整流幕在防控水库水华中的应用研究综述

通过分析整理国内外相关研究资料,阐述整流幕的研究进展及其在国内水库的应用前景。结合水温分层、异重流等理论知识,分析应用整流幕的水动力背景,进而深入探究整流幕的控藻机理;整流幕应用水动力学原理,使能量交换、水团混合、水体分层等过程发生变化,进而改变影响藻类生长及演替的主要生境要素,如光照、水温和营养盐等,从而防控水华。应用整流幕前,通常将库区划分为上游、中游及下游3段。基于库区内不同河段的水流特性,并结合对整流幕类型及适用条件的分析,可以有针对性地开展整流幕方案以达到更好的效果。研究结果可为水库水生态环境保护提供参考。     

Influence of the gas—liquid separator design on hydrodynamic and mass transfer performance of split-channel airlift reactors

Three geometric configurations of gas–liquid separators were used in split-channel airlift reactors (0·1 m³ liquid volume; riser-to-downcomer cross-sectional area ratio = 0·7; aspect ratio = 3.6) to test the effect of geometry on hydrodynamic performance and oxygen transfer behaviour. For otherwise fixed conditions, the design of gas–liquid separators affected the induced liquid circulation rate, the depth of penetration of the bubble layer in the downcomer, the gas holdup in the downcomer, the mixing time and the overall volumetric gas–liquid oxygen transfer coefficient. The gas holdup in the riser was only marginally affected by the design of the separator. The impact of the various separator designs on hydrodynamic behaviour could be explained as emanating from a combination of the gas–liquid separating ability of the design and its hydraulic resistance.     

Pilot-scale two-phase extraction of canola

An extraction process was developed in our laboratory for rapeseed (canola) with 10% (w/w) ammonia in methanol, containing 5% (vol/vol) water, and hexane to simultaneously produce an improved meal and a high-quality oil. To remove the hazards associated with the use of ammonia, a two-phase solvent extraction, with 0.08% (w/w) sodium hydroxide replacing the ammonia, was tested on a semipilot scale with a Szego mill and a Karr reciprocating-plate extraction column. Flooding curves and appropriate agitation parameters were examined for this system. Then, the effects of polar solvent-to-seed ratio, slurry-to-hexane flow ratio, plate amplitude and plate agitation frequency on extraction efficiency were investigated. The process is technically viable for industrial application. A meal that contained 0.9% residual oil, 44.4% protein and 2.79 mmol/kg glucosinolates (moisture and oil-free basis) and a miscella with 19.5% oil were obtained.     

Vapor levitation epitaxy reactor hydrodynamics

Vapor Levitation Epitaxy (VLE) is a new epitaxial growth technique for III-V compound semiconductor crystals, characterized by upward stagnation flow of a reactant gas stream against a floating, circular semiconductor substrate wafer. In this work, the hydrodynamics of the process have been mathematically modeled by a complete solution of the governing Navier-Stokes equation to obtain radial and axial velocity profiles, pressure distribution under the wafer, and levitation height as a function of operating parameters. In addition, experimental measurements of levitation height as a function of gas flow rate for different wafers and gases have been performed. By the addition of experimental constants to the analytical solution of levitation height to account for system non-idealities, the functional dependences predicted by theory have been verified. In comparison to the complex flow occurring in other vapor phase epitaxy techniques, the hydrodynamics in the VLE reactor are simple, well behaved, and can be fully described by a few algebraic equations.     

Simulation of heat transfer and hydrodynamics for metal structured packed bed

Modeling and simulation based on computational hydrodynamics and heat transfer for metal structured packed bed are carried out to predict the flow field and temperature field, and to evaluate its performance in transport aspect. The comparison between the simulation results for the metal structured packed bed and the experimental heat transfer performance as well as pressure drop of the conventional pellet packed bed is made, which quantitatively validates that transport performance of the metal structured packed bed is much better. Furthermore, the effects of geometric parameters and the property of solid phase on heat transfer of the metal structured packed bed are discussed. It is found that at low Re, the specific surface area is a key factor to determine the heat transfer capability of the structured bed. However, when Re turns to be high, the property of solid phase and voidage of the structured packed bed will play an important role in the evaluation of its heat transfer. In light of above results, some feasible methods are available to enhance the heat transfer performance.     

用水动力学方法改善水驱开发效果

应用水动力学方法分析分井组周期性调整注水强度的水驱开发机理，分析和矿场试验结果均表明，在注水油田开发进入中高含水期，采用分井组周期性调整注水强度的方法可以改善水驱开发效果。在提高水驱原油采收率方面比单纯的周期注水法效果好，与常规法注水相比可提高原油采收率３％～１０％。该法具有简单易行、投资小、见效快、经济效益好等优点，对注水油田开发有一定的借鉴作用。     

流体力学方程在尿素工业生产中的应用

用流体力学原理分析预分离器与预蒸馏塔位差对预分离器分离效果的影响，提出选择适宜位差的方法。     

三峡船闸系统联合调试期水力学原型观测

三峡船闸金属结构及机电设备无水、有水(抽水)系统联合调试条件下，各级输水系统的原型水力学监测工作于2002年6月至2003年5月间进行。安全监测的主要项目包括闸室输水特性、阀门区段输水特性、门楣通气、闸室空化特性、阀门段空化特性、阀门及人字门启闭特性、阀门与人字门门体动力特性，监测内容多达20项。抽水调试期中间级闸首工作水头分别达到了30m、40m、46m和设计工况的45．2m，初始淹没水深达到了26m的设计条件，并进行了双边输水和单边输水、现地控制和集中控制等操作运行条件的比较。本次监测成果系统性及完整性较好，不仅为各级闸阀启闭控制系统的调试提供了可参比数据，也为船闸的验收、鉴定、运行管理提供了科学依据，保证了三峡围堰期蓄水发电和五级船闸试通航目标的实现，对国内外开展高水头船闸的设计和运行亦有十分重要的参考价值。     

苜蓿草地侵蚀产沙过程及其水动力学机理试验研究

利用人工模拟降雨试验，定量研究了不同降雨强度（45mm/h、87mm/h、127mm/h）下20°陡坡苜蓿草地的产流产沙变化规律，分析了苜蓿草地侵蚀产沙的水动力学机理。试验结果表明，苜蓿草地累积径流量和累积产沙量与降雨时间呈很好的幂函数关系，随着降雨时间的增大而增大。在45mm/h和87mm/h降雨强度时，草地径流量和侵蚀产沙量呈高-低-稳定的变化趋势，在127mm/h降雨强度时，草地径流量和侵蚀产沙量呈高-低-高的变化趋势。苜蓿草地的水土保持作用通过改变土壤的入渗特性实现，草地坡面入渗率与径流量和产沙量呈明显负线性相关。从水动力学角度对苜蓿草地径流剪切力和单位水流功率与输沙率的关系进行了分析，得出试验条件下苜蓿草地的临界径流剪切力值为2.857N/m2，临界单位水流功率值为0.0114 m/s，输沙率随径流剪切力和单位水流功率的增大而增大。