bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Chronic Ethanol on Enkephalin in the Hypothalamus and Extra‐Hypothalamic Areas
Authors: Chang Guo‐Qing , Barson Jessica R. , Karatayev Olga , Chang Si‐Yi , Chen Yu‐Wei , Leibowitz Sarah F.
Published: February 2010

Background: Ethanol may be consumed for reasons such as reward, anxiety reduction, or caloric content, and the opioid enkephalin (ENK) appears to be involved in many of these functions. Previous studies in Sprague–Dawley rats have demonstrated that ENK in the hypothalamic paraventricular nucleus (PVN) is stimulated by voluntary consumption of ethanol. This suggests that this opioid peptide may be involved in promoting the drinking of ethanol, consistent with our recent findings that PVN injections of ENK analogs stimulate ethanol intake. To broaden our understanding of how this peptide functions throughout the brain to promote ethanol intake, we measured, in rats trained to drink 9% ethanol, the expression of the ENK gene in additional brain areas outside the hypothalamus, namely, the ventral tegmental area (VTA), nucleus accumbens shell (NAcSh) and core (NAcC), medial prefrontal cortex (mPFC), and central nucleus of the amygdala (CeA).

Methods: In the first experiment, the brains of rats chronically drinking 1 g/kg/d ethanol, 3 g/kg/d ethanol, or water were examined using real‐time quantitative polymerase chain reaction (qRT‐PCR). In the second experiment, a more detailed, anatomic analysis of changes in gene expression, in rats chronically drinking 3 g/kg/d ethanol compared to water, was performed using radiolabeled in situ hybridization (ISH). The third experiment employed digoxigenin‐labeled ISH (DIG) to examine changes in the density of cells expressing ENK and, for comparison, dynorphin (DYN) in rats chronically drinking 3 g/kg/d ethanol versus water.

Results: With qRT‐PCR, the rats chronically drinking ethanol plus water compared to water alone showed significantly higher levels of ENK mRNA, not only in the PVN but also in the VTA, NAcSh, NAcC, and mPFC, although not in the CeA. Using radiolabeled ISH, levels of ENK mRNA in rats drinking ethanol were found to be elevated in all areas examined, including the CeA. The experiment using DIG confirmed this effect of ethanol, showing an increase in density of ENK‐expressing cells in all areas studied. It additionally revealed a similar change in DYN mRNA in the PVN, mPFC, and CeA, although not in the NAcSh or NAcC.

Conclusions: While distinguishing the NAc as a site where ENK and DYN respond differentially, these findings lead us to propose that these opioids, in response to voluntary ethanol consumption, are generally elevated in extra‐hypothalamic as well as hypothalamic areas, possibly to carry out specific area‐related functions that, in turn, drive animals to further consume ethanol. These functions include calorie ingestion in the PVN, reward and motivation in the VTA and NAcSh, response‐reinforcement learning in the NAcC, stress reduction in the CeA, and behavioral control in the mPFC.
Effect of a Comprehensive Lifestyle Modification Program on the Bone Density of Male Heavy Drinkers
Authors: Matsui Toshifumi , Yokoyama Akira , Matsushita Sachio , Ogawa Ryuichi , Mori Shuka , Hayashi Emiko , Roh Sungwon , Higuchi Susumu , Arai Hiroyuki , Maruyama Katsuya
Published: February 2010

Background:  Heavy alcohol drinking is implicated in osteoporosis. Although abstinence is rapidly followed by a restoration of osteoblastic activity, little is known about the contributions of alcohol‐related factors or the effectiveness of a lifestyle modification program (LMP) on bone density.

Methods:  We conducted a study of 138 male alcoholic patients to investigate whether drinking history and concurrent factors were associated with the bone density of the calcaneus. A 2.5‐months LMP in an institutionalized setting was completed by 20 of them, and its effect on bone density, serum parathyroid hormone (PTH), and 1.25‐(OH)2 vitamin D levels were assessed.

Results:  The patients had a high prevalence of daytime drinking (93.5%), continuous drinking (84.1%), and current smoking (82.0%) with mean duration of alcohol abuse of 30.0 ± 12.8 years. The patients had lower bone density than a reference control group (Z‐scores: −0.45 ± 1.02). Multiple stepwise regression analysis identified age, poor activities of daily living (ADL), continuous drinking, absence of liver cirrhosis, depression, and dementia as determinants of low bone density. The bone density of the 20 participants in the LMP improved 2.3% (p = 0.0003) with a more ameliorating effect on bone density than a conventional abstinence therapy (p = 0.014 for interventional effect). The upper normal range of PTH levels at baseline were significantly decreased, and 1.25‐(OH)2 vitamin D levels also had a trend toward decrease during the abstinence.

Conclusions:  Alcoholic patients may have many complications such as poor ADL and dementia, which are independently associated with decreased bone density. The results of this study support the idea that comprehensive approach to lifestyle factors to minimize risk of osteoporosis is the best way to improve bone density.
Explanations of Risk in Families Without Identified Mutations for Hereditary Nonpolyposis Colorectal Cancer
Authors: Ersig Anne L. , Ayres Lioness , Hadley Donald W. , Koehly Laura M.
Published: February 2010

Purpose: Genetic testing for hereditary forms of cancer does not always identify a causative mutation. Little is known about personal or family response to these indeterminate results when a hereditary form of cancer is suspected. This study explored thoughts about and responses to risk for hereditary nonpolyposis colorectal cancer (HNPCC) when a family member has received indeterminate genetic test results.

Design: In this qualitative study, data were gathered from index cases who received indeterminate genetic test results through a longitudinal study offering genetic counseling and testing for HNPCC. First‐degree relatives of these indeterminate index cases were also invited to participate in the qualitative interview.

Methods: Semistructured telephone interviews were conducted with index cases and their at‐risk first‐degree relatives. Data were analyzed using the within‐ and across‐case method.

Findings: The across‐case analysis led to the development of the Awareness and Surveillance Trajectory, which describes individual interpretations of and responses to risk, based on personal and family history. Explanations of risk addressed the meaning of cancer in the family and provided context for individual interpretations. They were identified using within‐case analysis and organized into a typology: innate, exceptional, idiosyncratic, and undeveloped explanations.

Conclusions: Members of families without identified HNPCC mutations vary in their explanations for, interpretations of, and responses to indeterminate genetic test results.

Clinical Relevance: Explanations of family risk and interpretations of individual risk offer healthcare providers valuable information. In combination with the Awareness and Surveillance Trajectory, assessment of these beliefs can facilitate development of individualized recommendations and strategies for possible preventive actions.
Patch testing in patients treated with systemic immunosuppression and cytokine inhibitors
Authors: Wee Jamie S. , White Jonathan M. L. , McFadden John P. , White Ian R.
Published: February 2010

Background: Currently, there is little data available on the reliability of patch testing in patients taking immunosuppressive agents other than systemic corticosteroids.

Objectives: We present data from 38 patients who were patch tested whilst taking various immunomodulating agents to determine if positive reactions can be elicited.

Patient/materials/methods: Between September 2006 and May 2009, 38 patients attending the St John's Institute of Dermatology were patch tested whilst taking immunosuppressive agents including azathioprine, ciclosporin, infliximab, adalimumab, etanercept, methotrexate, mycophenolate mofetil, and tacrolimus.

Results: Positive patch test reactions of varying degrees and significance were elicited in: 2 of 10 patients on azathioprine; 5 of 11 patients on ciclosporin; 1 patient on ciclosporin and Fumaderm®; 1 patient on infliximab; 1 patient on infliximab and methotrexate; 1 of 2 patients on adalimumab; 1 patient on etanercept and methotrexate; 3 of 4 patients on methotrexate; 1 of 3 patients on mycophenolate mofetil; and 1 patient on mycophenolate mofetil and tacrolimus. Negative patch test reactions occurred in 1 patient on azathioprine and ciclosporin; 1 patient on infliximab and azathioprine; and 1 patient on mycophenolate and ciclosporin.

Conclusions: Positive patch test reactions can be elicited in patients taking azathioprine, ciclosporin, infliximab, adalimumab, etanercept, methotrexate, mycophenolate mofetil, and tacrolimus. However, it remains unclear what effect these immunosuppressive drugs may have on suppressing allergic patch test reactions and further studies should be carried out to determine the reliability of testing in these circumstances.
Hairdressers with dermatitis should always be patch tested regardless of atopy status
Authors: O’Connell Rachel L. , White Ian R. , Mc Fadden John P. , White Jonathan M. L.
Published: February 2010

Background: Allergic contact dermatitis is common in hairdressers because of their exposure to chemicals used in hair dyes and permanent wave solutions. Atopic individuals are known to have a higher prevalence of leaving the profession due to morbidity associated with hand eczema.

Objectives: To assess which chemicals are responsible for allergic contact dermatitis in hairdressers and whether the prevalence is the same according to atopy status.

Methods: A total of 729 hairdressers who had been patch tested were retrospectively identified. Allergic reactions to relevant allergens from the extended European baseline series and hairdressing series were analysed against history of atopic eczema.

Results: Of the total, 29.9% of patients had a current or past history of atopic eczema. The most frequent positive allergens from the European baseline series were nickel sulfate (32.1%) and p‐phenylenediamine (19.0%) and from the hairdressing series were glyceryl monothioglycolate (21.4%) and ammonium persulfate (10.6%). There was no significant difference between people with or without a history of atopic eczema, except for fragrance mix I and nickel sulfate.

Conclusions: We present findings from the largest cohort of hairdressers patch tested from a single centre. It is necessary to patch test hairdressers with dermatitis, regardless of a history of atopy. Strategies to reduce prevalence of allergic contact dermatitis are required.
Improving venous ulcer healing: designing and reporting randomised controlled trials
Authors: Weller Carolina D , McNeil John , Evans Sue , Reid Christopher
Published: February 2010

The randomised controlled trial (RCT) is often considered the gold standard for judging the benefits of treatments. The application of randomised controlled clinical trials to treatments of venous ulcer healing has lagged behind that of other areas of medicine. To interpret the results of an RCT, readers must understand a variety of aspects of their design, analysis and interpretation.

Venous ulcer disease has a high prevalence and has a significant socioeconomic impact in most parts of the world. The management of venous ulcers causes a considerable strain on the health system and is likely to worsen in future. The multi‐layer high compression system is described as the current gold standard for treating venous ulcers. A recent meta‐analysis of bandaging systems found that multi‐layer compression bandages appeared to be superior to single‐layer bandages in promoting venous ulcer healing. However, it was noted that many of the studies had small sample sizes and the quality of research in the area was poor.

The consolidating standards of reporting trials (CONSORT) statement can help clinicians to discern high‐quality studies from ones of poorer quality. This paper discusses how CONSORT can help clinicians and researchers to design and report quality studies to contribute to evidence‐based venous ulcer healing.
The economics of pressure relieving surfaces: an illustrative case study of the impact of high‐specification surfaces on hospital finances
Authors: Trueman Paul , Whitehead Sarah J
Published: February 2010

Pressure ulcers are associated with a significant economic burden that, in many cases, is recognised as being avoidable. The effectiveness of pressure relieving surfaces is well documented and acknowledged in clinical guidelines on the prevention and management of pressure ulcers. Whilst pressure relieving surfaces are more expensive than traditional hospital mattresses, judicious use, targeted to patients most at risk, can help to reduce the incidence and costs of pressure ulcers in hospital settings. This review paper includes a summary of pivotal clinical evidence on pressure relieving surfaces as well as a suggested approach for modelling their financial impact on hospital budgets. Simple financial modelling suggests that pressure relieving surfaces could lead to financial savings for a hospital when used appropriately.
The European and American Use of Exploratory Approaches for First‐in‐Human Studies*
Authors: Silva‐Lima Beatriz , Carlson David , Jones David R. , Laurie David , Stahl Elke , Maria Vasco , Janssens Walter , Robinson William T.
Published: February 2010

Exploratory approaches for first‐in‐human clinical studies have evolved over the last few years and have stimulated the issuance of national regulatory guidances in some European countries as well as the United States. With the increasing implementation of these approaches and the recent preparation of a multiregional regulatory guidance (ICH M3 rev2), an exchange of experiences on the opportunities and challenges of exploratory clinical trials was desirable; thus, a workshop focusing on the use of this clinical approach was planned and conducted in Lisbon, Portugal, March 18–19, 2009 sponsored by the Portuguese Health Authority (INFARMED) and DIA. The structure of the workshop focused in three main areas. Regulatory representatives from Portugal, Belgium, Germany, the United Kingdom and the United States formally reviewed their experiences. This was followed by a discussion on issues from an ethics review perspective as well as an insight to the opportunities in the area of biologics. The industry perspective was presented by representatives from Merck, Pfizer, J&J, Novartis, Speedel, AstraZeneca, GSK, and Roche. Finally, through break out sessions, issues were identified to be addressed moving forward. It is the purpose of this paper to report on the outcome of this workshop. Clin Trans Sci 2010; Volume #: 1–4
Principles of Human Subjects Protections Applied in an Opt‐Out, De‐identified Biobank
Authors: Pulley Jill , Clayton Ellen , Bernard Gordon R. , Roden Dan M. , Masys Daniel R.
Published: February 2010

BioVU, the Vanderbilt DNA Databank, is one of few biobanks that qualifies as non‐human subjects research as determined by the local IRB and the federal Office of Human Research Protections (OHRP). BioVU accrues DNA samples extracted from leftover blood remaining from routine clinical testing. The resource is linked to a de‐identified version of data extracted from an Electronic Medical Record (EMR) system, termed the Synthetic Device (SD), in which all personal identifiers have been removed. Thus, there is no identifiable private information attached to the records. The Belmont Report enumerates the importance of the boundary between practice and research, and three principles: Respect for Persons, Beneficence, and Justice, which constitute the essential ethical framework by which IRBs and ethics committees judge the risks and benefi ts of research involving human subjects. BioVU was developed by designing and implementing new procedures, for which there were no previously established methods, which are consistent with the principles of the Belmont Report. These included special oversight and governance, new informatics technologies, provisions to accommodate patients’ preferences, as well as an extensive public education and communications component. Considerations of core principles and protections in the practical implementation of BioVU is the focus of this paper. Clin Trans Sci 2010; Volume #: 1–7
Survey of Community Engagement in NIH‐Funded Research
Authors: Hood Nancy E. , Brewer Tracy , Jackson Rebecca , Wewers Mary Ellen
Published: February 2010

Community engagement is an innovative and required component for Clinical and Translational Science Awards (CTSAs) funded by the National Institutes of Health (NIH). However, the extent of community engagement in NIH‐funded research has not been previously examined. This study assessed baseline prevalence of community engagement activities among NIH‐funded studies at a large Midwestern university with a CTSA. An online survey was e‐mailed to principal investigators of recent NIH‐funded studies (N = 480). Investigators were asked to identify what types of community engagement activities had occurred for each study. Responses were received for 40.4% (194/480) of studies. Overall, 42.6% reported any community engagement activities. More collaborative types of engagement (e.g., community advisory board) were less common than activities requiring less engagement (e.g., sharing study results with community members). Studies with more collaborative community engagement were less likely to be described as basic or preclinical research compared to all other studies. Given NIH's inclusive call for community engagement in research, relatively few NIH‐funded studies reported community engagement activities, although this study used a broad definition of community and a wide range of types of engagement. These findings may be used to inform the goals of CTSA community engagement programs. Clin Trans Sci 2010; Volume *: 1–4
Fatigue Analysis and Lifetime Estimation of Centrifugal Compressor Impeller Blades
Authors: Mao Yijun , Qi Datong , Xu Qingyu
Published: February 2010

A multistage centrifugal compressor installed in an air-separation plant was equipped with the inlet guide vanes (IGVs) at the first stage. The impeller blades of the first stage cracked when the compressor just ran about three months. A weakly coupled fluid-structure interaction (FSI) is numerically calculated to analyze the high cycle fatigue (HCF) failure and estimate the lifetime of the impeller blades. In order to obtain the time dependent aerodynamic loads on the impeller blades, three-dimensional unsteady compressible viscous flow in the first whole stage of the centrifugal compressor is simulated. And then, a data interpolation tool is developed to transfer the physical information from fluid meshes to structure meshes, and also, time dependent data is transferred into frequency dependent data using Fast Fourier Transform (FFT). The free vibration mode and forced vibration response of the impeller blades are calculated using finite element method (FEM) and the cyclic symmetry structure of the rotating impeller is modeled by a single segment. According to the numerical result, the HCF lifetime of the impeller blades is estimated using a local stress-strain method. Numerical result shows that the predominated frequency of unsteady aerodynamic loads acting on the impeller blades is equal to the frequency of the IGVs-impeller blades interaction. Both the predicted stress concentration region and lifetime of the impeller blades agree reasonably well with factual fracture case. This study shows that it is feasible to use the weakly coupled FSI simulation to predict the fracture region and lifetime of centrifugal impeller blades.
Numerical Investigation Into Non-Synchronous Vibrations of Axial Flow Compressors by the Resonant Tip Clearance Flow
Authors: Drolet Martin , Thomassin Jean , Vo Huu Duc , Mureithi Njuki W.
Published: February 2010

This work investigates Non-Synchronous Vibrations (NSV) encountered in a turbine engine axial flow compressor using a Computational Fluid Dynamics (CFD) approach. It has been proposed that the resonance of the tip clearance flow in compressor blades could be the physical mechanism behind NSV. This work’s emphasis is on being able to computationally capture this resonance and predict the critical NSV speed using CFD. This would considerably reduce the costs involved in future hardware design and testing. The model uses the same compressor blade geometry on which experimental validation of the proposed NSV theory was conducted. The flow interaction with blade vibratory motion is modeled using a moving mesh capability and a SAS-SST turbulence model is used for computation. A review of the proposed theory on NSV is done. The CFD model is first verified with experimental data and then characterized to ensure that the simulations are conducted at the proper NSV conditions, in order to assess the resonance of the tip clearance flow. Evidence of this resonance behavior is presented and critical NSV speeds are identified based on numerical results for two different inlet temperature cases and are validated against experimental data. Further study of the actual flow structure associated with NSV is done. Additional remarks on the numerical results are discussed. An iterative design methodology to account for NSV is also proposed based on the current numerical study.
Investigation of Wake Transport in a Turbine Blade Channel and Its Effect on the Boundary Layer Development
Authors: Bijak-Bartosik Edyta , Elsner Witold
Published: February 2010

The paper presents the results of experimental investigations of the wake migration within the blade passage of a steam turbine blade cascade. The upstream wakes were generated by the wheel with cylindrical bars rotating at the plane perpendicular to the flow direction. The bars diameter was chosen to match the loss of a representative turbine blade as well as the flow pattern at the inlet to the blade cascade. The measurements were performed with the use of hot-wire technique and double X-wire probe. The application of phase averaging allowed one to reproduce the wake convection. The wake movement was visualized by the perturbation velocity vectors and fluctuating components. Dense spatial resolution of measuring points allows for calculation and analysis of selected terms of turbulent kinetic energy transport equation. The results confirm experimental and numerical observations done already for high-loaded blade profiles, which reveal that as the wake passes through high spatial velocity gradient area the turbulent production appears. The turbulent production causes the increase of turbulent kinetic energy (TKE). The analysis confirms also that the convection is mainly responsible for the wake deformation and that the distortion of shape and wake width change especially at the edges of channel is caused by “jet effect”. It also was proved that the role and share of turbulent diffusion is of minor importance and only a slight increase of diffusion is observed in the rear part of the blade channel close to the suction side, where TKE production appears. It was shown also that transition starts not when the wake touches the boundary layer edge, but earlier under the high energy core of the impacting wake. The earlier start of the transition could be due to pressure coupling caused by high energetic small scale structures.
Experimental Investigation of the Influence of Inlet Distortion on the Stall Inception in a Low Speed Axial Compressor
Authors: Jiang Huabing , Lu Yajun , Yuan Wei , Li Qiushi
Published: February 2010

Inlet distortion is one of the major concerns for high maneuverability airplanes. An experiment is performed to investigate the influence of inlet distortion on the stall inception in a low speed axial compressor, where the distorted inlet flow field is simulated with a flat baffle placed upstream of the compressor. The flow field around a rotor blade is measured using 2D Digital Particle Image Velocimetry (DPIV) under both uniform and distorted inlet flow conditions. A comparison of flow fields reveals that the distorted inlet flow condition makes the compressor flow fields asymmetric. Flow separation and blockage within Distorted Sector A and Transition Sector B are more severe compared to Sector C. The distorted Sector A and Transition Sector B are the key regions that degrade compressor performance and stability. The large axial velocity makes the flow field within the Undistorted Sector C vigorous, which helps to suppress flow separation and blockage. Compressor rotor blades experience loading and unloading in a revolution period and the compressor exhibits strong dynamic response when it operates under distorted inlet flow conditions. Time-related pressure signals acquired at the rotor exit are utilized to analyze the development of the stall disturbance and the stall characteristic of the compressor. The development period of the stall disturbance is prolonged by the dynamic response of the compressor flow field under the distorted inlet flow condition. Dynamic development of the stall disturbance induced by inlet distortion reduces the compressor stall intensity. The frequency associated with the rotating stall cell is related to the rotating velocity of stall cells, which keeps the same value for uniform and distorted inlet flow conditions. Consequently, the stall inception of the compressor is influenced by the distorted inlet flow condition. The disturbance initiated in Distorted Sector A will experience development and damping when it propagates circumferentially, and might fail to survive the damping within Undistorted Sector C. Stall inception occurs only when the damping within Undistorted Sector C is insufficient to prevent its growth. The dynamic development of the disturbance can reasonably explain the influence of inlet distortion on compressor performance.
Automatic Design Optimization of Rotors Supported on Tilting Pad Bearings
Authors: Untaroiu Costin D. , Untaroiu Alexandrina , Younan Amir , Allaire Paul E.
Published: February 2010

This study considers the optimization of a rotor supported on bearings using an automatic design approach. A finite element approach is used to model the rotor-bearing system and the dynamic speed-dependent coefficients of the bearing are calculated using a bulk flow code. A numerical example of a rotor-bearing system is employed to demonstrate the merits of the present design approach. A few geometric characteristics of the rotor together with the parameters defining the configuration of tilting pad bearing are considered as design variables into the automatic optimization process. The power loss in bearings, stability criteria, and unbalance responses are defined as a set of objective functions and constraints. The complex design optimization problem is solved using heuristic optimization algorithms, such as genetic, and particle-swarm optimization. Whereas both algorithms found better design solutions than the initial design, the genetic algorithms exhibited the fastest convergence. The high performance of the best solution obtained in the optimization design suggests that the proposed approach has good potential for improving design of rotor-bearing systems encountered in industrial applications.
Identification of Squeeze Film Damper Force Coefficients From Multiple-Frequency, Non-Circular Journal Motions
Authors: Delgado Adolfo , San Andre´s Luis
Published: February 2010

In rotor-bearing systems, squeeze film dampers (SFDs) provide structural isolation, reduce amplitudes of rotor response to imbalance, and in some instances, increase the system threshold speed of instability. SFDs are typically installed at the bearing supports, either in series or in parallel. In multi-spool engines, SFDs are located in the interface between rotating shafts. These intershaft dampers must ameliorate complex rotor motions of various whirl frequencies arising from the low speed and the high speed rotors. The paper presents experiments to characterize the forced response of an open ends SFD subject to dynamic loads with multiple frequencies, as in a jet engine intershaft damper. The test rig comprises of a stationary journal and a flexibly supported housing that holds the test damper and instrumentation. The open ends SFD is 127 mm in diameter, 25.4 mm film land length, and radial clearance of 0.125 mm. The damper is lubricated with ISO VG 2 oil at room temperature (24 °C, feed pressure 31 kPa). In the experiments, two orthogonally positioned shakers deliver forces to the test damper that produce controlled amplitude motions with two whirl frequencies, one fixed and the other one varying over a specified range that includes the test system natural frequency. The test data collected, forces and motions versus time, are converted into the frequency domain for parameter identification. The identified viscous damping coefficients are strong functions of the amplitude of journal motion, lying within predictions from classical formulas for circular centered orbits and small amplitude motions about an eccentric journal position. The damper inertia coefficients agree well with predictions derived from a fluid flow model that includes the effect of the feed groove.
A Cyclic Life Prediction Approach for Directionally Solidified Nickel Superalloys
Authors: Mu¨cke Roland , Woratat Piyawan
Published: February 2010

The performance of heavy duty gas turbines is closely related to the material capability of the components of the 1st turbine stages. In modern gas turbines single crystal (SX) and directionally solidified (DS) nickel superalloys are applied which, compared to their conventionally cast (CC) version, hold a higher cyclic life and a significantly improved creep rupture strength. SX and DS nickel superalloys feature a significant directionally dependence of material properties. To fully exploit the material capability, the anisotropy needs to be accounted for in both, the constitutive and the lifing model. In this context, the paper addresses a cyclic life prediction procedure for DS materials with transverse isotropic material symmetry. Thereby, the well-known local approaches to fatigue life prediction of isotropic materials under uniaxial loading are extended towards materials with transverse isotropic properties under multiaxial load conditions. As part of the proposed methodology, a Hill type function is utilized for describing the anisotropic failure behavior. The coefficients of the Hill surface are determined from the actual multiaxial loading, the material symmetry and the anisotropic fatigue strength of the material. In the paper we first characterize the anisotropy of DS superalloys. We then present the general mathematical framework of the proposed lifing procedure. Later we discuss a validation of the cyclic life model by comparing measured and predicted fatigue lives of test specimens. Finally, the proposed method is applied to the cyclic life prediction of a gas turbine blade.
On the Influence of Strain Gauge Instrumentation on Blade Vibrations of Integral Blisk Compressor Rotors Applying a Discrete Model
Authors: Beirow Bernd , Ku¨hhorn Arnold , Nipkau Jens
Published: February 2010

The effect of blade frequency mistuning on the forced response of HPC-blisks is studied by means of experimental and numerical investigations applying discrete mechanical low degree of freedom models. Besides the mistuning resulting from manufacturing and inhomogeneous material also strain gauge (S/G) induced mistuning is considered. Blade by blade measurements supported by numerical calculations are used to determine mistuning distributions within an iterative approach. Due to the stiffness contribution of high temperature S/G, a significant increase of blade alone frequencies can be proved. It is shown within laser scanning measurements that this S/G induced mistuning can cause strongly localized mode shapes. Since S/G signals are used to monitor also non-instrumented blade resonances in engine-tests, it is reasonable to consider the S/G contribution within model-updates. The numerical models introduced in this paper are adjusted to experimentally determined blade alone frequency distributions. Within simulations of the forced response it is shown in principle, that the S/G-instrumentation also affects the response of non-instrumented blades which is important with regard to the S/G calibration process. Additional investigations are addressed to the consequences of small variations in measured mistuning distributions on the maximum forced response, i. e. resulting from a changing ambient temperature while measurement or a limited frequency resolution. In this context, a strong dependence on the engine order excited, the damping level and thus the flow conditions could be proved. As an example all investigations presented in this paper are carried out for two stages of a research compressor.
Analysis of Random Vibration for Mistuned Bladed Disk
Authors: Kaneko Yasutomo , Mori Kazushi , Ueda Osamu
Published: February 2010

When calculating the vibratory response of bladed turbine disks, it is assumed that all blades on a given disk are identical. This leads to the prediction that all blades experience the same amplitude. However, it has been shown experimentally that significant variations in these amplitudes occur for different blades on the same disk. These variations arise due to the effects of mistuning, which refers to small differences in blade characteristics. Although the mistuning effect on the resonant response has been studied systematically, few papers have researched the mistuning effect on the random vibration. This paper, first, presents the analysis method of the mistuning effect on the random vibration. Second, the mistuning analyses for the random vibration and the resonant vibration of the bladed turbine disk are carried out, and the both results are compared. From these results, the mistuning effect on the random vibration is clarified.
Computational Study of the Effects of Shock Waves on Film Cooling Effectiveness
Authors: Zhang Chad X.-Z. , Hassan Ibrahim G.
Published: February 2010

The performance of a louver cooling scheme on a transonic airfoil has been studied numerically in this paper. Film cooling holes are located near the passage throat. The Mach number at the location of the jet exit is close to unity. A comparison of film cooling effectiveness between numerical prediction and experimental data for a circular hole shows that the numerical procedures are adequate. In addition to the shock wave effects and compressibility, curvature effect was also studied by comparing cooling effectiveness on the airfoil surface with that on a flat plate. Substantially higher cooling effectiveness for the louver cooling scheme on the airfoil was predicted at blowing ratios below 1 in comparison to other cooling configurations. At higher blowing ratios than 2 the advantages of the louver cooling scheme becomes less obvious. It was also found that for the same cooling configuration the cooling effectiveness on the transonic airfoil is slightly higher than that on a flat plate at moderately low blowing ratios below 1. At high blowing ratios above 2 when the oblique shock becomes detached from the leading edge of the hole exits, dramatic reduction in cooling effectiveness occurs as a result of boundary layer separation due to the strong shock waves. A coolant-blockage and shaped-wedge analogy was proposed and found to be able to qualitatively explain this phenomenon satisfactorily.
Experimental and Analytical Studies on Flexure Pivot Tilting Pad Gas Bearings With Dampers Applied to Radially Compliant Pads
Authors: Kim Daejong , Rimpel Aaron
Published: February 2010

Hydrodynamic flexure pivot tilting pad gas bearings (FPTPGBs) can enable successful operation of oil-free microturbomachinery, and FPTPGBs with radially compliant pads (FPTPGB-Cs) permit rotor centrifugal and/or thermal growth to exceed original bearing clearances and achieve higher speeds. This work presents the experimental and analytical study of such bearings and the application of dampers behind the pad radial compliance structure. A time domain orbit simulation method was implemented as the primary analysis tool to predict rotor-bearing response to imbalance, the presence and location of critical speeds, etc., and compare with test results. Experiments demonstrate the stable hydrodynamic operation of FPTPGBs with a ∼28.6 mm, 0.8 kg rotor above 120 krpm for the first time. The rotor-bearing system was intentionally destabilized in tests by increasing bearing clearances, and viscoelastic dampers added behind the FPTPGB pads delayed the onset of subsynchronous vibrations (from 43 krpm without damper to above 50 krpm with damper). Midrange subsynchronous vibrations of the destabilized system initiated at ∼20 krpm were suppressed by ∼25 krpm due to the stabilizing effect of rotor centrifugal growth. The viscoelastic dampers had a negligible effect on suppressing these midrange subsynchronous vibrations in experiments, but this was not demonstrated in simulations, presumed to be due to much lower stiffness contribution of the damper at lower frequencies.
Research on Nonlinear Fluid-Solid Interaction Dynamic Lubrication in Floating Ring Bearings
Authors: Yang JinFu , Yang ShengBo , Chen Ce , Fu ZhongGuang , Yuan Ping , Wu WenFeng
Published: February 2010

An experiment of floating ring bearings and flexible rotor in a micro turbo-engine is carried out. Nonlinear behavior of fluid-solid interaction in floating bearings is studied. And frequency characteristics And frequency characteristics of five typical vibrations regions in floating ring bearings test are presented. Furthermore, the difference and correlation between synchronous frequency characteristic in critical speed and subsynchronous whirl frequency harmonic response characteristic are illustrated._Based on the analytical expressions of load capacity and whirl frequency in single oil film lubrication bearings, the stability of inner and outer film in floating ring bearings is analyzed. It is shown that when half-speed oil whirl occurs in outer and inner oil film, the journal whirl ratios approach 0.5 and 0.3 respectively, which fairly corresponds with theoretical analysis. The paper can be a experimental and theoretical support for future performance evaluation and design of floating ring bearings.
Validation of an Efficient Unstructured Time-Domain Rotor/Stator Interaction Method
Authors: Burgos Manuel A. , Contreras Jesus , Corral Roque
Published: February 2010

A method to address the rotor/stator interaction problem on an edge-based Reynolds Averaged Navier-Stokes solver is presented. The implementation of the phase-lagged boundary conditions and a new original conservative discretization of the sliding plane in unstructured grids is discussed in detail. Results of the present method are compared with the experimental results obtained at NLR for a subsonic fan.
A Blade Resonance Prediction Using Fluid-Structure Interaction Calculation Method and Comparison With the Test
Authors: Kariya Daisuke , Yamamoto Toshiyuki , Ishihara Kunihiko
Published: February 2010

In this study, nozzle-wake resonance of a low-speed axial fan blade is numerically analyzed, and compared with the test. The numerical method is fluid-structure interaction (FSI) calculation, which combines unsteady structural FEM and unsteady CFD. Instantaneous blade surface pressure distribution is calculated by CFD, which is used as a boundary condition of unsteady FEM. Blade response is then calculated by FEM, and the deformation of the blade is transferred to CFD. Advantage of this method is that it can include the effects of real geometry, blade/vane arrangement, operating conditions, etc. Aerodynamic damping is also included. In this study commercial codes are used for both CFD and FEM. On the other hand, the authors have built a test rig of low-speed two-stage axial fan, specially designed for this study. The second stage rotor (2R hereafter) blades are intentionally designed to have a resonance of 1st bending mode near design speed. Vibratory stress, amplitude, and unsteady surface pressure of 2R blades were measured. Comparison of measurement and calculation revealed the potential of FSI method. Though there were some discrepancies between prediction and measurement, the blade response was reasonably explained by lift fluctuation estimated from blade surface pressure.
Analysis and Redesign of the Stationary Components for a Low Flow Coefficient Centrifugal Compressor Stage
Authors: Wang Zhiheng , Xi Guang
Published: February 2010

A low flow coefficient centrifugal compressor stage is characterized by the small relative outlet width, and is often one of the latter stages in the multistage compressor. The low flow coefficient stage is known to give lower stage efficiency in comparison with the conventional stage, which still leaves much more space to be improved with modern tools such as CFD techniques. In the paper the flow in a CO2 centrifugal compressor stage with a low design flow coefficient of 0.008 is simulated based on the 3D viscous CFD codes. The analysis shows the impeller gives a favorable performance over a wide range of low flow coefficient, but the high losses exist in the stationary components and this incurs the poor performance of the whole stage. In this case, the diffuser, the return channel and the meridional plane are redesigned. The redesigned stage has distinct improvements on the performance and the flow structure.
Rotordynamic Stability Under Partial Admission Conditions in a Large Power Steam Turbine
Authors: Gao Lin , Dai Yiping , Wang Zhiqiang , Xu Yatao , Ma Qingzhong
Published: February 2010

At present, the majority of power steam turbines operate under part-load conditions during most of their working time in accordance with the fluctuation of power supply. The load governing method may cause partial admission in control stage and even some pressure stages, which impacts much on the stability of the rotor system. In this paper, CFD and FEM method were used to analyze the effect of partial admission on rotor system stability. A new approach is proposed to simplify the 3D fluid model for a partial admission control stage. Rotordynamic analysis was carried out to test the stability of the HP rotor of a 600 MW steam turbine under different load conditions. 13 different governing modes on the rotor stability were conducted and data were analyzed. It is found that rotor stability varies significantly with different governing modes and mass flow rates, which is consistent with the operation. Asymmetric fluid forces resulted from partial admission cause a fluctuation of the dynamic characteristics of the HP bearings, which consequently affect the stability of the rotor system. One of the nozzle governing modes in which the diagonal valves open firstly is demonstrated as the optimal mode with the maximum system stability. The optimization has been applied to 16 power generation units in China and result in improved rotor stabilities.
Design Methods of Friction Damping at Blade-Disk Joints
Authors: Hong Jie , Chen Lulu , Ma Yanhong , Yang Xin
Published: February 2010

Friction at blade-disk joints is an important source of damping that reduces low frequency resonant amplitudes to acceptable levels in blade-disk assemblies. An effective method is proposed to predict nonlinear forced response of bladed disks taking account of the nonlinear force at blade-disk joints in frequency domain, which syncretizes the excellencies of harmonic balance method, dynamic softness method and tracking motion method. Constrained Mode Shapes are introduced to express the relative motion which occurs at the contact interfaces of blade roots. Compared to using free mode shapes, fewer number of constrained mode shapes is required in order to obtain the accurate resonant response of a system with friction dampers when the contact state is fully stick. It is more efficient to predict the nonlinear forced response of bladed disks taking account of the nonlinear force at blade-disk joints. Based on this method, the effect of Boundary Conditions on the resonant frequencies and forced response levels under different engine rotational speeds is investigated. Large error in the prediction of forced response levels under low engine rotational speed by using traditional methods is found. The effects of preload distribution at blade roots and excitation level are also investigated.
Effects of Upstream Wake Phasing on Transonic Axial Compressor Performance
Authors: Nolan S. P. R. , Botros B. B. , Tan C. S. , Adamczyk J. J. , Greitzer E. M. , Gorrell S. E.
Published: February 2010

The effect on rotor work, of the phase of an upstream wake relative to the rotor, is examined computationally and analytically for a transonic blade row. There can be an important impact on time-mean performance when the time-dependent circulation of the shed vortices in the wake is phase-locked to the rotor position, as occurs when there is strong interaction between rotor static pressure field and upstream vanes. The rotor work is found to depend on the path of the wake vortices as they travel through the blade passage; for configurations examined, the calculated change in time-mean rotor work was approximately three percent. It is shown that the effect on work input can be analyzed in terms of the influence of the time-mean relative stagnation pressure nonuniformity associated with the unsteady (but phase-locked) wake vortex flow field, in that changes in vortex path alter the location of the nonuniformity relative to the rotor. Lower pressure rise and work input occurs when the rotor blade is embedded in a region of low time-mean relative stagnation pressure than when immersed in a region of high relative stagnation pressure. In addition to the work changes, which are an essentially two-dimensional effect, it is demonstrated that the location of the wake may affect the tip clearance flow, implying a potential impact on pressure rise capability and rotor stability limits. Model calculations are presented to give estimates of the magnitude and nature of this phenomenon.