bluuebunny/crossref_metadata_2025_split huggingface dataset:
About the Distribution of the Mach Number and Losses Under Consideration of the Diffusion Factor: Profile Distribution and Losses for Low Pressure Turbine Profiles With High Diffusion Factors Under Steady Flow Conditions
Authors: Brachmanski Roland , Niehuis Reinhard 
Published: September 2016

The results of this investigation consist of two linear cascades at high diffusion factors. The present measurements for each low pressure turbine profile were conducted at midspan under a range of Reynolds- and exit Mach numbers. The exit Mach number was varied in a range covering low subsonic up to values where a transonic flow regime on the suction side of the blade could be expected. The variation of the exit Mach number was also used to create different locations of the maximum Mach number and to evaluate the resulting total pressure losses.
This work focuses on two profiles with a diffusion factor in a range of 0.18 ≤ DF ≤ 0.22, which is considered as a comparable level for the two cascades. The profile A is a front-loaded design and has shown no obvious flow separation on the suction side of the blade. Compared to the profile A the design B is a more aft-loaded profile which indicates flow separation on the suction side for all investigated Reynolds numbers.
The integral total pressure losses were evaluated by wake traverses downstream of the profile. To determine the isentropic Mach numbers and the character of the boundary layer along the suction side of the profile, static pressure tappings and measurements with a flattened Pitot probe were carried out. Numerical studies were also conducted to investigate further the influence of a reduced turbulence intensity on the boundary layer of the suction side of design B.
The results show that the optimum of the integral total pressure losses are significantly dependent on the Reynolds number. Therefore a correlation between the maximum Mach number on the suction side and the integral total pressure losses has been successfully established. A significant change of the turbulence intensity at the inlet of the cascade leads to shift of the location of the maximum Mach number. It also results in an equivalent change of the total pressure losses, which has been predicted by the trend line. However, the trend lines, which are based on the data of the integral total pressure losses of an attached boundary layer, are not able to predict the integral total pressure loss or the location of the maximum Mach number on the suction side of the blade since an open separation bubble occurs.
Acoustic Mode Analysis: Numerical and Experimental Results of a Turning Mid Turbine Frame
Authors: Zerobin S. , Bader P. , Faustmann C. , Marn A. , Göttlich E. , Heitmeir F. 
Published: September 2016

In the present paper, a comparison of the numeric and experimental results obtained from the acoustic mode analysis for a turning mid turbine frame (TMTF) is presented. The investigated turning mid turbine frame is part of the two-stage two-spool test turbine located at the Institute for Thermal Turbomachinery and Machine Dynamics of Graz University of Technology. In this specific test turbine a transonic turbine stage (HP) is followed by a low pressure turbine stage (LP) consisting of a TMTF with 16 highly 3D-shaped turning struts and a counter-rotating low pressure rotor.
The experimental dataset is obtained by a measurement section downstream of the low pressure rotor which is instrumented with acoustic sensors. This microphone array is wall flush mounted in the outer casing which is traversable over 360 degrees in circumferential direction. The numerical setup consists of the whole test turbine including the experimental measurement section downstream of the low pressure rotor. Since the periodicity of the test setup equals 90 degrees the CFD calculations were performed accordingly using the unsteady inhouse Navier-Stokes code LINARS.
For both, numerical and experimental datasets the same post-processing tools are used in order to perform the acoustic mode analysis of the unsteady data. At first a comparison in terms of noise generation and propagation of the results is done by the frequency spectra, the emitted sound pressure and sound power level of both rotors independently. Since the emitted sound pressure level rises to a maximum at the first blade passing frequency of the HP rotor as well as the LP rotor the further analysis focuses on these two specific frequencies only. Therefore the acoustic field at those frequencies is characterized by azimuthal and radial modes. For a correct comparison between the numerical and experimental results numeric data taken from the same geometric locations as the microphones’ positions (thus the measurement locations) is processed.
Hence, this paper provides a deep insight into the capability of using unsteady CFD calculation in combination with the acoustic mode analysis in order to obtain the noise generation and propagation in turbines.
Coupled CFD and Heat Transfer Analysis for a Small Scale Gas Turbine Combustor
Authors: Pişkin Altuğ , Topal Ahmet 
Published: September 2016

Gas turbine combustor design process has significant number of design parameters because of contained complex phenomena. One of the most complicated of these is the heat transfer process of combustor liners. Heat transfer studies are performed in preliminary design phase by the help of one-dimensional tools and combustor geometry is shaped to satisfy design requirements. However; in the detail design phase, a fine tuning can be required to optimize it by using 3D CFD analysis. Conjugate heat transfer is a powerful tool to simulate interaction between reacting flow and combustor liners in detail design phase. But it is difficult to use computationally expensive conjugate heat transfer analysis in design iterations for calculating liner metal temperatures because of the high computation times. Its application will be mainly limited to optimized final geometries and steady simulations. On the other hand, when the 3D liner temperatures are required for structural evaluation during the preliminary design phase; coupled analysis of Finite Element Analysis (FEA)/ Computational Fluid Dynamics (CFD) can provide quick alternative solution. Coupled analysis requires lower mesh size and less calculation time comparing to the conjugate analysis. During a coupled analysis, an iterative boundary information exchange is conducted until the desired convergence criterion is reached.
In this study, a series of numerical analyses are evaluated and the relevant rig test thermal paint results are presented. Numerical analyses consist of coupled analyses with various boundary condition cases. Some of these cases have the complete set of boundary conditions and they assumed as comparable to the test condition. In the coupling process, FEM use the near wall gas temperature data that comes from CFD solution and CFD uses wall temperature data that comes from the FEM solution. Heat transfer coefficients are not coupled and they are obtained from empirical heat transfer correlations.
An atmospheric combustor test rig was used to apply thermal paint and thermocouple measurements were taken from the combustor outer liner. Numerical and experimental values of the liner temperatures are also compared and analyzed.
Thermodynamic Multi-Criteria Optimization of the Unified Engine Core for the Line of Turbofan Engines
Authors: Rybakov Viktor N. , Kuz'michev Venedikt S. , Tkachenko Andrey Y. , Krupenich Ilia N. 
Published: September 2016

Although development of the line of gas turbine engines on the basis of a unified engine core is a widely used practice, the method of selection of the most efficient values of engine core parameters has virtually never been published.
The paper describes the method of optimization of values of engine core parameters jointly with optimization of values of every engine forming the line of engines developed on the basis of this core. Both stages of optimization are multi-objective and fulfilled using the results of simulation of engine as a subsystem of the airframe.
Multicriteria Optimization of Axial Low Pressure Compressor of Gas Turbine Power Plant
Authors: Popov Grigorii , Goriachkin Evgenii , Kolmakova Daria , Novikova Yulia 
Published: September 2016

The paper shows a method of the gas-dynamic refining of three-stage axial compressor based on the joint usage of mathematical optimization software IOSO and CFD complex NUMECA. The optimizer is used for automatic change of the compressor geometry in order to find the optimal design. The aim was to preserve the original design, for this reason only the geometrical parameters of rotor blades and guide vanes were varied without changing the contours of the meridional flow part and blade roots.
The optimization task was multiobjective. It was necessary to find a compromise between the efficiency increase and improvement of the gas-dynamic stall margins of the compressor at the primary operational mode and to prevent the deterioration of parameters at other modes. Compressor parameters were calculated at three engine modes, corresponding to the temperature of the air at the engine inlet — −15 °C, +15 °C, and +45 °C, at each step of the optimization. Parameters of the compressor were calculated in operational and stall points of its characteristics at the modes corresponding to −15 °C and +15 °C. Parameters of compressor were calculated in choking point at the mode corresponding to −+45 °C. The optimization problem was solved in two formulations with different degree of parameters variation at the modes of operation corresponding to the −15 °C and +45 °C.
Finite volume model of the compressor that is used in the optimization was created in the meshing software NUMECA AutoGrid. Configuring and solution of the task were carried out in the solver NUMECA FINE/Turbo. Comparison of calculated characteristics of the base compressor with the experimental data was performed before optimization.
Analysis of the impact of optimized compressor on the engine operation was performed. The position of the working line of base and optimized compressor variants was indicated. It was shown that optimized compressor has efficiency increase by 1.1% compare to the base while operating as the engine component.
Spanwise Spectra, Reynolds Stresses and Correlations From DNS of Turbine Like APG Boundary Layers
Authors: Simens Mark P. , Gungor Ayse G. 
Published: September 2016

It is becoming more apparent that to be able to fully understand the adverse pressure gradient boundary flow in general or downstream of reattachment it is needed to understand the relation between the upstream flow structures and the downstream flow structures. In this work the results for three different direct numerical simulations (DNS) of adverse pressure gradient (APG) flows are presented. The three cases have the same overall characteristics with respect to the imposed APG and the Reynolds number Reδ099 at the inlet. However, the first case has no additional perturbations imposed, in the second case the flow is tripped by a trip wire and in the third case a periodic wake is superimposed on the flow. The main points that are discussed are the spanwise spectra, two-dimensional correlations, and Reynolds stress budgets for the three different flow cases. Attention is in particular directed to a comparison between the three different cases.
The most important conclusion is that the flow downstream of reattachment is strongly correlated with the flow structures at transition for almost the whole numerical domain.
Radial Stages With Non-Uniform Pressures at Diffuser Inlet
Authors: Japikse David , Krivitzky Eric M. 
Published: September 2016

The design of centrifugal stages with an impeller and a downstream diffuser has generally been based on the assumption of axisymmetric flow at the impeller discharge. Flow entering the diffuser has customarily been assumed to also be axisymmetric, at least on a time-averaged basis, while laying out the diffuser vanes, establishing the preferred incidence, and sizing the throat areas. Recent stage studies have shown that the flow is often not fully axisymmetric, that not all diffuser passages perform the same way even at the design or best efficiency points, and that the actual time-averaged diffuser inlet flow conditions (distortion) may be changing from one operating point to another.
In this study, comprehensive time-averaged (steady) results from one test rig with a large array of impeller exit pressure taps is examined. Supporting results from five other test rigs are reviewed to broaden the picture of possible flow states. Hypotheses, suitable for future evaluation, are given to begin the explanation of the actual flow states and to guide further research. The current status of CFD to understand these phenomena is discussed.
An Investigation Into the Variation of Centrifugal Compressor Sensitivity to Inlet Swirl With Initial Form Parameter Selection
Authors: Krivitzky Eric M. 
Published: September 2016

Fixed-geometry centrifugal compressors have inherent limitations in the off-design operating range and performance that can be delivered. Variable inlet swirl, typically introduced with variable inlet guide vanes, has been a frequent tool implemented across many industries to extend the stable operating range and off-design efficiency. However, a review of available data in the literature reveals a large disparity in the effectiveness of variable inlet swirl for useful map movement. An ideal configuration responds to preswirl with a significant reduction in the mass flow at instability along with increased efficiency. Unfortunately, some cases reveal no movement in the surge line, with increases in inlet swirl only serving to reduce the stage efficiency.
This study investigates underlying causes for the variation in sensitivity to inlet swirl amongst various compressor designs, represented by form parameters. An analytical model is established and then verified using CFD and selected test data to explore fundamental causes for decreased sensitivity to inlet swirl. Analytical and computational results suggest a new understanding of the governing parameters for inlet swirl sensitivity, and thus provide insight into the scenarios when inlet swirl is an effective tool for manipulation of performance characteristics. Synthesizing the underlying trends, guidelines are developed for design selections and operational situations when inlet swirl can be effectively implemented as a means to extend the stable operating range and off-design efficiency.
Investigation on the Effect of Streamwise Grooves on Controlling Corner Flow Separation
Authors: Yi Weilin , Li Jiabin , Yu Jia , Ji Lucheng 
Published: September 2016

Flow separations often take place in the junction of blades and endwalls and limit seriously the aerodynamic loading increase of turbomachinery, which are caused mainly by mixing of the boundary layers on blades and endwall surfaces and the transverse secondary flow generated by the pressure difference between the pressure and suction side.
Firstly, focusing on a linear diffusion cascade with 42 degrees turning angle, it can be found that the transverse secondary flow can be reduced by inviscid hub and the flow separation is eliminated further through the numerical comparison between the viscous and inviscid hub cases. So the transverse secondary flow is the dominate factor for the flow separation in this cascade. We should try to control the transverse secondary flow to reduce the flow separation.
Secondly, based above analysis, the flow separation can be controlled effectively if we can cut off the secondary flow. So nine kinds of streamwise groove schemes are designed and analyzed. It can be seen that the streamwise grooves at the end wall inhibit obviously the transverse secondary flow but the flow structure change is different at different span. There is an optimum combination of width and height of groove, and the height is more important than width.
Thirdly, the detailed flow analysis of best scheme with smaller width, moderate height are carried out. It can decrease the separation zone scope at the corner zone, reduce the energy loss coefficient and also reduce the flow loss.
Clinical Utility of On-Demand Multiplex Respiratory Pathogen Testing among Adult Outpatients
Authors: Green Daniel A. , Hitoaliaj Letiana , Kotansky Brian , Campbell Sheldon M. , Peaper David R. 
Published: September 2016

ABSTRACT

Multiplex tests for respiratory tract infections include up to 20 targets for common pathogens, predominantly viruses. A specific therapeutic intervention is available for individuals testing positive for influenza viruses (oseltamivir), and it is potentially beneficial to identify non-influenza viruses to avoid unnecessary antibiotic use. We evaluated antimicrobial prescriptions following respiratory pathogen testing among outpatients at a large Veterans Administration (VA) medical center. Results of the FilmArray respiratory panel (BioFire, Salt Lake City, UT) from 15 December 2014 to 15 April 2015 were evaluated among 408 outpatients, and patient medical records were reviewed. Differences in antibiotic and oseltamivir prescription rates were analyzed. Among 408 patients tested in outpatient centers (emergency departments, urgent care clinics, and outpatient clinics), 295 (72.3%) were managed as outpatients. Among these 295 outpatients, 105 (35.6%) tested positive for influenza virus, 109 (36.9%) tested positive for a non-influenza virus pathogen, and 81 (27.5%) had no respiratory pathogen detected. Rates of oseltamivir and antibiotic prescriptions were significantly different among the three test groups (chi-squared values of 167.6 [
P
< 0.0001] and 10.48 [
P
= 0.005], respectively), but there was no significant difference in antibiotic prescription rates between the non-influenza virus pathogen group and those who tested negative (chi-square value, 0;
P
= 1.0). Among adult outpatients, testing positive for influenza virus was associated with receiving fewer antibiotic prescriptions, but no such effect was seen for those who tested positive for a non-influenza virus. These data suggest that testing for influenza viruses alone may be sufficient and more cost-effective than multiplex pathogen testing for outpatients.
Comprehensive Genome Scale Phylogenetic Study Provides New Insights on the Global Expansion of Chikungunya Virus
Authors: Chen Rubing , Puri Vinita , Fedorova Nadia , Lin David , Hari Kumar L. , Jain Ravi , Rodas Juan David , Das Suman R. , Shabman Reed S. , Weaver Scott C. 
Published: September 2016

ABSTRACT
Since the India and Indian Ocean outbreaks of 2005 and 2006, the global distribution of chikungunya virus (CHIKV) and the locations of epidemics have dramatically shifted. First, the Indian Ocean lineage (IOL) caused sustained epidemics in India and has radiated to many other countries. Second, the Asian lineage has caused frequent outbreaks in the Pacific islands and in 2013 was introduced into the Caribbean, followed by rapid spread to nearly all of the neotropics. Further, CHIKV epidemics, as well as exported cases, have been reported in central Africa after a long period of perceived silence. To understand these changes and to anticipate the future of the virus, the exact distribution, genetic diversity, transmission routes, and future epidemic potential of CHIKV require further assessment. To do so, we conducted the most comprehensive phylogenetic analysis to date, examined CHIKV evolution and transmission, and explored distinct genetic factors associated with the emergence of the East/Central/South African (ECSA) lineage, the IOL, and the Asian lineage. Our results reveal contrasting evolutionary patterns among the lineages, with growing genetic diversities observed in each, and suggest that CHIKV will continue to be a major public health threat with the potential for further emergence and spread.

IMPORTANCE
Chikungunya fever is a reemerging infectious disease that is transmitted by
Aedes
mosquitoes and causes severe health and economic burdens in affected populations. Since the unprecedented Indian Ocean and Indian subcontinent outbreaks of 2005 and 2006, CHIKV has further expanded its geographic range, including to the Americas in 2013. Its evolution and transmission during and following these epidemics, as well as the recent evolution and spread of other lineages, require optimal assessment. Using newly obtained genome sequences, we provide a comprehensive update of the global distribution of CHIKV genetic diversity and analyze factors associated with recent outbreaks. These results provide a solid foundation for future evolutionary studies of CHIKV that can elucidate emergence mechanisms and also may help to predict future epidemics.
Influenza Virus Susceptibility of Wild-Derived CAST/EiJ Mice Results from Two Amino Acid Changes in the MX1 Restriction Factor
Authors: Nürnberger Cindy , Zimmermann Vanessa , Gerhardt Melanie , Staeheli Peter 
Published: September 2016

ABSTRACTThe interferon-regulatedMx1gene of the A2G mouse strain confers a high degree of resistance against influenza A and Thogoto viruses. Most other laboratory inbred mouse strains carry truncated nonfunctionalMx1alleles and, consequently, exhibit high virus susceptibility. Interestingly, CAST/EiJ mice, derived from wildMus musculus castaneus, possess a seemingly intactMx1gene but are highly susceptible to influenza A virus challenge. To determine whether the enhanced influenza virus susceptibility is due to intrinsically reduced antiviral activity of the CAST-derivedMx1allele, we generated a congenic C57BL/6J mouse line that carries theMxlocus of CAST/EiJ mice. Adult animals of this line were almost as susceptible to influenza virus challenge as standard C57BL/6J mice lacking functionalMx1alleles but exhibited far more pronounced resistance to Thogoto virus. Sequencing revealed that CAST-derived MX1 differs from A2G-derived MX1 by two amino acids (G83R and A222V) in the GTPase domain. Especially the A222V mutation reduced GTPase activity of purified MX1 and diminished the inhibitory effect of MX1 in influenza A virus polymerase activity assays. Further, MX1 protein was substantially less abundant in organs of interferon-treated mice carrying the CASTMx1allele than in those of mice carrying the A2GMx1allele. We found that the CAST-specific mutations reduced the metabolic stability of the MX1 protein althoughMx1mRNA levels were unchanged. Thus, the enhanced influenza virus susceptibility of CAST/EiJ mice can be explained by minor alterations in the MX1 restriction factor that negatively affect its enzymatic activity and reduce its half-life.IMPORTANCEAlthough the crystal structure of the prototypic human MXA protein is known, the importance of specific protein domains for antiviral activity is still incompletely understood. Novel insights might come from studying naturally occurring MX protein variants with altered antiviral activity. Here we identified two seemingly minor amino acid changes in the GTPase domain that negatively affect the enzymatic activity and metabolic stability of murine MX1 and thus dramatically reduce the influenza virus resistance of the respective mouse inbred strain. These observations highlight our current inability to predict the biological consequences of previously uncharacterized MX mutations in mice. Since this is probably also true for naturally occurring mutations inMxgenes of humans, careful experimental analysis of any natural MXA variants for altered activity is necessary in order to assess possible consequences of such mutations on innate antiviral immunity.