bluuebunny/crossref_metadata_2025 huggingface dataset:
Contemporary Approaches to the Literature of the First World War: A Critical Survey
Authors: Scutts Joanna
Published: June 2006

Contemporary studies of First World War literature share a sense of common ancestry in Paul Fussell’s 1975 study The Great War and Modern Memory, in which the author proclaims irony as the defining mode of war writing, and identifies the archetypal writer as a young, upper‐class English infantry officer. Post‐Fussellian critics worked first to expand this narrow canon, primarily through the rediscovery and evaluation of neglected writing by women. Critics also began to question the war canon’s assumed separation from mainstream modernism, and argued that these two strands of postwar literary production were in fact fundamentally entwined. In the 1990s, cultural studies approaches generated productive readings of the war literature in its wider context, alongside non‐fiction and ephemeral writings, non‐literary artistic productions, and public memorial efforts. This interdisciplinary approach was complemented by a new internationalism: comparative historiography, championed by Jay Winter, aimed to correct the mistaken assumptions that arose from a conventional focus on the political and cultural affairs of any single country. Taken together, these trends are evidence that the current priority in this ever‐expanding field is to acknowledge and explore the diversity of the war experience.
Guidelines for Family Business Boards of Directors
Authors: Lane Suzanne , Astrachan Joseph , Keyt Andrew , McMillan Kristi
Published: June 2006

Governance reform of publicly held corporations is an important topic these days, but a critical subtext has been missing from this often searing debate. Namely, what is the significance of these governance reforms, de jure and de facto, for the publicly held corporation's distant, smaller, but economically robust brethren—namely, the closely held, family-owned business? Should these family-owned entities be held to the same governance guidelines and standards that apply to those firms making up the ranks of the Fortune 500, for example? To put it another way, does one size fit all? We caution that many of the most popularized corporate governance practices may be detrimental to family businesses. Many of these recommendations may harm family unity or might be too complex for private firms, and many are applicable only to very large, public companies with dispersed ownership. Popular corporate governance practices are focused toward a market model of corporate governance, found prevalently in the United States and United Kingdom, which involves companies with a widely dispersed shareholder base and a majority of independent, outside board members. In contrast, the typical family-owned business exhibits characteristics of the control model of corporate governance, found prevalently in continental Europe, Latin America, and Asia, which involves companies with a concentrated shareholder base and family member “insiders” active in management and the board. As a result of these differences, many of the new laws and recommendations may actually be harmful to family-owned businesses.
Achieving Sustained Competitive Advantage: A Family Capital Theory
Authors: Hoffman James , Hoelscher Mark , Sorenson Ritch
Published: June 2006

Although it has been long asserted that family businesses hold advantages over nonfamily businesses, to date, there have been very few theories developed as to exactly why family businesses hold competitive advantages over nonfamily businesses. This article introduces the concept of family capital and proposes that family capital has potential impact on business performance. Specifically, this article suggests that family businesses with high levels of family capital possibly do hold a sustained competitive advantage over family businesses with low levels of family capital and/or nonfamily businesses.
State‐of‐the‐Evidence Reviews: Advantages and Challenges of Including Grey Literature
Authors: Benzies Karen M. , Premji Shahirose , Hayden K. Alix , Serrett Karen
Published: June 2006

Background: Increasingly, health policy decision‐makers and professionals are turning to research‐based evidence to support decisions about policy and practice. Systematic reviews are useful for gathering, summarizing, and synthesizing published and unpublished research about clearly defined interventions. State‐of‐the‐evidence reviews are broader than traditional systematic reviews and may include not only published and unpublished research, but also published and unpublished non‐research literature. Decisions about whether to include this “grey literature” in a review are challenging and lead to many questions about whether the advantages outweigh the challenges.

Aims: The primary purpose of this article is to describe what constitutes grey literature, and methods to locate it and assess its quality. The secondary purpose is to discuss the core issues to consider when making decisions to include grey literature in a state‐of‐the‐evidence review.

Methods: A recent state‐of‐the‐evidence review is used as an exemplar to present advantages and challenges related to including grey literature in a review.

Results: Despite the challenges, in the exemplar, inclusion of grey literature was useful to validate the results of a research‐based literature search.

Conclusion: Decisions about whether to include grey literature in a state‐of‐the‐evidence review are complex. A checklist to assist in decision‐making was created as a tool to assist the researcher in determining whether it is advantageous to include grey literature in a review.

Worldviews on Evidence‐Based Nursing 2006; 3(2):55–61.
Constructing a New Approach to Developing Evidence‐Based Practice with Nurses and Older People
Authors: Tolson Debbie , Irene Schofield , Booth Jo , Kelly Timothy B. , James Louise
Published: June 2006

Purpose: Providing evidence‐based nursing care to older people is central to the international development agenda. This paper is a report on the first 5 years (2000–2005) of a participatory research project, the purpose of which was to collaborate with practitioners and older people to develop approaches to promote the attainment of evidence‐based nursing care across Scotland.

Design: Many theoretical influences shaped the design of this action research study including realistic evaluation, participatory social learning theory, and descriptions of communities of practice. Multiple methods of data collection were used during four action cycles. The inaugural community of practice comprised 30 nurses, a second group of 30 nurses joined midway, followed by a third group of 15 nurses, and finally, an older person‐carer community of 21 members was established.

Findings: Project outputs included the construction of an internet‐based, practice‐development college. A procedural model for developing and demonstrating care guidance drawn from a diversity of evidence and reflective of an agreed set of principles was piloted and endorsed by the national standard setting agency. A preliminary version of a promising approach to practice development, “the Caledonian Model,” was delineated for future testing and refinement.

Conclusion: This work indicates the merits of using participatory research to find solutions to the challenge of promoting evidence‐based practice. Evaluation data suggest that in combination, the approaches developed in this project empower nurses to work with older people to champion developments even in seemingly unfavorable conditions.

Worldviews on Evidence‐Based Nursing 2006; 3(2):62–72.
An Integrative Research Review: Effective School‐Based Childhood Overweight Interventions
Authors: Cole Kristen , Waldrop Julee , D’Auria Jennifer , Garner Heather
Published: June 2006

PURPOSE.  To describe theoretical and methodological characteristics of effective school‐based interventions that used healthy lifestyle education, dietary habits, and/or physical activity in children ages 4 to 14.

DESIGN.  Integrative research review.

METHODS.  Stetler's model of research utilization.

RESULTS.  Social Cognitive Theory was the stated or implied theory in eight of the 10 studies. Healthy lifestyle education was initiated in nine studies, dietary habits in four, and physical activity in eight. Four of the 10 studies used a combination of all three interventions; three used a combination of two interventions; and three used only one intervention.

PRACTICE IMPLICATIONS.  Social Cognitive Theory and the role of social learning are useful when designing interventions for preventing and treating childhood overweight.
Comparison of Rotordynamic Analysis Predictions With the Test Response of Simple Gas Hybrid Bearings for Oil Free Turbomachinery
Authors: Osborne Deborah A. , San Andre´s Luis
Published: June 2006

Current applications of gas film bearings in high-speed oil-free microturbomachinery (<0.4 MW) require calibrated predictive tools to successfully deploy their application to mass-produced systems, for example, oil-free turbochargers. The present investigation details the linear rotordynamic analysis of a test rotor supported on externally pressurized gas bearings. Model predictions are compared with the test rotordynamic response determined through comprehensive experiments conducted on a small rotor supported on three lobed hybrid (hydrostatic/hydrodynamic) rigid gas bearings. Predictions for the rotor-bearing system synchronous response to imbalance show good agreement with measurements during rotor coastdowns, and manifest a decrease in damping ratio as the level of external pressurization increases. The rotor-bearing eigenvalue analysis forwards natural frequencies in accordance with the measurements, and null damping ratios evidence the threshold speeds of rotordynamic instability. Estimated whirl frequency ratios are typically 50% of rotor speed, thus predicting subsynchronous instabilities at lower rotor speeds than found experimentally when increasing the magnitude of feed pressurization. Rationale asserting the nature of the discrepancies calls for further analysis.
Reliability Indexed Sensor Fusion and Its Application to Vehicle Velocity Estimation
Authors: Lee Hyeongcheol
Published: June 2006

Reliability indexed sensor fusion (RISF) is a new estimation techique which uses process and measurement noise covariances as the reliability index in an adaptive Kalman filter framework. In RISF, noise covariances are assumed to be highly uncertain and determined by engineering knowledge. The uniform boundedness of the RISF with incorrect noise covariances is proved in the sense that the error covariance is bounded if specified conditions are satisfied. The RISF technique is then applied to the vehicle longitudinal and lateral velocity estimation. Multiple sensors, such as the whell speed sensors, the accelerometers, the yaw rate sensor, and the steering angle sensor, are used for the velocity estimation. Test results show the accuracy of the vehicle velocity estimation by the proposed RISF technique.
Chemical-Looping Combustion for Combined Cycles With CO2 Capture
Authors: Consonni Stefano , Lozza Giovanni , Pelliccia Giampaolo , Rossini Stefano , Saviano Francesco
Published: June 2006

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is carried out through an intermediate agent—a metal oxide—circulated across two fluidized bed reactors: a reduction reactor, where an endothermic reaction reduces the metal oxide and oxidizes the fuel, and an oxidation reactor, where an exothermic reaction oxidizes the metal oxide in air. Overall, the system carries out the same job of a conventional combustor, with the fundamental advantage of segregating the oxidation products (CO2 and H2O) into an output flow free of nitrogen and excess oxygen. The flow exiting the reduction reactor consists of water and CO2, the latter readily available for liquefaction, transport and long-term storage. The hot, vitiated air from the oxidation reactor is the means to produce power through a thermodynamic cycle. This paper reports of a study supported by the ENI group to assess the potential of the integration between CLC and combined gas-steam power cycles. More specifically, we focus on four issues: (i) optimization of plant configuration; (ii) prediction of overall efficiency; (iii) use of commercial gas turbines; (iv) preliminary economic estimates. The CLC system is based on iron oxides which, to maintain their physical characteristics, must operate below 900–1000°C. Given the crucial importance of the temperature of the vitiated air generated by CLC on the performance of the combined cycle, we consider two options: (i) “unfired” systems, where natural gas is fed only to the CLC system, (ii) “fired” systems, where the vitiated air is supplementary fired to reach gas turbine inlet temperatures ranging 1000–1200°C. Results show that unfired configurations with maximum process temperature 850–1050°C and zero emissions reach net LHV plant efficiencies ranging 43%–48%. Fired cycles where temperature is raised from 850 to 1200°C by supplementary firing can achieve 52% net LHV efficiency with CO2 emission about one half of those of a state-of-the-art combined cycles. Fired configurations allow significant capital cost and fuel cost savings compared to unfired configurations; however, a carbon tax high enough to make them attractive (close to 50 €/ton) would undermine these advantages.
GTPOM: Thermo-Economic Optimization of Whole Gas Turbine Plant
Authors: Knight Richard , Obana Mitsuru , von Wowern Christer , Mitakakis Athanasios , Perz Erhard , Assadi Mohsen , Mo¨ller Bjo¨rn F. , Sen Pratyush , Potts Ian , Traverso Alberto , Torbidoni Leonardo
Published: June 2006

Trends towards distributed power generation and the deregulation of energy markets are increasing the requirement for software tools that optimize power generation plant design and operation. In this context, this paper describes the GTPOM (thermo-economic optimization of whole gas turbine plant) European project, funded in part through the European Commission’s 5th Framework Programme, focusing on the development and demonstration of an original software tool for the thermo-economic analysis and optimization of conventional and advanced energy systems based on gas turbine plant. PSEconomy, the software tool developed during the GTPOM project, provides a thermo-economic optimization capability for advanced and more-conventional energy systems, enabling the complex trade-offs between system performance and installed costs to be determined for different operational duties and market scenarios. Furthermore, the code is capable of determining the potential benefits of innovative cycles or layout modifications to existing plants compared with current plant configurations. The economic assessment is performed through a complete through-life cycle cost analysis, which includes the total capital cost of the plant, the cost of fuel, O&M costs and the expected revenues from the sale of power and heat. The optimization process, carried out with a GA-based algorithm, is able to pursue different objective functions as specified by the User. These include system efficiency, through-life cost of electricity and through-life internal rate of return. Three case studies demonstrating the capabilities of the new tool are presented in this paper, covering a conventional combined cycle system, a biomass plant and a CO2 sequestration gas turbine cycle. The software code is now commercially available and is expected to provide significant advantages in the near and long-term development of energy cycles.
Supplementary Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the Industrial Formulation IAPWS-IF97 for Water and Steam
Authors: Kretzschmar H.-J. , Cooper J. R. , Dittmann A. , Friend D. G. , Gallagher J. S. , Knobloch K. , Mareš R. , Miyagawa K. , Stöcker I. , Trübenbach J. , Wagner W. , Willkommen Th.
Published: June 2006

In modeling steam power cycles, thermodynamic properties as functions of the variables enthalpy and entropy are required in the liquid and the vapor regions. It is difficult to perform these calculations with IAPWS-IF97, because they require two-dimensional iterations calculated from the IAPWS-IF97 fundamental equations. While these calculations are not frequently required, the relatively large computing time required for two-dimensional iteration can be significant in process modeling. Therefore, the International Association for the Properties of Water and Steam (IAPWS) adopted backward equations for pressure as a function of enthalpy and entropy p(h,s) as a supplement to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam (IAPWS-IF97) in 2001. These p(h,s) equations are valid in the liquid region 1 and the vapor region 2. With pressure p, temperature T(h,s) can be calculated from the IAPWS-IF97 backward equations T(p,h). By using the p(h,s) equations, the two dimensional iterations of the IAPWS-IF97 basic equations can be avoided. The numerical consistency of pressure and temperature obtained in this way is sufficient for most heat cycle calculations. This paper summarizes the need and the requirements for the p(h,s) equations and gives complete numerical information about the equations. Moreover, the achieved quality of the equations and their use in the calculation of the backward function T(h,s) is presented. The three aspects, numerical consistency with the IAPWS-IF97 basic equations, consistency along subregion boundaries, and computational speed important for industrial use are discussed.
Analysis of Oil Film Thickness and Heat Transfer on a Piston Ring of a Diesel Engine: Effect of Lubricant Viscosity
Authors: Harigaya Yasuo , Suzuki Michiyoshi , Toda Fujio , Takiguchi Masaaki
Published: June 2006

The effect of lubricant viscosity on the temperature and thickness of oil film on a piston ring in a diesel engine was analyzed by using unsteady state thermohydrodynamic lubrication analysis, i.e., Reynolds equation and an unsteady state two-dimensional energy equation with heat generated from viscous dissipation. The oil film viscosity was then estimated by using the mean oil film temperature and the shear rate for multigrade oils. Since the viscosity for multigrade oils is affected by both the oil film temperature and shear rate, the viscosity becomes lower as the shear rate between the ring and liner becomes higher. Under low load conditions, the viscosity decreases due to temperature rise and shear rate, while under higher load conditions, the decrease in viscosity, is attributed only to the shear rate. The oil film thickness between the ring and liner decreases with a decrease of the oil viscosity. The oil film thickness calculated by using the viscosity estimated by both the shear rate and the oil film temperature gave the smallest values. For multigrade oils, the viscosity estimation method using both the mean oil film temperature and shear rate is the most suitable one to predict the oil film thickness. Moreover, the heat transfer at ring and liner surfaces was examined.
A Numerical Simulation Capability for Analysis of Aircraft Inlet-Engine Compatibility
Authors: Hale Alan , Davis Milt , Sirbaugh Jim
Published: June 2006

Two primary aircraft propulsion subsystems are the inlet and the engine. Traditionally these subsystems have been designed, analyzed, and tested as isolated systems. The interaction between the subsystems is modeled primarily through evaluating inlet distortion in an inlet test and then simulating this distortion in engine tests via screens or similar devices. Recently, it has been recognized that significant improvements in both performance and operability can be realized when both the inlet and the engine are designed with full knowledge of the other. In this paper, a computational tool called Turbine Engine Analysis Compressor Code is used to evaluate the effect of inlet distortion on a three-stage military fan. This three-stage military fan is further connected to an F-16 inlet and forebody operating at an angle of attack and sideslip to demonstrate the effect of inlet distortion generated by flight maneuvers. The computational approach of simulating an integrated inlet-engine system is expected to provide additional insight over evaluating the components separately.
Bump-Type Foil Bearing Structural Stiffness: Experiments and
Predictions
Authors: Rubio Dario , San Andrés Luis
Published: June 2006

Gas foil bearings (FB) satisfy many of the requirements noted for novel oil-free turbomachinery. However, FB design remains largely empirical, in spite of successful commercial applications. The mechanical structural characteristics of foil bearings, namely stiffness and damping, have been largely ignored in the archival literature. Four commercial bump-type foil bearings were acquired to measure their load capacity under conditions of no shaft rotation. The test bearings contain a single Teflon-coated foil supported on 25 bumps. The nominal radial clearance is 0.036mm for a 38mm journal. A simple test setup was assembled to measure the FB deflections resulting from static loads. The tests were conducted with three shafts of increasing diameter to induce a degree of preload into the FB structure. Static measurements show nonlinear FB deflections, varying with the orientation of the load relative to the foil spot weld. Loading and unloading tests evidence hysteresis. The FB structural stiffness increases as the bumps-foil radial deflection increases (hardening effect). The assembly preload results in notable stiffness changes, in particular for small radial loads. A simple analytical model assembles individual bump stiffnesses and renders predictions for the FB structural stiffness as a function of the bump geometry and material, dry-friction coefficient, load orientation, clearance and preload. The model predicts well the test data, including the hardening effect. The uncertainty in the actual clearance (gap) upon assembly of a shaft into a FB affects most of the predictions.
Effects of Manufacturing Tolerances on Regenerative Exchanger Number of Transfer Units and Entropy Generation
Authors: Shang Wei , Besant Robert W.
Published: June 2006

A prime concern with the design of ultra-compact heat exchangers is the impact on performance of flow channel variations due to flow channel hydraulic diameter variations caused by manufacturing tolerances. This paper uses analytical methods to show that as the standard deviation in flow channel sizes, caused by manufacturing tolerances in a rotary regenerative exchanger, is increased compared to the average flow channel diameter the effective number of transfer units decreases. Depending on the operating conditions, the entropy generation number either increases or decreases with increasing flow channel size variations. These findings extend previous findings that showed that flow channel variations cause lower pressure drops and effectiveness.
A Modular Code for Real Time Dynamic Simulation of Gas Turbines in Simulink
Authors: Camporeale S. M. , Fortunato B. , Mastrovito M.
Published: June 2006

A high-fidelity real-time simulation code based on a lumped, nonlinear representation of gas turbine components is presented. The code is a general-purpose simulation software environment useful for setting up and testing control equipments. The mathematical model and the numerical procedure are specially developed in order to efficiently solve the set of algebraic and ordinary differential equations that describe the dynamic behavior of gas turbine engines. For high-fidelity purposes, the mathematical model takes into account the actual composition of the working gases and the variation of the specific heats with the temperature, including a stage-by-stage model of the air-cooled expansion. The paper presents the model and the adopted solver procedure. The code, developed in Matlab-Simulink using an object-oriented approach, is flexible and can be easily adapted to any kind of plant configuration. Simulation tests of the transients after load rejection have been carried out for a single-shaft heavy-duty gas turbine and a double-shaft aero-derivative industrial engine. Time plots of the main variables that describe the gas turbine dynamic behavior are shown and the results regarding the computational time per time step are discussed.
Design Study of a Humidification Tower for the Advanced Humid Air Turbine System
Authors: Araki Hidefumi , Higuchi Shinichi , Marushima Shinya , Hatamiya Shigeo
Published: June 2006

The advanced humid air turbine (AHAT) system, which can be equipped with a heavy-duty, single-shaft gas turbine, aims at high efficiency equal to that of the HAT system. Instead of an intercooler, a WAC (water atomization cooling) system is used to reduce compressor work. The characteristics of a humidification tower (a saturator), which is used as a humidifier for the AHAT system, were studied. The required packing height and the exit water temperature from the humidification tower were analyzed for five virtual gas turbine systems with different capacities (1, 3.2, 10, 32, and 100MW) and pressure ratios (π=8, 12, 16, 20, and 24). Thermal efficiency of the system was compared with that of a simple cycle and a recuperative cycle with and without the WAC system. When the packing height of the humidification tower was changed, the required size varied for the three heat exchangers around the humidification tower (a recuperator, an economizer, and an air cooler). The packing height with which the sum total of the size of the packing and these heat exchangers became a minimum was 1m for the lowest pressure ratio case, and 6m for the highest pressure ratio case.
Safe Dynamic Operation of a Simple SOFC/GT Hybrid System
Authors: Stiller Christoph , Thorud Bjørn , Bolland Olav
Published: June 2006

The current work shall prove the feasibility and show methods to safely operate a simple SOFC/GT hybrid system under part-load and load change. Dynamic and steady state studies on a detailed model of a SOFC/GT hybrid system have been performed. A design point is selected. Steady-state part-load behavior is shown by means of performance maps. An operation line with fairly constant temperatures in the upper part-load regime and an almost constant efficiency down to approximately 25% part-load is proposed and the dynamic behavior of the system on rapid load changes is investigated. Strategies for the dynamic controlling of power by manipulating fuel flow are shown that might enable the system to adapt to a new setpoint power quite quickly.
The Influence of In Situ Reheat on Turbine-Combustor Performance
Authors: Chambers Steven , Flitan Horia , Cizmas Paul , Bachovchin Dennis , Lippert Thomas , Little David
Published: June 2006

This paper presents a numerical and experimental investigation of the in situ reheat necessary for the development of a turbine-combustor. The flow and combustion were modeled by the Reynolds-averaged Navier-Stokes equations coupled with the species conservation equations. The chemistry model used herein was a two-step, global, finite rate combustion model for methane and combustion gases. A numerical simulation was used to investigate the validity of the combustion model by comparing the numerical results against experimental data obtained for an isolated vane with fuel injection at its trailing edge. The numerical investigation was then used to explore the unsteady transport phenomena in a four-stage turbine-combustor. In situ reheat simulations investigated the influence of various fuel injection parameters on power increase, airfoil temperature variation, and turbine blade loading. The in situ reheat decreased the power of the first stage, but increased more the power of the following stages, such that the power of the turbine increased between 2.8% and 5.1%, depending on the parameters of the fuel injection. The largest blade excitation in the turbine-combustor corresponded to the fourth-stage rotor, with or without combustion. In all cases analyzed, the highest excitation corresponded to the first blade passing frequency.
Identification of Frequency-Dependent Parameters in a Flexible Rotor System
Authors: Wang Qingyu , Maslen Eric H.
Published: June 2006

In a rotor-bearing system, there are usually some under- or unmodeled dynamic components that are considered frequency dependent, such as foundations, bearings, and seals. This paper presents a method to identify the dynamic behavior of these components using an otherwise accurate engineering model of the system in combination with available measurements of system frequency response functions. The approach permits treatment of flexible rotors and allows that the system test excitations and measurement sensors are not collocated. Because all engineering models contain some residual error and all measurements incorporate an element of noise or uncertainty, the quality of the identified parameters must be estimated. This paper introduces application of μ analysis to solve this problem, resulting in acceptable solution time and hard guarantees of solution reliability. Two illustrative examples are provided, showing that the presented approach is an efficient method to identify and bound these parameters.
A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics
Authors: Pachidis Vassilios , Pilidis Pericles , Talhouarn Fabien , Kalfas Anestis , Templalexis Ioannis
Published: June 2006

Background . This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.
Study on Biomass Pyrolysis Kinetics
Authors: Zhang Xiaodong , Xu Min , Sun Rongfeng , Sun Li
Published: June 2006

Pyrolysis is the most fundamental process in thermal chemical conversion of biomass, and pyrolysis kinetic analysis is valuable for the in-depth exploration of process mechanisms. On the basis of thermal gravity analysis of different kinds of biomass feedstock, thermal kinetics analysis was performed to analyze the pyrolysis behavior of biomass. With the apparent kinetic parameters derived, a kinetic model was proposed for the main reaction section of biomass pyrolysis process. The pyrolysis characteristics of three kinds of biomass material were compared in view of corresponding biochemical constitution. Through model simulation of different pyrolysis processes, the diversity in pyrolysis behavior of different kinds of biomass feedstock was analyzed and pyrolysis mechanism discussed. The results derived are useful for the development and optimization of biomass thermal chemical conversion technology.
Brush Seal Temperature Distribution Analysis
Authors: Dogu Yahya , Aksit Mahmut F.
Published: June 2006

Brush seals are designed to survive transient rotor rubs. Inherent brush seal flexibility reduces frictional heat generation. However, high surface speeds combined with thin rotor sections may result in local hot spots. Considering large surface area and accelerated oxidation rates, frictional heat at bristle tips is another major concern especially in challenging high-temperature applications. This study investigates temperature distribution in a brush seal as a function of frictional heat generation at bristle tips. The two-dimensional axisymmetric computational fluid dynamics (CFD) analysis includes the permeable bristle pack as a porous medium allowing fluid flow throughout the bristle matrix. In addition to effective flow resistance coefficients, isotropic effective thermal conductivity as a function of temperature is defined for the bristle pack. Employing a fin approach for a single bristle, a theoretical analysis has been developed after outlining the brush seal heat transfer mechanism. Theoretical and CFD analysis results are compared. To ensure coverage for various seal designs and operating conditions, several frictional heat input cases corresponding to different seal stiffness values have been studied. Frictional heat generation is outlined to introduce a practical heat flux input into the analysis model. Effect of seal stiffness on nominal bristle tip temperature has been evaluated. Analyses show a steep temperature rise close to bristle tips that diminishes further away. Heat flux conducted through the bristles dissipates into the flow by a strong convection at the fence-height region.
On LMI-Based Optimization of Vibration and Stability in Rotor System Design
Authors: Cole Matthew O. T. , Wongratanaphisan Theeraphong , Keogh Patrick S.
Published: June 2006

This paper considers optimization of rotor system design using stability and vibration response criteria. The initial premise of the study is that the effect of certain design changes can be parametrized in a rotor dynamic model through their influence on the system matrices obtained by finite element modeling. A suitable vibration response measure is derived by considering an unknown axial distribution of unbalanced components having bounded magnitude. It is shown that the worst-case unbalanced response is given by an absolute row-sum norm of the system frequency response matrix. The minimization of this norm is treated through the formulation of a set of linear matrix inequalities that can also incorporate design parameter constraints and stability criteria. The formulation can also be extended to cover uncertain or time-varying system dynamics arising, for example, due to speed-dependent bearing coefficients or gyroscopic effects. Numerical solution of the matrix inequalities is tackled using an iterative method that involves standard convex optimization routines. The method is applied in a case study that considers the optimal selection of bearing support stiffness and damping levels to minimize the worst-case vibration of a flexible rotor over a finite speed range. The main restriction in the application of the method is found to be the slow convergence of the numerical routines that occurs with high-order models and/or high problem complexity.
Aerodynamic Instability and Life-Limiting Effects of Inlet and Interstage Water Injection Into Gas Turbines
Authors: Brun Klaus , Kurz Rainer , Simmons Harold R.
Published: June 2006

Gas turbine power enhancement technologies, such as inlet fogging, interstage water injection, saturation cooling, inlet chillers, and combustor injection, are being employed by end users without evaluating the potentially negative effects these devices may have on the operational integrity of the gas turbine. Particularly, the effect of these add-on devices, off-design operating conditions, nonstandard fuels, and compressor degradation∕fouling on the gas turbine’s axial compressor surge margin and aerodynamic stability is often overlooked. Nonetheless, compressor aerodynamic instabilities caused by these factors can be directly linked to blade high-cycle fatigue and subsequent catastrophic gas turbine failure; i.e., a careful analysis should always proceed the application of power enhancement devices, especially if the gas turbine is operated at extreme conditions, uses older internal parts that are degraded and weakened, or uses nonstandard fuels. This paper discusses a simplified method to evaluate the principal factors that affect the aerodynamic stability of a single-shaft gas turbine’s axial compressor. As an example, the method is applied to a frame-type gas turbine and results are presented. These results show that inlet cooling alone will not cause gas turbine aerodynamic instabilities, but that it can be a contributing factor if for other reasons the machine’s surge margin is already slim. The approach described herein can be employed to identify high-risk applications and bound the gas turbine operating regions to limit the risk of blade life reducing aerodynamic instability and potential catastrophic failure.
Enhancing Flow Field Measurements Through Adaptive Multidimensional Data Sampling
Authors: Franken Arnoud R. C. , Ivey Paul C.
Published: June 2006

A way to gain insight into the flow field conditions in turbomachinery is by carrying out a series of point measurements in a cross section of the flow, for example, with a miniature multihole pressure probe. A problem commonly encountered in situations like these is the selection of a suitable measurement grid layout and density for obtaining all essential information in a cost-effective and timely manner. In order to achieve the latter, a novel adaptive multidimensional data sampling technique has been developed at Cranfield University. This paper describes the underlying principles of this technique, the algorithms utilized, and the results obtained during its successful application to data sets of two different flow fields in a high-speed research compressor.
Nominal and Robust Feedforward Design With Time Domain Constraints Applied to a Wafer Stage
Authors: Gelder Edgar de , Wal Marc van de , Scherer Carsten , Hol Camile , Bosgra Okko
Published: June 2006

A new method is proposed to design a feedforward controller for electromechanical servo systems. The settling time is minimized by iteratively solving a linear programming problem. A bound on the amplitude of the feedforward control signal can be imposed and the McMillan degree of the controller can be fixed a priori. We choose Laguerre basis functions for the feedforward filter. Since finding the optimal pole location is very difficult, we present a computationally cheap method to determine the pole location that works well in practice. Furthermore, we show how the method can account for plant and/or reference signal uncertainty. Uncertainty in servo systems can usually be modeled by additive norm-bounded dynamic uncertainty. We will show that, because the feedforward controller is designed for a finite-time interval, we can replace the dynamic uncertainty set by a parametric one. This allows us to design a robust feedforward controller by solving an LMI problem, under the assumption that the transfer functions of the plant, sensitivity, and process sensitivity depend affinely on the uncertainty. If the uncertainty set is a finite set, which is usually the case for uncertainty in the reference profiles, the feedforward design problem reduces to a linear program. These classes of uncertainty sets are well suited to describe variations in the plant and in the reference profile of a wafer stage, which is important for the practical application of the filter. Experimental results for a wafer stage demonstrate the performance improvement compared to a standard inertia feedforward filter.
Torque Control of Electrorheological Fluidic Resistive Actuators for Haptic Vehicular Instrument Controls
Authors: Vitrani M. A. , Nikitczuk J. , Morel G. , Mavroidis C. , Weinberg B.
Published: June 2006

Force-feedback mechanisms have been designed to simplify and enhance the human-vehicle interface. The increase in secondary controls within vehicle cockpits has created a desire for a simpler, more efficient human-vehicle interface. By consolidating various controls into a single, haptic feedback control device, information can be transmitted to the operator, without requiring the driver’s visual attention. In this paper, the experimental closed loop torque control of electro-rheological fluids (ERF) based resistive actuators for haptic applications is performed. ERFs are liquids that respond mechanically to electric fields by changing their properties, such as viscosity and shear stress electroactively. Using the electrically controlled rheological properties of ERFs, we developed resistive-actuators for haptic devices that can resist human operator forces in a controlled and tunable fashion. In this study, the ERF resistive-actuator analytical model is derived and experimentally verified and accurate closed loop torque control is experimentally achieved using a non-linear proportional integral controller with a feedforward loop.
Feedback Control of Braking Deceleration on Railway Vehicle
Authors: Nankyo Masanobu , Ishihara Tadashi , Inooka Hikaru
Published: June 2006

An increase of the deceleration in high-speed and high-density train operations degrades riding comfort and frequently causes wheel skids. This requires an introduction of the control technology to upgrade the control performance of brake systems on railway vehicles. We are now studying control methods for a mechanical brake that uses friction and pneumatic pressure, including nonlinear elements as the basis of a brake force. Furthermore, the system itself has certain “dead time,” which is not negligible and makes control difficult. One of our targets is to develop a brake control device that can control the deceleration in accordance with a decelerating pattern that optimizes the riding comfort of trains and prevents wheel skids. In this paper, a design method of the controller for the deceleration tracking control and the system compensating the dead time are proposed. Finally, the effects of them are confirmed through computer simulations and experimental results on a dynamo test stand.
Modeling and Analysis of Automatic Transmission Engagement
Dynamics-Nonlinear Case Including Validation
Authors: Deur Joško , Asgari Jahan , Hrovat Davor
Published: June 2006

A typical control-oriented automatic transmission model does not include some mostly nonlinear effects such as transmission component friction and backlash, Stribeck clutch friction, clutch drag, and engine block dynamics. It is shown in this paper that such a model cannot provide an accurate description of the power train dynamics during park/reverse and park/drive engagements. An analysis of the influence of various nonlinear effects on the engagement dynamic behavior is presented. The relevant nonlinear effects are incorporated in the basic power train model. The extended model is experimentally validated for typical engagement operating modes.
Active Vibration Control of a Flexible Beam Using a Buckling-Type End Force
Authors: Nudehi Shahin , Mukherjee Ranjan , Shaw Steven W.
Published: June 2006

In this paper, we explore the use of end forces for vibration control in structural elements. The process involves vibration measurement and observer-based estimation of modal amplitudes, which are used to determine when to apply an end load such that it will remove vibration energy from the structure. For this study, we consider transverse vibration of a cantilever beam with a buckling-type end load that can be switched between two values, both of which are below the buckling load. The stability of the control system is proven using Lyapunov stability theory and its effectiveness is demonstrated using simulations and physical experiments. It is shown that the effectiveness of the approach is affected by the bandwidth of the actuator and the attendant characteristics of the filter, the level of the control force, and the level of bias in the end force. The experiments employ a beam fitted with a cable mechanism and motor for applying the end force, and a piezoelectric patch for taking vibration measurements. It is shown that the first two modes of the beam, whose natural frequencies are less than the bandwidth of the motor, are very effectively controlled by the proposed scheme.
Neuro-Adaptive Friction Compensation for Single-Link Flexible Robots Using Serial-Gray-Box Modeling Strategy
Authors: Bazaei Ali , Majd Vahid Johari
Published: June 2006

In this paper a previously offered black-box filtered-error neural-approximation-based control method for singularly perturbed flexible-link arms (FLA) is extended to a serial-gray-box method that assumes only the friction torques as unknown functions. Unlike the former method the knowledge of the unknown part is not used in design implementation of the fast control component. Because the neural network weights are updated adaptively the gray-box friction compensation method is applicable even when the friction functions change with time. Moreover, due to incorporation of the available first-principles knowledge into the control law the method exhibits dimensional extrapolation property with respect to nonfrictional measurable parameters of the plant. The capability of the gray-box method in the presence of static friction unmodeled dynamics are examined. Simulation results show that the proposed gray-box-based method provides better control modeling performances with less number of integrators in comparison with the black-box-based method. A procedure for determination of the parameters of the distributed mass-spring model is offered closed-form exact solutions for the equivalent deflection angle the spring coefficient the slope of the flexible-mode friction characteristic are derived. The gray-box method also works better than a newly developed Lyapunov-type controller which can be regarded as a robust control schema.
Nondiagonal QFT Controller Design for a Three-Input Three-Output Industrial Furnace
Authors: Garcia-Sanz M. , Barreras M.
Published: June 2006

This paper addresses the temperature control of a three-input (power supplies) three-output (temperature sensors) industrial furnace used to manufacture large composite pieces. Due to the multivariable condition of the process, the strong interaction between the three control loops and the presence of model uncertainties, a sequential design methodology based on quantitative feedback theory is proposed to design the controllers. The methodology derives a full matrix compensator that improves reliability, stability, and control. It not only copes with furnace model uncertainties but also enhances the reference tracking and the homogeneousness of the composite piece temperature while minimizing the coupling effects among the furnace zones and the operating costs.