bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear Power: Time to Start Again
Authors: Rezak William D.
Published: December 2008

One of America’s best kept secrets is the success of its nuclear electric power industry. This paper presents data which support the construction and operating successes enjoyed by energy companies that operate nuclear power plants in the US. The result—the US nuclear industry is alive and well. Perhaps it’s time to start anew the building of nuclear power plants. Let’s take the wraps off the major successes achieved in the nuclear power industry. Over 20% of the electricity generated in the United States comes from nuclear power plants. An adequate, reliable supply of reasonably priced electric energy is not a consequence of an expanding economy and gross national product; it is an absolute necessity before such expansion can occur. It is hard to imagine any aspect of our business or personal lives not, in some way, dependent upon electricity. All over the world (in 34 countries) nuclear power is a low-cost, secure, safe, dependable, and environmentally friendly form of electric power generation. Nuclear plants in these countries are built in six to eight years using technology developed in the US, with good performance and safety records. This treatise addresses the success experienced by the US nuclear industry over the last 40 years, and makes the case that this reliable, cost-competitive source of electric power can help support the economic engine of the country and help prevent experiences like the recent crisis in California. Traditionally, the evaluation of electric power generation facility performance has focused on the ability of plants to produce at design capacity for high percentages of the time. Successful operation of nuclear facilities is determined by examining capacity or load factors. Load factor is the percentage of design generating capacity that a power plant actually produces over the course of a year’s operation. This paper makes the case that these operating performance indicators warrant renewed consideration of the nuclear option. Usage of electricity in the US now approaches total generating capacity. The Nuclear Regulatory Commission has pre-approved construction and operating licenses for several nuclear plant designs. State public service commissions are beginning to understand that dramatic reform is required. The economy is recovering and inflation is minimal. It’s time, once more, to turn to the safe, reliable, environmentally friendly nuclear power alternative.
A Synopsis of Cooling Tower Pump Sump Modeling Experience
Authors: Werth David E.
Published: December 2008

Cooling tower pump sumps are often designed according to the Hydraulic Institute (HI) Standards [1]. However, when geometric or economic limitations lead to deviations from these standards, a physical hydraulic model study is often conducted. This paper summarizes a number of recent physical model studies and brings to attention some of the recurring problems observed during the physical model studies. Performance comparisons are made between stations strictly adhering to the established design standards and those with minor or significant variations.
A Practical Numerical Simulation Approach for 3D Wet Steam Flow
Authors: Zhang Dongyang , Sturmayr Andreas , Liu Jianjun , Jiang Hongde
Published: December 2008

A numerical approach-FAWS which is based on analytical Wilson point parameters and aims at simulating non-equilibrium wet steam flow in steam turbine for industrial application is developed successfully and described systematically in this paper. The 3D viscous condensation flow in an operating steam turbine stage is specially analyzed. The numerical accuracy of FAWS and some phenomena of condensation flow in 2D cascade are displayed and analyzed. Relevant results show that FAWS can be a useful tool to design the stage working in wet steam.
Heat Transfer Characteristics in Cylindrical Furnaces and Combustors
Authors: Khalil Essam E.
Published: December 2008

The recent advances in numerical methods and the vast development of computers had directed the designers to better development and modifications to airflow pattern and heat transfer in combustion chambers. Extensive efforts are exerted to adequately predict the heat transfer characteristics in the combustor zones and to reduce the emitted pollution and noise abatement to ultimately produce quite and energy efficient combustor systems. The Present paper fosters mathematical modeling techniques to primarily predict what happens in cylindrical and three-dimensional combustion chambers simulating boiler and industrial furnaces in terms of heat transfer characteristics and interactions. The present work also demonstrates the effect of chamber design and operational parameters on performance under various operating parameters. The governing equations of mass, momentum and energy are commonly expressed in a preset form with source terms to represent effects of pressure gradients, turbulence and heat transfer. Fluid flow and heat transfer characteristics in combustors play an important role in the efficiency, thermal balance and performance. The present paper discusses the various combustion modeling assumptions and those of the heat transfer in furnaces. The results are obtained in this work with the aid of the three-dimensional program 3DCOMB; applied to axisymmetrical and three-dimensional complex geometry with and without swirl. The numerical grid comprises, typically, 288000-grid node covering the combustion chamber volume in the X, R or Y and Z coordinates directions. The numerical residual in the governing equations typically less than 0.001%. Examples of large industrial furnaces are shown and are in good agreement with available measurements in the open literature. One may conclude that heat transfer characteristics in combustors are strongly affected by the inlet swirl, inlet momentum ratios, combustor geometry; both micro and macro mixing levels are influential. Higher tangential velocities and turbulence characteristics are demonstrated in situations with higher swirl intensities. The present modeling capabilities can adequately predict the local flow pattern and turbulence kinetic energy levels in complex combustors.
NOx Control for Stationary Sources and Utility Applications
Authors: McGowan Thomas F.
Published: December 2008

NOx control is coming to electric generation utilities and industrial plants in a big way. Federal regulations, ozone non-attainment areas, ozone “transport regions,” acid rain provisions of the Clean Air Act, and corporate goals for emission reductions are all motivators. This paper explores regulations, the chemistry of NOx formation, and practical and cost-effective ways to reduce NOx at its source, as well as “end-of-pipe” methods for the major targets: coal fired boilers, gas and oil boilers, and gas turbines.
The Diagnosis of Turbine Component Degradation: Case Histories
Authors: Kubiak S. J. , Garci´a-Gutie´rrez A. , Urquiza B. G. , Sierra E. F. , Siqueiros A. J. , Basurto-Pensado M. A.
Published: December 2008

In this paper several cases of steam and gas turbine components wearing-out are described. The wearing-out of the steam path components were identified during operation of the machine and verified during overhaul. The diagnosis of the wearing out principally of the blades and seals was carried out before the overhauls. The diagnosis results were useful to indicate major problems to the personal of the plants. The estimation of degrees of wearing-out of the steam turbine components was conducted applying a simplified flow equation [1] considering three key pressures. As far as the gas turbine is concerned the output capacity and pressures, temperature and air and gas flow were measured and analyzed. The results obtained during on-line analysis were confirmed by measurements of the dimensions of wearied-out components during the overhaul which were treated as an input data to a program which calculated losses. Also, the results obtained from a special computer program proved the usefulness of the applied methods.
New Options for Improving Operation and Reducing Maintenance in Diverter Valves
Authors: Brotzman John M.
Published: December 2008

Diverter valves are a critical link to the reliability and availability of a combined cycle plant. The flexibility that they allow is somewhat offset by the requirement for maintenance. Reducing maintenance is a huge advantage in operation. New designs allow for greatly reduced maintenance and huge improvements in reliability, availability and maintainability.
Offshore Wind Farms for Hydrogen Production Subject to Uncertainties
Authors: Kassem Nabil
Published: December 2008

Wind power is a source of clean, nonpolluting electricity, which is quite competitive, if installed at favorable wind sites, with fossil fuel and nuclear power generation. Wind power is an intermittent electricity generator; which does not provide electric power on an “as needed” basis. The major challenge in wind energy assessment is how accurately the wind energy can be predicted and the capital investment cost is estimated. Therefore, wind energy is subject to some uncertainties, which must be accounted for to provide meaningful and reliable estimates of performance and economic figures-of-merit. Off-peak power from wind farms can be utilized for hydrogen production using water electrolysis. This study applies methods of risk analysis to evaluate the simultaneous effect of multiple input uncertainties, and provide an assessment of the-techno-economic viability of offshore wind farms for electrolytic hydrogen production. The capacity factor of wind turbine has a dominant effect on the wind power economy.
Selection and Operation of Variable Speed Boiler Feed Pumps in a Triple Pressure Combined Cycle Plant
Authors: Flory Alan , Warburton Anthony
Published: December 2008

This paper discusses various issues that pertain to the proper selection and operation of variable speed boiler feed pumps in a combined cycle plant equipped with a triple pressure boiler. There are numerous selection criteria to be met in order to achieve the best operational efficiency with variable speed pumps. In addition, it is imperative that all cases of operation be analyzed to ensure proper pump selection. The triple pressure Heat Recovery Steam Generator (HRSG) is typically found in the combined cycle plant. Unlike its fossil fired predecessor, it requires a high component flow through each section of the HRSG. By far the most difficult choice when selecting the boiler feed pump for the boiler arrangement is how to balance the pressure and flow requirements of each section of the boiler with the pressure requirements that result from varying loads on the plant. The primary benefit of the variable speed pump is economy of operation at reduced load, yet this is also the very issue that makes selection difficult. Each pressure component of the HRSG has varying requirements that are non-linear with plant demand. A secondary but less tangible benefit from variable speed operation is improved life of system components, with the most significant benefit relating to the main feedwater control valve. However, coincident with the benefits of the variable speed pump are several operational and selection complications that make proper design challenging. Some of the issues to consider in the initial design include: control scheme, thermal plant design, and potential operational modes, all of which contribute to the challenges in designing the pump intermediate and high pressure sections for variable speed operation. These issues are analyzed and discussed. In addition, various details critical to pump design and selection that have been acquired through recent experience are incorporated in the various sections. If successfully selected and properly planned to work in concert with the remaining plant hardware, the benefits of a variable speed pump can be significant. The reduced power input to the pump can be a significant financial savings along with several less quantifiable but equally valuable benefits like increased control valve life, increased pump life and better resistance to system upsets.
Examining the Fracture of Multi-Layered Coatings by Rheological Modeling of Hertzian Indentation
Authors: Kireitseu Maksim
Published: December 2008

The present paper describes an application of Hertzian indentation with rheological models as a method for determining the fracture of any multi-layered brittle coating. The advantage of the method revealed here is that the only quantity to be measured is a deformation or a fracture load. Use of a refined stress intensity factor formulation for surface-breaking cracks in steep stress gradients has enabled accurate estimates to be made of the minimum loads necessary to propagate cracks by Hertzian indentation. At present the analysis only applies for the case where the sphere and the substrate are made of similar materials. However, the analysis is comprehensive in that it can be applied to sphere/substrate systems with any value of Poisson’s ratio, elastic, plastic and viscous properties of materials that may be included in appropriate rheological models for study a strain-deformation state. By measuring this minimum load (and that is the only quantity that must be measured) an accurate estimate of fracture may easily be made with application of rheological modeling. Two further points are worthy of note. Because the only quantity that must be measured is a fracture load, it is possible that this method of determining fracture can be automated with equipment and software. Also, the existence of an absolute minimum fracture load, for a given sphere size, suggests that the Hertzian indentation test could find use as a localized proof-test.
Operational Reliability Improvement of Plants Through Intelligent Fault Detection and Diagnosis
Authors: Odoom E. Ricky
Published: December 2008

Real-time Fault Detection and Diagnosis of modern dynamic process plants are continuously receiving increasing attention both theoretically and practically. In recent years, attempts have been made to apply Artificial Intelligence techniques to the Fault Detection Diagnosis task for improving the operational reliability of complex dynamic plants. The aim of this paper is to discuss the basic concepts, issues and tools of some of the emerging intelligence technologies for Fault Detection and Diagnosis schemes. The emphasis is given to the methods, which are based on Artificial Intelligent systems and which are appropriate for diagnosing faults in complex dynamic plants.
Framework for Operational Reliability Program Development, Implementation, and Management
Authors: Odoom E. Ricky
Published: December 2008

A methodology is proposed in this paper for the development, implementation, and management of Operational Reliability program suitable for power plant as well as other process plants. The methodology is a comprehensive integrated approach combining safety aspects and the operating reliability of plant’s systems. The framework for the methodology is divided into seven modules. Implementation strategies for the Operational Reliability program are discussed followed by a proposed Decision Support System for managing the program.
Coupled CFD and Thermal Steady State Analysis of Steam Turbine Secondary Flow Path
Authors: Moroz Leonid , Tarasov Alexander
Published: December 2008

The main purpose of this work is to conduct coupled CFD analysis of the steam flow in the secondary part of turbine and study thermal rotor/stator steady state. We consider a 11 stage high-pressure cylinder of a power steam turbine with extended terminal labyrinths. Domain of interest is only the secondary flow path of the cylinder, therefore the shroud and blades are beyond the scope of this work. All blades are virtually removed and on the imaginary cylindrical surface the effective boundary conditions are assigned. This takes into account heat fluxes that came to disks/diaphragms from blades in reality. Practical engineering method of obtaining axi-symmetric solution has been developed and results are presented and discussed. Thermal state analysis shows a significant influence of secondary steam bleeding on temperature distribution of rotor and stator.
Hybrid Dual-Fuel Combined Cycles for Small-Scale Applications With Internal Combustion Engines
Authors: Petrov Miroslav P. , Stenhede Thomas , Martin Andrew R. , Hunyadi Laszlo
Published: December 2008

Hybrid dual-fuel combined cycle power plants employ two or more different fuels (one of which is typically a solid fuel), utilized by two or more different prime movers with a thermal coupling in between. Major thermodynamic and economic advantages of hybrid combined cycle configurations have been pointed out by various authors in previous studies. The present investigation considers the performance of natural gas and biomass hybrid combined cycles in small scale, with an internal combustion engine as topping cycle and a steam boiler/turbine as bottoming cycle. A parametric analysis evaluates the impact of natural gas to biomass fuel energy ratio on the electrical efficiency of various hybrid configurations. Results show that significant performance improvements with standard technology can be achieved by these hybrid configurations when compared to the reference (two independent, single-fuel power plants at the relevant scales). Electrical efficiency of natural gas energy conversion can reach up to 57–58% LHV, while the efficiency attributed to the bottoming fuel rises with up to 4 percentage points. In contrast to hybrid cycles with gas turbines as topping cycle, hybrid configurations with internal combustion engines show remarkably similar performance independent of type of configuration, at low shares of natural gas fuel input.
A Computational Analysis of Multiphase Flow Cyclonic Separator for Clean Combustion in Power Plants
Authors: Sierra Fernando Z. , Jua´rez David , Garci´a Juan C. , Kubiak Janusz , Nicola´s Rube´n
Published: December 2008

In this paper a numerical computation of the flow dynamics in a compact cyclonic separator (CCS) for multiphase mixtures is presented. The study is directed to power plants consumption requirements where fuel gas must be free of solid particulate. A finite volume approach has been employed with body-fitted coordinates in a 3-D solution of the CCS dynamics. The cylindrical geometry under study includes aspect ratios in the range 2.5<R<3.8 (where R = height/diameter). The CCS has three exits as follows: one on the top for gas; one on the bottom for low particle concentration liquid; and the last one tangentially located on the lower part of the CCS for high particle concentration liquid. The turbulence was resolved using a RNG model, while the interactions between each component of the flow were addressed using a mixture slip model. The three-phase liquid-gas-solid mixture considered was gasoil-propane-mineral coal particles with the composition in volume fraction of liquid to gas of 0.9 to 0.1 in addition to 109 kg/m3 of 40 microns coal particles as the disperse phase. The results indicate that reversible flow of liquid through the upper gas-outlet may be a function of the outlet pressure conditions. Also, velocity conditions of the income mixture flow at the inlet defined the residence time of the flow during the operation of the CCS, which affects the separation too. In this work density profiles are shown to indicate the regions of up flow for gas and liquid drag. The presence of a third phase in the form of solid particles affects the flow patterns in a CCS.
Design of Composite Rehabilitation Technologies for Power Generation Facilities
Authors: Charest John A. , Witt Sarah
Published: December 2008

Deterioration of components and structures at power generating facilities has caused unscheduled plant outages, personnel safety concerns, and significant impact on operating budgets. However, a new technology is now available that can increase the usable life of components and structures, while significantly reducing the economic burden normally associated with repair or replacement options. This technology, known as “Fiber Reinforced Polymers” or FRP, utilizes carbon fibers and high strength epoxy resins to restore or enhance the structural and or pressure boundary capacity of plant equipment and structures. This technology utilizes the high strength of the carbon fibers to add additional structural capacity to the existing member. This is accomplished through the superior adhesive bond provided by the epoxy. The design determines the orientation of the fibers to add strength in the direction of static and dynamic loading conditions. The repairs to the affected items are performed in-place and completed during relatively short durations. Small crews perform the work and can do internal strengthening with access through only a manhole. Power generation facilities and electrical transmission/distribution networks have typically shunned the use of composite materials to rehabilitate structures or components. The technology and engineering associated with FRP repair methods provides an effective mechanism to rehabilitate piping, pumps, heat exchangers, water boxes, structural shapes and numerous other items while minimizing the cost typically associated with direct replacement.
The Isoengine: A Novel High Efficiency Engine With Optional Compressed Air Energy Storage (CAES)
Authors: Linnemann Claus , Coney Mike W. , Price Anthony
Published: December 2008

A novel high efficiency reciprocating piston engine — the isoengine — is predicted to achieve net electrical efficiencies of up to 60% in units of 5 to 20 MWe size. The high efficiency and at the same time a high specific power output are achieved by integrating isothermal compression, recuperative preheating and isobaric combustion into a novel power cycle. The isoengine can utilize distillate oil, natural gas or suitable biofuels. While the first commercial isoengine is envisaged to have a power output of 7 MW, a 3 MW prototype engine is currently being tested. Since compression and combustion are performed in different cylinders, these processes can also be performed at different times such that the isoengine can be used to create a highly efficient small-scale compressed air energy storage (CAES) system. In such configuration, the engine can operate at more than 140% nominal load for a limited time, which depends on the air storage capacity.
A Thirty Year Service Exam: Titanium Tubed Surface Condensers
Authors: Schumerth Dennis J.
Published: December 2008

The first installation of Grade 2 titanium condenser tubing in a US powerplant occurred in the fall of 1971 as a partial retube of the then, PG&E Moss Landing Unit No. 7 generating station. At the time of this partial retube, “Mighty Moss” was the largest fossil powerplant in the USA generating 750 MWe. Conversely, the first complete titanium-tubed surface condenser installation occurred in 1972 at the 490 MWe ConEdison - Arthur Kill Unit #3. Following comparative testing of competing tube materials, a partial titanium retube, followed by a complete replacement of the remaining aluminum bronze (C608800) tubes, eliminated severe corrosion problems after only 17 months of operation. Thirty years later, both the Moss Landing Unit No. 7 (Duke Energy) and Arthur Kill Unit #3 (an NRG holding) remain fully operational units and a growing fleet of nearly 300 new, modularized and retubed titanium surface condensers have been installed worldwide. These units have provided powerplant operators with three decades of corrosion-free operation — indeed a new industry hallmark of availability and capability. Citing the outstanding performance of titanium over the past 30 years as historical precedent, this paper will provide a brief overview of prior art, investigate new and relevant data, highlight recent process improvements, predict future applications and of course, identify the inevitable cautionary notes.
Effective Utilization System of Unused Energy in Aquarium
Authors: Okamoto Satoru
Published: December 2008

This paper introduces a heat pump system with a latent heat storage utilization seawater installed in an aquarium. For heating purpose such as air conditioning in order to maintain the indoor conditions at constant temperature and constant relative humidity, and cooling water supply to the fish tank in the aquarium, heat from seawater is collected as the heat source for the heat pump system. With regard to the heat pump system using low-temperature unutilized heat source, development is introduced on a heat source load responsive heat pump system, with combines a load variation responsive heat pump utilizing seawater with a latent heat (ice plus water slurry) storage system using nighttime electric power serving for electric power load leveling. The experimental COP (Coefficient of performance) of the proposed heat exchanger from seawater and latent heat storage cooling assisted heat pump system will be shown in detail.
Windage and Axial Friction Losses of High Speed Generator
Authors: Ren Wei-Min
Published: December 2008

Air-cooled generators have been fulfilling a wide range of applications recently. Concurrent with a low cost target, the market demands high efficiency and high performance designs. Windage and friction losses, caused by rotor rotation and cooling gas flowing through the ventilation circuits, represents one of the largest loss components in air-cooled generators. Carefully managing the windage and friction loss is critical to ensure the success of air-cooled generators. This work is motivated by development of air-cooled high-speed generators. In such applications, the flow inside the annular gap between the rotor and stator is highly turbulent. The flow characteristics are not fully understood. Physics-based correlations, which calculate the windage and friction losses, don’t exist in the literature. The purpose of this work is to develop such transfer functions for machine design. Numerical simulations, using commercial CFD code FLUENT 6.0 and Design of Experiment (DOE) method, have been carried out to study the flow characteristics in the annular space between the cylindrical rotor and stator. All simulations were performed using an axial-symmetric model, along with RNG k-ε turbulence model and enhanced wall treatment. In the study, the generator rated speed ranged from 5000 to 20000 rpm; the Taylor number ranged from 1750 to 78000; and the Mach number ranged from 0.25 to 1.0. The effect of axial flow on windage loss was carefully studied. Axial flow exhibited a strong impact on windage loss. The CFD results are rationalized. Transfer functions for windage and axial friction losses are created. They provide a better basis to explore the design space at the early stage of the product development.
The Prospects for Ocean Thermal Energy Conversion: The Ocean Thermal Gradient Hydraulic Power Plant
Authors: Beck Earl J.
Published: December 2008

The Steam Lift Pump of the Ocean Thermal Gradient Hydraulic Plant is patterned after the well-known but apparently not well understood air lift pump, which is an effective but inefficient device for increasing the head on pumped liquid, usually water. Instead of pumping compressed air, an expensive and largely unsuitable gas into the bottom of the pump tube, a partial vacuum is applied to the Steam Lift Pump, at an absolute pressure just below the saturation pressure of the pumped liquid. Cavitation bubbles grow from nuclei formed by degassing the incoming liquid in a cavitating venturi of special design. The low density foam formed by the steam bubbles is pumped to a maximum theoretical height (head) about 4 times the sum of the pressure head of the immersion of the pump tube in the liquid and the head of water supported by the vacuum. The bubbles are broken, their steam content condensed and the resulting dense water flows through an hydraulic turbine.
Investigation of a Duct Burner Design Using CFD in Comparison With Full-Scale Experiments
Authors: Lorra Michael A. , Schnepper Carol A. , Somers Stephen
Published: December 2008

Most new duct burners are supplied to heat recovery steam generator (HRSG) manufacturers for use in cogeneration systems. Key components of a simple cycle cogeneration plant include a turbine, generator, turbine exhaust gas duct, duct burner (optional), HRSG and downstream flue gas cleaning equipment. New developments in gas turbine technology are changing the boundary conditions for supplemental firing. In response, John Zink has an ongoing research project for the development of new duct burners achieving ultra low NOx emissions maintaining a good flame quality. The scope of this research work includes computational fluid dynamic modeling (CFD) and experimental testing of current design duct burner to obtain baseline data comparable with CFD results, and various experimental configurations through a full range of expected operating conditions. Experimental testing is performed in a test furnace at John Zink Company, Tulsa. Turbine exhaust gas (TEG) is simulated using John Zink Duct burners, which are supplied with air from a combustion air fan. Different O2 levels can be achieved by a combined water/steam injection. The temperature level of the TEG to the test burner can be adjusted with an air-cooled heat exchanger. Temperature and concentration measurements can be made at the test burner location and in the stack. Flame length, as well as NOx and CO emissions were measured for each data point. CFD modeling focused on the performance effects of turbine exhaust gas flow mal-distribution and the investigation on how reliable CFD models are, regarding flame stability calculations and NOx production. The results of this comprehensive testing and results from the CFD calculations will be compared and presented.
A Study of Droplet Erosion on Two L-0 Turbine Stages
Authors: Lam Tony C.-T. , Dewey Robert
Published: December 2008

Water droplet erosion continues to pose a serious potential threat to the critical path of maintenance outages. Despite advances in techniques and processes to mitigate erosion, combined cycle arrangements still result in an unexpected level of wetness within the steam, which can produce extensive damage to the last stage blade rows. A procedure is discussed that has been used successfully to manage the critical reliability issues that are raised once conditions of water droplet erosion are found. Erosion rate is estimated from (1) empirical models obtained from the literature, (2) for the steam flow conditions specific to the unit, and (3) with stresses obtained from analysis of the damaged blades. Two applications are presented to demonstrate how the erosion rates were used to provide a basis for two very different strategies, both of which were able to avoid the prohibitive cost of extending the immediate outage to obtain and install new replacement rows.
Improvement of Selective Catalytic Reduction System Performance in Combined Cycle Power Plants
Authors: Sobolevskiy Anatoly , Czapleski Tom , Murray Richard
Published: December 2008

Environmental regulations are very stringent in the U.S., requiring very low emissions of nitrogen oxides (NOx) from combined cycle power plants. Selective Catalytic Reduction (SCR) systems utilizing vanadium pentoxide (V2O5) as the active material in the catalyst are a proven method of reducing NOx emissions in the exhaust stack of gas turbines with heat recovery steam generators (HRSG) to 2–4 ppmvd. These low NOx emissions levels require an increase of SCR removal efficiency to the level of 90+ % with limited ammonia slip. The distribution of flow velocities, temperature, and NOx mass flow at the inlet of the SCR are critical to minimizing NOx and ammonia (NH3) concentrations in HRSG stack. The short distance between the ammonia injection grid and the catalyst in the HRSG complicates the achievement of homogeneous NH3 and NOx mixture. To better understand the influence of the above factors on overall SCR system performance, field testing of combined cycle power plants with an SCR installed in the HRSG has been conducted. Uniformity of exhaust flow, temperature and NOx emissions upstream and downstream of the SCR were examined and the results served as a basis for SCR system tuning in order to increase its efficiency. NOx mass flow profiles upstream and downstream of the SCR were used to assess ammonia distribution enhancement. Ammonia flow adjustments within a cross section of the exhaust gas duct yielded significantly improved NOx mass flow uniformity after the SCR while reducing ammonia consumption. Based on field experience, a procedure for ammonia distribution grid tuning was developed and recommendations for SCR performance improvement were generated.
Effective Maintenance PM Task Selection Requirements
Authors: August J. K. , Vasudevan Krishna , Magninie W. H.
Published: December 2008

Developing an effective scheduled maintenance program requires a profound awareness of risk tolerance, dominant failure modes, failure symptoms, diagnostic methods, and work practices. Effective PM task selection is hard work. Identifying applicable and effective tasks quickly and consistently for critical equipment is the first step towards reliable, cost-effective operations. Automating the PM task selection process by using relational database software removes developmental ambiguity, which speeds up analysis, but poses practical problems. Preventive maintenance (PM) work order development can be standardized and automated to achieve this objective.
The Advanced Low Pilot Ignited Natural Gas Engine: A Low NOx Alternative to the Diesel Engine
Authors: Srinivasan Kalyan K. , Krishnan Sundar R. , Singh Satbir , Midkiff K. Clark , Bell Stuart R. , Gong Weidong , Fiveland Scott B. , Willi Martin
Published: December 2008

High nitrogen oxides (NOx) and particulate matter (PM) emissions restrict future use of conventional diesel engines for efficient, low-cost power generation. The advanced low pilot ignited natural gas (ALPING) engine described here has potential to meet stringent NOx and PM emissions regulations. It uses natural gas as the primary fuel (95 to 98 percent of the fuel energy input here) and a diesel fuel pilot to achieve compression ignition. Experimental measurements are reported from a single cylinder, compression-ignition engine employing highly advanced injection timing (45°–60°BTDC). The ALPING engine is a promising strategy to reduce NOx emissions, with measured full-load NOx emissions of less than 0.25 g/kWh and identical fuel economy to baseline straight diesel operation. However, unburned hydrocarbons were significantly higher for ALPING operation. Engine stability, as measured by COV, was 4–6 percent for ALPING operation compared to 0.6–0.9 percent for straight diesel.
CFD Modeling of Cogeneration Burner Applications and the Significance of Thermal Radiative Heat Transfer Effects
Authors: Tenbusch A. F.
Published: December 2008

Industrial burners provide process heat for a wide range of applications including cogeneration power production. In such applications a (typically) natural gas fired stationary turbine powers an electric generator and indirectly powers a heat recover steam generator (HRSG). The HRSG steam cycle operates by reclaiming the residual thermal energy of the gas turbine exhaust (GTE) flow. Burners are used to reheat the GTE and increase plant capacity during peak demand periods. CFD modeling is used in the design of burner systems for HRSG applications. GTE flow exiting the turbine unit is passed through a diffuser and then expanded into ductwork where the steam system heat exchangers are located. The expansion of the GTE flow from the turbine diffuser to the full cross section of the ductwork is usually severe and creates an uneven flow distribution. Flow correcting structure may be needed to distribute the flow depending upon the severity of the duct expansion. CFD modeling is used to predict the flow distribution of the GTE and guide the design of any necessary flow correcting structure. Burners are typically installed in an array upstream of the application heat exchanger inlet. CFD combustion, heat transfer, and flow analysis is employed in the burner system design process to locate the burner array, determine any necessary flow baffling, and to ensure and provide a uniform thermal distribution at the downstream heat exchanger inlet. Excessive thermal variation in the GTE flow entering the heat exchanger results in large temperature gradients that can lead to thermal cracking and fatigue of the heat exchanger surfaces. CFD modeling is used to ensure that the burner system design produces a uniform flow and temperature distribution at the heat exchanger inlet region downstream of the burners. This report presents a case study of a CFD flow, heat-transfer, and combustion analysis for a typical HRSG burner application. Two CFD models were constructed for the analysis. The first model included the coupled effects of flow, heat transfer, and combustion for the entire HRSG model volume, but excluded the effects of thermal radiation. The second model included a sub-domain of the HRSG volume near the burner and included the additional effects of thermal radiation, both surface radiation and the effects of the radiatively participating flue gas. Radiative effects were included in the second model by employing the Discrete Transfer Method. Results of the study showed the significant role thermal radiative heat transfer had on the resulting temperature predictions downstream of the flame zone.
Qualification of Laser Welded High Performance S44660 Ferritic Stainless Steel for Condenser Tube Applications
Authors: Fritz James D. , Kovach Curtis W.
Published: December 2008

The laser tube welding process has for the first time been used to produce power plant steam condenser tubing in the high performance ferritic stainless steel grade UNS S44660. This material has traditionally been produced as welded tubing by the gas tungsten-arc welding process for use in seawater and other severe cooling water environments. To verify the corrosion resistance of this new product, corrosion tests have been conducted on production tubing to compare the traditional and new welding processes. The acidified ferric chloride test was used for evaluation because it is a meaningful aggressive test capable of measuring resistance to localized pitting corrosion, the most common potential failure mode for stainless steels used in cooling water environments. Pitting tests conducted over a range of temperatures produced a critical pitting temperature of 65°C for laser welded-annealed tube. This critical pitting temperature was demonstrated to be equal to that of as-produced S44660 sheet material or that of gas tungsten-arc produced tubing. The tubing met all other metallurgical and mechanical property quality requirements. When pitting did occur it exhibited no preference for initiation at welds. Thus, laser welded. high performance stainless condenser tubing should be fully capable of providing good performance in severe cooling water environments.
Effect of Hydrogen Peroxide on Premixed Iso-Octane/Air Combustion
Authors: Mulenga Mwila C. , Ting David S.-K. , Reader Graham T. , Zheng Ming
Published: December 2008

The effect of hydrogen peroxide (H2O2) on premixed isooctane/air combustion was numerically investigated using detailed chemical kinetics (Peters’ mechanism) via CHEMKIN. Two cases were examined: one-dimensional, planar, adiabatic, premixed flame, which is of fundamental importance to many combustion systems including internal combustion engines, and zero-dimension, adiabatic Homogeneous Charge Compression Ignition (HCCI). Initial conditions investigated were at 298 K and 1 atm for the premixed flame and 343 K and 1 atm for the HCCI. The effects of H2O2 addition on combustion characteristics including burning velocity, flame temperature, species concentration and ignition delay were deduced. Hydrogen peroxide was utilized as a possible means of emissions reduction. Specifically, the potential of CO reduction due to increased intermediate OH species was studied. The utilization of H2O2 as a means of controlling ignition timing was also explored.
Characteristics of Ammonia-Nitric Oxide Combustion
Authors: Liu Rui , Ting David S.-K. , Checkel M. David
Published: December 2008

The combustion characteristics of premixed ammonia-nitric oxide mixtures at atmospheric and elevated conditions were numerically examined. The laminar burning velocity, flame temperature and flammability limits were determined using the GRI 3.0 and the Miller-Bowman 1989 reaction mechanisms in CHEMKIN. A freely propagating adiabatic flame was assumed to facilitate the investigation. The laminar burning velocities and the flammability limits predicted with the two mechanisms were compared with experimental values measured in a constant volume combustion chamber. The predicted flammability limits are at ammonia-nitric oxide equivalence ratios of 0.2 and 3.5. The predicted laminar burning velocity increases with the unburnt mixture temperature and decreases with the pressure with a peak value at ammonia-nitric oxide equivalence ratio of 0.9. The Miller-Bowman 1989 mechanism predicts results closer to the measured values than the GRI 3.0 mechanism when the laminar burning velocity is concerned. For the adiabatic flame temperature, the predictions from both mechanisms agree well with each other.
Cycling Tolerance: Natural Circulation Vertical HRSGs
Authors: Fontaine Pascal
Published: December 2008

The US market is currently making a double jump in its HRSG requirements. Heretofore, HRSGs were used largely in industrial size cogen applications. According to the PURPA (Public Utility Regulatory Policy Act), public utilities were required to purchase that electric power generated in excess of the steam host’s needs. Thus, HRSGs were relatively small and operated under constant conditions. Now, HRSGs are much larger (utility size) and also more complex due to the introduction of triple pressure plus reheat behind powerful heavy duty gas turbines. With the onset of deregulation and consequent merchant power, combined cycle plants are now required to supply electrical power to the grid as and when needed with consequent day/night and weekday/weekend cycling. Those merchant plants have to come on and off line with minimal notice and be run sometimes at partial loads. Even units which were originally designed for base load are all eventually forced to cycle as new more efficient power plants are built. Thus, substantial changes in basic HRSG design are needed to cope with these changes. Coincidentally, the types of service projected for USA HRSGs have been in effect in Europe for over two decades. For this reason, European HRSG manufacturers/operators have adopted cycling tolerant Vertical HRSGs based on designs which permit the tubes to expand/contract freely and independently of one another, as distinguished from the more rigid horizontal gas pass design. Thus, fatigue stresses related to load following swings are minimized. This is just an illustration of the specific features of the Vertical European HRSGs for minimizing damages due to cycling related fatigue stresses. Vertical HRSG design shall be considered not only in terms of smaller footprint, but also as a solution to cycling related problems. As generally recognized, the cycling criterion is an integral part of HRSG design. This paper presents solutions to HRSG design issues for cycling tolerant operation. It relates to published data on problems observed with cycling Horizontal HRSGs, and it describes how these problems can be overcome. Concepts, design features and calculation methods applied to cycling tolerant HRSGs are reviewed in detail. Vertical HRSGs have been criticized because of their need for circulation pumps. Interestingly, the need for such pumps was eliminated a decade ago, with the advent of natural circulation for Vertical HRSGs up to 1800 psia (124 bar A) operating pressure.
Influence of Driven Rods on Performance of Grounding Grids in Stratified Soils
Authors: El-Drieny S. A. , Metwally I. A. , El-Saadawi M. M.
Published: December 2008

The variation in soil structure has a great influence on the grounding grid performance. This influence can be measured in terms of ground resistance, touch and step potentials. This paper presents a comprehensive experimental study for the influence of adding driven rods on the performance of grounding grids. The study is applied on three constructed scale models. The models have been performed to simulate a single-, double- and triple-layer soils. A comparison between results obtained experimentally and that computed by mathematical equations is introduced.
Graphical User Interface (GUI) for Stochastic Optimal Power Flow in the Deregulated Power Markets
Authors: Yamin H. Y.
Published: December 2008

This paper presents the Graphical User Interface (GUI) for the Stochastic Optimal Power Flow (SOPF) in deregulated power markets. SOPF is a C++ software package that incorporates a probabilistic approach for the evaluation of composite reliability of generation, load forecast and fuel prices using different probability distributions. GUI is a Visual Basic package incorporated with Microsoft Access and PowerPoint for visualization. GUI provides several simple user interface screens for handling the inputs, processes, and results. Several screens are designed and presented in this paper to show the crucial role for the GUI.
Comparative Thermodynamic Analysis of Combined and Steam Injected Gas Turbine Cycles
Authors: Yadav R. , Kumar Pradeep , Saraswati Samir
Published: December 2008

This paper presents a comparative study of first and second law thermodynamic analysis of combined and recuperated and non-recuperated steam injected gas turbine cycles. The analysis has been carried out by developing a computer code, which is based on the modeling of various elements of these cycles. The gas turbine chosen for the analysis is MS9001H developed recently by GE and the steam cycle is having a triple-pressure heat recovery steam generator with reheat. It has been observed that the combined cycle is superior to the steam injected cycle, however, the gap narrows down with increasing compressor pressure ratio and high value of turbine inlet temperature. The detailed exergy losses have been presented in various elements of combined and steam injected cycles.
Investigation of the Energy Budget in an Internal Reforming Tubular Type Solid Oxide Fuel Cell Through Numerical Computation
Authors: Li Pei-Wen , Schaefer Laura , Chyu Minking K.
Published: December 2008

Based on a numerical computation simultaneously solving the fields of flow, heat and mass transfer, the energy budget in a tubular type solid oxide fuel cell is delineated for better understanding of the energy conversion performance and the heat transfer characteristics. It is found that the Joule heating due to ion and electron conduction in cell components is at the same level as that of the thermal energy released from the electrochemical reaction. The energy budget varies significantly with the operating current density of the fuel cell because the Joule heating and thermal energy increase in different manner with the operating current density.
Advanced Mixed Cycles Based on Steam-Methane Reforming and Air Blown Combustion
Authors: Gambini M. , Vellini M.
Published: December 2008

In this paper the overall performance of a new advanced mixed cycle (AMC), fed by hydrogen-rich fuel gas, has been evaluated. Obviously, hydrogen must be produced and here we have chosen the steam-methane reforming for its production, quantifying all the thermal and electric requirements. At first, the thermodynamic performance of this cycle has been investigated in comparison with that attainable by combined cycle power plants (CC). Then, the power plants have been integrated with the fuel production system. Including all the material and energetic flows, the overall performance has been evaluated. The main result of the performed investigation is that, while the two power plants attain the same efficiency level without H2 production requirements (about 56% for AMC and 55.8% for CC), the AMC power plant achieves a net electric efficiency of about 48% when integrated with H2 production plant: it is about 3 points higher than the efficiency evaluated for the CC equipped with the same H2 production plant (about 45%). The final carbon dioxide emissions are about 0.0742 and 0.079 kg/kWh for AMC and CC respectively.