bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanobiotechnology for the Prevention of Dialysis‐related Amyloidosis
Authors: Stamopoulos Dimosthenis , Bouziotis Penelope , Benaki Dimitra , Zirogiannis Panagiotis N , Kotsovassilis Kostantinos , Belessi Vassiliki , Dalamagas Vassilis , Papadopoulos Kostantinos
Published: March 2009

Abstract:  Dialysis‐related amyloidosis is related to the inefficient removal of β2‐microglobulin (β2‐m) that is mainly responsible for the formation of amyloid fibrils deposited on the joints and in the heart, blood vessels and digestive system. Magnetically assisted hemodialysis (MAHD) can be used for the prevention of dialysis‐related amyloidosis. MAHD is based on ferromagnetic nanoparticle‐targeted binding substance conjugates (FN‐TBS Cs) that should be administered to the patient before the dialysis session. The TBS should have a high affinity for β2‐m so that the conjugates bind with the β2‐m in the bloodstream. The complex FN‐TBS–β2‐m will be selectively removed during dialysis by means of a “magnetic dialyzer” that is installed at the dialysis machine in series to the conventional dialyzer. We have examined the in vitro applicability of MAHD by employing biocompatible Fe3O4 and bovine serum albumin (BSA) as constituents of the FN‐TBS Cs. We evaluated the binding capacity of both bare Fe3O4 FNs and Fe3O4‐BSA Cs for β2‐m concentrations ranging from mild to severe conditions. Finally, we conducted mock‐dialysis experiments for the evaluation of several technical issues related to MAHD. β2‐m is adsorbed onto the Fe3O4‐BSA Cs not only almost instantly, but also very efficiently. The employed Cs do not chemically interact with the materials used in standard dialyzers, as agglomerates were not observed in the capillaries of the conventional dialyzers. MAHD may become an efficient modality for the prevention of dialysis‐related amyloidosis because β2‐m concentrations ranging from mild to severe conditions can be adequately handled.
On‐line Hemodiafiltration in Southeast Asia: A Three‐year Prospective Study of a Single Center
Authors: Tiranathanagul Khajohn , Praditpornsilpa Kearkiat , Katavetin Pisut , Srisawat Nattachai , Townamchai Natavudh , Susantitaphong Paweena , Tungsanga Kriang , Eiam‐Ong Somchai
Published: March 2009

Abstract:  Growing evidence suggests the superiority of on‐line hemodiafiltration (HDF) compared with the conventional hemodialysis technique in many aspects; however, on‐line HDF is still not used worldwide, including in Southeast Asia. The purpose of this study is to compare various clinical outcomes between on‐line HDF and high‐flux hemodialysis (HFHD). This was a single‐center three‐year prospective observational study that demonstrated the clinical parameters after switching from HFHD to on‐line HDF in 22 HDF patients, whose average age was 58.1 ± 13.3 years. The incidence of intradialytic undesired events, including hypotension, decreased and an apparent increase in appetite and an improvement in overall well‐being were recorded by most patients after switching to on‐line HDF. The data for dry weight, body mass index, and normalized protein nitrogen appearance, which represent nutritional status, showed a significant improvement while still maintaining a satisfactory albumin level. The adequacy in terms of urea reduction ratio significantly increased. The serum predialysis β2‐microglobulin levels were reduced by 25.7% from 31.1 ± 3.1 to 23.1 ± 4.8 mg/L (P < 0.05) at six months and remained constant during the three years of follow‐up. The patients' lipid profile was well controlled, and the mean C‐reactive protein value was still maintained in the normal range. In conclusion, our three‐year experience showed that on‐line HDF is a well‐tolerated treatment with a lower incidence of intradialytic undesired events. The potential benefits may include the effective removal of higher molecular weight uremic toxins and an improved nutritional status, along with a low inflammatory state.
Hemofiltration With the Cascade System in an Experimental Porcine Model of Septic Shock
Authors: Rimmelé Thomas , Wey Pierre‐François , Bernard Nicolas , Monchi Mehran , Semenzato Nicolas , Benatir Farida , Boselli Emmanuel , Etienne Jérôme , Goudable Joëlle , Chassard Dominique , Bricca Giampiero , Allaouchiche Bernard
Published: March 2009

Abstract:  High‐volume hemofiltration (HVHF) has been suggested as an adjuvant treatment of septic shock because of its capacities to remove inflammatory mediators from blood. Nevertheless, HVHF presents some important drawbacks, such as the depletion of low molecular weight molecules (nutriments, vitamins, trace elements and antibiotics) due to the high ultrafiltration rate, or the significant financial cost and nursing workload due to the frequent changes of large amounts of expensive sterile substitution fluids. A new hemofiltration system called “Cascade” has been developed, allowing very high ultrafiltration rates (120 mL/kg/h) limiting these drawbacks by using a special extracorporeal circuit. The objective of this study was to assess the technical feasibility of the Cascade system and to compare its hemodynamic impact to that of the standard HVHF system. Twenty sepsis‐induced pigs were randomized in two groups: one group was hemofiltered with the standard HVHF system and the other with the Cascade system during a six‐hour session. No technical problems were observed with the Cascade system during the experiment. At the end of the experiment, colloid requirements (989 ± 355 mL vs. 1913 ± 538 mL, P = 0.006), epinephrine requirements (0.82 ± 0.42 mg vs. 3.27 ± 3.02 mg, P < 0.001), lactic acidosis (pH = 7.33 ± 0.08 vs. 7.10 ± 0.07, P < 0.001) and mean pulmonary arterial pressure were less pronounced in the Cascade group. These results suggest that Cascade hemofiltration is technically feasible and safe. Moreover, compared with standard HVHF, it can reduce the severity of porcine septic shock.
Isolation and characterization of 12 microsatellite loci for cross‐species amplification in the cyprinid gudgeons Squalidus chankaensis and S. japonicus
Authors: KAKIOKA RYO , WATANABE KATSUTOSHI , TAKESHIMA HIROHIKO , NISHIDA MUTSUMI
Published: March 2009

Twelve dinucleotide markers were successfully isolated and characterized from a microsatellite‐enriched genomic library obtained for the gudgeon Squalidus chankaensis biwae. These markers were also available for the congeners S. c. tsuchigae and S. japonicus from Japan, which had five to 46 alleles and an expected heterozygosity ranging from zero to 0.946. Linkage equilibrium was observed at all loci, and most loci did not show significant deviation from Hardy–Weinberg equilibrium. The isolated microsatellite markers will be useful for genetic diversity studies of Squalidus populations.
Characterization of polymorphic microsatellite DNA markers in Hakea oldfieldii Benth. (Proteaceae)
Authors: BYRNE M. , HANKINSON M.
Published: March 2009

A genomic library was constructed and 13 polymorphic microsatellite markers were developed for Hakea oldfieldii, a woody shrub endemic to southwest Western Australia. Polymorphism was investigated for these markers in 28 individuals from a single population located in restricted habitat at the base of the Whicher Range south of Busselton. Expected heterozygosity ranged from 0.279 to 0.770 and averaged 0.633. Observed heterozygosity ranged from 0.321 to 0.786 and averaged 0.598. The number of alleles per locus ranged from 2.0 to 6.0 and averaged 4.5. These markers will be used to assay genetic diversity and pollen dispersal in this species.
Acute exercise modulates the Foxo1/PGC‐1α pathway in the liver of diet‐induced obesity rats
Authors: Ropelle Eduardo R. , Pauli José R. , Cintra Dennys E. , Frederico Marisa J. S. , De Pinho Ricardo A. , Velloso Lício A. , De Souza Cláudio T.
Published: March 2009

PGC‐1α expression is a tissue‐specific regulatory feature that is extremely relevant to diabetes. Several studies have shown that PGC‐1α activity is atypically activated in the liver of diabetic rodents and contributes to hepatic glucose production. PGC‐1α and Foxo1 can physically interact with one another and represent an important signal transduction pathway that governs the synthesis of glucose in the liver. However, the effect of physical activity on PGC‐1α/Foxo1 association is unknown. Here we investigate the expression of PGC‐1α and the association of PGC‐1α/Foxo1 in the liver of diet‐induced obese rats after acute exercise. Wistar rats swam for two 3 h‐long bouts, separated by a 45 min rest period. Eight hours after the acute exercise protocol, the rats were submitted to an insulin tolerance test (ITT) and biochemical and molecular analysis. Results demonstrate that acute exercise improved insulin signalling, increasing insulin‐stimulated Akt and Foxo1 phosphorylation and decreasing PGC‐1α expression and PGC‐1α/Foxo1 interaction in the liver of diet‐induced obesity rats under fasting conditions. These phenomena are accompanied by a reduction in the expression of gluconeogenesis genes, such as phosphoenolpyruvate carboxykinase (PEPCK) and glucose‐6‐phosphate (G6Pase). Thus, these results provide new insights into the mechanism by which exercise could improve fasting hyperglycaemia.
Characteristics and physiological role of hyperpolarization activated currents in mouse cold thermoreceptors
Authors: Orio Patricio , Madrid Rodolfo , De La Peña Elvira , Parra Andrés , Meseguer Víctor , Bayliss Douglas A. , Belmonte Carlos , Viana Félix
Published: March 2009

Hyperpolarization‐activated currents (Ih) are mediated by the expression of combinations of hyperpolarization‐activated, cyclic nucleotide‐gated (HCN) channel subunits (HCN1–4). These cation currents are key regulators of cellular excitability in the heart and many neurons in the nervous system. Subunit composition determines the gating properties and cAMP sensitivity of native Ih currents. We investigated the functional properties of Ih in adult mouse cold thermoreceptor neurons from the trigeminal ganglion, identified by their high sensitivity to moderate cooling and responsiveness to menthol. All cultured cold‐sensitive (CS) neurons expressed a fast activating Ih, which was fully blocked by extracellular Cs+ or ZD7288 and had biophysical properties consistent with those of heteromeric HCN1–HCN2 channels. In CS neurons from HCN1(−/−) animals, Ih was greatly reduced but not abolished. We find that Ih activity is not essential for the transduction of cold stimuli in CS neurons. Nevertheless, Ih has the potential to shape the excitability of CS neurons. First, Ih blockade caused a membrane hyperpolarization in CS neurons of about 5 mV. Furthermore, impedance power analysis showed that all CS neurons had a prominent subthreshold membrane resonance in the 5–7 Hz range, completely abolished upon blockade of Ih and absent in HCN1 null mice. This frequency range matches the spontaneous firing frequency of cold thermoreceptor terminals in vivo. Behavioural responses to cooling were reduced in HCN1 null mice and after peripheral pharmacological blockade of Ih with ZD7288, suggesting that Ih plays an important role in peripheral sensitivity to cold.
Developmental alterations in the functional properties of excitatory neocortical synapses
Authors: Feldmeyer Dirk , Radnikow Gabriele
Published: March 2009

In the neocortex, most excitatory, glutamatergic synapses are established during the first 4–5 weeks after birth. During this period profound changes in the properties of synaptic transmission occur. Excitatory postsynaptic potentials (EPSPs) at immature synaptic connections are profoundly and progressively reduced in response to moderate to high frequency (5–100 Hz) stimulation. With maturation, this frequency‐dependent depression becomes progressively weaker and may eventually transform into a weak to moderate EPSP facilitation. In parallel to changes in the short‐term plasticity, a reduction in the synaptic reliability occurs at most glutamatergic neocortical synapses: immature synapses show a high probability of neurotransmitter release as indicated by their low failure rate and small EPSP amplitude variation. This high reliability is reduced in mature synapses, which show considerably higher failure rates and more variable EPSP amplitudes. During early neocortical development synaptic vesicle pools are not yet fully differentiated and their replenishment may be slow, thus resulting in EPSP amplitude depression. The decrease in the probability of neurotransmitter release may be the result of an altered Ca2+ control in the presynaptic terminal with a reduced Ca2+ influx and/or a higher Ca2+ buffering capacity. This may lead to a lower synaptic reliability and a weaker short‐term synaptic depression with maturation.
Exploration of New Concepts for Mass Detection in Electrostatically-Actuated Structures Based on Nonlinear Phenomena
Authors: Younis Mohammad I. , Alsaleem Fadi
Published: March 2009

This study presents an effort to explore the exploitation of dynamic instabilities and bifurcations in micro-electro-mechanical systems to realize novel methods and functionalities for mass sensing and detection. These instabilities are induced by exciting a microstructure with a nonlinear forcing composed of a dc parallel-plate electrostatic load and an ac harmonic load. The frequency of the ac load is tuned to be near the fundamental natural frequency of the structure (primary resonance) or its multiples (subharmonic resonance). For each excitation method, local bifurcations, such as saddle-node and pitchfork, and global bifurcations, such as the escape phenomenon, may occur. This work aims to explore the utilization of these bifurcations to design novel mass sensors and switches of improved characteristics. One explored concept of a device is a switch triggered by mass threshold. The basic idea of this device is based on the phenomenon of escape from a potential well. This device has the potential of serving as a smart switch that combines the functions of two devices: a sensitive gas/mass sensor and an electromechanical switch. The switch can send a strong electrical signal as a sign of mass detection, which can be used to actuate an alarming system or to activate a defensive or a security system. A second type of explored devices is a mass sensor of amplified response. The basic principle of this device is based on the jump phenomena encountered in pitchfork bifurcations during mass detection. This leads to an amplified response of the excited structure making the sensor more sensitive and its signal easier to be measured. As case studies, these device concepts are first demonstrated by simulations on clamped-clamped and cantilever microbeams. Results are presented using long-time integration for the equations of motion of a reduced-order model. An experimental case study of a capacitive sensor is presented illustrating the proposed concepts. It is concluded that exciting a microstructure at twice its fundamental natural frequency produces the most promising results for mass sensing and detection.
Performance of Nanoscale Quantum Well Thermoelectrics
Authors: Krommenhoek Daniel , Elsner Norbert , Ghamaty Saeid , Jovanovic Velimir
Published: March 2009

Alternating 10 nm thermoelectric films of N-type Si/SiGe and P-type Si/SiGe and B4C/B9C have been fabricated on various substrates, electrically joined and thermoelectric properties measured from 40°K up to 700°K. These nanoscale thermoelectric films demonstrate excellent thermoelectric power factors significantly higher than current bulk thermoelectric materials. The implications of the measured thermoelectric Seebeck coefficient data and electrical resistivity data for alternating 10 nm films that are grown to thicknesses of one to 10 microns means efficiencies of 15% at 200°C temperature differences and efficiencies of 30% at 400°C temperature differences. Utilizing Seebeck and resistivity data obtained by Hi-Z and UCSD, along with published bulk thermal conductivity data, which is conservative, unique thermoelectric module and generator concept designs for both power generation and cooling are presented over wide temperature and power ranges.
Heat Conduction in Metal Hydride Nano-Particles
Authors: Smith Kyle C. , Gilbert Peter D. , Polster Christopher S. , Fisher Timothy
Published: March 2009

Metal hydrides hold significant potential for use in solid-state hydrogen storage through reversible chemical reactions of metal constituents and hydrogen. Managing heat loads in the system is critical to controlling system performance because a substantial amount of the energy content in hydrogen gas is released during the exothermic hydrogen uptake process, and this process must occur in only a few minutes for vehicle applications. These materials often are used in a powder form in which the initial particle size is 50–100 micrometers. However, as the material is cycled by hydriding (M+H2→MH) and dehydriding (M+H2←MH), particle size can decrease by several orders of magnitude. For the solid metal hydride phase, relative contributions of the electronic and phononic thermal conductivities are quantified with varying composition and particle size. Particle size effects are approximated by a boundary scattering term in the phononic thermal conductivity formulation. Also, the electronic contribution to thermal conductivity is estimated as a function of hydrogen content. The results reveal that overall thermal conductivity is highly material-specific. Materials with large electronic contributions in the pure metal state are relatively unaffected by particle size, while those with lower electronic contributions exhibit a substantial decrease in thermal conductivity with particle size.
Thermionic Emission From Alkali Potassium-Intercalated Carbon Nanotube Arrays for Direct Energy Conversion
Authors: Westover Tyler L. , Dighe Aalap , Amama Placidus , Lilovich Nicholas , Fisher Timothy S.
Published: March 2009

Vacuum and solid-state thermionic electron emission are potentially efficient means for converting heat or solar energy directly into electrical power. However, low work function materials must be developed before reasonable efficiency can be realized with a power generation device based on thermionic emission. In this work, carbon nanotube (CNT) arrays have been doped with potassium atoms using a two-zone vapor method to lower their work functions to 2–4 eV. We have previously shown that carbon nanotube emitters prepared in this way are stable in atmospheric air although undesirable oxide compounds can form on the carbon nanotube surface. Using a hemispherical electron energy analyzer to obtain thermionic emission energy distributions, we show that low work function emitters can be prepared from potassium-intercalated CNT mats at temperatures as low as 400°C and that emitters prepared in this way can be stable at temperatures up to 620°C.
The Self-Induced Unsteadiness of Tip Leakage Vortex and Its Effect on Compressor Stall Inception
Authors: Tong Zhiting , Lin Feng , Chen Jingyi , Nie Chaoqun
Published: March 2009

The self-induced unsteadiness of tip leakage vortex (TLV), which appears in a compressor rotor working in a range of operating points on its characteristics, from wide-open throttle all the way to the stall limit, is investigated experimentally. The research aims are twofold, to clarify the three modes in TLV development process through experimental evidences and to explore the effect of this in-blade TLV unsteadiness on stall inception. In the first half of the paper, in order to detect the unsteadiness and ensure its existence in the experimental environment (not just in computational results), phase-locked Mean and Root-Mean-Square (RMS) contours are used to track the time-averaged trajectories of the TLV, while a power spectral density (PSD) analysis provides a means to identify the magnitude and the frequency of the oscillation. With all of the above, the three modes of the TLV development, which are steady, in-blade unsteady and cross-blade unsteady TLV, can be clearly demonstrated. In the second half of this paper, various tip jet injections are applied to test the effects of the unsteady TLV on stall inception. It is found that a spike stall precursor is originated from circumferential locations where the strongest unsteady TLV are. At those locations, tip jet injections that are designated to directly alter the characteristics of TLV improve the stall margin effectively. Further, the injections are arranged over the rotor tip in difference axial locations and switched on at different points of compressor characteristic, demonstrating that if the injection misses the tip vortices or interferes with TLV too late, little or even no improvement in stall margin can be gained. These results show that the unsteady TLV are closely related to spike stall inception in this single rotor, which implies that the initiation of compressor stall could be manipulated by properly altering the characteristics of TLV unsteadiness.
Analysis of Combustor Acoustic Resonances Using an Efficient Transient Solver
Authors: Brun Klaus , Kurz Rainer , Simmons Harold R. , Nored Marybeth G.
Published: March 2009

To reduce combustion induced dynamic vibrations, a thorough understanding of a combustor’s acoustic characteristics at all operational conditions is imperative. Acoustic methods that rely on the solution of the wave equation are not adequate to accurately predict acoustic resonance in any real combustor with thermal gradient and velocities. Also, solutions of the 3-D transient Navier-Stokes equations are impractical, even with today’s fast computers. A method is described herein that utilizes an efficient one-dimensional transient Euler solver to determine all acoustic resonance frequencies of a combustor at a given operating condition. Area changes, viscous losses, local temperatures, and open/closed wall-boundaries are modeled with a two-equation model. The analysis method was utilized to determine the dynamic pressures of a 20 MW industrial gas turbine’s combustor. Results compared favorably to field testing results of the same gas turbine.
A Method to Compare Turbine Engine Airstart Times
Authors: Casey Wade , Malloy Donald , Arnold Steve , Shaff Gregory , Kidman David
Published: March 2009

Turbine engine airstarts are conducted throughout the aircraft airspeed/altitude envelope in ground-based simulation test facilities and in flight tests to ensure safe and reliable engine operation. Differences in airstart times are attributable to variations in engine turnaround speed (the engine core speed at which the airstart is initiated in spooldown airstarts); combustor lightoff time; installation effects such as customer bleed and power extraction; starter motor torque; fuel flow scheduling; and engine-to-engine variation and degradation. An analytical approach is presented to account for these differences and adjust engine airstart time for a low-bypass, twin-spool, military, turbofan engine. Two examples are presented illustrating the difference in airstart times and the analytical approach used to adjust the start times.
A Method for Estimating the Onset of Acoustic Instabilities in Premixed Gas-Turbine Combustors
Authors: Ibrahim Z. M. , Williams F. A. , Buckley S. G. , Twardochleb C. Z.
Published: March 2009

For given acoustic frequencies of premixed gas-turbine combustors, a classical method not currently in use is explored for assessing whether acoustically driven oscillatory combustion will occur. The method involves cataloging linear amplification and attenuation mechanisms and estimating magnitudes of their rates. Linear approximations to nonlinear mechanisms are included in an effort to obtain a reasonably complete description. A stability index is defined such that oscillation is predicted to occur when the value of the index exceeds unity. The method is tested on the basis of new experiments and experimental data available in the literature. Moderate success is achieved in rationalizing these experimental results. The objective of the method is to enable quick and inexpensive decisions to be made for a wide variety of potential design configurations and operating conditions, without the complexity of computational fluid dynamics. The approach therefore may complement other approaches already in use.
Enthalpy Determination Methods for Compressor Performance Calculations
Authors: Ransom David , Brun Klaus , Kurz Rainer
Published: March 2009

In the field of compressor performance simulation and measurement, the most commonly used method to evaluate compressor performance is based on the analysis of inlet and discharge pressures and temperatures. Combined with gas mixture properties and known mass flow rate, it is a simple process to determine overall compressor power and efficiency. However, the critical step in this process is the conversion of pressure, temperature, and gas property information into both actual and ideal enthalpy differences. In addition to the abundance of equation of state (EOS) formulations, there are also multiple methods commonly applied for the calculation of the enthalpy differences. This paper reviews several of the methods used for this critical calculation and provides a comparison using multiple gas compositions.
Subsynchronous Vibrations in Rotating Machinery: Methodologies to Identify Potential Instability
Authors: Kar Rahul , Vance John
Published: March 2009

Rotordynamic instability can be disastrous for the operation of high speed turbomachines in the industry. Most ‘instabilities’ are due to de-stabilizing cross coupled forces from variable fluid dynamic pressure around a rotor component, acting in the direction of forward whirl and causing subsynchronous orbiting of the rotor. However, all subsynchronous whirling are not unstable and methods to diagnose the potentially unstable kind from the benign are critical to the health of the rotor-bearing system. In this study, methods to demarcate between the two are detailed. Orbit shape, “frequency tracking” and agreement of subsynchronous frequencies with known eigenvalues are used as diagnostic tools. It is shown that a change in synchronous phase angle produced by de-stabilizing cross coupled forces can be used as a definitive indicator of incipient instability. Typical signatures of subharmonic vibrations induced from non-linear stiffness of the rotor- bearing system are examined analytically and through experiments.
Effects of Air Injection on Performance of Highly-Loaded Compressor Cascades
Authors: Song Yanping , Chen Huanlong , Chen Fu , Wang Zhongqi
Published: March 2009

The effects of air injection on the performance of highly-loaded straight blade compressor cascade and compound lean blade cascade were investigated numerically. Air injection was implemented via the hole/slot penetrating through the pressure and suction surfaces under the effect of the pressure difference between the two sides. Various injection configurations including one-hole, multi-hole and slot configurations were studied in the straight blade cascade first to find the optimum injection configuration in this case. Then the mechanism of the injection slot on the performance improvement of the straight blade cascade was discussed in detail. The results show that air injection provides the low-momentum fluid near the suction surface with kinetic energy, to enhance its ability to withstand the adverse pressure gradient within the compressor cascade. Among the hole/slot configurations, the slot configuration (the radial width of 4.0mm) has the most favorable results in through-flow capacity enhancement and total loss reduction, and is used in the compound lean cascade study. The effects of air injection on the performance improvement in the compound lean blade cascade are less significant than those in the straight blade cascade though the compound lean blade cascade with the injection slot has the most improvement in the aerodynamic performance when the slot is placed at an appropriate location in this study.
Micro Gas Turbine Based Test Rig for Hybrid System Emulation
Authors: Pascenti Matteo , Ferrari Mario L. , Magistri Loredana , Massardo Aristide F.
Published: March 2009

The Thermochemical Power Group (TPG) is building at the laboratory of the University of Genoa, Italy, a new high temperature fuel cell - micro gas turbine physical emulator based on commercial machine technology. The aim of this new test rig is the experimental analysis of the coupling of commercial machines with fuel cell stacks focusing the attention on the critical phases of start-up, shutdown and load changes. The experimental facility is composed of a Turbec T100 micro gas turbine package modified for the fuel cell emulator connection, a set of pipes designed for by-pass, measurement or bleed reasons, and a high temperature volume designed for the RRFCS stack dimension physical emulation. This experimental approach is essential for model validations, and to test different transient operative procedures and control systems without any risk for an expensive real fuel cell stack. This paper shows the preliminary experimental data obtained with the machine in stand alone configuration, focusing the attention on the comparison of these results with the tests performed with the external pipes. Furthermore, a theoretical transient model of this new experimental facility has been developed with the TRANSEO tool. It is essential for the rig design and to perform preliminary results necessary to prevent dangerous conditions during the tests. This paper reports a preliminary verification of this model performed with the facility.
The Effect of an Upstream Ramp on Cylindrical and Fan-Shaped Hole Film Cooling: Part I — Aerodynamic Results
Authors: Barigozzi Giovanna , Franchini Giuseppe , Perdichizzi Antonio
Published: March 2009

The present companion papers report the results of an experimental investigation on possible beneficial effects of an upstream ramp on discrete hole film cooling. This analysis was carried out on a flat plate model. Two hole geometries have been considered: cylindrical and fan-shaped with conical expanded exit. To compare different cooling schemes, a combined aero-thermal analysis was performed. Tests have been carried out at low speed and low inlet turbulence intensity level, with blowing ratios varied in the range 0.3–1.0. The aerodynamic investigation has been performed through the measurements of discharge coefficients and detailed flow field measurements. Surveys were carried out by traversing a flattened Pitot tube. Additional turbulence measurements have been carried out by means of hot wire traverses. All this information, together with the adiabatic effectiveness results presented in Part II of this paper, allowed drawing a comprehensive picture of the complex aero-thermal flow field in the injection region. The upstream ramp provided a moderate improvement in the case of cylindrical holes, as it allows the coolant to diffuse someway, before interacting with the mainflow, but it produced also a significant increase of aerodynamic losses. The fan shaped hole geometry without the ramp resulted to be the best solution, as it provides a coolant injection with a good lateral spreading and a low turbulence level.
The Effect of an Upstream Ramp on Cylindrical and Fan-Shaped Hole Film Cooling: Part II — Adiabatic Effectiveness Results
Authors: Barigozzi Giovanna , Franchini Giuseppe , Perdichizzi Antonio
Published: March 2009

The present companion papers report the results of an experimental investigation on possible beneficial effects of an upstream ramp on discrete hole film cooling. This analysis was carried out on a flat plate model. Two hole geometries have been considered: cylindrical and fan-shaped with conical expanded exit. To compare different cooling schemes, a combined aero-thermal analysis was performed. Tests have been carried out at low speed and low inlet turbulence intensity level, with blowing ratios varied in the range 0.3–1.0. Part I was focused on the aerodynamic analysis: it has been shown that the introduction of a ramp is always detrimental, as it gives a strong loss increase (+5%). Fan-shaped hole was instead the best solution, as it gives losses comparable with the cylindrical one, reduced turbulence mixing and jet dilution. Part II of this paper faces the thermal analysis. The thermal behaviour of the cooled surface has been analysed using the wide banded TLC’s technique, so to obtain adiabatic effectiveness distributions. Additional air temperature measurements have been carried out by traversing a thermocouple downstream of injection holes. The upstream ramp was found to provide a thermal protection improvement (+40%) only at low blowing rate in the case of cylindrical hole. The application of a ramp upstream of a fanshaped hole was instead detrimental for all blowing conditions. The fan shaped hole geometry with no ramp resulted to be the best solution also in terms of adiabatic effectiveness (50% higher than the cylindrical one at BR = 0.5).
Advanced Capabilities for Gas Turbine Engine Performance Simulations
Authors: Alexiou A. , Baalbergen E. H. , Kogenhop O. , Mathioudakis K. , Arendsen P.
Published: March 2009

This paper describes the integration of advanced methods such as component zooming and distributed computing, in an object-oriented simulation environment dedicated to gas turbine engine performance modelling. A 1-D compressor stage stacking method is used to demonstrate three approaches for integrating numerical zooming in an engine model. In the first approach a 1-D compressor model produces a compressor map that is then used in the engine model in place of the default one. In the second approach the results of the 1-D analysis are passed to the 0-D component through appropriate ‘zooming’ scalars. In the final approach the 1-D compressor component directly replaces the 0-D one in the engine model. Distributed computing is realized using Web Services technology. The implementation steps for a distributed scenario are presented. The standalone compressor stage stacking method, in the form of a shared library, is placed in a remote site and can be accessed over the internet through a Web Service Operation (server side). An engine simulation is set up containing a 1-D compressor component which acts as the client for the Web Service operation. Future development of the tool’s advanced capabilities is finally discussed.
Vibration Control for Integrally Bladed Disks Using Friction Ring Dampers
Authors: Laxalde Denis , Thouverez Fabrice , Lombard Jean-Pierre
Published: March 2009

A damping strategy for integrally bladed disks (blisks) is discussed in this paper; this involves the use of friction rings located underside the wheel of bladed disks. The forced response of the blisk with friction rings is derived in the frequency domain using a frequency domain approach known as Dynamic Lagrangian Frequency-Time method. The blisk is modeled using a reduced-order model and the rings are modeled using beam elements. The results of some numerical simulations and parametric studies are presented. The range of application of this damping device is discussed. Parametric studies are presented and allow to understand the dissipation phenomena. Finally some design and optimization guidelines are given.
Quasiturbine: Low RPM High Torque Pressure Driven Turbine for Top Efficiency Power Modulation
Authors: Saint-Hilaire Gilles , Saint-Hilaire Roxan , Saint-Hilaire Ylian
Published: March 2009

The Quasiturbine turbo-machine is a pressure driven, continuous torque and symmetrically deformable spinning wheel. Excluding conventional turbines, the next step in the world of engine research is to make the gas engines as efficient as the diesel engines and the diesel engines as clean (or better) as the gas engines. Turbine characteristics help achieving this goal. The Quasiturbine (Qurbine or Kyotoengine) is a new engine technology that was conceived in early 1990 and patented in 1996 and later. The Quasiturbine is inspired by the turbine, perfects the piston and improves upon the Wankel engine. Efficient and compact, the Quasiturbine is also an engine concept optimization theory based on «volume pulse shaping» at design. While current technologies adapt combustion processes to engine design, the Quasiturbine theory tends to adapt the engine design to combustion processes. It is a non-eccentric crankshaft, true rotary engine (no piston like movement), that uses a 4 face articulated rotor with a free and accessible center, rotating without vibration nor propulsive dead time and producing a strong torque at low RPM under a variety of modes and fuels. The Quasiturbine goes along the best modern engine development strategy, which is to get as many ignitions as possible per minute, with a mechanical device rotating as slowly as possible. Quasiturbine allows designs with up to «7 conceptual degrees of freedom», substantially more than conventional turbine or piston engine, permitting to better shape the compression and relaxation volume pulse and further improved optimization. Taking full advantage of its unique short and fast linear ramp volume pulsed properties, its AC Model is a natural HCCI «detonation - knocking» engine. Such a detonation Quasiturbine has very little low-power-efficiency-penalty, is multi-fuel compatible (including direct hydrogen combustion), offers a drastic reduction in the overall propulsion system weight, size, maintenance and cost. Because Quasiturbine cycle is pressure driven instead of aerodynamically driven, it has a comparatively flat high efficiency characteristic in regard to RPM, load and power, which makes it most suitable for power modulation applications like in transportation and windmill energy storage and recovery systems. Used in Stirling and Brayton cycles, the Quasiturbine offers new ways to recover and transform thermal energy.
Heat Transfer in Trailing Edge, Wedge-Shaped Cooling Channels Under High Rotation Numbers
Authors: Wright Lesley M. , Liu Yao-Hsien , Han Je-Chin , Chopra Sanjay
Published: March 2009

Heat transfer coefficients are experimentally measured in a rotating cooling channel used to model an internal cooling passage near the trailing edge of a gas turbine blade. The regionally averaged heat transfer coefficients are measured in a wedge-shaped cooling channel (Dh = 2.22cm, Ac = 7.62cm2). The Reynolds number of the coolant varies from 10,000 to 40,000. By varying the rotational speed of the channel, the rotation number and buoyancy parameter range from 0–1.0 and 0–3.5, respectively. Significant variation of the heat transfer coefficients in both the spanwise and streamwise directions is apparent. Spanwise variation is the results of the wedge-shaped design, and streamwise variation is the result of the sharp entrance into the channel and the 180° at the outlet of the channel. With the channel rotating at 135° with respect to the direction of rotation, the heat transfer coefficients are enhanced on every surface of the channel. Both the non-dimensional rotation number and buoyancy parameter have proven to be excellent parameters to quantify the effect of rotation over the extended ranges achieved in this study.
Effect of Temperature and Crystal Orientation on the Plasticity (SLIP) Evolution in Single Crystal Nickel Base Superalloy Notched Specimens
Authors: Siddiqui Shadab , Arakere Nagaraj K. , Ebrahimi Fereshteh
Published: March 2009

A comprehensive numerical investigation of plasticity (slip) evolution near notches was conducted at 28°C and 927°C, for two crystallographic orientations of double-notched single crystal nickel base superalloys (SCNBS) specimens. The two specimens have a common loading orientation of <001> and have notches parallel to the <010> (specimen I) and <110> (specimen II) orientation, respectively. A three dimensional anisotropic linear elastic finite element model was employed to calculate the stress field near the notch of these samples. Resolved shear stress values were obtained near the notch for the primary octahedral slip systems ({111} <110>) and cube slip systems ({100} <110>). The effect of temperature was incorporated in the model as changes in the elastic modulus values and the critical resolved shear stress (CRSS). The results suggest that the number of dominant slip systems (slip systems with the highest resolved shear stress) and the size and the shape of the plastic zones around the notch are both functions of the orientation as well as the test temperature. A comparison between the absolute values of resolved shear stresses near the notch at 28°C and 927°C on the {111} slip planes revealed that the plastic zone size and the number of activated dominant slip systems are not significantly affected by the temperature dependency of the elastic properties of the SCNBS, but rather by the change in critical resolved shear stress of this material with temperature. The load required to initiate slip was found to be lower in specimen II than in specimen I at both temperatures. Furthermore, at 927°C the maximum resolved shear stress (RSS) on the notch surface was found to be greater on the {100} slip planes as compared with the {111} slip planes in both specimens. The results from this study will be helpful in understanding the slip evolution in SCNBS at high temperatures.
Improved High Pressure Ratio Centrifugal Compressor
Authors: Krain H. , Hoffmann B. , Rohne K.-H. , Eisenlohr G. , Richter F.-A.
Published: March 2009

The paper describes the development and the experimental as well as theoretical investigation of a new transonic, high specific speed centrifugal compressor rotor of 6.2:1 pressure ratio. Performance measurement results, laser measurements and calculated 3D results are shown for the new rotor and are compared with the corresponding data of a same type predecessor rotor. A 2% gain in stage efficiency and a 0.2 bar increase in stage pressure ratio are found at design speed by performance measurements. With the help of optical measurements and 3D stage calculations it is shown that the flow at the exit of the new rotor is more uniform/homogeneous. The degree of uniformity increases with decreasing pressure ratio, i.e. in the compressor part load region. Deeper insight into the internal rotor and the vaned diffuser flow is obtained from the 3D stage calculations showing less flow separation in the new rotor but significant secondary flow in the small span diffuser. The investigations are indicating that a further improvement of stage performance seems to be possible by an additional optimization of the vaned diffuser.
An Experimental and Numerical Investigation of the Effect of Cooling Channel Crossflow on Film Cooling Performance
Authors: Kissel Harald Peter , Weigand Bernhard , von Wolfersdorf Jens , Neumann Sven Olaf , Ungewickell Antje
Published: March 2009

This paper presents an experimental and numerical investigation into film cooling performance over a flat plate. As previous studies have shown, the flow situation at the entry-side of the cooling hole shows a notable effect on film cooling performance. The present investigation takes this into account feeding the cooling holes from an internal cooling channel and not from a stagnant plenum. High resolution heat transfer coefficient and adiabatic film cooling effectiveness distributions received from transient liquid crystal experiments are presented. The Reynolds numbers of the hot gas channel and the coolant crossflow feeding the holes are varied. Furthermore, the effects of 45° angled ribs, introduced into the cooling channel, are investigated. The experiments are performed at constant blowing, momentum and pressure ratios. Numerical calculations of the adiabatic film cooling effectiveness for selected configurations using FLUENT are presented. Comparison reveals the influence of coolant channel Reynolds number and the introduced ribs on the cooling hole flow pattern leading to a changed film cooling performance.
Experimental Investigation of Turbulence Structure in a Three-Nozzle Combustor
Authors: Boehm Benjamin , Dreizler Andreas , Gnirss Markus , Tropea Cameron , Findeisen Jens , Schiffer Heinz-Peter
Published: March 2009

Proper mixing of fuel, primary and secondary air is a major issue to optimize engine performance in terms of efficiency and pollutant emissions. The underlying turbulent flow field determines these mixing processes. Most experimental and numerical investigations are performed in single nozzle combustors for reasons of optical accessibility and simplicity. The focus of the present study is to compare the variation of the non-reacting turbulent flow field for the case of single-nozzle and three-nozzle operation. In addition, the influence of secondary air entrainment is investigated. The flow configuration is based on commercial geometries. Using a two component laser Doppler velocimeter (LDV) the mean and fluctuating velocities of all three components, as well as two Reynolds-stress components were measured. The autocorrelation function and spectral distributions of the fluctuating velocity signal clearly revealed coherent fluid motions. These observations, together with high speed-flow visualisations indicate a precessing vortex core (PVC). An additional lower frequency for all three nozzles in operation revealed a pulsation of the recirculation zones. A major result of this investigation is that the size and shape of the internal recirculation zones were significantly influenced by operation of adjacent nozzles. Furthermore the generation of PVCs were augmented in the three-nozzle configuration. The additional secondary air entrainment interacts with the primary flow, changing the size and shape of the recirculation zone and affecting the low frequency pulsation.
Flexure Pivot Tilting Pad Hybrid Gas Bearings: Operation With Worn Clearances and Two Load-Pad Configurations
Authors: San Andre´s Luis , Ryu Keun
Published: March 2009

Gas film bearings enable the successful deployment of high-speed micro-turbomachinery. Foil bearings are in use; however, cost and lack of calibrated predictive tools prevent their widespread application. Other types of bearing configurations, simpler to manufacture and fully engineered, are favored by commercial turbomachinery manufacturers. Externally pressurized tilting pad bearings offer a sound solution for stable rotor support. This paper reports measurements of the rotordynamic response of a rigid rotor, 0.825 kg and 28.6 mm in diameter, supported on flexure pivot tilting pad hybrid gas bearings. The tests are performed for various imbalances, increasing supply pressures, and under load-on-pad (LOP) and load-between-pad (LBP) configurations. Presently, the initial condition of the test bearings shows sustained wear and dissimilar pad clearances after extensive testing reported earlier, see Ref. [1]. In the current measurements, there are no noticeable differences in rotor responses for both LOP and LBP configurations due to the light-weight rotor, i.e. small static load acting on each bearing. External pressurization into the bearings increases their direct stiffnesses and reduces their damping, while raising the system critical speeds with a notable reduction in modal damping ratios. The rotor supported on the worn bearings shows a ∼10% drop in first critical speeds and roughly similar modal damping than when tested with pristine bearings. Pressurization into the bearings leads to large times for rotor deceleration, thus demonstrating the little viscous drag typical of gas bearings. Rotor deceleration tests with manually controlled supply pressures eliminate the passage through critical speeds, thus paving a path for rotordynamic performance without large amplitude motions over extended regions of shaft speed. The rotordynamic analysis shows critical speeds and peak amplitudes of motion agreeing very well with the measurements. The synchronous rotor responses for increasing imbalances demonstrate the test system linearity. Superior stability and predictable performance of pressurized flexure pivot gas bearings can further their implementation in high performance oil-free microturbomachinery. More importantly, the measurements show the reliable performance of the worn bearings even when operating with enlarged and uneven clearances.