bluuebunny/crossref_metadata_2025 huggingface dataset:
Cogeneration: History, Current Status, and Future Challenges
Authors: Aung K.
Published: May 2008

Cogeneration is defined as the sequential production of thermal and electrical energy from a single fuel source. Increasing costs of fuel and energy, together with the concerns for the environment due to pollutant emissions are driving factors for the implementation of cogeneration in industries. This paper discusses the history, current status and future of cogeneration. The discussion of cogeneration is based on the prime movers used in the cogeneration systems, and two case studies are provided as examples of the application of cogeneration in manufacturing and industrial plants.
Impact on Overall Efficiency of Component Efficiency Increases for an Existing Thermal Electrical Generating Station
Authors: Rosen Marc A.
Published: May 2008

Most electrical generating utilities are striving to improve the efficiencies of their existing thermal electric generating stations, many of which are old. Exergy methods have been shown to provide meaningful insights that can assist in increasing the efficiency of conventional coal-to-electricity technologies. Here, exergy analysis is used to assess measures for improving the efficiencies of coal-fired electrical generating stations. This scope of the study is limited to minor practical improvements, which can be undertaken with limited effort and cost and are not overly complex. The plant considered is the coal-fired Nanticoke Generating Station (GS) in Ontario, Canada. The findings suggest that the results of exergy analyses should be used, along with other pertinent information, to guide efficiency improvement efforts for thermal generating stations. Also, efficiency improvement efforts should focus on plant components responsible for the largest exergy losses: the steam generator (where large losses occur from combustion heat transfer across large temperature differences), the turbines, the electrical generator and the transformer. Possible improvements in these areas should be assessed in conjunction with other criteria, and other components should be considered where economically beneficial improvements can be identified.
Test of Innovative Nozzle Design for Film Cooling System to Maximize Turbine Efficiency
Authors: Malo-Molina Faure J. , Wong Kau-Fui V. , Brankovic Andreja
Published: May 2008

The ideal design of a turbine blade external film cooling system should contain a minimal uniform cooling film while simultaneously maximizing turbine efficiency. The current research reports on the tests on the pressure drop, hydraulic resistance, and mass flow rate of nine different nozzles. The effectiveness of the resulting film of cold air depends upon the mass flow rate and the shape, size, distribution and directional angles of these tiny nozzles. Of the orifices tested, the orifice shaped with the biggest spherical counter-sink inlet, allows the air to exit with the highest momentum. This shape produces the lowest hydraulic resistance and the highest blowing ratio.
Experiences With an Alternate Energy Systems Course
Authors: Hodge B. K.
Published: May 2008

Experiences with a technical elective course, ME 4353/6353 Alternate Energy Systems, are delineated. Alternate Energy Systems (AES) was devised for senior and beginning graduate students in mechanical engineering (ME) and presents a first-order introduction to the plethora of alternate energy technologies now considered as available, viable, or promising. The AES course covers basic principles, economic considerations, application potentials, and advantages and disadvantages of a variety of alternate energy technologies. The course topics, contents, and goals are discussed in detail in the paper. After two offering, the AES course meets the stated purpose of the course and has become a popular elective even though the workload and effort required are significant.
Teaching Applied Thermodynamics With EES
Authors: Pourmovahed A. , Jeruzal C. M. , Nekooei S. M. A.
Published: May 2008

Applied Thermodynamics is a graduate course at Kettering University. Undergraduate Thermodynamics serves as the only prerequisite. This course covers the concepts introduced in undergraduate thermodynamics and continues with the coverage of thermodynamic relations, mixtures and solutions, psychrometry, phase and chemical equilibrium, and chemical reactions. These concepts are then applied in detail to various power and refrigeration cycles. Topics such as mole fraction, mass fraction, enthalpy of formation, adiabatic flame temperature and the application of the Second Law to reacting mixtures are covered. Team projects are incorporated into this graduate course. Recent projects included a turbojet engine and a non-ideal regenerative steam power plant. The objective of the first project was to compute component efficiencies and the thrust force for a jet engine. The second project aimed to optimize the thermal efficiency of a non-ideal regenerative steam power plant by varying the feed-water heater pressure. Both projects utilized the Engineering Equation Solver (EES), a general equation solver with built-in functions for thermodynamic and transport properties. This article describes the projects and presents the solution techniques and the computed results. For the jet engine, computed results are based on actual test data obtained in Energy Systems Laboratory at Kettering University.
Reliable Performance Evaluation of Single Cells Through an Effective Experimental Test Rig and Measure Chain
Authors: Lunghi Piero , Bidini Gianni
Published: May 2008

Fuel cells are known to be efficient and environmental friendly electricity generation devices. Great expectations are put on their contribution for future ultra-clean energy production. Nevertheless, the requests from deregulated energy market prompt fast commercialization of systems that are not yet fully optimized. Low efficiencies of first generation commercial fuel cell plants could result in failure when satisfying end users’ requirements thus creating an obstacle for subsequent market penetration. In this context, the availability of reliable data on fuel cells, necessary for their correct integration in full energy systems for plant optimization and feasibility assessment constitutes a priority. On the other hand, while measuring fuel cells performance is a difficult task nevertheless within reach for most research departments; the challenge for the scientific community is to reliably assess performance dependence on all the most relevant input parameters. As a result, most of the experimental data find on literature on fuel cells performances refer to voltage measures at increasing currents for fixed gas compositions and flow rates. In this work an experimental facility has been set up, test rigs have been designed and constructed both for fuel cells and reforming section testing; the main aim was to allow great operational flexibility. Great attention has been paid on test procedures and on input parameterisation as well on reliable advanced control systems. Dependence on the most relevant input parameters, i.e. current density, operating temperature, fuel and oxidant utilization factor, fuel humidification and dilution has been deeply analysed. Performances have been analysed both in terms of output voltage and efficiency and in terms of time degradation and expected total lifetime. The contribution of the work done consist in defining adimensional parameters which, thanks to their direct relation with the theoretical equations which govern a fuel cell, can greatly improve performance evaluation capability of experimental tests. Moreover those parameters can represent a way to standardize test procedures and constitute a means for comparing and exchanging results in a easier and effective way. A second contribution consist in designing and developing a unique control system that can improve test reliability thanks to the feature that allows to change single parameters while keeping the others constant and greatly enhance the number of experimental points that can be obtained in a test.
Performance Enhancement of Fuel Cells Systems Through Series and Parallel Connections of Multi Stack Arrays
Authors: Lunghi Piero , Bove Roberto
Published: May 2008

Fuel cells have been known theoretically for more than a century. Recently conceived high temperature fuel cells, by guaranteeing higher degrees of efficiencies and greater fuel flexibility, have the potential to yield a radical change in the future of distributed electricity market promising high efficient and ultra-clean power generation. In the last years progress has been so relevant that they seem to be on the verge of commercialization. All plants commissioned seem to consider the parallel flow solution i.e. in which primary fuel flow splits to enter all the stacks that works with nominally equal operational parameters. The present work analysed the possibility of disposing stacks in an array, thus leading to a combination of series and parallel fluid dynamic connection so that one cell anode may have as input the exhaust of another cell anode. The aim is to allow some cells to work with low utilization factors and therefore at greater voltages. Different solutions have been analysed with a tool obtained from the integration of a proprietary code for cells simulation, with Aspen+ flowsheet. Code predictions of cells performances have been validated by experimental campaigns [Lunghi and Burzacca 2002]. The results showed that a noticeable performance increase can be obtained with the proposed configuration without any significant complication in the process. The authors believe that this should be considered as a very interesting research field and strongly encourage participation of the scientific community.
Water Balance in PEM Fuel Cells
Authors: Izenson Michael G. , Hill Roger W.
Published: May 2008

Fuel cells based on polymer electrolyte membranes (PEMs) are attractive power sources because they are efficient, non-polluting, and do not rely on non-renewable fossil fuels. Water management is a critical design issue for these fuel cells because the PEM must be maintained at the proper water content to remain ionically conducting without flooding the electrodes. Furthermore, portable PEM power systems should operate at water balance. That is, water losses from the cell should be balanced by the rate of water production from the fuel cell reaction. A portable system that operates at water balance does not require an external supply of water. The rate of water production depends on the cell’s electrochemical characteristics. The rate of water loss depends on the flow rates of reactants and products, transport of water and fuel across the PEM, and the stack operating temperature. This paper presents the basic design relationships that govern water balance in a PEM fuel cell. Specific calculations are presented based on data from hydrogen/air and direct methanol fuel cells currently under development for portable power systems. We will show how the water balance operating point depends on the cell operating parameters and show the sensitivity to off-design conditions.
Optimal Scheduling and Filtering of Distorted Multi-Sensor Data
Authors: Suranthiran Sugathevan , Jayasuriya Suhada
Published: May 2008

In this paper, a framework to schedule and filter distorted multi-sensor outputs is developed. The distortion caused by sensor nonlinearity is considered. As the distorted signal is not a true representation of the original signal, it is often necessary to develop and incorporate signal recovery schemes. Once such a scheme is developed, implementation may be straightforward if the system is employed with a single sensor. When the bandwidth of a signal of interest is very high, the use of a single sensor may not be feasible. High cost and accuracy are major concerns worth noting. It is proposed that a good practical solution to this problem is to employ an array of low bandwidth sensors. Practical Implementation of recovery schemes is very challenging and difficult in this case due to a possible overlapping of multi-source data. This sensor scheduling problem is investigated in detail and a data fusion scheme based on the optimization of weighted error function is initiated and developed for the two-sensor case. Simulation results are presented to validate the fusion procedure developed.
The Road to Smart Transducer Technology
Authors: Lopez-Reyna C. E. , Zemel J. N.
Published: May 2008

The past decade has seen three distinct trends emerge in sensor technologies. The first is biosensing wherein measurements as diverse as detecting aromas in food processing to highly sophisticated detection of DNA and proteins have become staples of contemporary engineering efforts. The second important trend is the continuing decrease in the physical size of sensing elements embodied by the replacement of “micro” by “nano” in fabrication and technology. These two efforts in biosensing and the decreasing size of electronic and sensing components have transformed not only virtually every area of research, development and engineering, they are powerfully influencing many aspects of everyday life. The third trend, and the one that will be examined in this paper, involves efforts to fuse information technology with sensing technologies. The rubric “smart transducer technologies” has been given to these activities to connote this fusion.
Advancing Sensor Technology for Aerospace Propulsion
Authors: Figueroa Fernando , Mercer Carolyn R.
Published: May 2008

NASA’s Stennis Space Center (SSC) and Glenn Research Center (GRC) participate in the development of technologies for propulsion testing and propulsion applications in air and space transportation. Future transportation systems and the test facilities needed to develop and sustain them are becoming increasingly complex. Sensor technology is a fundamental pillar that makes possible development of complex systems that must operate in automatic mode (closed loop systems), or even in assisted-autonomous mode (highly self-sufficient systems such as planetary exploration spacecraft). Hence, a great deal of effort is dedicated to develop new sensors and related technologies to be used in research facilities, test facilities, and in vehicles and equipment. This paper describes sensor technologies being developed and in use at SSC and GRC, including new technologies in integrated health management involving sensors, components, processes, and vehicles.
A Modular Approach to Fuel Cell Modeling: Analysis of a SOFC Cathode
Authors: Celik Ismail B. , Gemmen Randall S. , Pakalapati Suryanarayana R.
Published: May 2008

A modular modeling strategy is outlined for fuel cells. As a stepping stone towards this modeling paradigm, the cathode-oxidizer assembly of a typical solid oxide fuel cell (SOFC) has been modeled. Various cases were simulated, and the spatial distributions of electric-potential, current, temperature and oxygen concentration have been calculated. An assessment of the results showed some surprising consequences. Detailed resolution of the current density distribution within the cathode has revealed highly non-uniform electrical field thin cathodes. This may have significant consequences concerning distribution of thermal stresses and structural integrity of the fuel cell.
Automated Stability Analysis of a Vehicle in Combined Pitch and Roll
Authors: Sprague James K. , Liu Shyi-Ping
Published: May 2008

This paper presents a rigid body modeling approach using ADAMS™ for an overturning stability analysis of a vehicle stopped at an arbitrary heading angle on a steep grade. The vehicle is modeled as a six-degree-of-freedom rigid body with multiple contact forces acting on the ground. A gravity vector bounded by sets of spherical coordinates is applied to the vehicle to represent the physics of a vehicle stopped on a grade with any arbitrary combination of pitch and roll angles. A design of experiments study is performed to locate the overturning stability boundaries within given levels of design parameters. Results are output using two effective graphical means of depicting the stability regions and magnitude of contact forces.
Thermoeconomic Diagnosis: Zooming Strategy Applied to Highly Complex Energy Systems — Part 2: On the Choice of the Productive Structure
Authors: Verda Vittorio , Serra Luis , Valero Antonio
Published: May 2008

The thermoeconomic diagnosis strategy introduced in the accompanying paper (part 1 [1]) is a zooming technique consisting of a successive localization of anomalies. At each step the required productive structure to be adopted becomes even more detailed, focusing the analysis on a more specific part of the system. The detail of a productive structure has two different levels: the number of components and the number of productive flows. The first one is selected according to the precision desired in locating the anomalies. A larger number of components (or subsystems) allows one to locate the anomalies in smaller control volumes, providing more precise indications for maintenance. The number of flows is partially dependent on the number of components. Once the number of components is fixed, the productive flows can be increased by separating exergy into its components or introducing fictitious flows, such as negentropy (see for example [2]). This decision also affects the results of the thermoeconomic analysis when it is adopted for diagnosis purposes. In this paper, the effects of the productive structure on the diagnosis results are carefully analyzed. Depending on the selected productive structure, the accuracy of the diagnosis results can be significantly improved.
A Multiple Operating Point Minimization Technique for Gas Turbine Operating State Determination
Authors: Pinelli M. , Spina P. R. , Venturini M.
Published: May 2008

Gas turbine operating state determination can be performed using Gas Path Analysis (GPA) techniques, which use measurements taken on the machine to calculate the characteristic parameters that are indices of the machine health state. The number and type of characteristic parameters that can be evaluated depend on the number and type of the available measured variables. Thus, when there are not enough measured variables to determine all the characteristic parameters, some of them have to be estimated independently of the actual gas turbine health state. In this way, variations due to aging or deterioration which, in the actual machine, may occur on these last characteristic parameters, cause estimation errors on the characteristic parameters assumed as problem unknowns. In the field application of GPA techniques the available instrumentation is often inadequate to ensure reliable operating state analysis. This problem may be partially overcome using a multiple operating point minimization technique. This consists of the determination of the characteristic parameters that minimize the sum of the square differences between measured and computed values of the measurable variables in multiple operating points. In this way the lack of data is overcome by data obtained in different operating points. This paper describes a procedure for gas turbine operating state determination based on a multiple operating point minimization technique and presents a study aimed at selecting the best set and number of operating points that have to be used.
The Hardware-in-the-Loop Simulation Study on the Control Strategy of Gas Turbine
Authors: Zhang Huisheng , Su Ming , Weng Shilie
Published: May 2008

A 3-shaft gas turbine engine for ship propulsion was taken as an object to establish the hardware-in-the-loop simulation system, which is composed of computers, real physical parts, measuring instruments, interfaces between physical parts and computers, and the network for communication, as well as the relevant software including mathematical models of the gas turbine engine. “Hardware-in-the-loop” and “volume inertia effects” are the two major features of this simulation system. In comparison with traditional methods for gas turbine simulation, the new simulation platform can implement simulation in real time and also can test the real physical parts performance through integration of the real physical parts and the mathematical model in a computer.
Performance Improvement of an Industrial Chiller Through the Optimization of the Control Logic
Authors: Barelli Linda , Bidini Gianni , Fantozzi Francesco
Published: May 2008

According to the tasks agreed within the Kyoto protocol, in terms of CO2 emissions reduction, the European Community is promoting energy saving. The introduction of energetic classification for electrical household appliances, makes consumption as a parameter of choice for consumers and thus represents a relevant tool for the promotion of energy saving. Therefore the interest in the evaluation and minimization of electric consumption for industrial appliances is also evident. The aim of the present study is to investigate alternative control solutions to improve the performance and diminish the energy consumption of an industrial chiller. This was carried out through software modeling of the system and experimental validation of the best performing solutions. Simulated trends show good agreement with experimental data and allow the definition of a suitable PID controller that performs good temperature regulation while slightly reducing energy demand. Further ameliorations were considered and preliminary results are shown both for optimal control and neural modeling of the chiller. Results obtained encourage to continue in the development of better performing regulators, also through neuro–fuzzy logic control.
Instability Due to Interacting Hydraulic and Mechanical Dynamics in Backhoes
Authors: Margolis Donald , Shim Taehyun
Published: May 2008

A backhoe is a tractor-like vehicle that has a hydraulically actuated bucket loader at the front and a hydraulically actuated backhoe shovel at the rear. The operator sits inside a canopy or cab that is mounted to the tractor chassis, and operates the hydraulic controls. The cab is typically isolated somewhat from the chassis using cab mounts. There are instances when the bucket is raised or lowered or wrapped that an instability of the entire machine is excited. In this mode, a frequency oscillation of the vehicle occurs and the operator is unable to keep his hands on the controls. This instability is investigated here and demonstrated through simulation. The instability described here is due to an interaction between the mechanical dynamics and hydraulic dynamics of the machine. All instabilities require an energy source, and, in this case, the energy comes from the fuel. It turns out that the hydro-mechanical interaction has positive feedback components and produces an instability. In order to expose the fundamental cause of the instability, a model is needed that allows the interaction of mechanical and hydraulic components. Bond graphs are a logical choice for development of the model. Bond graphs are a concise pictorial representation of the interactive dynamics of all types of energetic systems. They allow the model to be developed in pieces and then put together into an overall computational model. This procedure is demonstrated for the system here. The end result is a reasonably low order model that exposes the fundamental cause of the instability in backhoes. It also allows assessment of cures for the problem, some requiring redesign of components, and some requiring an automatic stabilization control system.
The Helical Turbine and Its Applications for Hydropower Without Dams
Authors: Gorlov Alexander M.
Published: May 2008

The objective of this paper is to introduce an environmentally friendly Helical Turbine that has been developed to operate in free or ultra low-head water currents without dams. The turbine is a cross flow unidirectional rotation machine that makes it particularly valuable for ocean applications, such as reversible tidal streams in ocean bays, estuaries and canals, streams in open ocean, underwater currents generated by wave fluctuations etc.
Safety and Comfort Analysis of Optimal Seats With Active and Semi-Active Suspension
Authors: Bouazara M. , Richard M. J. , Rakheja S.
Published: May 2008

A generalized nonlinear model is formulated for dynamic analysis of suspension seats with passive, semi-active and active dampers. The model incorporates coulomb friction due to suspension linkages and bushings, forces arising from interactions with the elastic limit stops, a linear suspension spring and nonlinear damping force on the basis of passive, semi-active and active dampers, while the contribution due to biodynamics of the human operator is considered to be negligible. The semi-active and active dampers are charcterized by force generators in accordance with the control laws based upon suspension mass velocity. Two different suspension seats are experimentally assessed in the laboratory under sinusoidal and random excitations arising from an urban bus, and the measured data is used to demonstrate the validity of the proposed generalized model. The results showed reasonably good agreement between the model results and the measured data. Optimal model parameters are selected using the sequential unconstrained minimization technique with an objective to minimize the acceleration due to vibration transmitted to the occupant mass. The comfort and safety performance characteristics of the optimal suspension seat with semi-active and active dampers are evaluated under both the sinusoidal and random excitations on the basis of the guidelines provided in ISO-2631. From the results it is concluded that the comfort performance of a suspension seat with semi-active and active dampers can be considerably enhanced, in the 20% to 30% range.
Using Experimental Data for Predicting Performance and Emissions of a Real Gas Turbine Plant
Authors: Lazzaretto Andrea , Toffolo Andrea , Trolese Sebastiano
Published: May 2008

Precise performance evaluation at design and off-design operations is needed for a correct management of power plants. This need is particularly strong in gas turbine power plants which can quickly react to load variations and are very sensitive to ambient conditions. The paper aims at presenting a simple tool to determine the values of the thermodynamic quantities in each point of the plant and the overall plant performances of a real gas turbine plant. Starting from experimental data, a zero-dimensional model is developed which properly considers the effect of ambient conditions and water injection for pollutant abatement at different load settings under the action of the control system. An emission model taken from the literature is also included, after tuning on experimental data, to predict carbon monoxide and nitrogen oxide pollution.
Contamination Prevention of the Sulfur Dioxide Using Structured Packing
Authors: Cha´vez Rosa H. , de J. Guadarrama Javier
Published: May 2008

The atmospheric contamination is a significant problem for the population of the big cities. This problem has its origin in the burning of heavy oil, that is carried out to liberate its energy content. Its use as a primary source of energy has high pollution effects in its process due to the formation and expulsion of gases and particles as a consequence of its combustion that contaminate the atmosphere. Although it has had enough relative elements of legal type relative to the contamination, specially atmospheric contamination, there is a lack of solutions adapted to the characteristics of the problem for each country. The present work quantifies the improvements in mass transfer, using absorption column with structured packing of high efficiency for the recovery of the SO2, through the process of removal of SO2 in the form of CaSO3. For such study, the hydrodynamic and mass transfer models are used to design the column, as well as to prove different packings (national production, denominated ININ in Mexico, SulzerBX, Mellapak and Raschig) to evaluate the separation efficiency. It is discussed that the ININ packing was one of the best of those tested because it has the highest separation efficiency.
FEA Rotating Tire Modeling for Transient Response Simulations
Authors: Chang Y. P. , El-Gindy M.
Published: May 2008

A full nonlinear finite element P185/70R14 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum. The virtual tire/drum/cleat finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. In addition to the tire model itself, the rim was also included and rotated with the tire, with proper mass and rotational inertial effects. The FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this P185/70R14 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. Also the paper presents the prediction of tire standing waves phenomenon, and computer animations of the standing waves phenomenon were carried out for the first time. The effects of different tire inflation pressures and tire axle loadings were investigated with respect to their influences on the formation of standing waves. The parameters adopted in this FEA tire model were validated against experimental work and showed excellent agreement.
A Low Emission Power Plant: An Integrated Technique to Remove Major Pollutants
Authors: Ergut Ali , Levendis Yiannis A.
Published: May 2008

This manuscript presents an integrated approach for the simultaneous reduction of major combustion-generated pollutants from powerplants. This approach combines dry-sorbent injection for SO2 concentration reduction, coal injection (reburning) for NOx reduction in conjunction, with a ceramic honeycomb filter for particulate emission capture. A succinct economic analysis was conducted to show the financial feasibility of the system, as compared with other state of the art systems. The performance of low-cost commercial sorbent, calcium carbonate [CaCO3] as well as sodium bicarbonate [NaHCO3] was evaluated in this laboratory. The sorbent powders were blended with three types of pulverized coal (bituminous, sub-bituminous and lignite coal) to achieve NOx reduction and results were contrasted with the performance of the more costly sorbent calcium formate [Ca(COOH)2], which forms porous calcium oxide. The sorbents were injected in a simulated effluent gas containing SO2 and NO at a gas temperature of 1150°C (1423 K), upstream of the ceramic filter, which was kept at 600°C (873 K). Most of the tests have been run in the Ca/S range 1–2. The fuel-to-air equivalence ratio, φ, was in the neighborhood of 2 for all tests. This integrated sorbent/filter method is cost-effective in comparison to current technologies, on both capital cost ($/kW) and levelized cost ($/ton pollutant removed) bases, if a limestone/coal mixture is used as the sorbent for fossil fuel plants. Capital costs for the filter/sorbent combination are estimated to be in the range of $61–105/kWe for new plants of different size. Since current technologies are designed for removing one pollutant at a time both their cost and space requirements are higher than those of this integrated technique. At the minimum projected removal efficiencies for SO2/NOx of in the order of 40% and particulate removal efficiencies in the order of 99%, the levelized costs are projected to be $203–261/ton of combined pollutant SO2/NOx and particulates removed from coal fired power plants.
Simulation of a PV-Micro-Hydro-Hydrogen System Feeding the Energy Requests of a Residential Building in a Remote Area of the Alps: Part I — Simulation of Micro-Hydro Power Primary Input
Authors: Macagno S. , Santarelli M. , Porporato A.
Published: May 2008

The purpose of the work is a simulation model (in the Matlab environment) of a hypothetical stand-alone energy system in design conditions. This system is based just on renewable sources (solar and micro-hydroelectric energy) integrated with a hydrogen energy system (electrolyzer, hydrogen storage, PEM (proton exchange membran fuel cell). It could supply the whole electric and part of the heat requests of a small residence situated in a remote mountainous area (e.g. an isolated village in the Italian Alps) during a complete year of operation. The work is made up of two. The subject of this first paper is the simulation of the performances of the micro-hydro power source. To obtain the flow duration curve necessary for a correct design of the micro-turbine, the following hypothesis have been made: the behavior of the mountain basin is modeled like a linear reservoir, the rainfall is described as a marked Poisson process and the snowmelt is modeled using the empirical temperature-index approach. The result of the simulation is the hourly electrical output as a function of the daily flow of available water. A single micro-turbine is enough for this basin. The maximum value of electric power obtained during spring months corresponds to 1400 W and the annual electric energy produced by this plant is in the order of 4 MWh/yr.
Considerations for Minimum Lap Time Calculation on a Race Track
Authors: Di Pierro Marco , Schuller Juergen
Published: May 2008

While methods for vehicle modeling are well established for simulation of handling behavior, there is still a lack of driver models, which are important for the realization of closed-loop maneuvers in a virtual environment. This paper will present preliminary considerations for the development of such a driver model. First, trajectory planning strategies have to be generated and evaluated. To achieve this, a method will be deduced, which calculates the maximum velocity at each point of an arbitrary trajectory, taking into account simplified vehicle characteristics in terms of maximum longitudinal and lateral accelerations and considering the frictional ellipse. Thus, the minimum necessary time for each trajectory can be calculated, this being a possible parameter to rate the quality of a trajectory for a given course. The feasibility of the method is demonstrated with the Nuerburgring race track.
Simulation of a PV-Micro-Hydro-Hydrogen System Feeding the Energy Requests of a Residential Building in a Remote Area of the Alps: Part II — Integrated System
Authors: Macagno S. , Santarelli M. , Borchiellini R. , Cali` M.
Published: May 2008

The paper presents a simulation model of a hypothetical stand-alone energy system based just on renewable sources (solar irradiance and micro-hydro power) integrated with a system for the production of hydrogen (electrolyzer, storage and PEMFC). Such a system has been designed to supply the electricity needs of a residential user (a small residential building in a isolated village of a valley of the Alps in Italy) during a complete year of operation, without integration of traditional energy devices based on fossil fuels. A simulation in the Matlab environment has been developed to determine the energy performance of this system during a complete year of operation. The simulation of the operation of the system has been made on an hourly basis as a succession of steady states. The technical feasibility of the system will be evaluated, through the analysis of some variables (e.g. the production and consumption of electricity along the year by the different components, the production, storage and utilisation of hydrogen, etc.). The analysis will show that in a complete year nearly the 50% of the electrical load required from the final user will be given by the PEMFC, even if the micro-hydro turbine and the PV array produce a very high amount of energy. Moreover, the electricity produced by the PEMFC is the 38.5% of the input electric energy sent to the electrolyzer; this value indicates the mean annual efficiency of the conversion chain of the production and utilization of hydrogen inside this plant.
Fuel Cell Gas Turbine Hybrid Simulation Facility Design
Authors: Tucker David , Liese Eric , VanOsdol John , Lawson Larry , Gemmen Randall S.
Published: May 2008

Fuel cell hybrid power systems have potential for the highest electrical power generation efficiency. Fuel cell gas turbine hybrid systems are currently under development as the first step in commercializing this technology. The dynamic interdependencies resulting from the integration of these two power generation technologies is not well understood. Unexpected complications can arise in the operation of an integrated system, especially during startup and transient events. Fuel cell gas turbine systems designed to operate under steady state conditions have limitations in studying the dynamics of a transient event without risk to the more fragile components of the system. A 250kW experimental fuel cell gas turbine system test facility has been designed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to examine the effects of transient events on the dynamics of these systems. The test facility will be used to evaluate control strategies for improving system response to transient events and load following. A fuel cell simulator, consisting of a natural gas burner controlled by a real time fuel cell model, will be integrated into the system in place of a real solid oxide fuel cell. The use of a fuel cell simulator in the initial phases allows for the exploration of transient events without risk of destroying an actual fuel cell. Fuel cell models and hybrid system models developed at NETL have played an important role in guiding the design of facility equipment and experimental research planning. Results of certain case studies using these models are discussed. Test scenarios were analyzed for potential thermal and mechanical impact on fuel cell, heat exchanger and gas turbine components. Temperature and pressure drop calculations were performed to determine the maximum impact on system components and design. Required turbine modifications were designed and tested for functionality. The resulting facility design will allow for examination of startup, shut down, loss of load to the fuel cell during steady state operations, loss of load to the turbine during steady state operations and load following.
Hydrogen: A Very Promising Energy Carrier for the Future
Authors: Kakatsios Xenophon K.
Published: May 2008

As we enter the new century, new fuels may be required for both stationary power and transportation to ameliorate the triple threats of local air pollution, global climate change and dependence on unstable nations for imported oil. Shifting away from fossil fuels may be essential within decades if citizens in the developing world achieve even a significant fraction of the per capita energy consumption enjoyed by the industrial nations. Business-as-usual or evolutionary shifts in energy consumption patterns may not be adequate. New paradigms and new energy initiatives may be required to protect the environment while providing the energy services we have come to expect. Hydrogen could play a significant role as a clean energy carrier in the future for both stationary and transportation markets. Produced from renewable energy or nuclear power, hydrogen could become the backbone of a truly sustainable energy future – an energy system that consumes no non-renewable resources and creates no pollution or greenhouse gases of any type during operation. However, to achieve this potential, hydrogen must overcome serious economic, technological and safety perception barriers before it can displace fossil fuels as the primary energy carrier throughout the world. In this paper we explore the current status of hydrogen and fuel cell systems compared to other fuel options for reducing pollution, greenhouse gas emissions and suggest the introduction of hydrogen into the energy economy.
Fourier Series Neural Network Analysis of a Steer-by-Wire System
Authors: Mills Val D. , Wagner John R. , Haque Imtiaz
Published: May 2008

Automotive steering system research has traditionally focused on improving vehicle handling and safety, as well as investigating lateral dynamic issues. The emergence of hybrid vehicles provides a motivation for steer-by-wire technology in terms of power source availability and improved performance. From a design perspective, steering systems are difficult to accurately model due to the inherent nonlinearities present in the steering assembly, chassis, wheels, and tire/road interface. One modeling strategy that merits further attention is the Fourier Series Neural Network (FSNN) which has been proven effective for the characterization of dynamic systems. A neural network can approximate nonlinear functions to a high degree of accuracy, given an adequate network structure and sufficient training. In this paper, a Fourier Series activation function neural network will be studied to identify a steer-by-wire system. A behavioral model has been developed for the driver interface and directional control assembly of the rack and pinion steer-by-wire system. Representative numerical results are presented to demonstrate the FSNN’s ability to predict the system’s overall transfer function. This engineering tool may provide an attractive alternative to rigorous system modeling, and inherently captures the response characteristics due to the nonlinear behavior.
Bubbling From Microscopic Holes Into Pool Water Simulating Nucleate Boiling: Bubble Coalescence and Water Layer Under the Coalescent Bubble
Authors: Koizumi Yasuo , Iitani Kenichiro , Ohtake Hiroyasu
Published: May 2008

Air bubbling into stagnant water from microscopic holes was examined. As the blowing-out velocity was increased, bubbles became to coalescence each other after detachment from the holes and formed coalescent bubbles. Large bubbles departed from the coalescent bubbles intermittently. When the bubbles on the surface became large, the bubbles coalesced on the surface to form the coalescent-large bubble. The distance between the bottom wall and the coalescent bubble, which is often referred to as the thickness of the macro layer in the nucleate boiling, tended toward increasing with an increase in the blowing-out velocity contrary to the macro-layer theory. It was suggested that the occurrence of the CHF condition could be explained by combining the bubble crowding on the surface (the bubble crowding model) and the periodical leave of the coalescent bubble from the surface (the macro layer model).
A Non-Source Term Methodology in Simulation of Solidification
Authors: Xiao Yumin , Amano R. S. , Lee E. K. , Choi Youn-Suk , Xie Jianhui
Published: May 2008

In this paper a non-source term method is developed to solve the energy equation. In this new method the discrete form of the energy equation remains the same and no extra source term is introduced. The mushy-zone is treated as a porous media during solidification. This method is incorporated into the existing finite volume based CFD code. Test cases analyzed in this paper include solidification of pure metal, pure metal solidification with natural convection due to the buoyancy, and binary alloy mushy flow problem with variable Cp. The calculated results are in good agreements with available published data. This method can be applied to simulate a wide range of melting/solidification processes.
Liquid Films Falling Over Horizontal Tube Banks: Deviations From Idealized Flow Patterns and Implications for Heat and Mass Transfer
Authors: Killion Jesse D. , Garimella Srinivas
Published: May 2008

Liquid films falling over banks of internally cooled horizontal tubes are often used to absorb mass from a surrounding vapor. This arrangement is particularly suitable for absorption processes where the vapor has a high heat of absorption and where high transfer rates and low pressure drops are required, as is the case of absorption heat pumps and other chemical processes. When the liquid film presents a significant resistance to heat and mass transfer, understanding the motion of the film is critical. However, mathematical models of these types of systems in the literature have generally made use of many simplifying assumptions about the behavior of the falling liquid. The formation, detachment, and impact of droplets and the associated waves and film disturbances can all affect the mixing of the liquid and can enhance transfer rates accordingly. The objective of this paper is to identify and visually document these deviations from idealized film behavior and discuss their implications on the heat and mass transfer processes, which are important to consider in the development of mechanistic models of the absorption process.
Local Discrete-Operator Interpolation Solution of the Phase-Field Model
Authors: Yang Tianliang , Xu Ying , McDonough J. M. , Tagavi K. A.
Published: May 2008

This paper reports continuing work on application of discrete-operator interpolation (DOI) in solving the one-dimensional phase-field model applied to melt-front tracking. DOI is a numerical technique for computing function values not computed at the original grid points of a finite-difference (or finite element) scheme so as to satisfy the discrete governing equations at the new points. The previous study showed that the DOI technique works quite well for the phase-field model problem. The shortcoming of earlier work was global (in space) application of DOI. Due to the fact that at any instant in time, the melt-front of the phase-field model exists within only a small region of space, it is more efficient to employ a local DOI technique. Local DOI interpolates the numerical solutions only in the melt-front region while a standard numerical method is applied in other regions. In this paper, we describe the phase-field model together with the details of the local DOI method and their numerical implementations. The results of the phase-field model are obtained using a Crank-Nicolson finite-difference scheme. The local DOI results are compared with direct numerical simulation results obtained on a very fine grid to demonstrate the advantages of this method.
Production Paradigms and Paradoxes
Authors: Gardiner Keith M.
Published: May 2008

Paradigms convey notions of fixed prescribed practices and examples that offer solutions to deal with the vagaries of human organizations and behavior. To define something as a paradigm freezes a sometime evanescent concept and fixes it with a phrase that enhances popular understanding and adoption. Paradigms offer a simplicity and degree of standardization to ideas that often become cliches, and, as such, inevitably entrain paradoxes. The world of production and manufacturing consists of multiple complex enterprises, industries, organizations, processes, relationships and cultures. There are many contradictions, contrasts, and dichotomies that change with time. This paper endeavors a historic and philosophic essay on some of the origins and paradoxes that surround our currently recommended production systems practices.
Novel Gas Turbine Cycle With Integration of CO2 Recovery and LNG Cryogenic Exergy Utilization
Authors: Deng Shimin , Jin Hongguang , Cai Ruixian , Lin Rumou
Published: May 2008

In this paper we propose a new gas turbine cycle, which employs a semi-closed recuperative gas turbine with LNG utilization. Nitrogen is selected as working fluid with air induced at the inlet of compressor. The inlet temperature of the compressor is kept pretty low with LNG cooling, and turbine inlet temperature can be very high because of internal combustion, and higher average temperature of heat absorption of the cycle is achieved due to recuperation. As a result, the cycle efficiency can reach as high as 70% (TIT=1250°C). Furthermore, along the process of LNG vaporization, turbine exhaust is cooled down; CO2 in the mixture is solidified and separated without extra power consumption. Two different natural gas sendout pressures (7.0 and 3.0 MPa) are considered. Their performances are simulated and a comprehensive analysis is carried out. The performance of the new cycle, CO2 recovery, and heat transfer in LNG vaporizer are discussed in detail. The new cycle proposed here is based on the integration of carbon dioxide recovery and LNG cryogenic exergy utilization, and it will contribute to both improvement on power generation efficiency and reduction of greenhouse gas emission.