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Second Law analysis or exergy analysis is a useful instrument to find ways to improve the efficiency of energy utilization. The method presents the magnitude and locations of true energy losses in an energy system. The pulp and paper industries have a big potential for increasing the energy efficiencies. An integration of a gas turbine with an existing steam turbine plant is one possible way to increase the energy efficiency and the power production. The cogeneration plant analysed in this paper is a hybrid combined plant in which two types of fuels are used. The exhaust gas from a combined cycle gas turbine via a waste heat recovery steam generator (HRSG) is used as preheated combustion air in a supplementary fired steam boiler. Saturated steam from the HRSG is assumed to be superheated in a boiler in which sludge, bark and other types of biomass are being used as fuels. To reduce the waste of energy, a flue gas driven fuel dryer is connected to evaporate some of the moisture in these biomass fuels. The study shows the effect of using a combined cycle instead of a simple steam cycle and the effect of using a fuel dryer. Among the configurations investigated, a plant with both a gas turbine and a fuel dryer yields the highest exergy efficiency and total efficiency. However, the net power efficiency is higher for a plant without a fuel dryer than for one with a fuel dryer.

Late in the summer of 1967 Southland Paper Mills, Inc. placed in operation a 52,000-kw combined cycle power plant. The plant utilizes two 13,550-kw gas turbines and one 25,000-kw single automatic extraction condensing steam turbine. The power plant furnishes the total power requirements for their new Sheldon mill. This paper presents background data on the mill and describes the power plant in some detail. Flow diagrams are presented and reviewed. Features of the generating equipment and the steam generators are described. Switchgear and load coordination is discussed. The operation and reliability of the plant to date are summarized and the combined cycle in terms of paper mill requirements is evaluated.Copyright © 1969 by ASME

The gas turbine or Brayton cycle offers many advantages over a conventional power plant, especially when installed in a cogeneration mode. These advantages include physically compact packages, high reliability, improved system economics and full operating flexibility to meet variable electrical/steam demand. Until recently, the primary disadvantage of the gas turbine cycle has been that internal burning of dirty fuels caused unacceptable erosion and corrosion of turbine blading. In the simple cycle gas turbine modified for indirect heating, the compressor discharge air passes through the tube side of a heat exchanger before passing on to the turbine. Heat is transferred to the air via the combustion products of alternative fuels passing through the shell side of the heat exchanger. This paper discusses the potential of the indirectly heated gas turbine burning wood in a cogeneration configuration with a back-pressure steam turbine.Copyright © 1980 by ASME

This paper reports the results of experiments and finite element simulations on the structural response of piping systems to internal detonation loading. Specifically, the work described in this paper focuses on the forces that are produced at tee-junctions that lead to axial and bending structural responses of the piping system. Detonation experiments were conducted in a 2-in. (50 mm) diameter schedule 40 piping system that was fabricated using 304 stainless steel and welded to ASME B31.3 standards. The 4.1 m (162-in.) long piping system included one tee and was supported using custom brackets and cantilever beams fastened to steel plates that were bolted to the laboratory walls. Nearly-ideal detonations were used in a 30/70 H2-N2O mixture at 1 atm initial pressure and 300 K. Pressure and hoop, axial, and support strains were measured using a high-speed (1 MHz) digital data acquisition system and calibrated signal conditioners. It was concluded that detonations propagate through the run of a 90° tee with relatively little disturbance in either direction. The detonation load increases by approximately a factor of 2 when the detonation enters through the branch. The deflections of the cantilever beam supports and the hoop and axial pipe strains could be adequately predicted by finite element simulations. The support loads are adequately predicted as long as the supports are constrained to the piping. This paper shows that with relatively simple models, quantitative predictions of tee forces can be made for the purposes of design or safety analysis of piping systems subject to internal detonations.

Several experimental apparatus have been designed in the past to evaluate the effectiveness of under-platform dampers. Most of these experimental setups allow to measure the overall damper efficiency in terms of reduction of vibration amplitude in turbine blades. The experimental data collected with these test rigs do not increase the knowledge about the damper dynamics and therefore the uncertainty on the damper behavior remains a big issue. In this paper a different approach to evaluate the damper-blade interaction has been put forward. A test rig has been purposely designed to accommodate a single blade and two under-platform dampers. One side of each damper is in contact with a ground support specifically designed to measure two independent forces on the damper. In this way both the normal and the tangential force components in the damper-blade contact can be inferred. Damper kinematics is rebuilt by using the relative displacement measured between damper and blade. This paper describes the concept behind the new approach, shows the details of the new test rig and discuss the blade frequency response from a new point of view.

This paper explores an automated methodology to design eight-bar linkages for five positions, by constraining the user defined 4R open chain and 6R closed chain using RR dyads. The application in focus is that of rectilinear motion. The paper lays down the rules for systematic selection of link pairs for the application of RR constraints, that help automate the synthesis of eight-bar linkages. The methodology performs a random search within the user specified tolerance zones around the task specifications to increase the number of candidate linkage solutions. These linkages are then subjected to forward kinematic analysis using the Dixon determinant elimination procedure to find all possible linkage configurations over the range of motion of the input link. Linkages that have all the task configurations on one branch ensure their smooth movement through them. The result is an array of defect-free eight-bars that can perform approximate rectilinear motion. This method provides increased flexibility and control over the synthesized linkage compared to other known rectilinear motion linkages, owing to the ability to specify the backbone chain. A couple of examples are presented to illustrate the results.

The primary focus of this paper is to investigate the loss sources in an advanced GE transonic compressor design with high reaction and high stage loading. This advanced compressor has been investigated both experimentally and analytically in the past. The measured compressor efficiency is significantly lower than the efficiency calculated with various existing tools based on RANS and URANS. The general understanding is that some important flow physics in this modern compressor design are not represented in the current tools. To pinpoint the source of the efficiency miss, an advanced test with detailed flow traverse was performed for the front one and a half stage at the NASA Glenn Research Center. In the present paper, a Large Eddy Simulation (LES) is employed to determine whether a higher-fidelity simulation can pick up any additional flow physics that can explain past efficiency miss with RANS and URANS. The results from the Large Eddy Simulation were compared with the NASA test results and the GE interpretation of the test data. LES calculates lower total pressure and higher total temperature on the pressure side of the stator, resulting in large loss generation on the pressure side of the stator. On the other hand, existing tools based on the RANS and URANS do not calculate this high total temperature and low total pressure on the pressure side of the stator. The calculated loss through the stator from LES seems to match the measured data and the GE data interpretation. Detailed examination of the unsteady flow field from LES indicates that the accumulation of high loss near the pressure side of the stator is due to the interaction of the rotor wake with the stator blade. The strong rotor wake interacts quite differently with the pressure side of the stator than with the suction side of the stator blade. The concave curvature on the pressure side of the stator blade increases the mixing of the rotor wake with the pressure side boundary layer significantly. On the other hand, the convex curvature on the suction side of the stator blade decreases the mixing and the suction side blade boundary layer remains thin. The jet velocity in the rotor wake in the stator frame seems to magnify the curvature effect in addition to inviscid redistribution of wake fluid toward the pressure side of the blade.

International audience; Aircraft engine manufacturers are developping a new generation of turbojet engines featuring a lower impact on the environment, increased performances as well as reduced gas consumption. The efficiency of an engine is mostly driven by the operating clearance between the rotating parts and the stator. Accordingly, modern designs focus on the minimization of these clearances. In this context, unavoidable rotor imbalances or mistuning stemming from manufacturing processes as well as distortions resulting from thermal expansion or assembly conditions may generate blade-tip/casing contacts that are now considered as non-accidental operating conditions. In order to minimize the consequences of such events, an abradable coating is sprayed along the inner surface of the casing and acts as a fuse when the blade and the casing are in contact. However, even when an abradable coating is used, significant structural damages and wear as well as blade failures have been witnessed experimentally. The understanding of the physical phenomena at play called, on one hand, for throrough experimental investigations of rotor/stator contacts on full-scale stages of compressors and underlined that blade failure is mainly due to vibratory fatigue although the abradable coating is worn. On the other hand, numerical simulations have been performed to better understand the blade dynamics: over the last decade Snecma and its academic partners jointly developed a code for the simulation of COntacts between ROtor and Stator: COROS. This code allows for the simulation of contacts—with a Lagrange multiplier contact treatment procedure—between full 3D models of engine components and accounts for abradable coating material removal. In particular, the simulation of experimental setups with COROS highlighted the correlation between the blade vibratory response and the abradable material removal. Yet still an experimental code, this paper addresses the integration of COROS within the design process of aircraft engine blades at Snecma. The paper focuses on ongoing research for the identification of critical parameters in the arising of interactions as early as the design stage of components. A particular attention is paid to the mechanical properties of the abradable coating for which both experimental and numerical investigations are detailed.

In this paper we present a small portion of the results from the 2011 SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 150,000 in order to study the Vortex-Induced Vibration (VIV) response in uniform current profiles. This paper presents the experimental results collected from a series of tests where the towing speed was continuously varied while the cylinder and carriage traversed the basin. As the cylinder is accelerated (or decelerated) the incident current speed is continuously changing which means that multiple modes can be excited consecutively in a single tow through the basin. These varying towing speed tests are collectively referred to as ‘ramp tests’. The response data collected in these ‘ramp tests’ are presented in terms of CF response amplitudes and strains and are carefully compared with the response data collected during conventional steady towing speed tests. The data shows that when the acceleration of the carriage is kept below a critical value the ‘ramp tests’ are then able to provide VIV response information which is equivalent to that obtained from many constant speed tests. One ramp test provides the equivalent response data of (up to) 10 constant speed tests in a single run. This paper also introduces a dimensionless parameter γ, which determines if the proposed acceleration for a ramp test is within acceptable limits and may be used as a substitute for many constant speed tests. The parameter can be used to determine the appropriate acceleration or deceleration rate in order to ensure that a ramp test will yield suitable VIV response data. The parameter also allows one to know quickly whether or not fully developed VIV is possible in a given set of unsteady flow conditions.

This paper presents a detailed study of the structural integrity of conventional and modified railroad bearing adapters for onboard monitoring applications. Freight railcars rely heavily on weigh bridges and stations to determine cargo load. As a consequence, most load measurements are limited to certain physical railroad locations. This limitation provided an opportunity for an optimized sensor that could potentially deliver significant insight on bearing condition monitoring as well as load information. Bearing adapter modifications (e.g. cut-outs) were necessary to house the sensor and, thus, it is imperative to determine the reliability of the modified railroad bearing adapter, which will be used for onboard health monitoring applications. To this end, this study quantifies the impact of the proposed modifications on the adapter structural integrity through a series of experiments and finite element analyses. The commercial software Algor 20.3TM is used to conduct the stress finite element analyses. Different loading scenarios are simulated with the purpose of obtaining the conventional and modified bearing adapter stresses during normal and abnormal operating conditions. This information is then used to estimate the lifetime of these bearing adapters. Furthermore, this paper presents an experimentally validated finite element model which can be used to attain stress distribution maps of these bearing adapters in different service conditions. The maps are also useful for identifying areas of interest for an eventual inspection of conventional or modified railroad bearing adapters in the field.Copyright © 2014 by ASME

This paper reports the validation of a three-dimensional numerical simulation of the mixture preparation in a direct-injection hydrogen-fueled engine. Computational results from the commercial code CONVERGE are compared to the experimental data obtained from an optically accessible engine. The geometry used in the simulation is a passenger-car sized, four-stroke, spark-ignited engine. The simulation includes the geometry of the combustion chamber as well as the intake and exhaust ports. The hydrogen is supplied at 100 bar from a centrally located injector with a single-hole nozzle. The comparison between the simulation and experimental data is made on the central vertical plane. The fuel mole concentration and flow field are compared during the compression stroke at different crank angles. The comparison shows good agreement between the numerical and experimental results during the early stage of the compression stroke. The penetration of the jet and the interaction with the cylinder walls are correctly predicted. The fuel spreading is under predicted which results in differences in flow field and fuel mixture during the injection between experimental and numerical results. At the end of the injection, the fuel distribution shows some disagreement which gradually increases during the rest of the simulation.

A windcatcher is a structure placed on the roof of a building for providing natural ventilation for interior space working by wind power. It draws out the inside stale air to the outside and supplies the outside fresh air for the building’s interior space. In this paper, the effect of different types of windcatcher’s inlet\outlet on the air flow, flow velocity and flowrate through a three-dimensional room fitted with a two-sided windcatcher is observed numerically, using a commercial computational fluid dynamics (CFD) software package. The standard RANS K-ε CFD method is used in the simulations. The flow pattern, flow velocity and flowrate of the inside ventilation flow is considered for the six different types of a two-sided windcatcher’s inlet\outlet. It is found that the shape of the inlet\outlet of windcatcher strongly affects flow pattern, flow velocity and flowrate and the performance of square windcatcher is higher than the circular one specially in ventilating the living area (lower part) of a room.

This article is not permitted to be available for open access by the publisher. For accessing this article, http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1919956 Although it is well known that the flow entering a turbine of a turbocharger engine is highly unsteady, engine manufacturers prefer to use turbine performance predictions that are based on steady-state performance maps, which inherently lead to inaccuracies in the turbine's behavior and mismatches between turbocharger turbines and engines. The reason for this preference is due to the turbocharger turbine design software that are generally available to engine manufacturers being based on and compatible with steady-state performance maps and this fact led researchers to investigate how the inaccuracies of this steady-state treatment of the turbine can be alleviated. To this effect, this paper investigates how modelling techniques on Ricardo Wave, a 1D gas dynamics engine simulation software, gives rise to more accurate turbine swallowing curve predictions using steady-state maps. In particular, the turbine being investigated is that of Szymko [1], which is a twin nozzleless mixed-flow turbine that is being powered by a 10 litre, 6 cylinder 4 stroke diesel engine with an operating range from 800-2000 RPM for which 800, 1200 and 1600 engine RPM relate to 40, 60 and 80Hz exhaust gas pulse frequencies at the turbine. The main investigation in this paper is to demonstrate the capability of the engine simulation software to deal with unsteady flows and specifically to show the significant effect of accounting for the volute design in the single turbine wheel entry model. The data obtained in this investigation were compared with those of Szymko [1], which offered a validated set of data to compare against.

This paper presents a comparison made of different fatigue calculation methods used in the maritime industry today, with the aim of having a higher control of a fatigue failure site. To provide an overview of the different fatigue calculation methods, a comparison study was performed, as well as a local weld parameter study for two typical fillet welded joints. The two methods used for this study were the structural hot spot and effective notch stress method. Two fillet welded joints were provided by Aker Solutions MMO AS, Bergen, Norway. The first joint is a rectangular hollow section from a davit, built as a truss. The second model is a part of a K-joint from a semi-submersible (Aker H3 design). Both joints were analysed using fine 3D finite element models. The two different fatigue life calculation methods yielded different fatigue lives for the weld toe, with inconclusive results regarding their conservatism which is discussed in the paper. An increased weld toe radius gave a higher fatigue life for the weld toe, while the larger weld size increased the fatigue life in the weld root. Any weld size effect regarding fatigue life in the weld toe could not be established. Based on the effective notch stress method calculations, there was an indication of weld root failure for the K-joint of the drilling unit. Fatigue life improvement methods only increasing weld toe fatigue life are not recommended based on these results.

Cracking of the last stage blades of the low pressure (LP) turbines has been observed after 2007 in the 2 steam turbo-generator (TG) units out of the 4 units at the West Burton Power Plant UK. These 2 units were retrofitted with the new design LP rotor including blades in 1995 and 1997. Recent vibration measurements during machine transient and steady state operations confirms that the TG sets are running close to the machine critical speed and the blades are expected to have high vibration. Now the Unit 3 is fitted with the blade tip timing (BTT) system to monitor the LP1 last stage blades. Hence the present effort to compare the vibration of the blades by the BTT system with the bearing vibration to establish the correlation such that the status of the blade vibration can be accessed even without BTT measurement and the correlation may be used for other units with similar dynamics. The paper presents the comparison of the in-situ vibration measurement on bearings during machine run-up with online BTT data, observations, and possible correlation.Copyright © 2013 by ASME

Radioactive waste systems and structures (RWSS) are safety-critical facilities in need of monitoring over prolonged periods of time. Structural health monitoring (SHM) is an emerging technology that aims at monitoring the state of a structure through the use of networks of permanently mounted sensors. SHM technologies have been developed primarily within the aerospace and civil engineering communities. This paper addresses the issue of transitioning the SHM concept to the monitoring of RWSS and evaluates the opportunities and challenges associated with this process. Guided wave SHM technologies utilizing structurally-mounted piezoelectric wafer active sensors (PWAS) have a wide range of applications based on both propagating-wave and standing-wave methodologies. Hence, opportunities exist for transitioning these SHM technologies into RWSS monitoring. However, there exist certain special operational conditions specific to RWSS such as: radiation field, caustic environments, marine environments, and chemical, mechanical and thermal stressors. In order to address the high discharge of used nuclear fuel (UNF) and the limited space in the storage pools the U.S. the Department of Energy (DOE) has adopted a “Strategy for the Management and Disposal of Used Nuclear Fuel and High-Level Radioactive Waste” (January 2013). This strategy endorses the key principles that underpin the Blue Ribbon Commission’s on America’s Nuclear Future recommendations to develop a sustainable program for deploying an integrated system capable of transporting, storing, and disposing of UNF and high-level radioactive waste from civilian nuclear power generation, defense, national security, and other activities. This will require research to develop monitoring, diagnosis, and prognosis tools that can aid to establish a strong technical basis for extended storage and transportation of UNF. Monitoring of such structures is critical for assuring the safety and security of the nation’s spent nuclear fuel until a national policy for closure of the nuclear fuel cycle is defined and implemented. In addition, such tools can provide invaluable and timely information for verification of the predicted mechanical performance of RWSS (e.g. concrete or steel barriers) during off-normal occurrence and accident events such as the tsunami and earthquake event that affected Fukushima Daiichi nuclear power plant. The ability to verify the conditions, health, and degradation behavior of RWSS over time by applying nondestructive testing (NDT) as well as development of nondestructive evaluation (NDE) tools for new degradation processes will become challenging. The paper discusses some of the challenges associated to verification and diagnosis for RWSS and identifies SHM technologies which are more readily available for transitioning into RWSS applications. Fundamental research objectives that should be considered for the transition of SHM technologies (e.g., radiation hardened piezoelectric materials) for RWSS applications are discussed. The paper ends with summary, conclusions, and suggestions for further work.Copyright © 2013 by ASME

In pressure vessels stainless steel weld-overlay cladding is a widely used technique to provide a protective barrier between the corrosive environment and the ferritic low alloy base metal. While the cladding layers enhance corrosion resistance, the induced residual stresses due to the deposition of weld layers are of major concern. It is of paramount importance to understand how residual stresses interact with service loading when the vessel is pressurized. Therefore, knowledge of the initial residual stresses due to cladding is an essential input for structural integrity assessment of pressure vessels. In the present paper the Contour Method was conducted to measure residual stresses in an austenitic steel cladded plate that was fabricated from a ferritic steel base plate with three layers of austenitic stainless steel weld metal cladding deposited on the top surface. The Contour Method was chosen for various reasons. First, it provides a full 2D variation of residual stresses over the plane of interest. Second, it is not limited by the thickness of components or microstructural variations and finally it should potentially capture the variation of residual stresses in each individual weld beads and due to the possible phase transformation in the ferritic base material. The map of longitudinal residual stresses was measured by sectioning the test component along a transverse plane at mid-length. The measured residual stresses were in good agreement with published results in the open literature.

With increasing incentives for reducing the CO2 emissions offshore, optimization of energy usage on offshore platforms has become a focus area. Most of offshore oil and gas platforms use gas turbines to support the electrical demand on the platform. It is common to operate a gas turbine mostly under part-load conditions most of the time in order to accommodate any short term peak loads. Gas turbines with flexibility with respect to fuel type, resulting in low turbine inlet and exhaust gas temperatures, are often employed. The typical gas turbine efficiency for an offshore application might vary in the range 20–30%. There are several technologies available for onshore gas turbines (and low/medium heat sources) to convert the waste heat into electricity. For offshore applications it is not economical and practical to have a steam bottoming cycle to increase the efficiency of electricity production, due to low gas turbine outlet temperature, space and weight restrictions and the need for make-up water. A more promising option for use offshore is organic Rankine cycles (ORC). Moreover, several oil and gas platforms are equipped with waste heat recovery units to recover a part of the thermal energy in the gas turbine off-gas using heat exchangers, and the recovered thermal energy acts as heat source for some of the heat loads on the platform. The amount of the recovered thermal energy depends on the heat loads and thus the full potential of waste heat recovery units may not be utilized. In present paper, a review of the technologies available for waste heat recovery offshore is made. Further, the challenges of implementing these technologies on offshore platforms are discussed from a practical point of view. Performance estimations are made for a number of combined cycles consisting of a gas turbine typically used offshore and organic Rankine cycles employing different working fluids; an optimal media is then suggested based on efficiency, weight and space considerations. The paper concludes with suggestions for further research within the field of waste heat recovery for offshore applications.

This paper presents a concept for producing a Statically Balanced Shape-Shifting Surface (SB-SSS). In this context, an SB-SSS is a surface that can require near-zero magnitude force changes to accomplish a change in shape while retaining effectiveness as a physical barrier. This paper focuses on how to statically balance a specifically-designed compliant mechanism and how to incorporate this mechanism into a polygonal cell. The mechanism consists of a compliant Peaucellier-Lipkin linkage layered with a pre-stressed link as the balancer. Prior art is presented that can show how a polygonal cell can be incorporated into a surface via a tiling array. Specifically shaped overlapping thin plates are used to retain the physical barrier requirement. The demonstration of a virtually zero-force Shape-Shifting Surface (SSS) suggests that SSS’s can be designed with a wide range of force-displacement properties, i.e. ranging from that of a square of the parent material to the zero-force mechanism presented here. Applications for an SB-SSS may be macro-scale or micro-scale and may include sensors, biomedical applications, defense applications, and variable stiffness materials.Copyright © 2012 by ASME

This paper presents an accurate and efficient three-dimensional computational model (3D numerical wave tank), based on fully nonlinear potential flow (FNPF) theory, and its extension to incorporate the motion of a laboratory snake piston wavemaker, to simulate experiments in a large-scale 3D wave basin (i.e. to conduct “virtual” or numerical experiments). The code is based on a higher-order boundary element method combined with a Fast Multipole Algorithm (FMA). Particular efforts were devoted to making the code efficient for large-scale simulations using high-performance computing platforms to complement experimental 3D wave basins. The numerical simulation capability can serve as an optimization tool at the experimental planning and detailed design stages. To date, waves that can be generated in the NWT include solitary, Cnoidal, and Airy waves. In this paper, we detail the model, mathematical formulation, and wave generation. Experimental or analytical comparisons with NWT results are provided for several cases to assess the accuracy and applicability of the numerical model to practical engineering problems.Copyright © 2012 by ASME

Investigations of human motor control using functional magnetic resonance imaging (fMRI) are increasingly receiving attention, with applications in fields such as motor learning and rehabilitation. In these neuroscience studies, force and position sensors are used to control haptic devices and safely interact with the human motion in an MR environment. However, conventional force sensors such as strain gauges are known to cause electromagnetic interference originating from electrical cables, transducers, and electronics. Light transmission through optical fibers is one alternative that avoids these problems. Since optical fibers do not produce electromagnetic noise, they can be used in an MR environment without electromagnetic interference. In this paper, we propose a novel design of an MRI-compatible grasping force sensor based on these principles. The sensor structure was designed to fit into an MRI scanner with its inclined double parallel mechanism, and was specifically adapted to precision grip tasks. This paper presents the sensor design and preliminary characterization in a non-MR environment.Copyright © 2012 by ASME

In the last few years, a significant research effort has been made for developing and enhancing Direct Injection (DI) for compressed natural gas (CNG) engines. Several research projects have been promoted by the European Community (EC) in this field with the objective of finding new solutions for the automotive market and also of encouraging a fruitful knowledge exchange among car manufacturers, suppliers and technical universities. This paper concerns part of the research activity that has been carried out by the Politecnico di Torino, AVL List GmbH and Siemens AG within the EC VII Framework Program (FP) InGAS Collaborative Project (CP), aimed at optimizing the control phase of a new injector for CNG direct injection, paying specific attention to its behavior at small injected-fuel amounts, i.e., small energizing times. The CNG injector which was developed within the research project proved to be suitable to be used in a DI SI engine, featuring a pent-roof combustion chamber head and a bowl in piston, with reference to both homogeneous and stratified charge formation. Fuel flow measurements made by AVL on the four-cylinder engine revealed a good linearity between injection duration and fuel mass-flow rate for injection durations above a reference value. In order to improve the injector characterization at short injection durations, an experimental and numerical activity was designed. More specifically, a multidimensional CFD model of the actual injector geometry was built by Politecnico di Torino, and purposely-designed simulation cases were carried out, in which the needle-lift time-history was defined on the basis of experimental measurements made by Siemens. The numerical model was validated on the basis of experimental data concerning the total injected-fuel amount under different conditions. Then, the model was applied in order to evaluate the dynamic flow characteristic by taking also the inner geometry of the injector valve group into account, so as to establish a correlation to the needle lift measurements done by Siemens for injector characterization. In the paper this dynamic behavior of the injector is analyzed, under actual operating conditions, and its impact on the nozzle injection capability is discussed. The simulation results did not show significant oscillations of the stagnation pressure upstream of the nozzle throat section, and thus the resultant mass-flow rate profile is almost proportional to the needle-lift one. As a consequence, in order to characterize the injector flow behavior in the nonlinear region (short injection duration), the measurement of needle lift is sufficient.

Measuring infrasonic sound sets high requirements on the instruments used. Typically the measurement chain consists of a microphone and a preamplifier. As the input resistance of the preamplifier forms a high pass filter with the capacitance of the microphone in the picofarad range, measuring ultra low frequencies becomes a challenge. The electric preamplifier presented in this paper together with a prepolarized condenser microphone form a measurement system. The developed preamplifier connects the microphone signal directly to the input of an operational amplifier with ultra high input impedance. The bias current for the preamplifier further complicates the signal amplification. A configuration of two diode-connected FETs providethe input bias current. The resulting input impedance of nearly 1 TW yields a total lower limiting -3 dB cutoff frequency of 8 mHz and a dynamic range of 95 dB. Being able to measure down to ultra low frequencies in the infrasonic frequency range will aid actors in the debate on wind turbine noise. Sonic booms from supersonic flights include frequencies down to 10 mHz and the preamplifier proposed in this paper will aid scientists trying to modify the N-shaped shock wave at high level which prohibits flights in land zones.

This paper presents design and analysis of a rigid link finger, which may be suitable for a number of adaptive end effectors. The design has evolved from an industrial need for a tele-operated system to be used in nuclear environments. The end effector is designed to assist repair work in nuclear reactors during retrieval operation, particularly for the purpose of grasping objects of various shape, size and mass. The work is based on the University of Southampton’s Whole Arm Manipulator, which has a special design consideration for safety and flexibility. The paper discusses kinematic issues associated with the finger design, and to the end of the paper specifies the limits of finger operating parameters for implementing control laws.Copyright © 2002 by ASME

A loss-of-coolant accident is one of the design-basis accidents for a high-temperature gas-cooled reactor (HTGR). Following the depressurization of helium in the core, if the accident is not mitigated, there exists the potential for air to enter the core through the break and oxidize the in-core graphite structure in the modular pebble bed reactor (MPBR). This paper presents the results of the graphite oxidation model developed as part of the Idaho National Engineering and Environmental Laboratory’s Directed Research and Development effort. Although gas reactors have been developed in the past with limited success, the innovations of modularity and integrated state-of-art control systems coupled with improved fuel design and a pebble bed core make this design potentially very attractive from an economic and technical perspective. A schematic diagram of a reference design of the MPBR has been established at a major component level (INEEL & MIT, 1999). Steady-state and transient thermal hydraulics models will be produced with key parameters established for these conditions for all major components. Development of an integrated plant model to allow for transient analysis on a more sophisticated level is now being developed. In this paper, preliminary results of the hypothetical air ingress are presented. A graphite oxidation model was developed to determine temperature and the control mechanism in the spherical graphite geometry.

In recent years new technologies, novel products, improved services and better contracting procedures are emerging and showing great potential for increased performance and safety. This is increasingly evident for applications in sectors like offshore, petrochemical and refining, ship and submarine building, nuclear power, hydropower, oil and gas transfer lines where failures are can lead to hazards to life. One such technology is a non-gasketed pipe connection and is recognised by the authors as representative of an ‘emerging technology’. It is based on several un-orthodox principles and does consist not only of a pair of welding neck flanges, but of an all-inclusive entire system, comprising bolts, washers, nuts, wrenches, procedures and training. This paper is based on two years of experimental and finite element studies [Ref 1,2] of both standard/conventional ANSI (gasketed) and modern non-gasketed flanged joints. This has led to a deeper understanding of the requirements for a successful assembly and long term usage. ANSI and VCF joints have been subject to internal pressure, axial and lateral forces, with these loads having been applied both singly and in combinations. Mode of load acting in the joint i.e. static or dynamic has been studied for both kinds of joints. Experimental and analytical results have been compared. Some practical considerations on the use of important emerging technology i.e. non-gasketed pipe joints in comparison to conventional gasketed systems are presented. Of fundamental importance is an insight into the mechanism of the bolted joint showing the effect from an external load on a preloaded bolt. It is found that it can be made near zero hence, in a properly built, non-gasketed bolted joint a static mode rules, and therefore the stamina of such a joint is unlimited. Other practical issues of fabrication, handling, surface damage and assembly, have been examined in the lab and on site and a summary of results is presented. In addition a probability risk assessment has been undertaken and results compared with the standard (conventional) ANSI type joints. In addition this paper demonstrates that the novel system is an efficient and well -engineered alternative to traditionally designed joints.

In this paper an existing cogeneration plant (134 MWel and 225 MWth) based on gas turbine and steam cycle technology, has been investigated. The main goal of the work is to analyse different repowering options for the plant taking into account the capital cost of the new devices, the cost of the fuel and the cost related to the CO2 emissions. For the analysis of the repowering alternatives the Thermoeconomic Analysis has been utilised. Two different approaches have been used for the CO2 emissions cost evaluation: the classical Carbon Tax approach using political charges on the unit ton of emitted CO2, and one proposed by the Authors linked to the efficient utilization of energy resources in the plants, and based on the exergy analysis. In the paper the two procedures for the evaluation of the charges on the CO2 emissions and their influence on the choice of the repowering option, and how they promote the adoption of a high efficiency repowering solutions have been discussed.

Austenitic stainless steel tube and pipe systems are a vital part of today’s sanitary (hygienic) processing facilities. Product contact surface welds in the tubular systems usually cannot be ground or conditioned, so it is essential that the as-welded surfaces are suitable for cleaning-in-place (CIP). The American Welding Society AWS Dl8 Committee was formed in respond to the request by the 3-A Sanitary Standards Committee for help in preparing welding standards for use in the manufacture and construction of dairy and food product processing plants. The 3-A Sanitary Standards Committees develop and promulgate sanitary design standards for dairy and food processing, packaging and handling equipment and systems. AWS D18.1:1999 Specification for Welding of Austenitic Stainless Steel Tube and Pipe Systems in Sanitary (Hygienic) Applications developed covers the requirements for gas tungsten arc welding (GTAW) or TIG welding as it is also known, of austenitic stainless steel tube and pipe 1/4 in. (6 mm) diameter and larger. Sanitary processing systems is intended to include those systems handling products for human and animal consumption. Such products include dairy, meat, poultry, vegetable, beverage, and other products consumed by humans and animals. The paper also includes design and operation guidelines that have proven useful to engineers and users of austenitic stainless steel piping systems. Paper published with permission.

The subject of this paper is the validation of the newly developed booster bleed valve control logic, which has been implemented into the new BR715 turbo fan jet engine. The booster compressor is protected from surges in the low power regime as well as during transient operation by opening a booster bleed valve. This bleed valve is situated just after the booster compressor and passes bleed air into the bypass duct, hence unloading the booster compressor in critical operational conditions. The BR715 jet engine takes advantage of a newly developed logic driving this valve. Monitoring input parameters such as spool and flight speeds as well as altitude, the combined steady state and transient logic provides the capability of appropriately positioning the valve. This ensures maintaining an optimum performance of the engine throughout the whole operating range. Furthermore the logic allows for reaction on special requirements such as surge events. During testing for certification of this engine, extensive handling tests have been performed. The performance of the logic was investigated in detail and the results are documented within this paper. They prove the logic to be working very successfully. The booster compressor is totally protected from surge in the low power regime during steady state conditions. For transient operation, especially during rapid decelerations as well as during bodie manoeuvres of the engine, the core logic for the transient modulation showed extremely effective behaviour. The various schedules inside the logic were partially varied for testing. This paper comprises this development process and each table’s contribution to the booster compressor’s behaviour is explained in detail.

Fuel cells are emerging as a major new power generation technology that is particularly suitable for distributed power generation, high-efficiency, and low pollutant emission. An interesting combined cycle, the “HYBRID,” has recently been scoped “on paper” that portends the potential of ultra-high efficiency (approaching 80%) in which a gas turbine is synergistically combined with a fuel cell into a unique combined cycle. This paper introduces hybrid technology to the gas turbine community as a whole, and summarizes the current and projected activities associated with this emerging concept.

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.

In this paper the mixing of stator wakes in turbomachinery is considered. An extension is made to the existing model of Denton (1993), which addresses the effects of acceleration before mixing. Denton showed that if a total pressure wake was accelerated mixing loss diminished and vice versa. Here a total temperature wake is shown to exhibit a reverse trend. An attempt is also made to better understand the work transfer process between a stator wake and a rotor. The paper concentrates on axial turbines, but a brief look at compressors is included. It is argued that the freestream work is not the same as the wake work and the concept of ‘Differential Work’ is introduced. A simple steady velocity triangle based model is proposed to give an estimate of the ratio of wake work to freestream work (μ see later). The model is compared to an unsteady CFD result to offer some verification of the assumptions. It is concluded that the rotodynamic work process tends to reduce total pressure wake depths in turbines and compressors and therefore mixing losses. The mixing loss due to total temperature wakes is less strongly affected by the differential work process.

This paper describes some of the requirements for bearing dampers to be used in an aircraft engine and briefly discusses the pros and cons of various types of dampers that were considered as candidates for active control in aircraft engines. A disk type of electrorheological (ER) damper was chosen for further study and testing. The paper explains how and why the choice was made. For evaluating potential applications to aircraft engines, an experimental development engine (XTE-45) was used as an example for this study. Like most real aircraft engines, the XTE-45 ran through more than one critical speed in its operating speed range. There are some speeds where damping is desirable and other speeds where it is not. Thus, the concept of a damper with controllable forces appears attractive. The desired equivalent viscous damping at the critical speeds along with the available size envelope were two of the major criteria used for comparing the dampers. Most previous investigators have considered the ER damper to produce a purely Coulomb type of damping force and this was the assumption used by the present authors in this study. It is shown in a companion paper (Vance and San Andres, 1999), however, that a purely Coulomb type of friction cannot restrain the peak vibration amplitudes at rotordynamic critical speeds and that the equivalent viscous damping for rotordynamics is different from the value derived by previous investigators for planar vibration. Control laws for Coulomb damping are derived in Vance and San Andres, (1999) to achieve minimum rotor vibration amplitudes in a test rig while avoiding large bearing forces over a speed range that includes a critical speed. The type of control scheme required and its effectiveness was another criterion used for comparing the dampers in this paper.

This paper describes a theoretical model for analysing the dynamic characteristics of wedge-shaped underplatform dampers for turbine blades, with the objective that this model can be used to minimise the need for conducting expensive experiments for optimising such dampers. The theoretical model presented in the paper has several distinct features to achieve this objective including: (i) it makes use of experimentally-measured contact characteristics (hysteresis loops) for description of the basic contact behaviour of a given material combination with representative surface finish, (ii) the damper motion between the blade platform locations is determined according to the motion of the platforms, (iii) three-dimensional damper motion is included in the model, and (iv) normal load variation across the contact surfaces during vibration is included, thereby accommodating contact opening and closing during vibration. A dedicated non-linear vibration analysis program has been developed for this study and predictions have been verified against experimental data obtained from two test rigs. Two cantilever beams were used to simulate turbine blades with real underplatform dampers in the first experiment. The second experiment comprised real turbine blades with real underplatform damper. Correlation of the predictions and the experimental results revealed that the analysis can predict (i) the optimum damping condition, (ii) the amount of response reduction and (iii) the natural frequency shift caused by friction dampers, all with acceptable accuracy. It has also been shown that the most commonly-used underplatform dampers in practice are prone to rolling motion, an effect which reduces the damping in certain modes of vibration usually described as the lower nodal diameter bladed-disc modes.

This paper describes the experimental application of adaptive control to Hybrid Squeeze Film Damper (HSFD) supported rotors. The HSFD has been shown to be an adaptive damper capable of providing infinite damper configurations between short and long damper configurations. Previously, theoretical investigations of the adaptive control of HSFD concentrated on the development of the model reference adaptive control (MRAC) method, as well as development of a nonlinear reference model. Simulations of the performance of the adaptive controller during run-up and coast-down indicated the superior performance of the adaptive controller. In this paper, the adaptive controller is tested on a multi-mode rotor. A test rig is designed and developed using computer control. A simple reference model is investigated consisting of a second order system. Three forms for adaptation gain are studied. The results of the experimental investigation illustrated the performance capabilities of the adaptive controller applied to the HSFD, and moreover indicated the possibility of simple design for the adaptive controller. [S0742-4795(00)01603-3]

The present paper describes the application of the exergy method to several power cycles of current interest in the Brazilian power scene. The ability of the exergy method to highlight component irreversibilities is of particular interest in this investigation. In this paper the exergy analysis for a simple gas turbine cycle, a combined gas/steam cycle, a combined gas/steam/freon cycle and a chemically recuperated gas turbine have been performed. As a yardstick for comparison a standard gas turbine engine with and without a steam bottoming cycle has been employed. The fuel considered is natural gas. The analysis of this system has been carried out using the exergy method. For the simple gas turbine cycle a biomass fuel has been employed as an alternative. The attraction of this fuel is its low impact on the environment and its plentiful supply in many regions in Brazil.

This paper covers 35 years of operation with the ROLLS-ROYCE Marine PROTEUS Gas Turbine in the Swedish Navy SPICA class Torpedo Boats and the NORRKÖPING class Missile Boats. 54 installed PROTEUS Gas Turbines in 18 boats have accumulated nearly 300 000 running hours. The service is intended to continue until year 2010. The paper describes: • Experience from operation. • Technical problems and their solutions. • Major modifications. • Life extension program. • Problem areas. • The future of the PROTEUS within Swedish Navy. The Swedish Navy operation of PROTEUS engines in fast surface attack ships is demanding and the environment is harsh. This causes great strain to the entire machinery. With the Gas Turbine Propulsion new Ship maneuvering technique had to be developed and adopted. Initial installation and engine problems had to be cured. Throughout the years several technical problems have turned up and been solved. The largest number or serious engine damages has been Power degradation and broken Compressor or burnt Turbine Blades and Vanes. Mainly as a result of a fouled Compressor, incorrect Bleed Valve setting or corrosion. Next largest engine problem has been vibration. In the early days engine related but nowadays generated by the installation or other equipment in the ship. All efforts laid down by involved personnel has greatly contributed to improve the reliability of the engine and its installation. New problems will certainly show up by age and changed operational procedures, thus calling for a continued improvement work. Spare parts accessibility will be the limiting factor for future PROTEUS operation. Therefore cooperation with ROLLS-ROYCE and the remaining operators in Spare Parts production and for exchange of Spare Parts is essential.

This paper describes an experiment on a GHH BORSIG Type THM 1304-10 Gas Turbine engine to test the effects of variable vane setting on the vibration behaviour of the blades in all 10 stages of the axial compressor. The rotor was fitted with a network of strain-gauges. An analogue telemetry system was arranged using standard hardware and special application software to display in real-time and to log the full range of frequencies and amplitudes for all instrumented blades. The data acquisition system is described together with a presentation of the live display which allowed engineers to interact with measured results to maximise the benefits of the test whilst all strain-gauges were still functional. Tests were arranged to maximise the vibration data collected at all points before gauge mortality was experienced. Prior to the test, blades were vibrated statically to determine shapes of the first four vibration modes. The paper discusses the fixing techniques for the gauges, the modal shape measurement technique and the calibration of the strain-gauges. The telemetry system architecture and multiplexing arrangement are described together with examples of typical test data and the conclusions concerning the effects on blade vibration of different variable inlet guide vanes (IGV) settings.Copyright © 1998 by ASME

Effect of unsteady wakes on aerodynamic and heat transfer characteristics of a turbine blade in a cascade were analyzed both experimentally and theoretically. Comprehensive aerodynamic data were collected for different wake passing frequencies that are typical of turbomachinery. Hot-wire probes were used for collection of boundary layer data on suction and pressure surfaces of the turbine blade. Heat transfer measurements were made using steady liquid crystal techniques. Boundary layer data were analyzed through intermittency function to get insight into the transition process under unsteady wake flow conditions. The experimental and theoretical results presented in this paper confirm the general validity of the unsteady boundary layer transition model developed by Chakka and Schobeiri (1997). This model is based on a relative intermittency function, which accounts for the effects of periodic unsteady wake flow on the boundary layer transition. Three distinct quantities are identified as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition analysis presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting heat transfer coefficients are compared with the experimental data.Copyright © 1998 by ASME

The subject of this paper is the development and first analysis of the performance of a new booster bleed valve control logic to improve the surge margin of the booster compressor in the new BR715 turbofan. The booster compressor is driven by the LP spool of the two spool engine, comprising an aerodynamically tuned system out of fan root and booster compressor. The flow delivered at the exit of the booster compressor must be accepted by the following HP compressor. This matching is not always possible, since the rates of change of the spool speeds during transients behave differently as do pressure rise and mass flow. Hence the transient handling of the booster compressor is difficult with respect to its surge stability. To aid in this situation it is a common practice to position a booster bleed valve after the booster compressor, which passes bleed air into the bypass duct. The BR715 jet engine takes advantage of a newly developed logic driving this valve. Monitoring input parameters such as spool and flight speeds as well as altitude, the logic provides the capability of appropriately positioning the valve, thereby maintaining an optimum performance of the engine throughout the whole operating range. Furthermore the logic allows for reaction on thrust reverser deployment or more serious events such as surge and foreign object damage. Much effort has been put into the development of the newly designed transient valve logic, which in its main part is based on the rate of change of the pressure at the exit of the HP compressor. This logic ensures a sufficient surge margin in case of deceleration or reslams of the engine. A simulation of the logic was set up, connected to a synthesis program for the two spool engine and used for the development. After this basic testing, the logic was implemented in the BR715 engine, which first ran in April 1997. The actual data from basic handling tests performed with this engine were analysed and checked against simulation results. The paper describes the logic in detail and contains first results. They prove a proper working of the logic and show the strong effect of the booster bleed valve.

An approach to improving the thermal cycle efficiency of combustion turbine (CT) based power plants is to develop thermal cycles with interceding, reheat, recuperation and humidification. Until recently, this was viewed by combustion turbine manufacturers as cost prohibitive and involving new operating and maintenance challenges. Also, early attempts by some manufacturers to develop sophisticated thermal cycles resulted in the realization that significant funds, personnel, and time are required. This investment could not be justified, particularly considering the availability of efficient and economical combined cycle (CC) plants.Therefore, increased efficiency for both simple and CC power plants has been achieved by raising the firing temperature and pressure of the basic Brayton cycle. However, every increase in the CT firing temperature required progressively higher development cost and increased NOx control challenges, which has re-awakened interest in advanced cycles.The Department of Energy’s Federal Energy Technology Center (FETC), in cooperation with combustion turbine manufacturers, is working on an Advanced Turbine Systems Program. The program goal is to develop technologies to provide a significant increase in natural gas-fired CC power generation plant efficiency with thermal efficiency target values in excess of 60%. Materials published in the program show that participating large CT original equipment manufacturers (OEM), are relying heavily on an increase in the CT’s firing temperature to approximately 2600 F (1700 K), with associated advancement in materials and cooling techniques, to achieve the target efficiency. Also employed are some improvements in component efficiency and various methods of utilization of heat in the bottoming cycle. The development of the necessary sophisticated materials and cooling techniques requires very significant development costs and is based on long duration and expensive experimental investigations and field demonstrations. Increasing the bottoming cycle efficiency primarily depends on the practicality of engineering solutions and capital vs operating cost trade-offs, and not on technology advancements.The current Cascaded Humidified Advanced Turbine (CHAT) technology, which utilizes existing, commercially proven combustion turbine and industrial hardware integrated in sophisticated thermal cycles, offers an achievable, practical and cost-effective alternative to a current CC plant. Current CHAT plants require relatively minimal engineering developments associated primarily with a) modification of the power shaft CT’s compressor discharge and turbine inlet plenums — for interfacing the HP shaft and other thermal cycle components — a very important engineering task, but not comparable in complexity to the development associated with further increase of the CT inlet temperature; and b) engineering of an HP expander with an inlet temperature of 1600 F (1145 K), essentially integrating steam turbine and industrial expander technologies.As it was shown collectively in the previously published references, in addition to an efficiency equal to that for CC plants (based on the same CTs), CHAT plants have significantly lower (10–20%) specific capital costs and have important operating advantages (higher than CC efficiency at part-load operation, with excellent load following and dynamic benefits, including rapid start capability). Those features reduce both the CHAT plant cost of electricity and offer a method to improve improve the economics of power generation systems due to the operational flexibility added by a CHAT plant.One of the most effective ways to increase the CHAT plant efficiency is to increase the HP expander inlet temperature from the current level of 1600 F (1145 K), which represents the level of the combustion turbine technology of the late 1960’s – early 1970’s. EPRI and ESPC have identified that a CHAT plant, based on the current combustion turbine technology (with turbine inlet temperature (TIT) of 2550 F (1670 K)), could achieve the ATS Program target efficiency of 60% with an HP expander inlet temperature of approximately 2000 F (1365 K). HP expanders with this relatively low turbine inlet temperature, as shown later, will require cooling of only the first stage nozzles and stage blades, if the newest single crystal alloys are used. However, the increase of the HP expander inlet temperature will be complicated by the relatively-high inlet pressure. This presents a significant engineering challenge, particularly if one would like to preserve the excellent start-up characteristics and other dynamic benefits of the CHAT plant.EPRI and ESPC are co-sponsoring the development of a high pressure expander with a target inlet temperature of 2000 F (1365 K). It will be shown that this HP expander, when integrated with a power shaft based on W 501 FA modified for the CHAT application, results in a power plant that will achieve the ATS Program target efficiency of 60%.This paper presents a) current CHAT plant’s performance and cost characteristics, b) findings of the project for the development of the HP expander with target temperature of 2000 F (1365 K), and c) a comparison of the advanced CHAT concept’s performance and development costs to those of the ATS program. This paper also shows how, in the future, the new ATS technology can be incorporated into even more efficient, cost-effective and reliable CHAT power plants.Copyright © 1997 by ASME

At the time of the start of the GT PRIME upgrade project, the eight General Electric MS7001 gas turbines in combined cycle service at the Wharton Station of Houston lighting and Power each had 85,000 hours of operation with 2000 starts. The units were ready for their second major overhaul. A number of hot gas path components required replacement at that time. Rather than replacing components one by one, the user devised a Program for Reliability, Improved Maintenance, and Efficiency (GT PRIME). We will discuss turbine condition, design changes, reduced emissions, and increased output in the paper. Actual user experience on maintenance and operating costs resulted in some special requirements to be satisfied in addition to the expected parts replacement. General Electric had developed many improved parts for newer units, all of which could be easily applied to older machines. The use of these newer production MS7001EA parts increase component life, parts availability, inspection intervals, system reliability and performance. These will be described in the paper. These 1972 vintage turbines achieved a 50PPM NOx level by injecting water at a high rate of flow which resulted in the need for more frequent combustion inspection intervals. The development of a dry low NOx system for the unit allowed the combustion inspection interval to double while reducing NOx to 25PPM. The improvement in component efficiencies in the gas path resulted in increased output and improved the heat rate. These changes had a significant impact on customer operating costs which resulted in a very attractive payback period. We will discuss expected versus actual output, heat rate and emissions results for all eight units. The upgrade of the first unit started in 1992 and the last unit was completed in 1996. A detailed listing of uprate program schedule by unit is listed in Figure #1.

Water, in the liquid or vapor phase, injected at various locations into the gas turbine cycle has frequently been employed to improve engine performance while simultaneously reducing NOx emissions. Commercial steam injected gas turbines have been designed to inject small amounts of steam (less than 15% of air flow), generated in a heat recovery boiler, into or downstream of the combustor. Recently, it has been proposed to inject larger amounts of water (as high as 50% of air flow) and operate combustors near stoichiometric conditions. All these methods increase turbine mass flow rate without increasing air flow rate and consequently increase specific power. The increase in specific power for naval applications means smaller intake and exhaust stacks and therefore less impact on topside space. The present paper presents a new concept, in naval propulsion plants, to decrease NOx production and increase specific power with a water fog (droplet spray) injected (WFI) directly into the inlet of the engine compressor. The simulated performance of a simple-cycle gas turbine engine using WFI is reported. The paper describes the computer model developed to predict compressor performance resulting from the evaporation of water passing through the stages of an axial flow compressor. The resulting effects are similar to those of an intercooled compressor, without the complications due to the addition of piping, heat exchangers, and the requirement for a dual spool compressor. The effects of evaporative cooling on compressor characteristics are presented. These results include compressor maps modified for various water flow rates as well as estimates of the reductions in compression work and compressor discharge temperature. These modified compressor performance characteristics are used in the engine simulation to predict how a WFI engine would perform under various water injection flow rates. Estimates of increased output power and decreased air flow rates are presented.

Advances in silicon-on-insulator (SOI) integrated circuit technology and the steady development of wider band gap semiconductors like silicon carbide are enabling the practical deployment of high temperature electronics. High temperature civilian and military electronics applications include distributed controls for aircraft, automotive electronics, electric vehicles and instrumentation for geothermal wells, oil well logging and nuclear reactors. While integrated circuits are key to the realization of complete high temperature electronic systems, passive components including resistors, capacitors, magnetics and crystals are also required. This paper will present characterization data obtained from a number of silicon high temperature integrated evaluated over a range of elevated temperatures and aged at a selected high temperature. This paper will also present a representative cross section of high temperature passive component characterization data for device types needed by many applications. Device types represented will include both small signal and power resistors and capacitors. Specific problems encountered with the employment of these devices in harsh environments will be discussed for each family of components. The goal in presenting this information is to demonstrate the viability of a significant number of commercially available silicon integrated circuits and passive components that operate at elevated temperatures as well as to encourage component suppliers to continue to optimize a selection of their product offerings for operation at higher temperatures. In addition, systems designers will be encouraged to view this information with an eye toward the conception and implementation of reliable and affordable high temperature systems.Copyright © 1998 by ASME

This paper presents results of experimental as well as numerical investigations of the aerodynamic performance of film-cooled transonic turbine blades. Taking into consideration to non-dimensional similarity, the experiments were performed on a cascade test rig using superheated steam as fluid. The investigated blading corresponds to a typical high pressure turbine vane used in the high subsonic regime. In order to determine the effect of the blown-out cooling fluid on the aerodynamic performance of the cascade, the measurements were performed over a wide range of realistic exit Mach numbers, mass flow rate ratios, coolant injection locations and main-to-coolant flow density ratios. The paper presents the results of the experimental investigation in the form of outlet angles and loss terms, and compares and discusses these for a number of variations. It was found that below a critical mass flow ratio, the kinetic loss coefficient varies only little with flow rate whereas above this critical flow ratio, the loss coefficient increases rapidly. A comparison of the different injection locations shows that the suction side is very sensitive with regard to main flow disturbances while injection on the pressure side and the trailing edge only has a small effect of the loss terms. Consideration of different coolant-to-mainstream density ratios clarifies that the influence of this parameter on the loss terms can be neglected. The paper also addresses a simple numerical code which is based on the „TOTLOS“ model of Hansel and adapted to the above-mentioned problem, and compares and discusses the results of the experimental and numerical investigations.

Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each others weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both. To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed.

Waste heat recovery from power plants and industries requires a new type of electricity generators and related technological developments. The current research work is aimed at the design of a multi-kilowatt thermoacoustic electric generator, which can be employed as the bottoming cycle of a gas-turbine power plant or for industrial waste heat recovery. The proposed device converts thermal energy into acoustic power and subsequently uses a piezoelectric alternator to convert acoustic power into electricity. The challenge in designing such a device is that it has to be acoustically balanced and the performance of the device is greatly affected by numerous parameters such as frequency of the traveling acoustic wave, heat exchanger parameters, regenerator dimensions, acoustic feedback loop, etc. The proposed device is a lab-scale demonstration targeted to produce a few kilowatts of electric power from a 20 kWth heat source. To achieve the acoustically balanced configuration of the device, DeltaEC software is used. The DeltaEC model outcomes are used to arrive at the optimized design of the device and its components. The analytical method, the optimized geometrical dimensions of thermoacoustic components and the minimum required conditions of heat source input are presented in this paper.

The design and testing of instrumentation systems for the measurement of steady and unsteady turbine blade surface pressure and boundary layer condition for a turbine stage operating at design Mach and Reynolds numbers is presented. The boundary layer condition is monitored by an array of suction and pressure surface heated thin-film gauges. This paper describes the desigo of a forty channel constant temperature bridge to drive these gauges. The bridge fits into the centre of a sub-shaft driven by the turbine wheel. The amplified bridge output is transferred from the rotor via an array of light emitting diodes. The surface pressure is recorded by unpackaged pressure transducer chips laid into the surface of the blade. This paper also describes the circuitry necessary to drive these transducers. The position of these circuits and the transmission method are the same as those used for the thin film gauges. Both systems have a bandwidth sufficient for the resolution of vane-blade interactions.Copyright © 1997 by ASME

The provision of an ignition source in the central region of a liquid-fired combustor reduces the requirement for wide spray angles, rich primary zones, and their associated performance drawbacks such as high levels of soot and NOx formation and high liner wall temperatures. Various ignition devices have been considered for providing centrally located ignition sources. The current paper presents a study of one alternative concept — the integral catalytic torch ignitor/injector — as a means for providing both combustor light-off and enhanced flame stability in the combustor primary zone. An integral catalytic torch in a fuel injector offers the potential to significantly improve ignition arid flame stability and thus the opportunity to operate combustor primary zones at leaner conditions, which may improve emissions, pattern factor, and combustor liner durability. This paper presents computational and experimental results for a conventional liquid-fired combustor with the addition of a catalytic torch (replacing the pilot pressure atomizer) down the centerline of an air-blast fuel injector. The benefits of a lean primary zone with an integral catalytic torch/injector were investigated both computationally and experimentally by comparing combustor performance with standard and successively leaner primary zones. Pattern factor and emissions are compared with different primary zone jet configurations to observe if the central torch can enhance the operability of leaner primary zones in conventional combustor geometries. The experimental and computational results suggest that the integral catalytic torch can provide more than adequate ignition capabilities with improved combustor emissions when it is combined with a relatively lean operating primary zone.

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.