bluuebunny/crossref_metadata_2025 huggingface dataset:
Periglacial structures within fluvio‐aeolian successions of the end of the Last Glaciation – examples from SE Poland and NW Ukraine
Authors: Zieliński Paweł , Sokołowski Robert J. , Fedorowicz Stanisław , Zaleski Iwan
Published: November 2013

The nature of permafrost and related environmental conditions in the Weichselian Late Pleniglacial and Lateglacial are reconstructed based on the assessment of frost structures that are best documented in the Loess Belt and in plateau areas composed of glacial till. Investigations were conducted in the central‐eastern part of the European Sand Belt (SE Poland and NW Ukraine) on a fluvio‐aeolian sedimentary succession and took into account its chronological context given by luminescence dating. Various generations of periglacial structures found in these deposits indicate not only the development of permafrost (ice‐wedge pseudomorphs) and decreased humidity (composite wedge casts) but also the degradation of permafrost (large‐scale involutions) and, finally, the establishment of deep seasonal frost (frost cracks). The diversity of structures in the study region appears to result from local conditions rather than increasing continentality of climate towards the east.
Internalization routes of cell‐penetrating melanoma antigen peptides into human dendritic cells
Authors: Buhl Timo , Braun Andrea , Forkel Susann , Möbius Wiebke , van Werven Lars , Jahn Olaf , Rezaei‐Ghaleh Nasrollah , Zweckstetter Markus , Mempel Martin , Schön Michael P. , Haenssle Holger A.
Published: November 2013

Optimized delivery of antigens combined with sustainable maturation of dendritic cells (DCs) is crucial for generation of effective antitumoral immune responses. Multiple approaches for ex vivo antigen loading and improvement in immunogenicity have been described. We have recently established a single‐step protocol consisting of a fusion peptide (a sequence of the melanoma antigen Melan‐A and a cationic cell‐penetrating HIV TAT domain) bound in complexes with a toll‐like receptor agonist. As the exact cellular uptake mechanisms of TAT‐coupled antigens have been a matter of considerable debate and significantly depend on cell type, cargo and concentrations, we evaluated internalization routes into human immature DCs in comparison with non‐phagocytic cell lines. We found that Melan‐A‐TAT fusion peptide uptake by DCs is mainly energy dependent, superior compared with polylysine‐coupled Melan‐A and significantly higher in DCs as compared with Jurkat cells or HUVECs. Furthermore, we could track the uptake of the fusion peptide exclusively through early endosomes to lysosome compartments after 90 min by fluorescence microscopy and immunoelectron microscopy. Specific endocytosis inhibitors revealed major internalization of the fusion peptide by DCs via clathrin‐mediated endocytosis, whereas uptake by non‐phagocytic HUVECs differed significantly, involving macropinocytosis as well as clathrin‐mediated endocytosis. As our understanding of the processes involved in internalization of TAT‐coupled cargos by human DCs broadens, and DC activation becomes available by single‐step procedures as described, further development of simultaneous DC maturation and intra‐cellular peptide targeting is warranted.
Vitalist strategies in contemporary Western herbal medicine
Authors: Hiller Sabine
Published: November 2013

Vitalism has long been discredited and considered superfluous in the life sciences. How does contemporary Western herbal medicine (CWHM) justify its continued adherence to vitalism? While the appeals made to philosophy, science and complexity theory by CWHM authors are unsuccessful, vitalism plays an important role in providing a distinct professional identity.
Gene–environment interactions at the FKBP5 locus: sensitive periods, mechanisms and pleiotropism
Authors: Zannas A. S. , Binder E. B.
Published: November 2013

Psychiatric phenotypes are multifactorial and polygenic, resulting from the complex interplay of genes and environmental factors that act cumulatively throughout an organism's lifetime. Adverse life events are strong predictors of risk for a number of psychiatric disorders and a number of studies have focused on gene–environment interactions (GxEs) occurring at genetic loci involved in the stress response. Such a locus that has received increasing attention is the gene encoding FK506 binding protein 51 (FKBP5), a heat shock protein 90 cochaperone of the steroid receptor complex that among other functions regulates sensitivity of the glucocorticoid receptor. Interactions between FKBP5 gene variants and life stressors alter the risk not only for mood and anxiety disorders, but also for a number of other disease phenotypes. In this review, we will focus on molecular and system‐wide mechanisms of this GxE with the aim of establishing a framework that explains GxE interactions. We will also discuss how an understanding of the biological effects of this GxE may lead to novel therapeutic approaches.
Knowledge, attitudes and competence in nursing practice of typhoon disaster relief work among Chinese nurses: A questionnaire survey
Authors: Jiang Lin , He Hong‐Gu , Zhou Wen‐Guang , Shi Su‐Hua , Yin Ting‐Ting , Kong Yue
Published: November 2013

The aim of this paper is to examine the relationships among nurses' knowledge of, attitudes towards and level of competence in nursing practice, as well as factors influencing nurses' competence in nursing practice, in typhoon disaster relief work. A cross‐sectional descriptive study was conducted using a self‐developed questionnaire to obtain data from 607 nurses working in four tertiary hospitals and two secondary hospitals in Fujian, China, in November 2011. Our findings show that the nurses' average percentage scores on their responses to questions in the domains of knowledge, attitudes and practice were 66.33%, 68.87% and 67.60%, respectively. The findings demonstrated a significant positive relationship between nurses' attitudes and their practice. Nurses' working unit, prior training in typhoon disaster relief, current position of employment and attitudes were significant predictors of nurses' competence in practice. The results indicate that strategies need to be developed for nurses to improve their knowledge, attitudes and practice.
Sensitivity of Two Quinoa (ChenopodiumquinoaWilld.) Varieties to Progressive Drought Stress
Authors: Sun Y. , Liu F. , Bendevis M. , Shabala S. , Jacobsen S.‐E.
Published: November 2013

Quinoa (ChenopodiumquinoaWilld.) is a highly nutritious Andean seed crop which shows great potential to grow under a range of hostile environments. The objective of this study was to investigate the differences of drought tolerance of a Bolivian (Achachino) and a Danish (Titicaca) variety, and especially drought‐related adaption strategies. Soil water status was expressed as the fraction of transpirable soil water (FTSW). Relative stomatal conductance (RSC), relative transpiration (RT) and relative leaf water potential (RLW) were calculated by determining stomatal conductance, transpiration rate and leaf water potential of the drought‐treated plants relative to those of fully irrigated plants. The responses of RSC, RT and RLW to decreasing FTSW were described by a linear‐plateau model. The critical value of FTSW was the threshold of FTSW where the parameters studied decreased. The thresholds increased CS for stomatal conductance, CT for transpiration and CLfor leaf water potential. Achachino showed significantly lower CT and CL when compared with Titicaca, implying that transpiration and leaf water potential were less affected under mild drought conditions in the Bolivian variety. CS in Achachino was significantly higher than CL and CT, which indicated that stomatal conductance declined before transpiration and leaf water potential were reduced. Such difference was found in Titicaca where reduction of leaf area had more effect on transpiration than stomatal closure. Slower growth rate and smaller leaf area in combination with a lower stomatal conductance was found to contribute to drought resistance in Achachino. ABA concentration in the xylem sap tended to increase in both varieties after 2 days onset of drought, prior to decline in leaf water potential. Titicaca showed significantly (P < 0.05) higher ABA concentration when compared with Achachino under both fully irrigated and drought conditions. Titicaca had higher xylem nutrient concentration in comparison with Achachino in both fully‐watered and drought plants at day 2 after onset of soil drying. It was concluded that Titicaca was more sensitive to progressive drought than Achachino which avoided water loss by means of lower growth rate and smaller leaf area.
Comparative Analysis of mRNA Expression of Surface Antigens between Histiocytic and Nonhistiocytic Sarcoma in Dogs
Authors: Yamazaki H. , Takagi S. , Oh N. , Hoshino Y. , Hosoya K. , Okumura M.
Published: November 2013

Background

Definitive diagnosis of histiocytic sarcoma (HS) in dogs is relatively difficult by conventional histopathological examination because objective features of HS are not well defined.

Hypothesis

Quantitative analysis of mRNA expression of selected cellular surface antigens (SAs) specific to HS in dogs can facilitate objective and rapid diagnosis.

Animals

Dogs with HS (n = 30) and dogs without HS (n = 36), including those with other forms of lymphoma (n = 4), inflammatory diseases (n = 6), and other malignant neoplasias (n = 26).

Methods

Retrospective clinical observational study. Specimens were collected by excisional biopsy, needle core biopsy, or fine needle aspiration. To determine HS detection efficacy, mRNA expression levels of selected SAs specific to HS in dogs, including MHC class IIα, CD11b, CD11c, and CD86, were quantitatively analyzed using real‐time quantitative polymerase chain reaction.

Results

Each SA mRNA expression level was significantly higher in HS dogs than in non‐HS dogs (P = .0082). Cutoff values for discriminating between HS and non‐HS dogs based on these expression levels were calculated on the basis of receiver‐operating characteristic analysis. Accuracy of the cutoff values, including MHC class IIα, CD11b, CD11c, and CD86, was 87.9, 86.4, 86.4, and 84.8%, respectively.

Conclusions and Clinical Importance

Our results suggest that quantitative analysis of mRNA expression of the selected SAs could be an adjunctive diagnostic technique with high diagnostic accuracy for HS in dogs. Substantial investigation is required for exclusion of diseases with similar cell types of origin to lymphoma.
Time to adequate oxygenation following ventilation using the Enk oxygen flow modulator versus a jet ventilator via needle cricothyrotomy in rabbits
Authors: Wong Carrie F. P. , Yuen Vivian M. , Wong Gordon T. C. , To Jensen , Irwin Michael G.
Published: November 2013

Introduction

Limited information is available on the management of the ‘cannot intubate, cannot ventilate’ (CICV) situation in infants. We compared the time to achieve adequate oxygenation following rescue ventilation using the Enk oxygen flow modulator (OFM) with a jet ventilator in a simulated CICV situation using the rabbit as an infant respiratory model.

Methods

Following institutional ethics committee approval, needle cricothyrotomy was performed under direct vision in nine anesthetized rabbits following surgical exposure of the larynx. After ensuring adequate level of anesthesia and analgesia, and confirming proper positioning of the 18G cannula, apnea was induced by the administration of myorelaxant and the SpO2 was allowed to drop to 75% before initiating rescue ventilation via either the OFM or jet ventilator.

Results

Five rabbits were ventilated with the OFM and four with the jet ventilator. Ventilation was maintained with either device for 15 min. All rabbits were successfully rescued using either device. There was no statistical difference in the time required for SpO2 to return to 80%, 85%, 90%, and 95%.

Conclusions

Both devices facilitated successful rescue ventilation through a needle cricothyrotomy.
Implicit memory formation using the word stem completion task during anesthesia in children
Authors: Bonett Emily , Pham Xiuzhi , Smith Katherine R. , Howard Kelly , Sheppard Suzette , Davidson Andrew
Published: November 2013

Aims

To determine whether there is evidence of implicit memory formation during pediatric anesthesia using the word stem completion task.

Background

In adults, there is mixed evidence for implicit memory formation during anesthesia; however, there is no evidence in children. Implicit memory in adults has been detected using the word stem completion task. This test has not been used in a pediatric anesthetic setting.

Methods

A total of 200 patients aged 7–12 were randomized to hear one of the two lists of 10 words played continuously while anesthetized. Group 1 heard List A and Group 2 heard List B. Postoperatively, 194 completed a word stem completion task where they were required to complete the stems (the first part of words) corresponding to the words on the two word lists combined, with the first word that came to mind.

Results

Group 1 completed a mean of 2.78 words correctly from List A and a mean of 2.70 words correctly from List B. Group 2 completed a mean of 3.29 words correctly from List A and a mean of 3.66 words correctly from List B. For List A, there was no evidence (P = 0.70) for an association between intraoperative exposure to this list and the odds of successfully completing a stem from this list with the corresponding target word. There was little evidence (P = 0.09) for an association with List B.

Conclusion

This study found no strong evidence that children form implicit memories for auditory words during anesthesia. Given the difference between lists, future research is warranted using carefully chosen word stems.
The Role of Pain Catastrophizing in Experimental Pain Perception
Authors: Kristiansen Frederik L. , Olesen Anne E. , Brock Christina , Gazerani Parisa , Petrini Laura , Mogil Jeffrey S. , Drewes Asbjørn M.
Published: November 2013

Background

Pain is a subjective experience influenced by multiple factors, and tremendous variety within individuals is present. To evaluate emotional state of pain, catastrophizing score can be used. This study investigated pain catastrophizing ratings in association with experimental pain perception.

Method

Experimental pain was induced using thermal heat and cold stimulation of skin, mechanical stimulation of muscle and bone, and thermal, mechanical, and electrical stimulation of the gastrointestinal tract in healthy participants (N = 41). Prior to experimental sessions, a pain catastrophizing questionnaire was filled out by each participant.

Results

Based on the median catastophizing score, participants were divided into two groups: noncatastrophizers and low‐catastrophizers. No significant difference was found between low‐catastrophizers and noncatastrophizers in thermal heat stimulation of skin, mechanical stimulation of muscle and bone, and rectal electrical stimulation (All P > 0.05). Low‐catastrophizers were more sensitive to visceral thermal stimulation (4.7%, P = 0.02) and visceral mechanical stimulation (29.7%, P = 0.03). For participants that completed the 120 seconds ice water stimulation, noncatastrophizers reported 13.8% less pain than low‐catastrophizers (P = 0.02). A positive correlation between PCS score and pain perception on cold pressor test was found (r = 0.4, P = 0.02). By extrapolating data, further analysis of the total group was performed and no differences (both P > 0.05) were observed.

Conclusion

Even small increments in pain catastrophizing score can influence pain perception to deep and tonic stimulations. Catatrophizing may partly explain the variability found in experimental pain studies.
COMPARISON BETWEEN ULTRASONOGRAPHIC AND CLINICAL FINDINGS IN 43 DOGS WITH GALLBLADDER MUCOCELES
Authors: Choi Jihye , Kim Ahyoung , Keh Seoyeon , Oh Juyeon , Kim Hyunwook , Yoon Junghee
Published: November 2013

Cholecystectomy is the current standard recommended treatment for dogs with gallbladder mucoceles. However, medical management with monitoring has also been recommended for asymptomatic dogs. The purpose of this retrospective study was to compare ultrasonographic patterns of gallbladder mucoceles with clinical disease status in a group of dogs. For each included dog, the ultrasonographic pattern of the mucocele was classified into one of six types: type 1, immobile echogenic bile; type 2, incomplete stellate pattern; type 3, typical stellate pattern; type 4, kiwi like pattern and stellate combination; type 5, kiwi like pattern with residual central echogenic bile; and type 6, kiwi like pattern. A total of 43 dogs were included. Twenty‐four dogs, including 11 dogs with gallbladder rupture, were symptomatic. Nineteen dogs were asymptomatic. Cholecystectomy (n = 19), medical therapy (n = 17), or monitoring (n = 6) treatments were applied according to clinical signs and owners’ requests. One dog suspected of having gallbladder rupture was euthanized. Frequencies of gallbladder mucocele patterns were as follows: type 1 = 10 (23%), type 2 = 13 (30%), type 3 = 5 (12%), type 4 = 11 (26%), type 5 = 4 (9%), and type 6 = 0. In dogs with gallbladder rupture, type 2 (8/13) was the most common. No significant correlations were found between ultrasonographic patterns of gallbladder mucoceles and clinical disease status or gallbladder rupture. Findings indicated that ultrasonographic patterns of gallbladder mucoceles may not be valid bases for treatment recommendations in dogs.
Engineering a Pressurised Wind Tunnel Aimed at Developing CO2 Turbomachinery
Authors: Sánchez D. , Monje B. , Chacartegui R. , Barragán J. M. , Pajuelo E. , Gómez J. R. , Sánchez T.
Published: November 2013

The number of people researching the supercritical CO2 power cycle has largely increased in the last few years. Just to mention, in contrast to the one or two technical papers in the topic submitted yearly to Turbo Expo until 2011, the number of contributions in the topic has rocketed to twenty in the last conference held in Copenhagen. Such astounding and unexpected growth has eventually given rise to the International Gas Turbine Institute creating a new dedicated technical committee. Nevertheless, in spite of the large attention captured by the SCO2 power cycle, most efforts are devoted to the adaption of existing equipment (turbomachinery and heat exchangers) rather than to analysing the particular features of this unconventional working fluid. Hence, the test plants already in operation as well as the numerous CFD analyses under development rely on the existing ideal-gas based knowledge typically used by the gas turbine industry. This is the reason why the compressors in these test plants are far from their theoretical performance (typically 65% real vs. 80% theoretical efficiency).

The partnership formed by the University of Seville and Altran has engineered a first-of-a-kind wind tunnel for aerodynamic testing of carbon dioxide flows at high pressure. This unique facility incorporates special features like new seals, variable pressure operation and remote data acquisition which cannot be adapted from conventional wind tunnels. This development is expected to provide the industry with a tool to increase the efficiency of SCO2 turbomachinery by large what would eventually allow for a faster and wider deployment of the technology. The university of Seville and Altran are currently raising capital to construct the facility.
Study on Transient Vibration of Mistuned Bladed Disk Passing Through Resonance
Authors: Kaneko Yasutomo
Published: November 2013

In a variable speed engine, it is impossible to avoid the resonance during operation. In a constant speed engine, the resonance during start-up or shut-down also cannot be avoided. Therefore, the increase of the acceleration rate in passing through the resonance has been considered as one of the effective methods for reducing the vibratory stress of the blade and increasing the reliability of the turbomachinery. In this study, the transient vibration analysis of the mistuned bladed disk passing through the resonance is carried out, using the conventional modal analysis method and the numerical integration method. First, the mistuned bladed disk is modeled by the equivalent spring-mass model, and the steady frequency response analysis is carried out by the Monte Carlo simulation, in order to obtain the worst mistuning pattern. Second, for the mistuned bladed disk of the worst mistuning pattern, the transient vibration analysis in passing through the resonance is carried out, and the effect of the acceleration rate and the blade damping on the transient vibration response is examined in detail. From these results, it is concluded that the larger the acceleration rate is, the smaller the mistuning effect is.
Compressor Modifications for 300 MW IGCC Gas Turbine Stable Behaviour
Authors: Cerri Giovanni , Basilicata Carmine , Giovannelli Ambra
Published: November 2013

Economic reasons, leading to the use of coal and the environmental concerns, call for clean technologies for the electric power production. Accordingly the adoption of Integrated Gasification Combined Cycle (IGCC) plants with Carbon Capture and Storage (CCS) has been pushed. Such a technology is promising but it still shows some critical aspects. Some of them are related to stable and controllable operations of commercially available Gas Turbines (GTs) designed to be fed with Natural Gas (NG) once the original fuel is replaced by the hydrogen-rich syngas produced in an IGCC-CCS plant.

The thermo-physical properties of the H2-rich syngas require investigations and modifications of the combustor and of the turbomachines to meet stable and safe GT behaviour. Such properties strongly affect the matching between GT compressor and expander.

To run the GT with the syngas, various options can be taken into account. Some of them do not require GT flow function modifications, while other options involve compressor and expander structural changes.

In the present paper some compressor modifications that can be adopted to maintain an F Class GT performance and stability are explored. Such modifications have been analysed by means of a high fidelity quasi-one-dimensional model based on an Elemental Component Finite Volume approach for the GT sizing and analysis. Results have been compared and deeply discussed.
Labyrinth Seal and Pocket Damper Seal High Pressure Rotordynamic Test Data
Authors: Vannini Giuseppe , Cioncolini Stefano , Del Vescovo Giuseppe , Rovini Massimiliano
Published: November 2013

The current centrifugal compressor design for the Oil & Gas market is more and more challenging, and the presence of many competitors is pushing technology towards both a casing size reduction and a rotational speed increase. The first point is leading to an increase in the number of wheels per rotor (to do the same service), and the second point is forcing to cross two or even three rotor modes (hence a higher control of rotor damping is necessary). The two points together are leading to increase the rotor “Flexibility Ratio” (defined as the ratio between the Maximum Continuous Speed and the first critical speed at infinite support stiffness according to [1]), and finally the rotordynamic stability is very much challenged.

The centrifugal compressors rotordynamic stability is strongly related to the internal seals’ dynamic behaviour, and for this reason, the authors’ company decided several years ago to develop internally a High Pressure Seal Test Rig [2] to measure internal seals stiffness and damping. The rig is now in operation, and in a previous paper the authors described its main capabilities, the applied identification procedures and the preliminary test results captured for a long Labyrinth seal (smooth rotor, straight toothed stator) tested up to 200bar.

This paper is intended to show more data for the same long Laby with special focus on some peculiar test as:

• Negative preswirl test

• Single frequency vs. Multi-frequency test

• Offset vs. Centered Seal test

The negative preswirl test shows a drastic change in the effective damping (from destabilizing to stabilizing) and provides a support in favor of the selection of swirl reversal devices at seals upstream.

The multi-frequency excitation test approach (based on the concurrent presence of several frequencies not multiples at each other) is compared with a single frequency excitation providing similar results and thus confirming the soundness of the multiple effects linear superimposition assumption.

The effect of a static offset (simulating the real position of a rotor inside an annular seal) is also investigated proving that the relevant impact is negligible within the range of eccentricity explored (10% of seal clearance).

Moreover, a Pocket Damper Seal (PDS) with the same nominal diameter, clearance and effective length has been tested (up to 300bar) and compared with the Laby. As expected, the PDS shows both a higher effective stiffness and damping at the same test conditions, so the promising results already collected in a previous test campaign which was performed on a smaller scale and lower pressure test rig [3] were mostly confirmed with the only exception for the effective damping cross-over frequency which was lower than expected.
Creep-Fatigue Life Prediction of Stop and Regulating Valves on the Intermediate-Pressure Section of a 1000MW Steam Turbine
Authors: Mao Jianfeng , Zhang Junhui , Wang Weizhe , Liu Yingzheng
Published: November 2013

The stop®ulating integrated valve on the intermediate-pressure (IP) section of a 1000MW steam turbine is presented in this paper. A multiaxial model based on continuum damage mechanics (CDM) is applied to life prediction of the valve. The transient stress and the temperature fields of the valve in a 1000MW supercritical steam turbine are investigated by using finite element method (FEM) for fatigue-creep. Since the turbine typically runs 120 days between starts, a simplified mission profile for a 120-day block was created. Accordingly, the 120-day loading block with plasticity and creep was run repetitively to achieve a 22 years creep-fatigue life prediction. The interaction between creep and fatigue was considered in total damage in proper order. Due to highly complex stress and structure, the multiaxial factors for fatigue and creep are assessed from the temporal and spatial points of view respectively. Furthermore, the creep-fatigue damage of the integrated valve is discussed in relation to the multiaxial factors. The results drawn from the multiaxial CDM model give a satisfactory life prediction on the valve.
Analysis of an Oscillating Wing in a Power-Extraction Regime Based on the Compressible Reynolds-Averaged Navier-Stokes Equations and the K–ω SST Turbulence Model
Authors: Campobasso M. Sergio , Piskopakis Andreas , Yan Minghan
Published: November 2013

The aerodynamic performance of an oscillating wing device to extract energy from an oncoming air flow is here investigated by means of time-dependent turbulent flow simulations performed with a compressible Reynolds-averaged Navier-Stokes research solver using the k–ω Shear Stress Transport model. Previous studies of this device have focused primarily on laminar flow regimes, and have shown that the maximum aerodynamic power conversion can achieve values of about 34 %. The comparative analyses of the energy extraction process in a realistic turbulent flow regime and an ideal laminar regime, reported for the first time in this article, highlight that a) substantial differences of the flow aerodynamics exist between the two cases, b) the maximum efficiency of the device in turbulent conditions achieves values of nearly 40 %, and c) further improvement of the efficiency observed in turbulent flow conditions is achievable by optimizing the kinematic characteristics of the device. The theory underlying the implementation of the adopted compressible turbulent flow solver, and several novel algorithmic features associated with its strongly coupled explicit multigrid integration of the flow and turbulence equations, are also presented.
Anti-Optimisation Applied to the Analysis of Rotor/Stator Interaction
Authors: Butlin Tore , Batailly Alain
Published: November 2013

There is a drive towards minimising operating clearances within turbomachines in order to limit reverse leakage flows and hence improve their efficiency. This increases the likelihood of contact occurring between the blade and the casing, which can give rise to high amplitude vibration. Modelling this interaction represents a significant computational challenge. The non-linear contact precludes the use of well-established linear methods, and is also subject to uncertainties: the contact law is imprecisely known and the exact geometry of imperfections that trigger contact may be unknown.

In this paper a novel approach is presented that aims to account for the uncertainties associated with the non-linearity in a non-probabilistic way. The worst case is sought, by framing the system as a constrained anti-optimisation problem. The target to be maximised represents a metric of the output of interest. The degrees of freedom of the anti-optimisation are the non-linear input forces (considered as external loads), and the constraints are designed to capture what is thought to be known about the non-linear contact law and geometry.

A realistic three-dimensional model of a turbine blade is used to explore the approach, with contact considered at the leading and trailing edge. The blade dynamics are described in terms of a linear transfer function matrix and the target metric of interest is chosen to be the peak displacement of the contact points. The non-linearity is taken to result from an offset shaft, giving a sinusoidal clearance variation. The blade is driven at constant frequency and the scope of the study is limited to finding bounds on periodic solutions. A variety of constraint conditions are explored that describe aspects of the non-linearity. For example, only compressive forces are permitted (no tension from the contact), and the displacement must not exceed the clearance.

The method yields encouraging initial results: constraints can be identified that give efficient estimates of the upper bound response of the system as a function of drive frequency. The results are compared with a benchmark time-domain simulation and are found to correctly over-predict the response without being overly conservative. Broad trends are also in agreement with the benchmark solution. The proposed method appears to be a promising approach for efficiently accounting for uncertainties associated with the non-linearity and thus improving blade design.
Common Practice for Verification of Integrity of New Emerging Technologies for Heavy Crude Oil Pumping Applications
Authors: Delgado Hector , Kurz Rainer , Brun Klaus
Published: November 2013

In the current emerging development of technologies for heavy crude oil pumping, it is essential to be able to predict and verify the reliable operation of new pumping technologies. Engineering studies are required for verification of the reliable operation of crude oil pumps and pumping systems. The specific requirements to be met by the pump and pumping system for ensuring reliable operation vary depending on their characteristics. However, it has been commonly based on the author’s experience to perform several analyses specifically for heavy crude oil applications including positive displacement pumps. Such analyses include skid mechanical vibration study, coupled acoustic-mechanical piping analysis, and lateral and torsional rotordynamic study.

This paper presents a case study where the previously mentioned studies are conducted for a gas turbine driven screw pump train. A lateral rotordynamic analysis has been conducted by the turbomachinery original equipment manufacturer (OEM) and its details are not included in this paper. The results from the skid mechanical vibration study confirm that vibration issues are not predicted during normal or transient operation. A coupled acoustic-mechanical analysis identifies areas of concern that can then be addressed to avoid excessive vibration levels on the piping. Finally, results from a torsional rotordynamic study verify that vibration levels are expected to be within allowable limits.
Study on the Influence of Total Pressure Distortion on End Wall Flow Field in a Supersonic Compressor
Authors: Sun Peng , Gao Haiyang , Zhong Jingjun , Yang Muxiao
Published: November 2013

Inlet total pressure distortion has great effects on the performance and stability of compressors. The Non-uniform flow influences the flow field of rotor tip and stator hub more significantly. If stall occurs, it often begins in one or both of these two regions. Which region is more sensitive to the nonuniform flow and how the mechanism of distorted flow influences the compressor flow field are topics of great importance and should be studied carefully.

In this paper, the exploration of how the inlet total pressure distortion influences the flow field of rotor and stator end walls will base on the study of one-stage supersonic compressor with one rotor and one stator. Two aspects of the results will be analyzed in detail. The first aspect is about the dynamic response of shock wave to the inlet parameters in rotor casing area, the variation of shock wave intensity and structure with inlet flow parameters, and the mechanism of shock motion. The process of flow parameters variation in rotor cycle can be divided into four stages. The second aspect is about the analysis on the flow parameters near end walls and development of corner separation in stator. The study indicates that corner separation is induced by the distorted flow near stator hub and casing. Flow structures in each passage are different due to the different positions of distorted regions. The relationship between intensity and range of corner separation, and the change of inlet velocity angle and flow capacity, will be discussed in detail.
Two Phase CFD Modelling of a Spiral Bevel Gear Using Particle Injections and a Wall Film Model
Authors: Turner A. , Morvan H. P. , Simmons K.
Published: November 2013

The capability to model an aeroengine internal gearbox in its entirety using CFD is currently hampered by the complexity of the two-phase, highly rotating system and the computational resource required. The University of Nottingham’s Technology Centre in Gas Turbine Transmission Systems has developed a representation of a shrouded gear based around a cone geometry with momentum sources driving the flow that works well for single phase flow. The next phase of the study is to investigate the capability and limitations of this momentum source model for two phase flow and a significant step towards this is reported here.

In this paper a geometrically representative shrouded gear model is generated and oil droplets are released at key inlet locations. The impact locations of these droplets are mapped to generate data for comparison with the momentum source model. A thin film model is applied such that film build up can be investigated. Droplets entering the shroud at inlet impact towards the lower part of the shroud whereas those introduced at a location representing an into-mesh jet impact more evenly along the shroud. The film model is computationally expensive: computations show film building up towards the top of the shroud but attaining steady state has not been possible.

Droplets are released and tracked within the momentum source CFD model. Droplets do not impact the shroud at comparable locations to the representative geometry cases showing that the momentum source representation cannot be used to examine in detail oil behaviour under the shroud. Overall bulk flows cannot yet be compared and further necessary work is identified.
Blade Tip Shape Optimization for Enhanced Turbine Aerothermal Performance
Authors: De Maesschalck C. , Lavagnoli S. , Paniagua G.
Published: November 2013

In high-speed unshrouded turbines tip leakage flows generate large aerodynamic losses and intense unsteady thermal loads over the rotor blade tip and casing. The stage loading and rotational speeds are steadily increased to achieve higher turbine efficiency, and hence the overtip leakage flow may exceed the transonic regime. However, conventional blade tip geometries are not designed to cope with supersonic tip flow velocities. A great potential lays in the modification and optimization of the blade tip shape as a means to control the tip leakage flow aerodynamics, limit the entropy production in the overtip gap, manage the heat load distribution over the blade tip and improve the turbine efficiency at high stage loading coefficients.

The present paper develops an optimization strategy to produce a set of blade tip profiles with enhanced aerothermal performance for a number of tip gap flow conditions. The tip clearance flow was numerically simulated through two-dimensional compressible Reynolds-Averaged Navier-Stokes (RANS) calculations that reproduce an idealized overtip flow along streamlines. A multi-objective optimization tool, based on differential evolution combined with surrogate models (artificial neural networks), was used to obtain optimized 2D tip profiles with reduced aerodynamic losses and minimum heat transfer variations and mean levels over the blade tip and casing. Optimized tip shapes were obtained for relevant tip gap flow conditions in terms of blade thickness to tip gap height ratios (between 5 and 25), and blade pressure loads (from subsonic to supersonic tip leakage flow regimes) imposing fixed inlet conditions. We demonstrated that tip geometries which perform superior in subsonic conditions are not optimal for supersonic tip gap flows. Prime tip profiles exist depending on the tip flow conditions. The numerical study yielded a deeper insight on the physics of tip leakage flows of unshrouded rotors with arbitrary tip shapes, providing the necessary knowledge to guide the design and optimization strategy of a full blade tip surface in a real 3D turbine environment.
Balancing Efficiency and Stability in the Design of Transonic Compressor Stages
Authors: Ellbrant Lars , Eriksson Lars-Erik , Mårtensson Hans
Published: November 2013

The paper describes an efficient design method for highly loaded transonic compressor stages which considers a balance between efficiency at the design point and stability at part-speed. Because of the high dimensionality of the problem, two levels of model complexity are included in the design method. The first level consists of optimizing the rotor and stator profiles positioned at three streamtubes along the span. The streamtube height and radius variations are included in the computational domain and it is analyzed using a 3D RANS solver incorporating a mixing plane between the components. Due to the relatively low complexity of this quasi-3D analysis, it is fast enough to explore a large design space. With the aid of the resulting pareto-fronts, the designer can select profiles with the appropriate trade between stability and efficiency. The initial 3D compressor stage is generated based on the selected 2D profiles and the method continues to the higher complexity mode where the 3D shapes of the rotor and stator are optimized to gain further performance improvements. To verify that the design method is feasible, it is used to re-design the first compressor stage of a three-stage highly loaded transonic compressor. The compressor stage designed with the presented design method has higher part-speed stability without a compromise in the efficiency compared to the original design. This is also verified when analyzing the new design in the full compressor module.
Physics of Vibrating Airfoils at Low Reduced Frequency
Authors: Vega Almudena , Corral Roque
Published: November 2013

The unsteady aerodynamics of low pressure turbine vibrating airfoils in flap mode is studied in detail using a frequency domain linearized Navier-Stokes solver. Both the travelling-wave and influence coefficient formulations of the problem are used to highlight key aspects of the physics and understand different trends such as the effect of reduced frequency and Mach number. The study is focused in the low-reduced frequency regime which is of paramount relevance for the design of aeronautical low-pressure turbines and compressors. It is concluded that the effect of the Mach number on the unsteady pressure phase can be neglected in first approximation and that the unsteadiness of the vibrating and adjacent airfoils is driven by vortex shedding mechanisms. Finally a simple model to estimate the work-per-cycle as a function of the reduced frequency and Mach Number is provided. The edge-wise and torsion modes are presented in less detail but it is shown that acoustic waves are essential to explain its behaviour. The non-dimensional work-per-cycle of the edge-wise mode shows a large dependence with the Mach number while in the torsion mode a large number of airfoils is needed to reconstruct the work-per-cycle departing from the influence coefficients.
A Reduced-Order Model for Turbomachinery Flows Using Proper Orthogonal Decomposition
Authors: Brenner Thomas A. , Carpenter Forrest L. , Freno Brian A. , Cizmas Paul G. A.
Published: November 2013

This paper presents the development of a reduced-order model based on the proper orthogonal decomposition (POD) method. The POD method has been developed to predict turbomachinery flows modeled by the Reynolds-averaged Navier–Stokes equations. The purpose of using a POD-based reduced-order model is to decrease the computational cost of turbomachinery flows. The POD model has been tested for two configurations: a canonical channel with a bump case and the transonic NASA Rotor 67 case. The Rotor 67 case has been simulated at design wheel speed and at three off-design conditions: 70, 80, and 90% of the wheel speed. The results of the POD-based reduced-order model where in excellent agreement with the full-order model results. The computational time of the reduced-order model was approximately one order of magnitude smaller than that of the full-order model.
Validation of a CFD Methodology for Variable Speed Power Turbine Relevant Conditions
Authors: Ameri Ali A. , Giel Paul W. , McVetta Ashlie B.
Published: November 2013

Analysis tools are needed to investigate aerodynamic performance of Variable-Speed Power Turbines (VSPT) for rotorcraft applications. The VSPT operates at low Reynolds numbers (transitional flow) and over a wide range of incidence. Previously, the capabilities of a published three-equation transition and turbulence model in predicting the transition location for three-dimensional heat transfer problems were assessed. In this paper, results are presented of a post-diction exercise using a three-dimensional flow in a transonic linear cascade comprising VSPT blading. The measured pressure distributions and integrated spanwise total pressure losses and flow angles for two incidence angles corresponding to cruise (i = +5.8°) and takeoff (i = –36.7°) were used for this study. For the higher loading condition of cruise and the negative incidence condition of takeoff, overall agreement with data may be considered satisfactory but areas of needed improvement are also indicated.
Efficient Computation of Large Pitch Ratio Transonic Flow in a Fan With Inlet Distortion
Authors: Sharma Gaurav , Zori Laith , Connell Stuart , Godin Philippe
Published: November 2013

Modeling the unsteady flow of a fan subject to an inlet distortion is computationally expensive due to the need to model the full-annulus. Using the Fourier Transformation (FT) method in ANSYS CFX, which recognizes phase-shifted periodic boundary conditions, the fan inlet distortion simulation can be achieved efficiently by solving just two passages. The FT method can handle very large inlet distortion to blade passage pitch ratios such as the case of the problem simulated in this work. The analysis considers transonic flow through a fan with high bypass ratio subjected to an inlet total pressure distortion. The inlet disturbance traverses the inlet once per revolution and is intended to simulate the inlet flow distortion seen by an aircraft engine fan during take-off conditions. The pressure ratio across the fan is chosen so that the fan moves from a started to un-started condition as the disturbance moves past the inlet. This condition will provide a rigorous test of the FT method. The FT method is validated by comparing to the equivalent full-annulus unsteady solution. The FT unsteady solution compares remarkably well with the reference solution and is able to reproduce the detailed dynamics of the shock movement. Moreover, the solution from the FT method is also able to reproduce the efficiency, viscous effects and blade loading from the full-annulus case. The FT solution is obtained with a 5X reduction in CPU time and a 10X reduction in memory requirement.
Inverse Design of 3D Multi-Stage Transonic Fans at Dual Operating Points
Authors: Page James H. , Hield Paul , Tucker Paul G.
Published: November 2013

Semi-inverse design is the automatic re-cambering of an aerofoil, during a computational fluid dynamics (CFD) calculation, in order to achieve a target lift distribution while maintaining thickness, hence “semi-inverse”. In this design method, the streamwise distribution of curvature is replaced by a stream-wise distribution of lift. The authors have developed an inverse design code based on the method of Hield (2008) which can rapidly design three-dimensional fan blades in a multi-stage environment. The algorithm uses an inner loop to design to radially varying target lift distributions, an outer loop to achieve radial distributions of stage pressure ratio and exit flow angle, and a choked nozzle to set design mass flow. The code is easily wrapped around any CFD solver.

In this paper, we describe a novel algorithm for designing simultaneously for specified performance at full speed and peak efficiency at part speed, without trade-offs between the targets at each of the two operating points. We also introduce a novel adaptive target lift distribution which automatically develops discontinuous changes of calculated magnitude, based on the passage shock, eliminating erroneous lift demands in the shock vicinity and maintaining a smooth aerofoil.