蜗壳断面面积变化规律对离心泵的水力性能有重要影响.采用CFD数值模拟的方法研究了5种蜗壳断面面积变化对泵性能的影响规律.研究结果表明N型模型水力性能最好,U型模型水力性能最差,两者的扬程和效率分别相差5.01％和9.47％;适当减缓后2个断面的面积变化速度,可以有效减小隔舌处和扩散段的低速区.随着流量的增大,蜗壳面积变化规律对压力脉动峰峰值的影响逐渐减小;U型、倒S型、线性模型的压力脉动主频均出现在叶频处,N型和S型模型的压力脉动主频在设计工况时出现在叶频处,在偏工况时出现在低于轴频处,且N型和S型模型总体压力脉动较小.在偏工况时,各模型主频处压力脉动幅值上升,且受蜗壳面积变化影响较大.整体而言,拥有良好水力性能的蜗壳应符合螺旋段尾部面积增长较慢、螺旋段前半段面积适当增大的规律.

为掌握光照变化对无蓄电池光伏灌溉系统运行特性的影响,搭建光伏灌溉系统开式试验台,试验测量了不同光照强度下的系统性能.试验结果表明:较低光照强度下喷头工作压力、射程随光照强度增大而增大,较高光照强度下随光照强度上下波动,射程变化趋势与工作压力变化趋势一致,但旋转周期变化趋势与工作压力呈相反规律;喷头工作压力变化趋势与光伏水泵出口压力、光伏组件输出功率变化趋势一致;光照强度1000 W/m2附近系统运行参数达到阈值,喷头射程与工作压力最大值分别为9.8 m和0.44 MPa,水泵流量与出口压力最大值分别为1.68 m3/h和0.45 MPa;未达到阈值前,影响水泵与喷头运行的主要因素是光照强度,运行参数变化幅度较大,达到阈值后影响因素主要为光照强度和温度,运行参数变化幅度较小;较低光照强度下,组合平均喷灌强度随着光照强度增大而增大;较高光照强度下,组合平均喷灌强度随着光照强度上下变化,与光伏组件输出功率的变化趋势一致;随着光照强度增大,喷头喷灌均匀系数和分布均匀系数逐渐趋近最高值,喷灌均匀系数最高达到88％.

In order to reveal the influence of the blade placement angle on the performance of shaftless pump-jet thruster, CFD method was used to numerically simulate the internal flow at different placement angles of blade, and analyze the change rules of external characteristics, thrust, internal flow field distribution and pressure pulsation of the pump. The results show that under the design conditions, with the increase of the blade placement angle, the pump-jet head and thrust of the model pump gradually increase, and the efficiency gradually decreases; compared to 0°blade placement angle, the head increases by 5.99%, the thrust increases by 2.08%, and the efficiency decreases by 7.6% at +4°blade placement angle; the pressure at the inlet of the blade decreases significantly, the flow rate of the fluid in the impeller gradually decreases, and the vortex intensity at the outlet of the impeller gradually increases and the vortex area decreases; the change of the blade placement angle has no effect on the main frequency of the pressure pulsation in the pump jet, but has a significant effect on the amplitude of the pressure pulsation beyond main frequency, especially the pressure pulsation at the flange and the middle of the flow channel. The research results have certain reference value for the design of low-noise shaftless pump-jet thruster.

为明确隔舌安放角对旋流泵性能及非定常流动特性的影响,该研究设计了不同隔舌安放角的蜗壳模型,基于Navier-Stokes方程和RNG k-?湍流模型对旋流泵进行了全流场数值模拟,并通过能量性能和压力脉动试验对数值模拟方法进行了验证.能量性能预测结果表明,存在最优隔舌安放角使泵扬程和效率均达到极大值.流场分析结果表明,隔舌安放角对蜗壳隔舌及扩散段的流态具有较大的影响:较小的隔舌安放角会减小蜗壳喉部的过流面积,使无叶腔内流体的旋转运动受阻,致使循环流与隔舌的动静干涉作用增强;过大的隔舌安放角会造成扩散段产生大尺度的漩涡和回流.压力脉动分析表明,隔舌处压力脉动分布特征受安放角和测点位置共同影响:随隔舌安放角的增大,隔舌处的压力脉动先降低后增大,安放角由30°增大至45°时,2倍轴频(fn)的脉动最大降幅约47％,安放角继续增大至50°时,(0.25～0.5)fn的低频脉动最大增幅约86％;随着测点与叶轮轴向距离增大,隔舌处的压力脉动逐渐减小,叶轮一侧的脉动幅值约为泵体进口一侧的2倍.涡量场分析表明:蜗壳隔舌处频率为2fn的压力脉动由入口螺旋状入流发展扩散产生;隔舌处涡核分布的不对称性是导致蜗壳隔舌处压力分布不对称的原因.适当增大隔舌安放角能有效改善旋流泵隔舌处内流的稳定性,并一定程度提升旋流泵扬程和效率.综合各项性能表明该模型泵隔舌安放角45°时性能最优.研究结果可为旋流泵优化设计提供理论参考.

为研究不同导叶时序位置下离心泵性能变化,以一台节段式2级离心泵为研究对象,采用RN G k-ε湍流模型对不同导叶时序位置下泵内流场进行数值计算.以次级导叶相对于首级导叶的周向顺时针旋转10°为一个时序位置,共设计6种时序方案.研究结果表明:在1.0Qd工况下,相比较无导叶时序方案,当旋转角度φ为导叶叶片间夹角的1/2时,泵扬程和效率的增加幅度达到极大值,分别为0.18％和0.16％;导叶时序对泵性能的影响随着流量的增大不断增大;各监测点处压力脉动主频幅值均随着次级导叶时序角度的增大呈先减小后增大趋势,当首级导叶和次级导叶交错角为30°时脉动主频幅值达到最小,相较于无导叶时序方案最大降低幅度达34.3％;改变导叶时序可有效降低多级泵级间的旋涡大小和强度,从而降低泵内的压力脉动强度.

【Objective】 Photovoltaic has been increasingly used to power irrigation systems in China, but optimizing its power output and operating load is an issue that is poorly understood. This paper aims to address this by taking sprinkler irrigation systems powered by photovoltaic as an example. 【Method】 The photovoltaic system used in this work was battery-free, and the experiment was conducted in a test rig in which the operation of the system under different nozzle numbers was measured and compared. 【Result】 ①Water pressure in the nozzles varied with light intensity, and the variation decreased as the duration of light intensity increased. The saturated light intensity under two loads was 300 W/m2, lower than that under four loads. ②With the increase in the number of sprinkler nozzles, the saturated working pressure in the nozzles decreases. The saturated water pressure in the sprinklers under two nozzles was about 450 kPa, and it reduced to 435 kPa when the nozzle numbers increased to four, indicating that the illumination intensity required to reach the saturated pressure in the sprinkler system increased as the number of nozzles increased. ③With the increases in sprinkler head numbers, the falling of water droplets in the radial direction and the difference in water droplets between the sprinkler sections both decreased. Water distribution under two nozzles was approximately trapezoidal, while under four nozzles the distribution became triangle from where the nozzles were to the far ends. ④The uniformity coefficient of the sprinkler irrigation system increased as the number of nozzles increased, and the maximum uniformity coefficient under four sprinkler nozzles was 2% larger than that under two nozzles. 【Conclusion】 Increasing the number of nozzles can increase the saturated light intensity of the system and reduced the saturated water pressure in the nozzles. The light-height of the pumps, rotational speed and flow rate all decreased as the light intensity transient amplitude increased. The pump flow, head curve and the pipeline characteristic curve move to the right of the intersection point, and the system running at fast flow condition can reduce nozzle pressure and improve sprinkler irrigation uniformity.

智能马桶的健康检查涵盖人体的各项指标,包括体重、体温、血压、血糖等各种信息,能够让人们轻松了解自身的健康情况,及早预防疾病.对智能马桶的发展研究现状进行综述,并对目前智能马桶应用的健康监测技术加以分析,主要是人体按摩、体温体重监测和尿液分析三个方面,引发了对智能马桶的家庭健康检查系统思考,认为智能马桶的发展,代表了智能家居不可阻挡的未来发展趋势.

It stated that it is necessary to reform the practical teaching of machinery majors and thus proposed new ideas of constructing the practical education system, which researches the reform measures of the practical teaching from different angles, such as construction of "double-qualification" teaching staffs, innovation of practice teaching contents and teaching methods and so on, based on the increasing urgent need for high-quality machinery personnel brought by the rapid development of Chi-na's economy and the current situation of machinery talents training.

In order to study the hump of pump performance curve in low specific speed centrifugal pumps ,using RANS method algorithm to CFD calculations of internal full flow of low specific speed centrifugal pump in two schemes ( has a hump and without the hump ) to calculate and analysis .Differences of the internal flow structure are emphatically analyzed in two schemes when hump phenomenon occurs .The results show that the performance curve appeared hump ,the flow structure differences of the impel-ler flow passage near the volute tongue in two programs are the most obvious .Low speed area in the pressure side of the impeller blade in the passage can significantly increase accompanied by vortex flow .The flow of imports also appear obvious vortex flow , losses increased by the impact of the vortex flow .Meanwhile,the "jet-wake"phenomenon of the channel outlet also mutate ,cau-sing exports hydraulic losses increase .Therefore,the increase of these losses is the significant cause of hump phenomenon .

In order to reveal the internal flow characteristics of a 90o bending duct with square section at different inlet velocities, PIV measurements of velocity distribution were carried out for bending ducts at different sections and radii. The experimental results suggest that the flow behavior within a bending duct can be measured by PIV. Velocity profiles vary little before the fluid entering the bending section. Rotating flow forms due to the restraint of the bending wall when the fluid enters the bending section, resulting in a velocity increase at the inner wall of the bending duct and a velocity decrease at the outer wall of the bending duct. On the contrary, the velocity decreases at the inner wall of the bending duct and increases at the outer wall of the bending duct when the fluid passes through 60o. Flow velocity tends to be uniform when the fluid passes through 90o. Velocity profile was different with different radius and the velocity near the inner wall is higher than that near the outer wall. Maximum velocity occurs at 50o and 60o, and its location is found to be dependent on the inlet velocities and independent on other flow characteristics in the bending duct.

In order to study internal flow variation of low specific speed pump, an experimental investigation of internal flow in the pump was conducted at three different flow rates on six phase position by means of PIV (particle image velocimetry). The dynamic pressure and velocity vector distribution was obtained. The results of experiment show that dynamic pressure distribution of the impeller is in substantial agreement at design conditions for different phase position. The dynamic pressure increases with the increase of radius. The maximum of w/u ratio is near suction surface at the t=0 and t=2T/6, but in the middle flow field at the t=4T/6. The results show that the effects of the volute tongue on the w/u ratio are more significant. The absolute velocity in the volute increases with the increase flow rate. The absolute velocity in the volute is in substantial agreement at the same flow rate condition for different phase positions.

The hump in performance curve of low specific speed centrifugal pumps affects the reliability obviously, which is still not solved today. In order to study inner flow mechanism of the hump, two hydraulic models are designed according to the same design requirements, in which scheme 1 has hump phenomenon and scheme 2 has no hump phenomenon. The performance of the two models is tested to validate the design. Then the internal flow of two model pumps are tested and analyzed by particle image velocimetry (PIV) system. The results show when performance curve appears hump, low speed area at the pressure side of the impeller blade increases rapidly, and vortex appeared at blade pressure surface of several channels. In the gap between impeller outlet and volute base circle, the flow rate of recirculation increases. The velocity difference between the impeller outlet and base circle of the volute also increases significantly, which results in increase of the hydraulic loss in the pump and causes hump phenomenon of the performance curve. The research results of the study can provide theoretical references to control the hump phenomenon of low specific speed centrifugal pumps.

Based on AutoCAD 2010, Visual C++. NET 2008 and ObjectARX 2010 the hydraulic design software of pump suction chambers, called PXSS, was successfully developed. The PXSS could design all kinds of pump suction chambers. Key technologies in the development process of software PXSS were introduced. A pipeline pump suction chamber and a spiral-shaped suction chamber were designed with the PXSS software. The two examples show that the PXSS can realize the parametric drawing of the pump suction chamber and improved the efficiency of the design staffs. So, it could be applied to engineering practice.

Adhesion is a peculiar phenomenon of micro/nano-machine.When the strength of the component's material meets the demand,the adhesion and friction in the micro/nano-machines are the main cause of their failure.To overcome or reduce adhesion has become the hotspot in the micro/nano-electromechanical systems(MEMS/NEMS) research field.The adhesion issue in the micro/nano-machines is introduced.The mechanisms of adhesion and various adhensive models used in adhesive contact are analyzed.The micro/nano-machines' design principle of anti-adhesion using surface energy method and asperity integral method is illustrated.Various anti-adhesion methods such as release dry processes,real contact area reducing,and surface energy reducing,are presented.

On the bases of many designs and tests , provides the hydraulic design way on computer aideddesign of double-channel impeller, and with some main parameters. Gives the values of inlet speed coefficientKD1 and outlet speed coefficient KD2 , and introduces the ways of calculating radius R1 of front cover board andradius R2 of back cover board. A midline equation of impeller plan channel and a change rule of channelsection area are suggested in this paper for the first time.

系统研究了双流道泵蜗壳的设计方法.给出了双流道泵蜗壳的主要结构参数的计算方法,以及蜗壳的结构形式.首次归纳总结出了双流道泵的面积比系数,并用最小二乘法拟合出了面积比系数的计算公式.

利用几何法推导出双流道泵叶轮轴面图前、后盖板型线方程以及轴面图流道中线方程.首次给出了双流道泵叶轮轴面图流道中线分点的计算方法.研究结果将会对双流道泵叶轮水力设计CAD软件的开发和手工绘型提供很大帮助.

系统论述了单流道叶轮水力设计的新方法，新方法较原方法简单、可靠和实用，尤其便于编制计算机辅助设计软件。在对现有的优秀单流道叶轮水力模型进行归纳总结的基础上，给出了用速度系数法设计轴面图时的各速度系数值。借鉴双流道叶轮水力设计中平面图的设计方法，提出了新的单流道叶轮平面图水力设计方法。介绍和分析了新的流道截面面积变化规律和平面图流道中线方程，同时还给出了编程方法及其设计实例的实验结果。

An improved way of single channel impeller hydraulic design is discussed in this paper, it is more simple than the former design method, which is especially fit to program CAD software. Based on summing up many excellent hydraulic models of single channel impeller, it gives various kinds of coefficient values of axial section. Inspect the design way of plan hydraulic design of double channel impeller, it provides the new design way of plan hydraulic of single channel impeller. It introduces a new change ruler of section area and an equation of plan channel midline. At last, a programming way and an example of design are given.