Volume 15 (2017)
  Special Issue I

Journal full text: Vol 15 SP 1

Contents


Pages

941–951 O.L. Akangbe and D. Herak
Mechanical behaviour of selected bulk oilseeds under compression loading
Abstract |
Full text PDF (400 kB)

Mechanical behaviour of selected bulk oilseeds under compression loading

O.L. Akangbe and D. Herak*

Czech University of Life Sciences, Faculty of Engineering, Department of Mechanical Engineering, Kamycka 129, Praha 6 – Suchdol, CZ16521 Prague, Czech Republic
*Correspondence: herak@tf.czu.cz

Abstract:

Cold pressing or compressive mechanical expression of oil from bulk oilseeds without thermal treatments or appreciable thermal effects facilitates the preservation of quality in expressed oils and enhances their stability in storage. Mechanical response of bulk oilseeds during cold expression which are vital to equipment design vary with crops and are not completely understood. Mechanical behaviours of bulk seeds of camelina, pumpkin and sesame relevant to cold pressing were investigated at moisture contents of 7.04, 8.60 and 6.06% (d.b.), 80 mm pressing depth and a compressive force of 100 kN, applied uniformly at 10 mm min-1. Deformation varied with incremental force and among crops at peak compression. Deformations in Camelina, Sesame and Pumpkin seeds were 40.2, 41.6 and 50.9 mm at peak compression. Oil point pressures of Sesame, Camelina and Pumpkin seeds were 3.83, 7.49 and 8.83 MPa, respectively. Oil recovery at the applied load was similar in Camelina and Sesame but significantly lower in pumpkin seeds. Volume energy requirement for the expression of oil from camelina, pumpkin and sesame seeds were 2.56, 1.72 and 1.46 MJ m-3, respectively. An assessment of the pressed cake after oil expression revealed that the materials were capable of further deformation under compression.

Key words:

, , , ,




952–963 D. Berjoza and I. Jurgena
Effects of change in the weight of electric vehicles on their performance characteristics
Abstract |
Full text PDF (378 kB)

Effects of change in the weight of electric vehicles on their performance characteristics

D. Berjoza¹* and I. Jurgena²*

¹Latvia University of Agriculture, Technical Faculty, Institute of Motor Vehicles, 5 J. Cakstes boulevard, LV-3001 Jelgava, Latvia
²Latvia University of Agriculture, Faculty of Economics and Social Development, Institute of Business and Management Science, 18 Svetes str., LV-3001 Jelgava, Latvia
*Correspondence: dainis.berjoza@llu.lv; inara.jurgena@llu.lv

Abstract:

One of the parameters of electric vehicles that can affect their dynamic and range characteristics is their weight. Converting a vehicle with an internal combustion engine into an electric one, it is possible to vary its batteries and their placement. It is also possible to choose batteries of various capacities for serial electric vehicles, for example, Tesla Model S. Not only the costs of electric vehicles but also such performance characteristics as dynamics and travel range per charge depend on the number of batteries and the total weight of the electric vehicles. The research developed and approbated an algorithm for calculating comparative parameters for electric automobiles. The algorithm was approbated on 30 electric automobiles of various makes. Energy consumption per km distance travelled shows the exploitation cost of an electric automobile. According to this indicator, the most economical electric automobiles were as follows: Renault Twizy (67.8 Wh km-1), Tazzari Zero (87.9 Wh km-1) un Renault Zoe ZE22 (93.6 Wh km-1).

Key words:

, , , , ,




964–970 G. Birzietis,, V. Pirs, I. Dukulis and M. Gailis,
Effect of commercial diesel fuel and hydrotreated vegetable oil blend on automobile performance
Abstract |
Full text PDF (383 kB)

Effect of commercial diesel fuel and hydrotreated vegetable oil blend on automobile performance

G. Birzietis¹,*, V. Pirs¹, I. Dukulis¹ and M. Gailis¹,²

¹ Latvia University of Agriculture, Faculty of Engineering, Motor Vehicle institute, 5 J. Cakstes boulv., LV-3001 Jelgava, Latvia
² Riga Technical University, Faculty of Mechanical Engineering, Transport and Aeronautics, Department of Automotive Engineering, Viskalu 36, LV-1006 Riga, Latvia
*Correspondence: gints.birzietis@llu.lv

Abstract:

The new fuel ‘Pro Diesel’ that contains hydrotreated vegetable oil (HVO) was recently introduced in Baltic market. It raised some interest on performance of the new fuel among fleet and individual consumers. The authors evaluated and compared performance of modern M1 class automobile, using regular fossil diesel fuel and Pro Diesel fuel.
Torque, power and fuel consumption of the vehicle have been evaluated on chassis dynamometer, in steady state and driving cycle mode.
Depending on test conditions, engine power and torque was increased up to 2%, and fuel consumption reduced up to 3.9%, when diesel fuel/ HVO blend was used.

Key words:

, , , , , ,




971–980 R. Chotěborský,, M. Linda and M. Hromasová
Wear and stress analysis of chisel
Abstract |
Full text PDF (720 kB)

Wear and stress analysis of chisel

R. Chotěborský¹,*, M. Linda² and M. Hromasová²

¹ Czech University of Life Sciences, Faculty of Engineering, Department of Material Science and Manufacturing, Kamycka 129, CZ165 21 Prague, Czech Republic
² Czech University of Life Sciences, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamycka 129, CZ165 21 Prague, Czech Republic
*Correspondence: choteborsky@tf.czu.cz

Abstract:

The object of research is stress analysis of worn chisel. The interaction between soil particles and chisel leads to change of shape and dimension of a worn chisel or other agriculture tools. The wear rate depends on the velocity of the chisel in the soil, position in the soil and shape of a chisel. These factors change the dimension and shape of chisel during its service life. The modern chisel includes sintered carbides on a tip. Sintered carbides plates are effective protection for wear resistance. But the body of the chisel is not protected and its wear resistance is lower than the tip. The service life of the tip is much higher than the body of the chisel. Stresses of the body of the chisel are stationary during the service life. The aim of this study is determining of optimising process of the strength of steel for chisels.

Key words:

, , ,




981–998 M. Gailis, and V. Pirs
Experimental analysis of combustion process in SI Engine using ethanol and ethanol-gasoline blend
Abstract |

Experimental analysis of combustion process in SI Engine using ethanol and ethanol-gasoline blend

M. Gailis¹,²* and V. Pirs²

¹ Riga Technical University, Faculty of Mechanical Engineering, Transport and Aeronautics, Department of Automotive Engineering, Viskalu 36A, LV 1006 Riga, Latvia
² Latvia University of Agriculture, Faculty of Engineering, Motor Vehicle Institute, Liela street 2, LV 3001 Jelgava, Latvia
*Correspondence: maris.gailis@rtu.lv

Abstract:

Effect of fuel composition and ignition timing on combustion parameters of spark ignition (SI) port fuel injection (PFI) engine had been studied experimentally. The engine was fuelled with an ethanol and ethanol-gasoline blend E85. The engine was operated at steady speed at 1,500 min-1 and four load points have been used. Minimal ignition timing advance for maximal brake torque (MBT) at stoichiometric air/ fuel ratio for the tested fuels were found. The fuels were tested at their respective MBT timing and gasoline MBT timing. MBT timing was retarded by 8–11% for ethanol and 5–10% for E85 fuel, comparing to gasoline MBT timing. Indicated mean effective pressure (IMEP) was not affected by ignition timing in tested conditions. Maximal cylinder pressure was increased and flame development phase was extended, when gasoline MBT was used with fuels with high ethanol content at tested conditions.

Key words:

, , , , , , , ,




999–1005 V. Hartová, and J. Hart
Comparison of reliability of false rejection rate by monocriterial and multi-criteria of biometric identification systems
Abstract |
Full text PDF (305 kB)

Comparison of reliability of false rejection rate by monocriterial and multi-criteria of biometric identification systems

V. Hartová¹,* and J. Hart²

¹ Czech University of Life Sciences Prague (CULS), Faculty of Engineering, Department of Vehicles and Ground Transport, Kamýcká 129, CZ165 21 Prague, Czech Republic
² Czech University of Life Sciences Prague (CULS), Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague,
Czech Republic
*Correspondence: nverca@seznam.cz

Abstract:

Biometric user identification is a highly topical theme these days. The most widespread areas are identification of a person on the basis of fingerprints and identification on the basis of facial features. Testing was performed on the 4 biometric systems. Systems using fingerprint were LA 2000M and iEvo ULTIMATE, and systems disposing even the scan faces were D-Station, IFace 800. Measurements showed that the higher reliability have biometric identification systems which identify the person on the basis of one parameter. From the results it is also seen that sabotage of biometric identification devices that identifies on the the basis of two or more parameters is much simpler than those that identify only using fingerprint or scan of face.

Key words:

, , ,




1006–1013 P. Hrabě,, D. Herak and Č. Mizera
Utilization of the elementary mathematical model for description of mechanical behaviour of composites reinforced by Ensete Ventricosium fibres
Abstract |
Full text PDF (348 kB)

Utilization of the elementary mathematical model for description of mechanical behaviour of composites reinforced by Ensete Ventricosium fibres

P. Hrabě¹,*, D. Herak² and Č. Mizera²

¹ Czech University of Life Sciences, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ165 21 Prague, Czech Republic
² Czech University of Life Sciences, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: hrabe@tf.czu.cz

Abstract:

This article is focused on the utilization of elementary mathematical model for description of mechanical behaviour of composites materials reinforced by fibres of Ensete Ventricosium under tension loading. Elementary mathematical model was derived for unidirectional fibres oriented in the direction of tension loading and it was experimentally verified. As a matrix it was used a two-component resin Gluepox Rapid and as a reinforcement they were used fibres of Ensete Ventricosum. Experimental samples with different volume fibres ratio contained 40, 60, 80, 100, 120 and 140 fibres were tested on tensile equipment MP Test – 5.050. In this study the elementary mathematical model was utilized for description of dependency between modulus of elasticity, rupture stress and volume fibres ratio. From this research follows that data determined from derived elementary mathematical model are significant (on the level of significance 0.05) with experimentally determined data. This derived elementary mathematical model can be used as background for further research related to the modelling of mechanical behaviour of composites reinforced by fibres.

Key words:

, ,




1014–1023 M. Hromasová, P. Kic, M. Müller and M. Linda
Evaluation of quality and efficiency of ventilation equipment by scanning electron microscopy
Abstract |
Full text PDF (642 kB)

Evaluation of quality and efficiency of ventilation equipment by scanning electron microscopy

M. Hromasová¹*, P. Kic², M. Müller³ and M. Linda¹

¹Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamýcká 129, CZ165 21 Prague, Czech Republic
²Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague, Czech Republic
³Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: hromasova@tf.czu.cz

Abstract:

The aim of this research is an evaluation of the quality and function of ventilation equipment in basement rooms. There was analysed the function of ventilation system in relation to the quality of outdoor and indoor environment. The concentration of air dust was measured by exact instrument DustTRAK II Model 8530 aerosol monitor inside and outside the building. Using the special impactors the PM1, PM2.5, PM4, PM10 size fractions were also measured. Particles separated from the ventilation equipment were examined with SEM (scanning electron microscopy) using a microscope TESCAN MIRA 3 GMX. Obtained results of measurements were evaluated by statistical instruments and concentrations of different size of dust particles were analysed. The size of particles outlet the ventilation equipment was ca. of 55% lower than the size of the particles inlet the ventilation equipment. The difference in tested sizes of the dust particles in the ventilation equipment and outlet the ventilation equipment, i.e. in the place of cleaned air inlet into the basement room, was statistically proved. The diversity of impurities caught by the ventilation equipment and impurities moving in the air in the tested room is obvious from the results of SEM analysis.

Key words:

, , ,




1024–1032 P. Jirsa and J. Malaťák
Dry sorption stabilization of flue gases in biological waste incinerating facility with heating power under 5 MW
Abstract |
Full text PDF (350 kB)

Dry sorption stabilization of flue gases in biological waste incinerating facility with heating power under 5 MW

P. Jirsa* and J. Malaťák

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Praha-Suchdol, Czech Republic
*Correspondence: pjirsa@tf.czu.cz, jirsa.petr@gmail.com

Abstract:

Biological and medical waste is always classified as hazardous material such as it must be treated according to its hazardous characteristics. One of the best methods for disposal seems to be a thermal degradation. This research examines the effect of finely crushed sorbent Ca(OH)2 and NaHCO3 to eliminate these hazardous substances in a small incinerating facility with heating power under 5 MW. The experiment took place in an existing incinerating plant with capacity 250 kg h-1. Sorbents were injected into a flue gas flow at two different places. It was observed that the temperature of flue gas and the residence time significantly influence the sorbent refining effect that is caused by quantity of collision in flue gas stream. Sorbents were dosed into a system with a theoretical consumption excess to serve sufficient refining effect. At dosing rate of 7 kg h-1 Ca(OH)2 the concentration of SO2 decreased by 34.5% and HCl by 59.0% referring to the initial concentration. At dosing rate of 5 kg h-1 NaHCO3 the concentration of SO2 decreased by 32% and HCl by 44.8% referring to an initial concentration. Tested sorbents react with acidic compounds with different efficiency and preferably react with different acid compounds.

Key words:

, , , ,




1033–1040 A. Kešner,, R. Chotěborský and M. Linda
Determining the specific heat capacity and thermal conductivity for adjusting boundary conditions of FEM model
Abstract |
Full text PDF (478 kB)

Determining the specific heat capacity and thermal conductivity for adjusting boundary conditions of FEM model

A. Kešner¹,*, R. Chotěborský¹ and M. Linda²

¹ Department of Material Science and Manufacturing Technology Faculty of
Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ165 21 Prague – Suchdol, Czech Republic
² Department of Electrical Engineering and Automation, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ165 21 Prague – Suchdol, Czech Republic
*Correspondence: kesner@tf.czu.cz

Abstract:

One of modern way of the heat treatment process of agricultural tools such as chisels or tines is FEM modelling. FEM models needs the accurate boundary conditions for successful solution. Specific heat capacity and thermal conductivity are important parameters for the design of the physical properties of heat treatment. These parameters are used for the formation of the temperature field during the cooling process at the heat treatment. More accurate parameters allow you to better estimate the final microstructure in the entire cross-section of the material. Specific heat capacity and thermal conductivity are known from material sheets, but they are stated as constant values. This is the reason why this work is focused on the determination of specific heat capacity and thermal conductivity of steel during the quenching. For the experiment in this work was chosen material 25CrMo4. The values of specific heat capacity and thermal conductivity were determined by comparing the experimentally measured cooling curves and cooling curves generated by the mathematical model. The dependences of specific heat capacity and thermal conductivity were compared in temperature, so that the relationships of cooling curves were statistically significant under alfa level 0.05.

Key words:

, , ,




1041–1049 M. Kotek, P. Jindra, P. Prikner and J. Mařík
Comparison of PM production in gasoline and diesel engine exhaust gases
Abstract |
Full text PDF (620 kB)

Comparison of PM production in gasoline and diesel engine exhaust gases

M. Kotek*, P. Jindra, P. Prikner and J. Mařík

Czech University of Life Science Prague, Faculty of Engineering, Department of Vehicles and Ground Transport, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: kotekm@oikt.czu.cz

Abstract:

The article is focused on different kind of combustion engines and their particulate matter production. The first part of experiments dealt with particulate matter production under defined driving cycle and operating regimes. The second part of experiments was carried out to measure the maximal PM production under engine’s full load regime. The experimental vehicle engines were manufactured by Skoda Auto a.s., equipped with modern fuel injection systems. Two representatives of diesel engines were chosen: the engine EURO-4 1.4 TDI with PD (Unit injector) injection system and the EURO-6 1.6 TDI with common rail injection system and DPF. As two representatives of gasoline EURO-4 engines were chosen: 1.2 MPI with non-direct fuel injection system and 2.0 FSI with direct stratified fuel injection system. The analysis of the particulate matters was carried out on a TSI Engine Exhaust Particle Sizer 3090 that is able to classify particles from 5.6 nm to 560 nm. In the case of diesel engines the results proved expectable decrease in PM production due to usage of diesel particulate filter (DPF). The older engine without DPF produced more than hundred times higher PM production under all operating regimes of driving cycle. The result of gasoline engines confirmed increased PM production of direct injection systems especially under higher engine load. FSI engine in driving cycle reached up twenty times higher PM production than MPI engine.

Key words:

, , , , , , , ,




1050–1056 V. Křepčík, J. Lev and F. Kumhála
Development and testing of apparatus for wooden chips voids measurement
Abstract |
Full text PDF (333 kB)

Development and testing of apparatus for wooden chips voids measurement

V. Křepčík¹*, J. Lev² and F. Kumhála¹

¹ Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
² Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Physics, Kamýcká 129, CZ165 00 Praha 6 - Suchdol, Czech Republic
*Correspondence: krepcik@tf.czu.cz

Abstract:

The interparticle porosity of wooden chips (commonly called voids) is a very important factor which significantly affects properties of wooden chips, i.e. bulk density, combustion speed or dielectric properties. Dielectric properties can be used for the measurement of its moisture content and it is the moisture content which is one of the most important factors that affect wooden chips calorific value. This paper is focusing on the development of measuring apparatus for wooden chips voids measurement. The principle of measuring apparatus is based on a gas displacement method. Measuring apparatus is composed from two chambers; both with the same volume. One from chambers is comparative one and second is experimental one. The pressure operating range was from 1,000 to 1,500 Pa. Results showed nontrivial behaviour of wooden material with the change of moisture content which was probably caused by different structures of tested materials.

Key words:

, ,




1057–1066 A. Krofova, M. Müller and P. Kic
Influence of chemical cleaning of adhesive bonded surface on working environment and adhesive bond quality
Abstract |
Full text PDF (459 kB)

Influence of chemical cleaning of adhesive bonded surface on working environment and adhesive bond quality

A. Krofova¹*, M. Müller¹ and P. Kic²

¹Czech University of Life Sciences Prague, Faculty of Engineering, Department Material Science and Manufacturing Technology, Kamýcká 129, CZ165 21, Czech Republic
²Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21, Czech Republic
*Correspondence: krofovaa@tf.czu.cz

Abstract:

Undesirable chemical substances are released into the environment at single manufacturing operations, namely at a chemical treatment /cleaning of an adhesive bonded surface. The chemical treatment /cleaning of namely metal adhesive bonded surface before an application of the adhesive represents a significant factor having an influence on a resultant adhesive bond strength, i.e. adhesive and cohesive strength.
Producers do not provide information about releasing harmful substances into the atmosphere, i.e. mass values of a flow of polluting substances used at the chemical cleaning of the adhesive bonded surface. These cleaning agents were experimentally investigated.
The aim was to evaluate an adhesive bond quality depending on the chemical treatment of the adhesive bonded surface and the intensity of the chemical agent release into the atmosphere. The adhesive bond quality was evaluated by means of mechanical tests and SEM analysis.
The increase of the adhesive bond strength does not conclusively occur when using the chemical treatment of the adhesive bonded surface compared to the adhesive bonds with only mechanical treatment of the adhesive bonded surface, except for the chemical cleaning in the acetone bath. This treatment proved always in a positive way.

Key words:

, , ,




1067–1071 V. Lapkovskis, V. Mironovs, I. Jevmenov, A. Kasperovich and V. Myadelets
Multilayer material for electromagnetic field shielding and EMI pollution prevention
Abstract |
Full text PDF (348 kB)

Multilayer material for electromagnetic field shielding and EMI pollution prevention

V. Lapkovskis¹*, V. Mironovs¹, I. Jevmenov², A. Kasperovich³ and V. Myadelets³

¹ Riga Technical University, Scientific Laboratory of Powder Materials, Kipsalas str. 6B-331, LV-1048 Riga, Latvia
² Rubber Products Llc, Jurkalnes str. 15/25, LV-1046 Riga, Latvia
³ Belarussian State Technological University, Department of Technology of petrochemical Synthesis and Polymer Materials Processing, Sverdlova str. 13a, BY220006 Minsk, Belarus
*Correspondence: lap911@latnet.lv

Abstract:

A significant growth of scientific activities related to electromagnetic fields interaction with equipment and living organisms have turned into an up-to-date research trend in recent decades. Power transmission lines, electric devices, and portable electronics have become a source of electromagnetic pollution. Therefore, a question of electromagnetic shielding is a substantial criterion for workplace safety. Current paper suggests a possible solution based on loose materials and rubber compounds for essential protection of people and equipment against electromagnetic influence.

Key words:

, , , ,




1072–1083 M. Linda, G. Künzel and M. Hromasová
A dynamic model of electric resistor’s warming and its verification by micro-thermocouples
Abstract |
Full text PDF (767 kB)

A dynamic model of electric resistor’s warming and its verification by micro-thermocouples

M. Linda, G. Künzel and M. Hromasová*

Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: hromasova@tf.czu.cz

Abstract:

The object of research is a resistor, a real electronic component, loaded by constant or impulse power. As a first approximation, resistor follows 1st order dynamic system, i.e. heating of the hottest spot on its surface is exponential to the power increase. The validity of this model is confirmed by measurements in a constant power loading regime. In an impulse power loading, it is only valid when the pulse duration approaches time constant of the resistor. The aim of this article is to show more credible model warming of the resistor, which is valid even for the case of pulse duration (ms) much shorter than the time constant of the resistor. The model can reveal an overload which does not lead to destruction of the resistor. Dynamic model of the resistor is based on its construction. Typically, an insulating ceramic rod is coated with a resistive layer connected with outlet wires on both sides, all being coated with insulating lacquer layer. The resistive layer is a source of heat flow. Formulation of the model comes from general power balance in a form of three differential equations and it is solved using Scilab. The input variable is the impulse power and the outputs are temperature changes in the ceramic rod, the resistive layer and the lacquer layer, compared to the ambient temperature. The simulation allows to determine solutions for various parameters including very short power pulses, which are confirmed experimentally.

Key words:

, , , ,




1084–1093 J. Malaťák, J. Bradna and J. Velebil
The dependence of COx and NOx emission concentrations on the excess air coefficient during combustion of selected agricultural briquetted by-products
Abstract |
Full text PDF (324 kB)

The dependence of COx and NOx emission concentrations on the excess air coefficient during combustion of selected agricultural briquetted by-products

J. Malaťák*, J. Bradna and J. Velebil

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: malatak@tf.czu.cz

Abstract:

The issue of CO, CO2 and NOx emissions is very extensive and important. The aim of the paper is the experimental determination of the CO, CO2 and NOx emission dependencies on the amount of excess air. Materials used for the experiments were several types of briquetted biomass. Crops used were Czech knotweed (Reynoutria × bohemica), Rumex hybrid OK 2 (Rumex patientia × Rumex tianschanicus), meadow hay and timothy grass (Phleum pratense). For all samples proximate and elemental analyses were performed (semiautomatic calorimeter LECO AC-600 elemental analyser CHN628 + S and analyser LECO TGA-701) and stoichiometric calculations of combustion were made. Combustion device used in combustion tests was a hot air stove with a grate fireplace and with manual fuel supply. The combustion process was monitored by analyser Madur GA-60. Parameters monitored during the combustion tests were primarily the flue gas temperature and the emission levels of carbon monoxide, carbon dioxide and nitrogen oxides.
Analyses and calculations of plant biomass samples indicate their good properties for energy use. The gross calorific value was as high as 19.55 MJ.kg-1 in the sample of Rumex OK 2. Limiting factor is the high quantity of ash in plant material. The briquettes from timothy grass achieved 5.77% wt. ash in the dry matter. The excess combustion air had positive influence during combustion test. On the other hand, this caused heat loss by departing flue gases, wherein the flue gas temperature reached high values. The excess air coefficient also significantly affected the emission levels of carbon dioxide and monoxide and nitrogen oxides in the flue gases. Results were statistically analysed and complemented by regression equations, which in practice can be used to optimize the combustion process in boilers with manual fuel supply.

Key words:

, , , ,




1094–1100 Č. Mizera,, D. Herák and P. Hrabě
Mathematical model describing the drying curves of false banana´s fibre (Ensete ventricosum)
Abstract |
Full text PDF (294 kB)

Mathematical model describing the drying curves of false banana´s fibre (Ensete ventricosum)

Č. Mizera¹,*, D. Herák² and P. Hrabě³

¹,² Czech University of Life Sciences Prague, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ165 21 Praha 6 Suchdol, Czech Republic
³ Czech University of Life Sciences Prague, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ165 21 Praha 6 Suchdol, Czech Republic
*Correspondence: mizera@tf.czu.cz

Abstract:

Drying processes play an important role in the preservation of agricultural products. They are defined as a process of moisture removal due to simultaneous heat and mass transfer. This study was focused on the analysis of drying curves of fibres of false banana (Ensete ventricosum). The fibres of Ensete ventricosum, originally from Ethiopian region Hawasa, were used in this experiment. Moisture content of freshly harvested fibres Mc =78.4 ± 1.4 % (w.b.) were determined. The fibres were dried at different air temperatures Td =40, 60, 80 and 100 ± 1 °C. To determine the drying curves the drying moisture balance (Radwag, MA 50.R, Poland) was used. Measured data were analysed by computer software Mathcad 14. Experimental drying curves at different temperatures and drying rate were determined. Basic mathematical model describing the loss of mass by drying of the Ensete fibres was represented. The model coefficients were statistically significant suggesting that the determined model could be used as a background for further research focused on Ensete fibre application.

Key words:

, ,




1101–1106 A. Mäkiranta, B. Martinkauppi and E. Hiltunen
Seabed sediment – a natural seasonal heat storage feasibility study
Abstract |
Full text PDF (304 kB)

Seabed sediment – a natural seasonal heat storage feasibility study

A. Mäkiranta*, B. Martinkauppi and E. Hiltunen

University of Vaasa, Faculty of Technology, Electrical Engineering and Energy Technology, P.O. Box 700, FI-65101 Vaasa, Finland
*Correspondence: anne.makiranta@uva.fi

Abstract:

The new discovery among renewable energy resources, seabed sediment, has been utilised as a heat source for 42 houses in Vaasa since 2008. Sediment heat is annually loaded by the Sun. In this study the amount of annually charged energy is estimated. The difference of sediment temperatures between the coldest and the warmest month during the year is a key value in the approximation of the loaded energy. Sediment temperatures are measured once per month via optical cable by distributed temperature sensing (DTS) method. The monitoring period is three years, 2014–2016. The estimation of incoming energy (575 MWh) versus known exploited energy (560 MWh) is reasonable. Despite of the extraction this seasonal heat storage in the seabed of the Baltic Sea seems to reload well annually.

Key words:

, , ,




1107–1118 M. Müller
Mechanical properties of resin reinforced with glass beads
Abstract |
Full text PDF (786 kB)

Mechanical properties of resin reinforced with glass beads

M. Müller

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences, Kamýcká 129, CZ165 21 Prague, Czech Republic
Correspondence: muller@tf.czu.cz

Abstract:

The research was focused on the evaluation of a loading speed and a size of the particle filler in a form of glass beads B159 and B112 on resultant behaviour of a composite material and during its application in a structural adhesive bond. A fall of the tensile strength of the composite material of ca. 60% is obvious from the experiment results when adding both fillers (B159 as well as B112). This composite material showed in the positive way as the adhesive at the adhesive bonds. The experiment results proved the positive influence of adding the particle filler of the spherical shape – glass beads B159 (the fraction size 85.23 ± 31.23 μm) on the adhesive bond strength. The adhesive bond strength was increased up of 14% at the filler glass beads B159. However, adding the filler into the resin proved that this filler eliminated the influence of various loading speeds. Adding the filler into the resin changed a fracture surface. An analysis of a scanning electron microscopy (SEM) proved a good wettability of the filler, the resin and the adhesive bonded material (a structural carbon steel S235J0). A crack propagation was concentrated around the filler B112 (151.59 ± 53.04 μm), namely at higher value of the loading speed, i.e. 10 mm min-1. The crack propagation is a consequence of this. Higher particles show in a negative way namely at an initiation of the fracture surface.

Key words:

, , ,




1119–1126 P. Neuberger and P. Kic
The use of unsteady method for determination of thermal conductivity of porous construction materials in real conditions
Abstract |
Full text PDF (312 kB)

The use of unsteady method for determination of thermal conductivity of porous construction materials in real conditions

P. Neuberger¹* and P. Kic²

¹ Czech University of Life Sciences Prague, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ165 21 Prague, Czech Republic
² Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: neuberger@tf.czu.cz

Abstract:

The possibility to determine the thermal conductivity of construction materials outside the laboratory conditions is useful for professional practice mainly for control and inspection activities on real existing buildings. The requirement to determine the thermal conductivity can be useful above all for different thermal insulation materials but for other materials as well, even for compact soils or rocks. This paper describes methods and instrument which can be used for these measurements, as well as the results of measurement of porous building materials. Measurements presented in this paper were carried out by the needle and surface sensor. Four different materials were selected for verification of technical parameters of Isomet 2104. Besides the thermal conductivity there were determined also thermal diffusivity and volume-specific heat capacity of materials. The carried out measurements confirmed the applicability of this device for practical measurements of thermal conductivity in real conditions. For porous materials, there were determined significant differences between the data presented by the manufacturer or in the literature and measured values, in some cases. Differences between the measured values of thermal diffusivity and volume-specific heat capacity of porous materials were always statistically significant. Authors tested different materials including thermal insulation based on agricultural products.

Key words:

, , ,




1127–1140 D. Novák,, P. Kvasnová, J. Volf and V. Novák
Measurement of weld joint parameters and their mathematical modelling
Abstract |
Full text PDF (862 kB)

Measurement of weld joint parameters and their mathematical modelling

D. Novák¹,*, P. Kvasnová¹, J. Volf² and V. Novák²

¹ Matej Bel University, Faculty of Natural Sciences, Department of Technology, Tajovského 40, SK974 01 Banská Bystrica, Slovakia
² Czech University of Life Sciences Prague, Faculty of Engineering, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: daniel.novak@umb.sk

Abstract:

The article deals with verifying of weld quality of weld joints created by laser beam welding technology, primarily in agricultural components such as reel screws. We presents both metallographic check of the weld structure using electron microscopy, RTG-microanalysis and micro hardness measurement as well as used mathematical models of the welding process and respective weld joints geometry.
First the laser beam welding technology and concerned agricultural components are introduced. Further we specify individual steel types as well as laser types and we define specific welding parameters used in our measurements. We selected several samples of weld joints, which are further examined them in detail using optical microscopy, micro hardness measurements and RTG microanalysis. We further determined the weld shape, measured dimensions of individual weld joints as well as we checked the weld joints structure.
We further introduced a mathematical model based on the program ANSYS. The model can simulate temperatures, speed field and tensions within the weld joint, basing on known thermal conductivity of the base material and specified welding conditions. Using the model, we can predict the shape of the weld and the temperatures within the material. Finally, individual welding parameters and obtained weld joint samples are briefly discussed and the applicability of the model is evaluated.

Key words:

, , , ,




1141–1151 V. Papez and S. Papezova,
Optimization of the balancer for LiFePO4 battery charging
Abstract |
Full text PDF (415 kB)

Optimization of the balancer for LiFePO4 battery charging

V. Papez¹ and S. Papezova²,*

¹ Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Electrotechnology, Technicka 2, CZ166 27 Pague 6, Czech Republic
² Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamycka 129, CZ165 21 Prague 6 ˗ Suchdol, Czech Republic
*Correspondence: papezovas@etf.czu.cz

Abstract:

Balancers of various constructions are currently used for the operation control of the batteries connected in series. Unidirectional balancers ensure proper charging of all battery cells in a way that the first loaded cells should not be overcharged. Active balancers distribute the power, supplied to already-charged cells, to other cells; the power is further consumed by the passive balancers. Bidirectional balancers enable distributing the power between the cells during the discharge process, as well. This process thus protects the fastest discharging cells against the deep discharge. Passive balancers are most often used in batteries charged by the currents up to 20 A. If there are not big differences between individual cells in the battery, passive balancers reduce the efficiency of the charging process by only a few percent. They are the cheapest and most reliable. Optimally adjusted balancers with very low internal resistance deteriorate the efficiency only by about 1%. Commercially available balancers, working on the principle of a switch, periodically connecting the load resistor to the cell, deteriorate the efficiency to a greater extent, by about 5%. Optimized balancers, whose construction is described in the paper, work on a principle of a linear feedback controller. They can work with a maximum charging current up to 20 A, they have very low dynamic resistance of about 1 mW, and are absolutely stable. Their properties are further compared both with previously used circuits and commercial circuits.

Key words:

, ,




1152–1161 S. Papezova, and V. Papez
Endurance LiFePO4 battery testing
Abstract |
Full text PDF (335 kB)

Endurance LiFePO4 battery testing

S. Papezova¹,* and V. Papez²

¹ Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamycka 129, CZ165 21, Prague 6 ˗ Suchdol, Czech Republic
² Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Electrotechnology, Technicka 2, CZ166 27 Pague 6, Czech Republic
*Correspondence: papezovas@etf.czu.cz

Abstract:

A lithium-iron-phosphate (LiFePO4) battery is nowadays considered one of the best types of batteries. Manufacturers and mostly suppliers indicate that LiFePO4 batteries have much longer lifespan than other batteries, and thus convincing their customers of lower operating costs than at other types of batteries, although their purchase price is several times higher. In connection with the problem of replace Pb batteries in the backup sources of security systems with LiFePO4 batteries, there has been necessary to determine the real parameters of available cells under conditions in which they operate. The paper describes the battery tests, in which their real parameters, comparable with the parameters indicated by the suppliers, are tested. The tests lie in automatic long-term cyclical charging and discharging of the multi-cell battery. Operating parameters are continuously monitored, recorded and evaluated by the computer. Individual cells are equipped with balancers and protection circuits that prevent from exceeding the maximum voltage during charging, as well as the voltage drop below a minimum level during discharging. The results of long-term tests on LiFePO4 WB-LYP40AHA Winston Battery are presented. The first test was conducted with 100% depth of discharge (DOD). New cells, after the first charge and discharge, showed the capacity about 115% of the rated capacity, the capacity drop c. 0.015 to 0.02% per cycle and the capacity drop to 80% after 950 cycles, which represents a lifetime of about 5% less than state the manufacturers.
A second test was conducted with 50% depth of discharge. Here, again after the first charge and discharge, new cells exhibited the same capacity as in the first case, i.e. c. 113% of the rated capacity. After 1,000 cycles, the cell capacity decreased to 107% of the rated capacity, which corresponds to the expected lifetime of 5,000 cycles.

Key words:

, , ,




1162–1169 B. Peterka,, M. Pexa, J. Čedík, D. Mader and M. Kotek
Comparison of exhaust emissions and fuel consumption of small combustion engine of portable generator operated on petrol and biobutanol
Abstract |
Full text PDF (266 kB)

Comparison of exhaust emissions and fuel consumption of small combustion engine of portable generator operated on petrol and biobutanol

B. Peterka¹,*, M. Pexa¹, J. Čedík¹, D. Mader¹ and M. Kotek²

¹ Czech University of Life Sciences Prague, Faculty of Engineering, Department for Quality and Dependability of Machines, Kamycka 129, CZ165 21 Prague 6, Czech Republic
² Czech University of Life Sciences Prague, Faculty of Engineering, Department of Vehicles and Ground Transport, Kamycka 129, CZ165 21 Prague 6, Czech Republic
*Correspondence: peterka@oikt.czu.cz

Abstract:

The paper is focused on the comparison of exhaust emissions and fuel consumption of small internal combustion engines operated on petrol and biobutanol. In case of this research, small engines are represented by combustion engine of portable power generator with nominal power of 4.8 kW equipped with carburettor for fuel mixture preparation. Exhaust emissions and fuel consumption were measured while gradual loading of the combustion engine. BrainBee emission analyser, Bruker FTIR spectrometer and EEPS particle analyser was used for the measurement. The mass fuel consumption was monitored using laboratory scale Vibra. The initial hypothesis expected that exhaust emissions and fuel consumption will be higher in case of use of nonstandard fuels. From the viewpoint of particles count can be stated, that their productions are at very low level for both kinds of used fuels. Production of carbon monoxide and hydrocarbons is higher than in case of usual automobile engine due to simple engine control system and absence of additional emission control device (catalytic converter). The fuel consumption increased while using n-butanol as a result of its lower calorific value.

Key words:

, , ,




1170–1181 S. Petrásek and M. Müller
Mechanical qualities of adhesive bonds reinforced with biological fabric treated by plasma
Abstract |
Full text PDF (670 kB)

Mechanical qualities of adhesive bonds reinforced with biological fabric treated by plasma

S. Petrásek and M. Müller

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences in Prague, Kamýcká 129, CZ165 21, Prague, Czech Republic
*Correspondence: petrasek@tf.czu.cz

Abstract:

The paper deals with the utilization of a biological reinforcement in the area of an adhesive layer at structural adhesive bonds. A significant disadvantage of adhesive bonds is uneven layer of an adhesive, which can be eliminated by various technological procedures. One possibility is to use a reinforcing even layer. The primary aim of this paper was to experimentally investigate an influence of the surface plasma treatment of natural fabrics (flax, cotton) at different intervals of plasma affecting (0 to 90 seconds and power 350 W) on mechanical properties of the adhesive bond. There were positive results from reinforcing the adhesive bond by a layer of linen and cotton. Strength characteristics of reinforced adhesive bond were increased compared to non–reinforced adhesive bonds. When the linen was used, the strength was increased by 43.2% and when the cotton then 15.5% strength increase could be seen. When modifying the surface by plasma, next adhesive bond’s strength increase was seen. Using the linen there was approx. 47% strength increase, using the cotton the strength increase was approx. 38% compared to non–reinforced adhesive bonds (without reinforcing phase). It is obvious from the results that plasma modifying showed better results when the cotton was used as the reinforcing material. SEM analysis proved that adhesion was improved with plasma surface modification of biological fibres. In other words the distance between the warp and the resin was significantly decreased for 87.1% when using the cotton and by 46.5% when the linen was used.

Key words:

, , ,




1182–1188 H. Pihlap, A. Annuk, A. Allik and M. Hovi
Indirect measurement of the battery capacity of smart devices
Abstract |
Full text PDF (277 kB)

Indirect measurement of the battery capacity of smart devices

H. Pihlap*, A. Annuk, A. Allik and M. Hovi

Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, EE51014, Tartu, Estonia
*Correspondence: heino.pihlap@student.emu.ee

Abstract:

A crucial part of portable electronic devices (smartphones, smart watches, Tablet PCs, GPS devices, etc.) are the batteries. The dominant trend in the design of these devices is such that the users are not supposed to replace the batteries, i.e. the device’s battery is meant to last for the entire lifetime of the device. This makes it important to know the capacity of the battery in order to estimate the expected life of the portable device. As there is no access to the terminals of these batteries, it is not possible to use traditional direct methods to evaluate the capacity of the battery and an indirect method needs to be used. The aim of the given research is to propose different indirect methods of battery capacity measurement and assess their accuracy.

Key words:

, , ,




1189–1197 M. Polák
Experimental evaluation of hydraulic design modifications of radial centrifugal pumps
Abstract |
Full text PDF (642 kB)

Experimental evaluation of hydraulic design modifications of radial centrifugal pumps

M. Polák

Czech University of Life Sciences in Prague, Faculty of Engineering, Kamýcká 129, CZ165 21, Praha 6, Czech Republic
Correspondence: karel@tf.czu.cz

Abstract:

In the field of small hydropower, pump units in turbine mode (PAT) are frequently used as alternative to conventional turbines. In order to maximize their operation efficiency, it is possible to optimize the performances of these engines through various simple innovative modifications which relate mainly to the geometry of the flow parts. This paper deals with the results of several successful modifications verified on one such engine. While various simple modifications led to the increase of overall efficiency and power output by few percentages, power output increased by nearly 30% with the innovated runner blades geometry. The modifications also had positive effects on the pump’s operation, with significant increases in flow rate, head and total efficiency.

Key words:

, , , ,




1198–1203 J. Pošta, B. Peterka, Z. Aleš, J. Pavlů and M. Pexa
Selection and evaluation of degradation intensity indicators of gas combustion engine oil
Abstract |
Full text PDF (260 kB)

Selection and evaluation of degradation intensity indicators of gas combustion engine oil

J. Pošta, B. Peterka, Z. Aleš, J. Pavlů* and M. Pexa

Faculty of Engineering, Czech University of Life Sciences Prague, Kamycka 129, CZ16521 Prague 6, Czech Republic
*Correspondence: jindrichpavlu@seznam.cz

Abstract:

The paper is focused on the analysis of data obtained during the operation of gas combustion engines running on biogas. The observed engines were running continuously in cogeneration units of biogas plants. The long-term operational monitoring of engines operating on biogas was carried out using tribotechnical diagnostics methods focused on oil properties. Each of individual indicators was determined in obtained time series. As critical indicators oils were identified oxidation, sulfation, nitration and total acid number. The prerequisite for correct selection of the oil change interval is knowledge on evolution of critical indicators over time. In the reference case, oil oxidation was identified as critical indicator. This knowledge allows to optimize intervals of oil sampling and oil change interval on the basis of time series evaluation.

Key words:

, , , ,




1204–1222 V. Raide, R. Ilves, A. Küüt, K. Küüt and J. Olt
Existing state of art of free-piston engines
Abstract |
Full text PDF (792 kB)

Existing state of art of free-piston engines

V. Raide,* R. Ilves, A. Küüt, K. Küüt and J. Olt

Institute of Technology, Department of Agricultural and Production Engineering, Estonian University of Life Sciences, Fr.R. Kreutzwaldi 56, EE51014 Tartu, Estonia
*Correspondence: veljo.raide@emu.ee

Abstract:

Free-piston engines (FPE), as power generators for electricity and hydropower solutions, have come under intensive research and development during the last decade. The rapid development of information technology provides an opportunity to return to FPE technology development due to better levels of control and management in terms of the engine’s work. What is more, changed environmental requirements are imposing stricter conditions upon the development of internal combustion engines. More effective solutions which ensure lower exhaust emissions, which are able to consume a variety of conventional and renewable fuels without any engine modification or rebuild taking place, and which work well with a very wide variety of ambient temperature conditions. However, commercially available or production-ready compact and stable free-piston engine solution are still absent. The objectives of this article are the innovative and novel features of FPE and their influence on engine operations and power production. The article maps the FPE technology and conducts a fact analysis. Various technical solutions, experiments, and mathematical calculations are discussed and are presented critically, along with potential pros and cons. This paper will epitomise the discussions outlined above with one possible theoretical technical solution for FPE, this being the electrical power generator.

Key words:

, ,




1223–1231 T. Sereika,, K. Buinevičius,, E. Puida and A. Jančauskas
Biomass combustion research studying the impact factors of NOx formation and reduction
Abstract |
Full text PDF (374 kB)

Biomass combustion research studying the impact factors of NOx formation and reduction

T. Sereika¹,*, K. Buinevičius¹,², E. Puida¹ and A. Jančauskas²

¹ Kaunas University of Technology, Faculty of Mechanical Engineering and Design, Department of Thermal and Nuclear Energy, Studentų st. 56, LT–51424 Kaunas, Lithuania
²UAB ‘Enerstena’ Centre of Research and Development, Partizanų st. 89, LT–50312 Kaunas, Lithuania
*Correspondence: titas.sereika@ktu.edu

Abstract:

Aim of this study was to identify potential NOx reduction factors and determine impact of nitrogen quantity in the fuel, during combustion process and conversion to nitrogen oxides. Experiments were performed using moving grate biofuel boiler with two staged air inlets, which represents industrial boiler operating principles. Combustion was performed using agricultural wastes: grain middlings, buckwheat hulls, corn pellets and mixtures with wood pellets. These types of fuels in combustion process generate about two times bigger amount of nitrogen oxides than wood pellets. The result of research shows, that the amount of nitrogen in the fuel has the greatest impact for NOx generation compared to all NOx formation forms. It was found that a smaller quantity of nitrogen, has bigger impact factor, than higher quantity of nitrogen, in biomass, for NOx formation during combustion. It was noticed that during combustion process the amount of carbon monoxide is inversely proportional to NOx values. The impact factor of nitrogen conversion to NOx and CO potential of reducing NOx is presented by formula in this paper.

Key words:

, ,




1232–1241 K. Sirviö, S. Niemi, S. Heikkilä and E. Hiltunen
Effects of sulphur on the storage stability of the bio and fossil fuel blends
Abstract |
Full text PDF (371 kB)

Effects of sulphur on the storage stability of the bio and fossil fuel blends

K. Sirviö*, S. Niemi, S. Heikkilä and E. Hiltunen

University of Vaasa, Faculty of Technology, PL 700, FIN-65101 Vaasa, Finland
*Correspondence: katriina.sirvio@uva.fi

Abstract:

In this study, the aim was to find out if mixing two common fuels together could be beneficial for both the environment and storage stability of fuel. It is obvious, that adding biodiesel to fossil fuel will decrease its sulphur content and reduce its carbon monoxide and hydrocarbon, sulphur dioxide and soot emissions. But will the high sulphur content enhance the storage stability of the biodiesel? Four B20 samples were produced, consisting of 20 vol% biodiesel and 80 vol% fossil diesel. The samples were prepared from rapeseed methyl ester (RME), low sulphuric fossil diesel fuel and high sulphuric diesel solvent. The blends had different sulphur contents of 6, 76, 149 and 226 mg kg-1. For these B20 fuel samples, the parameters were compared that correlate with the storage stability of the fuel blends. The studied parameters were the oxidation stability (OSI, according to EN 15751:2015), acid number (AN, according to EN 14104:2003) and kinematic viscosity (KV, by Stabinger SVM 3000 rotational viscometer). The measurements were carried out straight after mixing the blends, and again after 4, 8 and 12 weeks. According to the results, the fuel containing less sulphur slightly lost its oxidation stability within three months. Instead, the oxidation stability of high sulphuric samples improved within the same time frame. As a conclusion, the study gave a reason to assume that – in spite of its known drawbacks – the sulphur may be favourable to fuel blends’ storage stability but the phenomenon and chemistry should be studied in more detail.

Key words:

, , , , , ,




1242–1250 P. Valášek and K. Habrová
Influence of sisal fibres on tribological properties of epoxy composite systems
Abstract |
Full text PDF (400 kB)

Influence of sisal fibres on tribological properties of epoxy composite systems

P. Valášek* and K. Habrová

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ16521 Prague, Czech Republik
*Correspondence: valasekp@tf.czu.cz

Abstract:

Composite are materials, which synergically combine properties of the matrix and fillers. An interaction of polymers – resins – with biological kind of fillers can optimize their mechanical properties in the same way as synthetic fillers. Biological fillers have many advantages, which include low price and satisfying mechanical properties. Significant disadvantages are different properties of fibers – for example, fibre diameter and strength – which are caused by the biological essence of this material. The design of new composite materials based on natural renewable resources is essential for an environment and is also attractive from an economic point of view. This paper describes the hardness and resistance to abrasive wear of epoxy resins filled with unordered short sisal fibers (3, 6 and 9 mm). Scanning electron microscopy was used to assess the fibers and interaction between fibers and epoxy resin.

Key words:

, ,