bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Extreme-Value Probabilistic Framework for Predicting Fatigue Crack Initiation Life of Notched Components
Authors: Owolabi Gbadebo , Whitworth Horace
Published: August 2012

Traditional deterministic methods for predicting the fatigue life of notched components require a number of approximations based on heuristics and phenomenological data rather than solid theoretical underpinning and still yield unsatisfactory and inconsistent results when applied to complex components under service loads. Microstructural inhomogeneities in the materials are still an important issue, but are not explicitly accounted for in the traditional deterministic methods. Recent developments in computational crystal plasticity and microstructure-scale modeling have provided deeper understanding of the complex correlations between properties and structures and further indicate the limitations of conventional fatigue life prediction approaches. These modeling approaches have the potential to substantially reduce the need for costly large scale experimental programs to determine scatter in fatigue, for example. At present, however, there is a lack of simulation-based strategy for considering interactive effects of stress/strain field gradients at the notch-root and microstructure-scale behavior in predicting notch-root fatigue crack initiation. In this paper, the distribution of a shear-based fatigue indicator parameter computed within a well-defined fatigue damage process zone at the notch are used along with a novel probabilistic mesomechanics approach to obtain the probability distribution of fatigue crack initiation of notched components, thus extending fatigue life prediction to explicitly incorporate microstructure sensitivity via probabilistic arguments. The new probabilistic framework presented in this paper takes into account the complete plastic shear strain field around the notch root and also links the variation in the materials microstructure and associated slip activations to observable scatter in fatigue strength of the notched component. The use of such probabilistic approach can be beneficial as it avoids conservatism that may result from the use of deterministic approach for fatigue life prediction.
Research and Practice on the In-Situ Calibration System for Flowrate of Pump-Test-Rig
Authors: Cheng Li , Che Xiaohong , Luo Can , Yan Bipeng
Published: August 2012

In order to assure the accuracy of pump test rig and stability of measurement, it would be equipped with flow meter of high precision and calibration system. A volume-weight method for in-situ calibration is brought out to achieve bidirectional calibration. The two way calibration can be done on the pump test rig. According to the design objective, the pump, weight tank, pool, commutator and standard measuring cylinder were calculated and selected. Based on measurement uncertainty method, the system uncertainty consisted of uncertainty of standard measuring cylinder, calculagraph, commutator and calibration sensor of volume method. The calculation formulas of these uncertainties are presented. The total expanded uncertainty of system is 0.136% and the stability of flowrate is 0.0212%. Results from calculation and pressure pulse experiment indicate that the combination of the convert-frequency facility with invariableness’ pool can maintain the pressure stability of test. The volume-weight calibration method, which combined with the weight method and volume method, can assure the accuracy and also reduce the expensive. It could be applied in similar test rigs.
Numerical Simulation of Relationship Between Flow Pattern and Hydraulic Performance of Tubular Pump
Authors: Cheng Li , Luo Can , Liu Chao
Published: August 2012

The bulb tubular pump had advantages of large capacity and low head. This type of pump has been widely used for water transportation project or irrigation and drainage. Nowadays China East Routine of South-to-North Water Transfers Project partly uses bulb tubular pumping station. In order to study the relationship between the flow pattern and hydraulic performance of bulb tubular pump system, the SIMPLEC algorithm, based on the RNG k-ε model with Wall-Function Law, is applied for the solution of the discretization governing equation. Using multiple reference frames, the flow detail of whole pumping system was attained. The calculation results were agreement with the test ones. The flow patterns of different operating point were analyzed. There were large eddy areas in the inlet of blades when pump systems were operated in small flowrates. The flow patterns of BEP (Best Efficiency Point) and large flowrate were good. The static pressure of suction face of leading edge was low and the static pressure of pressure face of leading edge was highest during BEP and small flowrate point. There were part low static pressure areas of leading edge of pressure surface and part high static pressure area of leading edge of suction surface during large flowrate point. The relationship between hydraulic loss of bulb of tubular pump and flowrate depended on the operating points and did not follow the quadratic law of traditional pipe. The optimal design of turbular pump should be mainly focused on the flow pattern of blades and guided vanes.
Enhanced Selective Non-Catalytic Reduction (SNCR) for Refinery Applications: Pilot-Scale Test Data With a Hydrogen Promoter
Authors: Swanson Larry , Zhou Wei , Moyeda David , Samuelson Christopher
Published: August 2012

Selective non-catalytic reduction technology (SNCR) is an effective and economical method of reducing NOX emissions for a wide range of industrial combustion systems. It is widely known that the traditional SNCR temperature window is centered around 1,200 to 1,255 K [1]. However, for some applications, the flue gas temperatures in boilers, oxidizers, and heaters range from 950 to 1150 K. At these lower temperatures, injection of an amine reagent into flue gas no longer actively reduces NOX, but instead passes through the system and exits as ammonia slip. Earlier studies have shown that at lower temperatures, hydrogen and other promoters can be added to the system to shift the SNCR window to a lower temperature range, enhancing or promoting SNCR NOX reduction performance [2–5]. This extended abstract describes pilot-scale test results for an enhanced SNCR process (ESNCR) that uses hydrogen as the SNCR promoter. The impacts of flue gas temperature, hydrogen concentration, CO concentration, and SO2 concentration on ESNCR NOX reduction performance are presented.
Simulation of 3D Multistage Axial Compressor Using a Fully Conservative Sliding Boundary Condition
Authors: Im Hongsik , Chen Xiangying , Zha Gecheng
Published: August 2012

Multistage 3D steady and unsteady viscous computations are conducted for a transonic axial compressor with an IGV, rotor and stator blade row. A fully conservative sliding technique is developed with high order shock capturing schemes to better capture the interaction between stationary and rotating blade row. A 1/7th annulus is used for the unsteady simulation with a phase lag BC. For comparison purpose, a steady simulation of the same multistage compressor with single blade passage is performed using the mixing plane approach. It is shown that the sliding BC captures wake propagation very well in the interaction between blade rows. The unsteady multistage simulation using sliding BC and phase lag BC predicts almost identical loading distribution to the steady state simulation at the mid-span, but have significant loading distribution difference at tip section.
Design Optimization of Turbo-Machinery Components With Independent FEA and CFD Tools in an Optimization Software Environment: A Mid-Span Shroud Ring Study Case
Authors: Wu Yuan-Ting , Funk Christian K. , Hsu Pei-feng , Le Moine Jerome , Zhou Ran , Subramanian C. S. , Campbell Christian X. , Marra John J.
Published: August 2012

Shrouds are important for damping vibrations in gas turbine blades. In modern industrial high-output, high-efficiency engines, long turbine blades can require the use of a mid-span or partial-span damping ring. However, the inclusion of a mid-span damping shroud, or “snubber,” can have negative effects on the aerodynamic performance of the gas turbine stage and engine. Therefore, a method of iterative study and optimization was applied to minimize the drag force caused by the snubber, while maximizing the structural life of the blade. The approach used integrated design environment software to perform parametric studies of the design space in preparation for optimization of the blade snubber geometry. The drivers employed in Isight 4.0/4.5 [9] optimization software carried out the parametric study and reported the results to the designer. Considering these results, the designer chose the initial seeding geometry of the optimization driver which greatly reduced analysis time and the time required to reach the design objectives. This approach provides an integrated design workflow and facilitates parametric studies of advanced gas turbine blade component geometry, and the optimization of the component to meet targets of minimized aerodynamic drag force and maximized low-cycle fatigue life, goals crucial to the development of an advanced and efficient power generation gas turbine.
Spherical Wave Propagations of Multiple Energy Sources in Fluid-Saturated Elastic Porous Media
Authors: Han Lu , Dai Liming
Published: August 2012

This research focuses on quantitative analysis of elastic space waves propagating porous media saturated with fluid. Compressive wave propagations are described in three dimensional (3-D) spherical coordinates in terms of displacements of the fluid and solid of the porous media. The wave superposition properties under multiple energy resources are investigated. Relative displacements between the fluid and solid of a porous medium in 3-D domain are quantified with consideration of the wave propagations excited by multiple point energy sources. Numerical analyses are performed and practically sound results are obtained.
Numerical Simulation for Mechanical Behavior of U10Mo Monolithic Miniplates for Research and Test Reactors
Authors: Ozaltun Hakan , Shen Herman , Medvedev Pavel
Published: August 2012

This article presents assessment of the mechanical behavior of U-10wt% Mo (U10Mo) alloy based monolithic fuel plates subject to irradiation. Monolithic, plate-type fuel is a new fuel form being developed for research and test reactors to achieve higher uranium densities within the reactor core to allow the use of low-enriched uranium fuel in high-performance reactors. Identification of the stress/strain characteristics is important for understanding the in-reactor performance of these plate-type fuels. For this work, three distinct cases were considered: (1) fabrication induced residual stresses (2) thermal cycling of fabricated plates; and finally (3) transient mechanical behavior under actual operating conditions. Because the temperatures approach the melting temperature of the cladding during the fabrication and thermal cycling, high temperature material properties were incorporated to improve the accuracy. Once residual stress fields due to fabrication process were identified, solution was used as initial state for the subsequent simulations. For thermal cycling simulation, elasto-plastic material model with thermal creep was constructed and residual stresses caused by the fabrication process were included. For in-service simulation, coupled fluid-thermal-structural interaction was considered. First, temperature field on the plates was calculated and this field was used to compute the thermal stresses. For time dependent mechanical behavior, thermal creep of cladding, volumetric swelling and fission induced creep of the fuel foil were considered. The analysis showed that the stresses evolve very rapidly in the reactor. While swelling of the foil increases the stress of the foil, irradiation induced creep causes stress relaxation.
Identification of the Best Possible Configuration of the Shoulder Strap of a Three-Point Restraint for Motor Coach Occupant Rollover Protection
Authors: Thorbole Chandrashekhar K. , Renfroe David A. , Lankarani Hamid M.
Published: August 2012

The motor coach is an essential element of the mass transportation system in the United States and all around the globe. Rollover accidents associated with any motor coach without an adequate occupant protection system may result in serious or fatal occupant injuries. The seat belt is an essential safety device in protecting an occupant in a rollover accident. It has been observed that just a quarter roll of a bus results in fatal injuries to an unbelted occupant. This severe nature of occupant injury in a less severe bus roll is attributable to the large flying distance within the unpadded interior and the impact with other fellow occupants. In this situation the presence of a seat belt is mandatory to protect the occupants from serious injuries by preventing their ejection from their seats. The three-point restraint is the best possible solution for the motor coach seat belt requirement. The understanding of shoulder strap placement with respect to the occupant is important information. This information facilitates the best possible seat belt configuration for all occupants which will minimize the slippage of the shoulder strap during a rollover accident. The slipping of the shoulder strap is a function of rollover type, rollover direction, roll rate and the occupant location in a vehicle with respect to roll direction. A Finite Element bus model is used to conduct a trip rollover simulation at two different trip velocities. The motion file, as obtained from this simulation, is used to prescribe motion to a MADYMO facet bus model. The standard Hybrid III 50th percentile ATD (Anthropomorphic Test Device) is used to model all the belted occupants. The FE belt model is used to facilitate the simulation of slippage on the shoulder. This study demonstrates the best possible configuration of the three-point restraints for motor coach occupants in a rollover accident using the computational technique. Knowledge of this kind will help the industry to identify and implement seat belts with the best configuration for occupant rollover protection.
Specimen Thickness and Impactor Mass Effects on Drop-Weight Impact Studies of GLARE 5 Fiber-Metal Laminates
Authors: Yaghoubi A. Seyed , Liaw B.
Published: August 2012

Impact responses and damage induced by a drop-weight instrument on GLARE 5 fiber-metal laminates (FMLs) with different thicknesses were studied. The effect of impactor mass was also considered. The damage characteristics were evaluated using both nondestructive ultrasonic and mechanical sectioning techniques. The ultrasonic C-scan technique could only assess the contour of entire damage area whereas more details of damage were obtained using the mechanical cross-sectioning technique. As expected, thicker GLARE 5 FMLs offered higher impact resistance. When subjected to the same impact energy, the entire damage contour enlarged as the specimen became thicker. Under the same impact condition, by reducing the impactor mass, the contact force escalated while the contact stiffness increased. Experimental results showed that the threshold cracking energy varied parabolically with respect to the impact velocity, metal volume fraction (MVF) and the specimen thickness. By increasing the metal volume fraction of the panels, the threshold cracking energy decreased parabolically. On the other hand, for the same MVF value, the cracking energy increased as the impactor mass increased. By increasing the panel thickness, the threshold cracking energy condition increased parabolically; whereas under the same impact velocity, the threshold cracking energy increased by increasing the impactor mass.
Determination of Ballistic Limits of GLARE 5 Fiber-Metal Laminates: The Influences of Geometry, Thickness and Stacking Sequence
Authors: Yaghoubi A. Seyed , Liaw B.
Published: August 2012

In this paper, GLARE 5 fiber-metal laminates (FMLs) of two different geometries: 152.4mm×101.6mm (6″×4″) plate and 254mm×25.4mm (10″×1″) beam and with various thicknesses and stacking sequences were impacted by a 0.22 caliber bullet-shaped projectile using a high-speed gas gun. Velocities of the projectile along the ballistic trajectory were measured at different locations. For both geometries, the incident projectile impact velocity versus the residual velocity was plotted and numerically fitted according to the classical Lambert–Jonas equation for the determination of ballistic limit velocity, V50. The results showed that V50 varied in a parabolic trend with respect to the metal volume fraction (MVF) and the specimen thickness for both geometries. It was found that by changing the geometry from a plate to a beam, the ballistic limit velocity increased. On the other hand, changing the stacking sequence had a less pronounced effect on V50 for both geometries. The quasi-isotropic beam and plate specimens offered relatively higher ballistic limit velocities compared to other types of stacking sequences in their own geometrical groups. Furthermore, the cross-ply and unidirectional beam specimens showed relatively higher V50 compared to their plate counterparts. Experimental results showed that the ballistic limit was almost the same for the quasi-isotropic layup FMLs of both plate and beam geometries.
Preliminary Analysis of the Application of Composite Material in Marine Current Turbine
Authors: Wang Jifeng , Liu Yan , Yu Yanqiu , Mu¨ller Norbert
Published: August 2012

Advanced composite materials are broadly used because of their high strength to weight ratios and high corrosion resistance. A wound composite material wheel has been developed and is intended to be used for many purposes. One of these applications is marine current turbine. A major problem influencing the design and operation of water turbines is fatigue. Another challenge that water turbines have to face is that the turbines must be able to withstand large forces due to the increase in flow velocity. Considering these factors, implementation of composite materials in water turbine is explained in this paper. This novel design pattern of composite material marine current turbine shows many advantages compared to traditional turbines. This paper presents the preliminary analysis of the application of composite material in marine current turbine.
Diffuser-Augmented Composite Material Wind Turbine Design Using CFD
Authors: Wang Jifeng , Piechna Janusz , Gower Blake , Mu¨ller Norbert
Published: August 2012

A novel manufacturing approach similar to filament winding is able to produce high-performance and light-weight composite wheels in a rapid, inexpensive way by utilizing commercially available winding machines. In this study, a numerical investigation of a diffuser-augmented composite wind turbine is evaluated with a conventional bare wind turbine by using FLUENT in conjunction with the GAMBIT meshing tool. The extracted torque and power are calculated and compared for these two modeling designs. The simulation results show that the extracted power of a diffuser-augmented turbine can be 5 times the power extracted by a bare turbine of the same turbine area. This analysis procedure provides an insight into the hydrodynamic design and operation of a diffuser-augmented wind turbine in order to shorten the design period and improve technical performance.
Size Effects During Femtosecond Laser Interaction With Nanosized Metal Particles
Authors: Huang Jing , Zhang Yuwen , Chen J. K.
Published: August 2012

To obtain more in-depth knowledge about the microscopic process during laser sintering, phase change processes including melting, evaporation and resolidification during the irradiation of femtosecond laser on nanosized gold particles were simulated. Laser heat source term was revised to be in accordance with the spherical coordinates and actual situation in a sintering powder bed. The effects of multiple reflection and pulse energy overlapping in small particle size were considered. The results show that, when the particle size is big enough, the simulation results match those of old model. When the particle size is small and laser fluence is high, no resolidification takes place in the time range of the simulation. The laser fluence range to achieve partial melting is narrow when the particle is small. When the diameter is smaller than 400 nm, temperature gradient during the heating period is ignorable, which is different from the large particles. The threshold value of laser fluence to achieve vaporization is about two times higher than that of melting with the same particle size.
Feed-Forward Control of a Cracked Simply Supported Beam
Authors: Kaul Sudhir
Published: August 2012

This paper demonstrates the use of two feed-forward control algorithms in order to mitigate crack propagation in a simply supported beam with a pre-existing crack. The main objective of the control algorithms is to minimize or reduce transverse deflection at the crack location so as to contain the damage resulting from the pre-existing crack and, thereby, reduce the rate of crack propagation. A point-load sinusoidal excitation, from a known disturbance, is used as the input load acting on the beam. Two control algorithms are used — the first control algorithm computes a control force to eliminate transverse displacement at the crack location resulting from the excitation force, and the second control algorithm minimizes the mean square transverse displacement over a section of the beam that contains the crack. Both the control algorithms are a-causal and assume that the excitation input is completely known a-priori. Simulation results for a simply supported beam are presented and discussed in detail. It is observed that the rate of crack propagation can be significantly reduced by implementing the proposed feed-forward control algorithms, increasing the useful life of the damaged beam. Also, it is found that the transverse displacement over a significant length of the beam can be substantially reduced when the beam response is dominated by a specific mode.
Optimum Compression Ratio Variation of 4-Stroke, Direct Injection Diesel Engine for Optimum Performance
Authors: Al-Sood Maher M. Abou , Ahmed Mahmoud A. , Abdel-Rahim Yousef M.
Published: August 2012

A thermodynamic model for simulation the performance of a four-stroke direct-injection (DI) diesel engine is developed. The simulation model includes detailed sub-models for fuel burning rate, combustion products, thermodynamic properties of working fluid, heat transfer, fluid flow, and both soot and NOx formation mechanisms. To validate the model, comparisons between experimental and predicted results for different engines, operating under different conditions were conducted. Comparisons show that there is a good concurrence between measured and predicted values. An optimization analysis is conducted for seeking an optimum variation of compression ratio to achieve pre-set objective target of constant minimum brake specific fuel consumption (bsfc). The optimization analysis is performed under the constrain that the maximum pressure and temperature inside the cylinder not exceed the maximum allowable pressure and temperature of the conventional engine (constant rc). Varying compression ratio is optimized with the previous condition. Results indicated that, at the values of rc ranged between 16.4 and 17.8, the optimum bsfc is attained with an increase in brake power by about 3.8%, while the bsfc and soot emission are reduced by about 4.4% and 21%, respectively. In addition to an increase in NOx, maximum pressure (pmax), and maximum temperature (Tmax) by about 75%, 6% and 4.3%, respectively.
Failure Detection of Rotary Electronic Fuel Control (EFC) Valves via Fuzzy Pattern Classification
Authors: Tugsal Umut , Anwar Sohel
Published: August 2012

In this paper, a mathematical model has been developed and later combined with dynamic performance test methodology to investigate and understand the dynamic characteristics of different types of rotary Electronic Fuel Control (EFC) valves. The model takes into account the dynamics of the electrical and mechanical portions of the EFC valves. A recursive least squares (RLS) type system identification methodology has been utilized to determine the transfer functions of the different types of EFC valves that were investigated. Methods have been used both in frequency domain as well as time domain. Based on the characteristic patterns exhibited by the EFC valves, a fuzzy logic based pattern classification method was utilized to identify faulty EFC valves from good ones. The developed methodology was shown to provide robust diagnostics for a wide range of EFC valves.
Graetz Problem in Ducts of Circular and Some Non-Circular Cross-Sections With Viscoelastic Fluids
Authors: Abdelkader Filali , Khezzar Lyes , Siginer Dennis A. , Nemouchi Zoubir
Published: August 2012

An investigation of heat transfer with viscoelastic fluids in straight pipes of circular and some non-circular cross-sections is carried out. The influence of the rheological parameters on heat transfer enhancement with viscoelastic fluids in the entrance region of tube flow is investigated with negligible axial heat conduction and viscous dissipation. Numerical simulations are conducted with constant wall heat flux for the Graetz problem using the finite element based software Polyflow for viscoelastic fluids of the simplified Phan-Thien Tanner (SPPT) type. It is found that increasing the fluid elasticity, for all cross-sections, raises the normalized heat transfer coefficient for relatively low elasticity values but for high level of fluid elasticity the normalized heat transfer coefficient decreases.
A Model Wind Turbine Design-Build-Test Project
Authors: Post Scott , Boirum Curtis
Published: August 2012

This paper describes a semester-long class project for students in junior-level Fluid Mechanics courses. The goals of the project are to introduce students to engineering design and to incorporate material from other courses in engineering graphics, instrumentation and measurements, and manufacturing processes in a single project. Each team of 3–4 undergraduate students had to design, build, and test a scale model horizontal-axis wind turbine. The wind turbines were designed using solid modeling software, and constructed using either a rapid prototyping machine or a CNC milling machine. The wind turbines were about 15 to 20 cm (6 to 8 inches) in diameter when built, and were placed in a wind tunnel for testing. A small DC motor was used as an electric generator and coupled to the wind turbines through a straight shaft. A variable resistor was incorporated into the circuit so that the rotational speed of the turbine-generator apparatus could be varied. Students were graded based on the efficiency of their wind turbines in converting wind kinetic energy into electrical energy. An additional requirement was for the students to perform a literature review to assess the state of the art in commercial wind turbine technology.
Finite Element Dynamic Analysis of a Railway Seat Under Longitudinal Impact Condition
Authors: Caputo Francesco , Lamanna Giuseppe , Soprano Alessandro
Published: August 2012

For a railway vehicle, the structural integrity of the seat frame and of its connection to that of the coach is a very important aspect of the design phase addressed to the improvement of the passive safety performances, at most because the analysis of the accidents occurred in recent years shows that secondary impacts against vehicle interiors remain one of the main causes of injury. All regulations which apply to this task start from the assumption that whatever happens to the vehicle the seat must remain connected to the vehicle frame, as well as the different parts to each other. Numerical evaluations are obviously necessary to match with this design requirement; it would be desirable to apply multi-body (MB) codes to this task, as they are really fast, but unfortunately they can’t provide detailed results for what concerns the structural behaviour of the involved seat and vehicle components. For this reason, in the present work a full finite element model of a sled-test, including a FE dummy, has been developed, analysed and validated by comparison with the available experimental results; it has been also showed how this kind of numerical simulation is suited and necessary to evaluate the structural behaviour of the structural components of the seat frame. In the context of the presented study the MADYMO® code has been adopted to perform the preliminary MB analyses necessary to calibrate and evaluate the relevant parameters of dummy-seat contact surfaces and of seat-belt stiffness, while LS DYNA® code has been used for the structural dynamic FE analyses.
Towards an Exergy-Based Explosion Energy Model for Boiling-Liquid Expanding-Vapor Explosions
Authors: Ramirez Juan C. , Smyth Suzanne A. , Ogle Russell A.
Published: August 2012

A boiling liquid, expanding vapor explosion (BLEVE) occurs when a pressure vessel containing a superheated liquid undergoes a catastrophic failure, resulting in a violent vaporization of the liquid. The exposure of a pressure vessel to a fire is a classic scenario that can result in a BLEVE. The thermomechanical exergy of a pressure vessel’s contents provides — by definition — an upper bound on the work that can be performed by the system during the explosion. By fixing the values of ambient pressure and temperature (i.e., the dead state), exergy can be interpreted as another thermodynamic property. This rigorous and unambiguous definition makes it ideal to estimate the maximum energy of explosions. The numerical value of exergy depends on the definition of the dead state. In this paper we examine the effect of different definitions for the dead state on the explosion energy value. We consider two applications of this method: the contribution of the vapor head-space to the explosive energy as a function of the fractional liquid fill of the vessel, and the effect of the vessel burst pressure.
A Model Curriculum for Creativity Instruction Integrated Into the Bachelor Program of Engineering Professional Development
Authors: Panthalookaran Varghese
Published: August 2012

The creativity and innovation are of great importance for the new generation engineers who practice their profession in a globalized work place, gravely challenged by questions on sustainability of engineering products and services. Correspondingly, the students of engineering need to develop skills of creative problem solving and innovation. The paper presents a sample curriculum for creativity instruction to the students of engineering. It is aimed at familiarizing students with the creative thinking patterns of great engineers and inventors and to allow them to engage with key principles of creativity and innovation. The theoretical session of the course is planned for the Freshman Level. It consists of five modules namely, 1) Creativity and Innovation in Engineering, 2) Theories of Creativity, 3) Methods of Creative Problem Solving, 4) Team Creativity, and 5) From Creativity to Innovation. The practical sessions of the course is organized distributed in time over the entire Bachelor program spanning over four years in the form of “Hour of Creativity”. Through the practical sessions students are equipped to develop and implement creative concepts for their Senior Level Capstone Design Project (Final Project). Thus the creativity instruction is well-integrated to the Bachelor program of engineering professional development. The general effectiveness of the curriculum for creativity instruction is also discussed.
Numerical Simulations of Heat and Mass Transfer in Condensing Heat Exchangers for Water Recovery in Power Plants
Authors: Jeong Kwangkook , Bilirgen Harun , Levy Edward
Published: August 2012

Power plants release a large amount of water vapor into the atmosphere through the stack. The flue gas can be a potential source for obtaining much needed cooling water for a power plant. If a power plant could recover and reuse a portion of this moisture, it could reduce its total cooling water intake requirement. One of the most practical way to recover water from flue gas is to use a condensing heat exchanger. The power plant could also recover latent heat due to condensation as well as sensible heat due to lowering the flue gas exit temperature. Additionally, harmful acids released from the stack can be reduced in a condensing heat exchanger by acid condensation. Condensation of vapors in flue gas is a complicated phenomenon since heat and mass transfer of water vapor and various acids simultaneously occur in the presence of non-condensable gases such as nitrogen and oxygen. Design of a condenser depends on the knowledge and understanding of the heat and mass transfer processes. A computer program for numerical simulations of water (H2O) and sulfuric acid (H2SO4) condensation in a flue gas condensing heat exchanger was developed using MATLAB. Governing equations based on mass and energy balances for the system were derived to predict variables such as flue gas exit temperature, cooling water outlet temperature, mole fraction and condensation rates of water and sulfuric acid vapors. The equations were solved using an iterative solution technique with calculations of heat and mass transfer coefficients and physical properties. An experimental study was carried out in order to yield data for validation of modeling results. Parametric studies for both modeling and experiments were performed to investigate the effects of parameters such as flue gas flow rate, cooling water flow rate, inlet cooling water temperature and tube configurations (bare and finned tubes) on condensation efficiency. Predicted results of water and sulfuric acid vapor condensation were compared with experimental data for model validation, and this showed agreement between experimental data and predictions to within a few percent. The most important parameters affecting performance of the condensing heat exchangers was the ratio of cooling water to flue gas flow rates, since this determines how much heat the cooling water can absorb. The computer program simultaneously calculates both water vapor condensation and sulfuric acid condensation in flue gas along downstream. Modeling results for prediction of sulfuric acid vapor concentration in the flue gas were compared with measured data obtained by the controlled condensation method. An analytical model of sulfuric acid condensation for oil-firing showed two trends — steep reduction within the high temperature heat exchanger and smooth reduction within lower temperature heat exchanger, which is in agreement with experimental data.
Dynamic Force Response of Human Legs due to Vertical Jumps
Authors: Prajapati Kinjal , Barez Fred , Kao James , Wagner David
Published: August 2012

Jumping is a natural exertion that occurs during a variety of human activities including playing sports, working, skateboarding, dancing, escaping from hazardous events, rescue activities, and many others. During jumping, the ankles in particular are expected to support the entire body weight of the jumper and that may lead to ankle injuries. Each year hundreds of patients are treated for ankle sprains/strains with ankle fractures as one of the most common injuries treated by orthopedists and podiatrists. The knee joint is also considered the most-often injured joint in the entire human body. Although the general anatomy of the lower extremities is fairly well understood, an understanding of the injury mechanism during these jumping tasks is not well understood. The aim of this study is to determine the reaction forces exerted on legs and joints due to vertical jumps, through musculoskeletal simulation and experimental studies to better understand the dynamic jump process and the injury mechanism. The joint reaction forces and moments exerted on the ankle, knee and hip joint during takeoff and extreme squat landing of a vertical jump were determined through the application of musculoskeletal simulation. It is concluded that during extreme squat landing of a vertical jump, joint reaction forces and moments were highest in proximal/distal and anteroposterior direction may cause most likely injury to the hip joint ligaments, ankle fracture and knee joint, respectively.
A Numerical and Experimental Investigation of a Gas Propelled Liquid Droplet Impinging Onto a Heated Surface
Authors: Diaz Andres , Ortega Alfonso
Published: August 2012

Due to the higher rates of heat transfer and the spatial homogeneity of heat removal that can be achieved with spray cooling, these systems have been widely proposed for cooling high heat flux electronics. In particular, gas-assisted spray cooling systems, in which a vapor phase jet propels the liquid phase droplets to a target surface, have been shown to be even more efficient in removing heat than sprays consisting of droplets alone. However, in all the studies found in the literature, in which the basic problem has been approached as a single-droplet event, only the behavior of a free falling droplet has been studied. To date, there is no fundamental investigation of the physics of gas or vapor-assisted spray cooling. To study this problem an experimental and numerical investigation of the deformation process of a liquid droplet transported by a gas stream impinging on a heated surface was performed. A preliminary study [1] has shown that increasing air jet velocities leads to an augmentation in liquid-solid contact area. Nevertheless, for low We*, the increase in droplet spreading diameter is only a consequence of the increase in droplet kinetic energy before the impact rather than the pressure and shear stress imposed by the gas during the spreading. An order of magnitude analysis showed that shear effects are negligible compared to the normal pressure of the jet. A first order analytical model of the droplet spreading behavior indicated that the jet stagnation pressure acting on the droplet surface becomes important at relatively low Weo and higher We* by contributing to the reduction in liquid film thickness and to the augmentation in liquid-solid contact area. It was shown that the work done by the gas stream in deforming the liquid droplet must be at least 10% of the initial kinetic energy of the droplet to start having a significant effect on the droplet deformation during the early stage of impact.
Active Disturbance Rejection for Bipedal Walk of a Humanoid Robot Using the Motions of the Arms
Authors: Hill Joshua , Fahimi Farbod
Published: August 2012

A control system for the walking of a redundant biped robot in the swing phase is considered. The biped is a humanoid with 6DOF per leg and 3DOF per arm. The controller will be based on a full kinematic model of the robot to depict a more accurate behavior of the robot. The arms of the robot are used to compensate for disturbances the robot may experience during walking. Instead of controlling the robots ZMP, keeping it within the support polygon, all six foot support reaction components are controlled. First, a “shoe” with force sensors detect the forces and moments on the foot for feedback. The feedback from the joint servos provide position and velocity information. The support reaction and the joint position/velocities are fedback to a sliding mode controller, which makes adjustments to the arm links’ acceleration to compensate the shift in the reaction components. Simulations show the comparison of the ZMP shift when disturbances are applied with and without controlling the reaction forces to prove the effectiveness of the approach.
Identification of Multiple Damages in a Structure Using Embedded Sensitivity Functions and Optimization Techniques
Authors: Yang Chulho , Adams Douglas E.
Published: August 2012

A new method for identifying multiple damages in a structure using embedded sensitivity functions and optimization algorithms is presented in this work. Optimization techniques are used to minimize the difference between the measured frequency response functions from a damaged structure and the predicted FRFs from the baseline structure. The predicted FRF functions are calculated directly from the undamaged system response data using the embedded sensitivity functions and their Taylor series expansions. The optimal damage parameters are identified in engineering units as changes in stiffness, damping, or mass through the optimization process for minimizing the difference between those two FRFs. The method is applied to a two degree of freedom analytical model to determine the accuracy of the diagnostic results. Finite element analyses are then conducted on a three-story structure with damages in the form of stiffness and mass perturbations to demonstrate the applicability of this method to more complicated structural systems. It is shown that the suggested technique can detect and quantify multiple damages in a structure with high numerical accuracy in the level of the estimated damages.
Percentiles of von Mises Stress From Combined Random Vibration and Static Loading by Approximate Noncentral Chi Square Distribution
Authors: Tibbits Patrick A.
Published: August 2012

Firstly, a calculation for percentiles of von Mises stress in linear structures subjected to Gaussian random loads is extended to the case of Gaussian random loads having nonzero mean values, i.e., the inclusion of static loads. The development is restricted to the case of plane stress. The method includes calculation of a given percentile of von Mises stress to any desired accuracy, a rapid estimate of the percentile, and upper and lower bounds on the von Mises stress. The calculation expands the cumulative distribution function of the von Mises stress as a series of noncentral chi square distributions. Summation of a sufficient number of terms of the series calculates the percentile to the desired accuracy. The rapid estimate of the percentile interpolates the distribution of the von Mises stress in a small number of inverse noncentral chi-square distribution functions. The upper and lower bounds on the percentiles take advantage of the noncentral chi-square distribution of summations of normally distributed stress components. Second and third calculation methods arise from approximations of the distribution of quadratic forms of noncentral normal variables, or equivalently, linear combinations of noncentral chi square variables. These methods provide rapid estimates of percentiles of von Mises stress in linear structures under random loads having nonzero mean values. The accuracy and computational efficiency of the methods are reviewed and compared. The methods are expected to have wide application in design of and prognostics for components subjected to constant structural loads coupled with random loading arising from vibrations caused by wind, waves, seismic events, engines, turbulence, acoustic noise, etc.
Mathematical Modeling of De-Hydrogenation Micro-Reactors for Vehicles Using the Liquid Carrier of Hydrogen Fuel
Authors: Saleh Mohamed E. , Li Wei , Yao Shi-chune
Published: August 2012

When the organic liquid carrier of hydrogen is used as the fuel on a vehicle, a key component is the hydrogen releasing device, which requires large surface area of catalyst, small size and light weight. Micro-reactors with internal structure of micro pin-fin array is considered due to its high area-to-volume ratio and intimate impaction-contact with the fluids. To support the design of a first experiment, a mathematical model based on laws of conservation and chemical reaction is established. A surface-reaction efficiency has also been included to consider the possible effect of surface nonwetting in the hydrogen two-phase flow. This model has been demonstrated using the N-Ethyl Carbazole as the liquid carrier and Palladium as the catalyst. Due to the large gas generation rate, the numerical modeling indicates that the system operates at high void fraction with large slip ratio. This leads to an alternative system design of using segmented reactors with a hydrogen separator located in between. This leads to reduced size of the system and less catalyst material used.
Modeling and Optimization of Micro-Channel Heat Sinks for the Cooling of 3D Stacked Integrated Circuits
Authors: Narayan Varun , Yao Shi-Chune
Published: August 2012

3D IC stacking offers unique opportunities to extend the number of functions per package beyond conventional chip design architectures. A critical requirement for the reliability of such high density high heat flux devices is adequate thermal management in order to ensure the junction temperatures fall within the acceptable limit. Additional constraints are related with the through silicon via (TSV) placements and compactness of the system. Liquid cooling with integrated micro-channels is a promising technology to meet these demands; however, the modeling and determining the optimal design of these channels is challenging. In this paper, a fluid-fin coupled model for heat sink temperature has been derived in explicit and easy to use form, and its feasibility for geometrical optimization has been demonstrated with a design case of 3D IC from previous literature.
Analysis of Water Production of a 1.2 KW PEM Fuel Cell
Authors: Flores Juan G. Lozada , Carbajal Gerardo
Published: August 2012

Investigation of water production rate is one of the most important factors to evaluate the performance of a PEM Fuel Cell. In the present case water production rate was studied from the hydrogen and the air inputs with an additional consideration of the effect of the relative humidity of ambient air. A corrected model was used to evaluate the water production, and it was compared against experimental data. It was found that this new model is strongly enhanced and it becomes in a new focus of study. The fuel cell system was tested at steady state conditions during 2700 s at 245 W and 36 V. The mass flow rate of water produced by the experimental result was 1.444 grams/min, while the analytical result was 1.311grams/min; the error of the analytical data compared with the experimental data was 10.14 percent.
CFD Analysis of Scramjet Combustor Using Strut With Circular and Planer Injector
Authors: Pandey K. M. , Thangavel Sivasakthivel
Published: August 2012

The simulation of a supersonic reactive flow is an important tool for the investigation and development of Scramjet engines. Numerical investigations have become less expensive than experiments. In this research work mixing and combustion for different type of strut injector is studied especially for strut with circular injector and strut with planer injector, in this work DLR scramjet combustor model is used, it having length of 340mm, width of 40mm, inlet entry height of 50mm and exit height of the combustor is 62mm. In this combustor strut is placed at the distance of 77mm from the inlet. Total length of the strut is 32mm. Air entry Mach number is 2, temperature and pressure of the air is 340k and 1 bar, at the base of the strut hydrogen will be injected at a Mach number of 1, temperature and pressure of the Hydrogen is 250k and 1 bar. Combustion will be initiated using pre burning of small amount of hydrogen and oxygen. In this CFD analysis two-dimensional coupled implicit NS equation, the standard k-ε turbulence model and the finite-rate/eddy-dissipation reaction model have been applied to numerically simulate the flow field of the hydrogen fuelled scramjet combustor. From analysis it is found that strut with planer injector giving good mixing efficiency, combustion efficiency and total pressure loss is less as compared to strut with circular injector. In both cases subsonic regions at the channel symmetry axis are responsible for flame holding. If the combustor geometry is chosen in a favourable way these subsonic zones may be kept small. Moreover, the flames are away from solid walls thus minimizing the wall heat load.