bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerically Investigating the Effects of Cross-Links in Scaled Microchannel Heat Sinks
Authors: Dang Minh , Hassan Ibrahim , Kim Sung In
Published: October 2008

Thermal management as a method of heightening performance in miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and the industry. One of the current challenges is to design heat sinks with uniform flow distribution. A number of experimental studies have been conducted to seek appropriate designs for microchannel heat sinks. However, pursuing this goal experimentally can be an expensive endeavor. The present work investigates the effect of cross-links on adiabatic two-phase flow in an array of parallel channels. It is carried out using the three-dimensional mixture model from the computational fluid dynamics software, FLUENT 6.3. A straight channel and two cross-linked channel models were simulated. The cross-links were located at 1/3 and 2/3 of the channel length, and their widths were one and two times larger than the channel width. All test models had 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The results showed that the trend of flow distribution agrees with experimental results. A new design, with cross-links incorporated, was proposed and the results showed a significant improvement of up to 55% on flow distribution compared with the standard straight channel configuration without a penalty in the pressure drop. Further discussion about the effect of cross-links on flow distribution, flow structure, and pressure drop was also documented.
Grid Independence Via Automated Unstructured Adaptation
Authors: Chila Ronald J. , Kaminski Deborah A.
Published: October 2008

Grid independence is frequently an overlooked item in computational fluid dynamics (CFD) analyses. Results obtained from grid dependent solutions may prove to be costly, in that engineering design decisions can be made using potentially faulty information. An automated method for grid independence is developed for two-dimensional unstructured wall function grids. Grid independence is achieved via successive levels of adaptive refinement. Adaptive refinement is performed in an automated manner and is based on multiple field variables. Sensors are placed at strategic locations within the flow field, which are determined by examining the CFD solution of a uniform grid. Three cases are examined, the backward-facing step, flow over an asymmetric transonic airfoil, and hydrogen combustion in a channel. Grid independent solutions are obtained for all three cases. Results for each case compare well with experimental data and/or other numerical predictions.
A New Concept for Renewable Power Generation: Integrating Off-Shore Wind Turbines With a Unique Wave Power Generation System
Authors: Polido Edwin , Ulery James P. , Di Bella Francis A.
Published: October 2008

Off shore wind turbine farms are becoming more popular as the efficiency and per unit cost of the systems become more economical. Wave power generating systems have been conceptualized for centuries but only relatively recently, since the 1970’s, has private and public financial support been forthcoming to provide some model and full-scale testing. Northeastern University researchers are studying the integration of these two technologies. The objective is to reduce the combined cost per kW for the power generating system by accomplishing two distinct improvements: 1. sharing the electrical and civil engineering systems that are common to the integrated design, and 2. storing the ocean wave energy for use later when the wind energy is not sufficient to produce maximum wind turbine power. Several new concepts for wave power generation and storage are identified in the process. This paper will describe the current research at Northeastern University and the preliminary designs for the integrated wind turbine generator and wave power system using state-of-the-art wind turbines and air expander systems.
Design on the Gear Box of Combined Diesel or Gas Turbine Power Plant Experiment Rig
Authors: Tian Ying , Sun Yufeng , Lu Qingchun
Published: October 2008

The gearing of combined diesel or gas turbine (CODOG) power plant experiment rig is composed of gear box, which is one of the key parts in the CODOG power plant experiment rig. The diesel or gas turbine’s work and changeover are realized by the gear box. The paper introduces the structure and composing of the gear box in the CODOG power plant experiment rig. By a series of experiments, the gear box is proved that the design is reasonable and running is credible.
Investigation on Dynamic Rule Method for Optimum Load-Burdening About Turbine Units of Thermal Power Plant Basing on the Economy and Reliability
Authors: Ran Jingyu , Yang Lin , Zhang Li
Published: October 2008

The difference between the highest and the lowest load has become bigger and bigger with the development of the economics and society. How to got maximum economic benefit and higher operation reliability of unit has become the seeking goal of many researchers and workers. Although there are many methods (such as local optimum, inheritance arithmetic, Lagrange and Equivalent Polyhedron Method et al.) for the optimum regulating burden of thermal power units based on economy. However, the theme for the optimum regulating burden hasn’t been commendably solved. In this paper, it is first time to investigation on Dynamic Rule Method for optimum load-burden about turbine units of thermal power plant basing on the Economy and the Reliability (DRMER). First of all, the different optimum load method has been analyzed, and the DRMER is presented. And the same time, the optimum economical adjustment mathematic models with DRMER of regulating peak load for units are also presented, then the optimum load-burdening characteristics of units are ascertained in different optimum method, and the merit and demerit have been analyzed. The research results shows that DRMER is more proper to optimize load of unit, the economical benefits is higher than that of other optimum method obviously, and can get higher operation reliability of unit. The method and the results can be the reference of optimum economical load adjustment about the similar thermal power units.
Predicting Creep Initiation in Gas Turbine Blades
Authors: Lam Tony C.-T. , Tran Suong , Dewey Robert P.
Published: October 2008

The demand for increased performance from combustion turbines has pushed firing temperatures to the point where the life consumption of the hot section components may no longer be accurately monitored based on traditional engineering practices. For rotating blades in particular, creep rupture criterion such as strain limits, tend to be arbitrary, subjective and prohibit the use of statistical data available from material tests. This inhibits the application of a probabilistic treatment as a basis to answer the fundamental question of an operator responsible for the life cycle management of these costly parts, i.e. how does the chance of an in-service failure increase over the lifetime of the component. Presented in this paper is a more direct engineering approach that has been used to predict the risk of crack initiation and propagation due to creep in hot section parts. Results are compared first against the traditional method of designing against creep rupture, and then conclude with the risk analysis of an actual first stage gas turbine blade.
Flow and Thermal Structure of Burner-Wake Stabilized Elliptic Jet Flames in a Cross-Flow
Authors: Gollahalli S. R.
Published: October 2008

This study was conducted to delineate the coupling effects of the elliptic geometry of the burner and a crossflow on the combustion of gas jets. This paper presents the flow and thermal structure of burner-wake stabilized turbulent propane jet flames from circular (diameter = 0.45 cm) and elliptic (major axis/minor axis = 3) burners of equivalent exit area in a crossflow of air. The elliptic burner was oriented with its major axis or minor axis aligned with the crossflow. Experiments were conducted in a wind tunnel provided with optical and probe access. Flame structure data including temperature profiles and concentration profiles of CO2, O2, CO, and NO were obtained in the single flame configuration (at jet to crossflow momentum flux ratio = 0.0067), where a planar recirculation zone exists completely stabilized in the wake of the burner tube. This study is complementary to our previous study with a two-zone structure flame at jet/crossflow momentum flux ratio of 0.11. Results show that in this flame configuration, the peak NO concentration in the circular burner is higher than that in the elliptic burner flames. Carbon monoxide concentration was approximately same in the flame with circular burner and the elliptic burner with its major axis aligned with cross-flow; the CO concentration in the elliptic flame with the minor axis of the burner aligned with cross-flow was slightly smaller.
Baselining Strategies to Improve PM Implementation
Authors: August J. K. , Ramey Brian , Vasudevan Krishna
Published: October 2008

Content reviews optimize preventive maintenance (PM) strategy. However, reanalyzing strategy alone is pointless. Traditional PM optimization compares existing and revised PM’s at the final step. Ignoring preexisting source PM programs removes analysis bias, but makes implementation more difficult; continuity is lost. Baselining existing programs provides an alternative. PM changes are smaller, easier to control, and process oriented. Ineffective PM tasks can be removed with minor impact. Shop-floor ownership simplifies changes and speeds implementation, lowering costs. New maintenance development techniques improve upon older PM development processes, substantially reducing costs. Significant benefits can result in complex industrial maintenance applications.
Inverse Methodologies for Actual Status Recognition of Gas Turbine Components
Authors: Cerri Giovanni , Borghetti Sandra , Salvini Coriolano
Published: October 2008

A general methodology has been established to set up GT based plant simulators to perform analysis and to identify inverse model parameters. The attention is focused on three categories of inverse problems faced in setting up the plant simulator: i) sizing of components; ii) calibration on the basis of test acceptance data; iii) actual status recognition from data collected by the plant monitoring system. Due to the different nature and requirements of the above problems different solution approaches have been adopted: hybrid stochastic-deterministic algorithms for model calibration and neural techniques for status recognition. An application to a real plant shows the capabilities of the proposed methodology.
Advancements In Hydraulic Modeling of Cooling Water Intakes in Power Plants
Authors: Johansson Andrew E. , Stacy Philip S. , White Dean K. , Lin Fangbiao
Published: October 2008

Satisfactory hydraulic performance of pump intakes is very important to avoid flow conditions that would adversely affect the performance of cooling water and service water pumps in power plants. Hydraulic performance is best evaluated using physical hydraulic models. Typically, a hydraulic model is used to identify formation of any objectionable free surface and subsurface vortices, presence of any high swirl or pre-rotation and/or non-uniform axial velocity distribution at the impeller entrance. A model study would evaluate an initial design based on an acceptance criteria and derive remedial modifications as needed to meet the acceptance criteria. Over the past several years, modeling of pump intakes has evolved in terms of criteria for model scale selection, instrumentation accuracy and computerized data acquisition techniques, the use of computational fluid dynamics (CFD) to evaluate detailed approach flow patterns and the availability of Hydraulic Institute Standards (HIS) for acceptance criteria to evaluate hydraulic performance. Also, hydraulic model studies conducted by various laboratories over many years have contributed to the advancement of the knowledge about vortex formation, swirl and scale effects in models. To the benefit of all, these advancements have resulted in higher confidence in models with more efficient execution of the model studies at minimal costs. The purpose of this paper is to present advancements that have been made in the field of hydraulic modeling of pump intakes. Examples are provided to show how hydraulic models may be used to first identify unacceptable flow conditions and then to derive modifications to improve the hydraulic performance for both circulating water and cooling water pump intakes.
Experiments on Fault Analysis About Valves of 2D12 Reciprocating Compressors
Authors: Gao JingBo , Wang RiXin , Xu MinQiang
Published: October 2008

The fault in suction and discharge valves of reciprocating compressors model 2D12 usually occur in unplanned servicing. The fault features of valves which have many rings are difficult to extract. In the work, a lot of experiments about the leaks of broken rings, ring leaks and broken springs were made on the 2D12 reciprocating compressors in the factory. The sound over the every valve caps were collected by the B&K sensors and NI (National Instruments) products. In the paper, the sound signal of the special work passages about valves are analyzed with the time-frequency method, the fault feature pictures about the failures of rings and springs are given.
Renewable Energy: Myths, Legends, and Reality
Authors: Powell Charles A. , Johnson Thomas W.
Published: October 2008

With many States setting goals in the 2010–2020 timeframe for increased U.S. electricity production from renewable energy sources totaling nearly 100,000 MW nationwide, innovative solutions are required; as well as the suspension of several myths of conventional wisdom concerning renewable energy. Since Wind, Hydro and Solar are “opportunity” energy supplies not necessarily available when electricity demands are high; there is a great need for a renewable, “dispatchable” energy source that would be available anytime. Building on the experience of the Pulp and Paper Industry, waste-wood fueled IGCC units of 100MW size are practical today; and new gasification technologies being developed for power plants promise high efficiency, and competitive electricity pricing. With these new IGCC technologies, the US Department of Agriculture estimates there is more than enough wood waste to meet the renewable energy goals currently being considered, cost-competitively and environmentally responsibly.
Numerical Estimation of Losses in Steam Flow Through LP Turbine Stages
Authors: Dykas Slawomir , Wroblewski Wlodzimierz
Published: October 2008

The aim of this work is to estimate the losses in the steam flow through the LP steam turbine rotor and the whole stage. For steam flow two types of losses take place, aerodynamic (profile, secondary flow, leakage) and thermodynamic (due to the heat addition caused by condensation). Presented numerical results are split into two groups. In the first part of this work the comparison of the three different calculation methods of steam flow is carried out. To this end the geometry of LP steam turbine last rotor is chosen. The first method is a Streamline Curvature Method (SCM) used on the meridional plane with losses correlations, and the next two methods, commercial and an in-house CFD codes, solve the Reynolds averaged Navier-Stokes equations for a 3-D flow. Below the saturation line the first two codes model equilibrium steam properties, and the last one models non-equilibrium steam properties. Then for the geometry of the penultimate stage, with the use of an in-house CFD code, the comparison of the different types of condensation models on the losses prediction is examined.
Guidance on Conducting Tests of Inlet Chiller Systems Installed in GT Inlets
Authors: Sullivan Terry B. , Giampetro Michael
Published: October 2008

This paper provides comprehensive methodology on testing inlet chiller systems that are used for Gas Turbine Inlet Air Conditioning. It will serve as a guiding document for the Inlet Chiller Project Team formed by PTC 51, “Combustion Turbine Inlet Air Conditioning Equipment” for use in scripting that code’s section on Inlet Chiller Performance Testing. This paper shows the conceptual similarities that can be drawn between inlet chiller and overall plant performance testing, as well as detailing the pertinent test scopes and boundaries, identifying expected test objectives, and listing the applicable test boundary parameters to be used for correction. Addressing an industry need, this paper also offers guidance on testing these components / systems at conditions different than design. Current equipment code committees, such as ASME PTC 22 on Gas Turbines, and ASME PTC 46 on Overall Plant Performance Testing, have concluded that inlet air conditioning equipment must be out of service while testing the major plant equipment. This would require the inlet chilling system to be tested separately. This requirement dictates that a technically-sound method of inlet chiller testing be codified in a timely manner.
We Energies’ Pleasant Prairie Power Plant: AQCS Retrofit Project
Authors: Bichler Dan , Barnes Samuel R. , Hossain Aklima
Published: October 2008

We Energies’ Pleasant Prairie Power Plant (P4) is installing a wet flue gas desulfurization (WFGD) system on steam generating Units 1 and 2 for SO2 control and a selective catalytic reduction (SCR) system on steam generating Unit 1 for NOx control. Unit 2 already has a SCR system that was installed in 2002. This retrofit project also includes installation of a new chimney, limestone and gypsum handling equipment, and wastewater treatment equipment. This environmental improvement project, now under way at P4, is part of the Company’s plan for meeting current and pending air quality improvement commitments and environmental regulations. P4 consists of two 617 MW Riley PC subcritical boilers firing PRB coal. The two units currently share a common chimney. These units were commissioned in the early to mid 80s. When the current project is completed, P4 will have the lowest SO2 and NOx emission rates of any coal fired Wisconsin power plant. The new equipment will be capable of reducing SO2 emissions by up to 95 percent and NOx emissions by up to 90 percent. The current schedule has Unit 1’s WFGD and SCR system on line by December of 2006 and Unit 2’s WFGD system on line by May of 2007. This paper will outline the execution plan used to launch this multi-million dollar project and to maintain its schedule. The paper will also review the technical drivers that lead to the selection and performance specifications of the WFGD and an overview of the major equipment parameters including the materials of construction chosen for this project.
Seawater Scrubbing for the Removal of Sulfur Dioxide in a Steam Turbine Power Plant
Authors: Khawaji Akili D. , Wie Jong-Mihn
Published: October 2008

The most popular method of controlling sulfur dioxide (SO2) emissions in a steam turbine power plant is a flue gas desulfurization (FGD) process that uses lime/limestone scrubbing. Another relatively newer FGD technology is to use seawater as a scrubbing medium to absorb SO2 by utilizing the alkalinity present in seawater. This seawater scrubbing FGD process is viable and attractive when a sufficient quantity of seawater is available as a spent cooling water within reasonable proximity to the FGD scrubber. In this process the SO2 gas in the flue gas is absorbed by seawater in an absorber and subsequently oxidized to sulfate by additional seawater. The benefits of the seawater FGD process over the lime/limestone process and other processes are; 1) The process does not require reagents for scrubbing as only seawater and air are needed, thereby reducing the plant operating cost significantly, and 2) No solid waste and sludge are generated, eliminating waste disposal, resulting in substantial cost savings and increasing plant operating reliability. This paper reviews the thermodynamic aspects of the SO2 and seawater system, basic process principles and chemistry, major unit operations consisting of absorption, oxidation and neutralization, plant operation and performance, cost estimates for a typical seawater FGD plant, and pertinent environmental issues and impacts. In addition, the paper presents the major design features of a seawater FGD scrubber for the 130 MW oil fired steam turbine power plant that is under construction in Madinat Yanbu Al-Sinaiyah, Saudi Arabia. The scrubber with the power plant designed for burning heavy fuel oil containing 4% sulfur by weight, is designed to reduce the SO2 level in flue gas to 425 ng/J from 1,957 ng/J.
Preliminary Wave Rotor Design by Means of Basic Thermodynamic and Fluid Dynamic Laws
Authors: Siol Ulrich , Staudacher Stephan , Mu¨ller Norbert
Published: October 2008

Purpose and functionality of a wave rotor: A wave rotor can be a component of a combustion engine that is compressing air, using the thermal and potential energy of exhaust gas. Simply put, a wave rotor does the same job as a supercharger in a piston engine, or as an additional compressor-turbine stage in a gas turbine. Conventional supercharging methods use exhaust gas to run a turbine that is generating shaft power used to propel a compressor. However, a wave rotor creates “free” compression by utilizing shockwaves generated by clashing high pressure exhaust gas directly against the incoming air. Hence, a wave rotor provides additional power to the system for relatively minimal costs. Losses due to low compressor and turbine efficiency, and high thermal stress in the turbine, can be avoided. Engineering objectives include both the magnification of the gas turbine pressure ratio and of the turbine inlet pressure.
Small-Scale Decentralized Renewable Energy Systems for the Remote Communities of the Developing Countries
Authors: Islam Mazharul , Islam A. K. M. Sadrul , Amin M. Ruhul
Published: October 2008

About 2 billion people of the world, mostly in rural areas of the developing countries, do not have access to grid-based electricity. The most critical factor affecting their livelihoods is access to clean, affordable and reliable energy services for household and productive uses. Under this backdrop, renewable and readily available energy from the nature can be incorporated in several proven renewable energy technology (RET) systems and can play a significant role in meeting crucial energy needs in these remote far flung areas. RETs are ideal as distributed energy source and they can be incorporated in packages of energy services and thus offer unique opportunities to provide improved lighting, health care, drinking water, education, communication, and irrigation. Energy is also vital for most of the income-generating activities, both at the household or commercial levels. Access to energy is strongly connected to the achievement of the Millennium Development Goals (MDGs), which set targets for poverty reduction, improved health, and gender equality as well as environmental sustainability. Environmentally benign renewable energy systems can contribute significantly in the above-mentioned unserved or underserved areas in the developing countries to achieve both local and global environmental benefits. This is important in the context of sustainable development in: (i) poverty alleviation, (ii) education, (iii) gender equity and empowerment, (iv) health including other benefits like improved information access through Information and Communication Technology (ICT) centers, (v) better security, and (vi) increase in social or recreational opportunities. It is evident that proliferation of renewable energy resources through implementing their applications for meeting energy demand will promote all the three dimensions namely, social, economic and environmental of sustainable development in the developing countries. Several small scale enabling RET systems have been suggested in this paper in the light of above-mentioned issues of energy sustainability and they can significantly contribute to the improvement of the livelihood of the remote impoverished rural communities of the developing countries. With the current state of technology development, several RET systems (such as wind, solar photovoltaics, solar thermal, biomass and microhydro) have become successful in different parts of the world. In this paper, an exhaustive literature survey has been conducted and several successful and financially viable small-scale RET systems were analyzed. These systems have relevance to the economies of the developing countries that can be utilized for electrification of domestic houses, micro enterprises, health clinics, educational establishments and rural development centers.
CFD Aerodynamic Investigation of Air-Water Trajectories on Rotor-Stator Blade of an Axial Compressor
Authors: Mustafa Zainol , Pilidis Pericles , Amaral Teixeira Joao A.
Published: October 2008

In multistage axial-flow compressors, the droplet size distribution of the injected fluid depends upon the entry conditions. In general, droplet trajectory prediction is important for particulate laden flow turbomachinery as it helps to understand the pitting and the cutting of the blade leading and trailing edges as well as to improve the design of blade passages. An investigation was carried out using CFXTASCflow on the aerodynamics of an axial-flow compressor designed for operation with air while operating with an air-fluid droplet mixture during field operation. In this study, a 3D rotor-stator blade with constant rotor rotating speeds was simulated. Droplet trajectories in rotor-stator were predicted in connection with full 3D air flow field solved by k-ω SST method. The test matrix involved different initial droplet diameters with constant rotor shaft rotation. The liquid used was water. The main objective of the investigation is to provide a physically realistic model describing the movement of liquid phase in an industrial axial compressor. In order to achieve this objective, CFD simulations were developed for predicting the water particle trajectories inside an industrial axial compressor, the rate of evaporation of water droplets on axial compressor blades by inertial impaction, turbulent diffusion, pressure and temperature increments. Simulation of water droplet trajectories and evaporation of water droplet content in designed gas turbine engine were also undertaken. The velocities and trajectories of the droplets, on the blades and the amount of water evaporated were investigated. The results show that the initial conditions of the droplets (velocity and size) have substantial influence on the flow pattern.
Probabilistic Performance Analysis of Eroded Compressor Blades
Authors: Kumar A. , Nair P. B. , Keane A. J. , Shahpar S.
Published: October 2008

This paper presents a probabilistic analysis of the effect of erosion on the performance of compressor fan blades. A realistic parametric CAD model is developed to represent eroded blades. Design of Experiments (DOE) techniques are employed to generate a set of candidate points, which are combined with a parametric geometry modeling and grid generation routine to produce a hybrid mesh. A multigrid Reynolds-Averaged Navier Stokes (RANS) solver HYDRA with Spalart Allmaras turbulence model is used for Computational Fluid Dynamics (CFD) simulations. The data generated is used to create a surrogate model for efficient uncertainty propagation. This method is applied to a typical Rolls Royce compressor fan blade section. Monte Carlo Simulation, using the surrogate model, is executed for the probabilistic analysis of the compressor fan blade. Results show upto 5% increase in pressure loss for the eroded compressor fan blades.
Lessons Learned: Low Condenser Vacuum/High Condensate Dissolved Oxygen Levels at D. C. Cook Nuclear Power Plant
Authors: Sunder Raj Komandur S. , Harris Richard A.
Published: October 2008

During the summer of 2002, the main condenser vacuum started degrading at both Units 1 and 2 of the D. C. Cook Nuclear Power Plant. An evaluation of the high condensate dissolved oxygen levels that were being experienced at Unit 1 indicated performance degradation of the steam jet air ejector system. This paper describes the lessons learned from detailed analysis, inspection and evaluation of the design, performance and operation of the steam jet air ejector systems for both units of the D. C. Cook Nuclear Power Plant. Various corrective actions undertaken as well as proposed for future implementation are discussed and recommendations are provided for proper design, performance, operation and maintenance of the steam jet air ejector systems.
Increasing SCR NOx Removal From 85 to 93% at the Duke Power Cliffside Steam Station
Authors: Ake Terence R. , Erickson Clayton A. , Hutcheson Linton K.
Published: October 2008

Tests were completed at the Duke Power Cliffside Steam Station on the Unit 5 SCR system to increase NOx removal from an initial design value of 85% to an in-use operating level of 93%. These tests took place from May 24 to May 26, 2004 at the start of the third OTAG season for the SCR that was furnished by Riley Power, Inc., a Babcock Power Inc. company. Unit 5 is a balanced draft, subcritical boiler that operates at 590 MW firing eastern bituminous coal. Two SCR reactors are installed at the economizer outlet of the boiler including economizer bypasses for low load operation. Anhydrous ammonia is the reagent for NOx reduction. Each reactor had two initial catalyst layers when the unit was tested.
Field Experience in Fog Power Augmentation of Frame 9E Gas Turbine
Authors: Hain Y. , Litinetski V. , Litinetsky A.
Published: October 2008

Inlet air cooling by water fogging became very popular in recent years, because it is relatively simple and inexpensive technique for gas turbine power augmentation. Large experience established general practices of design, operation and maintenance of the fog systems. Nevertheless, fog systems could require some tuning to a specific gas turbine configuration and site conditions. Israel Electric Corporation (IEC) has implemented eight fog systems on 120–150 MW gas turbines, and each system was initially tuned to provide higher effectiveness. During hot weather conditions, noticeable additional power was obtained, which was very helpful to meet peak electricity demand. Based on these positive results, an additional six fog systems were installed on Frame 9E gas turbines. Initial operation of new fog systems revealed some unexpected problems. IEC undertook a thorough study of the problems including computational fluid dynamics (CFD) analysis of the inlet duct air flow. On the basis of the study results, significant modifications of the fog systems were carried out. Field tests of the modified systems showed that all goals of the modifications were successfully achieved.
Coupling Effect of Flexible Geared Rotor on Quick Return Mechanism
Authors: Chang J. R. , Hsu W. C.
Published: October 2008

Regarding the quick return mechanism, some researchers have neglected the rotor-mechanism coupling effect, and other researchers have combined the quick return mechanism with the motor but only considered the rotational motion of the rotor by assuming the rotor to be rigid and neglected the gear mesh dynamics. In the study, the rotor-mechanism coupling effect is investigated to find that the dynamic behaviors of the coupled system are different from those uncoupled systems. The coupling effect is mainly due to the flexibility of the shaft, the bearing, and the gear mesh. When the quick return mechanism is driven with the flexible geared rotor, the vibrations of the geared rotor have significant influences on the dynamic behaviors of the quick return mechanism. The traditional studies formulated the quick return mechanism only under the consideration of planar motion. However, the three dimensional vibration has to be considered for establishing the physical model of the coupled system. The main objective of this study is focused on the investigation of the coupling effect of the geared rotor on the quick return mechanism. The system model is formulated by using finite element method and following Hamiltonian approach. The numerical integration method is applied to obtain the dynamic response. The coupling effect of the geared rotor on the quick return mechanism is discussed by the parameter study. It is shown that the bearing stiffness and damping and the shaft radius have significant influences on the dynamic behavior of the mechanism.
Is Insufficient NPSH Available Always the Cause of Cavitation in Centrifugal Pumps?
Authors: Gairola Vidhu S.
Published: October 2008

Cavitation is often linked to the inability of the system to provide sufficient NPSH to the pump. Pump users often feel safe running a pump if the NPSH required by the pump is below what is available in the system. What is gas entrainment within process fluid and how does it affect pump performance? Is there a connection of entrained gas with cavitation? When flow through the pump is too low, a part of the mechanical energy that is put in for running the pump is converted to pressure energy and the remaining goes to heat the liquid. This raises the liquid temperature and eventually vaporizes it. This vapor stays within the process liquid as bubbles, which causes cavitation. All the above conditions cause cavitation. This paper describes how these conditions develop, and shows how to identify and then rectify them.
Determination of Journal Bearing Stiffness and Damping at Hydropower Generators Using Strain Gauges
Authors: Gustavsson Rolf K. , Lundstro¨m Mattias L. , Aidanpa¨a¨ Jan-Olov
Published: October 2008

In hydropower generators, the measurement of bearing load, vibration and shaft displacement are wildly used methods for indication of maintenance demand and troubleshooting. When measurement of bearing load and shaft displacement is performed the collected data make it possible to determine the bearing properties, such as stiffness and damping. In this paper a method to determine the bearing stiffness and damping properties for generator journal bearing in hydropower units is presented. The majority of hydropower generators are, however, not equipped with facilities for measurements of bearing loads. To provide the bearings with load sensors it is necessary to reconstruct the bearings, which is associated with heavy expenditures. In this paper an alternative method to obtain the bearing load is utilize, in which strain gauges installed on the generator bearing brackets is used. The collected data in the experiment were obtained from measurements on a 238 MW hydropower generator connected to a Francis type runner. The bracket that holds the generator bearing consists of 18 spokes and each of these spokes has been provided with strain gauges for load measurements. The displacement of the shaft has been measured relative to the generator-bearing casing. The generator-bearing model has been described as a system with two degrees of freedom containing both bearing stiffness and damping matrix as well as displacement and displacement velocity vector. When the calculation of the bearing properties are based on measured data, the irregularity in the calculated stiffness and damping has to be eliminated. To eliminate the unrealistic values of the calculated damping and stiffness, the samples that cause high condition numbers of the displacement–velocity matrix are neglected. The results of the calculation of bearing stiffness and damping are presented in polar plots. This method determines the bearing properties for the generator bearing in a certain point, the point where the generator shaft has its stationary position. The stationary position for the generator shaft depends on the static magnetic pull force acting on the generator rotor and the influence from the turbine. The influence on the bearing characteristics of nonstationary loads as acting on the bearing can be investigated. The non-stationary loads can for instance be rotor unbalance force, influence of thermal expansion and dynamical magnetic pull force. It is thereby possible to evaluate different loads effect on the generator bearing and in which way the bearing properties are affected.
Open Access Transmission System Pricing in a Restructured Power Sector: A Case Study of Ghana
Authors: Gboney William Kwasi
Published: October 2008

The emerging trend in power sector restructuring has made open-access use of the transmission system a critical element in the reform process. The principal purpose of this paper is to propose an open access pricing framework, which is fair, economically efficient, technically meaningful and practical to implement, and which will provide incentives for investment in needed transmission facilities. The proposed transmission pricing methodology takes account of transmission system constraints, connection charges, transmission line availability, congestion and transmission loss factor. Cost for connecting generators and consumers to substations are recovered through a connection charge. Compared to the Postage Stamp pricing philosophy currently used in Ghana where all customers pay a uniform rate, costs in the new pricing approach are assigned fairly and equitably to open access customers, based on the amount of ‘stress’ imposed on the transmission system. The proposed transmission pricing methodology offers an effective way of using price signals to relieve congestion and to send the correct signals in terms of locational advantage for future investment.
Case Study of an Alternative Solution to a High-Energy Drain Problem in a Surface Condenser
Authors: Kidwell Steven
Published: October 2008

During the startup of an early vintage steam turbine-generator unit (prior to engineered steam bypass systems), warming of the steam piping is commonly achieved through numerous small-bore steam line drains that “dump” into the main surface condenser. And in some cases, it is not unusual for these drains to be open till well beyond the point at which full throttle pressure and temperature are achieved at the turbine resulting in high-energy superheated steam flowing at sonic velocities. And most condensers built earlier than 1980 were ill equipped to handle these high-energy drains without damage. Midwest Generation’s Collins Station, like many others, was built before the EPRI guidelines for high-energy drains were written. Consequently, the initial condenser, provided by Southwestern Engineering, did not adequately address these drains. But unlike most other stations, Collins was operated from the beginning as a cycling station, i.e. 50–100 startups per year. Consequently, their condensers have had a significant portion of their operating lives devoted to startup situations with these drains in operation. As a result, the condensers began exhibiting wall distortion and thermal fatigue cracks less than a year into their service life. The station spent the next 25 years repairing, patching, and trying modifications, all without lasting success. In the Fall of 2002, they asked Raymond Professional Group to study the situation and formulate a cost-effective permanent repair.
Wet Flue Gas Desulfurization (WFGD) Slurry Spray Header Design System
Authors: Santavicca J. W.
Published: October 2008

The Babcock & Wilcox Company (B&W) has developed a rule-driven design (RDD) computer application to speed the design of its wet flue gas desulfurization (WFGD) slurry spray header system including support steel. The application, written using the RuleStream RDD system, captures the talents of the many people involved in the spray system’s design, including those involved in process engineering, design engineering technology, structural mechanics, and technical design. B&W’s design standards and best practices are blended with fabricator capabilities and industry standards to form the application rules. Third-party software (for example CAESAR II) and proprietary computer programs are leveraged by the application courtesy of the RuleStream RDD architecture. The application seeks to automate the routine first 80% of the design, while providing interfaces to complete the design or explore “what-if” situations. Interfaces allow the evaluation of spray coverage, pipe velocities, pressure drop, physical clearances, weights, and stresses. The application generates drawings, a solid model, and a bill of material for fabrication. Using the application, repeatable, consistent results are achieved. There is a higher confidence in the generated design and a reduction in design cycle time. This saved time may be allocated to exploring alternative designs, pursuing fabricator quotes, performing contract level analysis in the proposal phase, or may be applied to other areas of the WFGD design.
Challenging Project Requirements Lead to Unique Design for TID’s Walnut Energy Center
Authors: Baysinger Randy , Mathine Les , Clark Steve
Published: October 2008

The Walnut Energy Center (WEC) is a nominal 250 MW gas fired combined cycle power generation facility currently under construction by the Turlock Irrigation District (TID) in Turlock, California. TID is a publicly owned water and power agency located in California’s Central Valley. This paper describes how the Walnut Energy Center was designed to meet a unique and complex set of challenging functional, environmental, and economic requirements.
Development of a CFD-Based Coal Pipe Design Tool
Authors: Huang Gengxun , Bryden Kenneth M.
Published: October 2008

In a coal-fired power plant, pulverized coal, using air as a transport medium, is pneumatically transported toward different burner nozzles by splitting the large pipe into small pipes through bifurcators or trifurcators. The combustion efficiency of the burner is dependent on matching the air and coal in these pipes. Increasingly tight emission standards also make the balance of air and coal a very critical factor for the success of the power plant. Coal roping occurs when the gas-solid flow passes through a curved pipe. The momentum of the particles carries them to the outside of the wall, concentrating in a small region. Therefore, the particle concentration in this small region is much higher than the other part of the pipe cross-section. Coal roping upstream of a coal distributor (bifurcator) can create a significant imbalance in coal loading in the split between the two branches. This can significantly impact plant performance and increase NOx production. Previous research [2] has shown that coal rope characteristics depend on many parameters; the geometry (i.e., elbow radius of curvature-to-pipe diameter ratio, pipe orientation, orifice opening, and the locations of orifices) of the coal pipe, which is determined at the design stage, will strongly affect the coal distribution in the outlet of coal pipes. This characteristic of coal roping indicates that optimizing the pipe geometry may be helpful in getting a more uniform coal distribution at the pipe’s outlet cross-section and minimizing the problems caused by imbalance between burners. In this paper, we present the CFD-based coal pipeline design tool to achieve the evenly distributed coal particle distribution across the pipe cross-section.
Numerical Simulation of Pressure Drop Through a Rotating Plenum Fan
Authors: Borg John P.
Published: October 2008

In this paper the numerically determined pressure increase (ΔP) versus volumetric flow rate (CFM) curve at a given fan speed for a plenum fan is compared to experimental data. The simulations were carried out using a rotating fan blade section and a fixed inlet and outlet plenum with a three-dimensional tetrahedral computational mesh. The objective of this work is to assess the feasibility of approximating a 36” plenum ΔP-CFM fan curve using a low order computational approach and thereby assessing the effectiveness of using such an approach as a real time design tool. The measures of success of this work include demonstrating the ability to capture pertinent characteristics of the fan curve such as slope and roll-off of the ΔP-CFM curve. It was found that a fairly high resolution was required near the fan blade section in order to better approximate the ΔP-CFM curve. This higher resolution greatly increased the runtime. In addition, including a k-e turbulent model improved the pressure drop characteristics as compared having no turbulence model. It is hoped that an approach such as this will be adopted in the real time design and manufacture of plenum fans.
Scenarios for the Peruvian Rural Electrification Program
Authors: Mendoza G. Pedro , Arroyo U. Maximiliano , Jime´nez Wilson
Published: October 2008

The rural electrification program initiated in Peru in order to achieve the 2012 rural electrification target was developed to forecast energy systems from both conventional and renewable resources. This program has proposed three scenarios for gradual increasing of the amount of renewable energy generation (36% of the 2012 target). However, it’s necessary to analyze the situation because the renewable energy rural market shows a low income for private investors although it has a high social impact. So, there is still significant risk for the development of renewable energy systems that could be minimized by using decentralized biomass energy systems with the application of small-scale-technologies.
Turbine Generator Lubrication Oil Supply Reliability Improvements at Southern California Edison’s San Onofre Nuclear Generating Station
Authors: Simma Fred Y. , Chetwynd Russell J. , Rowe Stuart A.
Published: October 2008

San Onofre Nuclear Generating Station, SONGS, Unit 3 experienced substantial turbine damage in early 2001 after the turbine bearings lubrication oil supply failed. During a loss of off-site power incident, power was lost to the two AC powered turbine lubrication oil pumps due to a breaker failure in the switchgear and the DC powered emergency bearing lubricating oil pump failed to start due to a breaker trip. The SONGS turbine generators have no shaft driven bearing lubricating oil pumps and consequently the turbine generator coasted down from full speed to a full stop without lubricating oil. This resulted in significant bearing, journal and steam path damage that required a four-month duration repair outage during a time period where electricity was in short supply in the State of California. The generator hydrogen sealing system remained operable during this event, however it was discovered during the event follow up investigation that this system had vulnerabilities to failure similar to the bearing lubrication system. In order to prevent a reoccurrence of this extremely costly event, SONGS has taken actions to modify both of these critical turbine generator systems by adding additional, continuously operating pumps with new, independent power source and independently routed cables. The main challenge was to integrate the additional equipment into the existing lubrication and seal oil systems. The SONGS approach and findings are discussed as well as a summary of the work performed. This technical paper will be of interest to utilities with a need to improve turbine generator reliability issues.