Fluid Dynamic Aspects of Electrostatic Precipatators: Turbulence Characteristics in Scale Models

2003 ◽  
Vol 125 (4) ◽  
pp. 694-700 ◽  
Author(s):  
Aldo Coghe ◽  
Michele Mantegna ◽  
Giorgio Sotgia
Keyword(s):  
Fluid Dynamic ◽  
Perforated Plate ◽  
Hot Wire ◽  
Perforated Plates ◽  
Downstream Distance ◽  
Turbulence Decay ◽  
Scale Models ◽  
Electrostatic Precipitators ◽  
Semi Empirical ◽  
Good Agreement

The present work originated in an investigation on fluid dynamic aspects of electrostatic precipitators performed on scale models of an industrial apparatus. The experimental analysis of velocity and turbulence distribution, performed by hot-wire anemometry, confirmed that significant turbulence levels are found inside particle collectors. In fact, components used to spatially smooth the flow and lower its velocity peaks, such as hoods with wide divergence angles, turning vanes, and perforated plates, may also act as sources of turbulence and reduce the efficiency of electrostatic precipitators. These observations prompted a deeper analysis, both analytical and experimental, of the turbulence decay downstream perforated screens. A new simple semi-empirical model of turbulence decay is proposed, which has shown reasonably good agreement with experimental data, even at short downstream distance from the perforated plate, 50 to 250 hydraulic diameters.

Measurements of Turbulence Generated by 60 Percent Solid Perforated Plates

1986 ◽  
Vol 108 (1) ◽  
pp. 55-63 ◽  
Author(s):  
M. D. Checkel
Keyword(s):  
Wind Tunnel ◽  
Perforated Plate ◽  
Spark Ignition Engine ◽  
Test Cell ◽  
Hot Wire ◽  
Mean Flow ◽  
Perforated Plates ◽  
Percent Solid ◽  
Decaying Turbulence ◽  
Good Agreement

Combustion experiments simulating spark-ignition engine conditions require generation and measurement of high intensity, rapidly decaying turbulence in a combustion test cell. Turbulence is generated by drawing various perforated plates across the test cell and is measured by hot-wire anemometry in the test cell and behind the same perforated plates in a steadily flowing wind tunnel. To correlate test cell and wind tunnel turbulence measurements, a simple statistical model of hot-wire anemometer response in turbulence with negligible mean flow is used. Good agreement between the two measurements tends to confirm the model for this case and demonstrates the value of perforated plate turbulence generators in producing controllable, measurable turbulence for confined combustion research.

A Modelling Approach to the Design Optimization of Catalytic Converters of I.C. Engines

2003 ◽  
Author(s):  
Ming Chen ◽  
Karen Schirmer
Keyword(s):  
Design Optimization ◽  
Catalytic Converter ◽  
Plug Flow ◽  
Perforated Plate ◽  
Catalytic Converters ◽  
Screening Process ◽  
Perforated Plates ◽  
Semi Empirical ◽  
Modelling Approach ◽  
Catalyst Model

In this paper, a modelling approach to the design optimization of catalytic converters is presented. The first step of the optimization is the model-assisted sizing of catalysts. For a given inlet exhaust condition, a semi-empirical, experimentally calibrated, 0-D steady state catalyst model is employed to sort through a data base of catalysts under given restraints, yielding few successful candidates. Following this screening process, a 1-D transient plug-flow catalyst model is used to analyze the species concentrations and the temperature variation across the catalyst. The second step deals with the flow optimization of the catalyst converter under the given geometric restraints. A commercially available CFD package is employed to simulate isothermal flow and to evaluate flow uniformity characteristics in the catalytic converter. The substrate is modelled as porous media, where viscous and initial resistances are specified via empirical formula. With the help of the CFD tool, the flow in the converter can be optimized using appropriate boundary layer control methods. In a specific example, the effects of perforated plate on the flow separation in a wide-angle diffuser are demonstrated. This paper also addresses the issue of flow resistance of perforated plates.

Rapid Distortion of Homogeneous Turbulence Between Cylinders

2004 ◽  
Author(s):  
Babak Emami ◽  
Rui Liu ◽  
David S.-K. Ting ◽  
M. David Checkel
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flow ◽  
Closed Loop ◽  
Perforated Plate ◽  
Energy Dissipation Rate ◽  
Hot Wire ◽  
Mean Velocity ◽  
Length Scales ◽  
Turbulence Decay ◽  
The Mean

The effects of ‘half-full-half’ cylinders on the distortion of a turbulent flow are experimentally investigated. A single hot-wire anemometry unit is used to measure the stream-wise parameters of the flow. The cylinders are 15.2 cm (6 in) in diameter and 76.2 cm (30 in) in height installed in a closed loop wind tunnel with a 76.2 cm by 76.2 cm (30 in by 30 in) cross section. Turbulent flow with a nominal mean velocity of 7.6 m/s was generated by means of a perforated plate situated at the entrance of the wind tunnel. It was found that the mean velocity increases significantly as the flow passes through the contracting passage created by the cylinders, whereas the rms turbulence intensity decreases about 12% but shows an increase of up to 14% very close to the full cylinder. As the flow was distorted, the Kolmogorov length scales were elongated in the stream-wise direction, resulting in a decrease in the rate of turbulence decay which appears as a decrease in energy dissipation rate. The stream-wise integral length scales also increased due to the elongation of eddies in the stream-wise direction. Also, analysis of the turbulence fluctuating velocity in the frequency domain showed a redistribution of stream-wise turbulence kinetic energy from large to small scales during the distortion.

Turbulent Flow Downstream of a Perforated Plate: Sharp-Edged Orifice Versus Finite-Thickness Holes

2007 ◽  
Vol 129 (9) ◽  
pp. 1164-1171 ◽  
Author(s):  
Rui Liu ◽  
David S.-K. Ting
Keyword(s):  
Large Scale ◽  
Isotropic Turbulence ◽  
Finite Thickness ◽  
Qualitative Difference ◽  
Perforated Plate ◽  
Perforated Plates ◽  
Large Scale Structures ◽  
Power Law Decay ◽  
Turbulence Decay ◽  
Scale Structures

In this study, perforated plates with sharp-edged orificed openings and finite-thickness straight openings were applied to produce nearly isotropic turbulence in a wind tunnel. At the same nominal velocity, the orificed perforated plate was able to produce a higher level of turbulence due to the well-defined flow separation from its sharp edge openings. The integral length, L was found to be related to the square root of the turbulence decay coefficient in the power law decay of turbulence kinetic energy, A. The larger A associated with the orificed perforated plate gave rise to a larger L. The corresponding streamwise autocorrelation functions for the two perforated plates behaved differently, confirming the quantitative disparity in L and further indicates some qualitative difference in the large-scale structures generated.

scholarly journals Analysis of Radial Inflow Turbine Losses Operating with Supercritical Carbon Dioxide

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3561
Author(s):  
Antti Uusitalo ◽  
Aki Grönman
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Average Deviation ◽  
Loss Analysis ◽  
Specific Speed ◽  
Loss Models ◽  
Rotor Losses ◽  
Radial Turbines ◽  
Design Power ◽  
Good Agreement

The losses of supercritical CO2 radial turbines with design power scales of about 1 MW were investigated by using computational fluid dynamic simulations. The simulation results were compared with loss predictions from enthalpy loss correlations. The aim of the study was to investigate how the expansion losses are divided between the stator and rotor as well as to compare the loss predictions obtained with the different methods for turbine designs with varying specific speeds. It was observed that a reasonably good agreement between the 1D loss correlations and computational fluid dynamics results can be obtained by using a suitable set of loss correlations. The use of different passage loss models led to high deviations in the predicted rotor losses, especially with turbine designs having the highest or lowest specific speeds. The best agreement in respect to CFD results with the average deviation of less than 10% was found when using the CETI passage loss model. In addition, the other investigated passage loss models provided relatively good agreement for some of the analyzed turbine designs, but the deviations were higher when considering the full specific speed range that was investigated. The stator loss analysis revealed that despite some differences in the predicted losses between the methods, a similar trend in the development of the losses was observed as the turbine specific speed was changed.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

Preliminary Evaluation of Turbulence Level Influence in Heat Transfer Measurements

2004 ◽  
Author(s):  
Carlo Carcasci ◽  
Luca Innocenti ◽  
Marco Surace
Keyword(s):  
Heat Transfer ◽  
Initial Level ◽  
Measurement Techniques ◽  
Preliminary Evaluation ◽  
Turbulence Level ◽  
Hot Wire ◽  
Aluminum Foams ◽  
Transfer Coefficients ◽  
Perforated Plates ◽  
Heat Transfer Coefficients

Heat transfer coefficients have often been experimentally measured, taking into account Nusselt number as a function of Reynolds and Prandtl number. Most experimenters spend their effort to control turbulence level, set it to different values, or keep it unchanged during the tests, as it’s not easy to predict how its initial level may change final results. The aim of this work is to add some comprehension on how different turbulence incoming levels may affect heat transfer measurements, and when it’s possible or not to neglect such effects. Experimental setup features different duct geometries, and thermocromic liquid crystals coupled with hot-wire anemometers are used as main measurement techniques. Tests were performed for Reynolds number from 10000 to 50000 and turbulence level from 3% to 12%. Several turbulence manipulators were adopted, including aluminum foams and multi-perforated plates, and results show some interesting dependences of heat transfer from both turbulence level and grid features.

High Speed Flow through Perforated Plates

1960 ◽  
Vol 64 (590) ◽  
pp. 103-105
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Perforated Plate ◽  
Wire Mesh ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Perforated Plates ◽  
Speed Flow ◽  
Flow Through ◽  
Points Of View

The flow through porous screens has been widely studied from both the theoretical and experimental points of view. The most widely used types of screen are the wire mesh and the perforated plate, and the majority of the literature has been concerned with the former. Several attempts have been made to correlate the parameters governing the flow through such screens, i.e. the pressure drop, the flow conditions and the geometry of the mesh.

scholarly journals Numerical study of hydrogen mild combustion

2009 ◽  
Vol 13 (3) ◽  
pp. 59-67 ◽  
Author(s):  
Enrico Mollica ◽  
Eugenio Giacomazzi ◽  
Marco di
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Thermal Gradients ◽  
Radiation Model ◽  
Dynamic Simulations ◽  
Mild Combustion ◽  
Preheating Temperature ◽  
Nitric Oxide Emissions ◽  
Gas Recirculation ◽  
Good Agreement

In this article a combustor burning hydrogen and air in mild regime is numerically studied by means of computational fluid dynamic simulations. All the numerical results show a good agreement with experimental data. It is seen that the flow configuration is characterized by strong exhaust gas recirculation with high air preheating temperature. As a consequence, the reaction zone is found to be characteristically broad and the temperature and concentrations fields are sufficiently homogeneous and uniform, leading to a strong abatement of nitric oxide emissions. It is also observed that the reduction of thermal gradients is achieved mainly through the extension of combustion in the whole volume of the combustion chamber, so that a flame front no longer exists ('flameless oxidation'). The effect of preheating, further dilution provided by inner recirculation and of radiation model for the present hydrogen/air mild burner are analyzed.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

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