bluuebunny/crossref_metadata_2025 huggingface dataset:
Evacuation Systems for Steam Surface Condensers: Vacuum Pumps or Steam Jet Air Ejectors?
Authors: Nadig Ranga
Published: November 2016

In a steam power plant, steam from the steam turbine is condensed in a water cooled or air cooled condenser that operates under vacuum. The condensing capacity of the condenser is impaired by the presence of air. Air leaks into the condenser from flanged connections, turbine seals, valves and other equipment connected to the condenser. The air tends to collect in the condenser and impact its condensing capability. This trapped air has to be continuously evacuated to preserve the condensing capacity of the condenser.

The air can be evacuated from the condenser using the steam jet air ejector system or the vacuum pump system. The vacuum pump is driven by an electrical motor. The steam jet air ejector is driven by motive steam. In certain low suction pressure applications, a hybrid system consisting of a steam jet air ejector and vacuum pump or a three stage ejector system is used for evacuating the air from the condenser.

The evacuation packages perform two distinct services namely hogging and holding. During startup, or hogging operation, the evacuation system removes air from the steam space of the condenser and steam turbine. The pressure in the steam space is reduced from atmospheric pressure to typically 10.0” HgA or a pressure specified by the steam turbine supplier in about 30 minutes. During normal or “holding operation” with the steam turbine in service, the evacuation system removes a specified amount of air from the condenser.

The suitability of vacuum pump or steam jet air ejector systems for a given application depends on the availability of motive steam during startup, the costs associated with the usage of steam or electricity and the preferences of the end user. Each system has its advantages and disadvantages. In each case, there are numerous design details that must be addressed to ensure that the selected system meets the evacuation needs for the condenser.

This paper examines the various configurations of evacuation systems and discusses their suitability for the wide ranging operating scenarios in the condenser. A broad background on the design and operation of the evacuation system is included to assist the end user in making the proper selection of the evacuation system.
Feasibility Study of the Use of Ground-Coupled Condensers in Industrial Thermal Management
Authors: Languri Ehsan M. , Cunningham Glenn , Cui Jie , Idem Stephen
Published: November 2016

A closed loop cooling system that uses the earth as a heat sink to dissipate heat for the energy system’s thermal management is described. The proposed cooling approach employs a concentric tube heat exchanger situated above ground to transfer heat from the system (e.g., power plant condenser) to a separate cooling water loop buried at a specified depth below ground. A parametric study was performed to evaluate the efficacy of the thermal management potential of ground-coupled systems in industrial applications. It revealed that such a condenser design is generally capable of dissipating less than 1.5 MW of heat. A mathematical model is developed to size the required piping for different systems.
Numerical Investigation of the Flow Fields and Thermal Patterns in a Large Cold Store (I)
Authors: Kaood A. , Khalil E. E. , El-Hariry G. M.
Published: November 2016

Refrigeration for the cold storage of perishable foods has been utilized for more than a century. The need for refrigerated storage grows with hot weather. The frozen food industry expanded many times in freezer storage in a few decades after World War II. Cold storage facilities are also significant energy consumers that call for attention to thermal behavior as it greatly influences the cost. Proper design to improve thermal behavior of a refrigerated space requires the knowledge of air distribution and thermal conditions within the space. The frozen food quality is sensitive to both storage temperature and fluctuation in temperature. The present work made use of a computational fluid dynamics technique to adequately predict the cold storage airflow pattern variations within the cold room under various evaporator’s arrangements of sizes, numbers and positions. Design parameters included local temperatures and velocity distributions inside a large cold store using standard k-e model with mesh element 5,400,000 tetrahedral cells. Different optional designs utilizing different number of evaporators were investigated as well as the locations of these evaporators according to load estimation of the cold store.
A Numerical Study on the Performance of Fixed Oscillating Water Column Wave Energy Converter at Steep Waves
Authors: Anbarsooz Morteza , Faramarzi Ali , Ghasemi Amirmahdi
Published: November 2016

In the current study, a fully nonlinear two-dimensional numerical wave tank is developed using the commercial CFD software, Ansys Fluent 15.0, in order to study the absorption characteristics of an OWC at linear and highly nonlinear steep waves. The two-phase Volume-Of-Fluid (VOF) method is employed to predict the water free surface evolution. The numerical results are first validated against the available analytical data in the literature. The good agreement between the numerical results and those of analytics, revealed the capability of the developed numerical tank to study the performance of the OWC. Next, the simulations are performed for strongly nonlinear waves, up to the wave steepness of 0.069 (H/L=0.069), where H is the wave height and L is the wave length. The optimum pneumatic damping of the air turbine at such strongly steep and nonlinear waves is determined. Results show that the absorption efficiency of the OWC decreases considerably as the wave height increases. Moreover, the maximum wave energy absorption efficiency for the highly nonlinear waves occurs at a pneumatic damping coefficient lower than that of the linear theory.
The Straight-Bladed Morphing Vertical Axis Wind Turbine
Authors: MacPhee David , Beyene Asfaw
Published: November 2016

Blade pitch control has been extremely important for the development of Horizontal-Axis Wind Turbines (HAWTs), allowing for greater efficiency over a wider range of operational regimes when compared to rigid-bladed designs. For Vertical-Axis Wind Turbines (VAWTs), blade pitching is inherently more difficult due to a dependence of attack angle on turbine armature location, shaft speed, and wind speed. As a result, there have been very few practical pitch control schemes put forward for VAWTs, which may be a major reason why this wind turbine type enjoys a much lower market share as compared to HAWTs. To alleviate this issue, the flexible, straight-bladed vertical-axis turbine is presented, which can passively adapt its geometry to local aerodynamic loadings and serves as a low-cost blade pitch control strategy increasing efficiency and startup capabilities. Using two-dimensional fluid-structure action simulations, this novel concept is compared to an identical rigid one and is proven to be superior in terms of power coefficient due to decreased torque minima. Moreover, due to the flexible nature of the blades, the morphing turbine achieves less severe oscillatory loadings. As a result, the morphing blade design is expected to not only increase efficiency but also system longevity without additional system costs usually associated with active pitch control schemes.
Performance Evaluation of a Novel Small Wind Turbine: UAE Case Study
Authors: Zafar Sayem , Gadalla Mohamed , Al-Naiser Mohammad Ismail
Published: November 2016

A small personal use wind turbine (PWT) is studied and tested for power evaluation under different wind speed conditions. The wind turbine has small blades with FX 63137 airfoil. The blades are non-tapered and non-twisted to be economical and easy to manufacture. The blade span is 1.52 m which makes it small enough for personal domestic use yet big enough to produce sufficient power. The PWT size satisfies the requirements for rooftop small wind turbine for domestic power generation. The study is conducted in United Arab Emirates (UAE) and the PWT is installed in an open area to test under the natural conditions. Readings are recorded for wind speeds, generator RPMs, current and voltage for different timings and conditions. The PWT is tested at a variety of wind speeds to establish the operating range of the wind turbine. Using the calculated electrical power and wind power values, corresponding electrical efficiency is determined. Results are evaluated for electrical power and electrical efficiency against wind speed. The result suggests better performance and efficiency for continuous wind speed conditions. It also shows the PWT can effectively generate power under the conditions found in UAE.
The Science Behind Eddy Current and Remote Field Testing: For Condenser and Heat Exchanger Tubing
Authors: Van Name Christopher , Fischer Gary , Kocher James
Published: November 2016

With the increasing demand on the world’s power grids, now more then ever it is important to keep power plant condensers, feedwater heaters and balance of plant heat exchangers running at peak efficiency. While it is well known that keeping these units clean is important for maximizing power output, so too is monitoring each unit’s tube integrity and taking corrective action to prevent tube failure. The best way to monitor a unit’s tube integrity, detect patterns of tube wear and damage, and determine the specific wear and damage to a particular tube is through Non-Destructive Testing. Depending on the tube material, the best Non-Destructive Testing method to employ would be either Eddy Current Testing, Remote Field Testing or other variations of these electromagnetic techniques.

This paper will discuss the science behind Eddy Current and Remote Field Testing, how they differ and which one to select depending on the situation. It will look at the construction of the probes and how they work. It will explain the difference between use of a single frequency or multiple frequencies and the advantages of multi-frequency testing. The paper will also identify the necessary procedure for a successful Non-Destructive Test, including the types of tubes that can be tested and tube preparation.
Combined-Cycle Start-Up Procedures: Dynamic Simulation and Measurement
Authors: Mertens Nicolas J. , Alobaid Falah , Epple Bernd , Kim Hyun-Gee
Published: November 2016

The daily operation of combined-cycle power plants is increasingly characterized by frequent start-up and shutdown procedures. In addition to the basic requirement of high efficiency at design load, plant operators therefore acknowledge the relevance of enhanced flexibility in operation — in particular, fast start-ups — for plant competitiveness under changing market conditions. The load ramps during start-up procedure are typically limited by thermal stresses in the heat recovery steam generator (HRSG) due to thick-walled components in the high pressure circuit. Whereas conventional HRSG design is largely based on simple steady-state models, detailed modelling and dynamic simulation of the relevant systems are necessary in order to optimize HRSG design with respect to fast start-up capability. This study investigates the capability of a comprehensive process simulation model to accurately predict the dynamic response of a triple-pressure heat recovery steam generator with reheater from warm and hot initial conditions to the start-up procedure of a heavy-duty gas turbine. The commercial combined-cycle power plant (350 MWel) was modelled with the thermal-hydraulic code Apros. Development of the plant model is based on geometry data, system descriptions and heat transfer calculations established in the original HRSG design. The numerical model is validated with two independent sets of measurement data recorded at the real power plant, showing good agreement.
An Integrated Design Approach of Local Control System of a Linear Drive Single Facet Heliostat
Authors: Nageb M. M. , El-Samahy A. A. , Rady M. A. , Amin A. M. A. , Abd El-Hamid R. H. , Olasolo David
Published: November 2016

In a central receiver solar power plant, heliostats are arranged with respect to the central receiver so as to reflect the rays from the sun onto the power tower with high precision by tracking the sun in both the azimuth and elevation directions. The master control system of a solar power plant consists of different levels. The first level is local control; it takes care of the positioning of the heliostats when the aiming point and the time are given to the system, and informs upper level about the status of the heliostats field. The second logic level makes some important dispatch calculations of heliostats field. The most popular linear two-axis local driving system of heliostat consists of two linear driving actuators, the driving mechanism with rotary joints, and the controller. Traditional methods for heliostat design are often based on a sequential approach in which the mechanical structure is designed first and then the control system is advised. In order to reach the optimal design of heliostats, an integrated design approach that concurrently considers the interactions between the mechanical and control subsystems is necessary. In this article, an integrated design methodology of heliostat drive system is presented.

The methodology is based on modeling and simulation. The dynamic models that describe the behavior of the mechanical and control components are presented. These models involve mechanical and control design variables such as the motor parameters, power screw (including back lash), heliostat mass, load forces, and wind forces. Matlab, Solidwork, and Simulink are chosen to apply PID tracking control to heliostats, due to the ability to arbitrarily model complex mechanical systems, directly import properly constructed, third-party 3D CAD models, simulate integrated control, handle a variety of robotics nomenclature, and other features. The present methodology is employed for integrated design of a single facet small size heliostat with mirror area of 3 m2.The methods described in this article also show a way to rapidly simulate novel and complex heliostat geometries. Analysis of the heliostat drive system performance and dynamic characteristics according to mechanical and control design variables is conducted for the purpose of control system design and performance optimization. The drive system performance is evaluated in terms of positioning tracking errors, system response, and control system behavior. It is shown that the mechanical characteristics of the ball power screw actuator such as ball-screw diameter, lead, overall flexibility, stiffness, backlash, and inertia significantly influence the performance of drive system.
Combustion and Emissions Characteristics of a Brassica Carinata FAME and N-Butanol Blend
Authors: Muinos Martin , Harp Spencer , Kindo Benoit , Gaubert Remi , Soloiu Valentin
Published: November 2016

In this study, the combustion and emissions characteristics of a new biodiesel and biodiesel blend in a direct injection (DI), experimental diesel engine and was compared to ultra-low sulfur diesel #2 (ULSD#2) at 1500 rpm and 4 bar indicated mean effective pressure (IMEP). The biodiesel blend, C90+BU10, included 90% brassica carinata (25% erucic acid methyl ester) and 10% n-butanol bio-alcohol by mass. The lower heating value of C90+BU10 was 37.25 MJ/kg, compared to 42.6 MJ/kg for ULSD#2. The ignition delay of ULSD#2 was 9.0 crank angle degrees (CAD) and decreased to 8.5 CAD for C90+BU10, which can be attributed to the higher cetane number of the biodiesel blend. The apparent heat release rate for both fuels exhibited a premixed and diffusion burn phase, with the peak heat release rate being 142 J/degree for ULSD#2 and 129 J/degree for C90+BU10. Nitrogen oxide (NOx) emissions decreased by 7% for the C90+BU10 blend. The particulate matter (PM) emissions for C90+BU10 exhibited a decrease of 55%, from 0.21 g/kWh for ULSD#2 to 0.0096 g/kWh for C90+BU10. The renewable fuels used in the study proved to be capable of reducing soot by 55% without exhaust gas after treatment systems and without reducing combustion efficiency.
Generator Outages and Using Incentive Based Demand Response to Diminish Economic Impact
Authors: Asadinejad Ailin , Tomsovic Kevin
Published: November 2016

Incentive based demand response (IBDR) programs have significant unused potential especially for small customers. In this paper, an IBDR program is proposed for generator outages. Although not all generator outages lead to reliability concerns, they often result in market price volatility. Since outage conditions are an important factor in price volatility, the novel idea of generator outage ranking based on their economic effect is proposed. Reducing peak locational marginal price (LMP) can bring considerable saving for utilities. An IBDR program can decrease LMP significantly even with modest levels of participation. The proposed IBDR in this paper is implemented in only one region but still has system wide effects. Results show electrical distance from most expensive generator in a system is a good risk indicator for generator outages.
Experimental Study on the Heat Transfer Enhancement by the Combination of Transverse Groove Tube and Twisted Tape Inserts
Authors: Gui Miao , Bi Qincheng , Guo Yajun
Published: November 2016

Both transverse groove tube and twisted tape, as an alternative to traditional smooth tube in shell and tube heat exchanger, are useful techniques for the enhancement of heat transfer. In this paper, an experimental study for the combination of transverse groove tube and twisted tapes was carried out. The flow and heat transfer characteristics of heat transfer oil flowing in the transverse groove tube (TGT) fitted with continuous twisted tape (CT), discontinuous twisted tape (DT) and perforated twisted tape (PT) was investigated with the Reynolds numbers ranging from 600 to 8000, respectively. The effect of the geometrical parameters of twisted tapes on the heat transfer performance was considered. Finally, experimental correlations for friction factor and Nusselt number were developed. The comprehensive performance of heat transfer of the transverse groove tube fitted with twisted tapes was analyzed using traditional method and Entropy Generation Analysis, and the same conclusions can be obtained that the modified heat transfer enhancement tubes, TGT-CT, DT and PT, all show better effects of heat transfer enhancement than ST and ST-CT.
Achieving Deep Reduction in California CO2 Emissions via Renewable Resource Integration, Electrification, and Smart Grid Deployment
Authors: Ebrahimi Siavash , Brouwer Jack
Published: November 2016

The State of California has adopted a deep greenhouse gas emissions reduction target of 80 percent below 1990 levels by 2050, but decarbonizing the power generation sector cannot lead to such aggressive emissions reductions by itself since only 21 percent of total statewide GHG emissions originate from power generation. Therefore, widespread electrification, i.e., switching direct fossil fuel use to electricity, along with smart grid deployment, is essential for meeting deep emissions reduction targets. In this study, the load-balancing and emission impacts of electrifying end-use energy sectors while decarbonizing power generation, and deploying smart-grid technologies are analyzed using detailed modeling of infrastructure, feedstocks and economic dispatch of the electric grid. In the most comprehensive scenario, all end-use energy sectors are partly electrified by 2030 via replacing gas-fired end-uses with highly efficient electric technologies. The electric power generation sector is decarbonized through installing higher levels of renewable power meeting nearly 50 percent of total California electric energy demand in 2030. Various smart grid technologies including battery energy storage, demand response, and smart electric vehicle charging are implemented in the end-use sectors in order to accommodate and complement higher levels of renewable power resources. It is found that decarbonizing the electric power generation without electrifying end-use sectors increases CO2 emissions by 3.1 percent, while end-use electrification alongside utility scale and distributed renewable resource integration and smart grid technology implementation can yield up to a 29 percent reduction in CO2 emissions in 2030 compared to 1990 levels.
Cost Performance Tradeoff Study of Wind Systems: Grid-Scale Storage
Authors: Goudarzi Navid , Rudesill John , Pavlak Alex
Published: November 2016

Variability and uncertainty are the primary challenges for power generation from intermittent, non-dispatchable energy sources. This stochastic behavior could significantly increase the cost of energy. An earlier work developed an interdisciplinary economic model using three-year (2011–2013) wind/load data from two different sites, Pennsylvania New Jersey Maryland Interconnection LLC (PJM) in USA and EirGrid in Ireland. Results showed a wind plus natural gas system can reduce emission as much as 50% below that of an all-natural gas system, with only a slight increase in system cost. Energy storage can be a key element in obtaining energy and cost savings, together with providing availability, reliability, and security of energy supply to consumers. In this paper, grid-scale storage parameters variations (storage capacity, cost, and efficiency) are explored to obtain levelized cost trends for wind systems with storage.
Multi-Objective Optimization of Geometrical Parameters of Corrugated-Undulated Heat Transfer Surfaces Using CFD, Artificial Neural Networks and Genetic Algorithms
Authors: Wang Limin , Ji Chenglong , Chen Xun , Deng Lei , Chen Yiping , Che Defu
Published: November 2016

A three dimensional numerical simulation was performed to study the effect of the pitch (PU) and height (HU) of undulated plate (U-plate) and the height (Hc) of the corrugated plate (C-plate) on the heat transfer and fluid flow characteristics in the corrugated-undulated (CU) heat transfer surfaces. The mass, momentum and energy equations were solved using finite volume method by considering the steady state, turbulent and incompressible fluid flow. The numerical results showed a good agreement with the experimental data in reference. The average Nusselt number and friction factor were investigated in CU heat transfer surfaces with different geometrical parameters. To achieve a maximum heat transfer enhancement and a minimum pressure drop, the optimal values of these parameters were calculated using the Pareto optimal strategy. For this purpose, computational fluid dynamics analysis, multi-objective genetic algorithm and artificial neural networks were combined together and used in the optimization process. Finally, the optimal values of these geometrical parameters were presented.
Exergetic and Economic Analysis of Subcooling and Superheating Effect on Vapor Compression Refrigeration System
Authors: Karakurt A. Sinan , Gunes Umit , Ust Yasin
Published: November 2016

Refrigeration systems are one of the most common and the oldest thermodynamic system that almost equal to human history. Exergetic and economic effects of subcooling & superheating on vapor compression refrigeration system are analyzed and examined in terms of different refrigerants, working conditions (temperature and pressures), condenser and evaporator effectiveness and temperatures and isentropic efficiency of compressor behalf of coefficient of performance, exergetic efficiency, exergetic performance coefficient and ecological coefficient of performance. The results show that variations of the condenser and evaporator temperatures, pressure losses in heat exchangers and isentropic efficiency of compressor are highly related to performance and economic parameters such as heat exchange areas and power consumption for subcooling & superheating refrigeration system (SSRS).
One-Dimensional and Three-Dimensional Numerical Optimization and Comparison of Single-Stage Supersonic and Dual-Stage Transonic Radial Inflow Turbines for the ORC
Authors: Rahbar K. , Mahmoud S. , Al-Dadah R. K. , Moazami N.
Published: November 2016

Organic Rankine cycle is one of the most efficient technologies that can utilize low-to-medium grade heat sources and generate useful power. Radial inflow turbine (RIT) is the key component of the ORC and its efficiency has significant effect on the overall cycle performance. Obtaining high cycle thermal efficiency requires large pressure difference (expansion ratio) across the cycle. With the low speed of sound of organic fluids and the high expansion ratios, RIT becomes chocked with supersonic flow regime and shock waves that deteriorate the turbine efficiency and hence reduce the cycle performance. Therefore, developing highly efficient RIT that can both preserve the high expansion ratio requirements of the ORC and maintain the turbine isentropic efficiency is crucial. This paper proposed the complete 1-D and 3-D numerical optimization of two different configurations as single-stage supersonic and dual-stage transonic RITs. Initially, the integrated 1-D modelling of the ORC with RIT coupled with genetic algorithm optimization technique was conducted to maximize the cycle thermal efficiency. The results showed that the dual-stage RIT exhibited considerably higher turbine efficiency in both stages and hence higher cycle efficiency compared to the single-stage supersonic one. Both configurations were further optimized using the 3-D CFD optimization procedure to maximize the turbine efficiency. The CFD results showed that the optimization of each stage individually was successful as the turbine performance increased significantly. The results revealed that the optimizations were more effective for the dual-stage transonic turbine compared to the single-stage supersonic due to the presence of shock waves. Comparison of the optimized single-stage supersonic RIT and complete dual-stage transonic RIT showed that about 15.7%, 10.63kW and 16.08% higher turbine isentropic efficiency, turbine power and cycle thermal efficiency were achieved respectively with the latter configuration.
Influence of Rotational Speed on Thermal Performance of Tri-Sector Rotary Regenerative Air Preheater
Authors: Chen Xun , Duan Xue-nong , Wang Li-min , Yang Yi , Wang Dun-dun , Chen Yi-ping , Zhu Guang-ming , Che De-fu
Published: November 2016

This paper provides a detailed analysis of how a rotary regenerative air preheater’s performance parameters such as effectiveness, fluid and metal temperature fields, and ammonium bisulfate (ABS) deposition area vary with rotor rotational speed. A tri-sector rotary regenerative air preheater for a 600MW unit was studied as an example by use of effectiveness–modified number of transfer units (ε-NTU0) method and a finite difference method. The findings of the research are as follows: (1) There is a nonlinear relationship between matrix temperature distribution and rotational angle, and the degree of nonlinearity, represented by unsteady heat transfer correction factor Π, increases with decreasing rotational speed and varies between sectors; (2) There exist two equilibrium positions around the intersection points of matrix temperature curves for different rotational speeds, one occurring in the heating period and the other in the cooling period; (3) The act of reducing the rotor speed has two effects on ABS deposition. On the one hand, the height range of possible ABS deposition area will expand as the matrix temperature within the first third of gas sector’s angle range further decreases with decreasing rotational speed. On the other hand, after the rotational speed falls below a certain level, the hot-end matrix temperature climbs above the ABS formation temperature during part of the heating period, resulting in gasification and decomposition of the condensed product. The combined effect is yet to be examined through further theoretical and empirical analyses. (4) The trends of average outlet temperatures of primary and secondary air depend on rotor rotation direction and angles of sectors. (5) The effectiveness values calculated by ε-NTU0 method are greater than those acquired by the finite difference method, especially at low rotor rotational speeds.
Retracted: “Benchmark Thermodynamic Modelling Comparison of a Novel Modular Air-Cooled Condenser With Current Dry-Cooling Methodologies” [ASME 2016 Power Conference collocated with the ASME 2016 10th International Conference on Energy Sustainability and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology, ASME 2016 Power Conference, Charlotte, North Carolina, USA, June 26–30, 2016, Conference Sponsors: Power Division, Advanced Energy Systems Division, Solar Energy Division, Nuclear Engineering Division, ISBN: 978-0-7918-5021-3. Paper No. POWER2016-59589, pp. V001T04A010; 9 pages; doi:10.1115/POWER2016-59589]
Authors: ASME
Published: November 2016

This paper was withdrawn. ASME does not hold the copyright. December 21, 2018.

Copyright © 2018 by ASME
Experimental and Numerical Investigation of a Prototype Low NOx Gas Turbine Burner
Authors: Kundu Atanu , Klingmann Jens , Subash Arman Ahamed , Collin Robert
Published: November 2016

Clean gas turbine combustion research has gained popularity in power generation and propulsion industry in recent days. Present days, advanced efficient emission (NOx, CO and UHC) reduction combustion technologies are acknowledged for using the lean premixed combustion system. To support continuous development of eco-friendly combustion system, a 4th generation dry low NOx prototype downscaled burner (designed and manufactured by Siemens Industrial Turbomachinery AB) has been researched experimentally and numerically. The research burner has multiple stages, which includes a central Pilot (named as RPL/Rich-Premixed Lean) stages, Pilot stage and Main stage. The RPL combustion chamber holds the primary flame, which produces the temperature and high concentration of radicals. The radicals and hot product is reached to the forward stagnation point of the Main flame anchoring point. Swirled reactant mixture is delivered to the Main combustion zone and a strong recirculation zone is developed. The recirculated product is moved to the Main flame root and ignites the fresh mixture. The Main flame was visualized by applying Chemiluminescence and 2D OH-PLIF imaging techniques. Emission measurement was performed to quantify the burner operability and emission competency. Burner stage fuel splits are varied and their effects on flame stability was monitored thoroughly. Computational fluid dynamic (CFD) analysis was performed to understand the flow field and compare the experimental results with numerical analysis. CFD simulation can help to identify the approximate NOx formation region and flame locations inside the burner. RPL flow and Pilot fuel split shows significant contribution towards flame stabilization as experienced from experiment and CFD. A high temperature B-type thermocouple was positioned at the liner exit to measure the exhaust gas temperature. Numerical calculation prediction and measured temperatures showed good qualitative agreement. From the present experimental and numerical research, it is evident that the downscaled prototype gas turbine burner demonstrates a wide flame stability for various operating condition. The fundamental physics behind the flame stabilization and flame dynamics were explored using numerical and experimental research.
Mechanical Stress Optimisation in a Directly Illuminated Supercritical Carbon Dioxide Solar Receiver
Authors: Gardner Wilson , Kim Jin-Soo , McNaughton Robbie , Stein Wes , Potter Daniel
Published: November 2016

CSIRO is constructing a solar thermal driven high temperature supercritical carbon dioxide (sCO2) Brayton cycle test facility, which includes an absorber tube based solar receiver, at the CSIRO National Solar Energy Centre in Newcastle, Australia. The sCO2 facility is capable of producing high temperature CO2 at 700° Celsius.

In this paper the mechanical challenges of designing a sCO2 solar receiver are presented. The design is an optimization of the impact of having a high thermal gradient through the absorber tube wall as a result of high heat transfer and the effect of containing sCO2 under high pressure inside the absorber tube. The first drives the design toward needing a thin tube wall to reduce the thermal gradient stress, whereas the high pressure drives the absorber tube toward needing a thick wall. It is worth noting that the thermal stress being considered here are those within the tube wall thickness only and not about the effects of thermal expansion along the length.

The contradictory nature of these two drivers resulted in an iterative approach to choosing the receiver’s optimal absorber tube size with nine options investigated and compared for optimal mutual design conditions for pipe wall stresses cause by internal pressure and thermal gradient. This led to choosing the smallest available pipe size of 3/8 inch considering the available high heat resistant and high strength materials and conventional construction techniques for seamless pipe.

Going to smaller diameters would require eliminating pipe sizes from the selection and restricting the availability to standard tube sizes, and also eliminating the high heat resistant and high strength materials from the selection. The other factor in the design decision was to consider the constructability of an absorber tube based receiver that will allow conventional pipe fit up and welding techniques.

Ultimately, the sCO2 operating conditions still produced pipe wall stress high enough to limit the life of the solar receiver in the order of 1,000 hours due to high temperature material creep. This outcome is suitable for short lived experimental work but may not be suitable for commercial long lived projects. Building a commercially viable sCO2 solar receiver would require the selection of costly very high strength and creep resistant materials, or a receiver design that allows economic replacement of parts during the plant life, or the development of alternative receiver designs and construction techniques.
Transitional hemodynamics in intracranial aneurysms — Comparative velocity investigations with high resolution lattice Boltzmann simulations, normal resolution ANSYS simulations, and MR imaging
Authors: Jain Kartik , Jiang Jingfeng , Strother Charles , Mardal Kent‐André
Published: November 2016

Purpose

Blood flow in intracranial aneurysms has, until recently, been considered to be disturbed but still laminar. Recent high resolution computational studies have demonstrated, in some situations, however, that the flow may exhibit high frequency fluctuations that resemble weakly turbulent or transitional flow. Due to numerous assumptions required for simplification in computational fluid dynamics (CFD) studies, the occurrence of these events, in vivo, remains unsettled. The detection of these fluctuations in aneurysmal blood flow, i.e., hemodynamics by CFD, poses additional challenges as such phenomena cannot be captured in clinical data acquisition with magnetic resonance (MR) due to inadequate temporal and spatial resolutions. The authors’ purpose was to address this issue by comparing results from highly resolved simulations, conventional resolution laminar simulations, and MR measurements, identify the differences, and identify their causes.

Methods

Two aneurysms in the basilar artery, one with disturbed yet laminar flow and the other with transitional flow, were chosen. One set of highly resolved direct numerical simulations using the lattice Boltzmann method (LBM) and another with adequate resolutions under laminar flow assumption were conducted using a commercially available ANSYS Fluent solver. The velocity fields obtained from simulation results were qualitatively and statistically compared against each other and with MR acquisition.

Results

Results from LBM, ANSYS Fluent, and MR agree well qualitatively and quantitatively for one of the aneurysms with laminar flow in which fluctuations were <80 Hz. The comparisons for the second aneurysm with high fluctuations of > ∼ 600 Hz showed vivid differences between LBM, ANSYS Fluent, and magnetic resonance imaging. After ensemble averaging and down‐sampling to coarser space and time scales, these differences became minimal.

Conclusions

A combination of MR derived data and CFD can be helpful in estimating the hemodynamic environment of intracranial aneurysms. Adequately resolved CFD would suffice gross assessment of hemodynamics, potentially in a clinical setting, and highly resolved CFD could be helpful in a detailed and retrospective understanding of the physiological mechanisms.
Local filtration based scatter correction for cone‐beam CT using primary modulation
Authors: Zhu Lei
Published: November 2016

Purpose

Excessive scatter contamination fundamentally limits the image quality of cone‐beam CT (CBCT), hindering its quantitative use in clinical applications. The author has previously proposed an effective scatter correction method for CBCT using primary modulation. A Fourier transform‐based algorithm (FTPM) was implemented to estimate scatter from modulated projections, with a few limitations including the assumption of uniform modulation frequency and magnitude that becomes less accurate in the presence of beam‐hardening and other nonideal effects. This paper aims to overcome the above drawbacks by developing a new algorithm for the primary modulation method with improved accuracy and reliability.

Methods

Incident x‐ray intensities for each detector pixel with and without the interception of the modulator blocker are estimated from a modulated flat‐field image. A new signal relationship is then developed to obtain a first scatter estimate from a modulated projection using a spatially varying modulation distribution. The method empirically adjusts the effective modulation magnitude for each projection ray to account for the beam‐hardening effects. Estimated scatter signals with high expected errors are discarded in the generation of the final scatter distribution. The author proposes a technique of local filtration to accelerate major portions of the signal processing, and the new algorithm is referred to as local filtration based primary modulation (LFPM).

Results

The study on the Catphan® 600 phantom shows that LFPM effectively removes scatter‐induced cupping artifacts on CBCT images and reduces the CT image error from 222 to 15 HU. In addition, the image contrast on eight contrast rods of the phantom is enhanced by a factor of 2 on average. On an anthropomorphic head phantom, LFPM reduces the CT image error from 153 to 18 HU and eliminates the streak artifacts observed on the result of FTPM with substantially improved image uniformity. On the Rando® phantom, LFPM reduces the CT image error from 278 to 4 HU around the object center.

Conclusions

As compared with the previously developed FTPM algorithm, LFPM enhances the imaging performance by using a more flexible data processing framework that does not require projection data downsampling or uniform modulation frequency and magnitude. It also becomes possible to discard suspicious scatter estimate values prior to the generation of a final scatter distribution and to model the beam‐hardening effects on modulation for improved scatter estimation accuracy. The presented research further exploits the potential of the primary modulation method on scatter correction and facilitates its clinical adoption in CBCT imaging.
Heparan sulfate differentially controls CXCL12α- and CXCL12γ-mediated cell migration through differential presentation to their receptor CXCR4
Authors: Connell Bridgette J. , Sadir Rabia , Baleux Françoise , Laguri Cédric , Kleman Jean-Philippe , Luo Lingjie , Arenzana-Seisdedos Fernando , Lortat-Jacob Hugues
Published: November 2016

One isoform of a chemokine must bind to heparan sulfate to productively engage its receptor.
Papers of note in
Science Translational Medicine
Authors: Ferrarelli Leslie K.
Published: November 2016

This week’s articles feature ways to treat asthma, retinopathy, and neuroinflammatory disease.
Paper of note in
Science Immunology
Authors: Foley John F.
Published: November 2016

This week’s article describes how short-chain fatty acids produced by a skin bacterium stimulate an inflammatory response in keratinocytes.
Male pheromones and high temperature reduce life span
Authors: VanHook Annalisa M.
Published: November 2016

In nematodes, male pheromones shorten the life span of hermaphrodites but stimulate reproduction, and a neuropeptide protects against high temperature–induced aging.
Randomized Trial of Food Effect on Pharmacokinetic Parameters of ABX464 Administered Orally to Healthy Male Subjects
Authors: Scherrer Didier , Rouzier Regine , Cardona Marine , Barrett P. Noel , Steens Jean-Marc , Gineste Paul , Murphy Robert L. , Tazi Jamal , Ehrlich Hartmut J.
Published: November 2016

ABX464 is an antiviral that provides a novel approach to the reduction and control of HIV infection. Investigation of food influence is important in the optimization of treatment. An open-label, food effect, randomized study which included 2 groups of 24 subjects each was carried out to assess the bioavailability and safety of single (group 1) and repeated (group 2) oral doses of ABX464 (50 mg) under fed or fasted conditions. The maximum concentration (
C
max
) and the area under the concentration-time curve from time zero to infinity (AUC
0–∞
) of ABX464 were demonstrated to increase with food after a single dose of ABX464 (219% and 188%, respectively). The apparent terminal elimination half-lives (
t
1/2
s) under fed and fasted conditions were comparable, at about 0.80 h. The median time to maximum concentration (
T
max
) was delayed from 1.5 to 2.8 h, and the ratio of the AUC
0–∞
obtained under fed conditions to the AUC
0–∞
obtained under fasted conditions (
F
rel
) was 2.69. Comparable results were obtained on day 1 and day 10 in group 2. The increases in
C
max
and AUC
0–∞
of the metabolite ABX464–N-glucuronide (ABX464-NGlc) were, however, much more limited when ABX464 was given with food. The
t
1/2
s were also comparable under the two conditions (around 100 h). Between day 1 and day 10, the
C
max
increased by 5% under the fasted condition and by 25% under the fed condition. The most common related treatment-emergent adverse events were headaches, vomiting, and nausea. It was concluded that food has a significant impact on the levels of ABX464 in plasma with a delay in absorption and increased relative bioavailability, with a lesser impact on its biotransformation into ABX464-NGlc. ABX464 was well tolerated under both fasted and fed conditions. (This study has been registered at ClinicalTrials.gov under registration no. NCT02731885.)
TLR7 Agonist GS-9620 Is a Potent Inhibitor of Acute HIV-1 Infection in Human Peripheral Blood Mononuclear Cells
Authors: Bam Rujuta A. , Hansen Derek , Irrinki Alivelu , Mulato Andrew , Jones Gregg S. , Hesselgesser Joseph , Frey Christian R. , Cihlar Tomas , Yant Stephen R.
Published: November 2016

GS-9620 is a potent and selective oral Toll-like receptor 7 (TLR7) agonist that directly activates plasmacytoid dendritic cells (pDCs). GS-9620 suppressed hepatitis B virus (HBV) in animal models of chronic infection and transiently activated HIV expressionex vivoin latently infected peripheral blood mononuclear cells (PBMCs) from virally suppressed patients. Currently, GS-9620 is under clinical evaluation for treating chronic HBV infection and for reducing latent reservoirs in virally suppressed HIV-infected patients. Here, we investigated thein vitroanti-HIV-1 activity of GS-9620. GS-9620 potently inhibited viral replication in PBMCs, particularly when it was added 24 to 48 h prior to HIV infection (50% effective concentration = 27 nM). Depletion of pDCs but not other immune cell subsets from PBMC cultures suppressed GS-9620 antiviral activity. Although GS-9620 was inactive against HIV in purified CD4+T cells and macrophages, HIV replication was potently inhibited by conditioned medium derived from GS-9620-treated pDC cultures when added to CD4+T cells prior to infection. This suggests that GS-9620-mediated stimulation of PBMCs induced the production of a soluble factor(s) inhibiting HIV replication intrans. GS-9620-treated PBMCs primarily showed increased production of interferon alpha (IFN-α), and cotreatment with IFN-α-blocking antibodies reversed the HIV-1-inhibitory effect of GS-9620. Additional studies demonstrated that GS-9620 inhibited a postentry event in HIV replication at a step coincident with or prior to reverse transcription. The simultaneous activation of HIV-1 expression and inhibition of HIV-1 replication are important considerations for the clinical evaluation of GS-9620 since these antiviral effects may help restrict potential local HIV spread uponin vivolatency reversal.
Acquisition of Carbapenem Resistance by Plasmid-Encoded-AmpC-Expressing Escherichia coli
Authors: van Boxtel Ria , Wattel Agnes A. , Arenas Jesús , Goessens Wil H. F. , Tommassen Jan
Published: November 2016

Although AmpC β-lactamases can barely degrade carbapenems, if at all, they can sequester them and prevent them from reaching their targets. Thus, carbapenem resistance in
Escherichia coli
and other
Enterobacteriaceae
can result from AmpC production and simultaneous reduction of antibiotic influx into the periplasm by mutations in the porin genes. Here we investigated the route and genetic mechanisms of acquisition of carbapenem resistance in a clinical
E. coli
isolate carrying
bla
CMY-2
on a plasmid by selecting for mutants that are resistant to increasing concentrations of meropenem. In the first step, the expression of OmpC, the only porin produced in the strain under laboratory conditions, was lost, leading to reduced susceptibility to meropenem. In the second step, the expression of the CMY-2 β-lactamase was upregulated, leading to resistance to meropenem. The loss of OmpC was due to the insertion of an IS
1
element into the
ompC
gene or to frameshift mutations and premature stop codons in this gene. The
bla
CMY-2
gene was found to be located on an IncIγ plasmid, and overproduction of the CMY-2 enzyme resulted from an increased plasmid copy number due to a nucleotide substitution in the
inc
gene. The clinical relevance of these genetic mechanisms became evident from the analysis of previously isolated carbapenem-resistant clinical isolates, which appeared to carry similar mutations.
A Novel
erm
(44) Gene Variant from a Human Staphylococcus saprophyticus Isolate Confers Resistance to Macrolides and Lincosamides but Not Streptogramins
Authors: Strauss Christian , Hu Yanmin , Coates Anthony , Perreten Vincent
Published: November 2016

A novel
erm
(44) gene variant,
erm
(44)
v
, has been identified by whole-genome sequencing in a
Staphylococcus saprophyticus
isolate from the skin of a healthy person. It has the particularity to confer resistance to macrolides and lincosamides but not to streptogramin B when expressed in
S. aureus
. The
erm
(44)
v
gene resides on a 19,400-bp genomic island which contains phage-associated proteins and is integrated into the chromosome of
S. saprophyticus
.