Three-Dimensional Modeling of Nonuniform Sediment Transport in an S-Shaped Channel

A three-dimensional numerical model was applied to compute uniform and nonuniform sediment transport and bed deformation in an S-shaped laboratory channel located at the University of Innsbruck, where detailed measurements of the velocity field and bed elevation changes were made. The channel had two bends, a trapezoidal cross section, and a slope of S = 0.005. Gravel with a mean diameter of 4.2?mm was used as movable bed material and for sediment feeding. Wu’s formula for multiple grain sizes was compared with van Rijn’s formula using one grain size. Fairly good agreement was found between the computed and measured bed elevations for both approaches, whereas Wu’s formula could further improve the numerical results. Looking at the physics of the erosion pattern, the computed scour areas were located slightly more downstream than what was observed in the physical model. The current study also includes several parameter tests: grid distribution in vertical, lateral, and longitudinal direction; time step; number of inner iterations/time step; active sediment layer thickness; and the Shields coefficient. The variation of those parameters gave some differences in the results, but the overall pattern of bed elevation changes remained the same.     

膜曝气生物膜-生态浮床组合装置开发及其水体净化效果研究

生物生态法是目前国内外治理河湖水体富营养化的主要方法,但使用单一净化装置的处理效果均不甚理想,故将生物生态法中的生物膜法、曝气富氧法和生态浮床法相结合,开发了一套新型膜曝气生物膜-生态浮床立式组合净化装置。试验结果表明,组合装置较水体自净和单一净化装置可显著提高水体净化效果。具体表现在:组合装置、生物膜反应器、生态浮床和河水自净作用对NH_4~+-N的去除率分别为98.0%、96.6%、66.6%和48.5%,组合装置较河水自净作用的去除率可提高49.5%;对TN的去除率分别为34.7%、26.9%、19.3%和9.6%,去除率可提高25.1%;对TP的去除率分别为60.7%、33.9%、86.9%和38.5%,去除率可提高22.2%;对COD_(Mn)的去除率分别为78.3%、53.1%、58.4%和40.2%,去除率可提高38.1%。同时,组合装置对叶绿素a同样具有最强的抑制作用且可大幅提高水体透明度,减少水体黑臭现象的发生,这一结果为该装置应用于受污染河道的水体修复提供了科学依据。     

多功能电动护理床的研制

基于人体工学原理和现代机械设计理论,采用机器人化的多自由度结构、多轴协调控制设计多功能电动护理床。床面采用多折床面结构形式,通过按键控制完成平躺、抬背、坐起、屈或伸腿等基本动作,并具有翻身、辅助解便与多轴同步等功能。应用仿真分析技术,优化了多功能护理床的机构,使床的结构符合人体工学原理。设计基于单片机的控制器控制各机构的驱动电动机来满足使用者的功能要求。完成了多功能护理床样机的研制。     

HYDRODYNAMICS AND STABILITYOF SLOT-RECTANGULAR SPOUTED BEDS. PART I: THIN BED

Spouted beds of rectangular cross-section with gas entry through bottom slots have been proposed as a means of overcoming scale-up difficulties of conventional spouted beds. A study was undertaken of bed hydrodynamics in a thin slot-rectangular column of width 150 mm and slot width 2 to 20 mm for four types of particles. Flow regimes and bed hydrodynamics are qualitatively similar to those in cylindrical spouted beds, but there are significant quantitative differences caused by the different geometry. Slot width exerts a strong influence on such features as flow regimes, maximum spoutable bed height, minimum spouting velocity, pressure drop and fountain height.     

TURBULENT RESISTANCE OF COMPLEX BED STRUCTURES

The influence of complex packing geometry on its frictional/hydrodynamic resistance was investigated both experimentally and theoretically. The complex bed structures were modelled using the cubic packing of spheres and different number of thin bands inserted between the spheres. The turbulent flow resistance of the model systems was determined experimentally on the basis of pressure drop and air flow rate measurements. In the theoretical approach these systems were regarded as compositions of two Representative Elementary Units (REU's) which contribute to the overall pressure drop within the apparatus. The values of the overall coefficient f₀ , characterising resistance of the complex geometry structures were correlated with the values of the local coefficients f_i , describing resistance of the particular REU?s. The latter ones were independently estimated using the Computational Fluid Dynamics (CFD) code.     

STUDIES OF TRANSESTERIFICATION OF KARANJA (Pongamia pinnata) OIL IN A PACKED BED REACTOR

Studies were made to determine the influence of different reaction temperatures and residence times on biodiesel yield by transesterification of karanja oil (Pongamia pinnata) in the presence of methanol using a solid acid heterogeneous catalyst in a continuous process. Recycle runs were conducted by further transesterification of the organic phases (first run mixture of methyl ester and unconverted oil) in the presence of methanol under similar conditions. High-pressure liquid chromatography (HPLC) reveals poor biodiesel yield even with an increase in the reaction temperature and residence time in the first run. Biodiesel yield obtained from the recycle runs, however, was greatly increased over that of the first-run biodiesel yield. Recycle transesterification at a reaction temperature of 240°C and residence time of 50 min gives a maximum yield value of 97.74%. Consequently, irrespective of the presence of high free fatty acids and other impurities in karanja oil, recycling the organic phase of the first run significantly enhances the biodiesel yield.     

Analysis of Fluid Dynamics Behavior of Conical Spouted Bed in Presence of Pastes

Abstract

A conical spouted bed (CSB) was employed to obtain the drying and fluid dynamics data in the presence of egg paste and glycerol for a range of operating conditions. In this case, egg paste was added continuously into the bed at several feed rates, whereas glycerol was fed in batch process. Under these conditions, minimum spouting velocity, pressure drop, fountain height, paste concentration, and film moisture content were evaluated. The results showed that ΔP_s and U_ms decreases with increasing glycerol concentration; however, U_ms presented an opposite behavior for egg paste. Fountain height increases with increasing glycerol into the bed. Film moisture content and homogenized egg paste concentration were maintained uniformly scattered at all points of the bed. In addition, the methodology proposed by Schneider and Bridgwater^{[ 1} Schneider , T. ; Bridgwater , J. The stability of wet spouted beds . Drying Technology 1993 , 11 ( 2 ), 277 – 301 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar] ^] showed itself to be appropriate for predicting stable spouting regimes. Furthermore, most of the experimental data of this study was compared to other results and to some empirical and mechanistic models reported in literature. Thus, our experimental data could be well described by an empirical model like Passos and Mujumdar's^{[ 2} Passos , M.L. ; Mujumdar , A.S. Effect of cohesive forces on fluidized and spouted beds of wet particles . Powder Technology 2000 , 110 , 222 – 238 . [CROSSREF] [Crossref], [Web of Science ®] , [Google Scholar] ^] model. On the other hand, the mechanistic model proposed by Cunha^{[ 3} Cunha , F.O. Contributions to the analyses of drying of pastes in spouted bed with inert particles . M.Sc. Thesis , Federal University of Sao Carlos , Brazil . 1999 . ( In Portuguese ). [Google Scholar] ^] overestimated the theoretical minimum spouting velocity at a range of values of 10 to 25%.     

温度对循环流化床双床气化中热解炉产物的影响

在循环流化床双床煤高温热解气化试验台上,以神木烟煤为燃料在不同温度下进行了热解气化试验,该试验台利用上下返料器将热解炉和气化炉耦合在一起,其中热解炉为N2气氛,气化炉通入空气作为气化剂,试验主要研究热解炉底部温度对热解煤气及热解炉底渣的影响。试验结果表明:随热解炉底部温度升高,热解煤气中H2体积分数升高,CH4,CO2体积分数降低,CO体积分数先降低后升高,热解煤气主要组分气体的收率增加。试验所取热解炉底渣样品的孔比表面积分布和孔比体积分布主要集中于中小孔(0—50 nm),其总比表面积和总孔体积大小顺序为在817℃最大,844℃次之,766℃最小,在N2气氛、1 200℃条件下,CO2反应的活性大小顺序为817℃最大,766℃次之,844℃最小。     

基于GSM和PIC单片机的无人清洁护理机的设计

文章以PIC单片机为“家庭长期卧床病人大小便清洁护理机”的主控制器,完成护理机各项参数的实时检测与控制,利用GSM模块TC35i将护理机报警信息以“手机短信”的形式实时发送到病人监护人的手机中,同时监护人也可用“手机短信”的形式发送命令远程控制家中护理机的运行,创新性地实现了护理机的“无人护理”功能.该设计将在很大程度上解决我国长期卧床病人家庭陪护人员紧缺和护理费用高昂的难题,将产生很大的经济效益和社会效益.     

河南油区稠油油藏水平井开发技术

河南油区稠油油藏通过直井蒸汽吞吐取得了较好的开发效果,但部分储量丰度较差的浅薄层稠油油藏及叠瓦状分布的条带状边水稠油油藏,采用常规直井开发,单井可采储量低,很难取得经济效益。为合理开发河南油区稠油油藏未动用储量,利用数值模拟技术,结合其地质特点,开展水平井开发技术研究,优化了水平井及注采工艺参数。结果表明:水平井目的层段垂深应大于150m;最佳水平段长度为80～150m;水平井与油水边界的距离大于60m后,基本未见边水入侵;水平井与断层距离大于20m时,断层不会开启;井底注蒸汽干度大于50%,开发效果明显改善;第1周期注汽量为2000t,油汽比和周期产油量均较高,分别为0.54t/t和1000t,吞吐效果较好;当注汽速度为300t/d时,优选注汽压力为14MPa、排液速度为20t/d左右比较合理。