An experimental investigation of oblique entry pressure losses in automotive catalytic converters

2009 ◽  
Vol 223 (11) ◽  
pp. 2561-2569 ◽  
Author(s):  
S S Quadri ◽  
S F Benjamin ◽  
C A Roberts
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Flow Distribution ◽  
Angle Of Incidence ◽  
Pressure Losses ◽  
Entry Pressure ◽  
Automotive Catalytic Converters

This study investigates oblique entry pressure loss in automotive catalyst monoliths. Experiments have been performed on a specially designed flow rig using different lengths of monolith (17—100 mm) over a range of Reynolds number and angles of incidence (0–75°). Losses were found to be a function of Reynolds number and angle of incidence and a general correlation has been derived. Computational fluid dynamics predictions of the flow distribution across axisymmetric catalyst assemblies have been performed. Incorporating the oblique entry loss provided much better agreement with experimental data with the assumption that such losses were constant above an angle of incidence of 81°.

The Application of Advanced Computational Methods to the Modeling of PBMR Source Terms

2004 ◽  
Author(s):  
Margaret Msongi Mkhosi ◽  
Richard Denning ◽  
Shoichiro Nakamura
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Radioactive Material ◽  
Dust Particles ◽  
Integrated Analysis ◽  
Computational Techniques ◽  
Turbulent Regime ◽  
Pebble Bed

The pebble bed modular reactor (PBMR) is a high temperature gas-cooled reactor which uses helium gas as a coolant. The PBMR design relies on the excellent heat transfer properties of graphite and a fuel design that is inherently resistant to the release of the radioactive material up to high temperatures. The safety characteristics of the PBMR concept are excellent. However, a very strong safety case will have to be made if a new generation of reactors is to be successfully introduced to a concerned public. Until recent developments in computational fluid dynamics methods, computer speed, and data storage, the coupled thermal-hydraulic, chemical, and mass transport phenomena could not be treated in an integrated analysis. This paper addresses one aspect of the interplay between the details of fluid flow and aerosol transport within the complex geometry of the pebble bed core. A very large quantity of graphite dust is produced by the interaction among the pebbles. The potential for the deposition of radionuclides on the surface of dust particles and their subsequent transport as aerosols is substantial. This effort focuses on the inertial deposition of these aerosols within the pebble bed. Inertial deposition in the low Reynolds number regime of laminar flow in pebble beds has been explored previously, but with less powerful computational techniques. Some experimental data are also available in this regime. No analyses or experimental data are available in the high Reynolds number turbulent regime in which the PBMR operates. This paper describes results of analyses of inertial deposition obtained with the FLUENT computational fluid dynamics code. The objective of the analysis is to obtain an expression for deposition within an asymptotic unit cell, removed from the boundary conditions at the entrance to the array. The results of analyses performed at different velocities and fluid densities in the turbulent regime were correlated against a modified Stokes number. The deposition correlation is well represented by the integral form of the normal distribution. Deposition for the time-averaged flow was found to be insensitive to the flow model. In the laminar regime, FLUENT results were found to be in agreement with earlier published results and experimental data. The stochastic behavior of eddies was also simulated within FLUENT using the k–ε model. Eddy-enhanced deposition results in greater deposition at all aerosol sizes in comparison with the time-averaged results, with significant deposition of aerosols predicted for small aerosol sizes. However, it is likely that these results are quite sensitive to the modeling of turbulence and they must be considered preliminary.

Computational Fluid Dynamics and Thermal Analysis of Leaf Seals for Aero-engine Application

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Vincenzo Fico ◽  
Michael J. Pekris ◽  
Christopher J. Barnes ◽  
Rakesh Kumar Jha ◽  
David Gillespie
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Thermal Analysis ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Boundary Conditions ◽  
Thermal Boundary Conditions ◽  
Leaf Pack ◽  
Aero Engine

Aero-engine gas turbine performance and efficiency can be improved through the application of compliant shaft seal types to certain sealing locations within the secondary air system. Leaf seals offer better performance than traditional labyrinth seals, giving lower leakage flows at design duties. However, for aero-engine applications, seal designs must be able to cope with relatively large off-design seal closures and closure uncertainties. The two-way coupling between temperatures of seal components and seal closures, through the frictional heat generated at the leaf–rotor interface when in contact, represents an important challenge for leaf seal analysis and design. This coupling can lead to leaf wear and loss, rotor overheating, and possibly to unstable sealing system behavior (thermal runaway). In this paper, we use computational fluid dynamics (CFD), finite element (FE) thermal analysis, and experimental data to characterize the thermal behavior of leaf seals. This sets the basis for a study of the coupled thermomechanical behavior. CFD is used to understand the fluid-mechanics of a leaf pack. The leaf seal tested at the Oxford Osney Laboratory is used for the study. Simulations for four seal axial Reynolds number are conducted; for each value of the Reynolds number, leaf tip-rotor contact, and clearance are considered. Distribution of mass flow within the leaf pack, distribution of heat transfer coefficient (HTC) at the leaf surface, and swirl velocity pick-up across the pack predicted using CFD are discussed. The experimental data obtained from the Oxford rig is used to develop a set of thermal boundary conditions for the leaf pack. An FE thermal model of the rig is devised, informed by the aforementioned CFD study. Four experiments are simulated; thermal boundary conditions are calibrated to match the predicted metal temperatures to those measured on the rig. A sensitivity analysis of the rotor temperature predictions to the heat transfer assumptions is carried out. The calibrated set of thermal boundary conditions is shown to accurately predict the measured rotor temperatures.

Swirling Flow Through Venturi Tubes of Convergent Angle 10.5° and 21°

2006 ◽  
Author(s):  
Jeff Gibson ◽  
Michael Reader-Harris
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Good Agreement

Computational Fluid Dynamics (CFD) was used to compute the effect of two bends in perpendicular planes on the performance of 4-inch Venturi tubes with β = 0.4, 0.6 and 0.75 for water at a Reynolds number of 350,000 and at various distances from the bend. Two types of Venturi tubes were analysed, the first having a standard convergent angle of 21°, the second having a non-standard convergent angle of 10.5°. Good agreement with experiment was obtained. Swirling axisymmetric flows were computed to help interpret experimental data.

scholarly journals Thermoelectric Generation with Impinging Nano-Jets

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 492
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Mikhail A. Sheremet
Keyword(s):  
Fluid Dynamics ◽  
Power Generation ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Conversion Efficiency ◽  
Reynolds Numbers ◽  
Thermoelectric Generation ◽  
Volume Fractions ◽  
Water Jets ◽  
Conversion Efficiencies

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations (between (Re1, Re2) = (250, 250) to (1000, 1000)), horizontal distance of the jet inlet from the thermoelectric device (between (r1, r2) = (−0.25, −0.25) to (1.5, 1.5)), impinging jet inlet to target surfaces (between w2 and 4w2) and solid nanoparticle volume fraction (between 0 and 2%) on the interface temperature variations, thermoelectric output power generation and conversion efficiencies are numerically assessed. Higher powers and efficiencies are achieved when the jet stream Reynolds numbers and nanoparticle volume fractions are increased. Generated power and efficiency enhancements 81.5% and 23.8% when lowest and highest Reynolds number combinations are compared. However, the power enhancement with nanojets using highly conductive CNT particles is 14% at the highest solid volume fractions as compared to pure water jet. Impacts of horizontal location of jet inlets affect the power generation and conversion efficiency and 43% variation in the generated power is achieved. Lower values of distances between the jet inlets to the target surface resulted in higher power generation while an optimum value for the highest efficiency is obtained at location zh = 2.5ws. There is 18% enhancement in the conversion efficiency when distances at zh = ws and zh = 2.5ws are compared. Finally, polynomial type regression models are obtained for estimation of generated power and conversion efficiencies for water-jets and nanojets considering various values of jet Reynolds numbers. Accurate predictions are obtained with this modeling approach and it is helpful in assisting the high fidelity computational fluid dynamics simulations results.

scholarly journals Computational Fluid Dynamics for Flow around a Circular Cylinder in the Critical Reynolds Number Regime

2012 ◽  
Vol 68 (2) ◽  
pp. I_645-I_652
Author(s):  
Naoki Kasuya ◽  
Hirokazu Hirano ◽  
Akira Maruoka ◽  
Naotsugu Sato
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Critical Reynolds Number

Separation in oscillating laminar boundary-layer flows

1971 ◽  
Vol 47 (1) ◽  
pp. 21-31 ◽  
Author(s):  
R. A. Despard ◽  
J. A. Miller
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Reverse Flow ◽  
Oscillation Amplitude ◽  
Hot Wire ◽  
Boundary Layer Flows ◽  
Laminar Boundary Layers ◽  
History Of

The results of an experimental investigation of separation in oscillating laminar boundary layers is reported. Instantaneous velocity profiles obtained with multiple hot-wire anemometer arrays reveal that the onset of wake formation is preceded by the initial vanishing of shear at the wall, or reverse flow, throughout the entire cycle of oscillation. Correlation of the experimental data indicates that the frequency, Reynolds number and dynamic history of the boundary layer are the dominant parameters and oscillation amplitude has a negligible effect on separation-point displacement.

Efficiency limits of fans

2019 ◽  
Vol 234 (5) ◽  
pp. 739-748
Author(s):  
Konrad Bamberger ◽  
Thomas Carolus
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Geometrical Parameter ◽  
The Self ◽  
Complex Geometries ◽  
Relevant Parameter ◽  
Optimization Scheme ◽  
Loss Models ◽  
Definition Of

The purpose of this work is to identify upper efficiency limits of industrial fans such as axial rotor-only fans, axial with guide vanes, centrifugal rotor-only and centrifugal with volute. The efficiency limit is always a function of the class, the design point within the class and the definition of efficiency (total-to-static and total-to-total). The characteristic Reynolds number is another relevant parameter. First, based on analytical and empirical loss models, a theoretical efficiency limit is estimated. A set of idealizing assumptions in the loss models yields efficiencies which are assumed to be an insuperable limit but may be unrealistically high. Second, more realistic efficiency limits are estimated using a computational fluid dynamics-based optimization scheme, seeking for the best designs and hence the maximum achievable efficiencies in all classes. Given the self-imposed constraints in the geometrical parameter space considered, the thus-obtained practical efficiency limits can only be exceeded by admitting more complex geometries of the fans.

scholarly journals Impact of FO Operating Pressure and Membrane Tensile Strength on Draw-Channel Geometry and Resulting Hydrodynamics

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 111
Author(s):  
Alexander J. Charlton ◽  
Boyue Lian ◽  
Gaetan Blandin ◽  
Greg Leslie ◽  
Pierre Le-Clech
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Shear Rate ◽  
Membrane Surface ◽  
Forward Osmosis ◽  
Transmembrane Pressure ◽  
Channel Height ◽  
Operating Pressure ◽  
Channel Geometry

In an effort to improve performances of forward osmosis (FO) systems, several innovative draw spacers have been proposed. However, the small pressure generally applied on the feed side of the process is expected to result in the membrane bending towards the draw side, and in the gradual occlusion of the channel. This phenomenon potentially presents detrimental effects on process performance, including pressure drop and external concentration polarization (ECP) in the draw channel. A flat sheet FO system with a dot-spacer draw channel geometry was characterized to determine the degree of draw channel occlusion resulting from feed pressurization, and the resulting implications on flow performance. First, tensile testing was performed on the FO membrane to derive a Young’s modulus, used to assess the membrane stretching, and the resulting draw channel characteristics under a range of moderate feed pressures. Membrane apex reached up to 67% of the membrane channel height when transmembrane pressure (TMP) of 1.4 bar was applied. The new FO channels considerations were then processed by computational fluid dynamics model (computational fluid dynamics (CFD) by ANSYS Fluent v19.1) and validated against previously obtained experimental data. Further simulations were conducted to better assess velocity profiles, Reynolds number and shear rate. Reynolds number on the membrane surface (draw side) increased by 20% and shear rate increased by 90% when occlusion changed from 0 to 70%, impacting concentration polarisation (CP) on the membrane surface and therefore FO performance. This paper shows that FO draw channel occlusion is expected to have a significant impact on fluid hydrodynamics when the membrane is not appropriately supported in the draw side.

scholarly journals Theoretical Analysis of Brush Seals Leakage Using Local Computational Fluid Dynamics Estimated Permeability Laws

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Lilas Deville ◽  
Mihai Arghir
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Principal Direction ◽  
Experimental Results ◽  
Leakage Flow ◽  
Cfd Analysis ◽  
Brush Seal ◽  
Brush Seals ◽  
Local Reynolds Number

Brush seals are a mature technology that has generated extensive experimental and theoretical work. Theoretical models range from simple correlations with experimental results to advanced numerical approaches coupling the bristles deformation with the flow in the brush. The present work follows this latter path. The bristles of the brush are deformed by the pressure applied by the flow, by the interference with the rotor and with the back plate. The bristles are modeled as linear beams but a nonlinear numerical algorithm deals with the interferences. The brush with its deformed bristles is then considered as an anisotropic porous medium for the leakage flow. Taking into account, the variation of the permeability with the local geometric and flow conditions represents the originality of the present work. The permeability following the principal directions of the bristles is estimated from computational fluid dynamics (CFD) calculations. A representative number of bristles are selected for each principal direction and the CFD analysis domain is delimited by periodicity and symmetry boundary conditions. The parameters of the CFD analysis are the local Reynolds number and the local porosity estimated from the distance between the bristles. The variations of the permeability are thus deduced for each principal direction and for Reynolds numbers and porosities characteristic for brush seal. The leakage flow rates predicted by the present approach are compared with experimental results from the literature. The results depict also the variations of the pressures, of the local Reynolds number, of the permeability, and of the porosity through the entire brush seal.

scholarly journals Modelling of working processes of non-contact oil free vacuum pumps by computational fluid dynamics (CFD) methods

2021 ◽  
Vol 2059 (1) ◽  
pp. 012003
Author(s):  
A Burmistrov ◽  
A Raykov ◽  
S Salikeev ◽  
E Kapustin
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Mathematical Models ◽  
Cfd Models ◽  
Ansys Cfx ◽  
Sst Turbulence Model ◽  
Computational Fluid Dynamics Cfd ◽  
Dynamic Meshing ◽  
Comparison With Experimental Data

Abstract Numerical mathematical models of non-contact oil free scroll, Roots and screw vacuum pumps are developed. Modelling was carried out with the help of software CFD ANSYS-CFX and program TwinMesh for dynamic meshing. Pumping characteristics of non-contact pumps in viscous flow with the help of SST-turbulence model were calculated for varying rotors profiles, clearances, and rotating speeds. Comparison with experimental data verified adequacy of developed CFD models.

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