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水轮机叶片的气蚀问题,一直是国内外重视而又未妥善解决的研究课题。选择聚氨酯作抗气蚀涂层材料,并作了初步的研究工作。对四种类型的聚氨酯材料作了物理性能对比试验。使用聚醚型聚氨酯,3,3′二氯,4,4′二氨基二苯基甲烷(MOCA)作固化剂,就分子量、官能度、固化剂、固化方式,填料等对涂层的物理性能进行了初步考察。使用15MnMoVCu、A_3钢,低温烧结工业糖瓷,有机玻璃等材料与醚型聚氨酯涂层材料在实验室水洞式(隧洞式)模拟气蚀试验装置上进行试验,结果表明聚氨酯材料具有八十八小时以上的抗耐效果,而其他材料在3～5(?)小时分别出现气蚀与剥落现象。涂层在144瓦小型转浆式水轮机叶片(中等气蚀强度)的实地运行试验表明能抗耐1050小时间断运行。进而在1.8万千瓦混流式水轮机叶片,3.6万千瓦轴流式水轮机叶片,4.17万千瓦混流式水轮机叶片分别进行了涂布试验,其中在4.17万千瓦混流式水轮机上的有些配方的涂层在累积运行七个月(5034小时)以后,在叶片背面出水边有80～00%的涂层面积无气蚀和脱落现象(整个进水边背面涂层基本完整无缺),能抗耐中等强度的气蚀破坏。水轮机运行过程中,由于气蚀破坏作用叶片材料受到严重破坏,关于这种气蚀破坏的机理,国内外都在大量进行研究和探讨,但尚无统一的论述和完整的理论。气蚀可发生在有液体相对快速运动的任何装置中。据报导这些设备中的气蚀破坏效应已有七十年资料记载。为了寻找解决的途径,国外报导使用一些实验室装置,模拟实际工作体系的气蚀效应,企图从设计、加工工艺、材质,以及金属与非金属涂层等方面进行研究。我们考虑采用有机高分子涂层,减缓和避免气蚀破坏、设想采用“以柔克刚”的手段,选用耐磨、耐水强度高,有弹性的聚氨酯材料,用作抗气蚀涂层。关于高分子抗气蚀涂层的研究,国内外都有一些报导,但均未妥善解决,而且由于试验方法不同结果也有差异。下面就一些试验情况进行讨论:
Cavitation erosion of turbine blades has always been a research topic that has not been adequately solved at home and abroad. Select polyurethane as anti-cavitation coating material, and made a preliminary research. The physical properties of four types of polyurethane materials were compared. Polyether polyurethane, 3,3 ’dichloro, 4,4’ diaminodiphenylmethane (MOCA) as a curing agent, the physical properties of the coating in terms of molecular weight, functionality, curing agent, curing mode, Conducted a preliminary inspection. Using 15MnMoVCu, A_3 steel, low temperature sintering of industrial sugar china, plexiglass and other materials and ether polyurethane coating material in a laboratory water tunnel (tunnel) simulated cavitation test device, the results show that the polyurethane material has 88 Hour or more of the anti-resistance effect, while other materials in 3 ~ 5 (?) Hours, respectively, cavitation and spalling phenomenon. Field trials of the coating on a 144-watt small slurry turbine blade (medium cavitation intensity) show that it is resistant to 1050 hours of intermittent operation. Further, coating experiments were carried out on Francis turbine blades of 18000kw, 36000kw axial turbine blades and 41,700kw Francis turbine blades, respectively. Some of the formulations on the 41,700kw Francis turbines were accumulating After running for 7 months (5034 hours), there is no cavitation and shedding of 80 ~ 00% of the coating area on the back of the blade (the back coating on the influent side is basically intact), resistant to medium-strength gas Erosion damage. During the operation of turbine, the material of vane is severely damaged due to cavitation damage. There are many studies and discussions on this mechanism of cavitation destruction at home and abroad, but there is no unified theory or theory. Cavitation can occur in any device that has relatively fast movement of the liquid. The cavitation damage effects reported in these facilities have been documented for seventy years. In order to find a solution to the problem, foreign reports use some laboratory devices to simulate the cavitation effect of the actual working system in an attempt to study the design, processing technology, materials, and metal and nonmetal coatings. We consider the use of organic polymer coatings to mitigate and avoid cavitation damage. We envisage the use of “soft-touch” means of use as a wear-resistant, water-resistant and elastic polyurethane material for anti-cavitation coatings. About the research of polymer anti-cavitation coating, there are some reports at home and abroad, but none of them are properly solved, and there are also differences due to different test methods. The following discussion of some experimental conditions: