bluuebunny/crossref_metadata_2025 huggingface dataset:
Global transport of thermophilic bacteria in atmospheric dust
Authors: Perfumo Amedea , Marchant Roger
Published: February 2010

Aerosols from dust storms generated in the Sahara‐Sahel desert area of Africa are transported north over Europe and periodically result in dry dust precipitation in the Mediterranean region. Samples of dust collected in Turkey and Greece following two distinct desert storm events contained viable thermophilic organisms of the genus Geobacillus, namely G. thermoglucosidasius and G. thermodenitrificans, and the recently reclassified Aeribacillus pallidus (formerly Geobacillus pallidus). We present here evidence that African dust storms create an atmospheric bridge between distant geographical regions and that they are also probably the source of thermophilic geobacilli later deposited over northern Europe by rainfall or dust plumes themselves. The same organisms (99% similarity in the 16S rDNA sequence) were found in dust collected in the Mediterranean region and inhabiting cool soils in Northern Ireland. This study also contributes new insights to the taxonomic identification of Geobacillus sp. Attempts to identify these organisms using 16S rRNA gene sequences have revealed that they contain multiple and diverse copies of the ribosomal RNA operon (up to 10 copies with nine different sequences), which dictates care in interpreting data about the systematics of this genus.
Living alone, lack of a confidant and psychological well‐being of elderly women in Singapore: the mediating role of loneliness
Authors: Lim Lena L. , Ng Tze Pin
Published: February 2010

Background: The “feminization of aging” and nuclearization of families calls for research to examine the mental health and well‐being of elderly women living alone. This study examined a proposed heuristic model whereby the relationship between living alone and lack of a confidant and psychological well‐being is mediated by feeling of loneliness.

Methods: Path analysis was performed on data of 1,205 community‐living older women aged 55 and above with psychological well‐being assessed by depressive symptoms (15‐items Geriatric Depression Scale) and SF‐12 MCS (mental component summary scale of the 12‐item Short‐Form Health Survey) quality of life scores assessed at baseline and follow‐up 1.5 years later.

Results: Goodness‐of‐fit indices used for the model showed good fits. All of the path coefficients were meaningful in absolute magnitude and significant at P<0.001. Living alone was associated concurrently with lack of a confidant (r=0.11), both of which predicts loneliness (path co‐efficient=0.09). Loneliness predicts more depressive symptoms (path coefficient=0.25) and SF‐12 MCS (path coefficient=−0.28) at baseline, as well as at follow‐up.

Conclusion: The findings suggest that loneliness mediates the relationship between living alone, lack of a confidant, and psychological well‐being. Living alone becomes detrimental when it leads to loneliness. Social programs directed at elderly women who are living alone should alleviate loneliness through satisfactory interpersonal relationships, and emotional and spiritual support.
Epigenetic modification of fetal baboon hepatic phosphoenolpyruvate carboxykinase following exposure to moderately reduced nutrient availability
Authors: Nijland Mark J. , Mitsuya Kozoh , Li Cun , Ford Stephen , McDonald Thomas J. , Nathanielsz Peter W. , Cox Laura A.
Published: February 2010

Decreased maternal nutrient availability during pregnancy induces compensatory fetal metabolic and endocrine responses. Knowledge of cellular changes involved is critical to understanding normal and abnormal development. Several studies in rodents and sheep report increased fetal plasma cortisol and associated increased gluconeogenesis in response to maternal nutrient reduction (MNR) but observations in primates are lacking. We determined MNR effects on fetal liver phosphoenolpyruvate carboxykinase 1 (protein, PEPCK1; gene, PCK1 orthologous/homologous human chromosomal region 20q13.31) at 0.9 gestation (G). Female baboon social groups were fed ad libitum (control, CTR) or 70% CTR (MNR) from 0.16 to 0.9G when fetuses were delivered by caesarean section under general anaesthesia. Plasma cortisol was elevated in fetuses of MNR mothers (P < 0.05). Immunoreactive PEPCK1 protein was located around the liver lobule central vein and was low in CTR fetuses but rose to 63% of adult levels in MNR fetuses. PCK1 mRNA measured by QRT‐PCR increased in MNR (2.3‐fold; P < 0.05) while the 25% rise in protein by Western blot analysis was not significant. PCK1 promoter methylation analysis using bisulfite sequencing was significantly reduced in six out of nine CpG‐dinucleotides evaluated in MNR compared with CTR liver samples. In conclusion, these are the first data from a fetal non‐human primate indicating hypomethylation of the PCK1 promoter in the liver following moderate maternal nutrient reduction.
Generalized Two-Phase Pressure Drop and Heat Transfer Correlations in Evaporative Micro/Minichannels
Authors: Lee Hee Joon , Liu Dong Yao , Alyousef Y. , Yao Shi-chune
Published: February 2010

Existing databases and correlations in literature on the microchannel pressure drop and heat transfer are reviewed in this paper. From this review, it is found that none of the existing correlations can cover the wide ranges of working fluids, operational conditions, and different microchannel dimensions. In addition, the importance of the Bond number, which relates the nominal bubble dimension or capillary parameter with the channel size, is revealed in this paper. Using the Bond number, improved correlations of pressure drop and heat transfer are established, which predict the existing data well over a wide range of channel sizes, fluids, and operational conditions.
Analysis of Electrode Degradation Through the Use of Synthetic Tissue Analog
Authors: Webster Mason J. , Herbert Derek M. , Pascoal Peter T. , Smith Justin C.
Published: February 2010

RF Ablation Efficacy Testing: Modern surgical techniques utilize radio frequency ablation tools in minimally invasive procedures around the world today. The safety and efficacy of these tools must be verified before being used in human trials. This verification is typically performed on bovine, ovine, or porcine tissues which simulate clinical use.
Polycentric Versus Single Axis Sagittal Femoral Geometry and Paradoxical Anterior Translation in Total Knee Implants
Authors: Williams John L.
Published: February 2010

Paradoxical anterior translation of the femur (undesirable anterior motion of the femoral side of the knee relative to the tibia) has been observed in patients with posterior cruciate ligament (PCL) retaining total knee devices in which the ACL is absent. Simulations of a double leg squat of several total knee implant designs were compared using measurements of tibio-femoral ‘contact positions’ similar to those published in fluoroscopic studies. The objective of the study was to examine if a femoral design with a single axis (single radius) of curvature in the para-sagittal plane undergoes paradoxical anterior translation in the same way as femoral designs with polycentric (multi-radius) geometry.
Design of a Portable Renal Replacement System Through Modeling and Experiment
Authors: Olson Jeffrey , Weaver Jason , Yang Yong , Ku David N. , Rosen David W.
Published: February 2010

There are approximately 65,000 patients on sustaining hemodialysis in the United States for renal disease. While hemodialysis is traditionally performed three times weekly, several studies have shown improved patient results with increased treatment frequency and shorter treatment time. A more portable hemodialysis treatment would represent an improvement over current treatments by giving patients the ability to dialyze at their convenience, and more often for shorter treatment times. A prototype wearable artificial kidney has been developed by Gura et al.
Finite Element Analysis of TMJ Implant
Authors: Kashi Ajay , Chowdhury Amit Roy , Saha Subrata
Published: February 2010

The TMJ is a bilateral joint of the jaw that functions as a single entity during normal masticatory activities, speaking, yawning and swallowing. TMJ replacement has been indicated in cases of joint trauma, advanced degenerative disease, tumors, developmental anomalies and ankylosis of the joint following injury. Alloplastic replacement of the TMJ (an artificial replacement in the form of a TMJ condylar implant with a glenoid fossa component that articulates with the undersurface of the skull on the temporal bone) renders the anatomical space devoid of the natural mandibular condyle (Fig. 1). Compared to hip and knee prostheses, TMJ implants have not been studied in detail. The goals of this study were to quantify the stress distribution in a commercially available TMJ implant (TMJ Implants, Inc, CO), bone and implant-bone interface, to compare the stresses and strains with different bone conditions, and to compare the stresses and strains with different implant materials using a finite element software package.
Comparison of Cervical Spine Fixation Devices
Authors: Hollis J. Marcus , Raducan Viorel
Published: February 2010

Injury to the cervical spine can be debilitating injury. Fracture the Dens of the C1-C2 motion segment can lead to gross instability of the cervical spine and neurological deficit. It is important to achieve stability operatively. Posterior fusion is considered by some to be a relatively safe operation compared to other procedures. Any spinal surgery which relies on boney stabilization post-operatively must provide a sufficiently small amount of movement initially to allow bone consolidation and healing.
Lumbar Disc Replacement Failures: Review of 29 Patients and Rationale for Revision
Authors: Rosen Charles , Kiester Douglas P. , Lee Thay Q.
Published: February 2010

The Charite III artificial disc replacement was approved for use in the United States in October of 2004 by the FDA. Another similarly designed lumbar disc replacement called the ProDisc II was also approved by the FDA a year later in January of 2006. The purpose of this study was to retrospectively review 29 patients with either the Charite III or the Prodisc II disc replacement surgery and complications.
Occupant Extremity Loading in Frontal Motor Vehicle Impacts: Prediction of Potential Orthopedic Implant Failure
Authors: Long Timothy J. , Bajgrowicz Darleen M.
Published: February 2010

The analysis of motor vehicle impacts and the resulting injury exposure to occupants with artificial joints can be correlated to a parameter referred to as delta-v. The delta-v of a vehicle involved in a motor vehicle impact is defined as the change of velocity of the vehicle at its center of gravity during impact. The delta-v is a function of the closing speed between the two vehicles and the mass of each vehicle. A general formula for delta-v is as follows: ΔVi=(1+ε)·(mj/(mi+mj))·Vc Where: Vc – closing speed between the two vehicles; ε – coefficient of restitution; m – mass of each vehicle.
Soft Tissue Fixation and Implant Development: Session Summary
Authors: van der Burg Erik
Published: February 2010

Sports medicine/joint preservation represents one of the fastest growing segments of orthopedic markets. It is estimated that the frequency of rotator cuff repair alone is increasing between 10 and 20% per year. Similar to the ongoing evolution in other medical specialties (cardiology, general surgery), an increasing number of joint preservation procedures are transitioning to less invasive techniques. However, there are significant unmet needs as soft tissue repair transitions from invasive open surgical techniques to less invasive arthroscopic methods.
Periprosthetic of the Femur and Acetabulum: An Emerging Problem
Authors: Muldoon Michael P.
Published: February 2010

Presentation will review the epidemiology, risk factors and treatments of fractures of the pelvis and femur associated with total hip arthroplasty. The attendee will be exposed to classification systems and treatment rationale base on accepted criteria. Additionally the at risk patient will be clarified in respect to types of implants, duration of service and pathologic comorbidities.
External Fixation of Distal Radius Fractures
Authors: Slutsky David
Published: February 2010

External fixation has been used for the treatment of distal radius fractures for more than 50 years. Although the fixator configurations have undergone considerable modification over time, the type of fixator itself is not as important as the underlying principles that provide the foundation of external fixation. Although volar plate fixation is currently in vogue, the indications for external fixation remain largely unchanged. New fixator designs have also expanded hrte traditional usage to include nonbridging applications that allow early wrist motion. The following discussion focuses on the myriad uses for external fixation as well as the shortcomings and potential pitfalls.
Dependence of Gas Stoichiometry on the Uniformity and Stability of a Segmented Proton Exchange Membrane Fuel Cell
Authors: Jou Bo-Shian , Weng Fang-Bor , Chi Pei-Hung , Su Ay , Hsu Chun-Ying , Chan Shih-Hung
Published: February 2010

This study developed an eight-segmented fuel cell for investigating local current distribution and stability along channel with six-pass serpentine flow field. The stoichiometry of anode was 1.2 and cathode was 4 as the benchmark for comparison. When the stoichiometry flow rate of cathode was 4 and anode decreased to 1.05, which caused the hydrogen starvation on the downstream. The decrease of cathode stoichiometry from 4 to 2 resulted in less water diffusing to membrane and slight decrease of the conductivity on the gas-inlet segment. The cathode stoichiometry of 1.2 showed better performance than the stoichiometry of 2 at 8th segment. The reason is the hydration of membrane by water produced. When the fuel cell was operating under full humidity at 0.5V constant voltage, the current density would oscillate with time at different cathode stoichiometry. This result indicated that the location causes channel water flooding and draining alternately. The oscillation decreased at lower cathode stoichiometry.
Numerical Studies of Heat Transport for Polymer Electrolyte Fuel Cell Stack in Sub-Freezing Environment
Authors: Sun Pengtao , Zhou Su
Published: February 2010

Two cases of heat transfer processes for a general polymer electrolyte fuel cell (PEFC) stack in a sub-freezing environment are studied in this paper: cooling-down and heating-up. We investigate the time consumption problem for both of these two cases in order to find the way to normally restart fuel cell stack without regard to electrochemical reaction. We consider the action of heat transfer in lieu of generated chemical energy to PEFC in sub-freezing environment by means of heat insulator. In the numerical simulation, we define a combined finite element/upwind finite volume discretization to approximate the heat transport equation for different cases of heat transport process, and obtain the stable and reasonable numerical solutions. These results correspondingly provide explicit ways to preserve heat in PEFC stack in the sub-freezing environment.
Measurement of Water Distribution in Anode of Polymer Electrolyte Fuel Cell Under Low Humidity Conditions
Authors: Nishida Kosuke , Yokoi Yohma , Tsushima Shohji , Hirai Shuichiro
Published: February 2010

During low humidity operation of polymer electrolyte fuel cells (PEFCs), water management in anode electrode is essential for achieving sufficient membrane hydration and high proton conductivity. In this study, the water vapor condensation in an operating PEFC under low humidity conditions was experimentally visualized by using water sensitive paper (WSP), and the water distribution on the anode side was investigated. WSP is a test paper for detecting water droplets, fog and high humidity, which is coated with a yellow surface. This test paper was inserted between the anode electrode and separator in the transparent fuel cell. Furthermore, the dew-point temperature at the anode outlet was simultaneously measured using a hygro-thermometer, and the effects of operating conditions and flow configuration on the water transports between the anode and cathode electrodes were discussed. It was found that the water vapor concentration on the anode side increases considerably after the startup because of the back diffusion of the product water, and the water condensation occurs from the downstream section of the anode channel in the co-flow arrangement. However, at high current densities, the amount of water in the anode decreases due to the water flux driven by electro-osmotic drag. The difference of the water vapor concentrations between the anode and cathode electrodes arises significantly with cell temperature, and the back diffusion flux of water toward the anode increases. The counter-flow pattern of anode and cathode gases is effective in achieving uniform water distribution in the anode flow field. The dry H2 at the anode inlet is humidified by the water diffused through the membrane from the cathode outlet, and thus sufficient water can be supplied all over the anode flow field.
The Application of a Portable DMFCs Stack With Fractal Current Collectors Using Hilbert Geometry for a Charger System
Authors: Lee Shah-Rong , Kuan Yean-Der , Sung Min-Feng , Chang Jing-Yi , Lee Shi-Min
Published: February 2010

The study develops a portable charger platform that contains a direct methanol fuel cell (DMFC) consisting of a set of planar DMFCs with current collectors, Fractal Hilbert Geometry and a power balance plant (BOP). The third order Hilbert geometry is used for the 35×35 mm2 current collectors. The system output design is set at 5V controlled by a power balance plant applied to 3C low power products. This paper discusses the Methanol feed rate, air flow rate, bipolar plate thickness and power balance plant layout for DMFC performance. To evaluate the reliability and efficiency of the DMFC power source, a data acquisition (DAQ) system connected to a real time monitor is used to assess the current and voltage output from the DMFC system while running different parameters. The results show the current of the charger system obtain 84 mA and 103 mA under 2V and 3V input voltage converters respectively. The transform efficiency for power balance plant is up to about 84% for 3V input voltage converter.
Microstructure, Sinterability and Electrochemical Properties of a Sm-Sr-(Co,Fe,Ni)-O Cathode System for Solid Oxide Fuel Cells
Authors: Baek Seung-Wook , Bae Joongmyeon
Published: February 2010

Samarium (Sm) is a rare earth material that shows promise for use in cathodes of intermediate temperature-operating solid oxide fuel cells (IT-SOFCs). Perovskite-structured oxide containing Sm has very attractive electrocatalytic properties, and spinel-structured oxide generally exhibits low thermal expansion, indicating its suitability for application as a SOFC cathode. In this paper, the characteristics of the various Sm-based oxide materials (Sm-Sr-(Co,Fe,Ni)-O) deposited on Sm0.2Ce0.8O1.9 (SDC) electrolyte pellets were investigated in terms of their microstructure, sinterability and electrochemical properties. The relationship between the composition and the sintering temperature was studied and discussed. Results show that the substitution of iron (Fe) and nickel (Ni) in Co-sites affects the sinterability, adhesion to the electrolyte and electrochemical activity, such that the different sintering temperatures for these compositions should be considered. The microstructure and sinterability of the cathodes were investigated using a scanning electron microscope (SEM). Area specific resistance (ASR) values for all cathode compositions were measured using AC electrochemical impedance spectroscopy (EIS).
Parameter Study of Steam Methanol Reforming With Cu/ZnO/Al2O3 Catalyst in a Microchannel Reactor
Authors: Lee Chun-I , Shiu Huan-Ruei , Chang Wen-Chen , Tsau Fang-Hei
Published: February 2010

Three-dimensional numerical simulations were performed to investigate the effect of methanol conversion and hydrogen product of a microchannel methanol steam reformer under various parameter conditions. In this simulation, the wall temperature of reactor (Tw), inlet flow rate of reactant, the different S/C ratios (steam to carbon ratio) and the thickness of the catalyst layer were taken into account to analyze product concentration and conversion rates along the channel length. The methanol conversion for methanol steam reforming on Cu/ZnO/Al2O3 catalyst was carried out at reaction temperature ranging from 200 to 260° under an atmospheric pressure. Furthermore, the reaction schemes considered the methanol steam reforming reaction and the reverse water gas-shift reaction. Regarding the distribution analysis of methanol reforming, the methanol conversion (η) and the product of hydrogen increase with the increase in wall temperature from 200 to 260°C and lower reactant flow rates. However, the result shows the methanol conversion increases and the hydrogen product decreases with less feed-in amount of methanol as the higher S/C. Additionally, the methanol conversion increase with higher thickness of catalyst layer from 10 to 70μm. The product of hydrogen, therefore, reaches a consistent distribution above 40μm along the channel length. Nevertheless, all of the operation parameter of exhaust stream at the reformer exit has the following composition: 75% H2, 24% CO2 and less than 1% CO. This research attempts to reveal a simplified methanol reforming model, which analyze the significant behavior and product distribution in qualitative/quantitative along the channel.
Effect of Operating Conditions on the Water Transport Phenomena at the Cathode of Polymer Electrolyte Membrane Fuel Cell
Authors: Seo Sang Hern , Lee Chang Sik
Published: February 2010

Water management is very important for polymer electrolyte membrane fuel cell because the fuel cell performance is decreased by flooding phenomena generated by liquid water in the cathode channels. In addition, the proton conductivity and water transport of membrane could become different by hydration contents of membrane. This study is observed water transport phenomena of cathode channels with a polymer electrolyte membrane fuel cell according to various operating conditions. In order to obtain the water images, the transparent fuel cell consists of polycarbonate window of the cathode end plate and gold coated stainless steel as the flow field and current collector of the cathode. To investigate the effects of operating conditions on the water transport, experiments were conducted under various operating conditions such as cell temperature, cathode flow rate and cathode backpressure. As operating time elapsed, it is observed that the water droplet formation, growth, coalescence and removal occurred in the cathode channel. It can be known that the high cathode flow rate prevents water flooding by removal of water in the cathode flow channel. Also, the quantity of water droplet was increased by the high cathode backpressure.
Operation Flexibility and Efficiency Enhancement for a Personal 7kW Gas Turbine System
Authors: Panne Tobias , Widenhorn Axel , Aigner Manfred , Masgrau Marcello
Published: February 2010

In the present paper a steady state analysis of an externally fired gas turbine cycle for decentralized combined heat and power generation is shown. For the basic cycle design the part load performance, the influence of turbine inlet temperature and the fuel flexibility is investigated. It is demonstrated that the gas turbine is perfectly suitable for the use of alternative fuels such as wood gas, sewage gas or fermentation gas. In addition to the basic design the efficiency enhancement potential of an internally fired gas turbine based on the same turbo machinery is investigated. It is shown that electrical efficiency might be increased by up to 12 percentage points by implementation of a pressurized combustion chamber. In the second part of the paper different SOFC/GT hybrid cycle arrangements are analyzed. The studies include both atmospheric and pressurized cycle arrangements, the latter for internally and externally fired gas turbine. For the presented studies a validated steady state in-house simulation tool is used.
Experimental Evaluation of the Transient Behavior of a Compressor Station During Emergency Shutdowns
Authors: Moore J. Jeffrey , Kurz Rainer , Garcia-Hernandez Augusto , Brun Klaus
Published: February 2010

The transient behavior of compressor stations, particularly under rapidly changing conditions, is of vital interest to operators. Predicting transient behavior is an important factor in avoiding damage during events such as emergency shutdowns. A limited number of “accidental” data sets from compressor manufacturers and users are available in the public literature domain. A variety of simulations and modeling approaches have been presented over the last few years at industry conferences. The available experimental data is not of sufficient quality and resolution to properly compare predictions with analytical results or simulations available in current software packages. Necessary information about the compressor, the driver, the valves, and the geometry of the system is often missing. Currently utilized software has not been adequately validated with full-scale realistic benchmark data, as this data is not available in the public domain. Modeling procedures and results of surge control system simulations seldom contain validation data achieved through actual testing. This type of transient test data for a dynamic surge condition is often difficult to obtain. The primary objective of this work is to develop experimental transient compressor surge data on a full scale test facility, which would facilitate the verification and comparison of existing and future transient surge models. Results of the testing and model comparisons will be documented. Relevant, dimensionless parameters will be presented and validated utilizing the test data. Conclusions from the testing and recommendations for the transient analysis software will be provided.
A Framework of Integrated Creep-Fatigue Modeling
Authors: Wu X. , Yandt S. , Zhang Z.
Published: February 2010

A framework of integrated creep-fatigue (ICF) modeling is proposed based on the deformation decomposition rule that the total inelastic strain (in a polycrystalline material) consists of intragranular deformation (ID) and grain boundary sliding (GBS). With consideration of the respective deformation mechanisms, the resulting constitutive laws are given in 3D tensor forms such that fatigue damage (ID) and creep damage (GBS) are represented in different strain spaces, respectively. Then, the creep-fatigue life consumption can be evaluated using a physics-based formula that captures the intricate interaction between a propagating fatigue crack and distributed creep damage, leading to final fracture.
Three Dimensional Heat Transfer Analysis of High Pressure Turbine Blade
Authors: Sipatov A. , Gomzikov L. , Latyshev V. , Gladysheva N.
Published: February 2010

The present tendency of creating new aircraft engines with a higher level of fuel efficiency leads to the necessity to increase gas temperature at a high pressure turbine (HPT) inlet. To design such type of engines, the improvement of accuracy of the computational analysis is required. According to this the numerical analysis methods are constantly developing worldwide. The leading firms in designing aircraft engines carry out investigations in this field. However, this problem has not been resolved completely yet because there are many different factors affecting HPT blade heat conditions. In addition in some cases the numerical methods and approaches require tuning (for example to predict laminar-turbulent transition region or to describe the interaction of boundary layer and shock wave). In this work our advanced approach of blade heat condition numerical estimation based on the three-dimensional computational analysis is presented. The object of investigation is an advanced aircraft engine HPT first stage blade. The given analysis consists of two interrelated parts. The first part is a stator-rotor interaction modeling of the investigated turbine stage (unsteady approach). Solving this task we devoted much attention to modeling unsteady effects of stator-rotor interaction and to describing an influence of applied inlet boundary conditions on the blade heat conditions. In particular, to determine the total pressure, flow angle and total temperature distributions at the stage inlet we performed a numerical modeling of the combustor chamber of the investigated engine. The second part is a flow modeling in the turbine stage using flow parameters averaging on the stator-rotor interface (steady approach). Here we used sufficiently finer grid discretization to model all perforation holes on the stator vane and rotor blade, endwalls films in detail and to apply conjugate heat transfer approach for the rotor blade. Final results were obtained applying the results of steady and unsteady approaches. Experimental data of the investigated blade heat conditions are presented in the paper. These data were obtained during full size experimental testing the core of the engine and were collected using two different type of experimental equipment: thermocouples and thermo-crystals. The comparison of experimental data and final results meets the requirements of our investigation.
Micro Gas Turbine Recuperator: Steady-State and Transient Experimental Investigation
Authors: Ferrari Mario L. , Pascenti Matteo , Magistri Loredana , Massardo Aristide F.
Published: February 2010

The aim of this work is the experimental analysis of a primary-surface recuperator operating in a 100 kW micro gas turbine, as in a standard recuperated cycle. These tests, performed in both steady-state and transient conditions, have been carried out using the micro gas turbine test rig developed by TPG at the University of Genoa, Italy. Even if this facility has mainly been designed for hybrid system emulations, it is possible to exploit the plant for component tests, such as experimental studies on recuperators. The valves installed in the rig make it possible to operate the plant in the standard recuperated configuration, and the facility has been equipped with new probes essential for this kind of tests. A wide-ranging analysis of the recuperator performance has been carried out with the machine operating in stand-alone configuration, or connected to the electrical grid, to test different control strategy influences. Particular attention has been given to tests performed at different electrical load values and with different mass flow rates through the recuperator ducts. The final section of this paper reports the transient analysis carried out on this recuperator. The attention is mainly focused on thermal transient performance of the component, showing the effects of both temperature and flow steps.
Gas Turbine Combustor Simulation With Various Turbulent Combustion Models
Authors: Wang F. , Huang Y. , Deng T.
Published: February 2010

Along with the development of computing technology, large-eddy simulation turns to be a useful tool for practical study. For fast estimation, the front line researchers still use the Reynolds-averaged Navier-Stokes (RANS) method nowadays. RANS still is the major tool for gas turbine chamber (GTC) designers, but there is not a universal method in RANS GTC spray combustion simulation at present especially for the two-phase turbulent combustion. Usually there are two main steps in two-phase combustion: the liquid fuel evaporation and the gas mixture combustion. Thus, three widely used turbulent combustion models: the Eddy-Break-Up and Arrhenius model (EBU), Laminar Flame-let Model (LFM) and Eddy-Dissipation-Concept (EDC) turbulent combustion models are firstly tested against a methane-air turbulent gas jet flame (Flame D) measured by Sandia Lab and next a two-phase turbulent swirl spray combustion in a complex GTC. The predictions of the LFM model are the best in jet flame simulation to show its ability in gas combustion prediction. The comparison between the simulation results and the experimental results showed that LFM model could properly consider the interaction between turbulence and chemistry in the gas combustion in most regions; EBU model overestimated the turbulent effect in most regions; though EDC model takes the chemistry effect into account, the turbulence seems be overestimated too. The simulated GTC performed well in experiments especially when the fuel-air mixture equivalence ratio (MER) in its main-reaction-zone (MRZ) is 0.7, so the three combustion models are all applied in this case, with the same 90° spray angel, same material properties and the same discrete ordinates (DO) radiation model. In LFM prediction, the high temperature regions are distributed around the margin of the circumfluence zone and the downstream regions after MRZ, which does not agree with the test observation. The LFM model deals well with the gas combustion, so the reason for this poor performance must be of kerosene evaporation. LFM model is a fast-chemistry model, but the kerosene reaction rate is not very fast and the evaporation makes the global reaction slower. Furthermore the mixture fraction is a conservation scalar in FLM model but it is changed by the kerosene evaporation especially in the MRZ where the kerosene was mainly vaporized. Generally, the EBU and EDC results are better: the high temperature regions are mostly in MRZ when MER is 0.7. The EDC model also has good predictions of different MERs in MRZ. When MER is 1.3, the unburned kerosene continue reaction after primary-air-holes; when MER is 0.3, there is nearly no kerosene there. Additionally, effects of the spray angle, material property are studied.
Optimization of Anti-Icing Limits for Alstom Gas Turbines Based on Theory of Ice Formation
Authors: Ojo Collins O. , Schwille Christine , Nemet Anton , Zierer Thomas , Nicklas Martin
Published: February 2010

Over the past years, Alstom gas turbines have been protected against icing based on a set of ambient temperature and relative humidity limits. These limits were derived mainly from operational and fleet experience. In recent times, the potential for optimizing these limits arose as they were observed to be too conservative. It is recognized that lowering the icing limits by a better understanding of the formation of condensate ice offers an opportunity for engine performance optimization while simultaneously ensuring adequate protection of the engine hardware. However, the level to which the original limits could be extended has not been known and this necessitated the setting up of a dedicated project to address the issue. This paper presents part of the results of the work done within this project and addresses how the new limits have been derived based on the thermodynamics of ice accretion at stationary and rotating surfaces of the compressor. The theory of ice accretion on the variable inlet guide vane (VIGV) and compressor blade surfaces as the intake air is expanded through the GT inlet system presented in this paper covers the process of condensation of moist air, the solidification of the condensate and the accumulation of the sub-cooled water condensate on surfaces with temperatures below 0°C. Using a state-of-the-art gas turbine modelling environment, relevant thermodynamic quantities including static and velocity components up to the first rotating plane of the compressor have been used to quantify the amount of condensate in the intake air at the first compressor rotating plane at various ambient conditions of temperature and humidity and at various engine operation modes (base load and part load operation). Empirical in-house relations for surface temperatures have been used to estimate the VIGV and the surface temperature of the first blade of the compressor. The theoretical results obtained have been validated on a heavy-duty gas turbine engine. Based on the confirmation of the theoretical results with engine data, the presented method can accurately be used to determine the anti-icing limits for a gas turbine. The approach is a generic one and is therefore applicable to all compressor designs for stationary gas turbines.
Alstom Post-Development of GT24 and GT26 Hot Gas Turbine Parts Reconditioning
Authors: Schro¨der N. , Drensky G. , Florjancic S.
Published: February 2010

Reconditioning of hot gas turbine parts is driven mainly by lifetime and performance requirements. Commonly, the first approach in reconditioning is to achieve an exact reproduction of a new manufactured part, by following new part specifications. However, this may prove to be too costly and unnecessary. The unique OEM experience, allows ALSTOM to widen these specifications in order to optimize repair costs, improve throughput time and possibly reduce parts scrap rate without sacrificing lifetime and performance. This post-development is based on MI calculations re-calibrated and reinsured by extensive empirical field feedback and performance statistics over the whole GT fleet with millions of operating hours. This paper presents an overview of the required area of the OEM’s expertise and field data within post development, substantiated by examples from daily operations. The work is performed in order to ensure safe remaining part lifetime along with full functionality and known performance impact. Parameters influencing the remaining part lifetime are micro-structural degradation, crack allowances, coating properties and minimum wall thicknesses, while, parameters influencing performance are airflow specifications, radial clearances, sealing design and surface roughness. Furthermore, different manufacturing techniques and new technologies get investigated and then implemented whenever there is an opportunity to optimize process cost effectiveness and reach higher quality standards. This is done in order to ensure that the company retains its competitive edge over other reconditioning companies. As the complexity of components varies, the unique knowledge of each component allows ALSTOM to develop the most favorable reconditioning processes. This enables state-of-the-art reconditioning and repair methods to be utilized. Thus ensuring optimum throughput time, while minimizing scrap rates and maintaining performance and lifetime requirements. This unique experience and knowledge from the reconditioning processes is transferred as a benefit to the customer and also utilized in future designs, resulting in improved new part designs and optimized life cycle costs.
Numerical Analyses of High Reynolds Number Flow of High Pressure Fuel Gas Through Rough Pipes
Authors: Cadorin Margherita , Morini Mirko , Pinelli Michele
Published: February 2010

In this paper, a CFD commercial code is used to evaluate the pressure drop through pipes in a stream of high pressure gas. Preliminarily, a grid sensitivity analysis is carried out by comparing CFD results with analytical results. Hybrid grids are used for this task. Each grid is characterized by a different number and thickness of layers in order to investigate the behavior of the grid with respect to the boundary layer. Then, the model based on the best performer grid is validated by using a literature test case, in which high pressure gas flow through a rough pipe is experimentally studied. Various equations of state (i.e. constant properties, ideal gas and Redlich-Kwong equation) and boundary conditions (e.g. pressure, mass flow, etc.) are taken into consideration. Finally, the model is used to extrapolate the behavior of different gases (i.e. natural gas, biogas and hydrogen-methane mixture) flowing at high pressure through pipes of different roughness.
Assessment of Compressors in Gas Storage Applications
Authors: Kurz Rainer , Brun Klaus
Published: February 2010

An analytical model is generated that allows the evaluation of the compression system. It is also used to derive general rules for optimizing a system. Several strategies for the compression system (single compressors, multiple compressors with a single driver in series and parallel configuration, multiple compressors with individual drivers) are evaluated based on said model.
Analytical Prediction Technique for Internal Leakage in an External Gear Pump
Authors: Wahab Abdul
Published: February 2010

Gear pumps are commonly found in Aero-engine high pressure part of fuel system. Their objective is to start the engine, to provide take off flow at the required pressure and to prime a fuel system. Development of Electric Fuel Metering Pumps for micro turbine has optimized the fuel system by eliminating the need for control valves. The correct prediction and control of tip leakage flow rate in a gear pump is crucial for efficient fuel metering. In this paper, an approach has been presented for obtaining the above prediction in a simple analytical and explicit method. Orifice equation is incorporated to predict leakage flow rate at different inlet/outlet pressure differences. A variable pressure ratio positive displacement pump test rig is utilized to conduct experiments on micro turbine gear pump. The results obtained with proposed method compare favorably with the one obtained by experimental techniques. In many cases, there is hardly a distinction between prediction and the experimental results.
Simulation of a Micro Turbine’s Dynamic Behavior in a Biomass Incineration Power Plant Based on the Pebble Heater Technology
Authors: Zimmermann Peter , Cardenas Alejandro , Hirsch Christoph , Sattelmayer Thomas
Published: February 2010

We present a dynamical simulation model of a Pebble Heater power plant using a 100kW micro turbine. The aim of the investigation is to provide data of the plant operation in order assess control strategies and controller parameter settings in order to avoid plant instabilities. Furthermore the model is used to provide the dynamical behavior of the plant for design operation as well as in emergency scenarios. The model was created in the object oriented simulation language Modelica. The parts are presented and the dynamical model is validated with experimental data obtained on a laboratory set up of the gas turbine. The plant operating procedures are described and crucial scenarios are identified that require simulation to verify plant operation stability. The results show, that the regular plant operation should be stable within the control margin available to the system. The model provides the prediction of the influence of Pebble Heater design on the overall plant performance, allowing to optimize the plant economics. Furthermore the requirements on the elements of the emergency procedures could be calculated.
Numerical and Experimental Investigation of a Semi-Technical Scale Burner Employing Model Synthetic Fuels
Authors: Di Domenico Massimiliano , Kutne Peter , Naumann Clemens , Herzler Juergen , Sadanandan Rajesh , Stoehr Michael , Noll Berthold , Aigner Manfred
Published: February 2010

In this paper the development and the application of a numerical code suited for the simulation of gas-turbine combustion chambers is presented. In order to obtain an accurate and flexible framework, a finite-rate chemistry model is implemented, and transport equations for all species and enthalpy are solved. An assumed PDF approach takes effects of temperature and species turbulent fluctuations on the chemistry source term into account. In order to increase code stability and to overcome numerical stiffness due to the large-varying chemical kinetics timescales, an implicit and fully-coupled treatment of the species transport equations is chosen. Low-Mach number flow equations and k-ε turbulence model complete the framework, and make the code able to describe the most important physical phenomena which take place in gas-turbine combustion chambers. In order to validate the numerical simulations, experimental measurements are carried out on a generic non-premixed swirl-flame combustor, fuelled with syngas-air mixtures and studied using optical diagnostic techniques. The combustor is operated at atmospheric and high-pressure conditions with simulated syngas mixtures consisting of H2, N2, CH4, CO. The combustor is housed in an optically-accessible combustion chamber to facilitate the application of chemiluminescence imaging of OH* and planar laser-induced fluorescence (PLIF) of the OH-radical. To investigate the velocity field, particle image velocimetry (PIV) is used. The OH* chemiluminescence imaging is used to visualise the shape of the flame zone and the region of heat release. The OH-PLIF is used to identify reaction zones and regions of burnt gas. The fuel composition is modelled after a hydrogen-rich synthesis gas, which can result after gasification of lignite followed by a CO shift reaction and a sequestration of CO2. Actual gas compositions and boundary conditions are chosen so that it is possible to outline differences and similarities among fuels, and at the same time conclusions about flame stability and combustion efficiency can be drawn. A comparison between experimental and numerical data is presented, and main strengths and deficiencies of the numerical modelling are discussed.
Experimental and Numerical Studies of Diesel Spray Evaporation and Combustion in a Gas Turbine Matrix Burner
Authors: Bohn Dieter , Willie James F. , Ohlendorf Nils
Published: February 2010

Lean gas turbine combustion instability and control is currently a subject of interest for many researchers. The motivation for running gas turbines lean is to reduce NOx emissions. For this reason gas turbine combustors are being design using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel must first be atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. One problem that is associated with running gas turbines lean and premixed is that they are prone to combustion instability. The matrix burner test rig at the Institute of Steam and Gas Turbines at the RWTH Aachen University is no exception. This matrix burner is suitable for simulating the conditions prevailing in stationary gas turbines. Till now this burner could handle only gaseous fuel injection. It is important for gas turbines in operation to be able to handle both gaseous and liquid fuels though. This paper reports the modification of this test rig in order for it to be able to handle both gaseous and liquid primary fuels. Many design issues like the number and position of injectors, the spray angle, nozzle type, droplet size distribution, etc. were considered. Starting with the determination of the spray cone angle from measurements, CFD was used in the initial design to determine the optimum position and number of injectors from cold flow simulations. This was followed by hot flow simulations to determine the dynamic behavior of the flame first without any forcing at the air inlet and with forcing at the air inlet. The effect of the forcing on the atomization is determined and discussed.