含沙水流中闸门槽蚀损的实验研究

在工作断面为矩形的文透里型空化管中进行了挟沙水流中闸门槽的空蚀与磨损实验．门槽的宽深比B／D＝1．5，材质为铝，沙样为黄河沙与塑料沙．泥沙颗粒在门槽中的冲撞部位在滞点附近，其运动轨迹为随机性质的波段状．门槽下游不同部位的蚀损程度不同，严重部位在门槽下游分离型空腔的重附点附近．对不同挟沙浓度与水流流速对壁面蚀损量的影响进行了实验，结果表明，随着含沙量的提高，蚀损量增加．在本实验条件下，铝试件的特征蚀损点划率与含沙量的关系为N＝ASm＋B，与流速的2．66次方成比例，硬度较高的黄河沙，其蚀损量高于塑料沙．     

CAVITATION CHARACTERISTICS OF HIGH VELOCITY FLOW WITH AND WITHOUT AERATION ON THE ORDER OF 50 m/s

Experimental study of cavitation characteristics with and without aeration was conducted at the flow velocity 50m/s in the non-circulating type water tunnel in the Hydraulics Laboratory at Zhejiang University of Technology. Variations of pressure and cavitation number with air concentration, pressure waveforms as well as cavitation erosion level of concrete specimen with and without aeration were obtained. The effects of cavitation control by aeration were analyzed.     

Critical size effect of sand particles on cavitation damage

The critical size of the sand particles in liquid is determined by means of the special vibratory apparatus, and it is related to various effects on the cavitation damage. The increase of the sand size or concentration would aggravate the cavitation damage if their sizes are larger than this critical size, conversely, this damage would be relieved.     

ON THE RELATION BETWEEN CAVITATION INCEPTION AND FLOW PATTERN ON PROPELLER BLADES

Oil flow visuallization on the model propellers with and without tripping devices atthe leading edge is revealed in this paper. Roughing leading edge with sand blasting was to simu-late the flow at full-scale condition. The observations of cavitation inception and the detection ofcavitation erosion were made in uniform and non-uniform flow respectively so as to consider theeffects of flow pattern on cavitation inception and to investigate the causes of difference in thelocations of cavitation erosion between model propeller and prototype. In addition, calculationsof the pressure distributions and the behaviour of boundary layer on the propeller blade were alsodone by using theoretical method. It is necessary to gain a better understanding of cavitation in-ception of the propeller.     

金属材料空蚀试验方法研究进展

根据水流流动的模拟特性,将金属材料空蚀试验设备进行分类,介绍了主要设备的原理、发展、性能和优缺点,探讨了其主要特征参数及影响规律。通过对不同设备所得试验结果的分析比较,总结出金属材料空蚀试验的一些规律。认为当前应致力于各设备试验方法的标准化研究,通过大量标准化的流体-温度-材料-设备试验,确定金属材料空蚀破坏与特征参数的关系,对设备功能的开发等也提出了一些粗浅的认识。     

浑水条件下偏心铰弧形闸门的空化空蚀

在空化空蚀试验台上，对黄河小浪底水利枢纽排沙洞偏心铰弧形闸门顶水封的1:1切片，进行缝隙空穴流试验。直接观测其在清、浑水条件下原型可能出现的空化空蚀状况。同时，分析了浑水对空化的影响后表明，浑水的产压级高于清水，浑水的空蚀强度大于清水，且均随浑水的浓度增加而加大。     

Cavitation erosion in bloods

The cavitation in a mechanical heart valve(MHV) is a serious concern. In most of the investigations of the MHV cavitation in vitro, the tap water, the distilled water, or the glycerin are used as the test liquids, instead of the real blood. Therefore, the effects of the liquid properties on the cavitation can not be well revealed. In this paper, the cavitation erosion in the porcine bloods is experimentally investigated as well as in the tap water and the distilled water by means of a vibratory apparatus. The results show that the blood produces a weaker intensity of the cavitation erosion than the tap water or the distilled water. The cavitation erosion decreases with the decrease of the liquid temperature or with the increase of the concentration of the blood, especially with the increase of the liquid viscosity. It is the viscosity that could be a major dominant factor affecting this erosion. The temperature or the concentration of the blood changes the viscosity, and in turns changes the intensity of the cavitation erosion.     

PRESSURE CHARACTERISTICS OF CAVITATION CONTROL BY AERATION

1.INTRODUCTION Alotofhighdams,whicharegreaterthan100minheight,havebeensofarcompletedinChi na.Andmanysuperhighdamsover200mhighsuch asErtanandLongtanHydropowerStationswere completedorareunderconstruction.Someof themevenhavetheheightontheorderof300m suchasXiaowanandXiluoduHydropowerSta tions[1].Accordingtoincompletestatistics,nearly30superhighdamswhicharegreaterthan200min heighthavebeensofarcompletedintheworld[2].Becauseoftheheadincrease,flowvelocityin thesehighdamscanreachseveral dozenm…     

高海拔地区气压环境对高速水流空化特性的影响

为定量评价高海拔地区的低气压环境对水流空化特性的影响程度,通过理论计算单气核临界压强在不同气压条件下的变化,分析单气核临界压强变化对初生空化数的影响程度,并进行不同海拔高程下水流空化数的敏感性分析。研究成果表明:低气压环境下,气核初生空化数和水流空化数均减小,但水流空化数减小的程度远远大于初生空化数减小的程度,其他条件相同的前提下,高海拔地区的高速水流空化空蚀风险增大。研究结论可为高海拔地区高速水流的空化空蚀设计和评价提供参考。     

空化形成机理和比尺效应

高速水流容易发生空化，为进一步研究空化的形成机理和影响因素。对空化形成机理和液体粘性、表面张力、气核状况等影响因素的最新研究成果进行了综合分析。水流空化试验中存在比尺效应，指出并建立了空化比尺效应的经验公式。对空化机理的研究还有待进一步深入。     

CAVITATION CONTROL BY AERATION AND ITS COMPRESSIBLE CHARACTERISTICS

1. INTRODUCTION So far a lot of high dams that are greater than 100 m in height have been constructed in China. And many super high dams over 200 m in height, such as those at the Ertan and Longtan Hydropower Stations, were completed or are under construc…     

液体抗拉强度与空化比尺效应

本文讨论了在动水力学法测量液体抗拉强度时小文杜时管中有空化，而喉部却出现了“负抗拉强度”的原因。同时利用小文杜里管作为空化器件，探讨了空化比尺效应，说明液体抗拉强度只是影响了临界空化压力pc，而在产生初生空化时,空泡也同样影响到参考点的压力pu。     

三峡工程表孔体型空化试验研究

根据三峡工程溢流坝表孔设计体型,通过减压试验 ,研究了体型的空化特性。成果表明：WES曲线坝面为免空蚀体型; 挑流鼻坎虽有弱空化现象,但空蚀的可能性不大;工作门槽体现为蒸汽型空化特征,其强度 随工作水头增大而加剧。对两道门槽进行局部体型修改后,两者的空化特性均有明显的改善 。要达到完全免除空化之目的,有待进一步优化。     

AN EXPERIMENTAL STUDY ON INCIPIENT CAVITATION EROSION OF FLOOD DISCHARGE TUNNEL WITH ORIFICE

Serial grades of cement mortar specimens have been tested on the model of con-crete-lining flood discharge tunnel with orifice,The results show that incipient cavitation erosionnumber is much smaller than incipient cavitation number.Based on the principle of bubble dy-namics,the flow speed effect on incipient cavitation erosion number for cement mortar is pre-sented.     

突扩跌坎掺气设施深化研究

高速水流下的空化空蚀和高水头下的闸门止水问题是高水头泄水建筑物运行所遇到的2大问题。为深入研究突扩跌坎掺气设施,进一步了解其水力特性和空化特性,以某水利枢纽孔板泄洪洞中闸室通气系统和突扩跌坎掺气设施为具体研究对象,通过建立比尺 1∶20 的局部水工模型,分析研究了通气孔风速、流态、压力、掺气浓度等水力特征参数,并将试验结果与原型观测结果进行了对比。结果表明:该工程布置的掺气效果良好,试验所得通气管内风速随闸门开度变化的趋势、水流掺气浓度、压力及其脉动在数值上与原型观测结果均一致,说明工程原型观测与模型试验对比验证是成功的。理论研究和实际运用均表明,结合闸门止水和掺气减蚀要求的突扩跌坎布置,是符合实际需求且安全可行的,同时也是解决高水头条件下闸门止水和掺气减蚀的有效措施,具有广泛的推广应用价值。     

STUDY ON A NEW APPROACH OF CAVITATION EROSION TEST FOR NONMETALLIC MATERIALS

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初生空化数公式的优化研究

初生空化数是衡量过流体型是否发生空化的判别标准。传统的托马公式认为液流负压值达到液体饱和蒸汽压时即发生空化。近来研究表明,气核和液体抗拉强度等对初生空化有重要影响。有学者认为把托马公式中的液体饱和蒸汽压替换为临界压强更为合理。本文在已有研究的基础上,对空化初生机理和影响空化初生的因素进行分析。认为空化仅是气核克服表面张力和液体饱和蒸汽压膨胀而形成的,并没有克服液体抗拉强度,且在空化源附近的液体几乎不具有抗拉强度,并基于此提出新的初生空化数公式。     

NUMERICAL PREDICTION OF SILT ABRASIVE EROSION IN HYDRAULIC TURBINE

1.INTRODUCTIONTherearemanyhydraulicturbinesoperatedinsiltladenriversintheworld.Thepresenceofsolidparticlesintheflowoftencauseabrasivedegradationofcertainpartsofthehydraulicturbinewhichareespeciallyexposedtotheflow.Theerosivewearduetohydroabrasiondependsprimarilyonthesurfacematerialandonthematerialoftheabrasiveparticlesinwater.Thefluiddynamicsoftheparticlemotionalsoplayaveryimportantroleinthistribologicalsystem.Therelativevelocityofparticlesandthefrequencyofimpactarekeyfactorsindetermining…     

万家寨水电站水中含沙对空化压力的影响

对万家寨水电站含沙量对水力机械内空化压力的影响进行了研究，并利用自行研制的测量装置实测了黄河万家寨水电站含沙水样的初生空化与，临界空化压力．实测结果表明，随着含沙量的增大，初生空化与临界空化压力值均有所提高，且接近线性关系．这一成果可用于所有含沙河流上的水电站水轮机与水泵站水泵合理确定安装高程时的参考．这样做可以减少空蚀与泥沙磨损给运行带来的经济损失．     

明流隧洞工作门掺气设施的试验研究

在对某水电站放空洞工作闸门的常压及减压模型试验中，进行了工作闸门的体型比较；讨论了通风洞的进气量、明流洞坎下沿程水流的修气浓度、掺气坎减免空蚀的保护长度；还探讨了门槽空化的特性以及工作闸门掺气设施的方案优化。