bluuebunny/crossref_metadata_2025 huggingface dataset:
Anti‐inflammatory mechanism of metformin and its effects in intestinal inflammation and colitis‐associated colon cancer
Authors: Koh Seong‐Joon , Kim Jung Mogg , Kim In‐Kyoung , Ko Su Hyuk , Kim Joo Sung
Published: November 2013

Background and Aim

The aim of this study is to evaluate the effect of metformin on intestinal inflammation.

Methods

COLO205 cells were pretreated with metformin and stimulated with tumor necrosis factor (TNF)‐α. Expression of interleukin (IL)‐8 was determined by luciferase assay and real‐time PCR. Inhibitor of kappaB (IκB) phosphorylation/degradation and adenosine monohosphate‐activated protein kinase (AMPK) activity were evaluated by Western blotting. DNA‐binding activity of transcription factor nuclear factor‐kappaB (NF‐κB) was assessed by electrophoretic mobility shift assay. In an acute colitis model, mice were given 4% dextran sulfate sodium (DSS) for 5 days. IL‐10−/− mice were used to evaluate the effect of metformin on chronic colitis. In an inflamation‐associated tumor model, mice were given a single intraperitoneal injection of azoxymethane followed by three cycles of 2% DSS for 5 days and 2 weeks of free water consumption.

Results

Metformin significantly inhibited IL‐8 induction in COLO 205 cells stimulated with TNF‐α. Metformin attenuated IκBα phosphorylation and NF‐κB DNA‐binding activity. Administration of metformin significantly reduced the severity of DSS‐induced colitis. In addition, DSS‐induced IκB kinase (IKK) activation was significantly reduced in mice treated with metformin. Metformin significantly attenuated the severity of colitis in IL‐10−/− mice, induced AMPK activity in intestinal epithelial cells, and inhibited the development of colitic cancer in mice.

Conclusions

These results indicate that metformin suppresses NF‐κB activation in intestinal epithelial cells and ameliorates murine colitis and colitis‐associated tumorigenesis in mice, suggesting that metformin could be a potential therapeutic agent for the treatment of inflammatory bowel disease.
The Oxytocin–Bone Axis
Authors: Colaianni G. , Tamma R. , Di Benedetto A. , Yuen T. , Sun L. , Zaidi M. , Zallone A.
Published: November 2013

We recently demonstrated a direct action of oxytocin (OT) on skeletal homeostasis, mainly mediated through stimulation of osteoblasts (OBs) formation and through the reciprocal modulation of osteoclast (OCs) formation and function. Thus, mice lacking the hormone or its receptor develop a low turnover osteoporosis that worsens with age in both sexes. The skeletons of OT (Ot) and OT receptor (Oxtr) null mice display a pronounced decrease in vertebral and femoral trabecular volume. At the cellular level, OBs from Ot KO and Oxtr KO mice exhibit lower mineralization activity and, at the mRNA level, all master genes for osteoblast differentiation are down‐regulated. Moreover, OT has dual effects on OCs: it increases osteoclast formation both directly, by activating nuclear factor kB (NFkB) and mitogen‐activated protein kinase (MAPK) signalling and, indirectly, through the up‐regulation of receptor activator nuclear factor‐kappaB ligand synthesis by OBs. On the other hand, it inhibits bone resorption by triggering cytosolic Ca2+ release and nitric oxide synthesis in mature OCs. OT is locally produced by osteoblasts acting as paracrine‐autocrine regulators of bone formation modulated by oestrogens. The oestrogen signal involved in this feedforward circuit is nongenomic because it requires an intact MAPK kinase signal transduction pathway, instead of the classical nuclear translocation of oestrogen receptor. The ability of oestrogen to increase bone mass in vivo is to some extent OXTR‐dependent. Thus, Oxtr KO mice injected 17β‐oestradiol did not show any effects on bone formation parameters, whereas the same treatment increases trabecular and cortical bone in wild‐type mice. An intact OT autocrine‐paracrine circuit appears to be essential for optimal skeletal remodelling.
Diphenyl diselenide differently modulates cardiovascular redox responses in young adult and middle-aged low-density lipoprotein receptor knockout hypercholesterolemic mice
Authors: Mancini Gianni , de Oliveira Jade , Hort Mariana Appel , Moreira Eduardo Luiz Gasnhar , Ribeiro-do-Valle Rosa Maria , Rocha João Batista Texeira , de Bem Andreza Fabro
Published: November 2013

Objectives

The present work aimed to investigate the effect of (PhSe)2 on cardiovascular age-related oxidative stress in hypercholesterolemic mice.

Methods

To this end, LDL receptor knockout (LDLr−/−) mice, 3 months (young adult) and 12 months (middle-aged) old, were orally treated with (PhSe)2.

Key findings

Hypercholesterolemia, regardless of age, impaired the mitochondrial antioxidant defence in the cardiac tissue, which was characterized by a decline in mitochondrial aortic glutathione (GSH) levels and increased reactive oxygen species production in the heart. (PhSe)2 treatment improved GSH levels, thioredoxin reductase (TRxR) and GSH reductase (GR) activity, and decreased malondialdehyde levels in the heart of young adult LDLr−/− mice. Moreover, (PhSe)2 increased GPx activity in both age groups, and GR activity in the aorta of middle-aged LDLr−/− mice.

Conclusions

Therefore, (PhSe)2 enhances the antioxidant defences in the cardiovascular system of LDLr−/− mice, which could explain its success as an anti-atherogenic compound.
Cardiovascular, Colloid Osmotic Pressure, and Hemostatic Effects of 2 Formulations of Hydroxyethyl Starch in Healthy Horses
Authors: Epstein K.L. , Bergren A. , Giguère S. , Brainard B.M.
Published: November 2013

Background

Lower molecular weight and molar substitution formulations of hydroxyethyl starch (HES) solutions might maximize cardiovascular function and colloid osmotic pressure (COP) and minimize adverse effects on coagulation.

Hypothesis/Objectives

To compare effects of 1 low and 1 high molecular weight and molar substitutionHESsolution on cardiovascular variables,COP, and hemostasis in normal horses.

Animals

Eight healthy adult horses.

Methods

Randomized, crossover designed study: 10 mL/kg bolus of 6%HES(600/0.75) (hetastarch) (HS), 6%HES(130/0.4) tetrastarch (TS), and 0.9% NaCl (NS). Variables recorded included central venous pressure (CVP), noninvasive arterial blood pressure, packed cell volume (PCV),COP, and automated platelet analysis (CT).

Results

Central venous pressure was increased for 8 hours after all treatment (baseline = 8.4 ± 3.8; 8 hours = 10.3 ± 3.5 cm H2O;P < .001).HSandTSproduced an increase in systolic arterial pressure (HS= 109.1 ± 11.9;TS= 109.5 ± 10.9 mmHg) and mean arterial pressure (HS= 80.4 ± 13.0;TS= 82.3 ± 10.1 mmHg) compared toNS(SAP= 103.2 ± 13.2 [P = .023];MAP= 74.2 ± 11.4 mmHg [P = .048]).PCVdecreased transiently withHS(baseline = 37.1 ± 4.4%; 1.5 hours = 31.6 ± 3.9%) andTS(baseline = 38.4 ± 3.9%; 1.5 hours = 32.2 ± 3.3%), but notNS(P = .007).COPwas greater withHS(1 hour; 24.0 ± 2.1 mmHg) andTS(8 hours; 25.9 ± 2.1 mmHg) thanNS(1 hour = 20.8 ± 2.6; 8 hours = 22.9 ± 3.1 mmHg;P < .001).CTwas greater at 8 (HS= 178.6 ± 36.9;TS= 121.9 ± 33.3;NS= 108.3 ± 23.6 seconds) and 24 hours (HS= 174.2 ± 41.7;TS= 100.8 ± 26.0;NS= 118.7 ± 38.7 seconds;P < .001) in horses receivingHSthanTSorNS.

Conclusion and Clinical Importance

BothTSandHSresulted in more effective volume expansion and arterial pressure support thanNS.TSproduced a more sustained effect onCOPwith shorter duration of adverse effects on platelet function thanHS.
UV‐laser‐based microscopic dissection of tree rings – a novel sampling tool for δ13C and δ18O studies
Authors: Schollaen Karina , Heinrich Ingo , Helle Gerhard
Published: November 2013

UV‐laser‐based microscopic systems were utilized to dissect and sample organic tissue for stable isotope measurements from thin wood cross‐sections.

We tested UV‐laser‐based microscopic tissue dissection in practice for high‐resolution isotopic analyses (δ13C/δ18O) on thin cross‐sections from different tree species. The method allows serial isolation of tissue of any shape and from millimetre down to micrometre scales. On‐screen pre‐defined areas of interest were automatically dissected and collected for mass spectrometric analysis.

Three examples of high‐resolution isotopic analyses revealed that: in comparison to δ13C of xylem cells, woody ray parenchyma of deciduous trees have the same year‐to‐year variability, but reveal offsets that are opposite in sign depending on whether wholewood or cellulose is considered; high‐resolution tree‐ring δ18O profiles of Indonesian teak reflect monsoonal rainfall patterns and are sensitive to rainfall extremes caused by ENSO; and seasonal moisture signals in intra‐tree‐ring δ18O of white pine are weighted by nonlinear intra‐annual growth dynamics.

The applications demonstrate that the use of UV‐laser‐based microscopic dissection allows for sampling plant tissue at ultrahigh resolution and unprecedented precision. This new technique facilitates sampling for stable isotope analysis of anatomical plant traits like combined tree eco‐physiological, wood anatomical and dendroclimatological studies.
Adherence to Pharmacological Pain Therapy in Patients with NonMalignant Pain: The Role of Patients' Knowledge of Pain Medication
Authors: Timmerman Leon , Stellema Rudolf , Stronks Dirk L. , Groeneweg George , Huygen Frank J. P. M.
Published: November 2013

Background

Nonadherence to pharmacological therapy is a common and underexposed problem in patients with chronic nonmalignant pain. It may lead to treatment failure and increased healthcare costs.

Methods

In this prospective observational study we analyzed the association between knowledge and adherence in the chronic nonmalignant pain population. We included 96 patients treated with a new pharmacological prescription. During the initial visit (T0), demographic variables, pain intensity, knowledge of the prescription (name, dose, and frequency), self‐reported adherence to the prescription, and general knowledge of pharmacological pain therapy (according to the Pain Knowledge Questionnaire, Dutch Language Version (PKQ‐DLV) were recorded. During two follow‐up visits (T1, T2), apart from demographics, these parameters were measured again.

Results

Adherence rates were 42%, 42%, and 46% at T0, T1 and T2, respectively. 53%, 59%, and 48% of patients had knowledge of their current prescription, and mean scores on the PKQ‐DLV were 56, 55, and 52 percent of the maximum scores, respectively, at T0, T1 and T2. A multivariate binary logistic regression analysis resulted in a significant contribution of knowledge of the prescription and of age to the prediction of adherence.

Conclusions

Knowledge of the analgesic prescription is associated with adherence and significantly contributes to the prediction of adherence to analgesic therapy. An interventional study is needed to determine whether increasing knowledge will improve medication adherence and therapy outcome in patients with chronic nonmalignant pain.
An inherited variant in the gene coding for vitamin D‐binding protein and survival from cutaneous melanoma: a BioGenoMEL study
Authors: Davies John R. , Field Sinead , Randerson‐Moor Juliette , Harland Mark , Kumar Rajiv , Anic Gabriella M. , Nagore Eduardo , Hansson Johan , Höiom Veronica , Jönsson Göran , Gruis Nelleke A. , Park Jong Y. , Guan Jian , Sivaramakrishna Rachakonda P. , Wendt Judith , Pjanova Dace , Puig Susana , Schadendorf Dirk , Okamoto Ichiro , Olsson Håkan , Affleck Paul , García‐Casado Zaida , Puig‐Butille Joan Anton , Stratigos Alexander J. , Kodela Elizabeth , Donina Simona , Sucker Antje , Hosen Ismail , Egan Kathleen M. , Barrett Jennifer H. , van Doorn Remco , Bishop D. Timothy , Newton‐Bishop Julia
Published: November 2013

An association between low serum vitamin D levels and poorer melanoma survival has been reported. We have studied inheritance of a polymorphism of the GC gene, rs2282679, coding for the vitamin D‐binding protein, which is associated with lower serum levels of vitamin D, in a meta‐analysis of 3137 melanoma patients. The aim was to investigate evidence for a causal relationship between vitamin D and outcome (Mendelian randomization). The variant was not associated with reduced overall survival (OS) in the UK cohort, per‐allele hazard ratio (HR) for death 1.23 (95% confidence interval (CI) 0.93, 1.64). In the smaller cohorts, HR in OS analysis was 1.07 (95% CI 0.88, 1.3) and for all cohorts combined, HR for OS was 1.09 (95% CI 0.93, 1.29). There was evidence of increased melanoma‐specific deaths in the seven cohorts for which these data were available. The lack of unequivocal findings despite the large sample size illustrates the difficulties of implementing Mendelian randomization.
Production of discernible disease phenotypes in Canna by five plant viruses belonging to the genera Potyvirus,Cucumovirus and Badnavirus
Authors: Rajakaruna P. , Shafiekhani M. , Kim T. , Payton M. , Chauhan R. , Verchot J.
Published: November 2013

Cannas are tropical and subtropical flowering perennial plants. The genus contains many species but most commercially grown cultivars are interspecific hybrids selected for their attractive foliage and flowers. Canna production is so lucrative that there are farmers and nurseries dedicated solely to its production. The specific issue that the canna industry faces is virus diseases. In this study, rhizomes of 24 canna cultivars were gathered and diagnostics conducted to detect Bean yellow mosaic virus (BYMV, Potyvirus), Canna yellow mottle virus (CaYMV, Badnavirus), Canna yellow streak virus (CaYSV, Potyvirus), Cucumber mosaic virus (CMV, Cucumovirus) and Tomato aspermy virus (TAV, Cucumovirus). Visual assessment of disease symptoms and diagnostic tests were carried out to identify the prevalent diseases and describe the symptoms that are associated with virus infection. BYMV, CaYMV and CaYSV caused severe mosaic and necrosis either in the leaf lamina or veins of infected leaves. Potyvirus infection suppressed red colouration in the foliage of some varieties. CaYMV and CaYSV often appeared in the same plant, suggesting they might represent a viral complex. CMV and TAV were rarely seen in these populations. Interestingly, CaYMV but not CaYSV could be mechanically inoculated to Phaseolus vulgaris plants.
Generalized α-investing: Definitions, Optimality Results and Application to Public Databases
Authors: Aharoni Ehud , Rosset Saharon
Published: November 2013

The increasing prevalence and utility of large public databases necessitates the development of appropriate methods for controlling false discovery. Motivated by this challenge, we discuss the generic problem of testing a possibly infinite stream of null hypotheses. In this context, Foster and Stine suggested a novel method named α-investing for controlling a false discovery measure known as mFDR. We develop a more general procedure for controlling mFDR, of which α-investing is a special case. We show that, in common practical situations, the general procedure can be optimized to produce an expected reward optimal version, which is more powerful than α-investing. We then present the concept of quality preserving databases which was originally introduced by Aharoni and co-workers, which formalizes efficient public database management to save costs and to control false discovery simultaneously. We show how one variant of generalized α-investing can be used to control mFDR in a quality preserving database and to lead to significant reduction in costs compared with naive approaches for controlling the familywise error rate implemented by Aharoni and co-workers.
Specific IgG4: Possible Role in the Pathogenesis and a New Marker in the Diagnosis of Anisakis‐associated Allergic Disease
Authors: Daschner A. , Fernández‐Fígares V. , Rodero M. , Valls A. , De Frutos C. , Ubeira F. M. , Cuéllar C.
Published: November 2013

IgG4 and IgE are immunoglobulin isotypes which are mediated by the same Th2‐mediated mechanism. The postulated pathogenic and protective function of IgE or IgG4, respectively, in allergic disease is opposite in parasitic infection. The possible role of IgG4 against recombinant major allergens on the appearance of different forms of Anisakis simplex‐associated allergic disease was studied. Gastro‐allergic anisakiasis (GAA) and Anisakis‐sensitization‐associated chronic urticaria (CU+) were compared for specific IgE, IgG4 and the respective recognition of Ani s 1 and Ani s 7. Gastro‐allergic anisakiasis showed higher IgE and IgG4 levels against crude extract and both recombinant allergens. Whereas IgE recognition of Ani s 7 did not differ and supports both clinical entities to be associated with previous acute parasitism, the IgE recognition rates of Ani s 1 and IgG4 recognition of both Ani s 1 and Ani s 7 were higher in GAA. IgG4 levels were associated with IgE, but also with age, time to last parasitic episode and frequency of fish intake. Logistic regression analysis showed that the presence of specific IgG4 against Ani s 7 was an independent marker associated with GAA. In the diagnosis of Anisakis‐associated allergic disease phenotypes (GAA versus CU+), measurement of specific IgG4 against recombinant allergens could be useful. Further, evaluation of specific IgE and IgG4 facilitates more insight into the protective versus pathogenic potential of IgE and IgG4.
3 TESLA MAGNETIC RESONANCE IMAGING OF THE OCCIPITOATLANTOAXIAL REGION IN THE NORMAL HORSE
Authors: Gutiérrez‐Crespo Beatriz , Kircher Patrick R. , Carrera Ines
Published: November 2013

The aim of this study was to describe the appearance of the ligamentous structures of the occipitoatlantoaxial (OAA) region in the normal horse by 3 tesla (3T) magnetic resonance imaging (MRI). The MRI images of the longitudinal odontoid ligament, tectorial membrane, dorsal and ventral atlantoaxial ligaments, dorsal atlantooccipital membrane with its reinforcing ligaments, and the lateral atlantooccipital ligaments of 10 horse cadavers were evaluated. All ligaments and membranes were identified in all planes, except for the lateral atlantooccipital ligament in the sagittal plane due to its cranioventrolateral course. All were iso to mildly hypointense to musculature of the neck in T1W with the exception of the tectorial membrane that was moderately hypointense; moderately hypointense in PD‐SPIR, and markedly hypointense (isointense to cortical bone) in T2W. The PD‐SPIR was the best sequence to identify all ligaments and membranes from their cranial and caudal attachments. The longitudinal odontoid ligament, ventral atlantoaxial ligament, and reinforcing bands of the dorsal atlantooccipital membrane presented a characteristic striped heterogeneous signal behavior thought to be due to fibrocartilaginous content. The remaining ligaments and membranes showed homogeneous signal intensity. Special anatomical features in this species such as the fan‐shaped longitudinal odontoid ligament, absence of the transverse ligament and presence of the ventral atlantoaxial ligament were documented. Ligamentous structures that stabilize the equine OAA region were described with MRI in this study and these findings could serve as an anatomic reference for those cases where instability of this region is suspected.
Investigation on the Aerodynamic Performance of an Annular Exhaust System for a Small Turboshaft Engine
Authors: de la Calzada Pedro , Parra Jorge , Mínguez Belén
Published: November 2013

An annular exhaust system design for being used in the bench testing of MTR390-E turboshaft engine has been performed at ITP. The exhaust system is aimed at improving the aerodynamic performance at high power compared with an existing exhaust system used in the previous version of the engine. The exhaust cone emulates to some extend the exhaust system in the helicopter and it is comprised of outer and inner cones supported by three struts.

The CFD commercial code FLUENT is used to investigate the aerodynamic performance of the baseline design and to optimise the inner and outer cone angles in the new design based on 2D axisymmetric models. Representative radial exit turbine conditions and far field conditions are imposed in the model comprising the exhaust cones plus a large external domain. Two outer and inner cone angles and two inner cone lengths are analysed at low and high power conditions. The aerodynamic performance of the exhaust shows high sensitivity to the inlet flow angle which varies up to 30°/40° between the high and low power conditions.

In all the simulated cases a large separation region is generated after the inner cone. Due to the high swirling flow the separation bubble behind the plug growths downstream hence reducing the effective flow exit area compared with the geometry area and reducing the pressure recovery downstream once the flow has been separated from the inner cone. Although all cases show similar qualitative behaviour, the best case based on the computed figures of merit (i.e., lowest total pressure loss) is chosen for the new design.

In order to further optimise the behaviour of the exhaust at high power, in the new design the three struts are aligned with the flow angle at high power conditions (struts were axially oriented in the baseline design) and the resulting geometry is analysed by 3D CFD simulations. As expected, the orientation of the struts has a dramatic impact in the aerodynamic behaviour of the exhaust. The new design shows an improvement of 29% in pressure recovery at high power compared with the baseline configuration, although it shows a degradation of 12% at low power.

Both the baseline and the new exhaust systems are tested with the real engine in the test bench. The general aerodynamic performance of the new design is compared with the CFD simulation. As a consequence of the design change an important modification in the aerodynamic behaviour of the exhaust is obtained impacting the whole engine performance. Therefore a new performance model of the exhaust system is proposed to be implemented in the whole engine performance model in order to accurately simulate the behaviour of the engine coupled with the new exhaust.
Fatigue Crack Growth Analysis on a Rotor Blade Under Forced Response
Authors: Dompierre B. , Wyart E. , Mesbah M. , Thirifay F.
Published: November 2013

This paper focuses on the fatigue crack growth resulting from an aeroelastic behavior of a fan blade when operating under upstream distortion. The forced response of the first bending mode of the blade due to the inlet distortion is analyzed and the mechanical stability of blades is investigated.

The forced response of one blade is evaluated using an uncoupled approach. In this approach, the forced response is calculated in four steps. First, the modal analysis is obtained using Finite Element (FE) calculations. In the second step, the aerodynamic damping is obtained by performing the CFD (Computational Fluid Dynamics) simulation for a single rotor blade with a prescribed harmonic forced motion. The next step is the estimation of the excitation forces when the unsteadiness of the inlet flow has a frequency close to the eigenfrequency of the blade. In the end, by solving the equations of equilibrium forces of the structure, the forced response is computed.

Afterwards, a fatigue crack growth analysis is performed. The crack is assumed to initiate in the area of the maximum principal stress. The crack is inserted into the FE model using the Extended Finite Element Method (XFEM) [1, 2] which is implemented in an in-house plugin “Morfeo-crack” for Samcef (commercial finite element analysis software package). This method allows for easily inserting a crack while minimizing the difficulties inherent to the mesh adaptation since the crack does not need to be explicitly meshed. The calculations are performed under the Linear Elastic Fracture Mechanics hypothesis. Finally, the crack path as well as the lifespan are estimated.
Interaction of Rim Seal and Main Annulus Flow in a Low-Speed Turbine Rig
Authors: Pueblas Jesus , Corral Roque , Schrewe Sebastian
Published: November 2013

The influence of the sealing flows on the secondary flows of a low-pressure turbine has been assessed numerically using multi-row steady and unsteady simulations. The experimental data obtained at the Large Scale Turbine Rig (LSTR) at Technische Universität Darmstadt have been used to validate the numerical method and complement the simulations.

Steady and unsteady state solutions and experiments are compared to understand the importance of the unsteadiness in the accuracy of numerical simulations. It is concluded that unsteady rotor/stator simulations enhance the prediction of the stator secondary flows, especially in the tip region.

The effect of the sealing air is analysed, varying the cooling mass flow for two operating conditions. The penetration of the sealing flow in the main stream increases withthe cooling flow, displacing the horseshoe and passage vortices towards the mid-span.
The Design Study of Supercritical Carbon Dioxide Integral Experiment Loop
Authors: Ahn Yoonhan , Lee Jekyoung , Kim Seong Gu , Lee Jeong Ik , Cha Jae Eun
Published: November 2013

The Supercritical Carbon Dioxide cycle (S-CO2 cycle) can achieve relatively high efficiency in the moderate temperature (450–750°C) region because the cycle takes advantage of non-ideal properties variation near the critical point. The S-CO2 cycle was originally considered as an attractive candidate for power conversion cycle of the next generation reactors. However due to many benefits of the S-CO2 cycle, it is not only limited to the nuclear application but also considered in other conventional and renewable energy system applications including fossil fuel power plant systems, ship propulsion applications, concentrated solar power systems, fuel cell bottoming power cycles and so on. The major studies settle on the S-CO2 recompressing cycle (also known as Feher cycle) which reduces the waste heat and increases the recuperated heat by recompressing some portion of the flow without heat rejection to increase the thermodynamic efficiency of the cycle. To develop and verify the characteristics of the S-CO2 recompressing cycle, Korean Atomic Energy Research Institute (KAERI) and KAIST research team designed a Supercritical Carbon Dioxide Integral Experiment Loop (SCIEL). 550°C turbine inlet temperature and 20 MPa compressor outlet pressure condition are expected for SCIEL operation and the layout is recompressing cycle but other layouts will be studied as well. The experimental loop facility is designed for studying unique phenomena in components under various conditions and developing the strategy to improve the component performance and overall cycle efficiency. The operating condition and thermodynamic efficiency for SCIEL are evaluated from an in-house code developed by KAIST research team. The effect of the split flow, component sensitivity, and optimum cycle pressure ratio will also be analyzed for the preliminary design of SCIEL. Furthermore, turbomachinery sizes and heat exchanger sizes are estimated from other in-house codes developed by KAIST research team. The overall component specification and performance of SCIEL will be compared to other S-CO2 test loop facilities in other research institutes.
Probabilistic CFD Analysis of High Pressure Turbine Blades Considering Real Geometric Effects
Authors: Scharfenstein Jens , Heinze Kay , Voigt Matthias , Vogeler Konrad , Meyer Marcus
Published: November 2013

This paper addresses the consideration of variability due to manufacturing and abrasion of high pressure turbine (HPT) blades through probabilistic CFD investigations. Currently, the influences of those effects onto relevant aerodynamic quantities are covered by safety factors and conservative assumptions. The probabilistic investigation on the other hand, based on realistic input parameters, will enable designers to possibly reduce safety factors and provide the foundation for more robust blade designs.

In order to establish a sound statistical database, 500 new and used HPT blades were digitised with an optical 3D scanning system in order to record the outer geometric variability. As described in the work of Heinze et al. [1], the measured point clouds are parameterized using classical profile parameters and a process to rebuild various blade geometries has been developed. In terms of probabilistic investigations, in our case by applying sampling-based methods, a large number of 3D CFD simulations for a 1.5 HPT stage have been conducted using probabilistic blade geometries, followed by a sensitivity analysis and a detailed investigation of the probabilistic system behaviour. For visualization of possible correlations, the technique of Statistics on Passage (SoP) was chosen, as described in [2].
Simulating Periodic Unsteady Flows Using Cubic-Spline Based Time Collocation Method
Authors: Du Pengcheng , Ning Fangfei
Published: November 2013

Time periodical unsteady flows are typical in turbomachinery. Simulating such flows using conventional time marching approach is most accurate but extremely time consuming. In order to achieve a better balance between accuracy and computational expenses, a cubic-spline based time collocation method is proposed. In this method, the time derivatives in the Navier-Stokes equations are obtained by using the differential quadrature method, in which the periodical flow variables are approximated by cubic-splines. Thus, the computation of a time-periodical flow is substituted by several coupled quasi-steady flow computations at sampled instants. The proposed method is then validated against several typical turbomachinery periodical unsteady flows, i.e., transonic compressor rotor flows under circumferential inlet distortions, single stage rotor-stator interactions and IGV-rotor interactions. The results show that the proposed cubic-spline based time collocation method with appropriate time sampling can well resolve the dominant unsteady effects, whilst the computational expenses are kept much less than the traditional time-marching simulation. More importantly, this paper provides a framework on the basis of time collocation method in which one may choose more compatible test functions for the concerned specific unsteady flows so that the better modeling of the flows can be expected.
Experimental Study of the Flow and Pressure Drop Performances in Advanced Combustor Distributor Diffuser
Authors: Liang H. X. , Suo J. Q. , Li M.
Published: November 2013

Gas turbine engine uses diffuser system to decelerate the compressor exit flow velocity before it enters combustor, it is important to design the compact structure and high performance of the diffuser for gas turbine engine. The diffuser and combustor dome configurations are critical flow path parameters in the design of a low-pressure-loss, high-performance combustion system. With rising of the inlet Mach number of the combustor, dramatically increasing of the diffuser total pressure loss and flow separation. So a new distributor diffuser was designed. In this paper preliminary results from an experimental investigation into the aerodynamic performance on a rectangle combustor-diffuser system with seven distributor plates were presented. Measurements were taken in the diffuser section to assess the diffuser performance characteristics under various conditions, the appropriate outlet flow field can be attained by changing the plate area ratio and form. Tests were carried out to investigate the influence of distributor diffuser plate geometry. During these measurements for each parametric configuration, data were obtained at 24 different flow rates through the distributor diffuser, it gave the conclusion that the distributor diffuser area ratio could be more than traditional diffusers with shorter construction and higher pressure recovery performance, while the flow loss through it was not beyond the traditional limit. Overall static pressure recovery improves and overall total pressure loss reduces with increasing distributor diffuser area ratio, and the increased flow rates through the distributor diffuser gave rise to a higher total pressure loss. The total pressure loss fraction was less than 2.5% when Mach number changed from 0.3 to 0.38; if the area ratio was more than 2.1, the diffuser loss coefficient remained less than 0.3, pressure recovery coefficient more than 0.5 and area ratio up to 2.45. There exists an area ratio in 1.6∼2.0 which makes diffuser outlet flow field distribution more uniform; Baffle structure can adjust the flow field distribution of outlet diffuser. As a result, the distributor diffuser can be potentially satisfied with demands for high performance combustor.
Compressor Housing Design for Small Turbocharger Compressors
Authors: Chen Hua , Li Penny
Published: November 2013

Compressor housing can greatly impact the behavior of centrifugal compressors used in small turbochargers. This is particularly significant in passenger car applications, where constrains on size and cost of manufacturing pose particular challenges to maintaining aerodynamic efficiency. This paper describes the development of a new compressor housing that overcomes these issues whilst delivering good performance. The concept for the improved design was conceived from an understanding of the loss mechanism inside the housing and the relationship between flow losses and housing geometry. The choice of certain key housing geometric parameters was guided by studies using the Design of Experiment (DOE) method. Computational fluid dynamics (CFD) simulations were also employed in the design of the housing and its use is discussed for several different approaches to the rotor-stator interface. These include a “Mixing Plane”, a “Frozen Rotor” and a “Housing Only” interface model, amongst others. Each differs in its numerical accuracy and computational efficiency and it is important to balance these two factors when choosing a method. Additionally a spreadsheet was built to enable the manipulation of the 3D configuration of the compressor housing. By providing more direct control over the geometry, it reduces the need for extensive and time consuming CAD work. To minimize the fabrication cost for the new housing, die-cast manufacturing was subsequently explored for its smooth surface finish. The final result is a more compact compressor housing that achieves higher efficiency at a lower cost.
Effect of Different Geometrical Inlet Pipes on a High Speed Centrifugal Compressor
Authors: Yang Ce , Zhao Ben , Ma C. C. , Lao Dazhong , Zhou Mi
Published: November 2013

Two different inlet configurations, including a straight pipe and a bent pipe, were experimentally tested and numerically simulated using a high-speed, low-mass flow centrifugal compressor. The pressure ratios of the compressor with the two inlet configurations were tested and then compared to illustrate the effect of the bent inlet pipe on the compressor. Furthermore, different circumferential positions of the bent inlet pipe relative to the volute are discussed for two purposes. One purpose is to describe the changes in the compressor performance that result from altering the circumferential position of the bent inlet pipe relative to the volute. This change in performance may be the so-called clocking effect, and its mechanism is different from the one in multistage turbomachinery. The other purpose is to investigate the unsteady flow for different matching states of the bent inlet pipe and volute. Thus, the frequency spectrum of unsteady pressure fluctuation was applied to analyze the aerodynamic response. Compared with the straight inlet pipe, the experimental results show that the pressure ratio is modulated and that the choke point is shifted in the bent inlet pipe. Similarly, the pressure ratio can be influenced by altering the circumferential position of the bent inlet pipe relative to the volute, which may have an effect on the unsteady pressure in the rotor section. Therefore, the magnitude of interest spectral frequency is significantly changed by clocking the bent inlet pipe.
Assessing 1D Loss Models for the Off-Design Performance Prediction of Automotive Turbocharger Compressors
Authors: Harley Peter , Spence Stephen , Filsinger Dietmar , Dietrich Michael , Early Juliana
Published: November 2013

Single-Zone modelling is used to assess three 1D impeller loss model collections. An automotive turbocharger centrifugal compressor is used for evaluation. The individual 1D losses are presented relative to each other at three tip speeds to provide a visual description of each author’s perception of the relative importance of each loss. The losses are compared with their resulting prediction of pressure ratio and efficiency, which is further compared with test data; upon comparison, a combination of the 1D loss collections is identified as providing the best performance prediction. 3D CFD simulations have also been carried out for the same geometry using a single passage model. A method of extracting 1D losses from CFD is described and utilised to draw further comparisons with the 1D losses. A 1D scroll volute model has been added to the single passage CFD results; good agreement with the test data is achieved. Short-comings in the existing 1D loss models are identified as a result of the comparisons with 3D CFD losses. Further comparisons are drawn between the predicted 1D data, 3D CFD simulation results, and the test data using a nondimensional method to highlight where the current errors exist in the 1D prediction.
Simulation of Wind Farm Operations and Maintenance
Authors: Pérez Eduardo , Ntaimo Lewis , Ding Yu
Published: November 2013

We develop a discrete event-based simulation framework that mimics the operations of a commercial size wind farm. Each turbine is treated as separate module, so that the simulation can be easily scaled up to more than one hundred turbines for a farm. Each turbine module includes a structural element sub-module, degradation sub-module, power generation sub-module, sensing and maintenance scheduling sub-module. The simulator is specially designed to handle a large number of unorganized random events (turbine failures, waiting for parts, weather disruptions) and reflect in the simulator’s outputs the variation from parameters and operations. We report on implementation results and provide insights into wind farm operations under different maintenance strategies.
High Speed Testing and Numerical Validation of an Aggressive Intermediate Compressor Duct
Authors: Wallin Fredrik , Olsson Jörgen , Johansson Peter P. J. , Krüger Euodia , Olausson Martin
Published: November 2013

An experimental and numerical investigation of the flow in an s-shaped compressor duct is presented in this paper. The experimental test was conducted in the compressor test facility at STARCS in Bromma, Sweden. The duct was designed based on geometrical properties of corresponding low-speed tests performed at the Universities of Cambridge and Loughborough in the UK in the EU research project AIDA. For the high-speed test, the geometry was scaled to fit the downstream compressor, keeping the non-dimensional characteristics of the duct as similar to the low-speed configurations as possible. Extensive CFD calculations were performed to assist the set-up of the test and to predict the duct performance in detail. The duct was equipped with static pressure taps on hub and shroud as well as on the strut. The duct inlet and exit flowfields were scanned using a miniature five-hole pressure probe that provided total pressure, velocities and flow angles. Two different duct surface finishes were tested at two different compressor operational points. Using the five-hole probe results, the duct loss could be estimated and compared to that of the CFD. For the CFD analysis a surface roughness model was used to account for the different surface finishes of the duct. The results show that using the surface roughness model makes it possible to account for the increase in loss due to a rougher flow surface. The absolute loss values are however under-predicted by approximately 10% in the CFD compared to the experiments.
Reliability Evaluation of New Offshore Wind Farm Electrical Grid Connection Topologies
Authors: Kazemtabrizi B. , Crabtree C. , Hogg S.
Published: November 2013

In this paper, a composite generation transmission approach has been chosen for adequacy evaluation of wind farms integrated with conventional generating units. It has been assumed that the failure characteristics of a turbine’s underlying subassemblies possess the required Markov properties to be modeled as Markov processes. The wind farm along with the offshore connection grid has then been modeled in a sequential Monte Carlo simulation which also contains sequential chronological models for wind speed and load level variations over a specific period of time. The reliability of the wind farm is then evaluated against a series of load- and energy-based indices as well as overall productivity of the farm with different connections. The results indicate a potential improvement in the reliability of wind power output when in cluster-type topologies, where the converters are grouped and maintained in a central offshore platform, in comparison to conventional string-type topologies. Academic researchers involved in reliability modeling and risk analysis of renewable sources of energy, particularly wind, as well as industry professionals both in wind turbine manufacturing and operation and maintenance of offshore wind farms would equally benefit from the degree of detail and accuracy provided by the models presented in this paper.
Axial Compressor Aerodynamics Under Sub-Idle Conditions
Authors: Illana Enric , Grech Nicholas , Zachos Pavlos K. , Pachidis Vassilios
Published: November 2013

With stricter regulations on engine altitude relight capability, the understanding of low-speed axial compressor performance is becoming increasingly important. At such far off-design conditions, compressors behave differently from design point, with large changes in the flow phenomena and reduced reliability on the established empirical equations and assumptions.

This work focuses on the aerodynamics of a locked-rotor axial compressor at high inlet Mach number conditions, using a validated numerical simulation approach. In a locked-rotor compressor there is very little compression of the inflow. The air is forced to accelerate, with the rear stages seeing the highest velocities. Depending on the inlet Mach number, the velocity at the rear stages can be close to sonic, until choking conditions are reached. To predict accurately the zero-speed compressor performance close to the choking point, the corresponding blade aerodynamic coefficients are evaluated as a function of the blade’s physical parameters and the inlet Mach number. In addition, the blockage due to the separated flow as a result of the high negative incidences is investigated as a function of inlet Mach number, incidence, solidity and stagger angle. Models that predict the characteristics and choking mass flow of the compressor, require such data.

This work offers a better insight into the low-speed and locked rotor characteristics of the compressor. The zero-speed line can be calculated through a stage-stacking technique using the aerodynamic coefficients and flow blockage derived from the numerical simulations. Low-speed lines between the zero and idle-speed line can subsequently be created through interpolation. Using this methodology, it is possible to generate a complete sub-idle map for a multi-stage axial compressor, enhancing the predictive capability of whole engine performance solvers.
Development of a Novel Mixing Plane Interface Using a Fully Implicit Averaging for Stage Analysis
Authors: Hanimann Lucian , Mangani Luca , Casartelli Ernesto , Mokulys Thomas , Mauri Sebastiano
Published: November 2013

This paper describes the development and validation steps of a characteristics-based explicit as well as a novel fully implicit mixing plane implementation for turbomachinery applications. The framework is an unstructured 3D RANS in-house modified solver, based on open-source libraries.

Particular attention was paid to mass-conservation, accurate variables interpolation and algorithm stability in order to improve robustness and convergence. By introducing a specific interface, allowing the use of algebraic multigrid solvers together with multiprocessor computation, a speed up of the numerical solution procedure was achieved. The validation of both mixing plane algorithms is carried out on an industrial radial compressor and a cold air 1.5 stages axial turbine.
LES for Turbines: Methodologies, Cost and Future Outlooks
Authors: Tyacke James , Tucker Paul , Jefferson-Loveday Richard , Vadlamani Nagabhushana Rao , Watson Robert , Naqavi Iftekhar , Yang Xiaoyu
Published: November 2013

Flows throughout different zones of turbines have been investigated using Large Eddy Simulation (LES) and hybrid Reynolds-Averaged Navier-Stokes-LES (RANS-LES) methods and contrasted with RANS modelling, more typically used in the design environment. Cases studied include low and high-pressure turbine cascades, real surface roughness effects, internal cooling ducts, trailing edge cut-backs and labyrinth and rim seals. Evidence is presented that shows that LES and hybrid RANS-LES produces higher quality data than RANS/URANS for a wide range of flows. The higher level of physics that is resolved allows greater flow physics insight which is valuable for improving designs and refining lower order models. Turbine zones are categorised by flow type, to assist in choosing the appropriate eddy resolving method and to estimate computational cost.
Partial Arc Steam Admission Optimization in Order to Reduce Vibration of Steam Turbine With Tilting-Pad Journal Bearings
Authors: Nekrasov Alexander
Published: November 2013

In the investigated high pressure steam turbine, with increasing steam flow rate the exciting aerodynamic forces rise and cause high, but limited vibration of turbine bearings. The tilting-pad journal bearing load and load angle are changing as the steam flow rate changes in turbine with partial arc admission, and accordingly the dynamic characteristics of bearings change.

The field experiments results at fossil fuel power plant presented. The aim of experiments was the partial arc steam admission optimization to reducing the effect associated with change of bearing load/load angle. At first, conventional (consecutive) order of valve opening was investigated. In this case, the bearing vibrations are rising while steam flow and valve outlet pressure are increasing. At some “critical point” the vibration level rises stepwise. Situation repeats symmetrically during turbine unloading/loading.

In the second part of experiments, the consecutive order of valve opening was changed to “diagonal” one. As a result, the bearing vibration weakly depends on the steam flow rate and its value is significantly lower. Long-term turbine operation shows that “diagonal” steam admission is optimal for this type of turbine.

From the analysis of the forces vectors follows that the “critical point” corresponds to static force, which acts in the direction between neighbor tilting-pads. It is contrary to operation and idle modes where this force is acting on pad. The static steam force is bigger and bearing loading is lower at the “critical point”. Numerical investigation of rotor-bearing threshold stability was performed for different bearing loading conditions with exciting aerodynamic steam forces. Two configurations of bearings were included into the model: LBP and LOP — at the “critical point”. Consecutive and so-called “diagonal” orders of valve opening were modeled. Threshold capacity is higher for the “diagonal” valve opening order.