Contribution to the wastewater toxicity determination

Za određivanje toksičnosti otpadnih voda u našem laboratoriju uveli smo Offhausovu metodu. Upotrebljavamo Warburgov aparat i manometrijsku tehniku rada, odnosno Sapromat i volumetrijsku tehniku rada. Obje su aparature jako skupe i nisu dostupne svim industrijskim vodnim laboratorijama. Zbog toga smo pokušavali uvesti metodu prema Borovičkovoj i Zahrádku koja se koristi jednostavnim aparatima. Rezultati uspoređivanja pokazuju da je metoda prema Borovičkovoj i Zahrádku za određivanje toksičnosti odnosno inhibicijskih efekata otpadnih voda nesigurna pa je zbog toga ne preporučujemo.The Offhaus method for the wastewater toxicity determination was introduced in our laboratory. The determination can be carried out by Warburg apparatus and manometric technique of work or Sapromat and volumetric technique of work. Both apparatuses are rather expensive and therefore not easily available to all the industrial water laboratories. On that account we tried to introduce the method of Borovickova and Zahrádka which requires a simple equipment. Unfortunately the comparative results show that the method of Borovickova and Zahrádka of the waste water toxicity determination is unreliable and therefore cannot be recommended

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions

Multiphase phenomena in Diesel fuel injection systems

Fuel Injection Equipment (FIE) are an integral component of modern Internal Combustion Engines (ICE), since they play a crucial role in the fuel atomization process and in the formation of a fuel/air combustible mixture, consequently affecting efficiency and pollutant formation. Advancements and improvements of FIE systems are determined by the complexity of the physical mechanisms taking place; the spatial scales are in the order of millimetres, flow may become locally highly supersonic, leading to very small temporal scales of microseconds or less. The operation of these devices is highly unsteady, involving moving geometries such as needle valves. Additionally, extreme pressure changes imply that many assumptions of traditional fluid mechanics, such as incompressibility, are no longer valid. Furthermore, the description of the fuel properties becomes an issue, since fuel databases are scarce or limited to pure components, whereas actual fuels are commonly hydrocarbon mixtures. Last but not least, complicated phenomena such as phase change or transition from subcritical to transcritical/supercritical state of matter further pose complications in the understanding of the operation of these devices

Evaluation of Cavitation Erosion Behavior of Commercial Steel Grades Used in the Design of Fluid Machinery

The erosion response under cavitation of different steel grades was assessed by studying the erosion rate, the volume removal, the roughness evolution, and the accumulated strain energy. A 20 kHz ltrasonic transducer with a probe diameter of 5 mm and peak-to-peak amplitude of 50 lm was deployed in distilled water to induce damage on the surface of commercial chromium and carbon steel samples. After a relatively short incubation period, cavitation induced the formation of pits, cracks, and craters whose features strongly depended on the hardness and composition of the tested steel. AISI 52100 chromium steel showed the best performance and is, therefore, a promising design candidate for replacing the existing fluid machinery materials that operate within potential cavitating environments

Treatment of persistent organic pollutants in wastewater using hydrodynamic cavitation in synergy with advanced oxidation process

Persistent organic pollutants (POPs) are very tenacious wastewater contaminants. The consequences of their existence have been acknowledged for negatively affecting the ecosystem with specific impact upon endocrine disruption and hormonal diseases in humans. Their recalcitrance and circumvention of nearly all the known wastewater treatment procedures are also well documented. The reported successes of POPs treatment using various advanced technologies are not without setbacks such as low degradation efficiency, generation of toxic intermediates, massive sludge production, and high energy expenditure and operational cost. However, advanced oxidation processes (AOPs) have recently recorded successes in the treatment of POPs in wastewater. AOPs are technologies which involve the generation of OH radicals for the purpose of oxidising recalcitrant organic contaminants to their inert end products. This review provides information on the existence of POPs and their effects on humans. Besides, the merits and demerits of various advanced treatment technologies as well as the synergistic efficiency of combined AOPs in the treatment of wastewater containing POPs was reported. A concise review of recently published studies on successful treatment of POPs in wastewater using hydrodynamic cavitation technology in combination with other advanced oxidation processes is presented with the highlight of direction for future research focus

Time-domain homogenization of windings in 2-D finite element models

In this paper, the authors propose an original time-domain extension of the frequency-domain homogenization of multiturn windings in finite element (FE) models. For the winding type in hand (e.g., round conductor with hexagonal packing), an elementary FE model is used for determining dimensionless frequency and time-domain coefficients regarding skin and proximity effect. These coefficients are readily utilized for homogenizing the winding in the FE model of the complete device. The method is successfully applied to an axisymmetric 103-turn inductor. The results agree very well with those obtained by an accurate but very expensive FE model in which all turns are finely discretized. © 2007 IEEE.status: publishe

A Complete Open-Source Solution for Electromagnetic Field Computation

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Two-dimensional Harmonic Balance Finite Element Modelling of Electromagnetic Devices coupled to Nonlinear Circuits

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A general approach to the harmonic balance finite element method for the modelling of 2D and 3D electromagnetic devices

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A time-domain finite element homogenization technique for lamination stacks using skin effect sub-basis functions

info:eu-repo/semantics/publishe