Uncertainty Estimation in CFD Simulations of Erosion for Elbows

2021 ◽  
Author(s):  
Elham Fallah Shojaie ◽  
Thiana A. Sedrez ◽  
Farzin Darihaki ◽  
Siamack A. Shirazi
Keyword(s):  
Solid Particle ◽  
Turbulence Models ◽  
Uncertainty Estimation ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Cfd Simulations ◽  
Erosion Prediction ◽  
Erosion Models ◽  
Near Wall

Abstract Computational Fluid Dynamics (CFD) is used extensively in the industry and academia for analyzing the motion of solid particles and the associated solid particle erosion that may occur in various pipe components. However, CFD simulations always carry levels of inherent uncertainties due to the numerical approximations of governing equations, generated grid, and turbulence models. Also, because of the complex nature of solid particle erosion, additional uncertainties are added to erosion prediction simulations. Aspects such as particle size, number of impacts, particles’ initial condition, near-wall mesh effects, forces considered in particle tracking procedures, particle-particle interaction, and near-wall particle-fluid interactions are all possible sources of uncertainties associated with erosion prediction in CFD. Furthermore, unique problems that accompany discrete phase handling and erosion calculation needed for the industrial applications magnify the importance of uncertainty estimation in erosion calculations. Commercially available CFD codes are used with user-developed subroutines to investigate particle erosion prediction uncertainties, numerically in elbows, by considering gas and liquid flow for several pipe sizes. Moreover, different particle sizes, inlet flow velocities, turbulence models, wall functions, and erosion models are examined. According to the ASME’s Verification and Validation (V&V) standard, uncertainties are divided into 3 categories; input, numeric, and modeling. Thus, it is possible to utilize the ASME’s standard as guidance to predict uncertainty for erosion simulations. Furthermore, an extra parameter was considered for uncertainties to account for the uncertainties induced by different simulation procedures and erosion models. The current investigations resulted in developing a framework for estimating uncertainties of erosion simulation. For each simulation result, two bounds (upper and lower) were predicted for erosion. The results show that the Reynolds Stress turbulence model (RSM) and Arabnejad’s erosion model usually predict results corresponding to the lowest uncertainties.

scholarly journals Resistance of PVD Coatings to Erosive and Wear Processes: A Review

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 921
Author(s):  
Alicja Krella
Keyword(s):  
Wear Rate ◽  
Solid Particle ◽  
Coefficient Of Friction ◽  
Cavitation Erosion ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Pvd Coatings ◽  
Particle Erosion ◽  
Tribological Tests ◽  
Hydraulic Machines

Due to the increasing maintenance costs of hydraulic machines related to the damages caused by cavitation erosion and/or erosion of solid particles, as well as in tribological connections, surface protection of these components is very important. Up to now, numerous investigations of resistance of coatings, mainly nitride coatings, such as CrN, TiN, TiCN, (Ti,Cr)N coatings and multilayer TiN/Ti, ZrN/CrN and TN/(Ti,Al)N coatings, produced by physical vapor deposition (PVD) method using different techniques of deposition, such as magnetron sputtering, arc evaporation or ion plating, to cavitation erosion, solid particle erosion and wear have been made. The results of these investigations, degradation processes and main test devices used are presented in this paper. An effect of deposition of mono- and multi-layer PVD coatings on duration of incubation period, cumulative weight loss and erosion rate, as well as on wear rate and coefficient of friction in tribological tests is discussed. It is shown that PVD coating does not always provide extended incubation time and/or improved resistance to mentioned types of damage. The influence of structure, hardness, residence to plastic deformation and stresses in the coatings on erosion and wear resistance is discussed. In the case of cavitation erosion and solid particle erosion, a limit value of the ratio of hardness (H) to Young’s modulus (E) exists at which the best resistance is gained. In the case of tribological tests, the higher the H/E ratio and the lower the coefficient of friction, the lower the wear rate, but there are also many exceptions.

Representative volume element-based simulation of multiple solid particles erosion of a compressor blade considering temperature effect

2019 ◽  
Vol 234 (8) ◽  
pp. 1173-1184
Author(s):  
Bijan Mohammadi ◽  
AmirSajjad Khoddami
Keyword(s):  
Finite Element ◽  
Solid Particle ◽  
Representative Volume Element ◽  
Erosion Rate ◽  
Compressor Blade ◽  
Volume Element ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Representative Volume

Solid particle erosion is one of the main failure mechanisms of a compressor blade. Thus, characterization of this damage mode is very important in life assessment of the compressor. Since experimental study of solid particle erosion needs special methods and equipment, it is necessary to develop erosion computer models. This study presents a coupled temperature–displacement finite element model to investigate damage of a compressor blade due to multiple solid particles erosion. To decrease the computational cost, a representative volume element technique is introduced to simulate simultaneous impact of multiple particles. Blade has been made of Ti-6Al-4V, a ductile titanium-based alloy, which is impacted by alumina particles. Erosion finite element modeling is assumed as a micro-scale impact problem and Johnson–Cook constitutive equations are used to describe Ti-6Al-4V erosive behavior. In regard to a wide variation range in thermal conditions all over the compressor, it is divided into three parts (first stages, middle stages, and last stages) in which each part has an average temperature. Effective parameters on erosive behavior of the blade alloy, such as impact angle, particles velocity, and particles size are studied in these three temperatures. Results show that middle stages are the most critical sites of the compressor in terms of erosion damage. An exponential relation is observed between erosion rate and particles velocity. The dependency of erosion rate on size of particles at high temperatures is indispensable.

scholarly journals Particle-Based Numerical Simulation Study of Solid Particle Erosion of Ductile Materials Leading to an Erosion Model, Including the Particle Shape Effect

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 286
Author(s):  
Shoya Mohseni-Mofidi ◽  
Eric Drescher ◽  
Harald Kruggel-Emden ◽  
Matthias Teschner ◽  
Claas Bierwisch
Keyword(s):  
Solid Particle ◽  
Particle Shape ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Shape Effect ◽  
Particle Erosion ◽  
Erosion Model ◽  
Ductile Materials ◽  
Erosion Behavior ◽  
Numerical Predictions

Solid particle erosion inevitably occurs if a gas–solid or liquid–solid mixture is in contact with a surface, e.g., in pneumatic conveyors. Having a good understanding of this complex phenomenon enables one to reduce the maintenance costs in several industrial applications by designing components that have longer lifetimes. In this paper, we propose a methodology to numerically investigate erosion behavior of ductile materials. We employ smoothed particle hydrodynamics that can easily deal with large deformations and fractures as a truly meshless method. In addition, a new contact model was developed in order to robustly handle contacts around sharp corners of the solid particles. The numerical predictions of erosion are compared with experiments for stainless steel AISI 304, showing that we are able to properly predict the erosion behavior as a function of impact angle. We present a powerful tool to conveniently study the effect of important parameters, such as solid particle shapes, which are not simple to study in experiments. Using the methodology, we study the effect of a solid particle shape and conclude that, in addition to angularity, aspect ratio also plays an important role by increasing the probability of the solid particles to rotate after impact. Finally, we are able to extend a widely used erosion model by a term that considers a solid particle shape.

A Statistical Approach for Modeling Stochastic Rebound Characteristics of Solid Particles

2019 ◽  
Author(s):  
G. Haider ◽  
A. Asgharpour ◽  
J. Zhang ◽  
S. A. Shirazi
Keyword(s):  
Experimental Data ◽  
Solid Particle ◽  
Oil And Gas ◽  
Great Influence ◽  
Solid Particles ◽  
Process Equipment ◽  
Particle Impact ◽  
Solid Particle Erosion ◽  
Contributing Factors ◽  
Particle Erosion

Abstract During production of oil and gas from wells, solid particles such as removed scales or sand may accompany petroleum fluids. These particles present in this multiphase flow can impact inner walls of transportation infrastructure (straight pipelines, elbows, T-junctions, flow meters, and reducers) multiple times. These repeated impacts degrades the inner walls of piping and as a result, reduce wall thickness occur. This is known as solid particle erosion, which is a complex phenomenon involving multiple contributing factors. Prediction of erosion rates and location of maximum erosion are crucial from both operations and safety perspective. Various mechanistic and empirical solid particle erosion models are available in literature for this purpose. The majority of these models require particle impact speed and impact angle to model erosion. Furthermore, due to complex geometric shapes of process equipment, these solid particles can impact and rebound from walls in a random manner with varying speeds and angles. Hence, this rebound characteristic is an important factor in solid particle erosion modeling which cannot be done in a deterministic sense. This challenge has not been addressed in literature satisfactorily. This study uses experimental data to model particle rebound characteristics stochastically. Experimental setup consists of a nozzle and specimen, which are aligned at different angles so particles impact the specimen at various angles. Information regarding particle impact velocities before and after the impacts are obtained through Particle Tracking Velocimetry (PTV) technique. Distributions of normal and tangential components of particle velocities were determined experimentally. Furthermore, spread or dispersion in these velocity components due to randomness is quantified. Finally, based on these experimental observations, a stochastic rebound model based on normal and tangential coefficients of restitutions is developed and Computational Fluid Dynamics (CFD) studies were conducted to validate this model. The model predictions are compared with experimental data for elbows in series. It is found that the rebound model has a great influence on erosion prediction of both first and second elbows especially where subsequent particle impacts are expected.

A Combined CFD-Mechanistic Approach for Predicting Solid Particle Erosion in Annular Flow in Pipe Fittings and Elbows

2020 ◽  
Author(s):  
Farzin Darihaki ◽  
Elham Fallah Shojaie ◽  
Jun Zhang ◽  
Siamack A. Shirazi
Keyword(s):  
Multiphase Flow ◽  
Solid Particle ◽  
Annular Flow ◽  
Large Diameter ◽  
Solid Particles ◽  
Wall Material ◽  
Solid Particle Erosion ◽  
Flow Conditions ◽  
Particle Erosion ◽  
Wide Range

Abstract In internal flows, solid particles carried by the fluid could damage pipelines and fittings. Particles that are entrained in the fluid can cross streamlines and transfer a part of their momentum to the internal surface by impacts and cause local wall material degradation. Over the past decades, a wide range of models is introduced to predict particle erosion which includes empirical models, mechanistic models, and CFD which is currently the state-of-art numerical approach to simulate the erosion process. Multiphase flow under annular flow conditions adds to the complexity of the model. Although with the current computational capabilities transient CFD models are effectively applicable, this type of transient multiphase approach is not practical yet for engineering prediction of erosion especially for the large diameter applications with huge computational domains. Therefore, the presented combined approach could be utilized to obtain erosion rates for large diameter cases. Thus, an approach combining CFD and mechanistic multiphase models characterizing annular flow is developed to predict solid particle erosion. Different factors including film thickness in pipes and fittings which are affecting erosion under gas-dominated multiphase flow conditions are investigated. The results from the current approach are compared to experimental data and transient CFD simulations for annular flow in elbows showing a very good agreement with both.

Application of a Mechanistic Erosion and Abrasion Model to Pulverized Coal (PC) Injections

2021 ◽  
Author(s):  
Lawrence D. Berg ◽  
Soroor Karimi ◽  
Siamack A. Shirazi
Keyword(s):  
Solid Particle ◽  
Model Development ◽  
Empirical Models ◽  
Pulverized Coal ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Cfd Simulations ◽  
Injection Nozzle ◽  
Erosion Rates ◽  
Electrical Generation

Abstract Coal use for generation of electricity is used extensively world-wide accounting for 40% of total power generation. Even with reductions in use over the last 10 years, coal still accounts for 20% of total electrical generation in the United States. An often-overlooked aspect of Pulverized Coal (PC) combustion is the erosion and abrasion of the coal injection nozzles. Currently there are over 300 active PC boilers in the US and over 1000 worldwide, with each boiler having 20–40 high alloy cast injectors. Due to the high velocity of PC injection and associated elevated rates of metal loss, these nozzles require constant replacement. Replacement and costs associated with loss of revenue, required scaffolding and casting can be a significant part of Operation and Maintenance (O&M) of a PC boiler. In addition to the constant requirement for thousands of replacement injection nozzles every year, combustion performance, NOx reduction, carbon conversion and general boiler efficiency will be impacted by hardware that is out of specification, if not replaced in a “timely” manner. Significant research in the 1980’s [1] provided some insight into the loss-of-metal process during PC injection, but limitations of existing hardware and software prevented more than an empirical methodology to be developed. In parallel with the literature work and research specifically for PC coal erosion rates, generalized efforts were employed and reported [6–9]. Meng [4] summarized model development for solid particles transported by a liquid or gas as highly empirical with little commonality between the models developed by the various researchers. Meng also made specific recommendations for less empiricism in model development methodology. Although there are several state-of-the-art empirical models [6, 8 & 9] more recently, semi-mechanistic models have been developed to predict solid particle erosion (e.g. Arabnejad et al., [17]) and have been successfully applied to sand erosion and abrasion in pipelines. In the current study, this method is being applied to PC injection nozzles coupled to detailed computational fluid dynamics (CFD) simulations. The intent is to quantify nozzle material loss rates, due to impacting coal particles, as a function of geometry, local velocities, and coal properties. The method used is utilizing CFD to model flow of particles and their impingement velocity with the PC nozzles. Then erosion models that are a function of impingement speed, angle, frequency and materials properties to examine erosion rates. The insight gained from the modeling will allow improved nozzle design, increased duty life, more cost-effective supply, and elevated injection velocity. In particular, low NOx coal combustion can be critically dependent on utilization of elevated injection velocities, which previous empirical models discourage. This paper reports on the application of the erosion equations and methods developed at the Erosion/Corrosion Research Center of The University of Tulsa for predicting solid particle erosion of a PC injection nozzle that shows details of erosion patterns and parameters that are responsible for elevated erosion tendencies in the field. RJM-International is familiar with the nozzle from various applications that are associated with Low NOx operation. The advantages of utilizing semi-mechanistic erosion equations and models coupled with CFD simulations as compared to previous empirical methods are discussed. Shortcomings of applying the existing coal erosion model is also reported along with “next steps” required to successfully apply the method to PC injection nozzle designs for much higher combustion efficiencies than existing ones.

Investigation of Particle Size Effects on Solid Particle Erosion of Elbows in Series for Liquid-Solid Flows

2021 ◽  
Author(s):  
Yeshwanthraj Rajkumar ◽  
Soroor Karimi ◽  
Siamack A. Shirazi
Keyword(s):  
Particle Size ◽  
Solid Particle ◽  
Size Effects ◽  
Oil And Gas ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Particle Sizes ◽  
Particle Erosion ◽  
Particle Size Effects ◽  
In Series

Abstract The entrainment of solid particles within the produced fluids can cause solid particle erosion by impacting the piping of production and transportation facilities. Liquid dominated flows are commonly encountered in deep water subsea pipelines while producing oil and gas fluids. It is of great importance to predict the erosion pattern and magnitude for elbows in series in liquid-solid flows as in the oil and gas productions, liquids tends to produce more solid particles compared to gas-solid flows. In the current work, erosion of elbows in series for different particle sizes are investigated by using computational fluid dynamics (CFD) and compare the erosion pattern results with the results of paint removal experiments using a 76.2 mm diameter acrylic elbows, qualitatively. CFD simulations have been performed to study the particle size effects on erosion using Reynolds stress turbulence model (RSM) and Low-Reynolds number K-ε model. Grid refinement studies have been performed and particles are rebounded at the particle radius to accurately examine the effects of particle sizes on solid particle erosion of these elbows. The CFD results shows that significant erosion is observed at the inner wall of the first elbow for larger particles, and the maximum erosion can be seen towards the end of the second elbow for 300 μm particle size.

Improvements of Particle Near-Wall Velocity and Erosion Predictions Using a Commercial CFD Code

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Yongli Zhang ◽  
Brenton S. McLaury ◽  
Siamack A. Shirazi
Keyword(s):  
Solid Particle ◽  
Turbulent Velocity ◽  
Particle Impact ◽  
Solid Particle Erosion ◽  
Wall Region ◽  
Wall Function ◽  
Particle Erosion ◽  
Before And After ◽  
Simulation Results ◽  
Near Wall

The determination of a representative particle impacting velocity is an important component in calculating solid particle erosion inside pipe geometry. Currently, most commercial computational fluid dynamics (CFD) codes allow the user to calculate particle trajectories using a Lagrangian approach. Additionally, the CFD codes calculate particle impact velocities with the pipe walls. However, these commercial CFD codes normally use a wall function to simulate the turbulent velocity field in the near-wall region. This wall-function velocity field near the wall can affect the small particle motion in the near-wall region. Furthermore, the CFD codes assume that particles have zero volume when particle impact information is being calculated. In this investigation, particle motions that are simulated using a commercially available CFD code are examined in the near-wall region. Calculated solid particle erosion patterns are compared with experimental data to investigate the accuracy of the models that are being used to calculate particle impacting velocities. While not considered in particle tracking routines in most CFD codes, the turbulent velocity profile in the near-wall region is taken into account in this investigation, and the effect on particle impact velocity is investigated. The simulation results show that the particle impact velocity is affected significantly when near-wall velocity profile is implemented. In addition, the effects of particle size are investigated in the near-wall region of a turbulent flow in a 90 deg sharp bend. A CFD code is modified to account for particle size effects in the near-wall region before and after the particle impact. It is found from the simulations that accounting for the rebound at the particle radius helps avoid nonphysical impacts and reduces the number of impacts by more than one order-of-magnitude for small particles (25 μm) due to turbulent velocity fluctuations. For large particles (256 μm), however, nonphysical impacts are not observed in the simulations. Solid particle erosion is predicted before and after introducing these modifications, and the results are compared with experimental data. It is shown that the near-wall modification and turbulent particle interactions significantly affect the simulation results. Modifications can significantly improve the current CFD-based solid particle erosion modeling.

The Effect of Geometry of Outlet Channel of Nozzle Box on Solid Particle Erosion

2013 ◽  
Vol 773 ◽  
pp. 19-24
Author(s):  
Li Zhang ◽  
Yu Ting Zheng
Keyword(s):  
Solid Particle ◽  
Flow Characteristics ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Lagrange Method ◽  
Particle Trajectories ◽  
Outlet Channel ◽  
Control Stage

On the base of the original geometry of the outlet channel of nozzle box, four different geometry of the outlet channel were constructed. Using the Euler-Lagrange method, the flow characteristics of solid particles in the five different channels were numerical simulated. The particle trajectories and the erosion regions were discussed. The analysis showed that the different geometry of the outlet channel would effect the particle erosion in the channel and the stator of the control stage.

Reducing Solid Particle Erosion on Steam Turbine Stages

2016 ◽  
Author(s):  
Tie Chen ◽  
Gurnam Singh ◽  
Peter Millington ◽  
Brian Haller
Keyword(s):  
Steam Turbine ◽  
Solid Particle ◽  
Leading Edge ◽  
Cost Effective ◽  
Solid Particles ◽  
Solid Particle Erosion ◽  
Particle Erosion ◽  
Trailing Edge ◽  
Extension Ring ◽  
Blade Leading Edge

Solid Particle Erosion (SPE) damage can be found on steam turbine stages. These solid particles are caused by the exfoliation of iron oxides formed on the inner surfaces of both boiler tubes and steam pipes which are exposed to elevated temperature. They can damage both fixed and Moving Blades, as well as both outer extension ring and tip seals. Severe SPE damages can be expensive for the utility industry due to reduced efficiency and lost power generation, as well as increased costs of repair or replacement of eroded components. Thus it is very important to understand this phenomenon and propose cost effective solutions to reduce the damage. This study investigates the effects of SPE damage using particle trajectory calculations. This investigation confirms that “Bounce Back” is the dominant cause for the SPE damage on both Fixed Blade trailing edge and Moving Blade leading edge. The particles do not accelerate at same speed as steam, therefore they travel much slower when they hit the Moving Blade leading edge. Then they are thrown back towards the Fixed Blade to hit the trailing edge. Due to strong centrifugal forces, the particles are also thrown radically outwards and damage both outer extension ring and tip seals. Based on these enhanced understandings, a practical solution is proposed to reduce SPE damage. It is predicted to have negligible impact on the stage performance. Evidence from the latest inspection demonstrates that this solution is very effective in reducing SPE damage to the Fixed Blade trailing edge.

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