bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of enrofloxacin use in koalas (Phascolarctos cinereus) via population pharmacokinetics andMonteCarlo simulation
Authors: Black L. A. , Landersdorfer C. B. , Bulitta J. B. , Griffith J. E. , Govendir M.
Published: November 2013

Clinically normal koalas (n = 6) received a single dose of intravenous enrofloxacin (10 mg/kg). Serial plasma samples were collected over 24 h, and enrofloxacin concentrations were determined via high‐performance liquid chromatography. Population pharmacokinetic modeling was performed inS‐ADAPT. The probability of target attainment (PTA) was predicted via Monte Carlo simulations (MCS) using relevant target values (30–300) based on the unbound area under the curve over 24 h divided by the minimum inhibitory concentration (MIC) (fAUC0–24/MIC), and published subcutaneous data were incorporated (Griffithet al., 2010). A two‐compartment disposition model with allometrically scaled clearances (exponent: 0.75) and volumes of distribution (exponent: 1.0) adequately described the disposition of enrofloxacin. For 5.4 kg koalas (average weight), point estimates for total clearance (SE%) were 2.58 L/h (15%), central volume of distribution 0.249 L (14%), and peripheral volume 2.77 L (20%).MCSusing a targetfAUC0–24/MICof 40 predicted highest treatableMICs of 0.0625 mg/L for intravenous dosing and 0.0313 mg/L for subcutaneous dosing of 10 mg/kg enrofloxacin every 24 h. Thus, the frequently used dosage of 10 mg/kg enrofloxacin every 24 h subcutaneously may be appropriate against gram‐positive bacteria withMICs ≤ 0.03 mg/L (PTA > 90%), but appears inadequate against gram‐negative bacteria andChlamydiae in koalas.
The PI3K/Akt/mTOR axis in head and neck cancer: functions, aberrations, cross‐talk, and therapies
Authors: Vander Broek R , Mohan S , Eytan DF , Chen Z , Van Waes C
Published: November 2013

Head and neck squamous cell carcinoma (HNSCC) is one of the most morbid, mortal, and genetically diverse malignancies. Although HNSCC is heterogeneous in nature, alterations in major components of the PI3K/Akt/mTOR pathway are consistently observed throughout the majority of HNSCC cases. These alterations include genetic aberrations, such as mutations or DNA copy number variations, and dysregulation of mRNA or protein expression. In normal physiology, the PI3K/Akt/mTOR axis regulates cell survival, growth, and metabolism. However, alterations in this pathway lead to the malignant phenotype which characterizes HNSCC, among many other cancers. For this reason, both pharmaceutical companies and academic institutions are actively developing and investigating inhibitors of PI3K, Akt, and mTOR in preclinical and clinical studies of HNSCC. Many of these inhibitors have shown promise, while the effects of others are tempered by the mechanisms through which HNSCC can evade therapy. As such, current research aimed at elucidating the interactions between PI3K/Akt/mTOR and other important signaling pathways which may drive resistance in HNSCC, such as p53, NF‐κB, and MAPK, has become a prominent focus toward better understanding how to most effectively treat HNSCC.
The Impact of Modular Assembly on Supply Chain Efficiency
Authors: Feng Tianjun , Zhang Fuqiang
Published: November 2013

This article studies the impact of modular assembly on supply chain efficiency. In the modular assembly approach, a manufacturer acquires pre‐assembled modules from its suppliers, rather than the individual components, as in the traditional assembly approach. We analyze the competitive behavior of a two‐stage modular assembly system consisting of a manufacturer, and a supplier who pre‐assembles two components into a module. The firms can choose their own inventory policies and we show the existence of Nash equilibrium in the inventory game. Moving from the traditional to the modular approach has a twofold effect on the supply chain. First, we investigate the effect of centralizing the component suppliers. It can be shown that when there is no production time shift, the module supplier always holds more component inventories than suppliers do in the traditional approach, which yields a lower cost for the manufacturer. However, the suppliers, and therefore the supply chain may incur a higher cost in the modular approach. Second, we study the effect of a shift in production time from the manufacturing stage to the supplier stage. From numerical studies, it has been found that such a lead time shift always benefits a centralized supply chain, but not necessarily so for a decentralized system. Combining the two effects, we find that the modular approach generally reduces the cost to the manufacturer and the supply chain, which explains the prevalence of modular assembly from the perspective of inventory management. These results also provide some insight into how firms can improve supply chain efficiency by choosing the right decision structure and lead time configuration.
Scheduling of Multi‐skilled Staff Across Multiple Locations
Authors: Kuo Yong‐Hong , Leung Janny M.Y. , Yano Candace A.
Published: November 2013

We address the problem of assigning airline customer service agents (CSAs) to tasks related to departing flights, such as selling tickets and collecting boarding cards, at an international terminal of a large airport. The airline specifies minimum and target levels of staff and required (or desired) types and levels of skills for each location in each time period. The assignment problem is complicated by staff heterogeneity, time required for moves between locations, and lunch and rest‐break requirements. We present a mixed‐integer formulation that considers both staffing shortages and skills mismatches and show that the problem is NP‐hard. We derive valid inequalities that tighten the bounds within a branch‐and‐cut procedure, enabling us to obtain near‐optimal solutions for problems of realistic size very quickly. We also present a generalization to simultaneously optimize shift starting times and task assignments, which can aid in longer term workforce planning. Finally, we utilize our procedure to obtain managerial insights regarding the benefits of flexibility derived from more highly skilled staff, allowing more frequent moves, and choices of shift starting times. We also demonstrate the benefits of our procedure vs. a heuristic that mimics what an experienced scheduler might choose.
Epiphytic colonization of Ustilaginoidea virens on biotic and abiotic surfaces implies the widespread presence of primary inoculum for rice false smut disease
Authors: Fan J. , Guo X.‐Y. , Huang F. , Li Y. , Liu Y.‐F. , Li L. , Xu Y.‐J. , Zhao J.‐Q. , Xiong H. , Yu J.‐J. , Wang W.
Published: November 2013

Ustilaginoidea virens (Uv), the causative agent of rice false smut disease, infects developing rice spikelets at the booting stage, and transforms individual grains of the panicle into smut balls. Epidemics of the disease occur when the rice booting and heading stages coincide with rainy days. Using a green fluorescent protein (GFP)‐labelled Uv isolate that can form false smut balls on rice panicles, it was found that under high humidity and free water conditions the Uv isolate could colonize leaves of plants belonging to various families including the Poaceae (Oryza sativa, Echinochloa crusgalli, Digitaria sanguinalis and Leptochloa chinensis), the Brassicaceae (Arabidopsis thaliana) and the Solanaceae (Nicotiana benthamiana) without symptoms. Over several days, some conidia could germinate on the leaves of these plants and in water on the surface of Parafilm and cellophane, form hyphae and differentiate conidiophores to generate a large number of secondary conidia, while other conidia were able to directly produce secondary conidia. Conversely, in the absence of water some conidia could either bud to form new conidia or were converted into chlamydospores. These data indicate that Uv is one of a few fungal pathogens reported to have epiphytic characteristics. The rapid generation of a large number of spores on biotic and abiotic surfaces greatly increases the inoculum that can infect rice spikelets, resulting in the occurrence of rice false smut disease epidemics. These findings are important in the development of disease control strategies.
The Y123H substitution perturbs FvCYP51B function and confers prochloraz resistance in laboratory mutants of Fusarium verticillioides
Authors: Fan J. , Chen F. , Diao Y. , Cools H. J. , Kelly S. L. , Liu X.
Published: November 2013

Fusarium verticillioides reduces corn yield and contaminates infected kernels with the toxin fumonisin, which is harmful to humans and animals. Previous research has demonstrated that F. verticillioides can be controlled by the azole fungicide prochloraz. Currently, prochloraz is used as a foliar spray to control maize disease in China, which will increase the risk of resistance. Although F. verticillioides resistance to prochloraz has not been reported in the field, possible resistance risk and mechanisms resulting in prochloraz resistance were explored in the laboratory. Four prochloraz‐resistant strains of F. verticillioides were generated by successive selection on fungicide‐amended media. The mycelial growth rates of the mutants were inversely related to the level of resistance. All four mutants were cross‐resistant to the triazole fungicides triadimefon, tebuconazole and difenoconazole, but not to the multisite fungicide chlorothalonil or to the MAP/histidine‐kinase inhibitor fungicide fludioxonil. Based on the Y123H mutation in FvCYP51B, the four resistant mutants were subdivided into two genotypes: PCZ‐R1 mutants with wildtype FvCYP51B and PCZ‐R2 mutants with substitution Y123H in FvCYP51B. Wildtype FvCYP51B complemented the function of native ScCYP51 in Saccharomyces cerevisiae YUG37::erg11, whereas Y123H‐mutated FvCYP51B did not. For the PCZ‐R1 mutants, induced expression of FvCYP51A increased resistance to prochloraz. For the PCZ‐R2 mutants, disruption of FvCYP51B function by the Y123H substitution caused constitutive up‐regulation of FvCYP51A expression and thus resistance to prochloraz.
The Role of Emotion in Global Warming Policy Support and Opposition
Authors: Smith Nicholas , Leiserowitz Anthony
Published: November 2013

Prior research has found that affect and affective imagery strongly influence public support for global warming. This article extends this literature by exploring the separate influence of discrete emotions. Utilizing a nationally representative survey in the United States, this study found that discrete emotions were stronger predictors of global warming policy support than cultural worldviews, negative affect, image associations, or sociodemographic variables. In particular, worry, interest, and hope were strongly associated with increased policy support. The results contribute to experiential theories of risk information processing and suggest that discrete emotions play a significant role in public support for climate change policy. Implications for climate change communication are also discussed.
Bringing the Museum into the Classroom, and the Class into the Museum: An Approach for Content‐Based Instruction
Authors: Sederberg Kathryn
Published: November 2013

Through the example of a fourth‐semester course on modern German history, this article explores the application of interactive and experiential learning models inspired by museum pedagogy. In response to the ACTFL Standards and the 2007 MLA report, the teaching of culture has become a priority and educators continue to seek innovative ways to teach culture and to attain the goals of “comparisons” and “connections,” as well as translingual and transcultural competence. This article demonstrates that museum strategies can be productively transferred to content‐based foreign language instruction to provide learning experiences in which students interact critically with the objects of cultural archives. Both actual and virtual museum visits, as well as the integration of primary materials in the classroom, can further students' transcultural competence and critical thinking about the interrelations of culture and language, as well as provide intellectually and aesthetically engaging learning experiences.
STRUCTURAL AND FUNCTIONAL CHANGES RELEVANT TO MAXILLARY ARTERIAL FLOW OBSERVED DURING COMPUTED TOMOGRAPHY AND NONSELECTIVE DIGITAL SUBTRACTION ANGIOGRAPHY IN CATS WITH THE MOUTH CLOSED AND OPENED
Authors: Scrivani Peter V. , Martin‐Flores Manuel , van Hatten Ruth , Bezuidenhout Abraham J.
Published: November 2013

Some cats develop blindness during procedures with mouth gags, which possibly relates to maxillary arterial occlusion by opening the mouth. Our first aim was to use computed tomography (CT) to describe how vascular compression is possible based on morphologic differences between mouth positions. Our second aim was to use nonselective digital subtraction angiography to assess whether opening the mouth induces collateral circulation. Six healthy cats were examined. During CT, the maxillary artery coursed between the angular process of the mandible and the rostrolateral wall of the tympanic bulla. The median distance between these structures was shorter when the mouth was opened (left, 4.3 mm; right, 3.6 mm) vs. closed (left, 6.9 mm; right, 7.1 mm). Additionally, the distance was shorter on the side ipsilateral to the gag (P = 0.03). During nonselective angiography, with the mouth closed, there was strong sequential opacification of the external carotid arteries, maxillary arteries, maxillary retia mirabilia, cerebral arterial circle, and basilar artery. Additionally, there was uniform opacification of the cerebrum and cerebellum. With the mouth opened, opacification of the maxillary arteries (rostral to the angular processes) was reduced in all cats, the cerebral arterial circle and basilar artery had simultaneous opacification in four of six (67%) cats, and the cerebrum had reduced opacification compared to the cerebellum in four of six (67%). In conclusion, the maxillary arteries are situated such that they can be compressed when opening the mouth. Opening the mouth did not consistently induce collateral circulation sufficient to produce comparable cerebral opacification as when the mouth was closed.
Analysis of Flow and Heat Transfer Characteristics Around an Oval-Shaped Cylinder
Authors: Zhang Guan-Min , Tian Mao-Cheng , Zhou Nai-Xiang , Li Wei , Kukulka David
Published: November 2013

Numerical simulations and experimental study were carried out to investigate the flow and heat transfer characteristics of air flowing across different types of oval-shaped cylinders, for Reynolds numbers varying from 4000 to 50,000. These cylinders have axis ratios, ε, of 1, 1.5, 2, 3, 4, and 5 with the major axis parallel to the free-stream. Numerical results show the closer the distance to mainstream, the smaller the local velocity gradient is. The angular position of the minimum value of Cp decreases as ε decreases and the maximum value of Cf gradually increases with ε increasing. Oval-shaped cylinders have a higher favorable pressure gradient at the front of the cylinder and a lower adverse pressure gradient at the back of the cylinder for flows in inhibiting separation. Empirical correlations for each tube have been obtained by numerical simulation relating the dimensionless heat transfer coefficient with the Reynolds Number and Prandtl Number. Based on the presented results, it can be emphasized that the average heat transfer coefficient firstly increases and then decreases by increasing the axis ratio of the tube, implying that the elliptical tubes with a suitable axis ratio possess more advantages over circular tubes. Comparisons of the numerical results with the existing data verify the validation of the present study.
Compensation and Estimation of Friction by Using On-Line Input Estimation Algorithm
Authors: Jang Horng-Yuan , Luo Yong-Shun
Published: November 2013

In this paper, a compensation method of nonlinear friction using on-line input estimation (IE) method is developed. To illustrate the validity and performance of the proposed algorithm applied to positioning system, comparisons with the results using the Gomonwattanapanich method and robustness analysis are performed. The simulation result shows that the estimated friction torque does not need any assumption in the pattern of friction model in advance, the proposed algorithm has consistent robustness to diverse friction characteristics, and the method can significantly improve the performance of a control system.
Effect of Load Angle on Limit Load of Polyethylene Miter Pipe Bends1
Authors: EL-Bagory Tarek M. A. A. , Younan Maher Y. A. , Sallam Hossam E. M. , Abdel-Latif Lotfi A.
Published: November 2013

The aim of this paper is to investigate the effect of crack depth a/W = 0–0.4 and load angle (30 deg, 45 deg, and 60 deg) on the limit load of miter pipe bends (MPB) under out-of-plane bending moment with a crosshead speed 500 mm/min. The geometry of cracked and un-cracked multi miter pipe bends are: bend angle, α = 90 deg, pipe bend factor, h = 0.844, standard dimension ratio, SDR = 11, and three junctions, m = 3. The material of the investigated pipe is a high-density polyethylene (HDPE), which is applied in natural gas piping systems. Butt-fusion welding is used to produce the welds in the miter pipe bends. An artificial crack is produced by a special cracking device. The crack is located at the crown side of the miter pipe bend, such that the crack is collinear with the direction of the applied load. The crack depth ratio, a/W = 0, 0.1, 0.2, 0.3, and 0.4 for out-of-plane bending moment “i.e., loading angle ϕ = 0 deg”. For each out-of-plane bending moment and all closing and opening load angles the limit load is obtained by the tangent intersection method (TI) from the load deflection curves produced by the specially designed and constructed testing machine at the laboratory (Mechanical Design Department, Faculty of Engineering, Mataria, Helwan University, Cairo/Egypt). For each out-of-plane bending moment case, the experimental results reveals that increasing crack depth leads to a decrease in the stiffness and limit load of MPB. In case of combined load (out-of-plane and in-plane opening; mode) higher load angles lead to an increase in the limit load. The highest limit load value appears at a loading angle equal, ϕ = 60 deg. In case of combined load (out-of-plane and in-plane closing; mode) the limit load decreases upon increasing the load angle. On the other hand, higher limit load values appear at a specific loading angle equal ϕ = 30 deg. For combined load opening case; higher values of limit load are obtained. Contrarily, lower values are obtained in the closing case.
Mistuning Modeling and its Validation for Small Turbine Wheels
Authors: Hemberger David , Filsinger Dietmar , Bauer Hans-Jörg
Published: November 2013

The production of bladed structures, e.g. turbine and compressor wheels, is a subject of statistical scatter. The blades are designed to be identical but differ due to small manufacturing tolerances. This so called mistuning can lead to increased vibration amplitudes compared to the ideal tuned case.

The object of this study is to create and validate numerical models to evaluate such mistuning effects of turbine wheels for automotive turbocharger applications. As a basis for the numerical analysis vibration measurements under stand-still conditions were carried out by using a laser surface velocimeter (LSV). The scope of this investigation was to identify the mistuning properties of the turbine wheels namely the frequency deviation from the ideal, cyclic symmetrical tuned system. Experimental modal analyses as well as blade by blade measurements were performed. Moreover 3D scanning techniques were employed to determine geometric deviations.

Numerical FE models and a simplified multi degree of freedom model (EBM) were created to reproduce the measured mistuning effects. The prediction of mode localization and the calculated amplitude amplification were evaluated. The best results were obtained with a FE model that employs individual sectorial stiffnesses. The results also indicate that the major contribution to mistuning is made by material inhomogeneities and not by geometric deviations from ideal dimensions.

With the adjusted FE model a probabilistic study has been performed to investigate the influence of the mistuning on the amplitude amplification factor. It has been found that at a certain level of mistuning the amplification factor remains constant or slightly decreases. By introducing intentional mistuning a lower sensitivity as well as a decrease of the amplitude amplification could be achieved.
Flutter Amplitude Saturation by Nonlinear Friction Forces: An Asymptotic Approach
Authors: Martel C. , Corral R.
Published: November 2013

The computation of the friction saturated vibratory response of an aerodynamically unstable bladed-disk in a realistic configuration is a formidable numerical task, even for the simplified case of assuming the aerodynamic forces to be linear. The non-linear friction forces effectively couple different traveling waves modes and, in order to properly capture the dynamics of the system, large time simulations are typically required to reach a final, saturated state. Despite of all the above complications, the output of the system (in the friction microslip regime) is not that complex: it typically consists of a superposition of the aeroelastic unstable traveling waves, which oscillate at the elastic modal frequency and exhibit also a modulation in a much longer time scale. This large time modulation over the purely elastic oscillation is due to both, the small aerodynamic effects and the small nonlinear friction forces. The correct computation of these two small effects (small as compared with the elastic forces) is crucial to determine the final amplitude of the flutter vibration, which basically results from its balance. In this work we apply asymptotic techniques to obtain a new simplified model that gives only the slow time dynamics of the amplitudes of the traveling waves, filtering out the fast elastic oscillation. The resulting asymptotic model is very reduced and extremely cheap to simulate, and it has the advantage that it gives precise information about how the nonlinear friction at the fir-tree actually acts in the process of saturation of the vibration amplitude.
Stability Characteristics of Steam Turbine Rotor Seal System With Analytical Floating Ring Seal Force Model
Authors: Zhang Guang-hui , Wang Gui-long , Liu Zhan-sheng , Ma Rui-xian
Published: November 2013

The analytical oil film force model for floating ring seal is established including the effect of axial pressure gradient. The analytical model is based on the oil lubricated Reynolds equation and the short bearing assumption, where the fluid Lomakin effect is considered. The pressure distribution of the floating ring and static characteristics is studied by numerical simulation. The three dimensional flow model is established and solved by the CFD method. By employing the finite element method, the dynamic model of the floating ring seal-steam turbine rotor system is established. The critical speed, mode shape and dynamic response of the steam turbine rotor with different bearing support stiffness are obtained. The effect of the floating ring oil film force on the critical speed and instability speed with different bearing support stiffness is studied. The effects of floating ring parameters (groove geometrical dimensions) on dynamic response are studied, and the stability of floating ring seal-rotor system with variation of the factor is analyzed. The floating ring seal can play the role of increasing the supporting effect, which will increase the critical speed of the rotor system. The floating ring seal can cause the sub synchronous vibration and the groove can significantly increase the stability of system.
Small Horizontal Axis Wind Turbine: Analytical Blade Design and Comparison With RANS-Prediction and First Experimental Data
Authors: Gerhard Tom , Sturm Michael , Carolus Thomas H.
Published: November 2013

State-of-the-art wind turbine performance prediction is mainly based on semi-analytical models, incorporating blade element momentum (BEM) analysis and empirical models. Full numerical simulation methods can yield the performance of a wind turbine without empirical assumptions. Inherent difficulties are the large computational domain required to capture all effects of the unbounded ambient flow field and the fact that the boundary layer on the blade may be transitional.

A modified turbine design method in terms of the velocity triangles, Euler’s turbine equation and BEM is developed. Lift and drag coefficients are obtained from XFOIL, an open source 2D design and analysis tool for subcritical airfoils. A 3 m diameter horizontal axis wind turbine rotor was designed and manufactured. The flow field is predicted by means of a Reynolds-averaged Navier-Stokes simulation. Two turbulence models were utilized: (i) a standard k-ω-SST model, (ii) a laminar/turbulent transition model. The manufactured turbine is placed on the rooftop of the University of Siegen. Three wind anemometers and wind direction sensors are arranged around the turbine. The torque is derived from electric power and the rotational speed via a calibrated grid-connected generator.

The agreement between the analytically and CFD-predicted kinematic quantities up- and downstream of the rotor disc is quite satisfactory. However, the blade section drag to lift ratio and hence the power coefficient vary with the turbulence model chosen. Moreover, the experimentally determined power coefficient is considerably lower as predicted by all methods. However, this conclusion is somewhat preliminary since the existing experimental data set needs to be extended.
A Technological Effect Modeling on Complex Turbomachinery Applications With an Overset Grid Numerical Method
Authors: Billonnet Gilles , Castillon Lionel , Riou Jacques , Leroy Gilles , Paillassa André
Published: November 2013

The modeling of technological effects on complex turbomachinery flow is described in the paper. The Chimera method based on structured overlapping grids is applied using the ONERA solver elsA. The application of the method on two industrial test cases are presented. The first investigated application is an experimental configuration of a turbine vane with film-cooling. The film cooling system is made up of a very large number of holes. The Chimera method enables simulating the interaction between the cooling jets and the vane flow and improves heat flux prediction compared to simulations modeling cooling flows with wall boundary conditions. The second investigated application is a variable Inlet Guide Vane of an experimental compressor. The application includes the main flow vane, the pivot linking the hub wall with the IGV blade, and the built-in turntable within the shroud which ensures the blade fitting. The benefit of the overset grid method is highlighted by comparisons with computation results obtained on the smooth end-walls. For three different stagger angles (0°, 30° and 60°) the patterns of the secondary flows are presented as well as the comparisons of the calculated flow field with the available experimental data.
Supercritical Carbon Dioxide Brayton Cycle Development Overview
Authors: Kimball Kenneth J. , Rahner Kevin D. , Nehrbauer Joseph P. , Clementoni Eric M.
Published: November 2013

Bechtel Marine Propulsion Corporation (BMPC) is testing a supercritical carbon dioxide (S-CO2) Brayton system at the Bettis Atomic Power Laboratory. The 100 kWe Integrated System Test (IST) is a two shaft recuperated closed Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator using S-CO2 as the working fluid. The IST was designed to demonstrate operational, control and performance characteristics of an S-CO2 Brayton power cycle over a wide range of conditions. The IST design includes a comprehensive instrumentation and control system to facilitate precise control of loop operations and to allow detailed evaluation of component and system performance. A detailed dynamic performance model is being used to predict IST performance, support test procedure development and to evaluate test results.

An overview of IST testing progress and plans is provided. Testing in the IST was initiated in 2012. Initial test operations included successful system startup, initial transition to electrical power generation and increased power operations using independent speed control of the turbomachinery. Results of testing completed to date and future testing plans will be summarized.
Startup and Operation of a Supercritical Carbon Dioxide Brayton Cycle
Authors: Clementoni Eric M. , Cox Timothy L. , Sprague Christopher P.
Published: November 2013

Bechtel Marine Propulsion Corporation (BMPC) is testing a supercritical carbon dioxide (S-CO2) Brayton system at the Bettis Atomic Power Laboratory. The 100 kWe Integrated System Test (IST) is a two shaft recuperated closed Brayton cycle with a variable speed turbine driven compressor and a constant speed turbine driven generator using S-CO2 as the working fluid. The IST was designed to demonstrate operational, control and performance characteristics of an S-CO2 Brayton power cycle over a wide range of conditions.

Initial operation of the IST has proven a reliable method for startup of the Brayton loop and heatup to normal operating temperature (570°F). An overview of the startup process, including initial loop fill and charging, and heatup to normal operating temperature is presented. Additionally, aspects of the IST startup process which are related to the loop size and component design which may be different for larger systems are discussed.
Air-Based Bottoming-Cycles for Water-Free Hybrid Solar Gas-Turbine Power Plants
Authors: Sandoz Raphaël , Spelling James , Laumert Björn , Fransson Torsten
Published: November 2013

A thermoeconomic model of a novel hybrid solar gas-turbine power plant with an air-based bottoming cycle has been developed, allowing its thermodynamic, economic, and environmental performance to be analyzed. Multi-objective optimization has been performed to identify the trade-off between two conflicting objectives: minimum capital cost and minimum specific CO2 emissions. In-depth thermoeconomic analysis reveals that the additional bottoming cycle significantly reduces both the levelized cost of electricity and the environmental impact of the power plant (in terms of CO2 emissions and water consumption) when compared to a simple gas-turbine power plant without bottoming cycle. Overall, the novel concept appears to be a promising solution for sustainable power generation, especially in water-scarce areas.
Measurements of Rotordynamic Response and Temperatures in a Rotor Supported on Metal Mesh Foil Bearings
Authors: Chirathadam Thomas Abraham , San Andrés Luis
Published: November 2013

Gas bearings in power generation microturbomachinery (MTM) and for automotive turbocharger applications must demonstrate adequate thermal management without performance degradation while operating in a harsh environment. The paper presents rotor surface temperatures and rotordynamic measurements of a rigid rotor supported on a pair of metal mesh foil bearings (MMFBs) (L = 38.1 mm, D = 36.6 mm). In the tests, to a maximum rotor speed of 50 krpm, an electric cartridge heats the hollow rotor over several hours while a steady inlet air flow rate at ∼ 160 L/min cools the bearings. In the tests with the heater set to a high temperature (max. 200 °C), the rotor and bearing OD temperatures increase by 70°C and 25°C, respectively. Most rotor dynamic responses do not show a marked difference for operation under cold (ambient temperature) or hot rotor conditions. A linear rotordynamics structural model with predicted MMFB force coefficients delivers rotor response amplitudes in agreement with the measured ones for operation with the rotor at ambient temperature. There are marked differences in the peak amplitudes when the rotor crosses its (rigid body) critical speeds. The test bearings provide lesser damping than predictions otherwise indicate. Waterfalls of rotor motion show no sub synchronous whirl frequency motions; the rotor-bearing system being stable for all operating conditions. The measurements demonstrate that MMFBs can survive operation with severe thermal gradients, radial and axial, and with little rotordynamic performance changes when the rotor is either cold or hot. The experimental results, accompanied by acceptable predictions of the bearings dynamic forced performance, promote further MMFBs as an inexpensive reliable technology for MTM.
Application of a Statistical Methodology for Gas Turbine Degradation Prognostics to Alstom Field Data
Authors: Venturini Mauro , Therkorn Dirk
Published: November 2013

In this paper, a prognostic methodology is applied to gas turbine field data to assess its capability as a predictive tool for degradation effects. On the basis of the recordings of past behavior, the methodology provides a prediction of future performance, i.e. the probability that degradation effects are at an acceptable level in future operations. The analyses carried out in this paper consider two different parameters (power output and compressor efficiency) of three different Alstom gas turbine power plants (gas turbine type GT13E2, GT24 and GT26). To apply the prognostic methodology, site specific degradation threshold values were defined, to identify the time periods with acceptable degradation (i.e. higher-than-threshold operation) and the time periods where maintenance activities are recommended (i.e. lower-than-threshold operation).

This paper compares the actual distribution of the time points until the degradation limit is reached (discrete by nature) to the continuously varying distribution of the time points simulated by the probability density functions obtained through the prognostic methodology. Moreover, the reliability of the methodology prediction is assessed for all the available field data of the three gas turbines and for two values of the threshold. For this analysis, the prognostic methodology is applied by considering different numbers of degradation periods for methodology calibration and the accuracy of the next forecasted trends is compared to the real data.

Finally, this paper compares the prognostic methodology prediction to a “purely deterministic” prediction chosen to be the average of the past time points of higher-than-threshold operations.

The results show that, in almost all cases, the prognostic methodology allows a better prediction than the “purely deterministic” approach for both power and compressor efficiency degradation. Therefore, the prognostic methodology seems to be a robust and reliable tool to predict gas turbine power plant “probabilistic” degradation.
Effect of Inlet Swirl on the Model Leading Edge of Turbine Vane
Authors: Yin Hong , Qin Yanmin , Ren Jing , Jiang Hongde
Published: November 2013

Lean premixed combustion technology has been widely adopted in heavy duty and industrial gas turbine combustor. To enhance mixing and stabilize the flame, the large recirculation zone is built up by introducing strong swirling flow, which causes non-uniform flow field and has effect on the first stage vane, especially the leading edge.

This paper investigates the effect of swirling flow on the downstream vane film cooling. Test rig consists of a swirler nozzle (swirl number equals 0.45) and a model leading edge with three rows of film cooling holes. Five-hole probe and pressure sensitive paint measurements were carried out. The operating conditions range includes three blowing ratios, two density ratios of cooling flow and two distances between the swirler and the model leading edge. Numerical simulations were also conducted and compared with the accumulated experimental data.

Results show that the stagnation line of the model leading edge under swirling inlet flow condition is obviously altered compared with uniform inflow. Dividing the test model into three sections, film cooling effectiveness distribution has distinct characteristics in each section. Both ends of the model are mainly influenced by the flow direction. However the middle section performs differently since the vortex core impingement directly disturbs the film cooling ejection. Furthermore, detailed computational analysis reveals the swirling flow character and that the combined effect of total pressure and flow angle distribution dominates the film cooling of middle section.
On the Accurate Prediction of Tip Vortex: Effect of Numerical Schemes
Authors: Su Xinrong , Yamamoto Satoru , Yuan Xin
Published: November 2013

This work is conducted towards the accurate prediction of compressor tip vortex. Accurate computation of highly vortical flow is affected by many parameters, such as numerical scheme and turbulence model. In this work the effect of numerical scheme is studied using mesh refinement study and comparison of numerical results from central scheme and a newly developed high order upwind scheme. Behaviors of numerical methods in the tip vortex region are also theoretically and numerically analyzed. It is found the computed tip vortex is significantly affected by mesh resolution and numerical dissipation. Currently widely numerical strategy, i.e., mesh with moderate resolution and low order scheme would yield quite inaccurate result. Predicted tip vortex is always dissipated earlier and this highlights the advantage of high order scheme in predicting detailed flow features. Besides coarser mesh and low order method, analysis of numerical methods reveals a new finding, in that the designed order of accuracy is not guaranteed in the tip vortex region. For central scheme pressure based shock sensor is unnecessarily activated and excessive artificial dissipation is added. For high order upwind scheme it tends to use low order reconstruction and new method considering flow physics shows its improved vortex prediction capability. Conclusions from this work can be used in future numerical studies about tip vortex to improve the numerical accuracy.
Direct Measurements of Overall Effectiveness and Heat Flux on a Film Cooled Test Article at High Temperatures and Pressures
Authors: Lawson S. A. , Straub D. L. , Beer S. , Casleton K. H. , Sidwell T.
Published: November 2013

The energy requirements associated with recovering greenhouse gases from Integrated Gasification Combined Cycle (IGCC) or Natural Gas Combined Cycle (NGCC) power plants are significant. The subsequent reductions in overall plant efficiency also result in a higher cost of electricity. In order to meet the future demand for cleaner energy production, this research is focused on improving gas turbine efficiency through advancements in gas turbine cooling capabilities.

For this study, an experimental approach was developed to quantify overall effectiveness and net heat flux reduction for a film-cooled test article at high temperature and pressure conditions. A major part of this study focused on validating an advanced optical thermography technique capable of distinguishing between emitted and reflected radiation from film-cooled test articles exposed to exhaust gases in excess of 1000°C and 5 bar. The optical thermography method was used to acquire temperature maps of both external and internal wall temperatures on a test article with fan-shaped film cooling holes. The overall effectiveness and heat flux were quantified with one experiment. The optical temperature measurement technique was capable of measuring wall temperatures to within ±7.2°C. Uncertainty estimates showed that the methods developed for this study were capable of quantifying improvements in overall effectiveness necessary to meet DOE program goals. Results showed that overall effectiveness increased with an increase in blowing ratio and a decrease in mainstream gas pressure while heat flux contours indicated consistent trends.
Automated Optimization of an Axial-Slot Type Casing Treatment for a Transonic Compressor
Authors: Goinis Georgios , Voß Christian , Aulich Marcel
Published: November 2013

It has been shown in many cases that a notable aerodynamic stability enhancement can be achieved using casing treatments (CTs) on transonic compressors. This advantage, however, often involves degradation in efficiency at design point conditions. In order to analyze the correlations between efficiency, surge margin and other flow quantities on the one hand and the geometric parameters related to axial slots on the other, an automated multi objective geometry optimization of axial slots is performed. This involves the usage of time accurate URANS simulations for each new CT design the optimization tool proposes. The axial slots are generated using a parametric design, which can produce slots of different size, shape and position. Three operating points are simulated. One at design point (ADP) conditions, a second at reduced speed working line conditions and a third at reduced speed close to the stability limit. Based on the results of the CFD simulations two objective values are calculated. These are, first, an increased efficiency at working line conditions and, second, an increased surge margin at reduced speed. The test case used for the study is the first stage of DLR’s transonic research compressor Rig250. The rig is representative for the front stages of a heavy duty gasturbine compressor. The computational domain includes the IGV as well as the first rotor and stator. The rotor of the configuration is tip-critical for the studied part speed condition. The result of the optimization is a Pareto front with all optimal geometries regarding surge margin and efficiency. It is found that efficiency at design point can be exchanged against surge margin at reduced speed. The working principles and flow phenomena of the Pareto-optimal axial slots are analyzed in detail to obtain a better understanding of the mechanisms leading to the extension in surge margin.
The Nonlinear Harmonic Method Applied to the Combined Effects of Multi-Row Unsteady Flows
Authors: Vilmin S. , Lorrain E. , Debrabandere F. , Tartinville B. , Capron A. , Hirsch Ch.
Published: November 2013

The nonlinear harmonic method (NLH) and its extension to the modeling of the clocking effects can simulate the unsteady flows in multistage machines at drastically reduced CPU costs.

The blade row interactions that are reproduced are those between adjacent rotors and stators and also between successive rotors or successive stators. At an additional level of complexity, it appears that in stator1 / rotor / stator2 configurations the amplitude of the perturbation associated with a blade passing frequency (BPF) in a row is not only created by the adjacent row but is also modified in space by the interaction of the periodic disturbances coming from the other two rows. For instance, the spatial modes of the periodic disturbance in stator2 are provoked not only by the interaction with the adjacent rotor but also by an additional interaction with the periodic flow coming from stator1.

The present paper introduces a method that enables the identification of these modes for a general configuration row1 / row2 / row3. Any row can be a stator or a rotor and the time-varying disturbances are not only produced by the interaction with the adjacent row but also with the other rows. In particular, this is validated and illustrated for the calculation of the unsteady effects provoked in contra-rotating open rotors (CROR) by the engine pylon. Results are also shown for stator/rotor/stator configurations that shows the effects of clocking on the time harmonics.
Conversion of the AE 1107C From the V-22 Osprey Application to Marine Service
Authors: Green Zechariah D. , Padfield Sean , Barrett Andrew F. , Jones Paul G.
Published: November 2013

This paper presents a study on the conversion of the Rolls-Royce AE 1107C V-22 Osprey gas turbine engine into the MT7 Ship-to-Shore Connector (SSC) marine gas turbine engine. The US Navy led SSC design requires a propulsion and lift gas turbine rated at 5,230 shaft horsepower, which the AE 1107C variant MT7 is capable of providing with margin on power and specific fuel consumption. The MT7 leverages the AE family of engines to provide a propulsion and lift engine solution for the SSC craft. Extensive testing and analysis completed during the AE 1107C development program aided in the robust gas turbine design required to meet the needs of the SSC program. Requirements not met by the AE 1107C configuration were achieved with designs based on the AE family of engines and marine grade sub-system designs. Despite the fact that system integration and testing remain as key activities for integrating the MT7 with the SSC craft, conversion of the AE 1107C FAA certified engine into an American Bureau of Shipping Naval Vessel Rules Type Approved MT7 engine provides a low technical risk alternative for the demanding requirements of the SSC application.
Elastomer O-Rings as Centering Spring in Squeeze Film Dampers: Application to Turbochargers
Authors: Dousti Saeid , Kaplan Jason A. , He Feng , Allaire Paul E.
Published: November 2013

This study addresses the nonlinear dynamic behavior of O-ring seals as the centering spring in squeeze film dampers. An analytical model is developed to predict the restoring and hysteresis characteristics of elastomer O-rings and extends the existing models to non-axisymmetric load conditions. Also, the inclusion of axial seals increases the damping capacity of squeeze film dampers. O-rings forces are investigated for different sizes, installation preloads, and operating conditions and contrasted with squeeze film damper’s hydrodynamic forces. This model is incorporated in linear and time transient rotordynamic analyses of a vertical turbocharger. It is shown that the O-rings contribution in rotor response for low rotational speeds and low amplitude vibrations is dominant and can not be ignored.