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Wojciech Pawlak

Comparison of Computer-Simulation Results for a Jet Engine with Half-Ideal Gas and Ideal Gas as a Working Medium

Two simulative models for the same jet engine, plus simulation results of deceleration, acceleration and steady states of engine operation during ground tests, are presented in the article. The models differ from each other just with the working medium flowing through the engine. In the first model it was assumed that, while the working medium is flowing through the compressor, the isentropic exponent and average specific heat are functions of average total temperature, whereas, while it is flowing through the combustion chamber, turbine, and nozzle, these are functions of corresponding average temperatures of total pressure and combustion air factor. In the second model the working medium is treated as an ideal gas, with constant values of isentropic exponent and specific heat in some parts of the flow being analyzed.

Open access

Wojciech Pawlak

Porównanie Wyników Komputerowej Symulacji Turbinowego Silnika Odrzutowego Dla Przypadków Przepływu Czynnika Roboczego O Właściwościach Gazu Półdoskonałego I Doskonałego

Przedstawiono dwa modele symulacyjne tego samego turbinowego silnika odrzutowego oraz wyniki wykonanych na nich symulacji procesów pełnej akceleracji i deceleracji oraz stanów ustalonych, dla warunków naziemnych. Modele różnią się tylko sposobem traktowania czynnika roboczego. W pierwszym modelu przyjęto, że w przepływie przez sprężarkę wykładnik izentropy i średnie ciepło właściwe powietrza są funkcjami średniej temperatury spiętrzenia, natomiast w przepływie przez komorę spalania, turbinę i dyszę są one funkcjami odpowiednich średnich temperatur spiętrzenia oraz współczynnika nadmiaru powietrza. W drugim modelu czynnik roboczy potraktowano jako gaz doskonały, czyli taki, dla którego wartości wykładników izentrop i ciepeł właściwych czynnika roboczego w analizowanych fragmentach przepływu są stałe.

Open access

Józef Błachnio and Wojciech I. Pawlak

Abstract

Various types of damages to gas-turbine components, in particular to turbine blades, may occur in the course of gas turbine operation. The paper has been intended to discuss different forms of damages to the blades due to non-uniformity of the exit flow temperature. It has been shown that the overheating of blade material and thermal fatigue are the most common reasons for these damages. The paper presents results from numerical experiments with use of the computer model of the aero jet engine designed for simulations. The model has been purposefully modified to take account of the assumed non-homogeneity of the temperature field within the working agent at the turbine intake. It turned out that such non-homogeneity substantially affects dynamic and static properties of the engine considered as an object of control since it leads to a lag of the acceleration time and to increase in fuel consumption. The summarized simulation results demonstrate that the foregoing properties of a jet engine are subject to considerable deterioration in pace with gradual increase of the assumed non-homogeneity of the temperature field. The simulations made it possible to find out that variations of the temperature field nonhomogeneity within the working agent at the turbine intake lead to huge fluctuation of the turbine rpm for the idle run.

Open access

Józef Błachnio, Jarosław Spychała, Wojciech Pawlak and Artur Kułaszka

Abstract

The paper presents a non-destructive test method that makes it possible to assess condition of gas turbine blades based on the analysis of their images acquired in visible light. The results of high temperature’s influence on the condition of blades are revealed. The direct relationship between the temperatures of blades and discoloration of their surfaces is demonstrated. These relationships have been found out by the analysis of images in the form of first order statistical parameters derived wherefrom. The studies revealed alterations of the blade superalloy microstructures entailed by the effect of high temperature, hence the results in the form of first order statistical parameters could be correlated against alterations of the blade superalloy microstructures. Eventually, the variations of first order statistical parameters as well as variations of the blade superalloy microstructures could be determined as the functions of temperature. These relationships make it possible to assess how much the alloy microstructure is altered due to high temperature merely by discoloration of the blade surface. The innovative method can be used for in-flight evaluation of the superalloy overheating for gas turbine blades in operation.

Open access

Krzysztof Siczek, Wojciech Pawlak, Hubert Zatorski and Jakub Fichna

Abstract

Layers of silver particles are used in the studies on pathophysiology and treatment of diseases, both in pre-clinical and clinical conditions. Silver layers can be formed using different techniques and on different substrates. Deposition by magnetron sputtering on glass beads was used in this study. Silver absorption by the body was estimated by calculating the difference in thickness of the silver nanolayer deposited on a bead and measured before and after application of the bead in an animal model of gastrointestinal inflammation. Recommendations for the minimal thickness of silver nanolayer deposited on glass beads were worked out for further studies.

Open access

Józef Błachnio, Jarosław Spychała, Wojciech Pawlak and Dariusz Zasada

Abstract

The paper discloses a non-invasive method of visual inspection based on processing of images taken for blade surfaces in the spectrum of visible light and then analyzed with the use of a computer-aided technology. The method of computer-aided analysis of images for blade surfaces is presented in details along with the obtained outcome, whilst the results from metallographic investigation of the blade superalloy are disclosed as well. The comparison is made between the results obtained from the analysis of images for blade surface and the results from the metallographic investigation of their structures. Finally, the relationship is established between parameters of digital images taken for surfaces of gas turbine blades in the visible spectrum of electromagnetic waves and microstructural parameters of the turbine blade metal. The completed investigations and analyses reveal that troubleshooting of gas turbine blades, which employs digital processing of images taken for its surface, offers new opportunities to determine the condition of blades after a long-term impact of a working agent at high temperature.

Open access

Pamela Miśkiewicz, Iwona Frydrych, Wojciech Pawlak and Agnieszka Cichocka

Abstract

Basalt fibers and fabrics made of these are characterized by excellent thermal and mechanical properties. Therefore, basalt fabrics, due to a good resistance to high temperatures, are frequently applied in the personal protection equipment (PPE). In order to improve their thermal properties and, above all, the contact heat resistance, the process of physical vapor deposition was proposed. The process of Physical Vapor Deposition (PVD) involves producing a coating on a specific substrate as a result of physical deposition of molecules, ions or atoms of the selected chemical compounds. The method selected for the test is the magnetron sputtering. It involves depositing a uniform film of chromium on the surface of the basalt fabric. In order to improve the thermal properties – especially the contact heat resistance, two values of thickness of the chromium layer deposited on the basalt fabric surface were adopted for the test. Covering 1 µm and 5 µm with the chromium layer did not fulfil the expectations and the research will be continued.

Open access

Mariusz Kasprzyk, Wojciech Dyszkiewicz, Cezary Piwkowski, Krystian Pawlak, Jarosław Adamczak, Paweł Zieliński and Damian Zwaruń

Video-Assisted Thoracoscopic Surgery (VATS) Vs Thoracotomy in the Surgical Treatment of Recurrent Spontaneous Pneumothorax

The aim of the study was to compare surgical treatment results in cases of recurrent spontaneous pneumothorax following video-assisted thoracoscopic surgery (VATS) and thoracotomy. We assessed the recurrence rate after the procedures and postoperative complications, considering two patient groups.

Material and methods. The study group was comprised of 127 patients subjected to surgical treatment due to recurrent spontaneous pneumothorax during the period between 1996 and 2005. The group of 43 women and 84 men was between 15 and 79 years of age (mean age: 37 years). Video-assisted thoracoscopic surgery was performed in 67 cases, while the remaining 60 patients underwent thoracotomy. We performed the excision of the emphysematous blebs or apex of the lungs in 96 patients, partial pleurectomy with mechanical pleurodesis in 73 patients, subtotal pleurectomy in 33 cases, decortication of the lung in 30 cases, and chemical pleurodesis in 13 patients.

Results. Pneumothorax recurrence was significantly more frequent in the group of patients following the minimally-invasive approach (28% vs 8%). We observed no statistically significant differences considering patient gender in both groups. However, the VATS approach had a tendency to be performed in younger patients (average 33 yrs. in VATS vs 42 yrs. in the thoracotomy group). We performed partial pleurectomy and mechanical pleurodesis more often during VATS, while subtotal pleurectomy and lung decortication were performed more frequently during thoracotomy. The percentage of resections, considering emphysematous blebs or lung apexes was similar in both patient groups. We observed no differences considering the duration and amount of postoperative drainage, hospitalization period, or percentage of postoperative complications (pleural hematoma, prolonged air leak, residual pneumothorax) between both groups.

Conclusions. Apart from the excision of emphysematous blebs, subtotal pleurectomy should be considered in cases of patients subjected to video-assisted thoracoscopy. Subtotal pleurectomy could decrease the risk of recurrent pneumothorax, while having comparable percentages of postoperative complications as those following mechanical pleurodesis.

Open access

Katarzyna Oleśko, Hieronim Szymanowski, Maciej Gazicki-Lipman, Jacek Balcerzak, Witold Szymań Ski, Wojciech Pawlak and Anna Sobczyk-Guzenda

Abstract

This work initiates a series of reports aimed at a construction of rugate optical filters based on silicon rich materials of alternating gradients of refractive index n with the help of plasma enhanced chemical vapor deposition (PECVD) technique, The idea is to start deposition of high refractive index SixNy type of material using hexamethyldisilazane (HMDSN) vapor and nitrogen rich atmosphere, and then to gradually replace nitrogen with oxygen in that atmosphere in order to lower n down to a minimum characteristic of SixOy type of material. A return to initial gas composition should increase the index back to its maximum. In the present work, thin SixNyCz films were synthesized from a mixture of HMDSN vapor with gaseous NH3 and N2. The effect of NH3/N2 ratio on the coating morphology, its elemental composition, chemical bonding and optical properties was studied using scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultra-violet absorption spectroscopy and variable angle spectroscopic ellipsometry. The results show that films of the highest index of refraction and the lowest extinction coefficient have been deposited from the gas mixture containing 90 % of ammonia. These coatings are also characterized by the lowest carbon and the highest nitrogen contents.