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1

Heat transfer study from square cylinder immersed in water-based nanofluid: Effect of orientation

Kaur Jaspinder, Ratar Jatinder Kumar, Tiwari Anurag Kumar

Chemical and Process Engineering

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2022

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Vol. 43, nr 2

243-–250

EN

Heat transfer study from the heated square cylinder at a different orientation angle to the stream of nanofluids has been investigated numerically. CuO-based nanofluids were used to elucidate the significant effect of parameters: Reynolds number (1–40), nanoparticle volume fraction (0.00–0.05), the diameter of the NPs (30–100 mn) and the orientation of square cylinder (0–90). The numerical results were expressed in terms of isotherm contours and average Nusselt number to explain the effect of relevant parameters. Over the range of conditions, the separation of the boundary layers of nanofluids increased with the size of the NPs as compared to pure water. NPs volume fraction and its size had a significant effect on heat transfer rate. The square cylinder of orientation angle (45) gained a more efficient heat transfer cylinder than other orientation angles. Finally, the correlations were developed for the average Nusselt number in terms of the relevant parameters for 45 orientation of the cylinder for new applications.

2

Numerical Calculations with a Multi-layer Model of Mixed Sand Transport Against Measurements in Wave Motion and Steady Flow

Kaczmarek Leszek M., Radosz Iwona, Zawisza Jerzy

Rocznik Ochrona Środowiska

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2021

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Tom 23

629--641

EN

A multi-layer model is used to calculate time-dependent sediment velocity and concentration vertical profiles. This model, in which the differences in sediment transport at different distances from the bed are considered is intended both for the wave motion and steady flow. Numerical calculations were carried out for sediment transport during the wave crest and trough and total sediment transport as a sum of their absolute values. The model concept of variation in shear stress from the skin stress value above the bed to the stress value at the bed previously proposed for steady flow is extended here for the wave motion and verified by direct stress measurements. The calculations were carried out for mixed sand sediments with different grain size distributions including semi-uniform and poorly sorted grains. Comparison with the available small- and large-scale data from flumes and oscillating tunnels yields agreement typically within plus/minus a factor two of measurements.

3

Ranges of Backwater Curves in Lower Odra

Mańko R.

Civil and Environmental Engineering Reports

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2018

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Vol. 28, no. 4

25--35

EN

In the paper, the backwater curve ranges at the mouth of the Odra River with changing boundary conditions were analysed. The aim of the study is to determine which boundary condition, i.e. stage of lower cross-section or flow in upper cross-section, has a greater impact on the formation of the backwater curve at the mouth of the Odra River. Due to the complicated system of the Lower Odra River network (Międzyodrze and Dabie Lake), the analysis takes into consideration a section of the Odra River from a weir in Widuchowa upwards, thereby accepting as an axiom that the cross-section in Widuchowa is within the range of sea impact, regardless of other hydrological conditions.

PL

W pracy poddano analizie zasięgi krzywych spiętrzenia w ujściowym odcinku Odry przy zmiennych warunkach brzegowych. Celem pracy jest określenie, który warunek brzegowy tj. napełnienie stanowiska dolnego czy wartość przepływu w rzece ma większy wpływ na formowanie się krzywej spiętrzenia w ujściowym odcinku Odry. Ze względu na skomplikowany układ sieci rzecznej dolnej Odry (tj. Międzyodrze i jezioro Dąbie) do analizy przyjęto odcinek Odry od jazu w Widuchowej w górę koryta, zarazem przyjmując w obliczeniach, że stany wody w przekroju Widuchowa determinowane są wyłącznie stanami morza.

4

Analysis of controlled molecular dynamic flow in a channel with non-equal inlet and outlet cross-sectional areas

Najafi H. R., Karimian S. M. H.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1141--1153

EN

Thermo-fluid properties are required for numerical modeling of nano/micro devices. These properties are mostly obtained from the results of molecular dynamics (MD) simulations. Therefore, efforts have been made to develop methods for numerical evaluation of fluid properties such as pressure and velocity. One of the main challenges faced by numerical simulations is to simulate steady molecular flow in channels with non-equal inlet and outlet boundaries. Currently, periodic boundary conditions at the inlet and outlet boundaries are an inevitable condition in many steady flow molecular dynamics simulations. As a result, a nano-channel with different cross sectional areas at the inlet and outlet could not be simulated easily. Here, a method is presented to generate and control steady molecular flow in a nano-channel with different cross sectional areas at the inlet and outlet. The presented method has been applied to a converging-diverging channel, and its performance has been studied through qualitative and quantitative representation of flow properties.

5

Weryfikacja modelu stacjonarnego przepływu gazu w rurociągu

Chaczykowski M., Zarodkiewicz P.

Gaz, Woda i Technika Sanitarna

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2014

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Nr 8

294--298

PL

W artykule analizowano modele przepływu gazu pozwalające określać profile zmian ciśnienia i temperatury wzdłuż gazociągów w stanach ustalonych. Numeryczne rozwiązanie modelu dokładnego porównano z analitycznymi rozwiązaniami dwóch modeli uproszczonych o różnym stopniu złożoności i dokładności. Wyniki obliczeń weryfikowano na zbiorze danych rzeczywistych obejmujących dwa gazociągi wysokiego ciśnienia należące do krajowego systemu przesyłowego gazu ziemnego.

EN

In the paper pipeline gas flow models allowing for the determination of pressure and temperature profiles along the pipelines under steady-state conditions were analyzed. Numerical solution of the accurate model was compared with two analytical solutions of the simplified models of different complexity and accuracy. The calculation results were verified on a set of real data covering two high pressure gas transmission pipelines from within the polish gas transmission system.

6

Comparison of Average Energy Slope Estimation Formulas for One-dimensional Steady Gradually Varied Flow

Artichowicz W., Mikos-Studnicka P.

Archives of Hydro-Engineering and Environmental Mechanics

|

2014

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Vol. 61, nr 3-4

89–-109

EN

To find the steady flow water surface profile, it is possible to use Bernoulli’s equation, which is a discrete form of the differential energy equation. Such an approach requires the average energy slope between cross-sections to be estimated. In the literature, many methods are proposed for estimating the average energy slope in this case, such as the arithmetic mean, resulting in the standard step method, the harmonic mean and the geometric mean. Also hydraulic averaging by means of conveyance is commonly used. In this study, water surface profiles numerically computed using different formulas for expressing the average slope were compared with exact analytical solutions of the differential energy equation. Maximum relative and mean square errors between numerical and analytical solutions were used as measures of the quality of numerical models. Experiments showed that all methods gave solutions useful for practical engineering purposes. For every method, the numerical solution was very close to the analytical one. However, from the numerical viewpoint, the differences between the methods were significant, as the errors differed up to two orders of magnitude.

7

Metoda doboru płaszczowo-żebrowego rdzenia do pierścieniowego wymiennika ciepła o przepływie przeciwprądowym

Nakonieczny K.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

|

2013

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T. 44, nr 3

117-121

PL

Przedmiotem badań jest przeciwprądowy wymiennik ciepła o konstrukcji pierścieniowej z rdzeniem płaszczowo-żebrowym. Model cieplno-przepływowy urządzenia opracowano przy założeniu ustalonych w czasie warunków pracy wymiennika ciepła. Przenikanie ciepła przez ścianki oraz straty przepływowe ciśnienia płynów modelowano z wykorzystaniem wyników badań eksperymentalnych kompaktowych wymienników ciepła. Charakterystyczną cechą konstrukcji pierścieniowej jest obwodowa symetria naprzemiennie ułożonych kanałów przepływowych i wynikająca stąd symetria modelu obliczeniowego. Ze względu na układ kanałów, w części wlotowej i wylotowej wymiennika ciepła występuje przepływ krzyżowy płynów, a w części środkowej - przepływ przeciwprądowy. Do obliczeń wymiany ciepła w wymienniku wykorzystano metodę lokalnych bilansów energii, która umożliwia wyznaczenie pól temperatury i ciśnienia płynów w sposób iteracyjny. Na podstawie symulacji numerycznych przebadano rdzenie z ożebrowaniem płaskim prostym, przestawianym, falistym i żaluzjowym. Wyniki, ilustrujące zależność pomiędzy całkowitymi spadkami ciśnienia gazu, mocą cieplną urządzenia oraz natężeniem generacji entropii, zestawiono na wykresach.

EN

The study is devoted to analysis of an annular counter-flow heat exchanger with a shell-fin core. Thermo-hydraulic model of the device is valid for steady state conditions. Heat transfer across shells and fluid-flow pressure drops are modelled by using experimental data for compact heat exchangers. A circumferential symmetry of flow channels is reflected in the symmetry of computational algorithm. Due to the layout of flow paths, the inlet and the outlet parts of the heat exchanger are functioning in cross-flow, while the central part - in counter-flow arrangement. The computational algorithm is based on the distributed parameter model, where local energy balances are solved iteratively for the fluid temperature and pressure fields. Numerical simulations are used for thermodynamic assessment of the heat exchanger cores equipped with plane, strip, wavy and louvered fins. The results, illustrating a dependence between total pressure drops, heat transfer rate and entropy generation rate, are depicted in diagrams.

8

Numerical Analysis of Open Channel Steady Gradually Varied Flow using the Simplified Saint-Venant Equations

Artichowicz W.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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Vol. 15, No 3-4

317-328

EN

For one-dimensional open-channel flow modeling, the energy equation is usually used. There exist numerous approaches using the energy equation for open-channel flow computations, which resulted in the development of several very efficient methods for solving this problem applied to channel networks. However, the dynamic equation can be used for this purpose as well. This paper introduces a method for solving a system of non-linear equations by the discretization of the one-dimensional dynamic equation for open-channel networks. The results of the computations using the dynamic and energy equations were compared for an arbitrarily chosen problem. Also, the reasons for the differences between the solution of the dynamic and energy equation were investigated.

9

A study on a newly designed aortofemoral prosthetic Y graft

Fujimoto T., Nakano S., Iwamura H., Shiraishi Y., Yambe T., Umezu M.

Biocybernetics and Biomedical Engineering

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2008

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Vol. 28, no. 1

59-63

EN

Aortofemoral prosthetic Y grafts are applied for treating abdominal aortic aneurysms. In this study, experiments were conducted in order to demonstrate the effects of an incremental increase in branch diameter in a newly designed aortofemoral Y graft under conditions of both steady and pulsatile flow conditions. It was revealed that in Y grafts, the incremental increase by only 4 mm in the branch diameter affects hydrodynamic characteristics drastically under conditions of both steady and pulsatile flow conditions.

10

Badania przepływów transonicznych z kondensacją pary wodnej

Dykas S.

Zeszyty Naukowe. Energetyka / Politechnika Śląska

|

2006

|

z. 144

1-119

PL

Praca dotyczy zagadnień modelowania zewnętrznych i wewnętrznych ustalonych przepływów ściśliwych w zakresie prędkości okołodźwiękowych z uwzględnieniem zjawiska kondensacji pary wodnej. W pracy przedstawiona została metoda numeryczna, służąca do badań przepływów transonicznych pary wodnej oraz powietrza wilgotnego z kondensacją homogeniczną i/lub heterogeniczną. Opisany został szczegółowo model fizyczny oraz krótko przyjęta do obliczeń metoda numeryczna. Metoda obliczeniowa bazuje na rozwiązaniu uśrednionych równań Naviera-Stokesa (RANS), uzupełnionych o model turbulencji SST k-omega oraz fenomenologiczne modele kondensacji homogenicznej i heterogenicznej. Przedstawiono szereg wyników obliczeniowych służących do weryfikacji opracowanej metody numerycznej dla przepływu bez kondensacji. Dodatkowo dokonano szeregu obliczeń sprawdzających poprawność opracowanej metody dla przepływu pary wodnej oraz powietrza wilgotnego z kondensacją. Wyniki te wskazują na poprawność opracowanej metody zarówno dla przepływu jedno jak i dwufazowego. Przeprowadzono obliczenia w celu określenia poprawności obliczeń strat aerodynamicznych (efektów lepkościowych i falowych) oraz termodynamicznych (efektów nierównowagowych i przemian fazowych). Następnie przy użyciu zaprezentowanego kodu numerycznego przedstawiono wyniki analizy pola przepływu w kanałach łopatkowych rzeczywistych turbin parowych, jak i wokół skrzydła lotniczego. Dalsza część pracy zawiera dyskusję efektywności opracowanego narzędzia numerycznego i podsumowanie rezultatów wykonanych testów numerycznych. Końcowa część pracy zawiera opis stanowiska do badań eksperymentalnych jako wygodnego i taniego narzędzia do tworzenia szeregu danych eksperymentalnych służących do weryfikacji metod numerycznego modelowania przepływu z kondensacją homogeniczną i/lub heterogeniczną.

EN

This work deals with problems of numerical modeling of external and internal steady compressible transonic flows taking condensation process of water steam into consideration. In this work numerical method for research of transonic flows water steam and moist air with homogenous and/or heterogenous condensation is presented. The detailed description of physical model and short presentation of used numerical methods is carried out. Numerical method bases on the solution of Reynolds averaged Navier-Stokes equations (RANS) coupled with SST k-omega turbulaence model and models of homogeneous condensation. Many numerical results for code validation of the ideal gas flow without condensation process are discussed. Additionally, many numerical tests for wet steam and moist air flows with condensation are presented. These results show correctness of elaborated numerical code for the one- and two-phase flows. Test calculations for correct determination of the aerodynamic and thermodynamic losses are described. Next, by means of presented CFD code analysis of flows in real blade-to-blade steam turbine channels and around the wing are discusses. The next part of the work includes discussion of presented numerical code efficiency and summary of the carried out numerical tests. The final part presents description of the designed experimental stands as an convenient and effective tool for creation of the measurement data for verification of the numerical method modeling of the flow with homogeneous and/or heterogeneous condensation.

11

Symulacje numeryczne przepływów ustalonych metodą LES

Sobczak K.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2006

|

Nr 129, vol. 1

23-34

PL

W artykule przedstawione są wyniki weryfikacji poprawności działania programu do symulacji przepływów pulsacyjnych wykorzystującego metodę LES (Large Eddy Simulations) w zakresie przepływów ustalonych. Zaprezentowano porównania otrzymanych wyników symulacji numerycznych z wynikami dostępnymi w źródłach literaturowych. Przeanalizowano wpływ rozmiaru siatki oraz wartości stałej Smagorinskiego na poprawność rozwiązań.

EN

Verification results of the code operation for pulsating flow simulations developed with the LES (Large Eddy Simulations) method in the steady flow range are presented. A comparison of the numerical simulation results with available reference data is shown. The mesh size and the Smagorinski constant influence on the calculation correctness are analysed.

12

Dufour and soret effects on steady free convection and mass transfer flow past a semi-infinite vertical porous plate in a porous medium

Alam M. S., Ferdows M., Ota M., Maleque M. A.

International Journal of Applied Mechanics and Engineering

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2006

|

Vol. 11, no 3

535-545

EN

Steady two-dimensional free convection and mass transfer flow past a continuously moving semi-infinite vertical porous plate in a porous medium is studied theoretically, by taking into account the Dufour and Soret effects. The similarity equations of the problem considered are obtained by using usual similarity technique. The resulting equations are then solved numerically by shooting method using Runge-Kutta sixth-order integration scheme. The non-dimensional velocity, temperature and concentration profiles are displayed graphically for different values of the parameters entering into the problem. In addition, the skin-friction coefficient, the Nusselt number and Sherwood number are shown in tabular form.

13

Comprehensive circumscribing of non-linearity cases of a water supply system with smooth flow control

Orłowski R.

Archives of Hydro-Engineering and Environmental Mechanics

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2006

|

Vol. 53, nr 1

7-30

EN

The descriptions found in the literature, of cases of even relatively strong non-linearity of the water supply systems, as well as their mathematical treatment, are rare and incomplete. They refer mainly to the non-linearity with respect to smooth flow control components (for instance, to the operation of pressure reducing valves (PRV), flow reducing valves (FRV) and pumps with motors equipped with smooth rotational speed control - variable frequency drives (VFD)). The article proposes a formally correct method of a comprehensive solution of the above non-linearity cases based on successive simulations with some dynamic analysis of the sensitivity of the system to the operation of the smooth control components mentioned. An appropriate algorithm controlling the effectiveness of the calculations secures correct description of the behaviour of the system for an arbitrary, in practice, method of control of flows, even if all the proposed smooth control methods are used simultaneously. The effects of the use of the solutions presented in mathematical modelling are illustrated by selected results of simulation carried out for an existing water supply system.

14

Unsteady Couette-Poiseulle Flow with Variable Physical Properties in the Presence of a Uniform Magnetic Field

Attia H. A.

Mechanics and Mechanical Engineering

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2005

|

Vol. 9, nr 2

5--13

EN

The unsteady hydromagnetic Couette-Poiseulle flow and heat transfer of an electrically conducting fluid is studied in the presence of a transverse uniform magnetic field with variable physical properties. The viscosity and thermal conductivity of the fluid are assumed to vary with temperature. The fluid is subjected to a constant pressure gradient and an external uniform magnetic field perpendicular to the plates which are kept at different but constant temperatures. The effect of the magnetic field, the temperature dependent viscosity and thermal conductivity on both the velocity and temperature fields is reported.

15

Mixed Convection on a Vertical Flat Plate with Variable Magnetic Field

Dimian M. F., Hadhoda M. Kh.

Mechanics and Mechanical Engineering

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2005

|

Vol. 9, nr 2

15--28

EN

The steady laminar incompressible boundary layer mixed convection flow of an electrically conducting fluid on a vertical flat plate in the presence of an applied magnetic field has been studied. The effect of the induced magnetic field has been considered in the analysis. The resulting partial differential equations are transformed into a system of ordinary differential equations which have been solved numerically using shooting method. Two cases are considered here for the buoyancy force: (i) when it acts in the same direction as the forced flow (Tω > T∞), (ii) when it acts in the opposite direction to the forced flow (Tω < T∞). The velocity profiles, temperature profiles, the skin friction on the plate and the rate of heat transfer coefficient (Nusselt number) are computed and discussed for different values of the magnetic force number β, the thermal buoyancy force ╏, reciprocal of the magnetic Prandtl number a and viscous dissipation parameter (Eckert number) Ec for the two cases.

16

Ocena strat energetycznych w stopniach turbin parowych na podstawie obliczeń przepływów stacjonarnych i niestacjonarnych

Gardzilewicz A.

Archiwum Energetyki

|

2004

|

T. 33, nr 1/2

135-163

PL

W pracy przedstawiono analizę porównawczą strat przepływu przez stopnie turbinowe wyznaczonych w obliczeniach stacjonarnych i niestacjonarnych. Wykorzystane do porównań obliczenia zrealizowano przy pomocy kodu CFD FlowER. Zadanie rozdzielone zostało na dwie części. W pierwszej części dokonano testów weryfikacyjnych kodu, które wykonano w oparciu o pomiary stopni turbin modelowych. Wybrano najlepsze pod względem dokładności schematy numeryczne, dobrano wielkości siatek dyskretyzacyjnych oraz modele turbulencji. Pozwoliło to w drugiej części wykonać porównawcze obliczenia przepływu w układzie stacjonarnym i niestacjonarnym dla akcyjnych stopni turbinowych. Otrzymane wyniki i przeprowadzone analizy pozwoliły na ocenę stosowanych domknięć i przyjętych uproszczeń w zastosowaniu do obliczeń projektowych turbin parowych.

EN

The paper presents the comparative analysis of flow losses in turbine stages based on steady and unsteady flow calculations. The calculations were performed using Flower, a specialized CFD code. First, verifications tests of the code were made. They allowed selecting a proper numerical scheme, grid size and turbulence model to obtain the best possible accuracy. Next, comparative calculations of stationary and nonstationary flow through a system of impulse steam turbine stages were done. The obtained results made the basis for estimating the correctness of closure; and simplifications applied in design calculations of steam turbines.

17

Investigation of powder properties using alternating strain paths

Morgeneyer M., Schwedes J.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2003

|

Vol. 7, No 4

571-578

EN

Steady-state flow (ssf) of powders has been investigated using alternating strain paths, with precompacted powder samples sheared in alternating directions. The dependency of ssf on the level of precompaction is shown.

18

Zastosowanie metody Newtona-Kantorowicza do obliczania płaskich przepływów cieczy lepkiej w obszarach wielospójnych

Skutnik M.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2001

|

z. 15

317-322

PL

W pracy został przedstawiony algorytm numeryczny obliczania płaskiego, stacjonarnego ruchu cieczy lepkiej w kwadratowym zagłębieniu zjedna poruszającą się ścianką i jedną lub dwiema wewnętrznymi przegrodami. Do opisu płaskiego ruchu cieczy lepkiej wykorzystano quasi-liniowe równanie czwartego rzędu dla funkcji prądu, które zlinearyzowano metodą kolejnych przybliżeń Newtona-Kantorowicza. Obliczenia wykonano na siatce 72 x 72 dla liczb Reynoldsa Re ≤ 800.

EN

The paper contains the computational algorithm for the determination of steady plane motion in a square cavity whose top wall moves with a uniform velocity in its own plane and with one or two internal barriers. The steady plane motion of incompressible fluids can be written in the form of the fourth-order equation for the stream function. Then we use the Newton-Kantorovich method of the successive approximations to linearize this equation. The calculations are obtained on the grid 72 x 72 for the Reynolds numbers: Re ≤ 800.

19

Boundary problem for equations of steady gradually varied flow in open channels

Szymkiewicz R.

Archives of Hydro-Engineering and Environmental Mechanics

|

2001

|

Vol. 48, nr 4

23-37

EN

In this paper the problem of solution of ordinary differential equations describing a steady, gradually varied flow is discussed. It is shown that, apart from the initial problem usually solved for open channels, the formulation of the boundary problem is necessary when water levels are imposed at ends of channel. This approach is the mathematically correct formulation of the solution problem for steady, gradually varied flow equations. It enables us to determine directly the water profile and discharge for a single channel, as well as for channel network, instead of the trial and error method usually used. Moreover the formulation of boundary problem with respect to the Manning coefficient and lateral inflow is presented. To solve the listed problems the finite differences method is used.

20

Off-design behaviour of a three stage axial compressor with controlled diffusion airfoils

Bohne A., Hoynacki A., Niehuis R., Gallus H. E.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

|

1999

|

nr 115

37--46

EN

In order to provide detailed experimental data to improve the state-of-the-art design tools for turbomachinery, a three stage high speed axial compressor with CDA is investigated covering its operation range up to full-load conditions. The results of the steady flow measurements characterise the overall performance of the machine and the behaviour of the blading under off-design conditions. The results emphasise the remarkable dependence of secondary flow phenomena as the wake durability and the region affected by the tip clearance vortex on different load conditions. Furthermore a close correlation between the blade loading of the last stator and the overall compressor performance can be detected.