bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration of Magnetic Bearings in the Design of Advanced Gas Turbine Engines
Authors: Storace A. F. , Sood D. , Lyons J. P. , Preston M. A.
Published: February 2008

Active magnetic bearings provide revolutionary advantages for gas turbine engine rotor support. These advantages include tremendously improved vibration and stability characteristics, reduced power loss, improved reliability, fault tolerance, and greatly extended bearing service life. The marriage of these advantages with innovative structural network design and advanced materials utilization will permit major increases in thrust-to-weight performance and structural efficiency for future gas turbine engines. However, obtaining the maximum payoff requires two key ingredients. The first is the use of modern magnetic bearing technologies such as innovative digital control techniques, high-density power electronics, high-density magnetic actuators, fault-tolerant system architecture, and electronic (sensorless) position estimation. This paper describes these technologies and the test hardware currently in place for verifying the performance of advanced magnetic actuators, power electronics, and digital controls. The second key ingredient is to go beyond the simple replacement of rolling element bearings with magnetic bearings by incorporating magnetic bearings as an integral part of the overall engine design. This is analogous to the proper approach to designing with composites, whereby the designer tailors the geometry and load-carrying function of the structural system or component for the composite instead of simply substituting composites in a design originally intended for metal material. This paper describes methodologies for the design integration of magnetic bearings in gas turbine engines.
Medway: A High-Efficiency Combined Cycle Power Plant Design
Authors: Leis D. M. , Boss M. J. , Melsert M. P.
Published: February 2008

The Medway Project is a 660 MW combined cycle power plant, which employs two of the world’s largest advanced technology MS9001FA combustion turbine generators and an advanced design reheat steam turbine generator in a power plant system designed for high reliability and efficiency. This paper discusses the power plant system optimization and design, including thermodynamic cycle selection, equipment arrangement, and system operation. The design of the MS9001FA combustion turbine generator and the steam turbine generator, including tailoring for the specific application conditions, is discussed.
Modeling and Control of HSFDs for Active Control of Rotor-Bearing Systems
Authors: El-Shafei A. , Hathout J. P.
Published: February 2008

This paper summarizes the development of hybrid squeeze film dampers (HSFDs) for active control of rotor vibrations. Previously, it was shown both theoretically and experimentally that HSFDs can be used for controlling rotor vibrations (El-Shafei, 1993). This is done by controlling the flow in a squeeze film damper through movable end seals, thus achieving the ability to change the damper from a short damper to a long damper and vice versa. However, the control of the HSFD was manual. In this paper, an automatically controlled circuit is developed for the HSFD, incorporating a pressure control servovalve for controlling the pressure in the sealing chambers. A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. The transient behavior of the system, including the sealing ring dynamics, illustrates that the open-loop system exhibits well-behaved, stable, and fast response. In addition it is shown that the HSFD can achieve any amount of damping between the short and long damper modes through the accurate positioning of the sealing rings. The simulation results illustrate that the automatically controlled HSFD can be a very useful device for the active control of rotors. A closed-loop control strategy with feedback on rotor speed is also investigated both from the points of view of steady state and transient behaviors. It is shown that this closed-loop strategy results in a much improved behavior of the rotor system.
Thermoeconomic Optimization of Sensible Heat Thermal Storage for Cogenerated Waste-to-Energy Recovery
Authors: Abdul-Razzak H. A. , Porter R. W.
Published: February 2008

This paper investigates the feasibility of employing thermal storage for cogenerated waste-to-energy recovery such as using mass-burning water-wall incinerators and topping steam turbines. Sensible thermal storage is considered in rectangular cross-sectioned channels through which is passed unused process steam at 1307 kPa/250°C (175 psig/482°F) during the storage period and feedwater at 1307 kPa/102°C (175 psig/216°F) during the recovery period. In determining the optimum storage configuration, it is found that the economic feasibility is a function of mass and specific heat of the material and surface area of the channel as well as cost of material and fabrication. Economic considerations included typical cash flows of capital charges, energy revenues, operation and maintenance, and income taxes. Cast concrete is determined to be a potentially attractive storage medium.
Aero-Engine Derivative Gas Turbines for Power Generation: Thermodynamic and Economic Perspectives
Authors: Horlock J. H.
Published: February 2008

Both the direct use of aero-engine hardware, in gas turbines for power generation, and the indirect influence of aero-engine technology, in the design of more conventional heavy-duty plants (including combined cycle gas turbines, CCGTs), are reviewed.
A Reduced Order Approach for the Vibration of Mistuned Bladed Disk Assemblies
Authors: Yang M.-T. , Griffin J. H.
Published: February 2008

A reduced order approach is introduced in this paper that can be used to predict the steady-state response of mistuned bladed disks. This approach takes results directly from a finite element analysis of a tuned system and, based on the assumption of rigid blade base motion, constructs a computationally efficient mistuned model with a reduced number of degrees of freedom. Based on a comparison of results predicted by different approaches, it is concluded that: The reduced order model displays structural fidelity comparable to that of a finite element model of the entire bladed disk system with significantly improved computational efficiency; and under certain circumstances both the finite element model and the reduced order model predict quite different response from simple spring-mass models.
Magnetic Thrust Bearing Operation and Industrial Pump Application
Authors: Allaire P. E. , Maslen E. H. , Lewis D. W. , Flack R. D.
Published: February 2008

Magnetic bearings represent a new bearing technology, which has some advantages over conventional fluid film and wiling element bearings for some applications. The paper describes the basic concepts of magnetic thrust bearing operation involving the magnetic actuator, electronic controls, power amplifier, and sensor. The magnetic actuator is a magnetic circuit, which generates attractive forces. These support the rotating shaft. While it is often thought that magnetic bearings are highly nonlinear devices, this paper demonstrates that they are linear in both the perturbation flux and current when used in a double acting configuration. Electronic feedback controls are used to stabilize the bearing. Example design parameters are presented for an application to an industrial canned motor pump.
Multi-objective Optimization of a Flexible Rotor in Magnetic Bearings With Critical Speeds and Control Current Constraints
Authors: Shiau Ting Nung , Kuo Chun Pao , Hwang Jiunn Rong
Published: February 2008

This paper presents the single objective optimization and the multi-objective optimization for a flexible rotor system with magnetic bearings. The weight of rotor shaft and the transmitted forces at the magnetic bearings are minimized either individually or simultaneously under the constraints on the critical speeds and the control currents of magnetic bearings. The design variables are the cross-sectional area of the shaft, the bias currents of magnetic bearings, and the positions of the disk and the magnetic bearings. The dynamic characteristics are analyzed using the generalized polynomial expansion method and the sensitivity analysis is also studied. For single objective optimization, the method of feasible directions (MFD) is applied. For multi-objective optimization, the weighting method (WM), the goal programming method (GPM), and the fuzzy method (FM) are employed. It is found that the system design can be significantly affected by the choices of the bias currents of magnetic bearings, the position of the disk with unbalance, and the magnetic bearings. The results also show that a better compromised design can always be obtained for multi-objective optimization.
Effects of Cycle Operating Conditions on Combustor Performance
Authors: Davis N. T. , McDonell V. G. , Samuelsen G. S.
Published: February 2008

To mitigate the environmental impact of next-generation gas turbine combustors, the emission performance at each condition throughout the load duty cycle must be optimized. Achieving this with a single combustor geometry may not be possible. Rather, the mixing processes and airflow splits must likely be modified as a function of load in order to (1) abate the emission of oxides of nitrogen, (2) maintain combustion efficiency, and (3) preclude lean blow-out over the entire duty cycle. The present study employs a model combustor to evaluate combustor performance as a function of load and explore the application of variable geometry to optimize performance at each condition. A parametric variation of flow splits is conducted at each load condition by independently adjusting the primary jet area and swirler choke area. The resultant impact on combustor performance is measured and quantified in terms of a cost function. The cost function is defined to increase with improving combustor performance (e.g., improving combustion efficiency and/or declining NOx emissions). Cycle operating conditions are found to alter the response mappings of efficiency and NOx. As a result, the optimal configuration of the combustor changes as the load is varied over the duty cycle. The results provide guidance on the application of active control.
Field Test Results of a Dry Low NOx Combustion System for the MS3002J Regenerative Cycle Gas Turbine
Authors: Maughan J. R. , Elward K. M. , De Pietro S. M. , Bautista P. J.
Published: February 2008

A dry low NOx combustion system for the MS3002J regenerative cycle gas turbine has been developed and successfully installed at two pipeline compressor stations. Preparation for the DLN retrofits began with initial field testing of the conventional system intended to characterize some of the unique features of the two-shaft, regenerative cycle machine that might affect the proposed premixed combustor design. Combustor transition pieces were instrumented with gas sampling probes for CO2 analysis. Fuel flow to each combustor was measured and controlled. Consequently, the fuel/air ratio, exit temperature, and air flow for each combustor could be determined over the operating range. The dry low NOx combustion system for the MS3002J R/C is based on an existing system for the MS6001B gas turbine. A description of the hardware and system operation is given, Because of the relatively high inlet temperature of the MS3002J R/C (950°F), some portions of the liner required highly efficient effusion cooling. A new transition piece seal was developed to reduce leakage and ensure uniform air flow throughout the machine. A control strategy was developed to guide the machine through diffusion modes of operation at low load to premixed combustion at higher loads. Results showed acceptable component temperatures throughout. Emissions measurements were consistent with previous laboratory measurements and met design targets of 33 ppm NOx and 25ppm CO (at 15 percent O2) over the required range. The fuel split between the two premixed flame zones was controlled over the load range of the turbine to optimize CO, NOx, and liner temperatures. Because of the high inlet temperature and low overall temperature rise, dynamic pressure activity was low. Following a successful inspection after 6000 hours of operation, the hardware inspection interval has been set at 12,000 h.
On-Engine Evaluation of Emissions Characteristics of a Variable Geometry Lean-Premixed Combustor
Authors: Yamada H. , Shimodaira K. , Hayashi S.
Published: February 2008

The design and on-engine testing of a lean-premixed, low-NOx combustor for a simple-cycle, single-shaft, 250-kW gas turbine engine of a pressure ratio of eight are described. A variable-geometry system composed of butterfly air valves was used to control the combustor air split between combustion and dilution. Fuel was staged to a direct-injection pilot burner, and a lean-premixed main burner was fitted to the combustor liner. The NOx emissions with natural gas fueling were found to be less than 20 ppm (at 15 percent O2) at and near full-load conditions with combustion efficiencies greater than 99.8 percent. Emissions data from early high-pressure rig tests of the combustor hardware are also presented.
A Coal-Fueled Combustion Turbine Cogeneration System With Topping Combustion
Authors: Bee´r J. M. , Garland R. V.
Published: February 2008

Cogeneration systems fired with coal or other solid fuels and containing conventional extracting-condensing or back pressure steam turbines can be found throughout the world. A potentially more economical plant of higher output per unit thermal energy is presented that employs a pressurized fluidized bed (PFB) and coal carbonizer. The carbonizer produces a char that is fed to the PFB and a low heating value fuel gas that is utilized in a topping combustion system. The topping combustor provides the means for achieving state-of-the-art turbine inlet temperatures and is the main contributor to enhancing the plant performance. An alternative to this fully coal-fired system is the partially coal, partially natural gas-fired air heater topping combustion cycle. In this cycle compressed air is preheated in an atmospheric pressure coal-fired boiler and its temperature raised further by burning natural gas in a topping gas turbine combustor. The coal fired boiler also generates steam for use in a cogeneration combined cycle. The conceptual design of the combustion turbine is presented with special emphasis on the low-emissions multiannular swirl burner topping combustion system and its special requirements and features.
Dynamic Response of a Cracked Rotor With Some Comments on Crack Detection
Authors: Meng G. , Hahn E. J.
Published: February 2008

By considering time-dependent terms as external excitation forces, the approximate dynamic response of a cracked horizontal rotor is analyzed theoretically and numerically. The solution is good for small cracks and small vibrations in the stable operating range. For each steady-state harmonic component, the forward and backward whirl amplitudes, the shape and orientation of the elliptic orbit, and the amplitude and phase of the response signals are analyzed, taking into account the effect of crack size, crack location, rotor speed, and unbalance. It is found that the crack causes backward whirl, the amplitude of which increases with the crack. For a cracked rotor, the response orbit for each harmonic component is an ellipse, the shape and orientation of which depend on the crack size. The influence of the crack on the synchronous response of the system can be regarded as an additional unbalance whereupon, depending on the speed and the crack location, the response amplitude differs from that of the uncracked rotor. The nonsynchronous response provides evidence of crack in the subcritical range, but is too small to be detected in the supercritical range. Possibilities for crack detection over the full-speed range include the additional average (the constant) response component, the backward whirl of the response, the ellipticity of the orbit, the angle between the major axis and the vertical axis, and the phase angle difference between vertical and horizontal vibration signals.
A Tabular Taylor Series Expansion Method for Fast Calculation of Steam Properties
Authors: Miyagawa K. , Hill P. G.
Published: February 2008

A new method is proposed for rapid and accurate calculation of steam properties in the regions of the state plane of greatest importance to the steam power industry. The method makes direct use of the derivatives of that Helmholtz function that is the best available wide-ranging scientific formulation of the properties of steam. It is rapid because, with a six-term Taylor series expansion, it uses property values and derivatives evaluated once and for all from the Helmholtz function and stored in tables pertaining to an optimized state plane grid configuration. The method eliminates the need for iterative property calculations and is amenable to any region of the state plane. For properties in the ranges of temperature from 0 to 800°C and pressure from 0 to 100 MPa the core memory requirement for three functions of any given pair of independent properties is less than 1 Mb. With this memory allocation it is possible everywhere in the stated range to satisfy the specific volume and enthalpy tolerances specified by the International Association for the Properties of Water and Steam. An optimized formulation of the method is demonstrated in this paper for enthalpy, entropy, and volume functions of pressure and temperature in the superheat region.
Zero-Emission MATIANT Cycle
Authors: Mathieu P. , Nihart R.
Published: February 2008

In this paper, a novel technology based on the zero CO2 emission MATIANT (contraction of the names of the two designers MAThieu and IANTovski) cycle is presented. This latter is basically a gas cycle and consists of a supercritical CO2 Rankine-like cycle on top of regenerative CO2 Brayton cycle. CO2 is the working fluid and O2 is the fuel oxidizer in the combustion chambers. The cycle uses the highest temperatures and pressures compatible with the most advanced materials in the steam and gas turbines. In addition, a reheat and a staged compression with intercooling are used. Therefore, the optimized cycle efficiency rises up to around 45 percent when operating on natural gas. A big asset of the system is its ability to remove the CO2 produced in the combustion process in liquid state and at high pressure, making it ready for transportation, for reuse or for final storage. The assets of the cycle are mentioned. The technical issues for the predesign of a prototype plant are reviewed.
A Numerical Investigation of the Cooling Effect of Compressed Natural Gas Throttling on Engine Delivery Ratio
Authors: Yacoub Y. , Marbun L. , Bata R.
Published: February 2008

A theoretical study was conducted to investigate the cooling effect of throttling compressed natural gas during the pressure regulation process. The concept of using this effect in cooling down the induction air was investigated. A thermodynamic model was developed for a typical fuel delivery system used on a vehicle fueled with compressed natural gas. The model was based on a set of integral conservation laws applied to each component of the fueling system. Several heat exchanging arrangements between the throttled gas and the inlet air were examined. The effect of the added heat exchanger on engine delivery ratio was examined for different engine sizes as well as for different operating conditions. An increase of 1 to 2.5% in engine delivery ratio was predicted due to the added heat exchanger.
The Effect of Time of Exposure to Elevated Temperatures on the Flammability Limits of Some Common Gaseous Fuels in Air
Authors: Wierzba I. , Ale B. B.
Published: February 2008

The flammability limits of methane, ethylene, propane, and hydrogen were experimentally determined at elevated initial mixture temperatures up to 350°C at atmospheric pressure for upward flame propagation in a steel test tube apparatus. The existence of preignition reactions at these levels of temperatures that may influence the value of the flammability limits was also investigated. The fuel-air mixtures were exposed to elevated temperatures over different periods of time before spark ignition (up to 2 h). It was shown that the flammability limits for methane widened approximately linearly with an increase in the initial mixture temperature over the entire range of temperatures tested and were not affected by the length of the exposure time to these temperatures before spark ignition. However, different behaviour was observed for the flammability limits of the other tested fuels—ethylene, propane, and hydrogen. At higher temperatures the flammability limits narrowed and were very significantly affected by the exposure time. The longer was the exposure time of fuel-air mixtures to the elevated temperatures, the narrower were their flammability limits.
Forced Harmonic Response of Grouped Blade Systems: Part I—Discrete Theory
Authors: Wagner L. F. , Griffin J. H.
Published: February 2008

The vibration of grouped blades on a flexible disk cannot be analyzed using procedures developed for individual, uncoupled groups. The bladed-disk system must be considered either in whole, or as a structure composed of cyclically symmetric sectors. The latter approach, while being computationally more economical, is more complicated to implement because both the structural system and the applied forces must be transformed to a system based on the geometry of a single sector. However, the sector transformation permits a natural ordering of the modes that cannot be obtained from a complete system model. This paper describes the development of the sector model, and the associated transformation of the applied harmonic forces typically prevalent in turbomachinery. The displacements are expressed in a series of the natural modes of a transformed sector, and expressions are developed for maximum displacements of the complete structure. This approach leads to an easier interpretation of the analytical results and an improved physical understanding of the response. For example, it is shown that a single harmonic, or engine-order excitation, can cause response in only a restricted subset of modes.
Forced Harmonic Response of Grouped Blade Systems: Part II—Application
Authors: Wagner L. F. , Griffin J. H.
Published: February 2008

The vibration of grouped blades on a flexible disk should, for purposes of economy and clarity of modal identification, be analyzed using procedures developed for cyclically symmetric structures. In this paper, a numerical model, based on the theory of cyclically symmetric structures, is applied to the vibration analysis, and in particular, the harmonic response, of a flexible disk supporting a number of groups, or packets, of turbine blades. Results are presented to show variations in the modal participation factors as a function of such parameters as disk flexibility, blade density, and the total number of assembled groups. It is also shown that many characteristics of the system spectra of natural frequencies are strongly dependent on the number of blade groups.
Ceramic Hybrid Bearings in Air-Cycle Machines
Authors: Burgmeier L. , Poursaba M.
Published: February 2008

Extensive research in the field of ceramic rolling contact bearings has been conducted over the past several years. The results of this research indicate that silicon nitride may offer significant improvements in rolling fatigue life and a possible increase in operating temperature. AlliedSignal Aerospace Systems & Equipment (ASE) and the Air Force Item Management Engineering Branch at Tinker Air Force Base are conducting a development program under contract to ARPA to introduce ceramic hybrid bearings into existing F-15, F-111, and C-130 aircraft fleets in a near-term program involving retrofitting mature air-cycle machines with such bearings. The air-cycle machine (ACM) is a complex bearing application, operating at very high speeds (up to 100,000 rpm) and at high temperatures. In more severe military ACM applications, mean times between failures (MTBFs) of 2000 and 3000 hours are common. The fleet would see an immediate benefit from improved bearing life. This paper describes the analytical approach to evaluating and comparing ceramic to steel bearings, describes the laboratory test program to verify performance, and discusses the life-cycle cost improvement and the flight test program.
Affordable Nacelle Technologies for Future Turbofans
Authors: Smith C. J.
Published: February 2008

Costs are playing an ever-increasing role in determining what the next generation of aircraft and engines will be. In addition to deciding to what extent wing/engine integration or drag-reducing laminar flow technologies can be employed, etc., the economic impact on both aircraft operation and engines launch and development costs must be evaluated. SFC or fuel burn advantages are no longer dominant to the extent they used to be and for some apparently promising technology concepts the cost disadvantages outweigh the aerodynamic advantages when both effects are transposed into aircraft direct operating costs. In addition, a simple metric has been evolved to rank different technology concepts and prioritize them in order to help determine the most deserving technologies for scarce development funds.
Subcritical Crack Growth Life Prediction for Ceramic Components of Advanced Heat Engines
Authors: Wu D. C. , Peralta A. D. , Menon M. N. , Cuccio J. C.
Published: February 2008

Advanced, high-strength ceramics are finding increasing application in advanced heat engines. To ensure the long-term reliability of components made from these materials, subcritical crack growth (SCG) from inherent flaws has to be taken into account, as this has been identified as the primary failure mode under sustained loading. In analyzing fast fracture data, data censoring is necessary to obtain estimates of the inherent strength distributions for competing failure-causing flaw populations. This is particularly important for ceramic designs, where size scaling is a necessary part of the design analysis. While data censoring has become common for fast fracture data, data censoring involving stress rupture data has yet to be widely applied. This paper describes fast fracture and stress rupture tests performed on an advanced silicon nitride ceramic, the test data and fractography results, censored data analysis for both types of data, derivation of the subcritical crack growth parameters, and application of these parameters to verification specimens. Implications of the findings and recommendations for future studies are also presented.
Surface Fouling in Aviation Fuels: An Isothermal Chemical Study
Authors: Jones E. G. , Balster W. J. , Pickard J. M.
Published: February 2008

Surface fouling in aircraft fuel lines that results from autoxidation of aviation fuel remains a serious and very complicated problem. This area has been studied using two Jet-A fuels, POSF-2827 and POSF-2980. The results of a series of dynamic experiments conducted in a single-pass, tubular heat exchanger operated at very slow flow rates under near-isothermal conditions are reported herein. Such studies, by minimizing complications resulting from fluid dynamics and heat flow, constitute a simpler global approach to the chemistry of fouling. The basis for the selection of experimental test conditions is discussed, and data from measurements of dissolved oxygen and surface deposition as a function of fuel stress duration are presented. The effects of parameters such as reaction temperature, tube diameter, experimental test time, and fuel dopants are considered.
Nondestructive Characterization of Ceramic Composites Used as Combustor Liners in Advanced Gas Turbines
Authors: Ellingson W. A. , Rothermel S. A. , Simpson J. F.
Published: February 2008

Nondestructive characterization (NDC) methods, which can provide full-field information about components prior to and during use, are critical to the reliable application of continuous fiber ceramic matrix composites in high-firing-temperature (>1350°C) gas turbines. [For combustor liners, although they are nonmechanical load-bearing components, both thermal characteristics and mechanical integrity are vitally important.] NDC methods being developed to provide necessary information include x-ray computed tomography (mainly for through-wall density and delamination detection), infrared-based thermal diffusivity imaging, and single-wall through-transmission x-ray imaging (mainly for fiber content and alignment detection). Correlation of the data obtained from NDC methods with subscale combustor liner tests have shown positive results at thermal cycling temperatures from 700°C to 1177°C.
Nondestructive Evaluation of Thermally Shocked Silicon Carbide by Impact-Acoustic Resonance
Authors: Bemis R. A. , Shiloh K. , Ellingson W. A.
Published: February 2008

Monolithic ceramics are under consideration as structural components for hot-stage sections of gas-fired turbine engines. In addition to manufacturing quality control, other important aspects for this application include life prediction modeling and time between engine overhauls. One nondestructive evaluation (NDE) method that provides information about material condition involves an analysis of resonant vibrations. In previous work by this general approach, changes in modal parameters have been related to bulk defect mechanisms such as microcracking due to thermal shock damage. In this work resonant vibrations from monolithic ceramic specimens were excited by an instrumented impact hammer and detected by a noncontact acoustic microphone over frequencies up to 100 kHz. Computer-based analysis of vibration signatures from test specimens allowed extraction of modal frequencies and damping constants. Downward shifts in detected resonant frequencies and increases in internal friction or (specific) damping capacity measurements were obtained from SiC cylindrical rings, and these measurements were shown to relate to thermal shock severity. This NDE method not only provides measurable parameters that could be used as accept–reject criteria for in-line process inspection, it also provides a means for tracking the mechanical integrity of in-service engine components to support life prediction modeling.
A Study on Low NOx Combustion in LBG-Fueled 1500°C-Class Gas Turbine
Authors: Nakata T. , Sato M. , Ninomiya T. , Hasegawa T.
Published: February 2008

Developing integrated coal gasification combined-cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of an air-blown entrained-flow type has a calorific value as low as 1/10 of natural gas. Furthermore, the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine. This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emissions from the ammonia in the fuel. The main fuel and the combustion air are supplied into a fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen. By testing under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.
Applications of Accurate Isentropic Exponent Determination for Fuel Gas Measurement
Authors: Pack D. J. , Edwards T. J. , Fawcett D.
Published: February 2008

This paper discusses the determination and application of the isentropic exponent to the various thermodynamic processes found in a high-pressure natural gas transmission system. Increasing demands for more precise measurement of natural gas, coupled with the need for greater efficiency and accountability of transportation and processing operations, had led to our research and development efforts into the more precise measurement of gas flow, and the determination of gas thermodynamic properties including isentropic exponent. The isentropic exponent has many applications, some of which include: • the determination of the expansion factor ε, for calculation of flow using an orifice or venturi-type meter; • the volumetric efficiency in a reciprocating compressor; • the determination of the compression head for a centrifugal compressor; • the engine power required for the given conditions for a gas compressor; • the calculation of discharge temperatures for compressors; and • the direct measurement of gas density. As can be appreciated, the application of an incorrect value for the isentropic exponent represents an error in the parameter determined. For large volume gas flows, this can translate into a significant cost penalty.
New 200 MW Class 501G Combustion Turbine
Authors: Southall L. , McQuiggan G.
Published: February 2008

The 501G 60-Hz combustion turbine has been developed jointly by Westinghouse Electric Corporation, Mitsubishi Heavy Industries, Ltd., and FiatAvio. It continues a long line of large heavy-duty single-shaft combustion turbines by combining the proven efficient and reliable concepts of the 501F with the latest advances in aero technology via the Westinghouse Alliance with Rolls-Royce. The output of the 501G is over 230 MW with a combined cycle net efficiency of 58 percent. This makes the 501G the largest 60-Hz combustion turbine in the world and also the most efficient.
The Effect of Twisted-Tape Width on Heat Transfer and Pressure Drop for Fully Developed Laminar Flow
Authors: Chakroun W. M. , Al-Fahed S. F.
Published: February 2008

A series of experiments was conducted to study the effect of twisted-tape width on the heat transfer and pressure drop with laminar flow in tubes. Data for three twisted-tape wavelengths, each with five different widths, have been collected with constant wall temperature boundary condition. Correlations for the friction factor and Nusselt number are also available. The correlations predict the experimental data to within 10 to 15 percent for the heat transfer and friction factor, respectively. The presence of the twisted tape has caused the friction factor to increase by a factor of 3 to 7 depending on Reynolds number and the twisted-tape geometry. Heat transfer results have shown an increase of 1.5 to 3 times that of plain tubes depending on the flow conditions and the twisted-tape geometry. The width shows no effect on friction factor and heat transfer in the low range of Reynolds number but has a more pronounced effect on heat transfer at the higher range of Reynolds number. It is recommended to use loose-fit tapes for low Reynolds number flows instead of tight-fit in the design of heat exchangers because they are easier to install and remove for cleaning purposes.
CT Multiscan: Using Small Area Detectors to Image Large Components
Authors: Sivers E. A. , Ellingson W. A. , Snyder S. A. , Holloway D. A.
Published: February 2008

The small size and dynamic range of the best two-dimensional X-ray detectors are impediments to the use of three-dimensional X-ray computed tomography (3D-XRCT) for 100 percent inspection of large ceramic components. The most common industrial 3D-XRCT systems use a “rotate-only” geometry in which the X-ray source and the area detector remain stationary while the component placed between them is rotated through 360 deg. This configuration offers the highest inspection speed and the best utilization of X-ray dose, but requires that the component be small enough to fit within the X-ray/detector “cone.” Also, if the object is very dense, the ratio of an unattenuated X-ray signal to that through the longest path in the component may exceed the dynamic range of the detector. To some extent, both of these disadvantages can be overcome by using “Multiscan CT,” i.e., scanning small overlapping regions of a large component separately while maximizing the X-ray dose to each. The over lapping scans can then be combined seamlessly into a single scan with optimal contrast.
New Technology Trends for Improved IGCC System Performance
Authors: Anand A. K. , Cook C. S. , Corman J. C. , Smith A. R.
Published: February 2008

The application of gas turbine technology to IGCC systems requires careful consideration of the degree and type of integration used during the system design phase. Although gas turbines provide the primary output and efficiency gains for IGCC systems, as compared with conventional coal-fired power generation systems, they are commercially available only in specific size ranges. Therefore, it is up to the IGCC system designer to optimize the IGCC power plant within the required output, efficiency, and site conditions by selecting the system configuration carefully, particularly for air separation unit (ASU) integration incorporated with oxygen blown gasification systems. An IGCC system, based on a generic, entrained flow, oxygen blown gasification system and a GE STAG 109FA combined cycle has been evaluated with varying degrees of ASU integration, two fuel equivalent heating values and two gas turbine firing temperatures to provide net plant output and efficiency results. The data presented illustrate the system flexibility afforded by variation of ASU integration and the potential performance gains available through the continued use of gas turbine advances. Emphasis is placed on system design choices that favor either low initial investment cost or low operating cost for a given IGCC system output.
A NOx Prediction Scheme for Lean-Premixed Gas Turbine Combustion Based on Detailed Chemical Kinetics
Authors: Polifke W. , Do¨bbeling K. , Sattelmayer T. , Nicol D. G. , Malte P. C.
Published: February 2008

The lean-premixed technique has proven very efficient in reducing the emissions of oxides of nitrogen (NOx) from gas turbine combustors. The numerical prediction of NOx levels in such combustors with multidimensional CFD codes has only met with limited success so far. This is to some extent due to the complexity of the NOx formation chemistry in lean-premixed combustion, i.e., all three known NOx formation routes (Zeldovich, nitrous, and prompt) can contribute significantly. Furthermore, NOx formation occurs almost exclusively in the flame zone, where radical concentrations significantly above equilibrium values are observed. A relatively large chemical mechanism is therefore required to predict radical concentrations and NOx formation rates under such conditions. These difficulties have prompted the development of a NOx postprocessing scheme, where rate and concentration information necessary to predict NOx formation is taken from one-dimensional combustion models with detailed chemistry and provided—via look-up tables—to the multidimensional CFD code. The look-up tables are prepared beforehand in accordance with the operating conditions and are based on CO concentrations, which are indicative of free radical chemistry. Once the reacting flow field has been computed with the main CFD code, the chemical source terms of the NO transport equation, i.e., local NO formation rates, are determined from the reacting flow field and the tabulated chemical data. Then the main code is turned on again to compute the NO concentration field. This NOx submodel has no adjustable parameters and converges very quickly. Good agreement with experiment has been observed and interesting conclusions concerning superequilibrium O-atom concentrations and fluctuations of temperature could be drawn.
Lean Blowout in a Research Combustor at Simulated Low Pressures
Authors: Sturgess G. J. , Heneghan S. P. , Vangsness M. D. , Ballal D. R. , Lesmerises A. L.
Published: February 2008

A propane-fueled research combustor has been designed to represent the essential features of primary zones of combustors for aircraft gas turbine engines in an investigation of lean blowouts. The atmospheric pressure test facility being used for the investigation made it difficult to approach the maximum heat release condition of the research combustor directly. High combustor loadings were achieved through simulating the effects on chemical reaction rates of subatmospheric pressures by means of a nitrogen diluent technique. A calibration procedure is described, and correlated experimental lean blowout results are compared with well-stirred reactor calculations for the research combustor to confirm the efficacy of the calibration.
Optimal Multistage Expansion Planning of a Gas Turbine Cogeneration Plant
Authors: Yokoyama R. , Ito K. , Matsumoto Y.
Published: February 2008

A multistage expansion planning problem is discussed concerning a gas turbine cogeneration plant for district heating and cooling using an optimization approach. An optimal sizing method for single-stage planning proposed by the authors is extended to this case. Equipment capacities and utility maximum demands at each expansion stage are determined so as to minimize the levelized annual total cost subject to increasing energy demands. A numerical study on a simple-cycle gas turbine cogeneration plant to be installed in a district development project clarifies the relationship between optimal expansion planning and energy demand trend, and shows the effectiveness of the proposed method.
The Synchronous Instability of a Compressor Rotor Due to Bearing Journal Differential Heating
Authors: de Jongh F. M. , Morton P. G.
Published: February 2008

The paper describes a synchronous vibration instability problem encountered on a centrifugal compressor with oil-lubricated bearings. The problem was solved by modification of the compressor rotor; however, the root cause was not completely understood at that time. A possible explanation was based on a theory that suggested differential heating of the bearing journals. It was decided to verify this theory by experiments. Therefore a test rotor was designed with identical rotor dynamic characteristics to those of the compressor rotor. To fill a gap in the published research on bearing thermohydrodynamics, an experimental technique was devised to measure the surface temperature variations around one of the journals of this rotor. The dependence of significant temperature differentials across the journal upon its orbit was confirmed.
The Application of a Thermal Efficiency Maximizing Control Strategy for Ignition Timing and Equivalence Ratio on a Natural Gas-Fueled Hercules G1600
Authors: Franklin M. L. , Kittelson D. B. , Leuer R. H.
Published: February 2008

A two-dimensional optimization process, which simultaneously adjusts the spark timing and equivalence ratio of a lean-burn, natural gas, Hercules G1600 engine, has been demonstrated. First, the three-dimensional surface of thermal efficiency was mapped versus spark timing and equivalence ratio at a single speed and load combination. Then the ability of the control system to find and hold the combination of timing and equivalence ratio that gives the highest thermal efficiency was explored. NOx, CO, and HC maps were also constructed from our experimental data to determine the tradeoffs between efficiency and emissions. The optimization process adds small synchronous disturbances to the spark timing and air flow while the fuel injected per cycle is held constant for four cycles. The engine speed response to these disturbances is used to determine the corrections for spark timing and equivalence ratio. The control process, in effect, uses the engine itself as the primary sensor. The control system can adapt to changes in fuel composition, operating conditions, engine wear, or other factors that may not be easily measured. Although this strategy was previously demonstrated in a Volkswagen 1.7 liter light duty engine (Franklin et al., 1994b), until now it has not been demonstrated in a heavy-duty engine. This paper covers the application of the approach to a Hercules G1600 engine.
Structure of Airblast Sprays Under High Ambient Pressure Conditions
Authors: Zheng Q. P. , Jasuja A. K. , Lefebvre A. H.
Published: February 2008

A single-velocity-component phase Doppler particle analyzer is used to survey and measure local variations in drop-size distributions and drop velocities in the nearnozzle region of a practical, contraswirling, prefilming airblast atomizer. The technique of laser sheet imaging is used to obtain global patterns of the spray. All measurements are taken with a constant pressure drop across the atomizer of 5 percent, at ambient air pressures of 1, 6, and 12 bar. The liquid employed is aviation kerosine at flow rates up to 75 g/s. The results show that increasing the air pressure from 1 to 12 bar at a constant air/fuel ratio causes the initial spray cone angle to widen from 70 to 105 deg. Farther downstream the spray volume remains largely unaffected by variations in atomizer operating conditions. However, the radial distribution of fuel within the spray volume is such that increases in fuel flow rate cause a larger proportion of fuel to be contained in the outer regions of the spray. The effect of ambient pressure on the overall Sauter mean diameter is small. This is attributed to the fact that the rapid disintegration of the fuel sheet produced by the contraswirling air streams ensures that the atomization process is dominated by the “prompt” mechanism. For this mode of liquid breakup, theory predicts that mean drop sizes are independent of air pressure.
The Advanced Cooling Technology for the 1500°C Class Gas Turbines: Steam-Cooled Vanes and Air-Cooled Blades
Authors: Nomoto H. , Koga A. , Ito S. , Fukuyama Y. , Otomo F. , Shibuya S. , Sato M. , Kobayashi Y. , Matsuzaki H.
Published: February 2008

It is very essential to raise the thermal efficiency of combined cycle plants from the viewpoint of energy saving and environmental protection. Tohoku Electric Power Co., Inc., and Toshiba Corporation in Japan have jointly studied the next generation of combined cycle systems using 1500°C class gas turbine. A promising cooling technology for the vanes using steam was developed. The blades are cooled by air, adopting the impingement cooling, film cooling, and so on. The cooling effectiveness was confirmed both for the vanes and the blades using a hot wind tunnel. This paper describes the design features of the vanes and the blades, and the results of the verification tests using the hot wind tunnel.
A Numerical Investigation of Premixed Combustion in Wave Rotors
Authors: Nalim M. R. , Paxson D. E.
Published: February 2008

Wave rotor cycles that utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented that illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed.