bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer Model of a 50 kW Solar Receiver–Reactor for Thermochemical Redox Cycling Using Cerium Dioxide
Authors: Zoller S. , Koepf E. , Roos P. , Steinfeld A.
Published: November 2018

This work reports on the development of a transient heat transfer model of a solar receiver–reactor designed for thermochemical redox cycling by temperature and pressure swing of pure cerium dioxide in the form of a reticulated porous ceramic (RPC). In the first, endothermal step, the cerium dioxide RPC is directly heated with concentrated solar radiation to 1500 °C while under vacuum pressure of less than 10 mbar, thereby releasing oxygen from its crystal lattice. In the subsequent, exothermic step, the reactor is repressurized with carbon dioxide as it cools, and at temperatures below 1000 °C, the partially reduced cerium dioxide is re-oxidized with a flow of carbon dioxide. To analyze the performance of the solar reactor and to gain insight into improved design and operational conditions, a transient heat transfer model of the solar reactor for a solar radiative input power of 50 kW during the reduction step was developed and implemented in ANSYS cfx. The numerical model couples the incoming concentrated solar radiation using Monte Carlo ray tracing, incorporates the reduction chemistry by assuming thermodynamic equilibrium, and accounts for internal radiation heat transfer inside the porous ceria by applying effective heat transfer properties. The model was experimentally validated using data acquired in a high-flux solar simulator (HFSS), where temperature evolution and oxygen production results from model and experiment agreed well. The numerical results indicate the prominent influence of solar radiative input power, where increasing it substantially reduces reduction time of the cerium dioxide structure. Consequently, the model predicts a solar-to-fuel energy conversion efficiency of >6% at a solar radiative power input of 50 kW; efficiency >10% can be obtained provided the RPC macroporosity is substantially increased, and better volumetric absorption and uniform heating is achieved. Managing the ceria surface temperature during reduction to avoid sublimation is a critical design consideration for direct absorption solar receiver–reactors.
Numerical Modeling of Polymer Electrolyte Fuel Cells With Analytical and Experimental Validation
Authors: Zhang S. , Reimer U. , Rahim Y. , Beale S. B. , Lehnert W.
Published: November 2018

A computational fluid dynamics model for high-temperature polymer electrolyte fuel cells (PEFC) is developed. This allows for three-dimensional (3D) transport-coupled calculations to be conducted. All major transport phenomena and electrochemical processes are taken into consideration. Verification of the present model is achieved by comparison with current density and oxygen concentration distributions along a one-dimensional (1D) channel. Validation is achieved by comparison with polarization curves from experimental data gathered in-house. Deviations between experimental and numerical results are minor. Internal transport phenomena are also analyzed. Local variations of current density from under channel regions and under rib regions are displayed, as are oxygen mole fractions. The serpentine gas channels contribute positively to gas redistribution in the gas diffusion layers (GDLs) and channels.
Correlations for the Prediction of Intermittency and Turbulent Spot Production Rate in Separated Flows
Authors: Dellacasagrande M. , Guida R. , Lengani D. , Simoni D. , Ubaldi M. , Zunino P.
Published: November 2018

Experimental data describing laminar separation bubbles developing under strong adverse pressure gradients, typical of ultra-high-lift turbine blades, have been analyzed to define empirical correlations able to predict the main features of the separated flow transition. Tests have been performed for three different Reynolds numbers and three different free-stream turbulence intensity levels. For each condition, around 4000 particle image velocimetry (PIV) snapshots have been acquired. A wavelet-based intermittency detection technique, able to identify the large scale vortices shed as a consequence of the separation, has been applied to the large amount of data to efficiently compute the intermittency function for the different conditions. The transition onset and end positions, as well as the turbulent spot production rate, are evaluated. Thanks to the recent advancements in the understanding on the role played by Reynolds number and free-stream turbulence intensity on the dynamics leading to transition in separated flows, guest functions are proposed in the paper to fit the data. The proposed functions are able to mimic the effects of Reynolds number and free-stream turbulence intensity level on the receptivity process of the boundary layer in the attached part, on the disturbance exponential growth rate observed in the linear stability region of the separated shear layer, as well as on the nonlinear later stage of completing transition. Once identified the structure of the correlation functions, a fitting process with own and literature data allowed us to calibrate the unknown constants. Results reported in the paper show the ability of the proposed correlations to adequately predict the transition process in the case of separated flows. The correlation for the spot production rate here proposed extends the correlations proposed in literature for attached (by-pass like) transition process, and could be used in γ–Reϑ codes, where the spot production rate appears as a source term in the intermittency function transport equation.
Heat Transfer Augmentation Using an Innovative Helicoidal Finned Absorber Plate in a Solar Air Heater—A Numerical Study
Authors: Purohit Shantanu , Madhwesh N. , Vasudeva Karanth K. , Yagnesh Sharma N.
Published: November 2018

This study presents an innovative idea to augment heat transfer to an air heater using helicoidal finned arrangement. A parametric analysis of the helicoidal shaped fin geometry is considered with helicoidal pitch ratio of 0.1666–0.3, fin diameter ratio of 1.75–2. For the placement of the fin beneath the absorber plate, longitudinal pitch ratio ranging from 0.0416 to 0.1666 are used. The flow Reynolds number used for the study ranges from 4800 to 25,000. The effects of helicoidal pitch ratio, wire diameter ratio and longitudinal pitch ratio on Nusselt number and friction factor have been discussed. It is seen from the analysis that there is a significant improvement in Nusselt number for the case of helicoidal fin of wire diameter ratio of 1 when compared to base model as well as straight fin model for the operating range of Reynolds number. It is also observed from the analysis that for the helicoidal fin configuration of helicoidal pitch ratio of 0.2333, friction factor appears to be moderate. Flow and roughness parameters for roughened solar air heater have been optimized using thermal-hydraulic enhancement factor (THEF). The study reveals that by the use of helicoidal fins, maximum enhancement in the Nusselt number is found to be 2.21 times when compared to the base model for longitudinal pitch ratio of 0.0416, helicoidal pitch ratio of 0.166 for a fixed wire diameter. The improvement obtained in performance corresponding to increased Nusselt number establishes the efficacy the helicoidal fin design for the absorber plate.
Nickel Aluminum Matrix Solid-Lubricating Composite Lubricated by Silver and Silver Vanadate Formed by Tribochemistry at Elevated Temperature
Authors: Zhu Shengyu , Tan Hui , Cheng Jun , Yu Yuan , Qiao Zhuhui , Yang Jun
Published: November 2018

The synergistic effect of solid lubricants plays a significant role in wide-temperature-range lubrication, where the combination of lubricious oxide and Ag is the promising solid lubricants. In this paper, the friction and wear performances of Ni3Al with the addition of Ag and V2O5 solid-lubricating composites were evaluated from room temperature to 1000 °C. It was found that Ni3Al matrix composite with the addition of V2O5 has high friction coefficient of 0.3–0.7, while Ni3Al matrix composite with simultaneous addition of Ag and 2 wt % V2O5 has a relatively low friction coefficient of 0.25–0.4 between room temperature and 1000 °C and wear rate with the magnitude of 10−5 mm3/N m at high temperatures. The results revealed that nickel aluminum matrix solid-lubricating composite lubricated by silver and in situ formed silver vanadate at elevated temperature achieves a wide-temperature-range lubrication, which is attributed to the synergistic action of silver and silver vanadate formed at high temperatures.
Repairing Automotive Dies With Directed Energy Deposition: Industrial Application and Life Cycle Analysis
Authors: Bennett Jennifer , Garcia Daniel , Kendrick Marie , Hartman Travis , Hyatt Gregory , Ehmann Kornel , You Fengqi , Cao Jian
Published: November 2018

Powder-based additive manufacturing technologies are developing rapidly. To assess their applicability, comparison of performance and environmental impacts between additive technologies and conventional techniques must be performed. Toyota manufactures over two million aluminum four-cylinder engines in the U.S. each year via die casting. The dies used in this process are traditionally repaired via tungsten inert gas (TIG) welding and only last an average of 20.8% of the number of cycles of the original die life before another repair is needed. A hybrid repair process involving machining away the damaged areas and then rebuilding them additively via powder-blown directed energy deposition (DED) has been developed. The die repaired via DED resulted in the same life as the original die. The use of DED repair eliminated the need for emergency repairs and nonscheduled downtime on the line because the DED repaired dies last for as many cycles as the original die before another repair is needed. Life cycle analyses were conducted comparing the traditional welding repair process to the DED repair process. The results show that the DED repair process results in significantly less damage to the assessed impact categories except for ionizing radiation. Therefore, it can be concluded that the DED repair process could lessen most environmental impacts compared to traditional welding repair. Further work toward increasing energy and material efficiencies of the method could yield further reductions in environmental impacts.
Dynamic Response of Pressure Compensated Variable Displacement Linkage Pump
Authors: Fulbright Nathaniel J. , Van de Ven James D.
Published: November 2018

The Variable Displacement Linkage Pump (VDLP) uses an adjustable planar linkage to vary the displacement of the piston. Previous work focused on dynamic modeling of the pump at fixed displacements and therefore did not account for the displacement control method or the dynamics of changing displacement. One key application of the VDLP is in pressure compensated, high-pressure water hydraulics. This paper expands on previous modeling work to include the behavior of the hydro-mechanical pressure compensation valves and the displacement control linkage. The multi-domain dynamic model captures the fluid dynamics in the pumping chambers and poppet-style control valves; the dynamics of the control valves; and the kinematics and kinetics of the two degree-of-freedom nine-bar pump linkage. The dynamic model was exercised in a simulation of the pump responding to changing demands in the output flow rate. Simulation results showed that quick response times of 100 milliseconds to a step in the load were achieved. Overshoot of the displacement is damped using an orifice in the control line. A physical prototype of the VDLP was used to validate the simulation results.
Floating Frame of Reference Formulation for a Flexible Manipulator With Hydraulic Actuation: Modelling and Experimental Validation
Authors: Mäkinen Petri , Dmitrochenko Oleg , Mattila Jouni
Published: November 2018

One of the current and future trends in robotics is to reduce the weight of a robotic manipulator by using lightweight materials, such as ultra-high-strength steel or composites. The reduction in weight results in material and fuel savings, which are highly relevant for heavy-duty, off-highway manipulators found in excavators, truck-mounted cranes, and forestry machines. Due to the highly demanding working conditions of such manipulators, hydraulic actuation is mainly used. Automated and accurate control of these manipulators is very challenging due to the nonlinearities present in the system. Recent studies indicate that nonlinear model-based control (NMBC) methods can provide the most advanced control performance in the case of hydraulic robotic manipulators. An accurate model capturing the dynamics of the physical system is required for effective NMBC design. The present study proposes a hybrid rigid-flexible model for a flexible manipulator combined with a hydraulic actuator, implemented with the help of the floating frame of reference formulation (FFRF). The designed model is validated by comparing simulations with experimental reference data obtained from an OptiTrack motion-capture system and other sensors. The comparative results demonstrate that the model is able to capture the system’s dynamics accurately, which motivates further research on developing NMBC methods using the FFRF.
Transmission of Fluid Borne Noise in the Reservoir
Authors: Fiebig W. , Wrobel J. , Cependa P.
Published: November 2018

The paper presents results of research on the transmission of fluid borne noise in reservoir filled with fluid. This type of transmission of vibrational energy in the fluid occurs in fluid power units, in which hydraulic pumps are immersed in the liquid in the tank i.e. in the vertical mounting of the electric motor on the reservoir. There are vibrating elements submerged in the fluid like pumps, pipe elements, filters, etc. Due to the vibration of these elements fluid borne noise will be generated which will be transmitted to the tank structure. The transmission of fluid borne noise is dependent on natural frequencies of the tank structure. Based on model investigations, the mechanism and factors influencing the intensity of transmission of fluid borne noise in a reservoir were presented. The results of simulations with FEM were compared with the results of experimental investigations.
Digital Hydraulic Winch Drives
Authors: Larsen Henrik B. , Kjelland Magnus , Holland Anders , Lindholdt Per N.
Published: November 2018

This paper presents the planned use of digital displacement high torque low speed motors to drive large winches in off-shore and maritime applications.

The digital displacement technology uses forced actuation of high- and low pressure valves for each cylinder chamber, i.e. valves are opened and closed by actuation forces independently of cylinder pressure and supply pressures. Motors equipped with the technology are well suited for low speed secondary controlled operation including start and stop. It also enables unloading of motor cylinders that are not needed to produce torque, whereby excellent efficiency at partial displacement is obtained.

A research project on application of multi digital motors on a winch with lifting capacity in the 150 t range is presented, and advantages of using such winch drives in off-shore and maritime lifting operations are discussed.

Positioning and metering are challenges in winch systems with traditional drives. A unique control scheme that allows very fine positioning of the motor shaft is presented. The performance of this method is shown in simulation and demonstrated with measurements on a motor.
Model-Based Control of a Digital Hydraulic Transformer-Based Hybrid Actuator
Authors: Linjama Matti
Published: November 2018

Energy-efficient motion control of hydraulic actuators is a challenging task. Throttle-free solutions have the potential for high efficiency. The main throttle-free approaches are pump-controlled systems, transformer-based solutions, and digital hydraulic solutions, such as switching transformers, multi-chamber cylinder and multi-pressure systems. This paper presents a novel solution based on a so-called digital hydraulic power management system (DHPMS). The DHPMS is freely rotating and a hydraulic accumulator is used for energy storage. In contrast to existing approaches, each actuator has its own DHPMS and a small accumulator to locally handle the power peaks. Only an average amount of power is needed from the hydraulic grid, radically reducing the size of the supply pump and the hydraulic piping and hosing. Pump flow is only 12.5% of the peak flow of the actuator in the case studied. Control of this type of system is challenging, and the model-based approach is used. The controller uses a simplified model and functionality is verified by using a detailed simulation model of the system. The results show that the approach is feasible but is demanding on the control valves. The system delay is also relatively long, which reduces the control performance in high-end systems. Nevertheless, this approach has potential in mobile machines, for example.
A Robust Pressure Controller for a Variable Speed AC Motor Pump: Application to Aircraft Hydraulic Power Packages
Authors: Trochelmann Nils , Bischof Stump Phillip , Thielecke Frank , Metzler Dirk , Bassett Stefan
Published: November 2018

Highly integrated electro-hydraulic power packages with electric motor-driven pumps (EMP) are a key technology for future aircraft with electric distribution systems. State of the art aircraft EMPs are robust but lack efficiency, availability, and have high noise emissions. Variable speed fixed displacement (VSFD-) EMPs, combining a permanent magnet synchronous motor and an internal gear pump, show promising properties regarding noise reduction and energy efficiency. Though, meeting the strict dynamic requirements is tough with this EMP-concept. Speed limitations and inertia impose strong restrictions on the achievable dynamic performance. Moreover, the requirements must be met under a wide range of operating conditions. For a prototype aircraft VSFD-EMP a robust pressure controller design is proposed in this paper. In a first step the operating conditions of the EMP are defined, analyzing environmental conditions and impacts of the interfacing aircraft systems. Nonlinear and linear control design models are developed and validated by measurements at an EMP test rig built for this project. A conventional cascade pressure control concept is selected. This is motivated by the demand for simple, reliable, and proven solutions in aerospace applications. A controller is designed by applying classical loop shaping techniques. Robust stability and performance of the system are investigated through a subsequent μ-analysis. Finally, the controller is tested under nominal and worst case conditions in nonlinear simulations.
A Hydraulic Piloting Concept of a Digital Cylinder Drive for Exoskeletons
Authors: Scheidl Rudolf , Mittlböck Simon
Published: November 2018

The use of a digital cylinder drive for exoskeletons was proposed in the recent year as a means to save weight, installation space, and energy. Also the hydraulic actuation of the switching valves of the digital drive was brought into discussion, in particular by a so called hydraulic digital counter concept. That concept was originally invented to realize a digital hydraulic amplifier. It uses a mechanical input and feedback, transfers this into binary switching states of the valves which switch the chambers of the digital cylinder either to tank or system pressure. It is now reconsidered with a hydraulic input, a special design of the valves appropriate for the sub-kilowatts power ranges of exoskeletons, and a special control strategy. The configuration of this system with a true binary counting property requires the input pressure thresholds to grow exponentially with the number of binary stages of the drive. That limits the number of feasible stages to approximately five or six, complicates the mechanical parts of the valves which realize the hysteretic response to the pilot pressure, and increases the hydraulic power for valve actuation. To overcome these problems the system is configured as a quasi binary counter which jumps over certain digits if the input flow is monotonous, thus, requires a reversal of input flow to realize those digits. A theory and a numerical model of the counter in this configuration and a proper counting control strategy of the hydraulic input are presented. With this much higher number of digits can be realized and valve design and configuration are eased.
Numerical Modeling of a Helical External Gear Pump With Continuous-Contact Gear Profile: A Comparison Between a Lumped-Parameter and a 3D CFD Approach of Simulation
Authors: Zhao Xinran , Vacca Andrea , Dhar Sujan
Published: November 2018

The concept of continuous-contact helical gear pumps (CCHGP) has been proposed and successfully commercialized in the recent past. Thanks to the continuous-contact rotor profile design and to the helical gear structure, this design eliminates the kinematic flow oscillation. This has important implications on the fluid borne noise generation, which is considered as one of the major sources of noise emissions and mechanical vibrations for positive displacement machines. Although the commercial success of the CCHGP concept, there is very little published studies about the underling physics at the basis of the functioning of this type of design. This is mostly due to the complexity of the fluid domain that characterize the functioning of CCHGP units. In this paper, a transient 3D CFD study is conducted for a reference CCHGP unit for high-pressure (up to 200 bar) fluid power applications. The results of the 3D CFD simulation are compared with those given by a lumped-parameter model developed at the Maha Fluid Power Research Center of Purdue University (USA), which was previously validated against experimental results. The results show how with a proper discretization of the fluid domain the CFD simulation approach can be used for the case of helical CCHGP units. Both models provide a good description of the main features of operation of the unit. The lumped parameter model is quicker, thus suitable for fast optimization studies. However, the CFD results not only can be used to support the main assumptions done on the lumped parameter model, they also permit to gain further insight on the operation of the CCHGP unit, particularly with respect to the flow features of the meshing process.
Review of Early Work on Digital Displacement® Hydrostatic Transmission Systems
Authors: Caldwell Niall
Published: November 2018

The paper describes the work done by the author (1) from 1999 to 2006 to develop the Digital Displacement Pump (DDP) and Pump/Motor (DDPM) and demonstrate the feasibility of off-highway vehicle applications.

The link between DDPM capacity and the solenoid valve performance was identified. Magnetic geometry was improved by parametric FEA, then time-domain behavior was improved with a hybrid FEA/lumped-parameter model.

Software improvements allowed variable speed and bidirectional operation, enabling the demonstration of the first Digital Displacement Transmission (DDT) systems on a vehicle, one featuring a load-sensing DDP and secondary control by DDPM displacement, and one featuring primary control by DDP displacement and a conventional axial motor.

A time-domain simulation was created of the primary-controlled vehicle, which yielded good comparison to experimental results. The deterministic nature of the DDP lends itself to model-based system design methods, which have since been used to develop larger commercial systems.

The first detailed analysis of DDP efficiency characteristics revealed profound differences to conventional variable displacement pumps, including exceptional part-load efficiency and the dominant effect of fluid compressibility. A peak overall efficiency of 97% was recorded for a DDP after analysis of loss sources prompted design improvement.
Online Controller Setpoint Optimization for Traction Control Systems Applied to Construction Machinery
Authors: Alexander Addison , Sciancalepore Annalisa , Vacca Andrea
Published: November 2018

The development of a suitable traction control system for off-road heavy machinery is complicated by several different factors, which differentiate these machines from typical on-road systems. One such difficulty arises from the fact that they are often operated on ground conditions which can vary widely and rapidly. Due to this, traction control systems designed for these vehicles must be robust to a large array of surface types, and they must be capable of reacting quickly to significant changes in those types. In order to accomplish this, this paper proposes an online parameter optimization technique suitable for tuning the setpoint of a control system to maximize the tractive potential of a construction vehicle in real time. The traction control principle itself is based on selectively braking wheels which are slipping. It also attempts to account for the interactions of the transmission systems that deliver power from the engine to the wheels. This research uses a wheel loader as a reference machine for assessing controller performance. Drawing on previous work in simulation and controller design, a system model was developed which incorporates the vehicle dynamics of the machine as well as the behavior of the electrohydraulic brakes. This system model was leveraged to understand the effect of different optimization schemes on the performance of the traction control.

The self-tuning algorithm is based on a compound optimization method utilizing both a system identification component and a parameter tuning component. The first part optimizes the model parameters to fit it as well as possible to measured slip-friction data. Based on the results of this, the second part draws from theories of wheel traction to maximize a balance of pushing force and traction effectiveness. The result is a method which can achieve the proper setpoint based on real-time data describing the ground condition. This system was run first in simulation and then on a modified vehicle system. In both cases, the algorithm allows the controller to find better setpoints to improve the traction control performance online.
Assessment of Failure Modes of Monolithic Fuel Plates
Authors: Ozaltun Hakan , Medvedev Pavel G. , Rabin Barry H.
Published: November 2018

Monolithic fuel is a fuel form that is considered for the conversion of high performance research reactors. In order to qualify this new fuel system, the fuel plates should meet the safety standards and perform well in reactor. The fuel system must maintain its mechanical integrity, sustain a geometric stability and should have stable and predictable irradiation behavior. The requirement to maintain mechanical integrity under normal operating conditions is primarily demonstrated by a successful testing of fuel plates up to the limiting conditions defined by the fuel performance envelope, including an adequate margin. Although large number of plates have been tested with satisfactory thermo-mechanical performance, post-irradiation examination of plates from previous RERTR-12 experiments have revealed that pillowing occurred in several plates, rendering performance of these plates unacceptable. To address such failures, efforts are underway to define the mechanisms responsible for the in-reactor pillowing, and suggest improvements to the fuel plate design and operational envelope. For this purpose, selected plates from previous experiments were simulated to understand the thermo-mechanical response of the plates to the fission density and thermally induced stresses. Simulation results were then comparatively evaluated with post-irradiation examinations of selected plates. The simulation results and experimental observations established a possible correlation between failure by plate pillowing, high porosity and a presence of tensile stress state. The study has implied that porosity leading to degradation of material properties, accompanied by a sufficiently large tensile stress state can lead to a pillowing-type failure at reactor shutdown. This paper presents these findings, discusses such failure modes, and the influence of fuel burn-up and power on the magnitude of the shutdown-induced tensile stresses.
Premature Degradation and Failure of Steam-Methane Reformer Heater System Components
Authors: Aumuller John J. , Carucci Vincent
Published: November 2018

Bulk hydrogen production in a petroleum refinery by steam–methane reforming utilizes high temperatures, moderate pressures and catalyst – filled tubes which generate high tube temperatures of up to 1,690 °F [920 °C] imposing relatively harsh performance demands on system components which are not usually encountered in other refinery or petrochemical plant equipment.

Creep rupture and high temperature cycling place a severe service duty on the catalyst tubes, tube outlet pigtails, the subheader train and the downstream steam generator leading to ruptured pigtails, cracking in sub-headers and break up of the ceramic tube sheet ferrules at the steam generator inlet tubesheet.

Although the industry has developed specific fit-for-purpose design practice standards augmented with detailed technical reports, reliability issues persist and regularly force premature shutdown of the reformer heater and downstream heat recovery equipment.

Among these practices are API Standard 530 and API TR 942-A. API 530 assists designers in the selection of materials and determination of pressure design thickness of heater tubes while API TR 942-A attempts to reconcile the contradictory industry experience where some operators have little or no problems while others suffer premature degradation and cracking of outlet pigtails and manifold components.

A reconciliation between application of industry design practices and equipment performance is presented in this paper to determine whether systemic issues contribute to the apparent situation; and, recommendations are made for pressure component design and material selection for steam-methane reformers.
Finite Element Analysis of a Pressure Vessel Subjected to an Internal Blast Load
Authors: Barsoum I. , Sadiq L.
Published: November 2018

The objective of the current work is to model a stainless steel SA 316L autoclave explosion and rupture that occurred during a research laboratory experiment designed to study the thermal decomposition of ammonium tetrathiomolybdate in the presence of dimethyl sulfoxide (DSMO) in an autoclave. The explosion was believed to have occurred because DMSO was used in excess in the experiment and heated beyond its decomposition temperature. The aim of the current study is to investigate the effect of internal blast load on a pressure vessel made of stainless steel AISI 316L through finite element analysis. Numerical simulation using FEA is performed to better understand the cause of failure of the pressure vessel. The finite element model predicts very well the structural response and subsequent failure of the actual incident and the results reveal that the root cause to failure was an internal blast load, which arose from the decomposition of DMSO at high temperature.
An Application of Singular Spectrum Analysis for Internal Valve Leakage Signals Denoising in a Natural Gas Pipeline
Authors: Zhu Shenbin , Li Zhenlin , Zhang Shimin , Yu Ying
Published: November 2018

Internal valve leakage in a natural gas pipeline not only brings huge economic losses to the petroleum enterprises, but also causes immeasurable environmental pollution. Therefore, the diagnosis of internal valve leakage and the prediction of leakage rates are the basis to ensure the safe operation of natural gas pipeline. In this paper, based on acoustic emission detection system, the internal valve leakage signals were collected, which were analyzed and processed to diagnose the internal valve leakage and predict the leakage rates. Due to the complex work environment and serious noise interference, the collected acoustic emission signals contain a large amount of environmental noise. Therefore, singular spectrum analysis was proposed to reduce the environmental noise in acoustic emission signals. Radial basis function neural network was used to predict the leakage rates. Experimental results demonstrate that pure internal leakage source signals can be obtained via singular spectrum analysis. The prediction accuracy of leakage rates based on the characteristic parameters of pure AE signals is better than the accuracy without signals denoising. Therefore, singular spectrum analysis is an effective denoising method for acoustic emission signals, which can improve the prediction accuracy of internal valve leakage rate.
Failure Analysis of Furnace Tube in the Radiation Section of Ethylene Cracking Furnace
Authors: Liu Wen , Sun GuoDong , Xing Jian , Hu Zhenlong , Cao Luowei , Zhuang Fakun
Published: November 2018

A crack was observed on the tube of radiation section of ethylene cracking furnace during operation. The material of the tube is KHR35CT-HiSi. This paper details the investigation into the failure and highlights the most probable cause of the failure based on available documents and experimental analysis, visual examination, chemical composition analysis, metallographic examination, scanning electron microscope analysis, energy spectrum analysis, X-ray diffraction analysis, fracture morphology observation was performed. Comprehensive data access, macro examination and the results of analysis, the failure of the furnace pipe is due to brittle fracture. The main reason for embrittlement of furnace tube is serious carburization of the pipe inside. Carburization can lead to two consequences. The first is to make the pipe become brittle; the second is the difference of the thermal expansion coefficient between carburization layer and non-carburization layer, which makes the pipe produce a large thermal stress, that can produce a micro crack in the Transitional position of the carburization layer and the non–carburization layer. The above two points are confirmed by experiments. The brittle fracture of tube is produced by the combined action of the micro crack and carburization.
Simplified Analysis of Strains Accumulated in the State of Elastic Shakedown Considering Multi-Parameter Loadings
Authors: Hübel Hartwig , Vollrath Bastian
Published: November 2018

In case of cyclic loading, strain may accumulate due to a ratcheting mechanism until the state of shakedown is possibly achieved. Design Codes frequently require strain limits to be satisfied at the end of the specified lifetime of the structure. However, this requirement is sometimes tied to misleading prerequisites, and little guidance is provided on how the strains accumulated in the state of shakedown can be calculated. Incremental elastic-plastic analyses which require to go step-by-step through many cycles of a given load histogram are rather costly in terms of engineering time and numerical effort. As an alternative, the Simplified Theory of Plastic Zones (STPZ) is used in the present paper. Being a direct method, effects from load history are disregarded. The theory is described shortly and exemplarily applied to a simplification of a pipe bend and a straight pipe, both subjected to combinations of several loads which vary independently from each other so that a multidimensional load domain is represented. It is shown that the Simplified Theory of Plastic Zones is well suited to provide reasonable estimates of strains accumulated in the state of elastic shakedown at the cost of few linear elastic analyses.
Modeling and Mitigation of Acoustic Induced Vibration (AIV) in Piping Systems
Authors: Ridens Brandon L. , Allison Timothy C. , Simons Sarah B. , Brun Klaus
Published: November 2018

This paper explores new analysis techniques and mitigation concepts developed to extend the current state of the art acoustic induced vibrations (AIV) analyses. These new methods are intended to provide more accurate evaluations of this phenomenon in an attempt to solve AIV problems found in blowdown and piping systems. Current screening methods for AIV are based on pass/fail data with minimal or undesired options for reducing the likelihood of failure for AIV events. Computational fluid dynamics simulations and finite element analysis in combination with lab testing of novel mitigation options using accelerometers, dynamic pressure transducers, and strain gages were performed to better understand the phenomenon and develop possible solutions to reduce the impact of AIV on piping systems.

Results of the testing and analyses performed at the Southwest Research Institute (SwRI) indicate that there is a possible correlation with acoustic modes, structural modes, and elevated stresses during AIV events. Minor reductions in dynamic pressure fluctuations throughout piping during AIV events can be made by changes in valve geometry and piping configurations. Results of CFD modeling and analysis demonstrate that computational analysis can be used to evaluate mitigation strategies and suggest that the use of a dampener as a mitigation technique may be successful in reducing the amplitudes of dynamic pressure waves in piping systems caused by AIV events.
Assembly of Bolted Flanged and Support Joints for Use in Elevated Temperature Exhaust Systems
Authors: Dorgan Jason E. , Gjinolli Agron E.
Published: November 2018

Ancillary exhaust system structural design for turbines typically employs a separation of responsibilities between the design and installation functions. The design expectations must be implemented correctly during the installation phase to allow long-term serviceability and success of the turbine exhaust system.

This paper will explore a case study reviewing bolt tightening of duct structural angle and plate flange joints using compressible high temperature fiberglass gasket material, as well as design suggestions for metal-on-metal duct sliding support joints to structural steel. Improper design and operation can lead to failure, downtime, warranty cost and reduced design life of the exhaust system. It is not uncommon for field installation personnel to modify key system design requirements during the installation phase; typically out of habit, perceived best practice, missed installation instructions and/or misunderstanding the system behavior. In addition, maintenance recommendations are often overlooked.

Literature provides extensive background for bolting of stationary metal-to-metal plate joints, rigid gaskets and pressure vessel joints. There is a gap with respect to structural angle and plate flange joint bolt tensioning using compressible fiberglass gaskets at low pressures and high temperatures. Much of the industry standard tightening philosophy is useful, but has not been extensively studied and written about with respect to flanges under high exhaust temperatures or for sliding joints exposed to thermal expansion.

This paper summarizes current industry practice, presents relevant test data and a case study, analyzes the effects of high thermal stresses, and recommends a tightening procedure for typical field applications of flange joints using high temperature gaskets, and the design of metal-to-metal sliding support joints.
Prediction of Fracture Toughness Temperature Dependence Over a Wide Temperature Range Using Simplified and Direct Scaling Method
Authors: Inoue Takashi , Meshii Toshiyuki
Published: November 2018

The fracture toughness KJc of the material in the ductile to brittle transition temperature (DBTT) range exhibits both test specimen thickness (TST) dependence and temperature dependence. Attention has been paid to the master curve (MC) method, which provides an engineering approach to address these two issues. Although MC is intended to be applied to arbitrary ferritic material whose yield stress is within the range of 275 to 825 MPa, the KJc value must be obtained to determine the material dependent reference temperature T0. The applicable range of MC method is restricted to T0 ± 50 °C. Previous studies indicate that additional pre-tests to obtain T0 are necessary; thus, there might be some unwritten requirement to the test temperature for the KJc temperature dependence prediction in MC method to work effectively. If testing must be conducted for the material of interest at some restricted temperature, a more flexible KJc temperature dependence prediction can possibly be obtained for a wide temperature range in the DBTT range, if the simplified and direct scaling (SDS) method, which predicts fracture “load” from yield stress temperature dependence proposed previously is applied. In this study, the SDS method was applied to two different steels: Cr-Mo steel JIS SCM440 and 0.55% carbon steel JIS S55C. Both tensile and fracture toughness tests were performed over a wide range of temperatures, specifically, −166 to 100 °C for SCM440 and −166 to 20 °C for S55C. The SDS method (i.e., fracture load is proportional to 1/(yield stress)) was initially validated for the specimens in the DBTT range. Finally, a simplified method was proposed and initially validated to predict the KJc temperature dependence, by applying the SDS using the EPRI plastic J functional form.
Three Dimensional Finite Element Analyses of Welding Residual Stresses of a Repaired Weld
Authors: Chen Mingya , Yu Weiwei , Xue Fei , Ku Francis , Chen Zhilin , Shi Jinhua
Published: November 2018

The objective of this study is to correct installation non-conformance of a surge line using the excavation and re-weld method which is widely used in nuclear power plants. The surge line with a backslope was not at the required design level after initial installation. In order to solve the problem, a repairing technology is shown as follows: the weld was successively excavated and welded again while the surge line slope was corrected with the help of jacks. Because many of the degradation mechanisms relevant to power plant components can be accelerated by the presence of welding residual stresses (WRS), the WRS caused by the repairing process need to be studied. In this paper, the WRS simulation technique employed in this project is sophisticated. It utilizes a 3-D finite element (FE) model, and simulates the weld sequencing and excavation. Moreover, the WRS simulation performed in this project not only uses the un-axisymmetric model, but also considers the deformation caused by the external jacking loads. The results show that the repairing process is effective, and strain damage induced by the welding repair is also acceptable.
Seismic Behaviour of Torsionally Coupled Structures Equipped With Viscoelastic Dampers
Authors: Paolacci Fabrizio , Ciucci Mariano
Published: November 2018

The paper deals with the seismic passive control of torsionally coupled structures, equipped with viscoelastic dampers. Based on the dynamic response of a three degrees of freedom model to a white noise input process, an energy-based design procedure is proposed, and its effectiveness is investigated through an extensive parametric analysis. Subsequently, the proposed methodology is applied to a seven-story torsionally coupled building.
A Resonating Lattice TMD to Reduce Pipeline Vibrations
Authors: Murugan Jaya Mahesh , Ceravolo Rosario , Matta Emiliano , Zanotti Fragonara Luca
Published: November 2018

There are numerous ways to realize vibration absorbers. In this study, a new method is proposed wherein an elastomeric lattice is used. The geometrical configuration of the lattice is designed such that it transfers energy from the main system and is dissipated by the inherent material damping of the lattice material. The applicability of this system is numerically evaluated for pipelines by using two simple lattices whose geometries were optimized and the performances under harmonic loads compared with that of the theoretical optimal TMD. Eventhough they were capable of reducing the vibrations significantly, it was found to be less efficient at small mass ratios while at large mass ratios, the lattices performed similar to the theoretical optimal TMD. Nevertheless, in order to use such systems for pipelines or pipeline like structures such as chimneys, further studies are required using improved lattice configurations that can work efficiently for the whole range of mass ratios.
Simplified Seismic Response Analysis Method Using Reduced Model of Piping System
Authors: Sakai Michiya , Shimazu Ryuya , Matsuura Shinichi , Tamura Ichiro
Published: November 2018

In the seismic response analysis of piping systems, finite element analysis is performed with analysis method guidelines [1]–[4] established based on benchmark analysis. However, since it takes a great deal of effort to carry out finite element analysis, a simplified method to analyze the seismic response of complex piping systems is required. In this research, we propose a method to reduce an equivalent spring-mass system model with low degrees of freedom, which can take into account the main mode of the complicated piping system. Simplified seismic evaluation is carried out using this spring mass system model with low degrees of freedom, and the accuracy of response evaluation is confirmed by comparison with finite element analysis.
Development of New Design Fatigue Curves in Japan: Discussion of Best Fit Curves Based on Fatigue Test Data With Large Scale Piping
Authors: Bodai Masaru , Fukuta Yuichi , Asada Seiji , Hayashi Kentaro
Published: November 2018

In order to develop new design fatigue curves for austenitic carbon steels & low alloy steels and stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society. The study on design fatigue curves was actively performed in the subcommittees.

In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database was constructed. Using this fatigue database, the accurate best-fit curves of austenitic carbon steels & low alloy steels and stainless steels were developed by applying tensile strength to a parameter of the curve.

Regarding design factors on design fatigue curves, data scatter, mean stress correction, surface finishing effect, size effect and variable loading effect were investigated and each design factor was decided to be individually considered on the design fatigue curves.

A Japanese utility project performed large scale fatigue tests using austenitic stainless steel piping and carbon and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect and surface finishing effect. Those test results were provided to the subcommittee and utilized the above studies.

In this paper, the large scale fatigue tests using austenitic stainless steel piping and the best-fit curve of austenitic stainless steel are discussed.