John M. Furlan

Comparison of 2D and 3D Predictions of Erosion Wear in Centrifugal Slurry Pump Casings

This paper deals with the prediction of erosion wear rate in slurry pump casings, with an emphasis on the comparison of two-dimensional and three-dimensional results. The two-dimensional analysis is carried out in the mid-plane of the pump normal to the pump axis. The dense solid-liquid flow field in the pump casing is modeled using an Eulerian-Eulerian model with a penalized finite element formulation to discretize the continuum equations. Erosion wear due to particle impact and sliding abrasion depends on the local velocity, shear stress, concentration of the particles and the empirically determined (particle-size dependent) wear rate coefficients used to relate the erosion wear to the local flow field properties.The wear rate predictions from the 2D and 3D codes are compared to analyze the three dimensional flow effects on the wear rate. Operating conditions under which the 2D solution departs significantly from the 3D solution are explored with the aim of determining the limitations of the 2D simulations. Three pumps with different casing width-to-depth ratio are analyzed. Flow conditions and the pump casing width-to-depth ratio affect the differences between the 2D and 3D casing wear predictions.Copyright

Effect of Particle Size Distribution on Erosion Wear in Centrifugal Pump Casings

The aim of this paper is to study the effect of particle size distribution on erosion rate characteristics in pump casings. The typically broad particle size distribution (PSD) found in industrial slurries is viewed in terms of a discrete number of size classes, each with a representative diameter. An Eulerian-Eulerian mixture model is used to compute the two-dimensional flow field and particle concentration distribution inside a pump casing. Erosion wear due to particle impact and sliding abrasion is then calculated using empirically determined (particle-size dependent) wear rate coefficients to relate the erosion wear to the local flow field properties. Wear rate predictions are compared for (a) multi-size, (b) D50 mono-size of the slurry, (c) the concentration-weighted mono-size, and (d) the average of D50 and D85 sizes. Depending on the operating conditions, the four predictions differ from one another, indicating that adjustments to mono-size predictions are essential to capture the effect of the PSD. Parametric study is performed to analyze the effect of the flow operating conditions, inlet particle concentration and PSD on the prediction of wear rates along the casing wall.Copyright

Wear Rate Prediction in Multi-Size Particulate Flow Through Impellers

A three-dimensional finite element formulation of multi-size particulate flow through a centrifugal impeller is presented. From the predicted flow field, the wear rate distribution along the impeller blades and shrouds is calculated using empirically determined impact and sliding wear coefficients. The computational domain consists of the three dimensional region enclosed between the two blades and the two shroud surfaces with upstream and downstream extensions. An Eulerian-Eulerian mixture model is used for the multi-size particulate flow, which consists of mixture continuity and momentum equations as well as the individual solids continuity and momentum equations.The effects of flow operating conditions on the wear rates are studied. A comparison of predicted wear rates from D50 or other mono-size simulations with multi-size particulate flow simulations shows that representing the slurry by a single particle size could result in substantial errors for different flow conditions.Copyright

Axi-Symmetric Multi-Size Particulate Flow Simulation Model of a Hydrocyclone

An axi-symmetric multi-size particulate Eulerian-Eulerian flow simulation model of a hydrocyclone is presented in this paper. Finite volume formulation on a collocated grid is implemented. The broad particle size distribution is divided into a specific number of size classes. The air core diameter is estimated using empirical correlations. Pure carrier eddy viscosity field (computed using a mixing length model) is modified to account for the presence of multi-size particles. The computed pressure drop, particle size distribution (PSD) of the overflow and underflow, separation efficiency curve and cutsize diameter obtained from the numerical solution are compared with experimental results.Copyright

Localized Particle Velocity and Concentration Measurement in Slurry Flow Using Ultrasound Technique

The study of slurry flow is important in the analysis and design of transport equipment that is resistant to solid particle erosion. Ultrasound transducers have been used to track particle concentration and particle velocity profiles across a representative pipe slurry flow.The aim of this work is to measure local particle concentration using an A-scan measuring technique and to utilize pulsed ultrasound Doppler Velocimetry (PUDV), which is a non-invasive flow measurement technique for both opaque and transparent fluids, to measure fluid velocity profiles and to determine the most appropriate setup for PUDV to measure the velocity profiles (i.e. transducer frequency, Doppler angle, transducer dimension). The PUDV will then obtain velocity measurements in a slurry pump. The effect of varying PUDV settings is also studied, and is found to generally be small.Computational fluid dynamics (CFD) modeling was performed. The numerical results were in good agreement with the experimental data, for both the local particle velocity and concentration. It has been found that the transducer with 80 degree Doppler angle and a large sized (14mm diameter) transducer give the best results for the local particle velocity measurements. These results will be considered as an introduction to use them as a guide for measuring the velocity profiles in the pump casing.© 2013 ASME

Localized Particle Concentration Measurement in Slurry Flows Using A-Scan Ultrasound Technique

In the design of slurry transport equipment, the effects of solid particle concentration on hydraulic performance and wear have to be considered. This study involves examining the acoustic properties of slurry flows such as velocity, backscatter and attenuation as a function of volume fraction of solid particles. Ultrasound A-mode imaging method is developed to obtain particle concentration in a flow of soda lime glass particles (diameter of 200 micron) and water slurry in a 1″ diameter pipe. Based on the acoustic properties of the slurry a technique is developed to measure local solid particle concentrations. The technique is used to obtain concentration profiles in homogeneous (vertical flow) and non-homogeneous (horizontal flow) slurry flows with solid particle concentrations ranging from 1–10% by volume. The algorithm developed utilizes the power spectrum and attenuation measurements obtained from the homogeneous loop as calibration data in order to obtain concentration profiles in other (i.e. non-homogenous) flow regimes. A computational study using FLUENT was performed and a comparison is made with the experimental results. A reasonable agreement between the experimental and computational results is observed.Copyright