Fluidic Valves for Variable-Configuration Gas Treatment

The paper surveys recent development in the highly specialized field of chemical engineering: vehicle exhaust gas aftertreatment, where variable configuration systems are currently introduced or considered. These respond to varying operating conditions by inserting into the gas treatment flowpath different reactors. The main practical problem are the valves for gas flow switching. Usual mechanical valves are costly, failure prone, heavy (especially the solenoid variants), and not robust enough to withstand the adverse conditions of high temperature, vibration, shocks and dripping water and mud at the usual locations under vehicle body. Fluidic no-moving-part valves, inexpensive and robust, are proposed as an attractive alternative. Especially in their novel axisymmetric layout, they may be very compact, in fact integral with reactor body. The qualitative change brought by the new approaches may provide an inspiration to other areas of chemical engineering

Fluidic valve for reactor regeneration flow switching

An unusual and in many respects advantageous no-moving-part valve is described,developed for switching fluid flows in a through-flow reactor that requires a periodic regeneration by temporary replacement of the process fluid by another, regeneration fluid. The unusual feature of the valve is that it is axisymmetric, built integrally into the inlet part of the reactor body. The valve operation is based upon a monostable axisymmetric variant of the Coanda effect of jet attachment to a wall. The jet is annular and there are two attachment walls of conical shape. The outer hollow cone is dominant while the auxiliary inner convex cone is small, almost vestigial. Concentrating on the performance in a no-spillover regime, experimental data obtained in cold-air laboratory tests using a full-scale model are compared with numerical flowfield computations, using unusual non-dimensional presentation

Development of a microfluidic unit for sequencing fluid samples for composition analysis

A microfluidic sample-sequencing unit was developed as a part of a high-throughput catalyst screening facility. It may find applications wherever a fluid is to be selected for analysis from any one of several sources, such as microreactors operating in parallel. The novel feature is that the key components are fluidic valves having no moving parts and operating at very low sample flow Reynolds numbers, typically below 100. The inertial effects utilized in conventional no-moving-part fluidics are nearly absent; instead, the flows are pressure-driven. Switching between input channels is by high-Reynolds-number control flows, the jet pumping effect of which simultaneously cleans the downstream cavities to prevent crosscontamination between the samples. In the configuration discussed here, the integrated circuit containing an array of 16 valves is etched into an 84mm diameter stainless steel foil. This is clamped into a massive assembly containing 16 mini-reactors operated at up to 400C and 4 MPa. This paper describes the design basis and experience with prototypes. Results of CFD analysis, with scrutiny of some discrepancies when compared with flow visualization, is included

On the design and simulation of an airlift loop bioreactor with microbubble generation by fluidic oscillation

Microbubble generation by a novel fluidic oscillator driven approach is analyzed, with a view to identifying the key design elements and their differences from standard approaches to airlift loop bioreactor design. The microbubble generation mechanism has been shown to achieve high mass transfer rates by the decrease of the bubble diameter, by hydrodynamic stabilization that avoids coalescence increasing the bubble diameter, and by longer residence times offsetting slower convection. The fluidic oscillator approach also decreases the friction losses in pipe networks and in nozzles/diffusers due to boundary layer disruption, so there is actually an energetic consumption savings in using this approach over steady flow. These dual advantages make the microbubble generation approach a promising component of a novel airlift loop bioreactor whose design is presented here. The equipment, control system for flow and temperature, and the optimization of the nozzle bank for the gas distribution system are presented. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved

Two-equation Turbulence Model Similarity Solution of the Axisymmetric Fluid Jet

This paper presents a general, universally valid solution of axisymmetric turbulent submerged jet flow, for which no fully satisfactory solution has been known. What has been available so far are either computational solutions for individual particular cases, lacking universality, or similarity solutions with inadequate turbulence models, some of them based upon assumptions of a speculative character (e.g. constant mixing length across the jet profile). The present approach uses a similarity transformation of the governing equations, which incorporate an advanced turbulence model. The results are shown to be in excellent agreement with available experimental data. The new solution provides a suitable basis for analysis of enigmatic aspects of axisymmetric jets, such as their "spreading anomaly"

Linear difference equations: stability analysis

Tato práce pojednává o vyšetřování asymptotické stability lineárních diferenčních rovnic na základě kritéria Schurova-Cohnova a Routhova-Schurova. Obě tato kritéria jsou realizována v programu Maple a jejich použití je demonstrováno na příkladech. Na Adamsově-Bashforthově metodě pro řešení počátečních problémů obyčejných diferenciálních rovnic 1.řádu je ilustrováno použití techniky pro lokalizaci hranice oblasti asymptotické stability této metody.This thesis deals with asymptotic stability investigation of linear difference equation. The Schur-Cohn criterion and discrete Routh-Schur criterion are introduced and demonstrated on several examples. Both criterions are implemented in Maple programming enviroment. Boundary locus technique is illustrated on a stability analysis of the Adams-Bashforth method for numerical solving of an initial value problem of first order ordinary differential equation.

Annular synthetic jet used for impinging flow mass-transfer

An annular synthetic jet was investigated experimentally, both with and without an opposing impingement wall. The experiments involved smoke visualization and mass transfer measurement on the wall by means of naphthalene sublimation technique. Two qualitatively different flow field patterns were identified, depending upon the driving amplitude level. With small amplitudes, vortical puffs maintain their identity for a relatively long time. If the amplitudes are large, breakdown and coalescence of the vortical train is much faster. Also the resultant mass transfer to the impingement wall is then much higher. Furthermore, a fundamental change of the whole flow field was observed at the high end of the investigated frequency range, associated with radical reduction of the size of the recirculation bubble

Computer aided design at electrotechnics

Tato práce se zabývá problematikou využití moderní výpočetní techniky pro účely podpory projektování v elektrotechnice. V úvodu seznamuje s obecnými základy projektování, důvody a stupni zpracovávaných dokumentací. Následuje kategorizace a rozdělení typů softwarových nástrojů podle účelu užití spojeno s popisem historického vývoje grafických systémů, od bitmapových k vektorovým. Ukončením je praktická ukázka realizační dokumentace zpracované specializovaným nástrojem Astra92 a.s.This work deals with questions how to take advantage of modern technology for support purposes in the projection in electro engineering. It the introduction it informs about common bases of the projecting, purposes and grades of processed documentations. It is followed by the categorization and dividing types of software tools according to the purpose of use linked with the description of historical development of graphic systems, from raster to vector. In the end there is a practical show of documentation realization processed by a specialized instrument Astra92 Inc.

Virtual server solution in CSN cluster in redundant NoSPOF mode

Diplomová práce se zabývá popisem virtualizace, jejími výhodami a možnými úskalí. Dále pak porovnáním nejpoužívanějších virtualizačních platforem, pro provoz clusteru ve vysoké dostupnosti v komerčním prostředí. Zároveň diplomová práce obsahuje návrh řešení CSV vysoce dostupného clusteru pro potřeby střední firmy. Navržené řešení je otestováno nad hypervisory Microsoft Hyper-V a VMWare vSphere. Testován je rozdíl výkonu, vysoké dostupnosti a ekonomických rozdílů obou platforem. Na základě těchto testů je pak vybrána optimální varianta pro provoz vysoce dostupného clusteru.This master thesis deals with the description of virtualization, advantages and disadvantages of virtualization. Furthermore, by comparing the most widely used virtualization platforms for cluster in high availability mode in a commercial environment. At the same time the thesis contains a solution of a CSV high availability cluster for the needs of a medium-sized company. The proposed solution is tested on Microsoft Hyper-V and VMWare vSphere hypervisors. Tests are aiming to difference in performance, high availability, and economic differences between the both platforms. Based on these tests, is selected the optimal solution for high-availability cluster.440 - Katedra telekomunikační technikyvýborn