bluuebunny/crossref_metadata_2025 huggingface dataset:
Masterpiece of epigenetic engineering – how Toxoplasma gondii reprogrammes host brains to change fear to sexual attraction
Authors: Flegr Jaroslav , Markoš Anton
Published: December 2014

The protozoan parasite Toxoplasma gondii is known to induce specific behavioural changes in its intermediate hosts, including humans, that are believed to increase the chance of its successful transmission to the definitive host, the cat. The most conspicuous change is the so‐called fatal attraction phenomenon, the switch from the mice's and rats’ natural fear of the smell of cats toward an attraction to this smell. The mechanism of this manipulation activity is unknown; however, many indices suggest that changes in the concentrations of dopamine and testosterone are involved. In this issue of Molecular Ecology, Hari Dass & Vyas () present results of a study showing that, by hypomethylation of certain regulatory elements of key gene, Toxoplasma is able to reprogramme the brain's genetic machinery in such a way that cat odour activates and changes the wiring of the medial amygdala circuits responsible for sexual behaviour. This study delivers the first clear evidence of a parasite's ability to use sophisticated epigenetic engineering techniques for the manipulation of the phenotype of its infected host.
Diet strongly influences the gut microbiota of surgeonfishes
Authors: Miyake Sou , Ngugi David Kamanda , Stingl Ulrich
Published: December 2014

Intestinal tracts are among the most densely populated microbial ecosystems. Gut microbiota and their influence on the host have been well characterized in terrestrial vertebrates but much less so in fish. This is especially true for coral reef fishes, which are among the most abundant groups of vertebrates on earth. Surgeonfishes (family: Acanthuridae) are part of a large and diverse family of reef fish that display a wide range of feeding behaviours, which in turn has a strong impact on the reef ecology. Here, we studied the composition of the gut microbiota of nine surgeonfish and three nonsurgeonfish species from the Red Sea. High‐throughput pyrosequencing results showed that members of the phylum Firmicutes, especially of the genus Epulopiscium, were dominant in the gut microbiota of seven surgeonfishes. Even so, there were large inter‐ and intraspecies differences in the diversity of surgeonfish microbiota. Replicates of the same host species shared only a small number of operational taxonomic units (OTUs), although these accounted for most of the sequences. There was a statistically significant correlation between the phylogeny of the host and their gut microbiota, but the two were not completely congruent. Notably, the gut microbiota of three nonsurgeonfish species clustered with some surgeonfish species. The microbiota of the macro‐ and microalgavores was distinct, while the microbiota of the others (carnivores, omnivores and detritivores) seemed to be transient and dynamic. Despite some anomalies, both host phylogeny and diet were important drivers for the intestinal microbial community structure of surgeonfishes from the Red Sea.
Vertical distribution of the soil microbiota along a successional gradient in a glacier forefield
Authors: Rime Thomas , Hartmann Martin , Brunner Ivano , Widmer Franco , Zeyer Josef , Frey Beat
Published: December 2014

Spatial patterns of microbial communities have been extensively surveyed in well‐developed soils, but few studies investigated the vertical distribution of micro‐organisms in newly developed soils after glacier retreat. We used 454‐pyrosequencing to assess whether bacterial and fungal community structures differed between stages of soil development (SSD) characterized by an increasing vegetation cover from barren (vegetation cover: 0%/age: 10 years), sparsely vegetated (13%/60 years), transient (60%/80 years) to vegetated (95%/110 years) and depths (surface, 5 and 20 cm) along the Damma glacier forefield (Switzerland). The SSD significantly influenced the bacterial and fungal communities. Based on indicator species analyses, metabolically versatile bacteria (e.g. Geobacter) and psychrophilic yeasts (e.g. Mrakia) characterized the barren soils. Vegetated soils with higher C, N and root biomass consisted of bacteria able to degrade complex organic compounds (e.g. Candidatus Solibacter), lignocellulolytic Ascomycota (e.g. Geoglossum) and ectomycorrhizal Basidiomycota (e.g. Laccaria). Soil depth only influenced bacterial and fungal communities in barren and sparsely vegetated soils. These changes were partly due to more silt and higher soil moisture in the surface. In both soil ages, the surface was characterized by OTUs affiliated to Phormidium and Sphingobacteriales. In lower depths, however, bacterial and fungal communities differed between SSD. Lower depths of sparsely vegetated soils consisted of OTUs affiliated to Acidobacteria and Geoglossum, whereas depths of barren soils were characterized by OTUs related to Gemmatimonadetes. Overall, plant establishment drives the soil microbiota along the successional gradient but does not influence the vertical distribution of microbiota in recently deglaciated soils.
Occurrence and social structure of Baird's beaked whales,Berardius bairdii, in the Commander Islands, Russia
Authors: Fedutin Ivan D. , Filatova Olga A. , Mamaev Evgeny G. , Burdin Alexandr M. , Hoyt Erich
Published: December 2014

The social structure of Baird's beaked whales is completely unstudied, and it is unknown if either females or males form long‐term social associations or occur in stable groups. In this paper we summarize our observations of individually identified animals over the span of 6 yr to provide insight on their long‐term social structure. We have identified 122 whales, with 28 of them encountered three times or more and thus included in the analysis of social structure. We found that the whales exhibited nonrandom patterns of social associations with some individuals preferentially associating with each other. Whales with more scarred skin had higher maximum association coefficients, which indicates that older animals and/or males were more inclined to form stable associations. Cluster analysis with a modularity test for gregariousness divided the whales into four clusters. Whales from the same clusters did not always occur together, but some individuals retained stable associations over several years. The strength of social relationships decayed over periods of months, with between‐year relationships showing little deviation from what would be expected if association was random. Generally these findings do not correspond to a stable society with fixed groups but instead suggest a fission‐fusion society with some stable alliances.
The Doctrine of ‘Divine Indwelling’ in Elizabeth of the Trinity and Caryll Houselander
Authors: Meszaros Julia
Published: December 2014

The present article examines the perspectives of two understudied, female spiritual writers, Elizabeth of the Trinity and Caryll Houselander, on the doctrine of ‘divine indwelling’. After a brief discussion of classical elaborations of this doctrine, the paper gives an account of Elizabeth's and Houselander's respective Trinitarian and Incarnational readings of God's indwelling of the human soul. This discussion shows that a given interpretation and experience of the divine indwelling is inevitably shaped by – and shapes – the particularity of one's concrete life context, as well as the doctrinal prism through which it is approached. It furthermore demonstrates that such different accounts nonetheless converge on key, and at times surprising issues, such as the reciprocal nature of divine indwelling, and its interdependency on the separation between God and the human being.
How Catholic Teaching about War Has Changed: The Issues in View
Authors: Beck Ashley
Published: December 2014

A feature of the First World War, was the consistent condemnation of it by Pope Benedict XV and his unsuccessful efforts to bring about a negotiated peace. This paper argues that the Pope realised that the nature of modern warfare demanded a new evaluation of war and that his teaching began a real shift and development in this teaching that is clearly discernible in the teachings of his successors and the Second Vatican Council, and the work of Catholic theologians and movements. However, we can see how in many ways this shift has not been recognised in the wider church, shown by the reluctance of local church leaders to question or condemn particular conflicts. On the basis of this shift the paper argues that the Catholic Church, now committed to “virtual pacifism”, should base its witness to peace on two paradigms: first, the unmasking of wickedness, seen above all in the culture engendered by the possession of nuclear weapons; and second, a marked distancing from the powers and claims of the modern nation state.
Articulation and oromyofunctional behavior in children seeking orthodontic treatment
Authors: Van Lierde KM , Luyten A , D'haeseleer E , Van Maele G , Becue L , Fonteyne E , Corthals P , De Pauw G
Published: December 2014

Objectives

The purpose of this controlled study is to document articulation and oromyofunctional behavior in children seeking orthodontic treatment. In addition, relations between malocclusions, articulation, and oromyofunctional behavior are studied.

Materials and Methods

The study included 56 children seeking orthodontic treatment. The control group, consisting of 54 subjects matched for age and gender, did not undergo orthodontic intervention. To determine the impact of the occlusion on speech, the Oral Health Impact Profile was used. Speech characteristics, intelligibility and several lip and tongue functions were analyzed using consensus evaluations.

Results

A significant impact of the occlusion on speech and more articulation disorders for/s,n,l,t/were found in the subjects seeking orthodontic treatment. Several other phenomena were seen more often in this group, namely more impaired lip positioning during swallowing, impaired tongue function at rest, mouth breathing, open mouth posture, lip sucking/biting, anterior tongue position at rest, and tongue thrust. Moreover, all children with a tongue thrust showed an anterior tongue position at rest.

Conclusions

Children seeking orthodontics have articulatory and oromyofunctional disorders. To what extent a combined orthodontic and logopaedic treatment can result in optimal oral health (i.e. perfect dentofacial unit with perfect articulation) is subject for further multidisciplinary research.
Rph23: A new designated additive adult plant resistance gene to leaf rust in barley on chromosome 7H
Authors: Singh Davinder , Dracatos Peter , Derevnina Lida , Zhou Meixue , Park Robert F.
Published: December 2014

We report on a new adult plant resistance (APR) gene Rph23 conferring resistance to leaf rust in barley. The gene was identified and characterized from a doubled haploid population derived from an intercross between the Australian barley varieties Yerong (Y) and Franklin (F). Genetic analysis of adult plant field leaf rust scores of the Y/F population collected over three successive years indicated involvement of two highly additive genes controlling APR, one of which was named Rph23. The gene was mapped to chromosome 7HS positioned at a genetic distance 36.6 cM. Rph23 is closely linked to marker Ebmac0603, which is flanked by markers bPb‐8660 and bPb‐9601 with linkage distances of 0.8 and 5.1 cM, respectively. A PCR‐based marker was optimized for marker‐assisted selection of Rph23, and on the basis of this marker, the gene was postulated as being common in Australian and global barley germplasm. Pedigree and molecular marker analyses indicated that the six‐rowed black Russian landrace ‘LV‐Taganrog’ is the likely origin of Rph23.
Right‐lateralized alpha desynchronization during regularity discrimination: Hemispheric specialization or directed spatial attention?
Authors: Wright Damien , Makin Alexis D. J. , Bertamini Marco
Published: December 2014

When actively classifying abstract patterns according to their regularity, alpha desynchronization (ERD) becomes right lateralized over posterior brain areas. This could reflect temporary enhancement of contralateral visual inputs and specifically a shift of attention to the left, or right hemisphere specialization for regularity discrimination. This study tested these competing hypotheses. Twenty‐four participants discriminated between dot patterns containing a reflection or a translation. The direction of the transformation, which matched one half onto the other half, was either vertical or horizontal. The strategy of shifting attention to one side of the patterns would not produce lateralized ERD in the horizontal condition. However, right‐lateralized ERD was found in all conditions, regardless of orientation. We conclude that right hemisphere networks that incorporate the early posterior regions are specialized for regularity discrimination.
Indicators of restoration success in riparian tropical forests using multiple reference ecosystems
Authors: Suganuma Marcio S. , Durigan Giselda
Published: December 2014

Forest restoration by planting trees often accelerates succession, but the trajectories toward reference ecosystems have rarely been evaluated. Using a chronosequence (4–53 years) of 26 riparian forest undergoing restoration in the Brazilian Atlantic Forest, we modeled how the variables representing forest structure, tree species richness and composition, and the proportion of plant functional guilds change through time. We also estimated the time required for these variables to reach different types of reference ecosystems: old‐growth forest (OGF), degraded forest, and secondary forest. Among the attributes which follow a predictable trajectory over time are: the basal area, canopy cover, density and tree species richness, as well as proportions of shade tolerant and slow growing species or individuals. Most of the variation in density of pteridophythes, lianas, shrubs and phorophythes, proportion of animal‐dispersed individuals, rarefied richness and floristic similarity with reference ecosystems remain unexplained. Estimated time to reach the reference ecosystems is, in general, shorter for structural attributes than for species composition or proportion of functional guilds. The length of this time varies among the three types of reference ecosystems for most attributes. For instance, tree species richness and proportion of shade tolerant or slow growing individuals become similar to secondary forests in about 40 years, but is estimated to take 70 years or more to reach the OGF. Of all the variables considered, canopy cover, basal area, density, and richness of the understory—by their ecological relevance and predictability—are recommended as ecological indicators for monitoring tropical forest restoration success.
Can you forgive? It depends on how happy you are
Authors: Jiang Feng , Yue Xiaodong , Lu Su , Yu Guangtao
Published: December 2014

This paper examined how individual group status and happiness influence forgiveness. In Study 1, happiness was treated as a trait difference: highly happy people, compared with very unhappy people, were found to be more willing to forgive murderers. More important, an interaction effect between happiness and group status on forgiveness was found, that is, highly happy people tended to be more forgiving when either ingroup or outgroup members were killed; unhappy people, however, tended to be less forgiving about murder when ingroup rather than outgroup members were killed. In Study 2, happiness was treated as an emotional state difference: happiness, rather than sadness, was found to bring greater forgiveness. Moreover, consistent with the interaction effect displayed in Study 1, happy participants tended to forgive more when ingroup or outgroup members were hurt; sad participants tended to forgive less when ingroup members rather than outgroup members were hurt. Implications for connections between happiness, group membership, and forgiveness are discussed.
Influence of the Hole Length-to-Diameter Ratio on Film Cooling With Cylindrical Holes
Authors: Lutum Ewald , Johnson Bruce V.
Published: December 2014

Film cooling experiments were conducted to investigate the effects of coolant hole length-to-diameter ratio on the film cooling effectiveness. The results from these experiments offer an explanation for the differences between the film cooling results for cylindrical hole injection configurations previously reported by Goldstein et al. (1974), Pedersen et al. (1977) and Sinha et al. (1991). The previously reported injection configurations differed primarily in coolant hole length-to-diameter ratio. The present experiments were conducted with a row of cylindrical holes oriented at 35 degrees to a constant-velocity external flow, systematically varying the hole length-to-diameter ratios (L/D = 1.75, 3.5, 5, 7 and 18), and blowing rates (0.52≤M≤1.56).

Results from these experiments show in a region 5≤X/D≤50 downstream of coolant injection that the coolant flow guiding capability in the cylindrical hole was apparently established after 5 hole diameters and no significant changes in the film cooling effectiveness distribution could be observed for the greater L/D. However, the film cooling effectiveness characteristics generally decreased with decreasing hole L/D ratio in the range of 1.75≤L/D≤5.0. This decrease in film cooling performance was attributed to (1) the undeveloped character of the flow in the coolant channels and (2) the greater effective injection angle of the coolant flow with respect to the external flow direction and surface. The lowest values of film cooling effectiveness were measured for the smallest hole length-to-diameter ratio, L/D = 1.75.
A Bulk-Flow Analysis of Multiple-Pocket Gas Damper Seals
Authors: Li Jiming , San Andrés Luis , Vance John
Published: December 2014

A bulk-flow model for calculation of the dynamic force characteristics in a single cavity, multiple-pocket gas damper seal is presented. Flow turbulence is accounted for by using turbulent shear stress parameters and Moody’s friction factors in the circumferential momentum equation. Zeroth order-equations describe the isothermal flow field for a centered seal, and first-order equations govern the perturbed flow for small amplitude rotor lateral motions. Comparisons to limited measurements from a four-pocket gas damper seal show the current model to predict well the mass flow rate and the direct damping coefficient. For a reference two-bladed teeth-on-stator labyrinth seal, the current model predicts similar rotordynamic coefficients when compared to results from a two control-volume bulk-flow model. Force coefficients from a reference single-cavity, four pocket gas damper depend on the rotor speed and pressure drop with magnitudes decreasing as the rotor whirl frequency increases. The multiple-pocket gas damper seal provides substantially more damping than a conventional labyrinth seal of the same dimensions. The damper seal cross-coupled stiffness coefficients are small though sensitive to the inlet circumferential pre-swirl flow.
Vortex Simulation of Rotor/Stator Interaction in Turbomachinery
Authors: Wu Xian Hong , Chen Mao Zhang
Published: December 2014

A new numerical method is presented in this paper to simulate rotor/stator interaction in turbomachinery by use of a vortex method based on a Lagrangian frame. The algorithm takes the result from steady solution as input, which can give an initial description of the unsteady disturbance flow field. To calculate the unsteady response to these disturbances, the Lagrangian vortex method is used to capture the convective process, and the deterministic vortex scheme to approximate the viscous diffusion process. The application of Baldwin-Lomax turbulence model in wakes is developed, so as to overcome the difficulties such as the much higher calculated viscosity in the outer region than that in the boundary regions, and the difficulty in continuously tracing moving wake centerlines encounted by other numerical methods. The agreement between the computational and experimental results is generally good. The sweeping characteristic of wakes, the influence of unsteadiness on incidence and the decaying features of unsteady velocities, pressure are included in the paper.
A Nonlinear Numerical Simulator for Three-Dimensional Flows Through Vibrating Blade Rows
Authors: Chuang H. Andrew , Verdon Joseph M.
Published: December 2014

The three-dimensional, multi-stage, unsteady, turbomachinery analysis, TURBO, has been extended to predict the aeroelastic and aeroacoustic response behaviors of a blade row operating within a cylindrical annular duct. In particular, a blade vibration capability has been incorporated so that the TURBO analysis can be applied over a solution domain that deforms with a vibratory blade motion. Also, unsteady far-field conditions have been implemented to render the computational inlet and exit boundaries transparent to outgoing unsteady disturbances and to allow for the prescription of incoming aerodynamic excitations. The modified TURBO analysis has been applied to predict unsteady subsonic and transonic flows. The intent is to partially validate this nonlinear analysis for blade flutter applications via numerical results for benchmark unsteady flows, and to demonstrate this analysis for a realistic fan rotor. For these purposes, we have considered unsteady subsonic flows through a 3D version of the 10th Standard Cascade and unsteady transonic flows through the first stage rotor of the NASA Lewis, Rotor 67 fan. Some general correlations between aeromechanical stabilities and fan operating characteristics will be presented.
Dynamics of Large-Scale Structures for Jets in a Crossflow
Authors: Muldoon Frank , Acharya Sumanta
Published: December 2014

Results of a three dimensional unsteady computational study of a row of jets injected normal to a cross-flow are presented with the aim of understanding the dynamics of the large scale structures in the region near the jet. The jet to cross-flow velocity ratio is .5. A modified version of the computer program (INS3D) which utilizes the method of artificial compressibility is used for the computations. Results obtained clearly indicate that the near field large scale structures are extremely dynamical in nature, and undergo breakup and reconnection processes. The dynamical near field structures identified include the counter rotating vortex pair (CVP), the horseshoe vortex, wake vortex, wall vortex and the shear layer vortex. The dynamical features of these vortices are presented in this paper. The CVP is observed to be a convoluted structure interacting with the wall and horseshoe vortices. The shear layer vortices are stripped by the crossflow, and undergo pairing and stretching events in the leeward side of the jet. The wall vortex is reoriented into the upright wake system. Comparison of the predictions with mean velocity measurements is made. Reasonable agreement is observed.
Erosion Rate Testing at High Temperature of Alloys and Coatings for Use in Turbomachinery
Authors: Tabakoff W.
Published: December 2014

Because of the serious consequences of turbomachinery erosion on their performance and life, it is important to have reliable methods for predicting their erosion when solid particles are ingested with the incoming flow. This is a very challenging problem since turbomachinery erosion is affected by many factors such as blade passage geometry, blade row location, rotational speed flow conditions, blade material and particles’ characteristics. Several studies which are essential to predicting blade surface erosion intensity and pattern, have been conducted at the University of Cincinnati’s Propulsion Laboratory over the past twenty-five years. This paper describes only some of the work done on erosion testing at high temperatures and velocities for different materials and coatings. The testing has been performed with a special high temperature erosion wind tunnel which simulates the aerodynamic conditions on the blades. The coated substrates reveal one order of magnitude less wear compared to some commercial non-CVD coatings on the same alloys. This study demonstrates that some coatings provide an excellent erosion resistance to INCO 718, LNCO 738, MAR-246, X-40 and Tungsten Carbide.
The GT24/26 Low Pressure Turbine
Authors: Jennions Ian K. , Sommer Thomas , Weigand Bernhard , Aigner Manfred
Published: December 2014

The GT24 and GT26 are the latest in a series of gas turbines from ABB. The GT24 is a 60 Hz, 183 MW turbine, while the GT26 is its (scaled) 50 Hz equivalent, producing 265 MW. They feature a 22 stage controlled diffusion aerofoil compressor, two combustors separated by a single stage high pressure turbine with a four stage low pressure (LP) turbine following the second combustor. This arrangement permits very high efficiencies while avoiding high temperatures and the need to use new, expensive materials.

The first GT24 was delivered to Jersey Central Power and Light, Gilbert, New Jersey, USA, at the end of 1995 and achieved baseload operation in May 1996. The engine was highly instrumented with some 1200 measurement points to evaluate component performance. Subsequently, a through-flow datamatch to the design point data was made for the LP turbine and is compared to a full 3D multistage analysis in this paper. The 3D analysis accounts for all the cooling and leakage flows that enter the turbine flowpath and maintains a steady flow calculation by means of interface planes between each blade row that remove any circumferential non-uniformity from the computational flow field. To complement this aerodynamic analysis, some heat transfer results from the ABB GT26 test facility in Birr, Switzerland are also shown.

The paper demonstrates how component technology for the first stage was verified at four universities and research centers concurrently with the design process. This experimental data supplemented the existing databases and engendered confidence in the overall aero/thermal design approach.
Development of a Smart Actuator for Turbine Engine Applications
Authors: Lorenz William
Published: December 2014

The application of distributed control systems to turbine engine controls offers the potential for major reductions in development time and costs for the engine control and the engine. Once the data bus and power bus are standardized for elements of a distributed control system, the industry will have a group of sensors, actuators, and controllers that could be interchangeable between applications. Software and hardware will still require modification to fit the specific application, however, great strides will have been made toward a “plug and play” capability between sensors, actuators, and controllers all tied together on the same data bus. The main controller in a distributed control system, except for software, would be interchangeable from engine to engine.

This paper describes the design and development of the electronics for a smart actuator and discusses the design considerations which were used to guide the requirements. Requirements unique to turbine engine applications include temperature environments to 30° C, a severe vibration environment, minimum size and weight, and very high reliability.

The electronics developed for the smart actuator were packaged on credit card sized printed wiring board modules. Two of these modules were packaged in a housing approximately 23×3.4×1.1 inches. The electronics operate from 28 volt DC power and communicate with the rest of the control system via the MEL-STD-1553B data bus. Although a hydraulic actuator was chosen as the demonstration vehicle, the electronic module is adaptable to any servo application and can be expanded to read any of the common engine sensors and operate solenoids.

The chosen actuator was intended as a development tool to expose the design problems of distributed systems. Therefore, this first demonstration unit was designed using electronic components rated for 125° C operation. AlliedSignal is currently a member of a consortium of companies under DARPA sponsorship developing a family of SOI (silicon-on-insulator) integrated circuits rated for 200° C operation. Our current 125° C design is compatible with the new devices being developed. A 200° C unit is planned for 1998. Further improvements in the metalization used in the SOI devices will allow reliable long term operation to about 300° C. Devices for this higher temperature range are expected to be available in 1999.
A Numerical Study of the Three-Dimensional Turbulent Flow in the Impeller of a High-Speed Centrifugal Compressor
Authors: Clayton R. P. , Leong W. U. A. , Sanatian R. , Issa R. I. , Xi G.
Published: December 2014

Numerical analysis of the three-dimensional turbulent flow in an unshrouded impeller of a high-speed centrifugal compressor has been conducted using the multi-purpose CFD code STAR-CD. The work presented in this paper concentrates mainly on assessing the effects of the modelling of the actual spinner geometry on the quality of the predictions as compared to the often used practice of simplifying the inlet geometry. Furthermore, the contribution of detailed modelling of the flow in the tip clearance is studied using a two-layer k-ε turbulence model. As well as a qualitative analysis of the throughflow and tip leakage, a systematic quantitative comparison between the predicted and measured mean velocities and flow angles is presented.
Comparison Between Calculated and Measured Free-Free Modes for a Flexible Rotor
Authors: Vázquez José A. , Barrett Lloyd E.
Published: December 2014

Many industrial machines nowadays are sold based on analysis performed on mathematical models of the rotors, bearings, substructures, and other components. The validity of the analysts therefore depends on the accuracy of the models themselves. When the rotor is available, modal testing may be used to validate the model of the rotor by comparing the calculated and measured free-free natural frequencies and mode shapes. This work presents additional tools for the verification of analytical models against experimental data. These tools use models of the rotor constructed from the measured data and the analytical model. A comparison of the first six calculated and measured free-free natural frequencies and mode shapes for a multi-mass flexible rotor is presented. The natural frequencies compare within 1.8%. The calculated and measured mode shapes were used to construct independent reduced order models of the rotor. These models were used to perform forced response and stability analyses. Forced response functions are presented comparing the forced response characteristics obtained from the two models. This provides a comparison between the measured and calculated forced response functions for the same number of modes. For the stability analysis, identical bearing models were added to both reduced order models. The eigenvalues were calculated using both models for a range of bearing stiffness and damping coefficients and were plotted for comparison.
Humid Air Turbine Cycles With Water Recovery: How to Dispose Heat in an Efficient Way
Authors: Desideri Umberto , Di Maria Francesco
Published: December 2014

Since the humid air turbine (HAT) cycle was first presented by Rao and Joiner (1990), several modifications were proposed to the original configuration to further improve its efficiency. In the last years, the attention was focused in the water recovery from flue gas and in determining the most suitable systems to separate water from gas and solving the problem of low temperature at the stack.

In all the above studies it was shown that condensing water from flue gas requires a significant flow rate of a cooling medium (generally water) which is needed to remove condensation heat which must then be disposed in the environment. This worsens power plant performance because large cooling towers are needed. On the other hand, the reduced cost of water treatment may compensate the additional costs of the condensation equipment.

In this paper, the introduction of an Organic Rankine Cycle (ORC), which transforms in mechanical power a fraction of the heat recovered from the HAT cycle, both in the water recovery system and in other heat exchangers, is presented. Results were obtained by using three different fluids and maximizing the ORC input exergy. The substances which were used are the conventional R502 refrigerant fluid, ammonia and the new HF134a, which is replacing phased-out CFCs in refrigeration systems.
Air Separation Unit Integration for Alternative Fuel Projects
Authors: Smith Arthur R. , Klosek Joseph , Sorensen James C. , Woodward Donald W.
Published: December 2014

Alternative fuel projects often require substantial amounts of oxygen. World scale gas-to-liquids (GTL) processes based on the partial oxidation of natural gas, followed by Fischer-Tropsch chemistry and product upgrading, may require in excess of 10,000 tons per day of pressurized oxygen. The remote location of many of these proposed projects and the availability of low-cost natural gas and byproduct steam from the GTL process disadvantages the use of traditional, motor-driven air separation units in favor of steam or gas turbine drive facilities. Another process of current interest is the partial oxidation of waste materials in industrial areas to generate synthesis gas. Synthesis gas may be processed into fuels and chemicals, or combusted in gas turbines to produce electricity. A key to the economic viability of such oxygen-based processes is cost effective air separation units, and the manner in which they are integrated with the rest of the facility. Because the trade-off between capital and energy is different for the remote gas and the industrial locations, the optimum integration schemes can also differ significantly. This paper examines various methods of integrating unit operations to improve the economics of alternative fuel facilities. Integration concepts include heat recovery, as well as several uses of byproduct nitrogen to enhance gas turbine operation or power production. Start-up, control and operational aspects are presented to complete the review of integrated designs.
Controlling the Secondary Flow in a Turbine Cascade by 3D Airfoil Design and Endwall Contouring
Authors: Duden Arno , Raab Irene , Fottner Leonhard
Published: December 2014

A highly loaded turbine cascade has been redesigned with the objective to reduce the secondary flow by applying endwall contouring and 3D airfoil design in the endwall regions. The overall loading and the axial area ratio of the cascade have been kept constant. With the tools of a 3D design environment a systematic study has been carried out regarding several features of the endwall pressure distribution and their influence on the secondary flow. Two optimized configurations have been investigated in a high speed cascade wind tunnel. The flow field traverses showed improvements concerning the radial extent of the secondary flow and a decrease in secondary loss of 26 per cent. Unfortunately this reduction was counterbalanced by increased profile losses and higher inlet losses due to increased blockage. The striking feature of the cascade with endwall contouring and 3D airfoil design was a significant reduction of the exit flow angle deviations connected with the secondary flow. The predictions obtained by the 3D Navier-Stokes solver TRACE_S showed a remarkable agreement with the experimental results.
Variable Cycle Installation for a Mach 2.7 Supersonic Civil Transport
Authors: Aleid Louay , Pilidis Pericles
Published: December 2014

A preliminary comparison of the installed performance of three variable cycle jet engine concepts for future Supersonic Transports is outlined in this paper. These engines, are: the Turbofan-Turbojet, the Mid-Tandem Fan engine and the Double Bypass Engine.

The comparison of the uninstalled performance, variable geometry, cycle changes, the effect of variable compressor stators on the running lines of the compressors and sizing assessments for each engine were carried out in Reference 4.

An estimate is now made of the installed performance by calculating the air friction, the pre-entry and the afterbody drags, plus the wave drag. A sizing calculation was carried out for the nacelles of all the engines. The uninstalled and installed fuel bills, for two standard missions, are also estimated.

These preliminary results indicate that the Turbofan-Turbojet and the Mid Tandem Fan engines are quite similar in terms of general suitability. The Mid Tandem Fan appears to be an attractive proposition from the point of view of sizing, however this comes with a small penalty in fuel consumption. The Double Bypass engine was found to be the least attractive of the powerplants investigated. The differences, however appear to be small.
Experimental and Numerical Conjugate Investigation of the Blowing-Ratio Influence on the Showerhead Cooling Efficiency
Authors: Bohn Dieter E. , Becker Volker J. , Kusterer Karsten A. , Rungen Agnes U.
Published: December 2014

This paper presents the experimental investigation of the flow and the numerical analysis of the flow and heat transfer in a turbine guide vane with showerhead cooling for two different blowing ratios. The aerodynamic results are compared with those of the experiments.

Starting with a showerhead design of two rows of ejection holes, two additional rows have to be used in an enhanced design due to hot gas contact in the leading edge area. Thus, the cooling gas mass flow is doubled when keeping the blowing ratio constant at m = 1.5. Lowering the amount of cooling gas needed whilst still guaranteeing sufficient cooling is the motivation for the analysis of the influence of a lower blowing ratio on the cooling efficiency. The investigated blowing ratios are m = 1.5 and m = 1.0.

The experiments are conducted using a non-intrusive LDA technique. The numerical results are gained with a conjugate heat transfer and flow computer code that has been developed at the Institute of Steam and Gas Turbines.

The results show that the blowing ratio has to be chosen carefully as the leading edge flow pattern and the heat transfer are strongly influenced by the blowing ratio. Lower blowing ratios lead to a better attachment of the cooling film and thus they hardly disturb the main flow. With the lower blowing ratio, the material temperature increases up to 1.5% of the total inlet temperature in the leading edge area on the pressure side, whereas it decreases locally for about 0.8% for the lower blowing ratio on the suction side. This is due to the enhanced attachment of the cooling gas film.
Experimental and Computational Investigation of Stepped Tip Gap Effects on the Flowfield of a Transonic Axial-Flow Compressor Rotor
Authors: Thompson Donald W. , King Paul I. , Hah Chunill , Rabe Douglas C.
Published: December 2014

The effects of stepped tip gaps and clearance levels on the flowfield of a transonic axial-flow compressor rotor were experimentally and computationally determined. This paper complements a previous experimental study by the authors regarding the effects of stepped tip gaps and clearance levels on the performance of an axial-flow compressor rotor. In the current study, the generation of blockage associated with the variation of geometry in the rotor tip region was examined. The shock-vortex interaction generating the blockage was characterized, and a theory and mechanism for relocation of blockage in the rotor tip region was developed. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested with stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were investigated consisting of three step profiles at each of three clearance levels. Computational Fluid Dynamic modeling of tip geometry effects also was performed. Increased tip clearance was found to increase the amount of flow blockage near the rotor tip. Stepped tip gaps were found to be an effective means of reducing the effects of tip region blockage, resulting in improved pressure ratio, efficiency, and mass flow. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an improved casing profile.
Testing and Modelling Gas Turbines Using Multisine Signals and Frequency-Domain Techniques
Authors: Evans Ceri , Borrell Antoni , Rees David
Published: December 2014

The frequency-domain identification of gas turbine dynamics is discussed. Models are directly estimated from engine data and used to validate linearised thermodynamic models derived from the engine physics. This work is motivated by the problems previously encountered when using time-domain methods. A brief overview of frequency-domain techniques is presented and the design of appropriate multisine test signals is discussed. Practical results are presented for the modelling of the fuel feed to shaft speed dynamics of a twin-spool engine. The gathered data are analysed and the frequency response functions of the engine are estimated. The identification of parametric s-domain models is discussed in detail and a comparison made between the identified models and the linearised thermodynamic models. The influence of engine nonlinearities on the linear models is also examined.
The Application of Expert Systems and Neural Networks to Gas Turbine Prognostics and Diagnostics
Authors: DePold Hans R. , Gass F. Douglas
Published: December 2014

Condition monitoring of engine gas generators plays an essential role in airline fleet management. Adaptive diagnostic systems are becoming available that interpret measured data, furnish diagnosis of problems, provide a prognosis of engine health for planning purposes, and rank engines for scheduled maintenance. More than four hundred operations worldwide currently use versions of the first or second generation diagnostic tools.

Development of a third generation system is underway which will provide additional system enhancements and combine the functions of the existing tools. Proposed enhancements include the use of artificial intelligence to automate, improve the quality of the analysis, provide timely alerts, and the use of an Internet link for collaboration. One objective of these enhancements is to have the intelligent system do more of the analysis and decision making, while continuing to support the depth of analysis currently available at experienced operations.

This paper presents recent developments in technology and strategies in engine condition monitoring including:

1) application of statistical analysis and artificial neural network filters to improve data quality;

2) neural networks for trend change detection, and classification to diagnose performance change; and

3) expert systems to diagnose, provide alerts and to rank maintenance action recommendations.
Heat Transfer and Pressure Drop in Pin-Fin Trapezoidal Ducts
Authors: Hwang J.-J. , Lia D.-Y. , Tsia Y.-P.
Published: December 2014

Experiments are conducted to determine the log-mean averaged Nusselt number and overall pressure-drop coefficient in a pin-fin trapezoidal duct that models the cooling passages in modem gas turbine blades. The effects of pin arrangement (in-line and staggered), flow Reynolds number (6,000 ≦ Re ≦ 40,000) and ratio of lateral-to-total flow rate (0 ≦ ε ≦ 1.0) are examined. The results of smooth trapezoidal ducts without pin arrays are also obtained for comparison. It is found that, for the single-outlet-flow duct, the log-mean averaged Nusselt number in the pin-fin trapezoidal duct with lateral outlet is insensitive to the pin arrangement, which is higher than that in straight-outlet-flow duct with the corresponding pin array. As for the trapezoidal ducts having both outlets, the log-mean averaged Nusselt number has a local minimum value at about ε = 0.3. After about ε ≧ 0.8, the log-mean averaged Nusselt number is nearly independent on the pin configuration. Moreover, the staggered pin array pays more pressure-drop penalty as compared with the in-line pin array in the straight-outlet-flow duct: however, in the lateral-outlet-flow duct, the in-line and staggered pin arrays yield almost the same overall pressure drop.
Heat Transfer in a “Cover-Plate” Pre-Swirl Rotating-Disc System
Authors: Pilbrow Robert , Karabay Hasan , Wilson Michael , Owen J. Michael
Published: December 2014

In most gas turbines, blade-cooling air is supplied from stationary pre-swirl nozzles that swirl the air in the direction of rotation of the turbine disc. In the “cover-plate” system, the pre-swirl nozzles are located radially inward of the blade-cooling holes in the disc, and the swirling air flows radially outwards in the cavity between the disc and a cover-plate attached to it.

In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder-Sharma and the Morse low-Reynolds-number k-ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disc” are compared with measured values obtained from a rotating-disc rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 × 106 to 1.5 × 106, and for 0.9 < βp < 3.1, where βp is the pre-swirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disc). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.
Testing of a Low Cooled Ceramic Nozzle Vane Under Transient Conditions
Authors: Dilzer M. , Gutmann Ch. , Schulz A. , Wittig S.
Published: December 2014

At the Institut für Thermische Strömungsrnaschinen, University of Karlsruhe (ITS) a design technology has been introduced to reduce the mechanically and especially the thermally induced stresses in ceramic components. The concept is based on a three-layered construction (outer ceramic shell - heat insulating layer - metallic core) and an optimization of the thicknesses of the single layers, in order to obtain a homogenous temperature distribution in the ceramic structure. The optimization is performed by finite element analyses in combination with failure probability calculations.

This methodology has been applied to increase the reliability of a first stage Sintered Silicon Carbide (SSiC) ceramic nozzle vane of a stationary gas turbine (70MW/1400°C). As a result it was found that the mechanically and thermally induced loads have been reduced considerably and do not exceed 100MPa, thus achieving adequate life based upon failure probability calculations. Even in a trip situation (fuel cutoff), when the highest loads do occur, the calculations demonstrate a significantly reduced failure probability.

The results of the finite element analyses were verified by simulating the typical operating conditions after fuel cutoff in a test rig.
Thermodynamic Performance Analyses of Mixed Gas-Steam Cycle (2): A Case Study of Aeroderivative Gas Turbine
Authors: Hanawa Kirk
Published: December 2014

There are a plenty of proposals to aim the gas turbine cycle thermal efficiency of 60%, such as “Steam-Cooled H-Tech. Combined Cycle”, “Methanol Conversion Regenerative Gas Turbine”, “Kalina Cycle” etc.*1, *2, *4, *5, *6, *7

This paper discusses the predicted performance behaviors of an assumed aircraft-derivative GT of 60MW, when applying into mixed gas-steam cycles like STIG, ISTIG(Intercooled Steam Injection GT) with reasonable minor modifications from the assumed gas turbine. By making case studies of steam-injected binary cycles according to the established analyses method in Part (1), typical calculation results for getting 60% efficiency are presented. The water-injected at LPC, ISTIG cycle is equivalent or superior to other improvement ideas, offering several features listed below.

1) Unnecessary to have a bottoming cycle, saving a lot of investment for the related equipment

2) Quick and stable response for changing duty load, by injecting metered water and steam without air holding vessels like water-cooled heat exchangers