2019, Vol. 17, Special Issue 1

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/5401

Sirvi

Nüüd näidatakse 1 - 20 35

Management of parts and components for units and assemblies in mechanical engineering industry and its impact on the environment
(2019) Mitrofanovs, V.; Boiko, I.; Geriņš, Ē.
Most of the service centers operating in the repair and maintenance of machines and mechanisms apply warehouse management systems based on event prediction, which ensures inventory replenishment based on the initial diagnosis of the units. Such methodology is enforced measure, since the components and assemblies, even from the same manufacturer, having similar functions, design and connecting components have their own engineering numbers and part numbers for ordering. Unfortunately, this method is relevant only with perfect logistics and minimal time factor. If these criteria cannot be fulfilled, the maintenance and repair time increases, especially at a distance from logistic centers. By reducing lost sales and quick customer satisfaction, own warehouse stocks based on statistical data increases. Unfortunately, none of the modern methods gives a 100% result and eventually leads to overstocking and formation of deadstock. On the other hands more and more components are made from composite materials, complex alloys, permanent joints are being used. But due to ineffective management the significant part of expensive components is became needless. The aim of this research is to develop an algorithm allowing to optimise the logistics chain and reduce the inventory and deadstock, reduce disposal of used and obsolete units and assemblies, resulting in significantly lower consumption of natural resources, energy and reduced negative impact of waste on the environment. Our research shows that in various fields of science there are being developed methodologies, which would solve the described tasks by combining those methodologies in a single algorithm.
Analysis of operation parameters of electric and gasoline vehicle in real driving
(2019) Krumbholc, M.; Kotek, M.
The reduction of transport-generated energy consumption and consequent emission production are currently a problem of global interest. Electric vehicles (EVs) are considered as one promising technological solution for limiting transport-generated energy consumption and emission production, but theirs operating parameters are strongly influenced by immediately operating conditions and it is often very problematic to prove or disprove benefits of EVs in real operation. The aim of this paper is to present comparison of operating parameters of the full-electric vehicle VW e-UP! with identical vehicle Skoda Citigo with gasoline engine in real driving. Both vehicles were tested together in several different areas of the Czech Republic. The experiment was focused on analysis of energy (fuel) consumption and production of exhaust gases (CO, CO2, NOX). VAGCOM diagnostics system was used for sensing engine operating parameters, GPS coordinate were measured by Garmin GPS-18x, vehicle Skoda Citigo was equipped by the PEMS analyzer VMK for RDE emission sensing (CO, CO2, HC, NOX). The results bring a real comparison between the electric vehicle and the vehicle with gasoline engine in terms of fuel consumption and emissions production.
Analysis of non-stationary flow interaction with simple form objects
(2019) Tipans, I.; Viba, J.; Irbe, M.; Vutukuru, S.K.
The paper is devoted to the analysis of a non-stationary rigid body interaction in a fluid flow. Initially, an approximate method for determining the forces due to fluid interaction with the rigid body is offered. For this purpose, the plane movement of a mechanical system with an infinite DOF (degrees of freedom) is reduced to 5 DOF motion: 3 DOF for the body and 2 DOF for the areas of compression and vacuum in fluid flow. Differential equations of non-stationary motion are formed by the laws of classical mechanics. The use of an approximate method has been quantified by computer modelling. The average difference in results was found to be small (< 5%). The analysis of the fluid (air) interaction is carried out for a rigid body of two simple geometries - flat plate and diamond. The results obtained are used to refine the parameters of the proposed approximate method that is addressed in the present study for fluid interaction with the non-stationary rigid body. Theoretical results obtained in the final section are used in the analysis of the movement of prismatic bodies in order to obtain energy from the fluid flow.
Usage of grid support inverter on long distribution grid lines
(2019) Osadčuks, V.; Pecka, A.; Galiņš, A.
The paper focuses on the evaluation of new possibilities to improve voltage quality in remote branches of 230 V grid. Decrease of power electronic costs may potentially make batterybacked inverters a viable alternative to the costly reconstruction of 230 V distribution grid connections, which are of poor quality or cannot match changing load requirements, extending power transmission lines or adding boost transformers. The object of the current study is a household-type consumer with 20 A single-phase connection to distribution line with a distance of 2 km to a 20 kV transformer station. The calculated resistance of the power line is 2.8 ohms. The load profile was captured during 5 days in summer and 10 days in winter and was used to calculate the capacity of the grid support equipment. Measurements indicated, that in the worst case 2% of time the voltage was below 10% of nominal and 8% of time – below 5% of it. This is outside of the regulatory limits of EU and national regulations. The experimental setup for a voltage quality improvement system was based on an OutBack Power Radian series grid inverter with 7 kW output power. Battery consisting of 12 V 120 Ah VRLA accumulators wired in 48 V system was used. The inverter was configured to work in grid support mode using battery power when the consumer’s active load increased above 1.2 kW. Results showed improvement in voltage quality over the full consumer load range. The total efficiency of the grid support system was 89%. The use of DC bus and batteries allows easy incorporation of renewable energy sources, thus giving the opportunity to scale power and battery capacity of the system. An Additional benefit of using a battery-backed inverter in grid support mode is that consumer can temporarily use more power that is allowed by grid due to its capacity constraints.
Suitability of 2.4 GHz and 5 GHz wireless communications in production processes
(2019) Hart, J.; Bradna, J.
Today, it is increasingly modern to use wireless transmissions in production. It is possible to send information messages, control messages and it is often possible to access the technologies as IoT (the Internet of Things). The aim of this work was to find out which of the selected Wi-Fi frequencies is more suitable for use in syrup processing equipment. The evaluation was performed on the basis of attenuation and download speed at each frequency (2.4 GHz and 5 GHz bandwidth). These frequencies have been chosen due to their massive deployment for wifi networks that currently dominate wireless communications. Measurements were made downloading files on different frequency bands. Mean and maximum data throughput and signal strengths were also measured. By measuring, it has been found that when using 2.4 GHz wireless Wi-Fi technology, you can very often encounter strong interference effects. Despite the theoretically worse 5 GHz frequency spread, you can achieve up to 30% better data throughput on average. The results show the suitability of 2.4 and 5 GHz Wi-Fi technology. The main finding is that, despite the worse frequency spread of 5 GHz, it is more appropriate. Not only due to speed but also in the future due to better transmission capacities and future channel expansion.
Thermal analysis of asynchronous machines under intermittent loading
(2019) Vondrášek, Z.; Ryženko, V.; Linda, M.
The operation of electric machines is accompanied by losses which are mostly converted to heat. The heat needs to be dissipated from the machine. With a properly dimensioned motor, the arising heat is balanced with dissipated one. After the motor is started at ambient temperature, all functional parts of the machine are gradually warmed until stabilized. Any overloading of the machine leads to stabilization at temperatures higher than expected by the designers. High temperatures in the machine could cause a crash by damaging an insulation. In case of machines with permanent magnets, the temperature affects their magnetic properties and can leads to demagnetization at the Curie temperature. Therefore, the measuring of temperature is so important for verifying the allowed warming of the motor. Contact and noncontact methods could be used for temperature measuring. Thermal warming and temperature distribution in an electric machine can be also determined by theoretical calculations based, for example, on the finite element method. This method is used by a number of computer software such as Ansys. The article deals with generation and propagation of heat in electric motors and with measuring of warming characteristics with a variable value of a load factor for intermittent periodic loading of asynchronous machine. The loading is carried out by the dynamometer. The temperature measurement is implemented by temperature sensors which are located on the stator winding of the asynchronous motor and are in operation for the whole time the motor is loaded.
Possibilities to identify defective electric automobile batteries
(2019) Berjoza, D.; Pirs, V.; Jurgena, I.
A pack of batteries is one of the most important and expensive assemblies for an electric vehicle. A pack of batteries is comprised of several batteries connected in series. The number of the batteries connected depends on the operating voltage of the vehicle’s on-board system as well as on the individual characteristics of the batteries used, e.g. the operating voltage of a single cell. One or several cells of a pack of batteries could be damaged if improperly exploiting an electric vehicle– excessively discharging the batteries or overloading the electric vehicle. If a self-converted vehicle does not use an intellectual BMS (battery management system) that can identify and register voltage drop for any individual cell in the high-load regime, e.g. when accelerating, it is difficult to identify and change the cells damaged. In case a cell does not demonstrate a complete failure, it is almost impossible to identify a defect in any regime other than the load regime. The research developed and compared three different methods for identifying defective battery cells. The methods were approbated on a converted Renault Clio. The experiment involved making voltage measurements in road tests, running the electric vehicle on a roll test bench and making voltage measurements of maximally discharged batteries in the no-load regime. A comparison of the measurement results revealed that the measurements made in the road tests were the most accurate and useful. After the experiment, the defective battery cells were replaced, thereby restoring the performance of the battery pack.
Management of wastewater from landfill of inorganic fiberglass
(2019) Tihomirova, K.; Denisova, V.; Golovko, K.; Kirilina–Gutmane, O.; Mezule, L.; Juhna, T.
Sustainability is one of the key factors in smart environment management and include the reduction of environment footprint. The waste and wastewater management plans are aimed on actions to reduce the amount of waste and environmental pollution. This includes collection of waste, logistics, storage, processing or valorisation and also treatment. The aim of this research was to evaluate environmental pollution risk and to demonstrate one of the wastewater management schemes to reduce the pollution level. Evaluation of the better management scheme was performed in one of the landfills in Latvia, where fiberglass waste and other inorganic waste is stored. Onsite evaluation results demonstrated the need to develop a better wastewater management scheme of inorganic fiberglass landfill. After that, laboratory–scale experiments for conventional coagulation and biodegradation tests have been performed for efficient management.
Reduction of moisture and thermal conductivity of wet walls by special plaster
(2019) Topol, M.; Kic, P.; Neuberger, P.
This paper is focused on the problems of moisture reduction in old buildings. Wet walls are very common problem of old buildings, but it can appears also in new buildings as well. The moisture in the wall influence the insulation quality; bigger heat losses continuously cause problems of worse heat balance, higher consumption of energy for heating and it can result in not sufficient indoor conditions in such a room or building. Old rural residential buildings and also agricultural buildings for housing of animals, storage of different materials, workshops etc. could be repaired and reconstructed by the used of some special methods. The application of special plaster can reduce the walls moisture as well as improve the thermal properties of the buildings by reduction of thermal conductivity. This paper includes the results of laboratory experiments focused on research of plaster properties (temperature, moisture and thermal conductivity) and tests provided in the real building. Different measuring principles, enabling mutual comparison of results were used for this research. The measurement results showed a significant effect of high wall moisture on the heat losses. Differences between the walls improved by new tested plaster and old untreated walls are discussed in this paper. Obtained results from this measurements and findings may be useful for further research in this issue as well as for the practical solutions for similar problems in many old buildings.
Half-cell potential mapping for corrosion risk evaluation of prestressed concrete ribbed panels from agricultural building after 20 years of service
(2019) Kiviste, Mihkel; Tamme, Valdek; Linnus, Lauri; Halgma, Riho; Estonian University of Life Sciences. Institute of Forestry and Rural Engineering. Chair of Rural Building and Water Management; Estonian University of Life Sciences. Institute of Forestry and Rural Engineering. Chair of Forest Management Planning and Wood Processing Technologies
Corrosion of steel is a significant problem in prestressed concrete structures as it decreases structural capacity and performance. In this research the 20-year-old prestressed concrete ribbed ceiling panels (of type PNS-12) with dimensions of 6 m (length) by 1.5 m (width) from an existing Estonian agricultural building (pigsty) are studied. The objective is to evaluate the corrosion risk of steel reinforcement of ribbed panels by means of a indirect (non-destructive) method and compare the results with a direct method. The methodology consists of a) non-destructive measurements of half-cell potential and b) comparision with actual condition of steel reinforcement after concrete removal (demolition). Non-destructive measurements were performed on the 10 longitudinal ribs of 5 ribbed panels, respectively. Steel half-cell potential maps were developed based on 900 measurement points recorded by half-cell (Great Dane). After destructive tests the ribbed panels including their longitudinal ribs were demolished and the concrete was carefully removed. The position and condition of steel details was photographed (direct method), which enabled the comparison with potential maps (indirect method). The results demonstrated that in general, half-cell potential maps give a rather good indication on the condition of corroding steel rebars with respect to intact details. Also, half-cell potential maps were found relatively useful in estimating the corrosion risk in the studied precast ribbed panels.
Physical-chemical properties and possible applications of clay minerals and humic acid composite materials
(2019) Jemeljanova, M.; Ozola, R.; Klavins, M.
Pollution caused by pharmaceuticals has become an increasingly serious issue, therefore innovative and cost – effective methods of pharmaceutical’s removal must be studied. Clay – humic acid composite materials can be considered as prospective and low cost sorbents for contaminants. The aim of this study is to develop clay mineral and humic acid composite materials and to characterise their possible applications. For this research, three types of clay minerals (montmorillonite, kaolinite and bentonite) were modified with three types of humic substances: technical humic acid from lignite, humic substances extracted from raised bog peat and technical K humate from lignite. The sorption was characterised according to the chosen clay mineral and humic acid type and concentration. The obtained material was characterised by Fourier Transform Infrared spectroscopy and Scanning Electron microscopy. The composite materials were tested for sorption of pharmaceuticals (chloropromazine hydrochloride). The obtained results characterise clay mineral and humic acid composite materials’ possible applications as sorbents for removal of pharmacologically active substances.
Combustion characteristics of compression ignition engine operating on rapeseed oil-diesel fuel blends
(2019) Čedík, J.; Pexa, M.; Mader, D.; Pražan, R.
The effect of biofuels on the operational parameters of the combustion engines, such as performance parameters or emission production, are monitored often. These changes are, however, based on the effect of biofuels on the course of combustion pressure inside the combustion chamber. The contribution deals with the effect of rapeseed oil-diesel fuel blends on the combustion characteristics of turbocharged compression ignition engine. The course of cylinder pressure was monitored and analysed and heat release rate was calculated. The brake specific fuel consumption, indicated and brake thermal efficiency were calculated and evaluated, in-cylinder temperature and ignition delay were also evaluated. As a test fuels a 5% and 20% concentrations of rapeseed oil in diesel fuel were selected while 100% diesel fuel was used as a reference. Turbocharged CI engine Zetor 1204 located in the tractor Zetor Forterra 8642 was used for measurement. During measurement the rotation speed of the engine was kept constant at approx. 1950 min-1 and the load of the engine was selected at approx. 20, 60, 80 and 100%. The results showed decreased cylinder peak pressure, decreased intensity of heat release rate and earlier end of combustion in all tested loads for both tested fuel blends in comparison with diesel fuel, while the lowest peak cylinder pressure was reached using fuel with 5% rapeseed oil. Fuel with 5% rapeseed oil also showed highest indicated efficiency. Ignition delay was found shorter with both of the blended fuels in comparison with diesel fuel.
Analysis of plant materials pre-treated by steam explosion technology for their usability as insulating materials
(2019) Schnabel, T.; Huber, H.; Petutschnigg, A.; Jäger, A.
Raw materials of annual plants fibres are not easily usable for industrial production applications. Pre-treatment of the annual plant fibres is necessary to increase the homogeneity of the material and to improve the material properties. This study deals with the influence of steam explosion treatment on the quality of annual plant fibres used as insulating material. Maize and wheat straw were selected for production of insulating panels. To clarify the changes within the structure of the plants due to the pre-treatment process material analysis was carried out using FT-IR spectroscopy and raster electron microscope. Furthermore, the bulk density and the thermal conductivity were analysed as important values for insulating materials. The results showed that the pre-treatment process homogenizes the materials and the processes could be used for the production of bulk insulation.
Linear pressing of coconut copra meal (Cocos nucifera L.) under different temperatures
(2019) Mizera, Č.; Herák, D.; Hrabě, P.; Saller, T.
Pressing of vegetable oils plays an important role in the food processing. This study described the compression behaviour of copra (Cocos nucifera L.) using the universal compression testing machine and vessel diameter of 60 mm with a plunger. The influence of heat treatment on oil recovery efficiency and specific mechanical energy were determined. Compression tests at the rate of 1 mm s −1 under five different temperatures 20, 40, 60, 80 and 100 °C were performed. The measuring range of force was between 0 kN and 50 kN. It has been found that the amount of obtained oil increased and specific mechanical energy decreased with increased temperature. Measured data were analysed by computer software Mathcad 14 (MathCAD 14, PTC Software, Needham, MA, USA). Mathematical model describing the mechanical behaviour of bulk copra under compression loading was represented.
An analysis of influences of blinds and solar radiation on microclimate in office rooms during summer days: a pilot study
(2019) Cao, D.V.; Kic, P.
Windows are the only part of a building that can directly penetrate the solar radiation into the occupied space and thus the shading devices are needed to control the solar penetration. In the office buildings, they usually use external blinds and internal blinds to reduce heat gains during summer caused by sunlight as well as solar radiation. Therefore, these blinds are main part to maintain thermal comfort for office workers. The aim of this paper is to present results of measurements in four big office rooms in different situations of blinds application. Then, the influence of the internal and external blinds on the internal microclimate conditions inside the large offices during the hot summer days with high solar radiation will be evaluate. The offices floor area is from 43.3 m2 to 59.5 m2 and height 2.8 m. The experiments in this research were focused on measurement and evaluation of globe temperature, indoor air temperature and relative humidity at level of working place during several hot summer days. Comparison of the results of short-term measurements in a room with open blinds and closed blinds has shown the influence of the blinds on the reduction of indoor temperature. More significant was the effect of external aluminium blinds. Solar energies passing through the windows into the interior were 3,476 W without blind and 305 W in case of aluminium venetian external blinds. When the maximum outside temperature was 29.9 °C and office workers used blinds with natural ventilation, the maximum air temperatures in four rooms were from 27.2 °C to 28.5 °C, which exceeded maximum recommended temperature (28 °C). The external aluminium venetian blinds and internal fabric vertical blinds did not maintain thermal comfort inside the offices during all summer days, but it can help in reduction of energy consumption for air-conditioning.
Effective control and battery charging system of an island PV power plant
(2019) Papez, V.; Papezova, S.
The paper presents a new concept of an autonomous PV power plant regulatory system with LiFePO4 batteries, which was functionally verified. The hardware system is significantly simpler and more operationally reliable. It also shows higher efficiency and lower acquisition costs than conventional commercial systems. The proposed control system was optimized for charging a multi-cell battery by PV electric energy. The system automatically maximizes the power supplied by the photovoltaic source and minimizes the power loss caused by balancing the individual cell charging processes. The problem of charge balancing is solved without the balancers. Battery cells are recharged from the separate converters supplying the PV power. The converters are controlled to observe a LiFePO4 battery charging mode while controlling the photovoltaic generator (PVG) load resistance based on an MPP monitoring. PVG power is not supplied to the charged cells, which are in this way protected from overcharging. The entire PVG power is fed to the cells to be charged. The transmission from the converters is controlled in order not to exceed the voltage and current limits at the terminals and to minimize the actual voltage deviation from the control voltage at the PVG output. The control voltage is generated as an MPP voltage approximation according to the load character-istics and the actual PVG operating conditions.
Research on influence of cyclic degradation process on changes of structural adhesive bonds mechanical properties
(2019) Kolář, V.; Tichý, M.; Müller, M.; Valášek, P.; Rudawska, A.
The paper deals with an influence of a cyclic degradation process on changes of a shear tensile strength of single lap-shear adhesive bonds and their elongation according to ČSN EN ISO 9142. Five one-component structural adhesives used in a construction of car body works were used within the research. The degradation of adhesive bonds is a significant factor which influences a quality and a service life of adhesive bonds exposed to environment. A main requirement in production companies is not only reaching satisfactory initial mechanical properties but namely ensuring a reliability and a safety of adhesive bonds during their usage. These reasons show a great importance of adhesive bonds tests either directly in the operating environment or by a simulation of operating conditions in laboratories. The degradation process of adhesive bonds worsens mechanical properties of not only the bond itself but also of the bonded material. This process is progressing and it is usually permanent and irreversible. It is a change of mechanical and physical properties which can endanger a safety and a reliability of parts, prospectively of the whole equipment. It can leads up to a complete failure of its function in the extreme case. A temperature, a moisture, a direct contact with water and chemicals or an atmospheric corrosion belong among the most serious degradation agents. It is important to take into regard time of the processes influence at the same time which can act either independently or concurrently when their effects grow stronger. From that reason the adhesive bonds were exposed to the cyclic degradation process according to the standard ČSN EN ISO 9142. Subsequently, the adhesive bonds mechanical properties were tested on universal testing machine and by means of SEM analysis (TESCAN MIRA 3). Results of mechanical tests proved a fall of the shear tensile strength of single lap-shear adhesive bonds after 42 cycles of the degradation process of 12.8 to 21.7%. The bond strength fall was gradual and it showed a linear trend at some adhesives. Other adhesives showed a significant fall after the exposition to the degradation process after which the strength fall stabilized.
Work posture load evaluation in medium size metal processing enterprise in Latvia
(2019) Kalkis, H.; Roja, Z.; Bokse, K.; Babris, S.; Roja, I.
The aim of this study was to evaluate the exposure of individual workers to ergonomic risk factors associated with upper, lower extremities and trunk WRMSDs and to assess entire body posture for risk of WRMSDs. The company that produces finished metal products (ironing boards) was chosen for the research. Rapid Entire Body Assessment (REBA) was used to assess the entire body posture for risk of WRMSDs. Rapid Upper Limb Assessment (RULA) method was used for ironing boards employees to evaluate exposure of the neck, trunk, arms and legs in relation to physical load. Our study proved that employees are subjected to WRMSDs due to the load on certain body parts during the work: shoulder and neck area, lower back, legs and arms. Forced work postures are an essential risk factor at work. Assemblers and packers are subdued to high risk level, but inspectors – to medium risk level, which corresponds to evaluation with RULA and REBA methods.
Effect of long-term operation of combustion engine running on n-butanol – rapeseed oil – diesel fuel blend
(2019) Holúbek, M.; Pexa, M.; Čedík, J.; Mader, D.
The short time use of biofuels in compression ignition engines is being studied by many authors. However, in many cases the real long–term operation of the engine on biofuels may cause problems. The article deals with the operation parameters of the combustion engine, fuelled by n-butanol – rapeseed oil – diesel fuel blend, during 70 hours operation in total. Two brand new diesel power generators Kipor KDE 6500 with output power of 4.6 kW were used for certain testing. The first generator was operated on 100% diesel fuel and it was used as a reference and the second generator was operated on experimental fuel containing 10% n-butanol – 20% rapeseed oil – 70% diesel fuel blend. The generators were equipped with single cylinder compression ignition engine Kipor KM 186 with the rated power of 5.7 kW. For the first 10 operating hours approx. 40% load was applied. Then, the generators worked for another 60 operating hours with approx. 70% load. The harmful emissions, smoke, fuel consumption and the amount of produced particles were also measured after 10 hours run-in period and then after another 60 hours of operation. Consequently, the results were compared. Measurements were carried out at gradually increasing electric power output, approx. 14%, 28%, 42%, 56%, 68%, 82% and 95% (in results can be found in Watts). Emission analyser and opacimeter BrainBee and Engine Exhaust Particle Sizer TSI were used for the measurements. The results showed increased production of emission of the engine running on fuel blend after 70 hours of operation. On the other hand, engine which operated on standard diesel reached lower fuel consumption. After 70 hours the blended fuel tended to produce more particles in comparison with diesel fuel.
Exhaust particle number of a non-road diesel engine fuelled by methyl esters with different fatty acid compositions
(2019) Ovaska, T.; Niemi, S.; Sirviö, K.; Nilsson, O.
The main aim of this study was to find out how methyl esters with different fatty acid compositions affect the exhaust particle numbers. Along with fossil diesel fuel oil (DFO) and renewable diesel (HVO), a high-speed non-road diesel engine was fuelled by rapeseed (RME) and soybean (SME) methyl esters. Particle numbers within the size range of 5.6–560 nm were measured by means of an engine exhaust particle sizer (EEPS). The exhaust smoke, gaseous emissions and the basic engine performance were also determined. During the measurements, the 4-cylinder, turbocharged, intercooled engine was run according to the non-road steady cycle. Methyl esters reduced particles within the size range of 70 to 200 nm. For RME and SME, both positive and significant correlations were found between the sum of the particle numbers detected above the size category of 23 nm and methyl palmitate (C16:0), methyl stearate (C18:0) and methyl linoleate (C18:2) contents at 10% load at rated speed. In terms of nitrogen oxide (NOx) and hydrocarbon (HC) emissions, HVO was beneficial while carbon monoxide (CO) emission was the lowest with DFO. The level in smoke emission was negligible.

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