bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocardiographic and Electrophysiologic Effects of Dexmedetomidine on Children
Authors: ERGUL YAKUP , UNSAL SERKAN , OZYILMAZ ISA , OZTURK ERKUT , CARUS HAYAT , GUZELTAS ALPER
Published: March 2015

Background

Dexmedetomidine (DEX) is a highly selective alpha‐2‐adrenergic agonist approved for short‐term sedation and monitored anesthesia care in adults. Its effects on the electrocardiography and cardiac conduction tissue are not well described in the literature. Therefore, we aimed to characterize the electrocardiographic and electrophysiologic effects of DEX in children.

Methods

Twenty children (11 boys and nine girls) between the ages of eight and 17 undergoing electrophysiology study and ablation of the supraventricular tachycardia had hemodynamic and cardiac electrophysiologic variables measured before and during the administration of DEX (1 microgram/kg IV over 10 minutes followed by a 10‐minute continuous infusion of 0.5 microgram/kg/h).

Results

A significant decrease in heart rate was seen after the administration of DEX, but the systolic‐diastolic‐mean arterial pressure, respiratory rate, and end‐tidal carbon dioxide did not change. Corrected sinus node recovery times and baseline sinus cycle lengths, which are markers of sinus nodal function, were both lengthened with the administration of DEX. Atrioventricular (AV) nodal function, as evidenced by the Wenckebach cycle length, the ventriculoatrial block cycle length, and AV nodal effective refractory periods, was lengthened significantly. We also found that DEX increased the atrial refractory period and diminished atrial excitability.

Conclusions

DEX significantly depressed sinus and AV nodal function in pediatric patients without significant electrocardiogram interval changes, other than a trend toward lower heart rates. Although no spontaneous AV nodal block and no clinically significant bradycardia were seen, we recommend that DEX be used with caution in patients at risk for bradycardia and/or AV nodal dysfunction due to its associated comorbidities.
Informed consent procedures with cognitively impaired patients: A review of ethics and best practices
Authors: Fields Lindy Marie , Calvert James Douglas
Published: March 2015

Aims

The objectives of this article are to discuss ethical issues of informed consent in cognitively impaired patients and review considerations for capacity determination. We will also discuss how to evaluate capacity, determine competence, and obtain informed consent when a patient is deemed incompetent. This review emphasizes how to carry out informed consent procedures when capacity is questionable and discusses measures supported for use when determining cognitively impaired patients' ability to consent.

Methods

Information was gathered from medical and psychological codes of ethics, peer‐reviewed journals, published guidelines from health‐care organizations (e.g.,AmericanMedicalAssociation), and scholarly books.GoogleScholar andPsycINFOwere searched for articles related to ‘informed consent’ and ‘cognitive impairment’ published inEnglish between 1975 and 2014. Relevant sources referenced in retrieved publications were subsequently searched and reviewed.

Results

We selected 49 sources generated by our search. Sources were included in our review if they presented information related to at least one of our focus areas. These areas included: review of informed consent ethics and procedures, review of cognitive impairment evaluations, recommendations for measuring cognitive capacity, and alternative forms of informed consent.

Conclusions

Patients' cognitive impairments can hinder the ability of patients to understand treatment options. Evaluating the capacity of patients with cognitive impairment to understand treatment options is vital for valid informed consent and should be guided by best practices. Thus, proper identification of patients with questionable capacity, capacity evaluation, and determination of competence, as well as reliance upon appropriate alternative consent procedures, are paramount.
Prevalence and determinants of declining versus stable hemoglobin levels in whole blood donors
Authors: Nasserinejad Kazem , van Rosmalen Joost , van den Hurk Katja , Baart Mireille , Hoekstra Trynke , Rizopoulos Dimitris , Lesaffre Emmanuel , de Kort Wim
Published: March 2015

BACKGROUND

A too short recovery time after blood donation results in a gradual depletion of iron stores and a subsequent decline in hemoglobin (Hb) levels over time. This decline in Hb levels may depend on individual, unobserved characteristics of the donor.

STUDY DESIGN AND METHODS

We used a data set of 5388 Dutch blood donors from the Donor InSight study. The statistical analysis is based on a Bayesian growth mixture model, which assumes that each donor belongs to one of several groups. Each group implies a different Hb trajectory, and donors with similar longitudinal trajectories belong to the same group. Analyses were performed for male and female donors separately.

RESULTS

For both sexes the model identified four groups of donors. Stable Hb trajectories were found among 14% of male donors and 15% of female donors; declining Hb trajectories were observed in the remaining groups of donors. The percentage of donor deferrals differed strongly between groups.

CONCLUSION

The model can be used to predict to which group a donor belongs, and this prediction can be updated after each donation. This is of high practical importance because early identification of donors with declining Hb levels could help to tailor donation intervals and to prevent iron deficiency and donor deferrals.
Efficacy of Postoperative Antimicrobial Use for Clean Orthopedic Implant Surgery in Dogs: A Prospective Randomized Study in 100 Consecutive Cases
Authors: Pratesi Andrea , Moores Andrew P. , Downes Ciara , Grierson James , Maddox Thomas W.
Published: March 2015

Objectives

To investigate whether administration of postoperative oral antimicrobial drugs has a beneficial effect on preventing surgical site infections (SSI) in clean orthopedic surgery involving stainless steel plating systems.

Study Design

Randomized prospective clinical study.

Animals

Dogs (n = 97).

Methods

One hundred consecutive cases (97 dogs) that had clean orthopedic surgery requiring stainless steel plate fixation were randomly assigned using a random number generator to either YES group (administration of postoperative oral antimicrobials) or NO group (no administration of postoperative oral antimicrobials). Dogs in YES group were administered oral cefalexin or potentiated amoxicillin for 7 days, whereas dogs in NO group were discharged without oral antibiotics. Minimum follow‐up was 12 months. Multivariable logistic regression was used to determine risk factors for SSI.

Results

Overall postoperative infection rate was 12.9%. Infection occurred in 2 cases (4.3%) administered postoperative oral antimicrobials and in 10 cases (21.3%) not administered postoperative antimicrobials. Total anesthetic time and use of oral antimicrobials were the only significant factors associated with SSI. Use of postoperative antimicrobials was associated with a significant reduction in the risk of infection by ~84% and risk of infection was increased by ~2% for each minute increase in anesthesia time.

Conclusions

Administration of oral postoperative antimicrobials had a protective effect against development of SSI in clean orthopedic implant surgery.
Form, function and phylogeny: comparative morphometrics of Lake Tanganyika's cichlid tribe Tropheini
Authors: Wanek Katrin A. , Sturmbauer Christian
Published: March 2015

Lake Tanganyika's cichlid fishes represent one of the most diverse species assemblages of the world. In this study we focused on the tribe Tropheini which occupies several trophic niches, mostly in rocky habitats. We analysed morphological variation of seventeen closely related species by means of geometric morphometric methods and related these data to ecological characteristics and phylogeny of the study species. It turned out that morphology mostly correlated well with ecological parameters, but not always closely with the degree of the phylogenetic relatedness of the species. Overall, body shapes in the tribe Tropheini are of great evolutionary plasticity, but variation is restricted to particular body parts: the preorbital region once again emerged as a key factor that facilitated their impressive radiation.
Comparison of Heat Transfer Measurements With Computations for Turbulent Flow Around a 180 Degree Bend
Authors: Besserman D. L. , Tanrikut S.
Published: March 2015

Results of detailed heat transfer measurements are presented for all four walls of a 180° 1:1 aspect ratio duct. Experiments using a transient heat transfer technique with liquid crystal thermography were conducted for turbulent flow over a Reynolds numbers range of 12,500–50,000. Computational results using a Navier-Stokes code are also presented to complement the experiments. Two near-wall shear-stress treatments (wall functions and the two layer wall integration method) were evaluated in conjunction with k-ε formulation of turbulence to assess their ability to predict high local gradients in heat transfer. Results showed that heat transfer on the convex and concave walls is a manifestation of the complex flow field created by the 180° bend. For the flat walls, the streamwise average Nusselt number increases to approximately two times the fully developed turbulent flow value. Ninety degrees into the bend, the importance of the cross-stream gradients is evident with the Nusselt number varying from approximately one to three times the fully developed turbulent flow value. The numerical predictions with two-layer wall integration k-ε turbulence model show very good agreement with the experimental data. These results reinforce the need to accurately predict local heat transfer rates in cooling passages of advanced turbine airfoils to enhance the durability of these components.
Wave Engine Aerothermodynamic Design
Authors: Weber Helmut E.
Published: March 2015

A method for aerothermodynamic preliminary design of a wave engine is presented. The engine has a centrifugal precompressor for the wave rotor which feeds high and low pressure turbines. Three specific wave engine designs are presented. Wave rotor blades are naturally cooled by the ingested air; thus combustion temperatures can be as high as 1900°K. Engine pressure ratios of over 25 are obtained in compact designs. It is shown that no nozzles at the end of the rotor blade passages yield the highest cycle efficiencies which can be over 50%. Rotor blades are straight and easily milled, cast or fabricated.
Experimental Study of the Swirling Flow in the Internal Volute of a Centrifugal Compressor
Authors: Ayder E. , Van Den Braembussche R.
Published: March 2015

A detailed study of the swirling flow in a rectangular volute of a centrifugal compressor is presented. The 3D flow field has been measured by means of a five hole probe at six different cross sections for three different operating points of the compressor.

For high mass flow, the large radial velocity component at the diffuser exit creates a strong swirling flow with a forced vortex type of velocity distribution. The centrifugal force resulting from this motion is balanced by the increase of static pressure from the swirl center to the volute wall. Due to the effect of circumferential curvature a zone of high through flow velocity occurs next to the volute inner wall.

Less swirl is generated for optimum mass flow resulting in smaller pressure gradients over the cross section. Low energy fluid accumulates near the inner wall of the cross section.

For low mass flow, a large region of separated flow is observed and more uniform static pressure has been measured over the cross section.

The effect of the tongue on the flow structure in the first and last cross section is also discussed.

This study is the follow-up of previous studies described in ASME paper 89-GT-183 and 90-GT-49. The results obtained verify the previous studies and provide a better understanding of the flow structure inside internal volutes of rectangular cross section.
A Contribution to the Study of Exit Flow Angle in Radial Turbines
Authors: Brizuela Edward A.
Published: March 2015

The emergence and evolution of relative whirling motions in the exducer region of an Inward Flow Radial Turbine is discussed. Existing models of relative motion are reviewed and expanded by consideration of the effect of centrifugal forces differences arising from velocity gradients. It is shown that the often observed phenomenon of outlet overturn/underturn is inherent to the use of straight-helix exducers.

Explicit mathematical relationships between exit velocities and radius are not available. If, however, such relationships could be considered linear, it is shown that two new reference radii may be identified such that the net outlet properties can be measured or computed at these locations as lump parameters. These radii are different from the often used hydraulic radius.

The new models and reference radii are verified using published experimental data.
Optical Measurements of Unducted Fan Flutter
Authors: Kurkov Anatole P. , Mehmed Oral
Published: March 2015

The paper describes a nonintrusive optical method for measuring flutter vibrations in unducted fan or propeller rotors and provides detailed spectral results for two flutter modes of a scaled unducted fan. The measurements were obtained in a high-speed wind tunnel. A single-rotor and a dual-rotor counterrotating configuration of the model were tested; however, only the forward rotor of the counterrotating configuration fluttered. Conventional strain gages were used to obtain flutter frequency; optical data provided complete phase results and an indication of the flutter mode shape through the ratio of the leading- to trailing-edge flutter amplitudes near the blade tip. In the transonic regime the flutter exhibited some features that are usually associated with nonlinear vibrations. Experimental mode shape and frequencies were compared with calculated values that included centrifugal effects.
Detailed Measurements of the Flow Field in a Transonic Turbine Cascade
Authors: Detemple-Laake E.
Published: March 2015

Systematic experimental investigations of the transonic flow through a plane cascade consisting of profiles designed for a highly loaded gas turbine rotor of a high pressure stage were performed. The experiments comprise side wall pressure distribution measurements in a blade passage and both profile pressure distribution and wake traverse measurements in various planes from midspan to the side wall. The parameters varied are the inlet flow angle and the downstream Mach number. Schlieren photopraphs and oil flow patterns on the blades and on the side wall are included. The experimental results are interpreted with respect to the existing flow models describing shock wave boundary layer interactions and secondary flow effects. The experimental data are compared with three-dimensional viscous numerical results.
Simulation of an Advanced Twin-Spool Industrial Gas Turbine
Authors: Zhu Ping , Saravanamuttoo H. I. H.
Published: March 2015

A full range mathematical model of the LM-1600 gas turbine has been developed, for future use in EHM studies. No data was available from the manufacturer other than sales brochures giving some design and off-design performance. The model was developed using generalized component characteristics and shows excellent agreement with field data from a pipeline operator.

A new method has been developed for doing the matching calculations, starting from the turbine (hot) end rather than from the compressor operating point. This method permits solution on a PC, and can be used for studying the full range of operating conditions and the development of fault matrices.
Design, Development, Testing, and Operational Experience of the Allison Model AG9130 Ship Service Gas Turbine Generator Set
Authors: Halsey Jack E. , Russom Dennis
Published: March 2015

Allison has developed both an engine and a ship service gas turbine generator set (SSGTG) for use in the U.S. Navy DDG-51 destroyer program. The engine is the Model 501-K34, which uses the technology of the new generation of Allison 501 engines. The generator set is the Model AG9130, a totally self-contained package powered by the Model 501-K34. The design concepts and resulting design for the engine and generator set are provided, as well as an overview of the performance characteristics. The ship’s electrical system is discussed, and the role of the generator set in that system is defined. The design features of the generator set are given with further discussion of the main components (the engine, speed reduction gearbox, generator, base and enclosure) and the mechanical support systems for these components (the gas turbine lube oil system, reduction gear/generator lube oil system, fuel system, seawater cooling system, starting system, bleed air system, cooling air system, fire protection system, water wash and icing detection system, and the electrical system). A review of the testing for both the engine and the SSGTG at Allison Gas Turbine and the Naval Ship Systems Engineering Station is presented. Installation and integration of the SSGTG into the ship closes the discussion.
Minimization of the Number of Cooling Holes in Internally Cooled Turbine Blades
Authors: Dulikravich George S. , Kosovic Branko
Published: March 2015

This work represents an extension of the earlier research on inverse determination of proper locations and sizes of a given number of coolant flow passages (holes) subject to specified surface temperatures and heat fluxes. The methodology is extended to allow designer to guess the required number of holes and the minimal allowable diameter of a hole. A constrained optimization algorithm is then used to minimize the total number of cooling holes, while satisfying user-specified hot surface temperatures and heat fluxes. Premature termination of the optimization process due to the existence of local minimas has been satisfactorily resolved by automatic switching of the objective function formulation whenever the local minima is detected. The convergence criteria of the iterative process, which can be specified by the user, was found to have a strong influence on the accuracy of the entire inverse design optimization algorithm.
Turbine Cascade Calculations Through a Fractional Step Navier-Stokes Algorithm
Authors: Giannakoglou K. , Simandirakis G. , Papailiou K. D.
Published: March 2015

An explicit, finite-difference, fractional-step Navier-Stokes method is presented for the prediction of two-dimensional turbomachinery cascade flows. The method also accounts for three-dimensional effects due to radius and streamtube thickness variations. The two-layer Baldwin-Lomax algebraic turbulent model is used to effect closure and its practical implementation is discussed in detail. Three different flow problems are examined and compared with experimental and numerical results obtained elsewhere. These cases deal with transonic flows in the last stage of a steam turbine rotor and a low solidity turbine cascade, as well as the subsonic flow around an isolated RAE2822 profile. The latter case was used for comparing two different transition criteria, implemented in the present code. C-type computational grids are used which are quasi-orthogonal in the near wall region.
3-D Loss Prediction Based on Secondary Flow and Blade Shear Layer Interaction
Authors: Katramatos D. T. , Kaldellis J. K.
Published: March 2015

The 3-D loss distribution along axial turbomachines has been investigated in the present work. For this purpose, our well documented secondary flow calculation method has been interactively coupled with our fast blade-to-blade shear layer calculation code, in order to predict the complete secondary flow and profile loss distribution.

The presence of an even moderate secondary flow field modifies the flow angle distributions, thus making clear the need of a reliable profile loss prediction method for off-design cases, especially in the presence of separation.

Accordingly, the blade-to-blade code predicts the profile loss distribution and subsequently provides the correct total pressure field for the secondary flow calculation.

The combination of the above mentioned codes finally gives a realistic picture of the flow quantities at any S3 surface along a machine at a minimal computer cost.

Several test cases, including axial compressor and turbine cascades as well as transonic axial compressor blade rows have been investigated. The results are in good agreement with the experimental data and are favourably compared with various recent correlations.
Viscous Flow Computations for Compressor/Combustor Diffuser Design to Allow Air Extraction for IGCC Systems
Authors: Agrawal Ajay K. , Yang Tah-Teh
Published: March 2015

A computational procedure based on the solution of fully elliptic Navier-Stokes equations on a body-fitted non-orthogonal grid was used to obtain flow fields in annular diffusers with a suction slot at the inner and outer walls. The turbulence effects were simulated by high Reynolds number form of the k-ε model. The calculation method was used to modify an industrial gas turbine (GE MS · 7001F) compressor/combustor annular diffuser to allow extraction of compressed airflow for coal gasification in simplified IGCC Systems. The air for gasification was extracted through a suction slot on the outer wall of the diffuser which was curved to improve the overall performance and to avoid flow separation; both of these insured by providing accelerated flow through the suction slot and nearly constant wall pressure downstream of the slot. Suction slot and outer wall geometries to result in the above conditions were determined by a trial and error procedure. The diffuser’s performance was further improved by extracting 6% of the compressed air through a slot at the inner wall, kept straight due to structural constraints. The resulting diffuser arrangement was relatively insensitive to the upstream disturbances.
Future Trends in Turboshaft Engines up to the 5000 Horsepower Class
Authors: Vogt Robert L.
Published: March 2015

Advanced technology now being demonstrated in the test cell will provide growth in existing engine ratings in the near term and substantially improve new technology engines early in the twenty-first century. The benefits these advancements provide; to the engines, to the salient characteristics important to users and designers, and to the vehicles they will power are discussed.
A 3D FEM Variational Aerodynamic Calculation and Performance Analysis of a Leaned Turbine Stator Cascade
Authors: Zhang Zhi-Gang , Zhou Dong-Mei , Li Yan-Sheng
Published: March 2015

An investigation into the pressure distribution in a turbine nozzle cascade with and without leaned blades has been made using a 3D subsonic variational FEM. We can conclude from our studies that the gas flow circulation is the essential factor of redistributing the secondary flow loss along the blade height in a leaned cascade. In addition, this paper recommends a direction for further research into the leaned stator cascade.
Unsteady Flow Within Centrifugal Compressor Channels Under Rotating Stall and Surge
Authors: Mizuki Shimpei , Oosawa Yoshimi
Published: March 2015

Unsteady flow patterns throughout a centrifugal compressor system during the rotating stall and the surge were measured experimentally. Various kinds of unsteady behaviors of the flow appeared both continuously and suddenly as the flow rate decreased. The part-span stall, the full-span stall, the mild and the deep stalls and the deep surge appeared clearly. The fluctuations caused by the full-span stall were seen even during the surge and affected the flow within the scroll through the vaneless diffuser. The experimental results were compared with those computed by the lumped parameter theory. The good agreements between them were obtained when the appropriate values were selected for the lumped parameters.
Active Suppression of Rotating Stall and Surge in Axial Compressors
Authors: Day I. J.
Published: March 2015

This paper reports on an experimental program in which active control was successfully applied to both rotating stall and surge in a multi-stage compressor. Two distinctly different methods were used to delay the onset of rotating stall in a four stage compressor using fast acting air injection valves. The amount of air injected was small compared to the machine mass flow, the maximum being less than 1.0%. In some compressor configurations modal perturbations were observed prior to stall. By using the air injection valves to damp out these perturbations an improvement of about 4.0% in stall margin was achieved. The second method of stall suppression was to remove emerging stall cells by injecting air in their immediate vicinity. Doing this repeatedly delayed the onset of stall, giving a stall margin improvement of about 6.0%. Further studies were conducted using a large plenum downstream of the compressor to induce the system to surge rather than stall. The resulting surge cycles were all found to be initiated by rotating stall and therefore the stall suppression systems mentioned above could also be used to suppress surge. In addition, it was possible to arrest the cyclical pulsing of a compressor already in surge.
Active Control of Rotating Stall in a Low Speed Axial Compressor
Authors: Paduano J. , Epstein A. H. , Valavani L. , Longley J. P. , Greitzer E. M. , Guenette G. R.
Published: March 2015

The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.
Three-Dimensional Flow and Mixing in an Axial Flow Compressor With Different Rotor Tip Clearances
Authors: Goto Akira
Published: March 2015

The effect of difference in rotor tip clearance on the mean flow fields and unsteadiness and mixing across a stator blade row were investigated using hot-wire anemometry, pressure probes, flow visualization and the ethylene tracer-gas technique on a single stage axial flow compressor. The structure of the three-dimensional flow fields was discussed based on results of experiments using the 12-orientation single slanted hot-wire technique and spectrum analysis of velocity fluctuation. High-pass filtered measurements of turbulence were also carried out in order to confirm small-scale velocity fluctuation which is more realistically referred to as turbulence. The spanwise distribution of ethylene gas spreading, estimated by the measured small-scale velocity fluctuation at the rotor exit, agreed quite well with that which was experimentally measured. This fact suggests the significant role of turbulence, generated within the rotor, in the mixing process across the downstream stator. The value of the maximum mixing coefficient in the tip region was found to increase linearly as the tip clearance became enlarged, starting from the value at midspan.
An Investigation of a Strong Shock-Wave Turbulent Boundary Layer Interaction in a Supersonic Compressor Cascade
Authors: Schreiber H. A. , Starken H.
Published: March 2015

Experiments have been performed in a Supersonic cascade facility to elucidate the fluid dynamic phenomena and loss mechanism of a strong shock-wave turbulent boundary layer interaction in a compressor cascade. The cascade geometry is typical for a transonic fan tip section that operates with a relative inlet Mach number of 1.5, a flow turning of about 3 degrees, and a static pressure ratio of 2.15. The strong oblique and partly normal blade passage shock-wave with a pre-shock Mach number level of 1.42 to 1.52 induces a turbulent boundary layer separation on the blade suction surface. Freestream Reynolds number based on chord length was about 2.7×106. Cascade overall performance, blade surface pressure distributions, Schlieren photographs, and surface visualisations are presented. Detailed Mach number and flow direction profiles of the interaction region (lambda shock) and the corresponding boundary layer have been determined using a Laser-2-Focus anemometer. The obtained results indicated that the axial blade passage stream sheet contraction (axial velocity density ratio) has a significant influence on the mechanism of strong interaction and the resulting total pressure losses.
The Influence of Blade Leaning on the Performance of an Integrated OGV-Diffuser System
Authors: Carrotte J. F. , Stevens S. J. , Wray A. P.
Published: March 2015

An experimental investigation has been carried out to study the performance of an integrated design of compressor outlet guide vane and combustor pre-diffuser system. The trailing edge of each OGV was located within the outwardly canted diffuser by a distance equal to 27% of the diffuser axial length. In order to obtain representative inlet conditions a rotor, providing a fully sheared velocity profile and an air outlet angle of approximately 40°, was located upstream of the OGVs. Compared with the measured performance when the trailing edge of each OGV was located at diffuser inlet, a small increase in total pressure loss and a corresponding decrease in static pressure recovery was observed for the shortened system. This change in performance reflected a deterioration in the flow conditions along the outer wall, with transitory stalling of the flow being observed at diffuser exit. By leaning the blades in a circumferential direction through angles of 10° and 15° the outer wall flow conditions could be progressively improved, although at the largest angle tested stalling of the flow occurred at the hub of each OGV. However, at a lean angle of 10° the performance, in terms of loss and flow stability, could be virtually restored to the levels obtained when the trailing edge of each OGV was located radially at diffuser inlet.
Numerical Simulation of Two-Phase Flow in Combustion Chambers
Authors: Hebrard P. , Courquet J. , Lavergne G.
Published: March 2015

The purpose of this paper is to describe a new approach in which one uses different kinds of post processing to obtain, from 2D or 3D computation codes, the representation of internal flow inside a combustion chamber as an association of elementary reactors (well stirred, plug flow…)

To reach this goal and, in order to test this method, different computation codes are used for the gas phase description: mean flow computation or unsteady codes like “R.V.M.” (Random Vortex Method) or “F.C.T.” (Flux corrected transport) - For the liquid phase behaviour, we use to kinds of Lagrangian transport schemes: one purely deterministic is linked to the mean gas flow computation, the second one provides individual instantaneous trajectories.

These various approaches are used for two kinds of 2D geometries: the backward facing step and a simplified afterburner geometry. Examples of residence time computations are presented for the liquid and gas phases and the effect of unsteady flow and drop sizes are demonstrated by experimental comparisons.
Three Dimensional Flow in a Linear Compressor Cascade at Design Conditions
Authors: Kang Shun , Hirsch Ch.
Published: March 2015

Experimental data measured upstream, inside and downstream of a large scale linear compressor cascade with NACA 65-1810 blade profile are presented. The flow is surveyed at 15 traverse planes with 14 (in half span) × 24 (in pitch) points inside a passage, and 14 × 33 points downstream exit plane. The measurements are obtained with a small size five hole probe, and wall static pressure taps. It is observed that the three dimensional flow inside and behind the cascade is characterized, not only by the conventional aspects, such as leading edge horseshoe vortices, passage vortices, trailing edge vortex sheet and corner vortices, but also by two spiral node points, formed from the three dimensional separation lines, on suction surface, and the resulting concentrated vortices.
A New Method for Calculating Burst Speed of Aeroengine Disks
Authors: Qilin Hong , Qixuan Zheng , Ping Wang , Guicang Hou
Published: March 2015

An approximate analytical large deformation method, based on Nadai deformation theory, for calculating the burst speed of aeroengine disks is presented in this paper. The basic equations are developed and the calculation procedures are illustrated. The burst speeds are calculated for some tested disks, and the calculation results are compared with the test results, the differences between two results are shown to be less than 8%. It shows that the new method is both simple and convenient. Therefore, it could be employed in the development of aeroengine disks.
The Effect of Blade Tip Geometry on the Tip Leakage Flow in Axial Turbine Cascades
Authors: Heyes F. J. G. , Hodson H. P. , Dailey G. M.
Published: March 2015

The phenomenon of tip leakage has been studied in two linear cascades of turbine blades.The investigation includes an examination of the performance of the cascades with a variety of tip geometries. The effects of using plain tips, suction side squealers and pressure side squealers are reported. Traverses of the exit flow field were made in order to determine the overall performance.

A method of calculating the tip discharge coefficients for squealer geometries is put forward. In linking the tip discharge coefficient and cascade losses a procedure for predicting the relative performance of tip geometries is developed. The model is used to examine the results obtained using the different tip treatments and to highlight the important aspects of the loss generation process.
Computation of a Wall Boundary Layer With Discrete Jet Injections
Authors: Kulisa P. , Leboeuf F. , Perrin G.
Published: March 2015

Cooling of turbine blades is often achieved with cold discrete jets introduced at the wall. In this paper, a new method for computation of a wall boundary layer with discrete jet interactions is presented. The jets are assumed to be arranged in rows and the flow is assumed locally periodic in the row direction.

The conservation equations are spatially averaged between two jet orifices. The resulting equations look like two-dimensional boundary layer equations, but with three-dimensional jet source terms.

The numerical method solves the boundary layer equations with a Keller box method. A strong interaction with inviscid flow is also introduced in order to avoid numerical difficulty in the jet region. Three-dimensional jet conservation equations are solved with an integral method, under the boundary layer influence. A coupling of the two methods is performed.

Comparisons with low speed experimental data are presented, particularly near the jet orifices. It is shown that the agreement between the results of computation and the experiments depends on the jet behaviour very near to the jet exit.
A Numerical Procedure of Three-Dimensional Design Problem in Turbomachinery
Authors: Xu J. Z. , Gu C. W.
Published: March 2015

A numerical method for solving the three–dimensional aerothermodynamic design problem with some type of the Mach number distributions on the blade surfaces is presented. In the usual aerothermodynamic design of a turbomachinery the three–dimensional coordinates of the blade is attained through the stacking of the cascade profiles and may not ensure the desired velocity distribution. To avoid this problem the present method will give new coordinates of the blade according to the required Mach number distribution. The method is based on the pseudostream function formulation and the treatment of the boundary conditions in the design problem is given. The numerical results show that the method is simple and useful in design.
Design of a High Performance Axial Compressor for Utility Gas Turbine
Authors: Sehra A. , Bettner J. , Cohn A.
Published: March 2015

An aerodynamic design study to configure a high efficiency industrial-size gas turbine compressor is presented. This study was conducted using an advanced aircraft engine compressor design system. Starting with an initial configuration based on conventional design practice, compressor design parameters were progressively optimized. To further improve the efficiency potential of this design, several advanced design concepts (such as stator ends bends and velocity controlled airfoils) were introduced. The projected polytropic efficiency of the final advanced concept compressor design having 19 axial stages was estimated at 92.8 percent, which is 2 to 3 percent higher than the current high efficiency aircraft turbine engine compressors.

The influence of variable geometry on the flow and efficiency (at design speed) was also investigated. Operation at 77 percent design flow with inlet guide vanes and front five variable stators is predicted to increase the compressor efficiency by 6 points as compared to conventional designs having only the inlet guide vane as variable geometry.
Three-Dimensional Navier-Stokes Computation of Turbomachinery Flows Using an Explicit Numerical Procedure and a Coupled k-ε Turbulence Model
Authors: Kunz R. F. , Lakshminarayana B.
Published: March 2015

An explicit, three-dimensional, coupled Navier-Stokes/k-ε technique has been developed and successfully applied to complex internal flow calculations. Several features of the procedure, which enable convergent and accurate calculation of high Reynolds number two-dimensional cascade flows have been extended to three-dimensions, including a low Reynolds number compressible form of the k-ε turbulence model, local timestep specification based on hyperbolic and parabolic stability requirements, and eigenvalue and local velocity scaling of artificial dissipation operators. A flux evaluation procedure which eliminates the finite difference metric singularity, at leading and trailing edges, on H- and C-grids, is presented. The code is used to predict the pressure distribution, primary velocity and secondary flows in an incompressible, turbulent curved duct flow for which CFD validation quality data is available. Also, a subsonic compressor rotor passage, for which detailed laser, rotating hot-wire and five-hole pressure probe measurements have been made is computed. Detailed comparisons between predicted and measured core flow and near wall velocity profiles, wake profiles, and spanwise mixing effects downstream of the rotor passage are presented for this case. It is found that the technique provides accurate and convergent engineering simulation of these complex turbulent flows.
Unsteady Rotor Dynamics in Cascade
Authors: Lee Yu-Tai , Bein Thomas W. , Feng Jin Zhang , Merkle Charles L.
Published: March 2015

A time-accurate potential-flow calculation method has been developed for unsteady incompressible flows through two-dimensional multi-blade-row linear cascades. The method represents the boundary surfaces by distributing piecewise linear-vortex and constant-source singularities on discrete panels. A local coordinate is assigned to each independently moving object. Blade-shed vorticity is traced at each time step. The unsteady Kutta condition applied is nonlinear and requires zero blade trailing-edge loading at each time. Its influence on the solutions depends on the blade trailing-edge shapes.

Steady biplane and cascade solutions are presented and compared to exact solutions and experimental data. Unsteady solutions are validated with the Wagner function for an airfoil moving impulsively from rest and the Theodorsen function for an oscillating airfoil. The shed vortex motion and its interaction with blades are calculated and compared to an analytic solution. For multi-blade-row cascade, the potential effect between blade rows is predicted using steady and quasi unsteady calculations. The accuracy of the predictions is demonstrated using experimental results for a one-stage turbine stator-rotor.
Design and Analysis of Ceramic and CMC Components for Advanced Gas Turbines
Authors: Kannmacher K. D. , Groseclose L. E.
Published: March 2015

Standard design methodology used for monolithic ceramic components uses Weibull probabilistic criteria. Finite element analysis modelling is performed to determine component reliability. Other important design considerations include time dependent behavior, ceramic to metal interfaces, and ceramic to ceramic interfaces. Design methodologies for composite structures increase the complexity of the design and analysis process due to the anisotropy of the material. This allows tailoring of the material architecture to accommodate specific component requirements.
Numerical Evaluation of a Two Dimensional Pitch and Yaw Vectoring Nozzle Using an Inviscid Flow Solver
Authors: Cheatham P. L. , Gridley M. C. , Walker S. H.
Published: March 2015

An Euler flow solver was applied to calculate the internal performance of a two dimensional pitch and yaw vectoring exhaust nozzle for aircraft control. Nozzle geometry parameters included pitch vector angle, yaw flap deflection, sidewall length, and sidewall deflection. These parameters as well as nozzle pressure ratio were varied to adequately represent the operating envelope of the nozzle. Freestream conditions were quiescent throughout, just as in the corresponding experimental validation data. Computed pressure distributions and nozzle performance were compared to experimental data with excellent agreement for most geometries and flow conditions.
Modeling and Computation of Flow in a Passage With 360° Turning and Multiple Airfoils
Authors: Shyy W. , Vu T. C.
Published: March 2015

Numerical modeling of the three-dimensional flows in a spiral casing of a hydraulic turbine, containing a passage of 360-degree turning and multiple elements of airfoils (the so-called distributor), is made. The physical model is based on a novel two-level approach, comprising of (1) a global model that adequately accounts for the geometry of the spiral casing but smears out the details of the distributor and represents the multiple airfoils by a porous medium treatment, and (2) a local model that performs detailed analysis of flow in the distributor region. The global analysis supplies the inlet flow condition for the individual cascade of distributor airfoils, while the distributor analysis yields the information needed for modeling the characteristics of the porous medium. Comparisons of pressure and velocity profiles between measurement and prediction have been made to assess the validity of the present approach. Flow characteristics in the spiral casing are also discussed.
The Impact Load on Containment Rings During a Multiple Blade Shed in Aircraft Gas Turbine Engines
Authors: Dewhurst T. B.
Published: March 2015

In the event of a multiple blade shed in an aircraft gas turbine engine, the impact load upon the containment ring is critical. A complete understanding of this load is necessary to design optimal rings, which are strong enough to contain blade fragments without incurring excess weight penalties. In this study a description of a multiple blade shed and subsequent ring failure is given. A finite element analysis of actual engine experiments is then used to determine the impact load on containment rings during a multiple blade shed. The situation modeled here is one where the initial blade fragments are contained but subsequent blade failures create large hoop stresses that result in brittle tensile failures in the ring.
Unsteady Aerodynamic Response of a Cascade to Nonuniform Inflow
Authors: Caruthers John E. , Dalton William N.
Published: March 2015

A solution method is developed for the small perturbation approximation to the inviscid, unsteady fluid equations for a 2-D cascade of airfoils. By introducing the unsteady field as a locally small perturbation from a nonuniform steady field, a first order coupling between the unsteady fluid properties and the gradients of the steady field properties results.

Results of this analysis procedure are compared with the experimentally determined unsteady pressure distribution on the vane of a low speed research compressor produced by the wakes from the upstream rotor. Correlation between experimental and analytical results is good. Similar comparisons of the data with an analysis method which approximates the vane as a 2-D cascade of flat plates at zero mean incidence did not exhibit acceptable correlation. The lack of correlation was particularly evident for the chordwise phase angle distribution.
Computer-Assisted Manufacturing of a Low Thermal Stress Gasturbine Inner Casing
Authors: Brinkmann Jürgen , Dietrich Peter
Published: March 2015

This technical paper describes the computer-assisted manufacturing of a newly developed gas turbine inner casing designed by Siemens/KWU for hot gas temperatures up to 1350 °C.

After explaining the most important design features, double wall casing with intensive impingement cooling, and details on the special materials involved, the manufacturing sequence and requisite special manufacturing techniques are described. The significant advantages and benefits of a CAD/CAM system tailored to the respective technique employed for this key aerodynamically-optimized item of a stationary gas turbine are elucidated in light of economic concerns and quality requirements and conditions imposed.

In conclusion, the transferability of the design principle described in this paper and its implementation in future-oriented developments in fabrication techniques employed in the manufacture of hot-gas-path casings at even higher temperatures are discussed.
5,000-Hour Stability Tests of Metal Sheathed Thermocouples at Respective Temperatures of 538°C and 875°C
Authors: Wang T. P. , Wells A. , Bediones D.
Published: March 2015

Metal sheathed mineral insulated thermocouples used for measurement of exhaust gas temperature in turbines and aircraft engines are usually not replaced after initial installation. Therefore, the change in calibration of these thermocouples during service is of interest. In this paper, two 5,000 hour stability tests were conducted on some standard and non-standard thermocouples in the laboratory in air atmosphere at 538°C, the mid temperature for gas turbine application and at 875°C, near the high end of aircraft engine applications. A comparison is made on calibration changes between laboratory and actual environment. Future work involving extension of the 875°C beyond 5,000 hours, laboratory testing in reducing atmospheres and insitu testing is proposed.