bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of Next Generation Catalyst Design Incorporating Advanced Materials and Processing Technology
Authors: Nickolas Sarento G. , Tuet Philip B. , McCarty Jon G. , Vilayanur Suresh R. , Boleda Alberto E. , Barry Joseph C.
Published: November 2008

A Kawasaki Heavy Industries M1A-13X gas turbine engine equipped with a Xonon Cool Combustion® System was used to validate performance of a next generation catalyst module design incorporating advanced catalyst materials over 8000 hours of continuous operation. The unit ran unattended, 24 hours a day, 7 days a week connected to the electrical grid. NOx emissions were measured to be less than 2.5 ppm throughout the guaranteed operating load range (70–100%). CO emissions were measured to be less than 10 ppm; typically less than 1ppm across the same load range. The new catalyst module design incorporates features and technology developed during the past several years where durability was a primary focus. Performance test results from previous durability tests were used to develop theoretical predictive models. These models proved invaluable in determining the optimal catalyst formulation as well as the required operating conditions throughout the life of the combustion system. Successful validation of the new catalyst module design has led to incorporation of these advanced materials and design techniques in commercial products and prototype units. It is believed that continued technology development, as well as performance data gathered from field units, will support extending product life beyond the current guarantee of 8000 hours.
Optimization of Thermodynamically Efficient Nominal 40 MW Zero Emission Pilot and Demonstration Power Plant in Norway
Authors: Hustad Carl-W. , Trondstad Inge , Anderson Roger E. , Pronske Keith L. , Viteri Fermin
Published: November 2008

In Aug 2004 the Zero Emission Norwegian Gas (ZENG) project team completed Phase-1: Concept and Feasibility Study for a 40 MW Pilot & Demonstration (P&D) Plant, that is proposed will be located at the Energy Park, Risavika, near Stavanger in South Norway during 2008. The power plant cycle is based upon implementation of the natural gas (NG) and oxygen fueled Gas Generator (GG) (1500°F/1500 psi) successfully demonstrated by Clean Energy Systems (CES) Inc. The GG operations was originally tested in Feb 2003 and is currently (Feb 2005) undergoing extensive commissioning at the CES 5MW Kimberlina Test Plant, near Bakersfield, California. The ZENG P&D Plant will be an important next step in an accelerating path towards demonstrating large-scale (+200 MW) commercial implementation of zero-emission power plants before the end of this decade. However, development work also entails having a detailed commercial understanding of the techno-economic potential for such power plant cycles: specifically in an environment where the future penalty for carbon dioxide (CO2) emissions remains uncertain. Work done in dialogue with suppliers during ZENG Project Phase-1 has cost-estimated all major plant components to a level commensurate with engineering pre-screening. The study has also identified several features of the proposed power plant that has enabled improvements in thermodynamic efficiency from 37% up to present level of 44–46% without compromising the criteria of implementation using “near-term” available technology. The work has investigated: i. Integration between the cryogenic air separation unit (ASU) and the power plant. ii. Use of gas turbine technology for the intermediate pressure (IP) steam turbine. iii. Optimal use of turbo-expanders and heat-exchangers to mitigate the power consumption incurred for oxygen production. iv. Improved condenser design for more efficient CO2 separation and removal. v. Sensitivity of process design criteria to “small” variations in modeling of the physical properties for CO2/steam working fluid near saturation. vi. Use of a second “conventional” pure steam Rankine bottoming cycle. In future analysis, not all these improvements need necessarily be seen to be cost-effective when taking into account total P&D program objectives; thermodynamic efficiency, power plant investment, operations and maintenance cost. However, they do represent important considerations towards “total” optimization when designing the P&D Plant. We observe that Project Phase-2: Pre-Engineering & Qualification should focus on optimization of plant size with respect to total capital investment (CAPEX); and identification of further opportunities for extended technology migration from gas turbine environment that could also permit raised turbine inlet temperatures (TIT).
Design Equations for Wire Mesh Bearing Dampers in Turbomachinery
Authors: Choudhry Vivek V. , Vance John M.
Published: November 2008

In a previous ASME paper the second author reported experiments on wire mesh bearing dampers (WMD) incorporated in a power turbine rotor-bearing system in order to enable a direct comparison between WMD and squeeze film dampers (SFD). The results showed that both WMD and SFD perform equally well for reducing the rotordynamic amplitudes of vibration. Moreover the WMD were found to have significant advantages over SFD. The damping provided by the wire mesh is independent of temperature changes and presence of turbine oil. Experiments by another investigator showed that WMD are capable of sustaining more than twice the unbalance as compared to SFD, which promises possible application to withstand blade loss loads. This paper presents empirically developed non-dimensional design equations for WMD, capable of predicting stiffness and damping for a wire mesh ‘donut’ subject to changes in various design, installation, and operational parameters.
Ceramic Recuperator and Turbine: The Key to Achieving a 40 Percent Efficient Microturbine
Authors: McDonald Colin F. , Rodgers Colin
Published: November 2008

Based on the use of state-of-the-art component technologies and the use of existing metallic materials, achieving an electrical efficiency anywhere near 40 percent in low pressure ratio recuperated microturbines is proving elusive. Current microturbines, rated at say 100 kW, operate with efficiencies approaching 30 percent. Advancing this to an upper level of about 35 percent is projected based on the ability to operate at turbine inlet temperatures greater than 1100C, and the utilization of a higher cost superalloy recuperator. This paper puts into perspective the challenge of trying to achieve 40 percent efficiency for small recuperated turbogenerator designs with radial flow components; the major constraints being associated with stress limitations in both the turbine and recuperator. Various publications (issued by both industry and the Government) often mention an efficiency goal of 40 percent for small gas turbines of this configuration, however, it needs to be recognized that the means to achieve this are beyond current high temperature metallic component capabilities. To achieve this “goal” necessitates increasing the operating temperature of the turbine and recuperator above 1100C and 800C respectively. Such advancements are projected to be technically and cost-effectively achievable by utilizing ceramic components, which with a dedicated development program, could perhaps become a reality in less than a decade to meet both future distributed power generation needs and defense applications, and be in concert with ever-demanding conservation goals and reduced emissions.
Development of a Liquid-Fueled Dry Low Emissions Combustor for 300kW Class Recuperated Cycle Gas Turbine Engines
Authors: Fujiwara Hiroshi , Koyama Masamichi , Hayashi Shigeru , Yamada Hideshi
Published: November 2008

The authors have developed a liquid-fueled, low-emissions, and single can combustor for the RGT3R, Niigata’s 300 kW class industrial gas turbine engine, with the goal of satisfying the most stringent environmental requirements for distributed power generation systems in Japan. This paper describes these development efforts, which included non-reacting Computational Fluid Dynamics (CFD) analysis and component and engine tests. The emissions target is less than 24 ppm nitrogen oxides (NOx), 60 ppm carbon monoxide (CO) and 60 ppm unburned hydrocarbons (UHCs) at dry 15% O2 correction for kerosene, while operating above 50% load. A lean premixed, pre-vaporized, axially staged combustion concept is used to minimize emissions levels to the strictest emissions regulations in urban areas such as Tokyo, Chiba, Saitama, Yokohama, and Osaka. This combustion system involves two pilot burners and two main mixture injection tubes that are extending into the combustion chamber to inject lean to ultra-lean premixed mixtures into the hot burned gas from pilot burners. Counter rotational swirl vanes are provided to pilot burners and main mixture injection tubes to prevent flashback into the premixing tubes. The RGT3R gas turbine engine operates smoothly with the developed DLE combustion system from idle to full load without combustion-driven pressure oscillations. A two-stage fuel control system employs liquid fuel supply for the pilot and main atomizers. As this paper describes, the emissions data from this engine meet the emissions goals.
Parametric Analysis of Hybrid MCFC Micro Gas Turbine System
Authors: Hao Hongliang , Zhang Huisheng , Weng Shilie , Su Ming
Published: November 2008

Fuel cells have been revealed to be a very attractive power generation system, promising highly efficient electricity generation and very low environmental impact. The integration of micro turbines and high-temperature fuel cells has been proposed in recent years as an extremely efficient solution for power generation. A molten carbonate fuel cell / micro gas turbine (MCFC/MGT) hybrid power system has theoretically demonstrated that it can achieve higher thermal efficiency than other conventional power generation systems. To understand operation characteristics of the MCFC/MGT hybrid power system, it is essential to analyze influence of operating and design parameters on its performance. Based on an existing 50KW MCFC stack, a steady-state thermodynamic model for MCFC/MGT hybrid power system is developed on the IPSEpro simulation platform and applied to a performance analysis. The characteristics under off-design and design condition for hybrid power system were also analyzed.
High Temperature Stability of MGC’s Gas Turbine Components in Combustion Gas Flow Environments
Authors: Nakagawa Narihito , Ohtsubo Hideki , Shibata Kohji , Mitani Atsuyuki , Shimizu Kazutoshi , Waku Yoshiharu
Published: November 2008

Melt growth composites (MGCs) have a unique microstructure, in which continuous networks of single-crystal phases interpenetrate without grain boundaries. Therefore, the MGCs have excellent high-temperature strength characteristics, creep resistance, oxidation resistance and thermal stability in an air atmosphere at very high temperature. In order to investigate the recession behavior of MGCs in combustion gas flow environment, we have just started the exposure tests to evaluate the influence of combustion gas flow environment on MGCs. The MGCs have about 95% of the initial flexural strengths after the exposure test for 10 hours at T = 1500 °C, P = 0.1–0.3 MPa, V = 150–250 m/s, PH2O = 15–45 kPa in the combustion gas flow environment. MGCs have excellent thermal stability and water vapor resistance in comparison with conventional ceramic materials such as Si3N4 and Al2O3 under the high temperature combustion gas flow environment.
Mechanical Behavior of Anti-Symmetrically Laminated Composite Blades
Authors: Hojo Masahiro , Hashimoto Ryosaku , Ogawa Akinori , Sofue Yasushi , Matsuda Yukio
Published: November 2008

Anti-symmetrically laminated composites have coupling effects between tensile stress and twisting deformation, and are very attractive as fan blade materials of aircraft engines. Blades fabricated by anti-symmetrically laminated composites can automatically adjust the stagger angle to better aerodynamic conditions with change of axial force or rotational speed owing to the coupling effects. Thus, the anti-symmetrically laminated composite blades are expected to improve aerodynamic efficiency and the stability of aircraft engines. In this paper, the mechanical behavior of anti-symmetrically laminated composite blades is evaluated by spin tests and finite element analyses. Three kinds of blades fabricated by carbon/epoxy laminated composites in different anti-symmetrical stacking sequences were tested. A non-contact measurement technique using a multi-channel optical fiber sensor was used for measurements of blade deformations at high-speed rotating conditions, up to 10,000 rpm. The twisted angle change at the blade tip could be successfully measured. The twisted angle change increased in proportion to the second power of rotational speed, and the maximum angle change was about 4 degree at 10,000 rpm. The finite element analysis results agreed well with the spin test results. Furthermore, the three-dimensional deformation of the test blades was evaluated based on finite element analyses.
Design Study of a Humidification Tower for the Advanced Humid Air Turbine System
Authors: Araki Hidefumi , Higuchi Shinichi , Marushima Shinya , Hatamiya Shigeo
Published: November 2008

The AHAT (advanced humid air turbine) system, which can be equipped with a heavy-duty, single-shaft gas turbine, aims at high efficiency equal to that of the HAT system. Instead of an intercooler, a WAC (water atomization cooling) system is used to reduce compressor work. The characteristics of a humidification tower (a saturator), which is used as a humidifier for the AHAT system, were studied. The required packing height and the exit water temperature from the humidification tower were analyzed for five virtual gas turbine systems with different capacities (1MW, 3.2MW, 10MW, 32MW and 100MW) and pressure ratios (π = 8, 12, 16, 20 and 24). Thermal efficiency of the system was compared with that of a simple cycle and a recuperative cycle with and without the WAC system. When the packing height of the humidification tower was changed, the required size varied for the three heat exchangers around the humidification tower (a recuperator, an economizer and an air cooler). The packing height with which the sum total of the size of the packing and these heat exchangers became a minimum was 1m for the lowest pressure ratio case, and 6m for the highest pressure ratio case.
Development of Gas Turbine Performance Models Using a Generic Simulation Tool
Authors: Alexiou A. , Mathioudakis K.
Published: November 2008

An approach for gas turbine engine modelling using a general purpose object-oriented simulation tool is described. A commercially available such tool that can be adapted to different fields, through the creation of reusable modelling component libraries representing parts or equipment of a physical system, is employed. Libraries are developed using an object-oriented language. The possibility for quick implementation of new models and rapid analysis of results, through the use of a graphical user interface is demonstrated. A turbofan model, developed for both steady state and transient performance simulation, is used to illustrate the advantages offered by this approach. Results are presented and compared to those produced by an industry-accepted model. The flexibility of incorporating particular features into a model is demonstrated by presenting the implementation of adaptive features and a study of engine frequency response.
CFD Investigation of the Effects of Different Diluents on the Emissions in a Swirl Stabilized Premixed Combustion System
Authors: Engdar Ulf , Hermann Fredrik , Gabrielsson Rolf , Klingmann Jens
Published: November 2008

Recently, new cycles for power generation, such as wet cycles and cycles for CO2 capture, have gained increasing interest. These new cycles use some sort of dilution in the air/fuel mixture, e.g. steam or CO2. Gas turbine cycles using LCV gases can also be said to fit this description. Almost all modern gas turbines use a lean premixed combustion system, since it combines low NOx emissions with high combustion efficiency. The main objective of this paper is to study the influence of different diluents on the NOx and CO emissions at different inlet temperature, equivalence ratio, pressure and mass flow. The studied combustor was a premixed swirl stabilized combustor with optical access and emission sampling equipment. The combustor uses Danish natural gas as its main fuel. Computational fluid dynamics (CFD) has been employed to perform the investigations. It is common knowledge that turbulence models based on the Buissinesq assumption are not generally capable of handling a highly swirling flow in a correct way. Therefore, a differential Reynolds stress model (DRSM) has been employed for modeling of the turbulence. The turbulent combustion has been modeled with the level-set flamelet library approach (FLA). In this approach a laminar flamelet is linked to turbulent flow field via a non-reacting scalar G and its variance. The laminar flamelet is modeled with separate code. This code solves the combustion development with a detailed reaction mechanism for a laminar, non-stretched and premixed one-dimensional flame. This is of great importance when emissions are to be predicted. All fluid dynamics computations were performed with the commercial CFD code Star-CD, version 3.20, where the FLA combustion model was implemented through Fortran based user subroutines. The computed flow field was validated against experimental data during non-reaction flow conditions. The computations showed good agreement with the experimental data. The computed CO and NOx emissions showed the same trends as the experimental data for the reacting case with an undiluted flame, when the equivalence ratio was altered. The computed emissions were used to build up an emission map for different dilutions during different operation conditions.
A Nonlinear Analysis of the Axial Steady State Response of the Hydrodynamic Thrust Bearing-Rotor System Subjected to a Harmonic Excitation
Authors: Shiau T. N. , Hsu W. C.
Published: November 2008

The purpose of this study is to investigate the nonlinear axial response of a thrust bearing-rotor system, which is subjected to an axial harmonic force. For the axial vibration of the rotor, the system forces include the external axial harmonic force and the reacting oil film forces, which are obtained by solving a time-dependent Reynolds Equation within the thrust pads of the thrust bearing. The time-dependent Reynolds Equation is solved by a finite difference method, and the system equation of motion is solved by the fourth-order Runge-Kutta method. A linear analysis is attempted in to evaluate its suitability for the situation under consideration. And the bearing stiffness and damping coefficients are investigated with parameters including the dimensionless wedge thickness, the initial oil film thickness and the rotor spin speed. The results show that the average steady state response will decrease as the harmonic axial force intensifies its fluctuating magnitude. The results also indicate that it will induce ultra-super harmonics when the axial harmonic force intensifies its fluctuating magnitude.
Axial Compressor Deterioration Caused by Saltwater Ingestion
Authors: Syverud Elisabet , Brekke Olaf , Bakken Lars E.
Published: November 2008

Gas turbine performance deterioration can be a major economic factor. An example is within offshore installations where a degradation of gas turbine performance can mean a reduction of oil and gas production. This paper describes the test results from a series of accelerated deterioration tests on a GE J85-13 jet engine. The axial compressor was deteriorated by spraying atomized droplets of saltwater into the engine intake. The paper also presents the overall engine performance deterioration as well as deteriorated stage characteristics. The results of laboratory analysis of the salt deposits are presented, providing insight into the increased surface roughness and the deposit thickness and distribution. The test data show good agreement with published stage characteristics and give valuable information regarding stage-by-stage performance deterioration.
Online Water Wash Tests of GE J85-13
Authors: Syverud Elisabet , Bakken Lars E.
Published: November 2008

This paper reports the results of a series of online water wash tests of a GE J85-13 jet engine at the test facilities of the Royal Norwegian Air Force. The engine performance was deteriorated by injecting atomized saltwater at the engine inlet. Then the engine was online washed with water injected at three different droplet sizes (25, 75 and 200 μm) and at water-to-air ratios ranging from 0.4% to 3% by mass. Engine performance was measured using standard on-engine instrumentation. Extra temperature and pressure sensors in the compressor section provided additional information of the propagation of deposits in the aft stages. The measurements were supported by visual observations. The overall engine performance improved rapidly with online wash. The build-up of deposits in the aft stages was influenced both by the droplet size and the water-to-air ratio. The water-to-air ratio was the most important parameter to achieve effective online washing.
Potential of a Reheat Gas Turbine System Using Inverted Brayton cycle
Authors: Iki Norihiko , Furutani Hirohide , Takahashi Sanyo
Published: November 2008

The concept of a small reheat gas turbine system is proposed and discussed. This reheat gas turbine consists positive-pressure part (Brayton cycle), negative-pressure part (inverted Brayton cycle) and heat exchangers. The system components are interchangeable with the micro gas turbine. This system can supply hot water and steam. This paper describes that the introduction of reheat and an inverted cycle to a fixed Brayton cycle is explored from various views. The thermal efficiency of electric power output (EFFEP) has a peak and thermal efficiency of heat output of hot water 1 (EFFQHW1) decrease with increase of the pressure ratio of Vacuum Turbine (PRVT). The thermal efficiency of heat output of hot water 2 (EFFQHW2) increases monotonously with PRVT. The overall efficiency of the improved cycle for cogeneration increases with PRVT although the overall efficiency of the original cycle decreases monotonously with PRVT. The PURPA efficiency of improved cycle has the peak around PRVT = 4. In the type2 cycle EFFEP has a weak peak of 31.4% when the inlet pressure of combustor 2 (Pcomb2) is 0.14MPa. The overall efficiency increases with Pcomb2. PURPA efficiency has a weak peak at Pcomb2 = 0.16MPa. Two axes system is examined. EFFEP reaches to 30.2% at the maximum. EFFQHW1 decreases slightly with increase of PRVT. EFFQHW2 increases with PRVT. The overall efficiency increases with PRVT. The PURPA efficiency also increases with PRVT.
Remote Monitoring and Diagnostic for Combined-Cycle Power Plants
Authors: Therkorn Dirk
Published: November 2008

Reliability and availability are both critical for competitive operation of high efficiency combined-cycle power plants in the liberalized electricity markets. Monitoring and diagnostic of operational data is successfully used to prevent unexpected plant shut downs and to schedule maintenance activities. A complete set of tools is presented, which is used to monitor combined-cycle power plant operation. The daily incoming data is analyzed with a physics-based performance model, with a neural network-based novelty detection tool and with an experience-based failure detection algorithm, which looks for fingerprints of known and possible component faults. A knowledge management system is used to support the assessment of the findings and the recommended actions are communicated to the power plant operators in the form of early warnings. The application of the different methods in parallel shall ensure that most of the emerging problems are detected before they result in damage that leads to a forced plant shut down. Most of the cases are simple measurement errors, although component deterioration and failures can also be detected. Experience with the ALSTOM early warning system for the GT24/GT26 power plants is shown to demonstrate the successful application of this approach.
Micro Gas Turbine With Ceramic Nozzle and Rotor
Authors: Matsunuma Takayuki , Yoshida Hiro , Iki Norihiko , Ebara Takumi , Sodeoka Satoshi , Inoue Takahiro , Suzuki Masato
Published: November 2008

A series of operation tests of a ceramic micro gas turbine has been successfully carried out. The baseline machine is a small single-shaft turbojet engine (J-850, Sophia Precision Corp.) with a centrifugal compressor, an annular type combustor, and a radial turbine. As a first step, an Inconel 713C alloy turbine rotor of 55 mm in diameter was replaced with a ceramic rotor (SN-235, Kyocera Corporation). A running test was conducted at rotational speeds of up to 140,000 rpm in atmospheric air. At this rotor speed, the compression pressure ratio and the thrust were 3 and 100 N, respectively. The total energy level (enthalpy and kinetic energy) of the exhaust gas jet was 240 kW. If, for example, it is assumed that 10% of the total power of the exhaust jet gas was converted into electricity, the present system would correspond to a generator with 24 kW output power. The measured turbine outlet temperature was 950°C (1,740°F) and the turbine inlet temperature was estimated to be 1,280°C (2,340°F). Although the ceramic rotor showed no evidence of degradation, the Inconel nozzle immediately in front of the turbine rotor partially melted in this rotor condition. As a second step, the Inconel turbine nozzle and casing were replaced with ceramic parts (SN-01, Ohtsuka Ceramics Inc.). The ceramic nozzle and case were supported by metal parts. Through tests with the ceramic nozzle, it became evident that one of the key technologies for the development of ceramic gas turbines is the design of the interface between the ceramic components and the metallic components, because the difference between the coefficients of linear thermal expansion of the ceramic and metal produces large thermal stress at their interface in the high-temperature condition. A buffer material made of alumina fiber was therefore introduced at the interface between the ceramic and metal.
Component Integration and Loss Sources in 3 – 5 kW Gas Turbines
Authors: Monroe M. A. , Epstein A. H. , Kumakura H. , Isomura K.
Published: November 2008

The performance of a regenerated gas turbine generator in the 3–5 kW power range has been analyzed to understand why its measured efficiency was on the order of 6% rather than the 20% suggested by consideration of its components’ efficiencies as measured on rigs. This research suggests that this discrepancy can be primarily attributed to heat and fluid leaks not normally considered in the analysis of large gas turbine engines because they are not as important at large scale. In particular, fluid leaks among the components and heat leakage from the hot section into the compressor flow path contributed the largest debits to the engine performance. Such factors can become more important as the engine size is reduced. Other non-ideal effects reducing engine performance include temperature flow distortion at the entrance to both the compressor and turbine. A cycle calculation including all of the above effects matched measured engine data. It suggests that relatively simple changes such as thermal isolation and leak sealing can increase both power output and efficiency of this engine, over 225% in the latter case. The validity of this analysis was demonstrated on an engine in which partial thermal isolation and improved sealing resulted in a more than 40% increase in engine output power.
Least Squares Based Transient Nonlinear Gas Path Analysis
Authors: Gro¨nstedt Tomas
Published: November 2008

A method for computing least squares estimates for transient nonlinear gas path analysis is derived. The solution to the optimal estimation problem is found by solving a system of nonlinear equations. A single iteration of the equation system requires integrating an extended set of nonlinear ordinary differential algebraic equations (ODAE). The additional differential equations originate from the differentiation of the least squares expression used to define optimality. The numerical efficiency of the extended ODAE algorithm is assessed by comparing it to an optimization based method. To illustrate the derived estimation technique a complete model of the Frank Whittle W1 engine is given within the paper. An example of the implementation of the extended ODAE method is demonstrated in the framework of this model. The performance of the method is also discussed and evaluated on a full nonlinear transient model of the RM12 fighter engine.
Characteristics of the Swirling Flow Generated by an Axial Swirler
Authors: Fu Yongqiang , Jeng San-Mou , Tacina Robert
Published: November 2008

An experimental investigation was conducted to study the aerodynamic characteristics of the confined, non-reacting, swirling flow field. The flow was generated by a helicoidal axial-vaned swirler with a short internal convergent-divergent venturi, which was confined within 2-inch square test section. A series of helicoidal axial-vaned swirlers have been designed with tip vane angles of 40°, 45°, 50°, 55°, 60° and 65°. The swirler with the tip vane angle of 60° was combined with several simulated fuel nozzle insertions of varying lengths. A two-component Laser Doppler Velocimetry (LDV) system was employed to measure the three-component mean velocities and Reynolds stresses. Detailed data are provided to enhance understanding swirling flow with different swirl degrees and geometries and to support the development of more accurate physical/numerical models. The data indicated that the degree of swirl had a clear impact on the mean and turbulent flow fields. The swirling flow fields changed significantly with the addition of a variety of simulated fuel nozzle insertion lengths.
Engine Performance Improvement by Controlling the Low Pressure Compressor Working Line
Authors: Martis Dan , Rowe Arthur , Pinquier Marie-Laure , Price Brian , Papaconstantinou Nicholas , Edwards Darryl , Perez Vincent , Mhanna Samer
Published: November 2008

The new algorithm provides closed-loop control of the LP Compressor working line in such a way as to maintain compressor stability and to provide increased power from the engine at the same firing temperature. This method is intended for the Trent 60, an aero-derivative engine designated for power generation and mechanical drive applications. The power benefit is achieved by operating at higher LPC pressure ratio and thereby increasing the inlet air flow and overall pressure ratio of the engine. Since the algorithm controls the working line, the threats to compressor stability related to the working line level are removed (including production scatter, deterioration and fouling) and the required surge margin can be safely reduced, providing a significant benefit in engine performance. The paper presents comparatively the structure of the current and new concepts, the main features of the controller and stresses the improved accuracy and reliability of new algorithms. The performance benefit is then assessed; the increase in power is about 3% at ISO, sea level conditions and varies with ambient temperature.
The Measurement and Prediction of Gaseous Hydrocarbon Fuel Auto-Ignition Delay Time at Realistic Gas Turbine Operating Conditions
Authors: Sims G.-J. M. , Clague A. R. , Copplestone R. W. , Menzies K. R. , MacQuisten M. A.
Published: November 2008

Auto-ignition delay time measurements have been attempted for a variety of gaseous fuels on a flow rig at gas turbine relevant operating conditions. The residence time of the flow rig test section was approximately 175 ms. A chemical kinetic model has been used in Senkin, one of the applications within the Chemkin package, to predict the auto-ignition delay time measured in the experiment. The model assumes that chemistry is the limiting factor in the prediction and makes no account of the fluid dynamic properties of the experiment. Auto-ignition delay time events were successfully recorded for ethylene at approximately 16 bar, 850K and at equivalence ratios between 2.6 and 3.3. Methane, natural gas and ethylene (0.5 < φ < 2.5) failed to auto-ignite within the test section. Model predictions were found to agree with the ethylene measurements, although improved qualification of the experimental boundary conditions is required in order to better understand the dependence of auto-ignition delay on the physical characteristics of the flow rig. The chemical kinetic model used in this study was compared with existing ‘low temperature’ measurements and correlations for methane and natural gas and was found to be in good agreement.
Implementation of Stochastic Methods for Industrial Gas Turbine Fault Diagnosis
Authors: Romessis C. , Mathioudakis K.
Published: November 2008

Implementation of stochastic diagnostic methods for diagnosis of sensor or component faults is presented. Two industrial gas turbines are considered as test cases, one twin and one single shaft arrangement. Methods based on Probabilistic Neural Networks (PNN) and Bayesian Belief Networks (BBN), are implemented. The ability for successful diagnosis is demonstrated on specific cases of sensor malfunctions, as well as on two types of compressor deterioration, fouling and variable vane mistuning. The examined diagnostic problem and the methods of PNN for sensor fault diagnosis and BBN for the diagnosis of component faults are first described. For each gas turbine case, the implementation of the diagnostic methods is shown and application to fault cases that occurred is presented. The effectiveness of the stochastic diagnostic methods demonstrates that they offer a powerful alternative diagnostic tool.
Adaptive Machining of Gas Turbine Components
Authors: Walton Paul
Published: November 2008

Whether to repair or replace gas turbine components has always been an issue. The case for repair has always been viewed with skepticism, especially when those parts to be repaired must be done by hand, as manual repair methods can result in high levels of scrap and non-conformance. Hand grinding, blending and polishing is still frequently found in many Gas Turbine (GT) components, but in this age of high technology, why is this the case? The problem lies with the fact that individual blades and vanes that make up full engine sets are not geometrically identical and do not lend themselves to being machined, blended or polished by standard Computer Numerical Controlled (CNC) machining technology. This is a problem for both the repair and manufacture sectors. Key Questions: • Where does this geometric variability come from and what does this mean in practice? • As the industry strives for more efficient engines blades and vanes have become increasingly complex. How does this impact the repair sector? • What are the key issues involved and how can we get around them? • What can repairers do to reduce their scrap rates and increase their output volume and quality? Software-based machining strategies are explored as an alternative to manual processes in the repair of GT components. With ever-increasing competition and reduced turnaround times, decisions to invest in technology are usually driven by a combination of technical, quality, economic and health & safety requirements.
Sensitivity Analysis of Transient Compressor Operation Behaviour in SOFC-GT Hybrid Systems
Authors: Hildebrandt Andre , Assadi Mohsen
Published: November 2008

This paper presents a sensitivity analysis of unsteady-state SOFC-GT-HS operation based on two different characteristic maps of centrifugal compressor taken from open literature and scaled by the law of similitude to match the design point of the Hybrid System. The system layout under investigation is a pressurised type comprising a low and high temperature recuperator. Computations are based on a one-dimensional finite element model of planar high temperature SOFC, which is validated against open literature. The reduced Moore and Greitzer model is used for compressor modelling. Calculation results of the coupled SOFC-GT-Hybrid System show that unsteady-state part-load operation is sensitive to the characteristics of compressor speed-lines but also to the load change operation procedure.
Design Considerations for Compact Ceramic Off-Set Strip Fin High Temperature Heat Exchangers
Authors: Subramanian Sundaresan , Akberov Roald , DeLosier Clayton Ray , Chen Yitung , Hechanova Anthony E. , Peterson Per F.
Published: November 2008

This paper deals with the development of a three-dimensional numerical model to predict the overall performance of an advanced high temperature heat exchanger design, up to 1000°C, for the production of hydrogen by the sulfur iodine thermo-chemical cycle used in advanced nuclear reactor concepts. The design is an offset strip-fin, hybrid plate compact heat exchanger made from a liquid silicon impregnated carbon composite material. The two working fluids are helium gas and molten salt (Flinak). The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on heat transfer enhancement. The effects of the fin geometry on the flow field and heat transfer are studied in three-dimensions using Computational Fluid Dynamics (CFD) techniques. The pre-processor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT that is based on the finite volume method is used to produce the numerical results. Fin dimensions need to be chosen that optimize heat transfer and minimize pressure drop. Comparison of the overall performance between two fin shapes (rectangular versus curved edges) is performed using analytical calculations (where available) as well as computational fluid dynamics techniques. The analytical calculations predict larger pressure losses than the numerical simulations. The model developed in this paper will be used to investigate the heat exchanger design parameters in order to find an optimal design.
Use of Inlet Guide Vanes for a Miniature Centrifugal Compressor
Authors: Li Xiaoyi , Zhou Lei , Kapat Jay , Chow Louis C.
Published: November 2008

A novel design for a high-speed, miniature centrifugal compressor for a miniature RTBC (reverse turbo Brayton cycle) cryogenic cooling system is the focus of this paper. Due to the geometrical restriction imposed by the cryocooling system, the outer radius of the compressor is limited to 2.5 cm. Such a small compressor must rotate at a high speed in order to provide an acceptable pressure ratio. Miniature design precludes the use of inducers with large angles. In order to compensate for the absence of conventional inducers, the proposed design uses inlet guide vanes (IGV) that produce preswirl at the impeller inlet. IGV is followed by a radial impeller and an axial diffuser. The design speed for this compressor is 313,000 rpm for an overall static-to-total pressure ratio of 1.7 with helium as the working fluid for the compressor and the cryocooling system. The analysis undertaken in this paper is for an aerodynamically similar design with air as the working fluid. The rotational speed is 108,000 rpm and the overall static-to-total pressure ratio of 1.55. This paper concentrates on computational prediction of the performance of the compressor. The three-dimensional transient simulation is performed by using sliding mesh model (SMM). Blade tip leakage is not considered in the computation presented here. The unsteady solution predicts the interaction between IGV and the impeller, and between the impeller and the diffuser. The isentropic efficiency of impeller is found to be 81% at the design point. Based on the results obtained in this study, the inlet angle of diffuser vanes is modified to match the gas flow at the impeller exit, resulting in an increase of the isentropic efficiency of diffuser from 8.6% to 74.8%. It is also found that the performance of upstream components — IGV and impeller, are not affected by the performance of the diffuser.
Development and Operation of a Pressurized Optically-Accessible Research Combustor for Simulation Validation and Fuel Variability Studies
Authors: Sidwell T. , Casleton K. , Straub D. , Maloney D. , Richards G. , Strakey P. , Ferguson D. , Beer S.
Published: November 2008

The U.S. Department of Energy Turbines Program has established very stringent NOx emissions goals of less than 3 ppmv for future turbine power generation. These future turbine power plants may operate on hydrogen-rich fuels, such as coal-derived synthesis gas (syngas), or pure hydrogen derived from shifting the syngas. Achieving these goals is expected to require improved combustor concepts which may be dramatically different than current combustor designs. Significant and costly experimental testing is usually required to assess new combustor concepts. Ideally, new concepts could be evaluated with numeric simulations to reduce development time and cost. However, current simulation capabilities are not sufficient to reliably capture the effects of fuel variations on flame extinction, emissions levels, and dynamic stability. Furthermore, very little data with controlled boundary conditions are available to check numeric predictions at actual turbine engine conditions, or simply to assess combustor performance without ambiguous boundary conditions. This paper presents a description of the development and operation of an optically-accessible research combustor, which is designed to provide fundamental combustion data at elevated pressure and inlet air temperature, and with precisely determined thermal, acoustic, and flow boundary conditions. The effects of fuel composition variations are investigated by blending of controlled quantities of hydrogen with natural gas. Recent test results — emissions data, dynamics data, and heat losses for hydrogen addition from 0 to 40% by fuel volume at two combustor pressures — and a description of future testing are also presented. The results show that the addition of hydrogen to natural gas in percentages as low as 5% of total fuel volume can significantly decrease the lean extinction limit, and promote stable operation at lower equivalence ratios while promoting lower NOx emissions. Dynamic pressures were measured, but combustion dynamics were not present due to the combustor configuration. The effect of heat losses on flame temperature and emissions were quantified.
The Use of 3D CFD Analysis in the Design of Air Intake Systems as a Visualisation Tool to Optimise Performance in Gas Turbine Applications
Authors: Hiner Stephen D.
Published: November 2008

An optimised inlet air system design is an important factor in the gas turbine (GT) industry. Optimising the design of the air intake system is an increasingly challenging process as both the layout complexity and range of features that can be included in the intake system expands. These may include a combination of insect or trash screens, weather protection and filtration systems, silencers, anti-icing systems, ventilation system off takes and inlet heating or cooling systems for power augmentation. Poor designs can result in inefficient use of these components as well as losses in engine performance due to excessive pressure losses or distortion in the flow entering the gas turbine. High flow distortion, velocity, pressure or temperature, can induce compressor surge and high acromechanical stresses in compressor blades and vanes. In extreme cases this may result in blade or vane failures. Computational Fluid Dynamics (CFD) analysis is a powerful tool for visualisation of the predicted flow through a hypothetical air inlet system prior to manufacture. The CFD output plots include flow streamlines and contours, of pressure, velocity or temperature, at any plane in the model. These enable pressure losses, flow distortion issues, potential recirculation areas and high local velocities within the system to be reviewed. This allows optimisation of the installation design to minimise system pressure loss and flow distortion, both through the components and at the engine interface. This paper, with reference to case studies of gas turbine applications, highlights the impact that CFD analysis can have on the design of intake systems to ensure that the best overall performance is obtained. The process of developing the CFD geometry and how significant features of an installation are modeled is outlined. Environmental and operational conditions, such as cross winds can impact the flow through an intake system; therefore, incorporation of such factors into the model boundary conditions are covered. Typical output metrics from the CFD analysis are shown from selected case studies; total pressure drop and flow distortion at the interface plane between the intake system and gas turbine. The importance of experienced interpretation of the CFD output to define potential intake design modifications to improve system performance is highlighted. In specific cases model testing has been carried out to validate CFD results. Case study examples are used to show the improvements made in air intake performance that contribute to increased operational efficiency of the gas turbine application.
Surface Damage Tolerance Analysis of a Gas Turbine Engine Rotor
Authors: Jameel Ahsan
Published: November 2008

DARWIN™ (Design Assessment of Reliability With INspection) is a simulation-based computer program for probabilistic fatigue life prediction of rotors and disks in commercial aircraft jet engines. This program is being developed by Southwest Research Institute® (SwRI®) and a team of major aircraft gas turbine engine manufacturers (General Electric, Pratt & Whitney, Honeywell, and Rolls Royce Indianapolis) as a major research and development initiative. This paper is a presentation of the experience of Honeywell in the use of DARWIN to assess probability of fracture (POF) due to surface damage in a highly stressed bolthole in a nickel component.
Engineering and Economic Analyses of a Coal-Fueled Solid Oxide Fuel Cell Hybrid Power Plant
Authors: Rao A. D. , Verma A. , Samuelsen G. S.
Published: November 2008

An advanced coal based power plant system that has an electrical efficiency of 60% on an HHV basis is defined. The solid oxide fuel cell (SOFC) hybrid has been shown to be an essential requirement in order to achieve such a high efficiency. The coal is gasified utilizing a high pressure air-blown advanced transport reactor (ATR). A thermo-economic analysis of this integrated gasification fuel cell (IGFC) plant is performed by comparing it to an integrated gasification combined cycle (IGCC) plant that utilizes a gas turbine combined cycle for power generation. Results of this thermo-economic analysis indicate that the required “break even” cost of the SOFC system is $400/kW on an installed cost basis such that the cost of electricity of IGFC plant is the same as that of the IGCC plant. Coproduction of H2 and capture of carbon emissions may be incorporated in the design without causing a major thermal penalty on the system performance when high temperature separation membranes are employed. An O2-blown gasifier is required for such applications. The technology development needs are addressed.
Development of Probabilistic Lifing System for Advanced Turbine Rotor Alloys
Authors: Gorelik M. , Lenets Y. , Menon M. N.
Published: November 2008

Application of advanced Nickel based alloys in gas turbine rotors has risen significantly in the last two decades. It was shown by other authors that the deterministic lifing approach may be inadequate for a range of advanced turbine alloys under certain service conditions, and that a probabilistic approach results in a more relevant physics-based predictive model for such cases. Additionally, recent changes in the engine certification and design guidelines published by the FAA, Air Force, Army and other agencies call for increased application of probabilistic analysis. Thus, probabilistic lifing models become one of the key enablers for successful design and application of advanced turbine engine materials. This paper will discuss the main elements of probabilistic lifing system development for a new alloy, including material characterization requirements, selection of appropriate modeling techniques and validation plans.