Wyniki wyszukiwania - BazTech

1

Review of loss models for high pressure turbines

Back da Trindade D., Bugała P., Simone D.

Journal of KONES

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2018

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Vol. 25, No. 2

38--44

EN

This article presents a literature review about the physical analysis of the loss models, which are used in offdesign procedure for high-pressure turbines. A high-pressure turbine is designed to have maximum performance at design point. However, engines are operating in different conditions, and the comprehension of off-design conditions is very important. The loss mechanisms are very complex and predictions considering empirical methods are a good approach to have preliminary results. Based on these results, different researches have proposed theories about the loss mechanisms, and over the time, these models have been modified to describe better the phenomena involved between blades and flow. Once the physical mechanisms behind the loss models are known, it is possible to compare them and understand the reason why the results given for some methods present a higher agreement to experimental or numerical data. In this framework, 2D numerical simulations of the flow around the blades of an axial high pressure turbine with different off design conditions have been realized, by using ANSYS FLUENT® code, to show the losses described by some of these models. Using these simulations a loss model has been selected and implemented in Matlab® to compare its results with the experimental data found in literature.

2

Deviation angle models in off-design high-pressure turbines

Bugała P.

Journal of KONES

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2018

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Vol. 25, No. 2

69--74

EN

In the article, a set of deviation angle models, which are used to predict the off-design performance high-pressure turbines, has been presented, basing on a literature study. The deviation angle is a deviation between the actual flow angle and the blade inclination angle. It is an essential parameter in turbine performance evaluation. This angle shall be obtained accurately in 1-D design and evaluation, so as to ensure the validity of blade profiling and calculation results. If deviation angle is ignored, the turbine will produce a lower change of tangential velocity, and consequently a lower torque, output work and enthalpy drop than intended by the designer. For this reason, the deviation angle model needs to be established. There exist a number of different deviation models, resulting in varying degrees of flow deviation when applied. In the article, correlations for gas outlet angle, dependent on the Mach number at outlet and determined by the blade loading towards the trailing edge has been presented. The main difficulty in establishing the deviation model is a continuity in defining the angle for all speed ranges (both subcritical and supercritical). Each of the models presented in the article deals with this problem in a different way. A few deviation models, briefly discussed in the article, are based on experimental data and one is based on analytical approach.

3

Review of design of high-pressure turbine

Bugała P.

Journal of KONES

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2017

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Vol. 24, No. 1

67--76

EN

The engine manufacturers adopt new measures in order to further improve the characteristics of a turbine engine. They pose new challenges to reduce a fuel consumption and an emission of pollution to the environment (including noise), but also keeping the highest level of reliability. Based on those considerations, current research in propulsion is conducted. Modern turbines are characterised by high inlet temperature. This has implications for engine efficiency, which is expressed with a change of mass, cross-section and fuel consumption. In this article, main trends in the development of turbine engines are presented. This analysis was carried out on the basis of Rolls-Royce engine data. The article presents literature review concerning the analytical methods of high-pressure turbines preliminary design. The aerodynamic design process is highly iterative, multidisciplinary and complex. Due to this, modern gas turbines need sophisticated tools in terms of aerodynamics, mechanical properties and materials. The article depicts simplified model of real turbine engine. As showed in the article, this model gives only a 10% error level in engine thrust value. The calculations may be used for preliminary engine analyses.

4

Interaction of heavy aircraft wakes

Bugała P., Dziubiński A.

Prace Instytutu Lotnictwa

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2016

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Nr 4 (245)

309--320

EN

In the next few years the problem of heavy aircraft wakes may increase on the account of continuous air transport growth. However, it can be noticed that even today the number of accidents resulting from an interaction with wakes is increasing. That is the reason why methods of wake vortex description should be searched for. The aim of this study is to analyze interaction of example aircraft wakes. In this paper the characteristics of vortex wake behind three-dimensional wing arc presented. It shows how a separation between aircraft affects the decay of vortex. Two- and three-dimensional calculations were performed using commercial RANS code. The following cases have been taken into consideration: flow past a full commercial aircraft, three-dimensional flow over the simplified wing and a two-dimensional analysis of vortex decay caused by the landing aircraft, including the separation effect. For all these cases a CFD simulation of the aircraft wakes was conducted. One of the main outcome of this work is a confirmation that the interaction between wakes consists of spreading out and lifting wakes. The achieved results show that the two-dimensional simulation is a sufficient tool for a preliminary analysis of wake vortices. Conclusions from this analysis can be used by the managements of busy international airports to enhance safety.

PL

W ciągu kilku kolejnych lat, problem wirów powstających za ciężkimi samolotami, może wzrastać z powodu rozwoju ruchu lotniczego. Jednak już dziś można zauważyć rosnącą liczbę wypadków spowodowanych interferencją z wirami. To jest powód, dla którego metody opisu wirów powinny stać się przedmiotem badań. Celem niniejszej pracy jest analiza interferencji wirów powstających za wybranym samolotem pasażerskim. W artykule zaprezentowano charakterystykę zaburzenia powstającego za trójwymiarowym skrzydłem. Niniejsza praca ukazuje wpływ separacji między samolotami na rozpad wirów. Dwu- i trójwymiarowe obliczenia zostały wykonane przy użyciu komercyjnego kodu RANS. Następujące przypadki zostały wzięte pod uwagę: przepływ za pełno wy miarowym samolotem komercyjnym, trójwymiarowa analiza wirów za uproszczonym skrzydłem oraz dwuwymiarowa symulacja rozpadu wirów za lądującymi samolotami z uwzględnieniem separacji. Dla wszystkich tych przypadków zostały przeprowadzone analizy CFD. Jednym z najistotniejszych rezultatów pracy jest potwierdzenie, że interakcja pomiędzy zaburzeniami polega na rozchodzeniu i unoszeniu się wirów. Uzyskane wyniki pokazują, że obliczenia dwuwymiarowe są wystarczające do wstępnej analizy wirów. Wnioski tych analiz mogą być wykorzystane przez zarządy zatłoczonych, międzynarodowych lotnisk do utrzymania odpowiedniego poziomu bezpieczeństwa.

5

Analiza numeryczna wpływu zaburzen za samolotem pasażerskim na operacje śmigłowcowe

Bugała P.

Prace Instytutu Lotnictwa

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2016

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Nr 3 (244)

239--248

PL

Turbulencja w śladzie aerodynamicznym ma wpływ na bezpieczeństwo lotów. Znajomość długotrwałości i charakteru wirów ją tworzących daje możliwość oceny ich wpływu na bezpieczeństwo lotu innych statków powietrznych. Możliwość przewidzenia reakcji samolotu czy śmigłowca, wlatujacego w obszar turbulencji, zwiększa szanse na podjęcie odpowiednich decyzji przez pilota. W ramach pracy przeprowadzono dwuwymiarową analizę obliczeniową metodą RANS z modelem turbulencji Spalart-Allmaras. Rezultaty symulacji numerycznych dotyczą opływu wokół śmigłowca Robinson R44 podczas operacji pod ścieżką lotu samolotu Boeing B-777. Wykonano również analizę trójwymiarową (3D) płata, w celu zweryfikowania wyników otrzymanych uproszczoną metodą dwuwymiarową (2D).

EN

Wake turbulence has an impact on flight safety. Knowledge of behaviour of appearing vortices gives an opportunity to assess the influence of wake on other aircrafts flight safety. The ability to predict the reaction of a plane or helicopter that enters the area of turbulence, increases the pilot's chances to make appropriate decisions. Within the framework of the paper, a two-dimensional calculations using RANS code with Spalart-AUmaras turbulence model were performed. The paper presents the results of CFD calculation of flow around Robinson R44 helicopter during operation under flight path after a Boeing B-777. A three-dimensional (3D) analysis of wing was also performed to verify the results from the simplified two-dimensional (2D) method.