bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-Structure Interaction Effects Modeling for the Modal Analysis of a Steam Generator Tube Bundle
Authors: Sigrist Jean-François , Broc Daniel
Published: May 2009

Seismic analysis of steam generator is of paramount importance in the safety assessment of nuclear installations. These analyses require, in particular, the calculation of frequency, mode shape, and effective modal mass of the system eigenmodes. As fluid-structure interaction effects can significantly affect the dynamic behavior of immersed structures, the numerical modeling of the steam generator has to take into account FSI. A complete modeling of heat exchangers (including pressure vessel, tubes, and fluid) is not accessible to the engineer for industrial design studies. In the past decades, homogenization methods have been studied and developed in order to model tubes and fluid through an equivalent continuous media, thus avoiding the tedious task to mesh all structure and fluid subdomains within the tube bundle. Few of these methods have nonetheless been implemented in industrial finite element codes. In a previous paper (Sigrist, et al., 2007, “Fluid-Structure Interaction Effects Modeling for the Modal Analysis of a Nuclear Pressure Vessel,” J. Pressure Vessel Technol., 123, pp. 1–6), a homogenization method has been applied to an industrial case for the modal analysis of a nuclear rector with internal structures and coupling effects modeling. The present paper aims at investigating the extension of the proposed method for the dynamic analysis of tube bundles with fluid-structure interaction modeling. The homogenization method is compared with the classical coupled method in terms of eigenfrequencies, eigenmodes, and effective modal masses.
Analyses on the Short-Term Mechanical Properties of Plastic Pipe Reinforced by Cross Helically Wound Steel Wires
Authors: Zheng Jinyang , Li Xiang , Xu Ping , Lin Xiufeng , Li Yaxian
Published: May 2009

Plastic pipe reinforced by cross helically wound steel wires, namely PSP, is a new plastic-matrix steel composite pipe developed in China recently. In order to understand the mechanical properties of PSP under internal pressure, a four-layer analytical model, which considers the torsion caused by the differences between the winding angles of the inner and outer steel wire layers, has been proposed using structural mechanics. The model includes an inner high density polyethylene (HDPE) layer, an inner steel wire layer, an outer steel wire layer, and an outer HDPE layer. To investigate the mechanical properties in inner and outer steel wire layers, the elastic parameters of the composite monolayer plate were deduced from the rectangle outside and circle inside model. During the elastic response of PSP subjected to internal pressure, the stresses and strains in four layers and pressures between the interfaces were obtained. Good agreement between theoretical results and experimental data was observed, which shows that the presented model can be employed to predict stresses, strains, and torsions in PSP. The failure modes and torque values between PSPs manufactured by two different methods were compared, and the influence of the change in the winding angle on the strain in the exterior surface was also discussed.
Effect of Precompression on Thickness of Pipe During Bending
Authors: Kale A. V. , Thorat H. T.
Published: May 2009

Straight pipes with a circular cross section are processed into smooth bends by various pipe bending techniques. After bending, the initial circular cross section is deformed with thickness change. These changes from ideal are normally referred to as “ovality” and “thinning.” Their influence on the subsequent behavior of curved pipes is not yet fully understood. The aim of this paper is to present a factual method to reduce thinning of the wall thickness of pipe during bending. A new mechanism is developed for bending of pipes. This mechanism has a provision of precompression (radial squeeze) of the pipe along the directrix of maximum deformation during bending. This is achieved by clamping the pipe using two parallel plates from top and bottom. In fact, the pipe is wrapped using two rollers—one from inside and one from outside in the horizontal plane—and two plates parallel to the horizontal plane—one from the top and one from the bottom. Experimentation is carried out on this mechanism, and thicknesses are measured at the grid points along the length of the pipe. From the experimental values of thicknesses on the tension and compression sides, dimensionless variations in wall thickness of various groups of pipes are computed for different precompression values. In order to represent the thickness at any point, a mathematical equation is derived. Analytical values of thickness variations on tension and compression sides are computed using this equation. Experimental and analytical results are compared, and its methodical approach is presented in this paper. Results show that precompression reduces thickness variation of the pipe after bending.
Development of Weighted Residual Based Lattice Boltzmann Techniques for Fluid-Structure Interaction Application
Authors: Kwon Y. W. , Jo Jong Chull
Published: May 2009

New computational techniques were developed for the analysis of fluid-structure interaction. The fluid flow was solved using the newly developed lattice Boltzmann methods, which could solve irregular shape of fluid domains for fluid-structure interaction. To this end, the weighted residual based lattice Boltzmann methods were developed. In particular, both finite element based and element-free based lattice Boltzmann techniques were developed for the fluid domain. Structures were analyzed using either beam or shell elements depending on the nature of the structures. Then, coupled transient fluid flow and structural dynamics were solved one after another for each time step. Numerical examples for both 2D and 3D fluid-structure interaction problems, as well as fluid flow only problems, were presented to demonstrate the developed techniques.
Structural Response of Piping to Internal Gas Detonation
Authors: Shepherd Joseph E.
Published: May 2009

Detonation waves in gas-filled piping or tubing pose special challenges in analysis and prediction of structural response. The challenges arise due to the nature of the detonation process and the role of fluid-structure interaction in determining the propagation and arrest of fractures. Over the past 10 years, our laboratory has been engaged in studying this problem and developing methodologies for estimating structural response. A brief overview of detonation waves and some key issues relevant to structural waves is presented first. This is followed by a summary of our work on the elastic response of tubes and pipes to ideal detonation loading, highlighting the importance of detonation wave speed in determining flexural wave excitation and possibility of resonant response leading to large deformations. Some issues in measurement technique and validation testing are then presented. The importance of wave reflection from bends, valves, and dead ends is discussed, as well as the differences between detonation, shock wave, and uniform internal pressure loading. Following this, we summarize our experimental findings on the fracture threshold of thin-walled tubes with pre-existing flaws. A particularly important issue for hazard analysis is the estimation of loads associated with flame acceleration and deflagration-to-detonation transition. We give some recent results on pressure and elastic strain measurements in the transition regime for a thick-wall piping, and some remarks about plastic deformation.
Further Study of Quasiperiodic Vibration Excitation Forces in Rotated Triangular Tube Bundles Subjected to Two-Phase Cross Flow
Authors: Zhang C. , Pettigrew M. J. , Mureithi N. W.
Published: May 2009

Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting-wear or fatigue. Detailed vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Some of this work has already been done. Somewhat unexpected but significant quasiperiodic forces in both the drag and lift directions were measured. These forces are generally larger in the drag direction. However, the excitation force frequency is relatively low (i.e., 3–6 Hz) and not directly dependent on flow velocity in the drag direction. On the other hand, much higher frequencies (up to 16 Hz) were observed in the lift direction at the higher flow velocities. The frequency appears directly related to flow velocity in the lift direction. The present work aims at (1) providing further evidence of the quasiperiodic lift force mechanism, (2) determining the effect of cylinder position on such quasiperiodic drag and lift forces, and (3) verifying the existence of quasiperiodic drag and lift forces in a more realistic larger tube array. The program was carried out with two rotated triangular tube arrays of different width subjected to air/water flow to simulate two-phase mixtures from liquid to 95% void fraction. Both the dynamic lift and drag forces were measured with strain gauge instrumented cylinders.
Impact Mitigation for Buried Structures: Demolition of the New Haven Veterans Memorial Coliseum
Authors: Woelke Pawel , Tang Margaret , McClennan Scott , Abboud Najib , Tennant Darren , Hapij Adam , Ettouney Mohammed
Published: May 2009

We present an overview of the analysis and design of mitigation schemes for buried structures subjected to impact loading, with a focus on the hazard evaluation to underground utilities from the demolition by implosion of the Veterans Memorial Coliseum in New Haven, CT. We discuss the analytical and numerical investigations validated by field testing conducted prior to the implosion and leading to the design of the mitigation schemes aimed at protecting the utilities buried under ground. All the designed and constructed mitigation schemes proved successful during the January 2007 implosion of the Veterans Memorial Coliseum.
Elimination of Thermoacoustic Furnace Vibration in a Gas-Fired Package Boiler: A Case Study
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: May 2009

A severe furnace vibration was developed in a gas-fired package boiler during an initial operation. The vibration occurred at higher loads and was characterized by an acoustic standing wave residing inside the furnace in the front-to-rear direction along a burner axis. Theoretical predictions indicated that the thermoacoustic behavior of the burner/furnace system operated in an unstable range explaining the underlying cause of the vibration problem. For the elimination of the vibration problem, a two-step solution was envisioned: (1) The mode of fuel injection was modified in order to affect the flame’s oscillatory behavior and its interaction with the acoustic waves in the enclosed spaces of the burner conduits and the furnace. This step was successful in mitigating the vibration in a still thermoacoustically unstable system. (2) A full elimination of the vibration may be achieved by making the system thermoacoustically stable by modifying the cold air portion of the system. Both the step 1 solution, which suppressed the thermoacoustic oscillation, and the step 2 solution of making the system thermoacoustially stable will allow the boiler to operate without vibration at all loads. This paper gives a detailed description of the issues involved.
Strength Model Uncertainties of Burst, Yielding, and Excessive Bending of Piping
Authors: Avrithi Kleio , Ayyub Bilal M.
Published: May 2009

Nuclear safety-piping is designed according to the ASME Boiler and Pressure Vessel Code, Sections III, NB-, NC-, and ND-3600 that use the allowable stress design method (ASD). The potential use instead of reliability-based design equations for nuclear piping could benefit the structural design by providing, among others, consistent reliability levels for piping. For the development of such equations, not only the probabilistic characteristics of the design variables are needed, but also the quantification of the uncertainties introduced by the strength models that are used in order to estimate the resistance of pipes subjected to different loadings. This paper evaluates strength models, and therefore provides necessary information for the reliability-based design of pipes for burst or yielding due to internal pressure and for excessive bending.
A Comparison of the tanh and Exponential Fitting Methods for Charpy V-Notch Energy Data
Authors: EricksonKirk Marjorie Ann , EricksonKirk Mark T. , Rosinski Stan , Spanner Jack
Published: May 2009

In the 1960s and 1970s, when the surveillance programs for currently operating commercial nuclear reactors were established, state of knowledge limitations resulted in the use of Charpy-V notch (CVN) specimens rather than fracture toughness specimens. Reasonable success has since been achieved in correlating CVN and fracture toughness parameters. Such correlations provide an important part of the technical basis for both current regulations and ASME codes. These correlations imply that trends manifest in CVN data must also appear in fracture toughness data, even though empirical evidence demonstrate that this is not always true. For example, the temperature dependence of CVN energy (CVE) in transition is thought to be a unique feature of each specific sample of ferritic steel that is tested, a view in sharp contrast with the now widely accepted view of a “master curve” for transition fracture toughness (KJc). Also, effects of product form on CVE temperature dependence and property correlations are widely reported, despite the fact that product form effects are absent from KJc properties. These observations suggest that the mapping of CVE behavior onto fracture toughness implicit to correlation-based regulations and ASME codes may produce erroneous trends in estimated values of fracture toughness. In this paper we investigate the hypothesis that the apparent differences between CVE and fracture toughness arise due to differences in how the temperature dependence of CVE and KJc data have historically been modeled. Our analysis shows that when CVE data are analyzed in a manner consistent with KJc data (i.e., transition and upper shelf data are partitioned from each other and analyzed separately rather than being fit with a continuous tanh function), the apparent differences between CVE and toughness characterizations are minimized significantly, and may disappear entirely. These findings demonstrate the differences between CVE and fracture toughness data to be an artifact of the tanh analysis method rather than an intrinsic property of CVE.
A Probabilistic Assessment Technique Applied to a Cracked Heat Exchanger Tube Subjected to Flow-Induced Vibration
Authors: Vincent Brady T. , Hassan Marwan A. , Rogers Robert J.
Published: May 2009

Flow-induced vibration is a common phenomenon in shell-and-tube heat exchangers. The resulting vibration can lead to component failure by fretting wear due to tube-to-tube support impact or by fatigue. Due to manufacturing considerations, many parameters such as support clearance, alignment, and friction at the supports are not exactly known and are represented by statistical distributions. This makes the use of deterministic equations inaccurate. This paper presents a methodology that can be used during component operation to monitor known flaws and ensure safe operation. The methodology incorporates Monte Carlo simulations to predict remaining service life of a vibrating heat exchanger tube with a small circumferential through-wall crack next to the tube sheet. Vibration excitation includes turbulence and low-level fluid-elastic forces. Leakage calculations are made on the through-wall crack as it grows to fracture. A Weibull distribution is given for the time-to-fracture and for the time for the leak rate to reach a threshold value. This statistical information can then be used to assess the remaining service life and whether LBB criteria will be met.
Strain Rate Dependence and Short-Term Relaxation Behavior of a Thermoset Polymer at Elevated Temperature: Experiment and Modeling
Authors: McClung A. J. W. , Ruggles-Wrenn M. B.
Published: May 2009

The inelastic deformation behavior of polymerization of monomeric reactants-15 (PMR-15) neat resin, a high-temperature thermoset polymer, was investigated at 288°C. The experimental program was designed to explore the influence of strain rate changes in the 10−6–10−3 s−1 range on tensile loading, unloading, and strain recovery behavior, as well as on the relaxation response of the material. The material exhibits positive, nonlinear strain rate sensitivity in monotonic loading. Nonlinear, “curved” stress-strain behavior during unloading is observed at all strain rates. The strain recovery at zero stress is profoundly affected by prior strain rate. The prior strain rate is also found to have a strong influence on relaxation behavior. The rest stresses measured at the termination of relaxation tests form the relaxation boundary, which resembles a nonlinear stress-strain curve. The results suggest that the inelastic behavior of the PMR-15 solid polymer at 288°C can be represented using a unified constitutive model with an overstress dependence of the inelastic rate of deformation. The experimental data are modeled with the viscoplasticity theory based on overstress. A systematic procedure for determining model parameters is presented and the model is employed to predict the response of the material under various test histories.
Numerical Simulation of the Flow-Sound Interaction Mechanisms of a Single and Two-Tandem Cylinders in Cross-Flow
Authors: Mohany A. , Ziada S.
Published: May 2009

A numerical simulation of the flow-excited acoustic resonance for the case of two-tandem cylinders in cross-flow is performed. The spacing ratio between the cylinders (L/D=2.5) is inside the proximity interference region. Similar simulation is performed for the case of a single cylinder. The unsteady flow field is simulated using a finite-volume method. This simulation is then coupled with a finite-element simulation of the resonant sound field, by means of Howe’s theory of aerodynamics sound, to reveal the details of flow-sound interaction mechanisms, including the nature and the locations of the aeroacoustic sources in the flow field. For the case of a single cylinder, acoustic resonance is excited over a single range of flow velocity. The main aeroacoustic source, which causes a positive energy transfer from the flow field to the acoustic field, is found to be located just downstream of the cylinder. For the case of two-tandem cylinders, the acoustic resonance is excited over two different ranges of flow velocity: the precoincidence and the coincidence resonance ranges. For the coincidence resonance range, the main aeroacoustic source is found to be located just downstream of the downstream cylinder, and the excitation mechanism of this resonance range is found to be similar to that of a single cylinder. However, for the precoincidence resonance range, the primary acoustic source is found to be located in the gap between the cylinders. Moreover, flow visualization of the wake structure for the two-tandem cylinders during acoustic resonance shows that for the precoincidence resonance range there is a phase shift of about 90 deg between the vortex shedding from the upstream and the downstream cylinders, which is different from the coincidence resonance range, where the vortex shedding from both cylinders seems to be in-phase.
Assessment Procedure for Multiple Volumetric Flaws in p-M Diagram
Authors: Konosu Shinji
Published: May 2009

Assessment of multiple volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service rules, such as ASME, BS, and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple cracklike flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two differently sized nonaligned volumetric flaws such as local thin areas is clarified by applying the body force method. Unlike multiple cracklike flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction that indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) diagram, which is a simple assessment procedure for vessels with volumetric flaws.
Stamina of a Nongasketed Flange Joint Under Combined Internal Pressure, Axial, and Bending Loading: An Experimental Study
Authors: Abid Muhammad , Nash David H.
Published: May 2009

Performance of a bolted flange joint is characterized mainly due to its “strength” and “sealing capability.” A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. A very limited work is found in the literature under combined internal pressure and bending loading. Due to the ignorance of this external loading, i.e., bending and axial in addition to the internal pressure loading, the optimized performance of the bolted flange joint cannot be achieved. The present design codes do not address the effects of combined loading on the structural integrity and sealing ability. To investigate joint strength and sealing capability under combined loading, an extensive experimental study of a nongasketed flange joint with two different assemblies and with different load combinations is carried out, and overall joint performance and behavior is discussed. Actual joint load capacity is determined under both the design and proof test pressure with maximum additional external loading (axial and bending) that can be applied for safe joint performance. In addition, application of combined load is also discussed in the light of equivalent pressure approach.
Thermal Shock Testing and Analysis of IN617 and Super 304H Samples
Authors: Shingledecker J. P. , Battiste R. L. , Carter P.
Published: May 2009

The DOE/OCDO sponsored Ultrasupercritical Steam Boiler Consortium is conducting thermal shock tests on austenitic and nickel-based materials to assess their use in thick-section boiler components. This paper describes the tests on CCA617 (a controlled chemistry version of IN617) and Super 304H thick-walled tubes. Details are given of the metallurgical analyses of the observed cracking in the bore and on the outside diameter of the samples, and of the thermal-mechanical analyses to explain the results. Elastic-plastic and elastic-plastic-creep analyses are used to calculate damage based on rupture life and creep strain accumulation. The results of the metallurgical and mechanical analyses are compared, and conclusions are drawn as to the accuracy and effectiveness of available high temperature life prediction techniques. The test conditions bear no relation to expected operating conditions. They are chosen to generate failure data.
Wind Effects on Dynamic Response of a Floating Roof in a Cylindrical Liquid Storage Tank
Authors: Matsui Tetsuya , Uematsu Yasushi , Kondo Koji , Wakasa Takuo , Nagaya Takashi
Published: May 2009

The dynamic response of a floating roof in a cylindrical liquid storage tank under wind loads is investigated analytically. Wind tunnel test in a turbulent flow is carried out to measure the wind pressure distributing over the roof surface. The measured data for the wind pressure is then utilized to predict the dynamic response of the floating roof, which is idealized herein as an isotropic elastic plate of uniform stiffness and mass. The dynamic interaction between the liquid and the floating roof is taken into account exactly in numerical sense within the framework of linear potential theory. The numerical results are presented, which illustrate the significant effect of wind loads on the dynamic response of liquid-floating-roof system in a storage tank.
A Numerical Study on the Sensitivity of the Discrete Element Method for Hopper Discharge
Authors: Kruggel-Emden H. , Rickelt S. , Wirtz S. , Scherer V.
Published: May 2009

Based on the time-driven discrete element method, granular flow within a hopper is investigated. The main focus is thereby set on hopper vessel design variables such as discharge rates and applied wall pressures. Within the used model contacts are assumed as linear viscoelastic in normal and frictional-elastic in tangential direction. The hopper geometry is chosen according to Yang and Hsiau (2001, “The Simulation and Experimental Study of Granular Materials Discharged From a Silo With the Placement of Inserts,” Powder Technol., 120(3), pp. 244–255), who performed both experimental and numerical investigations. The considered setup is attractive because it involves only a small number of particles enabling fast modeling. However, the results on the experimental flow rates reported are contradictory and are afflicted with errors. By an analysis of the hopper fill levels at different points of time, the correct average discharge times and flow rates are obtained. Own simulation results are in good agreement with the experimental flow rates and discharge times determined. Based on the thereby defined set of simulation parameters, a sensitivity analysis of parameters such as friction coefficients, stiffnesses, and time steps is performed. As flow properties, besides the overall discharge times, the discharge time averaged axial and radial velocity distributions within the hopper and the normal stresses on the side walls during the first seconds of discharge are considered. The results show a strong connection of the friction coefficients with the discharge times, the velocity distributions, and the stresses on the side walls. Other parameters only reveal a weak often indifferent influence on the studied flow properties.
Fracture Assessment Procedures for Steel Pipelines Using a Modified Reference Stress Solution
Authors: Tkaczyk Tomasz , O’Dowd Noel P. , Nikbin Kamran
Published: May 2009

An accurate defect assessment procedure is needed to ensure integrity of girth welded steel pipelines while avoiding unnecessary repairs. An integral part of such a procedure is an estimation scheme for the crack driving force. In this work, a modified reference stress solution was developed for the assessment of elastic-plastic pipes with surface breaking defects. For the particular case of interest (reeled offshore pipelines), the loading is phrased in terms of applied strain. The stress-based approach has therefore been extended to the case of strain/displacement control. The results obtained using the modified reference stress solution have been compared with a three-dimensional finite-element analysis. Very good agreement has been obtained. The predictions are also significantly better than those obtained from existing approaches. A comparison between the proposed method and full scale testing will be presented in a separate paper.
An Oxy-Hydrocarbon Model of Fossil Fuels
Authors: Lang Fred D. , Canning Tom
Published: May 2009

This paper asserts a new method of analyzing fossil fuels, useful for sorting coals into well defined categories and for the identification of outlying ultimate analysis data. It describes a series of techniques starting with a new multi-variant approach for describing the lower Ranks of coal, progressing to a classical, but modified, single-variant approach for the volatile and high energy Ranks. In addition, for a few special cases, multiple low and high Ranks are also well described by the multi-variant approach. As useful as these techniques are for analyzing fuel chemistry in the laboratory arena, this work was initiated in support of Exergetic Systems’ Input/Loss Method. At commercial coal-fired power plants, Input/Loss allows the determination of fuel chemistry based on combustion effluents. The methods presented allow equations to be developed independent of combustion stoichiometrics, which improve Input/Loss accuracy in determining fuel chemistry on-line and in real time.
Last-Stage Blade Failure Evaluation
Authors: Mazur Zdzislaw , Garci´a-Illescas Rafael , Aguirre-Romano Jorge , Pe´rez-Rodri´guez Norberto
Published: May 2009

A last stage turbine blades failure was experienced in two units of 660 MW. These units have one high-pressure turbine and two tandem-compound low-pressure turbines with 44-inch last-stage blades. The blades that failed were in a low pressure (LP) turbine connected to the high pressure (HP) turbine (LP1) and in LP turbine connected to the generator (LP2). The failed blades had cracks in their roots initiating at the trailing edge, concave side of the steeple outermost fillet radius. Laboratory evaluation of the cracking indicates the failure mechanism to be high cycle fatigue (HCF). The last-stage blades failure evaluation was carried out. The investigation included a metallographic analysis of the cracked blades, natural frequency test and analysis, blade stress analysis, unit’s operation parameters and history of events analysis, fracture mechanics and crack propagation analysis. This paper provides an overview of this failure investigation, which led to the identification of the blades torsional vibrations near 120 Hz and some operation periods with low load low vacuum as the primary contribution to the observed failure.
Vibration Fault Diagnosis Method Based on Compositive Characteristics of Rotor Vibration and Stator Current
Authors: Wan Shuting , Li Yonggang
Published: May 2009

Rotor vibration characteristics are first analyzed, when the rotor winding inter-turn short circuit fault, the air-gap dynamic eccentricity fault, the air-gap static eccentricity fault and the imbalance fault occurs. Next, the generator stator current characteristics on the faults also were analyzed, the results show that the faults can’t be diagnosed based only on rotor vibration characteristics or stator current characteristics. But considering the differences of compositive characteristics of the rotor vibration and stator current caused by different rotor faults, a new method of generator vibration fault diagnosis, based on compositive characteristics, is developed. Finally, the rotor vibration and stator current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.
Vibration Monitoring and Fault Diagnosis System of Turbine-Generator
Authors: Du Dongmei , He Qing , Li Hong
Published: May 2009

It is very important to monitor vibration and diagnose fault for the operating safety of turbine-generator. The remote monitor and diagnosis via the cyber-based technology is a necessity. The difference between browser/server mode and client/server mode is discussed. There are many advantages of applying Java technology. Using Java, a vibration monitoring and fault diagnosis system of turbine-generator based on browser/server mode is developed. The functions as well as the structure of the whole system are analyzed. Online transmission of batch data via Internet is presented, especially for different program languages. Java Applet technology is used to develop client program. With double-buffer method, a lot of graphic interfaces of dynamic making online are presented, which are not blinking. It is proved that the system is already adopted and functions well in several power plants.
Application of Neural Networks in Fault Diagnosis of Rotating Machinery
Authors: He Qing , Du Dongmei
Published: May 2009

The fault diagnosis method based on artificial neural networks is summarized. An object-oriented paradigm is introduced to fault diagnosis for large scale rotating machinery, for example, turbine-generator. A fault diagnosis method based on object-oriented artificial neural networks for more symptom domains is presented. The training patterns are constructed. A treatment for incomplete symptom domains and/or concurrent faults in diagnosing is given. Verification is carried out for the actual turbine-generator data with incomplete symptom domains.
The Kyoto Protocol: Some Considerations About Its Applications in Italy
Authors: Gambini Marco , Vellini Michela
Published: May 2009

Climate change is a very important environmental, social and economic global problem. During the last century, the Earth’s average surface temperature rose by around 0.6°C. Evidence is getting stronger that most of the global warming that has occurred over the last 50 years is attributable to human activities. Human activities that contribute to climate change include the burning of fossil fuels because it causes emissions of carbon dioxide (CO2), which is the main gas responsible for climate change. In order to bring climate change to a halt, global greenhouse gas emissions would have to be reduced significantly. The European Union (EU) is engaged in international efforts to combat climate change. The EU is also taking serious steps to address its own greenhouse gas emissions. In March 2000 the Commission launched the European Climate Change Programme (ECCP). The ECCP led to the adoption of a range of new policies and measures, among which the EU’s emissions trading scheme, which started its operation on 1 January 2005, will play a key role. In this paper, we want to shortly explain the mechanisms of the Kyoto Protocol, paying particular attention to the Emission Trading. We want to illustrate the European directive and the consequent Italian one: we will explain the Italian implementing norms that have been emitted for the period 2005–2007 and 2008–2012. Limiting then the analysis to the sector of electricity production, we want to show some examples of Italian power plants: we will illustrate them and we will estimate their CO2 emissions (according to a typical annual operation). The emission levels will be compared with CO2 quotas assigned in the period 2008–2012: these results will be commented in terms of the unavoidable economic implications that such allocation will involve. The CO2 quotas, assigned to Italy already for the period 2005–2007, involve a large control of these emissions: such situation will be reflected unavoidably on the increase of the kWh cost (it is already particularly high in comparison with the European average because of the particular energetic mix on which our electricity production is based): these effects could be particularly heavy for the competitiveness of our production system and for the modernization and the widening of our power plant park.
Performance Diagnostics of Pulverized Coal Fuelled Power Generation Plant Using Exergy-Based Specific Consumption Analysis
Authors: Li Hongtao
Published: May 2009

Exergy analysis approved to be a powerful tool for assessing the thermodynamic performance of energy conversion processes. As one of the extensions, the Specific Analysis Approach is trying to deliver the spatial and temporal information on decomposed exergy losses of an energy conversion process in both absolute and relative terms, in a way that users are familiar with. The conceptual and computational complexities of exergy analyses are left behind the easily understood and accessible thermodynamic performance indicators, such as specific fuel consumption of the total plant and of different equipment components, under different load and time series. In this paper, this approach has been implemented in diagnosing the operating performances of a 300MW pulverized coal fired unit. The results show clearly the energy saving potential of the whole plant, and of different components. The possible equipment failures at the state the data were acquired were diagnosed.
Numerical Analysis of the Blade Forces Caused by Wake/Blade Interaction in the Last Stage of a Steam Turbine
Authors: Garci´a J. C. , Kubiak J. , Sierra F. , Urquiza G. , Rodri´guez J. A.
Published: May 2009

In a steam turbine stage there is an interaction between blades and the flow field. The blades are subjected to the forces caused by the flow field, but also the flow field is affected by the blades and its movement. The nozzle wakes cause uneven pressure field downstream and produce alternating forces on blades which lead to blade vibrations. Some of the vibrations originated in this way may damage the blades and affect the turbine performance. The results of numerical computations about the forces acting on the blades as a result of the variations in the flow field in the axial clearance rotor-stator in the last stage of a 110 MW steam turbine are presented. The analysis is focused on discussing the pressure field because it is necessary for further computation of the useful life time. The flow field was resolved using computational fluids dynamics and the computed pressure field was integrated around the blades to get the forces acting on blades. These computed dynamical forces will be used in the blade useful life estimation and in the investigation to the failure causes of these blades. The Navier-Stokes equations are resolved in two and three dimensions using a commercial program based on finite-volume method. 2-D and 3-D geometry models were built to represent the dimensional aspects of the last stage of the turbine. Periodic boundary conditions were applied to both sides of a periodic segment of the 2-D and 3-D models with the purpose of reducing computational efforts. The computations were conducted in steady state and transient conditions. The results show that the force magnitude acting on blades has an harmonic pattern. Finally a Fourier analysis was used to determine the coefficients and frequency of a Fourier equation which can be used to calculate the alternating stresses on the blade in order to predict the useful life of the blades. Also, the pressure and velocity fields are shown between the diaphragm and rotor blades along the axial clearance.
Investigation Into a “Steam Whirl” Which Affected HP Rotors of 300 MW Steam Turbines
Authors: Kubiak Sz. Janusz , Childs Dara , Rodri`guez M. , Garci´a J. C.
Published: May 2009

In the past, several 300 MW steam turbine rotors were affected by vibrations, which appeared at bearing #1 during load conditions. At certain loads, vibrations of the #1 bearing increased considerably. Near full load the amplitude of vibration sometimes reduced to acceptable levels. Practically, the phenomena were partially cured by trim balancing of the HP rotor, readjusting the valve opening characteristics and by correction of the clearances in the sealing system. The results are briefly summarized. On the other hand, the simulation of the various parameters using rotordynamic codes was conducted to explain the phenomena analytically. In this part, the rotordynamic rotor model was constructed and the following simulations were carried out: rotor bearing instability, effect of the destabilizing steam forces on the rotor at the first row, effect of the seal rotordynamic forces and the valve opening sequence on the rotor stability. All results were analyzed to present general conclusions.
Using Microsoft Excel and Cimplicity HMI to Monitor and Control Energy Generation in a Cogeneration Plant
Authors: Marti´nez Alejandro Hinojosa , Vega-Galaz Jose Ramon , Diaz de Leon Herminia
Published: May 2009

Cimplicity is a Human-Machine interface software which acquires data from CNCs Robots and PLGs, data is then visualized on real time by an operator in a Cimplicity screen on a PC monitor. This software lets the operator perform operations, monitor and control status in a factory in an easy, natural, and intuitive way. This paper will focus on the use of Cimplicity HMI and Microsoft Excel in COMONSA, a cogeneration plant designed and installed by SEISA (International Energy Systems). The cogeneration plant is localized in Monclova, Coahuila, Mexico. This plant supplies energy and, heat to a metal manufacturing factory called INMAGUSA. In this case Cimplicity acquires data from a PLC connected to two reciprocating Engines, which are responsible of supplying heat and electrical energy to the factory, and other auxiliary devices that keep the cogeneration plant running. Cimplicity transforms the data received by the PLC and then displays it on screens while it is being stored on Excel sheets in predefined time intervals. A total of 1093 variables are displayed in 70 different screens. This paper will center on the variables, screens and programs created by the authors. Screens created for the purpose of making the process of invoicing easier for SEISA, for monitoring daily kWh and monthly factory consumption. And two algorithms programmed using Microsoft Visual Basic to facilitate optimal operation of the cogeneration plant.
Impact of Wireless Laser Based Shaft Alignment on Vibration and STG Coupling Failure
Authors: Endres Ned M. , Swan E. Peyton
Published: May 2009

Proper shaft-to-shaft alignment during normal machinery operation is essential for improved machinery reliability. Having the proper tools to perform an accurate coupling alignment are critical to maximized maintenance efficiency. Improvements in hardware and software technology have greatly simplified coupling alignment procedures. A comprehensive machine alignment consists of two elements: measurement of the shaft-to-shaft alignment and measurement of the thermal growth and dynamic movement of each bearing housing. Accurate measurement of these elements should be used to position the cold alignment condition in order to properly align the shaft under loaded conditions. Shaft-to-shaft alignment is typically measured using either laser or dial-indicator instrumentation. RoMaDyn used a laser based system utilizing bluetooth technology for shaft alignment readings. This system provides excellent accuracy, flexibility, and fast results. Often if unit casing temperatures change little immediately after a hot coast down, relative shaft to shaft thermal growth measurements can be acquired using laser coupling alignment readings. Hot and cold alignment data can then be incorporated into an alignment drawing to determine measured shaft relative thermal growth. The measured thermal growth readings or OEM calculated growth numbers are then incorporated into the cold unit alignment settings to provide the best hot alignment condition. This paper will discuss a recent case history involving chronic coupling failures at a customer’s facility. Acquired vibration and shaft alignment readings will be discussed. These measurements will illustrate the effects of alignment changes on machinery vibration levels and coupling reliability.
Numerical 3-D Conjugated Heat Transfer Simulation of a First Inter-Stage Internal Cooled Thermal Barrier Coated Gas Turbine Bucket
Authors: Herna´ndez Rossette Alejandro , Mazur C. Zdzislaw , Guridi Jesu´s Cordero , Polanco Eric Chumacero
Published: May 2009

As a gas turbine entry temperature (TET) increases, thermal loading on first stage blades increases too and therefore, a variety of cooling techniques and thermal barrier coatings (TBCs) are used to maintain the blade temperature within the acceptable limits. In this work a multi-block three dimensional Navier-Stokes commercial turbomachinery oriented CFD-code has been used to compute steady state conjugated heat transfer (CHT) on the blade suction and pressure coated sides of a rotating first inter-stage (nozzle and bucket) with cooling holes of a 60 MW Gas turbine. A Spallart Allmaras model was used for modeling the turbulence. Convection and radiation were modeled for a super alloy blade with and without TBC. The CFD simulations were configured with a mesh domain of nozzle and bucket inter-stage in order to predict the fluid parameters at inlet and outlet of bucket for validate with turbine inter-stage parameter data test of gas turbine manufacturer. The effects of blade surface temperature changes were simulated with both configurations coated and uncoated blades.
Reducing Cooling Tower Fill Fouling and Degradation With Water Quality Control
Authors: Olson Vickie G.
Published: May 2009

Cooling tower fill may be composed of wood or plastic, but it must provide adequate surface area for heat dissipation. Online and field water quality analysis can maximize tower efficiency and minimize maintenance. Uncontrolled levels of pH, bio-growth, or over-application of chemicals cause degradation of the material and plugging. Automatic control of pH conditioner can be accomplished with proven differential pH methods tied to analog and/or digital control. Oxidizing biocide application can be optimized with ORP and halogen analysis and control. Overuse of this type of biocide can also cause wood delignification that can affect the structural integrity of the tower. Another cause of fouling is excessive solids accumulation. Solids buildup can be minimized with side-stream filtration and/or clarification and monitored with low maintenance self-cleaning optical probes.
Advanced Supervision and Diagnostic System: The Tool for Improvement Reliability and Efficiency of Utility Boilers Burned Different Coals Type
Authors: Chudnovsky B. , Kogan B. , Talanker A. , Sella Y. , Cohen J.
Published: May 2009

Due to the past years experience, we have seen an influence on the coal purchase policies. The main reason for using coal other tan the original design coal, apart from economic considerations, is to reduce SO2 emission by using a low sulfur content coal as well as decreasing coal index (fixed carbon to volatile matter ratio) in order to reduce NOx emission etc. Hence, the power generation plant was originally designed to operate on a particular coal, and due to high restriction in environmental requirements, emissions regulations, have led to modifications of the coal type and firing mode, while the boilers must burn a different coal type and its blends. It may lead to boiler reliability degradation and as a result reducing the power plant availability and increasing operating and maintenance cost. In order to prevent a different faults in boiler operation and as a result a reliability reduction, special monitoring and diagnostic techniques is required for engineering analysis and utility production management. In this sense an on-line supervision system have developed and implemented for 575, 550, 360 Mw coal fired units. The aim of the system is to achieve more effective and reliable operation with emission reduction. It is a valuable aid for: (1) operation staff and process engineers to survey the equipment and overall plant performance, (2) electricity production management in order to implement maintenance and operation strategies. The developed system provides an on-line information regards furnace performance, including fireball location, increase in furnace exit temperature indicates that it’s necessity to activate furnace sootblowers to control steam temperatures and prevent excessive accumulations of slag and heat surfaces tube overheating. The developed system indicates the superheater and reheater surfaces midwall metal temperature which provides timely information to assist engineering personnel to optimize mode of operation, in order to activate the optimal number of sootblowing of the corresponded surfaces, etc. The system includes also an online analysis of the erosion impact on the boiler backpass heat surfaces. By the using the developed system we found a correlation between furnace fouling and NOx emission due to the effect of flame temperature on the rate of NOx formation. As a result an optimal mode of furnace operation and sootblowing practice is used to reduce the high cost of controlling NOx emission. The developed system allows to fond the proper coal blends which provide a high boiler efficiency and reliability while minimizing NOx emissions.