bluuebunny/crossref_metadata_2025 huggingface dataset:
Assembly and analysis of a qingke reference genome demonstrate its close genetic relation to modern cultivated barley
Authors: Dai Fei , Wang Xiaolei , Zhang Xiao‐Qi , Chen Zhonghua , Nevo Eviatar , Jin Gulei , Wu Dezhi , Li Chengdao , Zhang Guoping
Published: September 2017

Qingke, the local name of hulless barley in the Tibetan Plateau, is a staple food for Tibetans. The availability of its reference genome sequences could be useful for studies on breeding and molecular evolution. Taking advantage of the third‐generation sequencer (PacBio), we de novo assembled a 4.84‐Gb genome sequence of qingke, cv. Zangqing320 and anchored a 4.59‐Gb sequence to seven chromosomes. Of the 46,787 annotated ‘high‐confidence’ genes, 31 564 were validated by RNA‐sequencing data of 39 wild and cultivated barley genotypes with wide genetic diversity, and the results were also confirmed by nonredundant protein database from NCBI. As some gaps in the reference genome of Morex were covered in the reference genome of Zangqing320 by PacBio reads, we believe that the Zangqing320 genome provides the useful supplements for the Morex genome. Using the qingke genome as a reference, we conducted a genome comparison, revealing a close genetic relationship between a hulled barley (cv. Morex) and a hulless barley (cv. Zangqing320), which is strongly supported by the low‐diversity regions in the two genomes. Considering the origin of Morex from its breeding pedigree, we then demonstrated a close genomic relationship between modern cultivated barley and qingke. Given this genomic relationship and the large genetic diversity between qingke and modern cultivated barley, we propose that qingke could provide elite genes for barley improvement.
Rethinking Compassion: Toward a Political Account of the Partisan Gender Gap in the United States
Authors: Blinder Scott , Rolfe Meredith
Published: September 2017

Scholarship on the political gender gap in the United States has attributed women's political views to their greater compassion, yet individual‐level measures of compassion have almost never been used to directly examine such claims. We address this issue using the only nationally representative survey to include psychometrically validated measures of compassion alongside appropriate political variables. We show that even though women are more compassionate in the aggregate than men in some respects, this added compassion does not explain the gender gap in partisanship. Female respondents report having more tender feelings towards the less fortunate, but these empathetic feelings are not associated with partisan identity. Women also show a slightly greater commitment to a principle of care, but this principle accounts for little of the partisan gap between men and women and has no significant relationship with partisanship after accounting for gender differences in egalitarian political values.
From cytokines to pragmatic designs: changing paradigms
Authors: Heddle Nancy M.
Published: September 2017

Emily Cooley was a well‐respected medical technologist and morphologist with a remarkable skill set. She was highly regarded both professionally and personally. The “Emily Cooley Lectureship and Award” was established to honor her in particular and medical technologists in general. This article first reviews how a medical laboratory technologist was inspired to become a clinical researcher, then goes on to describe research that led to the discovery of cytokines as the cause of febrile nonhemolytic transfusion and the use of a pragmatic randomized controlled trial design to address evidence of harm when stored red blood cells were transfused. Important lessons for performing quality, meaningful research are highlighted.
Fatty acid synthase as a potential therapeutic target in feline oral squamous cell carcinoma
Authors: Walz J. Z. , Saha J. , Arora A. , Khammanivong A. , O'Sullivan M. G. , Dickerson E. B.
Published: September 2017

Oral squamous cell carcinoma (OSCC) is an aggressive and treatment‐resistant malignancy in both feline and human patients. Recent work has demonstrated aberrant expression of fatty acid synthase (FASN) and an increased capacity for lipogenesis in humanOSCCand other cancers. In humanOSCC, inhibition ofFASNdecreased cell viability and growth in vitro, and diminished tumour growth and metastasis in murine preclinical models. This study aimed to characterizeFASNas a therapeutic target in felineOSCC. Immunohistochemistry revealed highFASNexpression in primary felineOSCCtumours, andFASNexpression was detected inOSCCcell lines (3 feline and 3 human) by immunoblotting and quantitative real‐time‐polymerase chain reaction (qRT‐PCR). Orlistat, aFASNinhibitor, substantially reduced cell viability in both feline and humanOSCClines, although feline cell lines consistently displayed higher sensitivity to the drug.FASN mRNAexpression among cell lines mirrored sensitivity to orlistat, with feline cell lines expressing higher levels ofFASN. Consistent with this observation, diminished sensitivity to orlistat treatment and decreasedFASN mRNAexpression were observed in felineOSCCcells following incubation under hypoxic conditions. Treatment with orlistat did not potentiate sensitivity to carboplatin in the cell lines investigated; instead, combinations of the 2 drugs resulted in additive to antagonistic effects. Our results suggest thatFASNinhibition is a viable therapeutic target for felineOSCC. Furthermore, cats may serve as a spontaneous large animal model for human oral cancer, although differences in the regulation of lipogenesis between these 2 species require further investigation.
Integrated Design and Testing of an Anemometer for Autonomous Sail Drones
Authors: Luca Pugi , Benedetto Allotta , Enrico Boni , Francesco Guidi , Marco Montagni , Tommaso Massai
Published: September 2017

A correct estimation of both direction and intensity of wind velocity is fundamental for controlling an autonomous sail-boat. This kind of estimation has to be performed in a harsh environment considering the direct exposition of the sensor to salt, fog, and to any variable weather conditions. An important feature is represented by the sensor size, which has to be small compared to the drone size. Costs have to be optimized with respect to the overall small budget involved in the construction of the drone. Finally, extensive use on drones or in large sensor networks should be greatly advantaged by an easy substitutability in the case of accidental damage or system loss, an eventuality which is difficult to be completely avoided for large scale, prolonged monitoring activities. In this work authors propose a low cost ultrasonic planar anemometer with a very interesting price to performance ratio which is obtained by introducing a simple, original and innovative Arduino based architecture. Preliminary design and the results of calibration will be described, followed by testing activities performed on a low-speed large section wind tunnel, available at University of Florence supported by simple but effective computational fluid dynamic (CFD) simulations.
Slug Flow and Waves Induced Motions in Flexible Riser
Authors: Ortega Arturo , Rivera Ausberto , Larsen Carl M.
Published: September 2017

Flexible risers provide optimum solutions for deep water offshore fields. Reliable dynamic analysis of this kind of slender structure is crucial to ensure safety against long time fatigue failure. Beyond the effects from wave loads, the influence from transient internal slug flow on the slender structure dynamics should also be taken into account. In this study, two coupled in-house codes were used in order to identify and quantify the effects of an internal slug flow and wave loads on the flexible riser dynamics. One code carries out a global dynamic analysis of the slender structure displacements using a finite element formulation. The other program simulates the behavior of the internal slug flow using a finite volume method. The slug flow is influenced by the dynamic shape of the riser, while the time varying forces from internal slug flow plus external waves will influence the shape. Hence, a fully coupled analysis is needed in order to solve the coupled problem. By means of the distributed simulation, these two programs run synchronously and exchange information during the time integration process. A test case using hydrodynamic forces according to the linear Airy wave theory coupled with an internal unstable slug flow was analyzed and the results shown amplification of the dynamic response due to the interaction between the two load types, effects on the effective tension caused by the internal two-phase flow, and influence on the internal slug flow caused by the wave-induced response.
An Experimental Investigation on Mechanical and Wear Properties of Al7075/SiCp Composites: Effect of SiC Content and Particle Size
Authors: Rao Thella Babu
Published: September 2017

One of the major advantages of metal matrix composites (MMCs) is that their tailorable properties meet the specific requirements of a particular application. This paper deals with the experimental investigations done on the effects of the reinforcement particulate size and content on the Al7075/SiC composite. The composites were manufactured using stir casting technique. The effect of SiC particle size (25, 50, and 75 μm) and particulate content (5, 10, and 15 wt %) on the microstructural, mechanical properties, and wear rate of the composites was studied and the results were analyzed for varied conditions of reinforcement. Scanning electron microscope (SEM) examinations were used to assess the dispersion of SiC particles reinforced into the matrix alloy and was found with reasonably uniform with minimal particle agglomerations and with good interfacial bonding between the particles and matrix material. X-ray diffraction (XRD) analysis confirmed the presence of Al and SiC with the composite. The results of mechanical tests showed that the increasing SiC particle size and content considerably enhanced the ultimate tensile strength and hardness of the composites while the ductility at this condition was decreased. The highest ultimate tensile strength of 310 MPa and hardness of 126 BHN were observed for the composites containing 15 wt %. SiC at 75 μm. Lesser the wear resistance of the reference alloy while it was enhanced up to 40% with the composites. The wear resistance was increased up to 1200 m of sliding distance for all the composites, whereas for the composite containing 75 μm SiC particles, it was extended up to 1800 m.
Band Gap Characteristics of Nonrotating Passive Periodic Drill String
Authors: Alsaffar Yaser , Sassi Sadok , Baz Amr
Published: September 2017

A new class of drill strings is investigated whereby strategically designed and placed periodic inserts are utilized to filter out the vibration transmission along the drill strings. Such mechanical filtering capabilities allow the vibrations to propagate along the periodic drill string only within specific frequency bands called the “pass bands” and completely block it within other frequency bands called the “stop bands.” The design and the location of the inserts are selected to confine the dominant modes of vibration of the drill string within the stop bands generated by the periodic arrangement of the inserts in order to completely block the propagation of the vibrations. A finite element model (FEM) that simulates the operation of this new class of drill strings is developed to describe the complex nature of the vibration encountered during drilling operations. Experimental prototype of the passive periodic drill string was built and tested to demonstrate the feasibility and effectiveness of the concept of periodic drill string in mitigating undesirable vibrations. The experimental results are used to validate the developed theoretical model and to develop a scalable design tool that can be used to predict the dynamical behavior of this new class of drill strings.
A Biologically Inspired Coupled Microphone Array for Sound Source Bearing Estimation
Authors: Zhang Yaqiong , Yang Ming , Zhu Xinlei , Ta Na , Rao Zhushi
Published: September 2017

The Ormia ochracea, a species of parasitic fly, has a remarkable localization ability despite the tiny interaural distance compared with the incoming wavelength. The mechanical coupling between its ears enhances the differences of the two received signals, the main cues to locate the source. Inspired by the coupling mechanism, we present a miniature coupled two-microphone array for estimating sound source horizontal bearing. The coupled array consists of a standard two-microphone array and a two-input, two-output filter which implements the coupling. The relationship between filter parameters and time delay magnification is investigated to provide theoretical support for array design. With appropriate parameters, the time delay of received signals can be linearly magnified. Based on the linear magnification, we present a method for estimating source direction using the coupled array. The influence of time delay magnification on time delay estimation accuracy is explored through the general cross-correlation (GCC) method. Experiments are conducted to verify the coupled array and demonstrate its advantages on improving the resolution of estimation of time delay and accuracy of bearing estimation compared with the standard array with the same element spacing.
Evaluation of Methanol and Light Fuel Oil Blends Firing at a 50 MW Gas Turbine
Authors: Chudnovsky B. , Reshef M. , Talanker A.
Published: September 2017

Emissions reduction requirements lead to modification of the firing system to control NOx emission reduction, and/or the post combustion treatment of the flue gas to remove NOx, SO2 & particulates. It has also leads to installation of new renewable energy production systems. All of these measures are very expensive both in installation and operation costs, while utilities are looking for low cost options with a minimum impact on unit performance and reliability. Firing of methanol and its blends with other liquid fuels, in comparison with other renewable sources, is one of the main alternatives for meeting this target. Methanol is a clean burning fuel that is made from non-petroleum energy sources such as natural gas, coal, biomass and carbon dioxide. Using CO2 for methanol production leads to reducing of greenhouse gas emissions so that methanol can actually be called as enviro fuel. The blending of methanol with light fuel oil is one of the quickest and cheapest means for both replacing costly petroleum energy consumed in the existing power generation fleet and reducing emissions that lead to air pollution such as nitric oxides, carbon monoxide, air toxics and PM. Hence, methanol is a good candidate as an alternative fuel for power generation, since it is liquid and has several physical and combustion properties similar to fuel oil. For this reason, this study is aimed to evaluate gas turbine performance and emissions characteristics for different blends of methanol and light fuel oil. The results obtained from simulation of different light fuel blends were compared to those of actual burning. In this study we experimented with methanol fractions (from 0 to 100 % by heat) at different GT loads and found that the methanol and light fuel oil blends enabled us to significantly reduce NOx emissions with increasing of the methanol fraction. SO2 emissions were also reduced according to the methanol heat fraction. The final blend ratio optimization should be based upon environmental requirements and fuel price. CO emissions are slightly higher than the required level. Based on performed tests, the main reason for CO formation is high excess air, especially at partial loads and as a result of low combustion temperature (this conclusion is right for any fuel and its blends). In order to reduce CO emissions, proper air /fuel control is necessary (IGV, IBH etc). This conclusion is very important for conceptual design of gas turbines in general and particularly for GT conversion to methanol firing. Firing of methanol and its blends had no impact on GT performance and provides safe operation. The computer simulations provide support for these experimental findings and conclusions. The results of the performed tests analysis indicate that methanol firing is a potentially promising low cost technology for emissions’ reduction and may be implemented in existing and new gas turbines.
Reliability, Availability, Maintainability (RAM) for Wind Turbines
Authors: Kumar Nikhil , Rogers David , Burnett Thomas D. , Sullivan Eric , Gascon Martin
Published: September 2017

Wind based electric generation is one of the fastest growing energy sources in the world. With rapid development of wind farms, many challenges have emerged with respect to the reliability and availability of the in-service equipment. Additionally, with increasing size of wind turbine blades, both onshore and offshore, the serviceability and maintainability of the equipment poses its own unique challenge. There is also an inherent risk from the economics of energy production, which dictates that low-cost manufacturing methods are employed to produce cost-effective machines.

In our experience, there are additional risks associated with supply chains and limited availability and understanding of damage mechanisms and reliability data of the myriad manufacturers and models of turbines, blade design and associated equipment. Failure of different components results in different outage times and therefore impact operational and maintenance (O&M) costs in different ways. Achieving high availability targets requires a robust O&M plan.

The authors will highlight operational risks of large wind turbines and methodologies to improve reliability and availability for wind farms.
Upgradation of Low Grade Coal to High Quality Coal by Chemical Beneficiation Technique
Authors: Behera Sushanta Kumar , Chakraborty S. , Meikap B. C.
Published: September 2017

Low rank or grade coals (LGC) are widely distributed over the world. Coal plays a vital role in the global energy demand especially through power generation and it mitigates the energy poverty. The major challenges by the utility of coal as regarding to energy security, a risk of climate change, and increasing of the energy demands are the main portfolio to develop the advanced technology for coal beneficiation. The gradual depletion of high quality coal and cost effective which become a significant issue for power generation while the low grade coals were served as low cost fuel and as an alternative energy security issue. In current research the low grade coal (>35% ash) has been upgraded to higher grade (<10%) by chemical cleaning method. The low grade coal was selected from Mahanadi Coalfields Limited, Odisha, India. Each test was conducted of 50 g coal (250 μm particle size) with 40% NaOH at 100 °C for 3 h and followed with 20% of H2O2, H2SO4, HCl, and HF acids at similar conditions. The research study revealed that ash content (mineral matter) of coal is reduced to >70% by NaOH followed HF treatment as compared to other solvents. The greater liberation of mineral results increases the ash reduction from low grade coal because mineral associated in the coal matrix may formed elution by the leaching effect. The greater extent of demineralization was caused due to the high affinity of OH− and F− with minerals in the coal matrix. The characterization of pre and post treatment coal and coal ash was investigated by the FESEM, XRF and XRD analysis. Overall the current research study challenges the chemical cleaning of low grade coal has been efficient techniques for reducing the minerals to a certain limit.
Can Propane Displace Diesel as a Fuel for Power Generation?
Authors: Welch Michael , Patel Rajan
Published: September 2017

Access to electricity is a key necessity in today’s World for economic growth and improvements in quality of life. However, the global challenge is addressing the so-called Energy Trilemma: how to provide secure, affordable electricity while minimizing the impact of power generation on the environment. The rapid growth in power generation from intermittent renewable sources, such as wind and photovoltaics, to address the environmental aspect has created additional challenges to meet the security of supply and affordable electricity aspects of this trilemma. Fossil fuels play a major role in supporting intermittent renewable power generation, rapidly providing the security of supply needed and ensuring grid stability.

Globally diesel or other fuel oils are frequently used as the primary fuel or back-up fuel for fossil-fueled power generation plants at all scales, from a few kiloWatts to hundreds of MegaWatts, and helps provide millions of people with secure electricity supplies. But diesel is a high polluting fuel, emitting high levels of carbon dioxide (CO2) per unit of fuel input compared to natural gas, as well as high levels of combustion contaminants that are potentially hazardous to the local environment and human health. Additionally, diesel can be a high cost fuel in many countries, with imports consuming significant portions of sometimes scarce foreign currency reserves.

Most observers consider that natural gas is the ‘fuel of choice’ for fossil power generation due to its reduced CO2 emissions compared to coal and diesel. However, access to gas supplies cannot be guaranteed even with the increased availability of Liquefied Natural Gas (LNG) and Compressed Natural Gas (CNG). Additionally where natural gas is available, operators may opt for an interruptible gas supply contract which offers a lower tariff than a firm gas supply contract, therefore there is a need for a back-up fuel to ensure continuous power supplies. While traditionally diesel or Heavy Fuel Oil (HFO) has been used as fuel where gas is not available or as a back-up fuel, propane offers a cleaner and potentially lower cost alternative. This paper compares the potential economic, operational and environmental benefits of using propane as a fuel for gas turbine-based power plants or cogeneration plants.
Visualized Measurement on Evolution of Bubble Patterns in a Direct-Contact Heat Exchanger
Authors: Xiao Qingtai , Wang Shibo , Xu Jianxin , Wang Hua
Published: September 2017

Direct-contact heat exchanger involves the exchange of heat between two immiscible fluids at different temperatures. Considering that there is a linear relationship between the flow patterns of a bubble swarm and heat transfer coefficient, it is inevitably to investigate the evolution of flow patterns for heat transfer enhancement in different mixing systems. However, the dynamical complexity and random variability of multiphase flow have put forward a severe challenge to improve the accuracy and real-time performance of visualized measurement of multiphase flow. The entropy of an image shows its quality objectively. Generally speaking, if the value of image entropy is large enough, then the mixing uniformity is good enough. Hence, in this paper, image entropy is used to assess the mixing uniformity and estimate the homogeneous time in the direct-contact boiling heat transfer process. The evolution of bubbles movement is experimentally tracked using an imaging technique. Variations in time of image entropy values bring new insights to study and compare mixing performance of different direct-contact heat transfer process. The results show the evolutions of bubble patterns in a direct-contact exchanger have been successfully visualized measured.
Experimental Investigation on the Influences of Bluff-Body’s Position on Diffusion Flame Structures
Authors: Tong Yiheng , Li Mao , Klingmann Jens , Chen Shuang , Li Zhongshan
Published: September 2017

Effects of the bluff-body’s position on diffusion flame structures and flame instability characteristics were investigated experimentally. A flame regime diagram together with the corresponding flow fields were proposed to evaluate the influences caused by the alternation of bluff-body’s position. The disk shape bluff-body was placed 10 mm downstream or at the same height with the annular channel exit. The bulk velocity of the annular air flow varied from 0 to 8.6m/s while the central jet fuel velocity ranged from 0 to 30m/s. Various flame patterns including the recirculation zone flame, the stable diffusion jet flame, split-flashing flame and lifted flame were observed and recorded with a high speed camera. It is found that the flame has approximately the same patterns with different bluff-body’s positions, except for cases with high air flow rate (Ua > 6.8m/s) and low fuel flow rate (Uj < 5m/s). Under that operating conditions, placing the disk bluff-body 10 mm above the annular channel could better stabilize the flame. High speed Particle Image Velocimetry (PIV) was also used to get deeper insight into the characteristics of the flow fields and flame stabilization. The size and strength of the recirculation zone downstream of the bluff-body altered with the changing of bluff-body’s position and other operating conditions. The recirculation zone, in the burner with the bluff-body placed 10 mm above the air channel exit, was found larger and stronger than that in the other burner geometry. In the reacting case, a recirculation bubble was formed besides the bluff-body’s outer wall which enhanced the flame stabilization. It is also found that the combustion changed the flow fields by enlarging the recirculation bubbles downstream of the bluff-body.
Multicriteria Synthesis of Trigeneration Systems Assisted With Renewable Energy Sources and Thermal Energy Storage
Authors: Pina Eduardo A. , Lozano Miguel A. , Serra Luis M.
Published: September 2017

The increasing world energy demand as a result of society development brings forth a growing environmental concern. The use of high-efficiency alternative systems is becoming progressively more interesting due to economic reasons and regional incentives. The issue of finding the best configuration that minimizes total annual cost is not enough anymore, as the environmental concern has become one of the objectives in the synthesis of energy systems. The minimization of costs is often contradictory to the minimization of environmental impact. Multi-objective optimization tackles the conflicting objectives issue by providing a set of trade-off solutions, or Pareto solutions, that can be examined by the decision maker in order to choose the best configuration for the given scenario. The present work proposes a mixed integer linear programming model for the synthesis of a trigeneration system that must attend the electricity, heat, and cooling demands of a multifamily building complex in Zaragoza, Spain. The objective functions to be minimized are the overall annual costs and the overall annual CO2 emissions, considering investment, maintenance and operation costs. As a first approach, the single-objective configurations for each objective function are evaluated. Then, the Pareto frontier is obtained for the minimization of total annual costs and total annual CO2 emissions, allowing to obtain the best trade-off configuration, which brings results close to the optimal single objectives. It is worth mentioning that the treatment of the energy prices was simplified in order to keep on the same level of detail as energy CO2 emissions, which are given only on an annual basis. On the other hand, the optimization model developed can be further complicated in order to consider more complex situations.
Study on Optimization of Selective Non-Catalytic Reduction for W-Flame Boiler
Authors: Zhang Bo , Xu Hongjie , Zhang Xiangyu , Xiang Xiaofeng , Gao Ning , Lu Xu
Published: September 2017

For the optimal design of the selective non-catalytic reduction (SNCR) for a 600MW W-flame boiler, the SNCR process was simulated through method of chemical kinetics analysis and fluid dynamics analysis. The design temperature, de-nitrification efficiency in theory, position of spray gun and other parameters were determined and 46% de-nitrification rate was finally obtained. Chemical kinetics analysis, without considering the effect of reducing agent mixed with NOx, the theoretical efficiency is higher. Fluid dynamics analysis, taking into account the effect of mass transfer, the de-nitrification efficiency is lower than the theoretical value. In practical engineering, the mixed mass transfer is an important factor affecting the efficiency of SNCR. (CSPE)
Study on the Management Optimization of Design Interface About TG Package for HPR1000
Authors: Wang Zelei , Zhou Yigong
Published: September 2017

HPR1000 is a kind of third-generation advanced nuclear technology, which was developed independently by China. It plays an important role in nuclear markets all over the world. For mass construction, besides quality and safety, enhancing process management and construction period optimization should be taken into consideration, such as design interface control in turbine & generator (TG) package, to improve comprehensive competitiveness for HPR1000. The existing Interface Control Manual (ICM) is a good means used to control design interface, however there is no standard model to establish ICMs for HPR1000. Taking the system of condensation water extraction (TFE) for example, after analysis on the design interfaces between TFE and other related systems, a standard design interface module can be built for TFE. Other standard design interface modules can be built in the same way, so the standard ICM for HPR1000 can be formed by combining the standard design interface modules of every system. (CSPE)
Study of Gas Temperature Characteristics at the Bottom of the Platen Heaters of Boiler Employing Shenhua Bituminous Coal Based on Two-Level Air Staging Combustion System
Authors: Xie Jianwen , Fan Weidong , Zhang Jianwen
Published: September 2017

A 600MW tangentially fired sub-critical boiler with the volume heat load of 87.6kW/m3 at the case of BMCR was not originally equipped with the separated over fire air (SOFA) system. Shenhua bituminous coal with low ash fusion point and strong slagging characteristics is employed as its design coal. To prevent serious slagging on its platen heaters, it is necessary to employ 80% Shenhua bituminous coal with low ash fusion temperature blending 20% Shenhua bituminous coal with high ash fusion temperature. However, NOx emission value at the furnace exit reaches more than 370mg/m3 (O2 = 6%). In order to achieve a NOx emission limitation level below 100mg/m3 (O2 = 6%) for pulverized coal power boilers which meets the requirement from latest Chinese environmental protection regulation, while considering a low cost of retrofit, a comprehensive low NOx emission boiler retrofit scheme combining air-staged low NOx combustion technology and selective catalytic reduction of flue gas in the low temperature flue duct of boiler was selected preferentially. Two-level air staging technology has some obvious advantages including a little negative effect on the boiler’s combustion efficiency, and easily achieving deep air-staged combustion mode. Therefore, a study of numerical simulation concerning original combustion mode and optimized two-level air staging combustion mode was conducted. Due to excellent ignition and burnout characteristics of Shenhua bituminous coal with high volatile matter, low ash fusion temperature and reasonable configuration of upper and lower burnout air ports, the NOx emission level at the exit of furnace would be greatly reduced, and the fouling layer temperature of water wall obviously decreases, which means a definite improvement of clean degree of furnace. And the gas temperature at the bottom of platen heaters decreases about 20 °C while burning 100% Shenhua bituminous coal with low ash fusion temperature. However, its combustion efficiency would decline weakly. The performance of boiler was optimized by combustion tests after the retrofit. This boiler can fully burn Shenhua bituminous coal with low ash fusion temperature by use of two-level air staging system, and furnace soot blowing frequency also lowered. Consequently, exhaust gas temperature decreased, which achieved an increase of boiler efficiency by about 0.3%. In addition, NOx emission level decreased more than 60%, and was about 15 mg/m3 (O2 = 6%) lower than coal blending cases. To meet a full burning of Shenhua bituminous coal with low ash fusion temperature, it is suggested that two-level air staging technology should be applied to the retrofit of boiler. And then goals of low NOx emission and anti-slagging on the platen heaters can be achieved.
Chlorine Release Characteristics During Biomass Reburning in an Entrained Flow Reactor
Authors: Lu Ping , Shi Jiateng , Yin Xinyi
Published: September 2017

Five biomass including cotton stalk (CS), sunflower stalk (SS), wheat stalk (WS), rice husk (RH) and maize stalk (MS) were pyrolyzed in an entrained flow reactor under reburning condition. The chlorine release fraction was determined based on the analysis of each biomass and the relevant bio-coke measured by digital ion meter. The effects of biomass species, reaction temperature (T), residence time (τ), stoichiometric ratio (SR2), and initial oxygen content in the simulated flue gas on chlorine release were analyzed. The obtained results indicated that the chlorine release fraction increases with the increasing of reaction temperature, and all biomass have a higher chlorine release fraction of 94.6%–100% at high reaction temperature. Stoichiometric ratio has little influence on chlorine release. The chlorine release fraction shows a significant increase from 80.3% to 97.1% with increasing initial oxygen content in the simulated flue gas from 0% to 4%.
Large-Eddy Simulation With a New Flamelet Model for Partially Premixed Combustion in a Gas-Turbine Combustor
Authors: Tanaka Keisuke , Sato Tomonari , Oshima Nobuyuki , Kim Jiun , Takahashi Yusuke , Iwai Yasunori
Published: September 2017

Turbulent combustion flows in the partially premixed combustion field of a dry low-emission gas-turbine combustor were investigated numerically by large-eddy simulation with a 2-scalar flamelet model. Partially premixed combustion was modelled with 2-scalar coupling based on the conservative function of the mixture fraction and the level set function of the premixed flame surface; the governing equations were then used to calculate the gas temperature in the combustion field with flamelet data. A new combustion model was introduced by defining a nondimensional equilibrium temperature to permit the calculation of adiabatic flame temperatures in the combustion field. Furthermore, a conventional G-equation was modified to include spatial gradient terms for the adiabatic flame temperature to facilitate smooth propagation of a burnt-state region in a predominantly diffusion flame. The effect of flame curvature was adjusted by means of an arbitrary parameter in the equation. The simulation results were compared with those from an experiment and a conventional model. Qualitative comparisons of the instantaneous flame properties showed a dramatic improvement in the new combustion model. Moreover, the experimental outlet temperature agreed well with that predicted by the new model. The model can therefore reproduce the propagation of a predominantly diffusion flame in partially premixed combustion.
New Correlations of Weighted Sum of Grey Gases Model Applicable to Computational Fluid Dynamics for Oxy-Fuel Combustion and Implementation
Authors: Ge Xueli , Zhang Zhongxiao , Hu Xinglei , Wu Xiaojiang , Zhang Jian
Published: September 2017

Radiation heat transfer is the dominant model of heat transfer in the large scale industry boiler, especially in oxy-fuel combustion condition. Radiative properties of combustion gases and char oxidation in the oxy-fuel condition are obviously different from the air-fuel combustion, due to the N2 replaced by CO2. Through researchers proposed many helpful correlations based on the air-fuel Weighted-Sum-of-Grey-Gases-Model (WSGGM), the absorption coefficients were commonly constant or correlations were discrete by the classical molar ratio of H2O to CO2 (MR), which were mismatching the continuous value of MR in the real furnace. Meanwhile, the discrete MR is also not applied to the computational fluid dynamics (CFD). In this paper, new correlations for the WSGGM are determined as polynomial function of MR and temperature, which can be conveniently employed in Fluent by the form of user-defined-functions in C language. Parameters of model are fitted by total emittances calculated based on the timely HITEMP 2010 database. New correlations are validated by comparing the emittances with line-by-line calculations and other classical models. New correlations are employed in the CFD for the real industrial oxy-fuel combustion with the temperature range of 400–2600K, pressure path-length between 0.01 and 60 bar m. Several assumed test cases have been investigated to evaluate the accuracy of the models. Modified correlations for WSGGM give a better accuracy of the total emittances for the mixed combustion gases in the real furnace. New models including radiative and chemical reaction mechanisms have been employed to CFD modeling of combustion process for a tangentially fired 300MWe utility boiler. The industrial boiler is modeled by a partition meshing method with the hexahedral structured mesh. Due to the atmosphere shift from N2 to CO2, three aspects are essential to be modified for oxy-fuel: radiation model, char oxidation model and homogeneous volatile oxidation model. To investigate the performance of the furnace, air-fuel combustion selected as the conference, three other cases employed are defined as Oxy21 (vol21%, O2), Oxy26 (vol26, O2) and Oxy29 (vol29%, O2), respectively. Temperature profile and heat transfer are investigated for the different test cases. Meanwhile, the simulation and calculation heat transfer in the furnace are also compared. The results show the new modified simulation has an approximate 4–11% lower than the thermodynamic calculation. To achieve an identical heat flux and temperature distributions with the air-fuel case, the molar fraction 29% of O2 is essential for the selected implementation. (CSPE)
Evaluation of the Tube to Tubesheet Joining Process in an AL6XN® Feedwater Heater
Authors: Svensson Eric , Catapano Michael
Published: September 2017

Type 304 austenitic stainless steel is the most common tube material utilized for nuclear feedwater heaters, however, some utilities have experienced problems with Stress Corrosion Cracking (SCC), especially when they utilize brackish cooling water and have experienced condenser tube leaks. This has forced some utilities to explore other options when it comes to high pressure feedwater heaters (HP FWH) tubing materials. AL6XN® is considered a “super” stainless steel that is resistant to (SCC), however, it is not immune (AL6XN is a trademark of ATI Technologies).

Based on the relative inexperience and unknowns related to the use of AL6XN tubing in high pressure, nuclear feedwater heater applications, a detailed mock-up procedure was outlined as part of the replacement heater specification which would allow the evaluation of the tube to tubesheet joining processes. Since AL6XN can still be affected by SCC; steps were taken in order to minimize the imposed stress levels and any potential for the inadvertent inclusion of contaminants during the fabrication steps at the tube mill and at the feedwater heater Manufacturer’s shop. The desire to minimize stresses also applies at the tube to tubesheet joint, therefore, it was desired not to stress the tube more than absolutely necessary in achieving a reliable, leak tight joint. The mock-up details and procedures were therefore generated with these objectives in mind, so as to give consideration for the ability to check different configurations in order to determine the most efficient tube to tubesheet joining process.

Several tubes in the mock-up were subjected to a pull out test in order to quantify the joint strength in the different configurations. The mockup was then sectioned and inspected under a digital microscope to verify intimate contact between the tube and the tubesheet. Once the optimal procedure was identified, four identical HP FWHs were constructed utilizing AL6XN tubing. During heater production, over 30,000 tube ends were expanded, however, two tubes were identified to have failures as part of the tube expansion process.

This paper shall describe the procedures utilized in developing and analyzing the tubesheet mock-up as well the actions taken to identify the root causes of the tube failures.
Heat Transfer Performance of LiF–NaF–KF Salt in a Corrugated Receiver Tube With Non-Uniform Solar Flux
Authors: Guo Chaxiu , Zhang Dongwei , Zhou Junjie , Zhang Wujun , Wei Xinli
Published: September 2017

The heat flux on the receiver tube is non-uniform because of uneven solar flux and receiver structure, which causes overheating and thermal stress failure of receiver and affected safe operations of the Concentrated Solar Power (CSP) system. In order to reduce the temperature difference in receiver tube wall and improve the efficiency of CSP system, the ternary eutectic salt LiF-NaF-KF (46.5-11.5-42 wt.%, hereafter FLiNaK), which has a better high thermal stability than that of nitrate salts at operating temperature of 900 °C, is selected as HTF, and heat transfer performance of FLiNaK in a corrugated receive tube with non-uniform heat flux is simulated by CFD software in the present work. The numerical results reveal that the non-uniform heat flux has a great influence on the temperature distributions of the receive tube and FLiNaK salt. Compared with the result of bare tube, the corrugated tube can not only significantly reduce the temperature difference in tube wall and salt by improving the uniformity of temperature distribution but also enhance the heat transfer of the salt, where the heat transfer coefficient increases with the Reynolds number and heat flux. Moreover, the enhanced effect of the corrugated tube depends on both the pitch and the height of ridges. It is found that the heat transfer coefficient of the salt gets a maximum when the ratio of the height of ridge to the pitch is 0.2. The research presented here may provide guidelines for design optimization of receiver tube in CSP system.
Large-Eddy Simulation of Alkali Metal Reacting Dynamics in a Preheated Pulverized-Coal Jet Flame Using Tabulated Chemistry
Authors: Wan Kaidi , Wang Zhihua , Vervisch Luc , Xia Jun , Liu Yingzu , He Yong , Cen Kefa
Published: September 2017

This paper proposed an approach to modeling alkali metal reacting dynamics in turbulent pulverized-coal combustion (PCC) using tabulated sodium chemistry. With tabulation, detailed sodium chemistry can be incorporated in large-eddy simulation (LES), but the expenses of solving stiff Arrhenius equations can be avoided. The sodium release rate from a pulverized-coal particle is assumed to be proportional to the pyrolysis rate, as a simplification. The chemical forms of released sodium is assumed to be atomic sodium Na, because atomic sodium is predicted to be the favoured species in a flame environment. A detailed sodium chemistry mechanism including 5 sodium species, i.e., Na, NaO, NaO2, NaOH and Na2O2H2, and 24 elementary reactions is tabulated. The sodium chemistry table contains four coordinates, i.e., the equivalence ratio, the mass fraction of the sodium element, the gas-phase temperature, and the progress variable. Apart from the reactions of sodium species, hydrocarbon volatile combustion has been modeled by a partially stirred reactor concept. Since the magnitude of sodium species is very small, i.e., at the ppm level, and the reactions of sodium species are slower than volatile combustion, one-way coupling is used for the interaction between the sodium reactions and volatile combustion, i.e., the former having no influence on the latter. A verification study has been performed to compare the predictions on sodium species evolutions in zero-dimensional simulations using the chemistry table against directly using the detailed sodium mechanism under various initial conditions, and their agreement is always good. The PCC-LES solver used in the present study is validated on a pulverized-coal jet flame ignited by a preheated gas flow. Good agreements between the experimental measurements and the LES results have been achieved on gas temperature, coal burnout and lift-off height. Finally, the sodium chemistry table is incorporated into the LES solver to model sodium reacting dynamics in turbulent pulverized-coal combustion. Properties of Loy Yang brown coal, for which sodium data are available, are used. Characteristics of the reacting dynamics of the 5 sodium species in a pulverized-coal jet flame are then obtained. The results show that Na and NaOH are the two major sodium species in the pulverized-coal jet flame. Na, the atomic sodium, has a high concentration in fuel-rich regions; while the highest NaOH concentration is found in regions close to the stoichiometric condition. It should be pointed out that the proposed chemistry tabulation approach can be extended to modeling potassium reacting dynamics in turbulent multiphase biomass combustion. (CSPE)
A Comparative CFD Simulation Study of Two-Channel and Three-Channel Claus Reactors
Authors: Huang Shan , Zhou Qulan , Li Na , Tian Fangyong , Zhang Lisheng
Published: September 2017

The Claus reactors is widely used to recover elementary sulfur from hydrogen sulfide that is contained in fresh natural gas. It involves thermal oxidation of hydrogen sulfide and its reaction with sulfur dioxide to form sulfur and water vapor. To improve the efficiency of the process, we built two kinds of 3-dimensional Claus reactor models to explore the key factors that affect the combustion reactions. The two-channel Claus reactor consisted of an air channel and an acid gas channel (60% H2S, 33% CO2, 7%H2O) while the three-channel Claus reactor consisted of two air channels and an acid gas channel (60% H2S, 33% CO2, 7%H2O). The two-channel model was built according to the devices used in the factory while the three-channel model was improved by us from the two-channel model. In both the two models, air and acid gas turned into swirling flow in their channels respectively before their mixture. Then air and acid gas mixed and burned at the throat of the models. The most remarkable difference between the two kinds of Claus reactors was that the three-channel reactor had an additional inner air channel inside the acid gas channel that can be helpful to the mix of the acid gas and air. The second difference was that the two kinds of reactors had different deflectors to swirl in the flow fields. In this study, we compared the flow fields and concentration fields of the two kinds of Claus reactors by using a computational fluid dynamics (CFD) tool.

The simulation results indicated that the swirling intensity and the mix intensity played an important role in the combustion reactions. The efficiency of sulfur recovery in Claus reactors increased with an increase of the swirling intensity or the mix intensity. The stronger the swirling intensity or the mix intensity was, the sooner the mixture of air and acid gas reached to the best stoichiometric ratio. The three-channel reactor had a better performance than that of the two-channel reactor due to the additional inner air channel which can strengthen the mix of the acid gas and air from the inside of the acid gas. Moreover, the helix deflectors in the three-channel reactor had a better swirling performance than that of the vane deflectors in the two-channel reactor. From the comparison of the two models, we can obtain a way to improve the process of elementary sulfur recovery in the industry, which can be helpful to reduce pollution emissions and improve economic performance.