bluuebunny/crossref_metadata_2025 huggingface dataset:
A General Model for Two-Point Contact Dry-Friction Whip and Whirl: Further Advancements and Experimental Test Results
Authors: Wilkes Jason C. , Allison Tim
Published: August 2015

Numerous papers have investigated the behavior of dry-friction whip and whirl; most of them consider contact between a rotor and stator at a single location. For rotors running on multiple magnetic bearings, air bearings, or bushings, equipment failure may result in rub at more than one location. For these cases, it is important to have an analytical model that characterizes possible regions of two-point contact dry-friction whip and whirl.

The current work presents a general model to predict possible whirl regions for multi-contact dry-friction whip and whirl, allowing for an arbitrary phase between contact locations. In theory this method can be applied to more than two contact locations; however, a two-point contact example case is developed and compared to results from an experimental test rig developed to demonstrate multi-contact dry-friction whip and whirl in the current work.
CFD Modelling of Heat Soak-Back Phenomenon Inside a Gas Turbine Combustor
Authors: Ghazlani M. Ali , De Champlain Alain , Paquet Bernard , Kalla Smail , Davenport Nigel
Published: August 2015

The heat soak-back occurring in engines under post-shutdown conditions is a well-known phenomenon. This behavior is caused by the transmission of accumulated heat from hot parts or cavities during idle operation (such as turbines, contention rings, etc.) to colder ones (combustion chamber, injectors, etc.) when the airflow inside the engine approaches nullity. Then stagnant fluids in components such as the injectors (mainly TDE) and bearings become exposed to this heat which spreads by conduction, radiation and natural convection through the engine, and potentially leading fuel or oil to decompose and to form a build-up of carbon through a phenomenon called “coking”. Heat soak-back to engine components on shutdown, due to the thermal inertia of heated turbine parts, has the potential to cause deposits to build up in fuel injectors which can over time block the injectors. Blocked or partially blocked injectors must then be removed from the engine, inspected and sent for cleaning. Both soak-back and coking phenomenon have already been investigated by some motorists through experimental and structural (FEA) studies [1]. To the author’s knowledge however, no CFD model considering the airflow has yet been discussed, mainly because of the computing resources and the time it requires to simulate this unsteady phenomenon. As part of the present study and in order to fill in the gap on the availability of numerical data in the open literature for the heat soak-back occurring in a gas turbine combustor, the following investigation implies CFD simulation to predict the thermal behavior and magnitude of such a soak-back and its potential consequence on the fuel passages. A previous CFD simulation done by the authors showed that the use of a radiation model was required to provide some very reasonable results. As a follow up, the work to be presented in this paper will provide a more complete numerical soak-back procedure that can be used to predict the thermal behavior inside the combustor of a just shutdown gas turbine engine. Prior to the heat soak-back analysis, a non-premixed combustion model is run to simulate idle condition. Then these more realistic results for idle are used as initial conditions for the analysis of the transient heat dissipation occurring after shutdown. The following work includes a quick description of the experimental setup, and an introduction to the operational conditions for a simplified test rig. The full numerical procedure is then described. An analysis highlights the improved ability of the numerical model in predicting when the coking temperatures are reached using the adopted modeling techniques. It is observed that results obtained by the present model compare well with the experimental data to validate the simulation of this not so obvious natural convection phenomenon for a better understanding of this transient problem.
An Investigation on the Effect of Creep Shakedown on the Creep Behavior of an Industrial Gas Turbine Blade
Authors: Zhao Jun , Koul Ashok K. , Banerjee Avisekh
Published: August 2015

The creep life computation of gas turbine hot section components using any damage modeling technique requires typical inputs of stress and temperature under actual engine operating conditions. The magnitude of these inputs is governed by the static or dynamic transient loading conditions that a component may be subjected to during service. The long term creep damage accumulation process in a hot section component leads to strain accumulation in the component with time. The rate of change of this strain accumulation in different regions of a component is controlled by the magnitude of the local stress, stress gradient and temperature. In some regions, the creep damage accumulation process may lead to a substantial change in the local stress distribution, also called the “Creep Shakedown”, and this time-dependent stress redistribution can have a substantial impact on the component creep life.

The creep shakedown based creep life analysis of a GE Frame 7EA first stage turbine blade under off-design base-load engine operating conditions is studied. The evolution of the stress and strain in different regions of the blade with service time was analyzed using the finite element method. A user defined Garofalo model with hyperbolic sine creep rule was incorporated in the finite element analysis (FEA). The creep shakedown in the component is demonstrated to cause a local time-dependent stress redistribution effect in the FEA simulation. The significant stress variation and creep strain accumulation was observed in the creep critical regions where local stress raisers were present and/or a high temperature gradient due to internal cooling design existed. These effects are discussed in detail from a materials engineering perspective.
Enhancement of Film Cooling Effectiveness Using Backward Injection Holes
Authors: Park Sehjin , Jung Eui Yeop , Kim Seon Ho , Sohn Ho-Seong , Cho Hyung Hee
Published: August 2015

Film cooling is a cooling method used to protect the hot components of a gas turbine from high temperature conditions. For this purpose, high and uniform film cooling effectiveness is required to protect the vanes/blades from excessive thermal stress. Backward injection is proposed as one of the methods for the improvement of film cooling effectiveness. In this study, experiments were performed to investigate the effect of backward injection on film cooling effectiveness, using pressure sensitive paint (PSP) method. Four experimental configurations were composed of forward and backward injection cylindrical holes. The cylindrical holes were aligned in two staggered rows with pitch (p) of 6d and row spacing (s) of 3d. The injection angles (α) of the cylindrical holes were 35° and 145° for forward and backward injection, respectively. The blowing ratios (M) ranged from 0.5 to 2.0 and the density ratio (DR) was about 1. The results indicate that backward injection enhanced not only film cooling effectiveness but also the lateral cooling uniformity. At a high blowing ratio, all configurations demonstrated higher film cooling effectiveness with backward injection than with only forward injection; thus, the dispersion of the backward injection jets enhanced the lateral coverage over wide areas. Configuration, in particular, arranged with forward injection in the first row and backward injection in the second row, obtained the highest film cooling effectiveness among the four cases studied, due to the dispersion of the backward injection jets and the coolant supply from the forward injection jets at a high blowing ratio.
Low Emission, Liquid Fuel Combustion System for Conventional and Alternative Fuels Developed by the Scaling Analysis
Authors: Niguse Yonas G. , Agrawal Ajay K.
Published: August 2015

The objective of this study is to develop a theoretical basis for scalability considerations and design of a large scale combustor utilizing flow blurring (FB) atomization. FB atomization is a recently discovered twin-fluid atomization concept, reported to produce fine spray of liquids with wide range of viscosities. Previously, we have developed and investigated a small scale swirl-stabilized combustor of 7-kWth capacity. Spray measurements have shown that the FB injector’s atomization capability is superior when compared to other techniques, such as air blast atomization. However, despite these favorable results, scalability of the FB injector and associated combustor design has never been explored for large capacity, for example, for gas turbine applications. In this study, a number of dimensionless scaling parameters that affect the processes of atomization, fuel-air mixing, and combustion are analyzed, and scaling criteria for the different components of the combustion system are selected. Constant velocity criterion is used to scale key geometric components of the system. Scaling of the nonlinear dimensions and complex geometries, such as swirler vanes and internal parts of the injector is undertaken through phenomenological analysis of the flow processes associated with the scaled component. A scaled up 60-kWth capacity combustor with FB injector is developed and investigated for combustion performance using diesel and vegetable oil (soybean oil) as fuels. Results show that the scaled-up injector’s performance is comparable to the smaller scale system in terms of flame quality, emission levels, and static flame stability. Visual flame images at different air to liquid ratio by mass (ALR) show mainly blue flames, especially for ALR > 2.8. Emission measurements show a general trend of lower CO and NOx levels at higher ALRs, replicating the performance of the small scale combustion system. Flame liftoff height at different ALRs is similar for both scales. The scaled-up combustor with FB injector preformed robustly with uncompromised stability for the range of firing rates above 50% of the design capacity. Experimental results corroborate with the scaling methodology developed in this research.
System Integration and Techno-Economy Analysis of the IGCC Plant With CO2 Capture: Results of the EU H2-IGCC Project
Authors: Mansouri Majoumerd Mohammad , Assadi Mohsen , Breuhaus Peter , Arild Øystein
Published: August 2015

The overall goal of the European co-financed H2-IGCC project was to provide and demonstrate technical solutions for highly efficient and reliable gas turbine technology in the next generation of integrated gasification combined cycle (IGCC) power plants with CO2 capture suitable for combusting undiluted H2-rich syngas.

This paper aims at providing an overview of the main activities performed in the system analysis working group of the H2-IGCC project. These activities included the modeling and integration of different plant components to establish a baseline IGCC configuration, adjustments and modifications of the baseline configuration to reach the selected IGCC configuration, performance analysis of the selected plant, performing techno-economic assessments and finally benchmarking with competing fossil-based power technologies.

In this regard, an extensive literature survey was performed, validated models (components and sub-systems) were used, and inputs from industrial partners were incorporated into the models. Accordingly, different plant components have been integrated considering the practical operation of the plant. Moreover, realistic assumptions have been made to reach realistic techno-economic evaluations.

The presented results show that the efficiency of the IGCC plant with CO2 capture is 35.7% (lower heating value basis). The results also confirm that the efficiency is reduced by 11.3 percentage points due to the deployment of CO2 capture in the IGCC plant. The specific capital costs for the IGCC plant with capture are estimated to be 2,901 €/(kW net) and the cost of electricity for such a plant is 90 €/MWh.

It is also shown that the natural gas combined cycle without CO2 capture requires the lowest capital investment, while the lowest cost of electricity is related to IGCC plant without CO2 capture.
Recent Research Progress on Supercritical Carbon Dioxide Power Cycle in China
Authors: Wang Junfeng , Huang Yanping , Zang Jinguang , Liu Guangxu
Published: August 2015

China has started the investigations on supercritical carbon dioxide (S-CO2) power cycle since 2011. The aim of this project is to understand the feasibility and economics of coupling S-CO2 power cycle with Chinese Gen IV nuclear reactors. Up to now, the pre-concept design and feasibility evaluation has been accomplished. The focus in the next step is fundamental research on thermal-hydraulics and materials and Integral Test Loop design, construction, and operation.

Nuclear Power Institute of China (NPIC) has been a leader in S-CO2 power cycle development in China. With contractors and collaborators from China and UK, NPIC has constructed a natural circulation test loop and started the Integral Test Loop design. In this paper, an overview of the progress on S-CO2 power cycle development in NPIC is provided. The testing results from a small-scaled natural circulation test loop, the CFD code verification and validation, and the considerations and design features of Integral Test Loop will be summarized.
Adaptive Microslip Projection (AMP) for Reduction of Frictional and Contact Non-Linearities in Shrouded Blisks
Authors: Mitra Mainak , Zucca Stefano , Epureanu Bogdan I.
Published: August 2015

Reduced order models (ROMs) of turbine bladed disks (blisks) are essential to quickly yet accurately characterize vibration characteristics and effectively design for high cycle fatigue. Modeling blisks with contacting shrouds at adjacent blades is especially challenging due to friction damping and localized non-linearities at the contact interfaces which can lead to complex stick-slip behavior. While well-known techniques such as the harmonic balance method and Craig-Bampton component mode synthesis have generally been employed to generate ROMs in the past, they do not reduce degrees of freedom (DoFs) at the interfaces themselves. In this paper we propose a novel method to obtain a set of reduction basis functions for the contact interface DoFs as well as the remaining DoFs called adaptive microslip projection (AMP). The method is based on analyzing a set of linear systems with specifically chosen boundary conditions on the contact interface. Simulated responses of full order baseline models and the novel ROMs under various conditions are studied. Results obtained from the ROMs compare very favorably with the baseline model. The AMP procedure is also easily generalizable to other dynamic systems with Coulomb friction contacts.
Optimization of Two and Three Rotor Savonius Wind Turbine
Authors: Baz Ahmed M. , Mahmoud Nabil A. , Hamed Ashraf M. , Youssef Khaled M.
Published: August 2015

The present work investigates the performance of Savonius wind turbine using two or three rotors. The new turbine design was found to have higher power coefficient compared with single rotor design. The peak average power coefficient of the three rotors was computed to be 50% higher than that of the single rotor design. The torque coefficient was also higher than that of the single rotor turbine at high tip speed ratio. This improved performance is attributed to the favorable aerodynamic interaction between the rotors which accelerates the flow around the rotors and generates higher turning torque in the direction of rotation for each rotor. The optimized arrangement of rotors showed that the upstream rotor and one downstream rotor should have a similar direction of rotation while the second downstream rotor is rotating in opposite direction.
Transition From a Single to a Double Flame Structure in Swirling Reacting Flows: Mechanism, Dynamics, and Effect of Thermal Boundary Conditions
Authors: Taamallah Soufien , Shanbhogue Santosh J. , Sanusi Yinka S. , Mokhiemer Esmail M. A. , Ghoniem Ahmed F.
Published: August 2015

We examine experimentally the transition from a single flame stabilized along the inner shear layer (ISL) to a double flame stabilized along both the inner and the outer shear layers (OSL) and spreading over the outside recirculation zone (ORZ) in a fully premixed swirl-stabilized combustor. This work is mainly driven by previous studies demonstrating the link between this transition in the flame macrostructure and the onset of thermo-acoustic instabilities [1, 2]. Here, we examine the transition mechanism under thermo-acoustically stable conditions as well as the dominant flow and flame dynamics associated with it. In addition, we explore the role of changing the thermal boundary conditions around the ORZ and its effect on the presence or absence of the flame there. We start by analyzing the two flames bounding the transition, namely the single conical flame stabilized along the ISL (flame III) and the double conical flames with reactions taking place in the ORZ (flame IV). A dual chemiluminescence approach — using two cameras with a narrow field of view focused on the ORZ — is undertaken to track the progression of the flame as it reaches the ORZ. During the transition, the flame front, initially stabilized along the ISL, is entrained by OSL vortices close to where the turbulent jet impinges on the wall, leading to the ignition of the reactants in the ORZ and the ultimately the stabilization of the flame along the outer shear layer (OSL). This ORZ flame is also subject to extinction when the equivalence ratio (ϕ) is between values corresponding to flames III and IV. For ϕ lower than the critical transitional value, the flame kernel originating from the ISL-stabilized flame is shown to reach the ORZ but fails to grow and quickly disappears. For ϕ higher than the critical value, the flame kernel expands as it is advected by the ORZ flow and ultimately ignites the reactants recirculating in the ORZ. Sudden and extreme peak-to-peak values of the overall heat release rate are found to be concomitant with the ignition and extinction of the ORZ reactants. Finally, Different thermal boundary conditions are tested by modifying the heat flux through the combustion chamber boundary, particularly around the ORZ. We find that the transition is affected in different ways: while the transition from flame III to IV (i.e. as ϕ increases) is insensitive to these changes; flame IV persists at lower ϕ as its value is reduced when heat losses through the boundaries are diminished.
Flow Migration and Mixing in a High Pressure Turbine Rotor Passage With Axisymmetrically Contoured Endwall and Leakage Flow
Authors: Saxena Reema , Ayaskanta Arya , Simon Terrence W. , Moon Hee-Koo , Zhang Luzeng J.
Published: August 2015

The flow field in the passage of a high pressure gas turbine is quite complex, involving strong secondary flows, transverse pressure gradients and strong streamwise acceleration. This complexity may have an adverse effect on cooling of the hub endwall, which is subjected to high thermal loading due to the flat combustor exit temperature profile of modern low-NOx systems. Therefore, given material limitations, better cooling management techniques that can be included with certainty in new gas turbine designs are needed. In the present study, film cooling has been investigated experimentally in a stationary linear cascade. The flow is representative of a high pressure gas turbine rotor with combustor liner coolant introduced to the approach flow. Focus is on the endwall axisymmetric contouring and the cooling effect of leakage flow bled from the compressor through the stator-rotor disc cavity. Two endwall contours, ‘shark nose’ (gradual slope over a larger distance) and ‘dolphin nose’ (steep slope over a shorter distance), are considered and comparison is made under conditions of three mass flow rates (MFR) of leakage, 0.5%, 1.0% and 1.5% of the approach flow rate. The performance of both endwall contours is compared at different streamwise locations in terms of adiabatic effectiveness values over the endwall. This study gives enhanced insight into the physics of coolant flow mixing, migration and subsequent coverage over the endwall. The results show the cooling effects of the contoured shapes over a range of leakage flow rates in the strong secondary flow environment. It is found that the leakage flow plays a crucial role in enhancing coolant coverage over the endwall. To add to our knowledge of mixing effects, detailed thermal field data are taken in the leakage flow discharge region. Doing so helps explain the behavior of the flow as it is ejected into the passage and interacts with the mainstream flow.
Optimal Operation and Maintenance of Gas Compressor Stations: An Integrated Framework Applied to a Large-Scale Industrial Case
Authors: Xenos Dionysios P. , Lunde Erling , Thornhill Nina F.
Published: August 2015

This paper presents a framework which integrates maintenance and optimal operation of multiple compressors. The outcome of this framework is a multi-period plan which provides the schedule of the operation of compressors: the schedule gives the best decisions to be taken, for example when to carry out maintenance, which compressors to use online and how much to load them. These decisions result in the minimization of the total operational costs of the compressors while at the same time the demand of the plant is met. The suggested framework is applied to an industrial gas compressor station which encompasses large multi-stage centrifugal compressors operating in parallel. The optimization model of the framework consists of three main parts: the models of compressor maps, the operational aspects of compressors and a maintenance model. The results illustrate the optimal schedule for 90 days and an example of the optimal distribution of the load of the compressors for five days. Finally the results show the economical benefits from the integration of maintenance and optimization.
Characterization of Cellular Instabilities of a Flame Propagating in an Aerosol
Authors: Thimothée Romain , Chauveau Christian , Halter Fabien , Gökalp Iskender
Published: August 2015

This paper presents a fundamental study of two-phase combustion using a quasi mono-sized droplet aerosol configuration generated with the Wilson cloud chamber principle. Experiments were conducted under microgravity conditions to prevent droplet settling, using a dual chamber apparatus that ensures safe operation in these conditions. Two relevant parameters, the Sauter Mean Diameter and the number of droplets, were considered to describe the aerosols. In order to properly highlight the aerosol impact, the initial conditions were selected so as to avoid gaseous instabilities. It was found that the presence of an aerosol triggers cellular instabilities whereas the equivalent gaseous flame is totally stable. The cellularity of laminar flames increased both with the Sauter Mean Diameter and the number of droplets but differed in terms of cell size and flame shape. It was demonstrated that the aerosol flame speed can greatly exceed the gaseous flame speed. Conversely, the results also show that droplet evaporation during flame propagation can act as a thermal sink on the flame, and may thus reduce the flame speed.
Improvement of Turbine Vane Film Cooling Performance by Double Flow Control Devices
Authors: Kawabata Hirokazu , Funazaki Ken-ichi , Suzuki Yuya , Tagawa Hisato , Horiuchi Yasuhiro
Published: August 2015

This study deals with the studies of the effect of flow control double devices (DFCDs) on turbine vane film cooling. Aiming for improving film effectiveness, two semi-spheroid DFCDs per pitch were attached to the vane surface upstream of the cooling hole. Although the DFCDs were successfully applied to the flat plate film cooling in the previous study, the applicability to the turbine vane was to be investigated. In order to observe the flow field in detail, RANS simulation was conducted first. The DFCDs were installed upstream of each cooling hole of the pressure and suction sides of the vane to investigate the effect of the device position. In this paper, the effects of blowing ratio and cooling hole pitch were also investigated. The results obtained by CFD showed that the vortex generated from DFCD suppressed lift off of the secondary air. As a result, the film effectiveness became significantly higher than that without DFCD condition. Moreover, the improvement in the film effectiveness by DFCD was observed by both of the pressure and suction sides of the turbine vane. Based on the findings through RANS simulation, adiabatic effectiveness and total pressure loss coefficient measurement were performed in a linear cascade test facility. The experiment confirmed that the film effectiveness was improved when DFCDs existed.
Dewatering Studies on the Low Rank China Lignite Using N2, CO2 and Air
Authors: Chen Wei , Wang Yunlei , Annamalai Kalyan , Sun Jiafeng , Xie Zhimin
Published: August 2015

The integrated gasification and combined cycle (IGCC), uses low rank coal (higher moisture and volatile contents and lower heating value) as fuel for gasification (e.g Texaco gasifier of Tampa electric with low ash coal) and convert the solid fuel into synthetic gas mainly consisting of CO and H2. During the storage of fresh low rank but highly reactive coals near the IGCC plants, the coals undergo drying and low temperature atmospheric oxidation which raises the temperature, reduces the moisture and eventually causes spontaneous ignition if the temperature rises above about 800 °C in the coal piles for bituminous and 500 °C for lignite coals. Thus it is of interest to understand the dewatering mechanism of the low rank lignite by drying samples using N2, CO2 and air (which represents partial oxidation) as drying mediums. Fundamental experiments were performed on dewatering of coal samples using thermo-gravimetric analysis (TGA) with different particle sizes and drying mediums. A wide range of drying temperatures from 100 to 225 °C with a step of 25 °C was investigated at a residence time of about 30 minutes. There are no significant differences among moisture weight loss curves for the three drying mediums. It was found that the lignite lost only 5% mass at about 100 °C. With further increase in temperatures most of the mass loss occurred within the temperature range of 120 to 170 °C. The maximum moisture release rate occurred for the temperatures between 125 °C and 140 °C and hence serves as the optimal temperature range for removing the moisture. When drying temperature was below 140 °C, highest moisture release rate occurred in N2 environment while for CO2 environment, optimal temperature rose beyond 140 °C. The structure of the dewatered lignite samples were further investigated through Scanning Electron Microscopy (SEM) studies. When experiments were repeated in air, ignition occurred and corresponding ignition temperatures were obtained. The larger particles reveal lower ignition temperatures.
Numerical Investigation of Hydrogen Enriched Natural Gas in the SGT-800 Burner
Authors: Moëll Daniel , Lörstad Daniel , Bai Xue-Song
Published: August 2015

The effects of hydrogen enrichment in the SGT-800 3rd generation DLE burner fitted in an atmospheric combustion rig have been numerically investigated. Three different mixtures with 0%, 60% and 80% hydrogen enrichment to methane have been studied. In this study a URANS (Unsteady Reynolds Averaged Navier-Stokes) approach is applied. The chemistry is included through the use of laminar flamelet libraries in combination with a presumed PDF (Probability Density Function). The mean reaction rate is acting as a source term to a reaction progress variable, and is modelled using a fractal combustion model. In the methane simulations two turbulence models, k–ω SST and k–ω SST-SAS, were evaluated. The latter model was found to predict results in good agreement with measurement data. The dynamic behaviour of the flame is captured by the SST-SAS model but not by the standard SST model. For the hydrogen enriched methane simulations the validated SST-SAS model with a calibrated model constant for the mean reaction rate from the methane simulations was used. The overall results such as flame position and global pressure drop are in good agreement with experimental data. The time averaged flame stabilization point is moving upstream towards the burner exit nozzle when the hydrogen enrichment is increasing. The total pressure drop over the burner is increasing with the increasing hydrogen level.
Thermal Energy Storage for the Supercritical CO2 Brayton Cycle
Authors: Bueno P. C. , Bates L. , Anderson R. , Bindra H.
Published: August 2015

This paper examines the operation of a simple sensible thermal energy storage (TES) unit for use in concentrated solar power (CSP) plant applications using supercritical CO2 (sCO2) as the heat transfer fluid. The heat transfer characteristics of the system are described and it is shown that an advancing heat front, with a very high temperature gradient, is achieved through proper design. Typical charge and discharge times of 6 hours are studied to show how this method can be used in practical applications. It is shown that the TES can be effectively matched to a conceptual CSP plant to allow it to operate at night or during periods of reduced sunlight.
A Physics Based Reactor Network Model of a Rotating Detonation Engine Combustor
Authors: Roy Arnab , Ferguson Don
Published: August 2015

A Chemical Reactor Network (CRN) model of a Rotating Detonation Engine (RDE) combustor is presented in this article. Efforts have been made to quantify the exhaust product composition and explore the inherent thermodynamic processes such as detonation, expansion, shock, etc. Parametric studies have been carried out to delineate the effect of major operating and modeling parameters such as variation in equivalence ratio and reaction mechanism on emissions, as well as variation of local thermodynamic states in the RDE. The CRN model is developed based on the two-dimensional unwrapped instantaneous solution of the annular flow field generated from Computational Fluid Dynamics (CFD) simulation. The reactor zones have been identified utilizing the temperature and streamline distribution profile obtained from CFD. Key RDE features such as detonation, shock waves and expansion waves have also been incorporated. The CRN model predictions are compared with CFD solutions implemented using reduced reaction mechanisms. The major species composition at the RDE exhaust compares reasonably well with CFD results. The major objective of this study is towards development of a robust, efficient and preliminary design tool for RDE that — 1) is capable of predicting emissions with reasonable accuracy or at least appropriate trends, 2) can investigate the inherent complicated thermodynamic process and finally, 3) is able to provide a flexible and expandable approach that can be integrated into the combustor design methodology, allowing for a faster design iteration process.
CAE Based Brush Seal Characterization for Stiffness and Stress Levels
Authors: Duran E. Tolga , Aksit Mahmut F. , Ozmusul Murat
Published: August 2015

Brush seals are complex structures having variety of design parameters, all of which affect the seal behavior under turbine operating conditions. The complicated nature of the seal pack and frictional interactions of rotor, backing plate and bristles result in nonlinear response of the brush seal to variances of design parameters. This study presents CAE based characterization of brush seals, which aims to investigate the main effects of several brush seal design parameters on brush seal stiffness and stress levels. Characterization work of this study includes free-state rotor rub (unpressurized seal), steady state (pressure load without rotor interference) and pressurized-rotor interference conditions.
Health Monitoring and Degradation Prognostics in Gas Turbine Engines Using Dynamic Neural Networks
Authors: Vatani A. , Khorasani K. , Meskin N.
Published: August 2015

In this paper two artificially intelligent methodologies are proposed and developed for degradation prognosis and health monitoring of gas turbine engines. Our objective is to predict the degradation trends by studying their effects on the engine measurable parameters, such as the temperature, at critical points of the gas turbine engine. The first prognostic scheme is based on a recurrent neural network (RNN) architecture. This architecture enables ONE to learn the engine degradations from the available measurable data. The second prognostic scheme is based on a nonlinear auto-regressive with exogenous input (NARX) neural network architecture. It is shown that this network can be trained with fewer data points and the prediction errors are lower as compared to the RNN architecture. To manage prognostic and prediction uncertainties upper and lower threshold bounds are defined and obtained. Various scenarios and case studies are presented to illustrate and demonstrate the effectiveness of our proposed neural network-based prognostic approaches. To evaluate and compare the prediction results between our two proposed neural network schemes, a metric known as the normalized Akaike information criterion (NAIC) is utilized. A smaller NAIC shows a better, a more accurate and a more effective prediction outcome. The NAIC values are obtained for each case and the networks are compared relatively with one another.
3D Blade Stacking Strategies and Understanding of Flow Physics in Low Pressure Steam Turbines: Part II — Stacking Equivalence and Differentiators
Authors: Havakechian Said , Denton John
Published: August 2015

Optimization of blade stacking in Low Pressure (LP) steam turbine development constitutes one of the most delicate and time consuming parts of the design process. This is the second part of two papers focusing on stacking strategies applied to the last stage guide vane and represents an attempt to discern the aerodynamic targets that can be achieved by each of the well-known and most often used basic stacking schemes. The effects of lean and twist have been investigated through an iterative process, involving comprehensive 3D CFD modelling of the last two stages of a standard LP, where the basic lean and twist stacking schemes were applied on the last stage guide vanes whilst keeping the throat area unchanged. It has been found that it is possible to achieve the same target value and pattern of stage reaction by applying either tangential lean or an equivalent value of twist. Moreover, the significance of axial sweep on hub reaction has been found to become pronounced when the blade sweep is carried out at constant throat area. The importance of hub-profiling has also been demonstrated and assessed. Detailed analysis of the flow fields has provided an overall picture, revealing the differences in the main flow parameters as produced by each of the alternative basic stacking schemes.
Some Unresolved Features in the Physics of Quasi Two-Dimensional Flows Over Turbine Blading
Authors: Gostelow J. P. , Allan W. D. E. , Mahallati A.
Published: August 2015

Even for the ostensibly two-dimensional flow through cascades of blades, many details of the flow physics are neither well-understood nor well-predicted. Gaps in knowledge are identified that cover entire blade and nozzle vane surfaces from leading edge to trailing edge and beyond. To give improved prediction capability these gaps require improved understanding. The goal of this work is to draw attention to five most significant internal aerodynamic phenomena that affect turbomachinery blade performance and design. By drawing together important experimental results awareness can be raised of these features in blading aerodynamics that are not yet clearly understood. The emphasis is on quasi two-dimensional flows. As well as work on blade cascades this research draws on fundamental investigations over flat plates and circular cylinders. Similar behavior was observed between tests under strong adverse pressure gradients on triggered spots, wake-disturbed flat plate boundary layers, and on turbine blading.
Alternate Wind Turbine Blade Planform Design Studies for Low Wind Speeds
Authors: Gadamsetty Rajesh Kumar V. , Loganathan Jaikumar , Balaramudu Vasanth Kumar , Rao Ajay
Published: August 2015

Wind turbine design for low wind regimes is gaining importance as existing high wind sites are heavily utilized. Maximizing energy yield from a low wind regime while adhering to load constraints is the biggest challenge. Longer rotors and higher towers are currently being used to maximize energy capture and improve AEP. The focus of this work is to assess new blade planforms for low wind speed blade design. Planforms with maple shape are studied and a new design methodology based on lift force distribution is adopted. CFD analysis is carried out for the blade planforms to validate the design methodology and the results show similar performance trends as that of the conventional design method.
Air Force Academy Contributions to Development of the A-10 Drooped Leading Edge Modification
Authors: Yechout Thomas R. , Buscher Austin , Trochlil Steven , Rozsa Jordan , Pryor Lillian , Jenkins Jerome C.
Published: August 2015

To enhance overall performance of the A-10 Close Air Support Aircraft and enhance reliability and maintainability, the United States Air Force Academy (USAFA) Aeronautics Department proposed a fixed drooped leading edge configuration in the summer of 2011 to replace the current slat system located on the inboard leading edge of the wing. In the spring of 2012, the A-10 Systems Program Office at Hill AFB tasked the USAFA Department of Aeronautics to conduct an effort to evaluate the existing slats extended and slats retracted configurations as well as three drooped leading edge configurations so comparisons could be made [1–5]. This effort was a follow-on investigation of five drooped leading edge configurations plus two additional ones with geometric twist, and an additional one with fences. This wind tunnel evaluation was performed using a 1/20 scale model.

Of the eight configurations evaluated, the 11% drooped leading edge with fences performed the best in minimizing total pressure distortion across various angles of attack and sideslip. However, the 10% droop had better drag characteristics (determined in a parallel investigation) and was projected to have significant drag reduction benefits at the higher angles of attack which could improve sustained turning performance. Based on these combined results, the 10% droop was the USAFA recommended configuration in the Fall of 2012 for further evaluations by USAFA and Arnold Engineering and Development Complex (AEDC).
Acoustic transmission enhancement through a soft interlayer with a reactance boundary
Authors: Quan Li , Qian Feng , Liu Xiaozhou , Gong Xiufen
Published: August 2015

Research has shown that acoustic transmission enhancement (ATE) can occur in stiff materials with high acoustic impedance that include a soft interlayer with low acoustic impedance inserted between them without any opening (i.e., without any links between the two stiff materials). Previously, ATE was induced either by coupling acoustic surface waves or Love waves with the Fabry–Perot resonant modes inside the apertures or by the locally resonant modes of the structure. However, in this article ATE is achieved using wave-vector redistribution induced by a reactance boundary. An optimal boundary was designed to adjust the wave vector in the propagation direction, decreasing reflection caused by impedance differences. The role of boundary conditions on ATE was also clarified.
Simulating acoustic coherent backscattering enhancement from random aggregations of omnidirectional scatterers
Authors: Mookerjee Adaleena , Dowling David R.
Published: August 2015

Coherent backscatter enhancement (CBE) is a multiple scattering phenomenon that can lead to a doubling of the backscattered field intensity from a random aggregation of scatterers. It may be useful for remote sensing of scatterer aggregations, such as fish schools. This paper presents simulations of acoustic CBE from randomly placed omnidirectional point scatterers based on Foldy's field equations. The simulations are verified and validated through comparisons with Bragg scattering and Foldy's effective-medium theory, assessments of acoustic energy conservation, and comparisons with prior optical and acoustical CBE results. To make CBE comparisons with prior optics results, a CBE coherence function was postulated to account for resolution differences between the optics and simulation studies. For the higher-resolution optics studies, the postulated coherence function yields a CBE of 1.68, which matches optical CBE measurements. For the lower-resolution simulations, the same coherence function yields a CBE of 1.034, which agrees with appropriately extrapolated CBE simulation results, 1.030 ± 0.005. Assuming comparable resolution, the acoustics experiment and simulations both produce a CBE of approximately 1.5. The CBE peak is found to increase approximately monotonically with (k2σs)1/4(ks)–1, where k is the wave number, s is the average spacing between scatterers, and σs is a scatterer's cross section.
Induced Gamma-Band Activity During Voluntary Movement: EEG Analysis for Clinical Purposes
Authors: Amo Carlos , del Castillo Miguel Ortiz , Barea Rafael , de Santiago Luis , Martínez-Arribas Alejandro , Amo-López Pedro , Boquete Luciano
Published: August 2015

Objective:

Propose a simplified method applicable in routine clinical practice that uses EEG to assess induced gamma-band activity (GBA) in the 30–90 Hz frequency range in cerebral motor areas.

Design:

EEG recordings (25 healthy subjects) of cerebral activity (at rest, motor task). GBA was obtained as power spectral density (PSD). GBA — defined as the gamma index (Iγ) — was calculated using the basal GBA (γB) and motor GBA (γMOV) PSD values.

Results:

The mean values of Iγ were (IγR (right hand) = 1.30, IγL (left hand) = 1.22). Manual laterality showed a correlation with Iγ.

Conclusions:

Iγ may provide a useful way of indirectly assessing operation of activated motor neuronal circuits. It could be applied to diagnosis of motor area pathologies and as follow up in rehabilitation processes. Likewise, Iγ could enable the assessment of motor capacity, physical training and manual laterality in sport medicine.
Survivin promotes oxidative phosphorylation, subcellular mitochondrial repositioning, and tumor cell invasion
Authors: Rivadeneira Dayana B. , Caino M. Cecilia , Seo Jae Ho , Angelin Alessia , Wallace Douglas C. , Languino Lucia R. , Altieri Dario C.
Published: August 2015

Targeting the protein survivin could reduce metastasis by preventing energy production needed for cancer cell motility.
Exposure to SIV in utero results in reduced viral loads and altered responsiveness to postnatal challenge
Authors: Baker Chris A. R. , Swainson Louise , Lin Din L. , Wong Samson , Hartigan-O’Connor Dennis J. , Lifson Jeffrey D. , Tarantal Alice F. , McCune Joseph M.
Published: August 2015

Animals exposed to attenuated SIV in utero showed reduced viral replication and altered immune responses after pathogenic challenge postnatally.
Independent Co-Option of a Tailed Bacteriophage into a Killing Complex in
Pseudomonas
Authors: Hockett Kevin L. , Renner Tanya , Baltrus David A.
Published: August 2015

Competition between microbes is widespread in nature, especially among those that are closely related. To combat competitors, bacteria have evolved numerous protein-based systems (bacteriocins) that kill strains closely related to the producer. In characterizing the bacteriocin complement and killing spectra for the model strain
Pseudomonas syringae
B728a, we discovered that its activity was not linked to any predicted bacteriocin but is derived from a prophage. Instead of encoding an active prophage, this region encodes a bacteriophage-derived bacteriocin, termed an R-type syringacin. This R-type syringacin is striking in its convergence with the well-studied R-type pyocin of
P. aeruginosa
in both genomic location and molecular function. Genomic alignment, amino acid percent sequence identity, and phylogenetic inference all support a scenario where the R-type syringacin has been co-opted independently of the R-type pyocin. Moreover, the presence of this region is conserved among several other
Pseudomonas
species and thus is likely important for intermicrobial interactions throughout this important genus.

IMPORTANCE
Evolutionary innovation is often achieved through modification of complexes or processes for alternate purposes, termed co-option. Notable examples include the co-option of a structure functioning in locomotion (bacterial flagellum) to one functioning in protein secretion (type three secretion system). Similar co-options can occur independently in distinct lineages. We discovered a genomic region in the plant pathogen
Pseudomonas syringae
that consists of a fragment of a bacteriophage genome. The fragment encodes only the tail of the bacteriophage, which is lethal toward strains of this species. This structure is similar to a previously described structure produced by the related species
Pseudomonas aeruginosa
. The two structures, however, are not derived from the same evolutionary event. Thus, they represent independent bacteriophage co-options. The co-opted bacteriophage from
P. syringae
is found in the genomes of many other
Pseudomonas
species, suggesting ecological importance across this genus.
Prescribing for Australians living with dementia: study protocol using the Delphi technique
Authors: Page Amy , Potter Kathleen , Clifford Rhonda , McLachlan Andrew , Etherton-Beer Christopher
Published: August 2015

Introduction

Prescribing is complicated for people living with dementia, and careful consideration should be given to continuing and initiating all medicines. This study aims to elicit opinion and gain consensus on appropriate medicine use for people living with dementia in Australia to create a consensus-based list of explicit prescribing criteria.

Methods and analysis

A Delphi technique will be used to develop explicit criteria of medication use in adults aged 65 years and above. An interdisciplinary panel of Australian experts in geriatric therapeutics will be convened that will consist of a minimum of 10 participants. To develop the consensus-based criteria, this study will use an iterative, anonymous, multistaged approach with controlled feedback. Round 1 questionnaire will be administered, and subsequently qualitatively analysed. The round 1 results will be fed back to the panel members, and a round 2 questionnaire developed using questions on a five-point Likert scale. This process will repeat until consensus is developed, or diminishing returns are noted.

Ethics and dissemination

All participants will be provided with a participant information sheet, and sign a written consent form. Ethical approval has been granted from the University of Western Australia's Human Research Ethics Committee (HREC) (reference: RA/4/1/7172). We expect that data from this study will result in a paper published in a peer-reviewed clinical journal and will also present the results at conferences.