bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Blade-Row Spacing on the Flow Capacity of a Transonic Rotor
Authors: Chriss Randall M. , Copenhaver William W. , Gorrell Steven E. 
Published: December 2014

Results from the ongoing Air Force Stage Matching Investigation are presented. In the present work the effect of upstream blade row wakes on the flow capacity of a downstream stage (where the rotor sets the choking flow) is investigated. An embedded stage was simulated by placing a set of wake generators (similar to inlet guide vanes) in front of a highly loaded single stage transonic core compressor. The wake generator-to-rotor axial spacing was varied in addition to the vane count. A complete parametric test matrix was completed in order to determine which parameters were important to the choking flow capacity.
The results show that for axial spacings above 50% of the upstream axial blade chord, simple wake mixing alone fully accounts for the upstream flow losses and a simple mass flow rate correction based on the rotor face mass averaged total pressure is sufficient. At spacings closer than this, other effects or loss mechanisms may be present. If these loss sources do exist, they are of unknown origin and magnitude and so an embedded overflow condition for these spacings cannot be ruled out. Research is ongoing that will attempt to identify and clarify the relevant details associated with these close blade row spacings.
Total Operating Activities of Gas Turbine Components — Total Equivalent Operating Hours (TEOH)
Authors: Lee Jung-Ho 
Published: December 2014

Timely inspection and maintenance are essential requirements in maintaining the high Reliability, Availability and Maintainability (RAM) of gas turbine units. The timing of inspections is determined by using the concept of the amount of accumulated operating activities of units between the inspection intervals. In tradition, operating hours and number of startups are used to measure these activities. Indeed, they are two major factors of the activities.
Gas turbines in general run in various duties, environments and operation modes. Under these conditions, it is important to have a well-defined tool and correctly quantified total operating activities of components to plan for timely inspection and refurbishment.
In this paper, the single parameter of Total Equivalent Operating Hours (TEOH) is proposed to be used as a tool to serve the purpose. In developing the TEOH, the linear fraction rule of damage, a theory of interaction fraction rule of damage, a theory of interaction between the creep and fatigue damages is applied to find the equivalent operating hours from the number of startups.
A Reduced Order Model of Mistuning Using a Subset of Nominal System Modes
Authors: Yang M.-T. , Griffin J. H. 
Published: December 2014

Reduced order models have been reported in the literature that can be used to predict the harmonic response of mistuned bladed disks. It has been shown that in many cases they exhibit structural fidelity comparable to a finite element analysis of the full bladed disk system while offering a significant improvement in computational efficiency. In these models the blades and disk are treated as distinct substructures.
This paper presents a new, simpler approach for developing reduced order models in which the modes of the mistuned system are represented in terms of a sub-set of nominal system modes. It has the following attributes: the input requirements are relatively easy to generate; it accurately predicts mistuning effects in regions where frequency veering occurs; as the number of degrees of freedom increases it converges to the exact solution; it accurately predicts stresses as well as displacements; and it accurately models the deformation and stresses at the blades’ bases.
Steady-State and Transient Performance Simulation of a Turboshaft Engine With Free Power Turbine
Authors: Kong Changduk , Ki Jayoung , Koh Kwangwoong 
Published: December 2014

Steady-state and transient performance analysis programs for 200kw-class small turboshaft engine with free power turbine were developed. An existing turbojet engine was used for the gas generator of the developed turboshaft engine, and it was modified to satisfy performance requirements of this turboshaft engine. To verify the availability of steady-state performance program for this engine: the program was applied to the same type gas turbine test unit, and the analysis results were compared to experimental results.
The developed transient performance analysis program using the CMF (Constant Mass flow) method was utilized to analysis in the cases of fuel step increase and the ramp increase.
Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths
Authors: Rhode David L. , Allen Brian F. 
Published: December 2014

The effect of rounded labyrinth teeth tips and worn abradable lands has been found to give substantially increased leakage, which is well known to give reduced machine efficiency. Very little information concerning this exists, and some of the first measurements and visualization movies for stepped labyrinths are provided here to give an enhanced understanding of this phenomenon. A unique, very large-scale seal test facility was used. Glitter, and alternatively fluorescein dye, was employed as the flow tracer material. The flow visualization movies were digitally stored on the hard drive of a computer.
Large decreases of leakage resistance due to the presence of worn teeth as well as rub-grooves were found. For the cases considered, the leakage resistance decrease for the large step height configurations were 85 percent, 55 percent and 70 percent for the small, medium and large pre-rub clearances, respectively. It was also found that the resistance varied with wear geometry, in order from highest to lowest resistance, as: (a) ungrooved-unrounded-teeth, (b) ungrooved-rounded-teeth, (c) grooved-unrounded-teeth and (d) grooved-rounded-teeth. Further, a substantial tooth tip recirculation zone was visually observed only for the grooved-unrounded-teeth cases, and it was shown to be the mechanism by which the unrounded teeth give this configuration a higher resistance than do the rounded teeth.
Improved Operating Efficiency Through the Use of Stabilized Thermocouples
Authors: Jablin Jeff , Storar Michael R. , Gray Phillip L. 
Published: December 2014

The development of a “stabilized” temperature sensor has led to significant increases in turbine operating efficiency by maximizing output when compared with present sensor technology. These stabilized type K and E thermocouples are superior to existing standard non-stabilized thermocouples because they are not prone to the typical aging effects in the 400 to 600°C (752 to 1112°F) temperature range that can result in measurement errors.
A complete set of 18 stabilized type K thermocouples were installed on the exhaust of several gas turbines used for power generation. These thermocouples were subjected to normal operating conditions for a period of one year. During that year, the increase in turbine output has ranged from 0.5% to almost 2.0%. This increase in output also translates into significant cost savings. In addition, the stabilized thermocouples have given the turbine maintenance technicians more confidence in the accuracy of their temperature measurements and resulted in improved troubleshooting and decision making.
Experimental Investigation of the Aerodynamic Stability of an Annular Compressor Cascade Performing Tuned Pitching Oscillations in Transonic Flow
Authors: Hennings H. , Belz J. 
Published: December 2014

A prerequisite for aeroelastic stability investigations on vibrating compressor cascades is the detailed knowledge of the unsteady aerodynamic loads acting on the blades. In order to obtain precise insight into the aerodynamic damping of a vibrating blade assembly, a basic experiment was performed where unsteady pressure distributions were measured for subsonic and transonic flow conditions.
The experiments were performed on a non-rotating, two-dimensional section of a compressor cascade in an annular test facility. The cascade consists of 20 blades (NACA3506 profile) mounted on elastic spring suspensions. In order to measure the unsteady pressure distribution, the cascade was set to tuned pitching oscillations (traveling wave modes). Each blade was driven to controlled harmonic torsional motions around midchord by a magnetic excitation system and by inductive displacement probes which measure the feedback signal of the motion. Steady and unsteady pressures were measured by steady pressure taps and piezo-electric pressure transducers, respectively. The measurement of the unsteady aerodynamic response to a shock vibrating on the suction side of the blades was enabled by a dense spacing of transducers in this region.
The global aerodynamic stability is assessed by a damping coefficient evaluated from the out-of-phase parts of the unsteady moment coefficients and by the contributions from the local work coefficient, using the measured pressure data.
Hybrid Gas Turbine and Fuel Cell Systems in Perspective Review
Authors: White David J. 
Published: December 2014

The concept of hybrids combining fuel cell and gas turbine systems is without question neoteric, and probably is less than eight years old. However, this concept is in a sense a logical development derived from the many early systems that embodied the key features of rotating machinery to compress air. It was the introduction of high temperature fuel cells such as the solid oxide fuel cell (SOFC) that allowed the concept of hybrid gas turbine fuel cell systems to take root. The SOFC with an operating temperature circa 1000° C matched well with small industrial gas turbines that had firing temperatures on the same order.
The recognition that the SOFC could be substituted for the gas turbine combustor was the first step into the realm of fuel cell topping systems. Fuel cells in general were recognized as having higher efficiencies at elevated pressures. Thus the hybrid topping system where the gas turbine pressurized the fuel cell and the fuel cell supplied the hot gases for expansion over the turbine promised to provide a high level of synergy between the two systems.
Bottoming systems using the exhaust of a gas turbine as the working fluid of a fuel cell such as the molten carbonate fuel cell (MCFC) have been identified and are potential future power generation hybrid systems. The MCFC is especially well suited to the bottoming role because of the need to have carbon dioxide present in the inlet air stream. The carbon dioxide in the gas turbine exhaust allows the high temperature blower, normally used to recirculate and inject exhaust products into the inlet air, to be eliminated.
Hybrid systems have the potential of achieving fossil fuel to electricity conversion efficiencies on the order of 70% and higher. The costs of hybrid systems in dollars per kilowatt are generally higher than say an advanced gas turbine that is available today but not by much. The net energy output over the life of a hybrid topping system is similar to that of a recuperated gas turbine but possibly lower than a high-efficiency simple-cycle machine, depending on the efficiency of the hybrid.
Methodologies to aid in the selection of the hybrid system for future development have to be developed and used consistently. Life cycle analyses (LFA) provide a framework for such selection processes. In particular the concept of net energy output provides a mechanism to assign relative worth to competing concepts.
Analysis of Transonic Flow Fields Inside a High Pressure Ratio Centrifugal Compressor at Design and Off Design Conditions
Authors: Hah Chunill , Krain Hartmut 
Published: December 2014

This paper reports on an experimental and numerical study of detailed flow structures in a transonic centrifugal compressor impeller at various operating conditions. Experimental data were obtained from conventional and laser-two-focus measurements inside the impeller. Numerical results were obtained from steady, three-dimensional Reynolds-averaged Navier-Stokes calculations. Both the experimental data and the numerical solutions at the design condition indicate that the flow incidence is high near the hub and flow separation exists near the leading edge. Due to the flow separation, low momentum fluid migrates rapidly to the tip area resulting in further loss generation through increased shock/boundary layer interaction. At a higher flow rate, a second passage shock develops near the leading edge of the splitter blade, further increasing shock/boundary layer interaction.
Numerical studies were performed to explore possible design modifications for better efficiency and higher pressure rise. First, the blade camber near the leading edge was modified to improve the incidence. Second, the blade thickness was reduced by 50 percent. The incidence modification eliminates the flow separation near the leading edge and makes a more uniform flow split between the two channels, resulting in better flow distribution at the impeller exit. The simulated blade thickness reduction, along with the modified incidence, improves the efficiency by about 5 percent and increases the impeller pressure rise from 6.1:1 to 7.1:1.
Potent Plasmodium falciparum Gametocytocidal Activity of Diaminonaphthoquinones, Lead Antimalarial Chemotypes Identified in an Antimalarial Compound Screen
Authors: Tanaka Takeshi Q , Guiguemde W. Armand , Barnett David S. , Maron Maxim I. , Min Jaeki , Connelly Michele C. , Suryadevara Praveen Kumar , Guy R. Kiplin , Williamson Kim C. 
Published: December 2014

ABSTRACT

Forty percent of the world's population is threatened by malaria, which is caused by
Plasmodium
parasites and results in an estimated 200 million clinical cases and 650,000 deaths each year. Drug resistance has been reported for all commonly used antimalarials and has prompted screens to identify new drug candidates. However, many of these new candidates have not been evaluated against the parasite stage responsible for transmission, gametocytes. If
Plasmodium falciparum
gametocytes are not eliminated, patients continue to spread malaria for weeks after asexual parasite clearance. Asymptomatic individuals can also harbor gametocyte burdens sufficient for transmission, and a safe, effective gametocytocidal agent could also be used in community-wide malaria control programs. Here, we identify 15 small molecules with nanomolar activity against late-stage gametocytes. Fourteen are diaminonaphthoquinones (DANQs), and one is a 2-imino-benzo[d]imidazole (IBI). One of the DANQs identified, SJ000030570, is a lead antimalarial candidate. In contrast, 94% of the 650 compounds tested are inactive against late-stage gametocytes. Consistent with the ineffectiveness of most approved antimalarials against gametocytes, of the 19 novel compounds with activity against known anti-asexual-stage targets, only 3 had any strong effect on gametocyte viability. These data demonstrate the distinct biology of the transmission stages and emphasize the importance of screening for gametocytocidal activity. The potent gametocytocidal activity of DANQ and IBI coupled with their efficacy against asexual parasites provides leads for the development of antimalarials with the potential to prevent both the symptoms and the spread of malaria.
Efficacy and Safety of Faldaprevir, Deleobuvir, and Ribavirin in Treatment-Naive Patients with Chronic Hepatitis C Virus Infection and Advanced Liver Fibrosis or Cirrhosis
Authors: Zeuzem Stefan , Soriano Vicente , Asselah Tarik , Gane Edward J. , Bronowicki Jean-Pierre , Angus Peter , Lohse Ansgar W. , Stickel Felix , Müllhaupt Beat , Roberts Stuart , Schuchmann Marcus , Manns Michael , Bourlière Marc , Buti Maria , Stern Jerry O. , Gallivan John-Paul , Voss Florian , Sabo John P. , Böcher Wulf , Mensa Federico J. 
Published: December 2014

ABSTRACTPatients with advanced hepatic fibrosis or cirrhosis with chronic hepatitis C virus (HCV) infection represent an unmet need. The HCV NS3/4A inhibitor, faldaprevir, was evaluated in combination with the nonnucleoside NS5B inhibitor, deleobuvir, with or without ribavirin in treatment-naive patients with HCV genotype 1 infection in the SOUND-C2 study. Here, the efficacy and safety of this interferon-free regimen in a subset of patients with advanced liver fibrosis, including those with compensated cirrhosis, were assessed. Patients (n= 362) were randomized to once-daily faldaprevir with either twice-daily (BID) or three-times-daily (TID) deleobuvir for 16 (TID16W), 28 (TID28W and BID28W), or 40 (TID40W) weeks with or without ribavirin (TID28W-NR). Patients were classified according to fibrosis stage (F0 to F2 versus F3 to F4) and the presence of cirrhosis (yes/no). In total, 85 (24%) patients had advanced fibrosis/cirrhosis (F3 to F4) and 33 (9%) had cirrhosis. Within each treatment arm, differences in rates of sustained virologic response 12 weeks after completion of treatment (SVR12) between patients with mild to moderate fibrosis (F0 to F2) versus F3 to F4 did not show a consistent pattern and were not statistically significant (63% versus 47% for TID16W, 53% versus 76% for TID28W, 48% versus 67% for TID40W, 70% versus 67% for BID28W, and 40% versus 36% for TID28W-NR, respectively;P> 0.05 for each arm). The most frequent adverse events in patients with/without cirrhosis were gastrointestinal and skin events, which were mostly mild or moderate in intensity. The degree of liver fibrosis did not appear to affect the probability of achieving SVR12 following treatment with the interferon-free regimen of faldaprevir, deleobuvir, and ribavirin. (This study has been registered at ClinicalTrials.gov under registration no. NCT01132313.)
In Vivo
Pharmacokinetics and Pharmacodynamics of the Lantibiotic NAI-107 in a Neutropenic Murine Thigh Infection Model
Authors: Lepak Alexander J. , Marchillo Karen , Craig William A. , Andes David R. 
Published: December 2014

ABSTRACT

NAI-107 is a novel lantibiotic compound with potent
in vitro
activity against Gram-positive bacteria, including methicillin-resistant
Staphylococcus aureus
(MRSA). The purpose of this study was to examine the activity of NAI-107 against
S. aureus
strains, including MRSA, in the neutropenic murine thigh infection model. Serum pharmacokinetics were determined and time-kill studies were performed following administration of single subcutaneous doses of 5, 20, and 80 mg/kg body weight. The dose fractionation included total doses ranging from 1.56 to 400 mg/kg/72 h, divided into 1, 2, 3, or 6 doses. Studies of treatment effects against 9
S. aureus
strains (4 methicillin-susceptible
Staphylococcus aureus
[MSSA] and 5 MRSA) using a 12-h dosing interval and total dose range of 1.56 to 400 mg/kg/72 h were also performed. A maximum effect (
E
max
) model was used to determine the pharmacokinetic/pharmacodynamic (PK/PD) index that best described the dose-response data and to estimate the doses required to achieve a net bacteriostatic dose (SD) and a 1-log reduction in CFU/thigh. The pharmacokinetic studies demonstrated an area under the concentration-time curve (AUC) range of 26.8 to 276 mg · h/liter and half-lives of 4.2 to 8.2 h. MICs ranged from 0.125 to 0.5 μg/ml. The 2 highest single doses produced more than a 2-log kill and prolonged postantibiotic effects (PAEs) ranging from 36 to >72 h. The dose fractionation-response curves were similar, and the AUC/MIC ratio was the most predictive PD index (AUC/MIC, coefficient of determination [
R
2
] = 0.89; maximum concentration of drug in serum [
C
max
]/MIC,
R
2
= 0.79; time [
T
] > MIC,
R
2
= 0.63). A ≥2-log kill was observed against all 9
S. aureus
strains. The total drug 24-h AUC/MIC values associated with stasis and a 1-log kill for the 9
S. aureus
strains were 371 ± 130 and 510 ± 227, respectively. NAI-107 demonstrated concentration-dependent killing and prolonged PAEs. The AUC/MIC ratio was the predictive PD index. Extensive killing was observed for
S. aureus
organisms, independent of the MRSA status. The AUC/MIC target should be useful for the design of clinical dosing regimens.
Postexposure Prophylactic Effect of Hepatitis B Virus (HBV)-Active Antiretroviral Therapy against HBV Infection
Authors: Watanabe Tsunamasa , Hamada-Tsutsumi Susumu , Yokomaku Yoshiyuki , Imamura Junji , Sugiura Wataru , Tanaka Yasuhito 
Published: December 2014

ABSTRACT

Retrospective study indicates that hepatitis B virus (HBV)-active nucleoside (nucleotide) analogues (NAs) used for antiretroviral therapy reduce the incidence of acute HBV infections in human immunodeficiency virus (HIV)-infected patients. Learning from HIV postexposure prophylaxis (PEP), we explored the possibility of using NAs in PEP following HBV exposure, if preexposure prophylaxis is feasible clinically. Using freshly isolated primary human hepatocytes cultured
in vitro
, we analyzed the effect of HBV-active tenofovir and lamivudine in primary HBV infection and also the effect of treatment with these NAs after HBV infection. HBV-active NAs applied from 24 h before inoculation could not prevent the secretion of hepatitis B surface antigen into the culture medium, and cessation of the NAs after inoculation allowed the cells to establish an apparent HBV infection. In contrast, hepatitis B immune globulin was able to prevent HBV infection completely. NA treatment before infection, however, can control the spread of HBV infection, as detected by immunohistochemistry. Practically, starting NA treatment within 2 days of primary HBV infection inhibited viral spread effectively, as well as preexposure treatment. We demonstrated that preexposure NA treatment was not able to prevent the acquisition of HBV infection but prevented viral spread by suppressing the production of mature progeny HBV virions. The effect of postexposure treatment within 2 days was similar to the effect of preexposure treatment, suggesting the possibility of HBV PEP using HBV-active NAs in HIV- and HBV-susceptible high-risk groups.
Overexpression of Penicillin V Acylase from Streptomyces lavendulae and Elucidation of Its Catalytic Residues
Authors: Torres-Bacete Jesús , Hormigo Daniel , Torres-Gúzman Raquel , Arroyo Miguel , Castillón María Pilar , García José Luis , Acebal Carmen , de la Mata Isabel 
Published: December 2014

ABSTRACTThepvagene fromStreptomyces lavendulaeATCC 13664, encoding a novel penicillin V acylase (SlPVA), has been isolated and characterized. The gene encodes an inactive precursor protein containing a secretion signal peptide that is activated by two internal autoproteolytic cleavages that release a 25-amino-acid linker peptide and two large domains of 18.79 kDa (α-subunit) and 60.09 kDa (β-subunit). Based on sequence alignments and the three-dimensional model ofSlPVA, the enzyme contains a hydrophobic pocket involved in catalytic activity, including Serβ1, Hisβ23, Valβ70, and Asnβ272, which were confirmed by site-directed mutagenesis studies. The heterologous expression ofpvainS. lividansled to the production of an extracellularly homogeneous heterodimeric enzyme at a 5-fold higher concentration (959 IU/liter) than in the original host and in a considerably shorter time. According to the catalytic properties ofSlPVA, the enzyme must be classified as a new member of the Ntn-hydrolase superfamily, which belongs to a novel subfamily of acylases that recognize substrates with long hydrophobic acyl chains and have biotechnological applications in semisynthetic antifungal production.