MATEC Web of Conferences

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Online ISSN: 2261-236X
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The use of battery storage systems (BSS) is an increasingly common topic in the context of the operation of various types of renewable energy sources (RES). One of the applications may be to solve the problem of energy-free operation of small hydropower plants, where quite specific requirements are placed on the design of the BSS. In the context of optimal BSS design for a given application, this paper discusses the computer analysis capabilities that are essential in the design and performance verification phase of a BSS. The paper presents the possibilities of simulation methods in the field of electrical analysis of cell current load during charging and discharging processes, thermal analysis related to the selection of a suitable cooling system with respect to the operating mode of the battery system.
 
This paper presents an approach to the use of the PIV method in the diagnosis of sprays generated by an effervescent atomiser. Due to the different density of the liquid phase depending on the distance from the nozzle, problems arise with the correct exposure of images for PIV analysis. The aim of the authors of this paper is to outline the possibility of solving this problem by composing a velocity field from partial measurements. To meet the objectives of the paper, in-house PIV equipment (hardware and software) was used rather than a commercial setup. This allowed for easier handling of the measured data and more sophisticated post-processing than offered by commercial products. It is clear from the results presented that, despite the fundamental differences in the optical properties of the spray particles, it is possible to obtain a velocity field from the discharge zone to the spray region with fine droplets. Moreover, it is possible to combine velocity measurements in the spray cone with measurements in the surrounding environment. Research background: Spray is an environment with an abundance of tracers for PIV analysis (droplets), but their density, size and shape vary dramatically with distance from the nozzle. The use of PIV can therefore be challenging due to the demands of this method for correct image exposure. Purpose of the article: Introduction of the application of the PIV method for environments with variable density and size of tracer particles Methods: PIV, image processing. Findings & Value added: By taking an appropriate approach to acquiring the source PIV images, it is possible to obtain information about the velocities throughout the spray cone as well as in the surrounding environment. The application of the proposed method requires a sufficiently large source data set (images) and sophisticated postprocessing. However, as a result, it is possible to obtain an overall view of the velocity field in the spray cone starting from the area behind the nozzle to the fine droplet region.
 
The paper deals with numerical simulations of transonic flow through the turbine blade cascade consisting of flat profiles. The cascade is one of variants of the tip section of ultra-long blades, which were designed for the last stage of the steam turbine. CFD simulations were realized by means of the ANSYS CFX commercial software using the γ-Reθ bypass transition model completed by the two-equation SST turbulence model. Some simulations were made only by the SST turbulence model for comparison. Numerical results were compared with experimental data. Calculations performed for two nominal regimes and two computational domains. In addition to the standard computational domain, the calculation was performed for a domain with an extended output part for the suppression of reflected shock waves. The interaction of the inner branch of the exit shock wave with the boundary layer on the blade suction side leads in the both flow regimes to the flow separation followed by the transition to turbulence. The flow structure in the blade cascade obtained for the extended domain corresponds well to experimental results.
 
The paper deals with evaluation of experimental data obtained from the real-size 30 MW output Waste to Energy steam turbine. For many turbine regimes pressures in the last stage area were obtained. At the same time amplitudes of blade tips vibrations were measured of last rotor blades using the blade tip timing system and axial velocity of the steam at the last stage outlet. The obtained data are mutually correlated and relations are analysed between increased vibration values and pressure ratios at the last stage. Increased tip vibrations occur mainly in the area when the pressure ratio over the last blade tip and root is higher than one. In this case there is no expansion, but compression in the last stage of the turbine. The presented results contribute to understanding of processes in the last stage of the steam turbine, mainly for those regimes of turbine operation when its output is lower than 20 % of the nominal output, e.g. during the island regime.
 
Research background: Increasingly the implementation of vehicles with alternative propulsion such as battery or hydrogen vehicles there are higher demands on electricity production. The main factor affecting the environment such vehicles is mainly a source of electricity, which recharges the batteries of vehicles or hydrogen produced as fuel for fuel cells. Purpose of the article: Presented analysis examines the effectiveness of the experimental design of a local OFF-GRID photovoltaic system intended to support of alternative automotive drives. Methods: As a basis for determining the efficiency of the proposed device is the analysis of a run-in photovoltaic system is used installed in the same geographical conditions with data validation with database PV-GIS. Findings and added value: From the analysis of the investigated design of the photovoltaic system shows that electricity production during the year it is directly dependent on the intensity of global radiation. The proposed solution makes it possible to partially cover the energy requirements in transport with active use RES.
 
In this paper, a system which uses hot furnace gases from a metallurgical process to heat compressed air necessary for another energy process is presented. The applied construction of the recuperator ensures high temperatures of the heated air needed for its utilisation in a separate process. Their levels depend on the processes in the reactor. A limitation to the construction of the installation is creep resistance of the materials used to assemble the recuperator modules which operate under high-temperature regimes. The well-prepared gas dynamic design of the recuperator ensured low pressure loss for the flowing air. Furnace gases leaving the recuperation system still have a high energy potential which can be utilised. As it is not possible to manage such large amounts of additional energy, the problem will be solved in the future when necessary.
 
This paper presents the results of the drag coefficient estimations for different types of NREL airfoils based on the experimental data. Namely, it was S803, S807, S813, and S817 profiles with the same chord length. The investigations were conducted at three angles of attack α=0°, α=±5°, different chord-based Reynolds numbers 0.6×10⁵, 1.3×10⁵ and 2.6×10⁵. While, measuring cross-sections were placed behind the trailing edge at x∙c⁻¹≈0.2, 0.4 and 1.0. Experimental data were collected using a hot-wire split fiber probe 55R55, which allowed us to estimate the characteristics of turbulent flow in stream-wise and crosswise directions. According to the obtained results, the highest and lowest Cd values correspond to profiles S817 and S803, respectively. Moreover, the results show that more asymmetric profiles S803 and S807 have the lowest resistance at zero angles of attack. Research background: Application of Antonia and Rajagopalan methodology to drag assessment of various stream bodies. Purpose of the article: Comparative evaluation of the drag coefficients of the NREL airfoils based on instantaneous velocity distribution behind. Methods: Hot-wire anemometry with split fiber probe 55R55. Findings & Value added: The highest drag coefficient corresponds to the S817 profile. The asymmetry of the airfoil shape has a significant impact on its drag characteristics.
 
This paper deals with the demonstration of the non-uniformity of velocity profiles in a DN 200 air circular pipe as part of the development of a newly designed tomographic ultrasonic flowmeter. The flowmeter should measure the flow quality independently. Therefore, different aerodynamic conditions were created by placing mechanical obstacles at the entrance of the measuring chamber, and these conditions were experimentally verified. As an experimental channel substituting a section with ultrasonic sensors, a glass segment was placed at the inlet of a suction pipeline, in front of which perforated plates were inserted to break the uniformity of the velocity profile. The two-dimensional Particle Image Velocimetry (2D PIV) method was used to measure in a plane lying in the longitudinal axis of the channel. The experimental setup and PIV system parameters are described. The results are presented as velocity profiles and contour diagrams in cross-sections at different longitudinal positions in the channel. The results show that the requirement of non-uniformity is satisfied. The used disturbing plates disturb the axial symmetry of the profiles and create a backflow.
 
The development of organs in the human body does not end at birth. During the first five years of life, changes occur in the respiratory tract, not only in terms of its dimensions but also in the way it is used. Efforts to provide non-invasive treatment in the form of medical aerosols administered to children´s lungs during this period must be supported by knowledge of the flow pattern that significantly influences their transport and deposition. Research related to flow patterns in the adult human respiratory tract is quite widespread and the phenomena that occur during inhalation in different parts of the respiratory tract have been widely documented. In the case of the paediatric respiratory tract, research is relatively scarce due to the age of the patient and the desire to minimise interference with the paediatric organism. At the Brno University of Technology, we have the geometry of the airway of a ten-month-old infant, a scaled model of an adult to match the geometry of a five-year-old child based on scientific knowledge and also an adult model of the human respiratory tract. These geometries, together with knowledge of respiratory physiology were used to compare the changes in airflow behaviour that occur in the trachea during the first five years and compare it to fully developed adult human geometry. Computational Fluid Dynamics was used to investigate the model using a Large Eddy Simulation approach. The periods of life captured by the geometries differ not only in their dimensional difference but also in their approach to airway use. The impact of these differences has been captured in the paper.
 
This paper is devoted to the development of a new probe to measure a drift from cooling towers. The probe was named DPIK (Drop Hunter Isokinetic) and its development consists of a design of the aerodynamic and microelectronic part of the probe, verification methods, design and testing, verification tests in laboratory conditions and measurements on a model of the cooling tower. The paper deals mainly with the verification tools, as these methods are very closely related to the aerodynamic part of the probe design. Two options were chosen for verifying the probe principle. The first of these was the Interferometric Particle Imaging (IPI) method, the second was another optical method using similar experimental equipment Particle Image Velocimetry (PIV).
 
Many research is aimed at improving municipal solid waste disposal and producing usable energy. Pyrolysis technology not only decreases the volume of municipal solid waste, but it also produces pyrolysis oil, pyrolysis gas, and carbon, all of which have a high calorific value and are widely used in industrial activities. This article focuses on the plant-based pyrolysis of municipal solid waste and automotive plastic trash. The research also discusses the pyrolysis energy potential of municipal solid waste components such as plastics, biomass, rubber, and plastics. The energy potential of plastic waste from vehicle components was also investigated in this study, which used thermogravimetric and elemental analysers. According to the findings of the examination of the most common plastic waste from automobiles, it is possible to determine the potential treatment of this waste by pyrolysis. By analyse municipal solid waste, it was discovered that waste treatment by pyrolysis might lower the environmental load in Slovakia in the future, ensuring a greater quality of life, inexpensive and sustainable energy for humanity, and strengthening waste treatment innovation.
 
This article deals with conceptual design and experimental implementation of active shading system to reduce building heat gains. First, the problem of building overheating in the summer period and the requirement of lighting in the building interior is explained. Then, the concept of the automated shading system is presented as an efficient yet simple solution to this problem. Along with that, the initial phase of experimental verification, namely the design and additives used, is described. In conclusion, the results of the initial phase are discussed and the future stages of the project along with its significance for the industry are explored. Research background: The issue of overheating of utility buildings in the summer period and the requirement of sufficient lighting of their interior. Measurements in the respective literature and on-site in industrial buildings. Purpose of the article: Explaining the conceptual design of an automated shading system as a remedy to the overheating problem and also to raise awareness of this widespread issue. Methods: Direct measurements of the respective quantities in the industrial sites were conducted. Laboratory experiments along with measurements of several used shading solutions were conducted. Findings & Value added: Some substances showed promising results in creating a translucent heat barrier for sunlight. Further solutions are planned to be tested.
 
Know-how about energy and pressure losses in all steam turbine parts is crucial to guarantee enhanced operational reliability and efficiency. This paper focuses on studying pressure losses in the intermediate-pressure turbine inlet chamber. Measurements were performed on a complex model consisting of the turbine inlet chamber, a compact valve assembly situated upstream, and nozzles located downstream. These intermediate-pressure turbine parts are larger due to the greater volumetric mass flow than the high-pressure turbine parts. However, their inner parts are proportionately smaller, which causes greater pressure losses. Measurements were carried out in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences, where the model was installed in an in-draft wind tunnel. The results were complemented by numerical simulations performed in the Doosan Skoda Power company using ANSYS software tools. Pressure losses were evaluated using the total pressure loss coefficient and, as a result, can be predicted in similar turbine inlet chambers with the required accuracy.
 
The article deals with the optimization of biomass combustion in a small heat source using the optimal distribution of combustion air. Uneven distribution of combustion air was observed during certification tests and in real operation of the used heat source and has an impact on uneven combustion of biomass in the gasification chamber, on increasing emissions and combustion losses. In the first phase of the research, optimization was carried out using CFD simulations, then a transparent model of a real heat source was created, on which the real distribution of combustion air in the gasification chamber was observed using the Particle Image Velocimetry (PIV) method. The results of CFD simulations and the PIV method led to the optimization of the cross-sectional profiles of the four supply channels for gasification air supply. CFD simulations and subsequent PIV measurements on the experimental device were carried out without real combustion, only the air flow in the empty gasification chamber was investigated. This approach was chosen in order to simplify calculations and experiments and on the assumption that with optimal distribution of combustion air in the empty chamber, there will be an optimal even during real combustion. The flow of primary air in the gasification chamber in real operation is influenced by the size and shape of the inserted biomass and its location in the chamber, and this influence is random and difficult to verify. After optimization, the distribution of the primary combustion air in the gasification chamber is uniform and the same amount of air flows into the chamber through the four combustion air inlets.
 
The article analyzes the thermal management of a metal hydride storage tank for hydrogen in the mode of filling the storage tank with hydrogen when it is necessary to cool the metal hydride filling intensively. Cooling is carried out by boiling water at low pressure and therefore also at low temperatures of around 50 °C. In the article, a heat transfer model during boiling is developed and the limits of heat transfer during boiling at low temperatures are determined.
 
The grid turbulence past a grid made of row of prismatic circular rods (rod diameter = 10 mm, rod spacing = 20 mm) perpendicular to the flow is observed by using a pair of PIV cameras. The first one has field of view larger (81 mm), the second one smaller (31 mm), which increases the dynamical range, where the spectral turbulence properties can be explored. Energy spectra displays usual behavior approximately following k −5/3 law, the anisotropy originates at larger scales and the flatness describing strong rare events is connected with smaller scales. The spectral properties of vorticity do not collapse due to the different lengthscale of differentiation, which make questionable the previous research based on the vorticity statistics. Research background: Grid turbulence is the best experimentally accessible prototype of ideal homogenous and isotropic turbulence, although it is known, it is not exactly the ideal one. Purpose of the article: This contribution explores the possibility of expanding the limited dynamical range of PIV method. Methods: Particle Image Velocimetry is based on observing the motion of small particles carried by the flow. Findings & Value added: Anisotropy connected with large scales, flatness with small scales; it does not work for vorticity.
 
Hydrogen was established as one of the main pillars of energy stability in the Europe Union. One of the ways how to achieve this goal is natural gas enriched with hydrogen. Due to this is very important to know the properties of this fuel and its behaviour during combustion. The main scope of the research is to provide a better understanding of the emissions, efficiency, and performance of the heat source when combusting hydrogen and gas fuel mixture. In this paper is described hydrogen characteristics, hydrogen fuel preparation, an overview of gas fuel combustion in gas appliances with the hydrogen additive, a mathematical model for the combustion process estimation. In the conclusion, multiple predictive models were compared. We can state that, based on calculations of a numerical predictive model, as hydrogen concentration raised emissions, as nitrogen, carbon dioxide, wet exhaust, and water, are decreasing.
 
The paper deals the problem of pool boiling heat transfer on the surface produced by the modification with the laser beam. The laser enabled to produce grooves and roughness which have a positive impact on heat transfer. The distilled water and ethanol boiling performance of a horizontally located specimen is discussed and the test results are compared with the model of boiling heat transfer selected from the literature. The laser technique proved to be a valuable tool for producing surfaces that improve thermal performance during pool boiling.
 
The paper describes the development of a non-invasive flowmeter for lower flow rates and its first tests. This gauge is physically based on the interaction of fluid flow with an ultrasonic signal that passes through the fluid from the transmitter to the receiver. Ultrasonic flowmeters are currently relatively commonly used gauges, whose advantages such as non-invasiveness (i.e. zero pressure losses) and the ability to seamlessly measure the flow rates of any (for example opaque) liquids, without contact with the liquid, are widely known. However, there are still parts of the ultrasonic flowmeter measurement chain that are undergoing research and development. It can be signal processing itself (mainly), its design solution, measurement for different flow cases (measurement in a flow field with a uniform velocity profile, in a flow field with an axisymmetric velocity profile, in a flow field with a general velocity profile), validation of the applied signal processing approaches, evaluation of uncertainties. The flowmeter itself, which development is described in the paper, will be used for trouble-free measurement in air engineering, but also serves as a training device for building a more complex ultrasonic gauge. Therefore, this flowmeter contains more signal transmitters and receivers than it is usual and all transmitter-receiver combinations are captured during the measurement. This gauge is called ultrasonic tomograph and its principle is also outlined in the paper. Here, so far, without a reconstructed vector field.
 
With improves in computing hardware and CFD methods, it is possible to work with more complex geometries. The aim of this study is to describe the preparation and creation of a model from CT scans for a numerical study of air flow into the nasal cavities. Research background: The influence of pituitary tumor surgery on the change of geometric proportions of the nasal cavity is investigated in cooperation with the Neurosurgical Department. Purpose of the article: In pituitary tumor surgery, the nasal cavity is used as an access route to the Sella turcica where the pituitary gland is located. Geometric changes occur during surgery. These changes in the geometry of the nasal cavities affect the air flow into the nasal cavities and the sense of the smell of the operated patients. Methods: Based on CT scans of one patient, a procedure was created for creation of models of nasal cavities before and after surgery of pituitary tumor. The open-source software 3D Slicer was used for processing CT scans. Furthermore, the model before and after surgery was modified in CAD program Autodesk Inventor and program Ansys Space Claim. Meshing and subsequent solution of the finite volume method was solved in program Ansys Fluent 2021 R1. Findings & Value added: The models were created considering the anatomical structure of the cavities and were aligned into corresponding coordinate systems. Despite of the efforts to align the planes, inaccuracies occur between the planes. However, the results are comparable.
 
Not only traditional (conventional) but also non-traditional (unconventional) methods are used in metal forming. Unconventional methods will, as it turns out, have more scope than in the past, especially in relation to environmental constraints. One of the methods of unconventional forming is forming in a liquid environment, more precisely – sheet metal forming by applying hydrostatic pressure. This is the subject of the present.
 
Multiple technical and biological systems exhibit multiphase flow phenomena. The demands for accurate calculations of the physical phenomena that occur in engineering technologies have increased along with their rapid advancement. However, it is very hard to identify two- and multi-phase flow through experimental measurements, as a result, in addition to experimental measurements, numerical simulations are also performed, which can help improve our physical understanding of the complex phenomenon of phase transformations. The goal of numerical simulations of phase changes is to precisely simulate the real progress and experiment. These simulations operate on the basis of physical principles and correlation coefficients of phase changes. These correlation coefficients have a different range of values. The examination of the Lee model's correlation coefficients from the ANSYS Fluent environment, which is now the most popular for multiphase flow simulations, is the subject of the article that is being given. In this article is also described and tested the numerical simulation of interphase mass transport in a closed space. Research background: The article is focused on the problematics of multiphase flows. In ANSYS Fluent, there are many types of models, which are used for the numerical simulations of this phenomena. In models are included correlation parameters, which are specific for every single situation and are within the given ranges. This paper is about the Lee model, which correlation coefficients are in the range from 10⁻³ to 10². Purpose of the article: A detailed description of Lee's model with its testing on a heat pipe in the ANSYS Fluent program with determined correlation coefficients. Methods: The use of CFD simulation of multiphase flow to determine correlation coefficients. Findings & Value added: Testing the correlation coefficients of Lee's model and finding their appropriate values for the given situation.
 
Particulate air pollution in cities is caused by a variety of sources. One of the less-studied contributors is wind-induced particle resuspension. As the wind speed increases, particles are removed from surfaces. These particles cause an increase in the total concentration in the air. It is known that particles of 10-2.5 μm in size can be resuspended (PM10-2,5). Modern emission monitoring in cities also allows the monitoring of fine particles of 10, 2.5 and 1 μm in size. The size fractions can then be sorted into PM10-2,5, PM2,5-1 and PM1. When breathed in, particles of different sizes cause various serious health risks. This paper focuses on the identification of the resuspension process of different particle size fractions by a data processing method. Data measured by automatic emission monitoring are used. It is confirmed that the concentration increase can be dominated by the fraction PM10-2,5. However, a concentration increase of fractions PM2,5-1 and PM1 is also evident with increasing wind speed. Although the increase in the PM1 fraction is smaller than PM10-2,5, it is more severe due to the respiratory deposition dose. The resuspension of particles of different fractions has different behaviours during the year. PM10-2,5 particles are dominantly resuspended in the summer months. In winter, on the other hand, the proportion of PM2.5-1 and PM1 particles increases, which may be related to the heating season
 
The identification of cavitation is very important in technical practice for operational and especially economic reasons. The article deals with the use of another way to measure noise during cavitation. The current approach of measuring noise with an intensity probe is used in practice for identification, but it does not immediately address the position of the cavitation source for a given frequency range. Measurement by an acoustic camera is not entirely common in practice, but it allows to determine the location of the noise source for a given frequency range. To test the acoustic camera, the authors focused on the cavitating flow in a hydraulic circuit with three previously tested nozzles. Noise was measured for these nozzles using an acoustic intensity probe with two microphones. The results were evaluated by statistical methods and compared with measurements using an acoustic camera. The aim of the article is to point out the advantages of using this approach for accurate area identification of the problem. Research background: The work is focused on the issue of cavitation and its identification in the hydraulic circuit. For cavitation research, a variant of cavitation identification by noise was chosen. However, this measurement brings problems that are only revealed through more sophisticated and accurate measurements. Purpose of the article: The purpose of the article is to point out other possibilities of measuring cavitation noise using modern technologies and subsequently verify the results. Methods: Metody: A common way of measuring noise is to measure it with a suitably located acoustic intensity probe. A more modern approach is area noise measurement. Measurement methodology and benefits are described. Findings & Value added: The commonly used way of measuring noise using an acoustic intensity probe has proved to be insufficient, as it is not possible to distinguish the location of sources in the case of complex measurements. When using an acoustic camera, there are more sources of noise in a given circuit and they are detected according to the required frequencies in different places than expected. The article points out the specific identification of noise sources using the frequency spectrum of noise for selected elements.
 
When designing a hydropower plant with a long pressure penstock, special attention must be paid to the pressure conditions in the penstock, especially during emergency flow shutdown. In this paper, the main principles of the calculation of static pressure rise in the pressure pipeline during rapid flow shutdown are presented. The results obtained by analytical methods (calculation of direct and indirect water hammer) and numerical methods (mathematical modelling in Matlab software environment) are compared on specific examples. The influence of some input parameters of the numerical model on the results of the numerical calculation is analysed separately.
 
The multiphase flow in oil hydraulic systems has a very significant effect on the correct operation of the hydraulic system. Air can be found in various states in hydraulic systems, while free entrained air in the form of bubbles has the potential to be the most problematic. It especially affects the compressibility of the hydraulic liquid resulting in reduced stiffness of the hydraulic system. The actuators of the hydraulic mechanisms then do not achieve the fast response and the precision of movements depending on the input control signals. One possibility for the contamination of hydraulic fluid by air bubbles is through a phenomenon known as gaseous cavitation. This is a phenomenon in which gas is released when the pressure drops below the saturation pressure of the dissolved gas in the liquid. This article focuses on the experimental analysis of the flow through the throttle valve which is affected by the formation of air bubbles at the throttle edge of the valve. The regions of gaseous cavitation were observed at the different flow cross-section of the throttle valve. The throttle valve was placed into the block of transparent material to provide visualization of the individual measurements. The article is supplemented with photographs of the individual measurements showing the gaseous cavitation inception. Research background: flow cross-section, cavitation phenomenon, discharge coefficient. Purpose of the article: Effect of flow cross-section size and flow velocity on cavitation development. Methods: Experimental measurements. Findings & Value added: The investigation of the gaseous cavitation inception, Visualization of the individual measurements.
 
The circular cylinder turbulent wake is studied experimentally using Particle Image Velocimetry (PIV) method. The vorticity component parallel to the cylinder axis is evaluated from measured velocity field. Dynamics of the vorticity field is analysed using the Oscillation Pattern Decomposition (OPD) method. The 3 dominant modes corresponding to the 1st, 2nd and 3rd harmonics of Strouhal frequency are detected and presented. The corresponding topologies are characterized by waves of vortical systems. The results are similar to the dynamics of velocity field, however the procedure is much easier to implement, as only half number of degrees of freedom are active.
 
This paper deals with the experimental analysis of the effect of the braid angle on the behaviour of a hydraulic hose under pressure loading. The main structural elements of the hose are a rubber tube and a steel braid or spiral. The material of the braid and the number of braids influence the magnitude of the pressure load on the hydraulic hose. The angle of the braid affects the deformation of the hydraulic hose when the inner wall is loaded with fluid pressure. For hydraulic hoses, it is a requirement to maintain a neutral braid angle during manufacture to ensure a balance between axial and circumferential stresses under pressure loading. An experimental device was set up to measure the hoses. This device can be used to measure the diameter of the outer braid, the length and the tensile force of the hose in the axial direction and, where appropriate, to evaluate the angle of the outer braid of the hose as a function of the fluid pressure loading on the inner wall of the hose. The object of the research is to determine the effect of the braid angle on the behaviour of the hydraulic hose under pressure loading. Based on the measurements, the dependencies of the tensile force, the braid angle and the change in length of hydraulic hoses on the internal pressure were determined. In order to compare the measurement results, hydraulic hoses with different inner diameters and different numbers of braids or spirals were selected. Research background: Description of neutral braid angle, hydraulic hose geometry, tensile force of hose. Purpose of the article: Influence of braid angle on the hydraulic hoses behaviour under pressure loading. Methods: Experimental measurements. Findings & Value added: Determining of the change of length dependencies on the pressure, determining of the tensile force dependencies on the pressure.
 
Thermal comfort is one of the basic human needs. There are many options for transforming primary energy sources into heat and, in our countries today, into cold. The heat/cooling supply system needs to be optimised. The criterion is to minimise the final consumption of heat, primary energy sources and emissions, including CO2, while ensuring individual human thermal comfort.
 
This article focuses on vortex structure identification methods and their implementation into smoothed particle hydrodynamics (SPH) framework. The most common criteria based on the local velocity gradient tensor analysis like Q-criterion, Δ-criterion, and λ2-criterion are introduced together with their implementation for SPH data. A two-dimensional ‘double dam break’ problem was chosen as a test case because it results in a violent transient free-surface flow with emerging and vanishing eddies of various sizes and intensities. Q-criterion and Δ-criterion results were virtually identical, whereas λ2-criterion appeared to be the most restrictive in vortex identification, so it was the best in suppressing incorrect findings due to the numerical solution imperfection. The analysis of the problem was therefore conducted using the λ2-criterion.
 
Computational fluid dynamics (CFD) is becoming a widely used tool in the industrial fields. Experimental methods are expensive and time-consuming and CFD is a suitable substitute. In order to investigate the accuracy between the two methods, the radial force on a 6-bladed impeller was measured. The results reveal that the steady-steady analysis method fails, and higher accuracy is achieved using transient simulation. Fairly good accuracy is achieved when simulating the power parameters, where it is sufficient to use the steady-state method as well to save time. On the other hand, for force load detection, where the magnitude of the radial force varies with the position of the impeller, the transient method should be used. The distribution of the non-stationary radial force vectors is symmetric around the origin and lies mainly in 6 regions, which are the same as the number of impeller blades.
 
Aerosols in the atmosphere affect our health and quality of life. The most commonly measured property is their mass concentration. In this work was measured the mass concentration of aerosols by optical particle sizer in the range from 0.3 μm to 10 μm. It was realized in the laboratory with an automatic heat source for pellet combustion. Aerosols were firstly measured before the combustion process, then during combustion of three types of samples: pellets from pure sawdust, pellets from 5 % of disintegrated face masks FFP2 blended with spruce sawdust and from10 % of disintegrated face masks FFP2 blended with spruce sawdust. The lowest total mass concentration was measured during the combustion of pellets from pure spruce sawdust. However, results indicate that the combustion process does not have an impact on aerosol mass concentration in the laboratory space for the particle range 0.3-10 μm when an automatic heat source for pellets is used.
 
For a sample steel casting of a cylindrical shape that was cast in a metallic cylindrical mould, the analysis of influence and importance of the main boundary condition on the simulation accuracy of the temperature field in the system of casting-mould-environment was performed. For this system, the influence of the boundary condition on the frame of the mould, on the bottom of the mould, on the top of the casting, and on the casting-mould interface was analysed. As a comparing quantity for accuracy, the time-dependent temperature field (by means of isotherms) of the casting and of the mould and the total solidification time were selected. When the simulation considers the boundary conditions of one of these boundaries of the system, the heat transfer coefficient on the remaining three boundaries of the system is equal zero. The resultant heat flow along the axis is zero always. The conclusions can be used for fine-tuning of solidification models as well as for other applications; e.g. analysis and solution of inverse heat transfer problems.
 
The paper deals with the principles of hydraulic design of runners of axial turbines or pumps. The procedures of classical methods of hydraulic design of primary runner geometry and the possibilities of subsequent optimization of this geometry by CFD simulation are presented. In the paper, the advantages of the procedure of hydraulic design of the primary runner geometry of a tubular Kaplan turbine with the application of the classical methods and the subsequent CFD simulation are shown on a specific example. The purpose of the CFD simulation is to verify the achievement of the required parameters of the designed runner geometry and its possible fine-tuning and optimization.
 
For many people, the feeling of thermal comfort becomes an important aspect of helping to increase concentration at work or study. Creating an appropriate indoor microclimate becomes a huge challenge for many designers of modern construction. The most important assumption of the work is to compare the thermal sensations of a group of four, aged 23 to 30, staying in the lecture class of an intelligent building and in a climatic chamber with the same internal parameters. For this purpose, the Testo 400 environmental meter was used, collecting the necessary parameters from the environment, and specially created surveys describing people's thermal feelings during the study. The air temperature and relative humidity were as follows: 21.7 °C and 30.80 %, while for the climatic chamber the same data was applied, but at the end of the study both parameters increased to 21.9 °C and 40.50 %. Moreover, it turned out that people in the lecture hall felt worse than in the climatic chamber with similar internal values. In addition, the average Thermal Sensation Vote (TSV) response showed that the perceived environment is comfortable for the study group staying in the climatic chamber, as opposed to the feeling of influenza in the room. Unfortunately, the Predicted Mean Vote (PMV) for the room and chamber exceeded the set value described in the ISO 7730 standard.
 
Changing the impeller diameter is a frequently used method for adjusting pump performance parameters. In the case of conventional multi-blade impellers, this is done by reducing the diameter on the machine tool to the prescribed shape. The other dimensions of the pump (diffuser, inlet) remain unchanged. This method is called trimming. The article deals with the diameter reduction and subsequent modification of the performance parameters of a single blade pump. These pumps are characterized by certain specific features. First of all, it is an unsymmetrical impeller that must be both statically and dynamically balanced. This plays an essential role in the whole modification process. Research results obtained on a pump with an impeller diameter of 138 mm are presented. The change in diameter was monitored on a total of 3 impellers. Experiments were carried out in the laboratory of hydraulic machinery. The results were verified by CFD calculations. Research background: The article concerns the modification of impellers of single blade pumps. The effects of diameter modifications on multi-blade pumps are currently known. However, these have symmetrical impellers and can therefore be changed without restriction. For asymmetric (single blade) impellers, the problem is more complex as additional mass must be added to provide static and dynamic balance. Purpose of the article: The aim is to determine the nature of the change in performance parameters when the output diameter is changed. The results of the research can be applied in the prediction of the change in the operating point and the creation of tombstone charts. Methods: Two kinds of methods were used in the research: experiment and CFD calculation. A total of 4 impeller sizes were investigated. Findings & Value added: The results of the paper can be divided into two areas. In the experimental area, a device was designed to measure the characteristics of single blade pumps. Four impellers were manufactured and tested. In the area of CFD calculations, simulations of the hydraulic parameters around the best efficiency point (BEP) were performed. The calculation results were verified by experiment. The nature of the change of the BEP when the diameter of the impeller changes up to 87.9 % was found.
 
This article describes a methodology for the identification of cooling performance of a natural gas cooler relative to the shape of its heat-transfer surface and presents the outputs of numerical solutions for four different shapes of heat-transfer surfaces in coolers designated as C_A, C_B, C_C and C_D. Calculations were carried out for a cooler with a single row of tubes, and for coolers with two through six rows of tubes that were positioned above one another with an alternating arrangement. In all of the surface shapes, the boundary conditions were respected in order to facilitate the identification of the shape of the heat-transfer surface which is the most appropriate for achieving maximum cooling performance. Out of these four shapes, the best results were observed with the heat-transfer surface of the cooler designated as C_A. The cooling performance of a 1 m long tube with such a surface was 1,650 W.
 
Human life is inextricably linked to the generation of waste, whether at the municipal or industrial sphere. Waste is an important source of secondary raw materials and stored energy, which nowadays is advantageous to use. The most suitable way of waste recovery is its recycling and reuse. The share of waste that is unsuitable for recycling for various reasons is high, it currently exceeds the processing capacity of the Slovak Republic and is therefore deposited in landfills. The energy stored mainly in chemical bonds is therefore not used. The share of energy stored in this way is considerable, and its use would help not only in the field of rational waste management, but also in the field of power industry. The simplest way of energy recovery of waste is its direct combustion, more complex technologies are its gasification and pyrolysis. All technologies are called as Waste to Energy systems. Combustion of waste releases stored chemical energy, which is converted into heat, which is used for the production of electricity and heating. The products of gasification and pyrolysis are gaseous and liquid fuels that can be directly used in heat sources for the production of electricity and heat for heating, but also as an input material for the creation of high-grade fuels and for the chemical industry. The article deals with the conceptual design of a small facility for the recovery of waste, especially plastics, from the automotive industry and sorted municipal waste. The concept discusses the technical possibilities of preparing the input material, the technical ways of using it by gasification or pyrolysis, and the possibilities of using the resulting products of processing plastic waste. The assumptions for the design of a small waste recovery facility are verified on an experimental pyrolysis waste treatment device, the article contains the results of laboratory pyrolytic waste treatment and the properties of the resulting products.
 
In the paper, the course of post-reaction gas afterburning generated during the metallurgical process where the reduction of metal and semi-metal oxides is performed with the use of carbon is presented. Process waste gases can be an alternative source of energy to be used in the same process or converted to another. The participation of chemical enthalpy in the total energy stream of the post-reaction gas is 93 %, the rest is physical enthalpy. In the study, particular attention was paid to the proper mixing of fuel and oxidizer and to maintaining an appropriate ratio of excess combustion air λa. The dynamics of the post-reaction gas combustion processes was calculated according to several popular models but the best results were obtained using the two-step mechanism with reaction constants according to Westbrook-Dryer.
 
This article deals with the experimental and numerical analysis of the leakage characteristics of the proportional directional valve. These characteristics describe the flow through the directional valve in the region of the center position of the spool valve. The element under investigation is a three-position four-way directional valve with zero overlap and feedback from the valve spool position. The actual valve spool position is sensed by an inductive position sensor and processed by integrated electronics. By means of an offset on the integrated electronics, it is also possible to set the center position of the valve spool. By moving the valve spool, the size and direction of the working fluid flow in both directions can be controlled. Internal leakage occurs due to axial and radial clearances between the spool and the sleeve. The magnitude of the axial clearances that occur at the control edges is investigated. The blocked-line pressure sensitivity curve, leakage flow curve and center flow curve are determined by experimental measurements. Depending on the experimental measurement, the correction of the center position of the valve spool is then made using offset. The flow through the control edges at the center position of the valve spool was simulated using Ansys Fluent software. Subsequently, the geometry of the flow simulation model is adjusted. The adjustment is made to take into account manufacturing tolerances. Finally, the simulated dependencies including the effect of manufacturing tolerances are compared with the measured and analytically determined characteristics. Research background: Spool valve description, mathematical equations, flow analysis through valve, radial and axial clearance. Purpose of the article: Effect of axial clearance on leakage characteristic. Methods: Experimental measurements, numerical simulation. Findings & Value added: Determining the range of the center flow curve as a function of manufacturing tolerances
 
The article deals with the design of the diameter and the simulation of the distribution of the intensity of the electric field of the charging electrode of the electrostatic precipitator, given the supplied DC voltage. The purpose was to calculate the value of the critical intensity of the electric field, which must be exceeded when trying to achieve the state of corona discharge on the electrode, which is a condition for electrostatic separation. Subsequently, CFD simulations of two 3D models with electrode diameters of 1 and 4 mm were created, on which the distributions of the electric field intensity were observed at a DC voltage of 20 kV. The simulations confirmed the results of the calculations that the corona discharge at a voltage of 20 kV will occur only on an electrode with a diameter of 1 mm.
 
The article describes the results from the research and development of a cantilever microturbine designed for ORC power plants. The main objective of the paper was to compare different types of rotor seals and their effect on the turbine efficiency and rotor forces. The turbine stage and the numerical models used in the CFD system NUMECA FINE/Turbo are briefly described. The results are compared with the values obtained from measurements and previous simulations. The results show a relatively limited influence of the seal design on the turbine efficiency. The results also show the effect of the seal on the rotor axial force.
 
The use of refrigerants requires to meet ecology and legislation requirements. The aim of the legislation is also to reduce the global warming potential (GWP). Natural refrigerants such as carbon dioxide, ammonia, and hydrocarbons such as propane, isobutene, and propylene are used mainly because of their environmental benefits compared to synthetic refrigerants. This work compares two natural refrigerants: R-744 and R-290 and two synthetic refrigerants: R-134a and R-32. All these refrigerants are used mainly in heat pumps. In this work were calculated and compared the following performance parameters: heat rejected in the condenser, cooling power, compressor power, and the coefficient of performance (COP). The most important parameter is the coefficient of performance because when it decreases, electric energy consumption increases. It requires reaching a high value of COP. Further, this work deals with the economic analyses of selected refrigerants. The last aim of this article is their ecologic analysis based on the GWP factor.
 
The paper presents an approach to calculate the static pressure rise upstream of a valve in a pressure penstock of a hydropower plant (HPP), i.e. a valve upstream of a turbine, during an emergency closure of the flow. The calculated value of the pressure rise is applied for the design of the appropriate time of the valve emergency closure in the HPP penstock and for the sizing of the various parts of the HPP (structural and mechanical). The basic theoretical background of the problem, calculation relations, the range of validity of the used calculation relations are explained and then the procedure applied to the solution of a specific task from practice is explained.
 
Hydraulic scheme of the new die
The paper presents a new deep drawing sheet metal method in which, due to the complex geometric shape of the part, there are significant variations in the level of deformation in different areas of the piece. The method aims to im-prove the quality in the deep drawing process by reducing the variation of the wall thickness of the part, caused by the different degree of stretching of the sheet in different areas of it. In the proposed method the vertical movement of the punch is completed by two vertical rotational movements of it which will have the effect the increasing the flexibility of the deformation process, the active elements occupying the most favorable position dictated by the material flow in the die. It results an improved material deformability and a higher degree of deformation. Also, the new method offers a relatively simple constructive solution of the press and does not require long auxiliary times for assembly-disassembly.
 
Best validation performance for the ANN implemented.
Fig. Regression plots for ANN performance verification.
presents the cutting parameters and their levels. Table 1. Parameters and levels based on the full factorial design of experiments.
Experimental results.
The current work is a follow-up of previous research published by the authors and investigates the effect of CO2 laser cutting with variable cutting parameters of thin 3D printed wood flour mixed with poly-lactic-acid (PLA/WF) plates on kerf angle (KA) and mean surface roughness (Ra). The full factorial experiments previously conducted, followed a custom response surface methodology (RSM) to formulate a continuous search domain for statistical analysis. Cutting direction, standoff distance, travel speed and beam power were the independent process parameters with mixed levels, resulting to a set of 24 experiments. The 24 experiments were repeated three times giving a total of 72 experimental tryouts. The results analyzed using analysis of variance (ANOVA) and regression, to study the synergy and effect of the parameters on the responses. Thereby, several neural network topologies were tested to achieve the best results and find a suitable neural network to correlate inputs and outputs, thus; contributing to related academic research and actual industrial applications.
 
The article presents several current methods of remanufacturing hydraulic components, a trend that is encouraged, on the one hand, by concerns about reducing material consumption in the context of the circular economy - some of these materials being expensive or in short supply. On the other hand, remanufacturing by modern methods can lead to a decrease in energy consumption in the devices concerned, due to obtaining shapes that are difficult to achieve by classical procedures. Among the remanufacturing processes considered there are additive manufacturing, metal coating, reverse engineering, etc. An important step in the remanufacturing process is testing of components, which certifies the achievement of performances at least equivalent to those of the original products. To this end, the article presents a test bench solution with the help of which tests can be carried out on hydraulic devices such as hydraulic pumps and (linear or rotary) motors, hydraulic directional control valves or other types of valves.
 
One of the processes by which hardening of the surface layer and diminishing the heights of the surface roughness occur in the case of steel parts is vibroburnishing. The analysis of the conditions of using the vibroburnishing process of the cylindrical surfaces showed that the use of lubrication could influence the heights of the asperities resulting from the processing. The problem of conducting experimental research was formulated to highlight the intensity of the influence exerted by some input factors in the vibroburnishing process on the roughness of the processed surfaces, evaluated by using the roughness parameter Ra. An experimental program was designed aiming to use different values of ball diameter, ball pressing force, and initial roughness, in conditions of dry vibro-burnishing and using lubricating oil, respectively. The experimental results were processed using a software based on the least-squares method. The determined empirical mathematical models showed that, under the conditions in which the experimental tests were performed, the strongest influence on the value of the roughness parameter Ra is exerted by the initial surface roughness, followed by the size of the ball pressing force on the surface and by the ball diameter, the latter exerting very little influence. It was confirmed that the presence of a lubricant in the processing area results in a decrease in the size of the roughness parameter Ra, compared to the situation where such a lubricant is not used.
 
Most technological manufacturing lines include hydraulically operated stationary tools, devices and equipment. During a manufacturing cycle, there are phases, usually short, in which part of the hydraulic cylinders of the drive systems concerned, with small gauges and displacement speeds, have to generate / maintain high clamping or pressing forces, which implies functioning at high working pressures. The solution for such cylinders is to use modular hydraulic pumping units comprising: oil tank; low-pressure electric pump; hydraulic directional valve for starting, stopping and changing the direction of displacement of the cylinder; electric pump pressure control valve; pressure filter; return filter; oscillating hydraulic pressure intensifier (minibooster mounted directly on the cylinder). Such pumping units, which consume low pressure (in the primary side of the minibooster) to generate high pressure (in the secondary side of the minibooster), are cost-effective when it comes to the procurement of components, installing them, the space required for installation, and their maintenance, too. The classic applications of using them are for achieving and maintaining high pressure values, either in volumes of closed spaces (endurance tests on pipes and tanks), or at the active stroke end of hydraulic cylinders (hydraulic presses). The authors demonstrate, on a laboratory test bench, the following: - The range of applications of such pumping units can be extended in a third direction, namely for actuation of hydraulic cylinders with low gauge / speeds and constant high load (high working pressure) over the entire stroke; - The uniformity of displacement of these cylinders with load over the entire stroke, fed and actuated by such pumping units, is weakly affected by the pulsating mode of operation of the hydraulic pressure intensifier.
 
The paper proposes a method for identifying the front profile of a worm-type active element, consisting of a three-screw compressor. The purpose of this identification is to study the frontal enwrapping between the profiles of the driver and the driven element, in order to produce a possible replacement element. As is it well known, the two profiles are mutually enwrapping profiles, which means that the problem can be treated as a plane enwrapping problem. The identification of the profiles was performed by specific reverse engineering methods, the parts being scanned on an ATHOS 500 scanning system. Subsequently, the analytical shape of the driven screw was identified and, applying the “virtual pole” method, the corresponding shape of the driver screw profile was deduced. The obtained profile was compared with the real profile, obtained by 3D scanning. The obtained results demonstrated not only the good match between the theoretical and the real profile but also the simplicity and robustness of the method applied for the study of the enwrapping, namely the “virtual pole” method.
 
Top-cited authors
Mohd Mustafa Al Bakri Abdullah
  • Universiti Malaysia Perlis
Shahiron Shahidan
  • Universiti Tun Hussein Onn Malaysia
Juraj Gerlici
  • University of Žilina
Viktor Artiukh
  • Peter the Great St.Petersburg Polytechnic University
H. Kamarudin
  • Universiti Malaysia Perlis