bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Fuel Nozzle Displacement on Pre-Filming Airblast Atomization
Authors: Han Y. M. , Seol W. S. , Lee D. S. , Yagodkin V. I. , Jeung I. S.
Published: July 2002

In gas turbine combustors, optimum arrangement between a fuel nozzle and a swirler/prefilmer module must be sought to achieve satisfactory ignition and stability characteristics in addition to reduced level of emissions. However, due to thermal expansion of the combustor or misalignment of the fuel nozzle, the location of a fuel nozzle may vary. Displacement of a fuel nozzle may change the amount of fuel injected to the pre-filming device (usually the inner swirler wall) and the location of attachment, which in turn affects the thickness of pre-filming liquid sheet on the wall. As a result, the spray structure formed by pre-filming airblast atomization may be significantly changed. An experimental investigation is carried out to study the effects of fuel nozzle displacement on the structure of a spray formed by a dual orifice pressure atomizer and a counter-rotating dual swirler. The inner wall of the swirler is designed to be used as a pre-filming device. The behavior of droplets, the flow characteristics of the swirling air flow, and the interaction between droplets and the flow are studied. Optical diagnostic methods including a flow visualization and an Adaptive Phase/Doppler technique are used. Distributions of droplet size, number density, and liquid phase volume flux are presented for various fuel nozzle displacements, in addition to gas phase velocity.
Model of Human/Liquid Cooling Garment Interaction for Space Suit Automatic Thermal Control
Authors: Nyberg Karen L. , Diller Kenneth R. , Wissler Eugene H.
Published: July 2002

The Wissler human thermoregulation model was augmented to incorporate simulation of a space suit thermal control system that includes interaction with a liquid cooled garment (LCG) and ventilation gas flow through the suit. The model was utilized in the design process of an automatic controller intended to maintain thermal neutrality of an exercising subject wearing a liquid cooling garment. An experimental apparatus was designed and built to test the efficacy of specific physiological state measurements to provide feedback data for input to the automatic control algorithm. Control of the coolant inlet temperature to the LCG was based on evaluation of transient physiological parameters that describe the thermal state of the subject, including metabolic rate, skin temperatures, and core temperature. Experimental evaluation of the control algorithm function was accomplished in an environmental chamber under conditions that simulated the thermal environment of a space suit and transient metabolic work loads typical of astronaut extravehicular activity (EVA). The model was also applied to analyze experiments to evaluate performance of the automatic control system in maintaining thermal comfort during extensive transient metabolic profiles for a range of environmental temperatures. Finally, the model was used to predict the efficacy of the LCG thermal controller for providing thermal comfort for a variety of regimens that may be encountered in future space missions. Simulations with the Wissler model accurately predicted the thermal interaction between the subject and LCG for a wide range of metabolic profiles and environmental conditions and matched the function of the automatic temperature controller for inlet cooling water to the LCG.
Photo-Acoustic Measurement of Thermal Conductivity of Thin Films and Bulk Materials
Authors: Wang Xinwei , Hu Hanping , Xu Xianfan
Published: July 2002

The photoacoustic (PA) technique is one of many techniques for measuring thermal conductivity of thin films. Compared with other techniques for thermal conductivity measurement, the photoacoustic method is relatively simple, yet is able to provide accurate thermal conductivity data for many types of thin films and bulk materials. In this work, the PA measurement in a high frequency range is made possible by a newly developed PA apparatus, which extends the limit of the PA technique. Thermal conductivities of SiO2 with thicknesses from 0.05 to 0.5 μm on Si wafer, e-beam evaporated thin nickel film on Si wafer, and thermal barrier coatings are obtained. In addition to the commonly used phase shift fitting, which is only appropriate for thermally-thin films, an amplitude fitting method is developed and employed for measuring both thin films and bulk materials with smooth or rough surfaces. Comparing results by amplitude fitting to those obtained by other methods and reference values shows good agreements. Applications and limitations of the photoacoustic technique are discussed.
A Comparison of Thermal Stress/Strain Behavior of Elliptical/Round Solder Pads
Authors: Chiang Kuo-Ning , Liu Chang-Ming
Published: July 2002

As electronic packaging technology moving to the CSP, wafer level packaging, fine pitch BGA (ball grid array) and high density interconnections, the wireability of the PCB/substrate and soldering technology are as important as reliability issues. In this work, a comparison of elliptical/round pads of area array type packages has been studied for soldering, reliability, and wireability requirements. The objective of this research is to develop numerical models for predicting reflow shapes of solder joint under elliptical/round pad boundary conditions and to study the reliability issue of the solder joint. In addition, a three-dimensional solder liquid formation model is developed for predicting the geometry, the restoring force, the wireability, and the reliability of solder joints in an area array type interconnections (e.g., ball grid array, flip chip) under elliptical and round pad configurations. In general, the reliability of the solder joints is highly dependent on the thermal-mechanical behaviors of the solder and the geometry configuration of the solder ball. These reliability factors include standoff height/contact angle of the solder joint, and the geometry layout/material properties of the package. An optimized solder pad design cannot only lead to a good reliability life of the solder joint but also can achieve a better wireability of the substrate. Furthermore, the solder reflow simulation used in this study is based on an energy minimization engine called Surface Evolver and the finite element software ABAQUS is used for thermal stress/strain nonlinear analysis.
An Investigation of a Cause of Backfire and Its Control Due to Crevice Volumes in a Hydrogen Fueled Engine
Authors: Lee J. T. , Kim Y. Y. , Lee C. W. , Caton J. A.
Published: July 2002

To understand the occurrence of backfire in hydrogen fueled engines using an external (inducted) fuel supply, a fundamental study was completed using a modified experimental engine. A relation was found between the crevice volume in the combustion chamber and the occurrence of backfire. The results showed that the crevice around the spark plug electrode was not a major cause of backfire, but the combustion state of the mixture in the piston top land crevice, second land, and ring groove did have a direct affect on backfire occurrence. By increasing the top land crevice volume and the amount of blow-by gas, the equivalence ratio before backfire occurred was extended.
Modal Overlap and Dissipation Effects of a Cantilever Beam with Multiple Attached Oscillators
Authors: Drexel M. V. , Ginsberg J. H.
Published: July 2002

This work was prompted by a study performed by Strasberg [7] in which numerous small spring-mass-damper systems are attached to a large suspended mass representing the master structure. The isolated natural frequency of each attached system was selected to match in average the natural frequency of the isolated master structure. Strasberg found that the critical issue when an impulse excitation is applied to the master structure is the bandwidth of the isolated attached systems in comparison to the spacing between the natural frequencies of the system. Modal overlap, which corresponds to bandwidths that exceed the spacing of those frequencies, was shown to greatly influence the response of the master structure. Light damping, for which there is little or no modal overlap, corresponds to an impulse response that consists of a sequence of nearly periodic exponentially decaying pulses, and the transfer function for harmonic excitation of the master structure indicates that the substructure acts as a vibration absorber for the master structure. Increased damping leads to modal overlap, with the result that the impulse response consists of a single decaying pulse. The frequency domain transfer function indicates that the vibration absorber effect is enhanced. The present work explores these issues for continuous systems by replacing the one degree of freedom master structure with a cantilever beam. The system parameters are selected to match Strasberg’s model, with the suspended oscillators placed randomly along the beam. The beam displacement is represented as a Ritz series whose basis functions are the cantilever beam modes. The coupled equations are solved by a state-space eigenmode analysis that yields a closed form representation of the response in terms of the complex eigenmode properties. The continuous fuzzy structure is shown not to display the transfer of energy between the master structure and the substructure that was exhibited by the discrete fuzzy structure, apparently because of the asynchronous motion of the attachment points resulting from the spatial variability of the beam’s motion. The vibration absorber effect for harmonic excitation is only obtained for the heavy damping in the case of a beam.
Creep, Hysteresis, and Vibration Compensation for Piezoactuators: Atomic Force Microscopy Application
Authors: Croft D. , Shed G. , Devasia S.
Published: July 2002

This article studies ultra-high-precision positioning with piezoactuators and illustrates the results with an example Scanning Probe Microscopy (SPM) application. Loss of positioning precision in piezoactuators occurs (1) due to hysteresis during long range applications, (2) due to creep effects when positioning is needed over extended periods of time, and (3) due to induced vibrations during high-speed positioning. This loss in precision restricts the use of piezoactuators in high-speed positioning applications like SPM-based nanofabrication, and ultra-high-precision optical systems. An integrated inversion-based approach is presented in this article to compensate for all three adverse affects—creep, hysteresis, and vibrations. The method is applied to an Atomic Force Microscope (AFM) and experimental results are presented that demonstrate substantial improvements in positioning precision and operating speed.
Sensor Validation and Fusion for Automated Vehicle Control Using Fuzzy Techniques
Authors: Goebel Kai F. , Agogino Alice M.
Published: July 2002

This brief introduces a fuzzy sensor validation and fusion methodology and applies it to automated vehicle control in Intelligent Vehicle Highway Systems (IVHS). Sensor measurements are assigned confidence values through sensor-specific dynamic validation curves. The validation curves attain minima of zero at the boundaries of the validation gate. These in turn are determined by the largest physically possible change a system—in our example vehicles of the IVHS—can undergo in one time step. A fuzzy exponential weighted moving average time series predictor determines the location of the maximum value of the validation curves. Sensor fusion is then performed using a weighted average of sensor readings and confidence values, and—if available—the functionally redundant values calculated from other sensors.
Dynamic Analysis of Rectilinear Motion of a Self-Propelling Disk With Unbalance Masses
Authors: Das T. , Mukherjee R.
Published: July 2002

This paper investigates the dynamics of a rolling disk with three unbalance masses that can slide along radial spokes equispaced in angular orientation. The objective is to design trajectories for the masses that satisfy physical constraints and enable the disk to accelerate or move with constant velocity. The disk is designed to remain vertically upright and is constrained to move along a straight line. We design trajectories for constant acceleration, first using a static model, and then through detailed analysis using a dynamic model. The analysis based on the dynamic model considers two separate cases; one where the potential energy of the system is conserved, and the other where it continually varies. Whereas trajectories conserving potential energy are quite similar to those obtained from the static model, the variable potential energy trajectories are the most general. A number of observations related to the system center-of-mass are made with respect to both trajectories. Following the strategy for constant acceleration maneuvers, we give a simple approach to tracking an acceleration profile and provide some simulation results.
Energy Pumping in Nonlinear Mechanical Oscillators: Part II—Resonance Capture
Authors: Vakakis A. F. , Gendelman O.
Published: July 2002

We study energy pumping in an impulsively excited, two-degrees-of-freedom damped system with essential (nonlinearizable) nonlinearities by means of two analytical techniques. First, we transform the equations of motion using the action-angle variables of the underlying Hamiltonian system and bring them into the form where two-frequency averaging can be applied. We then show that energy pumping is due to resonance capture in the 1:1 resonance manifold of the system, and perform a perturbation analysis in an Oε neighborhood of this manifold in order to study the attracting region responsible for the resonance capture. The second method is based on the assumption of 1:1 internal resonance in the fast dynamics of the system, and utilizes complexification and averaging to develop analytical approximations to the nonlinear transient responses of the system in the energy pumping regime. The results compare favorably to numerical simulations. The practical implications of the energy pumping phenomenon are discussed.
A Two-Time-Scale Infinite-Adsorption Model of Three Way Catalytic Converters During the Warm-Up Phase1
Authors: Glielmo Luigi , Santini Stefania
Published: July 2002

New regulations for emission control require the improvement of the system composed by spark ignition internal combustion engine and three-way catalytic converter (TWC). In particular, an important problem is to minimize harmful emissions during the transient warm-up phase where the TWC is not working yet and, hence, a large amount of pollutants are emitted in the air. Toward this goal we present a dynamical thermo-chemical TWC model simple enough for the design and test of warm-up control strategies. The model is obtained through an asymptotic approximation of a more detailed model, i.e., by letting the adsorption coefficient between gas and substrate tend to infinity. Further, we present a fast integration algorithm based partly on a “method of lines” space-discretization, partly on the “method of characteristics” for “quasi linear” hyperbolic partial differential equations, the separation being allowed by a two time scale analysis of the system. The model has been identified, through a purposely designed genetic algorithm, and validated on experimental data.
Analysis and Prediction of Edge Effects in Laser Bending
Authors: Bao Jiangcheng , Yao Y. Lawrence
Published: July 2002

Laser forming of sheet metal offers the advantages of requiring no hard tooling and thus reduced cost and increased flexibility. It also enables forming of some materials and shapes that are not possible now. In single-axis laser bending of plates, the bending edge is found to be somewhat curved and the bending angle varies along the laser-scanning path. These phenomena are termed edge effects, which adversely affect the accuracy of the bending and result in undue residual stress. Numerical investigations are carried out to study the process transiency and the mechanism of the edge effects. Temperature dependency of material properties and strain-rate dependency of flow stress are considered in the numerical simulation to improve prediction accuracy. Numerical results are validated in experiments. Patterns of edge effects and resultant residual stress distributions are examined under a wide range of conditions. A more complete explanation for the mechanism of the edge effects is given.
A Fuzzy Adaptive Simplex Search Optimization Algorithm
Authors: Trabia Mohamed B. , Lu Xiao Bin
Published: July 2002

Most optimization algorithms use empirically-chosen fixed parameters as a part of their search strategy. This paper proposes to replace these fixed parameters by adaptive ones to make the search more responsive to changes in the problem by incorporating fuzzy logic in optimization algorithms. The proposed ideas are used to develop a new adaptive form of the simplex search algorithm whose objective is to minimize a function of n variables. The new algorithm is labeled Fuzzy Simplex. The search starts by generating a simplex with n+1 vertices. The algorithm then repeatedly replaces the point with the highest function value by a new point. This process has three components: reflecting the point with the highest function value, expanding, and contracting the simplex. These operations use fuzzy logic controllers whose inputs incorporate the relative weights of the function values at the simplex points. Standard minimization test problems are used to evaluate the efficiency of the algorithm. The Fuzzy Simplex algorithm generally results in a faster convergence. Robustness and sensitivity of the algorithm are also considered. The Fuzzy Simplex algorithm is also applied successfully to several engineering design problems. The results of the Fuzzy Simplex algorithm compare favorably with other available minimization algorithms.
Identification of Minimum Air Flow Design for a Desktop Computer Using CFD Modeling
Authors: Chang J. Y. , Yu C. W. , Webb R. L.
Published: July 2002

This paper reports the results of CFD analysis to cool the 30-W socketed CPU of a desktop computer with minimum air flow rate and minimum heat sink size. This was achieved using only the fan in the power supply for all air movement in the chassis. A duct was employed to direct the air flow over the CPU and then to the inlet air vents of the power supply. Use of this duct allowed more than 10°C reduction of the CPU case temperature, relative to an unducted design. The CFD analysis results were confirmed by experiment, and the predicted CPU case temperatures agreed within ±2.9°C of the experimental values for the ducted cases. This paper describes the methodology of CFD analysis for the heat sink/duct design, and describes experimental procedures to validate the predictions.
An Active Microvibration Isolation System for Hi-tech Manufacturing Facilities
Authors: Yoshioka H. , Takahashi Y. , Katayama K. , Imazawa T. , Murai N.
Published: July 2002

This paper presents an active microvibration isolation system using voice-coil linear motors, and pneumatic and piezoelectric actuators. This system is designed to reduce microvibration of the six degrees-of-freedom associated with the rigid body modes of the vibration isolation table by feeding back the pseudo absolute displacement and velocity of the table. To improve vibration isolation performance, a feed-forward control link is added to the sway components in each dimension. This system can also control bending modes of the table in the frequency range up to 200 Hz by employing a proposed Virtual Tuned-Mass Damper control strategy, which is a type of the pole assignment method. In this approach, the pole locations are chosen by a genetic algorithm. For ambient microvibration of the floor around 0.5 cm/s2 and for small earthquakes of around 8 cm/s2 a reduction by a factor of 100 was achieved in the acceleration of the vibration isolation table. Moreover, the vibration of the isolation table was decreased over the entire frequency range. This system also showed good vibration control performance when an impact excitation was applied directly to the table; vibration was damped out within about 0.1 sec. Additionally, the resonance amplitudes around the bending modes of the table were reduced from 1/5 to 1/15 by the Virtual Tuned-Mass Damper method.
Biphasic Poroviscoelastic Simulation of the Unconfined Compression of Articular Cartilage: II—Effect of Variable Strain Rates
Authors: DiSilvestro, Mark R. , Zhu, Qiliang , Suh Jun-Kyo Francis
Published: July 2002

This study investigated the abilities of the linear biphasic poroviscoelastic (BPVE) model and the linear biphasic poroelastic (BPE) model to simulate the effect of variable ramp strain rates on the unconfined compression stress relaxation response of articular cartilage. Curve fitting of experimental data showed that the BPVE model was able to successfully account for the ramp strain rate-dependent viscoelastic behavior of articular cartilage under unconfined compression, while the BPE model was able to account for the complete viscoelastic response at a slow strain rate, but only the long-term viscoelastic response at faster strain rates. We concluded that the short-term viscoelastic behavior of articular cartilage, when subjected to a fast ramp strain rate, is primarily governed by a fluid flow-independent (intrinsic) viscoelastic mechanism, whereas the long-term viscoelastic behavior is governed by a fluid flow-dependent (biphasic) viscoelastic mechanism. Furthermore, a linear viscoelastic representation of the solid stress was found to be a valid model assumption for the simulation of ramp strain rate-dependent relaxation behaviors of articular cartilage within the range of ramp strain rates investigated.
Experimental Measurement of Mode Shapes and Frequencies for Vibration of Plates by Optical Interferometry Method
Authors: Huang Chi-Hung , Ma Chien-Ching
Published: July 2002

Most of the published literature for vibration mode shapes of plates is concerned with analytical and numerical results. There are only very few experimental results available for the full field configuration of mode shapes for vibrating plates. In this study, an optical system called the AF-ESPI method with the out-of-plane displacement measurement is employed to investigate experimentally the vibration behavior of square isotropic plates with different boundary conditions. The edges of the plates may either be clamped or free. As compared with the film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Based on the fact that clear fringe patterns will appear only at resonant frequencies, both resonant frequencies and corresponding mode shapes can be obtained experimentally at the same time by the proposed AF-ESPI method. Excellent quality of the interferometric fringe patterns for the mode shapes is demonstrated.
The Rotating Tautochrone
Authors: Osler T. J. , Flores E.
Published: July 2002

In a recent paper by Flores and Osler, the authors investigated tautochrone curves in the xy-plane under an arbitrary potential Vy. In this paper we imagine that the xy-plane of the tautochrone curve is rotating about the y-axis with constant angular momentum. We find the differential equation of the tautochrone curves. While this differential equation is difficult to solve analytically, several exact solutions (in terms of elementary functions) are obtained in an indirect manner. Intuitive motivation for tautochrone motion is given.
Buckling of Barreled Shells Subjected to External Hydrostatic Pressure
Authors: Błachut J. , Wang P.
Published: July 2002

The paper considers barreling of a mild steel cylindrical shell as a way of improving its load carrying capacity when subjected to static external pressure. Numerical results show that the load carrying capacity can be increased from 1.4 to 40 times above the load capacity of mass equivalent cylinders. The effect of end boundary conditions on the ultimate load is examined together with sensitivity of buckling loads to initial geometric imperfections.
A Nonlinear, Transient, Single-Cylinder Diesel Engine Simulation for Predictions of Instantaneous Engine Speed and Torque
Authors: Filipi Z. S. , Assanis D. N.
Published: July 2002

A non-linear, transient, single-cylinder diesel engine simulation has been developed for predictions of instantaneous engine speed and torque. The foundation of our model is a physically based, thermodynamic, steady-state diesel engine simulation (Assanis, D. N., and Heywood, J. B., 1986, “Development and Use of a Computer Simulation of the Turbocompounded Diesel System for Engine Performance and Component Heat Transfer Studies,” SAE Paper 860329), which has been comprehensively validated for various engine designs. The transient extension of the parent model represents the diesel engine as a non-linear, dynamic system. The instantaneous crank-shaft speed is determined from the solution of the engine-external load dynamics equation, where the engine torque is tracked on a crank-angle basis. Validation of the transient model during rapid engine acceleration shows that both the cyclic fluctuations in the instantaneous crank-shaft speed line and the overall engine response are in good agreement with experimental measurements. Predictions of single-cylinder engine starting reveals the importance of selecting the proper value of the engine moment of inertia in order to control the amplitude of angular velocity fluctuations and ensure stable engine operation. It is further shown that the variation in the inertial forces on the reciprocating components with speed has a dramatic impact on the instantaneous torque profile, and consequently on angular velocity fluctuations.
Direct Numerical Simulation of a Fully Developed Turbulent Channel Flow With Respect to the Reynolds Number Dependence
Authors: Abe Hiroyuki , Kawamura Hiroshi , Matsuo Yuichi
Published: July 2002

Direct numerical simulation (DNS) of a fully developed turbulent channel flow for various Reynolds numbers has been carried out to investigate the Reynolds number dependence. The Reynolds number is set to be Reτ=180, 395, and 640, where Reτ is the Reynolds number based on the friction velocity and the channel half width. The computation has been executed with the use of the finite difference method. Various turbulence statistics such as turbulence intensities, vorticity fluctuations, Reynolds stresses, their budget terms, two-point correlation coefficients, and energy spectra are obtained and discussed. The present results are compared with the ones of the DNSs for the turbulent boundary layer and the plane turbulent Poiseuille flow and the experiments for the channel flow. The closure models are also tested using the present results for the dissipation rate of the Reynolds normal stresses. In addition, the instantaneous flow field is visualized in order to examine the Reynolds number dependence for the quasi-coherent structures such as the vortices and streaks.
Analysis of Reset Control Systems Consisting of a FORE and Second-Order Loop1
Authors: Chen Qian , Chait Yossi , Hollot C. V.
Published: July 2002

Reset controllers consist of two parts—a linear compensator and a reset element. The linear compensator is designed, in the usual ways, to meet all closed-loop performance specifications while relaxing the overshoot constraint. Then, the reset element is chosen to meet this remaining step-response specification. In this paper, we consider the case when such linear compensation results in a second-order (loop) transfer function and where a first-order reset element (FORE) is employed. We analyze the closed-loop reset control system addressing performance issues such as stability, steady-state response, and transient performance.
A Decentralized Fault Detection Filter1
Authors: Chung Walter H. , Speyer Jason L. , Chen Robert H.
Published: July 2002

In this paper, we introduce the decentralized fault detection filter, a structure that results from merging decentralized estimation theory with the game theoretic fault detection filter. A decentralized approach may be the ideal way to health monitor large-scale systems, since it decomposes the problem down into (potentially smaller) “local” problems. These local results are then blended into a “global” result that describes the health of the entire system. The benefits of such an approach include added fault tolerance and easy scalability. An example given at the end of the paper demonstrates the use of this filter for a platoon of cars proposed for advanced vehicle control systems.
Quick-Return Servomechanism With Adaptive Fuzzy Neural Network Control
Authors: Fung Rong-Fong , Lin Faa-Jeng , Wai Rong-Jong
Published: July 2002

The dynamic response of an adaptive fuzzy neural network (FNN) controlled quick-return mechanism, which is driven by a permanent magnet (PM) synchronous servo motor, is described in this study. The crank and disk of the quick-return mechanism are assumed to be rigid. First, Hamilton’s principle and Lagrange multiplier method are applied to formulate the mathematical model of motion. Then, based on the principle of computed torque, an adaptive controller is developed to control the position of a slider of the quick-return servomechanism. Moreover, since the selection of control gain of the adaptive controller has a significant effect on the system performance, an adaptive FNN controller is proposed to control the quick-return servomechanism. In the proposed adaptive FNN controller, an FNN is adopted to facilitate the adjustment of control gain on line. Simulated and experimental results due to periodic step and sinusoidal commands show that the dynamic behavior of the proposed adaptive FNN control system are robust with regard to parametric variations and external disturbances.
Liquid Fuel Impingement on In-Cylinder Surfaces as a Source of Hydrocarbon Emissions From Direct Injection Gasoline Engines
Authors: Li J. , Huang Y. , Alger T. F. , Matthews R. D. , Hall M. J. , Stanglmaier R. H. , Roberts C. E. , Dai W. , Anderson R. W.
Published: July 2002

Hydrocarbon (HC) emissions from direct injection gasoline (DIG) engines are significantly higher than those from comparable port fuel injected engines, especially when “late” direct injection (injection during the compression stroke) is used to produce a fuel economy benefit via unthrottled lean operation. The sources of engine-out hydrocarbon emissions for late direct injection are bulk flame quench, low temperatures for post-combustion oxidation, and fuel impingement on in-cylinder walls. An experimental technique has been developed that isolates the wall impingement source from the other sources of HC emissions from DIG engines. A series of steady-state and transient experiments is reported for which the HC emissions due to operation with a premixed charge using a gaseous fuel are compared to those when a small amount of liquid fuel is injected onto an in-cylinder surface and the gaseous fuel flow rate is decreased correspondingly. The steady-state experiments show that wetting any in-cylinder surface dramatically increases HC emissions compared to homogeneous charge operation with a gaseous fuel. The results of the transient fuel injection interrupt tests indicate that liquid-phase gasoline can survive within the cylinder of a fully warmed-up firing engine and that liquid fuel vaporization is slower than current computational models predict. This work supports the argument that HC emissions from DIG engines can be decreased by reducing the amount of liquid fuel that impinges on the cylinder liner and piston, and by improving the vaporization rate of the fuel that is deposited on these surfaces.
Model Development and Simulation of Transient Behavior of Heavy Duty Gas Turbines
Authors: Kim J. H. , Song T. W. , Kim T. S. , Ro S. T.
Published: July 2002

This paper describes models for the transient analysis of heavy duty gas turbines, and presents dynamic simulation results of a modern gas turbine for electric power generation. Basic governing equations have been derived from integral forms of unsteady conservation equations. Mathematical models of each component are described with the aid of unsteady one-dimensional governing equations and steady-state component characteristics. Special efforts have been made to predict compressor characteristics including the effect of movable vanes, which govern the operating behavior of a whole engine. The derived equation sets are solved numerically by a fully implicit method. A controller model that maintains constant rotational speed and target temperature (turbine inlet or exhaust temperature) is used to simulate practical operations. Component models, especially those of the compressor, are validated through comparison with test data. The dynamic behavior of a 150 MW class engine is simulated. The time-dependent variations of engine parameters such as power, rotational speed, fuel, temperature, and guide vane angles are compared with field data. Simulated results are fairly close to the operation data.
Thermomechanical Behavior of 96Sn-4Ag and Castin Alloy
Authors: Neu R. W. , Scott D. T. , Woodmansee M. W.
Published: July 2002

The time- and temperature-dependent deformation behavior of two Sn-Ag base alloys, 96Sn-4Ag and Castin (96.2Sn-2.5Ag-0.8Cu-0.5Sb), used as solder interconnect materials was determined over strain rates ranging from 10−6 s−1 to 10−2 s−1 and temperatures ranging from −55°C–125°C. Uniaxial strain rate jump tests along with isothermal and thermomechanical cyclic tests were conducted. The constitutive behavior of each alloy was modeled with both a simple power law creep equation and the McDowell unified creep-plasticity model. Accumulated deformation under unconstrained thermal cycling was also measured to determine the relative dimensional stability due to internal constraints in the alloy itself. Overall, the Castin alloy appeared to be more stable and was more resistant to inelastic deformation.
The Effect of Solder Paste Volume and Reflow Ambient Atmosphere on Reliability of CBGA Assemblies
Authors: Wu Y. P. , Tu P. L. , Chan Yan C.
Published: July 2002

To investigate the effect of stencil thickness and reflow ambient atmosphere on the reliability of ceramic ball grid array (CBGA) assemblies, three levels of stencil thickness, 0.10, 0.15, and 0.20 mm, were used to print solder paste on printed circuit board (PCB). After the CBGA modules were placed on PCBs, the specimens were divided into two groups, and reflowed in nitrogen and compressed air separately. Properties of the six groups of assemblies, such as shear strength, bending fatigue life, thermal shock cycles, and vibration fatigue life, were tested to find out the optimum assembling process. The results show that assemblies prepared with a stencil 0.15 mm thick yield maximized performance. And the nitrogen ambient atmosphere demonstrates a remarkable effect on improving the fatigue life. Theoretical models are given to qualitatively explain the relationship between the solder joint volume and performance. This work provides a guideline on how to determine the soldering process parameters of CBGA assemblies.
Analysis of Underactuated Mechanical Grippers
Authors: Montambault Serge , Gosselin Cle´ment M.
Published: July 2002

This paper presents the concept of underactuation applied to grippers and mechanical hands. The main objective of this work is the kinematic analysis and design of underactuated mechanisms. First, the kinematic and static modeling of these mechanisms is addressed and a general kinetostatic model is proposed. Then, a two-degree-of-freedom underactuated gripper based on a five-bar planar mechanism is studied in order to illustrate the usefulness of the model in a context of analysis and design.
Experimental Investigation of Thermo-Mechanical Characteristics in Laser-Assisted Machining of Silicon Nitride Ceramics
Authors: Lei S. , Shin Y. C. , Incropera F. P.
Published: July 2002

Laser-assisted machining (LAM) of silicon nitride Si3N4 is evaluated for its potential to become an economically viable process in fabricating precision ceramic parts. On-line measurements of cutting force and workpiece temperature are performed, and tool wear and surface integrity are examined. Tool wear characteristics are determined as a function of workpiece temperature, which is measured on-line using a laser pyrometer. Tool wear/failure mechanisms are characterized using optical microscopy, while application of scanning electron microscopy to heated and machined surfaces, as well as to chips, is used to infer material removal mechanisms and the extent of damage caused by LAM. The sub-surface damage of parts produced by LAM is compared with that of typical ground parts.
Time Optimal Swing-Up Control of Single Pendulum1
Authors: Xu Yongcai , Iwase Masami , Furuta Katsuhisa
Published: July 2002

Swing-up of a rotating type pendulum from the pendant to the inverted state is known to be one of most difficult control problems, since the system is nonlinear, underactuated, and has uncontrollable states. This paper studies a time optimal swing-up control of the pendulum using bounded input. Time optimal control of a nonlinear system can be formulated by Pontryagin’s Maximum Principle, which is, however, hard to compute practically. In this paper, a new computational approach is presented to attain a numerical solution of the time optimal swing-up problem. Time optimal control problem is described as minimization of the achievable time to attain the terminal state under the bounded input amplitude, although algorithms to solve this problem are known to be complicated. Therefore, in this paper, it is shown how the optimal time swing-up control is formulated as an auxiliary problem in that the minimal input amplitude is searched so that the terminal state satisfies a specification at a given time. Through the proposed approach, time optimal control can be solved by nonlinear optimization. Its approach is evaluated by numerical simulations of a simplified pendulum model, is checked satisfying the necessary condition of Maximum Principle, and is experimentally verified using the rotating type pendulum.
High Temperature Solar Absorber Material Measurement Technique
Authors: Bonometti Joseph A. , Hawk Clark W.
Published: July 2002

Basic material properties determine the amount of solar energy that is absorbed, transmitted or reflected and these values will often change with differing temperatures. This investigation developed a new approach to evaluate the material properties (i.e., reflectivity, absorptivity) of a solar absorber wall and experimentally tested the method using sample coupons. The reflectivity was measured both at ambient and elevated temperatures over a range of angles from 0 to 90 degrees. The same experimental data set was used to calculate the sample’s total reflectivity, by uniquely integrating the recorded intensities over a hemisphere. The test methodology uses the incident solar energy as the heating source, while directly measuring the reflected light (an integrated value over all visible wavelengths) and is suitable for test samples over 3,000 K.
Blade Life: A Comparison by Cumulative Damage Theories
Authors: Rao J. S. , Pathak A. , Chawla A.
Published: July 2002

A turbine blade is modeled as a rotating pretwisted beam and subjected to aerodynamic excitation from the flow path interference. The resonant stresses are determined using a modal analysis. With the help of steady steam bending and centrifugal stresses and the dynamic stresses, life estimates are made using the linear and nonlinear cumulative damage theories and a comparison of the results is presented. Based on these results, recommendations are made on the usefulness of different theories for practical application.
Performance of a Residential-Sized GAX Absorption Chiller
Authors: Priedeman Douglas K. , Garrabrant Michael A. , Mathias James A. , Stout Roger E. , Christensen Richard N.
Published: July 2002

This research effort involved experimentally testing an advanced-cycle, ammonia-water absorption chiller with a cooling capacity of 17.6 kW (5 refrigeration tons (RT)). The system was a generator-absorber heat exchange (GAX) cycle and was sized for residential and light commercial use, where very little absorption equipment is currently used. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. The findings of the research were cycle cooling load and coefficient of performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the chiller at essentially full load was measured at 0.68. A simulation of the GAX cycle was performed with a computer program that predicted the heat duties of each component and the cooling load of the cycle. The simulation of the GAX cycle and experimental testing compared closely. Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study consisted of testing a GAX cycle with a COP that approached the target value of 0.70 and identified improvements that must be made to reach the target COP value.
An Input-Output Linearization Approach to the Control of an n-Body Articulated Vehicle
Authors: Bolzern P. , DeSantis R. M. , Locatelli A.
Published: July 2002

The problem of path-tracking for an autonomous vehicle composed of a tractor and n−1 trailers with off-axle hitching is considered in this paper. It is shown that an input-output feedback linearization technique can be adopted both in forward and backward maneuvers, leading to the stabilization of the path-tracking offset dynamics about circular paths. The location of the guide-point needs to be selected according to the direction of motion, and, when moving backward, the off-axle distances must be all positive.
Predicting Product Aesthetic Quality Using Virtual Environments
Authors: Juster Neal P. , Maxfield John , Dew Peter M. , Taylor Stephen , Fitchie Martin , Ion William J. , Zhao Jeff , Thompson Martin
Published: July 2002

This paper describes a previously unreported application of virtual environments, the prediction of product aesthetic quality. Successful prediction of aesthetic quality without the production of a physical prototype requires the integration of a number of “software” models: an assembly model representing the manner in which the product is put together; an environment model providing a real world graphical context for the product; a behavior model representing how the product moves and deforms under use conditions; and a tolerance model representing the allowable variation in the product due to manufacturing variation. This paper presents the results of applying these models within an automotive design and manufacturing process during the development of a new automobile.
Rapid, Wide-Field Measurements of Complex Transient Shell Vibrations
Authors: Motriuk Roman W. , Schmidt Timothy
Published: July 2002

The mapping and evaluation of complex vibrational fields is often highly desirable in the pressure vessel and piping industry. It is also tedious and expensive using conventional technology such as strain gage and accelerometer arrays. This paper describes field and laboratory measurements made with a portable pulsed laser system that instantaneously captures displacement data over areas up to 2 m2, with submicron sensitivity. The results indicate that pulsed holographic or electronic speckle interferometry facilitates the evaluation of nonstationary vibrational fields with significant advantages over conventional techniques. Pulsed interferometry is an effective tool for rapidly determining locations of worst-case dynamic displacements and strains. Initial field measurements at a natural gas pumping station provided an exciting glimpse at both the measurement capability of the pulsed interferometry system and never before seen dynamic responses of turbo-compressor discharge piping. The piping immediate to the compressor discharge nozzle as well as a recycle pipe was investigated at a range of operating conditions. Several characteristic patterns were observed in the instantaneous operating deflection shapes. Most notable were spiral waves progressing both clockwise and counterclockwise relative to the axial flow direction. A “shock,” sudden drop in deformation, presumably caused by instantaneous back pressure, was also captured during an extensive statistical survey. Subsequently, laboratory measurements were made on a pressure vessel built to ASME Code requirements, with various internal fluid and pressure conditions. During shaker excitation, dynamic strains logged from gage rosettes were compared to captured displacements and mode shapes. Interestingly, the ratio of circumferential to axial dynamic strains was found to depend on the operating deflection shape of the vessel. Long, thin antinodes resulted in strain ratios expected for static loading, but short antinodes typical of higher frequency responses were accompanied by significantly increased axial strains. The authors intend to continue investigating the usefulness of pulsed interferometry measurements for the oil and gas industry. It is considered important to further correlate the interferometry measurements with traditional modal analysis and strain measurement techniques. Follow-up efforts will also attempt to quantify the relationship between wide-area vibrations and noise emanation from piping systems. An additional goal is to increase the efficiency of noise abatement solutions using insight obtained from wide-field vibration measurements.
On the Thermal Interaction Between an Isothermal Cylinder and Its Isothermal Enclosure for Cylinder Rayleigh Numbers of Order 104
Authors: Newport D. T. , Dalton T. M. , Davies M. R. D. , Whelan M. , Forno C.
Published: July 2002

An experimental investigation is made of the thermal interaction between a horizontal isothermal cylinder centrally located in a water-cooled isothermal cubical enclosure. The study is restricted to laminar flow and cylinder Rayleigh numbers of order 104. The application of interest is the cooling of electronic systems. This field is currently lacking in techniques that can measure the complex fluid phenomena encountered in real systems. The paper therefore begins with an experimental review of interferometry to assess its applicability as a potential solution to this need. Based on this review, a real time Digital Moire´ Subtraction interferometer is used to measure temperature profiles, and local Nusselt number distributions in two regions of interest: the plume impingement on the ceiling of the enclosure, and the upper corner region of the enclosure. A Mach-Zehnder interferometer is used for the cylinder Nusselt number distribution. Results are compared both qualitatively and quantitatively with a numerical simulation run on a commercial CFD package widely used for electronic system temperature predictions. The paper gives considerable insight into the nature of the enclosure heat transfer and an indication of the accuracy of a widely used predictive code.
A Scalable Multi-Functional Thermal Test Chip Family: Design and Evaluation
Authors: Benedek Zs. , Courtois B. , Farkas G. , Kolla´r E. , Mir S. , Poppe A. , Rencz M. , Sze´kely V. , Torki K.
Published: July 2002

Nowadays, thermal characterization of IC packages and packaging technologies is becoming a key task in thermal engineering. To support this by measurements, we developed a family of thermal test chips that allow a wide range of possible applications. Our chips are based on the same basic cell that is mainly covered by dissipating resistors and also contains a temperature sensor. These basic cells are organized into arrays of different size. The arrays are designed such that further “super arrays” can also be built for tiling up larger package cavities. The first members of the family, TMC9 and TMC81, have been manufactured. Our measurements show that the goals aimed at the design have been achieved.