bluuebunny/crossref_metadata_2025 huggingface dataset:
Bone marrow lesions of the distal condyles of the third metacarpal bone are common and not always related to lameness in sports and pleasure horses
Authors: De Guio Cécile , Ségard‐Weisse Emilie , Thomas‐Cancian Aurélie , Schramme Michael
Published: November 2018

The metacarpophalangeal joint is a common site of pain in horses. Little information is available about bone marrow lesions in the distal condyles of the third metacarpal bone in sports and pleasure horses. Aims of this prospective, retrospective, observational study were to evaluate the prevalence of bone marrow lesions in the distal condyles of the third metacarpal bone, to describe their anatomic distribution and to correlate lesions with the presence of lameness and the level and type of activity. All sports and pleasure horses undergoing standing low‐field MRI of the front fetlock region between 2009 and 2016 were included and divided into three lameness groups according to the results of diagnostic analgesia. Bone marrow lesions were analyzed and graded by one reader. Grades were compared between anatomical locations and between lameness groups. A total of 166 horses were sampled. The prevalence of bone marrow lesions was 76.5% (127/166). The dorsal aspects of the medial condyle (31%, 39/127) and of the sagittal ridge (28%, 36/127) were the most commonly affected locations. There was no significant difference between both forelimbs (lame limb and non‐lame limb) of the same horse. Lesion severity was neither significantly associated with the lameness group nor with the type or level of activity. The prevalence of bone marrow lesions in the distal condyles of the third metacarpal bone is high in this population and the clinical significance is not always clear. Further studies are required to elucidate the clinical significance of this finding in sports and pleasure horses.
Challenges and advances in atomistic simulations of potassium and sodium ion channel gating and permeation
Authors: DeMarco Kevin R. , Bekker Slava , Vorobyov Igor
Published: November 2018

Ion channels are implicated in many essential physiological events such as electrical signal propagation and cellular communication. The advent of K+ and Na+ ion channel structure determination has facilitated numerous investigations of molecular determinants of their behaviour. At the same time, rapid development of computer hardware and molecular simulation methodologies has made computational studies of large biological molecules in all‐atom representation tractable. The concurrent evolution of experimental structural biology with biomolecular computer modelling has yielded mechanistic details of fundamental processes unavailable through experiments alone, such as ion conduction and ion channel gating. This review is a short survey of the atomistic computational investigations of K+ and Na+ ion channels, focusing on KcsA and several voltage‐gated channels from the KV and NaV families, which have garnered many successes and engendered several long‐standing controversies regarding the nature of their structure–function relationship. We review the latest advancements and challenges facing the field of molecular modelling and simulation regarding the structural and energetic determinants of ion channel function and their agreement with experimental observations.
Thermo-Mechanical Safety Analyses of Preliminary Design Experiments for 238Pu Production
Authors: Hurt Christopher J. , Freels James D. , Jain Prashant K. , Ivan Maldonado G.
Published: November 2018

Safety analyses at the high flux isotope reactor (HFIR) are required to qualify experiment targets for the production of plutonium-238 (238Pu) from neptunium dioxide/aluminum cermet (NpO2/Al) pellets. High heat generation rates (HGRs) due to fissile material and low melting temperatures require a sophisticated set of steady-state thermal simulations in order to ensure sufficient safety margins. These simulations are achieved in a fully coupled thermo-mechanical analysis using comsolmultiphysics for four different preliminary target designs using an evolving set of pre- and postirradiation data inputs, and subsequently evolving solution scopes, from the unique pellet and target designs. A new comprehensive presentation of these preliminary analyses is given and revisited analyses of the first prototypical target designs are presented to reveal the effectiveness of evolving methods and input data.
Verification of Advective Bar Elements Implemented in the sierra/aria Thermal Response Code
Authors: Mills Brantley H. , Hetzler Adam C. , Deng Oscar W.
Published: November 2018

A thorough code verification effort has been performed on a reduced order, finite element model for one-dimensional (1D) fluid flow convectively coupled with a three-dimensional (3D) solid, referred to as the “advective bar” model. The purpose of this effort was to provide confidence in the proper implementation of this model within the sierra/aria thermal response code at Sandia National Laboratories. The method of manufactured solutions (MMS) is applied so that the order of convergence in error norms for successively refined meshes and timesteps is investigated. Potential pitfalls that can lead to a premature evaluation of the model's implementation are described for this verification approach when applied to this unique model. Through observation of the expected order of convergence, these verification tests provide evidence of proper implementation of the model within the codebase.
Modeling and Analysis of the Process Energy for Cylindrical Drawing
Authors: Li Lei , Huang Haihong , Zhao Fu , Zou Xiang , Mendis Gamini P. , Luan Xiaona , Liu Zhifeng , Sutherland John W.
Published: November 2018

As energy efficiency increases in importance, researchers have identified manufacturing processes as opportunities where energy consumption can be reduced. Drawing is one widely employed, energy intensive manufacturing process, which could benefit by analysis of energy consumption during operation. To optimize the energy consumption of the drawing process, this paper developed an explicit model to quantify the process energy for the cylindrical drawing process by analyzing the dynamic punch force during the process. In this analysis, the evolution of the stress and strain was analyzed in the drawn part by considering all the structure parameters of the drawn part. The stress and strain analyses were integrated into an overall process energy model, and the behavior of the model was classified into three categories, based on their physical mechanisms, i.e., deformation energy, bending energy, and friction energy. The model was validated using numerical experiments designed by the Taguchi method where two different kinds of materials were tested over 18 runs. The results from the numerical experiments were compared with those from the model, and show that the maximum variation of the process energy predicted by this model is less than 10% for a given part. Sensitivity analysis was performed on the model to understand the contributions of the process parameters on the process energy to guide process optimization for lower energy consumption. The established model can assist in the rapid design of drawn parts with lower embodied energy.
Event-Based Production Control for Energy Efficiency Improvement in Sustainable Multistage Manufacturing Systems
Authors: Li Yang , Wang Jun-Qiang , Chang Qing
Published: November 2018

There has been an increasing trend for manufacturers to shift toward sustainable manufacturing strategies in response to an ever-growing pressure from fluctuating energy price and environmental crisis. Reducing energy consumption is considered as an important step to achieve the sustainability of a production system. This paper proposes an event-based control methodology to improve the production energy efficiency through strategically switching appropriate stations to energy saving mode. Based on an event-based analysis of production dynamics, an analytical approach is developed to quantitatively predict the system level production loss resulted from an energy saving control event (ESCE). A genetic-based control algorithm is proposed to balance the trade-off between the gain from energy saving and the expense of throughput loss. The energy improvement analysis results in a fundamental understanding of production energy dynamics and a significant decrease of energy cost for a manufacturing facility. Numerical case studies are performed to validate the effectiveness of the proposed method. It is found that the control method can effectively reduce energy cost, while only slightly impacting production.
A Motion Synthesis Approach to Solving Alt-Burmester Problem by Exploiting Fourier Descriptor Relationship Between Path and Orientation Data
Authors: Sharma Shashank , Purwar Anurag , Jeffrey Ge Q.
Published: November 2018

This paper presents a generalized framework to solve m-pose, n-path-points mixed synthesis problems, known as the Alt-Burmester problems, using a task-driven motion synthesis approach. We aim to unify the path and motion synthesis problems into an approximate mixed synthesis framework. Fourier descriptors are used to establish a closed-form relationship between the path and orientation data. This relationship is then exploited to formulate mixed synthesis problems into pure motion synthesis ones. We use an efficient algebraic fitting based motion synthesis algorithm to enable simultaneous type and dimensional synthesis of planar four-bar linkages.
Analysis of Solar Receiver Performance for Chemical-Looping Integration With a Concentrating Solar Thermal System
Authors: Ma Zhiwen , Martinek Janna
Published: November 2018

This paper introduces a chemical-looping configuration integrated with a concentrating solar thermal (CST) system. The CST system uses an array of mirrors to focus sunlight, and the concentrated solar flux is applied to a solar receiver to collect and convert solar energy into thermal energy. The thermal energy then drives a thermal power cycle for electricity generation or provides an energy source to chemical processes for material or fuel production. Considerable interest in CST energy systems has been driven by power generation, with its capability to store thermal energy for continuous electricity supply or peak shaving. However, CST systems have other potential to convert solar energy into fuel or to support thermochemical processes. Thus, we introduce the concept of a chemical-looping configuration integrated with the CST system that has potential applications for thermochemical energy storage or solar thermochemical hydrogen production. The chemical-looping configuration integrated with a CST system consists of the following: a solar-receiver reactor for solar-energy collection and conversion, thermochemical energy storage, a reverse reactor for energy release, and system circulation. We describe a high-temperature reactor receiver that is a key component in the chemical-looping system. We also show the solar-receiver design and its performance analyzed by solar-tracing and thermal-modeling methods for integration within a CST system.
A Model of Mixed Lubrication Based on Non-Normalized Discretization and Its Application for Multilayered Materials
Authors: Dong Qingbing , Wang Zhanjiang , Zhu Dong , Meng Fanming , Xu Lixin , Zhou Kun
Published: November 2018

This study presents a generalized model of mixed elastohydrodynamic lubrication, in which the dimensional Reynolds equation is discretized according to a modified differential scheme based on the full analysis of the pressure balance within the lubrication region. The model is capable of a wide range of lubrication regimes from fully hydrodynamic down to boundary lubrication, and both the steady-state and the time-dependent conditions can be considered. A simplified computational procedure is proposed for elliptical contacts without the ellipticity parameters specified. The evolution of lubrication behavior at startup and shutdown conditions is investigated and the transient effect of surface waviness is discussed. The model application is then extended to contacts of multilayered materials, and the effects of the layer stiffness and the fabrication methods on the stress fields and lubrication performance are analyzed. The conclusions may potentially provide some insightful information for the design and analysis of functional materials and their engineering structures.
A Review of Switched Inertance Hydraulic Converter Technology
Authors: Yuan Chenggang , Pan Min , Plummer Andrew
Published: November 2018

Digital hydraulics is a new technology providing an alternative to conventional proportional or servovalve-controlled systems in the area of fluid power. Research is driven by the need for highly energy efficient hydraulic machines but is relatively immature compared to other energy-saving technologies. Digital hydraulic applications, such as digital pumps, digital valves and actuators, switched inertance hydraulic converters (SIHCs) and digital hydraulic power management systems, all promise high energy efficiency. This review introduces the development of SIHCs and evaluates the device configurations, performance and control strategies that are found in current SIHC research, particularly focusing on the work being undertaken in last 15 years. The designs for highspeed switching valves are evaluated, and their advantages and limitations are discussed. This article concludes with some suggestions for the future development of SIHCs.
High Precision Energy Saving Motion Control of Hydraulic Cylinder Based on Integration of Valves and Pump
Authors: Lyu Litong , Chen Zheng , Yao Bin
Published: November 2018

The independent metering approach makes the two chamber pressure states of the hydraulic actuator completely controllable, which offers the opportunity for energy conservation by reducing the working pressure. However, there still remains a great deal of throttling losses since the entire flow rate is throttling controlled with the valves. In order to avoid throttling losses, the direct pump controlled system might be an option, but the relatively slow dynamic response restricts its application in occasions with response and precision demands. To realize further energy conservation and simultaneous high precision tracking performance, this paper proposes a brand new hardware configuration which integrates the direct pump control, independent metering, and energy reuse methods and takes advantages of their respective strengths. The adaptive robust control approach is applied to deal with the nonlinear control problems. Comparative simulations are done with the focuses on energy consumption and tracking performance.
A Neural Network Strategy for Learning of Nonlinearities Toward Feed-Forward Control of Pressure-Compensated Hydraulic Valves With a Significant Dead Zone
Authors: Nurmi Jarmo , M. Aref Mohammad , Mattila Jouni
Published: November 2018

A velocity feed-forward-based strategy is an effective means for controlling a heavy-duty hydraulic manipulator; in particular, a typical valve-controlled hydraulic manipulator, to compensate for valve dead-zone and other hydraulic valve nonlinearities. Based on our previous work on the adaptive learning of valve velocity feed-forwards, manually labelling and identifying the dead-zones and the other nonlinearities in the velocity feed-forward curves of pressure-compensated hydraulic valves can be avoided. Nevertheless, it may take two to three minutes or more per actuator to identify a pressure-compensated valve’s highly nonlinear velocity feed-forward in real-time with an adaptive approach, which should be reduced for realistic applications. In this paper, inspired by brain signal analysis technologies, we propose a new method based on deep convolutional neural networks comparing with the previous method to significantly reduce this online learning process with the strong nonlinearities of pressure-compensated hydraulic valves. We present simulation results to demonstrate the effectiveness of the deep learning-based learning method compared to the previous results with an adaptive control-based learning.
System Approach in Noise Reduction in Fluid Power Units
Authors: Fiebig W. , Wrobel J.
Published: November 2018

The paper presents a methodology developed to reduce the noise emission in fluid power units. Investigations confirm that during the operation of fluid power units there are many coupled causes of noise generation. In order to propose changes aimed at reducing noise emission the location of sound sources, testing of dynamic properties of the mechanical structure of the power unit and identification of resonant phenomena should be carried out.
Analytical Description of the Static and Dynamic Behaviour of a Pressure Relief Valve
Authors: Osterland Sven , Weber Jürgen
Published: November 2018

The paper presents an explicitly straightforward formulation of the stationary and dynamic behaviour of a pressure relief valve (PRV). This makes it possible to consider the static, dynamic and robustness properties of a PRV during the analysis or design process.

A PRV can be understood as a self-regulating, cross-domain system. The governing equations are well known and widely used in literature. Usually, these include: a geometrical description of the flow area and the pressure surface, a flow equation, the pressure build-up equations, a spring-like counterforce, a flow force, a term for viscous friction and the inertia force. Together they form a system of ordinary non-linear differential equations of third order. So far, these equations had to be solved numerically in order to analyse or adapt the static or dynamic properties of a particular PRV.

In this paper, direct analytical solutions for stationary and dynamic cases are derived. This results in an explicit equation for the respective p-Q characteristic curve. In addition, a simple criterion for the stability of a PRV was found. As it turns out, the minimum requirement for viscous damping is directly anti-proportional to the gradient of the p-Q characteristic curve. It is empirically known that decreasing the gradient of the p-Q curve makes the system more susceptible to oscillations. However, this has not yet been shown mathematically elegant.

The method presented here calculates the static p-Q curve, the stability and natural frequencies of a PRV in a simple procedure using only elementary mathematics — no numerical scheme is required. Thus, the new method offers four main advantages. First, it is several orders of magnitude faster because it is not necessary to solve the differential equation system numerically. Secondly, the user does not require any special knowledge or advanced calculation tools — a simple spreadsheet program is sufficient. This eliminates licensing and training costs. Third, sensitivity and robustness analyses can be carried out easily because the dependencies are explicitly known. Last but not least, the understanding of a PRV is improved by knowing directly which parameters have what influence. The new method is tested and verified by comparison with conventional non-linear numerical simulations.
Closed Loop Position and Pre-Stress Control for a Morphing Aircraft Wing With Distributed Multi-Axis Pneumatic Actuation
Authors: Zhou Hongzhao , Plummer Andrew , Cleaver David
Published: November 2018

This paper presents the design and control of a morphing wing structure using an active tensegrity structure. A tensegrity structure, which is a set of compressive members (struts) stabilized by a set of tensile members (cables) is a good basis for creating a lightweight active structure, due to its potentially high stiffness-to-weight ratio, and the ease with which actuators can be embedded by replacing selected members in the structure. In this work, a multi-axis control scheme is developed for closed loop control of the shape and internal force (pre-stress) of the structure. An experimental prototype has been built, with 6 unidirectional pneumatic cylinders controlled by pulse-width-modulated switching valves. Shape change in terms of twisting and span-wise bending are demonstrated, and an optical motion tracking system is used to help investigate the dynamic position control of the structure. The structure can achieve ±15° twist change for wing angle of attack or ±10° span-wise bending in a 300mm span length. By simultaneously controlling the structural pre-stress, the geometric stiffness of the structure can also be varied. Future research is discussed, which will involve embedding the active structure in a wing aerofoil and testing in a wind tunnel.
Fuel Efficiency Analysis of Selected Hydraulic Hybrids in a Wheel Loader Application
Authors: Huova Mikko , Tammisto Jyrki , Linjama Matti , Tervonen Jussi
Published: November 2018

There is a potential for significant improvement on fuel efficiency of many mobile machines by using hybrid technology as the Diesel engines are often driven at very inefficient operating points in these applications. The load generated by the working hydraulics of a mobile machine is often rapidly changing and contains high peak powers compared to the mean power required. This paper studies three different hydraulic hybrids in a wheel loader application. The study is based on a measured sand-loading Y-cycle. In addition to the hybrid systems, a load sensing proportional valve based reference machine and a modified machine based on independent metering valves are analyzed. All five system alternatives are analyzed systematically to enable a comparison of their fuel efficiency. The study shows that the fuel consumption of the machine can be decreased up to 28 % in such load cycle by using a suitable hydraulic hybrid system.
A Multi-Agent Evolution Algorithm Used for Input Shaping of a Repetitive Non-Linear Dynamic System
Authors: Bender Niels C. , Pedersen Henrik C. , Bech Michael M. , Andersen Torben O.
Published: November 2018

This paper explores the challenges regarding designing a heuristic control algorithm for a dynamic non-linear system with multiple inputs and outputs. The presented algorithm aims to shape the voltage input (both magnitude and timing) applied to fast switching valves in a Digital Displacement® unit. This consists of multiple sub-systems, where optimal decisions must be made, based on the system design and performance criteria. In this regard good performance are defined as: low electrical energy required for switching, accurate switching timing and low plunger velocity near the seat. The proposed algorithm examines the design-space in a user-defined manner combined with stochastic decision making. The randomness of the algorithm is based on the standard deviation between located elite designs. This reveals several feasible input sequences to achieve the goal, and the optimums are benchmarked with a differential evolution algorithm. The techniques are demonstrated by simulation and the results compared showing similar performance of the optimums.
A General Approach to Low-Level Control of Heavy Complex Hybrid Hydromechanical Transmissions
Authors: Larsson L. Viktor , Krus Petter
Published: November 2018

This paper focuses on the low-level control of heavy complex hydraulic hybrids, taking stability and the dynamic properties of the included components into account. A linear model which can describe a high number of hybrid configurations in a straightforward manner is derived and used for the development of a general multiple input multiple output (MIMO) decoupling control strategy. This strategy is tested in non-linear simulations of an example vehicle and stability requirements for the low-level actuators are derived. The results show that static decoupling may be used to simplify the control problem to three individual loops controlling pressure, output speed and engine speed. In particular, the pressure and output speed loops rely on fast displacement controllers for stability. In addition, it was found that the decoupling is facilitated if the hydrostatic units have equal response. The low-level control of heavy complex hydraulic hybrids may thus imply other demands on actuators than what is traditionally assumed.
Novel Fine Positioning Method for Hydraulic Drives Utilizing On/Off-Valves
Authors: Huova Mikko , Linjama Matti , Siivonen Lauri , Deubel Till , Försterling Heino , Stamm Edgar
Published: November 2018

This paper studies a novel on/off-valve-based fine positioning method for hydraulic drives. The method proposed utilizes four on/off-valves in independent metering configuration to reach good positioning accuracy and low power losses. Previously, servo valves have been used in precise position control of hydraulic double acting cylinders. Another approach uses on/off-valves, which are typically driven by using pulse width modulation (PWM) or, if there are parallel connected valves, pulse code modulation (PCM). Typically, both cylinder sides are modulated simultaneously. The new concept proposed uses a cylinder model to calculate a correct opening sequence for the on/off-valves, such that the target piston position is reached. The method proposed modulates single cylinder side at a time in order to achieve small piston position step sizes. Despite relying on the modelled compressibility of the fluid, the method presented requires no knowledge about the bulk modulus of the fluid. It is enough that the bulk modulus of the fluid in both cylinder chambers can be assumed equal. The paper includes the design of the control method, a simulation study proving the validity of the method, and an experimental part investigating the performance in practice. The experimental results show a positioning accuracy of +/− 1 μm with an on/off-valve-based hydraulic drive, the maximum velocity of which is 0.7 m/s.
Modeling and Design of a Series Hydraulic Hybrid Powertrain for Compact Wheel Loaders
Authors: Wen Qunya , Wang Feng , Xu Bing
Published: November 2018

As an effective approach to improving the fuel economy of modern heavy-duty vehicles, hydraulic hybrids have shown great advantages in off-road vehicles. Wheel loader is one of the representative vehicles in off-road applications as they are usually designed for single and repetitive task such as loading material. In a typical short loading cycle, there are many accelerations and decelerations, showing great hybridization potentials. Therefore in this paper a series hydraulic hybrid powertrain has been proposed for compact wheel loader since its hydrostatic powertrain can be easily transformed to a series hydraulic hybrid with an additional hydraulic accumulator. The modeling and system design of the series hydraulic hybrid wheel loader have been presented. Three controllers have been designed for vehicle speed control, engine torque control and engine speed control respectively. A dynamic simulation model has been developed in MATLAB/Simulink. A rule-based energy management strategy (EMS) has been proposed for the series hydraulic hybrid wheel loader. Two different EMS schemes were investigated and compared through simulation studies.
Failure Analysis of Vessel Cover Under Internal Pressure Impulse
Authors: Yang Sha , Dong Qi , Zhang Liucheng
Published: November 2018

When under explosion, the cover of an explosion containment vessel will bear a much higher intensity of impulse loading because of the reflection and superposition of the shock waves, especially in cylindrical vessels. To assure the integrity of the explosion containment vessel closure, a thick steel plate is often used as the cover, while in the supporting part of the shell thickening or reinforcement is also needed. Tooth locks are widely used as a quick-actuating closure. Experiments and numerical simulations were conducted to examine the protective performance of the tooth lock covers. The deformation and failure results agree well with the experimental data. Three types of covers with different number of teeth are calculated. Main factors and weak spots are analyzed with the experimental data and the simulation data. This study may help in the designing of explosion containment vessels and evaluating the protective performance of vessel covers.
Development of Seismic Design Approach Using Inelastic Dynamic Analysis for Equipment and Piping Systems
Authors: Tamura Ichiro , Okubo Atsushi , Minakawa Yusuke , Iijima Tadashi , Goshima Nobuyoshi , Amino Masanori , Okuda Yukihiko , Okuma Shunji
Published: November 2018

Securing an adequate seismic margin has been important in safety reviews regarding the seismic design of equipment and piping systems in nuclear power plants, and there exists an increasing need for a more exact method for evaluating seismic margins. To this end, it is reasonable to take into account the reduction of seismic responses resulting from elastoplastic deformation. The authors, therefore, launched a research program to develop an approach to seismic design that uses elastoplastic dynamic analysis for equipment and piping systems. The allowable limit is one of the essential parameters, especially for our approach of using elastoplastic analysis, and was focused on in the program. We studied this approach by utilizing the conventional allowable limit and other potential limits such as the ductility factor. The applicability of the proposed approach was investigated by comparison with the conventional design method. For the investigation, nonlinear time-history analyses producing elastoplastic responses were conducted, and the results were compared with those of the conventional elastic analysis to quantify the response reduction leading to the seismic margin. For the comparison, the authors used three models that simulated a cantilever beam, tank, and core shroud. In this paper, the beam was constructed and applied to the analysis herein. In the next report, the authors will discuss the applicability of the three models. The cantilever beam is the simplest structure among the three models, and it might be useful for obtaining suggestive results from the analysis. The discussion on the beam, therefore, was conducted prior to the other two models, and, in addition, the sensitivity of model parameters such as yielding stress and secant stiffness will be examined in a parametric study using the model. In this paper, we outline the research program and present a scheme for developing the design approach of using elastoplastic analysis. Moreover, calculated analysis results for the cantilever beam are partly reported, and the applicability of the design approach of using elastoplastic analysis is discussed.
Research on Risk Assessment Method of Stick-Slip Vibration of the Bit Based on BP Neural Network Algorithm
Authors: Chen Chong , Zhang Shimin , Zhang Hang , Li Xiaojun , He Zichen
Published: November 2018

During the drilling process, the non-linear contacts between the bit and the bottom hole, the drill string and the borehole wall can cause the bit’s stick-slip vibration, which will shorten the life of the bit and even endanger the safety of the drill string. The severity of stick-slip vibration of a bit can be identified by the rotary speed of a bit, the triaxial accelerations of the drill string, the wellhead torque and other parameters measured by the measuring while drilling (MWD) tools in the downhole and devices on the surface. To evaluate the level of stick-slip vibration, this paper proposes a risk assessment method of sick-slip vibration based on backpropagation neural network (BPNN). According to the time and frequency domain analysis of the data collected from simulation, the feature parameters of the time and frequency domains of signals are extracted, and then the kernel principal component analysis (KPCA) is applied to reduce dimensions. Consequently, the feature vectors can be obtained, which become the input parameters of the BPNN. Based on BPNN algorithm, the stick-slip vibration of the bit is determined, and the classification of stick-slip vibration strength is carried out. The results show that this method can effectively identify the severity of stick-slip vibration of a bit. Therefore, this method is valid to evaluate the stick-slip vibration of a bit, which will help drillers adjust the drilling parameters practically according to the severity of vibration, so as to reduce the risks of stick-slip vibration during drilling and improve the efficiency and safety of drilling operation.
Application of Genetic-Algorithm-Based Data Reconciliation on Offshore Virtual Flow Metering of Gas-Condensate Field Production
Authors: Wang Dan , Gong Jing , Fan Di , Shi Guoyun , Yang Juheng
Published: November 2018

During present offshore gas-condensate production, flow meters, due to its exceedingly high cost, are being substituted by Virtual Flow Metering (VFM) Technology for monitoring total and single-well flow rates through sensor measurements and physical models. In this work, the inverse problem is solved by Data Reconciliation (DR), minimizing weighted sum of errors with constraints integrating multiple two-phase flow models. The DR problem is solved by Parallel Genetic Algorithm, without complex calculations required by conventional optimization. The newly developed VFM method is tested by data from a realistic gas-condensate production system. The results show good accuracy for the total mass flow rate with model calibration. Meanwhile, recommended single-well flow rate can be provided without physical meters. The method is proved of good robustness with individual pressure sensor invalid, even total flow rate measurements unavailable. The time cost of each reconciliation process can meet the demand of engineering application.
Optimal Design of Spent Fuel Containment Impact Limiter by Response Surface Method
Authors: Hu Haijun , Tong Qiqi , Li Yun , Wang Sheng , Fan Fei , Li Jiancang , Ye Hai , Sheng Peizhen
Published: November 2018

Impact limiters are attached near to the top and the bottom of a spent fuel containment body as shock absorbers to maintain the structural integrity of the containment not only in normal condition but also in hypothetical accident condition of 9m falling. Ellipsoidal-head-like metallic impact limiters are used for a spent fuel containment which is designed to carry 26 spent fuel assemblies. Main geometry dimensions of the limiters, such as diameter, thickness of the shell, length of straight flange and fillet radius, are design variables. The LS-DYNA software is applied to simulate the acceleration of containment in a falling accident. Sensitivity analyses of the variables on acceleration of spent fuel containment in the 9m falling accident are carried out. By response surface method, the best geometry dimensions which minimize the acceleration of the containment in falling accident are achieved. As showed in results, ellipsoidal head shaped metallic impact limiters work very well in the 9m falling accident. They could significantly decrease load factor and provide more safety margin.
Use of PVDF Wires As Sensors for Non Intrusive Pressure Measurement
Authors: Journaix Richard , Ancian Loïc , Salanon Rémi
Published: November 2018

One of the most challenging aspects when performing on-site piping troubleshooting is to obtain the most pertinent information possible regarding piping behavior: acceleration, stress, pressure levels, etc. This last parameter is always difficult to obtain because when pressure taps are available on the line, they are rarely in the area of interest.

PVDF (PolyVinyliDene Fluoride) wire makes it possible to perform non-intrusive pressure measurements but needs to be calibrated in order to have a good representation of phenomenon occurring inside the pipe. After development of a dedicated calibrator and calculation of the fluid/structure coupling coefficient, VibraTec is able to assess PVDF sensor sensitivity according to client’s installation characteristics.

Non-intrusive measurements provide a good accuracy regarding phenomenon amplitude and frequency localization even though some temperature restrictions apply to PVDF measurements.

Although PVDF sensors seem to be simple to implement, particular attention must be paid during installation as this has a direct influence on the PVDF response.
Piston-Lift Check Valve Flow Verification Using CFD
Authors: Laney Matthew , Farrell Ronald
Published: November 2018

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an extension of paper PVP2017-66269, “Check Valve Flow and Disk Lift Simulation Using CFD” [1], and utilizes some of the same concepts to characterize flow through piston-lift check valves. The previous example considered a swing check valve involving rotational movement; this example considers a vertical lift piston check valve involving translational movement. Specifically, CFD was used to determine valve flow coefficients (CV) as a function of disk lift position as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The CFX application, which is part of the ANSYS suite of finite element software, was used to determine the flow characteristics. As presented in PVP2017-66269, balancing flow-induced forces on the check element and considering the disk assembly weight, the valve lift behavior can be predicted. Results from the CFX analysis were compared to recent test results of a skirted disk-piston check valve and previous test results of a standard disk-piston check valve. The results showed good agreement in most cases. This validates that flow characteristics across valves with different types of check elements at different disk lift positions can be reliably predicted using CFD analysis. It is important to note that while the test results and CFD analysis showed good agreement, it was vital that actual testing be performed in order to validate the approach. This follows the recommendation outlined in the previous paper.
Effect of Defect Geometry of Localized External Erosion on Failure of Boiler Tubes
Authors: Kalu I. E. , Inglis H. M. , Kok S.
Published: November 2018

Boiler tubes experience reductions in wall thickness due to erosion and corrosion mechanisms while in use. Due to this localized thinning, the tube becomes susceptible to gross plastic deformation, which eventually causes the tube to rupture. This study presents a non-linear finite element analysis of different geometric configurations of localized boiler tube defects. A defected boiler tube with three variants of the localized thinned area, having different geometrical shapes (flat, n-shape and u-shape) was modeled and subjected to a simulated internal pressure. The effect of the defect geometrical shapes and their dimensions (shape aspect ratios, defect length, width and depth) on the failure of the tube while in use were investigated. From the numerical results, the stress concentration factors (SCF) associated with each defect were obtained, and it was observed that these play a more significant role than the amount of material removal in influencing the failure of the tubes. This relationship between the SCF and the defect geometry characteristics helps to predict which tube with a localized thinning geometry is safe for continued operation or will fail, and hence to categorize the severity of defects to prioritize maintenance spending. The result of this work will serve as a guide to categorize the severity of external boiler tube defects. This is relevant whenever a constrained economic environment does not allow for all boiler tubes with defects to be replaced.
Financial Optimization of a Preventive Replacement Strategy for Individual Components
Authors: Cluever Joseph , Esselman Thomas C. , Harvey Sam
Published: November 2018

Électricité de France (EDF) has developed the Investment Portfolio Optimal Planning (IPOP) software tool [1] to be released with the Integrated Life Cycle Management (ILCM) software tool developed by the Electric Power Research Institute (EPRI) [2]. IPOP is an extremely powerful tool that uses genetic algorithms to provide an optimal strategy for investment in spare components and preventive replacements of multiple components at multiple power plant stations across an entire fleet. A drawback of IPOP is that it requires an extensive amount of user information to run even a single component. In response, Component Optimization Analysis Tools (COATs) was developed to simplify the process of deriving an optimal strategy for purchasing spares and replacements for a single component. This paper describes a two-layer algorithm used in the replacement strategy optimization in COATs. The inner layer consists of a Monte Carlo simulation that estimates the Expected Net Present Value (ENPV) of a given replacement strategy. A strategy consists of: the age of a component at which it needs to be replaced, the age of a component at which a spare should be purchased, years left in the plant at which to skip a scheduled replacement, and the end of life at which the scheduled replacement is skipped; and the years left in the plant at which no more spares are purchased. The Monte Carlo analysis uses these four strategy inputs with component costs, acquisition times, and reliability curves with plant downtime costs to calculate an ENPV for that strategy. The outer layer of the algorithm is an optimization layer that can use either Bayesian optimization or genetic algorithms to maximize the ENPV. These optimization algorithms are routinely available in various software packages and effectively treat the ENPV Monte Carlo as a black box function. An efficiency comparison is given between the two optimization algorithms to demonstrate under which conditions each algorithm out performs the other.
Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry
Authors: Maharjan Dilesh , Hadj-Nacer Mustafa , Greiner Miles , Stefanov Stefan K.
Published: November 2018

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage.

Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.
Analysis of the Influence of the Cooling Patterns and the Shape of the Bulges on the Levels of Stress in the Cylindrical Section of Delayed Coke Drums
Authors: Vivas Gabriel A. , Moret Armando J. , Bello Roberto E. , Melian Luis M. , Bedoya Julian J.
Published: November 2018

Coke drums are thin-walled pressure vessels that experience low cycle fatigue due to thermal loadings. The delayed coking process is comprised by three major stages: heating, coking and cooling, which repeat at intervals between 20 and 48 hours. The cyclic changes of temperature increase the growth of bulges and cracks which with the passing of time, propagate and eventually cause failures due to the loss of containment. A better understanding of the phenomena of the thermal gradients and their influence on the generated stresses would reduce the effects of the damage mechanisms afflicting coke drums, for example; a continuous monitoring system could be implemented in order to control the cooling ramp to obtain a more homogeneous quenching around the cylinder of the coke drum and consequently increase its lifetime. It is been widely accepted that there is a relationship between high cooling rates in isolated zones and high axial stresses. However, this relationship has not been fully validated, since there are also been reported events of low cooling rates and high stresses. This study shows a predictable behavior (trend) that relates the spatial thermal gradients and the axial and circumferential stresses generated.

A coke drum in an upgrader facility was instrumented with two arrays or grids, each of them having 24 thermocouples and 2 strain gauges in zones with distinct bulges. One arrangement was located at an inward bulge while the other was located at an outward bulge. Computational models were carried out to reproduce the behavior of the instrumented zones with their actual deformations obtained from laser scanning. Finite element models were developed using a sequentially coupled thermo-mechanical analysis to determine the transient temperature and stress distributions. The effect of the circumferential thermal gradients on the stress levels in the instrumented cylindrical sections were analyzed, considering two cases; the first of them a perfect cylinder (without deformation) and the second one considering the presence of bulges in the area of interest.

The results indicate that there is a relationship between the circumferential thermal gradients [°C/m] or [°F/ft] and the axial stress levels, i.e., cold zones generate axial tensile stresses, and hot zones produce compressive axial stresses. This relationship is affected — exacerbated or counteracted — by the presence of the bulges. Additionally, the results obtained in this paper confirm those of previous investigations showing that outward bulges subject to pressure and thermal loading generate high stresses on its internal surface and low stresses on its external face whereas inward bulges produce the opposite effect.