Ústřední knihovna ČVUT
http://hdl.handle.net/10467/3646
ÚK2024-10-07T01:35:38ZExperimental investigation of an entropy production in a linear blade cascade
http://hdl.handle.net/10467/118170
Experimental investigation of an entropy production in a linear blade cascade
Flídr, Erik
The vortical structures in turbomachinery are crucial phenomena that significantly impact the machine’s efficiency. Therefore, investigating them is essential for a better understanding of the machine’s operation.The presented paper focuses on an experimental investigation of entropy production in a linear blade cascade composed of prismatic blades for two pitch-to-chord ratios, t/c = 0.6, and 0.9. The effects of the inlet flow angle, α1 = −20°, 5°, 30°, and outlet isentropic Reynolds number, Re2,is = (0.8, 1.2, 2.5, and 4.5) × 105, are examined based on pressure measurements.Entropy production is evaluated as a balance of fluxes through the inlet and outlet boundaries of the control volume. The paper provides a detailed discussion of the local distribution of entropy production and vorticity in the flow field, as well as their evolution with the tested parameters. The correlations between the integral values of entropy production and the tested parameters are also given.
2024-01-01T00:00:00ZNon-homogeneity effect on the vibration of the rectangular visco-elastic plate subjected to the linear temperature effect with quadratic thickness variation in both directions
http://hdl.handle.net/10467/118169
Non-homogeneity effect on the vibration of the rectangular visco-elastic plate subjected to the linear temperature effect with quadratic thickness variation in both directions
Aggarwal, Sudhanshu
The present work investigates the effect of non-homogeneity on the vibration of a rectangular visco-elastic plate. The plate is subjected to linear temperature variation in the x-direction with quadratic thickness variation in both directions. The quadratic variation has been considered in the material density of the plate only along the x-axis, and it is assumed that non-homogeneity transpires because of this variation. The governing differential equation is solved using the Rayleigh-Ritz technique. All four edges of the plate should be clamped to drive the frequency equation. Deflection and time period have been evaluated for several combinations of values of the thermal constant, constant of nonhomogeneity, taper constants, and length-to-width ratio (aspect ratio) for the first two vibrationmodes of the clamped plate. The results presented are compared with those found in the literature.
2024-01-01T00:00:00ZHydrothermal and mechanical performance of mortars containing waste brick powder
http://hdl.handle.net/10467/118168
Hydrothermal and mechanical performance of mortars containing waste brick powder
Brixi, Abderrahim; Ghembaza , Moulay Smaïne; Boudenne , Abderrahim
It is widely recognised that green building, environmental sustainability, and technical performance have recently become requirements in the field of civil engineering. For this reason, the new trend in research is to focus on the recycling and recovery of materials, even if some of them such as industrial waste are still underexplored. In this perspective, the main objective of this work is to study the influence of brick powder on the thermophysical and mechanical properties of mortars containing this type of waste, in different environments, and within the temperature range between ambient temperature and 50 °C. To this end, a number of mortar mixtures, in which cement was replaced by brick powder in different proportions, were studied and characterised according to technical standards in order to define the optimal substitution percentage. Three batches of samples were examined at different ages, i.e., 3, 7, 28, and 90 days. The samples of the first batch were kept in water at a temperature of 20 ± 2 °C with a relative humidity RH = 100 %, while those of the second batch were immersed and stored in water at 50 °C in order to simulate a hot and humid climate. As for the samples of the third batch, they were kept in a dry oven at 50 °C in order to investigate the effect of the hot and dry climate. The results obtained revealed that the partial replacement of cement by brick powder makes it possible to improve the thermal insulation characteristics but reduce the mechanical strength of the mortar. In addition, it was shown that in a hot and dry environment, the mechanical characteristics of the different mortars decrease as the rate of weight substitution of cement by brick powder rises. However, in a hot and humid environment, a reverse trend is observed. The findings also suggested that the optimal recommended rate of substitution of cement by brick powder is 20 %.
2024-01-01T00:00:00ZInvestigation the plastic flows in the metal stamping-drawing process at the die corner
http://hdl.handle.net/10467/118167
Investigation the plastic flows in the metal stamping-drawing process at the die corner
Onopchenko, Anton V.; Kurin, Maksym O.; Shyrokyi, Yurii V.; Horbachov, Oleksii O.
The present investigation covers the study of the influence of metal-plastic flow on the die corner for the deformed state of the blank and energy-power parameters during stamping-drawing. The influence of workpiece size and material on stress intensity and maximum deformation force has also been investigated both experimentally and theoretically. In addition, simulation of the stamping and drawing process was also presented. One type of die, with variations in diameter are considered different in the drawn part size and for each standard size four types of workpiece materials have been considered. The stamping process continued until the part failed structurally. The predicted test results show a dependence of the maximum load and stress intensity on both the diameter of the blank and the yield strength of the alloys and these data are in agreement with the actual measured values. Then, the method for calculating the processes of plastic deformation of metals based on a closed set of equations of continuum mechanics is proposed for the theoretical study of energy-power parameters of the technological processes. Comparison of the results of a full-scale experiment, simulation of metal flow at the die corner and theoretical calculations shows that the proposed theoretical model gives satisfactory results and can be effectively used for engineering calculations.
2024-01-01T00:00:00Z