Effects of applying a stochastic rebound model in erosion prediction of elbows and plugged tee

ABSTRACT Solid particle erosion is a complex phenomenon that depends on many factors such as particle and fluid characteristics, type of material being eroded, and flow geometry. Fittings used in the oil and gas industry such as elbows are susceptible to erosion when solid particles are present in the flow. The momentum of particles carries them across streamlines and the particles impinge the outer wall of the elbow resulting in erosion damage. In an erosive environment, plugged tees are commonly used instead of elbows to reduce the erosion especially where space considerations are important and long-radius elbows can not be used. However, it is unclear how much of a reduction in erosion occurs by replacing an elbow with a plugged tee. In order to compare the erosion in an elbow and a plugged tee exposed to the same flow conditions, a CFD-based erosion prediction model is applied. The model has three primary steps: flow modeling, particle tracking, and applying erosion equations. The results from the model agree with experimental findings for the elbow geometry. However, the simulation results for erosion rate generated for the plugged tee requires a stochastic approach. Results obtained with the erosion prediction model before and after this modification are shown

FEDSM2002-31286 APPLICATION OF CFD-BASED EROSION PREDICTION PROCEDURE FOR SUDDEN EXPANSIONS

ABSTRACT Pipe fittings used in the production of oil and gas can experience erosion damage from solid particles such as sand present in the produced fluid. The fittings disturb the flow, which often results in erosion. Certain geometries are more susceptible to erosion damage than others; for example, a sudden expansion can experience severe erosion under certain operating conditions. A sudden expansion can promote erosion for two reasons. First, a radial velocity develops downstream of the expansion. This velocity component drives particles toward the wall. Second, the sudden expansion causes a zone of elevated turbulent kinetic energy. The high level of turbulent kinetic energy results in large turbulent fluctuations, and these fluctuations can also force particles to the wall. A comprehensive model for predicting sand erosion has been developed by utilizing a commercially available computational fluid dynamics (CFD) code. This procedure involves flow modeling, particle tracking, and applying erosion equations. Due to the low sand concentrations a one-way coupling is used between the fluid and the particles. The goal of this study is to use the procedure to calculate erosion in sudden expansions and determine if modifications to the existing procedure are necessary. Simulation results for sand in air flowing through sudden expansions with different diameter ratios (1.25 to 2.00) are compared with experimental data. Both the simulations and data show that the maximum erosion rate evaluated in thickness loss per mass of sand passing through the geometry decrease with increasing expansion ratio

PARAMETRIC ANALYSIS OF EROSION IN 90 DEGREE AND LONG RADIUS BENDS

ABSTRACT Solid particle erosion has been recognized as a major concern in the oil and gas production industry. It has been observed that erosion can cause serious and costly damage to equipment and pipelines. Accordingly, different studies have been performed in order to investigate erosion caused by solid particles entrained in the flow. Both experimental and modeling approaches have been used in the past to analyze solid particle erosion under different conditions to be able to mitigate these problems. The goal of this paper is to use a Computational Fluid Dynamic (CFD) erosion model to predict erosion caused by particles flowing in 90 degree and long radius bends. The fluid flow model is coupled with a Lagrangian particle tracking approach. The CFD-based prediction procedure consists of three main steps: flow modeling, particle tracking and erosion calculation. The Reynolds Stress Model (RSM) is used as the turbulence model for all fluid flow simulations. Solid particles are injected from the inlet of the pipe and tracked throughout the bend. The effect of the number of particles released on the predicted maximum erosion magnitude has been investigated. In order to study the grid independency of the solution, erosion is predicted for 5 different grid spacings to accurately predict the flow and erosion rates. In order to assess the quality of the numerical predictions of the erosion rate, experimental data for single-phase (gas) flow with sand in a 3-inch pipe were used. The effects of particle size, fluid velocity, pipe diameter and radius as well as particle rebound model on erosion pattern and magnitude are also investigated. Comparison of these results with experimental erosion data demonstrates good agreement of the erosion trends. It is found that the location of highest erosion for singlephase (gas) flow at low pressure containing sand is around 45˚ in the elbow. It has been also observed that the 300 particles cause approximately two times higher metal loss compared to the 150 particles. This higher erosion magnitude is not only caused by the increase in particle momentum but also by the significant increase in particle sharpness for the 300 sand. Moreover, simulation results indicate that the increase in gas superficial velocity leads to an increase in the erosion magnitude. According to the results, erosion ratios were reduced exponentially with the increase in pipe diameter at constant flow conditions and particle properties. Furthermore, two available rebound models in the literature were investigated, and simulations illustrate that both methods are in reasonable agreement with experimental data

Experimental Study of Slug Characteristics: Implications to Sand Erosion

Sand erosion is a severe problem that many oil and gas producers have to deal with. Therefore, it is desirable to have a model that can predict erosion for various operating conditions. Predicting erosion is a complex problem due to the number of parameters that are involved. The complexity of predicting erosion increases when producing or transporting multiphase fluids through pipelines. It is well known that the characteristics of multiphase flow affect sand erosion in the pipelines. This work specifically concentrates on investigating multiphase-slug characteristics using a measurement technique based on Wire Mesh Sensor. A 16 × 16 dual Wire Mesh Sensor is installed before a standard 76.2 mm (3-inch) elbow for a horizontally oriented pipe. The distance by which the dual Wire Mesh Sensors are separated is 32 mm. The local void fraction is extracted where horizontal and vertical wires of the sensor intersect, utilizing the differences in conductance between gas and liquid as they pass through the crossings of the wires. The fluids used in these multiphase experiments were air and either water or water-Carboxy Methyl Cellulose mixture to increase the liquid viscosity. Experiments were conducted, where superficial gas velocity ranged from 9.1 m/s to 35 m/s, and superficial liquid velocity was 0.76 m/s. Three different liquid viscosities (1 cP, 10 cP and 40 cP) were used for performing the experiments. The void fraction data obtained using the dual Wire Mesh Sensors is utilized to achieve the interfacial velocities of the liquid slug. Further analysis of the data is conducted to obtain other slug characteristics such as the liquid slug body length distribution and frequency of the slugs. Additionally, liquid slug fronts and slug tails were identified. The differences in the characteristics of slug flow and pseudo-slug flow are addressed. Finally, the slug characteristics were utilized in order to enhance the understanding of sand particle impact velocities with the pipe wall and the resulting erosion in the horizontal pipelines and elbow.Copyright © 2013 by ASM

Experimental Investigation of Horizontal Gas-Liquid Stratified and Annular Flow Using Wire Mesh Sensor

Stratified and annular gas–liquid flow patterns are commonly encountered in many industrial applications, such as oil and gas transportation pipelines, heat exchangers, and process equipment. The measurement and visualization of two-phase flow characteristics are of great importance as two-phase flows persist in many fluids engineering applications. A wire-mesh sensor (WMS) technique based on conductance measurements has been applied to investigate two-phase horizontal pipe flow. The horizontal flow test section consisting of a 76.2mm ID pipe, 18m long was employed to generate stratified and annular flow conditions. Two 16 16 wire configuration sensors, installed 17 m from the inlet of the test section, are used to determine the void fraction within the cross section of the pipe and determine interface velocities between the gas and liquid. These physical flow parameters were extracted using signal processing and cross-correlation techniques. In this work, the principle of WMS and the methodology of flow parameter extraction are described. From the obtained raw data time series of void fraction, cross-sectional mean void fraction, time averaged void fraction profiles, interfacial structures, and velocities of the periodic structures are determined for different liquid and gas superficial velocities that ranged from 0.03m/s to 0.2m/s and from 9m/s to 34m/s, respectively. The effects of liquid viscosity on the measured parameters have also been investigated using three different viscosities. [DOI: 10.1115/1.4027799

The Effect of Viscosity on Low Concentration Particle Transport in Single-Phase (Liquid) Horizontal Pipes

Particle transport has been an active area of research for many years. Despite many excellent experimental and modeling studies contributing to the fundamental understanding of particle transport, the effect of viscosity is still not well-understood. There are limited experimental studies addressing the effect of viscosity on particle transport. Even among those limited studies, contradictory conclusions have been reported in the literature. A review of the single-phase proposed models also reveals that fluid viscosity has not been well addressed in the models as well. The main focus of this study is to investigate the effect of viscosity on particle transport in laminar and turbulent flows. Experiments were performed using a 0.05 m diameter pipe. Comparisons of the obtained data with previously reported data in the literature show similar characteristics. The current study finds that liquid flow regime in the pipe plays an important role on how viscosity affects the particle transport phenomenon. Discussions presented in this work to explain the obtained experimental data shed light on this less addressed physical parameter

Experimental investigation of the effect of 90° standard elbow on horizontal gas–liquid stratified and annular flow characteristics using dual wire-mesh sensors

Fluid flowing through pipelines often encounters fittings such as elbows. Although it is true that two-phase flow patterns observed in elbows are qualitatively the same as those seen in straight pipes, the presence of a pipe elbow can modify relative positions and local velocities of the two phases as they are subjected to forces in addition to those encountered in a straight pipe. That redistribution can affect pressure drop values, chemical inhibitor concentration and distribution to the top of the pipe, as well as the erosion pattern occurring from solid particles such as sand that is entrained in oil and gas transportation pipelines. In this work, a wire-mesh sensor technique based on conductance measurements of void fraction was applied to investigate two-phase pipe flow through a standard elbow. The horizontal flow test section, consisting of a 76.2 mm ID, 18 m long pipe, was employed to generate stratified-wavy and annular flow conditions. Two 16 × 16 wire-mesh configuration sensors were positioned either 0.9 m upstream or 0.6 m downstream of the bend. The experiments were conducted at superficial liquid velocities equal to 0.03 m/s and 0.2 m/s and superficial gas velocities that ranged from 9 m/s to 34 m/s. The effects of liquid viscosity on the measured parameters are also investigated using two different viscosities of 1 and 10 cP. Stratified–slug transition, stratified wavy and annular flow patterns were observed visually in the clear section placed upstream of the wire-mesh sensors. Analysis of time series void fraction data from the dual wire-mesh sensors allows the determination of mean void fraction, local time average void fraction distribution, liquid phase distribution around the tube periphery, interfacial structure velocities, as well as probability density function characteristic signatures within the cross-section of pipe before and after the elbow. The results indicate that the distribution of gas and liquid phases and interfacial velocities are significantly altered even 20 diameters downstream of the elbow