Martin Vašina

Effect of Oil Viscosity on Pulsating Flow in Pipe

The article deals with the influence of oil viscosity on pulsating flow in a pipe. A hydraulic resistance is placed at the end of the pipe. A pulsating pressure signal is generated by proportional directional valve. Time dependencies of pressure drops for different frequencies of the pulsating signal are measured at the beginning and the end of the pipe. A mathematical model of the hydraulic system is constructed using Matlab SimHydraulics software. There are simulated time dependencies of pressures at the beginning and at the end of the pipe. They are subsequently compared with an experiment.

Mathematical simulation and measurement of expansion of hydraulic hose with oil

Rad se bavi mjerenjem i matematickom simulacijom sirenja hidraulicnog crijeva, ukljucujuci ucinak modula stlacivosti ulja. Youngov modul elasticnosti hidraulicnog crijeva eksperimentalno je određen metodom ekspanzije i metodom kompresije. Modul elasticnosti hidraulicnog crijeva dobiven metodom ekspanzije određen je mjerenjem povecanja volumena ulja, sabijenog u ispitivanom crijevu nakon ekspanzije. Youngov modul elasticnosti hidraulicnog crijeva, dobiven metodom kompresije, određen je mjerenjem protoka ulja i porasta tlaka u hidraulicnom crijevu u odnosu na vrijeme. Modul stlacivosti ulja eksperimentalno je određen metodom ekspanzije i metodom kompresije ulja u celicnoj cijevi. Hidraulicni krug za simulaciju sirenja ulja u crijevu i celicnoj cijevi stvoren je primjenom softvera Matlab SimHydraulics. Povecanje volumena ulja nakon sirenja u hidraulicnom crijevu i celicnoj cijevi numericki je simulirano. Nadalje, vremenske ovisnosti smanjenja tlaka tijekom sirenja ulja u hidraulicnom crijevu i celicnoj cijevi numericki su simulirane. Rezultati matematickih simulacija uspoređeni su s eksperimentalnim tijekom primjene Youngova modula elasticnosti crijeva i modula stlacivosti ulja određenih metodom ekspanzije i metodom kompresije.

Effect of Surface Shape on Light Absorption

This paper deals with influence of surface shape on light absorption. The study was performed on polyvinylchloride samples with different grooves. It was investigated the influence of shape, width, depth and number of grooves on light absorption. The investigated material samples were produced on CNC milling machine. Experimental measurements of light absorbance were performed under diffuse daylight on the basis of illuminance ratio. Different factors, that have influence on light absorption, are evaluated in the conclusion of this work. It was found that the lowest light absorbance was obtained in case of the smooth polyvinylchloride sample. The material machining causes multiple reflections of light from groove surfaces. For this reason the light absorbance of the groove surfaces is higher compared to the smooth material sample.

Effect of Oil Flow Velocity on Hydraulic Shock

The article is focused on experimental investigation of oil dynamics in long pipe at non-stationary flow. The non-stationary flow is realized by sudden closing of seat valve at the end of the long pipe. For this reason the oil pressure is suddenly increased and hydraulic shock is created. There is described the influence of oil flow velocity on hydraulic shock in this article. The pressure is measured near the seat valve. Furthermore this process is mathematically simulated using Matlab SimHydraulics software and is compared with the experiment.

Evaluation of Oil Viscosity Influence on Hydraulic Shock in Long Pipe

This article is aimed at mathematical simulation and experimental measurement of dynamics of liquid and pipe wall during hydraulic shock. Liquid compressibility and hydraulic line elasticity are taken into account in this case. The mathematical model is created using Matlab SimHydraulics software. The long pipe is simulated by means of segmented pipe. Experimental measurement is performed on a hydraulic system, which consists of flow-controlled aggregate, long pipe and seat valve. The hydraulic shock is caused by step closing of the seat valve that is located at the pipe end. Pressures at the end of the long pipe, oil flow and temperature are experimentally measured.

Influence of Surface Shape and Perforation of Plastics on Sound Absorption

The aim of the paper is to study the effect of the surface shape and perforation of plastics on sound absorption. Samples with different asperity heights, depths and numbers of holes were prepared by means of CNC milling machine. Experimental measurements of frequency dependencies of the sound absorption coefficient were realized by the transfer function method using Kundt ́s impedance tube at normal incidence of acoustic wave on the investigated materials. The study was performed on two types of polyurethanes. Different factors, that have influence on sound absorption, are evaluated in the conclusion of this work. Both investigated materials are also compared in terms of their ability to absorb sound.