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Records added in 2019
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Showing records 1 to 25 of 1251. [First] Page: 1 2 3 4 5 Last
Study on Flow Field and Rotor Safety Characteristics of MSPs Based on Flow Thermo-Coupling
Yiming Chen, Rongsheng Zhu, Yonggang Lu, Zhenjun Gao, Junjun Kang
December 9, 2019 (v1)
Keywords: flow field, flow thermo-coupling, fluid-structure coupling, MSP (molten salt pump), thermal-structure coupling
In order to obtain the structural intensity under the operation conditions of MSP (molten salt pump), the rotor component of MSP is taken as the research object. In this paper, the influence of material properties change on the structural performance of MSP at different temperatures is analyzed. The stress distribution and strain distribution of MSP rotor components under different loads are investigated, and the intensity calculation of MSP rotor system is carried out to explore whether it meets the intensity requirements under high temperature operation, which lays a foundation for the high temperature test of MSP. The results show that the maximum deformation position of the blade working face appears at the outer edge of the impeller. When the fluid-structure coupling is applied, the blade strain law and the strain law during thermo-coupling are similar. The effect of the temperature field on the degree of blade deformation is not significant, provided that other factors remain the... [more]
Hydrodynamic and Hydrographic Modeling of Istanbul Strait
Mehmet Melih Koşucu, Mehmet Cüneyd Demirel, V.S. Ozgur Kirca, Mehmet Özger
December 9, 2019 (v1)
Subject: Other
Keywords: gravity driven flow, Istanbul Strait, numerical modeling, stratified flow
The aim of this study is to model the hydrodynamic processes of the Istanbul Strait with its stratified flow characteristics, and calibrate the most important parameters using local and global search algorithms. For that, two open boundary conditions are defined, which are in the northern and southern parts of the Strait. Observed bathymetric, hydrographic, meteorological, and water-level data are used to set up the Delft3D-FLOW model. First, the sensitivities of the model parameters on the numerical model outputs are assessed using Parameter EStimation Tool (PEST) toolbox. Then, the model is calibrated based on the objective functions, focusing on the flow rates of the upper and lower layers. The salinity and temperature profiles of the strait are only used for model validation. The results show that the calibrated model outputs of the Istanbul Strait are reliable and consistent with the in situ measurements. The sensitivity analysis reveals that the spatial low-pass filter coefficien... [more]
Chemically Enhanced Primary Sludge as an Anaerobic Co-Digestion Additive for Biogas Production from Food Waste
Xiaorong Kang, Yali Liu
December 9, 2019 (v1)
Subject: Biosystems
Keywords: chemically enhanced primary sedimentation, food waste, Renewable and Sustainable Energy, VFAs
In order to overcome process instability and buffer deficiency in the anaerobic digestion of mono food waste (FW), chemically enhanced primary sludge (CEPS) was selected as a co-substrate for FW treatment. In this study, batch tests were conducted to study the effects of CEPS/FW ratios on anaerobic co-digestion (coAD) performances. Both soluble chemical oxygen demand (SCOD) and protease activity were decreased, with the CEPS/FW mass ratio increasing from 0:5 to 5:0. However, it was also found that the accumulation of volatile fatty acids (VFAs) was eliminated by increasing the CEPS/FW ratio, and that corresponding VFAs concentrations decreased from 13,872.97 to 1789.98 mg chemical oxygen demand per L (mg COD/L). In addition, the maximum value of cumulative biogas yield (446.39 mL per g volatile solids removal (mL/g VSsremoval)) was observed at a CEPS/FW ratio of 4:1, and that the tendency of coenzyme F420 activity was similar to biogas production. The mechanism analysis indicated that... [more]
A Techno-Economic Analysis of Off-Grid Solar PV System: A Case Study for Punjab Province in Pakistan
Muhammad Irfan, Zhen-yu Zhao, Munir Ahmad, Abdul Rehman
December 9, 2019 (v1)
Keywords: CO2 mitigation, economic feasibility, off-grid solar PV system, remote regions, rural electrification
Fossil fuels are the primary sources of electricity generation in Pakistan. The energy demand and supply gap have intensified recently due to the massive population and fossil fuels are unable to meet the gigantic energy requirement of the country. Meanwhile, they also have adverse environmental impacts. Remote rural regions that are far away from the national grid do not have any means to fulfill their energy needs. The off-grid solar photovoltaic (PV) system has emerged to be the best energy option to electrify these remote regions. However, the strategic problem pertaining to local electricity generation is the absence of the area-specific generation capacity and economic feasibility data for solar energy. To address this problem, this study aims to assess the potential and economic viability of utilizing an off-grid solar PV system for rural electrification in the Punjab province of Pakistan. The research results reveal that there is an excellent solar irradiance in the rural areas... [more]
Effect of Physical and Mechanical Activation on the Physicochemical Structure of Coal-Based Activated Carbons for SO2 Adsorption
Dongdong Liu, Zhengkai Hao, Xiaoman Zhao, Rui Su, Weizhi Feng, Song Li, Boyin Jia
December 9, 2019 (v1)
Subject: Materials
Keywords: activated carbons, mechanical activation, physical activation, physicochemical structure, SO2 adsorption
The SO2 adsorption efficiency of activated carbons (ACs) is clearly dependent on its physicochemical structure. Related to this, the effect of physical and mechanical activation on the physicochemical structure of coal-based ACs has been investigated in this work. In the stage of CO2 activation, the rapid decrease of the defective structure and the growth of aromatic layers accompanied by the dehydrogenation of aromatic rings result in the ordered conversion of the microstructure and severe carbon losses on the surfaces of Char-PA, while the oxygen content of Char-PA, including C=O (39.6%), C−O (27.3%), O−C=O (18.4%) and chemisorbed O (or H2O) (14.7%), is increased to 4.03%. Char-PA presents a relatively low SBET value (414.78 m2/g) owing to the high value of Non-Vmic (58.33%). In the subsequent mechanical activation from 12 to 48 h under N2 and dry ice, the strong mechanical collision caused by ball-milling can destroy the closely arranged crystalline layers and the collapse of mesopo... [more]
Modeling and Analysis of Maximum Power Tracking of a 600 kW Hydraulic Energy Storage Wind Turbine Test Rig
Liejiang Wei, Peng Zhan, Zengguang Liu, Yanhua Tao, Daling Yue
December 9, 2019 (v1)
Keywords: energy storage system, hydraulic wind turbine, maximum power point tracking, tip speed ratio
An innovative wind turbine with a particular hydraulic transmission and energy storage system is proposed in this paper. The purpose of applying the hydraulic transmission is to remove the gearbox and power converter of traditional wind turbine and cooperate on wind resource storing with the energy storage system. To overcome the volatility and intermittence shortcomings of wind and improve the output power quality, hydraulic accumulators are used as the energy storage device for wind energy regulation. The original gearbox and generator in the nacelle of a Micon 600 wind turbine were removed and replaced with a hydraulic pump to make a test rig for the investigation into maximum power point tracking (MPPT) of this hydraulic wind turbine concept. The mathematical model of the entire test system is established according to the four function modules. The MPPT control strategy based on the tip speed ratio (TSR) is adopted and a control system containing three closed-loop controls is desig... [more]
Thermochemical Conversion of Napier Grass for Production of Renewable Syngas
Mohamad Syazarudin Md Said, Wan Azlina Wan Abdul Karim Ghani, Tan Hong Boon, Siti Aslina Hussain, Denny Kok Sum Ng
December 9, 2019 (v1)
Keywords: energy crop, gasification, Napier grass, Renewable and Sustainable Energy, solid biofuel
Fuel resource diversification is a global effort to deviate from non-renewable fossil fuels. Biomass has been identified as an alternative solid biofuel source due to its desirable properties and carbon neutrality. As reported in the literature, biomass can positively contribute towards combating climate change while providing alleviation for energy security issue. As part of efforts to diversify biomass resources, this work intends to explore the potential of Napier grass, one type of energy crop, for the production of renewable syngas via gasification. This energy crop is originally from Africa, which is highly productive with low cost (40 tonnes per year per hectare). Limited studies were conducted to analyze the potential of such an energy crop as a fuel source, which is the subject of this work. In order to analyze the full potential of such energy crop, the physical and chemical characteristics of this biomass was first analyzed. To determine the productivity of syngas from this... [more]
Sustainable Synthesis Processes for Carbon Dots through Response Surface Methodology and Artificial Neural Network
Musa Yahaya Pudza, Zurina Zainal Abidin, Suraya Abdul Rashid, Faizah Md Yasin, Ahmad Shukri Muhammad Noor, Mohammed A. Issa
December 9, 2019 (v1)
Keywords: artificial neural network, carbon dots, hydrothermal, organic, photoluminescence, response surface methodology, tapioca
Nowadays, to ensure sustainability of smart materials, it is imperative to eliminate or reduce carbon footprint related to nano material production. The concept of design of experiment to provide an optimal synthesis process, with a desired yield, is indispensable. It is the researcher’s goal to get optimum value for experiments that requires multiple runs and multiple inputs. Herein, is a reliable approach of utilizing design of experiment (DOE) for response surface methodology (RSM). Thus, to optimize a facile and effective synthesis process for fluorescent carbon dots (CDs) derived from tapioca that is in line with green chemistry principles for sustainable synthesis. The predictions for fluorescent CDs synthesis from RSM were in excellent agreement with the artificial neural network (ANN) model prediction by the Levenberg−Marquardt back propagation (LMBP) algorithm. Considering R2, root mean square error (RMSE) and mean absolute error (MAE) have all revealed a positive hidden layer... [more]
Prediction of Lithium-ion Battery Thermal Runaway Propagation for Large Scale Applications Fire Hazard Quantification
Mohamad Syazarudin Md Said, Mohd Zahirasri Mohd Tohir
December 9, 2019 (v1)
Keywords: cascade failure, fire and explosion, lithium-ion battery, thermal runaway propagation
The high capacity and voltage properties demonstrated by lithium-ion batteries render them as the preferred energy carrier in portable electronic devices. The application of the lithium-ion batteries which previously circulating and contained around small-scale electronics is now expanding into large scale emerging markets such as electromobility and stationary energy storage. Therefore, the understanding of the risk involved is imperative. Thermal runaway is the most common failure mode of lithium-ion battery which may lead to safety incidents. Transport process of immense amounts of heat released during thermal runaway of lithium-ion battery to neighboring batteries in a module can lead to cascade failure of the whole energy storage system. In this work, a model is developed to predict the propagation of lithium-ion battery in a module for large scale applications. For this purpose, kinetic of material thermal decomposition is combined with heat transfer modelling. The simulation is... [more]
Sustainable Personnel Scheduling Problem Optimization in a Natural Gas Combined-Cycle Power Plant
Emir Hüseyin Özder, Evrencan Özcan, Tamer Eren
December 9, 2019 (v1)
Keywords: analytic network process (ANP), electricity generation sector, goal programming (GP), natural gas combined-cycle power plant, Optimization, skill-based personnel scheduling
This paper deals with a sustainable personnel scheduling problem of personnel working in a large-scale natural gas combined-cycle power plant in Turkey. The proposed model focuses on employee complaints due to unfair work schedules and the results of balanced assignments based on power plant interruptions. Eighty personnel work in three shifts at this natural gas combined-cycle power plant. The model is solved with respect to some of the workers’ skills, and there are 20 criteria regarding skills. The analytic network process method is used to get the weights of workers’ skills, which are calculated and included in the model. Goal programming is used in this paper. Our proposed model gives cost minimization and fair work schedules for the power plant. Compared with the literature, the number and set of criteria are unique in terms of personnel competency in the energy sector. Minimizing cost and imbalanced assignments was achieved by the proposed model for the first time without consid... [more]
Numerical and Experimental Study of a Vortex Structure and Energy Loss in a Novel Self-Priming Pump
Hao Chang, Ramesh K. Agarwal, Wei Li, Ling Zhou, Weidong Shi
December 9, 2019 (v1)
Keywords: energy loss, entropy production, self-priming pump, vortex structure
The self-priming pump as an essential energy conversion equipment is widely used in hydropower and thermal power plants. The energy losses in the internal flow passage of the pump directly affect its work efficiency. Therefore, it is important to improve the internal flow characteristic of the pump. In the present work, a novel self-priming pump which starts without water is proposed; this pump can reduce the energy consumption as well as the time needed to start its operation. The spatial structure of the vortices in the pump is investigated by employing the Q criterion with the numerical solution of the vorticity transport equation. Based on the morphology, the vortices can be separated into three categories: Trailing Edge Vortex (TEV), Leading Edge Vortex (LEV) and Gap Leakage Vortex (GLV). Generally, the morphology of the TEV is more disorderly than that of LEV and GLV, and the intensity of TEV is significantly higher than that of the other two vortices. To determine the magnitude... [more]
A Comparative Study of Biogas Reactor Fluid Rheology—Implications for Mixing Profile and Power Demand
Luka Šafarič, Sepehr Shakeri Yekta, Jörgen Ejlertsson, Mohammad Safari, Hossein Nadali Najafabadi, Anna Karlsson, Francesco Ometto, Bo H. Svensson, Annika Björn
December 9, 2019 (v1)
Subject: Biosystems
Keywords: anaerobic digestion, Computational Fluid Dynamics, stirring, substrate, viscosity
Anaerobic digestion (AD) is an established process for integrating waste management with renewable energy and nutrient recovery. Much of the research in this field focuses on the utilisation of new substrates, yet their effects on operational aspects such as fluid behaviour and power requirement for mixing are commonly overlooked, despite their importance for process optimisation. This study analysed rheological characteristics of samples from 21 laboratory-scale continuous stirred-tank biogas reactors (CSTBRs) digesting a range of substrates, in order to evaluate substrate effect on mixing efficiency and power demand through computational fluid dynamics (CFD). The results show that substrate and process parameters, such as solids content and organic loading, all have a significant effect on CSTBR fluid rheology. The correlation levels between rheological and process parameters were different across substrates, while no specific fluid behaviour patterns could be associated with substra... [more]
Molecular Insights into Cage Occupancy of Hydrogen Hydrate: A Computational Study
Rui Ma, Hong Zhong, Jinxiang Liu, Jie Zhong, Youguo Yan, Jun Zhang, Jiafang Xu
December 9, 2019 (v1)
Subject: Materials
Keywords: density functional theory, hydrogen hydrate, molecular dynamics simulation, stability
Density functional theory calculations and molecular dynamics simulations were performed to investigate the hydrogen storage capacity in the sII hydrate. Calculation results show that the optimum hydrogen storage capacity is ~5.6 wt%, with the double occupancy in the small cage and quintuple occupancy in the large cage. Molecular dynamics simulations indicate that these multiple occupied hydrogen hydrates can occur at mild conditions, and their stability will be further enhanced by increasing the pressure or decreasing the temperature. Our work highlights that the hydrate is a promising material for storing hydrogen.
Study on the Compatibility of Gas Adsorbents Used in a New Insulating Gas Mixture C4F7N/CO2
Qingdan Huang, Yong Wang, Jing Liu, Yaru Zhang, Lian Zeng
December 9, 2019 (v1)
Subject: Materials
Keywords: adsorbents, desiccants, HF removal, insulating gas, perfluoroisobutyronitrile
An environment-friendly insulating gas, perfluoroisobutyronitrile (C4F7N), has been developed recent years. Due to its relatively high liquefaction temperature (around −4.7 °C), buffer gases, such as CO2 and N2, are usually mixed with C4F7N to increase the pressure of the filled insulating medium. During these processes, the insulating gases may be contaminated with micro-water, and the mixture of H2O with C4F7N could produce HF under breakdown voltage condition, which is harmful to the gas insulated electricity transfer equipment. Therefore, removal of H2O and HF in situ from the gas insulated electricity transfer equipment is significant to its operation security. The adsorbents with the ability to remove H2O but without obvious C4F7N/CO2 adsorption capacity are essential to be used in this system. In this work, a series of industrial adsorbents and desiccants were tested for their compatibility with C4F7N/CO2. Pulse adsorption tests were conducted to evaluate the adsorption performa... [more]
PIV and Statistical Analysis of a Swirling Bed Process Carried out Using a Hybrid Model of Axial Blade Distributor
Shazia Shukrullah, Muhammad A. Javed, Muhammad Y. Naz, Yasin Khan, Majeed A. S. Alkanhal, Hafeez Anwar
December 9, 2019 (v1)
Keywords: mesh-coupled annular blade distributor, particle image velocimetry, response surface analysis, swirling bed
An air distributor is a major component of industrial fluidized beds and its design significantly affects the quality of fluidization. In this study, a hybrid design of an annular distributor was tested for swirling fluidized beds (SFBs). Using this distributor design, a bed was operated in its uniform swirling regime of operation. A high-speed imaging method was used to capture images of the fluidized bed of particles. These images were processed using a binary cross-correlation technique and analyzed through particle image velocimetry (PIV) software. The velocity vector fields and corresponding velocity magnitudes at different locations in the bed were obtained for different bed weights, blade inclination angles, and superficial air velocities (SAVs). The Response Surface Analysis program was used to predict the bed velocity statistically. The statistical confidence interval for the bed velocity ranged from 0.49485 to 0.49998. The statistical fit and experimental values of the bed ve... [more]
Multi-Scale Multi-Field Coupled Analysis of Power Battery Pack Based on Heat Pipe Cooling
Ye Liu, Tao Jiang, Yanping Zheng, Jie Tian, Zheshu Ma
December 9, 2019 (v1)
Keywords: heat pipe, lithium-ion battery, multi-scale coupled analysis, thermal management system
Based on the study of the relationship between micro and macro parameters in the actual microstructure of the electrodes, a new multi-scale multi-field coupling model of battery monomer is established and the heat generation rate of the battery is obtained by detailed numerical simulation. According to the parameters of a certain electric vehicle and battery selected, the structure of the power battery pack and heat pipe cooling system is designed. Through multi-field coupling computational fluid dynamics simulation, the temperature difference of the battery pack is gained. By changing the fin spacing, the cooling scheme of the heat pipe is optimized, which ensures that the temperature difference is less than 5 K and the maximum temperature of the battery system is 306.26 K. It is found that increasing the discharge rate, the temperature difference increases rapidly. Increasing the air inlet velocity can improve the thermal uniformity of the battery pack, but changing the air inlet tem... [more]
A Fault Feature Extraction Method for the Fluid Pressure Signal of Hydraulic Pumps Based on Autogram
Zhi Zheng, Xianze Li, Yong Zhu
December 9, 2019 (v1)
Keywords: Autogram, feature extraction, fluid pressure, hydraulic pump, kurtosis
Center spring wear faults in hydraulic pumps can cause fluid pressure fluctuations at the outlet, and the fault feature information on fluctuations is often contaminated by different types of fluid flow interferences. Aiming to resolve the above problems, a fluid pressure signal method for hydraulic pumps based on Autogram was applied to extract the fault feature information. Firstly, maximal overlap discrete wavelet packet transform (MODWPT) was adopted to decompose the contaminated fault pressure signal of center spring wear. Secondly, based on the squared envelope of each node, three kinds of kurtosis of unbiased autocorrelation (AC) were computed in order to describe the fault feature information comprehensively. These are known as standard Autogram, upper Autogram and lower Autogram. Then a node corresponding to the biggest kurtosis value was selected as a data source for further spectrum analysis. Lastly, the data source was processed by threshold values, and then the fault could... [more]
Application of CFD to Analyze the Hydrodynamic Behaviour of a Bioreactor with a Double Impeller
Mohammadreza Ebrahimi, Melih Tamer, Ricardo Martinez Villegas, Andrew Chiappetta, Farhad Ein-Mozaffari
December 9, 2019 (v1)
Keywords: Computational Fluid Dynamics, dual-impeller, Optimization, Segment impeller, Stirred fermenter
Stirred bioreactors are commonly used unit operations in the pharmaceutical industry. In this study, computational fluid dynamics (CFD) was used in order to analyze the influence of the impeller configuration (Segment−Segment and Segment−Rushton impeller configurations) and the impeller rotational speed (an operational parameter) on the hydrodynamic behaviour and mixing performance of a bioreactor equipped with a double impeller. A relatively close agreement between the power values obtained from the CFD model and those measured experimentally was observed. Various parameters such as velocity profiles, stress generated by impellers due to the turbulence and velocity gradient, flow number, and mixing time were used to compare the CFD simulations. It was observed that the impeller’s RPM could change the intensity of the interaction between the impellers when a Segment−Rushton impeller was used. In general, increasing the RPM led to an increase in total power and the stress acting on the... [more]
Practical Solutions for Specific Growth Rate Control Systems in Industrial Bioreactors
Vytautas Galvanauskas, Rimvydas Simutis, Donatas Levišauskas, Renaldas Urniežius
December 9, 2019 (v1)
Keywords: batch-to-batch reproducibility, bioreactor control, biotechnological processes, specific growth rate control
This contribution discusses the main challenges related to successful application of automatic control systems used to control specific growth rate in industrial biotechnological processes. It is emphasized that, after the implementation of basic automatic control systems, primary attention shall be paid to the specific growth rate control systems because this process variable critically affects the physiological state of microbial cultures and the formation of the desired product. Therefore, control of the specific growth rate enables improvement of the quality and reproducibility of the biotechnological processes. The main requirements have been formulated that shall be met to successfully implement the specific growth rate control systems in industrial bioreactors. The relatively easy-to-implement schemes of specific growth rate control systems have been reviewed and discussed. The recommendations for selection of particular control systems for specific biotechnological processes ha... [more]
Preparation and Molecular Dynamics Simulation of RDX/MUF Nanocomposite Energetic Microspheres with Reduced Sensitivity
Xinlei Jia, Yingying Hu, Lanjuan Xu, Xuewen Liu, Youying Ma, Mingming Fu, Jingyu Wang, Jing Xu
December 9, 2019 (v1)
Subject: Materials
Keywords: improved emulsion polymerization, MD simulation, nanocomposite energetic microspheres, RDX/MUF
In order to improve the general problem of irregular coating morphology and low mechanical strength of the coating layer in existing coating desensitization technology, nano-cyclotrimethylene trinitramine/melamine-urea-formaldehyde (RDX/MUF) composite energetic microspheres were prepared by an improved emulsion polymerization, taking the MUF as the binder and RDX as the main explosive. In order to judge whether RDX/MUF possessed good stability, the combination of differential scanning calorimetry (DSC) and molecular dynamics (MD) simulation was used to determine the level of binding binding energy between urea-formaldehyde resin binder (UF) and RDX. In addition, to investigate the optimal reaction temperature for the preparation of MUF/RDX, the binding energy between UF and RDX at different temperatures was simulated. And then the morphology and thermal properties of the as-prepared composite energetic microspheres were analyzed by scanning electron microscopy (SEM) and DSC, the impact... [more]
Unsteady Characteristics of Forward Multi-Wing Centrifugal Fan at Low Flow Rate
Yuxin Lun, Xinxue Ye, Limin Lin, Cunlie Ying, Yikun Wei
December 9, 2019 (v1)
Keywords: centrifugal fan, frequency spectrum, large eddy simulation, pressure fluctuation, unsteady flow
The unsteady flow characteristics of a forward multi-wing centrifugal fan under a low flow rate are studied using the computational fluid dynamics (CFD) method. This paper emphasizes the eddy current distribution in terms of the Q criterion method, as well as pressure fluctuation, frequency spectrum, and kinetic energy spectrum analysis of internal monitoring points in a forward multi-wing centrifugal fan. The numerical results show that abnormal eddies mainly appear at the volute outlet and near the volute tongue, boundary layer separation occurs near the suction surface of the blade, and shedding eddies appear at the trailing edge of the blade with the time evolution. The unsteady flow characteristics of a forward multi-wing centrifugal fan at a small flow rate provide significant physical insight into understanding the internal flow law.
Numerical Analysis of Two-Phase Flow in the Cavitation Process of a Waterjet Propulsion Pump System
Weixuan Jiao, Li Cheng, Jing Xu, Chuan Wang
December 9, 2019 (v1)
Keywords: cavitation, numerical simulation, pump, two-phase flow, waterjet propulsion system
The waterjet propulsion system has been widely used in the military and civil fields because of its advantages of in terms of high efficiency and energy savings. In order to study the three-dimensional cavitation flow in the waterjet propulsion pump, the cavitation process of the waterjet propulsion pump was simulated numerically using the Zwart−Gerber−Belamri cavitation model and the RNG (Renormalization Group) k-ε model. The simulation results of cavitation on the waterjet propulsion pump and pump system show that, in the initial stage of cavitation, vapors first collect on the leading edge of the suction surface of the blade near the rim of the impeller. As the total pressure at the impeller inlet decreases, the cavitation region expands toward the trailing edge and the vapor fraction volume gradually increases. In order to simulate the cavitation state of the waterjet propulsion pump under the actual working conditions, a numerical simulation of the entire waterjet propulsion pump... [more]
Numerical Investigation on the Mechanism of Double-Volute Balancing Radial Hydraulic Force on the Centrifugal Pump
Ye Yuan, Shouqi Yuan, Lingdi Tang
December 9, 2019 (v1)
Keywords: centrifugal pump, double-volute, radial hydraulic force, steady pressure distribution, transient pressure variation
Double-volute is an effective technique to reduce radial hydraulic force on the centrifugal pump and thereby mitigate the pump-casing vibration induced by unsteady flow characteristics. The mechanism of the double-volute structure balancing radial force on the impeller and volute was investigated on the basis of volute cross-sections by using Computational Fluid Dynamics (CFD) method. The tested performances and simulated inner-flow characteristics of two pumps with single-volute and double-volute were compared in this paper. The performance-test results verify the veracity of CFD method and illustrate that double-volute pump has some losses in terms of pump head and operation efficiency. The numerical simulations reveal that double-volute pump has smaller radial-force magnitude than single-volute pump on the abnormal conditions. Steady pressure field and transient pressure variations of pumps were explored to account for radial-force characteristics of double-volute pump. Compared wit... [more]
Modeling and Analysis of Coal-Based Lurgi Gasification for LNG and Methanol Coproduction Process
Jingfang Gu, Siyu Yang, Antonis Kokossis
December 9, 2019 (v1)
Keywords: coproduction, cryogenic separation, Liquified Natural Gas, Lurgi syngas, methanol synthesis
A coal-based coproduction process of liquefied natural gas (LNG) and methanol (CTLNG-M) is developed and key units are simulated in this paper. The goal is to find improvements of the low-earning coal to synthesis natural gas (CTSNG) process using the same raw material but producing a low-margin, single synthesis natural gas (SNG) product. In the CTLNG-M process, there are two innovative aspects. Firstly, the process can co-generate high value-added products of LNG and methanol, in which CH4 is separated from the syngas to obtain liquefied natural gas (LNG) through a cryogenic separation unit, while the remaining lean-methane syngas is then used for methanol synthesis. Secondly, CO2 separated from the acid gas removal unit is partially reused for methanol synthesis reaction, which consequently increases the carbon element utilization efficiency and reduces the CO2 emission. In this paper, the process is designed with the output products of 642,000 tons/a LNG and 1,367,800 tons/a methan... [more]
Numerical Simulation of Darcy−Forchheimer 3D Unsteady Nanofluid Flow Comprising Carbon Nanotubes with Cattaneo−Christov Heat Flux and Velocity and Thermal Slip Conditions
Jamshaid ul Rahman, Umair Khan, Shafiq Ahmad, Muhammad Ramzan, Muhammad Suleman, Dianchen Lu, Saba Inam
December 9, 2019 (v1)
Keywords: carbon nanotubes, Cattaneo–Christov heat flux, Darcy–Forchheimer flow, nanofluid flow, numerical solution
A mathematical model comprising Darcy Forchheimer effects on the 3D nanofluid flow with engine oil as a base fluid containing suspended carbon nanotubes (CNTs) is envisioned. The CNTs are of both types i.e., multi-wall carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). The flow is initiated by an exponentially stretched surface. The impacts of Cattaneo−Christov heat flux along with velocity and thermal slip conditions are key factors in the novelty of the defined model. The boundary layer notion is designed to convert the compact form of equations into the component shape. Appropriate transformations lead to differential equations with high nonlinearity. The final non-dimensional system is solved numerically by a “MATLAB” function known as bvp4c. For both CNTs, different graphical sketches are drawn to present the influence of arising parameters versus related profiles. The outcomes show that higher slip parameter boosts the axial velocity, whereas fluid temperature... [more]
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