bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Linkage Shapes of Planar Mechanisms Using Topology Optimization
Authors: Berge Nathan , Campbell Matthew I.
Published: February 2017

Through the methods outlined in this paper, a procedure involving two cooperating optimization algorithms is developed to create balanced, structurally optimal planar mechanisms. Two systems are analyzed to demonstrate the approach. In the first example, a walking mechanism is analyzed under quasi-static loading, and topology optimization is performed to create stiff, lightweight linkages. In the second example, a quick-return Watt-II six-bar mechanism, counterweights are added to balance the mechanism using a numerical optimization technique. The inertial forces are calculated by simulation, and optimal linkage shapes are generated to support them using topology optimization.
Flow Behavior of FENE-P Fluids in Grooved Parallel Plates With Transverse Cavities
Authors: Filali Abdelkader , Khezzar Lyes , Alshehhi Mohamed
Published: February 2017

Numerical investigation of the flow behavior for Newtonian and viscoelastic FENE-P fluids in a parallel-plate channel with transverse rectangular cavities is carried out using ANSYS-POLYFLOW code. A two-dimensional, laminar and steady flow is considered and the flow behavior influenced by the generated vortices at the transverse rectangular cavities has been studied. The effect of Reynolds number, fluid elasticity and the rheological parameters of the FENE-P model L2, on the flow field is examined. In all non-Newtonian considered cases, different flow field were observed which shows different behavior compared to the Newtonian case.
Numerical Study of Premixed Combustion of Methane Stabilized on Porous Medium
Authors: Giovannoni Valerio , Sharma Rajnish N. , Raine Robert R.
Published: February 2017

The present study focuses on the numerical analysis of the combustion process occurring in a small scale cylindrical combustion chamber using a commercial computational code. The chosen diameter is 18 mm, being the same as the flat flame regenerative combustor currently under experimental investigation by the author (Giovannoni), and it includes a 10 mm thick porous flame holder and a 1 mm thick stainless steel outer wall. A 17 species and 73 reactions skeletal mechanism related to methane oxidation is employed for the simulations. A parametric study is performed and results in terms of temperature profiles, major species’ concentrations and flow velocities are presented. Results show that the flame holder can considerably affect combustion and heat losses from the combustor. In particular at low flow rates, when the laminar burning velocity is much higher than the flow velocity, heat is lost mainly through the flame holder to the walls and to the surroundings. At high flow rates the flame appears to be slightly lifted from the porous medium and heat is mainly dispersed to the walls. This causes preheating of the mixture upstream of the combustion through axial conduction in the wall, achieving superadiabatic temperature. It is also clear from the simulations that employing a flame holder with low thermal conductivity and high porosity yields benefits in limiting heat losses and in widening flammability limits.
Non-Parametric Identification of Asymmetric Signals and Characterization of a Class of Non-Linear Systems Based on Frequency Modulation
Authors: Ondra Václav , Sever Ibrahim A. , Schwingshackl Christoph W.
Published: February 2017

Non-parametric and parametric identification of a non-linear system is often performed by estimating instantaneous amplitude and frequency using the Hilbert transform. However, the Hilbert transform cannot be used for the accurate analysis of asymmetric signals and the reliable estimation of intra-wave frequency modulation. This paper proposes two alternatives to the Hilbert transform which not only avoid some of its mathematical and numerical issues, but also allow the above mentioned analyses. The first method, based on zero-crossing, allows the backbone and damping curves as well as the elastic and damping force characteristics of an asymmetric free decay to be identified. The application and accuracy of this method are demonstrated on the free decay of the system with off-centre clearance. The second method, based on direct quadrature, estimates intrawave frequency modulation frequency with sufficient resolution for characterization of non-linear systems which have stiffness non-linearities. The use of this method is shown on a system with cubic hardening stiffness.
Can-Crush Model and Simulations for Verifying Uncertainty Quantification Method for Sparse Stress-Strain Curve Data
Authors: Dempsey J. F. , Romero V. , Breivik N. , Orient G. , Antoun B. , Schroeder B. , Lewis J. , Winokur J.
Published: February 2017

This work examines the variability of predicted responses when multiple stress-strain curves (reflecting variability from replicate material tests) are propagated through a transient dynamics finite element model of a ductile steel can being slowly crushed. An elastic-plastic constitutive model is employed in the large-deformation simulations. The present work assigns the same material to all the can parts: lids, walls, and weld. Time histories of 18 response quantities of interest (including displacements, stresses, strains, and calculated measures of material damage) at several locations on the can and various points in time are monitored in the simulations. Each response quantity’s behavior varies according to the particular stress-strain curves used for the materials in the model. We estimate response variability due to variability of the input material curves. When only a few stress-strain curves are available from material testing, response variance will usually be significantly underestimated. This is undesirable for many engineering purposes. This paper describes the can-crush model and simulations used to evaluate a simple classical statistical method, Tolerance Intervals (TIs), for effectively compensating for sparse stress-strain curve data in the can-crush problem. Using the simulation results presented here, the accuracy and reliability of the TI method are being evaluated on the highly nonlinear input-to-output response mappings and non-standard response distributions in the can-crush UQ problem.
Analysis of Flow-Induced Whistle at the Joint of Suction Tube of Vehicle Climate Control System and its Coupling With the Tube Structural Mode
Authors: Kong Xiangjie , Pang Jian , Zhang Jun , Zhao Qin
Published: February 2017

Audible noise inside a vehicle compartment has substantial negative impact on the customer opinions on the vehicle quality. Since significant progress has been achieved on reducing the major noise sources, such as powertrain noise and wind noise, traditional minor noise sources, such as the refrigerant flow-induced whistle of the vehicle climate control system, become more audible and annoying due to their high frequency characteristics and the reduced masking level. In this paper, a high-pitched whistle around 6.6 KHz of the climate control system is investigated and studied experimentally and theoretically. A joint on the suction tube is identified as the noise source by a systematic approach. The mechanism of the noise generation, propagation and interaction are studied theoretically. Due to the excessively large gap (around 1 mm) at the joint, a wall cavity is formed at this location. When the R134a refrigerant flows over the joint, the induced tones inside the wall cavity are generated by the low-Reynolds number mean flow and transmitted through the tube walls. The magnitude of the whistle is increased more rapidly during the transmission as the result of the interaction with tube walls when the acoustic diametric mode is coupled with the structural circumferential mode. Good coincidence between the calculated and the tested results is found, which proves the accuracy of the proposed theoretical analysis. The modified design of the joint gap is implemented and the high-pitched whistle is eliminated. Finally, a guideline for suppressing the flow-induced whistle of the vehicle climate control system is provided.
Numerical Investigation on Slot Casing Treatment in a Transonic Axial Compressor Stage: Part 1 — Casing Treatment Design
Authors: Zhu Mingmin , Qiang Xiaoqing , Teng Jinfang
Published: February 2017

Slot-type casing treatment generally has a great potential of enhancing the operating range for tip-critical compressor rotors, however, with remarkable efficiency drop. Part I of this two-part paper was committed to develop a slot configuration with desired stall margin improvement and minimized efficiency loss. Steady simulation was carried out in a 1.5 transonic axial compressor stage at part design rotating speed. At this rotating speed this compressor stage operated at a subsonic condition and showed a rather narrow operating range, which needed to be improved badly. Flow fields analysis at peak efficiency and near stall point showed that the development of tip leakage vortex and resulting blockage near casing resulted in numerical stall. Three kinds of skewed slots with same rotor exposure and casing porosity were designed according to the tip flow field and some empirical strategies. Among three configurations, arc-curved skewed slot showed minimum peak efficiency drop with considerable stall margin improvement. Then rotor exposure and casing porosity were varied based on the original arc-curved skewed slot, with a special interest in detecting their impact on the compressor stability and overall efficiency. Result showed that smaller rotor exposure and casing porosity leaded to less efficiency drop. But meanwhile, effectiveness of improving compressor stability was weakened. The relation between efficiency drop and stall margin improvement fell on a smooth continuous curve throughout all slots configurations, indicating that the detrimental effect of casing treatment on compressor was inevitable. Flow analysis was carried out for cases of smooth casing and three arc-curved configurations at smooth casing near stall condition. The strength of suction/injection, tip leakage flow behavior and removal of blockage near casing were detailed examined. Larger rotor tip exposure and slots number contributed to stronger injection flow. The loss generated within the mixing process of injection flow with main flow and leakage flow is the largest source of entropy increase. Further loss mechanisms were interpreted at eight axial cuts, which were taken through the blade row and slots to show the increase in entropy near tip region. Entropy distributions manifested that loss generations with smooth casing were primarily ascribed to low-momentum tip leakage flow/vortex and suction surface separation at leading edge. CU0 slot, the arc-curved slots with 50% rotor tip exposure, was capable of suppressing the suction surface separation loss. Meanwhile, accelerated tip leakage flow brought about additional loss near casing and pressure surface. Upstream high entropy flow would be absorbed into the rear portion of slots repeatedly, resulting in further loss.
Mechatronic Design of a Mixed Conventional/Braking Actuation Mobile Robot
Authors: Simmons Jeremy W. , Nikshi Walelign M. , Bedillion Mark D. , Hoover Randy C.
Published: February 2017

This paper presents the design of a novel mixed conventional/braking actuation mobile robot (MAMR), which replaces conventional actuators used for steering with controllable brakes. The mechatronic design of a novel electromechanical braking actuator, its implementation in the MAMR, and the mechatronic design of the MAMR are presented. A motion experiment is also given as a demonstration. The MAMR presented in this paper implements a new platform for mobile robots which is composed of two electromechanical braking actuators and an omni-directional drive wheel. The electromechanical brake presented is an omni-directional ball transfer that is electronically lockable. When the brake is in the locked state, it generates a reactive friction force onto a dynamic system that, in the case of the MAMR, can be used to steer and brake. This platform offers a minimalistic approach to locomotion in mobile robots.
An Investigation of the Aerodynamic Performance of a Biomimetic Insect-Sized Wing for Micro Air Vehicles
Authors: Rubio Jose E. , Chakravarty Uttam K.
Published: February 2017

Biologically-inspired micro air vehicles (MAVs) are miniature-scaled autonomous aircrafts which attempt to biomimic the exceptional maneuver control during low-speed flight mastered by insects. Flexible wing structures are critical elements of a nature-inspired MAV as evidence supports that the wings of aerial insects experience highly-elastic deformations that enable insects to proficiently hover and maneuver in different airflow conditions. For this study, a crane fly (family Tipulidae) forewing is selected as the target specimen to replicate both its structural integrity and aerodynamic performance. The artificial insect-sized wing is manufactured using photolithography with negative photoresist SU-8 to fabricate the vein geometry. A Kapton film is attached to the vein pattern for the assembling of the wing. The natural frequencies and mode shapes of the artificial wing are determined to characterize its vibrations. A numerical simulation of the fluid-structure interaction is conducted by coupling a finite element model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. The deformation along the span of the wing increases nonlinearly with Reynolds number from the root to the tip of the wing. The coefficient of lift increases with angle of attack and Reynolds number. The coefficient of drag decreases with Reynolds number and angle of attack. The aerodynamic efficiency, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with angle of attack and Reynolds number.
Effects of Nasal Cavity and Pharyngeal Regions on Airflow Simulation and Particle Depositions in Lower Generations of the Airways
Authors: Taherian Shahab , Rahai Hamid , Aguilar Diego
Published: February 2017

This study evaluates the impact of excluding various regions of the upper respiratory system on particle depositions in lower airways. Three types of models were investigated, Type 1 includes nasal cavity, pharyngeal regions, trachea, and lower generations, Type 2 includes pharyngeal regions, trachea and lower generations, and finally Type 3 includes just the trachea and lower generations. Results indicate increased mean velocity, turbulent kinetic energy, and wall shear stress in hypopharynx and trachea regions for Types 1 and 2 models. There are strong secondary flows within the trachea just before the lower generations in these models, moving high velocity toward the wall regions, resulting in large velocity gradients and thus increased wall shear stress. For Type 3 model, only a small region experiences high velocity secondary flow and its distribution is significantly different than those of Type 1 and 2. Although total particle depositions differ between models, results show that for fine particles, the deposition ratios in lower airways are nearly the same.
Dynamic Reliability Evaluation of Space Systems: Case Study of Satellite Attitude Control
Authors: Pourgol Mohammad Mohammad , Farhadi Arash , Salehpour Oskouei Farzin
Published: February 2017

Based on the recent studies, the static fault tree technique is limited when applied to the analysis of time dependent complex systems. Dynamic fault Tree (DFT) method has been derived to address the limitation of the classic fault tree method. In this paper, the reliability is evaluated for of the position controlling system of the satellite using dynamical modeling techniques. Complexity of the current dynamic fault tree methods make them impractical in application to the real systems. At the first step, the simplification is made for solving the logical gates based on the Monte Carlo simulation. The flowchart has been developed for each of the dynamic gates. Then the simulation routines were developed to implement the suggested procedure to study the attitude control system of the LEO satellites. A new calculation algorithm has been introduced for solving C-SPARE gate which reduces the calculation time in comparison with that of the Monte Carlo method. LEO Satellite attitude control system are used here as the case study to demonstrate the proposed methodology.
A Fuzzy Logic Approach to Evaluate Transformer Fleet Risk From Geomagnetic Storms
Authors: Purushothaman Sujit
Published: February 2017

This paper presents a simple approach to evaluate risk to transformer units from geomagnetic storms. A simple fuzzy logic based approach was used to develop the model which is capable of categorizing transformers in a fleet into three risk categories, i.e., high, medium and low. This model may be used as a first screening step to evaluate a fleet of transformers without conducting time consuming simulations and studies. Critical factors that affect geomagnetically induced current (GIC) flow are used as input parameters to the model. These factors include location-specific, equipment-specific and geomagnetic storm event-specific factors. Location-specific factors include geomagnetic latitude of the location, earth conductivity structure at location and distance of location from coast. Equipment-specific factors include transformer rating and age. The storm event-specific factor of geoelectric field strength was used which is an indication of the return period of the geomagnetic disturbance event. The paper describes the implementation of this model to evaluate fleet risk for a 1 in 100 year event and the Carrington event (largest recorded geomagnetic storm in history). The fuzzy logic membership functions for the inputs are described in detail and the performance of the fuzzy logic model is evaluated.
A New Composite Allocation Method on Balance of Reliability and Maintainability Index With the Goal of Availability
Authors: Mu Hui-na , Cheng Li , Yi Xiaojian , Dhillon B. S. , Hou Peng
Published: February 2017

This paper proposes a new composite allocation method, which is composed by improved Fuzzy-AHP allocation method, old system data correction allocation method, and optimization allocation method. The objective of the new method is to minimize the system cost and allocate the reliability index and maintenance index of unit with the goal of system availability and the balance between them. For the solution of optimization problem in this paper, in order to prevent local optimum, improve the convergence efficiency and get the satisfied optimal solution, the improved GA method is put forward in this paper. First, the reliability index allocation method is proposed by the combination of optimization allocation method with the objective of minimum cost, the improved Fuzzy-AHP method with the consideration of the experts’ expectations, and the old system data correction allocation method. Then, based on constraints of the unit reliability allocation index and system availability index, the maintain-ability allocation method is proposed considering the minimum maintenance cost. In addition, the process of this new composite allocation method is formulated in this paper. Finally, the system cost, reliability index, and maintenance index of an integrated transmission device of an armored vehicle are allocated by this new composite allocation method. The result analysis shows that the allocation result of this new composite allocation method is reasonable and has engineering applicability. All in all, this new composite allocation method not only synthetically considers experts’ expectations on the new system, system cost and system reliability baseline information, but also associate the reliability index and maintenance index with the goal of system availability. In addition, this paper provides a new approach for reliability index & maintenance index of complex repairable systems in the early stages of product design.
Effect of Electric Energy Storage on the Performance of a Power Generation Unit-Organic Rankine Cycle System
Authors: Warren Harrison , Knizley Alta , Mago Pedro J.
Published: February 2017

Combined heat and power (CHP) systems simultaneously generate on-site electricity and provide useful heat by utilizing waste heat from a power generation unit (PGU). CHP systems can enhance energy production efficiency and energy sustainability by reducing grid dependency, often yielding cost savings in the process. Furthermore, CHP systems can provide savings over conventional systems in terms of operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDE). Typical CHP systems generate onsite power using a PGU, and the waste heat from the PGU is used to provide heating or hot water to the facility. Another variation for this system is to incorporate an organic Rankine cycle (ORC) to allow for increased potential reductions in operational cost, PEC, and CDE when compared to separate heat and power. This paper evaluates the effect of using electric energy storage on the performance of a PGU-ORC system. In the proposed system, the waste heat from a PGU is used to generate and to store electricity using an ORC coupled with electric energy storage (ES) (battery). Then, the electricity that is stored in the batteries could be used during the system operation at different times of the day so the PGU does not have to operate all the time. The PGU-ORC-ES system (with battery storage) is compared with a conventional system in terms of operational cost, PEC, and CDE. A restaurant building located in Chicago, IL is used to evaluate the potential of the proposed PGU-ORC-ES system. Results indicate that the addition of electric energy storage is beneficial to the proposed PGU-ORC system in terms of operational cost, PEC, and CDE. Furthermore, the effect of the size of the electric energy storage on the system performance is analyzed in this paper.
Atomistic Simulation Studies of the Effects of Defects on Thermal Properties of Ultra High Temperature Ceramics
Authors: Medyanik S. N. , Vlahopoulos N.
Published: February 2017

Due to the harsh environments created by high speeds, significant new demands are placed on materials used for constructing hypersonic vehicles. Ultra high temperature ceramics (UHTCs) like carbides and borides exhibit unique thermal properties, such as very high melting points and good thermal conductivities. These properties make the ceramic materials good candidates for applications like Thermal Protection Systems (TPS) of the hypersonic vehicles. However, thermal properties of UHTCs may be very sensitive to microstructures of the materials. Thus, atomic scale defects may impact certain thermal properties, such as thermal conductivity. The effects of such small defects may be properly studied only through atomistic simulation methods, such as molecular dynamics (MD). Previously, atomistic simulation studies have been performed for the effects of point defects on thermal properties in silicon carbide (SiC). In addition, atomistic simulations have been applied to assess thermal conductivity in zirconium diboride (ZrB2) for perfect crystals and polycrystals. However, to our knowledge, no studies of the effects of point defects have been performed for zirconium diboride. This paper applies atomistic simulations to assess the impact of point defects on thermal conductivity in ZrB2 perfect crystals. Recently derived interatomic potential for ZrB2 along with LAMMPS molecular simulation package and MedeA software environment are employed in this effort. Phonon part of the thermal conductivity is calculated using Green-Kubo method. Calculations for a perfect crystal are conducted first and the results are compared to experimental data available from the literature. Then, several types of point defects are considered (vacancies, substitutions, and interstitials) and their impact on the phonon conductivity is evaluated. It is found that even a small concentration of point defects may have substantial effect and result in a reduction in the thermal conductivity values by almost an order of magnitude. The obtained results are in good qualitative agreement with previous studies conducted for silicon carbide. The methodology which is utilized in this work, the modeling procedure, and the obtained results are discussed in this paper.
Analysis of Heat-Driven Combined Cooling and Desalination
Authors: Alelyani Sami M. , Fette Nicholas W. , Stechel Ellen B. , Doron Pinchas , Phelan Patrick E.
Published: February 2017

This paper investigates the opportunities for integrating thermally driven cooling systems with thermally driven desalination systems via cascade of reject heat. Single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) are selected for this study based on technical limitations and practical considerations. Cooling capacity and hourly water production are calculated from thermodynamic properties of the working fluids at different operating conditions using simple models for each of the constituent systems. Additionally, the second law of thermodynamics is applied with the aim of examining the entropy generation of each component as well as the total exergy destruction of the entire system. The results indicate that the total exergy destruction of the combined systems, which consist of an MED unit driven by either a single- or double-stage NH3–H2O refrigeration system, decreases by an average of 55% compared to stand-alone NH3–H2O and MED systems. Relative to stand-alone systems, although water production decreases by 30% and 9% when an MED unit is integrated with single- and double-stage NH3–H2O absorption systems, respectively, cooling capacity remains unchanged for the double-stage NH3-H2O–MED system, and only decreases by 16% for the single-stage NH3-H2O–MED system.
Development of Haptic Communication Device for Disabled Persons
Authors: Szabó Zoltán , Enikov Eniko T.
Published: February 2017

With the emergence of augmented and virtual-reality based information delivery technologies the gap between availability of communication devices for visually impaired people and sighted people is emerging. The current study describes a communication tool which provides a reading platform for visually impaired people by means of a haptic display. In this paper the development and human subject study based evaluation of an electromagnetic microactuator-array based virtual tactile display is presented. The actuator array is comprised of a 4 by 5 array of micro voice-coil actuators (tactors) providing vibrotactile stimulation on the user’s fingertip.

The size and performance of the actuators is evaluated against the thresholds of human tactile perception. It is demonstrated that a 2.65 mm (diameter) × 4 mm (height) generic tactor is suitable for practical applications in dynamic tactile displays. The maximum force of the actuator was 30 mN generated at current levels of 200 mA. At a stroke of 4.5 mm, the force is reduced to 10 mN. The peak force was generated at a displacement of 1.5 mm.

A total of 10 alpha-numeric symbols were displayed to the users via dynamically changing the location of the vibrating point in a predefined sequence, thus creating a tactile perception of continuous curve. Users were asked to sketch out the perceived symbols. Each subject carried out three experiments. The first experiment exposed all subjects to ten different characters. Data obtained from human subject tests suggest that users perceive most shapes accurately, however the existence of jump discontinuities in the flow of presentation of the curves lowers recognition efficiency most likely due to loss of sensation of solid reference point. Characters containing two or more discontinuous lines such as ‘X’ were more difficult to recognize in comparison to those described with a single line such as ‘P’, or ‘Z’. Analysis of the average character recognition rate from 10 volunteers concluded that any presented character was identified correctly in 7 out 10 tests. The second test included characters that were reused from the first experiment. Users had improved their character recognition performance as a consequence of repeated exposure and learning. A final set of experiments concluded that recognition of groups of characters, forming words, is the least efficient and requires further perfecting. Recommendations for improvements of the recognition rate are also included.
Dynamic Focusing of Electrospinning Process With Quadrupole Traps
Authors: Kyselica Rudolf , Enikov Eniko T.
Published: February 2017

Electrospinning is the most widely used production method for polymer fibers formed from an electrified fluid jet. This method is very versatile, relatively inexpensive and simple. When the sufficiently high electric potential (about 20kV) is applied to the polymer solution, the electrostatic forces overcome the surface tension of the polymer and a thin liquid jet is ejected from the nozzle. However, after short straight distance of the motion of the fiber it rapidly grows into an electric charge driven bending instability and results in a 3D spiraling trajectory leading to a very random deposition on the grounded collector. This significantly reduces the positive qualities of the fiber and its use in biomechanical engineering like a production of tissue scaffolds mimicking the structure of the extracellular matrix or a delivery of expandable chemo- and radio-therapeutic stents. In this work we present the initial results from investigating the feasibility of using dynamic focusing of the electrified jet in a linear quadrupole trap. This is a new alternative to the more generally used mechanical approach with rotating mandrel, could in principle lead to the ability to control the deposition location without the use of any moving components. The proposed approach was originally developed for trapping and transporting individual charged ions. In contrast to ions, an electrified continuous fiber represents an infinite degree of freedom system, with potentially much richer dynamics and unknown stability regions in the parameter space.

In order to understand the dynamics of the fiber, we present a discretized 2D reduced-order mathematical model which is investigated numerically. The resulting ODEs represent multi-dimensional form of a non-linear Mathieu’s and Meissner’s differential equations for harmonic, and step excitation functions, respectively. The model parameters were obtained from static experiments with electrodes compressing the fibers in a single plane. Finite-element model of the electrodes resulted in detailed potential maps, which were used to develop estimates of the required strength of the electrostatic field needed to steer the fibers.

The estimated parameters were used to obtain stable solutions of the reduced-order approximate of a spring-mass-charged dumbbell model of the fiber.
Analysis and Control of the 1st Order Interior Noise and Vibration Induced by Driveline Imbalance for 4WD Vehicle
Authors: Xia Yuanfeng , Pang Jian , Liu Rui , Li Wenjuan , Xu Jianchun
Published: February 2017

Based on the influence coefficient method of the single-plane and multi-plane imbalance, an experimental method of a 4WD driveline system imbalance is proposed. A sensitivity theory and a testing method of influence of the 4WD driveline system imbalance on the vehicle interior 1st order vibration and noise are proposed. According to the influence coefficient method of the single plane, this paper puts forward an imbalance separation method for the driveline components, especially the imbalance separation between the driveshaft and the axle. Based on the problems and phenomena of the 1st order interior vibration and noise induced by the driveline imbalance transferring through the body floor and the interior acoustic cavity, the driveline imbalance sensitivity, the dynamic imbalance of the driveshaft and the driveline system are analyzed separately. Finally, the control methods of the dynamic imbalance and sensitivity of the 4WD vehicle driveline system are provided.
Harmonic Response of a Layered Halfspace Using Reduced Finite Element Model With Perfectly-Matched Layer Boundaries
Authors: Jones Simon
Published: February 2017

The current paper investigates the use of perfectly-matched layers (PML) as absorbing elements for a finite element (FE) model simulating a semi-infinite medium. This formulation is convenient for application of Craig-Bampton reduction (CBR), which significantly reduce the number active degrees-of-freedom in the model in an attempt to improve the computational efficiency. The results from this investigation suggest the PML elements worked seamlessly with the FE elements to approximate the elastodynamic response of a 2D layered halfspace subjected to a surface load; the wave energy appears to be fully absorbed by the PMLs regardless of incident angle or wavelength. The size of the model is reduced by approximately 77% using the CBR, which transforms the system into a mixed set of coordinates, including both modal and spatial coordinates. The model reduction is accomplished by neglecting modal frequencies for the system above one and a half times the maximum forcing frequency of interest. By only transforming the frequency-independent FE section into modal coordinates, and leaving the frequency-dependent PML elements as spatial degrees-of-freedom, the mode-shapes must only be solved once and can then be reused for different forcing frequencies. The results from this investigation suggest this could provide computational benefits if a number of cases are being computed for different frequencies.
Comparison of Inlet Curved Disk Arrangements for Suppression of Recirculation in Centrifugal Pump Impellers
Authors: Hermez Munther Y. , Jawad Badih A. , Liu Liping , Fernandez Vernon , Yee Kingman , Oklejas Eli
Published: February 2017

The present work aims to numerically study the inlet flow recirculation and modified impeller interaction in a centrifugal pump. An optimization of modified shrouded impeller with curved disk arrangement to suppress the unsteady flow recirculation is pursued. This modification will enhance the impeller characteristics with a wider operation range at both low and high flow rates in a high speed centrifugal pump type. The unstable flow in the centrifugal pumps is a common problem that leads to damage in the pump’s internal parts, consequently increases the operating cost. At certain flow rates, generally below the Best Efficiency Point (BEP), all centrifugal pumps are subject to internal recirculation occurs at the suction and discharge areas of the impeller.

For decades, experimental work has been done to investigate the complex three-dimensional flow within centrifugal pumps impellers, before computational work gains momentum due to advancement of computing power and improved numerical codes. In this study the impeller with a curved disk arrangement has been investigated by using a three-dimensional Navier-Stokes code with a standard k-ε turbulence model. The purpose is to evaluate and select the optimum impeller modification that would increase the pump suction flow rate range. Three-dimensional numerical Computational Fluid Dynamics (CFD) tools are used to simulate flow field characteristics inside the centrifugal pump and provide critical hydraulic design information. In the present work, ANSYS v.16.1 Fluent solver is used to analyze the pressure and velocity distributions inside impeller suction and discharge passages.

The ultimate goal of this study is to manufacture and validate the most optimized and efficient centrifugal pump impeller with a curved disk. The best case curve identifies the highest increase of total pressure difference by 22.1%, and highest efficiency by 92.3% at low flowrates.
High-Frequency Vibration Analysis of Thin Plate Based on B-Spline Wavelet on Interval Finite Element Method
Authors: Geng Jia , Zhang Xingwu , Chen Xuefeng , Xue Xiaofeng
Published: February 2017

For the dynamic analysis of thin plate bending problems, the Finite Element Methods (FEMs) are the most commonly used numerical techniques in engineering. However, due to the deficiency of low computing efficiency and accuracy, the FEMs can’t be directly used to effectively evaluate dynamic analysis of thin plate with high modal density within low-high frequency domain. In order to solve this problem, the Wavelet Finite Element Methods (WFEMs) has been introduced to solve the problem by improving the computing efficiency and accuracy in this paper. Due to the properties of multi-resolution, the WFEMs own excellently high computing efficiency and accuracy for structure analysis. Furthermore, for the destination of predicting dynamic response of thin plate within high frequency domain, this paper introduces the Multi-wavelet element method based on c1 type wavelet thin plate element and a new assembly procedure to significantly promote the calculating efficiency and accuracy which aim at breaking up the limitation of frequency domain when using the existing WFEMs and traditional FEMs. Besides, the numerical studies are applied to certify the validity of the method by predicting state response of thin plate within 0∼1000Hz based on a special numerical example with high modal density. According to the literature, the frequency domain between 0 to 1000Hz contains the low-high frequency domain aiming at the numerical example. The numerical results show excellent agreement with the reference solutions captured by FEM and analytical expressions respectively. Among these, it is noteworthy that the relative errors between the analytical solutions and numerical solution are less than 0.4% when the dynamic response involved with 1000 modes.
Investigation of Shock Waves Generated by Electrical Wire Explosion
Authors: Liu Ben , Wang Deguo , Guo Yanbao
Published: February 2017

The shock waves generated by electrical explosion of wire (EEW) have been used for oil and gas exploitation in recent years. In order to discuss the characteristics of shock waves generated by underwater wire explosion, the experiment setup was build, which contains a high voltage power supply, a capacitor, a full-size designed electrodes and its support. The discharge part is put into a section of petroleum casing pipe. The shock waves were measured by a PCB blast pressure gauge, which is placed at a certain distance away from the wire core with flash installation and facing the center of perforation through the casing pipe. The results show that the energy deposition plays a crucial role in generating the shock waves. The peak pressure is mainly dependent on the vaporization of metal wire. The plasma channel discharge formed with a large energy deposition may enhance the shock waves. In frequency domain analysis, the shock wave has a wide-band frequencies range from 1 to 80 kHz. The strong shock waves play a main effect on the plug removal in the near wellbore area. Under a certain distance from the blast center, the shock waves with slow decay in time domain and frequency domain are able to stimulate the production layers in a long distance.
Performance Analysis of a Humid Air Turbine Cycle With an Aero-Derivative Gas Turbine
Authors: Chen Jinwei , Huang Di , Zhang Huisheng , Weng Shilie
Published: February 2017

Nowadays, the issues of the energy and environment become more and more serious with the demand of energy increasing drastically. The advanced gas turbine cycles provide the opportunities to solve these issues. Humid air turbine (HAT) cycle, which is one of the most promising cycles with high efficiency, low emissions and low unit investment costs, is a prominent representation of the advanced gas turbine cycles. In this paper, an aero-derivative three-shaft gas turbine was converted to the HAT cycle. The aero-derivative is one of the most efficient simple cycles, whose system efficiency can reach 40%. And it is an effective solution to transform the advanced technology from the aeronautical filed to the industrial application. In order to investigate the performance of the HAT cycle, the saturator model was established based on the saturation curve and the saturator working line. Additionally, it was validated that the saturator model was consistent with the steady state experimental results very well. The maximum error of the outlet air temperature is less than 0.8% and the maximum error of the outlet air humidity is less than 1.9%. Three different HAT cycle systems were designed and simulated on the MATLAB platform. The thermodynamic performance of the three HAT systems on the design point shows that case 2 is the better one, which means that the aftercooler does not have obvious benefits for system performance and NOx emissions. Then, the effects of the ambient temperature on the case 2 and simple cycle were investigated. The results show that the HAT cycle has the more favorable off-design performance than the simple cycle when the ambient temperature is changed.
A Parametric Study of Air-Pumping Phenomenon in Tire Grooves Using Computational Fluid Dynamics
Authors: Gautam Prashanta , Azizi Yousof , Chandy Abhilash J.
Published: February 2017

The tire/road interaction process results in generation of noise, which is transmitted and audible in the inside and outside of the car. In the recent years, the structural-borne noise in a tire has been extensively studied. However, very few studies have been conducted on air-borne noise. Various studies and indoor experimental measurements suggest that among all air-borne tire noise mechanisms, air-pumping mechanisms, i.e. rapid displacement of air near the tire/road contact patch, is the dominant source of noise for certain tires and operating conditions. This research focuses on studying air-pumping mechanisms and uses a previously developed computational model to predict air-borne noise generated using a hybrid approach. The basis of the hybrid approach is a direct prediction of near-field solution using compressible Navier-Stokes equations with turbulence modeling, combined with an analytical prediction of far-field acoustics using an acoustic model. Only the near-field acoustic characteristics are discussed in this paper. The tire rotation and groove deformations at the tire/road contact is modeled through mesh motion and prescribed deformation functions, thereby circumventing the need for coupling with a structural solver for fluid-structure interactions. The capability of the developed computational model in estimating the tire noise is shown and the effects of varying different parameters such as tire speed and geometry on the evolution of the estimated responses at various near-field receiver locations are studied.
A Generalized Solution on the Static Characteristics of Short Hydrodynamic Journal Bearings Using Harmonic Components
Authors: Yang Baisong , Tian Jiale , Zhou Jian , Yu Lie
Published: February 2017

A theoretical analysis has been done to investigate the static performance of short hydrodynamic journal bearings with a generalized film thickness expression by a sum of Fourier series equation. The hydrodynamic film thickness was written into a summation of an infinite harmonic component of trigonometric function. Reynolds equation with short bearing theory is solved for steady-state operations. In this paper, the steady-state analysis of the generalized hydrodynamic bearing has been done and compared with some typical journal bearings with respect to their harmonic components of film thickness, pressure distribution and load capacity. The relationship between the k-th order harmonic component of the film thickness H0,k and the static pressure component P0,k was established. It was found that the value of P0,k is directly determined not only by the k-th order harmonic component H0,k but also the (k−1)-th order component P0,k−1 indirectly produced by the previous harmonic component H0,k−1.This new investigation method can used to improve the performance of hydrodynamic journal bearings for shape optimization of hydrodynamic journal bearings.
Effects of Annealing Parameters on Nickel Catalyst Nanoparticle Size for Carbon Nanotube Synthesis Applications
Authors: Cody Jonathan W. , Kim Sungwon S.
Published: February 2017

The properties of carbon nanotubes are dependent, in part, on the size of the catalyst metal nanoparticles from which the carbon nanotubes are grown. Annealing is a common technique for forming the catalyst nanoparticles from deposited films. While there is ample work connecting catalyst film properties or catalyst nanoparticle properties to carbon nanotube growth outcomes, the control of catalyst nanoparticle size by means other than the variation of initial film thickness is less explored. This work develops an empirical correlation for the control of nickel nanoparticle equivalent diameter by modification of anneal plateau temperature and anneal plateau time, thereby providing an additional avenue of control for catalyst properties. It has been hypothesized that the size of catalyst nanoparticles can be predetermined by appropriate selection of the initial catalyst film thickness, plateau temperature, and plateau time of the annealing process. To this end, buffer layers of 50 nm titanium, followed by 20 nm aluminum, were deposited onto silicon substrates via electron beam evaporation. Nickel catalyst layers were then deposited with thicknesses of either 5, 10, or 20 nm. Samples of each of the three nickel layer thicknesses were annealed in an ambient air environment at different combinations of 500, 600, 700, 800, and 900 °C plateau temperature and 5, 10, and 15 minute plateau time. Representative time-temperature curves corresponding to each plateau temperature were also acquired. The end result was a set of 45 samples, each with a unique combination of initial nickel film thickness, anneal plateau temperature, and anneal plateau time. Resulting nanoparticles were characterized by atomic force microscopy, and distributions of nanoparticle equivalent diameter were collected via a watershed algorithm implemented by the Gwyddion software package. Comparison of the 45 parameter combinations revealed a wide range of nanoparticle sizes. In most cases, comparable equivalent diameters were obtained from a variety of parameter combinations. Thus, results provide multiple options for achieving the same nanoparticle diameter, for use in cases where additional restraints are present. To facilitate such decisions, a correlation was developed that connected catalyst nanoparticle diameter to the three process parameters of initial catalyst film thickness, anneal plateau temperature, and anneal plateau time. For example, a given initial Ni film thickness can be annealed to a specified nanoparticle size by selecting anneal plateau temperature and plateau time per the correlation, provided that comparable buffer layers were chosen. This correlation provides a more robust array of options for specification of catalyst nanoparticle size and final carbon nanotube properties for a specific application.