bluuebunny/crossref_metadata_2025 huggingface dataset:
Influencing circadian and sleep–wake regulation for prevention and intervention in mood and anxiety disorders: what makes a good homeostat?
Authors: Frank Ellen , Benabou Marion , Bentzley Brandon , Bianchi Matt , Goldstein Tina , Konopka Genevieve , Maywood Elizabeth , Pritchett David , Sheaves Bryony , Thomas Jessica
Published: December 2014

All living organisms depend on homeostasis, the complex set of interacting metabolic chemical reactions for maintaining life and well‐being. This is no less true for psychiatric well‐being than for physical well‐being. Indeed, a focus on homeostasis forces us to see how inextricably linked mental and physical well‐being are. This paper focuses on these linkages. In particular, it addresses the ways in which understanding of disturbed homeostasis may aid in creating classes of patients with mood and anxiety disorders based on such phenotypes. At the cellular level, we may be able to compensate for the inability to study living brain tissue through the study of homeostatic mechanisms in fibroblasts, pluripotent human cells, and mitochondria and determine how homeostasis is disturbed at the level of these peripheral tissues through exogenous stress. We also emphasize the remarkable opportunities for enhancing knowledge in this area that are offered by advances in technology. The study of human behavior, especially when combined with our greatly improved capacity to study unique but isolated populations, offers particularly clear windows into the relationships among genetic, environmental, and behavioral contributions to homeostasis.
Peripheral nasal‐temporal corneal asymmetry in relation to corneal thickness: a Scheimpflug imaging study
Authors: Jonuscheit Sven , Doughty Michael J. , Martin Raul , Río‐Cristóbal Ana , Cruikshank Victoria , Lang Sue
Published: December 2014

Purpose

To investigate the asymmetry of the peripheral cornea up to 5 mm nasally and temporally from the centre and to assess correlations with regional peripheral corneal thickness.

Methods

Central and peripheral corneal thickness was measured by Scheimpflug imaging (Pentacam) in 113 eyes of 113 healthy, pre‐presbyopic Caucasian subjects. Absolute and relative corneal thickness were analysed in 1 mm steps up to 5 mm to the nasal and temporal sides with the corneal apex as the central reference point. Nasal‐temporal asymmetry was calculated as the thickness ratio between corresponding off‐centre thickness measurements.

Results

The mean (±SD) central corneal thickness was 552 ± 36 μm. CT increased by 22% at 4 mm temporally to 672 ± 44 μm, and 32% at 4 mm nasally to 731 ± 45 μm. The nasal‐temporal asymmetry became greater with increasing distance from the corneal centre, with a mean difference of 59 ± 22 μm at 4 mm from the apex. The nasal‐temporal thickness ratio, based on this difference, was significantly related to the relative temporal (r = −0.41, p < 0.001, simple linear regression) and nasal corneal thickness (r = 0.61, p < 0.001).

Conclusions

A substantial and progressively increasing nasal‐temporal asymmetry in corneal thickness has been confirmed by Scheimpflug imaging, which is related to the magnitude of corneal thickness at peripheral locations. Pachymetry output data and models, including volume calculations, that assume symmetry to the corneal thickness profile may not provide optimum metrics for planning and predicting the outcome of corneal refractive surgery procedures.
Predictors of Food Insecurity among Older Adults in the United States
Authors: Goldberg Shari L. , Mawn Barbara E.
Published: December 2014

Objective

Food insecurity among U.S. households is a national concern. Since 2010, the U.S. Healthy People goal has been to reduce food insecurity to 6%. Despite this goal, 14.5% of households remained food insecure in 2013 (U.S. Department of Agriculture). The purpose of this study was to examine the antecedents of food insecurity among older adults through the lens of the social ecological model.

Design and Sample

This retrospective cross‐sectional study utilized secondary data from the National Health and Nutrition Examination Survey (NHANES) from the years 2007 and 2008 from a sample that included 2,045 adults 60 years of age and older.

Measures

Variables related to the constructs of the social ecological model were examined using descriptive, chi‐square, and logistic regression analyses.

Results

Analyses of the model indicated that the severity of depression, reports of financial support, and having ever received household food stamp benefits had statistically significant main effects on food insecurity among older adults.

Conclusions

The study findings have implications for nursing practice, education, and research and could facilitate the development of screening methods, interventions, and policy evaluation that focus on food insecurity at multiple spheres of influence among the targeted population.
Cinnamyl alcohol dehydrogenases in the mesocarp of ripening fruit of Prunus persica genotypes with different flesh characteristics: changes in activity and protein and transcript levels
Authors: Gabotti Damiano , Negrini Noemi , Morgutti Silvia , Nocito Fabio F. , Cocucci Maurizio
Published: December 2014

Development of fruit flesh texture quality traits may involve the metabolism of phenolic compounds. This study presents molecular and biochemical results on the possible role played by cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.195) during ripening [S3, S4 I (pre‐climacteric) and S4 III (climacteric) stages] of peach [Prunus persica (L.) Batsch] fruit with different flesh firmness [non‐melting flesh (NMF) ‘Oro A’/melting flesh (MF) ‘Springcrest’ and ‘Sanguinella’] and color (blood‐flesh Sanguinella). A total of 24 putative full‐length PRUPE_CAD genes were identified (in silico analysis) in the peach genome. The most abundant CAD isoforms, encoded by genes located on scaffolds 8 and 6, were probed by specifically developed anti‐PRUPE_CAD sc8 and by anti‐FaCAD (PRUPE_CAD sc6) polyclonal antibodies, respectively. PRUPE_CAD sc8 proteins (SDS‐PAGE and native‐PAGE/western blot) appeared responsible for the CAD activity (in vitro/in‐gel assays) that increased with ripening (parallel to PRUPE_ACO1 transcripts accumulation and ethylene evolution) only in the mesocarp of Oro A and blood‐flesh Sanguinella. Accumulation of PRUPE_CAD sc8 transcripts (semi‐quantitative RT‐PCR) occurred in all three cultivars, but in Oro A and Springcrest it was not always accompanied by that of the related proteins, suggesting possible post‐transcriptional regulation. Flesh firmness, as well as levels of lignin, total phenolics and, where present (Sanguinella), anthocyanins, declined with ripening, suggesting that, at least in the studied peach cultivars, CAD activity is related to neither lignification nor differences in flesh firmness (NMF/MF). Further studies are necessary to clarify whether the high levels of CAD activity/expression in Sanguinella play a role in determining the characteristics of this blood‐flesh fruit.
Percutaneous Thrombectomy of AVF: Immediate Success and Long‐term Patency Rates
Authors: Nassar George M. , Rhee Edward , Khan Abdul Jabbar , Nguyen Binh , Achkar Katafan , Beathard Gerald
Published: December 2014

The purpose of this study was to report the results obtained in a cohort of 520 cases of thrombosed arteriovenous fistulas (AVF) treated by percutaneous intervention over a period of 8 years. The methods used varied according to the individual characteristics of the case. A clinical success rate of 91.1% was obtained with no significant difference being noted among radial‐cephalic, brachial‐cephalic, and brachial‐basilic AVFs. The mean primary patency for this group was 227.3 ± 14.6 days, and the mean assisted primary patency was 677.2 ± 44.6 days. The lower arm AVFs had both a primary patency and an assisted primary patency that were significantly better than the upper arm cases (p = 0.006 and 0.002, respectively). The primary patency for radial‐cephalic AVFs was significantly better than that for brachial‐cephalic AVFs (p = 0.021), but not for brachial‐basilic cases (p = 0.122). Assisted primary patency for radial‐cephalic cases was significantly superior to the values for either patients with a brachial cephalic (p = 0.046) or a brachial‐basilic (p = 0.004). Complications occurred in seven cases (1.3%), all of which were venous ruptures. Blood flow was affected in four cases. Only one of these was salvaged with angioplasty balloon tamponade. In the remaining three cases, the AVF was lost.
Effects of kynurenine on CD3+ and macrophages in wound healing
Authors: Salimi Elizei Sanam , Poormasjedi‐Meibod Malihe‐Sadat , Li Yunyuan , Baradar Jalili Reza , Ghahary Aziz
Published: December 2014

As prolongation of the inflammation phase in a healing process frequently leads to wound impairment, here we queried whether kynurenine (Kyn) could modulate this phase of wound healing. To address this, a protein microarray, quantitative polymerase chain reaction (qPCR), flow cytometry for immune cells and immune cell proliferation in the presence and absence of Kyn were conducted and compared. The result of a protein microarray revealed that the expression of 12 pro‐inflammatory cytokines and chemokines was modulated in Kyn‐treated mouse splenocytes as compared with those of control. These findings were then evaluated by conducting a qPCR for the gene expression of these factors and showed a significant reduction in the gene expression of majority of these cytokines and chemokines (interleukin [IL]‐2, IL‐17, C‐X‐C motif chemokine ligand [CXCL] 10, CXCL1, C‐C motif ligand [CCL] 12, CXCL9, CCL4, CXCL2, and CCL5) in response to Kyn treatment. To test the anti‐inflammatory effect of Kyn in an animal model, dorsal surface wounds were generated in a mouse model and wounds received daily topical application of either nothing (control), dermal cream (second control), or Kyn cream using uninjured skin tissue as another control. The wounded tissues were harvested on days 3, 6, and 10 postwounding. As anticipated, the results of fluorescence‐activated cell sorting analysis revealed that upon wounding, the number of total infiltrated CD3+ cells and macrophages (CD11b+) significantly increased on day 3, peaked on day 6, and reduced on day 10 post‐wounding. Interestingly, as compared with those of uninjured and dermal cream alone‐treated wounds, Kyn treatment significantly reduced the number of infiltrated CD3+ cells, but not CD11b+ cells, at different time intervals examined. These findings collectively suggest that Kyn, as a small molecule, can potentially be used to overcome the difficulties associated with persistency of inflammation in healing wounds.
Hyperbaric oxygen therapy activates hypoxia‐inducible factor 1 (HIF‐1), which contributes to improved wound healing in diabetic mice
Authors: Sunkari Vivekananda Gupta , Lind Folke , Botusan Ileana Ruxandra , Kashif Abad , Liu Zhao‐Jun , Ylä‐Herttuala Seppo , Brismar Kerstin , Velazquez Omaida , Catrina Sergiu‐Bogdan
Published: December 2014

Hyperbaric oxygen (HBO) therapy has been used as an adjunctive therapy for diabetic foot ulcers, although its mechanism of action is not completely understood. Recently, it has been shown that HBO mobilizes the endothelial progenitor cells (EPCs) from bone marrow that eventually will aggregate in the wound. However, the gathering of the EPCs in diabetic wounds is impaired because of the decreased levels of local stromal‐derived factor‐1α (SDF‐1α). Therefore, we investigated the influence of HBO on hypoxia‐inducible factor 1 (HIF‐1), which is a central regulator of SDF‐1α and is down‐regulated in diabetic wounds. The effects of HBO on HIF‐1α function were studied in human dermal fibroblasts, SKRC7 cells, and HIF‐1α knock‐out and wild‐type mouse embryonic fibroblasts using appropriate techniques (Western blot, quantitative polymerase chain reaction, and luciferase hypoxia‐responsive element reporter assay). Cellular proliferation was assessed using H3‐thymidine incorporation assay. The effect of HIF in combination with HBOT was tested by inoculating stable HIF‐1α‐expressing adenovirus (Adv‐HIF) into experimental wounds in db/db mice exposed to HBO. HBO activates HIF‐1α at several levels by increasing both HIF‐1α stability (by a non‐canonical mechanism) and activity (as shown both by induction of relevant target genes and by a specific reporter assay). HIF‐1α induction has important biological relevance because the induction of fibroblast proliferation in HBO disappears when HIF‐1α is knocked down. Moreover, the local transfer of stable HIF‐1α‐expressing adenovirus (Adv‐HIF) into experimental wounds in diabetic (db/db mice) animals has an additive effect on HBO‐mediated improvements in wound healing. In conclusion, HBO stabilizes and activates HIF‐1, which contributes to increased cellular proliferation. In diabetic animals, the local transfer of active HIF further improves the effects of HBO on wound healing.
Measurement Uncertainties Encountered During Gas Turbine Driven Compressor Field Testing
Authors: Brun Klaus , Kurz Rainer
Published: December 2014

Field testing of gas turbine compressor packages requires the accurate determination of efficiency, capacity, head, power and fuel flow in sometimes less than ideal working environments. Nonetheless, field test results have significant implication for the compressor and gas turbine manufacturers and their customers. Economic considerations demand that the performance and efficiency of an installation are verified to assure a project’s return on investment. Thus, for the compressor and gas turbine manufacturers, as well as for the end-user, an accurate determination of the field performance is of vital interest. This paper describes an analytic method to predict the measurement uncertainty and, thus, the accuracy, of field test results for gas turbine driven compressors. Namely, a method is presented which can be employed to verify the validity of field test performance results.

The equations governing the compressor and gas turbine performance uncertainties are rigorously derived and results are numerically compared to actual field test data. Typical field test measurement uncertainties are presented for different sets of instrumentation. Test parameters that correlate to the most significant influence on the performance uncertainties are identified and suggestions are provided on how to minimize their measurement errors. The effect of different equations of state on the calculated performance is also discussed.

Results show that compressor efficiency uncertainties can be unacceptably high when some basic rules for accurate testing are violated. However, by following some simple measurement rules and maintaining commonality of the gas equations of state, the overall compressor package performance measurement uncertainty can be limited and meaningful results can be achieved.
Turbomachinery Blade Design Using a Navier-Stokes Solver and Artificial Neural Network
Authors: Pierret Stéphane , Van den Braembussche R. A.
Published: December 2014

This paper describes a knowledge-based method for the automatic design of more efficient turbine blades. An Artificial Neural Network (ANN) is used to construct an approximate model (response surface) using a database containing Navier Stokes solutions for all previous designs. This approximate model is used for the optimization, by means of Simulated Annealing (SA), of the blade geometry which is then analyzed by a Navier-Stokes solver.

This procedure results in a considerable speed-up of the design process by reducing both the interventions of the operator and the computational effort. It is also shown how such a method allows the design of more efficient blades while satisfying both the aerodynamic and mechanical constraints. The method has been applied to different types of 2D turbine blades of which three examples are presented in this paper.
Investigation of Detailed Film Cooling Effectiveness and Heat Transfer Distributions on a Gas Turbine Airfoil
Authors: Drost U. , Bölcs A.
Published: December 2014

In the present study film cooling effectiveness and heat transfer were systematically investigated on a turbine NGV airfoil employing the transient liquid crystal technique and a multiple regression procedure. Tests were conducted in a linear cascade at exit Reynolds numbers of 0.52e6, 1.02e6 and 1.45e6 and exit Mach numbers of 0.33, 0.62 and 0.8, at two mainstream turbulence intensities of 5.5% and 10%. The film cooling geometry consisted of a single compound angle row on the pressure side (PS), and a single or a double row on the suction side (SS). Foreign gas injection was used to obtain a density ratio of approximately 1.65, while air injection yielded a density ratio of unity. Tests were conducted for blowing ratios of 0.25 to 2.3 on the SS, and 0.55 to 7.3 on the PS.

In general film cooling injection into a laminar BL showed considerably higher effectiveness in the near hole region, as compared to a turbulent BL. While mainstream turbulence had only a weak influence on SS cooling, higher effectiveness was noted on the PS at high turbulence due to increased lateral spreading of the coolant. Effects of mainstream Mach and Reynolds number were attributed to changes of the BL thickness and flow acceleration. Higher density coolant yielded higher effectiveness on both SS and PS, whereas heat transfer ratios were increased on the SS and decreased on the PS. Comparison of the single and double row cooling configurations on the SS revealed a better film cooling performance of the double row due to an improved film coverage and delayed jet separation.
Application of Time-Shifted Boundary Conditions to a 3D Euler/Navier-Stokes Aeroelastic Code
Authors: Srivastava R. , Bakhle Milind A. , Keith Theo G. , Stefko G. L.
Published: December 2014

In the present work the unsteady aerodynamic characteristics of harmonically oscillating fan blades are investigated by applying a time-shifted boundary condition at the periodic boundaries. The direct-store method is used to implement the time-shifted boundary condition in a time-marching Euler/Navier-Stokes solver. Inviscid flow calculations for a flat plate helical fan, in a single-blade passage domain, are used to verify the analysis. The results obtained show good correlation with other published results as well as with the same solver using multiple blade passages stacked together. Significant savings in computer time is realized, especially for smaller phase angles.
Computation of Flutter of Turbomachinery Cascades Using a Parallel Unsteady Navier-Stokes Code
Authors: Ji Shanhong , Liu Feng
Published: December 2014

A quasi-three-dimensional multigrid Navier-Stokes solver on single and multiple passage domains is presented for solving unsteady flows around oscillating turbine and compressor blades. The conventional “direct store” method is used for applying the phase-shifted periodic boundary condition over a single blade passage. A parallel version of the solver using the Message Passing Interface (MPI) standard is developed for multiple passage computations. In the parallel multiple passage computations, the phase-shifted periodic boundary condition is converted to simple in-phase periodic condition. Euler and Navier-Stokes solutions are obtained for unsteady flows through an oscillating turbine cascade blade row with both the sequential and the parallel code. It is found that the parallel code offers almost linear speedup with multiple CPUs. In addition, significant improvement is achieved in convergence of the computation to a periodic unsteady state in the parallel multiple passage computations due to the use of in-phase periodic boundary conditions as compared to that in the single passage computations with phase-lagged periodic boundary conditions via the “direct store” method. The parallel Navier-Stokes code is also used to calculate the flow through an oscillating compressor cascade. Results are compared with experimental data and computations by other authors.
The Use of Case-Based Reasoning Technology to Aid Fault Isolation in a Modern Gas Turbine Engine Design
Authors: Hargrave S. M. , Fleming P. J.
Published: December 2014

The increasing numbers of commercial decision support tools based on Case-Based Reasoning (CBR) technology reflects the interest in the use of this technology to aid fault diagnosis, not only in gas turbine applications but also in the wider engineering domain. CASSIOPEE from CFM and ARIADNE from British Airways are but two examples of these types of support tool in the civil gas turbine engine arena. They reflect the trend of developing such systems from a historical database of maintenance arisings and necessarily apply to older engine designs. Further characteristics of which include older and less sophisticated aircraft maintenance systems, which provide limited diagnostic information and rely more heavily upon the experience of maintenance personnel to isolate engine faults successfully. It is this diagnostic experience which these CBR tools have attempted to capture and emulate; the case for a CBR-based tool in this instance is well proven.

More recent aircraft design have resulted in a more comprehensive on-board maintenance systems to aid maintenance personnel diagnose airframe and engine faults. Such an approach should rely less heavily upon the experience of the maintenance crew to isolate a fault successfully. The paper reports on the design and development of two CBR-based maintenance decision support tools for the Rolls-Royce Trent 800 and RB211-524 engines. One system is currently undergoing a trial to refine the design of the maintenance case base (the database over which the CBR engine searches to match the current fault symptoms to a historical event). The lessons learned from this field trial and future prospects for such a CBR-based maintenance aid are discussed.
Sawmill, Wood Waste Fuelled, 100% Recuperated, 5 MW Gas Turbine Co-Generation Plant
Authors: Lefcort Malcolm D. , Skodje E. L. S. (Ted)
Published: December 2014

Sawmills in the Canadian province of British Columbia (BC) will soon be confronted with a collective wood waste disposal problem (bark, sawdust and shavings) of about 3 Million bone dry tonne/y at an average wet basis moisture content of about 45%. About 40 existing sawmill beehive burners presently incinerate this waste. Emissions from these beehive burners exceed current provincial particulate limits. Markets for the waste — board plants, sawdust digesters, charcoal plants, etc. — are limited. The economics of 25 to 50 MW wood-fired, steam power plants is poor. 6¢/kW.h is needed to finance a plant; the major utility offers 2¢/kW.h.

This paper describes a 3 MW to 5 MW, Nuovo Pignone PGT-5 co-generation plant fuelled by the 2000°F (1093°C) exhaust from a Heuristic EnvirOcycler, a two-stage, wood waste incinerator. The exhaust meets BC’s particulate limit of 0.052 grains/dscf (120 mg/Nm3). 37 to 65 Million Btu/h (39 to 68 GJ/h) of waste heat can be recovered from the system exhausts. In this application the PGT-5’s external combustion chamber is replaced by a “recuperator”, i.e., a high temperature, gas-to-air, heat exchanger.

Two variations of the basic system are examined. One features a larger than necessary EnvirOcycler to generate additional steam in the waste heat boiler. The other variation discusses heating 1,550°F (843°C) air from the recuperator up to 1,796°F (980°C) with natural gas. The extra power generated can cost as little as 1.9¢/kW.h.
Physics of Airfoil Clocking in a High-Speed Axial Compressor
Authors: Dorney Daniel J. , Sharma Om P. , Gundy-Burlet Karen L.
Published: December 2014

Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and inviscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, as the Mach number increases the interaction between blade rows can be intensified due to potential effects. In the current study an unsteady, quasi-three-dimensional Navier-Stokes analysis has been used to investigate the unsteady aerodynamics of stator clocking in a 1-1/2 stage compressor, typical of back stages used in high-pressure compressors of advanced commercial jet engines. The effects of turbulence have been modeled with both algebraic and two-equation models. The results presented include steady and unsteady surface pressures, efficiencies, boundary layer quantities and turbulence quantities.

The main contribution of the current work has been to show that airfoil clocking can produce significant performance variations at the Mach numbers associated with an engine operating environment. In addition, the growth of turbulence has been quantified to aid in the development of models for the multi-stage steady analyses used in design systems.
Development of the Next Generation Gas Turbine Based Jet Air Start Unit for the US Navy
Authors: Zoccoli Michael J. , Cheeseman William H.
Published: December 2014

Main powerplants for aircraft in the US Navy inventory typically require a source of pneumatic power in order to initiate the engine start sequence. The equipment which is used as the source for this power is termed “UNIJASU”, or Universal Jet Aircraft Start Unit.

UNIJASU is a fully self-contained, transportable source of ground power which may be adapted to both land or carrier-based operations. At the nucleus of this unit is a modified T53 aircraft gas turbine, originally developed and fielded by the Lycoming Turbine Engine Division of Stratford Conn. In the current application, the T53 has been re-configured as a gas generator with specific provisions for extensive operation in a marine environment. Using the bleed machine concept, up to 30% of the engine massflow (equating to roughly 420 air horsepower) can be delivered to an aircraft starter upon demand. The present production source for the T53 engine is the AlliedSignal Engine Company, located at Phoenix, Az.

As of the writing date (mid-1997), the US Navy is in the process of procuring its next generation air start units via contract to AlliedSignal. This paper describes the salient features of a rigorous two-phase development program starting with the initial adaptation of the aircraft turbine engine to a naval ground power unit, and culminating with over 6000hrs of system level testing, inclusive of actual field evaluations.
Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor
Authors: Kassens I. , Rautenberg M.
Published: December 2014

In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller.

The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured.

Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.
Physical Explanations of Tip Leakage Flow Field in an Axial Compressor Rotor
Authors: Inoue Masahiro , Furukawa Masato , Saiki Kazuhisa , Yamada Kazutoyo
Published: December 2014

Structure of a tip leakage flow field in an axial compressor rotor has been investigated by detailed numerical simulations and appropriate post-processing. Physical explanations of the structure are made in terms of vortex-core identification, normalized helicity, vortex-lines, limiting streamlines, etc. The onset of the discrete tip leakage vortex is located on the suction surface at some distance from the leading edge. The vortex core with high vorticity is generated from a shear layer between the leakage jet flow and the main flow. The streamlines in the leakage flow are coiling around the vortex core. All the vortex-lines in the tip leakage vortex core link to ones in the suction surface boundary layer. The other vortex-lines in the suction surface boundary layer link to the vortex-lines in the pressure surface boundary layer and in the casing wall boundary layer. There are two mechanisms to reduce intensity of the tip leakage vortex: one is reduction of discharged vorticity caused by the linkage of vortex-lines between the suction surface and casing wall boundary layers, and another is diffusion of vorticity from the tip leakage vortex. Relative motion of the endwall has a substantial influence on the structure of the leakage flow field. In the case of a compressor rotor, it intensifies streamwise vorticity of the leakage vortex but reduces leakage flow loss.
The Role of Rotor Tip Clearance on the Aerodynamic Interaction of a Last Gas Turbine Stage and an Exhaust Diffuser
Authors: Willinger Reinhard , Haselbacher Hermann
Published: December 2014

An investigation of the aerodynamic interaction between a last gas turbine stage and an exhaust diffuser is presented. Special attention is given to the influence of the rotor tip gap on this interaction. Flow measurements downstream of a linear cascade of turbine blades with tip gap have been performed in a low speed cascade wind tunnel. The geometry of the cascade corresponds to the tip section of a gas turbine of fairly recent design. Five tip gaps lying in the typical range were investigated. The two essential results are the leakage loss and the underturning in the end wall region. The flow field of the turbine cascade supplied the inlet boundary condition for the subsequent numerical investigation of the flow field in an annular diffuser. The geometry of the annular diffuser is based on dimensions of exhaust diffusers of some heavy duty and aeroderivative gas turbines. The result of the investigation is the diffuser pressure recovery factor as a function of the gap of the upstream cascade. The results from the cascade measurements and the diffuser computations have then been coupled by means of an interaction model. For gaps of practical interest, specific work and efficiency of the last gas turbine stage followed by an exhaust diffuser are independent of the rotor gap.
Mode Localization of a Cracked Blade-Disks
Authors: Kuang J. H. , Huang B. W.
Published: December 2014

In this paper, the effect of blade crack on the mode localization of a rotating blade-disk is studied. Pretwisted taper beams are used to simulate blades of a blade-disk. The crack on the blade can be regarded as a local disorder of this periodically coupled blades system. An application of Hamilton’s principle and Galerkin’s method is used to formulate the equations of motion of the mistuned system. Effects of pretwisted angle, rotating speed and crack depth of the blade on the in-plane and off-plane mode localizations of a rotating system are investigated. Numerical results indicate that the increase of rotating speed, pretwisted angle and crack depth could enhance the localization phenomenon significantly.
Effect of High Freestream Turbulence With Large Length Scale on Blade Heat/Mass Transfer
Authors: Wang H. P. , Goldstein R. J. , Olson S. J.
Published: December 2014

The naphthalene sublimation technique is used to investigate the influence of high freestream turbulence with large length scale on the heat/mass transfer from a turbine blade in a highly accelerated linear cascade. The experiments are conducted at four exit Reynolds numbers, ranging from 2.4 × 105 to 7.8 × 105, with freestream turbulence of 3%, 8.5% and 18% and corresponding integral length scales of 0.9 cm, 2.6 cm and 8 cm, respectively. On the suction surface, the heat/mass transfer rate is significantly enhanced by high freestream turbulence due to an early boundary layer transition. By contrast, the transition occurs very late, and may not occur at very low Reynolds numbers with low freestream turbulence. In the turbulent boundary layer, lower heat/mass transfer rates are found for the highest freestream turbulence level with large length scale than for the moderate turbulence levels with relatively small scales. Similar phenomena also occur at the leading edge. However, the effect of turbulence is not as pronounced in the laminar boundary layer.
An Experimental Study on the Relationship Between Velocity Fluctuations and Heat Transfer in a Turbulent Air Flow
Authors: Denninger Michael J. , Anderson Ann M.
Published: December 2014

The work presented here is the first reported study to test the general correlation for turbulent heat transfer proposed by Maciejewski and Anderson (1996). A turbulent pipe flow apparatus was built for heat transfer and fluid studies. Tests were performed for a range of Reynolds numbers from 27,000 to 90,000. The heated wall temperature, adiabatic temperature, the wall heat flux and the maximum velocity fluctuations were measured at each Reynolds number. The non-dimensional groups recommended by Maciejewski and Anderson were formed and compared to the correlation. The results verify the correlation with agreement to within ±7% (as per figure 11). This study has important implications for the study of heat transfer in a wide range of fields, including the gas turbine industry. The development of a geometry independent correlation will lead to faster turn around times and improved engine design.
A Three Dimensional Computational Study of Windage Heating Within an Axial Compressor Stator Well
Authors: Ozturk H. K. , Childs P. R. N. , Turner A. B. , Hannis J. M. , Turner J. R.
Published: December 2014

Shrouded stator blades are sometimes used to prevent vibration problems, but more often they are used to eliminate blade over-tip leakage flows. A trench or recess referred to as a stator well must be provided in the rotor drum assembly in order to accommodate the stator shroud. This paper presents a computational study of the flow and windage generation within an axial compressor stator well. Windage heating levels for a three dimensional compressible solution of flow through a geometry comprising upstream and downstream stator well cavities, labyrinth seal and the stator blade row are quantified. The potential for hot fluid ejected from the upstream stator well seal into the mainstream annulus, migrating through the blade row and being re-ingested at the downstream stator well seal for further windage heating has been studied using a layered temperature boundary condition at entry to the stator row. The possible reconfiguration of detailed stator well geometry has been explored to identify options for controlling flow rate and reducing windage levels, other than controlling clearances, yielding a 9% reduction in flow rate and a 9% reduction in windage heating.
Integrated Condition Monitoring System Strategy at CEMIG
Authors: Hastings Michael M. , de Oliveira Wander Luiz , Metzker Raimundo Jorge Ivo
Published: December 2014

The condition monitoring section at the Brazilian power utility CEMIG is implementing an effective condition-based maintenance strategy that ensures the over 40 power plants spread out over a large area operate with minimal downtime and at a minimal maintenance cost. The condition monitoring system needed to fulfil CEMIG’s needs for the larger plants did not exist, so it was decided to integrate several monitoring systems for this purpose. A computerized, permanently installed vibration monitoring system is planned to be integrated to other systems dedicated to specific periodic machine condition monitoring applications (e.g. air gap monitoring, oil analysis, magnetic flux monitoring, partial discharge analysis). This integrated monitoring approach results in a distributed system with a single system technique for alarm handling, and a user interface and database for analysis, diagnosis and fault correlation. The vibration monitoring system will also be extended for importing process data from the existing distributed supervisory and control system for monitoring calculated performance parameters such as efficiency and head. Testing is also under way for investigating the possibility of more effectively monitoring cavitation without purchasing a separate stand-alone system. Several of the larger plants at CEMIG will eventually be remotely monitored this way, but this paper focuses primarily on the monitoring system, strategy and current operating experience at the Nova Ponte hydroelectric power station. Even before integrating the other monitoring systems, the installed condition monitoring section played a large role in ensuring the plant operates safely, cost effectively and with maximum availability. Although the monitoring system is installed at a hydro-electric power station, some examples are briefly given on how the same integrated monitoring system approach could equally be advantageous in detecting and/or diagnosing certain faults within gas turbines and compressors.
Characteristics of Heat Transfer in Rotating Cavities
Authors: Jerhamre Anders , Eriksson Lars-Erik
Published: December 2014

In rotating cavities the driving temperature difference for heat transfer is not easy to define or estimate. Traditionally, some reference temperature, here called bulk temperature, is used. This bulk temperature is closely connected to the heat transfer coefficient. In order to determine these characteristics, the assumption that the wall heat flux is linearly proportional to the temperature difference between wall and inlet air, is used. The slope is equal to the heat transfer coefficient and the x-intercept gives the difference between bulk temperature and inlet temperature. The validity of this assumption is thoroughly investigated by solving the Reynolds averaged Navier-Stokes equations for compressible, axisymmetric flow with a low Reynolds number k-ϵ-model. Rotational and buoyancy effects, which may introduce a non-linear relationship and also affect the local bulk temperature, are all taken into account in the CFD model.

Three different cases were investigated: one simple corotating disk cavity; one simple rotor-stator cavity, and finally one real engine application cavity. The rotational Reynolds numbers, mass flow rates and temperature differences were varied.

Results indicate that the Linear assumption is valid for a range of wall temperatures but not for regions where the local wall temperature affects the flow field, e.g. in corners. Furthermore, when the flow field undergoes a drastic change, new heat transfer characteristics must be determined, or be used with care. Since the heat transfer coefficient and bulk temperature are uniquely determined by the flow field, and not by the local wall temperature, it is not necessary to make a coupled, continuous calculation of the flow field and thermal distribution in the structure.
Fault Detection and Accommodation in Real Time Embedded Full Authority Digital Electronic Engine Controls
Authors: Martucci Angelo
Published: December 2014

Fault Detection and Accommodation Logic easily occupies at least fifty percent of the real time embedded software application program in the contemporary Full Authority Digital Electronic Engine Control (FADEC). Indeed, if a layman were to look at the logic distribution in a FADEC he might think the main purpose of the FADEC was to detect failures! This, of course, is not the case. It is true, however, that real world applications must be programmed to deal with the inevitable fact that system failures will occur. The success of the application program then depends not only on how well it controls the engine, but how well it detects, isolates and accommodates failures. In other words, the fault tolerance of an application is just as important as the robustness of the control algorithms.

Over the past two decades many basic Fault Detection and Accommodation (FDA) techniques have been developed and have become commonplace in FADECs. These techniques have been developed in such a way as to maximize an application’s Built In Test (BIT) effectiveness for both “hard”, “soft”, and intermittent failures, while minimizing failure annunciation due to “false alarm” events. These techniques have been implemented in both hardware and software.

This paper will present and discuss these basic FDA techniques for input signals, output signals, processors, memory devices and communication devices. Many of the newer FDA techniques will also be discussed. An overview of the key components of FDA, and the established “norms” for effective FDA will be added for completeness. Since the structure of FDA is dependent upon system architecture, the system under consideration is chosen as the Dual-Channel Full Authority Digital Electronic Engine Control. This is the configuration that is most commonly used in commercial and military engine control applications.
Biomass/Coal Derived Gas Utilization in a Gas Turbine Combustor
Authors: Hoppesteyn P. D. J. , Andries J. , Hein K. R. G.
Published: December 2014

Low calorific value fuel gas, obtained by pressurized fluidized bed gasification of coal/biomass mixtures, is combusted at 0.8 MPa with air or oxygen in a vertical cylindrical chamber (D = 0.28 m, L = 2.0 m). The fuel (T = 1060 K) and oxydizer (air at 350 K, oxygen at 460 K) are injected coaxially, resulting in an essentially axissymmetric flow pattern. Particles have been removed from the fuel gas stream by a cyclone, mounted between the gasifier and the combustor. A two-dimensional model, implemented in the CFD code FLUENT was developed for the calculation of temperatures, flow patterns and species concentrations throughout the combustor. The calculated results are compared with experimental data for two low calorific value fuel gas compositions and two oxidizer compositions at two axial combustor locations (X/L = 0.175 and X/L = 1). The results appear to justify further investigation of the applicability of the model to low calorific value fuel gas fired gas turbine combustors.
Steady-State and Dynamic Performance Prediction of an Indirect Fired Gas Turbine Plant
Authors: Crosa G. , Fantini L. , Ferrari G. , Pizzimenti L. , Trucco A.
Published: December 2014

The paper presents the first results of a research, in progress at the Istituto di Macchine e Sistemi Energetici of Genova University, about a gas-steam combined cycle with indirect fired gas-turbine.

The study has dealt with the gas turbine plant which is the most innovative part of the process. To select the design point of every component, a thermodynamic parametric analysis over a large range of pressure ratios and a large range of mass flow ratio through the two characteristic by-passes has been developed.

The off-design performances of the gas plant have been investigated and finally a proposal of control system has been made, tested using a simple mathematical model, able to analyse in the time domain the dynamic behaviour of the controlled gas plant.
A Parallel CFD Tool to Produce Faulty Blade Signatures for Diagnostic Purposes
Authors: Koubogiannis D. G. , Iliadis V. P. , Giannakoglou K. C.
Published: December 2014

In the turbomachinery field, many diagnostic systems utilize databases with symptoms corresponding to the most frequent operation faults. Thanks to Computational Fluid Dynamics (CFD), databases can be created without costly experiments, whereas the use of unstructured grids in combination with parallel processing makes the whole task easy and fast to accomplish. In this paper, a procedure that builds up a database for gas-turbine fault diagnosis is demonstrated. Advanced CFD tools that operate concurrently on multi-processor platforms are used. The so-prepared database contributes to the identification of faults through the analysis of the unsteady pressure signals that correspond to hypothetical sensors located in the inter-blade region. The pressure signals are post-processed in a similar way to the one experimentalists employ for fast-response pressure measurements. Symptoms related to displaced and/or twisted blades in an industrial high-speed compressor cascade, at design and off-design operating conditions, are analyzed.
Fluid Flow in a 180 Deg Sharp Turning Duct With Different Divider Thicknesses
Authors: Liou Tong-Miin , Tzeng Yaw-Yng , Chen Chung-Chu
Published: December 2014

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able to reasonably explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.
Analysis of Tip Leakage Effects in a High Subsonic Annular Compressor Cascade
Authors: Bonhommet-Chabanel C. , Gerolymos G. A.
Published: December 2014

This paper presents both experimental and numerical results of tip leakage effects in a High Speed Annular Cascade. The influence of the clearance size has been investigated. For validation purposes and a better understanding of the 3-D phenomena, a comparison of the measurements with three-dimensional Navier-Stokes computations using a k-ε closure with a low-Reynolds approach has been performed.

The high speed annular cascade facility has been specifically designed for studying tip leakage flows at the rear of high pressure compressors. In the vicinity of the clearance, the inlet swirl angle, created by a scroll, is of 60° from the axial direction and the Mach number is about 0.60. The blades are cantilevered (fixed on the casing with a clearance gap at the rotating inner wall). In order to obtain a picture of the flow field as complete as possible, different kinds of measurements have been used. 3D velocity measurements within the blade passages have been performed by means of a 3-D Laser Doppler Anemometer system. Furthermore, a five-hole probe with long stem was also used in the blade passage.

The experimental data are quite detailed and self-consistent. A leakage vortex can clearly be identified and, within the blade passage, seems to be responsible for a region of overturning above it. The clearance size has a direct impact on the inception point of the phenomena and on the direction and strength of the leakage vortex. The calculation was found to reproduce the same trends as the experiment and give good quantitative comparisons, although it overestimates the leakage effect at blade exit.