Modelling of the cavitation erosion of coatings manufactured by laser beam

Przedstawiono fizyczną interpretację procesu kawitacyjnego niszczenia powłok i zaproponowano sposób jego modelowania. Przyjęto założenie dotyczące generacji dyskretnych stanów energetycznych w obrębie powłoki oraz ich obsadzania w procesie migracyjnego transferu energii. Sprawdzono, czy wyniki teoretyczne właściwie opisują proces erozyjnego usuwania napoin wytworzonych wiązką laserową.The physical interpretation of the cavitation erosion of coatings was presented. A method of the modelling of the process was also proposed. Theory of the discrete states generation within the coating and their fixing due to energy migration was assumed. Experimental investigation of the extraction process of the layers made by laser beam were carried out and some comparisons between theoretical and experimental results were done

Deformability of flexible pipes loaded by internal pressure

Przedstawiono wyniki badań promieniowej odkształcalności cylindrycznych przewodów elastycznych obciążonych ciśnieniem wewnętrznym. Badanymi materiałami były przewody silikonowe, lateksowe i gumowe, o średnicy wewnętrznej 4-6 mm i grubości ścianki 1 mm. Z powodu specyficznego poziomu odkształceń badanych przewodów do pomiaru stanu odkształcenia przekroju przewodu wykorzystano cyfrową analizę obrazów mikroskopowych. Analiza wyników pomiarów pozwoliła wykazać, że w rozpatrywanym zakresie ciśnienia wewnętrznego część badanych przewodów wykazywała właściwości typowe dla materiałów sprężystych, a część dla lepkosprężystych.The investigation results and their analysis of radial deformability elastic pipes loaded on internal pressure is presented. The latex, silicone and rubber pipes with inner diameter 4-6 mm are considered. The elastic and viscoelastic properties of commercially available plastic pipes are described and discussed

Heat transfer in the flow of two immiscible liquids

W pracy przedstawiono wyniki badań doświadczalnych przebiegu procesu reaktywnej ekstrakcji kwasu cytrynowego z roztworu wodnego z użyciem dwutlenku węgla w stanie nadkrytycznym. Zbadano wpływ parametrów procesowych (temperatury, szybkości mieszania, czasu realizacji) na przebieg i efektywność procesu. Wyniki badań doświadczalnych prowadzonych z zastosowaniem dwutlenku węgla w stanie nadkrytycznym porównano z wynikami otrzymanymi przy użyciu rozpuszczalników organicznych: 1 -oktanolu i n-heptanu.In this paper the results of experiments of reactive extraction of citric acid from aqueous solution with the use of supercritical carbon dioxide are presented. The influence of process parameters (temperature, stirrer speed, time) on the process course and efficiency was investigated. The results of experiments obtained with the use of supercritical carbon dioxide were compared with those obtained using organic solvents: 1-octanol and n-heptan

Modeling of heat and mass transfer during thermal decomposition of a single solid fuel particle

The aim of this work was to investigate the heat and mass transfer during thermal decomposition of a single solid fuel particle. The problem regards the pyrolysis process which occurs in the absence of oxygen in the first stage of fuel oxidation. Moreover, the mass transfer during heating of the solid fuels is the basic phenomenon in the pyrolysis-derived alternative fuels (gas, liquid and solid phase) and in the gasification process which is focused on the generation of syngas (gas phase) and char (solid phase). Numerical simulations concern pyrolysis process of a single solid particle which occurs as a consequence of the particle temperature increase. The research was aimed at an analysis of the influence of particle physical properties on the devolatilization process. In the mathematical modeling the fuel grain is treated as an ideal sphere which consists of porous material (solid and gaseous phase), so as to simplify the final form of the partial differential equations. Assumption that the physical properties change only in the radial direction, reduces the partial derivatives of the angular coordinates. This leads to obtaining the equations which are only the functions of the radial coordinate. The model consists of the mass, momentum and energy equations for porous spherical solid particle heated by the stream of hot gas. The mass source term was determined in the wide range of the temperature according to the experimental data. The devolatilization rate was defined by the Arrhenius formula. The results of numerical simulation show that the heating and devolatilization time strongly depend on the physical properties of fuel. Moreover, proposed model allows to determine the pyrolysis process direction, which is limited by the equilibrium state

Modeling of heat and mass transfer during thermal decomposition of a single solid fuel particle

The aim of this work was to investigate the heat and mass transfer during thermal decomposition of a single solid fuel particle. The problem regards the pyrolysis process which occurs in the absence of oxygen in the first stage of fuel oxidation. Moreover, the mass transfer during heating of the solid fuels is the basic phenomenon in the pyrolysis-derived alternative fuels (gas, liquid and solid phase) and in the gasification process which is focused on the generation of syngas (gas phase) and char (solid phase). Numerical simulations concern pyrolysis process of a single solid particle which occurs as a consequence of the particle temperature increase. The research was aimed at an analysis of the influence of particle physical properties on the devolatilization process. In the mathematical modeling the fuel grain is treated as an ideal sphere which consists of porous material (solid and gaseous phase), so as to simplify the final form of the partial differential equations. Assumption that the physical properties change only in the radial direction, reduces the partial derivatives of the angular coordinates. This leads to obtaining the equations which are only the functions of the radial coordinate. The model consists of the mass, momentum and energy equations for porous spherical solid particle heated by the stream of hot gas. The mass source term was determined in the wide range of the temperature according to the experimental data. The devolatilization rate was defined by the Arrhenius formula. The results of numerical simulation show that the heating and devolatilization time strongly depend on the physical properties of fuel. Moreover, proposed model allows to determine the pyrolysis process direction, which is limited by the equilibrium state

Pyrolysis analysis of a single wood particle

Opisano proces pirolizy pojedynczej cząstki drewna. Za pomocą termograwimetrii, badań w piecu wysokotemperaturowym oraz metod radiograficznych przeprowadzono analizę procesu pirolizy. Analizowano szybkość dekompozycji termicznej i jej stopień w funkcji czasu. Badano poddane pojedyncze próbki w formie sosnowych sześcianów o boku 18 mm. Analiza termograwimetryczna mająca na celu wyznaczenie przedziałów, w jakich zachodzi proces, poprzedziła badania wykonane w piecu wysokotemperaturowym. Próbki po eksperymentach zostały poddane badaniom radiograficznym celem zobrazowania zmian gęstości drewna w funkcji czasu. Na zdjęciach zaobserwowano, iż piroliza zachodzi od naroży próbki, a następnie pozostaje tylko niespirolizowany rdzeń w środku próbki. Badania potwierdziły duże możliwości radiografii w ocenie pirolizy.Pyrolysis process of a single wood particie is described in the paper. Thermogravimetric and radiography techniques and pyrolysis in a high-temperature kiln were applied in the experiments. The thermal decomposition rate as a function of time was analyzed. Pine cubes with a side of 18 mm were used as samples. High-temperature kiln tests were preceded by thermogravimetric analysis aiming to determine temperature ranges in which the process took place. The samples after tests were analyzed using radiographic methods to visualize the changes in wood density as a function of time. It was observed on the photographs that pyrolysis started from sample corners, while only a core in the center of samples remained unchanged. Radiography experiments have a big potential in pyrolysis research

Transient one-dimensional model of coal carbonization in a stagnant packed bed

In the present paper, the one-dimensional model for heat and mass transfer in fixed coal bed was proposed to describe the thermal and flow characteristics in a coke oven chamber. For the purpose of the studied problem, the analysis was limited to the calculations of temperature field and pyrolytic gas yield. In order to verify the model, its theoretical predictions for temperature distribution during wet coal charge carbonization were compared with the measurement results found in the literature. In general, the investigation shows good qualitative agreement between numerical and experimental data. However, some discrepancy regarding the temperature characteristics at the stage of evaporation was observed