Deposition Velocity and Penetration Efficiency in a Square Channel Using a Lagrangian-Based Modeling Approach

2020 ◽  
Author(s):  
Byung-Hee Choi ◽  
Daniel Orea ◽  
Thien Nguyen ◽  
N. K. Anand ◽  
Yassin Hassan ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Numerical Study ◽  
Numerical Technique ◽  
Deposition Velocity ◽  
Stokes Number ◽  
Department Of Energy ◽  
Main Stream ◽  
Proof Of Concept ◽  
Square Channel ◽  
Lagrangian Framework

Abstract Texas A&M University is working on the development of gas cooled fast reactor cartridge loop under the Department of Energy VTR program. Our research project aims to develop and implement techniques to quantify the transport and deposition of particle inside the cartridge loop. Before the developed techniques are applied in a complicated actual facility, it is essential to verify and validate their performance using numerical simulations and to quantify their uncertainties. This article presents a numerical study of particle transport and deposition in a proof-of-concept facility. The proof-of-concept facility houses a series of three square duct test sections, each of which has a cross-section of 3 in.2 and a length of 24 in., for a combined total length of 72 in. The numerical simulation domain is based on the geometrical dimensions of the experimental facility. The main stream in the channel is solved using the Eulerian turbulence model, and the particle motion is interpreted in the Lagrangian framework. It is assumed that a well-mixed air–particle mixture at a constant temperature is injected into the horizontal channel. Lagrangian simulations of surrogate particles allow us to understand their behavior precisely. The Reynolds stress model is selected to reproduce the secondary flow and the associated secondary drag force. The state-of-the-art Lagrangian approach, in combination with a random walk model coupled with a computational fluid dynamics model, is employed to investigate the behaviors of the surrogate particles within the square channel. Gravitational settling is also considered. The deposition velocity and penetration efficiency are estimated for representing the characteristics of particle deposition in the proof-of-concept facility. Because the conventional method of measuring the deposition velocity is based on the Eulerian framework, it is not suitable for direct adoption in the Lagrangian framework. This study proposes a numerical technique to measure the deposition velocity; this technique can be efficiently used in the Lagrangian framework of the simulation. The results agree well with both our experimental measurements and correlations available in the literature. Using this technique, the correlations for the deposition velocity are established as functions of the normalized channel length, Stokes number, and Reynolds number. Finally, the relationship between the deposition velocity and penetration efficiency is examined, and a correlation is proposed. Consequently, the penetration efficiency can be directly compared with several conventional reference data based on the deposition velocity.

scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

Experimental Study of Surrogate Particle Transport and Deposition in a Square Channel Using Particle Tracking Technique

2019 ◽  
Author(s):  
Daniel Orea ◽  
Thien Nguyen ◽  
Rodolfo Vaghetto ◽  
N. K. Anand ◽  
Yassin A. Hassan ◽  
...  
Keyword(s):  
Experimental Study ◽  
Fluid Flow ◽  
Particle Tracking ◽  
Particle Transport ◽  
Particle Deposition ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Test Facility ◽  
Square Channel ◽  
Fluid Flow Characteristics

Abstract This paper presents an experimental study of hydrodynamics flow characteristics and particle transport in a test facility. Experimental measurements of fluid flow and particle deposition are studied under isothermal conditions using particle image velocimetry (PIV) and particle tracking velocimetry (PTV) techniques. These non-intrusive optical measurement techniques have been applied in experiment conditions of Reynolds number Re = 5,077 in a 3-inch square channel and 72-inches in total length. The fluid within the channel is air seeded with aerosol droplets while the measurements of particle transport is facilitated using surrogate particles dispersed in the channel flow. Results obtained from the PIV and PTV measurements included the hydrodynamics fluid flow characteristics, and characteristics of particle transports, such as particle velocity, particle diameter distributions and particle concentration profiles. Results from the preliminary test have shown 11.08% deposition of particles. To supplement this experimental work, upstream fluid flow characteristics were provided as boundary conditions for a comparable numerical study.

Effect of Blowing Ratio on Syngas Flyash Particle Deposition on a Three-Row Leading Edge Film Cooling Geometry Using Large Eddy Simulations

2009 ◽  
Author(s):  
Sai Shrinivas Sreedharan ◽  
Danesh K. Tafti
Keyword(s):  
Film Cooling ◽  
Particle Deposition ◽  
Numerical Study ◽  
Leading Edge ◽  
Stagnation Region ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Lagrangian Framework ◽  
Large Eddy ◽  
Turbine Vane

A numerical study is performed to investigate deposition and erosion of Syngas ash in the leading edge region of a turbine vane. The leading edge of the vane is modeled as a symmetric semi-cylinder with a flat after body. Three rows of coolant holes located at stagnation and at ±21.3° from stagnation are simulated at blowing ratios of 0.5, 1.0, 1.5 and 2.0. Large Eddy Simulation (LES) is used to model the flow field of the coolant jet-mainstream interaction and syngas ash particles are modeled using a Lagrangian framework. Ash particle sizes of 5 and 7 micron are considered. Under the conditions of the current simulations, both ash particles have Stokes numbers less than unity of O(1) and hence are strongly affected by the flow and thermal field generated by the coolant interaction with the mainstream. Because of this, the stagnation coolant jets are quite successful in pushing the particles away from the surface and minimizing deposition and erosion in the stagnation region. Overall, about 10% of the 5 μm particles versus 20% of the 7 μm particles are deposited on the surface at B.R. = 0.5. An increase to B.R. = 2, increases deposition of the 5 micron particles to 14% while decreasing deposition of the 7 micron particles to 15%. Erosive ash particles of 5 μm size increase from 5% of the total to 10% as the blowing ratio increases from 0.5 to 2.0, whereas 7 μm erosive particles remain nearly constant at 15%. Overall, for particles of size 5 μm, there is a combined increase in deposition and erosive particles from 16% to 24% as the blowing ratio increases from 0.5 to 2.0. The 7 μm particles, on the other hand decrease from 35% to about 30% as the blowing ratio increases from 0.5 to 2.

Numerical Study of Particle Transport and Deposition in a Horizontal Channel Using a Lagrangian-Based Modelling Approach

2019 ◽  
Author(s):  
Byung-Hee Choi ◽  
Daniel Orea ◽  
Thien Nguyen ◽  
N. K. Anand ◽  
Yassin Hassan ◽  
...  
Keyword(s):  
Particle Transport ◽  
Numerical Study ◽  
Measurement Techniques ◽  
Horizontal Channel ◽  
Primary System ◽  
Main Stream ◽  
Experimental Facility ◽  
Square Channel ◽  
Reactor Building ◽  
Test Reactor

Abstract Texas A&M University is participating in the U.S. Department of Energy (DOE) Office of Nuclear Energy’s Versatile Test Reactor (VTR) program to develop instrumentation and tools for a proposed fast spectrum test reactor. Our research project aims to develop and implement techniques to quantify the transport and deposition of fission products in the primary system of Gas Fast Reactors (GFRs) and ultimately in the reactor confinement. Developed techniques will be performed and tested in the NGNP Reactor Building experimental facility, which was previously 1/28 downscaled from General Atomics 350 MWth and built to study the reactor building responses to depressurization accidents. Prior to applying the techniques to the scaled facility, it is essential to verify and validate the performance of developing techniques using numerical simulations and quantify their associated uncertainties. This manuscript presents our numerical study of particle transport and deposition in an experimental channel. The channel has three test sections, each has 3-inch square cross-section, 24 inches in length for a combined total length of 72 inches. The experimental facility is built using transparent materials, allowing the applications of non-intrusive, laser-based measurement techniques, such as Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV). Details of the experimental setup, measurement techniques, and results of flow field characteristics and particle transports in the channel will be presented in an accompanied manuscript. The simulation domain is built upon the geometrical dimensions of the experimental facility, while upstream flow characteristics of the square channel obtained by PIV measurements are used as boundary conditions. State-of-the-art Lagrangian approach with random walk model is employed to investigate behaviors of surrogate particles within the square channel, coupled with computational fluid dynamics (CFD) model. While the main stream in the channel is solved by Eulerian turbulent model, motion of particles is tracked in Lagrangian framework. It is assumed that well-mixed air-particle mixture at a constant temperature is injected into the horizontal channel. Drag force, gravity force and turbophoresis force are adapted on this simulation and their competition are investigated. Comparisons and validations of simulations and measurements on the flow fields downstream of the channel and characteristics of particle transports and depositions within the square channel will be systematically investigated. Experimental and numerical uncertainties will be quantified using the accepted standard approaches.

PRELIMINARY STUDY ON NOVEL BEAM-TO-COLUMN CONNECTION BASED ON SMA PLATE

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Michael CH Yam ◽  
Ke Ke ◽  
Ping Zhang ◽  
Qingyang Zhao
Keyword(s):  
Friction Coefficient ◽  
Energy Dissipation ◽  
Numerical Study ◽  
Numerical Models ◽  
Numerical Technique ◽  
The Self ◽  
Hysteretic Behavior ◽  
The Novel ◽  
Energy Dissipation Capacity ◽  
Preliminary Study

A novel beam-to-column connection equipped with shape memory alloy (SMA) plates has been proposed to realize resilient performance under low-to-medium seismic actions. In this conference paper, the detailed 3D numerical technique calibrated by the previous paper is adopted to examine the hysteretic behavior of the novel connection. A parametric study covering a reasonable range of parameters including the thickness of the SMA plate, friction coefficient between SMA plate and beam flange and pre-load of the bolt was carried out and the influence of the parameters was characterized. In addition, the effect of the SMA Belleville washer on the connection performance was also studied. The results of the numerical study showed that the initial connection stiffness and the energy-dissipation capacity of the novel connection can be enhanced with the increase of the thickness of the SMA plate. In addition, the initial connection stiffness and energy-dissipation behavior of the novel connection can be improved by increasing the friction coefficient or pre-load of bolts, whereas the increased friction level could compromise the self-centering behavior of the connection. The hysteretic curves of the numerical models of the connection also implied that the SMA washers may contribute to optimizing the connection behavior by increasing the connection stiffness and energy-dissipation capacity without sacrificing the self-centering behavior.

The Influence of Volume Surface Ratio of Rectangle Air-Conditioning Duct on Particle Deposition

2011 ◽  
Vol 71-78 ◽  
pp. 3633-3638 ◽  
Author(s):  
Jie Zhang ◽  
Ze Hua Liu ◽  
Yuan Quan Liu ◽  
Hui Min Li ◽  
Yong Fei Ning
Keyword(s):  
Cross Section ◽  
Air Conditioning ◽  
Particle Deposition ◽  
Deposition Velocity ◽  
Vertical Wall ◽  
Influence Factors ◽  
Particle Model ◽  
Random Trajectory ◽  
Air Speed ◽  
The Given

This paper discusses particle deposition in rectangle air-conditioning duct using RSM (Reynold Stress Model) and random trajectory particle model. Particle with nominal diameters of 10-200μm are simulated at each of three nominal air speed: 4m/s, 6m/s and 8m/s, respectively, in the cross-section sizes of 160×120, 500×250, 1000×320mm. In simulation, the paper compares and analyzes the influence factors of particles deposition in volume surface ratio of the given duct. The results show that: 1) particle deposition velocity increases with volume surface ratio; 2) As the inlet air speed increasing, when the particles deposited to floor and vertical wall, the image of dimensionless deposition velocity Vs dimensionless relaxation time shows a coincident trend when the duct cross-section sizes are 500×250, 1000×320mm, but has great differences with the image of 160×120mm.

Optimized Chaotic Heat Exchanger Configurations for Process Industry: A Numerical Study

2013 ◽  
Author(s):  
Akram Ghanem ◽  
Thierry Lemenand ◽  
Dominique Della Valle ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Process Intensification ◽  
Point Of View ◽  
Square Duct ◽  
Square Channel ◽  
Duct Geometry

A numerical investigation of chaotic laminar flow and heat transfer in isothermal-wall square-channel configurations is presented. The computations, based on a finite-volume method with the SIMPLEC algorithm, are conducted in terms of Péclet numbers ranging from 7 to 7×105. The geometries, based on the split-and-recombine (SAR) principle, are first proposed for micromixing purposes, and are then optimized and scaled up to three-dimensional minichannels with 3-mm sides that are capable of handling industrial fluid manipulation processes. The aim is to assess the feasibility of this mass- and heat-transfer technique for out-of-laboratory commercial applications and to compare different configurations from a process intensification point of view. The effects of the geometry on heat transfer and flow characteristics are examined. Results show that the flux recombination phenomenon mimicking the baker’s transform in the SAR-1 and SAR-2 configurations produces chaotic structures and promotes mass transfer. This phenomenon also accounts for higher convective heat transfer exemplified by increased values of the Nusselt number compared to the chaotic continuous-flow configuration and the baseline plain square-duct geometry. Energy expenditures are explored and the overall heat transfer enhancement factor for equal pumping power is calculated. The SAR-2 configuration reveals superior heat-transfer characteristics, enhancing the global gain by up to 17-fold over the plain duct heat exchanger.

Flow structures and particle deposition patterns in double-bifurcation airway models. Part 2. Aerosol transport and deposition

2001 ◽  
Vol 435 ◽  
pp. 55-80 ◽  
Author(s):  
J. K. COMER ◽  
C. KLEINSTREUER ◽  
C. S. KIM
Keyword(s):  
Particle Deposition ◽  
Air Flow ◽  
Reynolds Numbers ◽  
Companion Paper ◽  
Stokes Number ◽  
Vortical Flow ◽  
Flow Structures ◽  
Particle Distributions ◽  
Deposition Patterns ◽  
Inlet Conditions

The flow theory and air flow structures in symmetric double-bifurcation airway models assuming steady laminar, incompressible flow, unaffected by the presence of aerosols, has been described in a companion paper (Part 1). The validated computer simulation results showed highly vortical flow fields, especially around the second bifurcations, indicating potentially complex particle distributions and deposition patterns. In this paper (Part 2), assuming spherical non-interacting aerosols that stick to the wall when touching the surface, the history of depositing particles is described. Specifically, the finite-volume code CFX (AEA Technology) with user-enhanced FORTRAN programs were validated with experimental data of particle deposition efficiencies as a function of the Stokes number for planar single and double bifurcations. The resulting deposition patterns, particle distributions, trajectories and time evolution were analysed in the light of the air flow structures for relatively low (ReD1 = 500) and high (ReD1 = 2000) Reynolds numbers and representative Stokes numbers, i.e. StD1 = 0.04 and StD1 = 0.12. Particle deposition patterns and surface concentrations are largely a function of the local Stokes number, but they also depend on the fluid–particle inlet conditions as well as airway geometry factors. While particles introduced at low inlet Reynolds numbers (e.g. ReD1 = 500) follow the axial air flow, secondary and vortical flows become important at higher Reynolds numbers, causing the formation of particle-free zones near the tube centres and subsequently elevated particle concentrations near the walls. Sharp or mildly rounded carinal ridges have little effect on the deposition efficiencies but may influence local deposition patterns. In contrast, more drastic geometric changes to the basic double-bifurcation model, e.g. the 90°-non-planar configuration, alter both the aerosol wall distributions and surface concentrations considerably.

Simulation of Two Designs of Micro-Mixers With Enhanced Advection Mechanisms

2011 ◽  
Author(s):  
S. A. Kazemi ◽  
M. Passandideh-Fard ◽  
J. Esmaeelpanah
Keyword(s):  
Numerical Study ◽  
Control Volume ◽  
Numerical Technique ◽  
Chaotic Advection ◽  
Mixing Efficiency ◽  
Mixing Length ◽  
Surface Development ◽  
Mixer Design ◽  
Gas Liquid Flow ◽  
Micro Mixer

In this paper, a numerical study of two new designs of passive micro-mixers based on chaotic advection is presented. The advection phenomenon in a T-shaped micro-mixer is enhanced using a segmented gas-liquid flow; and a peripheral/axial mixing mechanism. The simulations are performed for two non-reactive miscible gases: oxygen and methanol. The numerical model employed for this study is based on the solution of the physical governing equations namely the continuity, momentum, species transport and an equation to track the free surface development. The equations are discretized using a control volume numerical technique. The distribution of the species concentration within the domain is calculated based on which a mixing intensity factor is introduced. This factor is then used as a criterion for the mixing length. In the first micro-mixer design with a drop injection mechanism for a typical condition, the mixing length is reduced by nearly 15%. Compared to that of a simple T-shaped micro-mixer with the same flow rates, the two gases interface area is increased in axisymmetric micro-mixer leading to an increase of the mixing efficiency and a reduction of the mixing length. Also, the effects of the baffles height and span on the mixing efficiency and length in axisymmetric micro-mixer are studied. Having baffles in the channel can substantially decrease the mixing length.

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