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The Design and Aerodynamic Testing of DPIK Probe
Procházka, Pavel P. ; Barraclough, V. ; Skála, Vladislav ; Uruba, Václav
The isokinetic probe used to detect the liquid phase drift from the cooling tower is presented here. The main motivation is costs reduction that arises during standard drift measurements. The probe was developed in the framework of the grant project between private company 4Jtech and Institute of Thermomechanics. The aerodynamic design and optimization of this probe should fulfill one important criterion – to capture the droplets from the drift with maximal efficiency. Kalorimetric principle is then used to evaluate the amount of trapped water. Standard PIV (Particle Image Velocimetry) measurement technique and modified IPI (Interferometric Particle Imaging) methods were used to measure the flow field topology and the particle size distribution, respectively.
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Control system architecture for novel experimental microalgae photobioreactor Simbios
Věchet, Stanislav ; Krejsa, Jiří ; Chen, K. S.
Photo-bioreactors for growing biomass based on various microalgae cultures gains interests nowadays due to have possible positive impact to society because of the potential to serve as an atmospheric carbon dioxide removal (CDR) device, produce food or fuel. We present an overall architecture of a control system designed with focus to keep the photo-bioreactor alive for long term continuous operation without any human supervision needed. To test overall control system stability we design a custom build spiral photo-bioreactor (PBR) with novel hyperbolic shaped illuminated part. The shape of the illuminated part was design with the goal to increase the ratio of spiral part to volume due to the fact that the light is crucial for microalgae to grow. The control system was created from scratch while adopting reliable IoT sensors combined with highly reliable custom build embedded control system including a cloud data processing and storage. As a result we have scalable and reliable solution which is suitable for photo-bioreactors of various shapes and sizes to operate in fully autonomous mode without any human supervision needed.
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Design of the magnetically sensitive hydrodynamic bearing for the experimental rotor rig
Ferfecki, P. ; Zapoměl, Jaroslav ; Molčan, M.
In a hydrodynamic bearing, the relative motion between the rotating shaft and stationary housing is separated by a thin film of a lubricant. The magnetically sensitive lubricants with the promise of a semiactive control are able to improve the vibration response of the rotor system supported by the hydrodynamic bearings. A design of the magnetically sensitive hydrodynamic bearing is briefly introduced in this paper. The presented experimental rotor rig is proposed to analyse the large range of load conditions and rotational speeds of the bearing. The designed hydrodynamic bearing is intended to test the ferrofluids, magnetorheological oils, and nano-micro composite magnetic fluids. The apparent viscosity of the magnetically sensitive lubricant is altered by the magnetic field generated by the electric coil and thus the position of the bearing journal is shifted. The experimental measurement results show that the rheological behaviour of the lubrication layer with a magnetorheological fluid is significantly influenced by a magnetic field. The raising magnitude of the current in the electric coil leads to an increase in the bearing's load performance.
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Analysis of vibration of rotors with a thick rigid disc on the overhanging end supported by hydrodynamic bearings and loaded by uncertain unbalance effects
Zapoměl, Jaroslav ; Ferfecki, P. ; Molčan, M. ; Kozánek, Jan
Rotors of some rotating machines consist of a shaft and a rigid disc attached to its overhanging end. Because of manufacturing and assembling inaccuracies, the disc is unbalanced. In general case, the disc principal axis of inertia deviates from the shaft axis (both axes are skew lines) and the disc center of gravity is not situated on the shaft center line. Then the disc inertia effects are the source inducing the rotor lateral vibration. As magnitude of parameters specifying the disc unbalance is uncertain, application of an adequate method is required to perform the analysis. In addition, if the rotor is supported by hydrodynamic bearings, their nonlinear properties lead to rising complexity of the system vibration and to reducing its predictability. In the presented paper, the motion equation of a rigid disc has been derived. The shaft was represented by a beam body that was discretized into finite elements. The stiffness and damping parameters of the hydrodynamic bearings were linearized in vicinity of the rotor equilibrium position. Then vibration of the rotor is governed by a set of linearized motion equations. The fuzzy numbers were applied to consider uncertainty of the disc unbalance parameters. The presented procedure provides the approach to computational analysis of rotating machines with the rotor having a disc attached to its overhanging end and the geometrical, mechanical, or technological parameters of which have uncertain values.
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Damping of human vocal folds vibration
Radolf, Vojtěch ; Horáček, Jaromír ; Bula, Vítězslav ; Geneid, A. ; Laukkanen, A. M.
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal fold damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized on a male subject phonating on the vowel [o:]. The results show during the phonation offset a remarkable decrease of vibration frequency of the vocal folds and an increased damping ratio limiting to the value D≈ 0.2. The results for vocal folds’ damping are in agreement with previous measurements performed on humans using different methods.
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Advanced statistical evaluation of fatigue data obtained during the measurement of concrete mixtures with various water-cement ratio
Seitl, Stanislav ; Benešová, A. ; Blasón, S. ; Miarka, Petr ; Klusák, Jan ; Bílek, V.
The Basquin’s law is usually applied for the evaluation of fatigue properties of civil engineering \nmaterials. For materials like concrete, some researchers recommended applying the Weibull model. In this\ncontribution, Basquin’s law, Castillo-Canteli model and Kohout-Věchet model were applied for the advanced \nstatistical description of S−N curves (Wöhler curve). For the application of the models, the experimental data \nmeasured on reference concrete mixtures used for the development of self-healing concrete at the Faculty of \nCivil Engineering, TU Ostrava. Fitting data of applied models were compared and analyzed
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