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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.

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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.