bluuebunny/crossref_metadata_2025 huggingface dataset:
Soot Volume Fractions in Volatile Matter Envelope Flames of Bituminous Coal Particles in Air and Oxy-Fuel Combustion
Authors: Khatami Reza , Levendis Yiannis A.
Published: February 2014

This work calculated volume fractions of soot in volatile matter envelope flames which form around burning single particles of bituminous coal. Both conventional combustion in air and simulated oxy-fuel combustion, with oxygen mole fractions in the range of 20–40% in CO2, were studied. Particles of 75–90 μm were injected in a bench-scale, transparent drop-tube furnace (DTF), at wall temperatures of 1400K. Upon ignition, optical pyrometry and high-speed photography were implemented to optically diagnose the burning particles. The method of Timothy et al[1] was applied to determine the instantaneous spatially-average soot volume fraction in these envelop flames. Results showed that soot shell forming around the particle was thicker and more luminous in air than the shell forming at the same O2 concentration in CO2. The soot volume fraction was decreased when N2 in air was replaced by CO2. Average soot volume fraction in the envelope flames in air was in the order of 7×10−5, whereas it was in the range 3.5×10−5 – 5.0×10−5 in oxy-fuel atmospheres.
Waste Geothermal Hot Water for Enhanced Outdoor Agricultural Production
Authors: Dell Robert , Unnthorsson Runar , Wei C. S. , Foley William
Published: February 2014

In Iceland there is a super abundance of waste hot water from geothermal power plants. Some of this is re-purposed (sequentially used) for district heating and heated swimming pools. This vast underused energy source can also enable the growth of out of zone plants, enhance agricultural production by 20% and extend the growing season. The authors have developed and field tested an energy intensive shallow system of bottom heat using the existing heated sidewalk materials. Tomatoes that do not survive outdoors in Iceland have produced ripe fruit. A zucchinis harvest was documented and the test banana plant was still alive in September after the first frost. These plants all died in the control garden which had the same piping system, and identical soil types and depths. Heat transfer data, infrared analysis and plant growth data were gathered to preliminarily document and quantify the system’s viability and market potentials.
Calpine Improves Accuracy of Steam Flow Measurement With Top-Mounted Annubar Flowmeter
Authors: Verhaagen Don , Hausman Katie , Saopraseuth Emily
Published: February 2014

Getting steam out of the ground is the first crucial step in the conversion of geothermal steam into electricity. Getting it to the turbine and making the steam flow measurement is likewise important. It is at the turbine or, more precisely, just before the turbine, that many measurements are made. Performance Acceptance Tests (PAT’s) are conducted here to ensure that the equipment provided by the turbine manufacturer is performing as specified. The need for accurate steam flow measurement is critical on the main steam line (MSL). Historically, orifice plates, venturies and averaging pitot tubes have been used with greater or lesser success and with associated challenges. Orifice plates typically have high permanent pressure losses and averaging pitot tubes have small holes on their leading edge which can plug. A different solution is needed — one that provides an accurate and repeatable measurement with low maintenance requirements. In recent testing spanning over a year of operation, it was found that an Annubar™ flowmeter, installed in the top mounted position, provided the low permanent pressure loss, and met the accuracy, repeatability and maintenance requirements of the end user. Typically, in steam applications with Annubar primary elements, conventional wisdom dictates that the Annubar primary element and transmitter be positioned below the pipe. The previously recommended orientation has a number of issues particularly with geothermal steam and its constituents (silica scale, non-condensable gases,) plus the likelihood that pockets of condensate will form and lead to metallurgical issues including stress corrosion cracking, thus shortening the life of the primary element. The installation can be further enhanced with an automated nitrogen purge system that blows nitrogen through the Annubar primary element to ensure the ports remain clear. The MSL flow measurement is critical for regulatory compliance and performance monitoring. Knowing with precision and repeatability the volumetric steam flow rate is critical. The top-mounted Annubar flowmeter with nitrogen purge system, which has been in service for more than a year, has proven to be reliable and has provided precise, repeatable measurement of steam flow.
CFD Simulation of Turbulent Airflow Around Wind Turbine Airfoils
Authors: Halbrooks David N. , Cui Jie
Published: February 2014

The airflow around wind turbines has proved to be a difficult problem to approach by means of today’s Computational Fluid Dynamics (CFD) codes. One reason for this difficulty lies within the stall characteristics of turbine airfoils. For the purposes of this research, the popular commercial CFD code, FLUENT will be employed to facilitate the understanding of airflow around wind turbines through the study of various turbulence models. Parallel processing will be employed to enhance computational performance as well as lower simulation times. The system used for simulation is the National Renewable Energy Laboratory (NREL) Phase VI Wind Turbine. The coefficients of pressure for the airfoil shall be extracted from the simulated data and compared against data obtained during the NREL Phase VI Wind Turbine data campaign. Since power is a driving factor of the design of wind turbine blades, the aspect of power will also be examined and compared. After a baseline study has been concluded, a parametric study will be carried out that examines the effects of rotor angular velocity.
Performance Assessment of Turbojet Engine Operated With Alternative Biodiesel
Authors: Ibrahim Mohamed Noureldin , Ali Ahmed Hamza H. , Ookawara S.
Published: February 2014

This study investigated experimentally the performance of turbojet engine fueled by biodiesel obtained from different feedstocks. The engine is equipped with measuring sensors for pressure, temperature, thrust, shaft speed in addition to flow meter, data acquisition system and a control unit. The results of the effect of biodiesel fuel type and its blends on turbojet engine performance are presented. Three biodiesel fuels which are Cotton methyl ester (CTME), Corn methyl ester (CRME) and Sunflower methyl ester (SME) and their blends of B10, B20 and B50 (10%, 20% and 50% biodiesel/Jet A1 by volume) are used and compared with the engine recommended fuel (Jet A1). Moreover, in this study, the Biodiesel fuel is produced through transesterification process in which the triglyceride (oil) reacts with alcohol (methanol) to form the mono-alkyl ester (biodiesel) and glycerol. Physical and chemical properties of all produced and tested fuels are measured. The results clearly indicate that the produced biodiesel fuels have a higher density, kinematic viscosity, than JetA-1 fuel, while, the calorific value of biodiesel fuels is very close to JetA-1 fuel. Moreover, JetA-1 fuel has higher sulfur content than other biodiesel fuels. Also, the experimental results show that Engine speed for the cases of using biodiesel fuels is lower than JetA-1 fuel at the same fuel throttle valve opening. Moreover, the Biodiesel fuels have a lower fuel volume flow rate compared to JetA-1 at the same throttle valve opening that lead to decrease the engine static thrust as well as lower value of TSFC.
A Practical Guide for Recognizing Elastic Follow-Up in Existing Power Piping Systems and Minimizing its Effects
Authors: Kimball Lange
Published: February 2014

High temperature, high pressure steam piping can fail for many reasons. This can include some combination of metallurgical, operational, fabrication, erection and design short comings. This has proven that high-energy piping systems are not maintenance free and have a finite service life.

From a safety and reliability point of view it is increasingly important to determine when this life is expended before failure occurs. This requires that conditions that can reduce life are recognized. Once recognized, it is equally important that these conditions be addressed in a manner that will help prevent personnel injury, forced outages and high repair costs.

The ASME B31.1 Code states that piping is “subjected to strain concentrations due to elastic follow-up of the stiffer or lower stressed portions.” However, the phenomena of “elastic follow-up” is often overlooked in the design of creep prone piping such as main steam and hot reheat. It is also difficult to identify in the field. This paper addresses a methodology to recognize elastic follow-up in existing piping systems, possible consequences and the means to minimize its effect.
Thermosyphon Cooler Hybrid System for Water Saving Power Plant Heat Rejection
Authors: Carter Thomas P. , Furlong James W. , Bushart Sean P. , Shi Jessica
Published: February 2014

As noted in a Summer 2007 EPRI Journal article entitled Running Dry At The Power Plant, “Securing sufficient supplies of fresh water for societal, industrial, and agricultural uses while protecting the natural environment is becoming increasingly difficult in many parts of the United States. Climate variability and change may exacerbate the situation through hotter weather and disrupted precipitation patterns that promote regional drought.” Currently, in the United States, thermoelectric power production accounts for approximately 39% of freshwater withdrawals and 3% of overall fresh water consumption.

The Electric Power Research Institute, EPRI, as part of its Technology Innovation (TI) program, is collaborating with Johnson Controls to conduct a feasibility study comparing the performance of a water saving Thermosyphon Cooler Hybrid System (TCHS) with other heat rejection systems for power plant applications. The TCHS employs a sensible heat rejection device, a thermosyphon cooler (TSC) in conjunction with an evaporative heat rejection device, an open cooling tower, to satisfy the annual cooling requirements of a given power plant. By reducing the evaporative heat load, the TCHS can significantly reduce the annual water consumed for cooling while still maintaining peak power plant output on the hottest summer days.

Operational details of the Thermosyphon Cooler Hybrid System are presented. Additionally an overview of the cooling system simulation program, based on an 8,760 hourly analysis, used in the feasibility study is discussed. Results comparing the water use and additional fan power requirements between power plants employing a traditional all evaporative system and the TCHS are discussed for two different climatic locations. The concept of incorporating the cost of water, cost of power, the current plant operating conditions, and the current ambient dry bulb temperature into the TSC fan control strategy are also explored. The simulation program performance model is currently being validated with testing of a 1MW prototype TCHS at the Water Research Center near Cartersville, GA. Finally, a conceptual design for a power plant scale TCHS is presented.
Operation and Maintenance in Icelandic Geothermal Power Plants: Structure and Hierarchy
Authors: Atlason Reynir Smari , Unnthorsson Runar
Published: February 2014

The Icelandic geothermal industry can be traced back to 1908 and has developed an extensive knowledge from that time. Currently, seven geothermal power plants are operating on the island. The plants are operated and maintained efficiently by relatively few engineers. The power plants generally prefer marine engineers who have worked as chief engineers on fishing vessels. Marine engineers are preferred in the Icelandic geothermal sector because of their education and mentality learned while working on the sea. Teamwork, resourcefulness, proactive thinking and the will to assist with jobs beyond job description are among the qualities believed to be required.

This study was carried out in cooperation with three power companies who own and operate all the geothermal power plants in Iceland. The purpose was to study the geothermal power plants and their environment in order to identify the key factors for the effective operation and maintenance with few engineers. The results include a summary and an analysis of the structure and hierarchy and an analysis of the business environment. Lastly, the results from a comparison of work behavior between employees at geothermal plants, fishing vessels and from other sectors are presented. Results were not as expected; employees at the geothermal plant were less considered to their peers, more outspoken and seem to show less civic virtue to their companies.
Adaptive Control of Hybrid Ultracapacitor-Battery Storage System for PV Output Smoothing
Authors: Ye Yanzhu , Sharma Ratnesh , Shi Di
Published: February 2014

The integration of hybrid energy storage system (ESS) with PV has been considered an effective solution for PV power smoothing, e.g. the hybrid Ultracapacitor (UC)-Battery storage system. This paper proposes a fuzzy-logic-based adaptive power management system for smoothing PV power output, which manages the power sharing between the UC and Battery system. In this method, the real-time system dynamics are reflected in the adaptive control parameter settings. At the same time this method effectively considers the characteristics and operational constraints of the energy storage devices, e.g. SOC limit, charge/discharge current limit, etc., in order to sustain the system operation. A hybrid PV/UC/Battery power system is modeled by Matlab/Simulink. The simulation studies are performed to demonstrate the effectiveness and advantages of the proposed control method in PV fluctuation suppression, sustainable system operation, energy storage performance.
Using Infrared Thermography to Study Thermal Development in the Entrance Region of a Rectangular Microchannel
Authors: Chen W.-H. , Ho M.- X. , Pan Chin
Published: February 2014

Microchannel heat sink with its high heat transfer area density and potentially high heat transfer coefficient has been proposed for applications with high heat fluxes. The objective of this study is to investigate single-phase convection in the thermally developing region of a rectangular microchannel. An infrared thermography provides an effective approach for non-intrusive and spatio-temporal measurement of temperature. The entrance region, where the heat transfer coefficient is higher than that of the fully developed region, is of particular interest for microchannel cooling applications. The present study establishes an innovative benchmark experimental measurement uaing an infrared thermography. The experiments are conducted on a rectangular cross-section microchannel made of aluminum alloy 6061 with dimensions 22mm×1.5mm×0.3mm and covered on the top with a 5mm thick infrared transmitting germanium glass window. Consequently, the temperature distribution in the channel can be observed via the window directly. In order to measure the temperature correctly, all of the aluminum channel surface substrate was anodized such that emissivity can be increased to 0.95. The results show that the temperature distribution can be measured correctly using infrared thermography. And local heat transfer coefficient can be acquired successfully.
Feasibility and Applications of Supercritical Carbon Dioxide Brayton Cycles to Solar Thermal Power Generation
Authors: Schmitt J. , Willis R. , Frederick N. , Amos D. , Kapat J.
Published: February 2014

This paper focuses on unconventional thermodynamic cycles and their applications in alternative energy. It looks into these promising advancements, beginning with the exploration of trends in cost, efficiency, and the adoption of various sources of power. By studying historical trends, conventional means of obtaining energy are seen to be currently increasing in efficiency in smaller and smaller increments.

The second part of our study is the application of alternative configurations of the Brayton cycle. In particular, this paper analyzes a closed-cycle turbine with supercritical carbon dioxide as the working fluid. Beginning with a simple cycle calculation, this study adapts the cycle and explores the benefit of recuperated and combined cycle systems. A parametric study was also created, comparing the efficiency versus the specific power of each cycle. Consideration of supercritical carbon dioxide as the working fluid in turbomachine cycles may demonstrate an economic advantage in the global market.

This paper provides a perspective on the feasibility of these developments for realistic applications in industry. Also important to feasibility, it assesses trends in the cost of power generated by each cycle and energy source. With this information, choices may be made on which cycle is more economically promising in today’s market. The results of this study provide a clear indication of relative efficiencies. These efficiencies, in turn, determines the optimal design direction for a particular supercritical carbon dioxide cycle. In addition, the results provide insight into the effect of this technology on the cost and efficiency of concentrated solar power production.
Effects of Cavitation Damage on the Hydraulic Characteristics of a Gate Valve
Authors: Trivedi Vatsal , Farah Amjad , Harvel Glenn
Published: February 2014

This paper explores the effects of cavitation damage on the hydraulic performance of a gate valve. Cavitation is the phenomenon in which a fluid evaporates to form vapor bubbles which then subsequently implode. A Computational Fluid Dynamics (CFD) model of water flowing through a partially opened 1 inch (2.54 cm diameter) gate valve was developed using Unigraphics NX 7.5. NX 7.5 utilizes a k-ε turbulent flow 2-equation model. The low pressure and high velocity regions were identified in the CFD model to predict the location of the cavitation site in the valve. In order to simulate the effects of ageing due to cavitation, a gate valve was mechanically damaged in different stages. Damaged and undamaged valves were then inserted in a hydraulic test loop to observe the flow rate and pressure drop across the valves. The valves’ hydraulic loss coefficient was then calculated and compared. The cavitation index of the damaged and the undamaged gate valves was also calculated to predict the likelihood of cavitation.

The results show that the aged valve had lower loss coefficients at the corresponding opening positions compared to the ones for the non-aged valve. Also, it was observed that the aged gate valve had less likelihood of cavitation compared to the non-aged gate valve.
Analysis of a Hybrid PEMFC-SOFC Gas Turbine Power Plant
Authors: Gadalla Mohamed , Al Aid Nabil
Published: February 2014

In this study, a complete economic analysis of integrating different types of fuel cells in Gas Turbine power plants is conducted. The paper investigates the performance of a hybrid system that comprises of a SOFC (Solid-Oxide-Fuel-Cell), a PEMFC (polymer electrolyte membrane fuel Cell), and SOFC-PEMFC which is/are integrated into a Gas Turbine power plant. Detailed modeling, thermodynamic, kinetic, geometric models are developed, implemented and validated for the synthesis/design and operational analysis of the combined hybrid system. The economic analysis is considered to be the basic concepts for thermo-economic optimization of the power plant under investigation, with the aim of finding the optimum set of design/operating parameters. Moreover, one of the aims of this paper is to present a detailed economic analysis of a highly coupled PEMFC-SOFC–GT hybrid plant, paying special attention to the sources of inefficiency and analyzing their variations with respect to changes in their operational parameters.
Comparative Analysis of Conventional and Fuel Cell-Based Gas Turbine Power Plants
Authors: Gadalla Mohamed , Al Aid Nabil
Published: February 2014

The purpose of this paper is to conduct a complete comparative, energy and 2nd low analyses between different types of fuel cells integrated with a gas turbine power plant. Different levels of modeling for the solid oxide fuel cell (SOFC), the proton exchange membrane fuel cell (PEMFC) and the integrated systems are to be presented. The overall system performance is analyzed by employing individual models and further applying energy and exergetic analyses for different configurations of gas turbine power cycles. The study includes applying different proposed methods and techniques to enhance the overall efficiency of the integrated cycle. After performing the complete technical management of the complete system, a comparative study between conventional and PEMFC and SOFC cycles is investigated to highlight the corresponding advantages and disadvantages of each system. The following systems are tested and evaluated: (a) Conventional Gas Turbine System with a combustion Chamber (b) Integrated SOFC Stack into a Gas Turbine System (c) The Proposed Integrated System with both SOFC and PEMFC.
Remote Thermal Performance Monitoring and Diagnostics: Turning Data Into Knowledge
Authors: Jiang Xiaomo , Foster Craig
Published: February 2014

Gas turbine simple or combined cycle plants are built and operated with higher availability, reliability, and performance in order to provide the customer with sufficient operating revenues and reduced fuel costs meanwhile enhancing customer dispatch competitiveness. A tremendous amount of operational data is usually collected from the everyday operation of a power plant. It has become an increasingly important but challenging issue about how to turn this data into knowledge and further solutions via developing advanced state-of-the-art analytics. This paper presents an integrated system and methodology to pursue this purpose by automating multi-level, multi-paradigm, multi-facet performance monitoring and anomaly detection for heavy duty gas turbines. The system provides an intelligent platform to drive site-specific performance improvements, mitigate outage risk, rationalize operational pattern, and enhance maintenance schedule and service offerings via taking appropriate proactive actions. In addition, the paper also presents the components in the system, including data sensing, hardware, and operational anomaly detection, expertise proactive act of company, site specific degradation assessment, and water wash effectiveness monitoring and analytics. As demonstrated in two examples, this remote performance monitoring aims to improve equipment efficiency by converting data into knowledge and solutions in order to drive value for customers including lowering operating fuel cost and increasing customer power sales and life cycle value.
Applications and Benefits of RAM
Authors: Wodka Brian M.
Published: February 2014

This is a follow up article from last year’s ICONE/POWER Conference in Anaheim discussing the development of the new standard for ASME Codes and Standards Committee for the Reliability, Availability, and Maintainability (RAM) of Power Plants. The standard focuses on the priorities of safety, production, and efficiency, with the objective to create an availability program. This program defines an operating budget that supports an effective maintenance program, which in turn ensures the life span of the reliable equipment. The intent is to establish an industry recognized standard for RAM. Some general concepts of the new standard are presented here.
Effect of Acid Gas (H2S and CO2) Addition in Hydrogen/Air Flames
Authors: Selim Hatem , Ibrahim Salisu , AlShoaibi Ahmed S. , Gupta Ashwani K.
Published: February 2014

Results on the effect of acid gas (H2S and CO2) addition in hydrogen/air flame are reported. Different equivalence ratios examined ranged from fuel-rich conditions (Φ = 3.0), stoichiometric conditions (Φ = 1.0), and fuel-lean conditions (Φ = 0.5) to represent the range of conditions that may exist in actual operating Claus furnaces. Acid gas compositions examined are 100% H2S gas and 50% H2S/50% CO2 mixtures to represent a wide range of acid gas compositions encountered during processing of acid gases. Addition of 100% H2S gas in hydrogen/air flame degraded the rate of hydrogen oxidation. In addition, hydrogen sulfide combustion formed sulfur dioxide rather than more favorable elemental sulfur. On the other hand decomposition/production of H2S, SO2, and H2 was observed to occur faster in 50% H2S/50% CO2 acid gas stream. Presence of carbon monoxide was a distinct mark on the release of oxygen from CO2 into the reaction pool. The presence of carbon monoxide also triggered the formation of other sulfurous-carbonaceous compounds, such as COS and CS2. The formation of these compounds adversely impacts the Claus process performance. The results provide conditions under which such compounds are formed and also reveal conditions to alleviate them.
Agile HRSG
Authors: Radovich Michael
Published: February 2014

This paper describes a modification to a standard reheat HRSG (Heat Recovery Steam Generator) enabling it startup faster. It also allows the plant to operate the gas turbine in simple cycle and to operate the HRSG as a stand-alone auxiliary boiler. An external fan, pre-heater and burner are connected to the diffuser of the HRSG. When the gas turbine is out of service, the fan and burner are actuated, providing enough flue gas to allow the HRSG to operate as a small auxiliary boiler. Steam produced during this operation pressurizes the drum, heats the steam lines provides sealing steam for the steam turbine, and allows a vacuum to be maintained in the condenser. The system is designed to produce enough steam to synchronize a steam turbine. When the HRSG, condenser, circulating water system or steam turbine is removed from service, the HRSG is drained and the fan turned on without the burner, mixing tempering air to the exhaust of the gas turbine operating in a simple cycle mode. The tempering air lowers the flue gas temperature enough to allow the operation of the SCR system while preventing damage to the carbon steel tubes of the HRSG.
Case Study of Full-Length Tube Coating and Condenser Life Extension
Authors: Pearson Keith , Hill Larry , Horn Michael , Mitchell James
Published: February 2014

In the Spring of 2012 a 1950’s vintage natural gas unit located on a lake in Texas encountered multiple condenser tube failures of its Admiralty Brass tubes. Due to time and cost restraints, the option of retubing was not chosen to prepare the unit for the summer run. Instead, the full-length of approximately 5,500 tubes were epoxy coated. This included 1,150 tubes which had been plugged as leakers, but were unplugged and coated using a special leak sealing method of applying the epoxy lining. The coating process was completed in 10 days and all but 55 tubes were sealed by the coating process. These tubes were plugged and the unit was put into service. The unit has been running successfully since the project was completed with no heat rate penalty. The circumstances leading up to this situation are discussed along with the details of the coating process.
Energy and Exergy Based Analyses of a Multi-Fuelled SI Engine
Authors: Haq M. Z. , Morshed A.
Published: February 2014

The paper presents energy and exergy based analyses of a single cylinder, four-stroke, spark ignition engine fuelled by six different fuels namely iso-octane, methane, hydrogen, methanol, ethanol and n-butanol. Wiebe function is used to predict realistic burn rates. Since the Wiebe function parameters are generally optimized for conventional fuels, the current study modifies them for different alternative fuels using available burning velocity data. Heat losses throughout the cycle have been predicted by empirical correlations. Analyses are carried out to quantify energy and exergy of the premixed fuel-air mixture inside the engine cylinder at various phases of the cycle and some results obtained from the study are validated against data available in literature. Both energy and exergy destructions are found to be dependent on the fuels and engine operating parameters. Results show that at 1000 rpm, about 34–39% of energy contained in the fuel is converted into useful work and this quantity is found to increase with engine speed. Exergies associated with exhaust are found significantly lower than the corresponding energy values for all fuels. The present study highlights the necessity of both energy and exergy analyses to probe and identify the sources of work potential losses in SI engines in various phases of the cycle.
Resolution of the Thermal Binding Issue of Safety Related MOVs at NPP Krško
Authors: Balić Matija , Bajs Tomislav , Sember Bogoljub
Published: February 2014

Pressure Locking and Thermal Binding (PL/TB) are two different but related physical phenomena, which under certain conditions may prevent the opening of some types of valves.

According to the US Nuclear Regulatory Commission (NRC) NPP operators should evaluate all safety.related power operated gate valves in all operational configurations for susceptibility to PL/TB. Corrective actions are required for susceptible valves that shall assure performance of safety function within plant licensing bases.

NEK (NEK) first addressed this issue through the analysis of the Motor Operated Valves (MOV) that were included in the NEK MOV program. This approach resulted with 31 valves in Krško NPP being found as susceptible to TB, 21 of which to both TB and PL. Subsequently, a more thorough analysis was performed, which took into account realistic operational parameters and detailed deterministic and probabilistic assessment evaluation of accident scenarios. This produced a list of 8 valves susceptible to PL, and another 8 susceptible to TB.

Valves were screened according to their safety significance, safety function, type, operational history, and operational conditions. Where applicable, Probabilistic Safety Analysis (PSA) has been used as a tool to screen the risk from PL/TB to the safe plant operation. To reduce the risk from PL/TB occurrence, either physical modification of the valve (alteration of actuator gear ratio to provide more force), relevant part of the entire fluid system (flooding of sump suction lines), or simulation and testing to confirm actual ability to overcome increased forces (initiating a controlled TB condition, and testing to confirm actuator’s ability to perform), was used.

Methods used and results produced for TB are the subject of this paper.
Some Aspects of Steam Turbine Valves: Materials, Operations and Maintenance
Authors: Mutama Kuda R.
Published: February 2014

Steam turbine valves are the most essential components of modern steam turbines from an operation, performance, reliability and safety aspects of a modern power plant. Current designs are pushing the operational envelope and it is not uncommon for large ultracritical plants to run on pressures exceeding 4500 psi and 1200 °F. These conditions are not only challenging for materials of construction for turbines and boilers but also for main steam turbine valves. The tendency of materials to oxidize at these temperatures is all too common causing problems for valve heads, stems, discs, bushings and seats. OEMs around the world are pushing to develop valve components with 9–12% Cr martensitic steels and nickel based alloys which offer better creep strength at elevated temperatures. For existing power plants at temperatures of a 1000 to 1050 °F range there is a push to retrofit valve components with Incolloy 901 type, Inconel 718 and Stellite alloys. Scale build up in traditional alloys happens too quickly for the usual two year maintenance cycle. The application of better alloys for steam turbine valves makes it possible to increase the maintenance cycle from two to four or even six years, while increasing the operational reliability of the valve. Elimination of main steam valve failures removes risks of turbine overspeed events and increases plant availability. Solid particle erosion is not forgiving on valve parts such as stems, discs and valve seats and over a period of time, excessive wear causes the valve to be rendered unsafe to continued service. Nitrided materials and chrome-carbide-coated materials are much harder than the stem base material; and to slow down wear, a nitriding process is used to develop a thin, hard, wear-resistant surface. Some of the material often used for Stellite liners are Nitralloy 135M, 410 SS, 422 SS Nitrided, Incolloy 901 Nitrided, 347 SS, 13Cr-13Ni-10Co-3Nb-2.5W-2Mo. Different OEMs use a variety of alloys for valve seats, discs and stems. Antigalling characteristics are particularly favorable. Valve casings are cast materials and usually specifications include the ASTM A217 and ASTM A356. The ASTM A217 cast steels are typically, 1.25Cr-0.5Mo Grade WC6 and the 2.25Cr-1Mo Grade WC9 materials. Some of the problems experienced with steam turbine valves, are sticking to the valve seat requiring excessive pull-out force, wear of the seat surface, valves not closing properly due to oxidation build up, Stellite weld cracking, cutting or gouging due to solid particle erosion. The material presented in this paper is of interest to fossil power plant personnel experiencing challenges on valve performance and maintenance. The paper looks at all aspects of steam turbine valves as far as current trends in valve material, operation and maintenance and lastly, looks at recent occurrences of valve failures leading to steam turbine overspeed catastrophic failures around the world.
Alaska’s Renewables-Source Fuel Energy Storage Pilot Plant: Toward Community Energy Independence via Solid State Ammonia Synthesis (SSAS)
Authors: Leighty William C.
Published: February 2014

Alaska village survival is threatened by the high cost of imported fuels for heating, electricity generation, and vehicles. During Winter 2007–8, the price per gallon of heating oil and diesel generation fuel exceeded $8 in many villages. Many villagers were forced to move to Anchorage or Fairbanks. Although indigenous renewable energy (RE) resources may be adequate to supply a community’s total annual energy needs, the innate intermittent and seasonal output of the renewables — except geothermal, where available, which may be considered “baseload” — requires large-scale, low-cost energy storage to provide an annually-firm energy supply. Anhydrous ammonia, NH3, is the most attractive, carbon-free fuel for this purpose at Alaska village scale, because of its 17.8% mass hydrogen content and its high energy density as a low-pressure liquid, suitable for storage in inexpensive mild steel tanks. NH3 may be synthesized directly from renewable-source electricity, water, and atmospheric nitrogen (N2) via solid state ammonia synthesis (SSAS), a new process to be pioneered in Alaska.
Renewable Energy Bulk Storage for < $1.00 / KWh Capital Cost as Gaseous Hydrogen (GH2) and Liquid Anhydrous Ammonia (NH3) C-Free Fuels
Authors: Leighty William C. , Holbrook John H.
Published: February 2014

Electricity from diverse renewable energy (RE) resources may be converted to gaseous hydrogen (GH2) and anhydrous ammonia (NH3) carbon-free fuels and stored at < $1.00 / KWh capital cost in large, solution-mined salt caverns for GH2 and in large, refrigerated, “atmospheric” liquid surface tanks as NH3. This stored chemical energy is gathered and transmitted and distributed via continental-scale underground pipeline systems and converted to useful work, at residential to industrial scales, via combined-heat-and-power (CHP) plants, via direct space heating and cooling, and as transportation fuels. We thus solve RE’s severe transmission, storage, and integration problems via complete, optimized, systems design — from photons and moving air and water molecules to delivered energy services. We need to supply all energy, not just electricity, from diverse renewable energy (RE) resources, both distributed and centralized, where the world’s richest RE resources — of large geographic extent and high intensity — are stranded: far from end-users with inadequate or nonexistent gathering and transmission systems to deliver the energy. Electricity systems may be suboptimal, technically and economically, at such large scale. Electricity energy storage cannot affordably firm large, intermittent renewables at annual scale, while carbon-free GH2 and liquid NH3 fuels can: GH2 in large solution-mined salt caverns, NH3 in steel surface tanks, both pressurized and refrigerated.
An Engineer’s Guide to Eddy Current Testing
Authors: Bell Robert J. , Birks Albert S.
Published: February 2014

This paper applies to individuals charged with maintaining the reliability of shell and tube heat exchangers. These persons typically specify and/or retain the services of others to examine heat exchangers with nondestructive test methods, such as eddy current and are responsible for submitting run-repair-replace recommendations to management.

Electromagnetic Testing (ET) uses the electromagnetic characteristics of components made of conductive materials to determine their condition. Eddy Current Testing (ECT), an electromagnetic method that utilizes induced electrical currents, is usually used to examine non-ferromagnetic materials.

ECT’s high rate of examination, relatively good accuracy with thin wall components, repeatability and volumetric measurement make it an ideal method for examining nonmagnetic heat exchanger tubes. This paper will provide a brief description of the method, concentrating on ECT because most power generation industry heat exchanger tubing is non-ferromagnetic in nature. This paper will also address the following:

• Training and Certification of Technicians.

• ET signal analysis, an exacting science?

• ASME Section V, Appendix II vs. Appendix VIII for in-situ ECT of all heat exchanger tubing.

• Signal analysis variables and limitations.

• A need to know the potential degradation mechanisms.

• Condition assessment vs. eddy current testing.
Numerical Study to Quantify the Effects of Struts and Central Hub on the Performance of a Three Dimensional Vertical Axis Wind Turbine Using Sliding Mesh
Authors: Siddiqui M. Salman , Durrani Naveed , Akhtar Imran
Published: February 2014

A computational fluid dynamic (CFD) analysis is carried out to investigate the effects of struts and central hub in 3D on the overall performance prediction of a three dimensional vertical axis wind turbine (VAWT) with three Darrieus H-type blades. The VAWT has the outer diameter of 2.5m and finite unit length height with expected output of 2KVA. This type of small VAWT are expected to perform better on roof tops of the built-up urban area. The analysis is carried out using sliding mesh concept in commercial CFD software ‘Ansys Fluent 13’. It is observed that the struts and central hub assembly induce additional drag and generate strong vortices which caused a substantial decrease in the performance parameters of the turbine. The numerical simulation are carried out over a three dimensional VAWT with and without struts and central hub. It is found that both the cases show a similar trend of the torque ripple for any one blade while for the upstream path, on the contrary the blades experience a drop in performance from 220° to 360° due to the struts and central hub assembly. A detailed comparative analysis between both the cases is made over the TSR values range from 1.5 to 4.5. At TSR = 1.5, the performance coefficient of the cases with and without struts and central hub are same. However, for the case of struts and central hub, TSR 4 and above show negative values of power coefficients.
Strategies for the Prevention of Turbine Lube Oil System Failures
Authors: Ebner Wallace F.
Published: February 2014

Lube oil is the life blood of a turbine generator. When the oil system fails the damage can be extensive. This paper discusses, losses experienced on lube oil systems, and ways to prevent them. It presents some of the statistics regarding losses in the last 5 years and discusses some common themes. It explores root causes, ways to improve the chances of avoiding these failures, and the best practices that have proven successful.
Driving Water and Wastewater Utilities to More Sustainable Energy Management
Authors: Liner Barry , Stacklin Christopher
Published: February 2014

The Water Environment Federation (WEF) and industry leaders have identified the need for an energy roadmap to guide utilities of all sizes down the road to overall sustainable energy management through increased renewable energy production and energy conservation. This roadmap leverages a framework developed by the electric power sector. Known as the The Smart Grid Maturity Model (SGMM), the framework moved the industry toward “Smart Grid” technology. The basis of the Energy Roadmap originated at a workshop of water and power industry leaders convened by WEF in North Carolina in March 2012. Case studies were analyzed from successful utilities in Austria, Holland, Australia, and the United States. High level, strategic best practices were identified and organized into topic areas, which define the level of progression (enable, integrate and optimize) towards achieving energy sustainability.

As a living document, the roadmap is always under review by dedicated groups within the industry. A number of utilities worldwide have already taken the leap and begun this transformation towards resource recovery and many more are peering over the edge. The WEF Energy Roadmap is intended to guide utilities of all sizes as they progress toward becoming treatment plants of the future. While it is not practical for all wastewater treatment plants to become energy positive or neutral, all can take steps towards increasing energy sustainability.

A key component of the WEF Energy Roadmap is collaboration between water/wastewater utilities and electric utilities. This paper focuses on lessons learned and case studies about energy and water utilities working together to address energy-water nexus challenges. This paper examines perspectives both from energy use at water sector facilities and water use at energy sector facilities.
Replacement Pressure Parts Consideration for Replace In-Kind, Upgrade or Redesign
Authors: Knowles Sean , Lewis Mark
Published: February 2014

One of the largest costs after erection of a boiler is the maintenance cost. Typically these costs are manageable and modest except when replacement of pressure parts is required. When replacing pressure parts in a boiler the owner should take advantage of the opportunity to evaluate the boilers history, mechanical condition and thermal performance. This evaluation is critical as it can benefit the capital replacement cost and the maintenance cost after installation. Solutions can vary from replacement with an exact duplicate, upgrade to improve mechanical reliability, or modifications to improve the thermal performance. After an initial evaluation, further studies into future operating conditions such as cycling of the boiler, fuel changes and other plant modifications can greatly change the recommended replacement. Conducting an evaluation and developing a plan upfront will help support an optimized design and ensure the optimal replacement part is designed and installed. This paper discusses options and considerations to evaluate when developing a replacement plan for pressure parts utilizing current codes and standards.
Pyrolysis and Combustion Energetic Characterization of Coal-Biomass Fuel Blends
Authors: Agarwal Gaurav , Liu Gang , Lattimer Brian
Published: February 2014

A simultaneous thermogravimetric analyzer (STA) and a microscale combustion calorimeter (MCC) were used to investigate the energetic properties of coal, biomass and mixture samples. The STA was used to measure the gravimetric and energetic response of a pyrolyzing sample under inert atmosphere. A pyrolysis mathematical model was used to calculate the heat of pyrolysis of samples from the STA data. The MCC was used to quantify the dynamic heat output from the combustion of the gases produced during the pyrolysis process. The measurement of heat output as a function of temperature was used to calculate the heat of combustion of fuels. It was found that the co-pyrolysis of coal and biomass fuel mixtures exhibited a weighted additive gravimetric and energetic behavior, both from pyrolysis and combustion aspects. It was further validated and concluded that the weighted sum prediction for the heat of pyrolysis and heat of combustion for the coal-biomass fuel mixtures must be conducted on the basis of their individual volatile mass contributions, and not on the basis of initial fuel mixture proportion.
Experience Replacing Feedwater Heaters and Condensers due to Repowering and Uprating a Power Plant
Authors: Grinnan Mindy H.
Published: February 2014

This paper discusses the analysis and decision to replace the condensers and feedwater heaters at the JEA Northside station (formerly Jacksonville Electric Authority) in Jacksonville, Florida (see picture #1). The JEA uprated two power plants from 275 MW to 297.5 in 2002. These plants were built in 1964 and 1967 respectively.
Potential Drought Impacts on Electricity Generation in Texas
Authors: Yan Y. Eugene , Demissie Yonas K. , Wigmosta Mark S. , Tidwell Vince C. , King Carey W. , Cook Margaret A.
Published: February 2014

Many power plants in the Electric Reliability Council of Texas (ERCOT) region require a large amount of water for system cooling. To improve the understanding of potential risks of electricity generation curtailment due to drought, an assessment of water availability and its potential impacts on generation during drought was performed. For this impact analysis, we identified three drought scenarios based on historical drought records and projected climate data from the Geophysical Fluid Dynamics Laboratory global climate model, for greenhouse gas emission scenario A2 defined by the Intergovernmental Panel on Climate Change. The three drought scenarios are (1) 2011 drought conditions (the worst drought in history), with the current level of water use; (2) a single-year drought (2022) projected for the period of 2020–2030, with the assumed projected water use level for 2030; and (3) a multiple-year drought constructed with climate data for 1950–1957 and water demand projected for 2030. The projected drought scenario in 2022 and the historical droughts in 2011 and 1950–1957 represent two different precipitation patterns in the Texas-Gulf river basin.

The hydrologic model constructed for the Texas-Gulf river basin covers most of the ERCOT region. The model incorporates climate and water use data that correspond to three drought scenarios, respectively, to estimate evapotranspiration, water yield from watersheds, stream flow and water storage in reservoirs. Using criteria based on observed (< 50% storage) and predicted (< 55% storage) reservoir data, we identified 15 low-storage reservoirs in 2011, 10 in 2022, and 20 in 1956 (the last year of the multiple-year drought). The power plants that are supported by these reservoirs would be potentially at risk of being derated for thermoelectric cooling because of a lack of water supply. These power plants are located mainly in watersheds near and between Houston and Austin, as well as surrounding Dallas.