bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study of the Forcing Effect on the Flow and Heat Transfer in a Turbulent Wall Jet
Authors: Issa Johnny , Ortega Alfonso
Published: March 2016

The effect of the exit wall jet flow excitation on the flow and thermal behaviors of the turbulent wall jet is experimentally investigated. Various forcing amplitudes and frequencies are used in the presence and absence of a free stream flow. Forcing the flow showed to have a major impact on the fluid mechanics of the turbulent wall jet which was clearly shown in the velocity fields and the associated time-averaged quantities such as the wall jet spread and the maximum velocity decay. The normal direction at which the local maximum velocity occurs, also known as the wall jet spreading, is shown to move further away from the wall and is increased by more than 20% under some forcing conditions. The local maximum velocity decay with the downstream direction is reduced by more than 2.5% at further downstream locations. At a given location, the increase in the wall jet spreading together with the reduction in the mean velocity results in a decrease in the wall skin friction calculated using the slope of the mean velocity in the viscous sublayer, a behavior consistent with the literature. Due to its importance in enhancing heat transfer phenomena, the effect of the forcing on the streamwise velocity fluctuations is also investigated under the various forcing conditions. The profiles of the fluctuating component of the velocity, u’, are measured at various downstream locations since they are essential in understanding the growth of the disturbances. Forcing the wall jet increased u’ in the inner and outer regions and revealed the two peaks corresponding to the inner and outer shear layers respectively. This phenomenon is attributed to the added disturbance at the jet exit in addition to the disturbance growth with the downstream direction. The introduction of wall jet flow forcing at various amplitudes and frequencies showed a significant effect on the thermal behavior of the wall jet and was more pronounced in the absence of a free stream flow, a fact related to the evolution of the mixing layer with the downstream direction. In the absence of a free stream flow, Nusselt number decreases with increasing forcing amplitude and frequency in the region close to the jet exit. The decay of Nusselt number in the downstream direction showed an inflection point at further downstream locations which leads to a larger Nusselt number value than the one observed in the unforced case. This behavior is related to the enhanced mixing between the wall jet flow and the free stream due to forcing, which results in a reduction in the wall skin friction and consequently a decrease in the heat transfer rate from the wall.
Design, Prototyping and Preliminary Testing of a Ti-Al Gas Turbine Blade
Authors: Capata Roberto , Sciubba Enrico , Menna Luigi , Brotzu Andrea , Felli Ferdinando , Pilone Daniela
Published: March 2016

This work investigates the feasibility of manufacturing a turbine blade made of a Ti-Al intermetallic alloy by means of investment casting. The work is based on a multidisciplinary approach that combines a conventional CFD analysis of the flow field around the statoric and rotoric blades with the results of several metallurgical studies aimed at the optimization of the alloy composition by finding the best compromise among fracture toughness, oxidation resistance at high temperatures and mechanical properties. The combination of the two techniques lead to an iterative procedure (of which only the first two steps are reported in this paper): a conventional blade is first modeled and the corresponding investment cast is produced via a 3D printing technique; a first version of the blade is built; a modified blade shape is then obtained by a refined CFD study; as a last step the final version of the blade is cast. On the basis of standard operational specifications representative of modern gas turbines, a turbine blade was therefore designed, tested by CFD (ANSYS-FLUENT) to ensure proper fluid dynamic performance, and its levels of thermo-mechanical stress under working conditions were calculated via a commercial CAD software (ANSYS). The fully 3D version of the component was subsequently prototyped by means of fused deposition modeling. A full-scale set of blades (blade height approximately 7 cm, blade chord approximately 5 cm) was produced by means of investment casting in an induction furnace. The produced items showed acceptable characteristics in terms of shape and soundness. The blade alloy was analyzed by performing metallographic investigations and some preliminary mechanical tests. At the same time, the geometry was refined by a complete and more complex CFD study, and a slightly modified shape was obtained. Its final testing under operative conditions is left for a later study. The paper describes the spec-to-final product procedure and discusses some critical aspects of this manufacturing process such as the considerable reactivity between the molten metal and the mold material, the resistance of the ceramic shell to the molten metal impact at temperatures as high as 2073 K and the limit mold porosity that may compromise the component surface finish. Furthermore, a detailed account is provided for the CFD results that led to the modification of the original commercial shape: pressure, velocity and temperature fields in the statoric and rotoric channels are described in some detail, and a preliminary performance assessment of the turbine stage is presented and discussed.
Optimal Design of Solenoid Actuated Butterfly Valves Dynamically Coupled in Series
Authors: Naseradinmousavi Peiman
Published: March 2016

In this effort, we present novel nonlinear modeling of two solenoid actuated butterfly valves subject to a sudden contraction and then develop an optimal configuration in the presence of highly coupled nonlinear dynamics. The valves are used in the so-called “Smart Systems” to be employed in a wide range of applications including bioengineering, medicine, and engineering fields. Typically, tens of the actuated valves are instantaneously operating to regulate the amount of flow and also to avoid probable catastrophic disasters which have been observed in the practice. We focus on minimizing the amount of energy used in the system as one of the most critical design criteria to yield an efficient operation. We optimize the actuation subsystems interacting with the highly nonlinear flow loads in order to minimize a lumped amount of energy consumed. The contribution of this work is to include coupled nonlinearities of electromechanical valve systems to optimize the actuation units. Stochastic, heuristic, and gradient based algorithms are utilized in seeking the optimal design of two configurations of solenoid actuated valves. The results indicate that substantial amount of energy can be saved by an intelligent design that helps select parameters carefully but also uses flow torques to augment the closing efforts.
Performance of a Rooftop Wind Turbine System Having a Wind Deflecting Structure, Experimental Results
Authors: Rashidi Majid , Kadambi J. R. , Ebiana Asuquo
Published: March 2016

This work presents the results of an experimental work on a novel design for wind tower system. The system is intended for areas of low wind speeds. The wind tower consists of four rooftop turbines mounted alongside a cylindrical structure that acts as a Wind Deflecting Structure (WDS). This arrangement results in lowering of the cut-in wind speed for the turbine; the system allows the turbine rotors to operate in the areas that have normally low wind speeds, as low as 3 m/s. The nameplate rating of each of the turbines is 1.65. The four-turbine system was installed on the rooftop of a five story building in downtown Cleveland, Ohio. A fifth stand-alone wind turbine was installed on the rooftop of the same building as the reference in order to examine. Orientation of the four wind turbines is controlled by a close-loop active direction control sub-system using a double worm-gear reduction as its actuator. The output of the worm-gear unit has a spur gear pinion that meshes with an external gear that is an integral part of the outer race of the bearing that in turn supports the arm to which the four turbines are attached to. The wind power data from five turbines (four turbines on the tower & one reference turbine) were recorded by PLC’s. The data was updated and recorded every 10 seconds. This means that in every hour there were 360 data points for each of the turbines. For each day the number of data points for each turbine is 24 × 360 = 8640. The other information that is recorded every 1 second includes: the wind direction, wind speed, time, date and an index number. The experimental results show that the power output of the each of the turbines installed on the proposed system may be increased by an average factor of about 4 times compared to the power generated by the stand-alone turbine under the same wind flow condition.
Effect of Spark Ignition Timing on Copper Coated Spark Ignition Engine With Alcohol Blended Gasoline With Catalytic Converter
Authors: Krishna Maddali V. S. Murali , Priyadarsini Ch. Indira , Nagini Y. , Sarada S. Naga , Sri P. Usha , Srikanth D.
Published: March 2016

This paper reports performance evaluation of four–stroke, single–cylinder, water cooled, variable compression ratio (3–9), variable speed (2200–3000 rpm) spark ignition engine with brake power of 2.2 kW at a speed of 3000 rpm with copper coated combustion chamber (CCE) [copper-(thickness, 300 μ) was coated on piston crown, inner side of liner and cylinder head] with alcohol blended gasoline [20% methanol with 80% gasoline; 20% of ethanol with 80% of gasoline by volume) with varied spark ignition timing provided with catalytic converter with sponge iron as catalyst along with air injection and compared with engine with conventional combustion chamber (CE) with gasoline operation. Performance parameters and exhaust emissions (CO and UBHC) were evaluated at full load operation of the engine. Aldehydes (formaldehyde and acetaldehyde) were measured by wet method of 2,4, dinitrophenyle method at full load operation of the engine. Alcohol blended gasoline operation improved performance and reduced CO and UBHC emissions when compared with gasoline operation with both versions of the combustion chamber. At recommended and injection timing, CCE with test fuels improved performance and reduced pollution levels, when compared with CE. Catalytic converter with sponge iron as catalyst along with air injection significantly reduced pollutants with test fuels.
Ontology-Based Adaptive Object Model for Simulation Physical Parameter Management
Authors: Zhang Chengwei , Tian Ling , Wu Yuanhao
Published: March 2016

Simulation is widely used. It requires a great deal of various physical parameters, some of which are existing, some of which demand to be measured or tested. For a simulation parameter management system, the parameters should be queried easily and new type of parameters, rather than new parameters of the existing type, could be added dynamically. This paper presents a plug-and-play system for simulation physical parameter management based on ontology and AOM (Adaptive Object Model). It consists of a three-layer model: meta model layer, domain model and data instance layer. An interpreter engine is built according to the meta model layer. Domain expert, with little programming experience, could make or modify domain model by instantiating the meta model through Protégé. According to the domain model, interpreter engine could generate templates of both excel and database. The former acts as an importer for data, and the latter would be the model of a particular data record, taking advantage of non-predefined-schema NoSQL database. Thus, the system could be adaptive for any domain by modifying the domain model. Separated from the program itself, the domain model exists as an independent configuration file, which means this model could be edited with immediate effect during run-time. By collecting all the data of the same template, a statistic would be calculated. Once a new data is imported, the statistic would evolve with it. Applied in the development of the physical parameter management system for the flexible paper-like object in an ATM manufacturer, the system is demonstrated to be effective.
Comparison of Tidal Current Turbine Designs in Several High Speed Locations Around the United States
Authors: Mayeed Mohammed S. , Newaz Golam M. , Hall Dallin , Elder Davison
Published: March 2016

Tidal current energy is regarded as one of the most promising alternative energy resources for its minimal environmental footprint and high-energy density. The device used to harness tidal current energy is the tidal current turbine, which shares similar working principle with wind turbines. The high load factors resulting from the fluid properties and the predictable resource characteristics make marine currents particularly attractive for power generation. There is a paucity of information regarding various key aspects of system design encountered in this relatively new area of research. Not much work has been done to determine the characteristics of turbines running in water for kinetic energy conversion even though relevant work has been carried out on ship’s propellers, wind turbines and on hydro turbines. None of these three well established areas of technology completely overlap with this new field so that gaps remain in the state of knowledge. A tidal current turbine rated at 1–3 m/s in water can result in four times as much energy per year/m2 of rotor swept area as similarly rated power wind turbine. Areas with high marine current flows commonly occur in narrow straits, between islands, and around. There are many sites worldwide with current velocities around 2.5 m/s, such as near the UK, Italy, the Philippines, and Japan. In the United States, the Florida Current and the Gulf Stream are reasonably swift and continuous currents moving close to shore in areas where there is a demand for power. In this study tidal current turbines are designed for several high tidal current areas around USA for a tidal current speed range from 1 m/s to 2.5 m/s. Several locations around USA are considered, e.g. the Gulf Stream; Mississippi River, St. Clair’s river connecting Lake Huron to Lake St. Clair’s; Colorado River within Cataract Canyon etc. Tidal current turbines can be classified as either horizontal or vertical axis turbines. In this study several designs from both the classifications are considered and modeled using SolidWorks. Hydrodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and ultimate power generation capacity. From flow simulations, forces on the tidal current turbine blades and structures are calculated, and used in subsequent stress analysis using SolidWorks Simulation software to confirm structural integrity. The comparative results from this study will help in the systematic optimization of the tidal current turbine designs at various locations.
Modeling Circular Shear in Shape Memory Polymers With Triple Shape Effect Subjected to Crystallization Under Constant Shear
Authors: Moon Swapnil , Rao I. Joga , Cui Fangda
Published: March 2016

The capacity of a material to sense its environment and to change its shape on demand in a predefined way has tremendous technological significance for a wide variety of application areas. Shape memory polymers (SMPs) belong to this category of smart materials as they have the ability to undergo a shape change in a predetermined manner under the influence of an external stimulus. SMPs can recover their permanent shape after undergoing large deformation to a temporary shape on exposure to external triggers such as light, PH values and heat. Thermally induced SMPs are first generation SMPs and have been widely recognized. Crystallizable SMPs are a class of thermally induced SMPs whose temporary shape is due to formation of crystalline phases, and they will revert back to their permanent shape when the crystallization phase is melted through heating. Traditional crystallizable SMPs can only perform dual-shape memory cycles and this limits applications of crystallizable SMPs. Recently SMPs with triple shape effect have been reported that can switch from a second temporary shape to the first temporary shape and from there to the permanent shape under stimulation by heat. Our research focuses on modeling the mechanical behavior of these SMPs with triple-shape effect. The framework used in developing the model is built upon the theory of multiple natural configurations [3]. In order to model the mechanics associated with these polymers different stages of the shape fixation and recovery cycle and different phases of the material during this cycle need to be characterized. This includes developing a model for the amorphous phase and the subsequent semi-crystalline phases with different stress free states and melting of these phases. The model subsequently has been used to simulate results for a typical deformation cycle involving circular shear.
Plastic Collapse Behaviors of Tubulars With Recess Patterns
Authors: Zhao Haifeng , Iblings David , Barykin Aleksey , Mehdi Mohamed
Published: March 2016

The collapse strength of tubulars with recess patterns machined into their walls is an important topic for oilfield downhole tools as it applies to perforating guns, prepacked sand screens, and perforated and slotted liners.

This paper presents a study of the plastic collapse behavior of thick-walled tubulars (those with an outside diameter to thickness ratio of approximately 10) having different patterns of circular recesses (blind holes partially machined into the tubing wall) that are subjected to external pressure. An empirical relationship between the reduction in collapse strength and the periodic distribution of recesses was constructed to account for the weakening effects of recess diameter, recess depth, axial spacing, angular phasing, etc. This strength reduction factor was introduced into the Tamano formula to predict collapse strength of recessed tubulars. Applicability of this empirical formula was validated with the aid of nonlinear, post-buckling Finite Element Analyses (FEA). The modeling approach was verified by full-scale physical tests. However, results of the physical testing are not presented in this paper.

The strength reduction factor in combination with the Tamano formula provides a simple way of parametrically predicting the collapse strength of tubulars having circular recess patterns.
The New Rail System
Authors: Rowe Dale W.
Published: March 2016

The objective of this study was to define the elements of a rail system capable of achieving a 1000-fold increase in freight throughput, accommodate passenger travel, be capable of a phased implementation, be affordable and have a payback to an adopting railroad of less than seven years.

This paper describes a novel New Rail System, “NRS” that achieves the stated objectives. The NRS utilizes existing rail rights-of-way and tracks. It has the capability to accommodate both freight and passenger movement. In its initial implementation it supports speeds of 85 mph. Although no invention is required, three modifications to the railroad infrastructure are required, (1) elimination of at-grade crossings, (2) electrification, and (3) transition from diesel-electric locomotive powered trains to individual electrical powered pallets to allow flexible routing and sorting in the network.

The four elements defining NRS are; (1) self-powered 70-foot pallets, (2) freight and passenger payload modules (loadable and unloadable from the pallets), (3) pallet yards, accumulators and transfer stations, and (4) a pallet control system.

An initial cost-benefits analysis shows that if BNSF implemented the NRS on its Southern Transcon route between Los Angeles and Chicago a payback of the initial $21.2 billion investment can be achieved in under four-years.
LEFM to Investigate the Impact of Deteriorated Particles in Composite Material
Authors: Ahmed Waleed K. , Al-Rifaie Wail , Al-Douri Y. , Bourchak Mostefa
Published: March 2016

Due to its distinguished properties especially being isotropic, particulate reinforced composite is considered as one of the attractive material for wide range of applications, where the relatively low manufacturing cost is a desirable advantage. In the present analysis, deteriorated particles embedded in particulate reinforced composite have been investigated. The impact of the fractured particles is studied through the principles of fracture mechanics using finite element method. Mainly the stiffness variation of the composite due to the presence of the fractured particles is mainly predicted, since it is considered as an important factor especially from the view point of the damage-tolerant design of composite structures. A representative volume element (RVE) has been selected to represent the particulate composite with different particle volume fractions. It is important to point out that based on a previous investigation and comparison between two and three dimensional finite element analysis for a particulate reinforced composite, two-dimensional, plane strain finite element analysis is used to estimate the stresses and deformation that taken place. Uniaxial tensile stress perpendicular to the crack face of the fractured particle has been applied to the representative volume element. Due to symmetry of the studied geometries, quarter of the representative volume element is modeled via finite element method with a consistent mesh as possible to maintain reliable results. Linear elastic fracture mechanics (LEFM) is adopted through estimating stress intensity factor (SIF) of the cracked particles. Basically, the investigation covers the assessment of fractured particles with different crack lengths, where the particle’s stiffness is considered as a substantial parameter in the analysis in combination with others. Moreover, various particles volume fractions are taken into account to figure out their influence on the effective Young’s modulus of the representative volume element chosen for the studied cases. Multiple point constraints (MPC) technique is adopted in the finite element model to calculate the effective stiffness of the fractured particle. In general, it has been shown that there is a considerable influence of the deteriorated particles on increasing stress intensity factor levels at the crack tip as long as the crack length increases with respect to the particle size, and this basically depends on the stiffness ratio of the matrix/particle considered in the analysis. In the other hand, it has been noticed that a significant reduction in the effective stiffness of the particulate composite which is calculated based on the modeled representative volume element as a function of the crack length.
Thermal Performance of a Receiver Tube for a High Concentration Ratio Parabolic Trough System and Potential for Improved Performance With Syltherm800-CuO Nanofluid
Authors: Mwesigye Aggrey , Huan Zhongjie , Meyer Josua P.
Published: March 2016

In this paper, the thermal performance of a high concentration ratio parabolic trough system and the potential for improved thermal performance using Syltherm800-CuO nanofluid were investigated and presented. The parabolic trough system considered in this study has a concentration ratio of 113 compared with 82 in current commercial systems. The heat transfer fluid temperature was varied between 350 K and 650 K and volume fractions of nanoparticle were in the range 1–6%. Monte-Carlo ray tracing was used to obtain the actual heat flux on the receiver’s absorber tube. The obtained heat flux profiles were subsequently coupled with a computational fluid dynamics tool to investigate the thermal performance of the receiver. From the study, the results show that with increased concentration ratios, receiver thermal performance degrades, with both the receiver heat loss and the absorber tube circumferential temperature differences increasing, especially at low flow rates. The results further show that the use of nanofluids significantly improves receiver thermal performance. The heat transfer performance increases up to 38% while the thermal efficiency increases up to 15%. Significant improvements in receiver thermal efficiency exist at high inlet temperatures and low flow rates.
Computational Investigation of High Velocity Penetration of Copper Subjected to Impact From Nickel Projectiles
Authors: Liu Yucheng , Dou Yangqing , Hammi Youssef
Published: March 2016

A computational simulation of penetration between nickel projectile and copper plate with high velocity in macro scale has been built. It is the first time a comprehensive investigation of penetration between these two materials. A threshold velocity between a nickel projectile and a copper plate is determined by mathematical equation in this paper. ABAQUS/Explicit is used to verify this threshold velocity by setting different velocities under the same condition and displaying visual animation of penetration results. John-cook model has been chosen to represent two material plastic behaviors. The shapes of penetrator and target are shown in order to expose penetration procedure and phenomena. Stress patterns and perforation features are adopted to make a good understanding of Ni-Cu penetration mechanism from computational study.
System Reliability Analysis With Dependent Component Failures During Early Design Stage
Authors: Cheng Yao , Du Xiaoping
Published: March 2016

It is desirable to predict product reliability accurately in the early design stage, but the lack of information usually leads to the use of independent component failure assumption. This assumption makes the system reliability prediction much easier, but may produce large errors since component failures are usually dependent after the components are put into use within a mechanical system. The bound of the system reliability can be estimated, but is usually wide. This wide reliability bound makes it difficult to make decisions, such as evaluating and selecting design concepts, during the early design stage. This work develops a new methodology that makes the system reliability prediction more accurate by considering the dependence between component failures. The following situation is addressed: the reliability of each component and the distribution of its load are known, but the dependence between component failures is unknown. With a physics-based approach, an optimization model is established so that a narrow bound of the system reliability can be generated. Two examples demonstrate that the proposed methodology produces a narrower system reliability bound than the traditional reliability bound, thereby better assisting decision making during the early design stage.
Robust and Resilient Control for Time-Delay Wind Energy Conversion System
Authors: Alden Mohammed Jamal , Wang Xin
Published: March 2016

Wind energy is the fastest growing and most promising renewable energy resource. A robust and resilient delay independent control framework with a H∞ performance objective for a time delayed variable speed permanent magnet synchronous generator based wind energy conversion system is proposed. Based on the nonlinear dynamics, a third order linearized model for the wind energy conversion system is developed. It is assumed that the system has unstructured bounded uncertainties and it is exposed to bounded L2 type of disturbances. Moreover, fixed time delays are assumed to be existed in the input and state feedback signals. Linear matrix inequalities are utilized to convert the problem of controller existence into a convex optimization problem. Computer simulations conducted in Matlab verified the effectiveness of the proposed control in achieving asymptotic stability and meet the H∞ performance objective requirements.
Processing/Structure/Properties Relationships in Polymer Blends for the Development of Functional Polymer Foams
Authors: Rizvi Ali , Park Chul B.
Published: March 2016

In this study we present a comprehensive experimental investigation of the effect of polymer blending on the dispersed phase morphology and how the dispersed phase morphology influences the foaming behavior of the semicrystalline polymer matrix using three different material combinations: polyethylene (PE)/polypropylene (PP), PP/polyethylene terephthalate (PET) and PP/polytetrafluoroethylene (PTFE). Samples are prepared such that the dispersed phase domains exhibit either spherical or fibrillated morphologies. Measurements of the uniaxial extensional viscosity, linear viscoelastic properties and crystallization kinetics under ambient pressures and elevated pressures of carbon dioxide (CO2) are performed and the morphological features are identified with the aid of SEM. Batch foaming and lab-scale extrusion foaming experiments are performed, as a screening model for polymer processing, to show the enhancement of the foaming ability as a result of the blend morphology, taking into account the rheological behaviour and the effects of crystallization kinetics. The formation of high aspect ratio fibrils imparts unique characteristics to the semicrystalline matrix such as strain-hardening in uniaxial extensional flow, prolonged relaxation times, pronounced elastic properties and enhanced kinetics of crystallization. In contrast, the regular blends containing spherical dispersed phase domains do not exhibit such properties. Foam processing of the three blends reveals a marked broadening of the foaming window when the dispersed phase domains are fibrillated due to the concurrent increase in crystallization kinetics, improved elastic properties and strain hardening in extensional flow.
A New Method to Model Spherical Roller Bearings due to Self-Aligning Feature
Authors: Xing Yu , Xu Hua , Pei Shiyuan , Liu Xuejing , Wang Fengcai
Published: March 2016

This research presents an analytical model to describe the indeterminate contact status and analyze the loaded condition, then acquire the key design parameters so as to improve the carrying capacity of spherical roller bearings. The model based on the non-Hertzian contact theory is applied to reflect the indeterminate contact status due to the self-aligning feature. The loaded condition, which is including the load distribution, the size of the contact region and the maximum contact pressure, is calculated according to the force analysis of spherical roller bearings. The non-linear equations are solved by using secant method and the proposed model is validated by comparing with the published reference. The importance of the indeterminate contact status is illustrated by comparing with the computing results of the Hertzian contact model. The fitted method based on the least square method is used to obtain the equivalent stiffness and the load-deformation exponent, whereby the computing procedure is simplified. In view of the operating condition and the lubricated effect, properly increasing the osculation number or the number of the rollers will obviously improve the carrying ability of spherical roller bearings.
Design Considerations for Optimized Lateral Spring Structures for Wearable Electronics
Authors: Hussain Aftab M. , Hussain Muhammad M.
Published: March 2016

The market for wearable electronics has been gaining momentum in the recent years. For completely electronic wearable textiles with integrated sensors, actuators, computing units and communication circuitry, it is important that there is significant stretchability. This stretchability can be obtained by introducing periodic stretchable structures between the electronic circuits. In this work, we derive the equations and constraints governing the stretchability in horseshoe lateral spring structures. We have derived the optimum design and the parameters therein, to help develop the best spring structures for a given stretchability. We have also developed a figure of merit, called area efficiency of stretchability, to compare all two-dimensional stretchable systems. Finally, we experimentally verify the validity of our equations by fabricating a metal/polymer bilayer thin film based stretchable horseshoe lateral spring structures. We obtain a stretchability of 1.875 which is comparable to the theoretical maxima of 2.01 for the given parameters.
Effect of Loading Condition on Stress Intensity Factor for Threaded Fasteners Under Helix Angle Condition
Authors: Kumar Sundaram Suresh , Prakash Raghu V.
Published: March 2016

The effect of loading condition on the stress intensity factor (SIF) solution for a metric threaded bolt with helix angle consideration is investigated. Available SIF solutions for a nut loaded bolt do not consider the effect of helix angle of thread. Various loading conditions such as: (i) far field loading, (ii) thread face loading without helix angle, (iii) thread face loading with helix angle and (iv) nut loading with helix angle are considered in the present study. 3-D contact analysis is carried out to observe the stress distribution between the bolt and nut interface. A crack was introduced at the first thread of the bolt so that the crack faces experience opening mode of fracture under nut loading condition. The SIF estimated by each loading condition was compared with the SIF values computed taking into consideration the nut loading with helix angle. SIF solutions obtained under far field loading condition are lower than those obtained under other loading conditions at short crack depths (a/d = 0.1); at deep crack depths (a/d = 0.5), SIF obtained under nut loading condition are lower than those obtained under other loading conditions. At deep crack depths (a/d = 0.5) the effect of loading condition on SIF is more pronounced for an elliptic crack (a/c = 0.2) than semi circular crack (a/c = 1). Due to the combined effect of mode II and mode III fracture which is caused by helix angle, non symmetric distribution of SIF was observed along the crack front. It is noted that, crack growth rate derived from SIF under nut loading condition is lower than published data at the middle region (P/P0 = 0).
CFD Analysis of a Fluidized Bed Combustor Based on Co-Firing
Authors: Kumar Hemant , Mohapatra S. K. , Singh Ravi Inder
Published: March 2016

In this paper computational analysis of a real plant Bubbling Fluidized Bed (BFB) combustor has been done, using FLUENT 6.3, CFD code. Keeping in mind the biomass potential in the agricultural state like Punjab, India, various corporate sectors initiated the use of these renewable energy sources such as rice husk, paddy rejects and sugarcane baggase etc. in sharing with conventional fuels such as coal. The study has been done at Captive Power Plant (CPP) of Ambuja Cement Limited, Ropar, Punjab, India. The boiler, with 45TPH capacity, based on Fluidized Bed Combustion (FBC) system uses coal and biomass (70% coal and 30% biomass) as fuels.

Standard k–ε two-phase turbulence model has been used to describe the gas–solids flow in the BFB. The analysis of combustion is done by Non-Pre Mixed (NPM) approach in species model. In this paper temperature contours inside the furnace and mass fractions of O2 and CO2 have been obtained by CFD tool. Temperature in the vicinity of the bed was found up to 927 °C and at the exit of the furnace was found around 867 °C. The O2 concentration was found higher over the bed however the CO2 concentration was found more near biomass flame due to instantaneous combustion.
Effect of Fiber Waviness and Cluster on Effective Elastic Properties of Fiber-Reinforced Composites
Authors: Huang Bincheng , Sun Lingyu , Wang Ligang , Li Tongguang
Published: March 2016

Carbon fiber-reinforced polymers (CFRPs) are widely applied in lightweight automotive design due to their high specific stiffness and strength. However, it is difficult to achieve an ideal performance due to defects from manufacturing process. For example, fiber waviness and cluster are two typical manufacture defects in the process of Liquid Composite Molding (LCM). The effective elastic modulus of CFRPs with fiber waviness is studied by finite element method, and the stress-transfer mechanisms between the fibers and matrix is explained theoretically, the modified bridging model, which correlates the stress state in fibers with that in matrix. Additionally, the influence of fiber cluster on the effective elastic modulus of CFRPs is also investigated by finite element method. When the volume fraction of fibers in matrix is higher than 20%, the fiber waviness will decrease the longitudinal modulus E11 greatly, but also increase the transverse modulus E22 slightly. For CFRPs with cured fibers, the proposed modified bridging model has higher prediction accuracy than the rule of mixture. When the cluster degree is less than 1%, the effective elastic modulus of CFRPs with fibers distributed randomly will not be influenced obviously. For straight fibers, the reinforcement effect on elastic modulus E11 and shear modulus G12 decreases slightly with increasing cluster degree.
Measurement of Leadframe Strain in Electrically Active Power Semiconductors
Authors: Avery Seth M. , Lorenz Robert D.
Published: March 2016

In this work, thermal-mechanical leadframe strain in an electrically active IGBT was measured using electronic speckle pattern interferometry (ESPI). ESPI is a non-contact optical technique capable of high resolution surface displacement measurements. The significant contribution of this paper is an experimental methodology by which strain can be measured in electrically active devices. A 3-D ESPI test stand was developed, combining two cameras to simultaneously capture the local (interconnect level) and global (device level) displacements. Through the combination of incremental sub-loads and mathematical recorrelation of speckle patterns, device power loads have been measured (which would have been otherwise impossible due to speckle decorrelation, which limits measurement of large deformations). A model-based tracking technique was developed from coupled experimental noise measurements and FE modeling — allowing for optimal strain solution to be extracted from noisy displacement results. The developed and experimentally-validated thermal-mechanical FE strain model agreed to within 7% of ESPI strain measurements.
Effective Damping of a Flexible-Matrix-Composite Laminate With a Negative Effective Poisson’s Ratio
Authors: Kumar N. , Varela B. , Ghoneim H.
Published: March 2016

Two very important factors which determine the effectiveness of a pump are its volumetric and energy efficiencies. Yin and Ghoneim constructed a prototype of a flexible body pump with a very high volumetric efficiency or pumping potential (the relative volume reduction due to a relative input stroke) [1]. The high volumetric efficiency is attributed to the geometry of the pump’s structure (hyperboloid) as well as the high negative effective Poisson’s ratio of the 3-layer ([θ/β/θ]) flexible-matrix-composite (carbon/polyurethane) laminate adopted for the body of the pump. The energy efficiency was not evaluated. An important factor in assessing the energy efficiency of flexible-body pumps is the effective damping (a measure of the energy dissipation per cycle) of the flexible body material. An objective of the current work is to determine the effective damping inherent in the 3-layer laminate, as a function of the two angle orientations θ and β, employed for the design of the flexible body pump. Thereby, the best fiber angle orientation, for the highest volumetric as well as energy efficiency, can be considered. The contribution of this work is twofold: 1) viscoelastic characterization (longitudinal, transverse, and shear complex moduli, as well as the in-plane complex Poisson’s ratio) of the polyurethane/carbon composite, used in the Geo-polymer lab at RIT; the results may be utilized as benchmarks for other researchers using similar carbon/polyurethane in dynamic applications, and 2) provide a comprehensive study of the effect of the two angles θ and β on the effective damping factors of the three-layer laminate. Together with the similar study on the negative Poisson’s ratio [1], a better design of the laminate for the most efficient flexible-body pump performance can be established.
A Novel Magnetorheological Concentric Spiral-Flow Damper
Authors: Chang Kai Hsiang , Tong Jing Long , Chia Chou Min , Huang Kuang Yuh
Published: March 2016

In this article, a novel design of MR damper, concentric spiral flow MR damper, is proposed. It could improve the heat dissipation problem which is usually found in traditional MR damper. The proposed MR damper has a concentric spiral flow channel around the cylinder which not only separates coils from MR fluid, but also increases the length of flow channel in a fixed space.

Experimental studies has been conducted to demonstrate the performance of the proposed MR damper, the result shows the MR damper generates the maximum damping force of 188 N without applying magnetic field and 1251 N when inputting 1.5 A at low frequency, which means the damper has high range of adjustable damping force. The CSF-damper can be used to systems or structures with low dynamic response.
Thermodynamic Performance Analysis of a New CHP System With Absorption Heat Pump in a Direct Air Cooling Power Plant
Authors: Zhang Hongsheng , Zhao Hongbin , Li Zhenlin
Published: March 2016

A new waste heat recovery scheme based on absorption heat pumps (AHP) applied in CHP (Combined Heat and Power) system was proposed to decrease heating energy consumption of existing CHP systems by recovering waste heat of exhausted steam from a steam turbine of coal-fired direct air cooling units. Based on the establishment of thermodynamic analysis model, through adopting the design parameters of the 135 MW direct air-cooled power plants in China, the performances, especially the exergy losses of the unit as well as its subsystems mainly including six parts at different heating modes were obtained at one specific load. Compared with conventional heating mode, when the thermoelectric ratio is 100%, the power output increases around 3.81 MW, coal consumption rate decreases 11.69 g/(kW·h) and total exergy loss decreases 6.892 MW under 100% THA load, while the energy and exergy efficiencies of the integrated system increase 1.29 % and 1.25 %, respectively. Additionally, the change laws of total exergy loss, energy and exergy efficiency of integrated system at different loads also were studied. The results provide not only theory basis and scientific support for the design of the coal-fired power plants with absorption heat pump recovering waste heat, but also a new scheme of energy saving and optimization for the units.
Effect of Condition Monitoring on Risk Mitigation for Steam Turbines in the Forest Products Industry
Authors: Zhou Bin , Bhimavarapu Kumar
Published: March 2016

Industry has been implementing condition monitoring for turbines to minimize losses and to improve productivity. Deficient conditions can be identified before losses occur by monitoring the equipment parameters. For any loss scenario, the effectiveness of monitoring depends on the stage of the loss scenario when the deficient condition is detected. A scenario-based semi-empirical methodology was developed to assess various types of condition monitoring techniques, by considering their effect on the risk associated with mechanical breakdown of steam turbines in the forest products (FP) industry. A list of typical turbine loss scenarios was first generated by reviewing loss data and leveraging expert domain knowledge. Subsequently, condition monitoring techniques that can mitigate the risk associated with each loss scenario were identified. For each loss scenario, an event tree analysis was used to quantitatively assess the variations in the outcomes due to condition monitoring, and resultant changes in the risk associated with turbine mechanical breakdown. An application was developed following the methodology to evaluate the effect of condition monitoring on turbine risk mitigation.
A Model of Neuropeptide Transport in Various Types of Nerve Terminals Containing En Passant Boutons: The Effect of the Rate of Neuropeptide Production in the Neuron Soma
Authors: Kuznetsov I. A. , Kuznetsov A. V.
Published: March 2016

After being synthesized in the soma, neuropeptides are packaged in dense core vesicles (DCVs) and transported toward nerve terminals. It is known, from published experimental results, that in terminals with type Ib boutons DCVs circulate in the terminal, undergoing repeated anterograde and retrograde transport, while in type III terminals DCVs do not circulate in the terminal. Our goal here is to investigate whether the increased DCV production in the soma can lead to the appearance of DCV circulation in type III boutons. For this purpose we developed a mathematical model that simulates DCV transport in various terminals. Our model reproduces some important experimental results, such as those concerning DCV circulation in type Ib and type III terminals. We used the developed model to make testable predictions. The model predicts that an increased DCV production rate in the soma leads to increased DCV circulation in type Ib boutons and to the appearance of DCV circulation in type III boutons. The model also predicts that there are different stages in the development of DCV circulation in the terminals after they were depleted of DCVs due to neuropeptide release.
Hysteresis Switching LPV Control of a Wind Turbine System Covering Partial and Full Load Conditions
Authors: Xue Xiangming , Bu Yiming , Lu Bei
Published: March 2016

For variable-speed wind energy conversion systems, control objectives may be different in partial and full load regions (or in low and high wind speed regions). Typical control objectives are to maximize the energy capture at low wind speeds, and to maintain the generated power and the rotational turbine speed within safety limits at high wind speeds. In such a case, it is difficult to design a single robust controller covering both partial load and full load conditions. This paper presents a systematic switching control method for a variable-speed variable-pitch wind turbine over a wide wind speed region. The whole framework is based on the linear parameter-varying (LPV) control theory, which is an extension of robust control for linear systems to nonlinear ones. Two LPV controllers are designed, each suitable in a different wind speed region. A hysteresis switching logic is applied to guarantee the stability when the switching event occurs between the two controllers. Nonlinear simulations are conducted to demonstrate the proposed control scheme.