bluuebunny/crossref_metadata_2025 huggingface dataset:
Riding the Surge
Authors: Langston Lee S.
Published: July 2018

This article explores the advantages of gas turbines in the marine industry. Marine gas turbines, which are designed specifically for use on ships, have long been one of the segments of the gas turbine market. One advantage that gas turbines have over conventional marine diesels is volume. Gas turbines are the prime movers for the modern combined cycle electric power plant. Both CFM International (a joint venture of General Electric and France’s Snecma) and Pratt & Whitney are working on new engines for this multibillion dollar single-aisle, narrow-body market. Pratt & Whitney’s new certified PW1500G geared turbofans will have a first flight powering the first Bombardier CSeries aircraft. On land, sea, and air, the surge in gas turbine production is remarkable. The experts suggest that what the steam engine was to the 19th century and the internal combustion engine was to the 20th, the gas turbine might be to the 21st century: the ubiquitous prime mover of choice.
Working Away
Authors: Thilmany Jean
Published: July 2018

This article discusses the evolving trend of mobile applications and their increasing use by engineers. With the help of mobile applications for smartphone and tablet, engineers are discovering innovative ways to work that don’t have them tied to their desks. Apps allow engineers to bring drawings with them while on the road, to collaborate with other engineers, and to access information on the shop floor or in the field. Due to the very nature of the mobile platform on which they sit, applications can’t be used at every job. Their adoption depends on the type of work, the work environment, and employees’ attitude. If enough employees do have their own personal devices, there are apps that let employers update employees on the shop floor or in the field. Many engineers use mobile applications to collaborate with their design-team members or to show others, like customers or suppliers, how a product will look or will function. Engineers can also share computer-aided design drawings, design work, spec sheets, and the like through the technology.
IoT Puts a New Spin on Bearings
Authors: Brown Alan S.
Published: July 2018

As anyone who ever had a bearing fail knows, durability counts. However some bearing makers believe that predictability is more important than longer bearing life. By harnessing the Internet of Things (IoT) and other Industry 4.0 technologies—low-cost sensors, Big Data analytics, and machine learning—manufacturing companies want to catapult one of the world’s oldest mechanical devices into the digital future. In fact, bearings are emerging as a poster child for Industry 4.0. Yet this heady mixture of digital technology and physical products is also disrupting how companies monitor, operate, and service rotating equipment; the way they sell and service products; and who they partner with and compete against. This article delves into how bearing makers are embracing this disruption.
Developments in Fermentative Butanol Production as an Alternative Biofuel Source
Authors: Wayne Chew Kit , Ying Yap Jing , Sabariah Din Siti , Chuan Ling Tau , Monash Purushothaman , Loke Show Pau
Published: July 2018

Biobutanol is an attractive, economical, and sustainable alternative fuel to petroleum oil which are depleting in sources due to the diminishing oil reserves and creating an increase in the concentrations of greenhouse gases in the atmosphere. Alternative routes to sustainable bacterial fermentation for the production of biobutanol are being sought and prepared for commercialization. The challenges for implementing an economically competitive fermentation process for biobutanol production include the availability of cheaper feedstock by improvement toward large-scaled production, improvement of fermentation efficiency, and better strategies for solvent recovery. The development of biobutanol production was analyzed and various methods to increase the fermentative butanol production were discussed in detail. It was found that the implementations of metabolic engineering of the Clostridia sp., advanced fermentation techniques, and utilization of renewed substrates are among the potential and economically viable technology in the production butanol production. Besides, this review outlines several challenges and potential future work for the advancement of fermentative butanol production.
Influence of Oriented Perforation Design on Refracture Reorientation: Simulation and Experiment
Authors: Qi Minhui , Li Mingzhong , Guo Tiankui , Liu Chunting , Gao Song , Tang Shukai
Published: July 2018

The oriented perforating is the essential technique to guide the refracture reorientation, but the influence of the oriented perforation design on the refracture steering radius is still unclear. In this paper, the factors influencing the refracture reorientation were studied by simulation models and experiments. The effects of initial fracture, well production, and perforations on the refracture initiation and propagation were analyzed. Three-dimensional finite element models were conducted to quantify the impact of perforation depth, density, and azimuth on the refracture. The large-scale three-axis hydraulic fracturing experiments guided by oriented perforations were also carried out to verify the fracture initiation position and propagation pattern of the simulation results. The research results showed that perforations change the near-wellbore induced stress distribution, thus changing the steering radius of the refracture. According to the simulation results, the oriented perforation design has a significant influence on the perforation guidance effect and refracture characteristics. Five hydraulic fracturing experiments proved the influence of perforating parameters on fracture initiation and morphology, which have a right consistency between the simulation results. This paper presents a numerical simulation method for evaluating the influence of the refracture reorientation characteristics under the consideration of multiple prerefracturing induced-stress and put forward the oriented perforation field design suggestions according to the study results.
Optimal Stiffness Design for an Exhaustive Parallel Compliance Matrix in Multiactuator Robotic Limbs
Authors: Cahill Nathan M. , Sugar Thomas , Ren Yi , Schroeder Kyle
Published: July 2018

Comparatively slow growth in energy density of both power storage and generation technologies has placed added emphasis on the need for energy-efficient designs in legged robots. This paper explores the potential of parallel springs in robot limb design. We start by adding what we call the exhaustive parallel compliance matrix (EPCM) to the design. The EPCM is a set of parallel springs, which includes a parallel spring for each joint and a multijoint parallel spring for all possible combinations of the robot's joints. Then, we carefully formulate and compare two performance metrics, which improve various aspects of the system performance. Each performance metric is analyzed and compared, their strengths and weaknesses being rigorously presented. The performance benefits associated with this approach are dramatic. Implementing the spring matrix reduces the sum of square power (SSP) exerted by the actuators by up to 47%, the peak power requirement by almost 40%, the sum of squared current by 55%, and the peak current by 55%. These results were generated using a planar robot limb and a gait trajectory borrowed from biology. We use a fully dynamic model of the robotic system including inertial effects. We also test the design robustness using a perturbation study, which shows that the parallel springs are effective even in the presence of trajectory perturbation.
An Integrated Prognostics Approach for Pipeline Fatigue Crack Growth Prediction Utilizing Inline Inspection Data
Authors: Xie Mingjiang , Bott Steven , Sutton Aaron , Nemeth Alex , Tian Zhigang
Published: July 2018

Fatigue cracking is a key type of defect for liquid pipelines, and managing fatigue cracks has been a top priority and a big challenge for liquid pipeline operators. The existing inline inspection (ILI) tools for pipeline defect evaluation have large fatigue crack measurement uncertainties. Furthermore, the current physics-based methods are mainly used for fatigue crack growth prediction, where the same or a small range of fixed model parameters is used for all pipes. They result in uncertainty that is managed through the use of conservative safety factors such as adding depth uncertainty to the measured depth in deciding integrity management and risk mitigation strategies. In this study, an integrated approach is proposed for pipeline fatigue crack growth prediction utilizing ILI data including consideration of crack depth measurement uncertainty. This approach is done by integrating the physical models, including the stress analysis models, the crack growth model governed by the Paris’ law, and the ILI data. With the proposed integrated approach, the finite element (FE) model of a cracked pipe is built and the stress analysis is performed. ILI data are utilized to update the uncertain physical parameters for the individual pipe being considered so that a more accurate fatigue crack growth prediction can be achieved. Time-varying loading conditions are considered in the proposed integrated method by using rainflow counting method. The proposed integrated prognostics approach is compared with the existing physics-based method using examples based on simulated data. Field data provided by a Canadian pipeline operator are also employed for the validation of the proposed method. The examples and case studies in this paper demonstrate the limitations of the existing physics-based method, and the promise of the proposed method for achieving accurate fatigue crack growth prediction as continuous improvement of ILI technologies further reduces ILI measurement uncertainty.
Underwater Dynamic Response at Limited Points Expanded to Full-Field Strain Response
Authors: Chen Yuanchang , Joffre Dagny , Avitabile Peter
Published: July 2018

Expansion of real-time operating data from limited measurements to obtain full-field displacement data has been performed for structures in air. This approach has shown great success, and its main advantage is that the applied forces do not need to be identified. However, there are applications where structures may be immersed in water and the full-field real-time response may be needed for design and structural health assessments. This paper presents the results of a structure submersed in water to identify full-field response using only a handful of measured data. The same approach is used to extract the full-field displacements, and the results are compared to the actual full-field measured response. The advantage of this approach is that the force does not need to be identified and, most importantly, the damping and fluid–structure interaction does not need to be identified in order to perform the expansion. The results show excellent agreement with the measured data.
The Development and Mechanisms of the High Pressure Turbine Vane Wake Vortex
Authors: Lin Dun , Su Xinrong , Yuan Xin
Published: July 2018

The wake vortex is an important origin of unsteadiness and losses in turbines. In this paper, the development and underlying mechanisms of the shedding vortex of a high-pressure transonic turbine vane are studied and analyzed using the delayed detached eddy simulation (DDES) and proper orthogonal decomposition (POD). The goal is to understand the unsteadiness related to the wake vortex shedding and the wake evolution and mixing. Special attention is paid to the development of the wake vortex and the mechanisms behind the length characteristics. Interactions of the wake vortex with the shock wave and pressure waves are also discussed. First, the DDES simulation results are compared with published experimental data, Reynolds Averaged Navier-Stokes, and large eddy simulation (LES) simulations. Then, the development of the vane wake vortex, especially the different length characteristics from the cylinder vortex, is discussed. The reason of stronger pressure-side vortex shedding compared to suction-side vortex shedding is revealed. Wake-shock wave interaction and wake-pressure wave interaction are also investigated. The pressure waves are found to have a stronger effect than the shock wave on the spanwise motion and the dissipation of the wake vortex. An analysis of the losses through the turbine vane passage is carried out to evaluate the contributions of thermal and viscous irreversibilities. Losses analysis also confirms the strong interaction between the wake vortex and pressure waves. After that, POD study of the wake behavior was carried out. The results indicate that the shedding vortex is dominant in the unsteady flow. The phase relation between the pressure side wake vortex (PSVP) and the suction side wake vortex (SSVP) is confirmed.
Partially Premixed Combustion Application for Diesel Power Improvement
Authors: Walker Michael , Kelso Robert , Bowes Kevin , Hamilton Len , Prak Dianne Luning , Cowart Jim
Published: July 2018

A partially premixed combustion (PPC) approach was applied in a single cylinder diesel research engine in order to characterize engine power improvements. PPC is an alternative advanced combustion approach that generally results in lower engine-out soot and oxides of nitrogen (NOx) emission, with a moderate penalty in engine-out unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions. In this study, PPC is accomplished with a minority fraction of jet fuel injected into the intake manifold, while the majority fraction of jet fuel is delivered directly to the combustion chamber near the start of combustion (SOC). Four compression ratios (CR) were studied. Exhaust emissions plus exhaust opacity and particulate measurements were performed during the experiments in addition to fast in-cylinder combustion metrics. It was seen that as CR increased, the soot threshold equivalence ratio decreased for conventional diesel combustion; however, this afforded an increased opportunity for higher levels of port injected fuel leading to power increases from 5% to 23% as CR increased from 14 to 21.5. PPC allowed for these power increases (defined by a threshold opacity level of 3%) due to smaller particles (and lower overall number of particles) in the exhaust that influence measured opacity less significantly than larger and more numerous conventional diesel combustion exhaust particulates. Carbon monoxide levels at the higher PPC-driven power levels were only modestly higher, although NOx was generally lower due to the overall enriched operation.
Experimental and Numerical Investigation of the Mechanical and Aerodynamic Particle Size Effect in High-Speed Erosive Flows
Authors: Hufnagel Max , Staudacher Stephan , Koch Christian
Published: July 2018

Aircraft engines are subject to deterioration due to solid particle erosion. The environmental particulates encountered in service often feature broad particle size distributions and a generally large scatter of particle properties. In order to numerically calculate the erosive change of shape of the components, experimentally calibrated erosion models are required. Due to aerodynamic and mechanical particle size effects, erosion tests with different particle size distributions have to be calibrated individually. In this study, erosion experiments under high-pressure compressor conditions are conducted using a sand-blast type erosion rig. Flat plates out of Ti6Al4V were eroded at different impingement angles. The erodent used was quartz sand with size distributions corresponding to standardized Arizona Road Dust (ARD) grades A2, A3, and A4. The particle impact conditions were investigated using a high-speed shadowgraphy technique in combination with computational fluid dynamics (CFD) computations. Dimensional analyses were carried out in respect to the particle transport process and the material removal process. A nondimensional erosion model is derived. The experimental shadowgraphy results are corrected using numerically calibrated similarity parameters for the particle impact conditions. Thus, the influence of the aerodynamic particle size effect was eliminated by correcting the impact conditions. The isolated mechanical particle size effect is demonstrated. It is shown that wear increases and that the modeled erosion rate maximum shifts toward larger impact angles when using coarser particle size distributions.
Fabrication of Multimeasurand Sensor for Monitoring of a Li-Ion Battery
Authors: Knobloch Aaron , Kapusta Chris , Karp Jason , Plotnikov Yuri , Siegel Jason B. , Stefanopoulou Anna G.
Published: July 2018

This paper details the fabrication and testing of a combined temperature and expansion sensor to improve state of charge (SOC) and state of health (SOH) estimation for Li-ion batteries. These sensors enable the characterization of periodic stress and strain changes in the electrode materials of Lithium-ion batteries during the charge and discharge process. These ultrathin sensors are built on a polyimide substrate which can enable direct integration between cells without compromising safety or cell cooling design. Leveraging the sensor design and fabrication process used to create inductive coil eddy current (EC) sensors for crack detection, these sensors were characterized on three Panasonic 5 A-h cells showing the capability to measure expansion of Li-ion batteries. By sensing the intercalation effects, which cause cell expansion, improvements in estimation of SOH and SOC can be enabled through the use of physics-based battery models, which combine the thermal, mechanical, and electrochemical aspects of its operation.
Model Tests of a Caisson in Wet Towing for Assessing Resistance and Stability in Calm Water and Waves
Authors: Park Chang-Wook , Seo Jeonghwa , Hyung Rhee Shin
Published: July 2018

A series of model tests of a caisson in wet towing were conducted in a towing tank to assess the stability and effective power requirement in calm water and head sea conditions. The scale ratio of the model was 1/30, and the model-length-based Froude number in the tests ranged from 0.061 to 0.122, which is equivalent to 2 and 4 knots in the full scale, respectively. During the towing of the model, tension on the towline and six-degrees-of-freedom (6DOF) motion of the model were measured. Under the calm water condition, the effects of towing speed, draft, and initial trim variation on the towing stability and effective power were investigated. Initial trim improved stability and reduced required towing power. In head seas, effective power and towing stability were changed with the wavelength. It increased as the wavelength became longer, but the added resistance in long waves also stabilized the model with reduced yaw motion.
Numerical Prediction of Surface Wear and Roughness Parameters During Running-In for Line Contacts Under Mixed Lubrication
Authors: Zhang Yazhao , Kovalev Alexander , Hayashi Noriyuki , Nishiura Kensuke , Meng Yonggang
Published: July 2018

A stochastic model for predicting the evolutions of wear profile and surface height probability density function (PDF) of initial line contacts during running-in under mixed lubrication condition is presented. A numerical approach was developed on the basis of stochastic solution of mixed lubrication, which combined the Patir and Cheng's average flow model for calculation of the hydrodynamic pressure and the Kogut and Etsion's (KE) rough surface contact model for calculation of the asperity contact pressure. The total friction force was assumed to be the sum of the boundary friction at the contact asperities and the integration of viscous shear stress in the hydrodynamic region. The wear depth on the contact region was estimated according to the modified Archard's wear model using the asperity contact pressure. Sugimura's wear model was modified and used to link the wear particle size distribution and the variation of surface height PDF during wear. In the wear process, the variations of profile and surface height PDF of initial line contacts were calculated step by step in time, and the pressure distribution, friction coefficient, and wear rate were updated consequently. The effect of size distribution of wear particles on the wear process was numerically investigated, and the simulation results showed that the lubrication condition in which small wear particles are generated from the asperity contact region is beneficial to reduce friction coefficient and wear rate, and leads to a better steady mixed lubrication condition.
Microhardness Prediction Based on a Microstructure-Sensitive Flow Stress Model During High Speed Machining Ti-6Al-4V
Authors: Wang Qingqing , Liu Zhanqiang
Published: July 2018

Exploring the hardening mechanisms during high speed machining (HSM) is an effective approach to improve the fatigue strength and the wear resistance of machined surface and to control the fragmentation of chips in a certain range of hardness. In this paper, the microhardness variation is explored from the perspective of microstructural evolutions, as a direct consequence of the severe deformation during HSM Ti-6Al-4V alloy. A microstructure-sensitive flow stress model coupled the phenomena of grain refinement, deformation twinning, and phase transformations is first proposed. Then the microstructure-sensitive flow stress model is implemented into the cutting simulation model via a user-defined subroutine to analyze the flow stress variation induced by the microstructure evolutions during HSM Ti-6Al-4V. Finally, the relationship between the microhardness and flow stress is developed and modified based on the classical theory that the hardness is directly proportional to the flow stress. The study shows that the deformation twinning (generated at higher cutting speeds) plays a more important role in the hardening of Ti-6Al-4V compared with the grain refinement and phase transformation. The predicted microhardness distributions align well with the measured values. It provides a novel thinking that it is plausible to obtain a high microhardness material via controlling the microstructure alterations during machining process.
Pressure-Retarded Osmosis Thermosyphon
Authors: Arias Francisco J. , de las Heras Salvador
Published: July 2018

The basis of a novel method for passive solar water heating homologous to the traditional thermosyphon but driven by salinity gradient induced by changes of salinity gradient induced by evaporation at the collector is outlined. Its purpose, likewise than a thermosyphon, is to simplify the transfer of liquid while avoiding the cost and complexity of a conventional pump. However, in this concept, the fluid motion is not obtained from the tendency of a less dense fluid to rise above a denser fluid (natural convection) but rather by taking advantage of the energy released during the spontaneous mixing of the low-concentration (evaporated fraction) solution and the high-concentration (no-evaporated fraction) solution, which have been previously separated into two streams in the evaporator module. Finally, the possibility of driving the thermal osmosis by the strong thermal dependence of the solubility featured by many solutions rather than evaporation is envisaged. One important point in favor of the proposed thermosyphon driven by thermo-osmosis is that makes possible downward heat and mass transfer, i.e., heat and mass transport from the top roofs (where solar collectors are generally placed) to the bottom (inside the homes), and then the use of expensive and voluminous tanks so characteristic of current thermosyphons driven by natural convection is no longer needed.
Phenomenon and Mechanism of Spray Cooling on Nanowire Arrayed and Hybrid Micro/Nanostructured Surfaces
Authors: Chen Jian-nan , Xu Rui-na , Zhang Zhen , Chen Xue , Ouyang Xiao-long , Wang Gao-yuan , Jiang Pei-xue
Published: July 2018

Enhancing spray cooling with surface structures is a common, effective approach for high heat flux thermal management to guarantee the reliability of many high-power, high-speed electronics and to improve the efficiency of new energy systems. However, the fundamental heat transfer enhancement mechanisms are not well understood especially for nanostructures. Here, we fabricated six groups of nanowire arrayed surfaces with various structures and sizes that show for the first time how these nanostructures enhance the spray cooling by improving the surface wettability and the liquid transport to quickly rewet the surface and avoid dry out. These insights into the nanostructure spray cooling heat transfer enhancement mechanisms are combined with microstructure heat transfer mechanism in integrated microstructure and nanostructure hybrid surface that further enhances the spray cooling heat transfer.
Research on the Size Effect of Specific Cutting Energy Based on Numerical Simulation of Single Grit Scratching
Authors: Zhang Tao , Jiang Feng , Yan Lan , Xu Xipeng
Published: July 2018

A method of research on the size effect of the specific cutting energy based on the numerical simulation has been proposed. The theoretical model of the research on size effect of specific cutting energy using single grit scratching simulation has been presented. A series of single grit scratch simulations with different scratching depths have been carried out to acquire different material removal rates. Then, the specific cutting energy has been calculated based on the power consumed and the material removal rate. The relationship between the specific cutting energy and the material removal rate has been given which agrees well with that presented by Malkin. The simulation results have been analyzed further to explain the size effect of specific cutting energy.
Identification of the Actual Process Parameters for Finishing Operations in Peripheral Milling
Authors: Leal-Muñoz E. , Diez E. , Perez H. , Vizan A.
Published: July 2018

The evolution of the manufacturing industry has favored the use of new technologies that increase the level of autonomy in production systems. The work presented shows a methodology that allows for online estimation of cutting parameters based on the analysis of the cutting force signal pattern. The dynamic response of the tool is taken into account through a function that relates the response time to the input variables in the process. The force signal is obtained with a dynamometric platform based on piezoelectric sensors. The final section of the paper shows the experimental validation where machining tests with variable machining conditions were carried out. The results reveal high precision in the estimation of depths of cut in end milling.
Introduction of a New Three-Way Swirling Combustion Technology With Air Curtain Insulation Effect for Solid Waste
Authors: Choe Kangil , Chae Jaeou , Cheah Woon Yong , Na Sangkwon
Published: July 2018

In order to improve low combustion efficiency of typical incinerators like a stoker type, a new unique cyclone combustor, three-way swirling combustion (TSC), is being introduced through a commercial scale pilot plant experiment for refused plastic fuel (RPF). TSC provides air curtain insulation, substituting the refractory brick and lowering the generation of flying ash, for clinker prevention at the boiler. Its excellent emission measurement has also been reported. Through the study of three-dimensionless numbers (swirl number, Strouhal number, and Reynolds number) and previous researches conducted on cyclone combustors, their design criteria—geometrical and operational parameters—has been identified and suggested for future designs.
Tribological Evaluation of a UHMWPE Hybrid Nanocomposite Coating Reinforced With Nanoclay and Carbon Nanotubes Under Dry Conditions
Authors: Azam Muhammad Umar , Samad Mohammed Abdul
Published: July 2018

A novel hybrid polymer nanocomposite coating of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with nanoclay (C15A) and carbon nanotubes (CNTs) has been developed to protect metallic mating surfaces in tribological applications. The hybrid nanocomposite coatings were deposited on aluminum substrates using an electrostatic spraying technique. Ball-on-disk wear tests using a 440C stainless steel ball as the counterface were conducted on the coatings under dry conditions to determine the optimum amount of the loadings of the nanofillers and evaluate their tribological performance at different normal loads and linear velocities. Micro-indentation, raman spectroscopy, scanning electron microscopy (SEM), and optical profilometry techniques were used to characterize the coatings in terms of hardness, dispersion of the nanofillers, morphology, and wear mechanisms, respectively. Results showed that the UHMWPE hybrid nanocomposite coating reinforced with 1.5 wt % of C15A nanoclay and 1.5 wt % of CNTs did not fail even until 100,000 cycles at a normal load of 12 N and a linear speed of 0.1 m/s showing a significant improvement in wear resistance as compared to all other coatings evaluated in this study.
Thermohydrodynamic Analysis of High-Speed Water-Lubricated Spiral Groove Thrust Bearing Using Cavitating Flow Model
Authors: Lin Xiaohui , Jiang Shuyun , Zhang Chibin , Liu Xiang
Published: July 2018

A thermohydrodynamic lubrication model of turbulent cavitating flow for high-speed spiral groove thrust bearing was developed considering the effects of cavitation, turbulence, inertia, breakage, and coalescence of bubbles. Comparing with the classical thermohydrodynamic model, this model can predict not only the distributions of pressure and temperature rise but also the distribution of bubble volume and bubble number density. Static characteristics of the water-lubricated spiral groove thrust bearing in the state of turbulent cavitating flow were analyzed, and the influences of multiple effects on the static characteristics of the bearing were researched. The numerical calculation result shows that the bubbles are mainly distributed in inlet and outlet of the spiral groove, the distribution of bubble volume is skewed under the equilibrium state, and small bubbles account for a large proportion of the cavitating flow under high-speed condition. Furthermore, the load carrying capacity and the leakage flow of the bearing decrease due to the effect of cavitation under high-speed. The maximum temperature rise of the bearing decreases due to the effect of cavitation effect.
Targeted Energy Transfer From One Acoustical Mode to an Helmholtz Resonator With Nonlinear Behavior
Authors: Gourdon Emmanuel , Ture Savadkoohi Alireza , Alamo Vargas Valentin
Published: July 2018

Targeted energy transfer from one acoustical mode to a Helmholtz resonator (HR) with nonlinear behaviors is studied. For the HR, nonlinear restoring forces and nonlinear damping are taken into account. A time multiple scale method around a 1:1 resonance is used to detect slow invariant manifold (SIM) of the system, its equilibrium and singular points. Analytical predictions are compared with those which are obtained by direct numerical integration of system equations. Experimental verifications are performed and presented for free and forced vibrating system.
Topology Optimization and Prototype of a Three-Dimensional Printed Compliant Finger for Grasping Vulnerable Objects With Size and Shape Variations
Authors: Liu Chih-Hsing , Chiu Chen-Hua , Chen Ta-Lun , Pai Tzu-Yang , Hsu Mao-Cheng , Chen Yang
Published: July 2018

This study presents a topology optimization method to synthesize an innovative compliant finger for grasping objects with size and shape variations. The design domain of the compliant finger is a trapezoidal area with one input and two output ports. The topology optimized finger design is prototyped by three-dimensional (3D) printing using flexible filament, and be used in the developed gripper module, which consists of one actuator and two identical compliant fingers. Both fingers are actuated by one displacement input, and can grip objects through elastic deformation. The gripper module is mounted on an industrial robot to pick and place a variety of objects to demonstrate the effectiveness of the proposed design. The results show that the developed compliant finger can be used to handle vulnerable objects without causing damage to the surface of grasped items. The proposed compliant finger is a monolithic and low-cost design, which can be used to resolve the challenge issue for robotic automation of irregular and vulnerable objects.
Alternative Mooring Systems for a Very Large Offshore Wind Turbine Supported by a Semisubmersible Floating Platform
Authors: Liu Jinsong , Manuel Lance
Published: July 2018

As offshore wind turbines supported on floating platforms extend to deep waters, the various effects involved in the dynamics, especially those resulting from the influence of moorings, become significant when predicting the overall integrated system response. The combined influence of waves and wind affect motions of the structure and induce tensile forces in mooring lines. The investigation of the system response under misaligned wind-wave conditions and the selection of appropriate mooring systems to minimize the turbine, tower, and mooring system loads is the subject of this study. We estimate the 50-year return response of a semisubmersible platform supporting a 13.2 MW wind turbine as well as mooring line forces when the system is exposed to four different wave headings with various environmental conditions (wind speeds and wave heights). Three different mooring system patterns are presented that include 3 or 6 mooring lines with different interline angles. Performance comparisons of the integrated systems may be used to define an optimal system for the selected large wind turbine.
Long-Term NOx Emission Behavior of Heavy Duty Gas Turbines: An Approach for Model-Based Monitoring and Diagnostics
Authors: Lipperheide Moritz , Weidner Frank , Wirsum Manfred , Gassner Martin , Bernero Stefano
Published: July 2018

Accurate monitoring of gas turbine performance is a means to an early detection of performance deviation from the design point and thus to an optimized operational control. In this process, the diagnosis of the combustion process is of high importance due to strict legal pollution limits as aging of the combustor during operation may lead to an observed progression of NOx emissions. The method presented here features a semi-empirical NOx formulation incorporating aging for the GT24/GT26 heavy duty gas turbines: Input parameters to the NOx-correlation are processed from actual measurement data in a simplified gas turbine model. Component deterioration is accounted for by linking changes in air flow distribution and control parameters to specific operational measurements of the gas turbine. The method was validated on three different gas turbines of the GE GT24/GT26 fleet for part- and baseload operation with a total of 374,058 long-term data points (5 min average), corresponding to a total of 8.5 years of observation, while only commissioning data were used for the formulation of the NOx correlation. When input parameters to the correlation are adapted for aging, the NOx prediction outperforms the benchmark prediction method without aging by 35.9, 53.7, and 26.2% in terms of root mean square error (RMSE) yielding a root-mean-squared error of 1.27, 1.84, and 3.01 ppm for the investigated gas turbines over a three-year monitoring period.
Parametric Study and Optimization of Flow Characteristics of Wire-Nonparallel Plate-Type Electrostatic Air Accelerators
Authors: Zhang J. F. , Wang S. , Li H. Y. , Qu Z. G.
Published: July 2018

Wire and nonparallel plate electrode-type electrostatic air accelerators have attracted significant interest. The physical process involved in using accelerators is complicated. Moreover, mechanisms are unclear, especially for accelerators with double- and multiwire electrodes. In this study, the two-dimensional (2D) model of a wire–nonparallel plate-type accelerator validated by experiments is established with a finite element method. Onset voltage, average current, and outlet average velocity are analyzed with respect to different parameters. Onset voltage is derived by the proposed quadratic regression extrapolation method. Moreover, current is affected by interference and discharge effects, while velocity is also influenced by the suction effect. For the single-wire electrode, high wind speed can be obtained by either increasing channel slope or placing the wire near the entry section. For the double-wire electrode, velocity can be further increased when one of the wires is placed near the inlet and the distance between the two wires is widened. Comparatively, the velocity of the three-wire electrode is higher with larger gaps between wires and stronger discharge effect. The highest velocity is obtained by the four-wire electrode. Comparisons indicate that higher velocity can be obtained with weaker interference effect, stronger suction effect, and intensified discharge effect. Optimum parameter combinations are considered by the Taguchi method. Consequently, velocity can be enhanced by more than 39% after optimization compared with the reference design.
Improved General Correlation for Heat Transfer During Gas–Liquid Flow in Horizontal Tubes
Authors: Shah Mirza M.
Published: July 2018

Heat transfer to two-component gas–liquid mixtures is needed in many industries but there is lack of a well-verified predictive method. A correlation is presented for heat transfer during flow of gas–liquid nonboiling mixtures in horizontal tubes. It has been verified with a wide range of data that includes tube diameters of 4.3–57 mm, pressures from 1 to 4.1 bar, temperatures from 12 to 62 °C, gravity <0.1% to 100% earth gravity, liquid Reynolds number from 9 to 1.2 × 105, and ratio of gas and liquid velocities from 0.24 to 9298. The 946 data points from 18 sources are predicted with mean absolute deviation (MAD) of 19.2%. The same data were compared to five other correlations; they had much larger deviations. Therefore, the new correlation is likely to be helpful in more accurate designs.
Parametric Study on Fluid Dynamics of Pilot-Control Angle Globe Valve
Authors: Qian Jin-yuan , Gao Zhi-xin , Liu Bu-zhan , Jin Zhi-jiang
Published: July 2018

Globe valve is widely used in numerous industries, and its driving energy consumption accounts for high percentages of the whole piping system. In order to figure out novel globe valves with low energy consumption, the pilot control globe valve (PCGV) is proposed, which is made up of a main valve and a pilot valve. By the pressure difference of fluid itself, the opened/closed status of the main valve can be controlled by the pilot valve, which can save driving energy and shorten the response time. In order to fit PCGV in an angle displaced piping system, the pilot control angle globe valve (PCAGV) is developed. In this paper, with validated numerical methods, both steady and transient simulations focusing on the valve core diameter, the single/multi orifices, orifice diameters and their arrangements located on the valve core bottom are presented. The results show that the pressure difference increases with the increase of the valve core diameter and the decrease of the orifice diameter, and large orifice diameters (d > 12 mm) should be avoided in case the valve cannot be opened. As for the multi orifices, it can be treated as a single orifice which having similar cross-sectional area. Meanwhile, the opening time of the main valve also increases with the increase of the valve core diameter correspondingly. Besides, a fitting formula of pressure difference calculation depending on the inlet velocity and the valve core diameter is obtained, which is a power–law relationship.
Rolling Element Bearing Diagnostics Using Extended Phase Space Topology
Authors: Haj Mohamad T. , Samadani M. , Nataraj C.
Published: July 2018

This paper introduces a novel method called extended phase space topology (EPST) for machinery diagnostics and pattern recognition. In particular, the research focuses on fault detection and diagnostics of rolling element bearings. The proposed method is based on mapping the vibrational response onto the density space and approximating the density using orthogonal functions. The method has been applied to vibration data of a rotating machine where the data were measured by proximity probes. The method was applied to two operating conditions: constant operating speed and variable operating speed. As will be shown, the proposed feature extraction method has an outstanding capability in characterizing the system response and diagnosing the system. The method is evidently robust to noise, does not depend on expert knowledge about the system, requires no feature ranking or selection, and can easily be applied in an automated process. Finally, a comparison with utilization of statistical features is performed for each operating condition, which demonstrates that the proposed method performs better than the traditional statistical methods.
Analytical Method for Stroboscopically Sampling General Periodic Functions With Arbitrary Frequency Sweep Rates
Authors: Sequeira Dane , Wang Xue-She , Mann Brian
Published: July 2018

Parameter sweeps are commonly used to explore the behavior of dynamical systems. This paper derives exact solutions for the instances in time to stroboscopically sample the response of a dynamical system subject to varying input excitations. This work will enable more accurate bifurcation diagrams and Poincaré sections in parameter regimes where numerical approaches may lead to incorrect behavior characterization. The simplest case of a linear frequency sweep is first considered before generalizing the results to include more complex functions with nonlinear sweep rates and arbitrary phase shifts.
A Comparison of Equivalent Source Method and Monopole Time Reversal Method for Noise Source Localization
Authors: Bi Chuan-Xing , Li Yong-Chang , Zhou Rong , Zhang Yong-Bin
Published: July 2018

The equivalent source method (ESM) and monopole time reversal method (MTRM) are two popular techniques for noise source localization. These two methods have some similar characteristics, such as using the pressure field measured by a microphone array as the input and using similar propagation matrices obtained from the Green's function. However, the spatial resolutions of results obtained by these two methods are different. The aim of this paper is to reveal the reason resulting in this difference from a theoretical analysis and compare the performance of these two methods using results from numerical simulations and experiments. Using the singular value decomposition (SVD) technique, the difference between the two methods is found to be only the diagonal matrices of singular values, and the two methods are equivalent after simply replacing the diagonal matrix in the MTRM with its inverse. Comparison of the results demonstrates that the ESM can calculate the real source strength and obtain a high spatial resolution due to the significant amplification of evanescent waves in the inverse process. However, it does not work when the signal-to-noise ratio (SNR) is low or the measurement distance is large. The performance of ESM under these situations can be significantly improved by introducing a regularization procedure. While the MTRM fails to calculate the real source strength and locate the source at low frequencies due to the loss of information of evanescent waves, it works well at high frequencies even with a low SNR and a large measurement distance.
Numerical Analysis of the Pressure Peak Position Shift With Deadrise Angle in Two-Dimensional Wedge Water Entry
Authors: Zhang Xu , Liu Peiqing , Qu Qiulin , Zhao Yunke , Hu Tianxiang , Agarwal Ramesh K.
Published: July 2018

This study deals with the pressure peak position shift with deadrise angle during the initial phase of a two-dimensional (2D) wedge water entry. The finite volume method with volume of fluid (VOF) and dynamic mesh technique is used to simulate the water entry process of the 2D wedges with the moderate deadrise angles within the range α = 20 deg–60 deg. The results show that with the increasing deadrise angle, the pressure peak position shifts from the spray root to the wedge apex. And, the critical deadrise angle of pressure peak position shift is identified in the range between 40.8 deg and 41 deg, which is more precise than previous studies. In the initial stage of water entry of a 2D wedge, the pressure on wedge side is determined by the dynamic pressure term and unsteady term simultaneously. For the spray root position, at small deadrise angles, the unsteady term is stronger than the dynamic pressure term; at large deadrise angles, the former is weaker than the later.
Rotating Corrected-Based Cavitation Model for a Centrifugal Pump
Authors: Jian Wang , Yong Wang , Houlin Liu , Qiaorui Si , Dular Matevž
Published: July 2018

Cavitation has bothered the hydraulic machinery for centuries, especially in pumps. It is essential to establish a solid way to predict the unsteady cavitation evolution with considerable accuracy. A novel cavitation model was proposed, considering the rotating motion characteristic of centrifugal pump. Comparisons were made with three other cavitation models and validated by experiments. Considerable agreements can be noticed between simulations and tests. All cavitation models employed have similar performance on predicting the pump head drop curve with proper empirical coefficients, and also the unsteady cavitation evolution was well solved. The proposed rotating corrected-based cavitation model (rotating based Zwart-Gerber-Belamri (RZGB)) obtained identical triangle cavity structure with the experiment visualizations, while the others also got triangle structure but with opposite direction. The maximum flow velocity in the impeller passage appears near the shroud, contributing to the typical triangle cavity structure. A preprocessed method for instant rotating images was carried out for evaluating the erosion risk area in centrifugal pump, based on the standard deviation of gray level. The results imply that the unsteady rear part of the attached cavity is vulnerable to be damaged, where the re-entrant flow was noticed. This work presented a suitable cavitation model and reliable numerical simulation approach for predicting cavitating flows in centrifugal pump.
Effect of Water on the Interfacial Contact and Tribological Properties of Hoist Linings
Authors: Feng Cunao , Zhang Dekun , Chen Kai , Guo Yongbo
Published: July 2018

The purpose of this study is to explore the effect of water on the contact and friction properties of a friction lining. The results show that the water absorption capacity and the sensitivity to the water molecules of the friction lining determine the load-carrying capacity. The change of the actual contact area is related to the load-carrying capacity under dripping water condition. The presence of water played a role in lubricating the surface, which resulted in a reduction of the friction coefficient. In addition, water absorbed onto the surface of the lining to produce an absorbent layer, and the load-carrying capacity of the absorbent layer exerted a more intuitive effect on the friction coefficient.
Aerodynamic Effects of Tie-Boss in Extremely Long Turbine Blades
Authors: Radnic Tomáš , Hála Jindřich , Luxa Martin , Šimurda David , Fürst Jiří , Hasnedl Dan , Kellner Josef
Published: July 2018

Focus of this paper is aerodynamic investigation of tie-boss stabilization devices for extremely long rotor blades. This investigation covered measurements on multiple blade cascades and computational fluid dynamics (CFD) simulation of the flow past these cascades. Conclusions were drawn from results of the measurements and CFD and from the knowledge of prior investigation of the used blade cascade. Main focus of this paper is to describe influence of a tie-boss stabilization device on flow field in interblade channel. Tie-boss with more massive shape proved to cause lesser losses, while tie-boss with a tailored trailing edge showed lesser influence on flow turning.