2019, Vol. 17, Special Issue 1

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

Sirvi

Nüüd näidatakse 1 - 20 35

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.
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.
Analysis of operating parameters of hybrid vehicle under real traffic condition
(2019) Kotek, M.; Krumbholc, M.; Hartová, V.
Nowadays, protecting the environment and reducing harmful emissions is an increasingly discussed topic. One way to reduce vehicle emissions, especially for individual car traffic, is to use a hybrid drive. The advantages of the electric drive and the classic combustion engine are used here. By combining both types of drive, a synergetic effect is achieved, where both drives can be used in optimal operating mode. The aim of the experiment was to demonstrate the benefit of a hybrid vehicle in real driving. The operating parameters of the Lexus LX400h hybrid vehicle was compared to a conventional lowclass vehicle Škoda Fábia 1.2 HTP with a classic SI engine. The experiment took place on a route including typical urban, extra-urban and motorway traffic condition. During experiment, the engine operating parameters and CO, CO2, HC and NOX emissions were measured. The results show that the emission production and fuel consumption of the hybrid vehicle are significantly lower in urban traffic condition than the vehicle with classic internal combustion engine. On the contrary, in motorway conditions, the hybrid vehicle must use both drives, as higher performance is required to overcome higher driving resistances and therefore achieves higher fuel consumption and higher emissions than a conventional vehicle.
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 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.
Autonomous photovoltaic system for night-time lighting in the stable
(2019) Dang, M-Q.; Šafránková, J.; Libra, M.; Poulek, V.; Kouřím, P.; Sedláček, J.
Autonomous photovoltaic (PV) systems are suitable, for example, for powering various appliances or scientific instruments in the field, for automatic data collection, for signaling, etc. At the Czech University of Life Sciences Prague, we have designed an experimental autonomous PV system designed for night-time lighting for orientating in a stable for horses. The article describes the construction of a PV system with a PV panel rated at 170 Wp, with a lead-acid accumulator and a 1,5 W LED light source. The data collection was automated. The data evaluation shows that during the whole year, the PV system has been recharged and there was no lighting failure. The paper also presents important measured characteristics.
Behavior of B20 fuels in arctic conditions
(2019) Sirviö, K.; Niemi, S.; Help, R.; Heikkilä, S.; Hiltunen, E.
Several renewable and sustainable liquid fuel alternatives are needed for different compression-ignition (CI) engine applications to reduce greenhouse gas (GHG) emissions and to ensure proper primary energy sources for the engines. One of the shortcomings of several bio oils and first generation biodiesels has been their cold properties. Still, the need for alternative fuels is also present in arctic areas where the storing of the fuels may become problematic. The main aim of the current study was to determine how the storage related properties of fuel blends change if the fuels first freeze and then melt again. The samples were analyzed three times: as fresh, and after the first and second freezing-melting phase transitions. The share of renewables within the blends was 20 vol-%. Rapeseed methyl ester (RME) and animal-fat based methyl ester (AFME) were blended with LFO in a ratio of 80 vol-% of LFO and 20-vol% of RME or AFME. The investigated and compared properties were the FAME content of the neat FAMEs, and kinematic viscosity, density, oxidation stability index, and acid number of the blends. Cold filter plugging point was measured for AFME and its blend. According to the results, the quality of the FAMEs and their blends did not change significantly during the freezing over. The freezingmelting phase transition seems, thus, not to be as big a threat to the fuel quality as the high temperatures are. According to the results of this study, the studied fuels were feasible after the freezing-melting phase transition.
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.
Contamination of transmission and hydraulic oils in agricultural tractors and proposal of by-pass filtration system
(2019) Majdan, R.; Abrahám, R.; Uhrinová, D.; Nosian, J.
Tractors use various types of lubricating oils in transmission and hydraulic system. Oils are contaminated by different ways depending on the work of the lubricated system. There are general requirements on the cleanliness level of the oil in the tractor transmission and hydraulic system according to the standard DIN 51524. According to all that, this paper presents research conducted by two tractors. The tractor John Deere 8100 used only its own implements (ploughs, trailers etc.) and it was operated in compliance with user manual. In this tractor, the oil cleanliness level met the standard DIN 51524 because reached the stage 7 (NAS 1638). The tractor Zetor Forterra 124 41 contained extremely contaminated oil, it reached stage > 12 (NAS 1638), due to the non-standard operation which was opposite to the user manual. Both ways of tractor operation are typical for farmers activity in the Slovak Republic, depending on the tractor type and style of agricultural production at most. The second part of this paper is aimed at the proposal of by-pass filtration system to eliminate the oil contamination. The by-pass filtration system is the second stage of the oil filtration in the tractor, whereas the first one means standard tractor filter. Function of the system was tested according to the decrease of chemical elements concentration characterising the oil contamination and visual method based on filter and its change after operating of tested tractor. There was evaluated the decrease of concentration of Fe (41.6%), Cu (28.7%) and Si (20.5%) after by-pass filtration system was running under operational conditions. It can be concluded that the by-pass filtration system was proposed correctly and it is suitable for tractors operation.
Determining the influence of factors on retroreflective properties of traffic signs
(2019) Khrapova, M.
One of the distinguishing features of future autonomous cars is the ability to take into account and communicate with traffic infrastructure. Thereby detection and recognition of vertical traffic signing is an obvious requirement. Automatic recognition of traffic signs allows to check driver’s reaction time, if it is necessary to react, and in that way to contribute to and increase the road safety. It is especially important in the darkness when the retroreflective sheeting materials on the traffic signs help to increase visibility. Unfortunately, environmental conditions around the traffic signs exert considerable influence on the sign’s surface and alter their retroreflective properties. Many scientists explored different impacts on retroreflective properties of signs. Some impacts attracted more attention (such as detection distances and deterioration with age), some impacts were studied by several scientists only (such as dew and frost) and some factors were even omitted at all (e.g. the temperature during measurements of inservice signs). The paper is focused on the impact analysis of insufficiently explored factors influencing retroreflective properties of traffic sings. The findings of this research can support the development of further experimental research and could become a basis of reliable traffic signs usage on modern and smart roads.
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.
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.
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.
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.
Hydrogen production using waste aluminium dross: from industrial waste to next-generation fuel
(2019) Singh, K.K.; Meshram, A.; Gautam, D.; Jain, A.
This article describes the production of hydrogen from white aluminium dross, an industrial waste generated in the aluminium smelter plants. Hydrogen is generated by metal-water reaction between aluminium and water in presence of alkalis like sodium hydroxide and potassium hydroxide. Aluminium dross is described as a heterogeneous material with its major constituents being metallic aluminium, alumina and other salt fluxes like NaCl and KCl. Utilizing the metallic aluminium content entrapped in the matrix of alumina for the metal-water reaction has been the driving force for the waste recycling and simultaneous hydrogen production. Bulk aluminium dross was crushed and downsized. The finer fraction of the powdered aluminium dross is used for the experiments. The effects of dross in the alkaline solution, temperature of the solution and the time of the reaction were studied to understand the generation of hydrogen. The alkaline solution breaks the protective layer of alumina and exposes the entrapped aluminium content to water, thereby commencing the hydrogen liberation.
Hygrothermal analysis of masonry wall with wool glass interior insulation
(2019) Leiten, Kadri; Kirotar, Priit; Kiviste, Mihkel; Estonian University of Life and Science. Institute of Forestry and Rural Engineering
When the external appearance of the building is fixed due to heritage requirements the interior thermal insulation is the only possible solution for thermal upgrade of the building envelope. Applying internal insulation to existing buildings is known to pose a challenge in relation to hygrothermal risks, as this can lead to high relative humidity levels, condensation and ultimately, mould growth and decay. The case study building is under historical preservation and therefore this is not allowed to be insulated from outside. The paper describes the hygrothermal assessment of applying internal glass wool insulation and vapour barrier in masonry wall with air gap. In addition to the calculations the condition investigation was also performed. Data loggers measuring temperature and RH were applied during the period of 31.01.2013–16.02.2013. The conclusions were based to theoretical calculations (case study and DIN 4108-3) and practical measurement results based on the data logger values obtained. The calculations showed that glass wool and vapour barrier insulated system were in risk on condensation but the condensed water dries out during summer time. Due to the fact that logger measurements were recorded during the time when inside plastering was still in progress the relative humidity in the room was very high. As a result of calculations it is possible to build this type of wall effectively, but in this case it was not the most reliable way because of ongoing interior fitting.
Improving the quality of critical tractor parts through the dynamic stabilisation of the manufacturing process in regard to CNC machines
(2019) Olt, Jüri; Maksarov, V.; Efimov, A.; Estonian University of Life Sciences. Chair of Biosystems Engineering
This article focuses on the evaluation of a rod improvement which is considered in detail below. The rod in question is part of an hydraulic cylinder manufacturing process which takes place on CNC machines. The need for ensuring a process improvement in this area arose because the rod often breaks down under operational conditions. It was found that the cause of this is a finishing operation in the existing production process. The effect of charging which occurred during the grinding process brings about the embedding of abrasive particles into the workpiece surface layer. Therefore, at the running-in stage, the mating surfaces on the rod and the system being used to seal the rings both experience intense wear in their contact areas, with this being caused by abrasive microparticles which serves to reduce the performance characteristics of the part in question. However, even if we dispense with the grinding process, ensuring the necessary roughness of Ra = 0.63 μm at the machining stage alone will present problems of their own for a number of reasons. First and foremost is the connection with the phenomenon that results in an autooscillation processes which is generated by the manufacturing system, as well as the formation of flow chips during machining on CNC machines. In this regard, in order to avoid any negative factors creeping into the process, we propose that a new approach be taken in achieving the necessary surface roughness, one which is based on the suppression of the auto-oscillation process during machining by means of creating a selective metastable structure. At the machining stage, any inhomogeneous structure in the local chip formation area will be destroyed, thereby suppressing the auto-oscillation process and reducing the surface roughness. Eventually, the proposed method will allows the grinding operation to be dispensed with entirely from the manufacturing process.
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.
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.
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.

Sirvi

Sirvi 2019, Vol. 17, Special Issue 1 Pealkiri järgi

Tulemused lehekülje kohta

Sorteerimisvalikud