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1

Numerical investigation of noise generated by an axial fan installed in a pipeline

Romik Dawid

Vibrations in Physical Systems

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2022

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Vol. 33, nr 1

art. no. 2022104

EN

The article presents the results of numerical calculations of noise generated by an axial fan installed in a ventilation duct with a circular cross-section. The research takes into account the installation of the axial fan due to the distance of the rotor from the curvature of the pipeline. The uRANS turbulent flow modeling methods were used in the calculations. The uRANS stands for the Navier-Stokes equation with Reynolds averaging in the version that takes into account the non-stationarity of the flow. The purpose of the work is to determine the sound power in the vicinity of the sound source. The decisive parameters affecting the noise emitted will be the length of the installation in front of and behind the rotor. The propagation of acoustic disturbances in the far field was modeled using the aeroacoustic analogy of Ffowcs-Williams and Hawkings. Based on the calculations, the directional characteristics of the sound source were determined.

2

Predicting length of fatigue cracks by means of machine learning algorithms in the small-data regime

Badora Maciej, Sepe Marzia, Bielecki Marcin, Graziano Antonino, Szolc Tomasz

Eksploatacja i Niezawodność

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2021

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Vol. 23, no. 3

575--585

EN

In this paper several statistical learning algorithms are used to predict the maximal length of fatigue cracks based on a sample composed of 31 observations. The small-data regime is still a problem for many professionals, especially in the areas where failures occur rarely. The analyzed object is a high-pressure Nozzle of a heavy-duty gas turbine. Operating parameters of the engines are used for the regression analysis. The following algorithms are used in this work: multiple linear and polynomial regression, random forest, kernel-based methods, AdaBoost and extreme gradient boosting and artificial neural networks. A substantial part of the paper provides advice on the effective selection of features. The paper explains how to process the dataset in order to reduce uncertainty; thus, simplifying the analysis of the results. The proposed loss and cost functions are custom and promote solutions accurately predicting the longest cracks. The obtained results confirm that some of the algorithms can accurately predict maximal lengths of the fatigue cracks, even if the sample is small.

3

Dynamic stability of rotating systems in turbomachinery under API standards

Kozanecki Zbigniew, Tkacz Eliza, Łagodziński Jakub, Gizelska Małgorzata

Vibrations in Physical Systems

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2019

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Vol. 30, nr 2

art. no. 2019202

EN

The stability of rotating systems in turbomachinery has to account for the structure design, the actual geometry of bearings and all of the remaining forces, including operational data as well as temperature of the bearing lubricating oil. Thus, a study of the dynamic stability of rotating machines is complex and time consuming in terms of modelling and calculations. Even though it is recognized that other methods of analysis and acceptance criteria have been used to evaluate stability, API standardization procedures ensure appropriate notification and participation in the development process. According to these procedures, firstly we prepare a rotor technical documentation based on geometry measurements, frequently with optical scanning. Secondly, a theoretical analysis consisting of calculations with the finite element method based on the program that allows us to build a numerical model of rotor dynamics, is carried out. Then, the so-called “bump test” is performed to measure natural frequencies of a freely suspended rotor, which makes it possible to “tune” the theoretical model, making it compatible with the real object not only in terms of geometric dimensions and mass, but also from the point of view of the form and frequency of free vibrations. Thus, we obtain an experimentally verified numerical model which can be used for future machine diagnostics and other needs.

4

Evaluation of leakage through labyrinth seals with analytical models

Szymański Artur, Dykas Sławomir

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2019

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Vol. 23, No 1

61--79

EN

Secondary flows in turbomachinery highly affect the overall efficiency and rotorstability. A prime example of such a phenomenon are leakage flows. Despite their complexity, they can often be estimated with simple semi-empirical formulae, solved with hand calculations.Such an approach is much more cost and time effective during the design process. The formula econsists of a carry-over coefficient and a discharge coefficient elements. To evaluate the leakage properly, an adequate model of the carry-over coefficient has to be developed. This paper presents how the flow conditions and the cavity geometry changes in a straight through labyrinth sea laffect the amount of leakage. The effect of the number of teeth, the gap size, the Reynolds number and the pressure ratio are considered. The data to validate the results was obtained from an in-house experiment, where a vast number of cases was tested. Additionally, the study was supported by a two-dimensional steady-state CFD study. Eleven analytical models, including both very simple as well as more sophisticated methods, were solved according to the experimental case and compared. Six different seal configurations were examined. They included straight through seals with two and three straight knives for various gap sizes.The comparison highlighted differences in the results for models – a certain group presented underestimated results. However, another group of models – presented an excellent agreement with the experimental data. Based on this study, a group of models representing the results within the 10% uncertainty band was selected.

5

Concept of automated malfunction detection of large turbomachinery using machine learning on transient data

Barszcz Tomasz, Zabaryłło Mateusz

Diagnostyka

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2019

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Vol. 20, No. 1

63--71

EN

Large turbosets constitute a major source of electric energy in the world. They are critical machines which are vulnerable to several malfunctions which can decrease their availability and degrade the operation of the national electric grid system. The best source of data for assessment of the technical state are the transient data, measured during run-ups and coast-downs. The size of this data is very large and its analysis can be only performed by highly skilled vibration experts. The goal of this paper is to propose a method, which can apply Machine Learning for automated fault detection. In order to improve the quality of the learning process the method is accompanied by the ‘Digital Twin’ approach, where the simplified analytical rotordynamic model is tuned to a particular turboset and used in the learning process.

PL

Turbozespoły dużej mocy stanowią znaczną część źródeł energii elektrycznej na świecie. Są to maszyny krytyczne, które są wrażliwe na kilka rodzajów niesprawności. Mogą one obniżyć dyspozycyjność maszyn i wpłynąć negatywnie na prace całego systemu elektroenergetycznego. Najlepszym źródłem danych do oceny stanu dynamicznego są dane ze stanów przejściowych, mierzone podczas rozruchów i odstawień. Są to dane o bardzo dużych rozmiarach a ich analiza może być przeprowadzana tylko przez doświadczonych diagnostów. Celem artykułu jest propozycja metody, wykorzystującej metody uczenia maszynowego (Machine Learning) do automatycznego wykrywania uszkodzeń. W celu podniesienia jakości procesu uczenia metoda została uzupełniona o zastosowanie uproszczonego modelu analitycznego stanu dynamicznego turbozespołu. Model ten jest dostrajany do danego turbozespołu, a następnie stosowany do wygenerowania dodatkowych danych ze stanów przejściowych, które będą następnie użyte w procesie uczenia.

6

Prediction of secondary flow losses in an entrance duct to a low-pressure turbine

Jonak P., Borzęcki T., Kubacki S.

Archives of Mechanics

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2019

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Vol. 71, nr 1

65--90

EN

Secondary flow features and total pressure losses by means of the total pressure loss coefficient are discussed in an entrance duct, named a turbine central frame (TCF), to a four-stage low-pressure turbine (LPT) of aero-engine. The massaveraged total pressure losses are also analysed at outlets from selected components of the low-pressure turbine. The Reynolds-averaged Navier–Stokes (RANS) technique has been employed for prediction of mean flow characteristics. The numerical results are compared with experimental data obtained in Polonia Aero Lab in Zielonka (Poland). Good agreement is obtained between measured and predicted global flow characteristics and the pressure coefficient on a surface of an inlet guide vane. The high values of the loss coefficient are observed at endwalls, in cores of streamwiseoriented vortex structures near to the endwalls and in the wakes behind the vanes. It is found that the endwall losses contribute by far the most to the total losses at the outlets from the turbine central frame and first vane-row and they become lower at an outlet f rom the first blade-row and at outlets form consecutive vane- and blade-rows.

7

The effects of variable operational parameters on an aero engine labyrinth seals performance

Szymański A., Dykas S., Majkut M., Strozik M.

Transactions of the Institute of Fluid-Flow Machinery

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2018

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nr 140

83--104

EN

The paper presents the accurate assessment of the amount of gas flowing through three types of aero-engine expander sealing. Structures consisting of straight-through labyrinth seals – with one, two and three fins are considered. The study deploys two independent approaches. The first one focuses on the experimental research using high-precision test section with non-rotating labyrinth seals specimen connected to a high capacity vacuum installation. Experimentally tested seals are of actual size (model to engine scale is 1:1). High accuracy hot-wire anemometry probes, and orifice plate are deployed to evaluate the flow indicators accurately, allowing for comparison of different sealing structures. The second approach uses quasi-two-dimensional axissymmetric, steady-state Reynolds averaged Navier Stokes (RANS) computations to simulate the flow field. Various meshes and turbulence models were tested, presenting capabilities as well as limitations of specific computational approaches. The experimental and computational results were compared with literature data, showing a good agreement regarding overall trends, yet underlining some local discrepancies. This paper brings two significant findings. The 2D RANS methods tend to overestimate the leakage when compared with experimental results, and the difference is more significant for advanced arrangements. There is a notable difference between the performance of labyrinth seal with one fin and structure with two and three fins. In some operational areas, one-finned seal performs better than more advanced ones, reducing the leakage more effectively. This feature of one finned seal is not intuitive, as one would expect it to perform worse than a seal with two or three fins.

8

Use and calibration of 5-hole pressure probes to measurement of airflow velocity

Ruchała P., Grabowska K., Małachowski P., Santos L., Back D.

Journal of KONES

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2018

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Vol. 25, No. 2

319--327

EN

Multi-hole probes are simple and robust device to measurement of flow velocity magnitude and direction in wide range of angles of attack – up to 75°. They become popular as they may be easily use to measurement of unknown flow velocity, while optical methods, like PIV or LDA, require some knowledge about the flow for proper setting of measurement devices. Multi-hole probes are also more lasting in comparison with CTA hot-wire probes, which may be damaged by a dust. A multi-hole probe measures air pressure with one pressure tap on its tip and a few (usually 2, 4, 6 or more) taps on conical or semispherical surface of the probe tip. Based on measured pressures, some non-dimensional pressure coefficients are calculated, which are related to flow velocity direction (i.e. two angles in Cartesian or spherical coordinate system) and magnitude. Finding relations between these parameters is relatively complex, which for years was limiting application of multi-hole probes. The article summarizes methods of multi-hole probes calibration and use, which may be classified as nulling and non-nulling methods or – with other criteria – as global and local methods. The probe, which was presented in the article, was the 5-hole straight probe manufactured by Vectoflow GmbH and calibrated in the stand designed and manufactured at the Institute of Aviation. The local interpolation algorithm has been used for calibration, with some modifications aimed on mitigate of mounting uncertainty, which is related with the non-alignment of flow velocity direction and probe axis Results of calibration showed that the accuracy of presented methodology is satisfactory. The standard measurement uncertainty was assessed for 0.2° for the pitch angle and yaw angle, which is better than accuracy declared by the probe’s manufacturer (1.0°). The measurement uncertainty of the flow velocity is approximately 0.12 m/s, similarly like in manufacturer’s data.

9

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.

10

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.

11

An investigation of hot spot location at turbine inlet – numerical simulations for factor project test rig

Flaszyński P., Piotrowicz M.

Transactions of the Institute of Fluid-Flow Machinery

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2017

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nr 135

101--115

EN

The main objective of the presented paper is the investigation of a ﬂow structure and parameters distribution downstream of combustor simulator and its eﬀect on turbine inlet. The investigations are carried out by means of numerical simulations for combustor and turbine nozzle guide vane conﬁguration existing at test rig in DLR Goettingen. As the eﬀect, the hot spot location for diﬀerent relative positions of the swirler and nozzle guide vanes is shown. The presented results are obtained within a pre-test simulations supporting the ﬁnal design of the test section and they allow to draw conclusions for the required limiting cases investigated experimentally. The location of the hot spot is highly important for thermal loading of the ﬁrst stage rotor.

12

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.

13

The assessment of the calculation method for determining characteristics of one straight ﬁn labyrinth sea

Szymański A., Dykas S., Majkut M., Strozik M.

Transactions of the Institute of Fluid-Flow Machinery

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2016

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nr 134

89--107

EN

The method for the selection of a calculation scheme for the evaluation of the ﬂow behaviour of labyrinth seal with one straight ﬁn, against smooth wall, was presented. Experimental results were obtained from measurement data carried out on the in house, vacuum test section. The advantage of the test rig is a circular shape of the labyrinth specimen, providing similar shape to conﬁguration operated in practise. In computational ﬂuid dynamics study diﬀerent types of mesh resolution were tested, with variable volume discretization in the area of a labyrinth ﬁn tip. Moreover, a wide range of turbulence models basing on k-ε and k-ω, exploiting the (Reynolds Average Navier Stokes) scheme, for the ﬂow pattern evaluation, were examined. All obtained results were compared with literature data, covering research conducted on similar conﬁgurations. The presented study shows challenges as well as the possibilities of calculation simpliﬁcation and compares results obtained by means of simulations and experiment. The proposed method is characterised by excellent agreement of computational results with experiment data.

14

Experimental Investigations of Unsteadiness of Flow Fields in Impulse Two-Stage Model Turbine

Krysiński J., Smolny A., Błaszczak J. R.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2015

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nr 148

53--64

EN

The presented investigations were conducted on a modified impulse two-stage low-pressure model turbine with low-aspect ratio of airfoils. Real impulse turbine geometry has been used for both stages to investigate flow problems. A new supply system maintained very stable conditions at the inlet and flow-calming mesh-wiring and acoustic adaptation were built. These improvements allowed identification of different flow effects. A new measurement system was tested for investigations of influence of phenomena related, among others, to unsteady flow structures connected to vane indexing. It is of key importance for the turbine efficiency measurement.

PL

Przedstawione badania zostały przeprowadzone na zmodyfikowanym stanowisku badawczym niskociśnieniowej dwustopniowej turbiny akcyjnej o małej rozpiętości łopatek. Przy projektowaniu geometrii turbiny do badań zagadnień przepływowych oparto się na geometrii rzeczywistej turbiny. Nowy system zasilania zapewnił bardzo stabilne warunki na wlocie, dodatkowo wstawiono siatki uspokajające oraz adaptację akustyczną. Ulepszenia te zapewniły identyfikację różnych efektów przepływowych. Przetestowano nowy system pomiarowy na potrzeby badań wpływu zjawisk związanych, między innymi, ze strukturami niestacjonarnymi powiązanymi ze zmianą położenia kierownic. Jest to kluczowe zagadnienie z punktu widzenia pomiarów sprawności turbiny.

15

Epoka pionierska maszyn przepływowych w Politechnice Łódzkiej

Kryłłowicz W., Błaszczyk M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2015

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nr 148

39--52

PL

W artykule opisano cztery konstrukcje maszyn przepływowych, które powstały w latach sześćdziesiątych ubiegłego wieku w Katedrze Cieplnych Maszyn Przepływowych PŁ. Przedstawiono kolejno: silnik czołgowy CMP 501, sprężarkę 6D68, turbopompę pożarniczą TP 3000 (z silnikiem turbospalinowym CMP 504) oraz turbossawę papierniczą 4.68 PAP. Omówione zostały aspekty konstrukcyjne tych pionierskich maszyn, na tle ówczesnych realiów społeczno-ekonomicznych.

EN

Article contains four turbomachinery designs created in 60’s at the Institute of Turbomachinery, Łódź University of Technology. It presents: CMP 501 tang engine, 6D68 compressor, TP3000 fire engine turbopump (with CMP 504 internal combustion engine) and 4.68 PAP vacuum compressor for paper industry. All machines are presented in context of social and economic environment of that time.

16

Oil free bearing development for high-speed turbomachinery in distributed energy systems – dynamic and environmental evaluation

Tkacz E., Kozanecka D., Kozanecki Z., Łagodziński J.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 145

121--122

EN

Modern distributed energy systems, which are used to provide an alternative to or an enhancement of traditional electric power systems, require small size high-speed rotor turbomachinery to be developed. The existing conventional oil-lubricated bearings reveal performance limits at high revolutions as far as stability and power loss of the bearing is concerned. Non-conventional, oil-free bearings lubricated with the machine working medium could be a remedy to this issue. This approach includes a correct design of the machine flow structure and an accurate selection of the bearing type. Chosen aspects of the theoretical and experimental investigations of oil-free bearings and supports, including magnetic, tilting pad, pressurized aerostatic and hydrostatic bearings as well as some applications of oil-free bearing technology for high-speed turbomachinery are described in the paper.

17

Numerical analysis of a tip labyrinth seal of high rotating rotor

Szymański A., Dykas S., Wróblewski W., Rulik S.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 146

153--163

EN

Labyrinth seal constantly is a prime turbine sealing solution because of low price, low maintenance, minimal rub particulate contamination and high temperature capability. This work aims to perform detailed CFD investigation of high speed rotating labyrinth seal. There have been found an impact of rotational velocity and pressure ratio on discharge characteristics of the rotor. Discharge characteristics were calculated for variety of pressure ratios. Moreover influence of rotor roughness was shown in each case. Performed inquiry results were shown as relative mass flow rate in function of mentioned parameters. From variety of configurations, an optimal seal configuration – providing the lowest leakage can be found.

18

Monitoring and diagnostics of special-purpose turbomachines

Gizelska M.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

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nr 145

47--48

EN

In the operation of special-purpose turbomachines, diagnostic tools which enable control of the machine technical state and its operation parameters in the on-line mode are necessary. The acquisition and processing of the measurement data in real time, which are indicators of the machine functioning under various operating conditions, are crucial. The paper presents two types of computer designed diagnostic tools to monitor in real time the dynamic and thermodynamic parameters of special-purpose turbomachines. The first one monitors the dynamics of the rotating system with an active magnetic bearing, the second - monitors the instant value of polytropic efficiency of the compression process, which was designed for the industrial machine.

19

3D flutter analysis of 11th standard configuration using ANSYS CFX

Kubitz L., Rzadkowski R., Kunicka Z.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2014

|

nr 146

119--140

EN

In this study, numerical simulations of 3D viscous flutter were performed and compared with the available experimental results using ANSYS CFX. The calculations were carried out for bending oscillations of the cascade known as the Eleventh Standard Configuration. The developed numerical algorithm solves the 3D Reynolds-averaged Navier-Stokes equation together with k-ω, SST, S-A models using the explicit monotonous second-order accurate finite-volume scheme and moving hybrid H-O structured grid. Comparison of the calculated and the experimental results for the Eleventh Standard Configurations has shown good quantitative and qualitative agreement for local performances (unsteady pressure amplitude and phase distribution) at off-design conditions, benchmark solutions are provided for various values of the inter-blade phase angle 0, 180, -90, 90 deg.

20

Multidisciplinary design and optimization of gas turbine engine low pressure turbine at preliminary design stage

Bar W., Orkisz M., Moustapha H.

Journal of KONES

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2014

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Vol. 21, No. 3

15--22

EN

The gas turbine engine has evolved rapidly during past decades to provide a reliable and efficient business solution for global transportation. The engine design process is clearly a large contributor to this evolution. This process is highly iterative, multidisciplinary and complex in nature. The success of an engine depends on a carefully balanced design that best exploits the interactions between numerous traditional engineering disciplines such as aerodynamics and structures as well as lifecycle analysis of cost, manufacturability, serviceability and supportability. To take into account all of these disciplines and optimization should be used. Currently most of present state-of-art numerical modelling methods, which are used mainly at detailed design stage, are unsuitable for this task due to very high computational time. The solution to this problem can be found in multidisciplinary design and optimization at preliminary design stage with use of simple 1-2D models. This paper presents current aero engine design process and indicates possibilities of future improvements by utilization of proposed methodology, which take into account aerodynamic, thermodynamic and structures (blade, fixing and disc) calculations, connected in one multidisciplinary model, which is suited for optimization. All disciplinary models are presented and described in this paper as well as connection between them, with study over design variable, goal function and constrains that should be used. Moreover, a strategy of optimization is proposed as well as methods for acceleration of optimization process by use of surrogate. The presentation of methodology is followed by example optimization of low-pressure aero engine turbine.