bluuebunny/crossref_metadata_2025 huggingface dataset:
Augmented heme oxygenase‐1 expression in areca quid chewing‐associated oral submucous fibrosis
Authors: Tsai C‐H , Yang S‐F , Lee S‐S , Chang Y‐C
Published: March 2009

Objectives:  Heme oxygenase‐1 (HO‐1) is known as a stress‐inducible protein and functions as an antioxidant enzyme. HO‐1 is consistently and dramatically upregulated in a variety of fibrotic diseases. The aim of this study was to compare HO‐1 expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce HO‐1 expression.

Methods:  Twenty OSF specimens and 10 normal buccal mucosa were examined by immunohistochemistry. The mRNA levels of HO‐1 from fibroblasts cultured from OSF and normal buccal mucosa fibroblasts (BMFs) were evaluated by reverse transcription polymerase chain reaction. The effect of arecoline, the major areca nut alkaloid, was added to explore the potential mechanism that may lead to induce HO‐1 expression.

Results:  Heme oxygenase‐1 expression was significantly higher in OSF specimens (P < 0.05) and expressed mainly by fibroblasts, endothelial cells, and inflammatory cells. OSF demonstrated significantly higher HO‐1 mRNA expression than BMFs (P < 0.05). Arecoline was also found to elevate HO‐1 mRNA and protein expression in a dose‐dependent manner (P < 0.05).

Conclusions:  Taken together, the data presented here demonstrated that HO‐1 expression is significantly upregulated in OSF from areca quid chewers, and arecoline may be responsible for the enhanced HO‐1 expression in vivo.
A Case Report of Steroid‐resistant Antineutrophil Cytoplasmic Antibody‐related Vasculitis Successfully Treated by Mizoribine in a Hemodialysis Patient
Authors: Tokunaga Masaki , Tamura Masahito , Kabashima Narutoshi , Serino Ryota , Shibata Tatsuya , Matsumoto Mika , Miyamoto Tetsu , Miyazaki Mieko , Furuno Yumi , Fujimatsu Shinji , Muta Toshiyuki , Takeuchi Masaaki , Abe Haruhiko , Okazaki Masahiro , Otsuji Yutaka
Published: March 2009

Abstract:  Mizoribine (MZR) has shown to be effective against antineutrophil cytoplasmic antibody (ANCA)‐related vasculitis; however, no reports have described the successful treatment of steroid‐resistant ANCA‐related vasculitis with MZR in patients with renal insufficiency requiring hemodialysis. We herein report the case of a 39‐year‐old man undergoing hemodialysis in whom MZR successfully lowered the myeloperoxidase (MPO)–ANCA titer accompanied by remission of interstitial pneumonia, together with the pharmacokinetics of MZR. The patient developed severe renal insufficiency and interstitial pneumonia, and was started on hemodialysis. Although prednisolone was administered followed by azathioprine, the MPO–ANCA level and interstitial pneumonia showed insufficient improvement. Azathioprine was replaced by MZR and the administered dose of MZR was determined by measuring serum concentrations of MZR at the start of the dialysis session; this was because we confirmed that MZR could only be removed via dialysis, and that the serum concentration of MZR was maintained until the next dialysis session. The maintenance dose was finally set at MZR 75 mg after each dialysis. Subsequently, the ANCA titer decreased and interstitial pneumonia resolved without any MZR‐related side effects. This case demonstrates that MZR is safe and effective, even in patients with steroid‐resistant ANCA‐related vasculitis undergoing hemodialysis, and can be monitored by measuring serum concentrations of MZR.
Effect of Sevelamer Hydrochloride on Bone in Experimental Uremic Rats
Authors: Kuwahara Michio , Inoshita Seiji , Terada Yoshio , Sasaki Sei
Published: March 2009

Abstract:  Hyperphosphatemia in dialysis patients is known to cause secondary hyperparathyroidism and high‐turnover bone disease. Sevelamer hydrochloride (sevelamer) is a nonabsorbed, calcium‐free phosphate‐binder. We determined the effect of sevelamer on parathyroid hormone (PTH)‐induced high bone turnover. Rats were sham‐operated or 5/6‐nephrectomized (Nx) and fed a phosphate loading diet for 16 weeks or 5/6‐nephrectomized and fed a phosphate loading diet for 8 weeks and then fed the same diet containing 3% sevelamer for the subsequent 8 weeks (Nx‐S). Sevelamer significantly reduced serum PTH. The relative osteoid volume (OV/BV), osteoid surface (OS/BS), eroded surface (ES/BS), mineral appositional rate (MAR), volume‐referent bone formation rate (BFR/TV), and bone‐referent bone formation rate (BFR/BV) were measured for vertebral bone histomorphometric analysis. All parameters were statistically higher in the Nx rats than in the sham‐operated control rats. The administration of sevelamer attenuated increases in OV/BV, ES/BS, BFR/TV, and BFR/BV. For femur histomorphometric analysis, the porosity area (%) (PoAr/CtAr), osteoid surface on the periosteal surface, osteoid surface on the endocortical surface (OS/Es), mineral appositional rate on the periosteal surface, mineral appositional rate on the endocortical surface, bone formation rate on the periosteal surface, and bone formation rate on the endocortical surface (Es BFR) were calculated. All parameters were higher in the Nx group than in the control group. Sevelamer inhibited the elevation of PoAr/CtAr, OS/Es, and Es BFR. Our findings suggest that the decrease in PTH by sevelamer may be beneficial in the treatment of high PTH‐induced bone disease.
Selective Removal of Bisphenol A From Serum Using Molecular Imprinted Polymer Membranes
Authors: Kobayashi Takaomi , Takeda Kohei , Ohashi Atsushi , Makoto Makoto , Sugiyama Satoshi
Published: March 2009

Abstract:  Bisphenol A (BPA)‐imprinted membranes were prepared by hybridization of a porous polysulfone (PSu) scaffold with a BPA‐imprinted polymer powder copolymerized with dimethacrylate BPA and divinylbenzene. When exposed to a donor calf serum (DCS) solution containing 0.05–100 µM of BPA, the imprinted hybrid membrane (10 × 10 mm2) bound BPA at a capacity of 6.0 × 10−9–20 × 10−6 mol/g‐membrane. In contrast, a similar sized powder‐free PSu membrane bound BPA at a capacity of only 1.5 × 10−9–1.9 × 10−6 mol/g‐membrane. The difference in the binding capacities of the two membranes was attributed to the BPA‐imprinted powder hybridized in the PSu membrane. Clinical analyses confirmed that the DCS parameters remained nearly constant before and after the BPA binding. This observation suggests that BPA was removed selectively from the DCS solution by the imprinted hybrid membrane. Together, these results demonstrate that the molecular imprinting technique is very useful as a novel medical material adsorbent that can reduce exposure to the endocrine disruptor, BPA.
Regulatory Effect of Parathyroid Hormone on sRANKL‐Osteoprotegerin in Hemodialysis Patients With Renal Bone Disease
Authors: Doumouchtsis Konstantinos , Perrea Despoina , Doumouchtsis Stergios , Tziamalis Marios , Poulakou Maria , Vlachos Ioannis , Kostakis Alkis
Published: March 2009

Abstract:  Receptor activator of nuclear factor‐κB ligand (RANKL) and osteoprotegerin are newly identified molecules that contribute to the modulation of bone remodeling. RANKL activates osteoclast function by binding to RANK in either a soluble or membrane‐bound form, whereas osteoprotegerin (OPG) neutralizes its effects. The aim of this study is the evaluation of soluble RANKL (sRANKL)‐OPG in cohorts of hemodialysis patients and the establishment of possible correlations between their serum levels and those of other biochemical markers. We measured intact parathyroid hormone (iPTH), osteocalcin (OC), OPG, alkaline phosphatase (ALP), tartrate‐resistant acid phosphatase (TRAP) and sRANKL in 104 hemodialysis patients. The patients were studied as a whole and in two subgroups according to their bone turnover state. In patients with low serum levels of bone turnover markers (intact parathyroid hormone [iPTH] < 100 pg/mL, ALP < 100 U/L, TRAP < 4U/L; 33 patients), the following correlations were found: (i) positive correlations of iPTH with RANKL (r = 0.394, P = 0.023) and RANKL/OPG ratio (r = 0.49, P = 0.004); (ii) a negative correlation between iPTH and OPG (r = −0.365, P = 0.037). The subgroup of patients with normal or high serum levels of bone turnover markers (iPTH ≥ 150 pg/mL, ALP ≥ 100U/L, OC ≥ 40 ng/mL; 19 patients) exhibited the following significant correlations: (i) a positive correlation between OPG and iPTH serum level (r = 0.649, P = 0.003); and (ii) a negative correlation between RANKL/OPG ratio and iPTH (r = −0.464, P = 0.045). In conclusion, the observation that PTH favors RANKL and inhibits OPG production was only demonstrated in the serum of hemodialysis patients in a low turnover state. The positive correlation between serum OPG and iPTH in normal or high turnover rates implies a homeostatic mechanism to limit bone resorption, probably associated with skeletal resistance to PTH.
New sequence‐tagged site molecular markers for identification of sex in Distichlis spicata
Authors: EPPLEY SARAH M. , O’QUINN ROBIN , BROWN ANNA L.
Published: March 2009

Sex‐linked molecular markers have become valuable tools for understanding sex ratio evolution and sex‐specific physiology in pre‐reproductive plants. To develop new accurate methods for sexing Distichlis spicata juveniles and nonflowering individuals, we converted a random amplified polymorphic DNA–polymerase chain reaction marker that co‐segregated with the female phenotype into a set of sequence‐tagged site markers. We tested the marker pair on known males and females from populations in Oregon and California. A single band was obtained for all female samples but never for males.
Nine polymorphic microsatellite loci from the psyllid Cacopsylla pruni (Scopoli), the vector of European stone fruit yellows
Authors: SAUVION NICOLAS , LACHENAUD OLIVIER , MONDOR‐GENSON GWENAELLE , RASPLUS JEAN‐YVES , LABONNE GÉRARD
Published: March 2009

Cacopsylla pruni is the vector of European stone fruit yellows, a quarantine disease of Prunus trees. Nine polymorphic microsatellite markers were developed from enriched DNA libraries. Allelic variability was assessed in a collection of 149 females obtained from five localities covering a large geographical area in France. The number of detected alleles ranged from 8 to 37. Within the localities, observed and expected heterozygosities averaged across loci ranged from 0.39 to 0.55, and from 0.68 to 0.81, respectively. A heterozygote deficiency was detected for almost all loci, possibly due to a high null allele frequency. Other possible causes of the homozygote excess (mode of reproduction, inbreeding, assortative mating or Wahlund effect) are discussed. These variable microsatellite loci can provide tools to assess overall genetic variation in this important vector species. They will be used to search for population structure and migration patterns of C. pruni.
Stability and Stationary Response of a Skew Jeffcott Rotor With Geometric Uncertainty
Authors: Driot Nicolas , Berlioz Alain , Lamarque Claude-Henri
Published: March 2009

The aim of this work is to apply stochastic methods to investigate uncertain parameters of rotating machines with constant speed of rotation subjected to a support motion. As the geometry of the skew disk is not well defined, randomness is introduced and affects the amplitude of the internal excitation in the time-variant equations of motion. This causes uncertainty in dynamical behavior, leading us to investigate its robustness. Stability under uncertainty is first studied by introducing a transformation of coordinates (feasible in this case) to make the problem simpler. Then, at a point far from the unstable area, the random forced steady state response is computed from the original equations of motion. An analytical method provides the probability of instability, whereas Taguchi’s method is used to provide statistical moments of the forced response.
Topology Optimization of Large Motion Rigid Body Mechanisms With Nonlinear Kinematics
Authors: Sedlaczek Kai , Eberhard Peter
Published: March 2009

The modern design process of mechanical structures is increasingly influenced by highly sophisticated methods of topology optimization that can automatically synthesize optimal design variants. However, the typically finite-element-based methods are limited to design tasks with comparably small deflections and simple kinematics. They are not directly applicable to the difficult development process of large motion mechanisms, which remains mainly a manual task based on the engineer’s experience, intuition, and ingenuity. There, optimization techniques are only, if at all, used in the process of dimensional synthesis, where the geometrical properties and the orientation of individual links of a fixed mechanism topology are determined. In this work, two different approaches to optimization-based topology synthesis of large motion rigid body mechanisms are presented and investigated. The goal is to automatically synthesize a combination of linkage topology and joint types that represent the most suitable mechanism layout for a particular task. The first approach is based on a trusslike ground structure that represents an overdetermined system of rigid bars from which the most appropriate topology can be extracted from this ground structure by means of gradient-based optimization algorithms. In the second approach, a genetic algorithm is used to solve the intrinsically combinatorial problem of topology synthesis. Along with several examples, both approaches are explained, their functionality is shown, and their advantages, limitations, and their capability to improve the overall design process is discussed.
A Detailed Comparison of the Absolute Nodal Coordinate and the Floating Frame of Reference Formulation in Deformable Multibody Systems
Authors: Dibold Markus , Gerstmayr Johannes , Irschik Hans
Published: March 2009

In extension to a former work, a detailed comparison of the absolute nodal coordinate formulation (ANCF) and the floating frame of reference formulation (FFRF) is performed for standard static and dynamic problems, both in the small and large deformation regimes. Special emphasis is laid on converged solutions and on a comparison to analytical and numerical solutions from the literature. In addition to the work of previous authors, the computational performance of both formulations is studied for the dynamic case, where detailed information is provided, concerning the different effects influencing the single parts of the computation time. In case of the ANCF finite element, a planar formulation based on the Bernoulli–Euler theory is utilized, consisting of two position and two slope coordinates in each node only. In the FFRF beam finite element, the displacements are described by the rigid body motion and a small superimposed transverse deflection. The latter is described by means of two static modes for the rotation at the boundary and a user-defined number of eigenmodes of the clamped-clamped beam. In numerical studies, the accuracy and computational costs of the two formulations are compared for a cantilever beam, a pendulum, and a slider-crank mechanism. It turns out that both formulations have comparable performance and that the choice of the optimal formulation depends on the problem configuration. Recent claims in literature that the ANCF would have deficiencies compared with the FFRF thus can be refuted.
Ab-Initio Molecular Dynamics Study of Nano-Scale Thermal Energy Transport
Authors: Luo Tengfei , Lloyd John R.
Published: March 2009

Ab-initio molecular dynamics (MD) which employs density functional theory (DFT) is used to study thermal energy transport phenomena in nano-scale structures. Thermal equilibration in multiple thin layer structures with thicknesses less than 1 nanometer per layer is simulated. Different types of layer combinations are investigated. Periodic boundary conditions in all directions are used in all cases. Two neighboring layers are first set to different temperatures using Nose-Hoover thermostats, and then the process of energy equilibration is simulated with a “free run” (without any thermostat controlling the temperatures). The temperature evolutions in the two neighboring layers are computed. The atomic vibration power spectra are calculated and used to explain the phenomena observed in the simulation.
Growth of Carbon Nanotubes on Carbon Toray Paper for Bio-Fuel Cell Applications
Authors: Chandra Bhupesh , Kace Joshua T. , Sun Yuhao , Barton S. C. , Hone James
Published: March 2009

In recent years carbon nanotubes have emerged as excellent materials for applications in which high surface area is required e.g. gas sensing, hydrogen storage, solar cells etc. Ultra-high surface to volume ratio is also a desirable property in the applications requiring enhanced catalytic activity where these high surface area materials can act as catalyst supports. One of the fastest developing areas needing such materials is fuel-cell. Here we investigate the process through which carbon nanotubes can be manufactured specifically to be used to increase the surface area of a carbon paper (Toray™). This carbon support is used in bio-catalytic fuel cell as an electrode to support enzyme which catalyzes the redox reaction. Deposition of nanotubes on these carbon fibers can result in great enhancement in the overall surface area to support the enzyme, which increases the reaction rate inside the fuel cell. The present paper describes a method to achieve ultra-thick growth of multiwall carbon nanotubes (MWNT) on a carbon Toray™ paper using a joule heating process and gas-phase catalyst. Using this method, we are able to achieve rapid, high-density, and uniform MWNT growth. This method is also potentially scalable toward larger-scale production.
A Parametric Study on the Effects of Inlet Swirl on Compression System Performance and Operability Using Numerical Simulations
Authors: Davis Milt , Hale Alan
Published: March 2009

The integration of the airframe and propulsion system is a key design issue in the development and deployment of military aircraft. Many disciplines comprise this issue, one being the aerodynamic interaction between the inlet system and the engine. The external airframe and inlet system must capture flow from the free stream and deliver it to the installed engine in a manner that maintains engine stability. Using the existing SAE S-16 developed methodologies, inlet distortion has traditionally been characterized by consideration of total-pressure distortion, total-temperature distortion, or planar waves, either singularly or in combination. However, many gas turbine installations can generate significant flow angularity as well as total pressure distortion at the Aerodynamic Interface Plane (AIP). The flow angularities may have both radial- and circumferential-velocity components. Swirl is generally considered as being that portion of the flow vector which is directed circumferentially, since it is this velocity component which directly affects the work of a downstream fan or compressor. The objective of this paper is to demonstrate that simple but effective numerical simulations can provide qualitative insights into the effect of swirl on compression system performance and operability. The analysis presented in this paper uses both a single rotor and an advanced 2-stage fan exhibiting many modern military turbofan design features.
Development of Risk-Based Maintenance Software for Gas Turbines
Authors: Fujii Tomoharu , Fujioka Terutaka , Ablitt Chris , Speck Julian , Cane Brian
Published: March 2009

Risk-based maintenance software has been developed to perform risk-based maintenance and inspection planning on gas turbine hot gas path components. The software allows the user to easily prepare a risk matrix, plotting every active damage mechanism for each hot gas path component. Based on the result of the risk assessments the components can be ranked, allowing inspection plans to be focused and prioritized and aiding the user to identify the most appropriate and effective risk mitigating activity within the software. Risk assessments are performed on a component-by-component basis, with the software’s scope including all combustor and turbine hot gas path components. The software also contains comprehensive help documents to aid the user in identifying and assessing peculiar damage mechanisms and prescribing the most effective inspection methods for gas turbines.
Heat Transfer in a Channel With Inclined Target Surface Cooled by Single Array of Impinging Jets
Authors: Al-Hadhrami Luai M. , Shaahid S. M. , Al-Mubarak Ali A.
Published: March 2009

An experimental investigation has been carried out to study the heat transfer characteristics in a channel with heated target plate inclined at an angle cooled by single array of centered impinging jets. The target plate forms the leading edge of a gas turbine blade. The work includes the effect of various exit outflow orientations and crossflow and feed channel aspect ratios on the heat transfer characteristics for a given orifice-jet plate configuration. Three feed channel aspect ratios (H/d = 5, 7, 9) and have been examined. In general, it has been observed that Nu is high for higher aspect ratios. This increase can be attributed to increase in strength of impinging jets due to increase in feed channel aspect ratio. Additionally, for a given jet-orifice plate with centered holes and for a given Re = 18800, the heat transfer is almost the same through out the target surface for the outflow passing out in both the directions.
Performance Prediction for High Pressure-Ratio Radial Inflow Turbines
Authors: Qiu Xuwen , Baines Nick
Published: March 2009

This paper describes the latest developments in a method for predicting the design and off-design performance of radial inflow turbines, using a one-dimensional analysis. As such, it is suitable for preliminary design purposes and also for turbine map generation as an aid to the modelling of systems including such turbines. Previous development work has resulted in methods of loss correlation allowing the power output and efficiency to be predicted with confidence. The focus of this paper is on extending the calculation method to high-pressure ratios, and the accurate prediction of flow capacity for unchoked and choked conditions. A numerical method provides for the identification of subsonic, transonic, and supersonic flow regimes in the bladed rows of the turbine, and allows their solution in a consistent manner. Numerically stable and validated solutions have been obtained for a cryogenic expander case with the stage pressure ratios as high as 13.6. In this paper, we will report cases with pressure ratio up to 4.0, where the nozzle and rotor are operating at the choked condition. When a blade row is choked, the flow capacity depends on the throat area, and accurate predictions require that this area is known with confidence. Previous meanline methods have typically concentrated on unchoked flow conditions, in which it is not necessary to know the throat area accurately. In turbine design, the method thus enables the necessary throat areas to be established at an early stage in the design process, and this information is required for the subsequent blade design. In analysis, comparison with test data has revealed the importance of throat aerodynamic blockage, which has hitherto largely been overlooked in meanline prediction methods. Estimates of appropriate blockages have been obtained from such comparisons. An unusual feature of radial inflow turbine nozzles is the reduction of annulus area downstream of the blade row. This can lead to situations where it is the flow area at the trailing edge rather than the throat that limits the flow capacity in choking conditions. The method accommodates this by introducing additional deviation at the trailing edge to ensure that the throat remains choked for all blade row pressure ratios greater than the critical pressure ratio, and the flow between the throat and trailing edge develops in a form that is fully consistent with the basic principles of fluid motion.
Future Abradable Requirements Needed by Aerospace OEM’s and Their Material and Equipment Suppliers
Authors: Dorfman M. R. , Fiala P. , Hajmrle K. , Wilson S.
Published: March 2009

The cost of in-service clearance control coating failure analysis can be high to the aerospace OEM’s (Original Equipment Manufacturers). The failure analysis process is labor-intensive and time-consuming. It is for these reasons that OEM’s will be requiring vendors of materials and equipment to have: (1) greater in-process controls on spray process equipment, (2) greater statistical process control (SPC) documentation of key material manufacturing process variables, (3) increased documentation of cause and effect of powder manufacturing and spray process variables and better understanding of the influence of these variables on overall performance, and (4) more detailed coating/powder specifications. This paper will discuss the future needs of aerospace OEM’s in these four areas and specifically discuss how vendors are addressing these needs.
Effect of Flow Parameter Variations on Full Coverage Film-Cooling Effectiveness for a Gas Turbine Blade
Authors: Mhetras Shantanu , Han Je-Chin , Rudolph Ron
Published: March 2009

The effect of film cooling holes placed along the span of a fully-cooled high pressure turbine blade in a stationary, linear cascade on film cooling effectiveness is studied using the Pressure Sensitive Paint (PSP) technique. Effect of showerhead injection at the leading edge and the presence of compound angled, diffusing holes on the pressure and suction side are also examined. Six rows of compound angled shaped film cooling holes are provided on the pressure side while four such rows are provided on the suction side of the blade. The holes have a laidback and fan-shaped diffusing cross-section. Another three rows of cylindrical holes are drilled at a typical angle on the leading edge to capture the effect of showerhead film coolant injection. The film cooling hole arrangement simulates a typical film cooled blade design used in stage 1 rotor blades for gas turbines used for power generation. A typical blowing ratio is defined for each film hole row and tests are performed for 100%, 150% and 200% of this typical value. Tests are performed for inlet Mach numbers of 0.36 and 0.45 with corresponding exit Mach numbers of 0.51 and 0.68 respectively. The flow remains subsonic in the throat region for both Mach numbers. The corresponding free stream Reynolds number, based on the axial chord length and the exit velocity, are 1.3 million and 1.74 million respectively. Freestream turbulence intensity level at the cascade inlet is 6%. Results show that varying blowing ratios can have a significant impact on film-cooling effectiveness distribution. Large spanwise variations in effectiveness distributions are also observed. Similar distributions were observed for both Mach numbers.
Dynamic Instability Analysis of Internally Damped Rotors
Authors: Sino Rim , Chatelet Eric , Montagnier Olivier , Jacquet-Richardet Georges
Published: March 2009

This paper deals with the study of dynamic instabilities within rotating assemblies due to internal damping effects. In order to consider realistic mechanical properties, in terms of internal damping, a rheological model is associated to a general finite element beam approach, including transversal shear. After a description of the theoretical background (choice of internal damping model and equation of motion), an application illustrates the ability of the proposed model. The influence of damping on frequencies and on instability thresholds is investigated using a parametric study. Results are compared to those obtained from an analytical approach as well as from experiments.
On Coupling of RANS and LES for Integrated Computations of Jet Engines
Authors: Medic Gorazd , You Donghyun , Kalitzin Georgi
Published: March 2009

Large scale integrated computations of jet engines can be performed by using the unsteady RANS framework to compute the flow in turbomachinery components while using the LES framework to compute the flow in the combustor. This requires a proper coupling of the flow variables at the interfaces between the RANS and LES solvers. In this paper, a novel approach to turbulence coupling is proposed. It is based on the observation that in full operating conditions the mean flow at the interfaces is highly non-uniform and local turbulence production dominates convection effects in regions of large velocity gradients. This observation has lead to the concept of using auxilliary ducts to compute turbulence based on the mean velocity at the interface. In the case of the RANS/LES interface, turbulent fluctuations are reconstructed from an LES computation in an auxiliary three-dimensional duct using a recycling technique. For the LES/RANS interface, the turbulence variables for the RANS model are computed from an auxilliary solution of the RANS turbulence model in a quasi-2D duct. We have demonstrated the feasibility of this approach for the integrated flow simulation of a 20° sector of an entire jet engine.
Flow Fields and Droplet Diameter Distributions of Water and N-Heptane Sprays at Varied Boundary Conditions in a Generic Gas Turbine Combustor
Authors: Hage Michael , Dreizler Andreas , Janicka Johannes
Published: March 2009

The present study reports on non-reacting swirling flow fields and droplet diameter distributions of sprays at elevated pressures and reduced inlet air temperatures. The combustion chamber used in this study enabled optical access from three sides allowing the application of various laser based measurement techniques. It is equipped with an airblast atomizer nozzle typical for many gas turbines. The parameters of the boundary conditions, based on a reacting case for a partially premixed turbulent flame, were varied to such an extent that laser diagnostics were feasible. The effects of variation in chamber pressure (2–3 bar) and inlet temperature (250–350°C) are discussed. In order to investigate the influence of the atomized liquids, and thereby surface tensions, water sprays were analysed additionally for comparison to n-heptane. For single-phase isothermal air flows, mean velocities and RMS-values were measured using laser Doppler anemometry (LDA). The aim was solely to test the performance of the turbulence model in a subsequent numerical simulation and to allow for a characterization of the flow field in absence of the spray. In addition to the statistically independent LDA measurements, time series were recorded with the intention to gain structural information on the flow patterns. The autocorrelations derived from the time series revealed a periodic coherent structure within the flow pattern indicating the presence of a precessing vortex core (PVC) typical for swirl stabilized flows.
Numerical Investigation of Soot Formation in Laminar Ethylene-Air Diffusion Flames
Authors: Di Domenico Massimiliano , Gerlinger Peter , Aigner Manfred
Published: March 2009

In this work a new soot formation model is used to predict temperature, species and soot concentrations in laminar ethylene-air diffusion flames. The gas-phase chemistry is described by elementary reactions with transport equations solved for any species. The chemical paths yielding to soot are modeled by a sectional approach for Polycyclic Aromatic Hydrocarbons (PAHs). Soot dynamics is described by a two-equation model for soot mass fraction and particle number density. Phenomena like nucleation, growth and oxidation have been included both for PAHs and soot. Moreover, PAH-PAH and PAH-soot collisions are taken into account. Species, PAH and soot transport equations are implemented in the in-house DLR-THETA CFD code. The laminar, ethylene-air diffusion flame investigated experimentally by McEnally and coworkers (2000) is simulated in order to validate the model. An analysis of the main flame’s features as well as the interaction between them and the soot chemistry will be given. A qualitative correlation between local stoichiometric values and soot formation rate is assessed. In order to study the sensitivity of the combustion model to simulation parameters like the inlet temperature and kinetic mechanism, additional simulations are performed. Results are also compared with experimental data in terms of temperature, species mole fractions and soot volume fraction axial profiles.
Part Load Strategies of a Multi-MW Molten Carbonate Fuel Cell Gas Turbine Hybrid System
Authors: Karvountzi Georgia C. , Duby Paul F.
Published: March 2009

The goal of this study is to define the operating envelope of a 20MW molten carbonate fuel cell (MCFC)-gas turbine hybrid system, under part load conditions. The first part of the paper reviews our baseline fuel cell hybrid system model that predicts overall system LHV efficiency around 69% at full load. The second part of the paper consider several strategies: 1/ run fuel cell at full load and bypass gas turbine; 2 /run fuel cell at full load and gas turbine at part load; 3/ run fuel cell at OCV and gas turbine at full load; 4/ run fuel cell at part load and gas turbine at full load; and 5/run both fuel cell and gas turbine at part load. The best system part-load performance was achieved when the fuel cell operates at part load while the gas turbine is at full load. The highest operational flexibility is achieved when we part load both the fuel cell and the gas turbine. Depending on system targets and deliverables such as fuel cell voltage and fuel utilization or gas turbine firing temperature some of these modes may not be economical. A comparison with the performance of a conventional combined cycle 20MW power plant under part load was performed. The MCFC hybrid system showed better efficiency and better cost of electricity (COE) under part load operation than the gas turbine combined cycle part loaded.
Automatic Mixing Valve for Prescribed Injection Ratio Versus Variable Fuel Flow Rate
Authors: Cerri Giovanni , Chennaoui Laila , Miglioli Mauro , Botta Fabio
Published: March 2009

Using water or ethanol in fuel oils (including gasoline) results in a very fine atomization of the fuel due to micro-explosions (primary, secondary and tertiary) occurring during combustion. Thus the tiny nano-particles produced during combustion may better follow the flow and less particle impingement on the surfaces (tube walls, blades, etc.) occurs. The emulsion is produced by a device on board the engines using no chemical additives. Since the above engines operate at variable fuel flow rate from idle to full power there is a broad range of flow rates of the two liquids to be mixed. This paper deals with an automatic device that is capable of producing the prescribed injection ratio of the dispersed phase into the variable fuel oil flow rate. A design model has been developed to size the device. An ample description of the model and prototype is presented. Experimental validation of the model has been performed with the results discussed in this paper. The final automatic mixing valve arrangement is presented with the experimental set up. Parametric analyses of results together with the simulations are discussed.
Turbine Aerodynamic Performance Measurement Under Non-Adiabatic Conditions
Authors: Atkins N. R. , Ainsworth R. W.
Published: March 2009

The practical performance, both the efficiency and durability, of a High-Pressure (HP) turbine depends on many interrelated factors, including both the steady and unsteady aerodynamics and the heat transfer characteristics. The aerodynamic performance of new turbine designs has traditionally been tested in large scale steady flow rigs, but the testing is adiabatic, and the measurement of heat transfer is very difficult. Transient facilities allow fully scaled testing with simultaneous heat transfer and aerodynamic performance measurements. The engine matched gas-to-wall temperature ratio simulates more closely the boundary layer and secondary flow development of the engine case. The short duration of the testing means that the blades are effectively isothermal, with a rise of only a few degrees during a test. In order to isolate the aerodynamic losses, and thus the entropy generation due to the viscous losses, the entropy reduction due to heat transfer during the expansion needs to be determined. This entropy reduction is path dependent and requires knowledge of the full temperature and heat flux fields. This paper demonstrates a simple methodology for estimation of this entropy reduction, which allows the calculation of the adiabatic efficiency from the results of engine representative non-adiabatic testing. The methodology is demonstrated using a Computational Fluid Dynamics (CFD) prediction which is validated against experimental heat flux data. Details of the other corrections required for transient test techniques such as unsteady leakage flows are also discussed.
An Educational Software Suite for Teaching Design Strategies for Multistage Axial Flow Compressors
Authors: Bruna Dario , Cravero Carlo , Turner Mark G. , Merchant Ali
Published: March 2009

The T-AXI turbomachinery design system, an axisymmetric methodology recently developed with an educational purpose, has shown great capabilities in the redesign of existing axial flow gas turbine components. Different turbomachines, single or multistage configurations, have been already reproduced with excellent overall performance results: examples are the NASA/GE E3 HP compressor and LP turbine. In this paper the authors present a detailed analysis of the results of a “case-study” application of the code, as a complementary tool to be used during a turbomachinery design course. The NASA/GE E3 HP compressor has been chosen as the test case. Starting from the data available in open literature the different steps of the redesign have been reported: from the flowpath generation through the thermodynamic properties distributions to the overall turbomachine performance analysis. Particular attention has been given to some critical aero design parameters. The links to some interesting and useful literature sources are reported. The free-vortex, the only vortex law included in the first version of the code has been used for a first EEE compressor redesign. Different design vortex methodologies have been implemented in the new release of the code and their effects on the angular momentum are reported. The corresponding geometries can also be interfaced to a mesh generator and then the turbomachinery configurations analyzed by a 3-D Navier-Stokes solver. In this way the flow field can be carefully analyzed and the fluid-dynamic physics better understood. With the above software structure the student has the opportunity to test the effects of different design strategies on the turbomachinery performance and to understand the need of a hierarchy of tools that give complete information for the multistage turbomachinery design. Finally, in the last section of the paper, the authors present how a project such as T-AXI, developed from their research activity in turbomachinery, numerical methods and CFD, can be included in the education tool CompEdu.
External Heat Transfer on a Shrouded HP Gas Turbine Stage
Authors: Haller Brian R. , Hilditch Mary A.
Published: March 2009

A new, shrouded, high pressure turbine which was designed using a “Controlled Flow” philosophy has been tested in the Turbine Test Facility (TTF) at QinetiQ, Farnborough. Heat transfer results from this new design are reported along with turbine aerodynamics and unsteady static pressure on the rotor blade. This includes measurements on the HP shroud. The measurements are compared with 2D and 3D calculations of heat transfer. These are the first measurements and detailed predictions for this new turbine and provide a good indication of the “state-of-the-art”, i.e. where the designer can have confidence in the predictions and where further work is required.
Simulation of Acoustic Enhancement of Heat Transfer in a Droplet Heat Exchanger
Authors: Habte Melaku , Yavuzkurt Savas
Published: March 2009

Enhancement of heat transfer from a droplet exposed to acoustic fields is investigated. Investigation is part of a research project in enhancing the heat transfer in direct contact heat exchangers. Adding high intensity sound to Droplet Heat Exchanger (DHX) design produces relative gas motion around droplets otherwise entrained in the main flow field. Particles do not get fully entrained in the high frequency acoustic field giving rise to relative velocity. This enhances the heat transfer from droplets. Further benefits could be obtained by acoustic agglomeration of small droplets. DHXs have high contact area, no interface losses, low pressure drop and superior heat transfer characteristics compared to standard heat exchangers. With further enhancement of heat transfer by high intensity acoustic field application makes DHXs very attractive in many industrial applications such as droplet/particle reactors, humidifiers, gas scrubbers as well as ground based power generating gas turbines. In this paper, results of simulations of a single droplet exposed to acoustic fields of a range of sound intensity level (SPL) and frequency are presented. Spherical droplets are exposed to high intensity acoustic fields up to 175 dB with frequencies 25–2000Hz. Droplet size considered here is 100μm. Three dimensional (3-D) simulation of an oscillating flow field around a spherical droplet are carried out using FLUENT code. First, simulation results of space-averaged Nusselt numbers for steady flow around a single droplet are compared with available experimental data. Results were within 1–5% of each other. Simulations with acoustic field with and without steady velocity component were carried out and the results were compared with previous two dimensional studies as well as experimental and correlations of the same phenomena. The current simulation results are on average 22% higher than the 2D simulation results indicating the 3D nature of the flow. Space and time-averaged Nusselt numbers were more than 400% higher than the ones obtained without the acoustic field for acoustic Reynolds number 100 and frequency 50Hz and 30% higher than 2D simulation results. Finally, entrainment of droplets in the oscillating flow field was also considered. The result showed insignificant reduction (< 1%) in heat transfer rate compared to the case with no entrainment at all ranges of frequency (50–2000Hz).
Effects of Off-Design Operating Conditions on the Blade Row Interaction in a HP Turbine Stage
Authors: Persico G. , Gaetani P. , Osnaghi C.
Published: March 2009

An extensive experimental analysis on the subject of the unsteady periodic flow in a highly subsonic HP turbine stage has been carried out at the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano (Italy). In this paper the blade row interaction is progressively enforced by increasing the stator and rotor blade loading and by reducing the stator-rotor axial gap from 100% (very large to smooth the rotor inlet unsteadiness) to 35% (design configuration) of the stator axial chord. The time-averaged three-dimensional flow field in the stator-rotor gap was investigated by means of a conventional five-hole probe for the nominal (0°) and an highly positive (+22°) stator incidences. The evolution of the viscous flow structures downstream of the stator is presented to characterize the rotor incoming flow. The blade row interaction was evaluated on the basis of unsteady aerodynamic measurements at the rotor exit, performed with a fast-response aerodynamic pressure probe. Results show a strong dependence of the time-averaged and phase-resolved flow field and of the stage performance on the stator incidence. The structure of the vortex-blade interaction changes significantly as the magnitude of the rotor inlet vortices increases, and very different residual traces of the stator secondary flows are found downstream of the rotor. On the contrary, the increase of rotor loading enhances the unsteadiness in the rotor secondary flows but has a little effect on the vortex-vortex interaction. For the large axial gap, a reduction of stator-related effects at the rotor exit is encountered when the stator incidence is increased as a result of the different mixing rate within the cascade gap.
A Precise Full-Dimensional Design System for Multistage Steam Turbines: Part II — Key Technologies for Blade and Non-Blade Components, Engineering Application and Updating
Authors: Xu Xinzhong , Xu Kepeng , Li Baoqing , Chen Qing , Jiang Hongde
Published: March 2009

In this part of present paper the key technologies for steam turbine blade and non-blade components developed by using the precise, full-dimensional (PFD) system is described firstly. For blade components advanced aerodynamic concept and design method for customized after-loaded profile, compound-lean blade, tandem cascade, contoured endwall, and solid particle erosion protection for HP and IP first nozzle have been developed. For non-blade component including main steam inlet/control valve, LP exhaust hood, packing seal and cavity flow, casing opening and condenser, new aerodynamic and mechanical design has been developed. New blade and non-blade components were experimentally and numerically investigated to verify its performance. Finite element method (FEM) analysis for all key components is also illustrated in this paper. Secondly the approach of validation and updating for the PFD system is introduced. Based on a large amount of on-site performance test data in power plants the statistic accuracy for the PFD system is given. It shows that in comparison with conventional F3D design methodology another 1.5-2 percent of HP and IP overall section efficiency improvement has been achieved.
Advanced Controls for Fuel Consumption and Time-on-Wing Optimization in Commercial Aircraft Engines
Authors: Viassolo Daniel , Kumar Aditya , Brunell Brent
Published: March 2009

This paper introduces an architecture that improves the existing interface between flight control and engine control. The architecture is based on an on-board dynamic engine model, and advanced control and estimation techniques. It utilizes a Tracking Filter (TF) to estimate model parameters and thus allow a nominal model to match any given engine. The TF is combined with an Extended Kalman Filter (EKF) to estimate unmeasured engine states and performance outputs, such as engine thrust and turbine temperatures. These estimated outputs are then used by a Model Predictive Control (MPC), which optimizes engine performance subject to operability constraints. MPC objective and constraints are based on the aircraft operation mode. For steady-state operation, the MPC objective is to minimize fuel consumption. For transient operation, such as idle-to-takeoff, the MPC goal is to track a thrust demand profile, while minimizing turbine temperatures for extended engine time-on-wing. Simulations at different steady-state conditions over the flight envelope show important fuel savings with respect to current control technology. Simulations for a set of usual transient show that the TF/EKF/MPC combination can track a desired transient thrust profile and achieve significant reductions in peak and steady-state turbine gas and metal. These temperature reductions contribute heavily to extend the engine time-on-wing. Results for both steady state and transient operation modes are shown to be robust with respect to engine-engine variability, engine deterioration, and flight envelope operating point conditions. The approach proposed provides a natural framework for optimal accommodation of engine faults through integration with fault detection algorithms followed by update of the engine model and optimization constraints consistent with the fault. This is a potential future work direction.