Pulsirajući vodeni mlaz dobiven multiplikacijom impulsa

First theoretical papers, summarizing the high mechanical energy cumulation when high-speed drops impact on the solid surface as a result of the water hammer effect, have been known since 1960’s. Heymann has demonstrated that pressure maximum during the impact of a spherical drop of a liquid is several times higher than the presupposed maximum for the classical waterhammer effect. The mentioned maximum pressure exceeds the stagnation pressure of the continuous jet several times over. When developing devices for pulsed jet generation, a new generalization of the classical water hammer theory for high pressures has been introduced. Based on this a new patented principle of "pulse multiplication" has been formulated. The pulse multiplier is the source of high-pressure pulses with 100 % depth of modulation of discharge velocity of a liquid jet. It enables to significantly increase the jet disintegration effect without addition of abrasives.Prvi teorijski radovi, koji su opisivali stvaranje velike količine mehaničke energije kad kapljice velike brzine udare u čvrstu površinu kao rezultat hidrauličkog udara, poznati su još od 1960-tih. Heymann je pokazao da je maksimalni tlak kod udara loptaste kapljice tekučine nekoliko puta veći od pretpostavljenog maksimalnog u slučaju klasičnog hidrauličkog udara. Spomenuti maksimalni tlak nekoliko je puta veći od tlaka kontinuiranog mlaza u stanju mirovanja. Kod stvaranja uređaja za generiranje pulsirajućeg mlaza, za visoke je tlakove uvedena nova generalizacija klasične teorije hidrauličkog udara. Na tom je temelju zasnovan novi patentirani princip "multiplikacije impulsa". Multiplikator impulsa je izvor visokotlačnih impulsa sa 100 % dubinom modulacije izlazne brzine tekućeg mlaza. Omogućuje značajno povećanje dezintegracijskog učinka mlaza bez dodavanja abraziva.Web of Science23496795

EFFECTS OF ABRASIVES DURING ACCELERATED SIMULATION OF MECHANICAL CORROSION OF CEMENT COMPOSITES USING ABRASIVE WATER FLOW

The paper deals with the use of the abrasive water flow technology in an accelerated simulation of the process of mechanical degradation of surface layers of cement-based composites by flowing liquids. Effects of the abrasive particle size and the mass flow rate of abrasives in an abrasive water flow impacting on the surface of concrete samples have been studied. In addition, suitability of the application of the abrasive water flow for the simulation of real situation of the surface wear by flowing liquids has been evaluated

On the preparation of precursors and carriers of nanoparticles by water jet technology

Uporaba vodenog mlaza velike brzine proširila se u mnoga područja ljudskog djelovanja zbog njegovih jedinstvenih svojstava. Uz već tradicionalne tehnološke postupke počinje se primjenjivati u usitnjavanju mineralnih čestica. U ovom se radu analizira mogućnost usitnjavanja čestica primjenom abrazivne glave za miješanje koja stvara abrazivni vodeni mlaz velike brzine koji udara u čvrstu okomitu metu od volfram karbida. Čestice filosilikata (tj. sloja silikata) dimenzija kako mikrona tako i submikrona dobivene su ovom metodom. Ovom se metodom izbjegava stvaranje sekundarnih strukturnih defekata suprotno mehaničkim metodama usitnjavanja čestica. Nekoliko tipova mika (muskovit, vermikulit i biotit) i sitnozrnati kaoliniti usitnjeni su primjenom tehnologije vodenog mlaza. Rad se također bavi mogućnostima daljnje promjene dimenzija zrna čestica silikata te korištenja tako pripremljenih čestica kao supstance ili nositelja nanočestica.High-velocity water jet expanded into many fields of human activity due to its unique properties. Besides already traditional technological processes it begins to find its way also to the comminution of mineral particles. The paper analyzes the possibility of particle comminution using an abrasive mixing head used to generate high-velocity abrasive water jet and an impact of the jet to the solid perpendicular target made from tungsten carbide. Phyllosilicate (i.e. layered silicate) particles of both micron and submicron sizes were made by this method. The method avoids the formation of secondary structural defects which is in contrast to mechanical methods of particles comminution. Several types of micas (muscovites, vermiculite and biotite) and fine-grained kaolinites were comminuted using high-velocity water jet technology. The paper also deals with the possibilities of further change of silicate particles grain size and of using such prepared particles as precursors or carriers of nanoparticles

Measurement of Fine Grain Copper Surface Texture Created by Abrasive Water Jet Cutting

The paper presents results of experiments performed on copper with commercial purity to determine the influence of material grain size on both mechanical properties and texture of surface machined by abrasive water jet. An Equal Channel Angular Extrusion technology was used for creation of fine-grain copper samples. Hardness and grain size of fine-grain copper were measured, and, subsequently, surface of prepared copper samples was machined by abrasive water jet technology. Surface irregularities produced by the abrasive water jet were evaluated by means of surface profile roughness parameter Ra. It was found that the grain size of the material represents important factor affecting the final shape of surface topography in case of abrasive water jet machining

The measurement of the velocity of abrasive particles at the suction part of cutting head

U svrhu optimiziranja konstrukcije abrazivne rezne glave primjenom numeričke simulacije, potrebno je prikupiti što više podataka o tome što se događa u reznoj glavi. U Institutu za geoniku u Ostravi upravo je u tijeku razvoj numeričkog modela postupaka koji se odvijaju u reznoj glavi abrazivnog vodenog mlaza tijekom stvaranja i formiranja abrazivnog vodenog mlaza. Za verifikaciju modela potrebno je, između ostalog, odrediti ponašanje abrazivnih čestica na ulazu u reznu glavu. Stoga se vizualizacija abrazivnih čestica na ulazu, pomoću različitih parametara abrazivnog mlaza i njegove analize, provela primjenom tehnike shadowgraphy (backlighting-pozadinsko osvjetljenje). Rezultati su prikazani u ovom radu.To be able to optimize the design of the abrasive cutting head using the numerical simulation, it is necessary to gather as much information about processes occurring in the cutting head as possible. The development of numerical model of processes occurring in the abrasive water jet cutting head during the process of creation and forming of an abrasive water jet is currently in progress at the Institute of Geonics in Ostrava. The verification of the model requires, among other things, to determinate the behaviour of abrasive particles at the input of a cutting head. Therefore, the visualisation of abrasive particles at the input using various parameters of abrasive jet and its subsequent analysis were performed using the shadowgraphy (backlighting) technique. The results are presented in the paper

Comparison of the actual costs during removal of concrete layer by high-speed water jets

This paper describes the process of possible evaluation of costs of using high speed water jet technology for concrete removal methods. High speed water jet technology is a progressive technology of removing damaged concrete used in civil engineering since the 80's of 20th century. It has been changing and developing since that time. But there is little information in literature devoted to the economic evaluation of this technology. Detailed economic analysis is still missing. This paper aims to compare comprehensively in economic terms the costs of removing concrete using the technology of both continuous oscillating and pulsating oscillating water jets. The research was realized in cooperation with research institutions and industrial companies and was supported by state budget of the Czech Republic and from the European Union. The scheme of cooperation of the University, research institutions, industrial companies and government follows the Triple helix model

Fan water jets in concrete disintegration

In this paper, possibilities of high speed water jet technology nowadays usually applied in repair of concrete structures are extended by application of so called fan (flat) jet. In concrete disintegration, one can achieve interesting results by relatively low energy intensity using such jet in co-operation with acoustic pulse generator

Comparison of various types of nozzles for high-speed water jet generation

In the paper, three different types of nozzles for high-speed water jet generation are compared. The original methodology is used for comparison that is based on combination of three independent groups of measurement

Utilization Concept Mathematical Statistics for Monitoring of Transport Service Quality Standards in Choice Transport Company

Import 31/08/2009V diplomové práci se zabývám návrhem využití matematické statistiky při sledování úrovně kvality poskytovaných přepravních služeb městskou hromadnou dopravou Orlová. Uvádím současný stav zabezpečení dopravní obslužnosti města Orlová městskou hromadnou dopravou a příměstskou hromadnou dopravou. Jsou zde uvedena možná kritéria hodnocení kvality hromadné osobní dopravy a vybrané aplikace matematické statistika. Ze získaných poznatků jsou zpracovány návrhy na sledování úrovně kvality poskytovaných přepravních služeb s využitím matematické statistiky a údajů získaných z navrženého průzkumu.I solve utilization concept mathematical statistics for monitoring of transport service quality standards in Orlová urban mass transportation in the thesis. I depict present state of city transportation serviceability ensuring by urban mass transportation and intercity mass transportation. I declare possible criterions of mass passenger transportation quality values and chosen applications of mathematical statistics. Finally I compile concept for monitoring of transport service quality standards from gained experience with the use of mathematical statistics applications and obtained data from suggested inquiry.Prezenční342 - Institut dopravydobř