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Simulation of horizontal slug-flow pneumatic conveying with kinetic theory

GU Zhengmeng, GUO Liejin

《能源前沿（英文）》 2007年第1卷第3期页码 336-340 doi: 10.1007/s11708-007-0050-6

摘要： Wavelike slug-flow is a representative flow type in horizontal pneumatic conveying. Kinetic theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this paper. Wavelike motion of particulate slugs in horizontal pipes was numerically investigated. The formation and motion process of slugs and settled layer were simulated. The characteristics of the flow, such as pressure drop, air velocity distribution, slug length and settled layer thickness, and the detailed changing characteristics of slug length and settled layer thickness with air velocity were obtained. The results indicate that kinetic theory can represent the physical characteristics of the non-suspension dense phase flow of wavelike slug pneumatic conveying. The experiment in this paper introduced a new idea for the numerical calculation of slug-flow pneumatic conveying.

关键词： velocity distribution detailed slug-flow gas-solid theory

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城市给水管网恒定流和瞬变流数学模型研究

汪守东,沈永明,姜恒志

《中国工程科学》 2007年第9卷第12期页码 26-30

摘要：

首先基于节点方程法，建立了给水管网恒定流数学模型，并采用经改进的牛顿迭代法实现了对模型的求解；其次由特征线法建立了给水管网瞬变流数学模型，可预测管网运行中出现的有害水击，并求得可能出现的最大(最小)水压及其相应发生的位置。实例研究表明，建立的模型是可靠的，且具有计算速度快、精度高等优点，可以用于城市给水管网的水力平衡数值模拟研究和为设计者防护水击所采取的措施提供理论依据。

关键词：给水管网恒定流瞬变流水击牛顿迭代法

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Three-dimensional numerical simulation of flow in trapezoidal cutthroat flumes based on FLOW-3D

Danjie RAN, Wene WANG, Xiaotao HU

《农业科学与工程前沿（英文）》 2018年第5卷第2期页码 168-176 doi: 10.15302/J-FASE-2018217

摘要： To solve the common problem of flumes flow-measurement accuracy without sacrificing water head, a new type of trapezoidal cutthroat flume to measure the discharge in terminal trapezoidal channels is presented. Using the computational fluid dynamic method, three-dimensional flow fields in trapezoidal cutthroat flumes were simulated using the RNG three-dimensional turbulence model along with the TruVOF technique. Simulations were performed for 12 working conditions, with discharges up to 0.075 m ·s to determine hydraulic performance. Experimental data for the trapezoidal cutthroat flume in terminal trapezoidal channel were also obtained to validate the simulation results. Velocity distribution of the flume obtained from simulation analyses were compared with observed results based on time-averaged flow field and comparison yielded a solid agreement between results from the two methods, with relative error below 10%. The results indicated that the Froude number and the longitudinal average velocity increased along the convergence section and decreased in the divergent section. In the upper throat, the Froude number was less than 0.5, which meets the water measurement requirement, and the critical flow appeared near the throat section. The maximum water head loss of the trapezoidal cutthroat flume was less than 9% of the total head, compared to the rectangular cutthroat flume, and head loss of trapezoidal cutthroat flume was significantly less. Regression models developed for upstream depth versus discharge under different working conditions were satisfactory, with a relative error of less than 2.06%, which meets the common requirements of flow measurement in irrigation areas. It was concluded that trapezoidal cutthroat flumes can improve flow-measurement accuracy without sacrificing water head.

关键词： distribution of velocity Froude number head loss stage-discharge relationship trapezoidal cutthroat flume

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Effect of inlet box on performance of axial flow fans

LI Jingyin, TIAN Hua, YUAN Xiaofang

《能源前沿（英文）》 2008年第2卷第4期页码 390-394 doi: 10.1007/s11708-008-0087-1

摘要： Numerical investigations on 3D flow fields in an axial flow fan with and without an inlet box have been extensively conducted, focusing on the variation of fan performance caused by the internal flow fields and the velocity evenness at the exit of the inlet box. It is interesting to find that although the inlet box is well designed in accordance with basic design principles, there is a flow separation region in it. Furthermore, this flow separation and the resulting uneven velocity distribution at the exit lead to some decrease in the efficiency and an increase in the total pressure rise of the fan. This research shows that the inlet box needs further improvement and such a check on the flow fields is of value for the design of inlet boxes.

关键词： box velocity distribution accordance Numerical variation

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Characterization of 3D microstructure, thermal conductivity, and heat flow of cement-based foam using

《结构与土木工程前沿（英文）》 2021年第15卷第3期页码 643-651 doi: 10.1007/s11709-021-0709-9

摘要： This study presents the results of the 3D microstructure, thermal conductivity, and heat flow in cement-based foams and examines their changes with a range of densities. Images were captured using X-ray micro computed tomography (micro-CT) imaging technique on cement-based foam samples prepared with densities of 400, 600, and 800 kg/m³. These images were later simulated and quantified using 3D data visualization and analysis software. Based on the analysis, the pore volume of 11000 µm³ was determined across the three densities, leading to optimal results. However, distinct pore diameters of 15 µm for 800 kg/m³, and 20 µm for 600 and 400 kg/m³ were found to be optimum. Most of the pores were spherical, with only 10% appearing elongated or fractured. In addition, a difference of 15% was observed between the 2D and 3D porosity results. Moreover, a difference of 5% was noticed between the experimentally measured thermal conductivity and the numerically predicted value and this variation was constant across the three cast densities. The 3D model showed that heat flows through the cement paste solids and with an increase in porosity this flow reduces.

关键词： 3D pore volume distribution X-ray tomography 3D shape factor heat flow

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Numerical analysis of 3-D unsteady flow in a vaneless counter-rotating turbine

ZHAO Qingjun, WANG Huishe, ZHAO Xiaolu, XU Jianzhong

《能源前沿（英文）》 2007年第1卷第3期页码 352-358 doi: 10.1007/s11708-007-0053-3

摘要： To reveal the unsteady flow characteristics of a vaneless counter-rotating turbine (VCRT), a three-dimensional, viscous, unsteady computational fluid dynamics (CFD) analysis was performed. The results show that unsteady simulation is superior to steady simulation because more flow characteristics can be obtained. The unsteady effects in upstream airfoil rows are weaker than those in downstream airfoil rows in the VCRT. The static pressure distribution along the span in the pressure surface of a high pressure turbine stator is more uniform than that in the suction surface. The static pressure distributions along the span in the pressure surfaces and the suction surfaces of a high pressure turbine rotor and a low pressure turbine rotor are all uneven. The numerical results also indicate that the load of a high pressure turbine rotor will increase with the increase of the span. The deviation is very big between the direction of air flow at the outlet of a high pressure turbine rotor and the axial direction. A similar result can also be obtained in the outlet of a low pressure turbine rotor. This means that the specific work of a high pressure turbine rotor and a low pressure turbine rotor is big enough to reach the design objectives.

关键词： unsteady flow three-dimensional pressure distribution similar result unsteady simulation

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Development of a novel two-stage proportional valve with a pilot digital flow distribution

Qiang GAO, Yuchuan ZHU, Changwen WU, Yulei JIANG

《机械工程前沿（英文）》 2021年第16卷第2期页码 420-434 doi: 10.1007/s11465-020-0622-2

摘要： Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel two-stage proportional valve with a pilot digital flow distribution is proposed from the viewpoint of the dual nozzle-flapper valve’s working principle. In particular, the dual nozzle-flapper is decoupled by two high-speed on/off valves (HSVs). First, the working principle and mathematical model of the proposed valve are determined. Then, the influences of the control parameters (duty cycle and switching frequency) and structural parameters (fixed orifice’s diameter and main valve’s spring) on the main valve’s motion are analyzed on the basis of theory, simulation, and experiment. In addition, in optimizing the value of the fixed orifice’s diameter, a new design criterion that considers the maximum pressure sensitivity, flow controllability, and flow linearization is proposed to improve the balance between the effective displacement and the displacement fluctuation of the main valve. The new scheme is verified by simulations and experiments. Experimental results of the closed-loop displacement tracking have demonstrated that the delay time of the main valve is always within 3.5 ms under different working conditions, and the tracking error can be significantly reduced using the higher switching frequency. The amplitude–frequency experiments indicate that a ‒3 dB-frequency of the proposed valve can reach 9.5 Hz in the case of±50% full scale and 15 Hz in the case of 0%–50% full scale. The values can be further improved by increasing the flow rate of the pilot HSV.

关键词： two-stage proportional valve digital flow distribution high-speed on/off valve position tracking characteristic dynamic performance

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Removal, distribution and plant uptake of perfluorooctane sulfonate (PFOS) in a simulated constructed

Weichuan Qiao, Rong Li, Tianhao Tang, Achuo Anitta Zuh

《环境科学与工程前沿（英文）》 2021年第15卷第2期 doi: 10.1007/s11783-020-1312-3

摘要： Abstract • PFOS was removed by soil adsorption and plant uptake in the VFCW. • Uptake of PFOS by E. crassipes was more than that of C. alternifolius. • PFOS in wastewater can inhibit the removal of nutrients. • Dosing with PFOS changed the soil microbial community in the VFCW. A vertical-flow constructed wetland (VFCW) was used to treat simulated domestic sewage containing perfluorooctane sulfonate (PFOS). The removal rate of PFOS in the domestic sewage was 93%–98%, through soil adsorption and plant uptake, suggesting that VFCWs can remove PFOS efficiently from wastewater. The removal of PFOS in the VFCW was dependent on soil adsorption and plant uptake; moreover, the percentage of soil adsorption was 61%–89%, and was higher than that of the plants uptake (5%–31%). The absorption capacity of Eichhornia crassipes (E. crassipes) (1186.71 mg/kg) was higher than that of Cyperus alternifolius (C. alternifolius) (162.77 mg/kg) under 10 mg/L PFOS, and the transfer factor of PFOS in E. crassipes and C. alternifolius was 0.04 and 0.58, respectively, indicating that PFOS is not easily translocated to leaves from roots of wetland plants; moreover, uptake of PFOS by E. crassipes was more than that of C. alternifolius because the biomass of E. crassipes was more than that of C. alternifolius and the roots of E. crassipes can take up PFOS directly from wastewater while C. alternifolius needs to do so via its roots in the soil. The concentration of 10 mg/L PFOS had an obvious inhibitory effect on the removal rate of total nitrogen, total phosphorus, chemical oxygen demand, and ammonia nitrogen in the VFCW, which decreased by 15%, 10%, 10% and 12%, respectively. Dosing with PFOS in the wastewater reduced the bacterial richness but increased the diversity in soil because PFOS stimulated the growth of PFOS-tolerant strains.

关键词： Vertical-flow constructed wetland Perfluorooctane sulfonate Wetland plants Soil microbial community Effect Speciality: Wetlands Transformation Organic pollutants Phytoremediation Exposure assessment Sewage

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Method of internal 3D flow field numerical simulation for hydrodynamic torque converter

SHANG Tao, ZHAO Dingxuan, ZHANG Yuankun, GUO Xiangen, SHI Xiangzhong

《机械工程前沿（英文）》 2008年第3卷第1期页码 86-90 doi: 10.1007/s11465-008-0012-7

摘要： To enhance the performance of a hydrodynamic torque converter and thoroughly understand the trait of inside flow, a numerical simulation method of internal 3D flow for the three-element centrifugal hydrodynamic torque converter was systematically researched and expatiated in this paper. First, the internal flow field of each impeller was calculated. The curves that illustrate the relationships between the pressure differences of the inlet and outlet versus flux were drawn. Second, the concurrent working point of each impeller was approximately estimated. Finally, a calculation was performed considering the influence on each impeller. The flow field of a working point was solved by multiple calculations and the actual working condition was gradually determined. The pressure and velocity distributions of the flow field were proposed. The performance parameters of the hydrodynamic torque converter were predicted. The calculation method, and the proposed pressure and velocity distribution of the flow field, have practical significance for the design and improvement of a hydrodynamic torque converter.

关键词： velocity distribution calculation numerical simulation three-element centrifugal converter

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Discrete element method modeling of corn-shaped particle flow in rectangular hopper

He TAO, Baosheng JIN, Wenqi ZHONG, Xiaofang WANG,

《结构与土木工程前沿（英文）》 2010年第4卷第2期页码 267-275 doi: 10.1007/s11709-010-0035-0

摘要： Discrete element method (DEM) was developed to simulate the corn-shaped particles flow in the hopper. The corn-shaped particle was described by four overlapping spheres. Contact force and gravity force were considered when establishing the model. In addition, flowing characteristic of particles in the hopper was studied. The effect of friction coefficient on the wall pressure, voidage and velocity distribution was analyzed. The results show that the discharge rate decreases with the friction coefficient increasing; and the “over-pressure” phenomenon occurs in the discharging process for two different friction coefficients. The voidage also increases as the friction coefficient increasing. And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.

关键词： discrete  element   method  (DEM)   non-spherical voidage pressure velocity distribution hopper

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渠网恒定流及非恒定流数学模型的研究及应用

张明亮,沈永明

《中国工程科学》 2007年第9卷第8期页码 92-96

摘要：

从求解一维圣维南方程组的Preissmann 4点隐式差分格式出发, 建立了一维河网及渠网数学模型，并对计算中所涉及的一些关键技术问题进行了较为详细的阐述。利用模型对树状渠网的恒定流及复杂的环状渠网和河网的非恒定流对模型进行验证。验证结果表明，水位和流量过程计算值与Islam的计算值吻合较好，各渠道的流量分配计算结果精度也较高，为河网及渠网的水量调度提供了一个较为简便实用的工具，为建立渠网及河网的综合水质生态数学模型打下基础。

关键词： Preissmann格式渠网及河网流量分配水质模型

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圆形重力式网箱流场效应的试验研究

刘超,关长涛,崔勇,赵侠,李梦杰,李真真,王腾腾

《中国工程科学》 2014年第16卷第9期页码 69-77

摘要：

为探索圆形重力式网箱在动态流场中的水动力学特性，同时获得网箱系统内部与周围流场分布及流速变化规律，设计了4 种不同网目形状和不同网目大小的网箱模型（C1、C2、C3、C4），选取4 种不同水流流速（0.068 m/s、0.105 m/s、0.143 m/s、0.182 m/s），分别采用声学多普勒流速仪（ADV）和粒子图像测速（PIV）技术对网箱系统内外的流速及流场变化进行测定。结果表明，ADV试验与PIV技术测量结果基本一致；来流速度不同时，单个网箱范围内的水流衰减程度差异不大；来流速度相同时，小网目网箱的减流效果优于大网目网箱；网目大小相同时，菱形网目网箱减流效果优于方形网目网箱；群组网箱减流效果明显，且随着水流通过网箱数目的增加，网箱内与网箱后的流速降低明显，其中第2 个网箱中心的流速衰减率已经达到了67.6 %，第4 个网箱中心的流速衰减率为88.2 %，网箱后的流速衰减率为72.1 %。研究结果可为养殖生产实践中网箱类型的选择提供理论参考。

关键词：网箱 ADV PIV 流速流场分布

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气流速度对感烟火灾探测器响应灵敏度的影响

谢启源,苏国锋,袁宏永,张永明

《中国工程科学》 2005年第7卷第11期页码 76-80

摘要：

针对地下车库、空调出风口等存在高速气流的特殊场所，利用火灾探测综合模拟实验平台，根据气流是否影响烟颗粒生成过程，分别设计2种实验方案，分析比较了光电型与离子型两种感烟火灾探测器在不同气流条件下的响应灵敏度。实验结果表明，在烟颗粒生成过程不受气流影响的情况下，两种感烟探测器的响应灵敏度均随气流速度增大而下降。在气流影响烟颗粒生成过程的情况下，光电感烟探测器的灵敏度依然随着气流速度的增大而迅速下降；而离子型感烟探测器的灵敏度受气流速度影响较小，在高速气流条件下依然保持较高的灵敏度。综合分析表明，离子感烟探测器较适合在高速气流环境中工作。

关键词：气流速度感烟火灾探测器烟颗粒粒径分布

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我国低孔渗储层天然气资源大型化成藏特征与分布规律

赵文智,王红军,卞从胜,汪泽成,柳广弟

《中国工程科学》 2012年第14卷第6期页码 31-39

摘要：

低孔渗储层天然气资源是目前和未来一段时间我国天然气勘探和开发的主体，具有大型化成藏的特点。集中讨论了这类天然气资源大型化成藏的特征和分布规律，认识到成藏要素具有大型化发育与规模变化的特征，是天然气大型化成藏的基础；薄饼式、集群式成藏是天然气大型化成藏的主要样式；气源灶埋藏期规模“蓄能”和抬升期规模排气是大型化成藏重要气源输入；体积流和扩散流充注是天然气大型化成藏的主要运聚方式。低孔渗储层天然气藏的成藏分布具有近源性，成藏组合以大面积和大范围两种类型为主，成藏类型以地层—岩性圈闭为主，主要分布在海相克拉通盆地古隆起围斜区、陆内坳陷盆地广大斜坡区和向斜区以及前陆盆地缓翼斜坡等地区。低孔渗储层天然气资源大型化成藏认识的提出，提升了我国天然气资源发现潜力，扩展了勘探范围，为客观评价我国天然气主体资源总量和分布、推动有效发现大气田提供了理论基础。

关键词：低孔渗储层大型化成藏体积流扩散流薄饼式集群式

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CFD evaluation of pressure drop across a 3-D filter housing for industrial gas turbine plants

Fidelis I. ABAM,Samuel O. EFFIOM,Olayinka S. OHUNAKIN

《能源前沿（英文）》 2016年第10卷第2期页码 192-202 doi: 10.1007/s11708-016-0406-x

摘要： This paper investigated the flow distribution and total pressure drop across a designed 3-D filter housing integrated with a 3-stage filtration system using computational fluid dynamics (CFD). The filter housing model was proposed for a heavy-duty industrial gas turbine plant operating at an average ambient temperature of 20°C.The pressure drops across the classes of filters were 652.8 Pa, 2692.2 Pa, 887.8 Pa, 776.2 Pa and 2304.2 Pa for I-GB, GB-GA, GA-FA, FA-HA, and HA-O, respectively. The results obtained indicated an acceptable total pressure drop of 7.2% for the entire filter housing before filter clean-up. Although the CFD simulation result shows that small outlet flow velocity and transonic flows exist at the outlet of the filter housing, the designed filter housing was proved compatible with the studied GT, for inlet flow conditions between 600≤ ≤610 kg/s and 60≤ ≤70 m/s for the air flow rate and velocity, respectively. Furthermore, the designed filter housing could be adopted for the studied GT and locations of Usan and Maiduguri in Nigeria, and other locations with similar environmental conditions.

关键词： computational fluid dynamics (CFD) pressure drop flow distribution filter housing gas turbine