bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural Gas Decarbonization to Reduce CO2 Emission From Combined Cycles: Part B — Steam-Methane Reforming
Authors: Lozza Giovanni , Chiesa Paolo 
Published: August 2014

This paper discusses novel schemes of combined cycle, where natural gas is chemically treated to remove carbon, rather than being directly used as fuel. Carbon conversion to CO2 is achieved before gas turbine combustion. The first part of the paper discussed plant configurations based on natural gas partial oxidation to produce carbon monoxide, converted to carbon dioxide by shift reaction and therefore separated from the fuel gas. The second part will address methane reforming as a starting reaction to achieve the same goal. Plant configuration and performance differs from previous case because reforming is endothermic and requires high temperature heat and low operating pressure to obtain an elevated carbon conversion.
The performance estimation shows that the reformer configuration has a lower efficiency and power output than the systems addressed in Part A. To improve the results, a reheat gas turbine can be used, with different characteristics from commercial machines. The thermodynamic efficiency of the systems of the two papers is compared by an exergetic analysis.
The economic performance of natural gas fired power plants including CO2 sequestration are therefore addressed, finding a superiority of the partial oxidation system with chemical absorption. The additional cost of the kWh, due to the ability of CO2 capturing, can be estimated at about 13–14 mill$/kWh.
An Ericsson Cycle GT Design by LNG Cryogenic Heat Utilization
Authors: Hanawa Kirk 
Published: August 2014

In many LNG receiving terminals worldwide, the cryogenic heat of imported LNG which was liquefied by using 10% energy of natural gas supply1), 2), has been wasted into the sea water mainly through heat exchangers like ORVs (Open Rack Vaporizer)3). This cryogenic heat of 110 K (-256 F) class is considered, however, as an excellent energy source to apply thermodynamic cycles. Several literature, accordingly, are found to improve such high-grade energy potential of LNG regasification process as a low temperature sink, combining with fired heater at 1,100 K (1520 F) class or GT main exhaust gas at 700 K (800 F) class as a high temperature source, through Brayton and Rankine cycles5),6),7),8),9).
This paper presents a typical example of closed “Ericsson” cycle which has the minimum cycle temperature of 157 K (-176 F) from LNG cryogenic heat and the maximum of 550 K (531 F) from the partial HRSG exit heat mixed with the partial GT exit gas. This closed gas turbine, from viewpoints of minor modification to existing power plants and no energy impacts for high temperature source, which would be better than the above-described idea, is able to offer 35% thermal efficiency. And it is recognized that this system would be superior to existing cryogenic generation systems of 20% class operated by Rankine Cycle.
Power Plants Up-Rating Benefit From Technology Advancements: A Case Study
Authors: McCue Robert , von Rappard Axel W. 
Published: August 2014

Life cycle considerations, Reliability / Availability and Maintainability (RAM) experiences, as well as performance improvements, drive power producers not only to plan new power plants but also to upgrade older ones. The main driver, however, is competitiveness and this means cost of electricity for the end users and equipment availability for the shareholders. An up-rating is attractive if you can increase performance and reduce failure rate and thereby operating risks.
The first part of this paper describes the actual configuration of a combined cycle plant and the operating experience over the past three to five years. This refers to performance parameters — power and heat rate — as well as to RAM performance. Up-rating shows normally an advantage compared to new equipment concerning reliability, availability and maintainability. A cooperation of the parties involved — power producer and engine manufacturer (OEM) — is necessary, when all above-mentioned parameters are considered. The up-rating can improve the performance (power and heat rate), can keep reliability and availability at high values and can influence the maintainability positively.
The second part addresses the evaluation and the stepwise implementation of the solution and the summary of the results. Different power producers and ABB have worked closely together to evaluate the options and to develop the best solution. The conclusions will show how important the power producer / OEM relationship is when such upgrades are implemented and the results are measured. Due to the multitude of interfaces associated with gas turbine power plant upgrades, good co-operation is essential. This case study, is also the result of solutions developed with several power producers.
World’s First LM5000 to LM6000 Cogeneration Plant Repowering
Authors: McCarrick Michael T. , Rosencrance Robert K. 
Published: August 2014

With the introduction of GE’s latest and most efficient gas turbine, the LM6000 in 1992, and the end of production of GE’s LM5000 gas turbine in 1997, the concept of repowering aging LM5000 gas turbine powered cogeneration plants with LM6000 gas turbines was an idea that most LM5000 owners and operators dreamed about. The LM6000 is an ideal replacement for the LM5000 as they both have nearly the same mass flow and exhaust gas temperature (critical for Heat Recovery Steam Generator (HRSG) compatibility), are about the same physical weight and dimensions, and can be operated in the same power range. Also, as the LM6000 is a current production model, it has more readily available spare gas turbines and turbine parts, has a much improved heat rate, lower emissions level, and has an option (SPRINT), for added power. In December 1999, the UAE Oildale Energy Facility became the first plant to operate with a newly installed LM6000 in its former LM5000 package. (This March the second LM5000 to LM6000 repowering was completed for Calpine Corporation at their Greenleaf #1 Cogeneration Plant in Yuba City, CA.) Energy Services, Inc., GE’s authorized LM6000 repowering OEM, designed, engineered and project managed the repowering.
This paper will present the reasons UAE decided to repower; discuss the technical challenges encountered with, and modifications made to, the GEC ELM-150 cogeneration plant to accommodate the LM6000; review the schedule; and provide the economic benefits of the improved heat rate and reliability of the LM6000.
The Two-Flux Model Applied to Radiative Transfer and Forced Convection in the Laminar Boundary Layer on a Flat Plate
Authors: Malpica Freddy , Moreno Nathaly , Tremante Andrés 
Published: August 2014

This study presents the analysis of the thermal boundary layer considering combined convection and radiation in an absorbing, emitting and scattering medium flowing over a flat plate. At high temperatures the presence of thermal radiation alters the temperature distribution in the boundary layer, which in turn affects the heat transfer at the wall. In many industrial applications, such as in the cooling of turbine and compressors blades, radiative heat transfer plays an important role.
The treatment of heat transfer by combined convection and radiation in the boundary layer leads to a set of partial differential and integrodifferential equations, which must be solved simultaneously. The exact solutions are seldom possible and the investigators resort to approximate methods. In the present analysis the two-flux model is used to describe the radiative heat flux in the energy equation. This model reduces the equations that govern the problem to a set of coupled partial differential equations. A finite difference scheme, called “method of columns”, is used to transform the resulting equations into an ordinary differential equation system which simplifies the solution.
Results for the temperature profile and heat fluxes showed close agreement with the thin and thick limits.
The method proposed proves to be useful to investigate the effect of the different radiation parameters on the thermal boundary layer, and also to be accurate enough for engineering applications.
Prediction of a Laminar Separation Bubble Over a Controlled-Diffusion Compressor Blade
Authors: Hobson G. V. , Weber S. 
Published: August 2014

The paper describes the comparison of the prediction of the flow through a cascade of controlled-diffusion compressor blades with two Navier-Stokes solvers. Both codes solved the thin-layer N-S equations, however; one code performed implicit time marching whereas the other performed explicit time marching. Flow predictions were accomplished with the implicit code using the algebraic turbulence model of Baldwin and Lomax and the one-equation model of Spalart and Allmaras, while predictions were made with the explicit code using the two-equation model by Wilcox.
Predictions were made of the detailed laser-anemometry measurements of the flow field taken previously in a low-speed cascade wind tunnel. Comparisons were also made with the experimentally measured blade surface pressures and flow visualization of the extent of the laminar leading edge separation bubble. The one-equation turbulence model was combined with an intermittency based transition-length model for comparisons with fully turbulent calculations. Both codes predicted the leading-edge separation bubble satisfactorily when using higher order turbulence models.
Spinning Reserve Influence in a Power Generating System Integrated by Hydro Storage Plants
Authors: Bianchi M. , Gadda E. , Peretto A. 
Published: August 2014

During the weekday night hours, to satisfy the lowest load demand by a power generation system, the thermoelectric unit load following strategy may be managed with the hydro storage operation.
In this paper, a methodology, for the evaluation of fuel energy consumption of fossil fuel power generation system, with or without the hydro storage application, is presented, taking into account, particularly the spinning reserve presence.
It is shown that, when pumped storage power stations are considered, for the two homogeneous sets of fossil fuel power units (conventional and advanced) analyzed, an important role is played by the spinning reserve. Moreover, a considerable saving in daily fuel consumption is achievable in the case of advanced power units. It was also found that an increase in the thermoelectric load factor may reduce the hydro storage operation saving on the kWh variable cost.
Improved Processing Route for Aluminization of Gas Turbine Components
Authors: Kircher Thomas A. , Solovei David , Steck Joseph H. , Shankar Srinivasan (Shanks) 
Published: August 2014

Pack aluminizing and vapor-phase aluminizing (VPA) are common methods for producing protective coatings on aero and industrial gas turbine hot section components. SermAlcote® slurry aluminization is an alternative to many industrial pack and vapor-phase aluminizing processes. SermAlcote® slurry aluminization processes are designed to meet existing commercial specifications while offering significant improvements in cost, quality and turntime over competitive aluminizing processes. Advantages of this processing route include simplified masking, shorter thermal processing cycles, improved diffusion capacity (no powder, simplified racks), and elimination of powder handling/storage concerns.
Unlike conventional slurry aluminizing methods, the SermAlcote® process produces very uniform diffused aluminide coatings over a very wide range of applied slurry amounts. This simplifies the manufacturing process and produces high degree of process repeatability and uniformity.
Data and examples are presented in order to describe the characteristics of SermAlcote® slurry aluminization processes for producing aluminide coatings, platinum-modified aluminide coatings, and over-aluminized MCrAlY coatings.
Fluoride Ion Cleaning (FIC) at Sub-Atmospheric Pressure
Authors: Miglietti Warren , Cullen Tom 
Published: August 2014

The fluoride Ion cleaning (FIC) process is used to assist in the successful braze repair of nickel-based superalloy components. This process is especially effective in removing embedded oxides in cracks typically found in aircraft parts such as in combustors and turbine blades and vanes. Where, Al and Ti are present in the base metal, the FIC process depletes these elements from the surface, thereby improving the braze flow and repair of the cracked components. The objective of this paper is to show that mechanical properties of the braze repaired region can be adequate when the FIC process at sub-atmospheric pressure is utilized, prior to brazing. To achieve this, firstly entailed designing and producing specimens suitable to study the fatigue crack behavior of braze repaired cracks/joints under mechanical and thermal loading. The cracks/joints prior to brazing were either in an unclean form i.e. had an oxide layer on, or were fluoride ion cleaned at sub-atmospheric pressure. Fatigue crack propagation tests under constant load as well as under constant stress intensity factor range were conducted in order to study fatigue crack growth characteristics in the parent and braze repaired area. In addition, the resistance to thermal cycling was investigated using single-edge wedge specimens containing braze repaired joints.
For the unclean crack specimens, abnormally high crack growth rates were obtained from the brazed repaired area as compared to parent Ni-based material; whereas for the fluoride ion cleaned crack specimens, lower crack growth rates were experienced. Similarly for the unclean crack specimens, the thermal fatigue crack initiation life was significantly shorter compared with the fluoride ion cleaned crack specimens.
Experimental Investigation of Shock-Induced Blade Oscillation at an Elastically Suspended Turbine Cascade in Transonic Flow
Authors: Urban Brigitte , Stetter Heinz , Vortmeyer Nicolas 
Published: August 2014

Experimental investigations on shock-induced flutter in a linear transonic turbine cascade are presented. To examine the relation between trailing edge shock oscillations on adjacent blades in transonic flow and observed turbine blade vibrations, an elastic suspension system has been developed so that only aerodynamic coupling occurs in the system.
The experimental investigations have been performed on a linear test rig with superheated steam as working fluid. The test facility enables Mach and Reynolds numbers to be varied independently.
The investigated cascade consists of seven blades which are taken from the tip section of a transonic low pressure steam turbine blade. Each blade is attached by an elastic spring system which allows the respective blade to vibrate in a mode equal to the real blade’s first bending mode. By varying the individual spring stiffness it is possible to either get a tuned or mistuned cascade.
The examinations mainly deal with the oscillatory behavior of the blades with respect to a variation in the isentropic outlet Mach number. In addition, the complex shock-boundary-layer interaction on the blades’ suction sides is described.
An important result is that the maximum blade oscillation amplitude can be related to a specific outlet Mach number. At this Mach number all seven blades are vibrating with exactly the same frequency. This phenomenon is observed at both the tuned and the mistuned cascades.
Spectrum analysis shows that one of the major shock oscillation frequencies corresponds to the flutter frequency.
In addition to this frequency the spectrum analysis of the blade oscillation shows the dominant frequencies of the shock oscillation which are not natural blade frequencies.
The experimental results show that oscillating shocks in a linear cascade give high potential for aeroelastic excitation of transonic blades under certain flow conditions. Blade oscillations and shock characteristics are discussed in detail.
Numerical Investigation of Nonlinear Fluid-Structure Interaction in Vibrating Compressor Blades
Authors: Carstens Volker , Belz Joachim 
Published: August 2014

The aeroelastic behaviour of vibrating blade assemblies is usually investigated in the frequency domain where the determination of aeroelastic stability boundaries is separated from the computation of linearized unsteady aerodynamic forces. However, nonlinear fluid-structure interaction caused by oscillating shocks or strong flow separation may significantly influence the aerodynamic damping and hence effect a shift of stability boundaries. In order to investigate such aeroelastic phenomena, the governing equations of structural and fluid motion have to be simultaneously integrated in time.
In this paper a technique is presented which analyzes the aeroelastic behaviour of an oscillating compressor cascade in the time domain. The structural part of the governing aeroelastic equations is time-integrated according to the algorithm of Newmark, while the unsteady airloads are computed at every time step by an Euler upwind code, The link between the two time integrations is an automatic grid generation in which the used mesh is dynamically deformed as such that it conforms with the deflected blades at every time step.
The computed time series of the aeroelastic simulation of an assembly of twenty compressor blades performing torsional vibrations in transonic flow are presented. For subsonic flow, the differences between time domain and frequency domain results are of negligible order. For transonic flow, however, where vibrating shocks and a temporarily choked flow in the blade channel dominate the unsteady flow, the energy transfer between fluid and structure is no longer comparable to that of a linear system. It is demonstrated that the application of the time domain method leads to a significantly different aeroelastic behaviour of the blade assembly including a shift of the stability boundary.
Dynamic Response of a Rotor-Integral Squeeze Film Damper to Couple Imbalances
Authors: De Santiago Oscar , San Andrés Luis 
Published: August 2014

Squeeze film dampers (SFDs) are used in high speed rotating machinery to reduce rotor vibration amplitudes and to isolate transmitted loads through the bearing support structures. SFDs are also effective means to ameliorate destructive subsynchronous vibrations excited by hydrodynamic bearings, seals, impellers and other unknown sources. Modern jet engines demand lighter and flexible structures with compact components to obtain the largest power to weight ratios. This current trend makes evident rotordynamic phenomena that must be adequately addressed by dissipation elements such as SFDs.
Integral squeeze film dampers (ISFDs) incorporating built in elastic supports are of reduced weight and length, offer accuracy of positioning, and a split segment construction allowing easier assembly, inspection and retrofit. Yet ISFDs require of extensive experimentation to verify their dynamic forced performance and to prove their reliability for applications on high performance turbomachinery. Measurements of the synchronous response of a test rotor supported on ISFDs and due to couple-imbalances are hereby presented. Masses inserted at two axial planes in the rotor and out of phase by 180° excite the second (conical) mode of vibration of the test rotor. Peak rotor responses at the second critical speeds, vertical and horizontal, allow the determination of amplification factors from which system damping coefficients for the rotor conical motions are extracted. The measurements verify the damping capacity of ISFDs to reduce (conical mode) rotor vibrations.
Unsteady Flow Phenomena in a Centrifugal Compressor Channel Diffuser
Authors: Kang Jeong-Seek , Cho Sung-Kook , Kang Shin-Hyoung 
Published: August 2014

The aim of this paper is to understand the time averaged pressure field and unsteady pressure patterns in a high speed centrifugal compressor channel diffuser. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed for various flow conditions. Unsteady pressure signals from six fast-response sensors in the channel diffuser are analyzed by decomposition method and wavelet transform. Measured results are shown for various operating condition from choke to surge that the effect of operating condition is well discussed.
The strong non-uniformity in the pressure distribution is obtained over the diffuser shroud wall caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.
The pressure ratio waveforms by blade passing show regular oscillation not only for the normal but also for the surge conditions and the high frequency fluctuations are superposed on the oscillating pressure waveform as the flow rate increases. Periodic unsteadiness by blade passing does not decay in the diffuser channel. It depends on the operating point and is generally larger in the channel than in the vaneless space. Aperiodic unsteadiness rapidly decrease downstream of diffuser channel.
At surge, the spectrum becomes broad banded with peaks at the surge frequency as well as blade passage frequency and the impeller rotating frequency. The surge signal was analyzed using wavelet transform and it is found that surge signal is composed of not only surge scale and blade scale but also multi-scale aperiodic waves. The broadband spectrum in surge condition is due to this multi-scale aperiodic waves.
CFD Analysis of Unsteady Flow Interactions in a Centrifugal Compressor Stage
Authors: Koumoutsos A. , Tourlidakis A. , Elder R. L. 
Published: August 2014

This paper describes the unsteady flow analysis in a centrifugal compressor stage using a three dimensional CFD algorithm. The flow unsteadiness arising from the interaction between the impeller and the diffuser has been analysed using an algorithm suitable for equal or multiple number of rotor and diffuser blades.
The multi-block, structured grid CFD code TASCflow was used as a basis and algorithm development was undertaken to provide the required capability of modelling the unsteady interactions of the impeller and the diffuser.
The centrifugal compressor stage studied consists of an impeller with splitters and a vaned diffuser. The results presented are for off-design flow conditions where some experimental results were available for comparison. The results obtained for the steady-state model show a good agreement with the measurements.
In general the unsteady flow field obtained show a reasonable agreement with experimental data and demonstrates significant differences when compared to the steady state results especially in terms of the velocity field. A detailed analysis of the unsteady flow field is carried out using Fourier transforms of velocity and pressure at various locations of the flow field and the level of unsteadiness is determined as distributed to various frequencies. The unsteadiness in the impeller passage is much less than in the diffuser where a strong coupling is predicted in the vaneless space.