Example of pump cavitation in the engine (including schematic diagram)

1. Engine pump cavitation fault description

One case of pump cavitation in the BFM1015 water-cooled engine (Figure 2, Figure 3). 2 is a schematic diagram of equilibrium pore cavitation, and FIG. 3 is a schematic diagram of cavitation of the position of the impeller attached to the pump body.

 平衡孔气蚀示意图
Figure 2 Schematic diagram of equilibrium hole cavitation

2. Pump cavitation failure mechanism

The balance hole of the water pump is a hole that acts as a balancing pressure between the water inlet and the outlet of the pump. The cavitation generally occurs in a place with a large pressure difference. Therefore, the cavitation of the balance hole in the pump is normal during long-term use. Seriously even a larger area of ​​breakdown.

The cavitation phenomenon occurring in the position of the impeller attached to the pump body shown in Fig. 3 is more serious. Starting from the principle of the water pump, the water pump impeller rotates at a high speed, and the water in the water inlet chamber is turned to the water outlet chamber to complete the pumping function. As shown in Figure 4, the flow direction of the water in the pump, the water from the water inlet through the impeller rotates into the water outlet, and the coating part shown in the figure is the impeller inlet, the impeller inlet is the lowest pressure, if this place liquid Pressure equals

 叶轮贴合泵体位置的气蚀示意图
Figure 3: Cavitation diagram of the position of the impeller-fitted pump body

Or lower than the vaporization pressure Pv of the liquid at this temperature (the vaporization pressure of water is 47.36 kPa at 80 ° C), there will be a large amount of vapor and dissolved in the liquid from the liquid, forming a lot of steam mixed with the gas. Small bubbles. These small bubbles flow with the liquid to the high pressure zone (outlet chamber), because the bubble is vaporization pressure, and the pressure around the bubble is greater than the vaporization pressure, resulting in a pressure difference. Under this pressure difference, the bubble is crushed under pressure. And re-condensing, in the process of condensation, the liquid particles accelerate from the periphery to the center of the bubble, and at the moment of condensation, the particles collide with each other, resulting in a high partial pressure. The rupture and condensation of these bubbles occurs on the surface of the pump body that is in contact with the impeller, and the active gas (such as oxygen) in the water accelerates the damage of the pump surface, causing severe cavitation of the pump, and the pump is working under cavitation. The area where cavitation occurs is quickly destroyed into a honeycomb or sponge (Fig. 5).

水泵中水流方向
Figure 4 Water flow direction in the pump

气蚀示意图
Figure 5 Schematic diagram of cavitation

Metal processing online more relevant information: analysis of the causes of cavitation in pumps

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