Flow Of Solid-liquid Mixtures Research Articles

Current Situation and Prospect of Erosion Wear

The material loss and equipment failure caused by erosion wear is a serious problem in solid-liquid mixture flow in the mechanical, metallurgy, energy, building materials, transportation, aviation, aerospace, military and other industrial departments. Therefore, understanding the erosion wear mechanism, the influencing factors, and how to set up mathematical model are very important. Since the 1950s, the research on the erosion wear made great development. The purpose of this paper is to give a comprehensive review about previous research work of erosion wear. Firstly, the mechanism and influencing factors of erosion wear are introduced. Secondly, the forces of particle caused by fluid are analysed and several erosion models which tested by experimental with good results are introduced. Thirdly, the method of erosion numerical simulation combining computer software and CFD theory is introduced. Finally, based on the conclusion, some useful conclusions are drawn and the future research direction is prospected.

Optimization and erosion wear response of slurry pipeline material with and without coating

Background / Objectives: In this paper, erosion wear response of slurry pipeline material is optimized by utilizing Taguchi’s experimental technique. Methods / Statistical Analysis: The investigation of erosion wear due to solid–liquid mixture flow took place with the assistance of a slurry erosion pot tester. The pipe material namely stainless steel SS-317L is utilized to lead the erosion tests. This erosion test is set up to impact the rotational speed, solid concentration and time with multi sized slurry. Fly ash was utilized as the erodent material. Findings: In these erosion tests, four experiments were performed. These four tests are performed at four different speeds 600, 850, 1100 & 1350 rpm and the concentration of solid-liquid mixture is 30%, 40%, 50 & 60% with time duration of these experiments are 60, 120, 180 and 240 min. Improvements / Applications: For protective coating, High-velocity oxygen-fuel (HVOF) spray process is used for depositing to coating powders Stellite-6 and WC - 12Co - 4Cr on the material namely stainless steel SS-317L. The S/N ratio of with and without HVOF coating of SS-317L varies from 44.88 to 29.77 (Uncoated), 64.43 to 37.09 (Stellite-6) and 80.00 to 49.25 (WC-12Co-4Cr) respectively. Rotational speed was resolved as one of the predominant factor which impacts the erosion wear response of SS-317L. Keywords: Erosion wear, Fly ash, HVOF sprayed coating (Stellite-6 and WC-12Co-4Cr), Optimization, Rotational Speed, Stainless Steel (SS-317L), Taguchi methodetc.

Improvement of a physical model for blockage formation of solid–liquid mixture flow with freezing for core safety evaluation of SFRs

ABSTRACT The SIMMER code has been developed to analyze event progression during core disruptive accidents (CDAs) in sodium-cooled fast reactors. One of the key phenomena during CDAs is the discharge of molten fuel from the core region which reduces the reactivity effectively. The discharge flow is inhibited by blockage formation due to freezing of the molten fuel. Then, the blockage formation is enhanced by unmolten fuel which forms solid–liquid mixture flow with the molten fuel. A physical model for blockage formation of solid–liquid mixture flow with freezing in the SIMMER code is improved in this study to dissolve some inconsistencies between the modeling and the physical phenomena involved in the solid–liquid mixture flow with freezing for more precise evaluation of CDA. The improved model is validated with a systematical procedure through a benchmark analysis of an experiment. Consequently, experimental penetration behaviors are simulated reasonably by the SIMMER code analysis with the improved model while excessive blockage formation occurred in the analysis with the original model.

Sensitivity Analysis of Depth-Integrated Numerical Models for Estimating Landslide Movement

Landslides are natural phenomena that occur in slopes with thick layers of weathered soil or weak geological formations. High intensity of precipitation, earthquake, and human interference can cause a huge landslide disaster. To mitigate landslide risk, an appropriate investigation to determine the stability and movement mechanisms is important to predict its potential scale. This paper proposes a sensitivity analysis of depth-integrated numerical model of landslide movement by implementing solid friction and fluid friction as the shear resistance in the constitutive systems. The hyperconcentrated solid-liquid mixture flow model and Voellmy-fluid friction model are employed in the solid friction and fluid friction mechanism, whereas the Mohr-Coulomb model is used in the solid friction mechanism. In order to analyze model characteristics and sensitivity to the inputted parameters, the parametric studies on an imaginary slope were examined. The results show that the internal friction angle among input data strongly affects the runout distance and moving velocity. The Voellmy-fluid friction model produces more lateral tendency and wider deposit in transversal directions of landslide compared to other models. The numerical model along with three constitutive equations of shear resistance was applied to the Bishamon Landslide. The hyperconcentrated solid-liquid mixture flow model and Mohr-Coulomb model yield a good agreement with the actual deposition area, whereas the Voellmy-fluid friction model produces more lateral tendency in transversal directions. The calculated runout distance reaches more than 350 m and 10.3 to 13.9 m/s of maximum velocity.

Recent Research Status on Erosion Wear – An Overview

Material loss due to erosion wear is a serious problem associated with flow of solid-liquid mixtures. Slurry erosion limits the useful life of equipment and is therefore a critical parameter for design, selection and operation of the hydraulic transportation system. Engineering interest is to estimate the service life of equipment / components subjected to slurry erosion and to investigate the possibilities of enhancement of their life. To being with the research work, it is essential for a researcher to get acquainted with previous investigation carried out in the relevant domain. Hence, present overview is intended to put forward the various type of test rig used for the experimental work by various researchers. Also explore the effect of tribological parameters on erosion wear mainly slurry erosion like target material, erodent material, impact angle, impact velocity, particle size and solid concentration. Finally, some inference drowns from an overview and concludes future research scope that will be helpful to a new researcher in the field of slurry erosion wear.

Erosion Wear in A Slurry Pipe With Multisized Coal And Bottom-Ash Slurries

Presently, Erosion wear is one of the major problems in slurry transportation system affecting both initial cost and life of its components. In the present work, erosion wear due to solid–liquid mixture flow has been studied using a slurry erosion pot tester. The erosion tests have been conducted on two pipe materials namely mild steel and stainless steel (SS-304) to establish the influence of solid concentration and rotational speed. The erodent material was taken as coal and bottom ash. The solid concentration of the coal and bottom ash slurry was varies from 30-50% (by weight).The experiments were performed at four different speeds namely 500,800,1100 and 1400 rpm with time duration of 90 minutes. The test results obtained in terms of weight loss have shown that wear has a strong dependence on rotational speed, solid concentration and nature of piping materials.

Simulation of Reynolds number influence on heat exchange in turbulent flow of medium slurry

The paper deals with the numerical simulation of mass and heat exchange in turbulent flow of solid-liquid mixture in the range of averaged solid particle diameter from 0.10mm to 0.80mm, named further as the medium slurry. Physical model assumes that dispersed phase is fully suspended and a turbulent flow is hydro-dynamically, and thermally developed in a straight horizontal pipeline. Taking into account the aforementioned assumptions the slurry is treated as a single-phase flow with increased density, while viscosity is equals to a carrier liquid viscosity. The mathematical model constitutes time averaged momentum equation in which the turbulent stress tensor was designated using a two-equation turbulence model, which makes use of the Boussinesq eddy-viscosity hypothesis. Turbulence damping function in the turbulence model was especially designed for the medium slurry. In addition, an energy equation has been used in which a convective term was determined from the energy balance acting on a unit pipe length, assuming linear changes of temperature in main flow direction. Finally, the mathematical model of non-isothermal medium slurry flow comprises four partial differential equations, namely momentum and energy equations, equations of kinetic energy of turbulence and its dissipation rate. Four partial differential equations were solved by a finite difference scheme using own computer code. The objective of the paper is to examine the influence of Reynolds number on temperature profiles and Nusselt number in turbulent flow of medium slurry in the range of solids concentration from 0% to 30% by volume. The effect of influential factors on heat transfer between the pipe and slurry is analysed. The paper demonstrates substantial impact of Reynolds number and solids volume fraction on the Nusselt number. The results of numerical simulation are reviewed.

Development of a design methodology for hydraulic pipelines carrying rectangular capsules

The scarcity of fossil fuels is affecting the efficiency of established modes of cargo transport within the transportation industry. Efforts have been made to develop innovative modes of transport that can be adopted for economic and environmental friendly operating systems. Solid material, for instance, can be packed in rectangular containers (commonly known as capsules), which can then be transported in different concentrations very effectively using the fluid energy in pipelines. For economical and efficient design of such systems, both the local flow characteristics and the global performance parameters need to be carefully investigated. Published literature is severely limited in establishing the effects of local flow features on system characteristics of Hydraulic Capsule Pipelines (HCPs). The present study focuses on using a well validated Computational Fluid Dynamics (CFD) tool to numerically simulate the solid-liquid mixture flow in both on-shore and off-shore HCPs applications including bends. Discrete Phase Modelling (DPM) has been employed to calculate the velocity of the rectangular capsules. Numerical predictions have been used to develop novel semi-empirical prediction models for pressure drop in HCPs, which have then been embedded into a robust and user-friendly pipeline optimisation methodology based on Least-Cost Principle.

Computational fluid dynamics based optimal design of hydraulic capsule pipelines transporting cylindrical capsules

Rapid depletion of energy resources has immensely affected the transportation sector, where the cargo transportation prices are rising considerably each year. Efforts have been made to develop newer modes of cargo transportation worldwide that are both economical and efficient for a long time. One such mode is the use of energy contained within fluids that flows in the pipelines for transportation of bulk solids. After appropriate modifications to these pipelines, bulk solids can be transported from one location to another very effectively. Solid material can be stored in cylindrical containers (commonly known as capsules), which can then be transported, either singly or in a train through the pipeline. Both the local flow characteristics and global performance parameters associated with such pipelines need careful investigation for economical and efficient system design. Published literature is severely limited in establishing the effects local flow features on system characteristics of hydraulic capsule pipelines (HCPs). The present study focuses on using a well validated computational fluid dynamics (CFD) tool to numerically simulate the solid–liquid mixture flow in HCPs, installed both on-shore and off-shore, along-with the pipe bends. Local static pressure fields have been discussed in detail for a wide range of geometrical and flow related parameters associated with the capsules and the pipelines. Numerical predictions have been used to develop novel semi-empirical prediction models for pressure drop in HCPs, which have then been embedded into a pipeline optimisation methodology that is based on Least-Cost Principle. This novel optimisation methodology that has been developed for HCPs is both robust and user-friendly.

Development of Correlations for Predicting the Slurry Erosion of Ductile Materials

Material loss due to erosion is a serious problem associated with the flow of solid-liquid mixtures. In the present work, erosion wear tests have been carried out in a slurry pot tester for seven different ductile type materials namely aluminum alloy (AA6063), copper, brass, mild steel, AISI 304L stainless steel, AISI 316L stainless steel, and turbine blade grade steel using three different erodents namely, quartz, alumina, and silicon carbide. Experiments have been performed at different orientation angles of target material at the velocities of 3, 6, and 8.33 m/s for solid concentrations of 10%, 20%, and 30% (by weight) and particle sizes of 363, 550, and 655 μm. The contribution of cutting wear in the total wear of ductile material at various orientation angles has been determined. It is observed that the maximum cutting wear angle for the ductile material depends on its hardness and a correlation is developed for its prediction. Also a methodology is proposed for estimation of the total erosion wear rate as a contribution of cutting and deformation wear rates. It is seen that this procedure results in an error of ±18% in estimation of erosion wear rate for the present experimental data.

Solid-liquid mixture flow through a slim hole annulus with rotating inner cylinder

An experimental study was conducted to study solid-liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with rotating inner cylinder. Lift forces acting on a fluidized particle play a central role in many important applications, such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs and sediment transport, etc. Annular fluid velocities varied from 0.4 m/s to 1.2 m/s. Effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in the slim hole annulus have been measured for fully developed flows of water and of aqueous solutions of sodium carboxymethyl cellulose (CMC) and bentonite, respectively. For higher particle feed concentration, the hydraulic pressure drop of mixture flow increases due to the friction between the wall and solids or among solids.

Superplasticity and Deformation Mechanism of LD10 Aluminium Alloy

The commercial hot-rolled bars of LD10 alloy (grain size 25~75µm) are pretreated via proper recrystallization annealing (temperature 380°C, 420°C and 460°C) and solution annealing (temperature 500°C). The average elongation is increased from 158% to 270%, 223%, 219% and 233% respectively and the maximum elongation is 321% (500°C, 3.3×10-4s-1). The test results show that the alloy can present certain superplasticity owing to structural effect of dynamic recrystallization refining during superplastic deformation of coarse-grained LD10 alloy. Large and deep cavities form in grain boundaries and result in intergranular fracture after larger superplastic tensile deformation. And a large amount of metal filaments appear on grain surfaces. The formation of filaments is attributed to viscous flow of solid-liquid mixture in grain boundaries caused by grain-boundary sliding. The appearance of solid-liquid mixture makes grain-boundary sliding easier.

EFFECT OF HOLDING TUBE CONFIGURATION ON THE RESIDENCE TIME DISTRIBUTION OF MULTIPLE PARTICLES IN HELICAL TUBE FLOW

ABSTRACTThe flow of solid‐liquid mixtures in a novel tube configuration was investigated and the results were compared to those obtained with a single‐helical tube configuration. Residence time distribution (RTD) of polystyrene and acrylic particles as affected by different processing parameters was determined. The studied parameters included flow rate, carrier fluid consistency, particle concentration, and curvature ratio of the helical tube. Curvature ratio and flow rate were found to be the most important factors affecting the RTD of particles. Interactions between particles appeared to be important, as the RTD of acrylic particles decreased significantly whereas that of polystyrene particles increased slightly upon mixing the two types of particles.

Variation of Wear along the Volute Casing of a Centrifugal Slurry Pump.

Erosion wear at various locations inside the volute casing of a centrifugal slurry pump has been measured for the flow of solid-liquid mixtures. The measurements show that the wear increases all along the volute periphery with increase in the amount of solids suspended in the mixture. It is also observed that the wear is smaller when the pump operates near the best efficiency point flowrate (BEP) compared to that at lower flowrate.

Particle velocity profiles for solid-liquid food flows in vertical pipes part I. Single particles

Many food processing operations involve the flow of solid-liquid mixtures, often with simultaneous heat transfer. Prediction of the effects of processing requires understanding of the heat transfer and flow properties of the two phases. The fluid mechanics literature contains much information on the radial migration of particles in vertical flow, but it is not certain how this might apply to food processing. A series of experiments has been carried out to study the behaviour of single food simulant particles (5–10 mm) in carboxymethyl cellulose (CMC) solutions, in 44 mm vertical pipes, to study whether migration occurs. Results confirm that migration can be significant in laminar flows of food fluids: effects are greater for larger particles of high density flowing in low viscosity fluids.

Flow of solid-liquid mixtures in inclined pipes

The prediction of the flow characteristics of solid-liquid mixtures in inclined pipes has much practical importance, since long distance pipelines are bound to contain inclined sections. The three-layer model of Doron and Barnea (1993) was extended to account for the angle of inclination, which is expected to affect both the pressure drop and the limit deposit velocity. The extended model reproduces satisfactorily new experimental data as well as data of previous investigators. The additional effect of the gravitational force induces higher pressure gradients together with higher limit deposit velocity as the pipe's upward tilt is increased. For downwards inclination, the limit deposit velocity decreases drastically, and the pressure drop is reduced, since for downflow gravitation acts as a driving force.

Bed-load Rate in View of Two Phase Flow Dynamics

Discussions are made on the flow with bed-loads as well as on bed-load transport rates in view of solid-liquid two phase flow dynamics. Dynamic and kinematic conditions of the bottom or the interface between moving layer and non-moving one are described using constitutive relations of debris flows and momentum conservation equation. The equations governing flow field are derived, and solved numerically for velocity profile, sediment concentration profile, thickness of solid-liquid mixture flow, flow resistance, and sediment transport rates. These results emphasize that the flow with bed loads can be specified as a limit of debris flows.

Direct simulation of flows of solid-liquid mixtures

A finite element technique based on moving unstructured grids is developed to simulate the motion of a large number of solid particles in a flowing liquid. A generalized Galerkin finite element formulation which incorporates both the fluid and particle equations of motion into a single variational equation is developed for Newtonian fluids. The hydrodynamic forces and moments acting on the solid particles are eliminated in the formulation, so need not be computed explicitly. An arbitrary Lagrangian-Eulerian (ALE) technique is adopted to deal with the motion of the particles. In the implementation, the nodes on the particle surface are assumed to move with the particle. The nodes in the interior of the fluid are computed using Laplace's equation, to guarantee a smoothly varying distribution of the nodes. At each time step, the grid is updated according to the motion of the particles and checked for element degeneration. If unacceptable element distortion is detected, a new finite element grid is generated and the flow fields are projected from the old grid to the new grid. This generalized ALE Galerkin finite element approach gives rise to a set of non-linear algebraic equations which is solved via a quasi-Newton scheme. The corresponding linearized system is solved with an iterative solver using a preconditioned generalized minimal residual algorithm. Initially, the particles are positioned randomly in the fluid, with zero velocity. The particles are then released and the motion of the combined fluid-particle system is simulated using a procedure in which the positions of the particles and of the mesh grids are updated explicitly, while the velocities of the fluid and the solid particles are determined implicitly. Using the developed numerical procedure, we study the Poiseuille flow of solid-liquid mixtures in a vertical channel. The computation is performed within a unit cell which is periodic in the direction along the channel. The gravity is directed along the channel walls, and a pressure gradient is applied against the gravity and drives the flow. The solid particles are slightly heavier than the liquid. The effects of the applied pressure gradient, the particle Reynolds number and the fraction of the solid loading on the flow pattern of the solid-liquid mixture are studied. It was found that when the applied pressure gradient is large enough to overcome the gravity, the particles migrate away from the channel walls and there is a clear liquid layer next to the wall which lubricates the flow. As the particle Reynolds number is increased, particles interact more strongly and large clusters of particles are formed in the flow.

Pressure drop and limit deposit velocity for solid-liquid flow in pipes

Experimental data of pressure drop and flow patterns for the pipe flow of solid-liquid mixtures were obtained. Special emphasis was put on the range of low mixture flow rates, where a stationary bed is expected. The new experimental data and other data from the literature compare favorably with the three-layer model of Doron and Barnea (1993, Int. J. Multiphase Flow 19, 1029–1043).

THE PSEUDOHOMOGENEOUS FLOW APPROXIMATION FOR DISPERSED TWO-PHASE SYSTEMS

ABSTRACT The unsuitabllity of a continuum model for turbulent flow of solid-liquid mixtures has been demonstrated by a number of experimental studies which employed industrial slurries and a wide range of pipe diameters. However effective particle sizes and slurry viscosities are difficult to define for such mixtures. Using spherical glass particles of median diameter 125 μm and 240 μm, vertical flow experiments have been conducted in a test pipeline 26.17 mm in diameter. These experiments confirm earlier sand flow measurements by showing that wall friction decreases as particle size increases, in the absence of Bagnold stress or Coulombic friction effects. Using a turbulent flow simulation, and assuming a linear increase of solids concentration in a thin layer near the pipe wall, dimensionless excess wall frictional resistances have been calculated. These predictions are likely to be valid for fine particles which do not display Bagnold stress or Coulombic friction effects. The turbulent flow simulations...