Expert Yogi
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| Cavitation erosion, sediment wear and their combined action are the important reasons for the damage of all kinds of pumps at present. Through experimental and numerical simulation research, it is found that the mechanism of cavitation erosion, wear and their combined action is the basis for developing the optimal design method of fluid machinery and improving the ability of fluid machinery to resist cavitation erosion, sediment wear and damage. Since the factors that affect cavitation erosion, sediment wear and their combined action behavior include not only flow field parameters such as velocity and pressure, but also sand particle and material properties, since the 1970s, the research in this field has been carried out and made progress in the aspects of cavitation erosion, wear and combined action mechanism, the interaction between various factors, as well as the anti-wear materials of pumps to improve wear resistance.
The protection of sediment abrasion of wear-resistant pumps is also based on the successful countermeasures selected after studying the causes. In turn, it provides theoretical support for the study of the mechanism of the rapid destruction of the flow surface of hydraulic machinery.
In terms of the classification of wear, the commonly used classification is adhesive wear, abrasive wear (abrasive wear), friction oxidation and fatigue wear. Wear resistant water pumps and turbines should be subject to abrasive wear if they work in sandy rivers. According to Lorentz's opinion, abrasive wear can be divided into three categories: consolidated abrasive, semi consolidated abrasive and free abrasive. Consolidated abrasive particles such as sandpaper, grinding wheel, file, etc. The abrasive particles are fixed on the surface of a material and cannot be moved. The result of wear is that the abrasive particles are ground, fallen off and damaged. Semi consolidated abrasive particles are not fixed, so the abrasive particles can slide and roll, but the degree of freedom is still small. For example, the bulldozer's shoveling and ploughing in piles of sediment belong to this kind of wear. Free abrasive particles, such as air flow or water flow, carry out contact or relative movement on the ground object, and furrows appear on the ground object. When the abrasive particles are fine, they can also grind the ground object smooth. At this time, the movement of abrasive particles has greater freedom. It can roll, slide, jump, etc. freely. The results of long-time wear are wavy and grooved. The sediment wear of wear-resistant pumps and turbines and the wear of wind and sand on fan blades during wind power generation belong to a type of free abrasive wear.
The surface damage of flow passage components seen by pumps and turbines working in clear water medium is called cavitation erosion. When bubbles in water burst in the high-pressure area, thousands of atmospheric pressures can be generated. When bubbles burst on the metal surface, they will have an impact on the metal, which is the basic consensus on cavitation erosion at present. In addition to cavitation erosion, there is also sediment abrasion on the surface of water pump and turbine flow passage parts working in sediment laden water flow. This kind of cavitation erosion and abrasion that exist at the same time is called sediment abrasion (combined action of abrasion and cavitation erosion). Wear and cavitation are caused by two distinct mechanisms, which are on the material surface of flow passage parts; There are also obvious differences in the characteristics of damage. In the test of muddy water tunnel, the submicroscopic observation of various parts of the specimen around the fluid can clearly show the differences between them and the changes of interaction and alternation.
prevent water ring vacuum pump unit from being corroded to methods |
Which pumps can resist sediment abrasion?
