bluuebunny/crossref_metadata_2025 huggingface dataset:
Constrained-Equilibrium Modeling of Methane Oxidation in Air
Authors: Nicolas Ghassan , Janbozorgi Mohammad , Metghalchi Hameed
Published: April 2014

The Rate-Controlled Constrained-Equilibrium (RCCE) has been further developed and applied to model methane/air combustion process. The RCCE method is based on local maximization of entropy or minimization of a relevant free energy at any time during the non-equilibrium evolution of the system subject to a set of constraints. The constraints are imposed by slow rate-limiting reactions. Direct integration of the rate equations for the constraint potentials has been employed. Once the values of the potentials are obtained, the concentration of all species can be calculated. A set of constraints has been developed for methane/air mixtures in the method of Rate-Controlled Constrained-Equilibrium (RCCE). The model predicts the ignition delay times, which have been compared to those predicted by detailed kinetic model (DKM) and with shock tube experimental measurements. The DKM includes 60 H/O/C1–2/N species and 352 reactions. The RCCE model using 16 constraints has been applied for combustion modeling in a wide range of initial temperatures (900–1200 K), pressures (1–50 atmospheres) and fuel-air equivalence ratio (0.6–1.2). The predicted results of using RCCE are within 5% of those of DKM model and are in excellent agreement with experimental measurements in shock tubes.
Some Experimental Results on Internal Fire Whirls in a Vertical Shaft
Authors: Gao Y. , Zou G. W. , Li S. S. , Chow W. K.
Published: April 2014

Earlier studies on burning a pool fire in a vertical shaft model indicated that appropriate sidewall ventilation provision is a key factor for the onset of an internal fire whirl. Experiments on burning a pool fire inside a real-scale shaft model of 9 m tall were performed to further investigate the swirling motion. The full-scale modeling burning tests were carried out at a remote site in China. Four different ventilation openings were arranged. Results of onsetting of internal fire whirls for the four tests will be reported.
Structural Health Monitoring Using Piezoelectric Transducers and Wavelets
Authors: Shih Hui-Ru , McIntyre Albert C.
Published: April 2014

Structural Health Monitoring (SHM) is the process of monitoring and assessing the state of health for aerospace, civil, and mechanical engineering infrastructure. SHM offers the opportunity to reduce inspection efforts and optimize maintenance and mission planning. SHM is a highly emerging field of technology. It brings together a variety of disciplines. To stimulate students’ desire for pursuing advanced study in science, technology, engineering, and mathematics (STEM) and well prepare them for their future careers, STEM educators need to dedicate their efforts to educate the students with this emerging technology. SHM is a field that requires a significant amount of background knowledge to build upon. At Jackson State University (JSU), four course modules (Smart Materials, Data Acquisition Systems, Lamb Waves, and Wavelet Analysis) have been developed and integrated into an existing course to help undergraduate students gain practical experience and have a firm grasp on this emerging vital tool. After taking the class, several students were selected to participate in a research activity sponsored by the Center for Undergraduate Research (CUR) at JSU. This paper describes the content covered in the modules as well as summarizes student perceptions of their learning and research experiences.
Static and Dynamic Analysis of a Clamp-Clamp Nano-Beam Under Electrostatic Actuation and Detection Considering Intermolecular Forces
Authors: Mojahedi Mahdi , Firoozbakhsh Keikhosrow , Barari Ahmad , Ahmadian Mohammad Taghi
Published: April 2014

Micro/nano gyroscopes which can measure angular rate or angle are types of merging gyroscope technology with MEMS/NEMS technology. They have extensively used in many fields of engineering, such as automotive, aerospace, robotics and consumer electronics. There are many studies of a variety of gyroscopes with various drive and detect methods and different resonator structures in last years. In case of electrostatically actuated and detected beam micro/nano-gyroscopes, DC voltages are applied in driving and sensing directions and AC voltage is utilized in driving direction in order to excite drive oscillation. The intermolecular surface forces are especially significant when the gyroscopes are working in vacuum without the effect of capillary forces and the separations between movable components are in the sub-micrometer range. In this paper, a new model is used to study the static and dynamic behavior and pull-in instability of the vibratory clamped-clamped beam micro/nano gyroscopes. The system is operated by electrostatic mechanisms and subjected to base rotation. In this model, the effects of the intermolecular attractions and fringing electrostatic fields are accounted. Nonlinear differential equations governing the dynamic motion of the system are obtained using extended Hamilton principle. The static and dynamic problems are solved for various values of nondimensional design parameters.
Proof-of-Concept Combined Shrouded Wind Turbine and Compressed Air Energy Storage System
Authors: Langness Chenaniah , Kolsky Daniel , Busch Tyler , Davidson Colin , Depcik Christopher
Published: April 2014

As the push for renewable energy sources continues, one significant drawback over fossil fuels is that they are not reliable. Wind is not guaranteed at all times, and the sun does not always shine. Moreover, the demand for electricity is variable due to daily and seasonal swings in power draw from the grid. Conventional power plants can increase or reduce production to meet seasonal demand, but usually cannot meet daily fluctuations. Therefore, power plants must maintain a relatively high level of electrical generation capacity throughout the day even if the current demand is low. A prime place to focus upon electrical demand fluctuations and the unreliability of the renewable sources is at the location of the changes in demand. Homes often sit vacant throughout the day and draw little power from the grid. When residents return in the late afternoon and evening, a sudden increase in demand occurs. To address this increase in demand at a local level, a small-scale proof-of-concept shrouded wind turbine (SWT) and compressed air energy storage (CAES) system was designed, built, and tested for an undergraduate capstone design project. The concept is that a small SWT charges the CAES system and when the residents return, the energy stored within the CAES system is released lessening the demand on the main electrical grid. The SWT was investigated due to the theorized increase in efficiency that the shroud provides by accelerating the air beyond ambient velocity at the location of the turbine blades. The CAES system consisted of a three-stage compressor that filled a high-pressure scuba tank. This air was then released in a controlled manner in order to operate an air motor coupled to an alternator that generated electricity. Testing of the SWT found that the prototype was too small to power the compressors for the CAES; however, the concept of the SWT was shown to hold true. Experiments using the CAES system demonstrated significant losses, but it did generate electricity. The small-scale prototype did reveal that the idea of focusing on the source of the power fluctuations is a viable option. As a result, by using many small power production and storage devices, the overall daily swings in demand for electricity can be corrected to levels that current power plants can meet.
Experimental Investigation to Evaluate the Performance of Helical Coiled Tube Heat Exchanger With Using TiO2 Nanofluid
Authors: Mahdi Qasim Saleh , Fattah Sahar A. , Juma Firas
Published: April 2014

Experimental investigation of heat transfer enhancement in heat transfer coefficient of shell and helical coil tube heat exchanger with and without addition nanofluid is carried out in the present work. Experimental work is included two parts: the first one is included design of helical coil heat exchanger with optimum curvature ratio (17), an optimum helical coil pitch has been used to study the heat transfer coefficient without nanofluid. The second part is included studying the effect of using (Oxide Titanium TiO2) nanoparticle powder with 20 nm diameter is dispersed in distilled water with different volume concentrations (0.2, 0.4, 0.6, and 0.8) % by volume on heat transfer coefficient. The experimental results showed that, when nanofluid was used there is an increase in heat transfer coefficient and thermal conductivity by (20) %. An empirical correlation has been found to show the variation of Nusselt number with Dean number by using nano fluid with error of (±5%).
On Smoothed Finite Element Methods
Authors: Liu G. R.
Published: April 2014

The paper presents an overview of the smoothed finite element methods (S-FEM) which are formulated by combining the existing standard FEM with the strain smoothing techniques used in the meshfree methods. The S-FEM family includes five models: CS-FEM, NS-FEM, ES-FEM, FS-FEM and α-FEM (a combination of NS-FEM and FEM). It was originally formulated for problems of linear elastic solid mechanics and found to have five major properties: (1) S-FEM models are always “softer” than the standard FEM, offering possibilities to overcome the so-called overly-stiff phenomenon encountered in the standard the FEM models; (2) S-FEM models give more freedom and convenience in constructing shape functions for special purposes or enrichments (e.g, various degree of singular field near the crack-tip, highly oscillating fields, etc.); (3) S-FEM models allow the use of distorted elements and general n-sided polygonal elements; (4) NS-FEM offers a simpler tool to estimate the bounds of solutions for many types of problems; (5) the αFEM can offer solutions of very high accuracy. With these properties, the S-FEM has rapidly attracted interests of many. Studies have been published on theoretical aspects of S-FEMs or modified S-FEMs or the related numerical methods. In addition, the applications of the S-FEM have been also extended to many different areas such as analyses of plate and shell structures, analyses of structures using new materials (piezo, composite, FGM), limit and shakedown analyses, geometrical nonlinear and material nonlinear analyses, acoustic analyses, analyses of singular problems (crack, fracture), and analyses of fluid-structure interaction problems.
Numerical Study of Straight Annular Seals Versus Convergent Annular Seals at Different Geometries, Surface Roughness, and Operating Conditions
Authors: Ustun Serafettin , Marsis Emanuel , Morrison Gerald
Published: April 2014

Annular seals are used in many turbomachineries to reduce the leakage from high to low pressure zones. In this paper, 2D CFD simulations are used to analyze the flow inside straight annular seals and convergent tapered annular seals with two different exit clearances. The working fluid used was water. The effect of the geometry and surface roughness on the seal performance was studied at different differential pressures and rotor speeds. Moreover, a new design parameter is introduced that relates the normalized axial pressure gradient to the axial wall shear stress for straight and convergent annular seals. This ratio was found to be constant at different seal geometries, exit clearances, differential pressures, and rotor speeds. This allows designers to consider the effects of various convergent tapered seal designs upon the rotordynamic characteristics of the seal without requiring individual CFD simulations.
Potential of a Medium Grade Low Heat Rejection Diesel Engine With Crude Tobacco Seed Oil
Authors: Murali Krishna M. V. S. , Kumar P. Pavan , Murthy P. V. K. , Baswaraju D.
Published: April 2014

Investigations were carried out to evaluate the performance of a medium grade low heat rejection (LHR) diesel engine consisting of air gap insulated piston with 3-mm air gap, with superni (an alloy of nickel) crown and air gap insulated liner with superni insert with different operating conditions of crude tobacco seed oil with varied injection timing and injection pressure.

Performance parameters of brake thermal efficiency (BTE), exhaust gas temperature (EGT), volumetric efficiency (VE), coolant load (CL) and sound intensity were determined at various values of brake mean effective pressure (BMEP) of the engine.

Exhaust emissions of smoke and oxides of nitrogen (NOx) were noted at different values of BMEP of the engine. Combustion characteristics of peak pressure (PP), time of occurrence of peak pressure (TOPP), maximum rate of pressure rise (MRPR) and time of occurrence of maximum rate of pressure (TOMRPR) were measured with TDC (top dead centre) encoder, pressure transducer, console and special pressure-crank angle software-package at the peak load operation of the engine.

Conventional engine (CE) showed deteriorated performance, while LHR engine showed improved performance with crude tobacco seed oil (CTSO) operation when compared with pure diesel operation at recommended injection timing and pressure. The optimum injection timing was found to be 32°bTDC (before top dead centre) with CE while it was 30°bTDC with LHR engine with vegetable oil operation. The performance of both version of the engine improved with advanced injection timing and higher injection pressure with test fuels. Peak brake thermal efficiency increased by 4%, volumetric efficiency decreased by 8%, smoke levels decreased by 4% and NOx levels increased by 37% with vegetable oil operation on LHR engine at its optimum injection timing, when compared with pure diesel operation on CE at manufacturer’s recommended injection timing of 27°bTDC.
Comparative Studies on Performance and Emissions of Two Stroke and Four Stroke Copper Coated Spark Ignition Engines With Methanol Blended Gasoline
Authors: Krishna M. V. S. Murali , Priyadarsini Ch. Indira , Ushasri P. , Murthy P. V. K. , Baswaraju D.
Published: April 2014

Investigations were carried out to evaluate the performance of two stroke and four stroke of single cylinder, spark ignition (SI) engines having copper coated engine [CCE, copper-(thickness, 300 μ)] coated on piston crown and inner side of cylinder head] provided with catalytic converter with sponge iron as catalyst with methanol blended gasoline (80% gasoline and 20% methanol by volume) and compared with conventional engine (CE) with pure gasoline operation.

Performance parameters — brake thermal efficiency (BTE), exhaust gas temperature (EGT), volumetric efficiency and exhaust emissions of carbon monoxide (CO) and un-burnt hydrocarbon (UBHC) were determined with different values of brake mean effective pressure (BMEP) of the engine and compared with one over the other of two stroke and four stroke SI engine with different versions of the engine.

Formaldehyde and acetaldehyde emissions were measured by 2, 4 dinitrophenyl hydrazine (2,4 DNPH) method at peak load operation of CE and CCE of two-stroke and four-stroke SI engine. The engine was provided with catalytic converter with sponge iron as catalyst. There was provision for injection of air into the catalytic converter.

Brake thermal efficiency increased with methanol blended gasoline with both versions of the engine. CCE showed improvement in the performance when compared with CE with both test fuels. Four-stroke engine decreased exhaust emissions effectively in comparison with two-stroke engine with both versions of the engine. Catalytic converter with air injection significantly reduced exhaust emissions with different test fuels on both configurations of the engine.
Three-Dimensional Mesh Morphing Methodology for Scouring Around Bridge Piers Based on Computational Fluid Dynamic Solution
Authors: Edwards Chris , Lottes Steven A. , Majumdar Pradip
Published: April 2014

Flow scour is the engineering term used to describe the erosion of a sediment bed due to fluid flow. Local scour occurs around objects placed in the path of flow, such as bridge piers and abutments. Severe damage or even failure of structures may occur if the amount of scour is too great. Due to the complexity of the fluid/structure interactions and cost of experiments, Computation Fluid Dynamics (CFD) methods are under development to predict the shape and depth of a scour hole. This study extends a previous 3-D iterative methodology, with several improvements to the scouring physics models, implemented in the commercial CFD software STAR-CCM+ to predict the scour hole formation around circular bridge piers. These improvements are inclusion of a variable critical shear stress (VCSS) for the initiation of motion of bed sediment, scouring normal to the sediment bed, and a sand slide model. Reynolds Averaged Navier-Stokes (RANS) equations and a k-ε turbulence model are used to resolve the flow field. The methodology uses a single phase implicit unsteady approach to obtain sediment bed shear stress values. Two moving boundary relations are employed to model the erosion and sand slide physics. One for the erosion rate is based upon an empirical correlation for critical shear stress combined with a sediment entrainment function of Van Rijn, and the other uses the slope of the sediment bed, to iteratively displace the sediment bed in a way that decreases slope as long as it exceeds the angle of repose of the sediment. This is accomplished by a user defined function to move the sediment bed at each time step and the mesh morphing procedure built into STAR-CCM+ to solve fluid-structure interaction problems to stretch the existing mesh to maintain cell quality throughout the flow domain as the bed is displaced. Simulation results have been compared to experimental data found in literature. It was found that simulations over predict the maximum scour depth by up to 35%, but show a large improvement in capturing the overall shape of the scour hole in comparison to models that do not include a sand slide model.
A Tunable Helmholtz Resonator for Active Noise Control
Authors: Nudehi Shahin S. , Charnley Stephen , Brandt Taylor , Nasserifar Parisa
Published: April 2014

In this study, a tunable Helmholtz resonator is proposed for active noise cancelation in a primary acoustic system. In the tunable Helmholtz resonator, the resonator’s top wall is replaced by a flexible membrane and four actuators are mounted on the side of the resonator. These actuators are connected to the membrane in order to tune its radial force (tension) by pulling or releasing the membrane during the operation. This causes the resonant frequency of the modified Helmholtz resonator to change due to the change in the membrane tension. The maximum noise attenuation is achieved when the the resonant frequency of the active resonator matches with the noise frequency in the primary system. In this paper, first mathematical modeling is used to derive nonlinear coupled differential equations for the tunable Helmholtz resonator with the membrane. The differential equations were linearized to obtain an analytical formulation for the resonant frequency of the tunable resonator in terms of the membrane tension. The analytical formulation for the resonant frequency was verified via simulation of the original nonlinear differential equations. Finally, to demonstrate the validity of the mathematical modeling of the tunable resonator, experimental results are provided.
Dynamic Particle Concentration for Bio-Signal Enhancement Based on an Optoelectric Microchip
Authors: Wang Kuan-Chih , Wereley Steven T. , Kumar Aloke , Chuang Han-Sheng
Published: April 2014

Concentration is a vital measure to collect samples in biology. The same measure can also benefit bio-signal enhancement. Conventionally, signal detection heavily relies on the sensitivity of sensors. However, background noise usually interferes with the accuracy as the sample concentration level is below a threshold. The signals are even weaker especially in miniaturized diagnostics or point-of-care devices. Alternatively, single cell/molecule detection[1] was developed to break the engineering limitation and achieve better detectability. However, challenge concerning to single cell/molecule capturing and manipulation is a potential barrier in the field. In addition, the effectiveness of sampling remains an open quest under study. As a result, concentrating samples provides a simple, rapid, and direct means for enhancing weak bio-signal detection.
Dynamic Modeling of Turbulence
Authors: Mazher A. K. , Mo Changki
Published: April 2014

This paper presents a new systematic and generalized approach to model turbulence dynamically. The suggested approach is based on the variational technique to solve a system of equations where the number of unknowns is larger than the number of equations. Turbulence closure problem results when averaging the Navier-Stokes (N-S) equations. Averaging transforms the N-S equations from a determinate set of equations describing turbulent flow field to an indeterminate set of equations that need additional information. Unknown terms, Reynolds stresses, appear as a results of averaging; and the solution of the averaged N-S equations depends on the proper selection of Reynolds stresses. In the dynamic modeling formulation of turbulence, the Reynolds stresses are selected to produce a best solution of the averaged N-S equations. The Reynolds stresses are computed via optimizing a performance index ‘I’. In the optimization process the averaged N-S equations are considered as constraints. The performance index ‘I’ is defined as a measure of the quality of solution. Averaging can be considered as a process by which we lose some information about the flow field. The lost information appears partially in the unknown terms “Reynolds stresses”. Hence, the performance index should include some measure of information losses which occur as the result of averaging. Classical approach does not rely on the N-S equations, itself as a complete description of turbulence, to derive a suitable turbulence models. The new concept will use the N-S equations, combined with the physics of turbulence, for an optimal selection of turbulence model through ‘I’. In this approach the model is not specified in advance, but it will be developed dynamically with the solution.
Buckling Measurement of Cylindrical Shells by Digital Image Correlation Method
Authors: Kuo Tzu-Yu , Wang Wei-Chung , Chu Chun-I , Chen Jia-He , Hung Te-Heng , Chang Jen-Yuan (James)
Published: April 2014

In this study, deformation of cylindrical shells under axial compressive load was studied and characterized by a noncontact detection technique, called digital image correlation (DIC). As opposed to commonly used strain gages for measuring structure strains at specific points, the DIC method can render not only 2D but also 3D full-field measurements for strain as well as structure deformation. The accuracy of strain measurement obtained using the DIC method was carefully validated by following ASTM standard E8 for strain measurement using strain gages in tensile tests. The DIC technique provided convenient measurements for characterizing the buckling behaviors of defective cylindrical shell samples. This study has engineering implications for providing 3D strain and deformation analyses to ensure structure reliability and safety.
Design Method of Octahedron Deployable Mast
Authors: Liu Heping , Luo Ani , Li Cheng , Ma Wentao , Song Jianhua
Published: April 2014

The truss-shape deployable structure is an important and mainly developed type of deployable structure. In this paper, the octahedron deployable mast is designed and analyzed to study the design method of the truss-shape deployable structure. First, a type of truss-shape octahedron, where several truss units are connected into a truss-shape mast, is presented. Then the mechanical performance of truss-shape mast is analyzed to explore whether strings of the mast can be taken away. The relationships of the positions and the orientations of the bars are used to determine the kinematic pairs connecting the bar group in the truss structure. Using the mechanical topology analysis and the screw theory, degree of freedom for the mechanism is computed. Lastly positions of the driving pairs are determined and an octahedron deployable mast is obtained. The scheme model of the deployable mast is implemented to further verify its rationality; meanwhile we will test the correctness of the design method for the deployable structure.
Identification of Appropriate Wavelet for Vibration Study of Mechanical Impacts
Authors: Nikravesh Seyed Majid Yadavar , Taheri Hossein , Wagstaff Peter
Published: April 2014

The purpose of this paper is to discuss the selection of the most appropriate wavelets to analyze the vibration response of structures due to mechanical impacts. For this reason the wavelet transformation is briefly introduced, then the different types of wavelets, which are commonly used in this type of application are presented. Subsequently, the effects of selecting different types of wavelet to study the vibrations of a mechanical system are evaluated using a mathematical model. Afterwards, the wavelet transform is used to analyze the experimental response caused by the impact of a hammer on a test plate. This shows that the existence of a zone of local response due to reinforcement under the plate’s cover can be distinguished using the wavelet analysis.
Single-Phase Ceramic Membranes Integrated With Combustion Processes
Authors: Zeng Pingying , Wang Kang , Falkenstein-Smith Ryan Leon , Ahn Jeongmin
Published: April 2014

La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) hollow fibre oxygen-permeable membranes were fabricated by extrusion technique. The oxygen permeability of a blank hollow fibre membrane was investigated with helium as sweeping gas. The oxygen permeation flux result was reported, agreeing very well with previous work. Then the hollow fibre membrane was packed with LSCF6428 catalyst and assembled as hollow fibre membrane reactor for methane combustion, aiming to separate the CO2 in the combustion exhaust from the nitrogen in air. The CO2 selectivity at various conditions was studied.
Combustion of Reformed Propane as Segue to Glycerin Reforming
Authors: Pickett Derek Kyle , Depcik Christopher David
Published: April 2014

Biodiesel is a potential fuel that reduces dependency on petroleum products. Although its upstream fabrication results in it being a renewable resource, the downstream components are the focus of this paper. Glycerin is a byproduct from biodiesel production and currently has few uses as a means to recover some of the energy required to produce biodiesel. One such option is to convert glycerin into a hydrogen rich mixture over a catalyst for subsequent use in an internal combustion engine. A unique reformer and engine/generator setup at the University of Kansas allows the exploration of propane reforming and its subsequent combustion as the first step into glycerin reforming. In particular, the analysis of propane reforming will lead to the specific experimental conditions (e.g., flow rates) needed prior to glycerin reforming. This paper will document the experimental side of propane reforming along with models used in its analysis and extrapolation to glycerin.
Analysis of Vapor Blanket Formation in the Porous Wick of a Loop Heat Pipe With High Heat Load
Authors: Huang X. M. , Jin X. , Chen B. B. , Liu W.
Published: April 2014

A loop heat pipe has different transport mechanisms depending on heat flux. The interface of liquid and vapor cannot maintain at the surface of the wick when heat flux is high, and a vapor blanket will form in the wick. To investigate when the vapor blanket appears and how it affects heat and mass transfer in the system is very import to minimize the device. A mathematical model of heat and mass transfer in the evaporator, coupled with analysis of fluid flow in the loop, is developed in the paper. The model is applied to calculate the critical heat load that the vapor blanket forms, and to analyze how the blanket delays. A comparison of theoretical results and experimental measurements is further presented. The consistence of the results validates the model and the mechanisms.
A Study on 3D Micro-Topographical Measurement of FRCMC Grinding Surface
Authors: Cao Xiaoyan , Lin Bin , Wang Yan , Wang Shaolei
Published: April 2014

Fiber-reinforced ceramic matrix composites (FRCMCs) have potential applications in aerospace and other high-tech fields. Meanwhile, it is significant to evaluate the grinding surface quality of FRCMCs. But according to FRCMCs’ anisotropic and non-homogeneous structure, it is difficult to evaluatethe surface quality with the traditionalmeasuring method used in metal material. The present paper studied the 3D micro-topographical measurement and evaluationfrom a new perspective. The research is based on some new discovery that the material enhanced fiber orientation played key role in micro-topographical of FRCMC grinding surface. Using a non-contact optical measurement instrument, the method was developed on 2.5D SiO2/SiO2 composite. Through a series of measuring experiments, we found that both starting position of measurement and sampling conditions affected on the measurement results. This paper recommendedoptimization measurement parameter valuesof sampling conditions, and also analyzedcharacteristics of the RCMC grinding surface topography on amplitude, wave distribution and surface supportcharacteristics in details. The results show that the optimal range of sampling interval is 40 μm to 70 μm, the range of sampling area is better more than 64mm2 and the range of sampling speed is 8 to 14mm/s. The measurement of surface topography is the bridge framed between the manufacture and parts performance, so theresearchobtained will be an important technical support on improvingthe processing quality of FRCMC.
Mechanical Engineering in Stimulating Well Production in the Oilfield
Authors: Surjaatmadja Jim B.
Published: April 2014

A mechanical oil field engineer could very well be the most diverse position within the industry. Various tasks, such as entering a wellbore to a depth of 25,000 ft to deliver equipment capable of pumping sand slurries at pressures greater than 15,000 psi and temperatures often higher than 350°F, are unique to the job. Yet, there are even more areas where the mechanical engineer could excel, to include stimulation (including fracturing/fracking), rock mechanics (static or dynamic), or even geomechanics.

This paper discusses examples of mechanical engineering improving traditional approaches to well stimulation technologies. In one example, the commonly known Bernoulli equations were used to formulate a unique formation fracturing technique. Using this technique, fracturing fluid zonal distribution, which traditionally has been performed using mechanical wellbore sealing devices, was diverted using dynamic isolation of a high-pressure wellbore operation (i.e., sealing using fluid velocity). The effectiveness of such a process was demonstrated by completing the task in less than one tenth of the time required when using conventional (mechanical) techniques.

In another example, fluid rheology parameters were applied to formation rock response, simulating the formation movements as if they were a very viscous, non-Newtonian fluid. The rock could hence be modeled as if it were plastic, using the Kelvin-Voigt relationship. The primary intent of this exercise was to provide an improved stimulation technique to the oil industry, thus providing much better producing wells in the future.
Theoretical and Experimental Study on Phononic Crystal Structures for Low-Frequency Noise Reduction in the Brake
Authors: Shen Li , Wu Jiu Hui
Published: April 2014

Phononic crystal is an artificial periodic structure in which elastic constants distribute periodically. In this paper, a two dimensional Bragg scattering phononic crystal was introduced into low-frequency noise reduction facility in the brake originally. Through the theoretical analysis by using Plane-wave Expansion Method to obtain the band diagram of a phononic crystal with holes periodically arranged in the 45 carbon steel plate and establishing the equivalent model in motion as the brake, we find an approximate bandgap between 0–5400Hz in the low-frequency range while the complete static bandgaps are distributed in the high-frequency range. It is believed that this kind of extremely low-frequency bandgap is due to the combination of the vibration of a single scatter and the interaction among scatters. In order to demonstrate the theory, contrastive experiment was taken. Noise spectrum diagram of the origin plate without holes was obtained in the first experiment. According to the equivalent model, the two dimensional air column/steel matrix phononic crystal structure in which filling rate was 40% was designed to apply in the test apparatus so that the frequency range (2050 to 2300Hz) of strong noise would be involved in this bandgap. Moreover, the noise in the whole frequency range (0–2550Hz) went down. This phenomenon proved that experiment result was coincident with theoretic consequence. The maximum decreasing amplitude of the noise reached as much as 25dB and the average decreasing amplitude was about 13dB from 2050 to 2300 Hz. In a word, this bandgap which is the combination effect of structure periodicity or the Mie scattering has an obvious extremely low-frequency characteristic in noise and vibration control in the brake.
Modeling of Tau Protein Transport in Axons
Authors: Kuznetsov Ivan A. , Kuznetsov Andrey V.
Published: April 2014

This paper develops a simplified analytical solution for the slow axonal transport of tau proteins. A six kinetic state model developed in Jung and Brown [1] was used to simulate transport of tau. The model was extended by accounting for tau degradation and diffusion in the off-track kinetic states. The analytical solution was obtained by assuming that transitions between anterograde and retrograde states are infrequent. This assumption was validated through an analysis of the sensitivity of the solution to changes in the values of the two kinetic constants that describe the transition rates between the anterograde and retrograde states, and by a comparison with the experimentally measured tau distributions reported in Konzack et al. [2]. The predicted average transport velocity of tau was also in the experimentally reported range.
A Numerical Study on the Effects of Unsteady Wind on Vertical Axis Wind Turbine Performance
Authors: Danao Louis Angelo , Edwards Jonathan , Eboibi Okeoghene , Howell Robert
Published: April 2014

Numerical simulations using RANS–based CFD have been utilised to carry out investigations on the effects of unsteady wind in the performance of a wind tunnel vertical axis wind turbine. Using a validated CFD model, unsteady wind simulations revealed a fundamental relationship between instantaneous VAWT CP and wind speed. CFD data shows a CP variation in unsteady wind that cuts across the steady CP curve as wind speed fluctuates. A reference case with mean wind speed of 7m/s, wind speed amplitude of ±12%, fluctuating frequency of 0.5Hz and mean tip speed ratio of 4.4 has shown a wind cycle mean power coefficient of 0.33 that equals the steady wind maximum. Increasing wind speed causes the instantaneous tip speed ratio to fall which leads to higher effective angle of attack and deeper stalling on the blades. Stalled flow and rapid changes in angle of attack of the blade induce hysteresis loops in both lift and drag. Decreasing wind speeds limit the perceived angle of attack seen by the blades to near static stall thus reducing the positive effect of dynamic stall on lift generation. Three mean tip speed ratio cases were tested to study the effects of varying conditions of VAWT operation on the overall performance. As the mean tip speed ratio increases, the peak performance also increases.
Flow Regime Identification of Horizontal Two Phase Refrigerant R-134a Flow Using Neural Networks
Authors: Kreitzer Paul J. , Hanchak Michael , Byrd Larry
Published: April 2014

Flow regime Identification is an integral aspect of modeling two phase flows as most pressure drop and heat transfer correlations rely on a priori knowledge of the flow regime for accurate system predictions. In the current research, two phase R-134a flow is studied in a 7mm adiabatic horizontal tube over a mass flux range of 100–400 kg/m2s between 550–750 kPa. Electric Capacitance Tomography results for 196 test points were analyzed using statistical methods and neural networks. This data provided repeatable normalized permittivity ratio signatures based on the flow distributions. The first four temporal moments from the mean scaled permittivity data were utilized as input variables. Results showed that only 80 percent of flow regimes could be correctly identified using seven flow regime classifications. However reducing to five more commonly used regimes resulted in an improvement to 99 percent of the flow regimes correctly identified. Both methods of neural network training resulted in errors that were off by mostly one flow regime classification. Further analysis shows that transition cases can oscillate between two separate flow regimes at the same time.
Development of a Mobile App for Learning System Dynamics
Authors: Zhu Weihang , Zhou Jiang , Islam Md. Aminul , Shufean Md. Abu , Liu Xinyu
Published: April 2014

This paper presents the development of a mobile app for learning System Dynamics. A course in System Dynamics is required in most mechanical and other engineering curricula. The app implements several types of the first order and the second order systems under various conditions. Based on the user inputs, the app solves the relevant System Dynamics equations and displays the graphs. The users are able to observe and analyze results by changing the parameters. The user-friendly app was developed for Android and iOS smartphone platforms. The developed app can serve as a complementary learning tool for System Dynamics in Mechanical Engineering. It may help students to understand important concepts and theories behind numerical results, such as the relationships between input and output, solutions in time-domain and frequency-domain, three vibration modes for the systems, and the effects of equation constants and input selections on output responses.
Impact Damage and Residual Strength of Composite Joints in Car Bodies
Authors: Sun Juanjuan , Sun Lingyu , Du Junmin , Wang Taikun
Published: April 2014

With the weight reduction requirements for vehicles and the cost reduction tendency for carbon fibers, carbon fiber reinforced plastics (CFRPs) will be applied more and more in automobile bodies in place of some steel materials. However, the structural design method using CFRPs is much different from that using steel. For example, the anisotropic material properties and the brittle plastics matrix need to be considered, and the connection between components is through adhesive joints, which is possibly weaker than the traditional spot welding. These features make CFRPs sensitive to impact loads, especially the repeated low-energy impact.

This paper presents a damage-based residual modulus and strength prediction method, which may be utilized in the design of composites components subject to repeated impact loads.

First, the CFRPs samples were impacted repeatedly by the pendulum hammer at a constant kinetic energy, 2J, and then, the residual bending modulus and strength were measured by static three-point bending machine. According to the test data, the relationship between impact number and residual stiffness and residual strength were established, and the damage factors after each impact were calculated. In subsequent numerical simulation, the damage accumulation effect was included in the one-step prediction model through replacing the initial modulus by the degradation modulus, and this method was verified numerically by comparison with N-step prediction results after N-times impact calculations. Finally, two kinds of composite joints were analyzed numerically, which provides theoretical guide for the design of composite joints in automobile body.
Low-Frequency Broadband Energy Harvesting Based on Locally Resonant Phononic Crystals
Authors: Zhang Siwen , Wu Jiu Hui
Published: April 2014

In this paper, a low-frequency broadband energy harvesting structure is proposed based on locally resonant phononic crystals (LRPCs). The low-frequency LR characteristics and energy harvesting capabilities of the proposed structure are investigated by using the finite element method. Energy localization effects are verified when local resonances occur, making the proposed LR structure work as an energy collector. Structure modifications are performed to improve the low-frequency energy collecting performance. For the suggested structure with composite units, sixteen resonant frequencies are found in the frequency range below 250 Hz, at which vibration energy is localized intensively in the piezoelectric folded beams. Based on the frequency response analysis, the composite structures are proved to have good energy harvesting capabilities over a broadband low frequency range, due to the multiple resonances and the high concentration of localized energy. These structures will be helpful for the self-powered microsystems, such as portable electronic devices, wireless sensors, microelectromechanical systems (MEMS) and so on, to extract energy from ambient low frequency vibrations.
Geometry-Based PSO for Mechatronic System Design Optimization
Authors: Yuan Wenqiang , Liu Yusheng
Published: April 2014

In this work, we present a new multi-objective particle swarm optimization algorithm (PSO) characterized by the use of the geometrization analysis of the particles. The proposed method, called geometry analysis PSO (GAPSO), firstly parameterize the data points of the optimization model of mechatronic system to obtain their parameter values, then one curve or one surface is adopted to fit these points and the tangent value and normal value for each point are acquired, eventually the particles are guided by the use of its derivative value and tangent value to approximate the true Pareto front and get a uniform distribution. Our proposed method is compared with respect to two multi-objective metaheuristics representative of the state-of-the-art in this area. The experiments carried out indicate that GAPSO obtains remarkable results in terms of both accuracy and distribution.
Effect of Operating Parameters on the Removal of Bone Cement by a Sawing Process
Authors: Sheehan Brian M. , Sagar Amrit , James Thomas P.
Published: April 2014

Currently, there are approximately 33,000 total knee arthroplasty revision surgeries each year. This number is expected to increase with the aging population. During revision surgeries, metal implants are often secured to the tibial plateau by creating a mantel of polymethylmethacrylate (bone cement) that must be removed during revision, often times by sagittal sawing. Presently, there are no published studies on the mechanics of bone cement removal by a sawing process. The aim of this research was to quantify the effect of blade speed and applied thrust force on the volumetric cutting rate of bone cement. A custom reciprocating saw with variable stroke length was used to conduct a three factor Design of Experiments. Two levels, without center-points, were sufficient to model the effect of stroke length, thrust force, and reciprocating speed on cutting rate. The results demonstrate a linear relationship between both force and cutting rate, and blade speed and cutting rate. A cutting rate model was developed by regression analysis of the experimental data. The model has applications in haptic feedback for surgical simulators. This study provides a basis for understanding the operational parameters of the bone saw, which is the first step in designing saw blades for cutting bone cement as these designs may differ significantly from those optimized to cut cortical bone.
Technology Outlook and Sustainability of the Synthetic Natural Gas Production Process Derived From Coal
Authors: Ramirez Orlando M. , Corredor Lesme
Published: April 2014

Natural gas is the most environmental friendly fossil fuel with a high energy content and has a promising future within the energy consumption outlook. For this reason, its production from coal is gaining a significant interest, converting the most abundant, stable, and low price fossil fuel to synthetic natural gas (SNG). In this paper a technology outlook and a sustainability assessment of the technical, economical, and environmental factors is developed. It was found that the sustainability of the process depends mainly on the local price of coal and natural gas, as well as, emerging SNG technologies, also known as direct methanation. The conventional methanation process, the indirect methanation, has high capital costs but it is currently the only proven large scale technology. Although the emerging technology has not yet been tested at a commercial scale, it has a better technical performance with an net efficiency increase of more than 10 percent as results of the process stage reduction which should lead to lower capital costs requirements. Regarding the environmental performance, the conventional process produces large amounts of CO2, approximately 1.3 kg CO2 for each kg of coal, that has to be compressed and sequestered to meet the environmental targets.
A Numerical Model to Study the Effect of Temperature on Electrical Conductivity of Polymer-CNT Nanocomposites
Authors: Oskouyi Amirhossein B. , Sundararaj Uttandraman , Mertiny Pierre
Published: April 2014

In this study the effect of the temperature on the electrical conductivity of nanocomposites with carbon nanotube (CNT) fillers was investigated. A three-dimensional continuum Monte Carlo model was developed and employed first to form a CNT percolation network. CNT fillers were randomly generated and dispersed in a cubic representative volume element. Periodic boundary conditions were applied in this model to minimize size effects while decreasing computational cost. CNT fibers that connected electrically to each other through electron hopping were recognized and grouped as clusters. In addition to tunneling resistance, the effect of intrinsic CNT resistivity was considered. A three-dimensional resistor network was subsequently developed to evaluate nanocomposite electrical properties. Modeling employing the finite element method was conducted to evaluate the electrical conductivity of the percolation network. Considering the determining role of tunneling resistance on electrical conductivity of CNT based nanocomposites, as well as results obtained from experimental studies, temperature was expected to play an important role in nanocomposite electrical properties. The effect of temperature on electrical conductivity of CNT nanocomposites was thus investigated through employing the developed Monte Carlo and finite element models. Other aspects, including the electrical behavior of the polymer, tunneling resistivity and the intrinsic resistivity of CNT were considered in this study as well. The comprehensiveness of the developed modeling approach enables an evaluation of results in conjunction with experimental data in future works.