蜗壳式离心泵外特性仿真与实验研究

为探索不同仿真方法的适用性,对ns=157的单级蜗壳离心泵不同工况的扬程和效率进行定常和非定常计算,并分别分析了定常计算时不同叶片夹角及非定常计算时不同时间步长的影响,通过与实验对比,得到的主要结论有:定常计算仅适用于额定工况外特性仿真,其扬程和效率计算误差分别为4.9%和2.9%,而定常多相位的计算误差分别为7.1%和3.2%;非定常仿真计算时,以4°为时间步长,并间隔20°保存一次计算数据,较好地预测出扬程曲线走势,额定工况扬程和效率计算误差约1.1%和1.8%,但小流量和大流量区间扬程计算误差达到10%左右。因此在水力优化设计时,若只关注高效点位置及其扬程和效率,可采用定常计算,若还关注扬程曲线走势,则应采用非定常计算。     

Experimental investigation on the transport of different fish species in a jet fish pump

A jet fish pump with a throat of ø60 mm was designed to study its performance in the transport of different fish species and the physiological changes in fish thereafter. Experiments were conducted to investigate the fish transport rate and energy required to transport each ton of fish when transporting Carassius auratus, commonly known as the Chinese goldfish, Megalobrama amblycephala, or Wuchang bream, and Ctenopharyngodon idella, the grass carp. Fish were examined for external injuries as well as for several important enzymes and hormones which are indicators of tissue injury and stress. The results showed that the transport rate for all three species of fish rose dramatically with an increase in the primary stream rate. In this experiment, the transport rates of C. auratus, M. amblycephala and C. idella reached 2357 ± 37.2 kg ∙ h⁻¹, 2888 ± 41.6 kg ∙ h⁻¹, and 2060 ± 40.2 kg ∙ h⁻¹, respectively. However, both injury rate and energy required to transport each ton of fish increased no matter whether the primary stream rate was too low or too high. Considering both transport rate and injury rate, the mean primary stream rate of 80 m³ ∙ h⁻¹ was determined to be the optimal operating condition in this experiment. Fish were stressed and most likely some of their organs were damaged. However, most physiological indexes almost fully recovered after several hours.     

Engineered-airlift pumps for aquaculture applications using multiphase flow analysis

Currently, very few aquaculture operations are employing airlift pump technology for water recirculation, aeration, and waste removal. This is likely due to the poor design and lower efficiency of traditional airlift design, the limited amount of research effort that has been invested in improving performance capabilities of air lift pumps and the general lack of awareness of the industry about the inherent advantages of airlift systems. A new efficient airlift pump is hydrodynamically designed by incorporating the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model utilizing Computational Fluid Dynamics (CFD) tools. The pump is designed to offer a substantial reduction in total energy usage as well as an improved quality of the culture products in order to make it attractive to aquaculture industry. In this study, both numerical and experimental investigations were carried out for airlift systems operating under two different submergence ratios of 50% and 90% in a lab setting using 2.54 cm diameter pumps. Also, the performance of a large-scale pumps of 10.16 cm diameters were also tested in an aquaculture raceway to determine its effect on the operation. The numerical results were found to be in agreement with the experiments within ±20% which is considered very reasonable for multiphase flow analysis. The present study was found to present a great tool for modelling the airlift pump performance, and potentially proposing new designs.     

纵横刀组协同式马铃薯种薯切块装置设计与试验

针对马铃薯种薯切块机械化程度低的问题,设计了一种纵横刀组协同式马铃薯种薯切块装置,对其关键部件进行设计,通过对马铃薯种薯切割过程的力学分析、运动学分析和能量学分析,建立了切种能量的数学模型,确定了影响马铃薯切种效果的主要因素。以切种效率、切种合格率为评价指标,以圆盘刀半径、输送辊与圆盘刀垂直中心距、圆盘刀轴转速和夹持辊轴转速为试验因素,进行了四因素四水平正交试验。对正交试验结果进行方差和极差分析,结果表明:当圆盘刀半径为180 mm、输送辊与圆盘刀垂直中心距为190 mm、圆盘刀轴转速为115 r/min、夹持辊轴转速为56 r/min时,切种效率为74.5 kg/min,切种合格率为98.8%,满足马铃薯切种作业要求。     

叶轮出口边对双蜗壳泵压力脉动的影响

泵的叶轮扫掠蜗壳隔舌时产生的压力脉动是引起船用泵振动噪声的原因之一.为尽可能弱化这一影响,分别设计了叶片出口边与前后盖板基本面垂直和倾斜的2种不同形式叶轮,将其配置在相同的双蜗壳中,通过数值计算与样机试验相结合的手段,对蜗壳内9个不同位置的压力脉动情况进行对比分析.结果表明:出口边倾斜的叶轮相比于出口边垂直的叶轮可明显改善蜗壳内次脉动的“驼峰”现象,且可以进一步降低隔舌处主波动的压力峰值;对蜗壳内2个隔舌稍前的位置,出口边倾斜的叶轮反而会使得该点的压力系数幅值明显增大,且该点主波动的周期数发生改变;2种叶轮出口边的不同形式对蜗壳出口位置的压力脉动的影响基本相同;采用出口边倾斜叶轮对改善因叶轮与隔舌间的液流压力脉动是可行的.     

分流叶片对高速井泵压力脉动的影响

针对高速井泵采用分流叶片设计带来的稳定性问题,运用Creo3.0软件建立了叶轮、导叶等关键零件的三维模型;在CFX数值模拟数据与外特性试验数据吻合较好的基础上,将分流叶片的进口直径d₁与叶轮外径D₂的比值定义为一个表达分流叶片综合特性参数的量纲一化系数σ.σ分别取值0.60,0.62,0.65,设计分流叶片长短不同的3个叶轮方案,且对各方案的动静干涉区域进行了详细的压力脉动数值模拟计算及分析.结果表明:压力脉动幅值大小与监测点和交界面的径向距离有关,径向距离越大,压力脉动幅值越小;各监测点压力脉动随分流叶片长度的减小逐渐减弱,当分流叶片长度减小到某一临界值以后,压力脉动基本保持不变;当σ=0.62时,压力脉动幅值较小,脉动周期清晰;除中流线上的监测点以外,各监测点压力脉动主频受叶轮叶频的影响较大,分流叶片对中流线上监测点的压力脉动影响较大.     

泡沫比例混合器在液下喷射灭火系统中的应用

提出了环泵泡沫比例混合器和泡沫压力比例混合器在相应灭火系统中的应用、安装和操作中应注意的问题，对两种泡沫比例混合器组成的系统进行了对比，认为环泵比例混合泡沫灭火系统采用正压进水，可以克服负压进水方式存在的缺陷，比较适合油库火灾的扑救；压力比例混合泡沫灭火系统灵活性、匹配性较差，适用于泡沫混合液流量相对不变的火灾扑救。     

Acoustic evaluation of the vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in Lake Biwa

SUMMARY: The vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in the pelagic waters of Lake Biwa was evaluated from June to September in 1995–97 from eight acoustic surveys using a quantitative echosounder. In each survey, echoes from a depth range of 3 m to the sea bottom were collected at a station every 2.7 s for 24 h together with measurements of vertical profiles of water temperature and chlorophyll-a. The ayu's echoes were identified using an underwater video camera. The ayu were observed near the maximum chlorophyll-a depth and above the thermocline. Their density was highest at depths of 4–11 m with 2–4 individuals/m ³ and was almost zero below 20 m. Echo signs were recorded as having a frequent duration of more than 1 h at night, whereas were of a shorter duration in the day. The fish stay in the epilimnion during the day without any clear vertical migration, but are distributed more uniformly at night. The advantages of remaining in the epilimnion are discussed in terms of food availability and predator avoidance.     

单位换算技术在水泵测试软件中的应用

水泵试验时,要采集诸多参数,并且根据这些参数计算出扬程、轴功率、NPSH等数值,不同国家这些参数采用的单位不同,企业必须能够按照客户要求的单位提供试验数据:并且有时客户要求得到水泵在特殊介质下进行试验得出的试验数据,同一台泵在每种介质下都做一遍试验不太现实,而且会提高企业的生产成本,提出将采集的数据进行单位换算,根据不同国家或者客户的特殊要求求出泵的试验数据,在实际应用中节省了试验成本,得到了企业的好评.     

迷宫螺旋槽的选取研究

以提高迷宫螺旋泵的扬程、流量、效率、汽蚀等性能参数为目标,给出不同使用条件下螺旋槽形状与几何参数的选取。