2018, Vol. 16, Special Issue 1

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/5379

Sirvi

Nüüd näidatakse 1 - 20 38

An assessment of stratification of exhaust gases from gasoline and diesel engine
(2018) Birkavs, A.; Smigins, R.
Research the aim of which was to find out stratification of main exhaust components outside the tailpipe of the vehicle was realized in Alternative Fuels Research Laboratory of Latvia University of Agriculture using two commercially produced testing vehicl es (diesel and gasoline) and exhaust gas analytical system AVL SESAM FTIR. Additionally there was created a gas testing camera allowing to measure concentration of exhaust gas components in different heights and windless conditions. Regulated and unregulat ed emissions from gasoline and diesel engines were measured and discussed. Results obtained during the measurements showed main stratification of toxic components from both engine types from 0.6 to 1.1 m from the ground making a risk to get some health pr oblems by inhalation, especially for children. Main components (NOx, CO, HC) of exhaust gases of gasoline engines stay in the air for about 15 minutes in height of 1.0 m from the ground level, while methane and acetylene stay in the air for a 15 minutes in height of 0.6 m from the ground level.
Battery capacity drop during operation
(2018) Papezova, S.; Papez, V.
A lithium - iron - phosphate ( LiFePO 4 ) battery is nowadays considered one of the best types of batteries. The paper deals with the evaluation of the drop in their capacity during operation. Based on the physical analysis of charging an d discharging processes, a mathematical model of the battery capacity has been developed during its lifetime. The decrease in capacity during battery operation is evaluated according to the loss of active material, which gradually diminishes due to a numbe r of different processes. The analysis of the loss of the active material is carried out, in particular, according to the depth of discharge, battery temperature, charging and discharging time, including the time when the battery is out of service. The tes ts were performed on the Winston Battery, Calb, Thunder Sky and Sinopoly batteries by cyclic discharging and charging at the 50%, 90% or 100% depth of discharge. Their real parameters were determined, compared to the model parameters and the parameters specified by the manufacturers and suppliers. Two automated systems were used for testing. During the test, in the tested battery with several cells, charging and discharging by a constant current were carried out automatically. Operating parameters of the te sted battery were continuously scanned, recorded and evaluated by the control computer. The capacity curves during the battery operation, determined by the type of models, were compared with the results of long - term real battery tests.
Capacitive frost depth indicator
(2018) Papez, V.; Papezova, S.
The depth of soil freezing , i.e., the depth at which water is frozen, is a significant factor in meteorology, as it affects many processes in agriculture, building, etc. Soil frost penetration is an important factor for overwintering organisms, but also for physical and chemical processes in soil, particularly for its mechanical properties. The de pth of freezing is normally determined directly, i.e. mechanically, using a special soil freezing meter, i.e., frost - depth indicator, according to the process of water freezing in the probe. Another method lies in determining the soil temperature by the in terpolation of the curves from the graph, as measured by soil thermometers according to the change in the resistivity of soil or water, when frozen. The principle of the frost - depth indicator function is to evaluate the temperature dependence of water perm ittivity, which decreases, when water is frozen, from ε r ~ 87 at 1 °C to ε r ~ 3.2 at - 1 °C , typical for ice. The water permittivity is evaluated by a measuring capacitor, which is adapted into the shape of the frost depth indicator probe, whose dielectric is deionized water. During freezing, the capacity is reduced in this area. The capacity of the partially frozen probe is directly proportional to the length of its non - frozen section. The measuring capacitor is a part of the resonant circuit of the oscilla tor. The frequency of the oscillator varies with the capacity of the probe and is further evaluated. The achievable measurement accuracy is approximately 2% for the probe of a 1m length and in direct evaluation by an autonomous counter. For the computer ev aluation, with the possibility to compensate the probe non - linearity, the measurement accuracy is approximately 0.5%.
Combustion property analyses with variable liquid marine fuels in combustion research unit
(2018) Hissa, M.; Niemi, S.; Sirviö, K.
The quality of ignition and co mbustion of four marine and power plant fuels were studied in a Combustion Research Unit, CRU. The fuels were low - sulphur Light Fuel Oil (LFO, baseline), Marine Gas Oil (MGO), kerosene and renewable wood - based naphtha. To meet climate change requirements a nd sustainability goals, combustion systems needs to be able to operate with a variety of renewable and ‘net - zero - carbon’ fuels. Due to the variations in the chemical and physical properties of the fuels, they generally cannot simply be dropped into existi ng systems. The aim of this research project was to understand how changes in fuel composition affect engine operation. The focus was on how various properties of the fuels impact on the combustion process – especially ignition delay and in - cylinder combus tion. The goal of the research project was to allow broad fuel flexibility without any or only minor changes to engine hardware. Before the engine tests, the CRU forms an easy and cost - effective device to find out the engine suitability of the fuel . The re sults showed that the ignition delay decreased expectedly with all fuels when the in - cylinder pressure and temperature increased. The differences in the maximum heat release rates between fuels decreased in high - pressure conditions. MGO had the shortest ig nition delay under both pressure and temperature conditions. Based on the CRU results MGO and kerosene are suitable to use in compression - ignited engines like the reference fuel LFO. In contrast renewable naphtha had a long ignition delay. If naphtha is us ed in a CI engine, the engine must be started and stopped with, e.g. LFO or MGO.
A comparative case study of the efficiency of collection systems for paper and biodegradable municipal solid waste
(2018) Chotovinský, O.; Altmann, V.
The need to increase municipal solid waste recycling rates has led to the study and analysis of recycling schemes from the perspective of the technical issues that may be involved. This paper compares two waste collection systems, which are operating in th e Vysočina region of the Czech Republic: a municipal solid waste collection system for paper (including cardboard) and a biodegradable municipal solid waste collection system. Both collection systems were introduced at different times to cover one selected urban area. The emphasis has been placed on an evaluation of the development of individual, separate collections between 2014 and 2016. Analysis of the technological operation and performance of the collections are observed and evaluated by measuring a ra nge of waste collection system indicators. Efficiency levels, especially when it comes to separate collections of both types of municipal solid waste, are compared to their relative representation in the remaining bulk of municipal solid waste. The changes in representation of these types of waste against those in the rest of the municipal solid waste shows which collection systems are more successful from the perspective of the implementation of the directive which covers landfill usage. The results also d escribe why systems could be more successful within the view of well - chosen or inappropriately - selected technological parameters for materials separation. The possibly statistically significant impact of paper waste production in terms of the relative amou nt of paper waste across the rest of the municipal solid waste has also been shown.
Comparison of predicted and real parameters of PV systems in the Czech Republic and Spain
(2018) Olšan, T.; Soucase, B. M.; Libra, M.
This paper compares predicted performance by a simulation software for a given new constructed PV system of crystalline silicon technology located in Prague with 10 kWp peak power and a similar system in Spain. Simulation software used for the sake of this paper was publicly available PVGIS from the website of its creators, parameters were set to be the same like in the real PV system. The difference between the predicted and the real data was calculated and then discussed in the result section of this pape r. Suggestion how to increase the accuracy of the prediction by the simulation software is in the discussion part of this paper.
Conceptual ‘Cradle to Gate’ analysis of GHG emissions from wood, agricultural plant and synthetic fibres
(2018) Kazulis, V.; Muižniece, I.; Blumberga, D.
Industrialization and fossil resource use has brought unprecedented anthropogenic carbon dioxide emissions. Use of synthetic fibre materials and unsustainable plant cultivation practices contribute to greenhouse gas emissions. The global market share of po lyester fibre (synthetic fibre made from fossil resources) exceeded the share of cotton fibre (natural fibre) for the first time in 2000 and since then polyester has remained the most popular fibre. The demand for textiles keeps increasing. In Northern Eur ope locally made fibres from wood, hemp and flax could substitute fossil based fibres decreasing the global GHG emissions and helping local economies to prosper. Multi - criteria analysis method TOPSIS was used to carry out a conceptual research evaluating G HG emissions from wood, agricultural plant and synthetic fibre acquisition under two scenarios: fossil fuels are used as energy sources & industrial fertilizers are used; and renewable energy sources are used & industrial fertilizers are not used. Results show that wood and plant fibres have smaller GHG emissions than synthetic fibres in both scenarios. Factors affecting emission performance are analysed.
Crop weight measurement sensor for IoT based industrial greenhouse systems
(2018) Avotins, A.; Potapovs, A.; Apse-Apsitis, P.; Gruduls, J.
No wadays the industrial management systems are changing by means of implementing various Internet of Things (IoT) technologies, allowing a simple integration of sensor technologies with wireless communications and development of cloud based database solution s. The industrial greenhouse management systems are not the exception in this regard, as they are becoming more and more popular with the use of various sensors for the automation of the vegetable and other crop cultivation process.The general aim they hav e is to raise the level of process automation, quality, energy efficiency and other important parameters. The implemented technologies and environment of industrial greenhouse can be different fir the research type laboratories, as they are focused on prod uction, therefore this research is conducted in cooperation with tomato producing industrial greenhouse of SIA ‘ Latgales darzenu logistika ’ focusing on IoT based crop weight measurement.
Detection reliability for passive infrared detectors in intrusion and hold-up alarm systems and their ergonomics
(2018) Hart, J.; Hartová, V.
Currently it is highly important for detectors to be able to achieve efficiency, reliability, and faultless operation, and to be ergonomic thanks to their assembly and being easy-to-fit. In the case of a proposal for the placement of detectors it is naturally important to determine position of the detector and the type of detector being used, but also to guarantee their capability to be able to detect anything when in use and their user and installation-friendliness. The problem of passive infrared (PIR) detectors affects a large proportion of intrusion and hold-up alarm systems (I&HAS). In a time of increasing property crime, it is highly important for PIR detector to actually be able to detect break-in attempts within the guarded area on a reliable basis and free of error. In the case of the installation of PIR detectors, it is naturally important not only to ensure correct installation, to gauge the external influences which may impact upon the detector and to ensure proper maintenance, but also to guarantee the capability of detection under more arduous conditions. The tests and comparisons which have been conducted examine both the normal operation of the PIR detectors and the ergonomics of these detectors. These tests are important both from an informative perspective and due to the opportunities to be able to develop potential counter-measures which could lead to their improvement.
Determination of conversion relations for the use of small hydrodynamic pumps in reverse turbine operation
(2018) Polák, M.
In small - scale hydropower, hydrodynamic pumps used in reverse mode are an important economical alternative to conventional water turbines. E fficient utilisation of these devices however requires taking into account all the specifics of the reverse pump operation and optimise the pump design for maximum utilisation of the hydro - technical potential of the deployment site. The article compares ex isting conversion models, describes initial theoretical assumptions and determines new conversion relations for the design of pumps as turbines (PAT) for the lowest power and specific speed category. The validity of the conversion relations is experimental ly verified on a hydraulic test circuit with a radial centrifugal pump tested in both pump and turbine operation modes. The results of the verification of the new conversion relations proved better correspondence to reality within this category of machines than that reported by the previously used conversion models.
Development and testing results of IoT based air temperature and humidity measurement system for industrial greenhouse
(2018) Avotins, A.; Apse-Apsitis, P.; Bicāns, J.; Gruduls, J.
In dustrial greenhouse control systems are changing and getting new capabilities, due to the evolution of the Internet of Things (IoT) technologies, allowing wirelessly integrate various sensor technologies and create a cloud - based database and analytic solut ions. Greenhouse systems typically are controlled by consuming single temperature and humidity measurement unit data (treated as an average value), this raises a question about the precision of such approach for application in a large industrial greenhouse . In this article IoT based temperature and humidity measurement system uMOL architecture is described and first measurement results of multi - point data collection with high resolution compared to existing single - point measurements.
Diagnostics of hydraulic fluids used in aviation
(2018) Obergruber, M.; Hönig, V.; Procházka, P.; Táborský, J.
Diagnostics is a maintenance industry that monitors performance, parameters, and follow – up. Diagnosing hydraulic fluids means comparing the parameters of the used hydr aulic fluid sample to the parameters of the clean fluid. It is also essentia l to monitor the limit values either by the aircraft manufacturer or by the manufacturer of the hydraulic fluid. This means that the manufacturer recommends the limitations of the liquid parameters. The measurements of the fluid samples give an overview of the liquid quality. Most businesses focus on so – called proactive maintenance. The main senses and objectives of proactive maintenance are: lubricant sample analysis, lubricant sta tus, machine status, next step recommendation, database saving and trend analysis. This article focuses on the quality of hydraulic fluid focused in aviation. The aim of the article was to determine the properties of the hydraulic fluid used in the A320 ai rcraft family, determine the interval of its exchange. Monitoring the state of the hydraulic fluid could contribute to the timely detection of the problem, thus avoiding a failure of the device or the system as a whole. The tracking proposal is an integral part of this article.
Effect of rubber powder from waste tyre rubbers on mechanical properties of one-component polyurethane putty
(2018) Tichý, M.; Müller, M.; Valášek, P.; Miturska, I.
The utilization of adhesives in technical practice is varied. Adhesives serve for a creation of strength bonds on the one hand, and on the other hand e.g. for cementing. The aim of the research is a modification of one - component polyurethane putty RPS 45 used in automotive industry to increase strength properties in an adhesive bond. An i nteraction between a filler in the form of rubber powder micro - particles and one - component polyurethane adhesive was investigated by means of SEM analysis. Sealing is a primary property of this putty. Sealing putties usually reach very small strength which can be increased by an admixture of the filler. In order to keep elastic properties, micro - particles of the rubber powder gained from tyre recycling process were used as the filler. An aspect of a loading speed of the adhesive bond is essential at the pra ctical application at which the adhesive bond can be failed in adhesive or cohesive layers. The adhesive bond can be perceived in terms of its function as a complex of three layers, i.e. an adhesive bonded material, the interaction between the adhesive and the adhesive bonded material and the adhesive layer itself. There are often states in the practices when the adhesive bonds are exposed to the loading which can be either a static or a dynamic one. That is why the research is focused not only on the evalu ation of the influence of the modification of the one - component polyurethane adhesive, but also on the influence of the loading speed of the adhesive bond. Tested speeds set on a universal testing machine Zwick/Roell Z150 were 2, 50 and 100 mm min - 1 . The r esults of mechanical tests proved a positive influence of the filler on the strength σ m higher by 42.68 ± 6.96% and the elongation at break ε b higher by 12.2 ± 20.95%. On the contrary, the stress at yield σ y was decreased.
Effect of sunflower and rapeseed oil on production of solid particles and performance of diesel engine
(2018) Čedík, J.; Pexa, M.; Holůbek, M.; Mader, D.; Pražan, R.
The development of biofuels for compression ignition engines is heading primarily to utilization of vegetable oils. Combusting of 100% vegetable oil in unmodified CI engine is usually not possible due to higher viscosity of the vegetable oil. In order to use 100% vegetable oil in CI engine the oil needs to be preheated, esterified or hydrotreated. Alternatively, in orde r to use raw vegetable oil in CI engine without preheating it is possible to use vegetable oil – diesel fuel blends or vegetable oil – butanol – diesel fuel blends in order to lower the viscosity of the fuel. The contribution focuses on comparison of the e ffect of sunflower and rapeseed vegetable oils on operational parameters of the turbocharged compression ignition engine, especially on production of solid particles. The measurement was carried out according to standardized NRSC test cycle. 5% and 20% con centration of vegetable oils in diesel fuel were used as a test fuels for the measurement while the diesel fuel was used as a reference. The count and size of solid particles were measured by means of EEPS particle analyser. Based on the measured values it can be stated that the slight increase of performance parameters occurred with strong effect on emissions production, especially on production of solid particles.
Evaluation of reed biomass use for manufacturing products, taking into account environmental protection requirements
(2018) Muizniece, I.; Kazulis, V.; Zihare, L.; Lupkina, L.; Ivanovs, K.; Blumberga, D.
In many countries reed is considered as invasive or unnecessary plant, because it is spreading rapidly, causing decrease in biodiversity and creating unacceptable living conditio ns for many bird species in their natural habitats. Due to environmental considerations it is necessary to cut reed, to decrease their over exceeding growth. Reed burning or leaving for decomposition on fields, that has been practiced until now, creates ad ditional carbon dioxide air pollution. Therefore, the question on what to do with cut reed has become vital from environmental protection perspective. In addition, this question applies to bioeconomy principles in compliance with their use in national econ omy, which makes it clear, that solutions for the use of reed biomass for production have to be found. But any production process can leave a negative effect on surrounding environment. Further to product production, economic motivation, possible market an d availability of resources are primarily essential to see whether it is worth to produce the product at all. Therefore, reed biomass use possibilities in production have to be analysed as a complex question, taking into account environmental and climate, economic and technological aspects. In this study, solutions to perspective reed biomass use are evaluated, considering environmental protection requirements. For this task, multi - criteria analysis method TOPSIS is used, which includes 11 environmental and climate, economic and technological criteria. Evaluation includes both – already existing and new products that are divided in 3 sectors: power industry, construction and other products. Results of the research clearly state, which of reed biomass made pr oducts are perspective, taking into account not only traditional economic and technological aspects, but also envi ronmental and climate aspects.
Exhaust particle size distributions of a non-road diesel engine in an endurance test
(2018) Ovaska, T.; Niemi, S.; Katila, T.; Nilsson, O.
The main objective of this study was to find out how th e non - road diesel engine running period of 500 hours affects the exhaust particle size distribution. By means of an engine exhaust particle sizer (EEPS), particle number was measured before the endurance test and after 250 and 500 hours of engine operation . The size distributions were determined at full and 75% loads both at rated and at intermediate speeds. The soot, gaseous emissions and the basic engine performance were also determined and lubricating oil was analysed a few times during the running perio d. A blend of low - sulphur fossil diesel and soybean methyl ester (B20) was used as fuel in the 4 - cylinder, turbocharged, intercooled engine which was equipped with a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) system. All em issions were measured downstream the catalysts. During the 500 hours of operation, the particle number increased considerably within an approximate size range of 7 to 30 nm . Between the initial and final measurements, no notable differences were observed i n the particle number emissions within a particle size range of 50 to 200 nm . The copper content of lubricating oil also increased significantly during the 500 hours’ experiment. One possible reason for the substantial increase in the nucleation mode parti cle number was assumed to be copper, which is one of the metallic elements originating from engine wear. The engine efficiency was almost equal, and the differences both in smoke and hydrocarbon emission were negligible throughout the 500 hours’ experiment.
Experimental research on compatibility of mineral and biobased hydraulic oils
(2018) Birkavs, A.; Smigins, R.
The use of biobased hydraulic oils becomes more popular in the different industries, but especially in agriculture machinery. This is stimulated by the fact that significant amount of hydraulic oils effluence in the environment and therefore leaves a negative impact to the e cosystem. Besides of that, the part of sold hydraulic oils grows and now forms approximately 15% of total oil consumption amounts worldwide (Nagendramma & Kaul, 2012) . The aim of this research was to study the compatibility of the comercially produced mine ral and biobased hydraulic oils, identify viscosity of a different mixtures in the entire work temperature range, as also changes of anti - frictional properties. Two different oils and three mixtures were tested. Special hydraulic experimental apparatus was established for visual observation of fluid properties. Sliding friction bench was used for the comparision of friction properties. The results showed that change of the working pressure and temperature of the hydraulic oil in the various mixtures of mine ral and biological hydraulic oils do not change its original appearance. It was observed that the highest viscosity 71 mm 2 s - 1 and worst anti - friction properties is for the 50% mix of mineral and biologial hydraulic oil at 20 °C ambient temperature.
Extraction of oil from rapeseed using duo screw press
(2018) Mizera, Č.; Herák, D.; Hrabě, P.; Kabutey, A.
This study was focused on the analysis of optimize the pressing process of rapeseeds ( B rassica napus L.) using screw press. For pressing of oil a screw press Farmer 20 – duo (Farmer 20, Farmet a.s., Ceska Skalice, Czech republic) was used. The screw rotation speed 10, 20, 30, 40, 55 and 65 rpm was used. Oil recovery efficiency and specific mechanical energy were decreased when the seed material troughput was increased. It has been found that the optimal operation point for screw press Farmer 20 – duo was at 20 kg h - 1 rapeseed throughput. The specific mechanical energy at the optimal operation point was 0.61 kWh kg oil - 1 Maximum oil recovery efficiency 82.6% was found at the lowest screw speed.
Factors influencing use of fuelwood and its environmental impacts in Tapanuli Utara regency, North Sumatra
(2018) Roubík, H.; Mazancová, J.; Brunerová, A.; Herák, D.
Deforestation and forest degradation, after burning of fossil fuels, is considered as the second leading cause of anthropogenic greenhouse emissions (accounting for over 17% of global carbon dioxide emissions) and has become an important issue concerning climate change mitigation. The provision of wood energy is generally thought to be a major contributor to forest loss. In Indonesia, more than half of the rainforest there, the third - largest swath in the world, has been felled in just a few years. Further more, permission has been granted to convert the majority of what remains into palm or acacia plantations. The logging and burning of forests to clear land for cultivation has made Indonesia one of the largest emitters of greenhouse gases. Therefore, the o bjective of this study was to assess the current level and influencing factors of the use of fuelwood among the rural population as well as the consequent environmental impacts in the target area in North Sumatra. The questionnaire survey using randomly se lected households (n = 196) was administered in Tapanuli Utara regency from July to August 2014; followed by several field visits from August to September 2016. Obtained data were analysed with descriptive statistics and cross tabulation. The results indic ate that fuelwood is a significant source of energy in the target area. For 31% of respondents it is the major energy source and for 64% it is a supplementary source. The high rate of use of wood as fuel corresponds to the poor financial situation of respo ndents and the easy accessibility of wood, but only from the surrounding area (own garden or adjacent land). Wood resources are often very distant (on average over 1,000 metres) as a consequence of high deforestation. This study reveals that there is a non - sustainable trend of forest conversion resulting in high land degradation in Tapanuli Utara regency.
Flash points of gasoline from Kukersite oil shale : Prediction from vapor pressure
(2018) Rannaveski, Rivo; Listak, Madis
The flash point of liquid fuels, especially of light distillates such as gasoline or naphtha, is an important parameter for the handling of such materials. In this work, flash points and volatility characteristics (vapor pressure, boiling point) of a numbe r of shale gasoline samples with different volatilities were measured. The shale gasoline fractions were produced from Kukersite oil shale using solid heat carrier retorting technology. Several existing correlations for calculating flash points of hydrocar bons and petroleum fractions are evaluated, and the absolute average deviations were found to be between 1.1 to 20.9 °C . New, easy - to - use correlations are proposed for estimating flash points for oil shale based gasolines from volatility characteristic tha t are readily available. The correlation proposed in this work are based on the vapor pressure at 20 or 37.8 °C (100 °F ), Reid vapor pressure (37.8 °C ) or boiling point. The average absolute deviations for these correlations were 0.82 to 0.93 °C , meaning t hey are comparable to or better than existing methods developed for petroleum oils, which mostly use boiling point as the input parameter, when applied to gasoline from Kukersite oil shale.

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