Some features of the cavitation phenomenon The throttles are widely used in hydraulic components and hydraulic systems, so cavitation phenomena are also widely present in various hydraulic systems. The cavitation phenomenon itself has some inherent characteristics. By studying these characteristics, not only can we further understand the nature of the cavitation phenomenon, but also can give a method to eliminate cavitation. When cavitation occurs, there are the following characteristics: (1) After cavitation occurs, although the pressure difference before and after the orifice continues to rise, the flow through the orifice no longer increases. This feature can be called the "occlusion" feature of cavitation. The reason for this characteristic is that the increased pressure difference is consumed in the vaporization zone generated by the cavitation. (2) The geometry of the throttle position inlet has a considerable influence on cavitation. After the cavitation occurs in the orifice with no fillet transition at the entrance, the “bubble curtain†generated by the cavitation is congested in the orifice, causing the occlusion of the orifice, which has a significant influence on the flow characteristics. However, the “bubble curtain†generated by the throttle with the corner transition at the entrance often occurs behind the orifice, and has less influence on the flow characteristics. Therefore, cavitation is more sensitive to the microstructure of the orifice and the orifice. (3) When cavitation occurs, it is accompanied by a lot of noise, which sounds like a scream. It was found through experiments that this was caused by the generation and collapse of air bubbles in the cavitation. At the same time, high pressure pulsation occurs in the hydraulic pressure, and the frequency of pulsation is above 200 Hz. If this pulsation is coupled with the natural frequency of other components, it may cause high frequency pulsation in the hydraulic system. The effect of cavitation on the engine operating characteristics. Cavitation during start-up acceleration By analyzing the start-up acceleration process of the vortex engine fuel supply regulation system, it can be seen that when the regulated valve is opened, the pump outlet pressure has basically risen to the rated pressure. At this point, the fuel regulating valve has not been opened and the restrictor supplies fuel to the combustion chamber separately. Since the pump outlet pressure p rises rapidly, the increase in the fuel pressure p is relatively delayed for a while, so the pressure difference before and after the restrictor is large. Compared with the flow characteristics of the restrictor, it can be seen that the cavitation phenomenon occurs in the restrictor at this time, which lasts for approximately 4 s. With the fuel regulating valve open, the fuel pressure rises rapidly to the second half of the acceleration section and the cruising state. The pressure difference before and after the restrictor decreases, and the cavitation phenomenon disappears. Therefore, in the acceleration section, cavitation occurs in the restrictor and lasts for about 4 seconds, which will certainly affect the normal operation of the oil supply regulation system.
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