沙粒粒径对水力机械材料磨蚀性能的影响

对于运行于多泥沙河流的水力机械而言磨蚀问题不可避免,磨蚀会造成水力机械过流部件失重、变形,带来效率下降、维护成本增加等问题。目前针对磨蚀破坏机理的研究尚不完善,该文利用旋转喷射磨蚀试验装置对4种水力机械常用材料进行5种不同沙粒粒径下的磨蚀试验,借助扫描电镜及激光共聚焦扫描电镜对试件磨蚀表面进行二维和三维形貌观察,探究沙粒粒径对水力机械材料磨蚀破坏失效行为的影响规律及作用机理。结果表明:沙粒粒径为0.043、0.147及0.248mm时,试件磨蚀累计质量损失与时间呈线性相关,而粒径为0.349与0.449mm时质量损失与时间满足Gauss函数关系;沙粒粒径会影响试件的磨蚀特征,粒径为0.043 mm时试件表面磨蚀破坏主要为沙粒的垂直冲击磨损与空蚀,无明显水平方向的切削磨损,粒径为0.147、0.248、0.349及0.449mm时试件表面的磨蚀破坏以水平方向的切削磨损和空蚀破坏联合为主,并伴有一定量的垂直冲击磨损;通过分析4种材料的磨蚀特征,发现磨蚀质量损失与粒径大小二者之间存在强相关区与弱相关区的关系。该研究可为合理控制水力机械过流粒径大小及制定抗磨措施提供参考。

Effect of silt diameter on abrasion performance of hydraulic mechanical materials

The abrasion problem is inevitable for hydraulic machineries which operate in sediment-laden rivers. Abrasion can induce serious wear damage such as material weight loss and distortion in hydro-equipment. The wear damage can lower the efficiency of hydraulic machineries, shorten the maintenance period, and increase maintenance cost. Therefore, it is necessary to study the abrasion mechanism to avoid the abrasion. The mechanism of abrasion failure has not been well understood at the present time, and there are still some arguments about the mechanism. Thus, in this research, a rotating abrasion test device was utilized to study the material abrasion of hydraulic machineries with different particle sizes. The test device was composed of a mixing tank, a speed-regulating motor, a diaphragm pump, a constant voltage system, a cooling system, a turntable room and a control cabinet. The turntable was driven by the speed-regulating motor at a high speed, and the test specimens were placed on the rotary table around the annulus. The same cavitation-induced holes were opened on the surface of the different specimens, and the cavitation would happen behind the cavitation-induced holes. Meanwhile, the test specimens were jetted with silt carrying flow which came from four nozzles. The nozzles with a diameter of 2.5 mm were equally distributed in the circumferential direction. Thus, both the cavitation and the impact wear could be observed on the test specimen surface. Four kinds of common materials used in hydraulic machineries were tested for 24 h, and the weight loss of specimens was weighed every 3 h with electronic scales. Two specimens with the same material were diagonally placed on the rotary table around the annulus. A total of 8 specimens were placed on the table. The averaged value of the same test specimens was recorded before and after the test. The change of the averaged value was defined as the weight loss of abrasion. The irregular massive sand came from Yellow River Garden Estuary. The used five particle sizes of sand were obtained with screen mesh. According to the wear condition of sand grains, the sand was changed regularly during the test to ensure the same geometric shape of sand grains. The sand was changed every 6 h in this test. The surface morphology observation of specimens was one of the most effective and intuitive methods for abrasion analysis. With the help of Search Engine Marketing (SEM) and Laser Scanning Confocal Microscope (LSCM), the 2D and 3D surface morphology of the specimens were observed after the abrasion test. The mechanism and influence law of the effect of particle sizes on the material abrasion failure behavior of hydraulic machinery were obtained by observing the surface abrasion morphology and the number of cavitation pits. The results showed that there was a linear relationship between the abrasive weight loss of specimens and the test time when the sand size was 0.043, 0.147 and 0.248 mm. However, when the particle size was 0.349 and 0.449 mm, the relationship of the weight loss and the test time matched the Gauss function. Meanwhile, the variation of sand particle size changed the character of specimen abrasion. When the sand particle size was 0.043 mm, the surface abrasion damage of specimens was mainly composed of vertical impact wear of sand particles and cavitation, and there was no obvious cutting wear in the horizontal direction. Nevertheless, when the sand particles were 0.147, 0.248, 0.349 and 0.449 mm, the abrasion failure on the surface of specimens contained cutting wear in the horizontal direction and cavitation damage. A certain amount of vertical impact wear can also be observed. A strong correlation region and a weak correlation region between the weight loss of specimen abrasion and the sand particle sizes were separated based on the analysis of the four materials abrasion characteristics.