Wyniki wyszukiwania - Biblioteka Nauki

1

Specific features of automobile brake linings

100%

Hlavňa V.

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tom Nr 2

21--33, 137--149

EN

Braking of road vehicles can be characterized as an active - either wanted or unwanted reduction of the force necessary for maintaining the required speed, decreasing the speed, stopping or keeping the vehicle at a standstill. During braking the vehicle loses the acquired motion energy which is most frequently transformed (in case of wanted braking) in the brake system of the vehicle into useless heat released to the environment. Brake force can be defined as the force acting against the motion of a vehicle which is, in case of wanted braking produced by the vehicle braking system. In case of wanted braking we usually begin with the equilibrium equation of vehicle forces. The paper deals with objective findings and assessment of possible causes leading to the braking system failure paying special attention to the brake lining. The user can approach the brake lining failure from two points of view: being aware or unaware of it. Laboratory tests can be used to objectively assess characteristics of brake linings. Both operational and laboratory test are performed to detect characteristics of brake lining materials. Apart from theoretical considerations, the paper also contains results of experiments performed with different brake lining materials used for trucks and passenger automobiles.

2

Circumfluence of the cylinder in a non-conventional combustion engine

63%

Hlavňa V. , Sojčák D.

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tom Vol. 13, No. 2

111-115

EN

When solving the project "A non-conventional energetic unit equipped with a cooling combustion engine" it was necessary to deal with flow and transfer of heat along the cylinder liner The contribution is a continuation of already published results gathered from experiments focused on the circumfluence of the combustion engine cylinder by a traditional cooler. The paper points out heat flows, velocity profiles, and turbulent intensity during the cylinder liner circumfluence by a non-conventional cooler – lithium bromide. Non-conventional cooling circuit of the engine, physical properties of the coolant for the engine (including specific heat capacity, absolute viscosity, density and thermal conductivity), model net, adaptation in the boundary layer area, velocity field in the vicinity of the inserted cylinder and the liner temperature profile from the side soaked with fluid, pressure field in the inserted cylinder chamber and temperature field of heat transfer, turbulent intensity on the cylinder liner and streamlines of the flow field are presented in the paper.The examined combustion engine will be able of a long-term operation when the alternate coolant is used

3

Emissions of the combustion engine as a source of cold for its extreme intercooling

63%

Hlavňa V. , Krakovsky J.

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tom R. 52, nr 2

20--27

EN

This paper contains results of mathematical modeling connected with non-conventional energetic system using the cooling combustion engine (the engine cooling circle is the ejector of absorption cooling). We especially have focused on the influence of a more intensive cooling on the engine ecological parameters. The paper is a continuation of previous publications and focuses on the results of the designed mathematical model of particulate matter formation and its experimental verification under extreme intercooling. Our previous achievements were already presented on scientific conferences and in professional journals.

4

Control of the air excess coefficient for the non-conventional engine

51%

Hlavňa V. , Sojčák D. , Isteník R.

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tom Vol. 13, No. 2

117-124

EN

One of the elements significant for the testing of combustion engines is the equipment for measurement of air consumed by the engine. The air excess coefficient, which depends on air consumption, is an important variable required for classification of combustion processes and evaluation for engine gas emissions. The paper deals with the solution of a flow field of a designed non-standardized measuring element with the objective of measurements and control of the air excess coefficient of the non-conventional combustion engine. In particular test stand (combustion engine – absorptive cooling equipmen)t, measuring element of the suction section of the combustion engine, modeling of the boundary layer, distribution of velocities and pressure field, distribution of density and temperatures in the flow field, course of static pressure and velocity in the measuring element axis for the engine torque, velocity profiles in cross sections, regulation of y+ parameter, comparison of velocities in dependence on torque, comparison of mass flow and pressure difference, contour of kinetic turbulent energy m2.s-2 for standardized and non-standardized measuring element, search dependence are presented in the paper.

5

Ice with a non-conventional cooling system temperature mapping

51%

Hlavňa V. , Sojčak D. , Istenik R.

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tom Vol. 14, No. 2

187-193

EN

Within the framework of the basic research task funded by the Agency for support of research and development we solve a problem of a more effective non-conventional usage of the part of energy taken away by the ICE cooling system. The energy is used for production of cold. Results ofpartial solutions and methodology of energetic evaluation have been already presented in various conferences and symposia as well as published in several professional journals. This contribution brings some newly acquired theoretical and practical experience gathered during the operation of a test laboratory sample of the cooling engine in a non-conventional energetic unit. Experiments were focused on temperature mapping. The basic scheme of a non-conventional energetic unit with a cooling engine, the view of a functional laboratory sample, surface temperature in the vicinity of evaporator - taken by thermal imaging, time course of changes in the engine torque, revolutions and temperature on the engine, temperatures in the evaporator, temperatures in the liquefier, temperatures in the absorber, temperatures in the evaporator, temperatures in the VBR exchanger are presented in the paper. The results of the experiment shown that there is a 10 - 15 % agreement with the results acquired through calculations. Theoretical assumptions and solutions carried out for the alternative cooling liquid of the cooling engine in a non-conventional energetic unit can be considered real. Within the framework of this consideration a test circuit is being prepared for experiments with alternative cooler.

6

The vehicle comfort case study

51%

Lack T. , Gerlici J. , Hlavňa V.

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tom nr 4

89-91

EN

The paper relates closely to theoretical considerations of vehicle comfort assessment published in the journal Horizonty dopravy - special No. 2006 under the title " Evaluation of Ride Comfort for Passengers". It can be understood as application of the mentioned theoretical considerations - as a case study. Influence of vibration on a standing and sitting person is assesed in the case study.