bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling and Performance Analysis of Stationary Gas Turbines Operating Under Rotational Speed Transients
Authors: Andade André L. S. , Venturini Osvaldo J. , Cobas Vladimir R. M. , Silva Vinicius Zimmerman 
Published: August 2021

Abstract
In order to increase the flexibility and performance of gas turbines, generally their manufacturers and research centers involved in their development are constantly seeking the expansion of their operational envelope as well as their efficiency, making the engine more dynamic, less polluting and able to respond promptly to variations in load demands. An important aspect that should be considered when analyzing these prime movers is the assessment of its behavior under transients due to load changes, which can be accomplished through the development of a detailed, accurate and effective computational model. Considering this scenario, the present work aims to develop a model for the simulation and analysis of the dynamic behavior of stationary gas turbines. The engine considered in this analysis has a nominal capacity of 30.7 MW (ISO conditions) and is composed by a two-spool gas generator and a free power turbine. The model was developed using T-MATS, an integrated Simulink/Matlab toolbox, develop by NASA. The gas turbine was evaluated under both permanent and transient regimes and each one of its component was analyzed individually. The assessment made it possible to determine the engine performance parameters such as efficiency, heat rate and specific fuel consumption and its operational limits (surge limits, stall, turbine inlet temperatures, etc.) under different load conditions and regimes. The results obtained were compared with available field data, and the relative deviations for the considered parameters were all lower than 1%.
A Comparison of Different Fluid-Structure Interaction Analysis Techniques for the Marine Propeller
Authors: Rehman Wajiha , Paboeuf Stephane , Tomy Joseph Praful 
Published: August 2021

Abstract
The performance of the propeller is crucial to determine the energy-efficiency of a vessel. Fluid-Structure Interactions (FSI) analysis is one of the widely used methods to determine the hydrodynamic performance of marine propellers. This article is about the validation of a design assessment tool known as ComPropApp which is developed by Cooperative Research Ships (CRS) partners. ComPropApp is a specially designed tool for the FSI analysis of isotropic and composite marine propellers by doing explicit two-way coupling of the BEM-FEM solvers. The Boundary Element Method (BEM) solver of ComPropApp gives it an edge over Reynolds Averaged Navier Stokes Equations (RANSE) solvers in terms of computation time and cost. Hence, it is suitable for the initial design stage. The propeller used in this study is developed under the French Research Project; FabHeli.
The validation is done by performing different types of FSI analysis through commercial RANSE solver (STAR-CCM+) and FEM solver (FEMAP) for only one inflow velocity of the open water case which is 10.3 m/s. The fluid solver of ComPropApp (PROCAL) is a Boundary Element Method (BEM) solver that is based on the potential flow theory while the structural solver (TRIDENT) is a FEM solver. The study is divided into four different cases; BEM-FEM one-way coupled FSI analysis, RANSE-FEM one-way coupled FSI analysis, BEM-FEM explicit two-way coupled FSI analysis with ComPropApp and RANSE-FEM implicit two-way coupled FSI analysis with STAR-CCM+. The calculated values of stresses, displacement, and forces from all the methods are compared and the conclusion is drawn.
Energy Saving Assessment of Triple-Hybrid Vapor Absorption Building Cooling System Under Hot-Dry Climate
Authors: Singh Gaurav , Das Ranjan 
Published: August 2021

Abstract
Thermally driven vapor absorption-based air-conditioning systems possess many advantages over the compression based systems. However, intermittent availability of input resources affects the operation of these absorption systems which causes discontinuous working. This study aims at examining the electrical and thermodynamic performance of a triple-hybrid vapor absorption-assisted air-conditioning system against a conventional system with the aid of EnergyPlus simulations for a small office building. The outside weather is subjected to hot-dry climatic condition. The heat input source includes biomass and solar energy-based resources. Auxiliary heat input is also used to ensure smooth operation. The performance of the absorption system is assessed at different generator temperature (70 °C–80 °C) and solar collector area (400 m2–500 m2). The results show that, by using absorption-based systems, a maximum of 34.1% electrical energy savings can be ensured at 500 m2 collector area with 70 °C generator temperature. The coefficient of performance of the absorption system escalates from 0.50 to 0.52 by increasing the generator temperature form 70 °C to 80 °C. Under the condition of 70 °C generator temperature and 500 m2 collector area, the absorption system can be made fully renewable energy dependent.
Optimizing Water Harvesting on Bioinspired Surfaces: A Mesoscopic Perspective
Authors: Chakraborty Souparna , Chaudhuri Abhirup , Bakli Chirodeep 
Published: August 2021

Abstract
The water crisis affects the lives of millions over the world. Minimizing water losses in major water-consuming industries like power plants is of utmost importance. Since cooling towers lead to huge amounts of water loss, implementing modifications for recovering a fraction of this lost water in the exhaust has been a topic of active research. These modifications are often inspired by biological species, especially in arid regions, which have adapted in different ways by collecting water from fog, and hence biomimetic has become popular for water harvesting techniques. We revisit the fog collection technique most commonly used in nature and compare the relative merits of the same with surface texture and wettability. Arrays of spines of three different configurations were considered in this study — namely cuboidal, cylindrical and conical shapes. A theoretical model is developed to carry out a comparative analysis of these configurations considered. The effects of Laplace pressure gradient, gravity, topography and tilt angle on droplet transportation along the spines were explored to decipher the most efficient water transport and collection route. The observations are explained by performing extensive Molecular Dynamics (MD) simulations to bring out the interplay of surface tension and roughness at the contact line verifying the proposed formulations. The conical-shaped spines exhibited maximum transport and collection efficiency for zero tilt angle. Both cuboidal and cylindrical shaped spines showed little or no water collection when the spines are oriented horizontally. This is due to the Laplace pressure gradient which arises from varying radii of curvature of the conical shaped spine which drives the water droplets towards the base but is absent for the other two cases considered. On the contrary, when there is some finite tilt angle, the contribution of gravity comes into consideration and the water collection rate of the conical and cylindrical spines becomes comparable. Both Laplace pressure gradient and gravity help in water transport in the conical case whereas only gravity assists the water transport process for cylindrical spines. Still, the water collection rate is almost the same for these two scenarios due to enhanced coalescence of liquid droplets for the cylindrical case as is observed from MD simulations. As the droplets coalesce, they get larger and gravity aids the transport process by overcoming the solid-liquid interaction strength. Cuboidal shaped spines show the least efficiency with only gravity to assist the transport process and no coalescence is observed in this case. Moreover, the geometrical disparity makes the tips of conical spines more hydrophobic compared to the others which further ameliorates the water collection efficiency.
Control of Wave Energy Converter With Losses in Electrical Power Take-Off System
Authors: Zhou Xiang , Zou Shangyan , Weaver Wayne W. , Abdelkhalik Ossama 
Published: August 2021

Abstract
A permanent magnet linear electrical machine power takeoff (PTO) unit is simulated on the direct drive wave energy converter in this paper, which is controlled to provide the required reactive power. A shape-based control is implemented to maximize the wave energy production (mechanical PTO) with the limiting constraints on the electric drive. Further, the linear electrical machine design is optimized such that the electrical power output is maximized (e.g., reduced power losses). The numerical simulations are conducted using MATLAB/Simulink and the Simscape toolbox. Linear wave theory is applied in modeling the buoy dynamics. Additionally, the PTO unit is composed of a linear electrical machine, an ideal inverter, and an ideal energy storage system. The results show the proposed PTO tracks the reference control accurately. The electrical power output is significantly improved by limiting the current in the PTO compared to a passive control.
Investigation of Air Extraction and Carbon Capture in an Integrated Gasification Combined Cycle (IGCC) System
Authors: Acharya Shisir , Wang Ting 
Published: August 2021

Abstract
Coal is one of the major sources of energy currently as it provides up to 38.5% of the total electricity produced in the world. Burning coal produces pollutants and large amounts of CO2, which contribute to climate change, environmental pollution, and health hazards. Therefore, it is our obligation to utilize coal in a cleaner way. Cleaner coal energy can be produced by using an ultra-supercritical Pulverized Coal (PC) power plant, or by employing the Integrated Gasification Combined Cycle (IGCC). Since the 1970s, the IGCC technology has been developed and demonstrated, but it has still not been widely commercialized. One of the methods to improve IGCC performance is to save the compression power of the air separation unit (ASU) by extracting the compressed air from the exit of the gas turbine as a portion of or the entire air input to the ASU. This paper investigates the effect of various levels of air integration on the IGCC performance. The results show that a moderate air integration ranging from 15% to 20% provides the most effective air-integration. An analysis of implementing a sour-shift pre-combustion carbon capture results in a significant loss of about 5.5 points in efficiency. This study also provides the effect of air integration and carbon capture on emissions including NOx, SOx, CO2, and water consumption.
Investigation of Phase Change Material Integrated With High Thermal Conductive Carbon Foam Inside Heat Sinks for Thermal Management of Electronic Components
Authors: Kumar Anuj , Kothari Rohit , Sahu Santosh K. , Kundalwal Shailesh I. , Sharma Akhalesh 
Published: August 2021

Abstract
In recent years phase change materials (PCMs) have emerged as a promising material for various thermal management applications. However, the lower thermal conductivity of PCM is a major hindrance in its widespread use. In the present study, an experimental investigation is carried out using high thermal conductive carbon foam (CF) embedded with PCM inside heat sink for thermal management of electronic components. Various configurations of heat sinks such as unfinned heat sink without PCM, unfinned heat sink integrated with PCM, unfinned heat sink integrated with CF-PCM composite, two finned heat sink integrated with PCM, and two finned heat sink integrated with CF-PCM composite are investigated. The vacuum impregnation technique is employed to infiltrate the PCM inside the CF. Heat flux is varied in the range of 1.5 to 2.5 kW/m2. Temperature variation of the heat sink base is used to compare the performance of various heat sinks. Unfinned heat sink without and with PCM is used for baseline comparison. Enhancement ratios are presented for various set point temperatures (SPT) such as 65 and 75°C. The highest enhancement ratio of 4.98 is obtained for two fin CF-PCM composite heat sink.
An Inverse Method for Parameter Retrieval in Solar Thermal Collector With a Single Glass Cover
Authors: Das Ranjan 
Published: August 2021

Abstract
The present article highlights the implementation of differential evolution (DE)-assisted metaheuristic optimizer to provide the solution of an inverse multi-variable problem related to a flat absorber solar collector consisting of a single glass. For satisfying a given heating requirement from the solar collector, the necessary tilt angle and the thickness of the glass cover are simultaneously predicted using the proposed DE methodology. The existing study of inverse multi-variable optimization analysis has been done for dynamic values of solar energy radiation and different ambient conditions commonly encountered in various geographical locations of India. Formulation of the current research involves the minimization of a newly proposed cost function involving the required and the acquired heat transfer rates from the solar collector in Euclidean space. The solution approach then utilizes a dynamic exchange between evolutionary metaheuristic DE and a well-validated forward solver containing analytical expressions of heat energy balance within the solar collector. Variations of cost function and the estimated design variables are mainly studied to visualize the algorithm’s behavior for a single gazing-based solar thermal device. Multiple possible groupings of the unknown parameters of the solar collector are revealed, which always collectively result in a desired heating requirement from the solar collector. Sensitivity indices related to the design variables are evaluated for ascertaining the relative importance of parameter selection. Encouraging opportunity is found towards the system’s size reduction through sparing selection of inclination angle. The current study provides a convenient and cost-effective tool to select the necessary inclination and glass covers to obtain low to medium heating requirements from the available incident solar energy.
Experimental Investigation of Ammonia and Sulfur Deposition Characteristics in Rotary Air Preheater
Authors: Gao Rongze , Sun Haojia , Wang Limin , Bu Yufan , Wang Chao , Che Defu 
Published: August 2021

Abstract
With the application of selective catalytic reduction (SCR) technology, the operation of rotary air preheaters is faced with a challenge, the fouling problem caused by ammonium bisulfate (ABS). In previous studies, within the operational temperature range of the preheater, the gaseous ammonia and sulfur trioxide (or H2SO4) in the flue gas can react to form ABS and ammonium sulfate (AS). The initial condensation temperature of ABS might be over predicted due to the effect of the formation of AS, which has a higher initial formation temperature than ABS. In this study, the effects of the deposition temperature, ammonia-sulfur molar ratio and molar product of inlet flue gas on the deposition characteristics of inducing ash deposition compounds were experimentally studied to provide guidance to prevent fouling and corrosion of rotary air preheaters. The results show that the main path to generate ABS is the reaction between H2SO4 and NH3. With the increase in the deposition temperature, the contents of NH4+ and SO42− in the sediments decrease continuously, and the proportion of AS deposition increases. On the contrary, with temperature decreasing, more ABS is deposited. When the molar ratio of ammo-sulfur in the inlet flue gas increases, the proportion of AS in the sediments increases, and the deposition rate also gradually increases. When the ammo-sulfur product in the inlet flue gas increases, the concentrations of both NH4+ and SO42− in the sediments increased in a nearly consistent trend. The variations of the ratio and deposition rates of the two ions in the sediments were not obvious. The ratio of NH4+ and SO42− remains at about 1.2, and the sediment is mainly ABS.
A Plan for Biomass Power Generation With Negative Carbon Emissions
Authors: Parker Marc A. 
Published: August 2021

Abstract
Worldwide energy consumption is accelerating at an unprecedented rate while humanity comes to understand the effects of climate change. Renewable resources such as wind and solar supply more energy every year, but the overwhelming majority of energy consumed is still from fossil fuels. The transition to zero carbon emission sources is important, but carbon negative energy could also become necessary in ensuring a sustainable global environment and economy. The most technically and commercially viable carbon negative solution is biomass-fueled power generation with carbon capture and sequestration. A conceptual design based on a biomass-fired circulating fluidized-bed boiler and developed using the Thermoflex software package (Thermoflow, Inc.) is presented that can be evaluated and pursued by the research, engineering, and business communities. Recommendations are proposed for siting and fuel supply in the Southeastern U.S., with an evaluation of some of the impacts from wood harvesting, processing, and transportation to the lifecycle carbon emissions. An economic analysis of this carbon negative concept indicates that certain policy proposals in the U.S. could make biomass power generation with carbon capture and sequestration an economically feasible resource. Results show that an owner and/or the public could realize a net benefit of up to $332/MWh above and beyond marginal energy or capacity values under aggressive carbon pricing.
Characterizing the Transitional Behavior of Wind Turbine Wake From Near to Far Wake Regimes
Authors: Kumar Ravi , Siram Ojing , Sahoo Niranjan , Saha Ujjwal K. 
Published: August 2021

Abstract
Knowledge of wind energy harvesting is an ever-growing process, and to meet the enormous energy demand, wind farms shall have a significant role. An efficient wind farm is required to have an in-depth knowledge of turbine wake characteristics. This article presents an experimental investigation of the wake expansion process defined by the transition of wake from near to far wake regimes. The study has been performed on models horizontal axis wind turbine (HAWT) composed of NACA 0012 profile, keeping the ratio of root chord to tip chord length is 5:2. A constant temperature hot-wire anemometer (HWA) has been used to examine the rotor’s fluctuating flow field. The subsequent time-averaged normalizes velocity deficit, and vortex shedding frequency are used for the flow characteristics. Time-averaged velocity deficit measurement suggests a drop in upstream velocity by 20–30% within the vicinity of rotor tip downstream of the rotor plane. The study shows that flow recovery is initiating from the near wake regime around 1.08R. Further, the spectral findings indicates the low frequency dominance within 4R (R being the rotor radius), and the Strouhal number falls close to 0.23. The present wind tunnel study on wake characteristics throws significant insight into further enhancing the WT wake modeling.
Rate of Torque Development and Torque Steadiness of the Lower Limb and Future Falls Among Community-Dwelling Older Adults Without Previous Falls: A Longitudinal 1-Year Study
Authors: Porto Jaqueline Mello , Freire Júnior Renato Campos , Capato Luana Letícia , Spilla Sállua Berlanga , Nakaishi Ana Paula Midori , Braz e Silva Elisa , Faccio Andrea Fernanda Forestieri , Abreu Daniela Cristina Carvalho de 
Published: August 2021

The objective was to investigate the association between rate of torque development (RTD) and torque steadiness (TS) of the lower limb and the occurrence of prospective falls in community-dwelling older adults without falls in the previous year. One hundred older adults performed the tests to obtain the RTD and TS of the hip, knee, and ankle. New episodes of falls were monitored through telephone contact for a prospective period of 12 months. The association of RTD and TS with the occurrence of prospective falls was verified by multiple logistic regression adjusted for confounding variables. There was no association between RTD of hip, knee, and ankle and prospective falls. Only the TS at 50% of the peak torque of the hip flexors was associated with the occurrence of future falls (p = .023). Identifying modifiable risk factors for the first fall in older adults is essential for the development of adequate prevention programs.
Protocol for a scoping review to evaluate the extent of utilisation of healthcare services by asthma patients in sub-Saharan African countries
Authors: Ndarukwa Pisirai , Chimbari Moses John , Sibanda Elopy 
Published: August 2021

IntroductionHealth systems in sub-Saharan African (SSA) countries are fragile and centralised. Consequently, majority of people have restricted access to healthcare services. Given the rise in the prevalence and burden of asthma in SSA, it is imperative to scrutinise the utilisation of healthcare services by people with asthma. We aim to understand, through this review, the extent of utilisation of healthcare services by asthma patients in SSA countries.Methods and analysisArksey and O’Malley’s scoping review methodology framework will be used to guide the conduct of this scoping review. We will conduct a search of the literature on the electronic databases: Medline, (using PubMed interface), EMBASE, EBSCOHOST, Web of Science and Google Scholar, grey literature sources and the reference lists of key studies to identify studies appropriate for inclusion. Two reviewers will independently screen all abstracts and full-text studies for inclusion. Registration of the proposed scoping review on the PROSPERO has indicated that no similar work has been or is being done elsewhere. We will review studies published on the subject from January 2009 to May 2020 in SSA.Ethics and disseminationThe proposed scoping review will contribute towards the knowledge base on utilisation of healthcare services particularly for people with asthma. This will provide a better understanding of the extent of utilisation of healthcare services by asthma patients and ultimately contribute to improvement of quality of care for people suffering from asthma. The results from the review will enlighten and guide healthcare practitioners and researchers on developing appropriate and feasible interventions to increase the utilisation of healthcare services by asthma patients in resource-constrained settings in SSA countries. Results of this scoping review will be disseminated through a peer-reviewed publication, conference presentations and a 1-day stakeholder meeting.PROSPERO registration numberCRD42020154127.