检索结果-内蒙古大学图书馆

Transition from bubble flow to slug flow along the streamwise direction in a gas-liquid swirling flow

CHEMICAL engineering SCIENCE 2019年 202卷 392-402页

作者： Liu, Wen Bai, Bofeng Changzhou Univ Jiangsu Key Lab Oil Gas Storage & Transportat Tec Changzhou 213000 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

Transition from bubbly to slug flow is a well-known phenomenon. In the channel with a swirler, a transition to slug flow at a lower gas superficial velocity than in the same channel without the swirler was observed in this work. The transition phenomenon from bubble flow to slug flow under the effect of swirl in a circular pipe was observed and investigated. Compared to the flow pattern (maintaining the bubble flow along a streamwise direction) in a non-swirling flow, we observe that bubble flow is transformed to a gas column downstream of the swirler, then broken up, and finally separated into gas slugs in the streamwise direction. The dynamic condition for the occurrence of a liquid bridge is proposed, then combined with a swirl decay model of a gas-liquid two-phase swirling flow;thus, the axial position for the transition from a gas column to a slug flow along the streamwise direction can be predicted. Whether slug flow always remains along the streamwise direction is closely related to its size. Under the effect of swirl, the void fraction is decreased and the pressure drop is increased compared with that in a non-swirling flow, and gradually approximates the values of a non-swirling flow along the streamwise direction. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Swirling flow Gas column Bubble Decay Slug flow

来源：评论

学校读者我要写书评

暂无评论

Application of the Improved Spacer Grid Model in Subchannel Analysis Code

引用

NUCLEAR TECHNOLOGY 2019年第1-2期205卷 352-363页

作者： Dong, Siying Liu, Wei Liu, Yang Shan, Jianqiang Xi An Jiao Tong Univ State Key Lab Multiphase Flow Xianning West Rd 28 Xian 710049 Shaanxi Peoples R China Nucl Power Inst China State Key Lab Reactor Syst Design Technol Chengdu Sichuan Peoples R China

In most subchannel analysis codes, spacer grids are simulated using an effective loss coefficient that can account only for the spacer grid's mean axial effect on the pressure drop. Since the mixing vane spacer grid (MVG) in a rod bundle has great influence on local flow fields, neglecting the effect of mixing vanes will degrade fidelity and resolution in thermal-hydraulic calculation. This paper focuses on improving the spacer grid model in subchannel analysis. First, cross-flow mixing effects of MVGs are accounted for by applying the distributed resistance method. By choosing resistance correlation appropriately and considering the geometric dimensions of mixing vanes, the source term of mixing vanes can be represented quantitatively in the axial and lateral momentum equations of a subchannel analysis code. Second, the Carlucci model is used to calculate mixing rates, and obstruction factor Fobs is introduced to consider turbulent mixing effects caused by spacer grids. The improved MVG cross-flow model and turbulent mixing model are implemented in the subchannel code ATHAS. Validation is provided for the 5 x 5 rod bundle experiments provided by Karoutas et al. [Proc. 7th Int. Mtg. Nuclear Reactor Thermal-Hydraulics (NURETH-7), Saratoga, New York (1995)] and high-quality experimental data provided by the Organisation for Economic Co-operation and Development/U.S. Nuclear Regulatory Commission Pressurized Water Reactor Subchannel and Bundle Test (PSBT) benchmark to demonstrate their effects and accuracy. From the validation, it can be concluded that the calculated lateral velocities agree well with those provided by the experimental data. In addition, the improved cross-flow and turbulent mixing models significantly increase the accuracy of predictions of exit subchannel coolant temperatures, with reduction in root-mean-square error to be 2.27 K.

关键词： Subchannel analysis spacer grid model mixing vanes distributed resistance method turbulent mixing

来源：评论

学校读者我要写书评

暂无评论

Dynamic modeling and behavior of parabolic trough concentrated solar power system under cloudy conditions

引用

ENERGY 2019年 177卷 106-120页

作者： Wang, Anming Liu, Jiping Liu, Ming Li, Gen Yan, Junjie Xi An Jiao Tong Univ MOE Key Lab Thermal Fluid Sci & Engn Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

As a promising application of solar energy, parabolic trough concentrating solar power with indirect thermal energy storage has been widely used in concentrating solar power plants constructed in China. The dynamic modeling and behavior of the power plants were important for achieving fast start-up and shut down and to overcome weather disturbances. This study investigated the dynamic characteristics of a 50 MW parabolic trough concentrating solar power plant with indirect thermal energy storage. Simplified cloud disturbances were simulated to obtain the dynamic characteristics of a power block coupled with solar field and thermal energy storage. Simulation results indicated that the thermal inertia of solar field is an order of magnitude larger than that of power block and thermal energy storage subsystems, and the heat transfer fluid temperature at the solar field outlet fluctuates within a narrow range at rated value under the control scheme of solar field. The disturbances caused by heat transfer fluid temperature fluctuation were reduced by thermal energy storage operation. To minimize the generation load fluctuation under thick-cloud condition, the thermal energy stored in solar field could be used to moderate the fluctuation caused by the start-up of thermal energy storage discharging exchanger. (C) 2019 Published by Elsevier Ltd.

关键词： Parabolic trough concentrating solar power Clouds disturbances Second-scale dynamic modeling Dynamic behaviors

来源：评论

学校读者我要写书评

暂无评论

Computational fluid dynamics investigation on the effect of co-firing semi-coke and bituminous coal in a 300MW tangentially fired boiler

引用

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF power AND ENERGY 2019年第2期233卷 221-231页

作者： Du, Yongbo Wang, Chang'an Wang, Pengqian Meng, Yi Wang, Zhichao Yao, Wei Che, Defu Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xian Thermal Power Res Inst Co Ltd Xian Shaanxi Peoples R China

In this paper, the effect of co-firing semi-coke in a 300MW tangentially fired boiler was numerically investigated. The results indicate that the incomplete combustion heat loss and NOx emission both increase with semi-coke co-fired ratio. Semi-coke may be injected into the furnace at a different height, which can lead to different thermal efficiency and NOx emission. It is suggested that semi-coke should not be fed from the top or bottom layer burners, since this could give rise to high carbon content respectively in fly ash and bottom slag. In addition, injecting semi-coke from the top burners could significantly increase the NOx emission. Under 1/2 co-firing ratio, the optimal fuel allocation is that feeding semi-coke from the B, D, and E layer burners. The growth in semi-coke particle size could increase the unburned carbon loss and NOx emission. It is highly recommended to reduce the unburned carbon loss under semi-coke co-fired condition by increasing the stoichiometric ratio of primary air for semi-coke. As it is increased from 0.25 to 0.3, the combustion efficiency of the co-fired condition is 99.47%, the same as when only firing bituminous coal, and the NOx emission is about 30% higher.

关键词： Pulverized boiler semi-coke co-firing NOx emission computational fluid dynamics

来源：评论

学校读者我要写书评

暂无评论

Non-equilibrium spontaneous condensation flow in cryogenic turbo-expander based on mean streamline off-design method

引用

CRYOGENICS 2019年 98卷 18-28页

作者： Niu, Lu Chen, Xingya Sun, Wan Chen, Shuangtao Hou, Yu Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Chongqing Univ Key Lab Low Grade Energy Utilizat Technol & Syst Chongqing 400044 Peoples R China

In a modem cryogenic liquefaction system, the turbo-expander is used to operate in the two-phase region so that a high cooling capacity can be provided. Compared with the expansion process in a conventional over-heated turbo-expander, non-equilibrium condensation occurs in the duct when the turbo-expander operates in the two-phase region, which varies the expansion process. In our previous works, the simulation by CFX can predict the nucleation process controlled by gaseous sub-cooling well, and the outlet liquid fraction has a good agreement with our experimental data. As the non-equilibrium condensation simulated by using CFX consumes much time and massive computing resource, it is not feasible to simulate the two-phase expansion in the turbo-expander in a wide off-design range. In this study, we investigate the non-equilibrium spontaneous condensation along the mean streamline of a cryogenic turbo-expander passage by using an off-design computational code compiled by Matlab. The two-phase off-design computational code is developed from our previous overheated off-design code. The calculation function of thermodynamic parameters on the mean streamline and non-equilibrium condensation module are integrated with this code. The variations of thermodynamic parameters on the mean streamline in a non-equilibrium condensation process are simulated. Nucleation onset, droplet growth/vaporization process, liquid fraction distribution are revealed. Droplet developing region is divided according to the droplet critical and mean radius. Simulation results of five two-phase cases are compared and analyzed, and different non-equilibrium condensation features and liquid fraction distributions are found. At last, isentropic efficiency and outlet liquid fraction are used to evaluate two-phase expansion performance, and it is found that the performance results from the simulation in five cases agree with experimental data well.

关键词： Cryogenic turbo-expander Two-phase off-design prediction Non-equilibrium condensation Liquid fraction Droplet growth

来源：评论

学校读者我要写书评

暂无评论

A high-safety and multifunctional MOFs modified aramid nanofiber separator for lithium-sulfur batteries

引用

CHEMICAL engineering JOURNAL 2021年 411卷 128540-128540页

作者： Liu, Jianwei Wang, Jianan Zhu, Lei Chen, Xin Ma, Qianyue Wang, Ling Wang, Xi Yan, Wei Xi An Jiao Tong Univ Dept Environm Sci & Engn State Key Lab Multiphase Flow Power Engn 28 Xianning West Rd Xian 710049 Peoples R China Weinan Normal Univ Sch Phys & Elect Engn Chaoyang St Weinan 714099 Peoples R China

High-level safety is the essential precondition for the future large-scale applications of the high-energy storage systems. In terms of the lithium-sulfur (Li-S) batteries, the low flash point and poor mechanical strength of the conventional polyolefin separator are the potential safety hazards to cause the fire and explosion in extreme environment. Herein, a thermotolerant and nonflammable hierarchical functional separator (Z-PMIA separator) is designed based on the poly(m-phenylene isophthalamide) (PMIA) membrane and the in-situ formed Co-containing zeolitic imidazolate framework ZIF-L(Co) secondary nanostructures. Benefiting from the feature of "Aramid" fibers and the special secondary ZIF-L(Co) nanostructures, the Z-PMIA separator not only guarantees high mechanical strength (suffering from a tensile strength of 15 MPa and a puncture force of 0.95 N) and remarkable thermal stability (no dimensional shrinkage even at 200 degrees C) but also effectively suppresses the polysulfide shuttle and lithium dendrite growth. As a result, the Z-PMIA separator delivers a high initial discharge capacity of 1391.2 mAh g(-1) and a discharge capacity of 961.1 mAh g(-1) after 350 cycles at 0.2C, with a slow capacity attenuation of 0.033% per cycle. Even under the conditions of high sulfur loading (9.23 mg cm(-2)) and low electrolyte/sulfur (E/S) ratio (8 mL g(-1)) or when running at a high temperature (80 degrees C), the Z-PMIA separator still enables a high charging/discharging performance, highlighting its promising commercial prospect for future high-safety and high-performance energy storage systems.

关键词： Lithium-sulfur batteries Safety separator Aramid nanofibers Shuttle effect Lithium dendrites

来源：评论

学校读者我要写书评

暂无评论

Non-thermal plasma coupled with MOF-74 derived Mn-Co-Ni-O porous composite oxide for toluene efficient degradation

引用

JOURNAL OF HAZARDOUS MATERIALS 2020年 383卷 121143-000页

作者： Feng, Xiangbo Chen, Changwei He, Chi Chai, Shouning Yu, Yanke Cheng, Jie Xijing Univ Shaanxi Key Lab Safety & Durabil Concrete Xian 710123 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Univ Chinese Acad Sci Natl Engn Lab VOCs Pollut Control Mat & Technol Beijing 101408 Peoples R China Columbia Univ Dept Chem Engn New York NY 10027 USA Chongqing Univ Sci & Technol Inst Hlth & Environm Chongqing 401331 Peoples R China

A novel strategy for removal of toluene by non-thermal plasma (NTP) coupled with metal-organic frameworks (MOFs) derived catalyst was proposed in this work. The MOF-derived porous trimetallic oxide catalyst (MnCoNiOx, MCNO) was prepared by simple pyrolysis of a MOF-74(Mn-Co-Ni) precursor. We found that the MCNO material can well synergy with NTP in total decomposition of toluene owing to its high specific surface area, regular porous structure and excellent reducibility, which endow superior catalytic activity and CO2 selectivity of NTP-MCNO system compared to that of NTP-MnOx, NTP-CoOx and NTP-NiOx. For instance, the toluene degradation efficiency can reach up to 75.7% in NTP-MCNO system with a low specific input energy of 101 J/L, much higher than that of NTP-MnOx (59.3%), NTP-CoOx (70.9%), NTP-NiOx (65.0%) and NTP alone (42.9%). Moreover, the formed ozone (O-3) can be well-controlled by the NTP-MCNO system due to the spinel-type oxides (MCNO) derived from MOF could generate more open-formwork structure and improve the mobility of oxygen. The results of this work would shed light on rational design and preparation of spinel-type oxides for oxidation applications, which provides guidance for further improvement of plasma-catalysis system.

关键词： Metal-organic frameworks Non-thermal plasma Porous MnCoNiOx oxide Toluene decomposition Selectivity

来源：评论

学校读者我要写书评

暂无评论

Stability and activity of a co-precipitated Mg promoted Ni/Al2O3 catalyst for supercritical water gasification of biomass

引用

INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2019年第30期44卷 15842-15852页

作者： Li, Sha Guo, Liejin Nanjing Univ Sci & Technol Sch Energy & Power Engn Nanjing 210094 Jiangsu Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China

We have investigated the stability and activity of a co-precipitated Mg promoted Ni/Al2O3 catalyst (Ni-Mg-Al) for supercritical water gasification (SCWG) of various biomass model compounds and real biomass. Phase stability and activity recovery of the Ni-Mg-Al catalyst were first compared with a catalyst prepared by impregnation method. It was found that the co-participated catalyst showed higher activity recoveries than the impregnated catalyst due to the stable Ni crystal size. Then, effects of SCWG variables including heating up rate, gasification temperature, catalyst loading amount and feedstock concentration, on the non-catalytic and catalytic gas yields and gasification efficiencies of glucose and phenol were evaluated. Results demonstrated that the presence of sufficient amount of Ni catalyst could realize complete carbon gasification of different organics, including phenol and real biomass. Catalyzed by Ni, CH4 was the more favored produced gas at 400-500 degrees C while H-2 yields were more abundant at 500-600 degrees C. Without catalyst, carbon gasification efficiencies of SCWG of different feedstock were in the order: glycerol > glucose > cellulose approximate to corncob approximate to poplar leaf approximate to sawdust > phenol, while those catalyzed by Ni were in the order: glycerol approximate to glucose approximate to cellulose approximate to phenol > corncob approximate to poplar leaf approximate to sawdust, illustrating that the co-precipitated Ni Mg Al catalyst is more active on catalyzing the gasification of water-soluble organics than real biomass. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Supercritical water gasification Nickel catalyst Hydrogen production Phenol Biomass

来源：评论

学校读者我要写书评

暂无评论

Study on Dynamic Characteristics of a 600MW Ultra-Supercritical Double-Reheat Boiler 10

Study on Dynamic Characteristics of a 600MW Ultra-Supercriti...

引用

10th International Conference on Applied Energy (ICAE)

作者： Wang, Zhu Liu, Ming Wang, Chaoyang Chong, Daotong Yan, Yunjie Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

Based on the GSE software, the simulation model of an ultra-supercritical double-reheat tower boiler was established, and its reliability was checked with design data. Then, the dynamic characteristics of the ultra-supercritical double-reheat boiler were studied. Simulation results reveal the response times of different input parameters greatly vary. When stepping disturbances to the feed-coal rate, feed-water rate, and feed-water temperature, the response time under feed-water's temperature disturbance is the longest, which is about 1, 800 s. When the same input parameter disturbs, the output parameters have the same response tendency with different amplitudes. Moreover, the fiercer the disturbance is, the more greatly the parameter changes. (C) 2019 The Authors. Published by Elsevier Ltd.

关键词： double-reheat dynamic characteristics GSE

来源：评论

学校读者我要写书评

暂无评论

Automatic differentiation approach for solving one-dimensional flow and heat transfer problems

引用

ANNALS OF NUCLEAR ENERGY 2021年 160卷 108361-108361页

作者： Niu, Yuhang He, Yanan Xiang, Fengrui Zhang, Jing Wu, Yingwei Tian, Wenxi Su, Guanghui Qiu, Suizheng Xi An Jiao Tong Univ Sch Nucl Sci & Technol Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Adv Nucl Energy & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Traditional reactor system analysis tools are confronted with challenging difficulties in model development, low accuracy, and poor convergence. To solve these problems, the automatic differentiation (AD) method that allows the automatic numerical calculation of derivatives of functions was adopted to develop the reactor system code in this paper. For the simulation of single-phase models, the steady and transient responses were presented to investigate the effects of the spatial and temporal discretization schemes on modeling accuracy and efficiency. Meanwhile, the comparison of convergence performance between the automatic differentiation using operator overloading (ADOO) and the traditional hand-coded method was completed. Further, in the case of two-phase flow problems, the high-order discrete schemes were applied in this code. It was demonstrated that the reactor system code with single-phase and five-equation two-phase flow models, which adopted the high-order discretization and the ADOO method, performed very well for one-dimensional flow and heat transfer problems. (C) 2021 Published by Elsevier Ltd.

关键词： Automatic differentiation Single-phase and two-phase flow High-order discretization flow and heat transfer

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：