bluuebunny/crossref_metadata_2025_split huggingface dataset:
Past, Present and Future of Combined Cycle Power Plants: From an A/E’s Perspective
Authors: Singh Anup 
Published: July 2014

In the 1970s, power generation from gas turbines was minimal. Gas turbines in those days were run on fuel oil, since there was a so-called “natural gas shortage”. The U.S. Fuel Use Act of 1978 essentially disallowed the use of natural gas for power generation. Hence there was no incentive on the part of gas turbine manufacturers to invest in the development of gas turbine technology.
There were many regulatory developments in the 1980s and 1990s, which led to the rapid growth in power generation from gas turbines. These developments included Public Utility Regulatory Policy Act of 1978 (encouraging cogeneration), FERC Order 636 (deregulating natural gas industry), Energy Policy Act of 1992 (creating EWGs and IPPs) and FERC Order 888 (open access to electrical transmission system). There was also a backlash from excessive electric rates due to high capital recovery of nuclear and coal-fired plant costs caused by tremendous cost increase resulting from tightening NRC requirements for nuclear plants and significant SO2/NOx/other emissions controls required for coal-fired plants. During this period, rapid technology developments took place in the metallurgy, design, efficiency, and reliability of gas turbines. In addition, U.S. DOE contributed to these developments by encouraging research and development efforts in high temperature and high efficiency gas turbines.
Today we are seeing a tremendous explosion of power generating facilities by electric utilities and Independent Power Producers (IPPs). A few years ago, Merchant Power (generation without power purchase agreements) was unheard of. Today it is growing at a very fast pace. Can this rapid growth be sustained? The paper will explore the factors that will play a significant role in the future growth of gas turbine-based power generation in the U.S. The paper will also discuss the methods and developments that could decrease the capital costs of gas turbine power plants resulting in the lowest cost generation compared to other power generation technologies.
Computational Study of Clocking an Embedded Stage in a 4-Stage Industrial Turbine
Authors: Dorney D. J. , Croft R. R. , Sondak D. L. , Stang U. E. , Twardochleb C. Z. 
Published: July 2014

Multi-stage turbines have inherently unsteady flow fields because of relative motion between rotating and stationary airfoil rows. This relative motion leads to viscous and inviscid interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of airfoils in adjacent rotating or non-rotating blade rows can alter these interactions, leading to different time-averaged losses and stage efficiencies. In addition, interaction between blade rows can intensify with increasing Mach number due to potential effects.
It has been shown in previous studies, both experimental and computational, that airfoil clocking can be used to improve the efficiency and reduce the unsteadiness in multiple-stage axial turbomachines with equal blade counts. While previous investigations have for the most part focused on two-stage turbines, the goal of the current research is to evaluate the effects of clocking an embedded stage within a larger turbine system. Quasi-three-dimensional simulations of airfoil clocking have been performed for a four-stage industrial turbine. Time-averaged and unsteady data (including performance quantities) are presented. The results show a 0.5% efficiency variation in the stage where the vanes were clocked, and smaller efficiency variations in the upstream and downstream stages. The overall efficiency of the turbine system varies with the efficiency of the clocked stage, although by a smaller amount.
Liquid Phase Diffusion Bond Repair of Siemens V84.2, Row 2 Vanes and Alstom Tornado, 2nd Stage Stator Segments
Authors: Miglietti Warren M. , Kearney John , Pabon Luis 
Published: July 2014

During the industrial turbine engine operation of the Siemens V84.2, Row 2 vanes, and the Alstom Tornado, 2nd stage stator segments, “craze-cracking” and isolated thermal fatigue cracks develop during engine operation. Other damages found include pitting and dents resulting from corrosion/erosion and FOD (foreign object damage), respectively. Erosion and oxidation damage is also commonly found on the airfoils. This paper describes the vacuum LPDB (liquid phase diffusion bond) repair process used to repair all of the above-mentioned damage.
As a means of qualifying the high temperature diffusion bond process, both metallurgical and mechanical property evaluations were carried out. The metallurgical evaluation consisted of optical and scanning electron microscopy. The wide gap diffusion bonded area consisted of a fine-grained structure with intermetallic phases dispersed both intergranularly and intragranularly. An Energy Dispersive X-ray analysis was also conducted and the results are reported.
The chemistry of the repaired area is similar to the base metal which may explain why mechanical tests revealed properties equivalent to that of the base metal. The mechanical evaluations undertaken were tensile tests at room temperature and elevated temperature, as well as stress rupture tests. These results were equivalent to mechanical properties of the IN738 and IN939 Ni-based superalloys, which is the base metal that the above mentioned vanes and stator segments are manufactured from.
Development of the Advanced Combustor Liner Composed of CMC/GMC Hybrid Composite Material
Authors: Igashira Ken-ichiroh , Matsubara Go , Matsuda Yoshihiro , Imamura Akira 
Published: July 2014

Research Institute of Advanced Materials Gas-Generator (AMG), a joint effort by the Japan Key Technology Center and 14 companies in Japan, has, since 1993, been conducting technological studies on an innovative gas generator that will use 20% less fuel, weigh 50% less, and emit 70% less NOx than the conventional gas generator through the use of advanced materials[1].
In the course of R&D, the feasibility of applying a gradient composite material with ceramic matrix composite (CMC) and glass matrix composite (GMC), which is expected to reduce the thermal stress of actual parts with temperature distribution, was evaluated based on its mechanical and thermal properties, productivity and stress analysis for an actual part as a combustor liner with 500 mm diameter, and non-cooled combustion tests for the liner outlet temperature of 1873 K.
Through our studies we have confirmed the applicability of the selected CMC/GMC hybrid composite as a combustor liner.
Development of the Hybrid Gas Turbine: 1st Year Summary — Research and Development on Practical Industrial Cogeneration Technology in Japan
Authors: Tanaka Ryozo , Tastumi Testuo , Ichikawa Yoshihiro , Sanbonsugi Koji 
Published: July 2014

Based on the successful results of the Japanese national project for 300 kW ceramic gas turbine(CGT302) development (this project was finished in March 1999), the Ministry of International Trade and Industry (MITI) started “Research and Development on Practical Industrial Co-generation Technology” project in August 1999.
The objective of this project is to encourage prompt industrial applications of co-generation technology that employs hybrid gas turbines (HGT; using both metal and ceramic parts in its high-temperature section) by confirming its soundness and reliability.
The development activities are performed through material evaluation tests and long-term operation tests for the HGT of the medium size (8,000-kW class). It is expected that the development can realize low pollution and reducing the emission of CO2 with highly efficient use of energy. The HGT will be developed by applying ceramic components to an existing commercial 7,000-kW class gas turbine.
The development targets are thermal efficiency of 34% or higher, output of 8,000-kW class, inlet temperature of 1250deg-C, and 4,000hrs of operation period for confirmation of reliability. The HGT for long-term evaluation tests and the test plant are under development. This paper gives the summary of last year’s developments in the HGT project.
Development and Evaluation of Ceramic Components for 8000-kW Class Hybrid Gas Turbine
Authors: Tsuruzono Sazo , Yoshida Makoto , Kubo Toshifumi , Ono Takashi , Fukudome Takero 
Published: July 2014

An 8000 kW class hybrid gas turbine (HGT) project, administered by the New Energy and Industrial Technology Development Organization (NEDO) and sponsored by the Ministry of International Trade and Industry (MITI), has been started in July 1999 in Japan[1]. The target of this project is improvement in thermal efficiency and output power by using ceramic components, and earlier commercialization of the gas turbine system. Ceramic components are used for stationary parts subjected to high temperature, such as combustor liners, transition ducts, and first stage turbine nozzles. The gas turbine development was conducted in cooperation with Kawasaki Heavy Industries, Ltd. (KHI).
Kyocera started a study on fabricating the ceramic HGT components after evaluating their shape, placement, and fabrication methods. For these ceramic components, we are using the SN282 silicon nitride material developed and used for ceramic gas turbine components in the previous ceramic gas turbine project (300kW CGT)[2-4]. We have started to accumulate the strength evaluation data, using test bars cut from the aforementioned components, and begun long term tensile creep testing to confirm the reliability of the ceramic components.
Analysis of a 115MW, 3-Shaft, Helium Brayton Cycle Using Nuclear Heat Source
Authors: Kumar K. Pradeep , Tourlidakis A. , Pilidis P. 
Published: July 2014

This paper describes the steady state performance analysis of a 3-shaft closed cycle helium turbine using nuclear heat source. The analysis is carried out using a computer program, which is specifically made for this cycle. The computer model was tested for various Turbine Entry Temperatures (TET) and absolute pressures. The analysis of the change was focused on the compressors, as these are relatively more critical than the rest of the equipments.
The change in TET triggered changes in shaft speed, mass flow rate, power output, absolute pressure etc. Adjustable guide vanes were used to study the operation with constant surge margin. The closed cycle was tested for various absolute pressures and it was established that the efficiency will not be affected in using the inventory control for the load variation.
Demand Based Reliability: A Proposed Measurement Approach
Authors: Steele Robert F. , DellaVilla Sal 
Published: July 2014

Significant change is taking place in the power generation market. We are witnessing structural change as we move to a deregulated and competitive global market. And we can also see significant technological change, as new products are driven towards improved efficiencies, greater output and environmental friendliness. Measuring the impact of these changes in terms of efficiency, output and reduced emissions is a straightforward exercise, and the ability to judge if the change has been positive is relatively objective.
However, these structural and technological changes have created challenges in terms of reliability and availability measurements.
• First, our measurement approach is obsolete and has no consideration for duty cycle… The demand, the mission profile, which must be achieved for the unit to meet its economic contribution value, is the single most important issue for power producers today.
• Second, if the measurements have no consideration for the demand that the unit must meet, then the measure is not tied to the profitability of the plant, and therefore the operators are forced to use non-standard measures to accommodate management reporting.
• And third, the strong relationship between effective plant operations and profitability demands “real time” data gathering from the unit control or plant DCS, and transformation of the data points into meaningful information for effective decision support, specifically related to the availability and reliability of systems, components, and the full plant, with a specific focus on measuring “demand” based availability and reliability.
This paper addresses the issue and the opportunities associated with developing both new standard for measuring demand related reliability and availability, as well as the focus on “real time” data capture.
Simulation of Temperature Field Redistribution Through Multistage Cooled Turbines
Authors: Granovski A. V. , Kostege M. K. , Ivanov M. Ja. , Nigmatullin R. Z. 
Published: July 2014

The paper presents the detail investigation of temperature field evolution through multistage cooled turbines. An investigation bases on simple enough numerical simulation and allows for transient, heat transfer, viscous and some other important effects on temperature field transformation. Herewith the special test data for a number of cooled turbines are used.
The developed numerical code has the following peculiarities:
- a time-marching method for the unsteady Euler equation system;
- a special algorithm of flow parameters averaging in mixing planes in the middle of axial gaps;
- a monotone implicit scheme of second or third order accuracy in space and time.
The code has been used for a numerical study of the flow pattern in a number of multistage aviation and industrial turbines. The described simulation demonstrates satisfactory correlation between the numerical and experimental data for temperature gradient attenuation in the flowpath of investigated cooled turbines.
Gas Path Blade Tip Seals: Abradable Seal Material Testing at Utility Gas and Steam Turbine Operating Conditions
Authors: Chappel Douglas E. , Vo Ly , Howe Harold W. 
Published: July 2014

Abradable seals have long been used to enhance turbomachinery performance by limiting blade tip leakage losses. Most of the literature regarding this subject has focused on aerospace gas turbine materials and conditions. Furthermore, testing and evaluation described in this literature has been conducted on disparate rigs, making direct comparison among the abradable materials investigated difficult.
This study broadens the scope of available data by evaluating fibermetal, thermal-sprayed and honeycomb abradable materials at conditions found in utility gas turbine compressors and steam turbines. High speed rub interaction, low speed rub interaction and erosion data were collected and are discussed in detail.
High-Temperature Fatigue Properties of Single Crystal Superalloys in Air and Hydrogen
Authors: Arakere Nagaraj K. 
Published: July 2014

Hot section components in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys such as PWA1480, PWA1484, CMSX-4 and Rene N-4 as these materials provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over their polycrystalline counterparts. Fatigue failures in PWA1480 single crystal nickel-base superalloy turbine blades used in the Space Shuttle Main Engine (SSME) fuel turbopump are discussed. During testing many turbine blades experienced Stage II non-crystallographic fatigue cracks with multiple origins at the core leading edge radius and extending down the airfoil span along the core surface. The longer cracks transitioned from stage II fatigue to crystallographic stage I fatigue propagation, on octahedral planes. An investigation of crack depths on the population of blades as a function of secondary crystallographic orientation (β) revealed that for β = 45+/- 15 degrees tip cracks arrested after some growth or did not initiate at all. Finite element analysis of stress response at the blade tip, as a function of primary and secondary crystal orientation, revealed that there are preferential β orientations for which crack growth is minimized at the blade tip.
To assess blade fatigue life and durability extensive testing of uniaxial single crystal specimens with different orientations has been tested over a wide temperature range in air and hydrogen. A detailed analysis of the experimentally determined Low Cycle Fatigue (LCF) properties for PWA1480 and SC 7-14-6 single crystal materials as a function of specimen crystallographic orientation is presented at high temperature (75 F – 1800 F) in high-pressure hydrogen and air. Fatigue failure parameters are investigated for LCF data of single crystal material based on the shear stress amplitudes on the 24 octahedral and 6 cube slip systems for FCC single crystals. The max shear stress amplitude [Δτmax] on the slip planes reduces the scatter in the LCF data and is found to be a good fatigue damage parameter, especially at elevated temperatures. The parameter Δτmax did not characterize the room temperature LCF data in high-pressure hydrogen well because of the noncrystallographic eutectic failure mechanism activated by hydrogen at room temperature. Fatigue life equations are developed for various temperature ranges and environmental conditions based on power-law curve fits of the failure parameter with LCF test data. These curve fits can be used for assessing blade fatigue life.
Antivirulence Activity of the Human Gut Metabolome
Authors: Antunes L. Caetano M. , McDonald Julie A. K. , Schroeter Kathleen , Carlucci Christian , Ferreira Rosana B. R. , Wang Melody , Yurist-Doutsch Sophie , Hira Gill , Jacobson Kevan , Davies Julian , Allen-Vercoe Emma , Finlay B. Brett 
Published: July 2014

ABSTRACT

The mammalian gut contains a complex assembly of commensal microbes termed microbiota. Although much has been learned about the role of these microbes in health, the mechanisms underlying these functions are ill defined. We have recently shown that the mammalian gut contains thousands of small molecules, most of which are currently unidentified. Therefore, we hypothesized that these molecules function as chemical cues used by hosts and microbes during their interactions in health and disease. Thus, a search was initiated to identify molecules produced by the microbiota that are sensed by pathogens. We found that a secreted molecule produced by clostridia acts as a strong repressor of
Salmonella
virulence, obliterating expression of the
Salmonella
pathogenicity island 1 as well as host cell invasion. It has been known for decades that the microbiota protects its hosts from invading pathogens, and these data suggest that chemical sensing may be involved in this phenomenon. Further investigations should reveal the exact biological role of this molecule as well as its therapeutic potential.

IMPORTANCE
Microbes can communicate through the production and sensing of small molecules. Within the complex ecosystem formed by commensal microbes living in and on the human body, it is likely that these molecular messages are used extensively during the interactions between different microbial species as well as with host cells. Deciphering such a molecular dialect will be fundamental to our understanding of host-microbe interactions in health and disease and may prove useful for the design of new therapeutic strategies that target these mechanisms of communication.
Inactivation of
thyA
in Staphylococcus aureus Attenuates Virulence and Has a Strong Impact on Metabolism and Virulence Gene Expression
Authors: Kriegeskorte Andre , Block Desiree , Drescher Mike , Windmüller Nadine , Mellmann Alexander , Baum Cathrin , Neumann Claudia , Lorè Nicola Ivan , Bragonzi Alessandra , Liebau Eva , Hertel Patrick , Seggewiss Jochen , Becker Karsten , Proctor Richard A. , Peters Georg , Kahl Barbara C. 
Published: July 2014

ABSTRACT

Staphylococcus aureus
thymidine-dependent small-colony variants (TD-SCVs) are frequently isolated from patients with chronic
S. aureus
infections after long-term treatment with trimethoprim-sulfamethoxazole (TMP-SMX). While it has been shown that TD-SCVs were associated with mutations in thymidylate synthase (TS;
thyA
), the impact of such mutations on protein function is lacking. In this study, we showed that mutations in
thyA
were leading to inactivity of TS proteins, and TS inactivity led to tremendous impact on
S. aureus
physiology and virulence. Whole DNA microarray analysis of the constructed Δ
thyA
mutant identified severe alterations compared to the wild type. Important virulence regulators (
agr
,
arlRS
,
sarA
) and major virulence determinants (
hla
,
hlb
,
sspAB
, and
geh
) were downregulated, while genes important for colonization (
fnbA
,
fnbB
,
spa
,
clfB
,
sdrC
, and
sdrD
) were upregulated. The expression of genes involved in pyrimidine and purine metabolism and nucleotide interconversion changed significantly. NupC was identified as a major nucleoside transporter, which supported growth of the mutant during TMP-SMX exposure by uptake of extracellular thymidine. The Δ
thyA
mutant was strongly attenuated in virulence models, including a
Caenorhabditis elegans
killing model and an acute pneumonia mouse model. This study identified inactivation of TS as the molecular basis of clinical TD-SCV and showed that
thyA
activity has a major role for
S. aureus
virulence and physiology.

IMPORTANCE
Thymidine-dependent small-colony variants (TD-SCVs) of
Staphylococcus aureus
carry mutations in the thymidylate synthase (TS) gene (
thyA
) responsible for
de novo
synthesis of thymidylate, which is essential for DNA synthesis. TD-SCVs have been isolated from patients treated for long periods with trimethoprim-sulfamethoxazole (TMP-SMX) and are associated with chronic and recurrent infections. In the era of community-associated methicillin-resistant
S. aureus
, the therapeutic use of TMP-SMX is increasing. Today, the emergence of TD-SCVs is still underestimated due to misidentification in the diagnostic laboratory. This study showed for the first time that mutational inactivation of TS is the molecular basis for the TD-SCV phenotype and that TS inactivation has a strong impact on
S. aureus
virulence and physiology. Our study helps to understand the clinical nature of TD-SCVs, which emerge frequently once patients are treated with TMP-SMX.