bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments in the Courtroom: Social Dynamics and Spectacles of Proof in Early Modern English Witch Trials
Authors: Darr Orna Alyagon
Published: December 2013

This article presents the composite social context surrounding the “experiments” that were used to prove witchcraft accusations in early modern England. It demonstrates that legal proof was not imposed by elite legislators and judges, or fashioned in accordance with the voice of scientific experts, but was shaped through complex social dynamics in which the middling sort and petty gentry fulfilled a crucial role. Through this process, popular beliefs percolated into judicial proceedings. Members of influential provincial families were the social agents who reconstructed old supernatural methods of proof into innovative rational experiments, often replicating public displays of proof that helped bolster the criminal charges and provided a competing arena of evidence. The article claims that the judges' cooperation with these “experiments” might have been an endeavor by the official legal system to circumvent the threat posed by a popular grassroots alternative to the exclusive jurisdiction of the court system.
Bioavailability of iron, zinc, folic acid, and vitamin A from fortified maize
Authors: Moretti Diego , Biebinger Ralf , Bruins Maaike J. , Hoeft Birgit , Kraemer Klaus
Published: December 2013

Several strategies appear suitable to improve iron and zinc bioavailability from fortified maize, and fortification per se will increase the intake of bioavailable iron and zinc. Corn masa flour or whole maize should be fortified with sodium iron ethylenediaminetetraacetate (NaFeEDTA), ferrous fumarate, or ferrous sulfate, and degermed corn flour should be fortified with ferrous sulfate or ferrous fumarate. The choice of zinc fortificant appears to have a limited impact on zinc bioavailability. Phytic acid is a major inhibitor of both iron and zinc absorption. Degermination at the mill will reduce phytic acid content, and degermed maize appears to be a suitable vehicle for iron and zinc fortification. Enzymatic phytate degradation may be a suitable home‐based technique to enhance the bioavailability of iron and zinc from fortified maize. Bioavailability experiments with low phytic acid–containing maize varieties have suggested an improved zinc bioavailability compared to wild‐type counterparts. The bioavailability of folic acid from maize porridge was reported to be slightly higher than from baked wheat bread. The bioavailability of vitamin A provided as encapsulated retinyl esters is generally high and is typically not strongly influenced by the food matrix, but has not been fully investigated in maize.
How Do Leaders and their Teams Bring about Organizational Learning and Outcomes?
Authors: Berson Yair , Da'as Rima'a , Waldman David A.
Published: December 2013

How do leaders generate a learning climate that yields favorable organizational outcomes? To address this question, we offer and test a model linking charismatic leadership with the team‐emergent states of shared vision and trust within the team, as predicting organizational learning climate, and long‐term assessments of organizational outcomes by key stakeholders. We examined this model in a sample of 69 Arab elementary schools in Israel using multiple sources of raters, predicting long‐term assessments by key stakeholders of respective schools (parents and superintendents) at 2 points in time: 1 year and 3 years following the survey of the teachers. In line with our expectations, we obtained an overall, indirect effect between charismatic leadership and organizational learning climate. We also found support for both the direct and indirect effects of leader charisma through trust within the team on organizational learning climate and school outcomes. Although charismatic leadership predicted shared vision among team members, shared vision did not predict organizational learning climate, and hence, our proposed mediating effects of shared vision on organizational learning climate and outcomes were not supported. We discuss both theoretical and practical implications for the effects of leaders on learning processes and outcomes.
Important Interactional Strategies for Everyday Public Health Nursing Practice
Authors: Porr Caroline J.
Published: December 2013

This Clinical Concepts article concerns the relational tools required by public health nurses to establish relationships with single mothers living on public assistance, mothers who are vulnerable and often stigmatized. The implications of stigmatization for relationship building are highlighted based on previous research investigating how public health nurses working in Canadian jurisdictions establish professional caring relationships with this cohort of mothers. Public health nurses employed interactional strategies including engaging in a positive manner and offering verbal commendations which served as effective relational tools to break through mothers' walls of defensiveness and to resume the dynamic process of relationship building. Building Relationship is a key practice standard for public health nurses and is instrumental to their work at both individual and community levels to improve social determinants of health. The author concludes with recommendations to facilitate building relationships during everyday public health nursing practice.
Validation of a Linearized Navier-Stokes Based Flutter Prediction Tool: Part 1—Numerical Methods
Authors: Kersken Hans-Peter , Ashcroft Graham , Frey Christian , Pütz Oliver , Stüer Heinrich , Schmitt Stefan
Published: December 2013

This is the first of two papers describing the validation of a tool chain for flutter prediction. This first paper provides an overview of the numerical methods and their verification. The second paper presents the detailed validation of the tool chain on the basis of experimental data obtained from measurements of an annular cascade sector comprising slightly twisted turbine blades.

The tool chain consists of commercial programs for grid generation, structural analysis and the computation of the steady flow, and software developed at DLR for data conversion, aeroelastic preprocessing, and solving the time-linearized RANS equations.

The time-linearized solver computes the unsteady flow in the frequency domain based on the linearization of the RANS equations about a steady solution which, in the process chain presented here, is provided by the commercial solver. We investigate the issues that arise from using different spatial discretization schemes and turbulence models for the computation of the steady and the time-linearized solutions. Results are presented for Standard Configurations 4, 10 and 11, and a freestanding turbine blade from a rear stage of a stationary gas turbine. It is shown that with an appropriate choice of the spatial discretization parameters good agreement with reference data can be obtained.
A Methodology for Evaluating the Damping Effectiveness of a Split Sleeve Damper Tube Design—With an Optimum Design for Rotor Application
Authors: Hsiao Jushin
Published: December 2013

A procedure is presented for calculating the damping effectiveness and quality factor for a tubular damping device that has application in rotary machinery. The design utilizes a split sleeve tube inserted inside a slightly larger tube that needs to be protected from vibration damage. The mechanism of energy dissipation for this damping design is primarily through mechanical work rather than through friction. Using the methodology developed in this paper, various split sleeve designs are evaluated, and an optimum configuration that has far superior damping capability is presented. More importantly, engineers now have a tangible method to parametrically optimize their design in the early stages of the development process, and to minimize the scope and cost of verification tests.
Numerical Study of a Rotor/Stator Interaction Case Experimentally Simulated With an Industrial Compressor
Authors: Batailly Alain , Legrand Mathias , Millecamps Antoine , Garcin Francois
Published: December 2013

Higher aircraft energy efficiency may be achieved by minimizing the clearance between the rotating blade tips and respective surrounding casing. A common technical solution consists in the implementation of an abradable liner which improves both the operational safety and the efficiency of modern turbomachines. Recently, unexpected abradable wear removal mechanisms were observed in experimental set-ups and during maintenance procedures. The present study introduces a numerical strategy capable to address this occurrence.

After focusing on the analysis of the experimental results, the good agreement between experimental observations and numerical results is illustrated in terms of critical stress levels within the blade as well as final wear profiles of the abradable liner. New blade designs are also explored in order to assess the impact of blade design on the outbreak of the interaction phenomenon. The prevalence of three dominant parameters in the interaction onset is shown: (1) blade design, (2) abradable material mechanical properties and (3) the need for a global distortion of the casing to synchronize blade-tip/abradable coating contacts.
Modeling Contact Dynamics of Vanes With Adjustable Upstream Flow Angles
Authors: Schurzig Daniel , Tatzko Sebastian , Panning-von Scheidt Lars , Wallaschek Jörg
Published: December 2013

In this paper, a simulation method is proposed for a sub-category of compressor vanes showing nonlinear behavior due to an adjustable upstream flow angle. The proposed algorithm computes the forced response of a single vane based on the New-mark time stepping scheme after reducing the structural matrices using the Craig-Bampton method. The contacts are modeled by Coulomb friction and Newton impact constraints. Contact forces are determined using linear complementarity conditions with decoupled orthogonal friction force directions. Different discretization methods for the cylindrical contact partners are proposed. Finally, numerical results are shown in order to validate the proposed algorithms.
Static and Rotordynamic Characteristics for a New Hole-Pattern Annular Gas Seal Design Incorporating Larger Diameter Holes
Authors: Vannarsdall Michael , Childs Dara W.
Published: December 2013

To reduce manufacturing cost and time, a new larger-diameter hole-pattern seal incorporating hole diameters of 12.27 mm, versus prior hole diameters of 3.175 mm has been proposed. The 12.27 mm hole-diameter seal had substantially better stability performance with higher effective damping and a markedly lower cross-over frequency. It had negative direct stiffness coefficients at low frequency, while the 3.175 mm hole-diameter seal did not.
Damping and Inertia Coefficients for Two Open Ends Squeeze Film Dampers With a Central Groove: Measurements and Predictions
Authors: San Andrés Luis
Published: December 2013

Aircraft engine rotors are particularly sensitive to rotor imbalance and sudden maneuver loads since they are always supported on rolling element bearings with little damping. Most engines incorporate Squeeze Film Dampers (SFDs) as means to dissipate mechanical energy from rotor vibrations and to ensure system stability. The paper quantifies experimentally the forced performance of a SFD comprising two parallel film lands separated by a deep central groove. Tests are conducted on two open ends SFDs, both with diameter D = 127 mm and nominal radial clearance c = 0.127 mm. One damper has film lands with length L = 12.7 mm (short length), while the other has 25.4 mm land lengths. The central groove has width L and depth 3/4 L. A light viscosity lubricant flows into the central groove via three orifices, 120° apart, and then through the film lands to finally exit to ambient. In operation, a static loader pulls the bearing to various eccentric positions and electromagnetic shakers excite the test system with periodic loads to generate whirl orbits of specific amplitudes. A frequency domain method identifies the SFD damping and inertia force coefficients. The long damper generates six times more damping and ∼three times more added mass than the short length damper. The damping coefficients are sensitive to the static eccentricity (up to ∼0.5c) while showing lesser dependency on the amplitude of whirl motion (up to 0.2c). On the other hand, inertia coefficients increase mildly with static eccentricity and decrease as the amplitude of whirl motion increases. Cross-coupled force coefficients are insignificant for all imposed operating conditions on either damper. Large dynamic pressures recorded in the central groove demonstrate the groove does not isolate the adjacent squeeze film lands but contributes to the amplification of the film lands’ reaction forces. Predictions from a novel SFD model that includes flow interactions in the central groove and feed orifices agree well with the test force coefficients for both dampers. The test data and predictions advance current knowledge and demonstrate SFD forced performance is tied to the lubricant feed arrangement.
Crack Initiation Behavior and its Estimation for a Gas Turbine Rotor Based on the EBSD Analysis
Authors: Kobayashi Daisuke , Ito Akihiro , Miyabe Masamichi , Kagiya Yukio , Yoshioka Yomei
Published: December 2013

Gas turbine rotors made of Ni-base superalloys were sometimes found to have cracks at the dovetail of the first and second stage wheel. In order to maintain the reliability of gas turbine rotors over the long term, in addition to the application of countermeasures such as the shot-peening process, it is essential to confirm the characteristics of crack initiation mechanisms and to predict the possibility of new cracking.

In this paper, first, the case study of crack initiation concerning a wheel dovetail crack has been carried out. Second, to reveal the characteristics of the crack, comparative evaluation between the actual crack and various mechanical fracture samples were conducted by using a scanning electron microscope (SEM) and the electron back-scatter diffraction (EBSD) method which can analyze crystallographic misorientation. As a result, it was found that even in relatively low temperatures, Inconel® Alloy 706 is subjected to brittle grain boundary oxidation when under constant high stress, i.e. a similar phenomenon to stress accelerated grain boundary oxidation (SAGBO), so called hold-time cracking (HTC).
Development of a High Efficiency and Long Life 500W Class H-Darrieus Type VAWT (Vertical Axis Wind Turbine) System Using Skin-Spar-Foam Sandwich Composite Structure
Authors: Kong Changduk , Lee Haseung
Published: December 2013

Since the energy crisis and the environmental issue have been focused due to excessive fossil fuel consumption, the wind power has been considered as an important renewable energy source. Recently, several MW class large scale wind turbine systems have been developed in some countries. Even though the large scale wind turbine can effectively produce the electrical power, the small scale wind turbines have been continuously developed due some advantages, for instance, it can be easily built by low cost without any limitation of location, i.e. even in city. In case of small scale wind turbines, the vertical axis wind turbine (VAWT) is used in city having frequent wind direction change, even though it has a bit lower efficient than the horizontal axis wind turbine. Furthermore, most small scale wind turbine systems have been designed at the rated wind speed of around 12m/s. This work is to design a high efficiency 500W class composite VAWT blade which is applicable to relatively low speed region. In the aerodynamic design of blade, the parametric studies are carried out to decide an optimal aerodynamic configuration. The aerodynamic efficiency and performance of the designed VAWT is confirmed by the CFD analysis. The structural design is performed by the load case study, the initial sizing using the netting rule and the rule of mixture, the structural analysis using FEM, the fatigue life estimation and the structural test. The prototype blade is manufactured by the hand lay-up and the matched die molding. The experimental structural test results are compared with the FEM analysis results. Finally, to evaluate the prototype VAWT including designed blades, the performance test is performed using a truck to simulate the various range wind speeds and some measuring equipments. According to the performance evaluation result, the estimated performance is well agreed with the experimental test result in all operating ranges.
Rotor Dynamics of Overhung Rotors: Hysteretic Dynamic Behavior
Authors: Marin Manuel A.
Published: December 2013

Overhung-configuration rotors are commonly used in the oil, gas and process industries. Examples of this type of equipment include power turbines, Fluid Catalytic Cracking (FCC) expanders, turbochargers and pipeline boosters. Generally, in overhung-configuration rotors, the mass concentration is near the bearing on the overhung end, so the rotor dynamics behavior of these overhung-configuration rotors is different than other equipments that have their mass concentrations between the bearing spans, such as multistage compressors.

Among the more important characteristics that directly affect the rotor dynamics of the overhung rotors are gyroscopic effects on the higher modes and the fluid-film journal bearings. Gyroscopic effects are more significant in overhung configurations because of the relatively large overhung mass. These rotors also have a short bearing span and a relatively stiff shaft, so the first two modes are characterized by rigid body motion, as long as the bearing supports are rigid, as in most pipeline boosters. For pipeline boosters it would be typical to describe them as subcritical machines. If the bearing supports are not rigid, as at the disc end of power turbines and FCC expanders, then the first mode can be amplified, and it would not be unusual to describe them as supercritical machines. This paper will assume that the bearing supports are rigid, as in most pipeline boosters.

A phenomenon observed in overhung rotors is known as the synchronous thermal instability or “Morton Effect”. The Morton Effect occurs when synchronous vibration produces non-uniform heating of the shaft under the bearing, leading the shaft end to develop a thermal bow. It is typical for this to happen on the overhung end of the rotor, where there is more unbalance to react with any thermal bow.

The paper examines the hysteretic dynamic behavior observed in an overhung rotor mounted on tilting pad journal bearings, presenting a series of analysis using state-of-the-art rotor dynamics programs, and comparing analytical results with measurements, handling possible variables associated with synchronous “hysteresis” vibration.
Wind Turbine Pitch Change Simulation With Helicoidal Vortex Model
Authors: Chattot Jean-Jacques , Braaten Mark E.
Published: December 2013

The vortex model has been extended to account for large changes in power, such as occur with abrupt changes in blade pitch. The wake is treated as a flexible spring, extending from the rotor to the far-field (Trefftz plane), along which the pitch varies according to the convected power history at the rotor. Results of test cases are compared with experimental data available from the Tjaereborg and NREL experiments, indicating that the code gives not only correct power levels asymptotically, but also predicts the transient overshoots and undershoots and recovery time accurately at a very low cost.
Forced Response in Axial Turbines Under the Influence of Partial Admission
Authors: Fridh Jens , Laumert Björn , Fransson Torsten
Published: December 2013

High cycle fatigue (HCF) due to unforeseen excitation frequencies or due to under predicted force magnitudes, or a combination of both causes control stage failures for steam turbine stakeholders. The objectives of this paper is to provide an extended design criteria toolbox and validation data for control stage design based on experimental data, with the aim to decrease HCF incidents for partial admission turbines.

The upstream rotor in a two stage air test turbine is instrumented with pressure transducers and strain gauges. Admission degrees stretching from 28.6% to 100% as one or two admission arcs are simulated by blocking segmental arcs immediately upstream of first stator vanes by aerodynamically shaped filling blocks. Sweeps across a speed range from 50 to 105% of design speed are performed at constant turbine pressure ratio during simultaneous high speed acquisition. A forced response analysis is performed and results presented in Campbell diagrams.

Partial admission creates a large number of low engine order forced responses because of the blockage, pumping, loading and unloading processes. Combinations of the number of rotor blades and low engine order excitations are the principal sources of forced response vibrations for the turbine studied herein.

Altering the stator and/or rotor pitches will change the excitation pattern. A relation between the circumferential lengths of the admitted and non-admitted arcs that dictates the excitation forces is observed that may serve as a design parameter.
Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle
Authors: Conboy Thomas , Wright Steven , Pasch James , Fleming Darryn , Rochau Gary , Fuller Robert
Published: December 2013

Supercritical CO2 (S-CO2) power cycles offer the potential for better overall plant economics due to their high power conversion efficiency over a moderate range of heat source temperatures, compact size, and potential use of standard materials in construction [1,2,3,4]. Sandia National Labs (Albuquerque, NM, US) and the US Department of Energy (DOE-NE) are in the process of constructing and operating a megawatt-scale supercritical CO2 split-flow recompression Brayton cycle with contractor Barber-Nichols Inc. [5] (Arvada, CO, US). This facility can be counted among the first and only S-CO2 power producing Brayton cycles anywhere in the world.

The Sandia-DOE test-loop has recently concluded a phase of construction that has substantially upgraded the facility by installing additional heaters, a second recuperating printed circuit heat exchanger (PCHE), more waste heat removal capability, higher capacity load banks, higher temperature piping, and more capable scavenging pumps to reduce windage within the turbomachinery. With these additions, the loop has greatly increased its potential for electrical power generation — according to models, as much as 80 kWe per generator depending on loop configuration — and its ability to reach higher temperatures.

To date, the loop has been primarily operated as a simple recuperated Brayton cycle, meaning a single turbine, single compressor, and undivided flow paths. In this configuration, the test facility has begun to realize its upgraded capacity by achieving new records in turbine inlet temperature (650°F/615K), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20kWe). Operation at higher speeds, flow rates, pressures and temperatures has allowed a more revealing look at the performance of essential power cycle components in a supercritical CO2 working fluid, including recuperation and waste heat rejection heat exchangers (PCHEs), turbines and compressors, bearings and seals, as well as auxiliary equipment. In this report, performance of these components to date will be detailed, including a discussion of expected operational limits as higher speeds and temperatures are approached.
Multiharmonic Analysis of Nonlinear Whole Engine Dynamics With Bladed Disc-Casing Rubbing Contacts
Authors: Petrov E. P.
Published: December 2013

A method has been developed for frequency domain analysis of steady state forced response in gas turbine engines in the presence of rubbing and snubbing contacts between bladed discs and casing and between other rotor and stator engine components. The multiharmonic contact interface elements have been derived for modelling the nonlinear contact interactions: (i) at bearings and (ii) bladed disc-casing rubbing contacts with using flexible models for rotor and stator structures. The elements allow for the asymmetry of the casing, the discrete blade contacts with casing, individual blade-casing gap values, nonlinear dependency of the contact forces on rotor-stator incursion and friction forces, intermittent contacts between blades and the casing. High accuracy and computational efficiency of the methods and models developed has been demonstrated on a set of test cases and on an example of analysis of a realistic gas turbine structure.
Detailed Compressor Degradation Effect Modeling for Single Blade Rows While Assessing Its Local and Overall Consequences
Authors: Kappis Wolfgang , Guidati Gianfranco
Published: December 2013

The detailed local and overall aerodynamic impact due to the basic degradation mechanisms of changed surface roughness (fouling), caused by deposits on the blading surface and/or corrosion, leading edge deformation, caused by erosion, and clearance increases, caused by rubbing due to structural ovalization and/or rotor sagging are assessed. The generic aerodynamic impact of these effects is assessed in a first step by detailed local issue focused CFD analyses. The resulting trend changes in the aerodynamic behavior for every individual blade row are in a second step transferred to an empirical model for loss and deviation prediction of a 1-dim. compressor mid-streamline code. This tool is used to predict row specific and compressor overall aerodynamics for a wide range of operating points. Applying the generic trend changes due to degradation therefore provides information on the local and overall compressor mismatching. Details on the process of assessing and transferring these physical consequences are shown and discussed.

The different degradation contributors are assessed individually and in combination. Beneath detailed aerodynamic changes, e.g. stage pressure ratios and feed pressures, resulting effects on the compressor map, reflecting mass flow, efficiency and operating range changes are considered. Some typical overall engine degradation measurements are used to validate the numerical assessments and to draw some final conclusions.

For end-users the conclusions of this paper can be used to optimize site-specific operation cycles, based on corresponding field findings and by application of the theoretical conclusions derived in this paper. This can finally trigger a re-assessment of washing intervals and washing types to be executed and/or even to give special focus on certain blade rows during major overhauls/inspections in respect to hand cleaning or even blading exchange.
Development and Experimental Performance Verification of a Magneto-Aerostatic Bearing for Cartridge of Dental Handpieces
Authors: Ting Guan-Chung , Huang Kuang-Yuh , Chang Keng-Ning
Published: December 2013

Bearings for high-speed rotors are the key component of dental handpieces. The friction induced by conventional ball bearings restricts its speed and reduces its efficiency. In order to significantly improve the efficiency of dental handpieces, a mini-type cartridge that integrates a turbine and a spindle with radial aerostatic bearings and axial passive magnetic bearings has been ingeniously designed and realized. Around the rotating spindle, there is a high-pressured air film built up by a pair of radial aerostatic bearings, and magnet rings are applied to create repulsive forces to axially support the rotating spindle. The high-pressured air film comes from the specifically designed separable orifice restrictors, which can be easily and precisely manufactured. Frictionless bearing effect can be achieved by aerostatic principle, and the magnetic principle is applied to create large repulsive force against the axial working force. A tri-directional air inlet is designed to reduce radial loading force of a spindle during working. The modularized form of the magneto-aerostatic bearing allows it to be easily assembled and replaced in the very compact space of a mini-type cartridge.

Through analytical simulations with fluid-dynamics software (CFD) and experiments, the magneto-aerostatic bearing is optimized to bring out efficient performance in its limited space. The experiments have verified that its noise level is 15dB lower than the conventional cartridge with ball bearings, and its startup air pressure is reduced from 0.4 bar to 0.1 bar. Under the same operation conditions, the newly developed cartridge with magneto-aerostatic bearings creates twice higher speed than that of the conventional one.
Manufacturing Experience in an Advanced 9%CrMoCoVNbNB Alloy for USC Steam Turbine Rotor Forgings and Castings
Authors: Vanstone Rod , Chilton Ian , Jaworski Pawel
Published: December 2013

Advanced 9–12%Cr martensitic stainless steels to enable extension of steam turbine operating temperatures beyond 565°C have been under development since the 1980s. Steam turbines with operating temperatures approaching 600°C based on the first generation of these improved alloys, which exploited optimised levels of Mo, W, V, Nb and N, entered service in the 1990s. Around the same time a second generation of advanced alloys was developed incorporating additions of Co and B to further enhance creep strength. These alloys have recently been exploited to enable steam turbines with operating temperatures of up to 620°C and this new generation of steam turbines is now beginning to enter service. This paper describes the background to the development of these alloys and the experience gained in their application to the manufacture of high temperature rotor forgings and castings.
Evaluation of a New Coating for Application to Ramjet Engine Combustion Chamber
Authors: Heshmat Hooshang , Walton James F. , Jahanmir Said
Published: December 2013

In the present study, the adhesion and thermal characteristics of a new high temperature coating are evaluated. The new Korolon™ 1350A is applied by a conventional spray gun process at room temperature and does not require a bond coat when applied to Ni-based alloys. The coating thickness was varied from 127 to 254 μm. The coating/substrate adhesion was evaluated using a conventional bend test that subjects the coating to large elastic/plastic deformations. The coating showed no sign of delamination or fracture when subjected to 180° bend. Bend testing was also conducted following thermal cycling (95 to 815 °C) of the specimens in air. The coating showed no sign of oxidative degradation or delamination in bend testing. The thermal characteristics of the coating were evaluated under both convective and conductive heating conditions, including a guarded hot plate apparatus. After extensive testing and measurement of differential temperatures across the test specimens, it was estimated that the thermal conductivity of the coating is approximately 1 W/m K. The coating was then applied to aerothrottle panels and tested in a ramjet simulation test facility with flowing hot air at 1,200 °C. During this experiment the surface temperature on the coated panels reached 720 °C. Examination of the panels subsequent to testing showed no sign of degradation. Consistent with bench testing, a maximum temperature difference of 316 °C was measured between the heated surface and the back face with the coating applied to the heated surface. The results confirmed that the new coating is promising for elevated temperature use as a thermal barrier coating.
A Superposition Approach for Time-Dependent Fatigue Crack Growth
Authors: Ma Fashang
Published: December 2013

High temperature fatigue crack growth is a combination of fatigue, creep and environmental attack, which greatly enhance fatigue crack growth. In order to understand the damage mechanisms and develop a physically based crack growth model, systematic experimental research has been conducted under various loading conditions for different specimen geometries made from a high strength nickel alloy.

Test results from this work showed that time-dependent fatigue crack growth rates differ significantly from those observed in conventional fatigue crack growth tests. Crack geometry and loading history significantly affect fatigue crack growth rate. These results suggest the need for a change in the K based superposition approach for time-dependent crack growth modeling.

A phenomenological model has been developed to predict time-dependent crack growth under various loading histories and crack geometries. In this model an effective stress intensity factor is defined to account for the effects of constraint loss of fracture mechanics due to crack-tip plasticity, and the creep stress relaxation on stress intensity factor. It is found the model can accurately predict the dwell crack growth rates for different crack geometries under various loading conditions.
Design for Global Sourcing for Gas Turbine Engine Support to Achieve Design Harmonization
Authors: Tang Yucheng , Zhao Zuozhi , Li Peng , Sun Junling , Song Jinyu
Published: December 2013

Fierce competition, fluctuating market and opportunities in emerging market are forcing companies to structure product design globally to reduce cost and improve efficiency. However, the solutions to old issues are always accompanied by new challenges. Traditional design flow is struggling to catch up with the pace of customer requirement. And mixed global design teams, composed of senior and junior designers, are trying to design with uniform quality.

A real case occurred was that an experienced designer provides a DIN solution when the manufacturing requirement was ASTM, which results additional round of product design. In order to reduce those risks and overcome the challenges, a multiobjective optimization framework for gas turbine engine support was developed to shorten the product development and find an optimal design solution. To manage the risks arising from sourcing, a concept of design for global sourcing (DfGs) was proposed and implemented by incorporating design standards database and supply chain interface during preliminary design stage. Three practical design cases were performed to validate the proposed method. The results demonstrated: 1) Cost and product development cycle was sharply reduced; 2) Design flexibility was achieved by DfGs concept; 3) Trade-off among conflicting design objectives was accomplished by cost estimation model.
Experimental Study on Influence of Cooling Air Flow Upon Surface Temperature of High-Temperature Turbine Blades in Gas Turbine
Authors: Wen Xueyou , Xiao Dongming , Gu Zhongming , Du Shugui
Published: December 2013

On the basis of the issues occurring in practical production, an experimental study on the influence of cooling media flow upon the surface temperatures of LP turbine blades is carried out on a turbine. The experiment results show that, when the tolerance range of the cooling media flow is narrowed, the surface temperature difference of the blades in blade row is also narrowed evidently, while it has no obvious relation to the “corresponding probability” between the cooling media flow and the blade surface temperature. A few blades even show a “full non-corresponding” relationship. The reason of this phenomenon is that the vortex-matrix type inner cooling structure of blades makes the casting process more complex. The experiment results are helpful to the confirmation of the water flow tolerance in reason and the perfection of the process detail.
Developments for Modeling of Droplets Deposition and Liquid Film Flow in a Throughflow Code for Steam Turbines
Authors: Fendler Yoann , Dorey Jean-Marc , Stanciu Mugurel , Lance Michel , Léonard Olivier
Published: December 2013

Modeling wetness phenomena in steam turbines can help to assess the weight of the different losses due to the liquid phase, and so provide a tool to evaluate possible design features and optimal operating conditions. Since this analysis involves a whole section flow path, throughflow approach is more suitable than 3D CFD. The paper presents a way to model deposition of fog droplets and motion of liquid film on blades in a wet steam turbine in a throughflow code. For deposition, the contribution of turbophoresis is taken into account by using the deposition rate model established by Zaichik et al. and the contribution of inertia is considered for deposition on the leading edges of blades. The liquid film model considers liquid film as a surface entity, the mass and momentum conservation equations being integrated on the film thickness to calculate the averaged film thickness and velocity. The liquid film is submitted to aerodynamic drag, blade friction and inertial effects. This model is validated with an experiment conducted at the University of Michigan. A parametric study on droplet size, thermodynamic conditions, friction velocity and on correction for rarefied gas effect has been performed on a single stage transonic turbine.
Novel Vertical-Axis Wind Turbine With Articulated Blading
Authors: Jericha H. , Göttlich E. , Selic T. , Sanz W.
Published: December 2013

In this work a novel vertical-axis wind turbine is presented which can catch a wide range of wind velocities at high efficiencies.

The wind turbine consists of a rotatable horizontal platform, where three symmetric blades are arranged which rotate with half of the platform angular speed but in opposite direction relative to it. The rotation of the blades allows them to adapt to the varying angle of attack of the wind during one revolution of the platform. The important characteristic is the design feature that the blades are inclined outwards to the vertical axis of the platform by an angle of about 20 deg. The inclination leads to an increased circumferential velocity along the blade span, so that the increasing wind velocity with height can be better captured. Also the chord length of the blades increases with the spanwise position.

In order to better utilize the wind flow, guide vanes can be arranged which increase the flow to those blades currently moving with the wind and in return flow can even give proper windshield.

The articulated blades are connected to the horizontal platform via a special planetary bevel gear box, so that the relative rotational movement of them is controlled by the rotating platform, in fact a rotating gear box. This unit itself is connected to a generator thus producing electrical energy. The wind turbine can be tracked to a changed wind direction by means of rotating the stationary center bevel-gear wheel, which at given wind direction is then kept at constant position.

In this paper the design of wind turbine is described in detail and the advantages of the novel vertical-axis turbine are discussed. First CFD investigations of a 2D section without guide vanes are presented. They show that maximum power can be achieved for a wide range of speed ratios. The calculated power coefficient is about 0.36, an interesting value for vertical-axis wind turbines.
Open-Loop Aerodynamic Performance Testing of a 105,000 rpm Oil-Free Compressor-Expander for Subsurface Natural Gas Compression and Reinjection
Authors: Rimpel Aaron M. , Allison Timothy C. , Moore J. Jeffrey , Grieco Joseph S. , Shy Perry C. , Klein John M. , Brady Jerry L.
Published: December 2013

An aerodynamic performance test stand has been developed for validation of the performance of a 105,000 rpm compressor-expander which is intended for subsurface natural gas reinjection. The turbomachine consists of a two-stage centrifugal compressor, which is driven by a single-stage expansion turbine. The rotor is supported by foil gas journal bearings and a spiral-groove gas thrust bearing. The test stand is configured for open-loop testing of the overall compressor and turbine performance with air as the working fluid and atmospheric pressure at the compressor suction and turbine discharge locations. Several performance curves were generated for each component ranging from 73,500–115,500 rpm (70–110% of design speed). In general, measured compressor head was slightly lower than predictions, while measured efficiencies were close to predicted values. The turbine had higher flow than predicted, due in part to a larger flow area in the turbine. The turbomachine has shown acceptable performance on the open-loop test stand, and further testing at higher-pressure closed-loop conditions are planned.
3-D Time Domain Unsteady Computation of Rotating Instability in Steam Turbine Last Stage
Authors: Zhang L. Y. , He L. , Stüer H.
Published: December 2013

The rotating instability phenomenon in a last stage of steam turbines at low mass flow conditions has been previously identified experimentally. Recently, the rotating instability has also been numerically studied in a whole annulus domain on 2D blade sections. In the present work, 3D simulations of unsteady flows are carried out on two model steam turbines over a range of mass flow conditions. The pressure-ratio volume-flow characteristics in rotor row tip region under different flow conditions are well captured in the computations in comparison with the experiment. The effect of blade scaling is examined to identify the influence of changing blade counts for a circumferential domain reduction, showing relatively small effects on the overall performance characteristics. The present 3D unsteady solutions on a reduced multi-passage domain have been able to predict a rotating instability in the rotor blade tip region, in accord with the corresponding experiment. Further Fourier analysis is carried out to examine the frequency pattern and spatial modal features. The 3D flow behavior is highlighted by comparison between the 3D and 2D calculations. The present results seem to suggest that the rotating instability onset in the rotor tip region is largely independent of the large scale flow separation in the downstream diffusor.
Integration of Unsteady Effects in the Turbocharger Design Process
Authors: Pesiridis Apostolos , Lioutas Sotirios , Martinez-Botas Ricardo F.
Published: December 2013

Turbocharger development is based on performance maps arising through steady state measurements, although the flow through the engine-turbocharger system is highly unsteady. This paper investigates the potential for integrating the effects from unsteady flow in the turbine map, in order to enhance the performance of the ICE-turbocharger system. It is, also, an initial attempt to set the framework for more accurate one-dimensional turbine simulations in order to improve the selection of turbocharger components and their matching with the ICE. The development of ‘equivalent unsteady’ maps is presented, based on energy-weighted averaging of available, unsteady, experimental data and its deviations from quasi-steady performance. The maps are subsequently used for a one dimensional (1D) simulation of a turbocharged diesel engine running at 800 RPM and 1600 RPM. A comparative assessment with results from simulations using a conventional steady-state map has shown important differences in turbine parameters (up to 12% lower efficiency and 6% lower mass flow parameter) but minor differences, of less than 1% in terms of engine performance and fuel consumption.
The Physics of H-Darrieus Turbines Self-Starting Capability: Flapping-Wing Perspective
Authors: Worasinchai Supakit , Ingram Grant L. , Dominy Robert G.
Published: December 2013

It has been widely reported that Darrieus turbines cannot self-start and that they require external assistance to accelerate to their operating tip speed ratios. However, recent experiments have shown conclusively that H-Darrieus rotors with fixed-pitch blades that employ a symmetrical aerofoil can reliably self-start in steady controlled environments. Previous attempts have also been made to model the starting characteristics but there still exists a significant discrepancy between the experimental data and model prediction, suggesting that our understanding of this starting characteristic remains weak. The investigation and explanation of the starting characteristics is the focus of this paper.

The investigation was made through a careful analysis of aerofoils that undergo Darrieus motion, giving some insights on how the blade experiences different flow conditions and how driving force is developed over the flight path. The analysis reveals that the aerofoil in Darrieus motion is analogous to flapping wing mechanism; the mechanism that fish and birds employ to generate propulsion. The explanation of flow physics and torque development can then be made through a simple pitch-heave concept.

The investigation using this concept together with observations of flapping creatures suggests that the key feature that promotes driving torque generation and the ability to self-start is the unsteadiness associated with the rotor. This unsteadiness is related to chord-to-diameter ratio. This, together with blade aspect ratio, and number of blades, is the reason why H-Darrieus turbines that employ a symmetrical aerofoil can self-start.
Unsteady Flow Analysis and Vibratory Stress Predictions for a High Work Single Stage Turbine Blade
Authors: Weber Kurt , Modgil Girish , Gegg Steve , Neerarambam Shyam , Zhang Moujin
Published: December 2013

The flow field in High-Work Single-Stage (HWSS) turbines differs from traditional turbine flow fields. Operating at increased pressure ratios, wakes and trailing edge shocks at the exit of the vane are more likely to cause a vibratory response in the rotating blade. This flow field can produce increased excitation at harmonics that correspond to the vane passing frequency and harmonics higher than the vane passing frequency. In this paper, blade vibratory stresses in a HWSS gas turbine stage are predicted using unsteady pressures from two Rolls-Royce in-house flow codes that employ different phase lagged unsteady approaches. Hydra uses a harmonic storage approach, and the Vane/Blade Interaction (VBI) code uses a direct storage approach. Harmonic storage reduces memory requirements considerably. The predicted stress for four modes at two engine speeds are presented and are compared with rig test strain gauge data to assess and validate the predictive capability of the codes for forced response. Strain gauge data showed the need to consider harmonics higher than the fundamental vane passing frequency for the max power shaft speed and operating at the conditions. Because of this, it was a good case for validation and for comparing the two codes. Overall, it was found that, stress predictions using the Hydra flow code compare better with data. To the best of the authors’ knowledge, this paper is a first in comparing two different phase lagged unsteady approaches, in the context of forced response, to engine rig data for a High-Work Single Stage turbine.