika
dynamika gazów
detonacja
powietrze atmosferyczne
wybuch
powybuchowa fala uderzeniowa
obciążenie konstrukcji
mechanics
gas dynamics
detonation
atmospheric air
explosion
blast wave
construction loading; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/241647.pdf Link otwiera się w nowym oknie
Opis:: Formulation of the propagation problem of the detonation wave in an explosive charge has been presented, and the solution method of the equations of motion has been worked out. The Jones, Wilkins and Lee equation of state has been used for detonation products. On the strength of a self-similarity of the problem, the equations of motion have been reduced to the set of ordinary differential equations that have been solved using the Runge-Kutta method of 4th order. Spatial distributions of parameters of detonation products have been obtained for arbitrary time instant of the process till the moment, at which the detonation front reaches the charge boundary that marks the end of the combustion process. It has been formulated the problem of a dispersion of detonation products into the surrounding air with regard to its climatic changes. In depicting properties of the air disturbed by the blast wave propagating throughout, it has been adapted the Brode calorific equation of state with eleven material constants, whereas the damp air has been treated as an mixture of ideal gases. The integral equations of motion have been solved by means of numeric scheme of the Godunov's method of disintegration the arbitrary discontinuity with assigning the primary blast wave front and the detonation products boundary. The other strong discontinuities, appearing in the flow, have been smoothed out by the dissipative numerical scheme. An influence of parameters of an atmospheric air has been examined, such as pressure p0 temperature T0 and humidity, on the blast wave characteristics. It has been found, that increasing the temperature of the undisturbed air results in decreasing pressure on the primary blast wave front, while growing the atmospheric pressure means growing pressure on the wave front too. The influence of humidity extends with increasing temperature and decreasing pressure. Pressures on the blast wave front in a damp air are always less in magnitude in comparison with values attained in a dry air. It has been ascertained, that the influence of all of three atmospheric parameters decreases with growing the propagating blast wave radius. The extreme influence on the pressure values in a blast wave creates the climatic variations in temperature, the least of all - the humidity variations. In many cases the influence of the last parameter may be ignored. Comprehensive properties of the dispersion of detonation products have been investigated, taking into consideration the variations of the atmospheric parameters. It has been determined, that the maximal range of the detonation products, estimated on the ground of discovering the dry air at the conventional conditions, must be extended to 17 values of a charge radius.
Sformułowano zagadnienie oraz opracowano metodę całkowania równań ruchu problemu rozprzestrzeniania się fali detonacyjnej w ładunku materiału wybuchowego (MW). Do opisu produktów detonacji zastosowano równanie stanu Jonesa, Wilkinsa i Lee'go. Korzystając z samopodobieństwa zagadnienia, równania ruchu sprowadzono do odpowiedniego układu równań różniczkowych zwyczajnych, który całkowano metodą Rungego-Kutty czwartego rzędu. Otrzymano przestrzenne rozkłady parametrów w produktach detonacji w dowolnym momencie trwania tego procesu aż do chwili dotarcia fali detonacyjnej do granicy ładunku, kończącej proces spalania. Sformułowano zagadnienie rozlotu produktów detonacji w otaczające ładunek powietrze atmosferyczne z uwzględnieniem jego zmian klimatycznych. Do opisu właściwości powietrza, zaburzonego przez rozchodzącą się w nim falę podmuchu, zastosowano kaloryczne równanie stanu Brode 'a z jedenastoma stałymi materiałowymi, natomiast wilgotne powietrze atmosferyczne traktowano jako mieszaninę gazów doskonałych. Całkowe równania ruchu rozwiązywano za pomocą schematu numerycznego metody rozpadu dowolnych nieciągłości Godunowa z wydzieleniem frontu pierwotnej fali podmuchu oraz granicy rozdziału produktów detonacji. Pozostałe silne nieciągłości, pojawiające się w trakcie ewolucji rozwiązania, ulegały naturalnemu rozmyciu przez dysypatywny schemat różnicowy Godunowa. Zbadano wpływ parametrów powietrza atmosferycznego, takich jak ciśnienie p0 temperatura T0 i wilgotność na charakterystyki powybuchowych fal uderzeniowych. Ustalono, że wzrost temperatury niezaburzonego powietrza powoduje spadek ciśnienia na froncie pierwotnej fali wybuchu, natomiast wzrost ciśnienia atmosferycznego oznacza również wzrost ciśnienia na powierzchni tej fali. Wpływ wilgotności rośnie ze wzrostem temperatury i spadkiem ciśnienia. W wilgotnym powietrzu ciśnienia na powierzchni fali wybuchu są zawsze mniejsze od wartości uzyskiwanych w powietrzu suchym. Ustalono, że wpływ wszystkich trzech parametrów atmosfery maleje ze wzrostem promienia rozchodzącej się fali wybuchu. Największy wpływ na wartości ciśnień w fali powybuchowej wywierają klimatyczne zmiany temperatury, najmniejsze - zmiany wilgotności. Wpływ tego czynnika można w wielu przypadkach pominąć i ograniczyć się do badania suchego powietrza. Zbadano ogólne własności procesu rozlotu produktów detonacji z uwzględnieniem zmian parametrów atmosfery. Ustalono, że maksymalny zasięg produktów detonacji, szacowany na podstawie badań suchego powietrza i atmosfery standardowej, należy przedłużyć do ok. siedemnastu promieni ładunku.
Dostawca treści:: Biblioteka Nauki

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