bluuebunny/crossref_metadata_2025 huggingface dataset:
Completely 1-complemented subspaces of Schatten spaces
Authors: Le Merdy Christian , Ricard Éric , Roydor Jean
Published: October 2008

We consider the Schatten spaces

S
p

S^p

in the framework of operator space theory and for any

1
≤
p
≠
2
>
∞

1\leq p\not =2>\infty

, we characterize the completely

1
1

-complemented subspaces of

S
p

S^p

. They turn out to be the direct sums of spaces of the form

S
p

(
H
,
K
)

S^p(H,K)

, where

H
,
K

H,K

are Hilbert spaces. This result is related to some previous work of Arazy and Friedman giving a description of all

1
1

-complemented subspaces of

S
p

S^p

in terms of the Cartan factors of types 1–4. We use operator space structures on these Cartan factors regarded as subspaces of appropriate noncommutative

L
p

L^p

-spaces. Also we show that for any

n
≥
2

n\geq 2

, there is a triple isomorphism on some Cartan factor of type 4 and of dimension

2
n

2n

which is not completely isometric, and we investigate

L
p

L^p

-versions of such isomorphisms.
Strong 𝐿^{𝑝}-solutions to the Navier-Stokes flow past moving obstacles: The case of several obstacles and time dependent velocity
Authors: Dintelmann Eva , Geissert Matthias , Hieber Matthias
Published: October 2008

Consider the Navier-Stokes flow past several moving or rotating obstacles with possible time-dependent velocity. It is shown that under suitable assumptions on the data, there exists a unique, local strong solution in the

L
p

−

L
q

L^p-L^q

-setting for suitable

p
,
q
∈
(
1
,
∞
)

p,q \in (1,\infty )

. Moreover, it is proved that this strong solution coincides with the known mild solution in the very weak sense.
Openness and convexity for momentum maps
Authors: Birtea Petre , Ortega Juan-Pablo , Ratiu Tudor
Published: October 2008

The purpose of this paper is finding the essential attributes underlying the convexity theorems for momentum maps. It is shown that they are of a topological nature; more specifically, we show that convexity follows if the map is open onto its image and has the so-called local convexity data property. These conditions are satisfied in all the classical convexity theorems and hence they can, in principle, be obtained as corollaries of a more general theorem that has only these two hypotheses. We also prove a generalization of the so-called Local-to-Global Principle that only requires the map to be closed and to have a normal topological space as domain, instead of using a properness condition. This allows us to generalize the Flaschka-Ratiu convexity theorem to noncompact manifolds.
Disintegrating tensor representations of nilpotent Lie groups
Authors: Abdennadher Jawhar , Ludwig Jean
Published: October 2008

Let

G
G

be a simply connected nilpotent Lie group and

H
H

a closed connected subgroup of

G
G

. Given an irreducible unitary representation

π
\pi

of

G
G

, we present an explicit disintegration of the restriction

π

|

H

\pi _{|H}

of

π
\pi

to

H
H

. Such a disintegration relies on the description of the double cosets space

H
╲
G
╱
B

H \diagdown G\diagup B

for an arbitrary closed connected subgroup

B
B

of

G
G

, and the well-known smooth disintegration of monomial representations of nilpotent Lie groups. As an application we get a concrete disintegration and a criterion of irreducibility for tensor products of a finite number of irreducible representations of

G
G

.
Neural control of shortening and lengthening contractions: influence of task constraints
Authors: Duchateau Jacques , Enoka Roger M.
Published: October 2008

Although the performance capabilities of muscle differ during shortening and lengthening contractions, realization of these differences during functional tasks depends on the characteristics of the activation signal discharged from the spinal cord. Fundamentally, the control strategy must differ during the two anisometric contractions due to the lesser force that each motor unit exerts during a shortening contraction and the greater difficulty associated with decreasing force to match a prescribed trajectory during a lengthening contraction. The activation characteristics of motor units during submaximal contractions depend on the details of the task being performed. Indexes of the strategy encoded in the descending command, such as coactivation of antagonist muscles and motor unit synchronization, indicate differences in cortical output for the two types of anisometric contractions. Furthermore, the augmented feedback from peripheral sensory receptors during lengthening contractions appears to be suppressed by centrally and peripherally mediated presynaptic inhibition of Ia afferents, which may also explain the depression of voluntary activation that occurs during maximal lengthening contractions. Although modulation of the activation during shortening and lengthening contractions involves both supraspinal and spinal mechanisms, the association with differences in performance cannot be determined without more careful attention to the details of the task.
The increase in pulmonary arterial pressure caused by hypoxia depends on iron status
Authors: Smith Thomas G. , Balanos George M. , Croft Quentin P. P. , Talbot Nick P. , Dorrington Keith L. , Ratcliffe Peter J. , Robbins Peter A.
Published: October 2008

Hypoxia is a major cause of pulmonary hypertension. Gene expression activated by the transcription factor hypoxia‐inducible factor (HIF) is central to this process. The oxygen‐sensing iron‐dependent dioxygenase enzymes that regulate HIF are highly sensitive to varying iron availability. It is unknown whether iron similarly influences the pulmonary vasculature. This human physiology study aimed to determine whether varying iron availability affects pulmonary arterial pressure and the pulmonary vascular response to hypoxia, as predicted biochemically by the role of HIF. In a controlled crossover study, 16 healthy iron‐replete volunteers undertook two separate protocols. The ‘Iron Protocol’ studied the effects of an intravenous infusion of iron on the pulmonary vascular response to 8 h of sustained hypoxia. The ‘Desferrioxamine Protocol’ examined the effects of an 8 h intravenous infusion of the iron chelator desferrioxamine on the pulmonary circulation. Primary outcome measures were pulmonary artery systolic pressure (PASP) and the PASP response to acute hypoxia (ΔPASP), assessed by Doppler echocardiography. In the Iron Protocol, infusion of iron abolished or greatly reduced both the elevation in baseline PASP (P < 0.001) and the enhanced sensitivity of the pulmonary vasculature to acute hypoxia (P= 0.002) that are induced by exposure to sustained hypoxia. In the Desferrioxamine Protocol, desferrioxamine significantly elevated both PASP (P < 0.001) and ΔPASP (P= 0.01). We conclude that iron availability modifies pulmonary arterial pressure and pulmonary vascular responses to hypoxia. Further research should investigate the potential for therapeutic manipulation of iron status in the management of hypoxic pulmonary hypertensive disease.
Instantaneous Liquid Flow Rate Measurement Utilizing the Dynamics of Laminar Pipe Flow
Authors: Manhartsgruber Bernhard
Published: October 2008

This paper deals with the utilization of the dynamic characteristics of laminar flow in circular pipes for the indirect measurement of flow rates. A discrete-time state space realization of the transmission line dynamics is computed via inverse Laplace transform and an identification and model reduction method based on the singular value decomposition. This dynamic system is used for the computation of the flow rate at one end of a pipe section. Special attention is paid to the identification of the speed of sound and the dimensionless dissipation number of the pipe section, since exact knowledge of these parameters is crucial for the reliability of the measurement results. First, experimental validation results are given in a limited range of operating frequencies between 100 Hz and 2000 Hz. Flow rate variations within ±1.2 l/min have been measured with an uncertainty of ±0.07 l/min at the 95% confidence level. The test fluid was mineral oil.
The Impact of Manifold-to-Orifice Turning Angle on Sharp-Edge Orifice Flow Characteristics in Both Cavitation and Noncavitation Turbulent Flow Regimes
Authors: Nurick W. H. , Ohanian T. , Talley D. G. , Strakey P. A.
Published: October 2008

The approach taken was to analyze the results in a manner consistent with application by design engineers to new and existing applications, while providing some insight into the processes that are occurring. This paper deals with predicting the initiation of cavitation, cavitation impacts on the contraction coefficient (Cc), as well as noncavitation impacts on discharge coefficient (Cd) from L/D of five sharp-edge orifices over a turning angle range between 60 deg and 120 deg. The results show that in the cavitation regime, Cc is controlled by the cavitation parameter (Kcav), where the data follow the 1∕2 power with Kcav, and inception of cavitation occurs at a Kcav of 1.8. In the noncavitation regime for conditions where the cross velocity is 0 the data are consistent with the first order equation relating head loss (HL) to the dynamic pressure where KL is constant and is consistent with in-line orifices. Cross flow has a significant impact on loss coefficient and depends on both the turning angle and manifold inlet to orifice exit velocity ratio.
The Influence of Slip Boundary Conditions on Peristaltic Pumping in a Rectangular Channel
Authors: Mandviwalla X. , Archer R.
Published: October 2008

The flow of an incompressible fluid is modeled in a channel of a rectangular cross section with two symmetric peristaltic waves propagating on the top and bottom. A low Reynolds number and a long wavelength are assumed. The effect on pumping of the inclusion of slip boundary conditions on the side walls is investigated.
Performance Considerations in Power Uprates of Nuclear Power Plants: A Case Study
Authors: Sunder Raj Komandur S.
Published: October 2008

This paper examines the impact of power uprates on the performance of nuclear power plants. Since the 1970’s, power companies have been using power uprates to increase the output of their nuclear power plants. The plant systems and components should be capable of accommodating the accompanying increases in flow conditions. The affected components include the turbine-generator, pipes, valves, pumps, heat exchangers, electrical transformer, etc. The Nuclear Regulatory Commission has classified power uprates as falling into three categories: (1) measurement uncertainty recapture power uprates, (2) stretch power uprates and, (3) extended power uprates. Measurement uncertainty recapture power uprates are up to 2% and are achieved by using enhanced techniques for calculating reactor power. This involves the use of state-of-the-art feedwater flow measurement devices to reduce the degree of uncertainty associated with feedwater flow measurement which, in turn, provide for a more accurate calculation of reactor power. Stretch power uprates are typically up to 7% and within the design capacity of the plant. The actual percentage increase in power is plant-specific and depends on the operating margins included in the plant design. Stretch power uprates usually involve changes to instrumentation setpoints, but do not involve major plant modifications. This is especially true for boiling-water reactor plants. In some limited cases where plant equipment is operated at near capacity prior to the power uprate, more substantial changes may be required. Extended power uprates may be up to 20% and, usually require significant modifications to major pieces of plant equipment such as the high pressure turbines, condensate pumps and motors, main generators, and/or transformers. Using a case study, this paper examines the performance considerations involved in power uprates of nuclear power plants. Affected components such as the turbine-generator, moisture separators, reheaters, feedwater heaters and, condensers are discussed. The use of a performance modeling tool in evaluating the impact of power uprates on nuclear plant performance is discussed. The paper provides conclusions and recommendations for ensuring optimal performance in light of power uprates.
Analysis of Turbine Cycle Performance Losses Using Entropy Balance Techniques
Authors: Sunder Raj Komandur S.
Published: October 2008

The first and second laws of thermodynamics find universal application in steady-state modeling and performance analysis of power plant cycles. While the first law deals with mass and energy balances and the use of enthalpy, the second law deals with the effectiveness of energy utilization and the concept of entropy in analyzing and evaluating losses occurring in power plant cycles. Performance losses are accompanied by increases in entropy. This paper examines the application of entropy balance in evaluating and quantifying losses occurring in a sample turbine cycle. While there are many sources of losses in a power plant cycle, the sources examined in this paper include the boiler, turbine, feedwater heaters, piping and, boiler feed pump. The methodology may be used to analyze and evaluate performance losses occurring in any power plant cycle.
Heat Recovery Steam Generator Optimization Using Analysis of Variance
Authors: Brusca S. , Lanzafame R.
Published: October 2008

The present work deals with the analysis and optimization of a heat recovery steam generator (HRSG) using the ANalysis Of VAriance (ANOVA). In order to obtain an optimum thermodynamic configuration of a three pressure levels HRSG, a mathematical model of the generator has been implemented using a generic thermodynamic code. Model management and HRSG control logic have been implemented using code’s macros and Microsoft Excel VBA programming languages. The model has been finely tuned and tested using real HRSG running data in the current plant configuration. Using the model, evaporators’ pressure levels have been modified and thermodynamic data elaborated using ANOVA technique. Results’ analysis shows that reducing low and medium pressure level in the HRSG, global steam production rises up. At the same time, exhaust gas temperature decreases showing a certain heat adsorption increase. On the basis of the results it is possible to state that the proposed HRSG configuration involves increases in plant steam and power production as well as in global efficiency with HRSG minimal modification.
Evaluating Performance Degradation in Gas Turbines: A Challenging Task
Authors: Zachary Justin
Published: October 2008

The degradation of thermal performance plays a significant role in the economic viability a combined cycle plant. The degradation is applicable not only to the performance guaranteed values for power output and heat rate but also to exhaust flow and exhaust temperature. While the performance degradation of turbo machinery has been a widely accepted fact, an accurate quantitative assessment of the phenomenon is extremely difficult and costly. The paper will review the potential causes of degradation, related to variability in the manufacturing of the equipment, site configuration, fuel composition quality, operational requirements and maintenance practices. The article will also address the impact on the performance guarantees, due to qualifications applied to degradation process terms such as “new and clean condition”, “fired and equivalent operating hours”, and “bench mark testing”. In a combined cycle configuration, due to lengthy commissioning activities of various systems, the acceptance performance tests are conducted only after a significant number of hours in operation have been accumulated. The article will discuss the viability and merits of conducting comparative testing during this commissioning period, aimed at the actual measurement of short-term deterioration. The potential obstacles and challenges of this testing program, associated with changes in the control system, hardware modifications and measurement uncertainty, will also be analyzed in details. The alternative option to account for the expected degradation is the use of correction curves supplied by the equipment manufacturers. The paper will review the suitability to specific project conditions of generically developed curves. In addition, the document will touch on how degradation evaluation may affect the Long Term Service Agreements (LTSA) between Owners and Equipment Manufacturers. Finally, the paper will offer suggestions on how performance and fuel quality continuous monitoring, careful operations and maintenance scheduling could reduce the actual degradation and provide a substantial economic benefit to the Owner.
Contribution on Rotordynamics Analysis With Gear Coupling: Application to Damage Tracking in Reducers
Authors: Kane Malal , Ferraris Guy
Published: October 2008

Most of the research on damage tracking has concentrated on the development of heuristic methods, but none of them can estimate the damage state continuously. In this paper, we focus on damage tracking, particularly the detection and quantification of damage of teeth in reducers and the influence of meshing stiffness on detecting damage. A formulation of an analytical and numerical model of a reducer is proposed into which, it is possible to introduce tooth damage in the gears. Vibratory behavior is analyzed using the wavelet transform. Functional relationships between the feature vector and the damage state are provided at the end of the paper. These functions can be used to perform full tooth damage detection and the model set up can be used to track damage as it occurs and predict its future progression in rotating machines.
Mitigation of Carbon Dioxide Emissions of Coal Power Stations
Authors: Chudnovsky B. , Jinjikhashvily G. , Schweitzer Y. , Talanker A. , Meir R.
Published: October 2008

Coal fired power stations are among factors mostly polluting atmosphere by greenhouse gases, especially by CO2. Strong efforts are done to reduce this pollution, increasing the generation efficiency by gasification of coal, development of super -critical power units and so on. For the existing power station good results may be achieved by simultaneous optimization of the operation condition including proper choice of the fired coal. An analysis of data collected in IEC, where more than 60% of electricity is generated in coal fired units, makes it possible to explore dependence of greenhouse gases emissions (CO2, SO2, NOx,) on the fired coals composition and operation condition. As a tool for the above data analysis computer technique, created in IEC, was used. The technique is based on a modular numerical model including elements corresponding to furnace, boiler, turbine and the whole power unit. It permits to reveal the influence of the coal composition on the boiler and the whole unit performance, as well as on the pollutant emissions. The technique application permitted to separate impact of the two factors: the coal composition and operation conditions on specific emissions of the pollutants. The main result of the study is that the optimization of operation condition while proper choice of the coal provides decrease of pollutants emissions. 2. Bioconversion of CO2 emitted by power stations by intensive photosynthesis is one of the mostly efficient ways for carbon emissions mitigation, especially in countries with high solar activity. Agricultural projects based on CO2 enrichment by flue gases -greenhouses, water ponds for macro and micro algae growing, forests, citrus orchards and other biological systems, if placed in the neighborhood of the coal-fired power stations with high content of CO2 in the flue gases, can be profitable also because of use of cheap low-potential heat and the station infrastructure. Efforts for removal of pollutant components of the flue gases will be compensated by high CO2 content. First steps in this direction have been done by IEC in collaboration with MATI Lev-ha-Galil, Hishtil Nurseries, ARO and IOLR, with support of the R&D Division of the Ministry of the National Infrastructure and showed feasibility of the proposal.
Testing Steam Turbines in Combined Cycle Applications
Authors: McHale Michael P. , Stone Kevin D.
Published: October 2008

ASME Performance Test Code 6.2 for testing of Steam Turbines in Combined Cycle Applications has been approved by the Board of Performance Test Codes and will be issued in 2005. PTC 6.2 provides procedures for the accurate testing of a steam turbine in a Combined Cycle application with or without supplementary firing and in cogeneration applications. The procedures for testing a Rankine cycle steam turbine in a Combined Cycle application differ from those used to test a Rankine cycle steam turbine in a cycle with regenerative feedwater heating because of differences in cycle configuration and test objectives. PTC 6.2 provides procedures for testing and calculating corrected turbine-generator output performance, not corrected heat rate. The Code contains rules and procedures for the conduct and reporting of steam turbine testing, including requirements for pretest arrangements, testing techniques, instrumentation, methods of measurement, and methods for calculating test results and uncertainty. This paper will focus on challenges that have been faced with conducting performance tests on steam turbines in combined cycles in the past, and how the Code has addressed these challenges. Challenges are driven primarily by the cycle configuration, operating practices, and the basis of guarantees. Subjects to be addressed in the paper include test instrumentation, test objectives, test calculations, and test uncertainty.
Predicting Performance of a Condenser With Plugged Tubes
Authors: Minner Gene L. , Weber Gerald
Published: October 2008

The electric power generated in a steam-power plant depends on condenser pressure. Plant performance personnel are frequently called upon to predict effects on megawatts generated and plant heat rate as condenser circumstances vary. The flow rate of circulating water to the condenser is one of the factors that impact the results when doing such predictions. This paper utilizes the PEPSE modeling program to evaluate the effect on the condenser back-pressure and power generation of plugging condenser tubes. The circulating water flow rate is the focal point of this analysis because it influences the heat transfer coefficient inside of the tubes of the condenser. This inside-tube convection heat transfer coefficient is an important contributor to the calculated overall condensing heat transfer coefficient and the resulting condenser pressure. Calculation of the condenser’s shell side pressure is based on the Heat Exchange Institute’s (HEI) methods that are standard in the industry. In operation the circulating water’s flow rate occurs at the point where the head of the circulating water pump balances the hydraulic pressure drops in the circuit. Equations are presented to account for circulating water pressure drops, as foundation for calculations of the hydraulic balancing. The equation methodology is then applied to an actual condenser design.
Successful Vibration Trouble-Shooting of Large Power Plant Rotating Machinery
Authors: Adams Maurice L. , Adams Michael L.
Published: October 2008

This paper presents several recent case studies where the application of cutting-edge measurement and computer modeling have been successfully combined to correctly diagnose and fix power plant rotating machinery excessive vibration problems. These case studies include large turbogenerators and feed water pumps. Each case presented here shows an overall trouble-shooting strategy appropriate to the specific problem symptoms, and describes the measurement and computer modeling phases that successfully resolved the specific problem in each case.
On-Line Heat Rate Monitoring as a Basis for an On-Line Turbine Diagnostic System
Authors: Bercovich Y. , Glickman S. , Levin L. , Gordinsky A. , Belfor V. , Berman M.
Published: October 2008

In this paper, a turbine on-line performance calculation system is presented. The system was implemented on a 575 MW unit of the Israel Electric Corporation and has been in operation for one year. The system was developed jointly by IEC and Berman Engineering Ltd. The main feature of the described system is the precision of the turbine heat rate calculation. This increased precision of the turbine heat rate calculation was accomplished by utilizing sophisticated statistical techniques, such as parametric and nonparametric regression, robust estimation, special filtration methods, autocorrelation methods, and uncertainty estimation methods. This high precision allows using the calculated heat rate as the main input to the turbine diagnostic system. The selection of turbine heat rate as the main diagnostic input is due to its high sensitivity to efficiency deviations of each turbine subsystem (turbine internal efficiency, condenser cleanliness, regenerative heaters’ cleanliness, etc.). However, despite this high sensitivity, the turbine heat rate cannot be used directly without implementing the sophisticated statistical techniques mentioned above because: • relatively small variation of the calculated heat rate over the entire turbine load range (only about 3%); • the presence of systematic and random measurement errors; • low signal/noise ratio as a result of the above items. In order to develop the techniques mentioned above, a detailed study of the error characteristics and error propagation was carried out. This study defined the problems which had to be solved in order to achieve an acceptably high precision of the calculation results. The current results allow using turbine heat rate as a tool for the following purposes: • turbine cycle efficiency estimation for all modes of operation and for turbine cycle scheme variations; • turbine internal condition estimation; • reliability control of measuring instrumentation which is used for turbine heat rate calculations; • determination of heat rate deviation which is above a preset acceptable value (heat rate “out of range”). The structure of the developed system is presented as well as examples of results which show the calculation precision. Also, examples are presented to illustrate how the heat rate can be using for identification of various abnormal situations which may impact the turbine cycle efficiency.
Introduction of Improved Orifice Flow Measurement Methods in ASME PTC 19.5
Authors: Keyser David R. , Friedman Jeffrey R.
Published: October 2008

This paper presents the new information on orifice flow metering in ASME Performance Test Code (PTC) 19.5, “Flow Measurement” [1], and discusses many of the clarifications that have been made based on experience and commentary to the review drafts of the Code. In particular, this paper expounds upon details regarding piping installation requirements for accurate measurement. A major advancement incorporated into ASME PTC 19.5 is the development of a coefficient of discharge equation that is based on fluid dynamic theory. The theoretical concept and a summary of the derivation of the new discharge coefficient equation for orifices are presented in this paper. It is shown that the calibration interpretation methodology introduced in PTC 19.5, which is similar to that developed earlier for nozzle calibrations, reduces the uncertainty of calibrated orifice metering sections, even when used outside the calibration range.
Rethinking the Benefits of CHP
Authors: Tucker C. Thomas
Published: October 2008

In recent years there has been great deal of effort made in promoting combined heat and power (CHP) and its related economic and environmental benefits. Much of this effort has been targeted at industries because they are generally the best suited to host a CHP system. In spite of the efforts and the assistance available, many industries do not seem overly enthusiastic about installing CHP. The primary reason appears to be that electric rates are low relative to typically used fuels such as natural gas. This translates into a longer return on investment than most companies can justify in the face of competing internal pressures. Trying to encourage industries to install CHP in a struggling economy is just that much more difficult. When CHP is installed, there is usually another motivating factor such as a “free” fuel or concerns about power reliability. Does this mean that CHP is not the great solution everyone has been talking about? The author does not believe so. However, maybe it is time to redefine the application of CHP by simply reconsidering the boundary under which it is typically applied. For example, by considering CHP at a State boundary as opposed to a facility boundary, CHP takes on an entirely new role. Expanded benefits can now include economic development, homeland security, environmental sustainability, improved power transmission and distribution and job creation.
Observation of Pressure Drop Behavior in an Operating Fuel Cell Stack
Authors: Barbir Frano , Gorgun Haluk , Wang Xinting
Published: October 2008

Pressure drop on the cathode side of a PEM (Proton Exchange Membrane) fuel cell stack has been studied and used as a diagnostic tool. Since the Reynolds number at the beginning of the flow field channel was <250, the flow through the channel is laminar, and the relationship between the pressure drop and the flow rate is linear. Some departure from linearity was observed when water was either introduced in the stack or produced inside the stack in the electrochemical reaction. By monitoring the pressure drop in conjunction with the cell resistance in an operational fuel cell stack, it was possible to diagnose either flooding or drying conditions inside the stack.
Dynamic Behaviour in a Hydro Power Rotor System Due to the Influence of Generator Shape and Fluid Dynamics
Authors: Karlsson Martin , Aidanpa¨a¨ Jan-Olov
Published: October 2008

Hydro power rotors are subjected to fluid and electromagnetic forces. In this paper measurements and simulations are shown for a hydro power rotor system. The simulation includes the influence of fluid forces in the turbine as well as the electro magnetic pull in the generator. The mechanical rotor system is modelled with the generator and the turbine treated as two rigid bodies, connected to an elastic shaft supported by three bearings. The fluid model in the turbine is based on results from the scientific literature. A model is suggested for the electro magnetic pull due to eccentricity and the shape of the stator core and the rotor rim. Results from the simulation are compared and analyzed with frequency spectrum from vibrations measurements. One can conclude that the unbalance together with geometric properties of the turbine and generator, are possible sources of the most dominant frequency peak in the measurements.
The Importance of Temporary Instrumentation in ASME Performance Testing
Authors: Kirpatrick Thomas Keith , Newland Wesley , Giampetro Michael
Published: October 2008

Due to the economics associated with power generation equipment, accurate data is of paramount importance for the demonstration of thermal performance for the primary power plant components. Since performance measurements and field acceptance tests are also used to base line a plant’s performance, inaccurate data might result in millions in financial loss over a plants life span. Therefore, having low measurement uncertainty associated with test instrumentation is a fundamental requirement. With advancement in (digital) instrumentation and control (I&C) systems for power plants, there has been a growing trend to utilize plant instrumentation in the execution of the American Society of Mechanical Engineers (“ASME”) performance tests. This paper will exhibit the issues with utilizing station instrumentation and provide guidance on the evaluation of these instruments. This paper will also discuss the importance of using instrumentation for the explicit use during testing (“Temporary Instrumentation”) in the conductance of ASME code level testing. Cases will be presented that demonstrate how Temporary Test Instrumentation has identified problems that would have otherwise been overlooked if station instrumentation had been used during thermal performance testing.
Scenarios for Evaluation of Technology Development Options for Power Generation Equipment
Authors: Franco Flavio J.
Published: October 2008

Several national and international organizations publish long term studies of possible future evolutions of primary and final energy consumption, installed power generation, adoption of new energy technologies and greenhouse gas emissions, for example, in the form of ‘scenarios’. Which scenario or combination of scenarios will come true depends on many factors, not least the choice of technologies to be developed and the amount of resources put into the development of the chosen technologies. Power generation equipment manufacturers thus have a strong influence on how the future of the energy world will unfold, through their technological choices and the investments they make to develop the technologies. However their own future also depends on how external factors evolve, including, for example, public opinion, economics, population growth, competitor technologies etc., which are also considered in the aforementioned scenarios. In this paper a discussion is made of the aspects of scenarios described in the literature that are relevant for technology strategic management within the time scales usually considered by commercial organizations. As a result, two scenarios are proposed, based on those presented by the International Energy Agency and on data from other sources.
Multi-Physics Simulations of Fuel Cells Using Multi-Component Modeling
Authors: Smirnov Andrei , Burt Andrew , Zhang Hanzhoug , Celik Ismail
Published: October 2008

Multi-physics simulations based on multi-component multi-solver modeling approach were performed for high-temperature fuel cells. The developed approach was primarily aimed at the design of complex multi-component engineering systems. It extends the libraries of earlier designed multi-physics system with component classes, which makes it particularly suitable for modeling of fuel cell systems. The C++ based class hierarchy enables simple implementations of different physical models based on general 3D PDE (partial differential equations) solvers, or simplified engineering 1D or 2D models. Simulations of solid-oxide fuel cells were performed using a combined transport solver in multi-species environment. The components included the PEN complex (anode, cathod, electrolyte), air/fuel channels, interconnects, seals and ambient environments. Species concentrations, mass, momentum, energy fluxes were solved for different components. Models for unsteady fluid dynamics of species, heat transport, electrochemistry and electric currents were combined within different components and interfaced for common variables at the inter-component boundaries. The results include distributions of temperature, species concentrations and mass fluxes inside co-flow and cross-flow fuel cells with different number of channels.
Real Time Simulation for Speed Control of Switched Reluctance Motor Drive Powered by a Fuel Cell System
Authors: Salem Meranda , Das Tuhin , Chen Xiang , Akella Shankar , Sivashankar Shiva
Published: October 2008

In a competitive world, using real-time simulation rather than off-line simulation provides significant advantage for imitating system dynamics in a real world. Real-time simulation could minimize decision risks for real implementation, shorten design cycle, enhance reliability of research results, and, last but not least, save research and development cost. Moreover, real-time simulation could be also implemented to include real hardware into the loop while is kept as flexible as an off-line numerical simulation. In this paper, a real time simulation mechanism is presented for studying switch reluctance motor (SRM) drive control powered by a fuel cell. The fuel cell stack model is simulated by a software package developed by Emmeskay, Inc., which can be operated in real time. The whole real time simulation is conducted on a two-node platform hosted by RT-Lab, a software product of Opal-RT Technologies, Inc. and engineered by fixed-step real time operating system. In particular, as an illustrating example, an SRM drive control model is first built and then connected with fuel cell stack model. The whole system model is then compiled and operated in real-time on the two-node platform. The real-time simulation result is validated by its off-line simulation counterpart. It is pointed out that this real-time simulation set-up could be easily converted into a hardware-in-the-loop (HIL) simulation carrying real hardware such as microcontroller, real motor, etc., when deemed as necessary. The simulation methodology presented in this paper also indicates a potential low cost approach to support experimentally real-time research and development activities for fuel cell related systems. Considering the high cost to build a real fuel cell system, the set-up described in this paper is extremely meaningful for research and development communities.
The Cities’ Role in the Switch From Destructable to Sustainable Energy Systems
Authors: Iyinbor Jude
Published: October 2008

Every time this Energy subject is mentioned, the stakeholders feel it is going to be an almost impossible task. Most people even feel it is going to change the way we live. There is no other option, we either choose to destroy the Earth now for our future generation, just because we want to continue to design energy systems in the usual way or we choose to sustain the Earth by changing our designs and the way we live. The better option is obvious, but the most important issue is the optimal approach to the solution. This paper will propose an easy approach by giving a guide to how our cities can be a key player as we switch from destructible to sustainable energy systems.
Advances in Desuperheating Technology for Reliable Performance of Combined Cycle Power Plants (CCPP)
Authors: Borzsony Peter , Sherikar Sanjay V.
Published: October 2008

This paper focuses on the advances in desuperheating technology, their application in reliable control of steam temperature in power stations and their implication as far as the overall reliability of cycling units. Typical problems with attemperators/ desuperheaters and the current approach to desuperheater selection are reviewed. Fundamental principles that govern the overall performance in attemperation/ desuperheating are described in conjunction with the analysis and experimental work behind it. Quantifiable, and verifiable, performance criteria for selecting desuperheaters based on the application of these fundamentals are provided. A prediction tool, which is based on the fundamentals approach and shows good agreement with field experience, is described.
Moisture Content Measurements on Sawdust With Radio Frequency Spectroscopy
Authors: Nystro¨m Jenny , Thorin Eva , Backa Stefan O. , Dahlquist Erik
Published: October 2008

The aim of the research described in this paper is to measure moisture content in biomass fuel with radio frequency spectroscopy. The advantage with this method is that radio waves penetrate large samples, and thereby gives an average moisture content representing the whole sample. The method is fast and is a small scale version of what can be applied in the future on-line for biomass fuel arriving in containers to the power plants. The moisture content is determined with a sensor that measure attenuation and phase shift for a frequency spectrum from 310 MHz to 900 MHz. The measurements are performed on sawdust with moisture contents normally occurring in power plants (from 34 to 65%). Multivariate data analysis is used for evaluation of the dielectric spectra from samples with known moisture content. Our results show that it is possible to measure moisture content in sawdust using radio frequency spectroscopy. A partial least square model is built on samples from sawdust. The moisture content varied between 34 and 60%. A standard error for the cross validation of 0.99% and a correlation factor of 0.99 was received. It is known that dielectric properties are also influenced by bulk density and temperature. Tests show that the influence of the bulk density is of greater importance. Further calibration measurements have to be performed to be able to make reliable measurements on the different bio fuels used at power plants.
Root Cause Analysis of a Gas Turbine Compressor Stator Blade Failure
Authors: Gavelli Filippo , Foulds Jude , Sire Robert , Kytomaa Harri
Published: October 2008

Three identical 85 MW combustion turbines experienced cracking and failure of several first stage compressor stator (S1) blades. The root cause analysis involved the following distinct stages: 1. Examination of failed blades including fractography and analyses of the mechanics of their fracture; 2. Blade vibration analysis to determine the modes of vibration and corresponding resonant frequencies; 3. Inlet plenum flow and acoustical analysis to identify possible sources of excitation. This paper summarizes the methodology and results of the root cause analysis investigation and outlines the convergence of results obtained from the independently conducted mechanical and acoustical analyses.
Energy Systems for Rural Communities in Peru
Authors: Mendoza G. Pedro , Arroyo U. Maximiliano , Jime´nez Wilson
Published: October 2008

Integration of renewable energy resources in rural communities is the basis to improve life quality due to two important factors: the first one is the necessity of energy, considering the difficulty to be connected to the national grid due to high installation costs and low electricity demand by potential consumers; the second factor is that preliminary studies have showed that it is possible to make use of about 1.052 kWh/m2/year in these places. Some windmills have been made with local technology design, construction and installation based on the knowledge, skills and material available to local communities, but now it seems necessary to make a first step to integrate modern equipment suited to local needs. Wind energy at the north desert coast rural areas in Peru is capable to develop sustainable projects based on wind energy systems, in order to revitalize rural communities, and help to feed the regional energy needs.
Transient Stefan Flows at Wet and Heated Equipment Boundaries
Authors: Gratton Luca J.
Published: October 2008

With emphasis on thermal losses from internally heated equipment in process applications, the results of conjugate heat and mass transfer modeling are presented for a category of Stefan flow involving vaporization in a semi-permeable heterogeneous media. The model simulates the initial stages of the drying process for wet, partially saturated insulation material abutting heated equipment. Dimensionless forms of the governing equations constitute the model basis for a transient, one-dimensional problem abstraction. Numerical solutions are obtained using finite-difference techniques. Model results are presented to demonstrate drying rate variation at high heat rates in the materials of interest to the applications. Summary results include drying rate, saturation distribution, and fluid velocity profiles with comparison of observed drying front penetration depth to existing literature.
Impact of the Evolution of Rule-Driven Design
Authors: Capozzi Thomas J.
Published: October 2008

Rule-driven design (RDD), sometimes referred to as knowledge-based engineering (KBE), has been available since the mid 1980s. As with all aspects of computer technology and software development, RDD platforms have changed dramatically over the last 20 years. The Babcock & Wilcox Company (B&W) has a long history engaged in using RDD and is currently implementing its third RDD platform. Part of that process involves the conversion of old RDD applications. Some of those applications are about to be placed into production, thus retiring their predecessors. The conversion of these applications highlights how RDD has evolved. This paper discusses the conversion of one of those applications and examines the significant changes that have occurred in RDD. The specific application investigated was developed to automate the mechanical design and arrangement of utility boiler burners. The RDD platform to which the new burner design application was converted is the RuleStream system. The discussion includes how the RuleStream system has changed the landscape of RDD and how that affects the approach taken to RDD application development. Many aspects of the application and the RDD platform are described, but of particular note are the impact of RuleStream’s database architecture for both rule development and model management, its integration with SolidWorks as its graphical interface, and its unique development environment.
Research on Life Assessment and Monitoring System of Steam Turbine
Authors: He Qing , Du Dongmei
Published: October 2008

Since steam turbine always operates at high temperature and pressure, life of the key components of steam turbine, such as, rotor, cylinder, bolt etc., must be considered. Furthermore, the involvement of large-scale steam turbine set in load adjustment makes the life assessment of those key components more important, which are main objects of life assessment and monitoring of steam turbine. Steam turbine suffers very large thermal stress and strain while startup, slowdown and load change, therefore, thermal stress is one of the significant monitoring parameters. Stress field is an important and full-distributed graphics. The 2-D discrete models and its finite element models of rotor and cylinder of steam turbine are analyzed in this paper. Taking rotor and cylinder as control objects; the boundary conditions are given, so that the temperature fields, thermal stress field and thermal strain, etc. are solved. Consequently, a life assessment and online monitoring system of steam turbine is developed, in which the temperature fields and stress fields of rotors and cylinders of high pressure (HP) and intermediate pressure (IP) of steam turbine are calculated and displayed on-line. In accordance with the stress fields, the life wastages caused by the operations, such as, start-up or slowdown or load change, etc., are calculated. The life remainder is the foundation of decision making of management and control of steam turbine operation, maintenance, safety etc.
A Whole Transfer Matrix Method for the Eigensolutions of Multi-Rotor Systems
Authors: Chai Shan , Gang Xianyue , Qu Qinwen
Published: October 2008

Based on the concept of coupling element, a whole transfer matrix method (WTMM) is developed for the eigensolutions of multi-rotor systems. To improve the calculating precision, the Riccati transformation is applied to whole transfer matrix method. Compared with substructure transfer matrix method, the whole transfer matrix method is more suitable to be used in practice because the structure does not need to be separated into substructures at linked point, unknown internal forces and displacements are not involved in, and the equilibrium equations and deformation compatibility equations do not need to be constructed. Some numerical examples are presented at the end of this paper.