Communications - Scientific Letters of the University of Zilina, 2006 (vol. 8), issue 2
Articles
A Solar Timber-Dryer Equipped with an Air Collector
Jozef Víglasky, Nada Langova, Peter Horbaj
Communications - Scientific Letters of the University of Zilina 2006, 8(2):5-9 | DOI: 10.26552/com.C.2006.2.5-9 
A generally well-known high energy requirement for technological processes of timber drying and the fact that the world's supply of the conventional energy sources has considerably decreased are the decisive factors forcing us to look for some new, if possible, renewable energy sources for this process emphasising their environmental reliability.One of the possibilities of how to replace, at least partly, the conventional energy sources - heat in a drying process is solar energy.Air-drying of timber usually has a series of disadvantages such as time expenditure, drying defects in the wood and inadequate final moisture content. To avoid these drawbacks,...
Nonconventional Principle of Conversion of Heat into Cold in an Internal Combustion Engine
Vladimir Hlavna, Dusan Sojcak, Rastislav Istenik
Communications - Scientific Letters of the University of Zilina 2006, 8(2):10-22 | DOI: 10.26552/com.C.2006.2.10-22
The paper presents results achieved by a team of 12 researchers from the Faculty of Mechanical Engineering of the University of Žilina who participated in the solution of the project of the above-mentioned title within the period of the years 2002 - 2005. The basic research project focuses on the cooling internal combustion engine as an element of qualitatively new equipment designed for more effective utilization of fuel energy by a nonconventional progressive principle of heat conversion cooled by thermocompression. The issue of permanently sustainable life is approached from three hierarchical levels: a first level is a cooling internal combustion...
Energy Evaluation of the Municipal Solid Waste Pyrolysis
Emilia Wagnerova, David Uricek
Communications - Scientific Letters of the University of Zilina 2006, 8(2):23-26 | DOI: 10.26552/com.C.2006.2.23-26
This contribution deals with possibilities of using pyrolysis as a method for municipal solid waste (MSW) disposal. Taking into account the possibilities of MSW separation, specific sorts of wastes were selected and subjected to laboratory experiments. The main aim of experimental measurements was to determine the distribution of the caloric value of an original sample in the products of pyrolysis. The aim of this research was to determine the energy content of selected MSW sorts and to recommend the method of their thermal disposal.
Unsteady Flow Simulation and Combustion of Ethanol in Diesel Engines
Jan Labaj, Dalibor Barta
Communications - Scientific Letters of the University of Zilina 2006, 8(2):27-37 | DOI: 10.26552/com.C.2006.2.27-37
The paper presents the survey of ethanol application as the fuel for diesel engines which is added to diesel fuel or injected to the inlet manifold. The paper describes unsteady flow simulation in the inlet manifold of a 4 cylinder diesel engine with injected ethanol (Martin Diesel UR IV). The calculation of mixing rates is based on transient spray-plume-growth with concentration and temperature profile applying the CFD code (software of Fluent Inc. USA). The calculation of combustion was performed using a RNG kε (renormalization group) turbulent model, standard wall function and a PDF model for chemical equilibrium of gas composition and kinetics...
Characteristics of a Diesel Engine with a Ceramic Coated Piston Head
Andrzej Mruk
Communications - Scientific Letters of the University of Zilina 2006, 8(2):38-43 | DOI: 10.26552/com.C.2006.2.38-43
In this age of fuel problems, the improvement in thermal efficiency of an engine is very important. One of the ways leading to this aim consists in reducing heat losses by the application of heat-insulating coatings on the elements of the combustion chamber. The article deals with the effect of the piston head heat-insulation on a Diesel engine running indicators and presents the results of the tests.
Breakdown of the Impeller Wheel of a TG2 Kaplan Turbine
Peter Palcek, Maria Chalupova
Communications - Scientific Letters of the University of Zilina 2006, 8(2):44-52 | DOI: 10.26552/com.C.2006.2.44-52
The paper deals with the investigation of the breakdown of the impeller wheel of a TG2 Kaplan turbine with the power of 36 MW that was operating for only 6.5 years. To find the cause, both methods of investigation of mechanical properties and analyses of microstructure and micrographics were used. On the basis of the results of individual analyses we found out that the primary cause of the impeller wheel breakdown was inconvenient material of the servomotor rod.
The Influence of Vehicle Maintenance Conditions on Chosen Electric Parameters of Starter During Combustion Engine Start-Up
Pawel Drozdziel
Communications - Scientific Letters of the University of Zilina 2006, 8(2):53-58 | DOI: 10.26552/com.C.2006.2.53-58
Necessary mechanical energy needed for initiation of self-dependent combustion engine work is transferred by crankshaft driving using an electrical starter. Changes of values of the static resistant moment and start-up resistant moment in the engine influence current input by the electric starter during start-up of the combustion engine. Overloads observed in the vehicle electric power system are the results of high value of current intensity input by the electric starter. It seems very important to find the answer how the vehicle maintenance conditions influence the chosen working electric parameters of the starter during the combustion engine start-up....
The Usage of Arcs Radii Profile Variation for the Synthesis of Railway Wheel and Rail Head Profiles
Tomas Lack, Juraj Gerlici
Communications - Scientific Letters of the University of Zilina 2006, 8(2):59-69 | DOI: 10.26552/com.C.2006.2.59-69
The presented article deals with one of the ways of profile geometry design of a railway wheel and railhead. The base for the creation of new profiles is an interactive attitude based on the modification of "the original shape which is defined by section of a railway wheel profile", with to each other connected and exactly defined arcs radii. It is possible to change them according to shape needs of the final geometrical characteristics.
Cooling Working Rolls of the Finishing Section of Wide-Strip Hot Rolling Mills
Peter Horbaj, Jozef Víglasky, Dusan Mikolaj
Communications - Scientific Letters of the University of Zilina 2006, 8(2):70-74 | DOI: 10.26552/com.C.2006.2.70-74
The contribution deals with heat nucleation in rolling on the hot wide strip mill as well as into following transfer to the rolls without friction heat being involved. This work has resulted in the computer program owned by author. It represents the most accessible computer technique and the dependence of the accepted heat amount on the revolutions and angle of bite, as well as the dependence on the temperature of the roll surface which may participate in the initiation and widening of the surface friction coefficient and roll stand sequence.
Older Low-Efficient Boilers Brown Coal-Fired, Generated Emissions and Diffusion of Imissions
Jozef Blaho, Jozef Víglasky, Peter Horbaj
Communications - Scientific Letters of the University of Zilina 2006, 8(2):75-80 | DOI: 10.26552/com.C.2006.2.75-80
At thermooxidizing processes generating energy from natural solid fuels, heat as its main product is accompanied with side products - solid waste and emissions, resulting in unfavourable effects on the environment. This contribution deals with the results of measurements and analyses regarding an old-fashioned type boiler unit fired by solid fuel. It showed low efficiency of older brown coal fired boilers currently used in many small companies. All of them generate pollutants - gaseous as well as solid emissions polluting the environment. Thus, they cause environmental damage in spite of their meeting emission and imission limits within their category....