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Experimental analysis on unsteady characteristics of sheet/cloud cavitating Venturi flow under the effect of dissolved air

Malekshah Emad Hasani, Wróblewski Włodzimierz, Bochon Krzysztof, Majkut Mirosław, Rusin Krzysztof

Archives of Thermodynamics

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2022

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Vol. 43, no 3

63--84

EN

The highly dynamic and unsteady characteristics of the cavitating flow cause many negative effects such as erosion, noise and vibration. Also, in the real application, it is inevitable to neglect the dissolved air in the water, although it is usually neglected in the previous works to reduce the complexity. The novelty of the present work is analysing the impact of dissolved air on the average/unsteady characteristics of Venturi flow by conducting sets of experimental tests. For this purpose, two different amounts of dissolved air at five pressure levels (i.e. five different sets of cavitation numbers) were considered in the study of cavitating flow inside a Venturi nozzle. The fast Fourier transform analysis of pressure fluctuations proved that the shedding frequency reduces almost by 50% to 66%, depending on the case, with adding the amount of dissolved air. However, the reduction of 14% to 25% is achieved by the vibration transducers. On the other hand, the cavity enlarges as well as bubbly flow is observed in the test chamber at a higher level of dissolved air. Furthermore, it is observed that the re-entrant jet, as the main reason for the cavity detachment, is more effective for the detachment process in cases with a lower level of dissolved air, where the re-entrant jet front penetrates more toward the leading edge.

2

An analysis of a cylindrical cyclone separator used in aircraft turbine engines

Szwarc Tomasz J., Wróblewski Włodzimierz, Borzęcki Tomasz

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2020

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nr 23(2)

131--142

EN

Cyclone separators are commonly used in the oil system of aircraft gas turbine engines to separate air from oil. The major advantages of cyclone separators are simple structure and high reliability that eliminate the need for frequent inspections. The efficiency of a cyclone separator has a decisive impact on oil quality, which directly affects the efficiency of the oil system. The new generation of engines requires more compact separator designs to reduce weight and minimize project costs while maintaining (and often increasing) an engine’s efficiency and reliability. To meet these requirements and optimize the separator structure, the flow of the air-oil mixture has to be modeled in the design process. The aim of this study was to present a numerical simulation of an aircraft turbine separator with the use of the volume of the fluid model.

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Modelowanie przepływu w olejowym separatorze turbinowego silnika lotnicznego

Szwarc Tomasz, Wróblewski Włodzimierz, Borzęcki Tomasz

Modelowanie Inżynierskie

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2019

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T. 40, nr 71

74--80

PL

Separatory cyklonowe są powszechnie stosowane w układach olejowych lotniczych silników turbinowych. Dzięki swojej prostej budowie cechują się bardzo dużą niezawodnością, a tym samym nie wymagają częstych przeglądów. Sprawność separatora ma decydujący wpływ na jakość oleju, co bezpośrednio przekłada się na efektywność pracy systemu olejowego. Zwiększona zawartość powietrza w oleju powoduje spadek ciśnienia w systemie oraz jego większe fluktuacje, które z kolei rzutują na prawidłowe smarowanie komponentów silnika (łożysk, kół zębatych). Nowe konstrukcje silników wymagają od inżynierów tworzenia bardziej kompaktowych konstrukcji separatorów w celu redukcji masy oraz redukcji kosztów projektu przy zachowaniu efektywności i niezawodności tych separatorów. W celu spełnienia powyższych wymagań konieczne jest zastosowanie w procesie modelowania przepływu mieszaniny olej o wo-po wietrznej i przeprowadzenie optymalizacji konstrukcji separatora. Kluczowym zagadnieniem we wstępnym etapie budowy algorytmu obliczeniowego jest identyfikacja cech geometrycznych separatora, które mają istotny wpływ na jego sprawność. W artykule omówiono separatory olejowe stosowane w silnikach lotniczych oraz scharakteryzowano podstawowe zjawiska w nich występujące. Przedstawiono główne parametry wpływające na ich pracę. Zaprezentowano wybrane modele matematyczne analizy przepływu dwufazowego, dwuskładnikowego wraz z modelowaniem turbulencji. Wskazano możliwości zastosowania danego modelu w zależności od rodzaju przepływu.

EN

Cyclone separators are commonly used in oil systems of air turbine engines. Thanks to their simple construction they are characterized by very high reliability thus they do not require frequent inspections. The efficiency of the separator has a decisive impact on the quality of the oil, which directly results in a change in efficiency of the oil system. Increased air content in the oil causes a pressure drop in the system and higher-pressure fluctuations, which in turn affect the proper lubrication of the engine components (bearings, gears). New engine designs require engineers to create more compact separator designs to reduce weight and project costs while maintaining (and often increasing) their efficiency and reliability. To meet these requirements, it is necessary to use the flow modeling of the oil-air mixture in the design process to optimize the construction of the separator. The key issue at the initial stage of the calculation algorithm is to identify the geometric features of the separator, which have a key impact on its efficiency. The article discusses oil separators used in aviation engines and characterizes the basic phenomena occurring in them. The basic parameters influencing the separator's work are given. Selected mathematical models of two-phase (two-fluid) flow analysis together with turbulence modeling are presented. The possibilities of using a given flow model, depending on its structure, are shown.

4

Research on unsteady cavitating flow around a Clark-Y 11.7% hydrofoil

Homa Dorota, Wróblewski Włodzimierz, Majkut Mirosław, Strozik Michał

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 3

765--777

EN

The paper concerns experimental and numerical investigations focused on the cloud cavitation phenomenon over a hydrofoil. The results of flow visualization by means of a high- -speed camera are presented. The cavitation cycles including vapour structures occurrence, development and collapse were recorded and described. Within the numerical investigation, transient calculations of cavitating flow were performed. OpenFOAM software was used. To model mass transfer between phases, the Kunz cavitation model was chosen. Turbulences were modelled by means of k-ω SST model. The vapour areas appearance, their shapes and changes in time were described and compared with experimental results. The characteristic features of cavitating flow were observed, however further adjustment of the cavitation model was advised.

5

Comparison of methods for the determination of Tesla turbine performance

Rusin Krzysztof, Wróblewski Włodzimierz, Strozik Michał

Journal of Theoretical and Applied Mechanics

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2019

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Vol. 57 nr 3

563--575

EN

A numerical and experimental investigation of the Tesla turbine is presented in the paper. The experiment is conducted for various inlet pressure and load. The roughness of the rotor disc is determined as it is a key factor to obtain high turbine efficiency and power. The numerical investigations are performed for the same conditions as in the experiment. The computational results are compared with the analytical model. Comparison of performance characteristics show a relatively good agreement between the experiment and CFD. The analytical model overestimates distributions of pressure and circumferential velocities, although the predicted power is on the similar level as in the experiment and CFD.