bluuebunny/crossref_metadata_2025 huggingface dataset:
Reproduction of invasive Amur honeysuckle (Lonicera maackii) and the arithmetic of an extermination strategy
Authors: Schulz Kurt E. , Wright Jessica
Published: August 2015

Ecological restorations often require removal of invasive species. The abundance of invasives has tended to catalyze research emphasizing removal, not broader understandings, of species mechanisms for persistence in the landscape (e.g. reproductive output and seed dispersal). Asiatic shrub honeysuckles (Lonicera spp.) are pernicious invaders throughout eastern North America. Heavy tree canopy cover apparently reduces growth and reproductive output in Lonicera maackii, which is widespread through the lower Midwestern United States. To help focus control efforts more effectively, we quantified the effect of tree canopy cover on vegetative growth, flowering, and fruit production under three canopy densities. Mean vegetative growth of flowering shoots was not affected by canopy cover. All aspects of sexual reproduction (flower production, fruit set, fruit number, fruit mass, seed number, and seed size) were strongly reduced by moderate shade. Although all individuals modify community and ecosystem properties, a limited number of high light individuals might also provide the greatest proportion of the seeds. Through model simulation of honeysuckle population structure in relation to canopy cover, we argue that it can sometimes be more efficient to initially target reproductive individuals in the high light edge and interior gap environments than to immediately focus on all individuals in the forest interior.
Characterizing and Communicating Risk with Exposure Reconstruction and Bayesian Analysis: Historical Locomotive Maintenance/Repair Associated with Asbestos Woven Tape Pipe Lagging
Authors: Boelter Fred W. , Persky Jacob D. , Podraza Daniel M. , Bullock William H.
Published: August 2015

Our reconstructed historical work scenarios incorporating a vintage 1950s locomotive can assist in better understanding the historical asbestos exposures associated with past maintenance and repairs and fill a literature data gap. Air sampling data collected during the exposure scenarios and analyzed by NIOSH 7400 (PCM) and 7402 (PCME) methodologies show personal breathing zone asbestiform fiber exposures were below the current OSHA exposure limits for the eight‐hour TWA permissible exposure limit (PEL) of 0.1 f/cc (range <0.007–0.064 PCME f/cc) and the 30‐minute short‐term excursion limit (EL) of 1.0 f/cc (range <0.045–0.32 PCME f/cc) and orders of magnitude below historic OSHA PEL and ACGIH TLVs. Bayesian decision analysis (BDA) results demonstrate that the 95th percentile point estimate falls into an AIHA exposure category 3 or 4 as compared to the current PEL and category 1 when compared to the historic PEL. BDA results demonstrate that bystander exposures would be classified as category 0. Our findings were also significantly below the published calcium magnesium insulations exposure range of 2.5 to 7.5 f/cc reported for historic work activities of pipefitters, mechanics, and boilermakers. Diesel‐electric locomotive pipe systems were typically insulated with a woven tape lagging that may have been chrysotile asbestos and handled, removed, and reinstalled during repair and maintenance activities. We reconstructed historical work scenarios containing asbestos woven tape pipe lagging that have not been characterized in the published literature. The historical work scenarios were conducted by a retired railroad pipefitter with 37 years of experience working with materials and locomotives.
Combination therapy for multidrug‐resistant cytomegalovirus disease
Authors: Stuehler C. , Stüssi G. , Halter J. , Nowakowska J. , Schibli A. , Battegay M. , Dirks J. , Passweg J. , Heim D. , Rovo A. , Kalberer C. , Bucher C. , Weisser M. , Dumoulin A. , Hirsch H.H. , Khanna N.
Published: August 2015

Multidrug‐resistant (MDR) cytomegalovirus (CMV) emerged after transient responses to ganciclovir, foscarnet, and cidofovir in a CMV‐seropositive recipient who underwent allogeneic hematopoietic stem cell transplantation from a CMV‐seronegative donor. Experimental treatments using leflunomide and artesunate failed. Re‐transplantation from a CMV‐seropositive donor supported by adoptive transfer of pp65‐specific T cells and maribavir was followed by lasting suppression. This case illustrates that successful MDR CMV therapy may require individualized multidisciplinary approaches.
Chromatin state analysis of the barley epigenome reveals a higher‐order structure defined by H3K27me1 and H3K27me3 abundance
Authors: Baker Katie , Dhillon Taniya , Colas Isabelle , Cook Nicola , Milne Iain , Milne Linda , Bayer Micha , Flavell Andrew J.
Published: August 2015

Combinations of histones carrying different covalent modifications are a major component of epigenetic variation. We have mapped nine modified histones in the barley seedling epigenome by chromatin immunoprecipitation next‐generation sequencing (ChIP‐seq). The chromosomal distributions of the modifications group them into four different classes, and members of a given class also tend to coincide at the local DNA level, suggesting that global distribution patterns reflect local epigenetic environments. We used this peak sharing to define 10 chromatin states representing local epigenetic environments in the barley genome. Five states map mainly to genes and five to intergenic regions. Two genic states involving H3K36me3 are preferentially associated with constitutive gene expression, while an H3K27me3‐containing genic state is associated with differentially expressed genes. The 10 states display striking distribution patterns that divide barley chromosomes into three distinct global environments. First, telomere‐proximal regions contain high densities of H3K27me3 covering both genes and intergenic DNA, together with very low levels of the repressive H3K27me1 modification. Flanking these are gene‐rich interior regions that are rich in active chromatin states and have greatly decreased levels of H3K27me3 and increasing amounts of H3K27me1 and H3K9me2. Lastly, H3K27me3‐depleted pericentromeric regions contain gene islands with active chromatin states separated by extensive retrotransposon‐rich regions that are associated with abundant H3K27me1 and H3K9me2 modifications. We propose an epigenomic framework for barley whereby intergenic H3K27me3 specifies facultative heterochromatin in the telomere‐proximal regions and H3K27me1 is diagnostic for constitutive heterochromatin elsewhere in the barley genome.
How we approach a patient with symptoms of leukostasis requiring emergent leukocytapheresis
Authors: Pham Huy P. , Schwartz Joseph
Published: August 2015

Hyperleukocytosis can induce leukostasis, which can lead to vascular obstructions (usually in the lungs and central nervous system), tumor lysis syndrome, and disseminated intravascular coagulation. Although it has not been conclusively shown to improve long‐term outcome, leukocytapheresis may be used as part of the management of hyperleukocytosis with or without leukostasis to rapidly reduce the white blood cell (WBC) burden. Since leukocytapheresis only temporarily decreases the WBC count, early initiation of more definite therapy, such as hydroxyurea and/or chemotherapy, is essential. In this article, clinical assessment of the patient's clinical status to determine the need for leukocytapheresis as well as a general guideline for management of the technical aspects and complications of the procedure are discussed.
BIG DATA: NEW SCIENCE, NEW CHALLENGES, NEW DIALOGICAL OPPORTUNITIES
Authors: Fuller Michael
Published: August 2015

The advent of extremely large data sets, known as “big data,” has been heralded as the instantiation of a new science, requiring a new kind of practitioner: the “data scientist.” This article explores the concept of big data, drawing attention to a number of new issues—not least ethical concerns, and questions surrounding interpretation—which big data sets present. It is observed that the skills required for data scientists are in some respects closer to those traditionally associated with the arts and humanities than to those associated with the natural sciences; and it is urged that big data presents new opportunities for dialogue, especially concerning hermeneutical issues, for theologians and data scientists.
WHAT CAN PIAGET OFFER LONERGAN'S PHILOSOPHY OF BIOLOGY?
Authors: Friel Chris
Published: August 2015

In Insight, Bernard Lonergan provides, albeit schematically, a unique philosophy of biology which he takes as having “profound differences” with the world view presented by Darwin. These turn on Lonergan's idea of “schemes of recurrence” and of organisms as “solutions to the problem of living in an environment.” His lapidary prose requires some deciphering. I present the broad lines of his philosophy of biology and argue that Jean Piaget's structuralism can shed light on Lonergan's intentions in virtue of his use of cybernetics and the isomorphism between biology and knowledge. In turn, Piaget draws on Waddington's restatement of epigenesis and I suggest that the result, “process structuralism,” is a viable alternative to the modern Darwinian synthesis.
Development of Low Emission Gas Turbine Combustors
Authors: Jung Seung-chai , Yang Siwon , Kim Shaun , Kim Ik Soo , Ahn Chul-ju , Cho Ju Hyeong , Yoon Jisu , Yoon Youngbin , Yoon Samson , Ryu Shiyang
Published: August 2015

Due to increasing environmental concerns, clean technology has become a key feature in industrial gas turbines. Swirler design is directly associated with the combustion performance for its roles in fuel distribution and flame stability. In this study, the development process of three new conceptual swirlers from Samsung Techwin is presented. Each swirler has unique features to enhance fuel-to-air mixing; Swirler 1 uses tangential air-bypass, Swirler 2 minimizes pressure loss using impeller-like design, and Swirler 3 has combined flow characteristics of axial and radial swirlers. Using extensive computational fluid dynamics (CFD) analysis, lead time and cost in manufacturing the prototypes were significantly reduced. The numerical methods were verified with a lab-scale combustion test; particle image velocimetry (PIV) measurement of cold flow, direct flame images, and OH planar laser induced fluorescence (PLIF) images were compared with result of large-eddy simulation (LES), and they showed good agreement. After design optimization using CFD, full-scale combustion tests were performed for all three swirlers. Flame from each swirler was visualized using a cylindrical quartz liner; direct images and OH chemiluminescence images of flames were obtained. Flame stability and blow-off limit at various air load were examined by gradually lowering the equivalence ratio. NOx and CO concentration were measured at the exhaust. All three swirlers satisfied low NOx and CO levels at the design conditions. The performance maps bounded by the NOx and CO limits and blow-off limit were obtained for all swirlers. Further efforts to maximize the combustors performance will be made.
Development of a Throughflow Method for Aerodynamic Analysis of Highly Loaded Axial Flow Compressors
Authors: Li Bo , Gu Chun-wei , Li Xiao-tang , Liu Tai-qiu , Xiao Yao-bing
Published: August 2015

In this paper, a novel engineering platform for throughflow analysis based on streamline curvature approach is developed for the research of a 5-stage compressor. It includes several types of improved loss and deviation angle models for the purpose of reflecting the influences of three-dimensional internal flow in highly loaded multistage compressors with higher accuracy. A spanwise mixing model considering viscous shear force with a no-slip condition is applied to improve assessment about the substantial amounts of radial energy and momentum exchange, a shock model accounting for shock geometry changes is also contained to better simulate transonic flow near the tip regions.

In order to validate the reliability and robustness of the method, series of test cases including a subsonic compressor P&W 3S1, a transonic rotor NASA Rotor 1B and especially an advanced high pressure core compressor GE E3 HPC have been conducted. Then the computation procedure is applied to the research of a 5-stage compressor which is designed for developing an industry gas turbine. The overall performance and aerodynamic configuration predicted by the procedure both at design- and part-speed conditions are analyzed and compared with experimental results, which show a good agreement. The throughflow method is verified as a reliable and convenient tool for aerodynamic design and performance prediction of modern highly loaded compressors. It is also qualified for further optimization of the 5-stage compressor.
On Test Uncertainties in Field Performance Tests
Authors: Kurz Rainer , Brun Klaus
Published: August 2015

Field testing of gas turbine or electric motor driven compressor packages requires the accurate determination of efficiency, capacity, head, or power consumption in sometimes less than ideal working environments. Nonetheless, field test results have significant implication for the compressor and gas turbine manufacturers and their customers. Economic considerations demand that the performance and efficiency of an installation are verified to assure the return on investment for the project. Thus, for the compressor and gas turbine manufacturers, as well as for the end-user, an accurate determination of the field performance is of vital interest.

This paper discusses a method to determine the measurement uncertainty and, thus, the accuracy, of test results under the typical constraints of a site performance test, for compressors capable of variable speed operation. Namely, a method is presented which can be employed to verify the validity of field test performance results.

Results are compared with actual field test results, using redundant methods. Typical field test measurement uncertainties are presented for different sets of instrumentation. The effect of different equations of state on the calculated performance is also discussed. Test parameters that correlate to the most significant influence on the performance uncertainties are identified and suggestions are provided on how to minimize their measurement errors.

Results show that compressor efficiency uncertainties can be unacceptably high when some basic rules for accurate testing are violated. However, by following some simple measurement rules and maintaining commonality of the gas equations of state, the overall compressor package performance measurement uncertainty can be limited and meaningful results can be achieved.
Numerical Study of Reynolds Number Effects on Steam Turbine Performance
Authors: Cheon J. H. , Milčák P. , Šťastný M.
Published: August 2015

The performance of blade profiles was examined with three linear cascade blades which represent hub, mid-span and tip section using numerical analysis. The Reynolds number was varied from 10,000 to 10,000,000 to capture the operating regime for typical steam turbines. Twelve different levels of surface roughness on the same profile were calculated using the roughness model in ANSYS-CFX. The ratios of surface roughness to chord length are in the range of ks/c = 4.2 × 10–5 ∼ 8.3 × 10−4. The CFD result was compared to Reynolds number correction curves from published literature (AMDC-KO, Aungier, Craig & Cox, Traupel, Sanders and Denton) and available measurement data. Based on these comparisons, a Reynolds number correction curve was properly selected for the estimation of steam turbine performance. Also, it was found that Reynolds number with hydraulically smooth surfaces has little influence on the change in flow angle and roughness does not significantly change outlet flow angle.
Fiber Laser Deposition of Nickel-Based Superalloys Using Filler Wire Feed
Authors: Zhang Y. N. , Cao X. , Wanjara P.
Published: August 2015

In this work, a continuous wave fiber laser welding system was used to deposit nickel-based superalloys Inconel 718 (IN 718) and Waspaloy using filler wire feed sources. The multi-bead and multi-layer deposits that were manufactured were characterized in terms of the macro- and microstructures, defects, and hardness in both the as-deposited and fully heat treated conditions. The tensile properties of the deposits in the heat treated condition were also determined and compared to the existing aerospace materials specifications. Using optimized laser processing parameters, high strength deposits could be manufactured, though minor weld metal liquation cracking for IN718 and strain-age cracking for Waspaloy were present, which compromised slightly the ductility as compared to wrought aerospace specifications for the two alloys. The successful development of the direct laser deposition process using wire feeding indicates the potential of employing the fiber laser technology to manufacture nickel-based superalloy aerospace components.
Polytropic Change of State Calculations With Condensation or Evaporation and its Use for Thermal Power Cycles
Authors: Wettstein Hans E.
Published: August 2015

In the paper [1] three polytropic change of state calculation methods for air gases and CO2 are compared. The conclusions are that the most used formulas can produce with the same input data deviations in terms of polytropic efficiency up to 1.5% points even for nearly ideal gases like nitrogen. The paper suggests therefore a recursive algorithm, which is based directly on the classic definition of a polytropic change of state. This definition assumes a constant dissipation rate during an adiabatic change of state. The proposed algorithm can be applied for any gas with an equation of state, which is an unambiguous function of the two variables pressure p and temperature T.

The latter condition is not fulfilled by steam in the wetness range because the specific volume v depends not only from p and T but also from the vapor fraction x. The aim of this paper is the development of an analogous recursive “constant dissipation rate algorithm” for a two phase mixture assuming equilibrium conditions between the vapor and the liquid fractions. The method shall be demonstrated with expanding wet steam. The result of the algorithm will be the discharge enthalpy, temperature and the discharge vapor fraction for given initial pressure and temperature, discharge pressure and polytropic efficiency.

Based on the developed formulas some well-known but nevertheless paradoxically perceived results and comparisons with expanding dry air can be shown.
Investigation in the Technical and Economic Feasibility of a Low-Pressure Steam Cycle for the Waste Heat Utilization of a Cogeneration Plant
Authors: Laux Christoph , Goebel Johannes , Neef Matthias , Gotter Andreas
Published: August 2015

This paper deals with the investigation in the technical and economic feasibility of a low-pressure steam cycle for the waste heat utilization of a combined heat and power (CHP) plant. The proposed steam cycle uses a pressure level below atmospheric pressure which allows to use the heat from the motor’s coolant for evaporation. The cycle is designed to increase the maximum electrical efficiency of a gas fired reciprocating engine and to increase operational flexibility for varying heat demand. Since organic Rankine cycle (ORC) plants are already being successfully used for waste heat recovery, advantages of the low-pressure steam Rankine cycle (SRC) over an ORC are highlighted.

Many ORC fluids are toxic or flammable and thus have an increased risk potential compared to water. An additional advantage of water compared to ORC fluids is the possibility of superheating above 500 °C.

The technical feasibility of the proposed cycle is studied by the detailed design of the individual system components such as turbine, heat exchangers and auxiliary parts. This includes the detailed thermodynamic design of the full cycle for the calculation of plant efficiencies.

As a basis for future experimental investigations, a cogeneration plant with an electrical output of 50 kWel was selected as a heat source for the steam cycle. The design geometries of the turbine and the heat exchanger are presented along with efficiency and cost predictions. A subsonic radial turbine with a rotational speed of 155,000 rpm was selected. The maximum turbine output is about 7.5 kW. The use of a flash evaporator is investigated to reduce the size and the costs for the evaporator.

The suggested steam cycle helps to increase the electrical efficiency of the CHP plant by 4.5% points from an original 36.5% to 41.0%. The steam cycle itself has an electrical efficiency of approximately 9%. Additionally, the condensation temperature in this steam cycle is high enough to be extracted as useful heat output to generate domestic water with a temperature of 50°C.
Application of the Transient Heat Transfer Measurement Technique in a Low Aspect Ratio Pin Fin Cooling Channel
Authors: Axtmann Meriam , von Wolfersdorf Jens , Meyer Georg
Published: August 2015

This study investigates on heat transfer enhancement in pin fin cooling channels. Experiments are conducted in a staggered pin fin array consisting of 15 rows. Heat transfer measurements are conducted in the pin fin cooling channel using the transient liquid crystal technique. The reference temperature is approximated by the fluid bulk temperature, acquired by thermocouples at specific positions. Thermal inertia of the used thermocouples is considered. One other problem that occurs while using relatively long thermocouples in short aspect ratio ducts is the heat conduction along the wires, the so called stem effect. This can lead to erroneous temperature measurements. The impact of the thermocouple immersion length on the temperature measurement is investigated. A detailed assessment of the space and time-wise varying temperature distribution is conducted for the appropriate reference temperature. This paper gives an overview about the experimental setup and the used transient measurement technique. Results are represented in terms of temperature distribution, heat transfer distribution and averaged Nusselt number at the endwall.
Analysis of Turbulent Scalar Flux Models for a Discrete Hole Film Cooling Flow
Authors: Ling Julia , Ryan Kevin J. , Bodart Julien , Eaton John K.
Published: August 2015

Algebraic closures for the turbulent scalar fluxes were evaluated for a discrete hole film cooling geometry using the results from the high-fidelity Large Eddy Simulation (LES) of Bodart et al. [1]. Several models for the turbulent scalar fluxes exist, including the widely used Gradient Diffusion Hypothesis, the Generalized Gradient Diffusion Hypothesis [2], and the Higher Order Generalized Gradient Diffusion Hypothesis [3]. By analyzing the results from the LES, it was possible to isolate the error due to these turbulent mixing models. Distributions of the turbulent diffusivity, turbulent viscosity, and turbulent Prandtl number were extracted from the LES results. It was shown that the turbulent Prandtl number varies significantly spatially, undermining the applicability of the Reynolds analogy for this flow. The LES velocity field and Reynolds stresses were fed into a RANS solver to calculate the fluid temperature distribution. This analysis revealed in which regions of the flow various modeling assumptions were invalid and what effect those assumptions had on the predicted temperature distribution.
Experimental and Numerical Investigation of a Counter-Rotating Mixed-Flow Single Stage Pump
Authors: Tosin Stefano , Friedrichs Jens , Dreiss Andreas
Published: August 2015

A prototype of a new generation of centrifugal pumps has been developed, with aim to improve typical weaknesses like narrow operable range due to slip and incidence losses in off-design conditions. The peculiarity of this pump is the absence of any stator blade, which has been substituted with a counter-rotating radial impeller. According to an exhaustive literature survey, the usage of a mixed flow impeller as a front rotor, followed by a radial-flow impeller seems to be a novel approach in pump design. The combination of a high specific speed impeller with a low specific speed rotating diffuser produces a flexible adaptability against aforementioned limits. Keep on adding energy to the fluid instead of just diffusing the flow, permits to reach a downsized hydraulics and an increased entire machine power density. The characteristic of such a pump needs to be analyzed as 3D-surface, both speeds are actually independent and for a fixed discharge the head rise and efficiency become surfaces. A new definition of optimized characteristic curve, with variable speed ratio, could be identified based on those performance maps. A special test rig has been built to measure the machine performance, distinguishing the mechanical losses of both shafts separately with no-load measurements. The sensitivity of the system on speed ratio variation has been explored. The experiments show the presence of different best speed ratios which maximize alternately the head or the efficiency. Additionally, the results confirm the possibility to expand the working range acting on the rotational speeds. Head rise and efficiency curves with varying speed ratio, as functions of the flow rate are finally shown using several diagrams, highlighting the advantages of this new design.
The 3-D Structure of Swirl-Stabilized Flames in a Lean Premixed Multi-Nozzle Can Combustor
Authors: Samarasinghe Janith , Peluso Stephen J. , Quay Bryan D. , Santavicca Domenic A.
Published: August 2015

Flame structure is an important aspect of the combustion process which must be considered in the design of gas turbine combustors as it can have a significant effect on the combustor’s static stability (blowoff) and dynamic stability (combustion instability). The relationship between flame structure and flame stability has been studied extensively in single-nozzle combustors. However, relatively few studies have been conducted in multi-nozzle combustor configurations typical of actual gas turbine combustion systems. In this paper, a chemiluminescence-based tomographic reconstruction technique is used to obtain three-dimensional images of the flame structure in a laboratory-scale five-nozzle can combustor. The images reveal the complex three-dimensional structure of this multi-nozzle flame, as well as, the effects of interacting swirling flows, flame-flame interactions and flame-wall interactions on flame structure.
Unsteady Pressure Interaction of an Axial Flow Fan With a Stabilization Ring in Tunnel and Metro Applications
Authors: Corsini Alessandro , Delibra Giovanni , Sheard Anthony G. , Volponi David
Published: August 2015

Ventilation fans operating in underground metropolitan tunnels are subjected to abrupt changes in operations due to the pressure wavefronts generated by the passage of the trains, and the magnitude of these pressure waves is increasing due to increasing speed of passing trains in modern mass transport systems. To avoid fans being driven into stall designers can fit fans with a stabilisation ring, i.e. a casing treatment that was found to mitigate the mechanical consequences of being inadvertedly driven into stall due to pressure pulses.

A stabilisation ring is a circumferential cavity in the casing of the fan, placed upstream of the rotor in order to allow the fluid to recirculate in stalled operations. A series of fins inside this cavity is used in order to drive the recirculating fluid back into the blade vane with a proper alignment with the leading edge of the rotor.

Following a previous RANS investigation that lead to the conclusion that the drive mechanism of the stabilisation ring onto the fan is based on azimuthal pressure unbalance we present here a U-RANS investigation aiming at understanding the dynamics of the interaction of the anti-stall ring with the fan and to provide insight on possible development of the geometry of the casing treatment.

The fan selected for this study is a real fan for tunnel and metro applications (9 rotor blades, 1490 rpm) with a real-geometry stabilisation ring (27 fins). Computations account for different operating points (peak efficiency, design point, peak pressure and stalled operations) and rely on the low-Reynolds cubic k-ε model of Lien et al. All the simulations were carried out with the open-source OpenFOAM code. Results were validated against available experimental data and then analysed to understand the unsteady interaction between the rotor of the fan and the cavity of the stabilisation ring.
Prediction and Analysis of Impact of TBC Oxidation on Gas Turbine Creep Life
Authors: Ogiriki E. A. , Li Y. G. , Nikolaidis Th.
Published: August 2015

Thermal Barrier Coatings (TBC) have been widely used in the power generation industry to protect turbine blades from damage in hostile operating environment. This allows either a high Turbine Entry temperature (TET) to be employed or a low percentage of cooling air to be used, both of which will improve the performance and efficiency of gas turbine engines. However, with continuous increases in turbine entry temperature aimed at improving the performance and efficiency of gas turbines, TBCs have become more susceptible to oxidation. Such oxidation has been largely responsible for the premature failure of most TBCs. Nevertheless, existing creep life prediction models that give adequate considerations to the effects of TBC oxidation on creep life are rare. The implication is that the creep life of gas turbines may be estimated more accurately if TBC oxidation is considered. In this paper, a performance-based integrated creep life model has been introduced with the capability of assessing the impact of TBC oxidation on the creep life and performance of gas turbines. The model comprises of a thermal, stress, oxidation, performance, and life estimation models. High Pressure Turbine (HPT) blades are selected as the life limiting component of the gas turbine. Therefore the integrated model was employed to investigate the effect of several operating conditions on the HPT blades of a model gas turbine engine using a Creep Factor approach. The results show that different operating conditions can significantly affect the oxidation rates of TBCs which in turn affect the creep life of HPT blades. For instance, TBC oxidation can speed up the overall life usage of a gas turbine engine from 4.22% to 6.35% within one year operation. It is the objective of this research that the developed method may assist gas turbine users in selecting the best mission profile that will minimize maintenance and operating costs while giving the best engine availability.
Numerical Investigation of the Nonreacting Swirling Flow Structure Downstream of Industrial Gas Turbine Burner With the Central Body
Authors: Zubrilin Ivan A. , Dmitriev Dmitriy N. , Matveev Sergey S. , Matveev Sergey G.
Published: August 2015

This paper will discuss the investigation of the nonreacting swirling flow downstream of the burner with the central body. This burner is designed for burning partially prepared fuel-air mixture. The burner consists of the axial swirler and the central body. The swirler plays the role of the premixer, and the central body is used to stabilize the flame. The simulation was conducted with the commercial software ANSYS Fluent 15.0. At present, the most widespread CFD approaches to the swirling flow investigation are URANS and LES. In this study URANS is used for obtaining flow charts and LES is used for detailed research of swirling flow structures. The influences of the model parameters (turbulence models, geometry simplification) and numerical parameters (the number of grid elements) on the burner pressure drop are shown in the simulation results. The LES results were compared with the experimental data on the flow structure downstream of the burner. The measurements were provided by 2D PIV with the imaging frequency of 500 Hz and 1000 Hz. It was found that in the investigated range of parameters the burner pressure drop changes slightly and is in good agreement with the experimental data. It was shown that the results of the PIV measurements with the different imaging frequency are in good agreement. The results show that flow behavior achieved in simulation is in accordance with the PIV measurements. It is shown that the flow separation from the central body trailing edge results in formation of large eddies and high velocity fluctuations. On the one hand it can contribute to the mixing of pilot fuel with air, but on the other hand it can lead to high amplitude pressure oscillations during combustion. The form and the frequency of the precessing vortex core were discovered. It was found that the maximum air flow rate through the recirculation zone is about 12% of the total air flow rate through the burner.
Optimisation of a High Pressure Ratio Radial-Inflow Turbine: Coupled CFD-FE Analysis
Authors: Shanechi Mohsen Modir , Odabaee Mostafa , Hooman Kamel
Published: August 2015

The optimisation of a 5.7 air pressure ratio single stage radial-inflow turbine applied in the Sundstrand Power Systems T-100 Multipurpose Small Power Unit (MPSPU) is performed using coupled CFD-FE method. The commercial software ANSYS-Vista RTD along with a built-in module, BladeGen, is used to conduct a meanline design and, consequently, create the 3D geometry of the flow passage. Carefully examining the proposed design against the geometrical and experimental data, ANSYS-TurboGrid is applied to generate computational mesh. CFD simulations are then performed with ANSYS-CFX in which three-dimensional Reynolds-Averaged Navier-Stokes equations are solved subject to appropriate boundary conditions. Conducting the CFD simulations, the pressure and temperature distributions are imported to the ANSYS-FE module. The von Mises stress σv distribution is then calculated taking into account the centrifugal force acting on the turbine wheel.

To obtain the optimised geometry, 25 major design points are regenerated where the meridional parameters, tip clearance, and blade thickness distribution are systematically changed. Furthermore, constraints are defined as high aerothermodynamic performance and acceptable vibration with a stress distribution less than yield limit of the turbine material. Results of coupled CFD-FE method show the power, efficiency, stress and deformation. Finally, performance of the optimised radial-inflow turbine indicates enhanced aero-thermodynamics (ηTS and) and structural performance (σv) compared to the MPSPU turbine design.
A Strategy for Parameterization and Optimization of Turbine Cooling Channels
Authors: Dieu Donavan , Deletrain Yves , Van Liefferinge Raphaël , Hirsch Charles
Published: August 2015

Cooled turbine blades represent a major component of gas turbine technology due their potential for enhancing overall cycle performance. Due to the difficulty of performing detailed experiments on these complex internal configurations, the only option is to rely intensively on high fidelity CFD modeling and subsequent optimization to enhance the heat transfer coefficient (HTC) by exploration of a broad design space.

The optimization strategy relies on the following steps: parametric modeling of cooling passages; automatic grid generation; validation of the most reliable turbulence models and boundary conditions; optimization process based on genetic algorithms.

The parametric blade modeler AutoBlade™ has been upgraded to generate CAD geometries of cooling channels, including ribs, different section shapes, U-turns.

From those geometries, the full hexahedral mesher HEXPRESS™ is able to automatically generate high quality unstructured meshes with the possibility to insert viscous sublayers to provide adequate resolution in boundary layer regions. The mesh generator can also deal with multi-domain problems allowing conjugate heat transfer (CHT) method.

CFD options were analyzed in order to obtain numerical results as accurate as possible for the optimization process. It appears that low Reynolds grids were necessary to reproduce the thermal effects due to the strong temperature gradient near solid walls. The preconditioning technique seems to be essential for density based flow to obtain realistic results for flows at low Mach number. The anisotropic EARSM turbulence model appears to provide good heat transfer predictions. In addition, the question to include or not CHT is raised: the study also compares the heat transfer obtained in case of imposed static temperature conditions on the coolant to the ones obtained by means of CHT. The results highlight that CHT is more realistic.

Optimization of HTC is performed on three baseline configurations by variation of geometric parameters including the aspect ratio of the channel cross section, the shape, position and size of the ribs. The main objective consists in maximization the heat fluxes while limiting the head loss.

The optimization process starts from an initial database of high-fidelity CHT simulations obtained by design of experiment methods. To predict a potential optimum, an evolutionary algorithm is run on an artificial neural network for a very quick evaluation of the objectives from the database. The process is iterative: starting from potential candidates, the CFD process is launched to validate the guess and populate the database.

Results and optimized geometries will be presented in the full paper.
Nonlinear Modal Analysis of Mistuned Periodic Structures Subjected to Dry Friction
Authors: Joannin C. , Chouvion B. , Thouverez F. , Mbaye M. , Ousty J.-P.
Published: August 2015

This paper deals with the dynamics of a cyclic system, representative of a bladed-disk subjected to dry friction forces, and exhibiting structural mistuning. The nonlinear complex modes are computed by solving the eigenproblem associated to the free response of the whole structure, and are then used to better understand the forced response to a traveling wave excitation.

Similarly to the underlying linear system, the tuned model possesses pairs of modes that can be linearly combined to form traveling waves, unlike those of the mistuned structure. However, due to the nonlinearity, the modal properties are not constant but vary with the vibration amplitude in both cases.

A qualitative analysis is also performed to assess the impact of the mistuning magnitude on the response, and suggests that further statistical investigations could be of great interest for the design of bladed disks, in terms of vibration mitigation and robustness.
Large Eddy Simulation of Boundary Layer Separation and Reattachment in a LPT Blade at Different Incidence Angles
Authors: Wang Yunfei , Liu Huaping , Song Yanping , Chen Fu
Published: August 2015

In order to predict the phenomenon of laminar flow separation, transition and reattachment in a high-lift low-pressure turbine (LPT), a self-developed large eddy simulation program to solve three dimensional compressible N-S equations was used to simulate the flow structures in T106A LPT blade passage. The outlet Mach number is 0.4 and the Reynolds number is 1.1×105 based on the exit isentropic velocity and the axial chord. The distributions of the time-averaged static pressure coefficient, kinetic loss coefficient and wall shear stress on the blade surface at +7.8° incidence angle agree well with the results of experiment and direct numerical simulation (DNS). The locations of laminar separation and reattachment point occur around 83.6% and 97% axial chord respectively. The evolutionary process of spanwise vorticity and large-scale coherent structure near the trailing edge on the suction side in one period indicates that the two-dimensional shear layer is gradually unstable as a result of spanwise fluctuation and Kelvin-Helmholtz (K-H) instability. The boundary layer separates from the suction surface and the hairpin vortex appears in succession, which leads to transition to turbulence. Analysis of the incidence angle effect on the boundary layer separation point as well as separation bubble scale was also performed. A small scale separation bubble exists around the leading edge at positive incidences. As the incidence angle changes from positive to negative, the separation bubble near the leading edge disappears and the boundary layer thickness reduces gradually. The separation point at the rear part of suction side moves downstream, yet the reattachment point barely changes. The Reynolds stress and turbulent kinetic energy profiles change dramatically at zero and positive incidence. This illustrates that the incidence angle has great influence on the development of the boundary layer and the flow field structures.
Advanced Rayleigh Pressure Loss Model for High-Swirl Combustion in a Rotating Combustion Chamber
Authors: Penkner Andreas , Jeschke Peter
Published: August 2015

This paper considers the effect of excessive total pressure losses for heat transfer problems in fluid flows with a high circumferential swirl component. At RWTH Aachen University, a novel gas generator concept is under research. This design avoids some disadvantages of small gas turbines and uses a rotating combustion chamber. During the pre-design of the rotating combustion chamber using CFD tools, unexpected high total pressure losses were detected. To analyze this unknown phenomenon, a gas-dynamic model of the rotating combustion chamber has been developed to explain the unexpected high Rayleigh pressure losses. The derivation of the gas-dynamic model, the physical phenomenon related to the high total pressure losses in high-swirl combustion, the influencing factors, as well as thermodynamic interpretation of the Rayleigh pressure losses, are presented in this paper. In addition, the CFD results are validated by the gas-dynamic model derived. The results presented here are of possible interest for a wide range of applications, since these fundamental findings can be transferred to all heat transfer problems in fluid flows with a high circumferential swirl component.
High Order Large Eddy Simulations for a Transonic Turbine Blade Using Hybrid Unstructured Meshes
Authors: Lu Yi , Dawes W. N.
Published: August 2015

Large eddy simulations were performed for a transonic turbine blade on hybrid unstructured meshes. High order accuracy in both space and time discretization is achieved by using a space time extension of flux reconstruction method(STEFR), and in particular, local time-stepping is enabled for time-accurate unsteady simulations. A piecewise integration in-cell method is introduced for shock-capturing within the STEFR method. This method is completely local in both space and time directions, without any explicit addition to the discretisation, which is suitable for the predictor-corrector type space time extension allowing local timestepping. A volume averaged compensation method is used to construct a conservative form of the Chain-Rule scheme for the flux divergence part of the flux reconstruction discretisation, which is proved stable and efficient to solve flow problems with physical discontinuities. This work successfully extends the application of the STEFR method to solve transonic/supersonic unsteady flows. The numerical validation for the 1D burgers equation and its comparison with traditional multi-stage Runge-Kutta method with uniform time-stepping, indicate that this piecewise integration in-cell method is accurate and more robust with STEFR method using local time-stepping.

A significant advantage of this method is the successfully implementation on hybrid unstructured meshes, which makes it very efficient and scalable to solve multi-scale, complex geometries flow problems. The moving shock, shock-boundary layer interaction, shock-wake interaction were crisply resolved and analyzed for the transonic turbine blade, VKI-LS59, and detail post-processing is presented with the comparison with experimental data in this paper.
Segmentation Effects on Brush Seal Leakage and Rotordynamic Coefficients
Authors: Pugachev Alexander O. , Gaszner Manuel , Georgakis Christos , Cooper Paul
Published: August 2015

This paper studies the effect of brush seal segmentation on the seal performance characteristics. A brush-labyrinth sealing configuration arranged of one brush seal downstream and two labyrinth fins upstream is studied experimentally and theoretically. The studied brush seal is of welded design installed with zero cold radial clearance. The brush seal front and back rings as well as the bristle pack are segmented radially in a single plane using the electrical discharge machining technique. The segmentation procedure results in loss of bristles at the site of the cuts altering the leakage flow structure in the seal and its performance characteristics. Two test rigs are used to obtain leakage, as well as rotordynamic stiffness and damping coefficients of the seal at different pressure ratios. The CFD-based model is used to predict the seal performance and to study in detail local changes in the flow field due to the segmentation. A back-to-back comparison of the performance of non-segmented and segmented brush seals, as well as baseline labyrinth seal is provided. The obtained results demonstrate that the segmentation in general negatively affects the performance of the studied brush-labyrinth sealing configuration. However, the segmented brush seal shows increased direct damping coefficients.
Revolutionary Geometries of Mobile Hydrokinetic Turbines for Wind Energy Applications
Authors: Siddappaji Kiran , Turner Mark G.
Published: August 2015

An abundant source of renewable energy is feasible by harnessing the kinetic energy of moving water using hydrokinetic turbines. The knowledge of wind turbine design, turbomachinery and fluid dynamic principles of incompressible flow can be applied to design traditional and novel geometries of mobile hydrokinetic turbines. A preliminary design is created using the Blade Element Momentum Theory (BEMT) which includes the Prandtl’s correction for tip losses and model corrections. The axial and angular induction factors are calculated iteratively taking into account the coefficient of lift and drag at a certain angle of attack for specific airfoils. Although BEMT does not account for the tip vortices and radial flow induced by the rotation, it provides a good initial geometry. The blade geometry can then be parametrically modified using an in-house 3-D blade geometry generator (3DBGB), and can be analyzed further using a 3-D CFD analysis system. Different configurations such as unshrouded single row, unshrouded counter rotating and shrouded nozzle-rotor-OGV can be explored based on a suitable power requirement. The shrouded design uses a traditional axial turbomachinery approach using 1-D meanline and axisymmetric design-analysis tools (T-AXI suite). Novel geometries with solidity varying spanwise can also be explored to take advantage of the flow across the turbine. A design and analysis system for hydrokinetic turbines is demonstrated. The system is linked to an optimizer to obtain blade shapes with maximum efficiency. A counter rotating design is explored and an optimum design with increased efficiency is obtained. A comparative study of the axial gap between the rotors in a counter rotating system is also presented to show its effect on the power coefficient. The turbine blade designs presented will revolutionize wind energy harness technology.