bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational and physiological background of the baroreflex sensitivity
Authors: Nieminen T. , Kähönen M. , Laitinen T. , Kööbi T.
Published: February 2010

All the commonly used definitions of baroreflex sensitivity (BRS) are based on a slope of linear relationship between systolic blood pressure and pulse interval (R–R interval). However, heart rate (HR) and R–R interval bear an inverse non‐linear relationship, which distorts determination of BRS when different HR levels are present. We analysed data of 117 healthy, normal‐weight, non‐smoking men and women aged 23–77 to show how BRS depends on the initial HR. In this data, 43% of variation in BRS is solely explained by HR. Comparisons of BRS between patients with different HR and even within the same patient with changing HR (e.g. tilt‐table test and nocturnal changes in HR) should be questioned. Consideration of the baseline HR is even more crucial, if the patients are subjected to an intervention affecting not only baroreflexes but also HR. If baseline HR is not taken into account, using the R–R interval in the estimation of BRS may lead to partially misleading values and possibly also to misinterpretation of physiological processes. We discuss alternative definitions of BRS to allow varying HRs.
Through Their Eyes Child and Adolescent Agency in the Urban Environment
Authors: Ellender Caroline
Published: February 2010

Abstract: There is an emerging approach in anthropology that investigates children and adolescents, not just as additions to adult‐centered studies, but as active social actors who experience, react to, change, and create the worlds around them. In this paper, I report on research which utilized a child‐centered focus to understand how children and youth in an inner‐city Southern community understand their local environments. I examine children's perceptions and negotiations in both their urban physical and social landscapes using ethnographic methods. I document children's particular modes of thought and actions which help them move through the urban world within and beyond the confines of their families.
The proteasome inhibitor bortezomib inhibits FGF‐2‐induced reduction of TAZ levels in osteoblast‐like cells
Authors: Eda Homare , Aoki Katsuhiko , Kato Soki , Okawa Yutaka , Takada Koji , Tanaka Takaaki , Marumo Keishi , Ohkawa Kiyoshi
Published: February 2010

Objectives: Bortezomib (PS‐341; Velcade™), a proteasome inhibitor, is used as a therapeutic agent for multiple myeloma. Bortezomib has been shown to strongly induce osteoblast differentiation and elevate the levels of osteoblast‐related differentiation markers in the serum of patients with myeloma. Bortezomib also reportedly increases the activity of the transcription factor, Runx2. However, the mechanism of action by which bortezomib‐elevated Runx2 activity mediates osteoblast differentiation remains unclear. On the other hand, fibroblast growth factor 2 (FGF‐2) is found at high levels in patients with multiple myeloma. We previously reported that FGF‐2 reduces the levels of the transcriptional coactivator with PDZ‐binding motif (TAZ). We therefore investigated the effects of bortezomib on TAZ protein levels in the presence of FGF‐2. Methods: Osteoblastic MC3T3‐E1 cells were treated with different concentrations of bortezomib in the presence or absence of FGF‐2 and various biologic responses were investigated by immunoblotting, RT‐PCR, quantitative PCR, and alizarin red staining. Results: We found that bortezomib inhibited FGF‐2‐induced reduction of TAZ levels through a pathway other than that used for proteasome inhibition, while maintaining TAZ function, which in turn, enhanced the expression of Runx2‐transcribed osteogenic differentiation markers. Bortezomib also suppressed the antimineralization effect of FGF‐2. Conclusions: These findings suggest that bortezomib inhibited FGF‐2‐induced reduction of TAZ and consequently stimulated osteogenic differentiation independently of proteasome inhibition. These findings may contribute to elucidate the osteolytic mechanism in multiple myeloma, and to the development of new drugs for multiple myeloma and other osteolytic diseases.
Rosiglitazone Inhibits Cell Proliferation by Inducing G1 Cell Cycle Arrest and Apoptosis in ADPKD Cyst‐Lining Epithelia Cells
Authors: Liu Yawei , Dai Bing , Fu Lili , Jia Jieshuang , Mei Changlin
Published: February 2010

Abstract:  Abnormal proliferation is an important pathological feature of autosomal dominant polycystic kidney disease (ADPKD). Many drugs inhibiting cell proliferation have been proved to be effective in slowing the disease progression in ADPKD. Recent evidence has suggested that peroxisome proliferator‐activated receptor γ (PPARγ) ligands have anti‐neoplasm effects through inhibiting cell growth and inducing cell apoptosis in various cancer cells. In the present study, we examined the expression of PPARγ in human ADPKD kidney tissues and cyst‐lining epithelial cell line, and found that the expression of PPARγ was greater in ADPKD kidney tissues and cyst‐lining epithelial cell line than in normal kidney tissues and human kidney cortex (HKC) cell line. Rosiglitazone inhibited significantly proliferation of cyst‐lining epithelial cells in a concentration‐ and time‐dependent manner. These effects were diminished by GW9662, a specific PPARγ antagonist. Cell cycle analysis showed a G0/G1 arrest in human ADPKD cyst‐lining epithelial cells with rosiglitazone treatment. Analysis of cell cycle regulatory proteins revealed that rosiglitazone decreased the protein levels of proliferating cell nuclear antigen, pRb, cyclin D1, cyclin D2 and Cdk4 but increased the levels of p21 and p27 in a dose‐dependent manner. Rosiglitazone also induced apoptosis in cyst‐lining epithelial cells, which was correlated with increased bax expression and decreased bcl‐2 expression. These results suggest PPARγ agonist might serve as a promising drug for the treatment of ADPKD.
The dynamics of fibroblast–myocyte–capillary interactions in the heart
Authors: Bowers Stephanie L.K. , Borg Thomas K. , Baudino Troy A.
Published: February 2010

In the heart, electrical, mechanical, and chemical signals create an environment essential for normal cellular responses to developmental and pathologic cues. Communication between fibroblasts, myocytes, and endothelial cells, as well as the extracellular matrix, are critical to fluctuations in heart composition and function during normal development and pathology. Recent evidence suggests that cytokines play a role in cell–cell signaling in the heart. Indeed, we find that interactions between myocytes and cardiac fibroblasts results in increased interleukin‐6 and tumor necrosis factor‐α secretion. We also used confocal and transmission electron microscopy to observe close relationships and possible direct communication between these cells in vivo. Our results highlight the importance of direct cell–cell communication in the heart, and indicate that interactions between fibroblasts, myocytes, and capillary endothelium results in differential cytokine expression. Studying these cell–cell interactions has many implications for the process of cardiac remodeling and overall heart function during development and cardiopathology.
Notch and cardiac outflow tract development
Authors: Jain Rajan , Rentschler Stacey , Epstein Jonathan A.
Published: February 2010

Congenital heart disease represents the most common form of human birth defect, occurring in nearly 1 in 100 live births. An increasing number of patients with these defects are surviving infancy. Approximately one‐third of congenital heart defects involve malformations of the outflow tract. Related defects are found in isolation and as part of common human syndromes. Our laboratory has investigated mechanisms of cardiac morphogenesis with particular attention to outflow tract formation. During cardiogenesis, neural crest cells interact with second heart field myocardium and endocardial cushion mesenchyme. Our recent work demonstrates that Jagged1/Notch signaling within the second heart field initiates a signaling cascade involving Fgf8, Bmp4, and downstream effectors that modulate outflow tract development and aortic arch artery patterning. Hence, complex tissue–tissue interactions and integration of multiple pathways converge to orchestrate proper patterning of the outflow region. The role of Notch signaling in adult cardiac homeostasis and disease is an area of active investigation.
Navigation within the heart and vessels in clinical practice
Authors: Beyar Rafael
Published: February 2010

The field of interventional cardiology has developed at an unprecedented pace on account of the visual and imaging power provided by constantly improving biomedical technologies. Transcatheter‐based technology is now routinely used for coronary revascularization and noncoronary interventions using balloon angioplasty, stents, and many other devices. In the early days of interventional practice, the operating physician had to manually navigate catheters and devices under fluoroscopic imaging and was exposed to radiation, with its comcomitant necessity for wearing heavy lead aprons for protection. Until recently, very little has changed in the way procedures have been carried out in the catheterization laboratory. The technological capacity to remotely manipulate devices, using robotic arms and computational tools, has been developed for surgery and other medical procedures. This has brought to practice the powerful combination of the abilities afforded by imaging, navigational tools, and remote control manipulation. This review covers recent developments in navigational tools for catheter positioning, electromagnetic mapping, magnetic resonance imaging (MRI)–based cardiac electrophysiological interventions, and navigation tools through coronary arteries.
Ag‐Cu‐Pb‐Bi‐S Minerals Newly Discovered from the Ohori Base Metal Deposit, Yamagata Prefecture, NE Japan: Implications for Bi‐metallogenesis in the Green‐Tuff Region
Authors: Yokoro Yu , Nakashima Kazuo
Published: February 2010

The Ohori deposit, one of the base metal deposits in the Green‐Tuff region, NE Japan, is composed of two types of mineralization; a skarn‐type (Kaninomata orebody) made by the replacement of the Miocene calcareous layer, and a vein‐type (Nakanomata orebody). While the ore mineral assemblage of the deposit (chalcopyrite, pyrite, sphalerite and galena) has been known for being rather simple, some Pb‐Bi‐S minerals have been discovered for the first time in the present study. The minerals mainly occur in the chalcopyrite‐rich ores of both orebodies. They essentially belong to the Pb‐Bi‐S system and contain Cu and Ag in minor amounts, which correspond to the lillianite–gustavite solid solution series (phases Z and X), cosalite, neyite, felbertalite, krupkaite and Bi‐bearing galena. The chalcopyrite‐rich (Bi‐bearing) ores from both orebodies are richer in chalcopyrite, pyrite and chlorite, and have higher homogenization temperatures (>300°C) of fluid inclusions, and higher FeS contents in sphalerite compared to the Bi‐free ores. In the Green‐Tuff region, Bi‐minerals have been reported from many base metal deposits. Most of these Bi‐bearing ore deposits are referred to as xenothermal‐type deposits, and are characterized by the following common features; composite mineralization of high‐ and low‐temperatures in the shallower environments, and close relationships with the Tertiary granitic rocks. The whole mineralization at the Ohori deposit also has a similar xenothermal character because of the coexistence of high‐temperature chalcopyrite‐rich ores with Pb‐Bi‐S minerals, which were formed by the influence of the Tertiary granitic rocks at a shallow depth.
Optimization of Intravascular Shear Stress and Oxidative Stress Assessment in Vivo
Authors: Ai Lisong , Hsiai Tzung K.
Published: February 2010

To assess shear stress in the tortuous and dynamic arterial circulation, we developed polymer- and catheter-based sensors that are both flexible and deployable. The flexible MEMS device provides an entry point to address spatial and temporal components of shear stress in the complicated arterial configuration. Theoretical and Computational Fluid Dynamics (CFD) analyses were performed. Fluoroscope and angiogram provided the geometry of aorta, and the Doppler ultrasound provided the pulsatile velocity for the boundary conditions. The development of micro electro mechanical systems (MEMS) and nano-scale sensors in our group have provided a means to undertake study of atherogenic hemodynamics and vascular oxidative stress in localizing early atherosclerosis.
Advanced Surface Mechanical Testing of Materials for Medical Applications
Authors: Poire´ Ethel
Published: February 2010

This paper presents an overview of two advanced surface mechanical testing techniques: the instrumented indentation testing and the single point scratch testing techniques. Both can be used for studying bulk or thick materials, they are however powerful tools in the cases of thin layers and small features, elastic materials and surfaces with poor optical contrast. Most samples can be tested “as is” or with minimal preparation.
Determining the Failure Potential of Total Hip Arthroplasty in Frontal Motor Vehicle Impacts: An Interdisciplinary Approach
Authors: Gomez Mark A.
Published: February 2010

Due to the ever increasing number of total hip arthroplasties performed every year, the loading conditions typically experienced by a patient during the activities of everyday living must be accounted for in both the design and testing of an artificial joint (5). The probability of implant failure must constantly be addressed. Further, knowledge of these loading conditions may be applied to accidental events such as motor vehicle impacts to determine the potential for failure of a total hip arthroplasty during such “abnormal” occurrences. Specifically, when considering loading conditions experienced during a motor vehicle accident, one could determine if the failure of an implant was due to the inadequacy of the implant, the failure of the bone around the implant, or a pre-existing degraded condition in the implant-bone construct. The goal of this presentation is to provide an outline of the types of data and analyses that are necessary to determine the nature of a failed total hip arthroplasty subsequent to a frontal motor vehicle impact. These include data from the patient’s medical records, biomechanical properties of bone, structural and material properties of implant materials, and accident vehicle dynamics. This information may then be consolidated and analyzed in a flowchart fashion to provide a most probable cause of implant failure.
Arthroscopy and Ligament Reconstruction in the Knee
Authors: Limpisvasti Orr
Published: February 2010

Ligament injuries in the knee are a common cause of disability in the active population. The advent of arthroscopy and arthroscopic surgical techniques has changed our ability to diagnose and treat these injuries. Arthroscopy has become the gold standard for diagnosis of intra-articular ligament injuries, as well as meniscal and articular cartilage pathology. It combines optimal visualization and the ability to manipulate tissue under anesthesia to best understand the degree of ligament injury and knee instability. Arthroscopy has also evolved into the primary means for the surgical treatment of injuries to intra-articular ligaments, articular cartilage, and meniscus.
Four Corner Intercarpal Arthrodesis
Authors: Rafijah Gregory
Published: February 2010

Intercarpal arthrodesis is a common motion sparring procedure for post-traumatic arthritis of the wrist. Untreated scaphoid non-union or scapholunate ligament injury often leads to progressive arthritis of the wrist that can be salvaged by proximal row carpectomy (PRC), limited intercarpal arthrodesis or total wrist fusion. Most surgeons elect to perform a motion sparring procedure in lieu of total wrist fusion. PRC is favored by many because of the ease of surgery and no need to obtain bony union. However, several reports are pessimistic about the out comes of the PRC operation in the long term. Most agree that the four corner arthrodesis with scaphoid excision is the optimal reconstruction to maintain wrist motion and strength and provide long-term durability.
Biomechanical Evaluation of Rotator Cuff Tear Progression and the Influence of Parascapular Muscle Loading
Authors: Oh Joo Han , Jun Bong-Jae , McGarry Michelle H. , Lee Thay Q.
Published: February 2010

Rotator cuff tears (RCT) commonly start at the anterior insertion of the supraspinatus and have been shown to propagate posteriorly. Early detection and repair of small or medium size tears has been shown to result in better clinical outcome and structural integrity than that of large or massive tears. However, it is unknown at which stage of rotator cuff tear propagation the biomechanical environment becomes altered. Previous biomechanical studies have not considered rotator cuff propagation based on the footprint anatomy, rotational glenohumeral joint kinematics, and the influence of anatomy-based muscle loading including pectoralis major and latissmus dorsi. Therefore, the purpose of this study was to determine the relationship between progressive rotator cuff tear and glenohumeral joint biomechanics using a rotator cuff tear progression model and anatomically based muscle loading including the influence of the pectoralis major and latissmus dorsi. Our hypotheses were 1) cuff tear progression will lead to abnormal glenohumeral joint biomechanics, specifically in kinematics (rotational range of motion and the path of humeral head apex) and abduction capability and 2) the pectoralis major and latissmus dorsi muscles will act as a stabilizer of the humeral head in large or massive tear.
Performance Behavior for Butane Direct Internal Reforming Solid Oxide Fuel Cell
Authors: Park Kwangjin , Bae Gyujong , Bae Joongmyeon
Published: February 2010

The reforming test using anode materials and the performance analysis of SOFC using pre-reformate gas were performed. When the reformate gas was supplied with steam, the maximum power density showed a relatively small variation compared to performance of SOFC using H2. When pre-reformate gas was supplied into the anode, SOFC which used Rh doped NiO/CGO91 (Ce0.9Gd0.1O2) as an anode material showed more stable performance than SOFC which used NiO/CGO91.
Influence of Non-Straight Parallel Channel Designs on Performance of Planar SOFC
Authors: Wattana Wassachol , Charoensuk Jarruwat , Charojrochkul Sumittra
Published: February 2010

The flow aerodynamic and friction loss which are usually considered for heat exchanger design are adapted for a channel design for solid oxide fuel cell stack. In this study the design concept is limited to a parallel configuration because of its simplicity. Heat and mass transfer rate can be improved by an introduction of the non-straight parallel channel design yielding higher fuel cell performance. In this paper, a three-dimensional computational model of SOFCs with non-straight parallel channel has been constructed using computational aided engineering tool, FLUENT. The aim of this work is to investigate the cell performance associated with underlying transport phenomena of different channel configurations by looking at distributions of velocity, pressure, hydrogen and oxygen concentrations and current density of each channel design. The influence of each flow channel design (serpentine-parallel, zigzag-parallel and wavy-parallel) on cell performance in SOFCs is discussed. The results indicate that the most enhanced cell performance, especially at high current density, is achieved by using a serpentine-parallel channel design with a trade-off on its greater pressure drop.
Thermal Conductivity Measurements of Gas Diffusion Layer Under Controlled Temperature, Humidity and Stress
Authors: Miyamoto Jun-ichi , Ooyama Junpei , Yamamoto Yoshiaki
Published: February 2010

In this work, thermal conductivities of gas diffusion layer (GDL) under controlled temperature, humidity and stress are measured. Additionally, we investigated the anisotropic thermal conductivity of GDLs. The experimental results showed that thermal conductivity of in-plane direction was much higher than that of trough-plane direction for all the samples that were measured. This result indicated thermal conductivity of GDLs to be strongly anisotropic since GDL is a highly porous material which contains large amount of air inside the GDL. Moreover, we found that thermal conductivity of GDL in the through-plane direction increased as the compression on the GDL was increased.
Effect of Excess Moisture on an Oxygen Reduction Reaction Mechanism in the Yttria Stabilized Zirconia and Strontium-Doped Lanthanum Manganite SOFC Composite Cathode
Authors: Izzo John R. , Grew Kyle N. , Chiu Wilson K. S.
Published: February 2010

Air-Independent solid oxide fuel cell (SOFC) systems are primarily used in naval applications. In this study a decomposed hydrogen peroxide (H2O2) stream is used as the oxidant. The fully decomposed diluted H2O2 oxidant stream contains 20% O2 and 80% H2O, and this water content is the basis for the studies performed. A computational model has been developed that couples local gas and charge transport with a detailed oxygen reduction mechanism and considers surface coverages in the presence of excess moisture. The model is used to study the detailed reaction mechanism and the performance of the cathode in the presence of a high water content oxidant stream.
Performance Analysis of CH4 Driven SOFC Short Stack
Authors: Kim Sunyoung , Yoon Sangho , Bae Joongmyeon , Yoo Young-Sung
Published: February 2010

The performance of a solid oxide fuel cell (SOFC) stack system driven by simulated reformate was investigated in this study. CH4 was used as a surrogate fuel for low hydrocarbon components in reformate gas. One of the motivations for this study is to articulate the effects of low hydrocarbons in reformate gas, such as CH4, on SOFCs. The effects of low hydrocarbons on SOFC have been widely investigated in SOFC button cells, but it does not provide the practical information to develop an SOFC system. Hence, we investigated the performance changes in SOFC stack operation with simulated reformate gas. Open-circuit voltage of the SOFC and discharge condition decreased as the fraction of CH4 in anode inlet gas was increased. The limit current density also decreased. As Eguchi et al. reported, CH4 does not directly participate in the electrode reaction (14). Hence, concentration overvoltage occurred in SOFC operation with CH4. The effect of CH4 on SOFC long-term performance will be investigated in future studies.
Numerical Modeling and Experimental Analysis of Air-Droplet Interaction in the Channel of a PEM Fuel Cell
Authors: Esposito Angelo , Motello Aaron , Pianese Cesare , Guezennec Yann G.
Published: February 2010

An accurate low order model (MVM, Mean Value Model) that captures the main water transport mechanisms through the components of a PEM Fuel Cell was developed. Fast simulation time was achieved through a lumped approach in modeling space-dependent phenomena. Evaporation and capillarity were assumed to be the predominant mechanisms of water flow through the gas diffusion media. The model innovative features are not only to simulate the water transport inside the porous media with relative simplicity but also to simulate the water transport at the interface between gas diffusion layer and gas flow channel. In order to preserve a light computational burden, the complex air flow–droplets interaction was modeled with several simplifying assumption and with the support of measured data. The physics that characterizes the single droplet-air flow interaction was analyzed with an experimental apparatus constructed to study the droplet growth and detachment process. Furthermore, the experimental findings were exploited to feed the numerical model with the missing theoretical information and empirical sub-models to guarantee accuracy. Thanks to the fast computational time of the mean value approach followed, the model is suitable for fuel cell design and optimization as well as diagnosis and control strategies development studies.
Transient Computational Analysis of Proton Exchange Membrane Fuel Cells During Load Change and Non-Isothermal Start-Up
Authors: Roy Arnab , Serincan Mustafa Fazil , Pasaogullari Ugur , Renfro Michael W. , Cetegen Baki M.
Published: February 2010

An investigation of the transient performance characteristics of proton exchange membrane fuel cells (PEMFC) undergoing load change and during above freezing low-temperature start-ups are presented. A transient, non-isothermal, three dimensional, single phase computational fluid dynamics based model is developed to describe the transient processes of a PEMFC with conventional channels in co-flow configuration. The model equations are solved using a multi-domain approach incorporating water transport through membrane and multi-component species transport through porous diffusion layer. The dynamic response of the characteristic parameters such as membrane hydration, species concentration, cell voltage and temperature are simulated undergoing step changes in operating current density and also during start up and the results are discussed in detail. Accumulation of water in the polymer electrolyte seems to control the response time for load response and also start-up times along with the temperature of the cell. Steady state and transient simulations are compared. Steady state predictions are compared with benchmark experimental data from literature and the species concentration distributions were found to be in good agreement.
Impact of Increased Anode CO Tolerance on Performance of Hydrocarbon-Fueled PEM Fuel Cell Systems
Authors: Hu Jenny E. , Pearlman Joshua B. , Bhargav Atul , Jackson Gregory S.
Published: February 2010

Recent advances in anode electrocatalysts for low-temperature PEM fuel cells are increasing tolerance for CO in the H2-rich anode stream. This study explores the impact of current day and future advances in CO-tolerant electrocatalysts on the system efficiency of low-temperature Nafion-based PEM fuel cell systems operating in conjunction with a hydrocarbon autothermal reformer and a preferential CO oxidation (PROx) reactor for CO clean-up. This study explores the effects of incomplete H2 cleanup by preferential oxidation reactors for partial CO removal, in combination with reformate-tolerant stacks. Empirical fuel cell performance models were based upon voltage-current characteristic from single-cell MEA tests at varying CO concentrations with new alloy reformate-tolerant electrocatalysts tested in conjunction with this study. A system-level model for a 5 kW maximum liquid-fueled system has been used to study the trade-offs between the improved performance with decreased CO concentration and the increased penalties from the air supply to the PROx reactor and associated reduction in H2 partial pressures to the anode. As CO tolerance is increased over current state-of-the-art Pt alloy catalysts system efficiencies improve due to higher fuel cell voltages. Furthermore, increasing CO tolerance of anode electrocatalysts allows for increased reformer efficiency by reducing PROx CO conversion requirements.
Comparison of Three Microturbine Primary Surface Recuperator Alloys
Authors: Matthews Wendy J. , More Karren L. , Walker Larry R.
Published: February 2010

Extensive work performed by Capstone Turbine Corporation, Oak Ridge National laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650°C (∼1200°F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650°C (∼1200°F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher Chromium and Nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120, a solid-solution-strengthened alloy with nominally 33 wt.% Fe, 37 wt.% Ni and 25 wt.% Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120 and the Allegheny Ludlum austenitic alloy AL 20-25+Nb. Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.
Comparison of Combustion Models and Reaction Mechanisms for FLOX® Combustion
Authors: Panne Tobias , Widenhorn Axel , Aigner Manfred
Published: February 2010

Flameless combustion is characterized by very low NOx and CO emissions. It has successfully been used in technical furnaces under atmospheric conditions for many years. For the use in modern gas turbines the combustors have to be redesigned to meet the typical operating condition, i.e. high pressure and temperature. The flameless combustion under gas turbine relevant conditions has successfully been simulated using a detailed chemistry model [1]. However computational costs and turnaround times are very high for these simulations. In this work the influence of different reduced reaction mechanisms on the heat release and on the temperature and flow field depending on the implied combustion model are investigated. As a benchmark the simulations are compared to experimental data obtained by OH* chemiluminescence and OH LIF measurements [2]. The simulations are performed on the basis of the commercial software package ANSYS CFX 11.0.
A Sparse Estimation Approach to Fault Isolation
Authors: Borguet S. , Le´onard O.
Published: February 2010

Least-squares-based methods are very popular in the jet engine community for health monitoring purpose. In most practical situations, the number of health parameters exceeds the number of measurements, making the estimation problem underdetermined. To address this issue, regularisation adds a penalty term on the deviations of the health parameters. Generally, this term imposes a quadratic penalisation on these deviations. A side-effect of this technique is a relatively poor isolation capability. The latter feature can be improved by recognizing that abrupt faults impact at most one or two component(s) simultaneously. This translates mathematically into the search for a sparse solution. The present contribution reports the development of a fault isolation tool favouring sparse solutions. It is very efficiently implemented in the form of a quadratic program. As a validation procedure, the resulting algorithm is applied to a variety of fault conditions simulated with a generic commercial turbofan model.
A Micro Gas Turbine Based Test Rig for Educational Purposes
Authors: Ferrari Mario L. , Pascenti Matteo , Magistri Loredana , Massardo Aristide F.
Published: February 2010

The Thermochemical Power Group (TPG) of the University of Genoa, Italy, has developed a new “Gas Turbine” laboratory to introduce undergraduate students to Gas Turbines and Innovative Cycles course, and Ph.D.s to advanced experimental activities in the same field. In the laboratory a general-purpose experimental rig, based on a modified commercial 100 kW recuperated micro gas turbine, was installed and fully instrumented. One of the main objectives of the laboratory is to provide both students and researchers with several experimental possibilities to obtain data related to the gas turbine steady-state, transient and dynamic performance including the effect of interaction between the turbomachines (especially the compressor) and more complex innovative gas turbine cycle configurations, such as recuperated, humid air, and hybrid (with high temperature fuel cells). The facility was partially funded by two Integrated Projects of the EU VI Framework Program (Felicitas and Large-SOFC) and the Italian Government (PRIN project) and it was designed with a high flexibility approach including: flow control management, co-generative and tri-generative applications, downstream compressor volume variation, grid-connected or stand-alone operations, recuperated or simple cycles, and room temperature control. The layout of the whole system, including connection pipes, valves, and instrumentation (in particular mass flow meter locations) was carefully designed, for educational purposes, by a group of Ph.D. students using CFD tools (Fluent), and it is presented in detail in this paper. The paper also shows, as an example of the possibilities offered by the rig, experimental data obtained by both Master and Ph.D. students. The tests presented here are essential for understanding commercial microturbine performance, control strategy development, and theoretical model validation.
Unsteady Simulations of Flow Field and Scalar Mixing in Transverse Jets
Authors: Ivanova Elizaveta , Di Domenico Massimiliano , Noll Berthold , Aigner Manfred
Published: February 2010

This paper presents numerical simulations of flow and scalar mixing in two different jet in crossflow configurations. The testcases are chosen to resemble the dilution mixing processes in gas turbine combustion chambers. Unsteady simulations employing two different computational approaches are presented: unsteady Reynolds-Averaged Navier-Stokes (URANS) and Scale-Adaptive Simulations (SAS). The results obtained by each method are compared, analyzed, and validated against experimental data. The importance of the reproduction of the large-scale unsteady coherent vortical structures in the numerical simulation is demonstrated. Both URANS and SAS revealed the typical jet in crossflow vortical structures. The SAS method was able to resolve smaller structures than URANS on the same computational grid. The quantitative prediction accuracy of time-averaged velocities and temperatures is satisfactory for both methods. In contrast, the steady-state Reynolds-Averaged Navier-Stokes (RANS) computations failed for the present testcases.
Feasibility Study of Some Novel Concepts for High Bypass Ratio Turbofan Engines
Authors: Dewanji Dipanjay , Rao G. Arvind , van Buijtenen Jos
Published: February 2010

The soaring fuel price and the burgeoning environmental concerns have compelled global research towards cleaner engines, aimed at substantial reduction in emission, noise and fuel consumption. In this context, the present research investigates the feasibility of some novel engine concepts, namely Geared Turbofan and Intercooled Recuperated Turbofan concepts, by hypothetically applying them into an existing state-of-the-art high bypass ratio engine. This paper made an effort to estimate the effects on the baseline engine performances due to the introduction of these two concepts into it. By performing steady state simulations, it was found that the incorporation of the Geared Turbofan concept into the existing Turbofan engine caused a significant reduction in thrust specific fuel consumption, engine weight, and fan blade tip speed. However, when simulations were also carried out by incorporating the Intercooler and Recuperator concept in the baseline turbofan engine, it did not demonstrate any substantial improvement in fuel consumption. It was observed that the fuel flow rate was influenced to a large extent by heat exchanger’s effectiveness and the pressure drop within it. The overall engine weight was also found to get increased due to the inclusion of massive heat exchangers necessary for the system.
Fluid Flow Inside a Rectangular Duct With Two Opposite Walls Roughened by Deepened Scales
Authors: Liou T. M. , Chang S. W. , Chen J. S. , Chan C. Y.
Published: February 2010

Laser-Doppler velocimetry (LDV) measurements supplemented by numerical simulation and flow visualization were performed to study flow characteristics and explain the reported heat transfer features in a rectangular channel with two opposite walls roughened by deepened scales. The study is lacking in the published literature. Ratios of scale print diameter to channel height, scale maximum depth to channel height and scale pitch to scale maximum depth were 1.0, −0.1, and 10 respectively. The scale-roughened section had a cross-sectional width to height ratio of 8. All measurements were undertaken at a fixed Reynolds number, based on hydraulic diameter and cross-sectional bulk mean velocity, of 10000 with air flows directed forward and downward. Results are documented in terms of distributions of mean velocity components, mean velocity vector field, fluctuation components, and turbulent kinetic energy. The distances attaining periodic fully developed flow condition are identified. Both LDV measurements and laser-sheet flow visualization unravel the presence of near-wall secondary vortex arrays in the cross-sectional planes. The fluid flow results are subsequently used to explain previously published heat transfer trends. The dominant flow dynamic factors are recognized to provide the logic for the differences in heat transfer enhancements attained by the forward and downward channel flows over the scaled walls. A comparison of the computed sizes of cavity trapped vortex illustrates the reported difference in heat transfer augmented by the scale and dimple roughened surfaces as well as by the turbulent and laminar flows.
Emission Reduction and Cooling Improvements Due to the Introduction of Passive Acoustic Damping in an Existing SGT-800 Combustor
Authors: Lo¨rstad Daniel , Pettersson Jan , Lindholm Annika
Published: February 2010

The Siemens SGT-800 combustor has been improved using acoustic damping resulting in significantly reduced levels of thermo-acoustic pulsations for all loads. Therefore the pilot fuel ratio can be reduced leading to reduced NOx emissions, which has been verified in a number of field engines. The acoustic attenuation is achieved by introducing a soft wall located on the impingement cooled combustor wall, where a number of parameters are controlling the acoustical design. The functionality and the location of the soft wall is selected to: (1) maximize the damping effect according to acoustic calculations and measured frequencies, (2) minimize the main flame NOx emission effect due to the reduced burner air flow by the bias flow entering into the combustion primary zone, (3) minimize the effect on the turbine inlet temperature profile and (4) maximize cooling and life improvement. All this is confirmed by calculations and engine tests. The introduction of a soft wall in an existing combustor design leads to changes of the cooling layout due to the convection cooled design, since half of the local cooling flow exits through the damping holes. In addition, the local cooling is significantly improved by the reduced heat load due to the bias flow, the cooling effect of the holes and the improved efficiency of the impingement cooling, due to reduced cross flow and optimum hole positioning. Therefore an adjusted impingement plate is introduced to balance these effects in order to improve the total cooling efficiency, which is verified by CFD. Conjugate heat transfer (CHT) has been used to study the interaction between the bias jets, the combustor cross flow and the nearby geometry including the TBC layer to estimate the thermal stress, and hence the risk of high local loading for the TBC and the holes. RANS predicts significantly higher local temperature gradients compared to LES. No issues around the soft wall holes have been detected in any engine, as predicted by the LES results. Due to very long simulation times for LES CHT due to slow temperature response time of the wall, an investigation of the results using different Cp for the solid materials are presented, which can be used to significantly speed up transient CHT.
Heat Transfer and Pressure Loss in Rectangular One-Side-Ribbed Channels With Different Aspect Ratios
Authors: Kunstmann Se´bastien , von Wolfersdorf Jens , Ruedel Uwe
Published: February 2010

An investigation was conducted to assess the thermal performance of W-shaped, 2W-shaped and 4W-shaped ribs in a rectangular channel. The aspect ratios (W/H) were 2:1, 4:1 and 8:1. The ribs were located on one channel wall. The rib height (e) was kept constant with a rib height-to-hydraulic diameter ratio (e/Dh) of 0.02, 0.03 and 0.06. The rib pitch-to-height ratio (P/e) was 10. The Reynolds numbers investigated (Re>90,000) are typical for combustor liner cooling configurations of gas turbines. Local heat transfer coefficients using the transient thermochromic liquid crystal technique and overall pressure losses were measured. The rib configurations were investigated numerically to visualize the flow pattern in the channel and to support the understanding of the experimental data. The results show that the highest heat transfer enhancement is obtained by rib configurations with a rib section-to-channel height ratio (Wr/H) of 1:1. W-shaped ribs achieve the highest heat transfer enhancement levels in channels with an aspect ratio of 2:1, 2W-shaped ribs in channels with an aspect ratio of 4:1 and 4W-shaped ribs in channels with an aspect ratio of 8:1. Furthermore, the pressure loss increases with increasing complexity of the rib geometry and blockage ratio.
Ethanol-Hydrocarbon Blend Vapor Prediction
Authors: Privat Romain , Garcia Freddy , Jaubert Jean-Noe¨l , Molie`re Michel
Published: February 2010

In the volatile fuel price environment of today, the quest for alternative fuels has become a heavy and long term trend in power generation worldwide. Incorporating alternative fuels in gas turbine installations raises multiple engineering questions relating to combustion, emissions, on-base and auxiliary hardware capability, safety etc. In 2008, GE carried out a field test aimed at characterizing the combustion of ethanol in a naphtha fuelled gas turbine plant. The testing strategy has been to locally prepare and burn ethanol-naphtha blends with a fraction of ethanol increasing from 0 to nearly 100%. During the engineering phase prior to this field test, it appeared necessary to develop a sufficient knowledge on the behavior of ethanol-hydrocarbon blends in order to establish the safety analysis and address in particular the risks of (i) a potential uncontrolled ignition event in the air blanket of fuel tanks and (ii) flash vaporization of a potential fuel pond in a confined environment. Although some results exist in the car engine literature for ethanol-gasoline blends, it was necessary to take into account the specificities of gas turbine applications, namely (i) the much greater potential ethanol concentration range (from 0 to 100%) and (ii) the vast composition spectrum of naphtha likely to generate a much larger Reid Vapor Pressure envelope as compared with automotive applications. In order to fulfill the safety needs of this field test, the “Laboratoire de Thermodynamique des Milieux Polyphase´s” (LTMP) of Nancy, France has developed a thermodynamic model to approach the vaporization equilibria of ethanol-hydrocarbons mixtures with variable ethanol strength and naphtha composition. This model, named PPR78, is based on the 1978 Peng-Robinson equation of state and allows the estimation of the thermodynamic properties of a multicomponent mixture made of ethanol and naphtha compounds by using the group contribution concept. The saturation equilibrium partial pressure of such fluids in the various situations of relevance for the safety analysis can thus be calculated. The paper reports the elaboration of this model and illustrates the results obtained when using it in different safety configurations.
Analysis and Calculation of Chemical Non-Equilibrium Turbulent Flow in a Scramjet Nozzle
Authors: Wang X. Y. , Xie G. N. , Sunde´n B.
Published: February 2010

In this paper, 7-species, 8-step finite-rate chemical reaction models of the non-equilibrium flow in a scramjet single expansion ramp nozzle have been investigated numerically. Chemical reactions and mass transfer under various freestream Mach numbers and flight height conditions are performed by the RNG k-ε turbulence model. The fluid flow in the nozzle is analyzed under non-equilibrium chemical reactions and frozen flow conditions. It is shown that the total temperature is obviously increased while the total pressure is evidently decreased in the chemical non-equilibrium flow at certain inlet conditions. The mass fractions of H2 and O2 are decreased while that of H2O is increased, and the mass fraction of N2 is almost identical throughout the whole reaction process. This indicates that combustion occurs in the nozzle, and the scramjet nozzle can supplement the combustion in a supersonic combustor so that the performance of the nozzle can be increased. It can be found that there are eddies in the chemical non-equilibrium flow because of the variations of the mass fractions of O2, H, O and OH. These eddies suggest that the variations of the mass fractions of O2, H, O and OH is non-monotonic. Although the flow is speeded up, the chemical reaction at the beginning part of the nozzle is faster than that downstream. The calculation shows that the non-equilibrium chemical reactions should always be considered in investigations of the flow and performance of scramjet nozzles.
Development of an Interactive Code for Design and Off-Design Performance Evaluation of Gas Turbines
Authors: Rezaei Zangmolk Behnam , Khaledi Hiwa
Published: February 2010

In this paper, development of a modular code for simulation of design and off-design performance of different gas turbines (with different shafts and technology) has been described. This interactive code will be used for different purposes in MPG Company. This turbomachinery and thermodynamic model is based on compressor and turbine maps and blade cooling has been considered with a cooling model. Component maps and effect of IGV have been developed from one of 1D, 2D or Q3d in-house codes. It is demonstrated that this model is accurate for prediction of gas turbine behavior at both design and off-design conditions. Effect of various control system — IGV constant, TIT constant and TET constant — is evaluated. These results show that IGV constant control system has the highest and TIT constant have the lowest efficiency for a simple cycle gas turbine. In contrast, the reverse is true in a combined cycle. Also the results show that the compressor is the most stable and away enough from surge line with IGV constant control system and has the highest efficiency.