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Inlet fogging of gas turbine engines has attained considerable popularity due to the ease of installation and the relatively low first cost compared to other inlet cooling methods. With increasing demand for power and with shortages envisioned especially during the peak load times during the summers, there is a need to boost gas turbine power. There is a sizable evaporative cooling potential throughout the world when the climatic data is evaluated based on an analysis of coincident wet bulb and dry bulb information. This data is not readily available to plant users. In this paper, a detailed climatic analysis is made of 122 locations in the US to provide the hours of cooling that can be obtained by direct evaporative cooling. This data will allow gas turbine operators to easily make an assessment of the economics of evaporative cooling. The paper also covers an introduction to direct evaporative cooling and the methodology and data analysis used to derive the cooling potential in different regions of the US. Simulation runs have been made for gas turbine simple cycles using a reference plant based on a GE Frame 7111EA gas turbine at the 122 locations studied in the US to provide a feel for the sensitivity of operation with inlet fogging.

Closed circuit steam cooling of blades and vanes in modern gas turbines is an promising alternative instead of film-cooling using compressor air. The temperature drop across the first-stage nozzle, which is convectively steam-cooled, is reduced significantly in comparison to an intensive film-cooled vane using compressor air. Thus, the firing temperature (temperature in front of the first-stage blade row) can be increased while the combustion temperature can remain as low as necessary for low-Nox purpose. In this paper, a steam-cooled test configuration consisting of a 3-vane cascade is numerically analysed. A computer code using a Conjugate Calculation Technique is applied. The CHTflow code has been developed at the Institute of Steam and Gas Turbines in Aachen. Due to the direct coupling of fluid flow and solid body, heat transfer boundary conditions at the external and internal surfaces become unnecessary. Validation of the code for a similar convection-cooled configuration is also given here. The presented investigations focus on the thermal load analysis and the cooling efficiency analysis of the test configuration. It consists of a planar cascade with a convection-cooled central vane where cooling fluid can be supplied to 22 radial passages. One main aspect of the paper is to show the influence of cooling steam conditions (low-, medium & high-pressure steam supply) on the local and global cooling efficiencies. The results show that, for reaching a defined cooling efficiency level, medium steam pressure supply might be advantageous in comparison to a high-pressure level in supply. Although a lower pressure level demands an increase in steam mass flow, the overall effect on the thermal efficiency of the whole process is acceptable if one keeps in mind the advantages of handling steam at lower pressure levels. For further comparison, convective air-cooling with reasonable cooling conditions and comparable flow and heat transfer characteristics is analysed. For the given geometry of the configuration, sufficient cooling of the trailing edge becomes problematic for steam- and air-cooling application.

The evaporative gas turbine cycle is a new high efficiency power cycle that has reached the pilot testing stage. This paper presents calculation results of a new humidification strategy based on part flow humidification. This strategy involves using only a fraction of the compressed air for humidification. Thermodynamically, it can be shown that not all the air needs to be passed through the humidification system to attain the intrinsic good flue gas heat recovery of an EvGT cycle. The system presented also includes live steam production and superheating by heat from the hottest flue gas region. The humidifier only uses the lower temperature levels flue gas heat, where it is best suited. The analyzed system is based on data for the aeroderivative Rolls Royce Trent as a gas turbine core. Part 2 of this 2-part paper presents the results based on data for the industrial gas turbine ABB GTX100. Simulation results include electric efficiency and other process datas as functions of degree of part flow. A detailed model of the humidifier is also used and described, which produces sizing results both for column height and diameter. Full flow humidification generates an electric efficiency of 51.5% (simple cycle 41%). The efficiency increases when the humidification air flow is reduced, to reach a maximum of 52.9% when air flow to the humidification amounts to around 12% of the intake air to the compressor. At the same time, total heat exchanger area is reduced by 50% and humidifier volume by 36% compared to full flow humidification. This calls for a recommendation not to use all the compressed air for humidification.

For small gas turbines a recuperator is mandatory to achieve high thermal efficiencies, 30 percent and higher. As the recuperator represents 25–30 percent of the overall machine cost, efforts are now being focused on establishing new low cost recuperator concepts for gas turbine engines. In this paper a comparison of four different heat transfer surfaces is performed for a recuperator for a representative 50 kW micro turbine. Two standard methods of comparison, the so-called volume goodness factor and the flow area goodness factor, were used to choose several promising heat transfer surfaces for design calculations of a recuperator heat transfer matrix. Thus a direct comparison of recuperator matrix dimensions, volume and weight is possible for the selected surfaces. The hydraulic diameter is equal for all surfaces thus only their thermohydraulic performances are compared. In this paper details of the heat transfer surface geometries as well as the resulting recuperator matrix dimensions, volumes and weights are presented.Copyright © 2001 by ASME

In the present paper, a comprehensive methodology for the thermo-economic performance optimization of an intercooled reheat (ICRH) gas turbine with recuperation for cogenerative applications has been presented covering a wide range of power-to-heat ratio values achievable. To show relative changes in the thermo-economic performance for the recuperated ICRH gas turbine cycle, results for ICRH, recuperated Brayton and simple Brayton cycles are also included in the paper. For the three load cases investigated, the recuperated ICRH gas turbine cycle provides the highest values of electric efficiency and Energy Saving Index for the cogenerative systems requiring low thermal loads (high power-to-heat ratio) compared to the other cycles. Also, this study showed, in general, that the recuperated ICRH cycle permits wider power-to-heat ratio range compared to the other cycles and for different load cases examined, a beneficial thermodynamic characteristic for the cogeneration applications. Furthermore, this study clearly shows that implementation of the recuperated ICRH cycle in a cogeneration system will permit to design a gas turbine which has the high specific work capacity and high electric efficiency at low value of the overall cycle pressure ratio compared to the other cycles studied. Economic performance of the investigated gas turbine cycles have been found dependent on the power-to-heat ratio value and the selected cost structure (fuel cost, electric sale price, steam sale price etc.), the results for a selected cost structure in the study are discussed in this paper.

Deregulation and growth in the power industry are causing dramatic changes in power production and distribution. The demand for peak power and potentially high revenues due to premium electricity rates has attracted independent developers to the concept of Merchant Power Plants (MPPs). Over 100,000 MW of greenfield capacity is currently being developed through approximately 200 merchant plants in North America. These MPPs will have no captive customers or long-term power purchase agreements, but will rely on selling electricity into a volatile electricity spot market. Because of this, MPPs need the capability to export as much power as possible on demand. MPPs must also have the capability to produce significant assets in order to compete in the marketplace, based on both technical and commercial operation factors such as value engineering, life-cycle cost management, and information technology. It is no surprise then, that almost all merchant project developers have specified combined cycle (CC) technology. The CC power plant offers the highest thermal efficiency of all electric generating systems commercially available today. It also exhibits low capital costs, low emissions, fuel and operating flexibility, low operation and maintenance costs, short installation schedule, and high reliability/availability. However, since gas turbines (GTs) are the basis for CC power plants, these plants experience power output reductions in the range of 10 to 15 percent during summer months, the period most associated with peak power demand. In order to regain this loss of output as well as to provide additional power to meet peak demands, the most common options are GT inlet fogging, GT steam injection, and heat recovery steam generator (HRSG) supplemental firing. This paper focuses on plant design, cycle performance, and the economics of plant configuration associated with these options. Guidelines are presented in this paper to assist the owner in selecting power enhancement options for the MPP that will maximize their Return on Equity (ROE).

With the deregulation of the power industry, the use of peaking power solutions such as Compressed Air Energy Storage (CAES) is receiving increasing attention. The CAES plant located in McIntosh, Alabama, owned and operated by Alabama Electric Cooperative, Inc. (AEC) is the subject of this paper. It is the only such plant in the USA and one of two in the world. In off-peak hours the plant pressurizes a cavern with compressed air. During peak hours the stored cavern air is then valved through the combustion turbines to produce any level of peaking power required between 10 and 110 megawatts. This prototype plant began operating in May 1991 and its reliability has been steadily improved. This paper describes the learning process and plant-wide equipment modifications that were made to bring the plant to its present state of reliable operation. Because the CAES operating conditions and operating modes differ from conventional gas turbines, anticipated and unanticipated problems arose. The plant is made up of “combustion turbine” type components, but because of the way the plant operates (- valving of air input - relatively high pressure and air flows at startup - abrupt air flow shutoff at shutdown), certain operating experiences are unique to a CAES plant and not seen on standard gas turbine plants. Among the areas discussed are: controls, stand-by combustor, low-pressure (LP) expander, cavern well liner, lube oil, exhaust flow damper, high-pressure (HP) combustors, LP combustors, fuel injectors, fuel handling, and hot gas path instrumentation. These topics are discussed in the problem, solution, recommendation format. The learning process described in the paper will serve as an invaluable guide to plant designers as future CAES plants are built.Copyright © 2001 by ASME

This is part two of a 2-part paper and presents calculation results of a part flow EvGT cycle based on gas turbine data for the ABB GTX100 (modified for intercooling). The evaporative gas turbine cycle is a new high efficiency cycle that has reached the pilot testing stage. This paper presents calculation results of a new humidification strategy based on part flow humidification. This strategy involves using only a fraction of the compressed air for humidification. Thermodynamically, it can be shown that not all the air needs to be passed through the humidification system to attain the intrinsic good flue gas heat recovery of an EvGT cycle. The presented system also includes live steam production and superheating, by heat from the hottest flue gas region, for injection. The humidifier then only uses the lower temperature levels, where it is best suited. The analyzed system is based on data for the ABB GTX100.gas turbine in intercooled mode. Part 1 of this 2-part paper presents the results based on data for the aeroderovative Rolls Royce Trent. Simulation results include electric efficiency and other process data as function of degree of part flow. A detailed model of the humidifier is used, which produces sizing results both for column height and diameter. Paper 1 includes detailed description of the modelling. For the GTX100-system, full flow humidification generates an electric efficiency of 52.6% (simple cycle 36.2%). The efficiency is virtually unaffected if the air portion to humidification is cut to 60% of accessible compressor air (represents 48% of compressor intake). If 30% of air from the compressor after cooling bleed (24% of intake)is led to the humidifier, the efficiency is reduced to 52.2%. On the other hand is the total heat exchanger area reduced by 20% and column volume by 50%. This calls for a recommendation not to use all the compressed air for humidification. It is recommended to use 15-30% of compressor intake air. The exact economic optimum depends on local fuel prices, CO2-taxes, interest rates et c.

The paper describes experience gained in design and development of gas turbine units for electrical generator or mechanical drive application featuring steam injection into the gas turbine combustion chamber combined with a water recovery system from the gas turbine exhausted gases (units are known as “Aquarius”). Prototype test rigs, and test results on prototype and commercial units are discussed. These units have power output of 16 MW (“Aquarius-16”) and 25 MW (“Aquarius-25”) with efficiency of 45% and 43%, ISO respectively. Special test rigs were designed and built to prove concept of water recovery from gas turbine exhausted gases and to study contact condenser operation over a wide range of ambient temperatures. The first prototype test rig, comprising of SPE “Mashproekt” GT 100K gas turbine engine, 100 kW electrical generator, waste-heat recovery boiler and contact type condenser started operation in 1986. To the Author’s knowledge there is one more plant in operation with water recovery from February 1993 located inside the “CARROZZERIA BERTONE” plant near Turin, Italy (Ennlo Macchi, Aurelio Poggio “A COGENERATION PLANT BASED ON A STEAM INJECTION GAS TURBINE WITH RECOVERY OF THE WATER INJECTED: DESIGN CRITERIA AND INITIAL OPERATING EXPERIENCE”, ASME paper 94-GT-17). The second prototype unit, “Aquarius-25”, comprising of SPE “Mashproekt” steam injected GT 15000S gas turbine engine, waste heat recovery boiler, contact water condenser and a generator (power output of 25 MW and efficiency of 43%) is currently in operation. This unit has accumulated more than 12,000 fired hours in development tests since January 1995. “Aquarius-16” - commercial mechanical drive unit with 16 MW power output and efficiency of 45% was built and factory tested in 1998 (more than 1600 fired hours). It was built around the SPE “Mashproekt” GT 10000S steam injected gas turbine engine. This unit is scheduled to start commercial operation at UKRGASPROM “Stavishenskaya” gas compression station (Ukraine) in 2001.

The presented paper describes a multi-disciplinary cooling selection practice applied to major gas turbine engine hot section components, including turbine nozzles, blades, discs, combustors and support structures maintaining blade tip clearances. The paper demonstrates the benefits of close interaction between participating disciplines, when this interaction starts in the early phase of the hot section development. The approach targets advances in engine performance and cost by optimizing the design process, often requiring compromises within individual disciplines.Copyright © 2001 by ASME

This paper describes new methods of cleaning large multistage axial compressors that are the part of Gas Turbine Unit (GTU). Existing, standard method of compressor cleaning are on-line and off-line. In both cases of compressor cleaning clean water and appropriate detergents are mixed to remove dirt deposits from the blade surface. The on-line system is attractive because the cleaning is done when GTU is under full load. The on-line compressor cleaning slows down inevitable dirt depositing. Offline cleaning is much more effective than on-line cleaning. The negative side of off-line cleaning is that GTU must be shut down. In case of large GTU the processes of shut down and start up require significant amount of time. This paper also incorporates the efforts required to install Inter-stage Injection System (IIS) in one GTU in Watson Cogeneration Company (WCC).Copyright © 2001 by ASME

The severe dependence of gas turbine output on ambient temperature has created the need for inlet cooling technologies. This paper focuses on the practical aspects of direct evaporative cooling by fogging of the inlet air to a gas turbine compressor. This paper covers several of the practical considerations relating to the location of nozzles, water quality and operations and maintenance issues that relate to implementation of such systems. A design and implementation checklist is provided to assist users in ensuring a reliable installation.Copyright © 2000 by ASME

The paper describes GE’s Remote Monitoring and Diagnostic (RM&D) system, its operation, its unique features and our experiences in applying it to improve performance and availability of heavy-duty gas turbine fleet worldwide. A key success factor of the system is that it relies upon an effective combination of advanced computer automation complemented by technical experts who have an in-depth understanding of the power generation equipment to achieve its objectives. The RM&D system enables GE experts to remotely access operational data of power plants operating world wide, and exercise sophisticated algorithms, which can detect abnormal operating conditions. The experts, with ready access to the design information, operation and maintenance information and in-depth knowledge about the turbines, identify and track operational signatures, which may indicate potential problems. The real key is to be able to distinguish false indications from the ones that are true early indicators of potential problems. In this paper we describe a design approach for developing a successful RM&D system. We illustrate our approach through various examples of performance, vibration and combustion diagnostics scenarios.

The U.S. Department of Energy is in its 7th year of a 9-year program to develop the next generation of advanced turbine systems (ATS). Under this program, partnerships between industry, universities, national laboratories, government agencies and institutions, and the U.S. Department of Energy (DOE) are performing research and development required to commercialize the ATS. The ATS Program is jointly sponsored by the U.S. DOE Offices of Fossil Energy and Energy Efficiency and Renewable Energy. Supporting R&D, recent ATS accomplishments and future advanced concepts for next generation gas turbine systems are described and discussed in this paper. As the ATS program winds down, DOE’s National Energy Technology Center (NETL) is evaluating the technology and market needs for continuing DOE support to develop advanced turbine systems. As part of this effort, NETL is sponsoring market and technology assessments, regional focus group discussions, and public workshops. The purpose of this paper is to provide the status of the ATS Program and the NETL perspective on potential options for future research and development needs, and public-private development programs addressing turbine based power generation for systems 30MW or greater in output.

Endwall heat transfer has become a major issue in the design of the inlet nozzle guide vane region of modern gas turbine engines. To compensate for high rates of convective heat transfer and the uncertain flow pattern along endwall surfaces, coolant flows are often excessive and distributed in a less than optimum fashion. In many instances, coolant is carried away or mixed into the core flow by the secondary flows without being effective. There is a need for more effective cooling concepts. In this paper, the results of an experimental study examining the thermal performance of bleed injection through an inclined slot positioned upstream of the nozzle airfoil leading edge plane are presented. This paper demonstrates that this type of combustor bleed cooling is a promising cooling concept. Testing is performed in a large-scale, guide vane cascade comprised of three airfoils between one contoured and one flat endwall. The Reynolds number, based upon approach velocity and true chord length, is 350,000 and the approach flow is with large-scale, high-intensity (9.5%) turbulence. Combustor bleed cooling flow is injected ahead of a contoured endwall with bleed-to-core mass flow ratios as high as 6%. Measurements are taken to document core flow temperature distributions at several axial positions within the cascade to evaluate surface adiabatic effectiveness values and local heat transfer coefficients. This film cooling arrangement offers significant thermal protection. The coolant is shown to provide thermal protection over most of the endwall as well as portions of the pressure and suction surfaces of the airfoils. To achieve this coverage, combustor bleed flow must be strong enough to overcome the influence of endwall region secondary flows.Copyright © 2000 by ASME

An empirical means of predicting the discharge coefficients of film cooling holes in an operating engine has been developed. The method quantifies the influence of the major dimensionless parameters, namely hole geometry, pressure ratio across the hole, coolant Reynolds number, and the freestream Mach number. The method utilizes discharge coefficient data measured on both a first-stage high-pressure nozzle guide vane from a modern aero-engine and a scale (1.4 times) replica of the vane. The vane has over 300 film cooling holes, arranged in 14 rows. Data was collected for both vanes in the absence of external flow. These noncrossflow experiments were conducted in a pressurized vessel in order to cover the wide range of pressure ratios and coolant Reynolds numbers found in the engine. Regrettably, the proprietary nature of the data collected on the engine vane prevents its publication, although its input to the derived correlation is discussed. Experiments were also conducted using the replica vanes in an annular blowdown cascade which models the external flow patterns found in the engine. The coolant system used a heavy foreign gas (SF6 /Ar mixture) at ambient temperatures which allowed the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. These experiments matched the mainstream Reynolds and Mach numbers and the coolant Mach number to engine values, but the coolant Reynolds number was not engine representative (Rowbury, D. A., Oldfield, M. L. G., and Lock, G. D., 1997, “Engine-Representative Discharge Coefficients Measured in an Annular Nozzle Guide Vane Cascade,” ASME Paper No. 97-GT-99, International Gas Turbine and Aero-Engine Congress & Exhibition, Orlando, Florida, June 1997; Rowbury, D. A., Oldfield, M. L. G., Lock, G. D., and Dancer, S. N., 1998, “Scaling of Film Cooling Discharge Coefficient Measurements to Engine Conditions,” ASME Paper No. 98-GT-79, International Gas Turbine and Aero-Engine Congress & Exhibition, Stockholm, Sweden, June 1998). A correlation for discharge coefficients in the absence of external crossflow has been derived from this data and other published data. An additive loss coefficient method is subsequently applied to the cascade data in order to assess the effect of the external crossflow. The correlation is used successfully to reconstruct the experimental data. It is further validated by successfully predicting data published by other researchers. The work presented is of considerable value to gas turbine design engineers as it provides an improved means of predicting the discharge coefficients of engine film cooling holes.

This paper describes a software package designed to optimize the economic and environmental performance of industrial cogeneration plants. The optimization is through a procedure, which optimizes the load allocation between the plant components. The computer procedure is capable of recognizing equipment status and establishes the optimum load allocation between the plant components minimizing an objective function. The objective function is related to the economic and environmental models of the plant components and to the plant boundary conditions. Two prototypes were realized based on two real cogeneration plant. The paper discusses the general modular description of the components and block diagrams of the systems. The model calibrations and load allocations are analyzed and discussed. Copyright © 2000 by ASME.

The objective of this paper is to investigate the modeling of transition in turbomachinery flows. Under steady state conditions four modes of transition can be identified. One of them, reverse transition, can be modeled sufficiently well by turbulence models. For the other modes — natural, bypass and separated-flow transition — specific models have to be applied. These transition models are either based on stability analysis or a statistic approach that describes the production and growth of turbulent spots in the intermittent flow. This paper focuses on separated flow transition. Different models are presented and a classification is attempted. Based on these findings specific models are chosen and implemented into a Navier-Stokes solver to be studied in more detail. First an annular compressor cascade is computed two-dimensionally and the results are compared with experiments. In a second step three-dimensional computations are performed and the effect of transition modeling is analysed.

There is a significant emphasis on peaking power, particularly recognized in the US power generation market. Orders for gas turbines are at their peaks, with OEMs taking orders for delivery in the year 2002, or later. Though a simple cycle GT is the recognized power plant of choice for daily cycle and peak power supply, it still has the highest fuel consumption rate per kWh produced (heat rate, Btu/kWh or Btu/kWh) with associated high emissions. The massive additions of GT power plants for primarily peak/cycling applications should generate needs for better utilization of installed capacities. The Compressed Air Energy Storage (CAES) plant is demonstrated as the best and cost-effective plant for storing significant amounts of the off-peak energy and releasing the peak energy as needed. This paper presents an innovative power plant concept, which is based on the integration of a conventional GT with the unfired CAES, air-bottoming cycle — denoted as GT-CAES. This concept is analyzed and compared to a conventional CAES cycle. Also, the paper presents characteristics of this concept based on ABB’s GT24/26 combustion turbine, the characteristics produced for a number of GT-CAES projects which are in various stages of development.

Power industry growth and deregulation are causing fundamental changes in the economics of power production and distribution. In order to remain competitive, power producers now seek to improve plant economics through cogeneration, the simultaneous generation of power and production of steam for process use. The majority of manufacturing processes are of a continuous type that require high flexibility for power and steam systems (i.e., require various flows and conditions of steam at various power production levels). This paper focuses on several ranges of process steam flows and conditions in order to provide a basis for comparison of the most common cycle configurations in combined cycle applications. A non-reheat, advanced technology gas turbine combined cycle facility will be used as the reference plant. Plant design, cycle performance, and economics of each configuration will be evaluated based on requirements of flexibility and process steam flows. This paper will provide guidelines for selection of cycle configurations for cogeneration power plants that will maximize Return on Equity for the owner.

This paper describes aerodynamic and heat transfer measurements, improved data analysis techniques, and CFD predictions for an extensive series of high-pressure turbine tests carried out in a large-scale, short-duration test facility. The focus of this work is on the test methods, aerodynamic and heat transfer instrumentation, and the heat flux data obtained on the HPT blade and vane pressure and suction surfaces, and on the blade platform. Heat transfer data are presented along three spanwise stream surfaces, and at five platform locations, for two Reynolds numbers, and for three different initial blade temperature levels. An analytical method for improving the interpretation of transient heat flux gage measurements and estimating the uncertainties in heat transfer coefficients is applied based on test facility characteristics, established 2D boundary layer heat transfer theory, and a detailed calculation of the transient temperature response of the heat flux gages as installed in the airfoils. The result is a systematic procedure for improved data reduction and correction of bias errors resulting from in-situ heat flux gage behavior in complex rotating rig tests. Three-dimensional aerodynamic calculations are compared with time-averaged unsteady pressure measurements on the airfoils. Boundary-layer heat transfer predictions are shown to be in fair agreement with the pitchline data but sensitive to assumptions regarding free-stream turbulence, uncertainties in inlet conditions, and variations in the applied surface Mach number distribution. Finally, full 3D heat transfer computations for the blade are discussed, with an emphasis on capturing overall 3D flow effects with sufficient accuracy for practical turbine airfoil cooling design. The results suggest that advanced analysis techniques, including 3D CFD, can be used effectively to compute not only mean values of the surface heat transfer coefficients, but also to quantify the uncertainties in the predictions and to identify the dominant sources of those uncertainties. This is an important step in creating a robust turbine cooling design process that accounts for environmental, manufacturing, and modeling variations. Future papers will present experimental and computational results for the blade tip and shroud, the vane endwalls, and TBC-coated airfoils.

As a reference for future papers on uprating and upgrading experience, this paper presents ABB ALSTOM POWER’s latest generation of modular uprating and upgrading solutions that provide the theoretical background and the technical solution for the gas turbines types GT11D, GT13D and GT11N/N1.Copyright © 2000 by ASME

In this paper, a Fiat Avio 701F gas turbine re-design process is presented. This already tested gas turbine has been modified, for a particular re-powering application: a reduction in the net power production is required, whereas efficiency and exhaust temperature have been improved by mean of increased hot gas temperature at the first nozzle inlet section. Consequently this re-powering solution clearly requires consistent re-design efforts to satisfy specific plant operating conditions. The gas turbine power output has been tuned to the required value by reducing the air inlet mass flowrate; the combustion chamber setting has been modified with particular attention to the control of pollutant emission level. The increase of inlet stator turbine temperature necessitated a complete review of the three cooled turbine stages. The aim of greater overall efficiency with inlet and exit turbine temperature increase also involved the introduction of a new blade material. For design tool flexibility the blade cooling design procedure has been improved making better optimization of the cooling system possible. In this paper a detailed description of the several gas turbine modifications with particular attention to the blade cooling design procedure and to the corresponding simulation results is reported. The modifications developed could also be introduced on the new version of the 701F, at full power capability, in order to get better efficiency and power.

The electricity supply industry is being restructured all over the world. Privatisation, with the emergence of Independent Power Projects (IPPs), especially in developing countries, and liberalisation of the power generation market are changing decision-making processes in a radical way. New challenges of deregulation and customer demands, and economic instabilities in south-east Asia, oblige electric utilities to face a double jeopardy: least-cost planning and least-risk investments. Consumers are encouraged to save energy and emission reduction policies are implemented to promote utilisation of high efficiency, clean power production technologies. The aim of this paper is to introduce the concept of life cycle risk management and Decision Support System (DSS) for open and combined cycle schemes, highlighting the market potential for Flexible Mid-size Gas Turbines (FMGT) in mid-merit applications. The DSS that has been developed at Cranfield University includes: plant simulation program, providing design and off-design performance, maintenance planning, component degradation, and load-following models. In addition several economic techniques based upon engineering finance and project accounting make power plant economic appraisals possible. The DSS also provides a Monte Carlo risk analysis in order to deal with technical and economic uncertainties in a very effective way. Case studies will stress several parameters that planners have to carefully assess when making decision in the context of the coming millennium, bringing all sorts of new challenges and areas of uncertainty that will be discussed in the paper.

Gas turbine cogeneration and district energy plants can provide significant environmental improvements to the long term mix of energy production, in terms of low air pollutants and greenhouse gases. This paper is intended to discuss the fundamental need to integrate plant efficiency considerations into the environmental permitting rules to address all air issues at the same time, as described in the 1992 Canadian gas turbine emission guideline. The paper also compares the relevant air emissions, primarily nitrogen oxides (NOx) and carbon dioxide (CO2), from modern gas turbine plants, and the Canadian operating experience with cost-effective emission prevention methods.Copyright © 1999 by ASME

This paper characterizes the performances of once-through heat recovery steam generators in combined cycle applications. Although the concept of once-through boilers has been extensively used for fired boilers, this circulation mode is rather new in combined cycles. Once-through circulation is required at very high pressures, including supercritical conditions, for which there is a possible advantage in terms of the plant efficiency. The concept is also certainly the best solution for high subcritical pressures, such as those required by repowering applications. In addition to cycle performance, this paper describes the advantages and disadvantages of the once-through in heat recovery applications. The operational behaviour of such heat recovery steam generators is discussed, together with the main design implications. A prototype plant running in supercritical steam conditions is also described, as well as some of its possible applications.

Rolls-Royce has identified phenomena associated with aeroelastic instability of brush seal bristles, when multiple seals are operated in series at high pressure loading. This paper gives a general overview of test experience to date. A brush seal test facility commissioned by Rolls-Royce at Oxford University is described, along with results from double and triple brush seal tests carried out using the facility. The effect of bristle pack instability on sealing performance is clearly identified in the paper. A design modification aimed at suppressing the instability is described. Results from the Oxford University tests show that the device significantly increases the operating range of multiple seal arrangements.Copyright © 1997 by ASME

Modern heavy duty gas turbines operate with high turbine inlet temperatures, and thus require a complex secondary air system to ensure that the blades and vanes are supplied with the required amount of cooling air. Gas turbines with high thermal efficiency and with low emissions require minimum amounts of cooling and sealing air which means that the design of the secondary air system must be extremely accurate. A previous paper introduced the secondary air system for the new Siemens Vx4.3A gas turbines and the calculation method used for its design. This paper deals with the detailed calculation of flow field losses in cooling air passages in rotating disks (rotating passages). The paper starts with a brief review of the work on this topic described in the literature and then presents a consistent model for the prediction of the flow field losses in rotating passages of different lengths and with varying upstream swirl. Particularly short passages with developing flow at the passage exit can he calculated using this model. The calculation system is completed by matching the correlations to experimental data.

States are required to develop and adopt anti-degradation policies and implementation procedures pursuant to federal regulations [1] to protect existing in stream water quality and water uses. States are requiring National Pollutant Discharge Elimination System (NPDES) dischargers from new sources, which could result in lowering of existing water quality, to perform an anti-degradation demonstration as part of the NPDES permit application process. These evaluations are appropriate where a proposed discharge may have a significant adverse impact on water quality. However, they are an unnecessary burden on both the permit applicant and the reviewing agency where the proposed discharge is minor relative to existing water quality. Therefore, de minimis evaluations provide a technical approach that States can use to avoid the need for, or limit the scope of, anti-degradation demonstrations where the impact at the proposed discharge is minor. This paper provides a de minimis evaluation approach for addressing anti-degradation as part of an NPDES permit application process. The approach, which ascertains what conditions would or would not constitute a “de minimis lowering of water quality,” was recently used in support of a new combined-cycle power plant in one of the central states.

The paper proposes a straightforward technique to quantify the performance of a gas turbine secondary air system. By recognising the air system as a component in its own right and performing the calculations suggested the systems engineer should be better able to develop and optimise a given air system. The effect of any requested compromise can also be better quantified to other component groups.Copyright © 2001 by ASME

The effect of operation of compressor bleed anti-icing on the performance of an industrial gas turbine is analysed. The effect of putting this system in operation is first qualitatively discussed, while the changes on various performance parameters are derived by using a computer engine performance model. The main point of the paper is the study of the effect of anti-icing system operation on parameters used for engine condition monitoring. It is shown that operation of the anti-icing system causes an apparent modification of such parameters, which may reduce the diagnostic ability of an on-line monitoring system and produce false alarms. It is shown that by incorporating the effect of anti-icing system operation into a diagnostic engine model, such problems can be avoided and the diagnostic ability of the system is not influenced by anti-icing activation. The analysis presented is substantiated through experimental data from a twin shaft gas turbine operating in the field.Copyright © 2001 by ASME

The Limay Bataan Power station, a 600 MW combined cycle, is now in its 8th successful year of operation. Operating on this specific heavy fuel oil, which is a high viscosity, high ashbearing heavy fuel residue from the refinery at Limay, requires a skilled and experienced crew as the quality of fuel was subject to major changes which are highly relevant to the operating mode. If not treated properly, this fuel could corrode blades within a short operating period. This paper describes the experiences gained on the fuel handling from the fuel treatment plant to the turbine and also addresses the operation of the combined cycle. Specific operating problems are discussed. The plant is fully operated and maintained by ALSTOM Power O&M Ltd with its local team that has greatly contributed to the success of the plant.

Reducing the number of blades in low pressure turbines is a desirable option for decreasing total operation costs. From an aerodynamical point of view this directly leads to an increased blade load. However, increasing the blade load above a certain level results in viscous effects like separation bubbles and finally full separation. This becomes especially significant for aero engine turbines, which operate at high altitudes and thus low Reynolds numbers. The underlying local flow phenomena and the effect on the aerodynamic performance of such configurations are addressed in this paper. This investigation is based on a three-stage low pressure turbine typical for aero engines. Different setups are employed with different number of guide vanes in certain stages. Furthermore, the Reynolds number is varied within a wide range. These configurations are investigated numerically using a modern steady-state transitional Navier-Stokes solver and experimental results from the same turbine. Based on this information, a detailed analysis of the viscous flow phenomena is performed with focus on the influence of separation bubbles on the loss production after the transition. These results are discussed with respect to blade count reduction.

Gas turbines are used to meet increasing power-generating needs throughout the world. Technologies for augmenting the capacity of new or existing installations are being devised. One common strategy is to employ evaporative cooling of gas turbine inlet air. This method is attractive because of simplicity and relatively modest hardware requirements. Another strategy is to recover exhaust heat in order to activate an absorption-refrigeration machine. The cooling machine output is then used to cool and dehumidify the compressor inlet air. In this paper, we delineate a heat recovery system for steam/power production, and an ammonia-water absorption machine. The ammonia-water technology offers an element of novelty in that it is capable of chilling the air to lower temperatures than the currently used lithium-bromide technology, or than the evaporative cooling approach. Performance calculations based on leading commercial software are offered. In a simple payback analysis based on the numbers obtained from the simulation, we discuss the potential of the technique.Copyright © 2001 by ASME

The rims of high pressure turbines in aeroengines are sealed with air via the internal air system. This sealing is required to avoid occurrence of hot gas ingestion into the rotor-stator cavities. Due to a rapid decrease of turbine disc life at higher temperatures, such ingestion would present a hazard to the integrity of the discs and subsequently to the safety of the aircraft. One of the driving factors for ingestion is the circumferential pressure variation downstream of vanes and blades due to the aerodynamic wakes. Small ingestion cavities close to the annulus are commonly used to damp down this pressure variation. Substantial ingestion into these cavities is permitted. The actual sealing of the rotor-stator cavity itself is accomplished with a secondary seal. A numerical simulation of the flow in an engine type rotor-stator cavity was carried out using a commercial CFD code. The cases studied comprise relevant features as rotor-stator and ingestion cavities, leakage across rotor blade shanks and circumferential pressure variation downstream of an NGV. The simulation was carried out at relevant engine temperatures and pressures. The paper will firstly present the effects of a variation of the rim sealing mass flow on the flow field, ingestion and temperature increase in the cavity. These results were solely gained by computational means. For validation of a new air system design, engine tests on the BR715 jet engine have been performed. The data measured in these tests not only serve for certification purposes, but also may be used as input for CFD calculations. Thus, the experimental data was the baseline for comparison with the results from the present study.

Turnkey and thermal island supply scopes present turbine manufacturers with a perfect way to sell their rotating products. The popularity of these plant configurations, along with the recent availability of more holistic test codes, has led to the need for an accurate and reasonable method of determining the thermal performance of the externally-purchased HRSG component. To assess a multiple pressure HRSG, it is advantageous and convenient to have one single criterion for the evaluation of performance, especially when this criterion provides for the compensation of the different outlet energy streams. The so-called Model Steam Turbine method of HRSG evaluation was developed for these reasons. The result of the calculation, a lone performance criterion, is the shaft power of the fictitious Model Steam Turbine. In this paper we will detail the components of the Model Steam Turbine calculation and explore the merits of this method. Some thoughts on performance corrections are also presented.

The gas turbine use in cogeneration plants for thermal and electric power production is constantly increasing especially for low power requirements. In this paper, firstly a thermodynamic analysis of a Below Ambient pressure discharge Gas Turbine (BAGT) has been evaluated and the BAGT cogenerative performance compared with those of a Brayton Cycle (BC) cogenerative power plant. Subsequently, an economic investigation of BAGT is carried out and the benefits, with respect to BC, evaluated. It resulted that the BAGT presents a higher electric efficiency and its employment may strongly increase the budget at disposal for the cogenerative plant investment.

The share of the gas turbine combined cycle plants tends to increase rapidly in the world of power generation. Under the circumstances, MHI is developing the several kinds of gas turbine to meet each customer’s needs. The ‘F’ series’ engine, which has a firing temperature of 1350–1400 degree C, is predominant in the current market, and the reliability improvement is constantly performed. As a result, the operational hours of 50,000, and the combined cycle efficiency of 55–57% (LHV) is achieved for F-series combined cycle. During the operating experience, any events occurred in field operation is solved. Also, countermeasure was implemented on every machine. Furthermore, robust design improvement is introduced, and commercial operation of the design achieved higher reliability and availability. In this paper, the operating experiences, design improvements and the F series gas turbine uprating program are introduced.

The contribution of the gas turbine in simple and combined cycle systems to power production in the United States has been steadily rising over the past 25 years. In 1998 their contribution to power production was approximately 15% and it increased over the past 5 years by 1.5 to 2%, annually. In parallel, the United States Department of Energy (DOE) has financially supported Advanced Technology development with good formulated goals for overall performance of plants including reliability, availability and maintainability (RAM). In this paper the authors evaluate RAM performance data from power plants over the past five years. This evaluation can be used as baseline or benchmark for further improvements. It takes into account the mode of operation being base load, cycling or peaking application and analyses the power plant on a year-by-year evaluation. All RAM-data came from the same source and are collected and analyzed according to standardized procedures. Availability will be reviewed for machines of different sizes and technologies. Maintainability will be analyzed as function of the size of units, energy production, and the mode of operation. Gas turbine simple and combined cycle power plants have been operated in peaking, cycling, base and continuous load operation. The flexibility is shown in different “Service Hours per Successful Start” and a correlation with the RAM parameters. To analyze and explain these differences will be the main result of this evaluation. The contribution shall help to evaluate the best solution for individual sites because efficiency and availability cannot always be increased in parallel.

Explosive growth in power plants in the US and elsewhere is occurring through combined cycle advanced gas turbine technology. Significant fuel expenditure savings are possible through such technology. Much of the recent advances have been possible through the transfer of aero engine design tools, elevated temperature materials, coatings, and sealing technologies. A balanced approach that melds the aero engine technologies and longstanding field experience from large industrial frame gas turbines is key to ensuring Reliability, Availability, Maintainability and Durability (RAM-D) design objectives are met. Future costs associated with power generation and distribution with these advanced gas turbine combined cycle power plants will undoubtedly be driven by major decisions of OEMs pertaining to design and validation approach, material selection, reparability, design criteria, and design features for quicker maintainability. In this paper, MHI’s approach for enhancing RAM-D performance and reducing O&M expenditures of advanced combined cycle gas turbines are described.

This paper describes the addition of conjugate capability to an existing Navier-Stokes code. Also, results are presented for an internally cooled configuration. The code is currently referred to as the Glenn-HT code, because of its origin at the NASA Glenn Research center and its proven ability to predict flow and Heat Transfer. In the past, the code had been called traf3d.mb. The addition of the conjugate capability to the code was accomplished with a minimum amount of changes to the code, with the understanding that if more advanced techniques were required they could be added at a later date. In the solid region, the density is constant and the velocities are of course zero which leaves only a simplified form of the energy equation to be solved. This simplified energy equation is solved using the same method as in the gas regions with only minor changes to the numerical parameters. At the interface between the gas and solid the wall temperature is set so as to produce the same heat flux in each region. Results are presented for a pipe flow to validate the implementation. Numerical and experimental results are then presented for flow over a flat plate that is cooled internally. Flat plate Reynolds numbers in the range 180,000 to 950,000, and coolant channel Reynolds numbers in the range 30,000 to 60,000 are presented.Copyright © 2001 by ASME

With the desire for increased power output for a gas turbine engine comes the continual push to achieve higher turbine inlet temperatures. Higher temperatures result in large thermal and mechanical stresses particularly along the nozzle guide vane. One critical region along a vane is the leading edge-endwall juncture. Based on the assumption that the approaching flow to this juncture is similar to a two-dimensional boundary layer, previous studies have shown that a horseshoe vortex forms. This vortex forms because of a radial total pressure gradient from the approaching boundary layer. This paper documents the computational design and experimental validation of a fillet placed at the leading edge-endwall juncture of a guide vane to eliminate the horseshoe vortex. The fillet design effectively accelerated the incoming boundary layer thereby mitigating the effect of the total pressure gradient. To verify the CFD studies used to design the leading edge fillet, flow field measurements were performed in a large-scale, linear, vane cascade. The flow field measurements were performed with a laser Doppler velocimeter in four planes orientated orthogonal to the vane. Good agreement between the CFD predictions and the experimental measurements verified the effectiveness of the leading edge fillet at eliminating the horseshoe vortex. The flowfield results showed that the turbulent kinetic energy levels were significantly reduced in the endwall region because of the absence of the unsteady horseshoe vortex.

This paper deals with fundamental research on heat transfer characteristics inside a cooling configuration designed for an ultra-high temperature turbine nozzle. The cooling configuration adopted in this study integrates impingement cooling and pin cooling devices into one body, aiming at the enhancement of the effective area for the impingement cooling. A large-scaled test model of this cooling system is constructed to measure its internal heat transfer distribution, where a number of pins are sandwiched between an impingement plate and a target plate. The target plate are provided with several air discharging holes. A focus of this study is on how the heat transfer characteristics depend on the effect of stand-off distance: a distance between these two plates. Ratios of the stand-off distance to the impingement hole diameter varies from 0.75 to 2.00. A transient measurement technique using narrow-banded thermochromatic liquid crystal (TLC) is employed to determine the heat transfer characteristics of the model. Numerical investigations using a commercial CFD code are also executed and those results are compared with the experimental data. It is accordingly found that the numerical results almost match the measurements. It is also shown that the addition of pins to the conventional impingement cooling system can produce about 50% increase in the effective cooling area.Copyright © 2001 by ASME

Significant change is taking place in the power generation market. We are witnessing structural change as we move to a deregulated and competitive global market. And we can also see significant technological change, as new products are driven towards improved efficiencies, greater output and environmental friendliness. Measuring the impact of these changes in terms of efficiency, output and reduced emissions is a straightforward exercise, and the ability to judge if the change has been positive is relatively objective. However, these structural and technological changes have created challenges in terms of reliability and availability measurements. • First, our measurement approach is obsolete and has no consideration for duty cycle… The demand, the mission profile, which must be achieved for the unit to meet its economic contribution value, is the single most important issue for power producers today. • Second, if the measurements have no consideration for the demand that the unit must meet, then the measure is not tied to the profitability of the plant, and therefore the operators are forced to use non-standard measures to accommodate management reporting. • And third, the strong relationship between effective plant operations and profitability demands “real time” data gathering from the unit control or plant DCS, and transformation of the data points into meaningful information for effective decision support, specifically related to the availability and reliability of systems, components, and the full plant, with a specific focus on measuring “demand” based availability and reliability. This paper addresses the issue and the opportunities associated with developing both new standard for measuring demand related reliability and availability, as well as the focus on “real time” data capture.

A secondary air system in modern aero engines is required to cool the compressor and turbine discs and make sure that no hot gas ingestion occurs into the cavities between the turbine discs, which could cause an inadvertent reduction of disc life. A high integrity solution for guiding the air from the compressor to the turbine is through an inner bleed from the compressor platform and through the space between the disc bores and the shaft connecting the fan with the low pressure turbine. Since strongly swirling air is taken from the compressor platforms to a much lower radius, a means of deswirling the air has to be used to avoid excessive pressure losses along the flow path. The paper describes a system utilizing tubeless vortex reducers to accomplish this deswirl, which are compared to a more conventional air system utilizing tubes. The working principles of both types of vortex reducer and guidelines for the design of a secondary air system using vortex reducers are explained with supporting evidence from rig tests and CFD calculations. Opportunities for the aerodynamic optimisation of the tubeless vortex reducer are elaborated and the experience gained using the system during the development of the BR700 engine is described.

In this paper the study of the flows over shrouded turbine blades with staggered-seals is presented by computing the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations along with a compressible non-linear k-e turbulence model. The swirl of the blade is coupled into the calculation. A multi-zone technique is used to generate the grids in the complex flow channel. The calculation results show that the leakage flow rate in the seal-channel is dominated by the pressure difference. It was also observed that the circumferential momentum transfer in the channel is very slow in the region in front of the seal tooth. The major effect of the rotating blade is the increase of local pressure distribution along the shrouded tip clearance path. However, the swirl motion of the blade tip does not significantly change the flow pattern in the axial-radial plane.Copyright © 2001 by ASME

A goal for computational analysis of combustors is to produce a tool for life prediction. An important part of this will be the prediction of the temperature field in the combustor walls. The complex geometries of combustor components make this a formidable task. In this paper a 3D coupled numerical flow/conjugate heat transfer calculation procedure is presented for a combustor heatshield. Proper account must be taken of the blockage and heat transfer effects of pedestals. A scheme has been developed to account for these effects without resolving the pedestals in the computational grid. Extra sink terms are included in the momentum equations to account for pedestal pressure drop. An extra energy equation is solved to determine the local pedestal temperature and to account for heat transfer between pedestals and fluid. This treatment has been validated against empirical data for arrays of pedestals in ducts with good agreement for friction factor and Nusselt number. The methodology is then applied to a generic heatshield geometry to indicate that a viable computational route has been developed for combustor heatshield analysis.

The performance increase for Heavy Duty (HD) gas turbines requires very high R&D efforts to improve life and reliability of the hot components. In fact the maximum temperature increase is the most important factor for the HD gas turbines development. Blade cooling of hottest and most loaded turbine stages becomes a fundamental key for R&D process in gas turbine design. Several innovations have been realised in last years about blade cooling and many industrial manufacturers have recently proposed new coolants, like steam or water. In this paper a detailed comparison among different cooling systems and coolants is proposed. Therefore performances of the most important HD gas turbine models are predicted and applications of the various cooling solutions are evaluated. An advanced cooling scheme based on air cooling closed loop is also studied. The simulations have been made from the point of view of blade cooling design and of global plant performances prediction. Interesting results have been obtained to confirm the present trend of R&D of HD gas turbines. Finally a wide comparison between different cooling solutions for several gas turbine models is presented.

Emprise Corporation designed and managed construction for a new state-of-the-art facility (Test Stand 8) and for a radical upgrade and renovation of a circa 1972 test facility (Test Stand 3). General Electric will use Test Stand 8 for prototype 9H (50 Hz) gas turbine testing, and will use Test Stand 3 for 7F (60 Hz) gas turbine testing. This paper summarizes the unique challenges and innovative solutions that were required for these projects.Copyright © 2001 by ASME

During more than 100 years engineers of the Swiss development center of A.-G. BBC Brown, Boveri & Cie., from 1988 onwards ABB Asea Brown Boveri Ltd, in 1999 ABB ALSTOM POWER Ltd and now ALSTOM Power Ltd in Baden, Switzerland have significantly contributed to the achievement of todays advanced gas turbine concept. Numerous “Firsts” are highlighted in this paper — ranging from the first realization of the industrial, heavy-duty gas turbine in the 1930s to todays high-technology Gas Turbine (GT) products, combining excellent performance, extraordinary low environmental impact with commercial attractiveness for global power generation. Interesting connections could be unveiled for the early parallel development of industrial and areo gas turbines.Copyright © 2001 by ASME