含沙水中泥沙与空化伴生机理研究

Aimed at the problem of severe abrasion of pumps caused by silt and cavitation along the the Yellow River, Guided by the strange phenomenon of ‘more silt in water, less cavitation abrasion on the surface of flow-part’, and using experiments and theoretical analysis, the relationship between characteristic of particles and Cavitation performance are studied to build the quantitative relation between them, then, the silt characteristic of several typical section of the the Yellow River and tension strength of silt-laden water can be obtained. To recover the mechanisms of the strange phenomenon that cavitation abrasion would be more weaken when sediment concentration exceeded critical value, the interactions of sands and cavitation are detailed studied for there are several possible reasons for the problem. Based on above studies, the results are applied to develop the theory of deciding the elevation of pump, which are the most important factors to prevent cavitation in pump. By the research program, the mechanisms of the quantitative relationship between characteristic of particles and Cavitation performance are built and the mechanisms of the strange phenomenon are revealed. The characteristic curve among cavitation , silt-laden water and can be obtained to correct the elevation of pump working in silt-laden water.

针对我国引黄泵站存在的严重泥沙磨蚀问题，以探索“超临界泥沙含量抑制空蚀”的机理为线索，实验研究和理论分析相结合，研究泥沙特性与液体空化性能的响应机制，建立固体颗粒特性与液体空化性能之间量化关系，得到黄河典型河段泥沙特性以及泥沙与含沙水空化性能的响应规律；针对“超临界泥沙含量抑制空蚀”的成因，研究高含沙水中泥沙特性与空化空蚀的伴生机制，揭示含沙量超过临界值之后抑制空蚀的机理；研究含沙水条件下水泵空化性能变化规律，提出含沙水流条件下水泵安装高程修正方法。通过本项目的开展，能够揭示固体颗粒表面特性与含沙水空化性能的响应机制；能够揭示泥沙对磨蚀的促进和抑制的机理；得到温度-含沙特性-空化性能关系曲线，完善现有基于清水介质的水泵安装高程修正方法，为含沙水中水泵安装高程修正提供依据。

针对我国引黄泵站存在的严重泥沙磨蚀问题，以探索“超临界泥沙含量抑制空蚀”的机理为线索，实验研究和理论分析相结合，主要开展了四个方面的研究工作：（1）水中空化成核的分子动力学模拟与研究；（2）固体颗粒特性与空化初生响应关系研究；（3）泥沙对空化空蚀效应影响的试验研究；（4）泥沙对离心泵汽蚀性能影响的实验研究。取得的主要成果和科学意义如下：. （1）通过分子动力学方法对含沙水中空化成核的研究，从理论上揭示了纯水和含杂质水中空化成核机理，揭示了离子与气体、固体表面亲疏水性对空化成核的影响机理，研究结果表明含沙水中所含有的杂质影响了水的空化性能，尤其是疏水性质的固体有效降低了水的抗拉强度、促进了空化的发生，从理论上为更好地认识和进一步探究含沙水中的空化性能提供了依据。. （2）固体颗粒特性与空化初生的研究结果表明：随固体颗粒浓度和粒径增大，初生、临界空化压强越大，研究结果表明颗粒浓度和粒径增大导致的气核数量增加是空化更易发生的主要原因，这也是引黄泵站虽然严格按照规范设计依然导致严重汽蚀破坏的重要原因。. （3）通过泥沙对空蚀破坏效应影响规律的实验研究，揭示了超过临界含沙量后空蚀破坏效应减轻的机理，在超过临界含沙量条件下，空蚀效应被抑制的原因并不是空化强度减弱了，而是固体颗粒对空泡溃灭能量缓冲、吸收和抑制作用的结果。. （4）通过清水和不同含沙浓度下的离心泵汽蚀试验，研究了含沙对离心泵汽蚀性能的影响规律，临界汽蚀余量会随着含沙浓度增大而增大。得到了水泵临界汽蚀余量与泥沙浓度的变化规律，给出了不同含沙量条件下水泵汽蚀余量的修订方法，为含沙水条件下合理确定水泵的安装高度提供了依据。. 通过本项目的开展，揭示了固体颗粒表面特性与含沙水空化性能的响应机制；揭示了泥沙对磨蚀的促进和抑制的机理；完善了现有基于清水介质的水泵安装高程修正方法，为含沙水中水泵安装高程修正提供了依据。