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1

Simulations of hot-gas flow in internally cooled cascade of turbine vanes

Sznajder Janusz

Journal of KONES

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2019

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Vol. 26, No. 2

151--158

EN

An experiment in cooling of gas turbine nozzle guide vanes was modelled numerically with a conjugate viscousflow and solid-material heat conduction solver. The nozzle vanes were arranged in a cascade and operated in highpressure, hot-temperature conditions, typical for first turbine stage in a flow of controlled-intensity, artificiallygenerated turbulence. The vane cooling was internal, accomplished by 10 channels in each vane with cooling-air flow. Numerical simulations of the experiment were conducted applying two turbulence models of the k-omega family: k-omega-SST and Transition SST implemented in the ANSYS Fluent solver. Boundary conditions for the simulations were set based on conditions of experiment: total pressures and total temperature on inlet to cascade, static pressure on the outlet of the cascade and heat flux on the surface of cooling channels. The values of heat flux on the surface of cooling channels were evaluated based on Nusselt numbers obtained from experiment and varied in time until steadystate conditions were obtained. Two test cases, one with subcritical outlet flow, and another one, with supercritical outlet flow were simulated. The result of experiment – distributions of pressure, surface temperature, and heat transfer coefficients on the vane external surface were compared to results of numerical simulations. Sensitivity of the vane surface temperatures and heat transfer coefficients to turbulence models and to boundary-condition values of parameters of turbulence models: turbulence energy and specific dissipation of turbulence energy was also studied.

2

Modelling of vane and rotor blade rows in simulations of gas turbine performance

Sznajder Janusz

Journal of KONES

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2019

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Vol. 26, No. 1

183--190

EN

A method of modelling of nozzle and rotor blade rows of gas turbine dedicated to simulations of gas turbine performance is proposed. The method is applicable especially in early design stage when many of geometric parameters are yet subject to change. The method is based on analytical formulas derived from considerations of flow theory and from cascade experiments. It involves determination of parameters of gas flow on the mean radius of blade rows. The blade row gas exit angle, determined in turbine design point is a basis for determination of details of blade contour behind the throat position. Throat area is then fixed based on required maximum mass flow in critical conditions. Blade leading edge radius is determined based on flow inlet angle to the blade row in the design point. The accuracy of analytical formulas applied for definition of blade contour details for assumed gas exit angle was verified by comparing the results of analytical formulas with CFD simulations for an airfoil cascade. Losses of enthalpy due to non-isentropic gas flow are evaluated using the analytical model of Craig and Cox, based on cascade experiments. Effects of blade cooling flows on losses of total pressure of the gas are determined based on analytical formulas applicable to film cooling with cooling streams blowing from discrete point along blade surface, including leading and trailing edges. The losses of total pressure due to film cooling of blades are incorporated into the Craig and Cox model as additional factor modifying gas flow velocities.

3

Neuronowy model wyznaczania energii szlifowania obwodowego elementów konstrukcyjnych silnika

Nikończuk P., Królikowski T., Bałasz B.

Logistyka

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2011

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nr 6

PL

W obecnych czasach duże naciski kładzie się na minimalizację zużycia energii, dotyczy to również obróbki materiałów. Aby minimalizować energię szlifowania, należy dysponować modelem reprezentującym zależności energii szlifowania od różnych parametrów. W artykule przedstawiono wstępne wyniki prac nad utworzeniem systemu ekspertowego w postaci sztucznej sieci neuronowej modelującej zależność energii szlifowania od głębokości szlifowania. Poszukiwanie nowych rozwiązań modelowania pozwoli osiągnąć w przyszłości nowe rozwiązania dla mikro i nanoszlifowania. Przewidywanie wyników sił składowych szlifowania pozwoli wyznaczyć pracę jaką należy wykonanć do usunięcia mikro i nanowarstwy.

EN

Nowadays, a lot of pressure is put on minimizing energy consumption in all areas of our lives, this also applies to materials processing. To minimize the energy of grinding, you must have a model that represents the grinding energy depending on various parameters. The article presents the preliminary results of work on the establishment of the expert system in the form of an artificial neural network modeling input energy dependence on the depth of grinding. Disadvantages of conventional methods of grinding (high energy related to the unit and the machined surface due to the effects of) restricts the use of conventional methods in micro-and nano-grinding. Searching for a new ways in modeling allows to develop the new methods of nano-grinding. Based on predicted results will make possible determination of energy required to remove microand nanolayers.

4

The influence of plastic working on the selection properties of the nickel -- aluminum alloy coatings

Starosta R., Skoblik R., Dyl T.

Journal of KONES

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2007

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Vol. 14, No. 2

441-448

EN

In the paper chance for practical application of plastic working to finishing coating was analyzed. Alloy coatings Ni-5%Al were obtain by flame spraying. These coatings have monophase structures of a solid solution. Steel (C45) samples with alloy coatings were cold and hot (950 oC) rolling and pressing. During of plastic working was used effective force to obtain of relative drafts s = 6%, 9%, 12% value. After finishing the adhesion reduction, cracks on the surface and cross- sections of coatings deposited on steel base wasn't observed. The largest value of strain hardening (Uhv ) of alloy coating Ni-5%Al was stated after pressing. The metallic coatings obtain by thermal flame spraying be characterized by big surface roughness. Studying coating was received average value of parameter of Ra = 13 jxm. The plastic working caused decrease surface roughness. Minimum value of Ra parameter was observed after hot rolling. It was found that maximal roughness was presented after pressing. The corrosion tests were performed in 0.01 M H2SO4 solution by potentiokinetic technique. The corrosion rate was dependent on method of plastic working. The increasing relative drafts resulted in rise corrosion current density and decrease in value of corrosion potential. Exception to the rule was found for hot rolling.

PL

W pracy przedstawiono wyniki badań nad możliwością zastosowania technologii obróbki plastycznej (walcowania na zimno i gorąco, oraz prasowania) do kształtowania wybranych właściwości natryskiwanych płomieniowo powłok stopowych Ni-5%Al o strukturze jednofazowej, a mianowicie granicznego roztworu stałego a, o maksymalnej 10% rozpuszczalności glinu w sieci krystalograficznej niklu. Celem pracy jest wstępna analiza możliwości zastąpienia tradycyjnie stosowanych metod wiórowej obróbki wykańczającej badanych powłok metodami powierzchniowej obróbki plastycznej. Próbki stalowe (C45) z nałożoną powłoką poddano procesowi walcowania na zimno uzyskując wartości gniotów względnych (s = 6, 9, 12%), walcowaniu na gorąco w temperaturze 950 oC (s = 6 i 12 %) oraz prasowaniu na zimno (s = 12%). Po obróbce plastycznej nie zaobserwowano złuszczeń i odwarstwień materiału na powierzchni rzeczywistej i przekroju poprzecznym powłok. Jakościowa ocena przyczepności powłok metodą tzw. szybkich zmian temperatury nie wykazała negatywnego wpływu odkształcenia plastycznego powłoki na badaną właściwość. Pomiary twardości wykazały, że największe umocnienie powłok nastąpiło po operacji prasowania na zimno (56%), najmniejsze po walcowaniu próbek na gorąco. Obróbka plastyczna przyczyniła się również do poprawy struktury stereometrycznej (chropowatości) powłok. Natryskiwane płomieniowo powłoki cechowały się znaczną wartością parametru Ra (13 jxm). Obróbka plastyczna spowodowała znaczny spadek wartości średniego arytmetycznego profilu nierówności. Pomiary profilometryczne wykazały, że najmniejsze wartości współczynnika Ra uzyskano dla powłok walcowanych na gorąco z największymi wartościami odkształcenia względnego, a najmniejsze dla próbek prasowanych. Polaryzacyjne badania korozyjne w środowisku 0,01 M H2SO4 wykazały, że w większości wypadków operacji obróbki plastycznej nastąpił wzrost gęstości prądu korozyjnego (small tilde 25%) jak i spadek potencjału korozyjnego (-10%). Wyjątkiem jest proces walcowania na zimno (s small tilde 12%), dla którego nie stwierdzono pogorszenia właściwości korozyjnych.

5

Selected problems of experimental investigation of dynamically loaded journal bearings

Sikora J., Kłopocki J., Majewski W.

Journal of KONES

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2007

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Vol. 14, No. 4

433-440

EN

In the paper some problems concerning relations between external bearing loadings and critical lining stresses are described for test stand with rotating load vector. According to the standard ISO 7905/1 this type of test stand, for dynamically loaded slide bearing, is recommended as a basic research unit for material testing in a complete bearing unit. The lining stress calculation results occurred being dependent on applied calculation model. The influence of sliding surface shape and housing stiffness on bearing fatigue have been considered. The MWO-stand operational principle, standard tested half-bearing, bearing housing of rigid profile, bearing housing of edge elastic profile, distribution of radial and circumferential stress in the slide layer of the bearing bush tested in MWO stand, typical damage of the bearing tested, finite element model geometry for bush and housing are illustrated in the paper. Performed calculations revealed that neglecting the shape and dimensions of the housing in calculation model of the contemporary thin-walled multilayer bearing bushes are leading to incorrect evaluation of critical stresses leading to fatigue cracks in slide layers of the bearing tested in machines with rotary load vector. That kind of bearing alloys is not employed in highly dynamically loaded bearings of contemporary machines, especially in IC engine bearing systems.

6

Comparative study of a few fem models of a surface coating system

Szymczyk W.

Journal of KONES

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2006

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Vol. 13, No. 4

41-49

EN

Multilayered coatings established on parts of internal combustion as well as jet engines may be used as TBC systems providing their better thermal-mechanical efficiency, tribological properties, wear resistance and an ability to withstand the influence of aggressive media. A comparative review of a few different FEM models of a surface coating system is presented which can be used for the needs of designing improved parts of engines. The coating system was established on a beryllium copper substrate and consisted of the NiCr midsurface and TiN external layers. The system was analyzed as a graded as well as functionally gradient material (FGM) with an assumed gradient function of material properties. The more advanced models use a micromechanical technique of modeling which enables consideration of microstructure influence on the residual stress distribution. They contain transition zones between the pure material volumes where the material properties change accordingly to the linear gradient function. Simulations of microstructural effects in the area of surface coating are strongly recommended. The results of micromechanical calculations are affected locally too strong to be excluded from considerations.