bluuebunny/crossref_metadata_2025 huggingface dataset:
Early CK‐MB Elevations Predict Ischemic Events in Stable Chest Pain Patients
Authors: Hedges Jerris R. , Young Gary P. , Henkel Gary F. , Gibler W. Brian , Green Terrence R. , Swanson J. Robert
Published: August 2009

ABSTRACT

Objective: To demonstrate that creatine kinase‐MB fraction (CK‐MB) elevations within three hours of presentation in the emergency department (ED) are associated with subsequent ischemic events in clinically stable chest pain patients.

Methods: Prospective cohort study at two university‐affiliated teaching hospitals. Participants were consenting ED chest pain patients 25 years old or older without evidence of rhythm or hemodynamic instability (n = 449). Exclusions included ST‐segment elevation ≥0.1 mV in ≥2 electrocardiogram leads, chest wall trauma, abnormal x‐ray studies, and incomplete data collection. Measurements included presenting and three‐hour CK‐MB levels, presenting ECG, initial clinical impression of coronary care unit need, and clinical follow up. Monitored adverse events included myocardial ischemia necessitating coronary angioplasty or cardiac bypass surgery, recurrent in‐hospital myocardial infarction, bradycardia requiring pacing, emergent cardioversion, cardiogenic shock, ventricular fibrillation, and death.

Results: Overall, nine (2%) of 449 patients experienced an ischemic event within the first 48 hours. All nine patients required either coronary angioplasty or bypass surgery. Four (44%) of the nine patients with 48‐hour ischemic events had elevated CK‐MB levels. Of 23 patients who had complications within one week of ED presentation, seven (30%) had elevated ED CK‐MB levels. An elevated CK‐MB level was associated with an ischemic event both within 48 hours (risk ratio 9.5; 95% CI 2.7–33.7) and within one week (risk ratio 5.2; 95% CI 2.3–11.7).

Conclusions: An elevated CK‐MB level within three hours of ED presentation is associated with a subsequent ischemic event in the clinically stable chest pain patient without ST‐segment elevation. However, the ED CK‐MB identifies only a minority of otherwise low‐risk patients who develop ischemic events; other markers for diagnosing myocardial ischemia in the ED are needed.
Emergency Department CK‐MB: A Predictor of Ischemic Complications
Authors: Hoekstra James W. , Hedges Jerris R. , Gibler W. Brian , Rubison R. Mike , Christensen Ronald A. ,   For the National Cooperative CK‐MB Project Group
Published: August 2009

ABSTRACT

Objective: To demonstrate that a positive CK‐MB in the emergency department (ED) predicts an increased risk for complications of myocar‐dial ischemia in patients admitted to the hospital for evaluation of chest pain.

Methods: 53 academic and community hospital EDs participated in this prospective observational cohort analysis of 5,120 patients with chest pain without ST‐segment elevation on the initial ED 12‐lead electrocardiogram. All patients were admitted for evaluation of chest pain in one of the participating hospitals as part of the National Cooperative CK‐MB Project. Patients were stratified by whether or not they had an elevated CK‐MB level in the ED. CK‐MB measurements were made on ED presentation and two hours later. Patient medical records were reviewed for inpatient diagnoses—myocardial infarction (MI) or other diagnosis —and for ischemic complications—cardiac‐related death, recurrent or delayed in‐hos‐pital MI, significant ventricular arrhythmias, new conduction defects, congestive heart failure, and cardiogenic shock.

Results: 369 (7.2%) of the 5,120 patients had MI. The proportion of patients with any complication in the MI group was 24%, while the complication rate in the non‐MI group was 0.4%. In all patients, regardless of final diagnosis, the relative risk of any complication was 16.1 (95% CI 11.0–23.6) in those with a positive ED CK‐MB versus negative ED CK‐MB patients. Similarly, the relative risk of death was 25.4 (95% CI 10.8— 60.2) in positive ED CK‐MB versus negative ED CK‐MB patients.

Conclusions: Multicenter data support the hypothesis that CK‐MB measurements can help risk‐stratify ED chest pain patients whose initial ECGs are without diagnostic ST‐segment elevation.
Selective Targeting of ER Exit Sites Supports Axon Development
Authors: Aridor Meir , Fish Kenneth N.
Published: August 2009

During neuron development, the biosynthetic needs of the axon initially outweigh those of dendrites. However, although a localized role for the early secretory pathway in dendrite development has been observed, such a role in axon growth remains undefined. We therefore studied the localization of Sar1, a small GTPase that controls ER export, during early stages of neuronal development that are characterized by selective and robust axon growth. At these early stages, Sar1 was selectively targeted to the axon where it gradually concentrated within varicosities in which additional proteins that function in the early secretory pathway were detected. Sar1 targeting to the axon followed axon specification and was dependent on localized actin instability. Changes in Sar1 expression levels at these early development stages modulated axon growth. Specifically, reduced expression of Sar1, which was initially only detectable in the axon, correlated with reduced axon growth, where as overexpression of Sar1 supported the growth of longer axons. In support of the former finding, expression of dominant negative Sar1 inhibited axon growth. Thus, as observed in lower organisms, mammalian cells use temporal and spatial regulation of endoplasmic reticulum exit site (ERES) to address developmental biosynthetic demands. Furthermore, axons, such as dendrites, rely on ERES targeting and assembly for growth.
Genetic loss of D‐amino acid oxidase activity reverses schizophrenia‐like phenotypes in mice
Authors: Labrie V. , Wang W. , Barger S. W. , Baker G. B. , Roder J. C.
Published: August 2009

Reduced function of the N‐methyl‐d‐aspartate receptor (NMDAR) has been implicated in the pathophysiology of schizophrenia. The NMDAR contains a glycine binding site in its NR1 subunit that may be a useful target for the treatment of schizophrenia. In this study, we assessed the therapeutic potential of long‐term increases in the brain levels of the endogenous NMDAR glycine site agonist D‐serine, through the genetic inactivation of its catabolic enzyme D‐amino acid oxidase (DAO) in mice. The effects of eliminating DAO function were investigated in mice that display schizophrenia‐related behavioral deficits due to a mutation (Grin 1D481N) in the NR1 subunit that results in a reduction in NMDAR glycine affinity. Grin 1D481N mice show deficits in sociability, prolonged latent inhibition, enhanced startle reactivity and impaired spatial memory. The hypofunctional Dao 1G181R mutation elevated brain levels of D‐serine, but alone it did not affect performance in the behavioral measures. Compared to animals with only the Grin 1D481N mutation, mice with both the Dao1G181R and Grin 1D481N mutations displayed an improvement in social approach and spatial memory retention, as well as a reversal of abnormally persistent latent inhibition and a partial normalization of startle responses. Thus, an increased level of D‐serine resulting from decreased catalysis corrected the performance of mice with deficient NMDAR glycine site activation in behavioral tasks relevant to the negative and cognitive symptoms of schizophrenia. Diminished DAO activity and elevations in D‐serine may serve as an effective therapeutic intervention for the treatment of psychiatric symptoms.
Irinotecan Side Effects Relieved by the Use of HI‐6 Oxime: In Vivo Experimental Approach
Authors: Vrdoljak Ana Lucić , Berend Suzana , Želježić Davor , Piljac‐Žegarac Jasenka , Pleština Stjepko , Kuča Kamil , Radić Božica , Mladinić Marin , Kopjar Nevenka
Published: August 2009

Abstract:  Some compounds, although not primarily designed as supportive drugs in chemotherapy, are promising candidates for clinical use. The ability of HI‐6 oxime to relieve the side effects of irinotecan was recently determined in vitro. In this animal study, we investigated the efficacy of HI‐6 in vivo, when given as a pre‐treatment and concomitantly with irinotecan. We evaluated the cholinesterase (ChE)/acetylcholinesterase (AChE) activity, the levels of oxidative stress markers, DNA damage and the radical scavenging capacity of HI‐6. Both HI‐6 and irinotecan inhibited ChE/AChE activity but showed different levels of ChE inhibition in plasma and AChE inhibition in the liver and brain tissue. We also observed a weak antioxidant capacity of HI‐6, undiscovered until now, and found an acceptable genotoxicity profile in three types of somatic cells in rats. The in vivo erythrocyte micronucleus assay showed that HI‐6 did not significantly change either the frequency of micronuclei or the ratio of polychromatic and normorchromatic erythrocytes. Taken together, our results provide a good argument in favour of HI‐6 as a promising molecule for further studies and eventual use in humans.
The Consideration of Synthetic Short Interfering RNA for Therapeutic Use
Authors: Li Jun , Liang Zicai
Published: August 2009

Abstract: Small RNA molecules can act as regulators of post‐transcriptional gene silencing and can target any given protein via the RNA interference pathway. This leads to the high expectation of small interference RNA (siRNA) as a therapeutic platform. Many companies and organisations are active in this development, which consequently forces siRNA’s pharmacokinetic studies because pharmacokinetics plays an important role in elucidating the pharmacodynamic and toxicological mechanism of test articles. In particular, pharmacokinetics is mandatory in investigational new drug application in many countries. Some pre‐clinical and clinical pharmacokinetic results have already been published and the fate of siRNA compounds in biological matrices has been explored in depth. The elucidation of the siRNA’s metabolism improves the rational design of siRNA for disease control. This review focuses on the study of synthetic siRNA pharmacokinetics, the challenges of siRNA as a therapeutic agent and the strategies involved for improving siRNA bioavailability from the view of siRNA metabolism.
Combination Therapy Using Verteporfin and Ranibizumab; Optimizing the Timing in the CAM Model
Authors: Debefve Elodie , Pegaz Bernadette , Ballini Jean‐Pierre , Van Den Bergh Hubert
Published: August 2009

Combining photodynamic therapy (PDT) using verteporfin (Visudyne®) with ranibizumab (Lucentis®) can optimize the overall treatment outcome by providing more efficacy in vessel closure, and thus reduce the need for retreatment in patients with wet age‐related macular degeneration. In this preclinical study in the chorioallantoic membrane (CAM) of the chicken embryo, we compare the vascular occlusion effects of verteporfin and ranibizumab as monotherapies with those observed in the combined therapy. In order to optimize the combination therapy, we varied the timing and sequence of the PDT and antivascular endothelial growth factor modalities. We observed that 1 day after PDT, the smaller blood vessels (∅ < 70 μm) of the CAM were selectively occluded, but as early as 2 days after PDT, both significant reperfusion and regrowth of new vessels were observed. Both these phenomena could be significantly delayed by application of ranibizumab. Ranibizumab itself did not induce any vascular occlusion. Under the applied conditions of combination therapy, the occlusion of the targeted blood vessels could be significantly extended to 3 days in this model compared with 1 day in the case of verteporfin monotherapy. Thus, in the present preclinical study, we demonstrate that for the applied conditions, the optimal time to administer ranibizumab is 24 h after PDT.
Competency‐Based Training: Objective Structured Clinical Exercises (OSCE) in Marriage and Family Therapy
Authors: Miller John K.
Published: August 2009

The field of marriage and family therapy (MFT) has recently engaged in the process of defining core competencies for the profession. Many MFT training programs are adapting their curriculum to develop more competency‐based training strategies. The Objective Structured ClinicalExamination(OSCE) is widely used in the medical profession to assess clinical competence. These examinations involve using simulated clinical situations as a tool in conducting summative evaluations of trainee competence. This article describes an adaptation of the OSCE procedures for competency‐based training of MFT students. Instead of using the procedures as a summative examination as is typical in medical education, this article proposes how to use them as formativeexercisesin the development of student competence. The development of the OSCE is discussed, including “blueprinting,” focused competencies, procedures, and feedback protocols. The article concludes with suggestions of how to continue the development of the OSCE for evaluation in MFT education.
On the Characterization of Lifting Forces During the Rapid Compaction of Deformable Porous Media
Authors: Barabadi Banafsheh , Nathan Rungun , Jen Kei-peng , Wu Qianhong
Published: August 2009

In a recent paper, Wu et al. (2005, “Dynamic Compression of Highly Compressible Porous Media With Application to Snow Compaction,” J. Fluid Mech., 542, pp. 281–304) developed a novel experimental and theoretical approach to investigate the dynamic lift forces generated in the rapid compression of highly compressible porous media, (e.g., snow layer), where a porous cylinder-piston apparatus was used to measure the pore air pressure generation and a consolidation theory was developed to capture the pore-pressure relaxation process. In the current study, we extend the approach of Wu et al. to various porous materials such as synthetic fibers. The previous experimental setup was completely redesigned, where an accelerometer and a displacement sensor were employed to capture the motion of the piston. The pore-pressure relaxation during the rapid compaction of the porous material was measured. The consolidation theory developed by Wu et al. was modified by introducing the damping effect from the solid phase of the porous materials. One uses Carman–Kozeny's relationship to describe the change in the permeability as a function of compression. By comparing the theoretical results with the experimental data, we evaluated the damping effect of the soft fibers, as well as that of the pore air pressure for two different porous materials, A and B. The experimental and theoretical approach presented herein has provided an important methodology in quantifying the contributions of different forces in the lift generation inside porous media and is an extension of the previous studies done by Wu et al.
A Porous Media Approach for Bifurcating Flow and Mass Transfer in a Human Lung
Authors: Kuwahara Fujio , Sano Yoshihiko , Liu Jianjun , Nakayama Akira
Published: August 2009

A porous media approach was proposed to investigate the characteristics of the bifurcating airflow and mass transfer within a lung. The theory of porous media was introduced in order to deal with a large number of bifurcations and a vast scale difference resulting from bifurcations. Upon introducing a two-medium treatment for the air convection and the diffusion in its surrounding wall tissue, the oxygen mass transfer between the inhaling air and the tissue was considered along with the effects of the blood perfusion on the mass transfer within the tissue. The overall mass transfer resistance between the inlet of the trachea and the blood in the capillaries was obtained on the basis of the porous media approach. The analysis reveals that there exists the optimal number of the bifurcation levels, namely, 23, that yields the minimum overall mass transfer resistance for the mass transport from the external air to the red blood cells. The finding is consistent with Bejan’s constructal law, namely, that for a flow system to persist in time, it must evolve in such a way that it provides easier access to its currents.
Therporaoustic Convection: Modeling and Analysis of Flow, Thermal, and Energy Fields
Authors: Mahmud Shohel , Fraser Roydon Andrew
Published: August 2009

The problem of therporacoustic (thermal-porous-acoustic) convection near a porous medium, representative of a stack in a thermoacoustic engine/refrigerator, is modeled and analyzed in this paper. Assumptions (e.g., long wave, short stack, and small amplitude oscillation) are made to enable simplification of the governing unsteady-compressible-viscous forms of the continuity, momentum, and energy equations to achieve analytical solutions for the fluctuating velocity and temperature and the complex Nusselt number. Boundary walls are assumed to be very thin in thickness and the conduction heat transfer inside the boundary walls are neglected in this paper. The derived analytical results are expressed mainly in terms of the Darcy number (Da), critical temperature gradient ratio (Γ0), Swift number (Sw), Prandtl number (Pr), and modified Rott’s and Swift’s parameters (fν and fk). The real part of the fluctuating flow complex Nusselt number approaches to the steady result, as reported in the literature, at the zero frequency limit. While in the high frequency limit, the real part of the complex Nusselt number matches well with the limit obtained by other oscillating flow researchers with slight differences explained by additional terms included in this work. A wave equation for the pressure fluctuation is modeled by combining the continuity, momentum, and energy equations and subsequent integrations which, in the inviscid no-stack limit, approaches the Helmholtz wave equation. Based on the derived energy flux density equation performance plots are proposed, which give the Swift number at the maximum energy transfer (Sw0) for a given Γ0 and Da.
Application of Delayed Detached Eddy Simulation and RANS to Compressor Cascade Flow
Authors: Gu Chunwei , Chen Meilan , Li Xuesong , Feng Fan
Published: August 2009

Spalart-Allmaras (S-A) model based Delayed Detached Eddy Simulation (DDES) is performed to investigate the flow field in a compressor cascade (NACA64A-905) with experimental data for calibration. The value of the modeling coefficient CDES in DDES is open for revision and depends heavily on the numerical schemes. The effects of CDES on the DDES results are studied and an optimal CDES value is estimated for the specific case, with MUSCL reconstructed Roe scheme incorporated in in-house CFD codes. CDES value of 0.2 is turned out reliable concerning both accuracy and convergence. S-A model is also performed for comparison. Results from different methods indicate that the time-averaged results by DDES with CDES of 0.2 are more consistent with the experimental results than those by S-A model. The instantaneous flow field predictions show that DDES is well capable of capturing the unsteady features of the cascade flow, especially the wake mixing process.
Influence of Blade Deterioration on Compressor and Turbine Performance
Authors: Morini M. , Pinelli M. , Spina P. R. , Venturini M.
Published: August 2009

Gas turbine operating state determination consists of the assessment of the modification, due to deterioration and fault, of performance and geometric data characterizing machine components. One of the main effects of deterioration and fault is the modification of compressor and turbine performance maps. Since detailed information about actual modification of component maps is usually unavailable, many authors simulate the effects of deterioration and fault by a simple scaling of the map itself. In this paper, stage-by-stage models of the compressor and the turbine are used in order to assess the actual modification of compressor and turbine performance maps due to blade deterioration. The compressor is modeled by using generalized performance curves of each stage matched by means of a stage-stacking procedure. Each turbine stage is instead modeled as a couple of nozzles, a fixed one (stator) and a moving one (rotor). The results obtained by simulating some of the most common causes of blade deterioration (i.e., compressor fouling, compressor mechanical damage, turbine fouling and turbine erosion, occurring in one or more stages simultaneously) are reported in this paper. Moreover, compressor and turbine maps obtained through a stage-by-stage procedure are compared to the ones obtained by means of map scaling.
High Temperature Radiation Heat Transfer Performance of Thermal Barrier Coatings With Multiple Layered Structures
Authors: Huang Xiao
Published: August 2009

Meeting the demands for ever increasing operating temperatures in gas turbines requires concurrent development in cooling technologies, new generations of superalloys, and thermal barrier coatings (TBCs) with increased insulation capability. In the case of the latter, considerable research continues to focus on new coating material compositions, alloying/doping existing yttria stabilized zirconia ceramics, and the development of improved coating microstructures. The advent of the EB-PVD coating process has made it possible to consider the creation of multiple layered coating structures to meet specific performance requirements. In this paper, the advantages of layered structures are first reviewed in terms of their functions in impeding thermal conduction (via phonons) and thermal radiation (via photons). Subsequently, the design and performance of new multiple layered coating structures based on multiple layered stacks will be detailed. Designed with the primary objective to reduce thermal radiation transport through TBC systems, the multiple layered structures consist of several highly reflective multiple layered stacks, with each stack used to reflect a targeted radiation wavelength range. Two ceramic materials with alternating high and low refractive indices are used in the stacks to provide multiple-beam interference. A broadband reflection of the required wavelength range is obtained using a sufficient number of stacks. In order to achieve 80% reflectance to thermal radiation in the wavelength range of 0.3 ∼ 5.3 μm, 12 stacks, each containing 12 layers, are needed, resulting in a total thickness of 44.9 μm. Using a one dimensional heat transfer model, steady state heat transfer through the multiple layered TBC system is computed. Various coating configurations combining multiple layered stacks along with a single layer are evaluated in terms of the temperature profile in the TBC system. When compared to a baseline single layered coating structure of the same thickness, it is estimated that the temperature on the metal surface can be reduced by as much as 90°C due to the use of multiple layered coating configurations. This reduction in metal surface temperature, however, diminishes with increasing scattering coefficient of the coating and total coating thickness. It is also apparent that using a multiple layered structure throughout the coating thickness may not offer the best thermal insulation; rather, placing multiple layered stacks on top of a single layer can provide a more efficient approach to reduce the heat transport of the TBC system.
Power Augmentation Study of an Existing Combined Cycle Power Plant by Overspray Inlet Fogging
Authors: Chiang Hsiao-Wei D. , Wang Pai-Yi , Li Hsin-Lung
Published: August 2009

With increasing demand for power and with shortages envisioned especially during the peak load times during the summer, there is a need to boost gas turbine power. In Taiwan, most of gas turbines operate with combined cycle for base load. Only a small portion of gas turbines operates with simple cycle for peak load. To prevent the electric shortage due to derating of power plants in hot days, the power augmentation strategies for combined cycles need to be studied in advance. As a solution, our objective is to add an overspray inlet fogging system into an existing gas turbine-based combined cycle power plant (CCPP) to study the effects. Simulation runs were made for adding an overspray inlet fogging system to the CCPP under various ambient conditions. The overspray percentage effects on the CCPP thermodynamic performance are also included in this paper. Results demonstrated that the CCPP net power augmentation depends on the percentage of overspray under site average ambient conditions. This paper also included CCPP performance parametric studies in order to propose overspray inlet fogging guidelines for combined cycle power augmentation.
An Object-Oriented Computer Code for Aircraft Engine Weight Estimation
Authors: Tong Michael T. , Naylor Bret A.
Published: August 2009

Reliable engine-weight estimation at the conceptual design stage is critical to the development of new aircraft engines. It helps to identify the best engine concept amongst several candidates. At NASA Glenn (GRC), the Weight Analysis of Turbine Engines (WATE) computer code, originally developed by Boeing Aircraft, has been used to estimate the engine weight of various conceptual engine designs. The code, written in FORTRAN, was originally developed for NASA in 1979. Since then, substantial improvements have been made to the code to improve the weight calculations for most of the engine components. Most recently, to improve the maintainability and extensibility of WATE, the FORTRAN code has been converted into an object-oriented version. The conversion was done within the NASA’s NPSS (Numerical Propulsion System Simulation) framework. This enables WATE to interact seamlessly with the thermodynamic cycle model which provides component flow data such as airflows, temperatures, and pressures, etc. that are required for sizing the components and weight calculations. The tighter integration between the NPSS and WATE would greatly enhance system-level analysis and optimization capabilities. It also would facilitate the enhancement of the WATE code for next-generation aircraft and space propulsion systems. In this paper, the architecture of the object-oriented WATE code (or WATE++) is described. Both the FORTRAN and object-oriented versions of the code are employed to compute the dimensions and weight of a 300-passenger aircraft engine (GE90 class). Both versions of the code produce essentially identical results as should be the case.
Measurements Versus Predictions for Rotordynamic Characteristics of a Flexure Pivot-Pad Tilting Pad Bearing in an LBP Condition at Higher Unit Loads
Authors: Hensley J. Eric , Childs Dara
Published: August 2009

Dynamic and static performance data are presented for a 117 mm diameter flexure-pivot tilting pad bearing in a load-between-pad configuration for speeds between 6000 and 12000 rpm and unit loads between 1–2.2 MPa. The present work is a continuation of 2005 tests on the same bearing by Al-Ghasem and Childs with unit loads at 0–1 Mpa. The rotordynamic coefficients are measured via a test rig that uses hydraulic shakers to excite the bearing stator. A psuedo-random excitation method is used to measure the complex direct and cross-coupled dynamic stiffness coefficients over a frequency range. The real and imaginary parts of coefficients are curve fitted to produce a constant-coefficient [K][C][M] bearing model. For the static load direction y, the direct added-mass coefficient Myy was needed to model the bearing’ “frequency dependence”. The direct unloaded mass coefficients Mxx was generally near zero. The analytical model generally predicted the correct trends for the change in rotordynamic coefficients with increasing loads but did not predict the measured orthotropy between results in the loaded and unloaded directions.
Effects of Blade Stack on Pipeline Compressor Impeller Performance
Authors: Cave Michael J.
Published: August 2009

Back to back testing of two centrifugal gas compressors used for natural gas pipeline transmission applications were completed. Blade geometry is very similar with the exception of stack of the impeller mean camber-lines. This resulted in significantly different lean angle distributions and rake at the exit of the two impellers. Both impellers performed exceptionally well in terms of efficiency and range, but with a marked difference in head making capability. CFD analysis using CFX-TASCflow was conducted to identify the underlying cause for the change in head. The CFD analysis was then validated using an experimental rig impeller that included traverse probe measurements at the pinch exit. Once the CFD was validated, a discussion is included on how to apply the knowledge learned to future impeller designs.
Stability Enhancement and Hysteresis Improvement of Axial Flow Fan by Discrete and Distributed Tip Injection Schemes
Authors: Roy Bhaskar , Veraarapu Subrahmanyam
Published: August 2009

An experimental study has been conducted to compare the effectiveness of injection schemes applied on an axial flow fan rotor tip. Injection was applied from the casing by varying different parameters e.g. injection angle, number of injection ports, and location of injection ports. The study was carried out in a low speed axial flow fan test rig at the Aerospace Engineering Department, IIT Bombay. The study is aimed at understanding the effect of tip injection on immediate post-stall hysteresis phenomena and stall margin gain. The study includes discrete and distributed injection schemes applied: i) only at the rotor tip mid chord, and ii) both at the leading edge and at the mid chord of the rotor tip (combined injection). The effect of injection applied have been studied (i) during recovery only, and (ii) during the entire period from unstalled flow to the end of recovery (hysteresis). It is observed that various tip injection schemes are successful, in varying degrees, in alleviating hysteresis. While discrete injection provides more stall margin gain, combined injection scheme is better in hysteresis recovery.
Experimental Heat Transfer and Discharge Coefficients for Single Confined Jet Impingement Normal to a Surface at Close Distances
Authors: Shapiro J. D. , Taslim M. E.
Published: August 2009

Heat transfer and flow discharge coefficients for confined jet impingement are being investigated for a single round jet impinging normal to a target surface less than one hole diameter from the jet origin. A search of open literature resulted in the availability of no discharge coefficient information, and limited heat transfer information, especially for the configuration of a confined jet in close surface impingement. The experiment has been conducted for a developing jet and utilizes liquid crystal thermography for heat transfer measurements. Nusselt numbers were obtained for jet Reynolds numbers between 15000 and 30000 with a gap to hole diameter ratio of 0.3 to 3. Discharge coefficient data were obtained for jet Reynolds numbers between 11000 and 59000, with a gap to hole diameter ratio of 0.2 to infinity. The heat transfer data obtained shows a secondary Nusselt number peak and similar trends to those seen in other close surface impingement studies. The data also show a crossover of Nusselt number at increasing radial distance from the jet stagnation point with increasing gap size which could be indicative of ambient air entrainment. The discharge coefficient data obtained show a decrease in discharge coefficient for a decrease in gap size. At constant pressure ratio conditions a large decrease in discharge coefficient is observed between pressure ratios of 1.05 and 1.11. The results of this study are applicable to many industrial applications. However, a discussion of close surface impingements applicability to gas turbines has been included, as well as a comparison of the experimental and numerical results.
Computational and Experimental Investigations of Jet Noise Reduction Concepts for Low-Bypass Ratio Military Gas Turbine Engines
Authors: Sinha N. , Kenzakowski D. C. , Ungewitter R. J. , Dash S. M. , Seiner J. M.
Published: August 2009

Computational and experimental activities supporting the design and evaluation of jet noise reduction concepts for low bypass-ratio military gas turbine engines are presented. Work has been focused on evaluations of lobed nozzle concepts, utilizing typical Field Carrier Landing Practice (FCLP) engine cycle conditions. At FCLP, the engine operates slightly over-expanded, with the result that jet noise emissions also include shock noise contributions. Reduction of nozzle exit area via introduction of lobes permits the nozzle to operate closer to ideal conditions, while also introducing vortices into the plume that may alter turbulence structure and noise emissions. Structured grid, computational fluid dynamics (CFD) investigations of isolated noise nozzles have been conducted. Determination of the optimal number of lobes for a nozzle has been a key objective of our studies. It was found that a six-lobe configuration is optimal, and that two-, three- and four- and twelve-lobe designs fail to provide performance improvement relative to the six-lobe design. While all lobe designs provided the same amount of area reduction for the baseline nozzle, the twelve-lobe configuration restricted the growth of the vortices introduced into the plume by the lobes. With reduced number of lobes, the far-field mixing of the exhaust plume remained unaffected, although some near-field benefits were observed. However, the turbulence characteristics, and hence noise, were not altered and the six-lobe design provided best performance, as demonstrated during tests at NCPA. The noise attenuation benefits of nozzle beveling were also assessed. These studies demonstrate the strong effect of dual jet interactions for the closely spaced, inward canted exhaust nozzles of a twin-engined aircraft. These dual nozzle plume-plume interactions have been found to have a very large effect on the turbulence structure, and hence noise. The analysis of lobed nozzle concepts with engine-engine interactions and vehicle aerodynamic/plume interactions has required the usage of multi-element unstructured grid numerics. Evaluations of aspirated lobe concepts were also conducted, where mass flux is introduced into the plume at the trailing edge of the lobes. Sensitivities to mass flow rates were examined and laboratory measurements of noise emissions in NCPA’s anechoic chamber are presented. Finally, impact of the lobes on nozzle performance during altitude flight are presented, along with CFD modeling upgrades required for performing simulations of complete aircraft/plume interactions.
Experimental and Numerical Investigation on Aeroacoustic Sound of Stator-Rotor System With Trailing Edge Blowing
Authors: Wu Yadong , Zhu Xiaocheng , Du Zhaohui
Published: August 2009

The noise radiation from industrial ventilation fans becomes one of the key points during design process, and reducing the noise level is the effort of all investigations. Recently, the trailing edge blowing (TEB) technique is used in the field of aeroengines and multistage turbo machines, which is used to reduce the interaction between wake and blade rows to improve the aeroacoustic performance of the rotating machines. In this paper the TEB technique is employed in the low speed ventilation fan with upstream stator. How to reduce blade passing frequency (BPF) noise and total noise level was investigated with experimental measurements and noise prediction based on CFD simulation flow filed. Based on the experimental measurements and noise predictions, the inlet flow of the low speed rotor is the main noise source for noise radiation. With TEB wake management and TEB up to the momentumless wake, the inlet flow for rotor was more uniform and shed wake from the rotor blades was weaken. The noise level from the fans was reduced.
Marine Gas Turbine Package for the Korean Navy PKX Program
Authors: Aye Naytoe , McAndrews Glenn , Mendenhall Bob
Published: August 2009

GE together with MTSI, Woodward, and Bibby Transmissions, has developed and delivered a compact gas turbine package for the Korean Navy. The prime mover is GE’s LM500 engine rated at 5500 shp. Remarkably, the period of execution was only 16 months including the development and construction of the production test cell. The paper will examine all phases of the propulsion system development from ship integration to sea trial results (scheduled for Spring 2008). Of particular interest is the design evolution of the high speed coupling shaft (HSCS). Of all of the component development activities, the HSCS was the most challenging. Progress in this particular area will benefit future marine propulsion programs requiring shock qualification.
Tip Clearance Vortex Oscillation, Vortex Shedding and Rotating Instabilities in an Axial Transonic Compressor Rotor
Authors: Hah Chunill , Bergner Jo¨rg , Schiffer Heinz-Peter
Published: August 2009

Unsteady flow characteristics in a modern transonic axial compressor operating near stall are studied in detail. Measured data from high-response pressure probes show that the tip clearance vortex oscillates substantially near stall. Instantaneous flow structure varies substantially among different blade passages even with uniform inlet flow. Fast Fourier transformation of measured wall pressure shows a dominant frequency component that is between 30% and 40% of the rotor speed. To identify and analyze this phenomenon, computational studies based on a single passage and full annulus were carried out. The flow field in a transonic compressor near stall is heavily influenced by the unsteady motion of tip clearance vortices. Therefore, a Large Eddy Simulation (LES) was carried out to capture transient characteristics of the tip clearance vortex more realistically. The wall pressure spectrum from the current full annulus analysis also shows a dominant frequency when the rotor operates near stall. The calculated peak frequency is about 30% of the rotor frequency. The dominant frequency, which is non-synchronous with the rotor blade, is due to rotating flow instabilities. Flow interactions across blade passages due to synchronized tip clearance vortex oscillation seem to be the main cause.
Unique Replacement Method Developed for the U.S. Navy’s Newest Gas Turbine Powered Warship
Authors: Hatcher Shaun D. , Driscoll Matthew J. , Boughner Abe L.
Published: August 2009

The Navy’s newest big-deck Amphibious Assault Ship, LHD 8 Makin Island, is currently under construction and scheduled for delivery in late 2008. LHD 8 utilizes a gas turbine propulsion system that replaces the steam propulsion system used on the previous seven ships of the class. LHD’s are similar in design to aircraft carriers with a full length flight deck and island to the starboard side. Additionally the LHD 8 machinery spaces are directly below storage decks for mission equipment. Because of internal arrangements and the convoluted routes of the intake ducting the traditional method of removing the gas turbines through the superstructure via shore side crane was not possible. The LHD 8 will utilize a method of change out from within the ship. The paper will discuss the design considerations involved in developing this changeout method as well as a review and discussion of the physical changeout demonstration conducted by the shipbuilder. The paper will discuss the design development process such as the environmental qualifications of ship hardware, ship integrity and survivability, special tooling developed for LHD 8, differences from the traditional changeout methods as well as the US Navy’s maintenance philosophy for this ‘first-of-class’ ship design. Included in the paper will be ship drawings, photos and diagrams of the change out hardware, removal routes, special tooling and support equipment.
Combining Lead Functions and Logistic Regression for Predicting Failures on an Aircraft Engine
Authors: Bryg David J. , Mink George , Jaw Link C.
Published: August 2009

The increasing demand for performance and durability of advanced aerospace systems has increased the need for health management of these systems. Effective health management involves seamless integration of failure diagnostics, failure prediction, part life estimation, and maintenance logistics. These capabilities have only partially been implemented in current health management systems. Hence the effectiveness of current management systems has not achieved its potential. To achieve the goal of effective prognostic and health management (PHM), promising technologies from various disciplines must be integrated. One of these technologies is logistic regression. In this method, aircraft engine takeoff data is combined with control system fault information and by introducing lead times prior to the fault. Lead times of 1, 7, 14, and 30 days were analyzed using logistic regression on the difference from expected thermodynamic values. The resulting equations give probability of failure over time. An example using real engine data from GE-F414 engines to predict engine stall and anti-ice valve failures are presented. The results show good predictability of these events between a week and a month in advance. For example, for the event of an imminent anti-ice valve failure, the true-negative fraction was 99.6% and the positive-predictive value was 93.1%. This methodology can be combined with an engine health monitoring (EHM) system to provide prognostic failure predictions. Receiver Operator Characteristic (ROC) curves were evaluated as an additional measure of the quality of the predictions. These ROC curves show that there is prognostic value with this approach. This methodology can be updated and refined with additional data. As the results get more refined, the reliability of the fleet can increase, costs can be reduced, and safety increased.
A Film-Cooling Correlation for Shaped Holes on a Flat-Plate Surface
Authors: Colban Will F. , Thole Karen A. , Bogard David
Published: August 2009

A common method of optimizing coolant performance in gas turbine engines is through the use of shaped film-cooling holes. Despite widespread use of shaped holes, existing correlations for predicting performance are limited to narrow ranges of parameters. This study extends the prediction capability for shaped holes through the development of a physics-based empirical correlation for predicting laterally-averaged film-cooling effectiveness on a flat plate downstream of a row of shaped film-cooling holes. Existing data was used to determine the physical relationship between film-cooling effectiveness and several parameters, including; blowing ratio, hole coverage ratio, area ratio, and hole spacing. Those relationships were then incorporated into the skeleton form of an empirical correlation, using results from the literature to determine coefficients for the correlation. Predictions from the current correlation, as well as existing shaped hole correlations and a cylindrical hole correlation were compared to the existing experimental data. Results show that the current physics-based correlation yields a significant improvement in predictive capability, by expanding the valid parameter range and improving agreement with experimental data. Particularly significant is the inclusion of higher blowing ratio conditions (up to M = 2.5) into the current correlation, whereas the existing correlations worked adequately only at lower blowing ratios (M ≈ 0.5).
Diagnosing Coupled Lateral-Torsional Vibrations in Turbomachinery
Authors: Rajagopalan Vinayaka N. , Vance John M.
Published: August 2009

Rotordynamic instability, commonly observed as subsynchronous vibration, is a serious problem that can cause heavy damage to a turbomachine or make it incapable of operation due to high vibration levels. However, all subsynchronous vibrations are not necessarily unstable. A way to quickly diagnose them would be helpful. In an earlier paper, the authors presented data from experiments that simulated various causes of sub-synchronous vibrations, some causes being genuine rotordynamic instabilities and some others being benign (stable), and identified ways to diagnose and classify the subsynchronous motions. In a continuation of the same study, subsynchronous vibrations due to coupled lateral-torsional effects are experimentally simulated, the objective being to signal-analyze these vibrations to find unique signatures that identify this cause and also be able to recognize if they are a true rotordynamic instability or not. To this end, a test rig was built with parallel shafts coupled by gears, driven by a DC motor at one end and loaded at the other end, to closely simulate a real-world machine. A torsional mathematical model for the test rig is also presented to predict its torsional natural frequencies. Experiments were conducted wherein the first torsional natural frequency was externally excited, with the shaft spinning at a higher speed. The result was a false sub-synchronous “instability” signal in the lateral measurements. A method to distinguish these vibrations from a genuine lateral non-synchronous instability is presented. Also, a new diagnostic method to classify the subsynchronous vibration as benign is elucidated.
Future Aero-Engines’ Optimisation for Minimal Operating Costs
Authors: Colmenares Fernando , Pascovici Daniele , Ogaji Stephen , Pilidis Pericles , Garci´a Alexander , Latorre Luis
Published: August 2009

While aircraft environmental performance has been important since the beginnings of commercial aviation, continuously increasing passenger traffic and a rise in public awareness have made aircraft noise and emissions two of the most pressing issues hampering commercial aviation growth today. The focus of this study is to determine the feasibility of vey-high bypass ratio, geared and contra-rotating aero engines (see figures 2–4) for short range commercial aircraft in terms of economics and environment. This involves optimising the engines’ design point to minimise the direct operating cost and evaluating the economic and environmental impact. The results present a great potential benefit of the geared turbofan compared to high BPR one (baseline) to reduce DOC; however this may involve NOx penalties, that is an increase of 11.6% in comparison to the baseline. The CRTF engine seems to be, at least according to the simulations, a very promising solution in terms of environmental and economical performance. This is one on the series of work that would be carried out using the design tool proposed. Further work on the assessment of more radical turbofans at different economical and environmental scenarios would be published when completed.
On the Coupling of Designer Experience and Modularity in the Aerothermal Design of Turbomachinery
Authors: Jarrett Jerome P. , Ghisu Tiziano , Parks Geoffrey T.
Published: August 2009

The turbomachinery aerodynamic design process is characterized both by its complexity and the reliance on designer experience for success. Complexity has led to the design being decomposed into modules; the specification of their interfaces is a key outcome of preliminary design and locks-in much of the final performance of the machine. Yet preliminary design is often heavily influenced by previous experience. While modularity makes the design tractable, it complicates the appropriate specification of the module interfaces to maximize whole-system performance: coupling of modularity and designer experience may reduce performance. This paper sets out to examine how such a deficit might occur and to quantify its cost in terms of efficiency. Two disincentives for challenging decomposition decisions are discussed. The first is where tried-and-tested engineering “rules of thumb” accord between modules: the rational engineer will find alluring a situation where each module can be specified in a way that maximizes its efficiency in isolation. The second is where there is discontinuity in modeling fidelity, and hence difficulty in accurately assessing performance exchange rates, between modules. In order to both quantify and reduce the potential cost of this coupling we have recast the design problem in such a way that what were previously module interface constraints become key system design variables. An example application of our method to the design of a generic turbofan core compression system is introduced. It is shown that nearly 1 percentage point equivalent compressor adiabatic efficiency can be saved.