尾矿坝中土工织物滤层反滤试验研究

土工织物作为滤层在尾矿坝排渗设施中已得到广泛应用,但由于工作条件复杂,土工织物经常发生淤堵,导致其排渗能力不足,严重影响尾矿坝的安全。为进一步认识尾矿坝中土工织物滤层的反滤特性,通过改进的梯度比试验装置,对无纺土工织物和不同孔径的有纺土工织物开展了一系列梯度比试验,对比分析了其保土性、防淤堵性和透水性。结果表明,在满足保土性的前提下,有纺土工织物孔径越大,系统的梯度比越小。在长期试验中,有纺土工织物相比于无纺土工织物更易发生淤堵。因此在尾矿工程中有纺土工织物可作为一种短期的排渗滤层,不建议作为长期排渗滤层使用。     

多层土工织物加固填土路基的特征分析

针对传统的极限平衡分析法不能较好地反映土工织物与土间的变形协调关系,采用非线性有限元法探讨了多层土工织物加固填土路基的变形与破坏特征.结果表明,在假定土工织物与土之间无相对位移条件下,土工织物的铺设层数对路基破坏面的位置影响不明显,路基的潜在破坏面近似为一通过坡趾处的圆弧面;离路基顶面越近,土工织物上的轴力越小;土工织物位于路基中部作用较大,而位于路基坡脚的轴力大为减小;铺设土工织物后,路基的稳定性提高较大,铺设层数越多,路基的安全系数增幅越大;铺设于路基体内的土工织物对减小地基体内的水平位移作用有限,实际工程中需采用其他措施约束地基体内水平位移的处理.     

无纺土工织物用于灰坝排水反滤的试验研究

本文结合国内某灰坝工程无纺土工织物滤层的试验研究,介绍并探讨了无纺土工织物滤层的渗滤特性和控制裂缝冲蚀特性,指出无纺土工织物的透水性是随上覆压力的增大而减小的,特别是低压阶段,压力变化对透水性的影响更为明显.建议在无纺土工织物滤层设计中,应选取相应压力条件下的透水性指标进行设计核定.     

模拟土工织物反滤作用的颗粒流分析方法

利用颗粒流（PFC）方法建立了土工织物PFC反滤模型,从细观层面分析了具有土工织物反滤结构的土体中水流挟持颗粒移动的特点及影响因素,探讨了PFC方法应用中引发的误差问题,并提出了解决方案。通过正交试验法分析了多因素影响下土工织物颗粒流反滤模型的孔隙率变化敏感性,进一步验证了土工织物淤堵试验中出现的渗透系数“峰值”现象及其产生的原因。     

土工袋无侧限压缩试验有限元数值模拟

土工袋作为一种袋装新材料的研究主要集中在室内试验方面,而数值模拟研究较少。为此,首先进行土工袋无侧限压缩试验,得到轴向压力—轴向位移关系曲线及对应的极限抗压强度。在此基础上,运用Abaqus有限元软件进行土工袋三维建模,模拟了土工袋无侧限压缩试验,土体采用摩尔库伦本构关系,袋子采用线弹性理想塑性模型,采用动态约束法模拟袋子与土体接触。结果表明,极限抗压强度模拟值与理论、试验值基本一致,袋内土体主要以侧向移动为主,沿边缘向中心袋子应力逐渐增大,土体应力逐渐减小。     

软土地基加筋用土工织物双向拉伸试验试样选型及其优化设计

在利用土工织物加固的软土地基工程中,土工织物处在双向受拉的一种力学状态,因此很有必要研究土工织物双向拉伸状态下的力学特性。根据现有的试验设备提出了9种不同型式的土工织物双向拉伸试样模型,借助有限元计算软件,对9种不同试样在双向拉伸条件下的受力情况进行了数值分析,并结合材料自身特点给出了各种试样优劣的评价原则及评价指标,通过对各个试样的指标值的对比分析,选取试样4作为备选试样,并采用控制变量的方法得到了试样4的关键尺寸与评价指标的函数关系。最后,通过定义目标函数的方法获得了目标函数取得最小值时试样尺寸的最优解。     

污泥脱水系统节能降耗研究

污水厂产生的污泥进行脱水需要消耗大量的能源。利用污水厂中的离心脱水机进行现场试验,采用正交试验法对转速、加药量、稀释水3因素进行组合试验,并进行分析,探索影响污泥脱水能耗的因素之间的主次关系以及最佳运行工况。     

土工袋减振效果振动台试验研究

为研究土工袋的减振效果,在振动台上通过对土工袋及其袋内材料天然河砂减振效果输入不同频率、不同振动加速度进行对比试验,对比分析了其顶部质量块响应加速度和土工袋层间加速度反应情况.试验结果表明,当振动台台面振动频率较大时土工袋的减振效果明显优于袋内材料天然河砂的减振效果,且输入振动加速度越大土工袋的减振效果越好.     

土工袋竖向减振特性试验研究

通过对不同袋内材料的土工袋及相应的袋内材料进行竖向减振效果激振试验,对比分析其最大加速度衰减率及频响函数,并探讨了不同层数及不同排列方式的土工袋组合体对竖向减振效果的影响.试验结果表明,加速度衰减大多集中于顶部三层土工袋内,且土工袋交错排列的减振效果较成列排列更好.     

Excel在单元分层及常规土工试验资料整理中的应用

基于Excel具有强大的制作表格、处理数据、分析教据等功能,构建了土工试验成果表及物理力学性质统计表.结果表明,此法可简便快速输入土工试验数据、自动完成各单元层物理力学性质指标统计工作,分层快速准确、统计计算结果精度高,大幅提高了勘察质量和工作效率,缩短了勘察资料整理周期,实用性强,值得推广应用.     

分离式热管小螺旋管蒸发段换热特性的实验研究

将小螺旋管应用于分离式热管的蒸发段。通过采用玻璃管和不锈钢管模拟分离式热管的蒸发段,对不同充液率和热流密度下,小螺旋管管内流体的流动与换热特性进行了实验研究。通过可视化实验观察小螺旋管蒸发段管内流型,初步分析热流密度和充液率对流型转换的影响,讨论壁温分布与管内两相流流型的关系。提出螺旋管内的脉冲震荡和二次回流使得管内流体的紊动强化,从而使平均换热系数和临界热流密度得以提高,不会产生壁温飞升,具有较好安全性的结论。     

Heat transfer characteristics of the evaporator section using small helical coiled pipes in a looped heat pipe

An experimental study was carried out for the heat transfer characteristics and the flow patterns of the evaporator section using small diameter coiled pipes in a looped heat pipe (LHP). Two coiled pipes: the glass pipe and the stainless steel pipes were used as evaporator section in the LHP, respectively. Flow and heat transfer characteristics in the coiled tubes of the evaporator section were investigated under the different filling ratios and heat fluxes. The experimental results show that the combined effect of the evaporation of the thin liquid film, the disturbance caused by pulsation and the secondary flow enhanced greatly the heat transfer and the critical heat flux of the evaporator section. In final, two dimensionless empirical correlations were proposed for predicting the heat transfer coefficients of the evaporator section before and after dryout occurs.     

Closed-ended oscillating heat-pipe (CEOHP) air-preheater for energy thrift in a dryer

The CEOHP air-preheater consisted of two main parts, i.e. the rectangular house casing and the CEOHP. The house casing was designed to be suitable for the CEOHP. The inside house casing divided the CEOHP into three parts, i.e. the evaporator, the adiabatic section and condenser section. The CEOHP air-preheater design employed copper tubes: thirty-two sets of capillary tubes with an inner diameter of 0.002 m, an evaporator and a condenser length of 0.19 m, and each of which has eight meandering turns. The evaporator section was heated by hot-gas, while the condenser section was cooled by fresh air. In the experiment, the hot-gas temperature was 60, 70 or 80 °C with the hot-gas velocity of 3.3 m/s. The fresh-air temperature was 30 °C. Water and R123 was used as the working fluid with a filling ratio of 50%. It was found that, as the hot-gas temperature increases from 60 to 80 °C, the thermal effectiveness slightly increases. If the working fluid changes from water to R123, the thermal effectiveness slightly increases. The designed CEOHP air-preheater achieves energy thrift.     

Heat transfer in a smooth scalene triangular duct with two rounded corners

Measurements of average heat transfer coefficients in a scalene triangular duct having two rounded corners were made at locations of 55 and 100 hydraulic diameters from the sharp-edged inlet to the channel. Individual side average heat transfer coefficients were obtained. Although there are small differences between the three sets of data, heat transfer coefficients averaged over the entire test section are adequately represented by the Colburn equation for smooth circulat tubes, with no effect of location of the test section.     

Flow Patterns and Heat Transfer for Flow Boiling in Small to Micro Diameter Tubes

An overview of the recent developments in the study of flow patterns and boiling heat transfer in small to micro diameter tubes is presented. The latest results of a long-term study of flow boiling of R134a in five vertical stainless-steel tubes of internal diameter 4.26, 2.88, 2.01, 1.1, and 0.52 mm are then discussed. During these experiments, the mass flux was varied from 100 to 700 kg/m²s and the heat flux from as low as 1.6 to 135 kW/m². Five different pressures were studied, namely, 6, 8, 10, 12, and 14 bar. The flow regimes were observed at a glass section located directly at the exit of the heated test section. The range of diameters was chosen to investigate thresholds for macro, small, or micro tube characteristics. The heat transfer coefficients in tubes ranging from 4.26 mm down to 1.1 mm increased with heat flux and system pressure, but did not change with vapor quality for low quality values. At higher quality, the heat transfer coefficients decreased with increasing quality, indicating local transient dry-out, instead of increasing as expected in macro tubes. There was no significant difference between the characteristics and magnitude of the heat transfer coefficients in the 4.26 mm and 2.88 mm tubes but the coefficients in the 2.01 and 1.1 mm tubes were higher. Confined bubble flow was first observed in the 2.01 mm tube, which suggests that this size might be considered as a critical diameter to distinguish small from macro tubes. Further differences have now been observed in the 0.52 mm tube: A transitional wavy flow appeared over a significant range of quality/heat flux and dispersed flow was not observed. The heat transfer characteristics were also different from those in the larger tubes. The data fell into two groups that exhibited different influences of heat flux below and above a heat flux threshold. These differences, in both flow patterns and heat transfer, indicate a possible second change from small to micro behavior at diameters less than 1 mm for R134a.     

特殊要求换热器导流锥筒的设计与试验

针对具有特殊要求——防止含有粘性微小颗粒的乙烯气体在换热器管程内沉积堵塞的实际确工程问题,提出通过气动模拟试验的技术途径,按照气体动力学的理论进行模型风洞试验,从而定导流锥筒的合理结构尺寸,排除流速迟缓区,确立较均匀的管程流场分布,以保证换热设备的正常工作。本试验结果已用于设备的施工设计与加工制造,该设计顺利通过了国外工艺专利商的审查,产生品已于1989年底加工完毕并交付现场安装使用。     

Experiments for liquid phase mass transfer rate in annular regime for a small vertical tube

The double film extraction technique was used to measure the deposition rate and the entrainment rate of droplets for vertical upward annular two-phase flow in a small diameter tube. The test section was a round tube of 5 mm in inside diameter, air and water were used as test fluids and the system pressure was varied within 0.14–0.76 MPa. It was shown in the present experimental conditions that the deposition rate was primarily influenced by the droplet concentration in the gas core and that the entrainment rate was correlated well with the dimensionless number denoting the ratio of interfacial shear force to surface tension force acting on the surface of liquid film. These results were consistent with available empirical correlations that were developed using the experimental data for larger diameter tubes.     

延迟焦化加热炉存在问题分析与整改

惠州炼油420×104t/a延迟焦化装置加热炉采用美国FW公司双面辐射斜面阶梯炉,每台加热炉由6个辐射室、1个对流室组成。每个辐射管程设置单独的一个炉膛。共用的对流室安装在辐射室上,用于原料预热和蒸汽过热。该加热炉运行16月后,出现对流炉管结焦、排烟温度上升、部分炉管堵塞等问题。造成对流段结焦的主要影响因素,是回炼催化油浆以及注水温度相对偏低,导致渣油中沥青质析出;排烟温度高的主要影响因素是炉管结焦与对流段取热不足。对此,增加两排对流管、一排注水管、一排低低压蒸汽过热管。操作方面,主要优化措施有:停止催化油浆进焦化回炼,提高注水温度,注水方式从单点注水改为两点注水;同时平稳操作,减少焦粉携带。通过技术改造与操作优化,加热炉运行平稳,排烟温度显著降低,基本消除了加热炉对流段的结焦因素,加热炉在线清焦周期明显延长。