bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Equation of State Model and CO2 Diluent on Combustion Characteristics of a Directly Heated Supercritical Oxy-Fuel Combustor
Authors: Chowdhury A. S. M. Arifur , Choudhuri Ahsan , Love Norman , Kim Hwanho , Ma Jiefu , Tsiava Remi 
Published: August 2017

Directly heated supercritical oxy-fuel power cycles have potential to offer a higher thermal efficiency and lower pollutant emissions compared to existing power cycles. Due to the fact that combustion occurs at the supercritical phase, usually at or above 30MPa, conventional gas turbine combustors cannot be used to produce electricity using this concept. Besides, oxy-fuel combustion produces relatively higher temperatures than the air-fuel combustion process, which introduces material limitations particularly at the high pressures. Motivated by the advantages of the directly heated supercritical phase combustion technique, the authors present a design of an injector inside a combustion chamber. The combustor presented in this paper is designed to operate at a 30MPa pressure. The current study incorporates methane as the fuel and oxygen as the oxidizer. The design process of such a combustor incorporates an immense amount of challenges since the fluid properties as well as combustion behavior at the supercritical phase are still largely unknown. However, in order to design this type of system a reasonable understanding of fluid behavior in the combustion environment is essential.
A commercial computational fluid dynamics simulation tool, ANSYS Fluent, is used to simulate the fluid flow and combustion inside the combustor. The real gas effect is added into the code by coupling equation of state with the fluid flow computation. The Lee Kesler equation, which is found in literature and in this paper to be the most relevant equation of state for this case, is implemented via user defined function along with Plocker Knapp mixing rule. The system presented in this study is intended to operate at a 1 MW power input. Carbon dioxide is delivered axially into the combustion chamber separate from fuel and oxidizer. The study shows more than 90% carbon dioxide needs to be recirculated to keep the combustor exit temperature below material operation limit of approximately 1450K. Thus, it is presumable that the combustion occurs in a carbon dioxide filled environment. The investigation has been performed by varying the carbon dioxide mass flow rate splitting between two inlets. It is observed that the 30%–70% split displays the optimum performance among all three cases. This condition offers wall temperature reduction, uniform exhaust products and an even temperature profile at the outlet of the combustor.
Experimental Study of Superheated Kerosene Jet Fuel Sprays From a Pressure-Swirl Nozzle
Authors: Manipurath Shaji S. 
Published: August 2017

The development of higher thermal stability fuels and the development of onboard fuel deoxygenation systems may permit the preheating of fuel up to about 755 K before the onset of pyrolysis. At a sufficiently high fuel temperature for a given combustion chamber pressure, the flash vaporization of liquid or supercritical state fuel can ensue upon injection into the chamber. The performance of standard aviation turbine engine fuel nozzles, designed for mechanically breaking up liquid sprays, may thus be significantly altered by the employment of severely preheated fuel.
An evaluation of heated and superheated Jet A-1 sprays from a pressure-swirl atomizer was implemented in a purpose-built test facility. Laser sheet imaging of the spray yielded simultaneous axial cross-sectional maps of Mie-scatter and fluorescence signals. In addition, particle image velocimetry was also used to measure the spray droplet velocity-field. The results indicated that increasing the fuel’s dimensionless level of superheat ΔT* from −1.8 to 0.6 yielded significant changes in the spray structure; specifically, finer droplet sizes, a more uniform dropsize distribution across the spray, increased spray cone angle till about ΔT* = −0.8 followed by a contraction thereafter, marginally increased spray penetration, and significantly higher localised near nozzle tip droplet velocities. The measurements supported the hypothesis that the initial hollow-cone spray structure evolves to a near solid-cone structure with a central vapour core as the fuel is superheated.
Application of 3D Fracture Mechanics for Improved Crack Growth Predictions of Gas Turbine Components
Authors: Bhachu Kanwardeep S. , Narasimhachary Santosh B. , Shinde Sachin R. , Gravett Phillip W. 
Published: August 2017

Fracture mechanics analysis is essential for demonstrating structural integrity of gas turbine components. Usually, analyses based on simpler 2D stress intensity solutions provide reasonable approximations of crack growth. However, in some cases, simpler 2D solutions are too-conservative and does not provide realistic crack growth predictions; often due to its inability to account for actual 3D geometry, and complex thermal-mechanical stress fields. In such cases, 3D fracture mechanics analysis provides extra fidelity to crack growth predictions due to increased accuracy of the stress intensity factor calculations. Improved fidelity often leads to benefits for gas turbine components by reducing design margins, improving engine efficiency, and decreasing life cycle costs.
In this paper, the application of 3D fracture mechanics analysis on a gas turbine blade for predicting crack arrest is presented. A comparison of stress intensity factor values from 3D and 2D analysis is also shown. The 3D crack growth analysis was performed by using FRANC3D in conjunction with ANSYS.
Validation of a Gas Turbine Thermodynamic Model Without Accurate Component Maps
Authors: Jarrett Anthony , Chen Ying 
Published: August 2017

The authors have developed an engine performance model for use within a physics-based analysis tool to predict gas turbine engine life. The model employs a multivariate optimization method to solve the gas turbine thermodynamic equations, and incorporates a calibration phase to capture the behavior of individual engines without requiring accurate component maps.
To validate this approach, a database of test cell data for a turboprop engine has been used. The data consists of approximately 80 engine tests; each one with five operating points. Using a cross-validation method, each engine was uniquely calibrated using four of the operating points, and then validated using parameters from the fifth operating point. To benchmark the calibration process, these analyses were repeated without the calibration stage.
The un-calibrated outputs showed a lack of both precision and accuracy, due to imprecision in the component maps, and variation from engine to engine. In contrast, the calibrated outputs of compressor discharge temperature (CDT), compressor discharge pressure (CDP), and turbine inlet temperature (TIT) were predicted within 1% error for more than 95% of all cases.
Although most of the key thermodynamic parameters were predicted accurately, we have found that the shaft power calculation demonstrates some significant deviations from the test cell data. This has been attributed to the formulation of the turboprop thermodynamic model, and ongoing work is attempting to mitigate this issue. This understanding of the characteristic engine algorithms will provide valuable guidance in selecting suitable engine parameters as inputs and references.
CAD-Based Adjoint Optimization of the Stresses in a Radial Turbine
Authors: Verstraete Tom , Müller Lasse , Müller Jens-Dominik 
Published: August 2017

The design optimization of turbomachinery components has witnessed an increased attention in last decade, and is currently used in many companies in the daily design cycle. The adjoint method proves to have the highest potential in this field, however, has still two major shortcomings before its full potential can be used: 1) the shape is mainly parameterized by its grid and the connection to the CAD model is lost, and 2) the optimization process includes only aerodynamic performance and neglects stress and vibration requirements. Within this paper a methodology is developed to include stress calculations into a gradient-based framework, which requires the differentiation of a stress analysis tool. To allow combining the sensitivities from the structural model with those from the aero performance, the CAD model is used for parameterizing the shape, effectively defining a parametrization that controls both the fluid and solid domain that remain linked to each other without creating voids between both models.
The method is tested on a radial turbine test case in which the meridional layout is optimized to reduce the maximum von Mises stresses in the material. The results demonstrate a significant reduction in stress concentrations with a limited computational cost.
Analysis of Operational Strategies of a SOFC/MGT Hybrid Power Plant
Authors: Hohloch Martina , Huber Andreas , Aigner Manfred 
Published: August 2017

The present work deals with the analysis of operational concepts for a SOFC/MGT hybrid power plant based on a test rig at the DLR, Institute of Combustion Technology. Here, a Turbec T100 micro gas turbine and a fuel cell emulator are used. The emulator is composed of two pressure vessels. The first represents the cathode volume of the fuel cell to simulate the residence time and pressure loss. The second is equipped with a natural gas combustor to emulate the varying heat input of the fuel cell. The MGT and the SOFC are connected via different piping paths.
The procedures start-up, load change and shutdown are analyzed in matters of temperature gradients, pressure gradients and fluctuations, as well as the air mass flow provided at the interconnections to the coupling elements. To achieve the required inlet conditions of the SOFC, transient operations, using the different piping paths, are investigated. Concepts for heating-up and cooling the SOFC using hot air from the recuperator and relatively cold air from the compressor outlet are experimentally tested and characterized. Selected critical situations and their effect on the SOFC are investigated. An emergency operation, its impact on both subsystems and limitations are shown. Further operational limits of the MGT control system and power electronic were observed and analyzed. Based on the experimental results, the applicability of the used MGT procedures in a hybrid power plant was reconsidered. Finally, adaptions and strategies for the operational concept are derived and discussed.
Simulation of Pneumatic Volumes for a Gas Turbine Transient State Analysis
Authors: Yepifanov Sergiy , Zelenskyi Roman , Sirenko Feliks , Loboda Igor 
Published: August 2017

The problem of pneumatic volumes constituting a gas turbine engine gas path and their effect on an engine transient belongs to the topical problems of modern turbomachinery engineering. Many researchers have been trying to find the most resource efficient method of volume modeling. The associated urgent problem is the integration of the volume models with an engine model.
Following the world trends, the present paper deals with the pneumatic volume simulation that considers different dynamic factors described with the mass, energy, and momentum conservation laws.
The developed dynamic volume models were examined and compared. The comparison cases included temperature and pressure change at the volume entrance and pressure change at the volume discharge. To reduce the computation time, the linearization of model equations was also proposed and proved.
Based on the comparison results, the guidelines and recommendations on the volume effect mathematical modeling and the volume model integration with the engine model have been made.
Sensitivity Analysis on the Effect of D32 and Dv90 on the Evaporation Efficiency of Gas Turbine Inlet Fogging for Power Augmentation
Authors: Chaker Mustapha 
Published: August 2017

Gas Turbine output is strongly dependent of the ambient air temperature. This decrease is usually occurs in the hot afternoon during the peak demand for power. One way to counter this drop in output is to cool the inlet air using one of the available cooling technologies such as the inlet fog cooling of gas turbine engines for power augmentation.
This technology is well-established with over 1,000 fogging systems installed all around the world on gas turbines of various makes and sizes ranging from 5MW to 250MW.
Two droplet diameters are used to characterize the droplet sizes from nozzles used in the fogging systems, namely D32 (Sauter mean diameter) and Dv90 (diameter for which 90% of the water volume in the spray is less than or equal to).
This paper will show the importance of each diameter on the performance of fogging systems. For this purpose, a heat and mass transfer theoretical model is developed to analyze the dynamics of evaporation of fog droplets. The model will quantify the evaporative efficiency of fog droplets for different D32 and Dv90 values derived from experimentally measured droplet size distributions at two typical ambient psychrometric conditions: hot and dry, and cold and Humid.
Design of a Wide-Range Centrifugal Compressor Stage for Supercritical CO2 Power Cycles
Authors: Pelton Robert , Allison Tim , Jung Sewoong , Smith Natalie 
Published: August 2017

Supercritical carbon dioxide (sCO2) power cycles require high compressor efficiency at both the design-point and over a wide operating range. Increasing the compressor efficiency and range helps maximize the power output of the cycle and allows operation over a broader range of transient and part-load operating conditions. For sCO2 cycles operating with compressor inlets near the critical point, large variations in fluid properties are possible with small changes in temperature or pressure. This leads to particular challenges for air-cooled cycles where compressor inlet temperature and associated fluid density are subject to daily and seasonal variations as well as transient events.
Design and off-design operating requirements for a wide-range compressor impeller are presented where the impeller is implemented on an integrally-geared compressor-expander (IGC) concept for a high temperature sCO2 recompression cycle. In order to satisfy the range and efficiency requirements of the cycle, a novel compressor stage design incorporating a semi-open impeller concept with a passive recirculating casing treatment is presented that mitigates inducer stall and extends the low flow operating range. The stage design also incorporates splitter blades and a vaneless diffuser to maximize efficiency and operating range. These advanced impeller design features are enabled through the use of direct metal laser sintering (DMLS) manufacturing. The resulting design increases the range from 45% to 73% relative to a conventional closed impeller design while maintaining high design point efficiency.
Zoonotic Risk, Pathogenesis, and Transmission of Avian-Origin H3N2 Canine Influenza Virus
Authors: Sun Hailiang , Blackmon Sherry , Yang Guohua , Waters Kaitlyn , Li Tao , Tangwangvivat Ratanaporn , Xu Yifei , Shyu Daniel , Wen Feng , Cooley Jim , Senter Lucy , Lin Xiaoxu , Jarman Richard , Hanson Larry , Webby Richard , Wan Xiu-Feng 
Published: August 2017

ABSTRACT

Two subtypes of influenza A virus (IAV), avian-origin canine influenza virus (CIV) H3N2 (CIV-H3N2) and equine-origin CIV H3N8 (CIV-H3N8), are enzootic in the canine population. Dogs have been demonstrated to seroconvert in response to diverse IAVs, and naturally occurring reassortants of CIV-H3N2 and the 2009 H1N1 pandemic virus (pdmH1N1) have been isolated. We conducted a thorough phenotypic evaluation of CIV-H3N2 in order to assess its threat to human health. Using ferret-generated antiserum, we determined that CIV-H3N2 is antigenically distinct from contemporary human H3N2 IAVs, suggesting that there may be minimal herd immunity in humans. We assessed the public health risk of CIV-H3N2 × pandemic H1N1 (pdmH1N1) reassortants by characterizing their
in vitro
genetic compatibility and
in vivo
pathogenicity and transmissibility. Using a luciferase minigenome assay, we quantified the polymerase activity of all possible 16 ribonucleoprotein (RNP) complexes (PB2, PB1, PA, NP) between CIV-H3N2 and pdmH1N1, identifying some combinations that were more active than either parental virus complex. Using reverse genetics and fixing the CIV-H3N2 hemagglutinin (HA), we found that 51 of the 127 possible reassortant viruses were viable and able to be rescued. Nineteen of these reassortant viruses had high-growth phenotypes
in vitro
, and 13 of these replicated in mouse lungs. A single reassortant with the NP and HA gene segments from CIV-H3N2 was selected for characterization in ferrets. The reassortant was efficiently transmitted by contact but not by the airborne route and was pathogenic in ferrets. Our results suggest that CIV-H3N2 reassortants may pose a moderate risk to public health and that the canine host should be monitored for emerging IAVs.

IMPORTANCE
IAV pandemics are caused by the introduction of novel viruses that are capable of efficient and sustained transmission into a human population with limited herd immunity. Dogs are a a potential mixing vessel for avian and mammalian IAVs and represent a human health concern due to their susceptibility to infection, large global population, and close physical contact with humans. Our results suggest that humans are likely to have limited preexisting immunity to CIV-H3N2 and that CIV-H3N2 × pdmH1N1 reassortants have moderate genetic compatibility and are transmissible by direct contact in ferrets. Our study contributes to the increasing evidence that surveillance of the canine population for IAVs is an important component of pandemic preparedness.
Screening of FDA-Approved Drugs for Inhibitors of Japanese Encephalitis Virus Infection
Authors: Wang Shaobo , Liu Yang , Guo Jiao , Wang Peilin , Zhang Leike , Xiao Gengfu , Wang Wei 
Published: August 2017

ABSTRACT

Japanese encephalitis virus (JEV), an arthropod-borne flavivirus, is a major cause of acute viral encephalitis in humans. No approved drug is available for the specific treatment of JEV infections, and the available vaccines are not effective against all clinical JEV isolates. In the study described here, a high-throughput screening of an FDA-approved drug library for inhibitors of JEV was performed. Five hit drugs that inhibited JEV infection with a selective index of >10 were identified. The antiviral activities of these five hit drugs against other flavivirus, including Zika virus, were also validated. As three of the five hit drugs were calcium inhibitors, additional types of calcium inhibitors that confirmed that calcium is essential for JEV infection, most likely during viral replication, were utilized. Adaptive mutant analysis uncovered that replacement of Q130, located in transmembrane domain 3 of the nonstructural NS4B protein, which is relatively conserved in flaviviruses, with R or K conferred JEV resistance to manidipine, a voltage-gated Ca
2+
channel (VGCC) inhibitor, without an apparent loss of the viral growth profile. Furthermore, manidipine was indicated to protect mice against JEV-induced lethality by decreasing the viral load in the brain, while it abrogated the histopathological changes associated with JEV infection. This study provides five antiflavivirus candidates and identifies cytoplasmic calcium to be a novel antiviral target for the treatment of JEV infection. The findings reported here provide therapeutic possibilities for combating infections caused by flaviviruses.

IMPORTANCE
No approved therapy for the treatment of Japanese encephalitis virus infection is currently available. Repurposing of approved drugs would accelerate the development of a therapeutic stratagem. In this study, we screened a library of FDA-approved drugs and identified five hit drugs, especially calcium inhibitors, exerting antiflavivirus activity that blocked viral replication. The
in vivo
efficacy and toxicity of manidipine were investigated with a mouse model of JEV infection, and the viral target was identified by generating an adaptive mutant.
Amblyopia and strabismus: trends in prevalence and risk factors among young adults in Israel
Authors: Shapira Yinon , Machluf Yossy , Mimouni Michael , Chaiter Yoram , Mezer Eedy 
Published: August 2017

AimsTo estimate the prevalence of amblyopia, present strabismus and amblyopia risk factors (ARFs) among young adults in Israel and to analyse trends over time of prevalence rates.MethodsWe conducted a cross-sectional study including 107 608 pre-enlistees aged 17.4±0.6 years born between 1971 and 1994. Across the birth years, the following trends of prevalence rates among young adults were analysed: prevalence of amblyopia, prevalence of strabismus, severity of amblyopia and prevalence of ARFs (strabismsus, anisometropia and isoametropia). Unilateral amblyopia was defined as best corrected visual acuity (BCVA) of <0.67 (6/9) in either eye or as an interocular difference of two lines or more. Bilateral amblyopia was defined as BCVA of <0.67 (6/9) in both eyes. The severity of amblyopia was classified as mild (BCVA ≥0.5 [6/12]), moderate (BCVA <0.5 [6/12] and ≥0.25 [6/24]) or severe (BCVA <0.25 [6/24]).ResultsThe prevalence of young adulthood amblyopia declined by 33%, from 1.2% to 0.8% (R2=0.87, p<0.001) across 24 birth years. This decline may be due to a drop in unilateral amblyopia from 1% to 0.6% (R2=0.93, p<0.001), while the prevalence of bilateral amblyopia remained stable (0.2%, p=0.12). The decline in amblyopia was apparent in mild and moderate amblyopia, but not in severe amblyopia. Strabismus and anisometropia were detected in 6–12% and 11–20% of subjects with unilateral amblyopia, respectively, without significant trends. Strabismic amblyopia remained constant in the entire population across years. Isoametropia was detected in 46–59% of subjects with bilateral amblyopia without a significant trend across birth years. Prevalence of strabismus in the study population decreased by 50%, from 1.2% to 0.6% (R2=0.75, p<0.001). In subjects with present strabismus, the prevalence of mild unilateral amblyopia increased, while moderate or severe unilateral amblyopia remained relatively stable.ConclusionAmong young adults, the prevalence of unilateral amblyopia, as well as the prevalence of present strabismus, decreased significantly over a period of a generation. The prevalence of strabismic, bilateral or severe (both unilateral and bilateral) amblyopia remained stable. The establishment of the national screening programme for children and the improved utility of treatment for amblyopia and strabismus coincide with these trends. Thus, it is possible that these early interventions resulted in modification of the ‘natural history’ of these conditions and their prevalence in adolescence.