bluuebunny/crossref_metadata_2025 huggingface dataset:
Sustained, Low‐Intensity Exercise Achieved by a Dynamic Feeding System Decreases Body Fat in Ponies
Authors: de Laat M.A. , Hampson B.A. , Sillence M.N. , Pollitt C.C.
Published: September 2016

Background

Obesity in horses is increasing in prevalence and can be associated with insulin insensitivity and laminitis. Current treatment strategies for obesity include dietary restriction and exercise. However, whether exercise alone is effective for decreasing body fat is uncertain.

Hypothesis

Our hypothesis was that twice daily use of a dynamic feeding system for 3 months would induce sustained, low‐intensity exercise thereby decreasing adiposity and improving insulin sensitivity (SI).

Animals

Eight, university‐owned, mixed‐breed, adult ponies with body condition scores (BCS) ≥5/9 were used.

Methods

Two treatments (“feeder on” or “feeder off”) were administered for a 3‐month period by a randomized, crossover design (n = 4/treatment). An interim equilibration period of 6 weeks at pasture separated the 2 study phases. Measurements of body mass (body weight, BCS, cresty neck score [CrNS], and morphometry), body fat (determined before and after the “feeder on” treatment only), triglycerides, and insulin sensitivity (SI; combined glucose‐insulin test) were undertaken before and after treatments.

Results

The dynamic feeding system induced a 3.7‐fold increase in the daily distance travelled (n = 6), compared to with a stationary feeder, which significantly decreased mean BCS (6.53 ± 0.94 to 5.38 ± 1.71), CrNS (2.56 ± 1.12 to 1.63 ± 1.06) and body fat (by 4.95%). An improvement in SI did not occur in all ponies.

Conclusions and Clinical Importance

A dynamic feeding system can be used to induce sustained (daily), low‐intensity exercise that promotes weight loss in ponies. However, this exercise may not be sufficient to substantially improve SI.
The European Survey on Adverse Systemic Reactions in Allergen Immunotherapy (EASSI): A paediatric assessment
Authors: Rodríguez del Río Pablo , Vidal Carmen , Just Jocelyne , Tabar Ana I. , Sanchez‐Machin Inmaculada , Eberle Peter , Borja Jesus , Bubel Petra , Pfaar Oliver , Demoly Pascal , Calderón Moises A.
Published: September 2016

Background

Safety data on ‘real‐life’ allergen immunotherapy (AIT) in children and adolescents is usually extrapolated from studies in adults.

Methods

Patients aged 18 or under initiating aeroallergen AIT were evaluated in a prospective European survey. Patient profiles and systemic reactions (SRs) were recorded. Descriptive, univariate and multivariate analyses were used to identify risk factors for SRs.

Results

A total of 1563 patients (mean ± SD age: 11.7 ± 3.9 years; rhinitis: 93.7%; asthma: 61.5%; polysensitization: 62.5%) and 1578 courses of AIT were assessed. Single‐allergen AIT was administered in 89.5% of cases (n = 1412; mites: 49%; grass pollen: 25.8%; tree pollen: 8.7%; Alternaria: 4.6%; dander: 0.8%; weed pollen: 0.6%). Subcutaneous AIT (SCIT) was used in 71.4% (n = 1127) of the treatments, including 574 (50.9%) with natural extracts. Sublingual AIT (SLIT) was used for the remaining 451 treatments (drops: 73.8%; tablets: 26.2%). The mean ± SD follow‐up period was 12.9 ± 3.3 months. The estimated total number of doses was 19,669 for SCIT and 131,550 for SLIT. Twenty‐four patients (1.53%) experienced 29 SRs. Respiratory (55.7%) and skin symptoms (37.9%) were most frequent. Anaphylaxis was diagnosed in 3 SRs (10.3%), and adrenaline was administered in 2 of these cases. In a univariate analysis, the risk of SRs was lower in mite‐sensitized patients and higher in cases of pollen polysensitization (>3), grass pollen extracts and the use of natural extracts (vs. allergoids).

Conclusions

In a real‐life paediatric setting, AIT is safe. SRs are infrequent and generally not severe. Pollen polysensitization, grass pollen extracts and natural extracts (vs. allergoids) were risk factors for AIT‐associated SRs.
One'sModus Ponens: Modality, Coherence and Logic
Authors: Stojnić Una
Published: September 2016

Recently, there has been a shift away from traditional truth‐conditional accounts of meaning towards non‐truth‐conditional ones, e.g., expressivism, relativism and certain forms of dynamic semantics. Fueling this trend is some puzzling behavior of modal discourse. One particularly surprising manifestation of such behavior is the alleged failure of some of the most entrenched classical rules of inference; viz.,modus ponensandmodus tollens. These revisionary, non‐truth‐conditional accounts tout these failures, and the alleged tension between the behavior of modal vocabulary and classical logic, as data in support of their departure from tradition, since the revisionary semantics invalidate some of these patterns. I, instead, offer a semantics for modality with the resources to accommodate the puzzling data while preserving classical logic, thus affirming the tradition that modals express ordinary truth‐conditional content. My account shows that the real lesson of the apparent counterexamples is not the one the critics draw, but rather one they missed: namely, that there are linguistic mechanisms, reflected in the logical form, that affect the interpretation of modal language in a context in a systematic and precise way, which have to be captured by any adequate semantic account of the interaction between discourse context and modal vocabulary. The semantic theory I develop specifies these mechanisms and captures precisely how they affect the interpretation of modals in a context, and do so in a way that both explains the appearance of the putative counterexamples and preserves classical logic.
Infant lung function predicts asthma persistence and remission in young adults
Authors: Owens Louisa , Laing Ingrid A. , Zhang Guicheng , Le Souëf Peter N.
Published: September 2016

Background and objective

Asthma in adults is associated with a persistent reduction in lung function from childhood, but this link has not been assessed back to infancy. Reduced infant lung function (ILF), a measure of antenatal and infant lung growth, is associated with asthma into adolescence. Our aim was to assess whether this link persists into adulthood and whether ILF can predict the remission of asthma symptoms in young adults.

Methods

The study cohort was an unselected full‐term birth cohort of 253 subjects enrolled antenatally with lung function assessments at 1, 6 and 12 months (maximum expiratory flow at functional residual capacity, V′maxFRC), and 6, 11, 18 and 24 years (spirometry) of age.

Results

Infants with V′maxFRC in the lowest quartile at 1 month had an OR of 5.1 (95% CI: 2–13, P = 0.001) for asthma at 24 years. Subjects with asthma at 24 years had a mean V′maxFRC at 1 month of 69% predicted (95% CI: 48–90%) versus 110% (95% CI: 101–119%) in non‐asthmatic patients (P = 0.001). Subjects with current versus resolved asthma symptoms at 24 years had a mean V′maxFRC at 1 month of 69% predicted (95% CI: 53–84%) versus 105% (88–123%), respectively (P = 0.003). Subjects with current asthma at 24 years had persistently lower lung function from infancy with a mean reduction of 16.2% (95% CI: 8.1–24.3%, P < 0.0001).

Conclusion

Reduced lung function in early infancy is predictive of persistent asthma in young adults and a persistent reduction in lung function, suggesting abnormal lung development and growth in utero or very early in life.
EigenPrism: Inference for High Dimensional Signal-to-Noise Ratios
Authors: Janson Lucas , Barber Rina Foygel , Candès Emmanuel
Published: September 2016

Consider the following three important problems in statistical inference: constructing confidence intervals for the error of a high dimensional (p > n) regression estimator, the linear regression noise level and the genetic signal-to-noise ratio of a continuous-valued trait (related to the heritability). All three problems turn out to be closely related to the little-studied problem of performing inference on the l2-norm of the signal in high dimensional linear regression. We derive a novel procedure for this, which is asymptotically correct when the covariates are multivariate Gaussian and produces valid confidence intervals in finite samples as well. The procedure, called EigenPrism, is computationally fast and makes no assumptions on coefficient sparsity or knowledge of the noise level. We investigate the width of the EigenPrism confidence intervals, including a comparison with a Bayesian setting in which our interval is just 5% wider than the Bayes credible interval. We are then able to unify the three aforementioned problems by showing that EigenPrism with only minor modifications can make important contributions to all three. We also investigate the robustness of coverage and find that the method applies in practice and in finite samples much more widely than just the case of multivariate Gaussian covariates. Finally, we apply EigenPrism to a genetic data set to estimate the genetic signal-to-noise ratio for a number of continuous phenotypes.
Self‐regulation in early childhood: The role of siblings, center care and socioeconomic status
Authors: Backer‐Grøndahl Agathe , Nærde Ane
Published: September 2016

Differences in children's self‐regulation are assumed to be explained by genetic factors, socialization experiences, and sociodemographic risk. As for socialization, little research has addressed the influence of having siblings or attending early center based child care on emerging self‐regulation. As regarding sociodemographic risk, few studies have been conducted in countries characterized by high equality and little poverty. In a longitudinal study following 1157 children, we investigated presence of siblings, center care exposure in the first 3 years of life (attendance, hours, and child group size), and family socioeconomic status (SES) as predictors of hot and cool effortful control (EC), at the child's age 48 months. The results showed that having a sibling was consistently related to better hot EC, whereas higher SES predicted better cool EC. A small effect implied that hours in center care at 36 months negatively predicted hot EC, whereas center care group size at 36 months modestly predicted better cool EC. Otherwise, center care variables were unrelated to self‐regulation.
A Self-Sufficient and Frequency Tunable Piezoelectric Vibration Energy Harvester
Authors: Karadag Cevat Volkan , Topaloglu Nezih
Published: September 2016

In this paper, a novel smart vibration energy harvester (VEH) is presented. The harvester automatically adjusts its natural frequency to stay in resonance with ambient vibration. The proposed harvester consists of two piezoelectric cantilever beams, a tiny piezomotor with a movable mass attached to one of the beams, a control unit, and electronics. Thanks to its self-locking feature, the piezomotor does not require energy to fix its movable part, resulting in an improvement in overall energy demand. The operation of the system is optimized in order to maximize the energy efficiency. At each predefined interval, the control unit wakes up, calculates the phase difference between two beams, and if necessary, actuates the piezomotor to move its mass in the appropriate direction. It is shown that the proposed tuning algorithm successfully increases the fractional bandwidth of the harvester from 4% to 10%. The system is able to deliver 83.4% of the total harvested power into usable electrical power, while the piezomotor uses only 2.4% of the harvested power. The presented efficient, autotunable, and self-sufficient harvester is built using off-the-shelf components and it can be easily modified for wide range of applications.
An Isothermal Model for Creep Rupture Prediction of Gas Turbine Airfoils With Thickness Effect
Authors: Menon M. N. , Kantzos P. T. , Greving D. J.
Published: September 2016

An isothermal model for creep rupture prediction of equiaxed gas turbine airfoils is presented. It provides a family of curves linear in log-log space between applied tensile stress and rupture time. Each curve represents a specific temperature. The model accommodates changes in slope with temperature by a temperature-time interaction term. In addition, it can capture phenomena that are solely temperature dependent such as thickness (grain size) effect observed in rupture of equiaxed turbine blade alloys. It represents an improvement over Larson-Miller (LM) formulation in which time and temperature are combined into a single parameter and assumed to have a unique value dependent only on the applied stress. It is also more accurate and less conservative than the LM model when extrapolating to lower stresses at a specific temperature, if the LM model shape is non-linear, curving downward. The isothermal formulation better preserves the accuracy of extrapolation and can model phenomena affecting stress rupture which are exclusively temperature dependent.
Rotordynamic Performance Predictions of Flexure Pivot Tilting Pad Bearings and Comparison to Published Test Data
Authors: Kim Tae Ho , Jang Kyung Eun , Choi Tae Gyu
Published: September 2016

This paper presents performance predictions for a Flexure Pivot® tilting pad bearing (FPTPB) and comparisons to published test data. The FPTPB has pads that tilt about a web pivot. The pivot is designed to have little rotational stiffness, which improves its rotordynamic stability. The Reynolds equation for an isothermal and isoviscous fluid was used to calculate the film pressure using the finite element method. The Newton–Raphson method was used to determine the journal eccentricity, journal attitude angle, and pivot deflections (tilting angle, and radial and circumferential displacements) simultaneously. A small perturbation of the journal center around its equilibrium position was employed to calculate the stiffness and damping coefficients. The whirl frequency ratio (WFR), which is the ratio of the frequency of unstable whirl motion to the rotor threshold speed, was calculated using the predicted dynamic coefficients. The predictive model used was for a four-pad FPTPB with a journal diameter of 116.81 mm and axial length of 76.2 mm. Each pad had a preload of 0.25, pivot offset of 0.5, and web pivot thickness of 2.125 mm. The rotor speed and specific load were varied up to 16 krpm and 345 kPa, respectively. Predictions were performed for the load-on-pad (LOP) and load-between-pad (LBP) configurations. The results show that the predicted journal eccentricity and attitude angle decrease as the rotor speed increases. The direct stiffness coefficients increase as the rotor speed increases, but the cross-coupled stiffness coefficients change little. As the static load increases, the direct stiffness coefficient in the vertical direction increases, but the other stiffness coefficients change little. The damping coefficients are affected little by the rotor speeds and static loads. A comparison of the predictions with published test data shows that the predictive model slightly overestimates the journal eccentricities and underestimates the absolute values of the journal attitude angles. The predicted stiffness coefficients agree well with the test data. However, large discrepancies in the damping coefficients were observed between the predictions and published data. The effect of the pivot thickness on the rotordynamic performance of the FPTPB was also studied. Predictions were performed for changes in the pivot thickness up to ± 20 percent in increments of 10 percent from the original value of 2.125 mm. The results show that the predicted maximum pressure, journal eccentricity, and attitude angle decrease with decreasing pivot thickness, but the minimum film thickness increases. As the pivot thickness decreases, the direct stiffness coefficients, direct damping coefficients, and absolute values of the cross-coupled damping coefficients increase. The whirl frequency ratio (WFR), which was found to be in reasonable agreement with the test data, decreases significantly with decreasing pivot thickness, which suggests improvement in rotordynamic stability.
Temperature Measurements at the Outlet of a Lean Burn Single Sector Combustor by Laser-Optical Methods
Authors: Doll U. , Stockhausen G. , Heinze J. , Meier U. , Hassa C. , Bagchi I.
Published: September 2016

High OPR engine cycles for reduced NOx emissions will generate new aggravated requirements and boundary conditions by implementing low emission combustion technologies into advanced engine architectures. Lean burn combustion systems will have a significant impact on the temperature and velocity traverse at the combustor exit. The highly swirling flow from the lean burn fuel injector interacts with the combustor wall cooling before exiting the combustor. As a large portion (up to 80%) of the total flow passes through the fuel injector, the combustor exit flow and temperature field is dominated by the fuel injector. With the transition to high pressure engines it is essential to fully understand and determine the high energetic interface between combustor and turbine to avoid excessive cooling with detrimental impacts to turbine and overall engine efficiency.

In this context the knowledge of temperature distributions at the combustor exit is of special importance. A lean burn single sector combustor was designed and built at DLR, providing optical access to the exit section. The sector was operated with a staged lean burn injector from Rolls-Royce Deutschland. Spatially resolved temperatures were measured at different operating conditions using planar laser-induced fluorescence of OH (OH-PLIF) and Filtered Rayleigh Scattering (FRS), the latter being used in a combustor environment for the first time. Apart from a conventional signal detection arrangement, FRS was also applied with an endoscope for signal collection, to assess its feasibility for future application in a full annular combustor with restricted optical access.

Both techniques are complementary in several respects, which justified their combined application and comparative assessment in this specific environment. OH-PLIF allows instantaneous measurements and therefore enables local temperature statistics, but is limited to relatively high temperatures. On the other hand FRS can also be applied at low temperatures, which makes it particularly attractive for measurements in cooling layers. However, due to the weak physical process of Rayleigh scattering, FRS requires long sampling times and therefore can only provide temporal averages. When applied in combination, the accuracy of both techniques could be improved by each method helping to overcome the other’s shortcomings.

In an accompanying paper, additional experiments are described which characterize the flow field at the combustor exit; the combined data provide comprehensive information on combustor exit conditions.
Effect of Bolts on Flow and Heat Transfer in a Rotor-Stator Disc Cavity
Authors: Noor Mohamed Sulfickerali , Chew John W. , Hills Nicholas J.
Published: September 2016

Previous studies have indicated some differences between steady CFD predictions of flow in a rotor-stator disc cavity with rotating bolts compared to measurements. Recently time-dependent CFD simulations have revealed the unsteadiness present in the flow and have given improved agreement with measurements. In this paper unsteady Reynolds averaged Navier-Stokes (URANS) 360° model CFD calculations of a rotor-stator cavity with rotor bolts were performed in order to better understand the flow and heat transfer within a disc cavity previously studied experimentally by other workers. It is shown that the rotating bolts generate unsteadiness due to wake shedding which creates time-dependent flow patterns within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disc temperature. A systematic parametric study is presented giving insight into the influence of number of bolts, mass flow rate, cavity gap ratio and the bolts-to-shroud gap ratio on the time depended flow within the cavity.
Simplified Determination of Aerodynamic Damping for Bladed Rotors: Part 1 — Experimental Validation at Rest
Authors: Beirow Bernd , Maywald Thomas , Figaschewsky Felix , Heinrich Christoph Rocky , Kühhorn Arnold , Giersch Thomas
Published: September 2016

Considering both a radial turbine rotor of a turbocharger and an axial compressor test blisk at rest, aerodynamic damping characteristics are experimentally and numerically analyzed. Linear dependencies of modal damping ratios on the ambient pressure or the acoustic impedance, respectively, could be shown within experiments carried out inside a pressure chamber. The impact of the ambient air clearly dominates the modal damping ratios compared to the minor contribution of the structure. Assuming that acoustic emission can be regarded as main source of aerodynamic damping a simplified approach for its determination is introduced which only depends on natural frequency, mode shape and acoustic impedance. It is shown that a satisfying match between experiment and computation is achieved for those cases which are dedicated to sufficiently small ratios between wave lengths of acoustic emissions and blade distances.
Creep Life Assessment of an Uncooled Turbine Blade Using Probabilistic Design
Authors: Sjodin Bjorn
Published: September 2016

The probabilistic method described in this paper is a general method that can be applied to a variety of problems. In this particular paper it is applied to a creep problem where the time to creep crack initiation in a turbine blade is studied for the case of 6 random input variables. A response surface is created with a few Finite Element calculations and distributions are chosen for the random variables. The failure event is defined and the life time distribution is solved for and at the end compared to operational experience with the blade. The blade is made of the material IN792 and the load case represents the gas turbine is running on full load and ISO inlet temperature conditions. A statistical tool has been used to compare the calculated lifetimes with field experience of the same. The match between our calculated expected lifetimes and the real observed lifetimes are very good.
Rational Design of Gas Turbine Engine Compressor to Provide the Required Dynamic Strength Level of Rotor Blades
Authors: Kolmakova Daria , Popov Grigorii , Shklovets Aleksandr , Ermakov Aleksandr
Published: September 2016

Compressors of gas turbine engines often operate under the conditions of uneven gas flow. Oscillations of the blades occur under the influence of circumferential flow unevenness.

The goal of the research was to find an acceptable method of reducing the level of dynamic stresses in the rotor blades. Motivation for the study was the problem of destruction of rotor blades of the last stage of Intermediate Pressure Compressor (IPC) which has been designed and produced at JSC “Kuznetsov” (Russia). The source of circumferential flow unevenness was middle annular frame located downstream the IPC. Seven struts with different maximum thickness are arranged irregularly in support passage.

The first approaches propose to reduce the dynamic stresses in blades by detuning the blades from the dangerous harmonic due to changes in their natural frequency.

The next two consist in reducing the circumferential unevenness of flow.

Thus, this study gives the ideas about methods of improving the dynamic strength of rotor blades of gas turbine engine compressors. On the basis of existing conditions (under development or existing compressor) it allows the selection of the most suitable method for reducing dynamic stresses.
2nd Quadrant Centrifugal Compressor Performance: Part II
Authors: Belardini Elisabetta , Pandit Rajeev , Satish Koyyalamudi V. V. N. K. , Rubino Dante Tommaso , Tapinassi Libero
Published: September 2016

The sizing of surge protection devices for both compressor and surrounding system may require the knowledge of performance curves in 2nd quadrant with a certain level of accuracy. In particular two performance curves are usually important: the pressure ratio trend versus flow rate inside the compressor and the work coefficient or power absorption law. The first curve allows estimating mass flow in the compressor given a certain pressure level imposed by system, while the second is important to estimate the time required to system blow down during ESD (emergency shutdown). Experimental data are routinely not available in the early phase of anti-surge protection devices and prediction methods are needed to provide performance curves in 2nd quadrant starting from the geometry of both compressor and system.

In this paper two different approaches are presented to estimate performance curves in 2nd quadrant: the first is a simple 1D approach based on velocity triangle and the second is a full unsteady CFD computation. The two different approaches are applied to the experimental data more deeply investigated in part I by Belardini E.[3]. The measurement of compressor behavior in 2nd quadrant was possible thanks to a dedicated test arrangement in which a booster compressor is used forcing stable reverse flow.

The 1D method showed good agreement with experiments at design speed. In off-design condition a correlation for deviation angle was tuned on experimental data to maintain an acceptable level of accuracy. With very low reverse flow rates some discrepancies are still present but this region plays a secondary role during the dynamic simulations of ESD or surge events.

The unsteady CFD computation allowed a deeper insight into the fluid structures, especially close to very low flow rates when the deviation of the 1D method and the experimental data is higher. An important power absorption mechanism was identified in the pre-rotation effect of impeller as also the higher impact of secondary flows.

These two methods are complementary in terms of level of complexity and accuracy and to a certain extent both necessary. 1D methods are fast to be executed and more easily calibrated to match the available experiments, but they have limited capability to help understanding the underlying physics. CFD is a more powerful tool for understanding fluid structures and energy transfer mechanisms but requires computational times not always suitable for a production environment. 1D method can be used for standard compressor and applications for which consolidated experience have been already gathered while CFD is more suitable during the development of new products or up to front projects in general.
New HP-/IP-Blades With Protective Coating for High Temperature Steam Application
Authors: Ettler Manuel , de Lazzer Armin , Schrey Albert , Schuerhoff Joerg
Published: September 2016

Today’s challenging requirements on thermal power plant cycle efficiency favor plants with steam temperatures up to 630°C. Cost competition, however, confines the application of particularly cost-intensive materials causing high manufacturing effort such as Ni-based alloys. Alternatives are martensitic steels containing less than 10% Cr. Due to the low Chromium content, these materials are less oxidation-resistant compared to 12% Cr-steels. Increased load-cycling requirements resulting from varying renewable energy production may result in decreased plant efficiency due to increased scaling and spallation of oxide layers during thermal transients. Hence, it is beneficial to protect such components against oxidation using coatings.

Investigations on various coating systems for their potential to serve as oxidation protection are described in this paper. These investigations consisted of a short-term screening program to identify the most promising coatings followed by an extensive test program including long-term steam exposure at high temperatures, thermal cycling, solid particle erosion tests as well as tests under operating conditions on samples and blades.

The test program revealed which coatings appeared to be the most promising solution for power plant applications, showing excellent oxidation protection capability of the base material in steam at high temperatures, structural stability upon thermal cycling and good solid-particle erosion protection. Tests under operational conditions have proven the functionality and stability of the coatings.
Reduction in Flow Parameter Resulting From Volcanic Ash Deposition in Engine Representative Cooling Passages
Authors: Wylie Sebastien , Bucknell Alexander , Forsyth Peter , McGilvray Matthew , Gillespie David R. H.
Published: September 2016

Internal cooling passages of turbine blades have long been at risk to blockage through the deposition of sand and dust during fleet service life. The ingestion of high volumes of volcanic ash therefore poses a real risk to engine operability. An additional difficulty is that the cooling system is frequently impossible to inspect in order to assess the level of deposition. This paper reports results from experiments carried out at typical HP turbine blade metal temperatures (1163K to 1293K) and coolant inlet temperatures (800K to 900K) in engine scale models of a turbine cooling passage with film-cooling offtakes. Volcanic ash samples from the 2010 Eyjafjallajökull eruption were used for the majority of the experiments conducted. A further ash sample from the Chaiten eruption allowed the effect of changing ash chemical composition to be investigated. The experimental rig allows the metered delivery of volcanic ash through the coolant system at the start of a test. The key metric indicating blockage is the flow parameter which can be determined over a range of pressure ratios (1.01–1.06) before and after each experiment, with visual inspection used to determine the deposition location. Results from the experiments have determined the threshold metal temperature at which blockage occurs for the ash samples available, and characterise the reduction of flow parameter with changing particle size distribution, blade metal temperature, ash sample composition, film-cooling hole configuration and pressure ratio across the holes. There is qualitative evidence that hole geometry can be manipulated to decrease the likelihood of blockage. A discrete phase CFD model implemented in Fluent has allowed the trajectory of the ash particles within the coolant passages to be modelled, and these results are used to help explain the behaviour observed.
Influence of Gas Feeding Position on the Performance of Radial-Inflow Hydrostatic Gas Ultra-Short Journal Bearings
Authors: Nie Chao , Yan Xiaojun , Chen Xia
Published: September 2016

To investigate the influence of gas feeding position on the performance of radial-inflow hydrostatic gas ultra-short (with a L/D value as 0.1) journal bearing two rotor-bearing system test rigs with two different feeding positions (central feeding and bottom feeding) for the journal bearing were designed. A rotor measurement system with an original rotational speed measurement program is built. Rotation experiments to measure the maximum rotational speed of rotors under different inlet pressure of journal bearing were conducted. It was found that, the rotor supported by the central feeding journal bearing worked better, and achieved a maximum rotational speed of 40000 rpm, (83.74m/s for the tip speed). While the test rig with bottom feeding journal bearing could not function well. To verify the reasons behind the failure mentioned above, the flow condition in the journal clearance and the rotor bottom clearance was analyzed by the CFD simulation. It shows that most of the journal bearing gas “leaks” into the rotor bottom clearance in the bottom feeding bearing test rig, disarranging the axial stability of the rotor and the normal functioning of the thrust bearings. In conclusion, the central feeding radial-inflow journal bearing is better than the bottom feeding one, for the better operability and higher maximum speed. And an ideal feeding position is supposed to make the journal bearing does not influence the axial stability of the rotor and the functioning of the thrust bearings.
Modular Tool for Design and Off-Design Analysis of Compression Trains for Oil and Gas Applications
Authors: Carcasci C. , Marini L. , Micio M. , Brogelli R. , Di Pillo P. L.
Published: September 2016

Compression trains for oil and gas applications must meet, now more than ever, the requirement of versatility. Production rates and compression demands of extraction fields significantly change during their operational life; this has pushed customers to ask for equipments designed to efficiently operate all over their lifespan in order to comply with energy saving and pollution reduction needs. For this reason modular simulation codes turn out to be the best choice compared with dedicated tools for specific compression plant configuration, since they provide flexibility without losing accuracy.

This paper presents the implementation, within a previously developed modular tool, of a design and off-design procedure for compression plant simulation. This tool is based on a wide library of elementary components analytically defined through equations that model their physical behaviour. For impellers, descriptive equations represent an in-house database of real stages characteristic curves, for all the other elementary components the equations arise from fundamental mechanical and thermodynamic laws. Physical properties of real gases are assessed by the use of suitable thermodynamic libraries. An implemented trust-region Gauss-Newton method, called TRESNEI, has been adopted to solve the mathematical model.

Numerical calculations, performed on two real compression train arrangements, have been devoted to validate the code over design and off-design simulation mode. Results have been compared with those obtained with a pre-existing in-house tool and with experimental data. Comparisons show both a satisfactory agreement between numerical and experimental data and a perfect matching between the simulation codes.
Design Optimization of a Utility Scale Wind Turbine Blade Using a Genetic Algorithm
Authors: Yassin Khaled , Diab Aya , Ghoneim Zakaria
Published: September 2016

Driven by the increasing fossil fuel prices, global warming and climatic change, the world is currently witnessing an increasing development in renewable energy technologies, particularly those of wind energy. As such, engineers around the world are trying to optimize the design of wind turbines to maximize the captured energy while simultaneously minimizing the cost. This work aims to develop a mathematical tool to be used to compare different wind turbine designs and hence to reach the ultimate goal of an optimized wind turbine rotor designed specifically to operate in the Saharan regions of North Africa and the Middle East. As a case study, the main aerodynamic and structural parameters of the NREL 5MW virtual rotor have been optimized for the wind conditions prevalent at the Zaafarana site in Egypt. Specifically, the airfoil chord lengths and twist angles — smoothed using Bezier curves — as well as the layup sequence of the spar caps have been considered i n the optimization process which was carried out using a Genetic Algorithm (GA) developed i n MATLAB and coupled with NREL’s FAST Modularization Framework. The results showed that the NREL 5MW wind turbine design optimized for the site specific wind conditions of Zaafarana using airfoil families with low-sensitivity to dust accumulation, achieved a drop of 2.41% of the Levelized Cost of Energy of Energy (LCOE) over that of the baseline design. The developed turbine rotor design is tested for structural integrity commensurate with IEC standards.
Experimental Investigation of Heat Transfer Augmentation by Different Jet Impingement Hole Shapes Under Maximum Crossflow
Authors: Singh Prashant , Ravi Bharath Viswanath , Ekkad Srinath
Published: September 2016

To achieve higher overall efficiency in gas turbine engines, hot gas path components are subjected to high heat transfer loads due to higher turbine inlet temperatures. Jet impingement has been extensively used especially as an internal cooling technique in the leading edge and mid-chord region of first stage vanes, which are subjected to highest heat loads. With the advent of additive manufacturing methods such as Direct Metal Laser Sintering (DMLS), designers are not limited to designing round or race track holes for impingement. The present study is focused on exploring new jet hole shapes, in an arrangement, typical of mid-chord region in a double wall cooling configuration. Transient liquid crystal experiments are carried out to study heat transfer augmentation by jet impingement on smooth target where the spent air is allowed to exit in one direction, thus imposing maximum crossflow condition. The averaged Reynolds number (based on jet hydraulic diameter) is varied from 2500 to 10000. The jet plate has a square array of jets with 7 jets in one row (total number of jets = 49), featuring hole shapes — Racetrack and V, where the baseline case is the round hole. The non-dimensional streamwise (x/dj) and spanwise (y/dj) spacing is 6 and the normalized jet-to-target-plate spacing (z/dj) is 4 and the nozzle aspect ratio (L/dj) is also 4. The criteria for the hole shape design was to keep the effective area of different hole shapes to be the same, which resulted in slightly different hydraulic diameters. The jet-to-target plate spacing (z) has been adjusted accordingly so as to maintain a uniform z/dj of 4, across all three configurations studied. Heat transfer coefficients are measured using a transient Liquid Crystal technique employing a one-dimensional semi-infinite model. Flow experiments are carried out to measure static pressures in the plenum chamber, to calculate the discharge coefficient, for a range of plenum absolute pressure-to-ambient pressure ratios. Detailed normalized Nusselt number contours have been presented, to identify the regions of high heat transfer augmentation locally, so as to help the designers in the organization of jet hole shapes and their patterns in an airfoil depending upon the active heat loads.
Effects of Upstream Sprayed Water on Steam Flow Conditions and Blade Vibrations of a Low Pressure Steam Turbine
Authors: Shibukawa Naoki , Ishikawa Yoshihiro , Iwasaki Yoshifumi , Chiba Kota
Published: September 2016

A shutdown operation of a large size steam turbine could possibly cause flashing phenomena of the pooled drain water in low-pressure heaters. The boiled steam is sometimes in the same amount as the main flow in the case where shutdown is executed during low load conditions, and returns to the steam flow path through the extraction lines. A series of experimental works with a subscale model turbine facility has been carried out to investigate the vibration stress behavior, and the steady and unsteady pressures under the flashing back conditions. It was observed that the blades of the two stages before the last stage (L-2) and a stage before the last stage (L-1) endured their peak vibration stresses immediately after the flash-back flow reached the turbine. In the meantime, the vibration stresses of the last stage (L-0) blades were reduced.

In this paper, the behavior of the water droplets and their vaporization in the steam path were mainly investigated. A series of experiment was conducted in which several amounts of controlled sprayed water were continuously supplied into the turbine. The transient steam condition and blade’s vibration stresses were measured at the same time. The results showed the possibility that sprayed water upstream can change the mass flow rate and temperature downstream to avoid the unstable steam flow and overheating of the long blades during low load operation.
Investigation of Time/Frequency Domain CFD Methods to Predict Turbomachinery Blade Aerodynamic Damping
Authors: Patil Sunil , Zori Laith , Galpin Paul , Morales JuanCarlos , Godin Philippe
Published: September 2016

Accurate and efficient prediction of blade aerodynamic damping is critical for the design of turbomachines such as gas and steam turbines. Traditional unsteady time-marching CFD methods used in aerodynamic damping calculations are expensive because they require simulation of many or all blade passages in a given blade-row. In order to reduce computational cost, one can use a pitch-change method and reduce the problem to a small sector of the geometry (one or two blades). Even still, the time-marching method is expensive as many vibration cycles must be simulated to reach a quasi-steady periodic state. To further reduce computational cost, a time/frequency solution method is required.

This paper uses an implicit pressure-based time/frequency solution method in combination with a Fourier transformation (FT) pitch-change method and validates its implementation in ANSYS CFX solver. Three cases are investigated, including Standard Configuration 11 (subsonic and transonic), and NASA Rotor 67 transonic fan. Predictions of unsteady pressure coefficient are compared against the experimental data and reference full wheel simulations, over a range of nodal diameters. Computational resources (CPU time) required by the time/frequency method are compared to time transient simulations and discussed in detail.
Film Cooling Performance Improvement With Optimized Hole Arrangements on Pressure Side Surface of Nozzle Guide Vane: Part II — Experimental Validation
Authors: Rhee Dong-Ho , Kang Young Seok , Cha Bong Jun , Kang Jeong-Seek , Lee Sanga , Yee Kwanjung
Published: September 2016

In the present study, the optimized configurations of film cooled turbine guide vanes proposed in Part I were validated experimentally and the effect of coolant mass flow rate on the performance was examined for those optimized configurations. A set of tests were conducted using an annular sector transonic turbine cascade test facility in Korea Aerospace Research Institute. The mainstream and the secondary air for cooling are supplied by 500 hp and 50 hp compressors, respectively, and the mainstream was heated approximately 20°C above the secondary flow by 300kW heater. To measure the film cooling effectiveness on the pressure side surface, the transient measurement method was used using a FLIR infrared camera system. The test section has five nozzle guide vanes with four passages. The three times scaled-up vane model is manufactured by a stereolithography method. The tests were conducted at mainstream exit Reynolds number based on the chord of 2.2×106 and the coolant mass flow rate ranging from 5 to 13% of the mainstream. The flow periodicity in the cascade passage was verified by surface static pressure measurements. The results showed that the optimized cases present better cooling effectiveness values in the overall region. The effect of coolant mass flow rate also presents the same trend. Comparison with the CFD results shows that the CFD results over-predict film cooling effectiveness by 10∼20 percentage points for baseline and 17∼23 percentage points for the optimized cases. This is probably partly due to the discrepancy of operating conditions such as inlet boundary condition and density ratio and partly due to the limitation of numerical method used in the optimization such as coarse grid near the surface. However, a quite good agreement is obtained qualitatively, which means the optimization process can be utilized as a reliable and efficient method for film cooling performance improvement.
Demonstrating the angular, wavelength and polarization dependence of surface plasmon resonance on thin gold films—An undergraduate experiment
Authors: Connolly Peter W. R. , Kaplan Andrey
Published: September 2016

This paper describes the design of a simple and compact optical system capable of examining fundamental properties of light coupling to surface plasmon resonance (SPR) on a thin gold film. The setup, involving a rotatable Attenuated Total Reflection device, from which the reflected light is focused by means of a parabolic mirror, allows for the investigation of the dependence of the reflected intensity on the angle of incidence without moving the detector. It additionally makes provision for a convenient exchange of light sources or the possibility to incorporate a broadband source suitable to investigate SPR at different wavelengths. Theoretical simulation of the experimental data is provided, as well as straightforward calculations for exploring the physics of light excited waves propagating on a surface.
Specular Reflection from Rough Surfaces Revisited
Authors: Yasuda Kensei , Kim Alvin , Cho Hayley , Timofejev Timofej , Walecki Wojciech J. , Klep James , Edelson Amy S. , Walecki Abigail S. , Walecki Eve S. , Walecki Peter S.
Published: September 2016

In his beautiful paper, Hasan Fakhruddin reported observations of mirror-like reflections in the rough surface of a ground glass plate. Similar effects have been recently employed for metrology of the roughness of optical diffusers used in modern light emitting device illumination systems. We report the observations of specular reflection in nontransparent rough surfaces at oblique angles, where roughness was treated as a variable. We present a simple trigonometry-based model explaining the observed phenomenon, which we experimentally validated using aluminum surfaces that have controlled roughness. The reported demonstration requires no special equipment, other than cellphone cameras, dielectric or metal plate, and sandpaper, and serves as an introduction to wave optics. This activity can be used to get further insight into everyday applications of wave optics for students already familiar with wave optics fundamentals.
Ripples in Reality
Authors: Lincoln Don , Stuver Amber
Published: September 2016

In a deep and dark corner of space, a cataclysm loomed. Two cosmic nemeses circled one another, locked in a macabre dance of death. Unfolding over millennia, the deadly waltz began leisurely enough. But with the dance came radiation and the energy loss that it implies. Orbit after orbit, the distance between the two protagonists shrank as their grip on each other tightened. Radiation carried away energy, but not angular momentum, so the orbital velocity grew to incomprehensible levels—well into the realm where Einstein’s theory of special relativity reigns supreme. With the closing distances, the inevitable occurred as the two twisted knots of spacetime approached each other and merged in a spasm that shook the universe so violently that the energy output briefly outshone the electromagnetic energy output of the entire universe. The two adversaries become one, finally merged together for all eternity. The traces of their ordeal died away, leaving only a fading death scream that spread throughout the cosmos, growing ever fainter. That is, until they passed through Earth. That was the moment that changed everything.
Einstein’s Elevator in Class: A Self-Construction by Students for the Study of the Equivalence Principle
Authors: Kapotis Efstratios , Kalkanis George
Published: September 2016

According to the principle of equivalence, it is impossible to distinguish between gravity and inertial forces that a noninertial observer experiences in his own frame of reference. For example, let’s consider an elevator in space that is being accelerated in one direction. An observer inside it would feel as if there was gravity force pulling him toward the opposite direction. The same holds for a person in a stationary elevator located in Earth’s gravitational field. No experiment enables us to distinguish between the accelerating elevator in space and the motionless elevator near Earth’s surface. Strictly speaking, when the gravitational field is non-uniform (like Earth’s), the equivalence principle holds only for experiments in elevators that are small enough and that take place over a short enough period of time (Fig. 1). However, performing an experiment in an elevator in space is impractical. On the other hand, it is easy to combine both forces on the same observer, i.e., gravity and a fictitious inertial force due to acceleration. Imagine an observer in an elevator that falls freely within Earth’s gravitational field. The observer experiences gravity pulling him down while it might be said that the inertial force due to gravity acceleration g pulls him up. Gravity and inertial force cancel each other, (mis)leading the observer to believe there is no gravitational field. This study outlines our implementation of a self-construction idea that we have found useful in teaching introductory physics students (undergraduate, non-majors).