bluuebunny/crossref_metadata_2025 huggingface dataset:
Mission Analysis and Operational Optimization of Adaptive Cycle Microturbofan Engine in Surveillance and Firefighting Scenarios
Authors: Palman Michael , Leizeronok Boris , Cukurel Beni
Published: July 2018

The current work focuses on mission-based evaluation of a novel engine architecture arising from the conversion of a microturbojet to a microturbofan via introduction of a variable speed fan and bypass nozzle. The solution significantly improves maximum thrust by 260%, reduces fuel consumption by as much as 60% through maintaining the core independently running at its optimum, and enables a wider operational range, all the meanwhile preserving a simple single spool configuration. Particularly, the introduction of a variable-speed fan enables real-time optimization for both high-speed cruise and low-speed loitering. In order to characterize the performance of the adaptive cycle engine with increased number of controls (engine speed, gear ratio, bypass opening), a component map-based thermodynamic study is used to contrast it against other similar propulsion systems with incrementally reduced input variables. In the following, a shortest path-based optimization is conducted over the locally minimum fuel consumption operating points, based on a set of gradient driven connectivity constraints for changes in gear ratio and bypass nozzle area. The resultant state transition graphs provide global optimum for fuel consumption at a thrust range in a given altitude and Mach flight envelope. Then, the engine model is coupled to a flight mechanics solver supplied with a conceptual design for a representative multipurpose unmanned aerial vehicle (UAV). Finally, the associated mission benefits are demonstrated in surveillance and firefighting scenarios.
The Effect of Stratification Ratio on the Macrostructure of Stratified Swirl Flames: Experimental and Numerical Study
Authors: Han Xiao , Laera Davide , Morgans Aimee S. , Lin Yuzhen , Sung Chih-Jen
Published: July 2018

The present paper reports experimental and numerical analyses of the macrostructures featured by a stratified swirling flame for varying stratification ratio (SR). The studies are performed with the Beihang Axial Swirler Independently Stratified (BASIS) burner, a novel double-swirled full-scale burner developed at Beihang University. Experimentally, it is found that depending on the ratio between the equivalence ratios of the methane–air mixtures from the two swirlers, the flame stabilizes with three different shapes: attached V-flame, attached stratified flame, and lifted flame. In order to better understand the mechanisms leading to the three macrostructures, large eddy simulations (LES) are performed via the open-source computational fluid dynamics (CFD) software OpenFOAM using the incompressible solver ReactingFoam. Changing SR, simulation results show good agreement with experimentally observed time-averaged flame shapes, demonstrating that the incompressible LES are able to fully characterize the different flame behaviors observed in stratified burners. When the LES account for heat loss from walls, they better capture the experimentally observed flame quenching in the outer shear layer (OSL). Finally, insights into the flame dynamics are provided by analyzing probes located near the two separate streams.
Assessment of CO2 and NOx Emissions in Intercooled Pulsed Detonation Turbofan Engines
Authors: Xisto Carlos , Petit Olivier , Grönstedt Tomas , Lundbladh Anders
Published: July 2018

In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption (SFC) and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors (PDCs), operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using computational fluid dynamics (CFD) data obtained for different combustor inlet pressure, temperature, and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.
Determination of Total Organic Carbon Content in Shale Formations With Regression Analysis
Authors: Wang Jianguo , Gu Daihong , Guo Wei , Zhang Haijie , Yang Daoyong
Published: July 2018

By correcting both the positive and negative ΔlogR separation resulting from the resistivity in organic-deficient shales, the traditional ΔlogR correlation is modified, validated, and applied to determine the total organic carbon (TOC) content in shale formations. The TOC content is determined once the Fisher distribution, which represents the significance of each model, and Student's t-distribution, which denotes the significance of every variable in the models, have achieved values equal to or higher than their respective threshold values at a confidence level of 95%. Using a total of 45 sets of logging measurements, the newly proposed correlation is found to be able to reproduce the measured TOC values with a root mean-squared absolute difference (RMSAD) of 0.30 wt % and root mean-squared relative difference (RMSRD) of 23.8%, respectively. Uranium concentration, apart from interval transit time and resistivity, is found to be key in determining the TOC content in organic-rich shale without other radioactive minerals. By combining the reading of DGR (i.e., the difference between the spectral gamma ray with the radioactivity and the computed gamma ray without uranium), the traditional ΔlogR technique has now been improved and extended to the negative ΔlogR separation resulting from the resistivity in organic-deficient shale higher than that in organic-rich shale.
Numerical Investigation of Thermal Separators Within the Evacuated Tubes of a Water-in-Glass Solar Water Heater
Authors: Soopee Asif , Khoodaruth Abdel Anwar Hossen , Murdan Anshu Prakash , Oree Vishwamitra
Published: July 2018

The effects of thermal separators within the evacuated tubes of a water-in-glass solar water heater (SWH) were numerically investigated using the commercial computational fluid dynamics (CFD) software ANSYS fluent. To validate the three-dimensional (3D) model, an experiment was performed for the passive operation of the SWH for a fortnight period, of which 3 h of recorded data was selected. The Boussinesq's approximation was employed, and the respective solar irradiance and ambient temperature profiles were incorporated. A maximum deviation of only 2.06% was observed between the experimental and numerical results. The model was then adapted for the case where thermal separators are inserted within the evacuated tubes of the SWH and both cases were run for two tilt angles, 10 deg and 40 deg. The temperature and velocity profiles within the evacuated tubes were analyzed alongside the temperature contours, thermal stratification, and overall thermal efficiency of the SWH. At a 40 deg tilt, without thermal separators, the flow streams within the evacuated tubes are restrained, and a chaotic thermal behavior was observed, thereby restricting thermal distribution to the water stored in the SWH tank. A lower tilt angle (10 deg) provided a more desirable thermal distribution. With thermal separators, however, the tilt angle preference was reversed. A faster and more uniform thermal distribution was achieved within the water tank, with a sizeable reduction in the thermal stratification at a 40 deg tilt. The overall thermal efficiency of the SWH was improved by 4.11% and 4.14% for tilt angles of 10 deg and 40 deg, respectively.
How Computational Grid Refinement in Three Dimensions Affects Computational Fluid Dynamics-Discrete Element Method Results for Psuedo-Two-Dimensional Fluidized Gas–Solid Beds
Authors: Volk Annette , Ghia Urmila , Jog Milind A.
Published: July 2018

Computational fluid dynamics (CFD)-discrete element method (DEM) simulations are designed to model a pseudo-two-dimensional (2D) fluidized bed, in which bed thickness is minimal compared to height and length. Predicted bed behavior varies as the simulations are conducted on increasingly refined computational grids. Pseudo-2D simulation results, in which a single computational cell spans the bed thickness, are compared against fully-three-dimensional (3D) simulations results. Both pseudo-2D and fully-3D simulations exhibit high accuracy when sufficiently refined. Indicators of bed behavior, such as bed height, bed height fluctuation, bubble generation frequency, and segregation, do not appear to converge as the cell size is reduced. The Koch-Hill and Gidaspow drag laws are alternately employed in the simulations, resulting in different trends of results with computational grid refinement. Grid refinement studies are used to quantify the change in results with grid refinement for both three-dimensional, uniform refinement, and for two-dimensional refinement on pseudo-2D computational grids. Grid refinement study results indicate the total drag converges as the computational grid is refined, for both 3D and pseudo-2D approaches. The grid refinement study results are also used to distinguish the relatively grid-independent results using the Koch-Hill drag law from the highly grid-dependent Gidaspow drag law results. Computational cell size has a significant impact on CFD-DEM results for fluidized beds, but the grid refinement study method can be used to quantify the resulting numerical error.
Unburnt Carbon From Oxygen-Enriched Combustion of Low-Quality Fuels at Low Temperatures
Authors: Haykiri-Acma H. , Yaman S.
Published: July 2018

This paper investigates the effectiveness of oxygen-enriched combustion process at low temperatures to avoid the unburnt carbon that remains in ash during conventional burning process. For this, thermal treatment of low-quality fuels such as olive pomace and Turkish lignite (Afsin-Elbistan) under oxygen-enriched conditions was tested in a tube furnace at temperatures between 400 and 700 °C under O2/N2 mixtures containing O2 ratios in the range of 25–50 vol %. The calorific value and the unburnt carbon content of the residues from these tests were used to investigate the combined effects of temperature and O2 concentration on unusable part of fuels. Thermal reactivity of untreated parent samples and the residues obtained from oxygen-enriched combustion was also compared based on differential thermal analysis (DTA) and derivative thermogravimetry (DTG) profiles. It was determined that oxygen-enriched conditions are able to remove the organic part of the fuels at low temperatures easily as O2 concentration increases and the oxygen-enriched conditions shifted complete burning temperature to lower values.
Demonstration of an Inverse Relationship Between Thermal Efficiency and Specific Entropy Generation for Combustion Power Systems
Authors: Haseli Y. , Hornbostel K.
Published: July 2018

Maximum thermal efficiency is commonly assumed to correspond to minimum entropy generation. However, previous work has disproven this assumption for various power generation systems. In order to reconcile these two optimization approaches, second law analysis is performed here in terms of specific entropy generation (SEG), defined as the total entropy generation per mole of fuel. An inverse relationship between thermal efficiency and SEG is derived here, and it is shown that maximum thermal efficiency always corresponds to minimum SEG for lean fuel/air mixtures. Furthermore, the maximum efficiency limit of conventional power plants is shown to differ from the Carnot efficiency. Finally, a modified second law efficiency is introduced, and it is shown that the exhaust combustion products are bounded by a theoretical minimum temperature.
Assessment of the Oil Scoop Capture Efficiency in High Speed Rotors
Authors: Paleo Cageao Paloma , Simmons Kathy , Prabhakar Arun , Chandra Budi
Published: July 2018

Experimental research was conducted into a scooped rotor system that captures oil from a stationary jet and directs it through passages within the shaft to another axial location. Such a system has benefits for delivering oil via under-race feed to aeroengine bearings where direct access is limited. Oil capture efficiency was calculated for three jet configurations, a range of geometric variations relative to a baseline and a range of operating conditions. Flow visualization techniques yielded high-speed imaging in the vicinity of the scoop leading edge. Overall capture efficiency depends on the amount of oil initially captured by the scoop that is retained. Observation shows that when the jet hits the tip of a scoop element, it is sliced and deflected upward in a “plume.” Ligaments and drops formed from this plume are not captured. In addition, some oil initially captured is flung outward as a consequence of centrifugal force. Although in principle capture of the entire supply is possible over most of the shaft speed range, as demonstrated by a simplified geometric model, in practice 60–70% is typical. Significant improvement in capture efficiency was obtained with a lower jet angle (more radial) compared to baseline. Higher capture efficiencies were found where the ratio of jet to scoop tip speed was lower. This research confirms the capability of a scoop system to capture and retain delivered oil. Additional numerical and experimental work is recommended to further optimize the geometry and increase the investigated temperature and pressure ranges.
Modeling Gel Fiber Formation in an Emerging Coaxial Flow From a Nozzle
Authors: Williams Harvey , McPhail Michael , Mondal Sourav , Münch Andreas
Published: July 2018

It is important to understand the operational aspects which affect the continuous fabrication of alginate gel fibers. These can be formed from a cross-linking reaction of an alginate precursor injected into a coaxial annular pipe flow with a calcium chloride solution. This is an example of an emerging solid interface that interacts with the flow in its neighborhood. We advance on earlier works by relaxing assumptions of a fixed spatial domain to explore and observe mechanisms controlling gel radius. We use two different models. The first one represents the gel layer as a capillary interface between two immiscible liquids and captures the effect of surface tension. A second model is introduced to treat the cross-linking chemical reaction and its effect on the viscosity as the alginate gel forms. Through numerical simulations and analytical approximations of the downstream behavior, we determine the shape of the fiber in the pipe flow and its impact on the flow velocity as well as on the total production of gel.
The Effect of Environmental Contour Selection on Expected Wave Energy Converter Response
Authors: Edwards Samuel J. , Coe Ryan G.
Published: July 2018

A wave energy converter must be designed to both maximize power production and to ensure survivability, which requires the prediction of future sea states. It follows that precision in the prediction of those sea states should be important in determining a final WEC design. One common method used to estimate extreme conditions employs environmental contours of extreme conditions. This report compares five environmental contour methods and their repercussions on the response analysis of Reference Model 3 (RM3). The most extreme power take-off (PTO) force is predicted for the RM3 via each contour and compared to identify the potential difference in WEC response due to contour selection. The analysis provides insight into the relative performance of each of the contour methods and demonstrates the importance of an environmental contour in predicting extreme response. Ideally, over-predictions should be avoided, as they can add to device cost. At the same time, any “exceedances,” that is to say sea states that exceed predictions of the contour, should be avoided so that the device does not fail. For the extreme PTO force response studied here, relatively little sensitivity to the contour method is shown due to the collocation of the device's resonance with a region of agreement between the contours. However, looking at the level of observed exceedances for each contour may still give a higher level of confidence to some methods.
BPNN–QSTR Modeling to Develop Isosteres as Sulfur-Free, Anti-Wear Lubricant Additives
Authors: Gao Xinlei , Wang Zhan , Wang Tingting , Song Ze , Dai Kang , Chen Hao
Published: July 2018

The principle of isosterism was employed to design low- or zero-sulfur anti-wear lubricant additives. Thiobenzothiazole compounds and 2-benzothiazole-S-carboxylic acid esters were employed as templates. Sulfur in the thiazole ring or in the branched chain was exchanged with oxygen, CH2, or an NH group. Similarly, the template's benzimidazole ring was replaced with a quinazolinone group. Quantitative structure tribo-ability relationship (QSTR) models by back propagation neural network (BPNN) method were used to study correlations between additive structures and their anti-wear performance. The features of rubbing pairs with different additives were identified by energy dispersive spectrometer-scanning electron microscope analysis. A wide range of samples showed that sulfur substitution in additive molecules was found to be reasonable and feasible. Combined effects of the anti-wear additive and the base oil were able to improve anti-wear performance.
A Highly Flexible Approach on the Steady-State Analysis of Innovative Micro Gas Turbine Cycles
Authors: Krummrein Thomas , Henke Martin , Kutne Peter
Published: July 2018

Steady-state simulation is an important method to investigate thermodynamic processes. This is especially true for innovative micro gas turbine (MGT)-based cycles as the complexity of such systems grows. Therefore, steady-state simulation tools are required that ensure large flexibility and computation robustness. As the increased system complexity result often in more extensive parameter studies also a fast computation speed is required. While a number of steady-state simulation tools for MGT-based systems are described and applied in literature, the solving process of such tools is rarely explained. However, this solving process is crucial to achieve a robust and fast computation within a physically meaningful range. Therefore, a new solver routine for a steady-state simulation tool developed at the DLR Institute of Combustion Technology is presented in detail in this paper. The solver routine is based on Broyden's method. It considers boundaries during the solving process to maintain a physically and technically meaningful solution process. Supplementary methods are implemented and described which improve the computation robustness and speed. Furthermore, some features of the resulting steady-state simulation tool are presented. Exemplary applications of a hybrid power plant (HyPP), an inverted Brayton cycle (IBC), and an aircraft auxiliary power unit (APU) show the capabilities of the presented solver routine and the steady-state simulation tool. It is shown that the new solver routine is superior to the standard Simulink algebraic solver in terms of system evaluation and robustness for the given applications.
A Mixed-Fidelity Numerical Study for Fan–Distortion Interaction
Authors: Ma Yunfei , Cui Jiahuan , Vadlamani Nagabhushana Rao , Tucker Paul
Published: July 2018

Inlet distortion often occurs under off-design conditions when a flow separates within an intake and this unsteady phenomenon can seriously impact fan performance. Fan–distortion interaction is a highly unsteady aerodynamic process into which high-fidelity simulations can provide detailed insights. However, due to limitations on the computational resource, the use of an eddy resolving method for a fully resolved fan calculation is currently infeasible within industry. To solve this problem, a mixed-fidelity computational fluid dynamics method is proposed. This method uses the large Eddy simulation (LES) approach to resolve the turbulence associated with separation and the immersed boundary method (IBM) with smeared geometry (IBMSG) to model the fan. The method is validated by providing comparisons against the experiment on the Darmstadt Rotor, which shows a good agreement in terms of total pressure distributions. A detailed investigation is then conducted for a subsonic rotor with an annular beam-generating inlet distortion. A number of studies are performed in order to investigate the fan's influence on the distortions. A comparison to the case without a fan shows that the fan has a significant effect in reducing distortions. Three fan locations are examined which reveal that the fan nearer to the inlet tends to have a higher pressure recovery. Three beams with different heights are also tested to generate various degrees of distortion. The results indicate that the fan can suppress the distortions and that the recovery effect is proportional to the degree of inlet distortion.
Tool Orientation Planning in Milling With Process Dynamic Constraints: A Minimax Optimization Approach
Authors: Huang Tao , Zhang Xiao-Ming , Leopold Jürgen , Ding Han
Published: July 2018

In five-axis milling process, the tool path generated by a commercial software seldom takes the dynamics of the machining process into account. The neglect of process dynamics may lead to milling chatter, which causes overcut, quick tool wear, etc., and thus damages workpiece surface and shortens tool life. This motivates us to consider dynamic constraints in the tool path generation. Tool orientation variations in five-axis ball-end milling influence chatter stability and surface location error (SLE) due to the varying tool-workpiece immersion area and cutting force, which inversely provides us a feasible and flexible way to suppress chatter and SLE. However, tool orientations adjustment for suppression of chatter and SLE may cause drastic changes of the tool orientations and affects surface quality. The challenge is to strike a balance between the smooth tool orientations and suppression of chatter and SLE. To overcome the challenge, this paper presents a minimax optimization approach for planning tool orientations. The optimization objective is to obtain smooth tool orientations, by minimizing the maximum variation of the rotational angles between adjacent cutter locations, with constraints of chatter-free and SLE threshold. A dedicated designed ball-end milling experiment is conducted to validate the proposed approach. The work provides new insight into the tool path generation for ball-end milling of sculpture surface; also it would be helpful to decision-making for process parameters optimization in practical complex parts milling operations at shop floor.
Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints
Authors: Wang Kaifeng , Upadhyay Piyush , Wang Yuxiang , Li Jingjing , Sun Xin , Roosendaal Timothy
Published: July 2018

Friction stir scribe (FSS) welding as a recent derivative of friction stir welding (FSW) has been successfully used to fabricate a linear joint between automotive Al and steel sheets. It has been established that FSS welding generates a hook-like structure at the bimaterial interface. Beyond the hook-like structure, there is a lack of fundamental understanding on the bond formation mechanism during this newly developed FSS welding process. In this paper, the microstructures and phases at the joint interface of FSS welded Al to ultra-high-strength steel were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that both mechanical interlocking and interfacial bonding occurred simultaneously during the FSS welding process. Based on SEM observations, a higher diffusion driving force in the advancing side was found compared to the retreating side and the scribe swept zone, and thermally activated diffusion was the primary driving force for the interfacial bond formation in the scribe swept region. The TEM energy-dispersive X-ray spectroscopy (EDXS) revealed that a thin intermetallic compound (IMC) layer was formed through the interface, where the thickness of this layer gradually decreased from the advancing side to the retreating side owing to different material plastic deformation and heat generations. In addition, the diffraction pattern (or one-dimensional fast Fourier transform (FFT) pattern) revealed that the IMC layer was composed of Fe2Al5 or Fe4Al13 with a Fe/Al solid solution depending on the weld regions.
A Combined Experimental-Numerical Method to Evaluate Powder Thermal Properties in Laser Powder Bed Fusion
Authors: Cheng Bo , Lane Brandon , Whiting Justin , Chou Kevin
Published: July 2018

Powder bed metal additive manufacturing (AM) utilizes a high-energy heat source scanning at the surface of a powder layer in a predefined area to be melted and solidified to fabricate parts layer by layer. It is known that powder bed metal AM is primarily a thermal process, and further, heat conduction is the dominant heat transfer mode in the process. Hence, understanding the powder bed thermal conductivity is crucial to process temperature predictions, because powder thermal conductivity could be substantially different from its solid counterpart. On the other hand, measuring the powder thermal conductivity is a challenging task. The objective of this study is to investigate the powder thermal conductivity using a method that combines a thermal diffusivity measurement technique and a numerical heat transfer model. In the experimental aspect, disk-shaped samples, with powder inside, made by a laser powder bed fusion (LPBF) system, are measured using a laser flash system to obtain the thermal diffusivity and the normalized temperature history during testing. In parallel, a finite element (FE) model is developed to simulate the transient heat transfer of the laser flash process. The numerical model was first validated using reference material testing. Then, the model is extended to incorporate powder enclosed in an LPBF sample with thermal properties to be determined using an inverse method to approximate the simulation results to the thermal data from the experiments. In order to include the powder particles' contribution in the measurement, an improved model geometry, which improves the contact condition between powder particles and the sample solid shell, has been tested. A multipoint optimization inverse heat transfer method is used to calculate the powder thermal conductivity. From this study, the thermal conductivity of a nickel alloy 625 powder in powder bed conditions is estimated to be 1.01 W/m K at 500 °C.
A Model for the Design of a Pomelo Peel Bioinspired Foam
Authors: Ortiz Jonel , Zhang Guanglu , McAdams Daniel A.
Published: July 2018

The structure of pomelo peel arouses research interest in recent years because of the outstanding damping and energy dissipating performance of the pomelo peel. Researchers found that pomelo peel has varying pore size through the peel thickness; the pore size gradient is one of the key reasons leading to superior energy dissipation performance of pomelo peel. In this paper, we introduce a method to model pomelo peel bioinspired foams with nonuniform pore distribution. We generate the skeletal open cell structure of the bioinspired foams using Voronoi tessellation. The skeleton of the bioinspired foams is built as three-dimension (3D) beam elements in a full-scale finite element model. The quasi-static and dynamic mechanical behaviors of the pomelo peel bioinspired foams could be derived through a finite element analysis (FEA). We illustrate our method using a case study of pomelo peel bioinspired aluminum foams under quasi-static compression and free fall impact circumstances. The case study results validate our method and demonstrate the superior impact resistance and damping behavior of bioinspired foam with gradient porosity for designers.
A Systematic Methodology Based on Word Embedding for Identifying the Relation Between Online Customer Reviews and Sales Rank
Authors: Suryadi Dedy , Kim Harrison
Published: July 2018

In the buying decision process, online reviews become an important source of information. They become the basis of evaluating alternatives before making purchase decision. This paper proposes a methodology to reveal one of the hidden alternative evaluation processes by identifying the relation between the observable online customer reviews and sales rank. This methodology applies a combined approach of word embedding (word2vec) and X-means clustering, which produces product-feature words. It is followed by identifying sentiment words and their intensity, determining connection of words from dependency tree, and finally relating variables from the reviews to the sales rank of a product by a regression model. The methodology is applied to two data sets of wearable technology and laptop products. As implied by the high predicted R-squared values, the models are generalizable into new data sets. Among the interesting findings are the statements of problems or issues of a product are related to better sales rank, and many product features that are mentioned in the review title are significantly related to sales rank. For product designers, the significant variables in the regression models suggest the possible product features to be improved.
Material Flow Visualization of Dissimilar Friction STIR Welding Process Using Nano-Computed Tomography
Authors: Liu Xun , Zhao Sheng , Chen Kai , Ni Jun
Published: July 2018

In this study, the friction stir welding (FSW) of aluminum alloy 6061-T6511 to TRIP 780 steel is analyzed under various process conditions. Two FSW tools with different sizes are used. To understand the underlying joining mechanisms and material flow behavior, nano-computed tomography (nano-CT) is applied for a 3D visualization of material distribution in the weld. With insufficient heat input, steel fragments are generally scattered in the weld zone in large pieces. This is observed in a combined condition of big tool, small tool offset, and low rotating speed or a small tool with low rotating speed. Higher heat input improves the material flowability and generates a continuous strip of steel. The remaining steel fragments are much finer. When the volume fraction of steel involved in the stirring nugget is small, this steel strip can be in a flat shape near the bottom, which generally corresponds to a better joint quality and the joint would fracture in the base aluminum side. Otherwise, a hook structure is formed and reduces the joint strength. The joint would fail with a combined brittle behavior on the steel hook and a ductile behavior in the surrounding aluminum matrix.
Pathways Toward Enhanced Techno-Economic Performance of Flow Battery Systems in Energy System Applications
Authors: Zheng Menglian , Sun Jie , Meinrenken Christoph J. , Wang Tao
Published: July 2018

Redox flow batteries have shown great potential for a wide range of applications in future energy systems. However, the lack of a deep understanding of the key drivers of the techno-economic performance of different flow battery technologies—and how these can be improved—is a major barrier to wider adoption of these battery technologies. This study analyzes these drivers and provides an extensive comparison of four flow battery technologies, including the all-vanadium redox (VRB), iron–chromium, zinc–bromine, and polysulfide–bromine flow batteries, by examining their current and projected techno-economic performances. We address the potential for performance improvements and resulting cost reduction by developing a component-based learning curve model. The model considers the near-term learning rates for various subcomponents of each of the four battery technologies as well as their technological improvements. The results show that (i) both technological improvements in the performance parameters as well as mass production effects could drive significant cost reductions for flow battery systems; (ii) flow battery systems could be cost-effective in a variety of energy system applications in the near future; and (iii) from a techno-economic perspective, VRB systems are more suitable for the applications that require low energy and high power capacities.
Reliability Analysis of Lead-Free Solders in Electronic Packaging Using a Novel Surrogate Model and Kriging Concept
Authors: Azizsoltani Hamoon , Haldar Achintya
Published: July 2018

A novel reliability evaluation procedure of lead-free solders used in electronic packaging (EP) subjected to thermomechanical loading is proposed. A solder ball is represented by finite elements (FEs). Major sources of nonlinearities are incorporated as realistically as practicable. Uncertainties in all design variables are quantified using available information. The thermomechanical loading is represented by five design parameters and uncertainties associated with them are incorporated. Since the performance or limit state function (LSF) of such complicated problem is implicit in nature, it is approximately generated explicitly in the failure region with the help of a completely improved response surface method (RSM)-based approach and the universal Kriging method (KM). The response surface (RS) is generated by conducting as few deterministic nonlinear finite element analyses as possible by integrating several advanced factorial mathematical concepts producing compounding beneficial effect. The accuracy, efficiency, and application potential of the procedure are established with the help of Monte Carlo simulation (MCS) and the results from laboratory investigation reported in the literature. The study conclusively verified the proposed method. Similar studies can be conducted to fill the knowledge gap for cases where the available analytical and experimental studies are limited or extend the information to cases where reliability information is unavailable. The study showcased how reliability information can be extracted with the help of multiple deterministic analyses. The authors believe that they proposed an alternative to the classical MCS technique.
Modeling of Gas Pressure and Dynamic Behavior of the Piston Ring Pack for the Two-Stroke Opposed-Piston Engine
Authors: Chen Wen-Bin , Liu De-Liang , Xu Jiu-Jun , Huang Ruo-Xuan , Chen Ze-Zhong , Du Feng-Ming , Yan Zhi-Jun
Published: July 2018

The piston ring pack and the ports on the cylinder linear wall have a great impact on the performance of the two-stroke opposed-piston engine. In this work, a piston ring pack model for this type of engine was generated to incorporate the exhaust ports. The effect of the exhaust ports was considered by modifying the existing friction force equation and the gas flow continuity equations. The developed model was implemented in an opposed-piston opposed-cylinder engine (a specific type of opposed-piston engine) to investigate the backpressure and the associated axial movement of all the rings of the piston ring pack under various working conditions. The results show that the gas pressure in all the regions of the piston ring pack and the axial movement of the rings are strongly affected by the exhaust ports. The gas pressure in some regions of the ring pack declines with the increase of the engine speed, while the effect of the combustion pressure (CP) on the axial movement of the ring pack can be neglected.
Structural Intensity Analysis on Irregular Shells
Authors: Pires F. , Vanlanduit S. , Dirckx J. J. J.
Published: July 2018

A method is presented to assess the transmission path of vibration energy and to localize sources or sinks on shells with arbitrary shape, constant thickness, and isotropic material properties. The derived equations of the structural intensity (SI) are based on the Kirchhoff–Love postulates and are formulated in terms of displacements, Lamé parameters, principal curvatures, and their partial derivatives with respect to the principal curvilinear coordinates (PCC). To test the accuracy of the method, two numerical models of thin shells with nonuniform curvatures were developed. The coordinates, displacements, and principal curvature directions (PCDs) at the shell's outer surface were used to estimate the SI vector fields and the energy density at the shell's middle surface. The power estimated from the surface integral of the divergence of the SI over the source was compared to the actual power injected in the shell. The absolute error in both models did not exceed 1%, showing that, in theory, the method is able to handle the high-order spatial derivatives of the displacement and geometry data. The qualitative effect of varying the internal damping in the models on the energy transmission was also investigated.
Modeling of Particle-Laden Cold Flow in a Cyclone Gasifier
Authors: Hadi Jafari Pantea , Misiulia Dzmitry , Hellström J. Gunnar I. , Gebart B. Rikard
Published: July 2018

Isothermal transient Eulerian–Lagrangian simulation of the turbulent gas–solid flow in a cyclone gasifier with two inlet tubes at 890 °C has been performed. The single-phase gas flow is modeled using SSG Reynolds stress turbulence model. Ten thousand representative solid particles of different sizes are injected from each inlet continuously at every second of simulation time. Particles are finally stopped as soon as they arrive at the outlet or reach the bottom plate of the gasifier. The effect of particle-to-gas coupling on the pressure and velocity of the flow and particles motion inside the gasifier is studied. The numerical approach can reasonably predict the impact of particle load on the gas flow as presented in the experimental results. Single particles are traveled throughout the transient gas flow field by using Lagrangian approach. High temperature of the gas flow inside the gasifier has significant effects on the swirl intensity reduction, damping the turbulence in the core region, pressure, and particle behaviors. However, the presence of solid particles does not have a notable influence on the swirl intensity and turbulence.
The Potential for the Use of Natural Gas and Propane As Alternative Fuels in the Marine Industry
Authors: Neiburger Par
Published: July 2018

Liberator Engine Company, LLC designs, develops and produces alternative fuel engines for vehicles around the globe. The Company’s 6.0 Liter Liberator™ gaseous fuels engine will have the ability to operate on Compressed Natural Gas, Liquefied Natural Gas or Liquid Propane Gas: clean, domestic, economical fuels. The Liberator engine will target OEM on road vehicles, as well as off road applications. The Liberator engine is also an excellent choice for the repower of existing diesel vehicles. The 6.0L Liberator™ engine will serve as a replacement engine for vehicle currently operating on a Cummins 5.9L diesel engine or Mercedes diesel 6.0L engine.

Paper published with permission.
The New Risk Perspective in Corrosion Management
Authors: Koch G. , Ripley G. , McKay D.
Published: July 2018

This paper describes a risk-based approach for corrosion management of offshore floating structures. The objective of this approach is to reduce the risk of corrosion related failures, reduce the associated downtime, while improving the cost-effectiveness of corrosion inspection and maintenance.

Corrosion is increasingly a significant challenge to the offshore industry and attributed to: an aging worldwide offshore fleet; assets being kept in operation for prolonged periods of time; units operating beyond their original “design basis”; and newer larger vessels in deeper, harsher environments with less opportunity for ship yard repair. Corrosion is particularly detrimental to the integrity of the unit, and if not managed properly will increase maintenance costs and downtime costs, possibly reducing the useful operational life of the unit. Although, there are several existing offshore corrosion design standards, experience still reveals a number of assets in poor and critical condition due to corrosion.

Clearly there is a need for a holistic approach on corrosion management during the full operational life of the asset. The presented methodology is based on the principles of ISO 31000 (Risk Management - Principles and Guidelines) to provide a solid consistent framework for corrosion management. The risk-based corrosion management process for offshore structures described in this paper consists of five (5) basic steps: Pre Assessment; Screening and Risk Ranking; Detailed Examination; Remediation and Repair; and Life Cycle Management.

Adopting the described risk based corrosion methodology will provide confidence to the operators and demonstrable evidence to key stakeholders that corrosion is being managed on their assets. It will account for life extension, reduce the risk of corrosion failure, and lower the cost of inspection and maintenance.

Paper published with permission.
Application of ASME Section VIII Division 3 Design Requirements to Offshore High Pressure Equipment
Authors: Sims J. Robert
Published: July 2018

Offshore oil and gas wells are being drilled into formations that have pressures up to 200 MPa (30,000 psi) and temperatures over 175°C (350°F). Most of the existing API Standards for pressure equipment, such as valves and blow out preventers (BOPs), are limited to pressures of about 100 MPa (15,000 psi). The design requirements in ASME Section VIII Division 3, Alternative Rules for Construction of High Pressure Vessels (Div. 3), can be adapted for the design of this equipment with some modifications. Since the strength of the materials used in these applications is limited due to environmental cracking concerns, it is necessary to accept some local yielding in areas of stress concentrations. Therefore, it is particularly important to apply the elastic-plastic analysis requirements in Div. 3 with appropriate limits on local strain as well as the robust fracture mechanics based fatigue analysis requirements.

Paper published with permission.
NFPA Marine Fire Protection Codes and Standards: An Overview
Authors: Colonna Guy R.
Published: July 2018

The National Fire Protection Association (NFPA) develops consensus codes and standards for fire and life safety for a wide array of occupancies, including the maritime industry. With documents originating in the early 1920’s, NFPA maritime safety standards reflect current practices in vessel design and operations, new hazards, and new technology. These documents include safe practices associated with confined space entry and hot work operations during construction, maintenance, and repair; shipyard fire protection safety management; and suppression system design, installation, and testing/maintenance. This presentation highlights those consensus standards contributing to safety management within the maritime industry.

Paper published with permission.
Development of Nanoparticle Probes for In Vivo Imaging of Atherosclerotic Plaques
Authors: Zhang Zihao , Tong Sheng , Bao Gang
Published: July 2018

Atherosclerosis, the formation of fatty plaques in the arterial lumen, is mediated by inflammatory macrophage infiltration in the lesion and ingestion of low-density lipoprotein (LDL), forming foam cells. Its progression will likely form a large necrotic core and fibrotic cap surface defects. The resulting intraplaque hemorrhage causes red blood cell infiltration and hemoglobin abundance, which oxidizes LDL to form cholesterol crystal aggregates (1). Hemorrhagic plaques could rupture and form artery-blocking emboli. Thus, it is critical to develop a tool to detect and locate unstable hemorrhagic plaques in live specimens.
Cardiac Vector Estimation in Fetal Magnetocardiography Using Realistic Approximations of the Volume Conductor
Authors: Tao Rong , Popescu Elena-Anda , Drake William B. , Jackson David , Popescu Mihai
Published: July 2018

Fetal magnetocardiography (fMCG) records the magnetic field generated by the electrical activity associated with the fetal cardiac muscle contraction and has emerged as an attractive tool for monitoring the fetal heart in-utero. The magnetic sensor array is placed above the maternal abdomen to receive the extremely weak magnetic signal of the fetal heart from 20 weeks of gestation onward. fMCG outperforms fetal electrocardiography (fECG) in its notably superior signal quality, as the magnetic field is considerably less affected by tissues with low electrical conductivity surrounding the fetal heart [1], which can drastically diminish the fECG signal amplitude.
Vascular Architecture of the Human Brain: Morphometric, Geographic and Territorial Analysis From MRA Data
Authors: Cebral Juan R. , Mut Fernando , Wright Susan , Ascoli Giorgio
Published: July 2018

Detailed knowledge of the brain vascular architecture is important not only for gaining insight into a variety of vascular pathologies and brain diseases, but also when creating arterial tree models to be used for imposing boundary conditions in numerical simulations [1]. A variety of methods have been developed to build realistic arterial trees [2, 3]. Most of these techniques require the specification of a number of parameters and constraints related to the arterial branch geometry and bifurcation characteristics. The purpose of this paper is to provide estimations of these parameters as well as information about the regional distribution of the arterial trees of the brain that can be used to guide or test methods for constructing arterial tree models.
Distensibility of the Atherosclerotic Carotid Artery: Relationship With Plaque Burden and Composition?
Authors: Canton Gador , Tang Dalin , Hippe Daniel S. , Yuan Chun
Published: July 2018

Arterial distensibility is a marker that can measure vessel wall functional and structural changes resulting from atherosclerosis [5] with applications including estimation of mechanical properties of the wall for biomechanical models. Although arterial segments affected by atherosclerosis are characterized by marked stiffening [2], little is known about the relationship between local specific atherosclerotic plaque features and wall stiffness. In particular, calcification has been shown to be associated with greater wall stiffness, however, this relationship is not consistent in different arterial segments [1,6]. For the carotid arteries, a more thorough understanding of the role of plaque features in determining wall stiffness might be offered by magnetic resonance imaging (MRI). Multi-contrast, high resolution MRI is an established imaging tool to quantify the components of carotid lesions, as well as plaque burden [8,9]. In addition, CINE MRI has been proven to be a reliable tool to measure arterial distensibility [3], an index frequently used to measure stiffness. In this study, our goals were to use MRI to characterize subject-specific wall stiffness in vivo in atherosclerotic carotid arteries, and to analyze the relation between stiffness and plaque burden and composition. CINE MRI was used to measure vessel wall stiffness; whereas a multi-contrast MRI protocol was applied to characterize vessel wall morphology and composition.
Combined viscous and dry friction damping of oscillatory motion
Authors: Hinrichsen Peter F. , Larnder Chris I.
Published: July 2018

The acceleration, velocity, and displacement of a glider on an air track undergoing oscillatory motion subject to viscous and dry frictional damping are investigated using an accelerometer, which allowed a detailed investigation of the dynamics, experimental observation of the predicted acceleration discontinuities due to the reversal of the friction force, and the variation of the drag with time, velocity, and displacement. The investigation included systematic variation of the air track air pressure to explicitly control the relative contribution of viscous and dry frictional damping. Although frictional damping of oscillatory motion has been treated by a number of authors, most investigations have been restricted to measurements of displacement only, with the primary interest being in the decay of the amplitude. In this paper, an exact theory of the acceleration of oscillatory motion, assuming viscous damping proportional to the velocity plus a Coulomb friction force independent of velocity or position, is presented and compared with experiment.