Cavitation phenomenon and solution 2.1 Cavitation Phenomenon Because the liquid near the inlet of the impeller blade is less than or equal to the saturated vapor pressure at the liquid transport temperature, the liquid evaporates, and at the same time, the gas dissolved in the liquid may escape to form a large number of bubbles , Bubbles flow with the liquid flow to the higher pressure at the leaf when the instantaneous coagulation collapse. At the moment when the bubbles condense and collapse, the liquid around the bubbles quickly flushes into the cavities formed by the bubbles to form a strong local high-frequency and high-pressure water hammer, and the metal surface is denuded due to fatigue. At the same time, the electrochemical corrosion of the metal surface occurs due to the presence of an active gas (such as oxygen) and the local high temperature generated when the bubbles condense. This process is called cavitation. 2.2 Factors Affecting Cavitation Influencing liquid pressure and saturated steam pressure will affect the occurrence of cavitation. 2.2.1 The impact of factors ①pump inlet structural parameters: including the shape of the impeller suction inlet, the width of the inlet edge of the blade and the edge of the blade inlet edge and the shape of the front cover. ② pump operating conditions: It includes the pump flow, head and speed and so on. ③ pump installation location: It includes the pump suction pipe hydraulic loss and installation height. ④ environmental factors: it includes the installation of atmospheric pressure at the pump site. 2.2.2 Influencing Factors It includes the nature of the media itself and the media operating temperature. 2.3 to solve several problems of centrifugal pump cavitation According to the above analysis of the impact of cavitation factor, we can get the following several solutions to solve the problem of centrifugal pump centrifugal pump: ①improve the structural parameters of the pump inlet This program is suitable for centrifugation Pump design and manufacturing phase, the method is rarely used in the production site. ② In the suction inlet of the pump, the induction wheel is added with the induction wheel to improve the anti-cavitation performance of the centrifugal pump and solve the cavitation problem. The effect is remarkable. And its simple structure easy to manufacture and install, easy operation and maintenance, low cost, without prejudice to the premise of production can be installed and debugged, especially suitable for promotion and application in the production site. ③ Reasonable design suction pipe and adjust the installation height Although this method can completely eliminate cavitation problems, but rarely used in the production site. This is because the pump suction pipe and installation height adjustment, large quantities, high construction costs, and by the construction environment constraints, only when the device parking or overhaul can be carried out at the same time, due to process conditions, adjust the pump Inhalation pipe and installation height will affect the follow-up process, with a chain reaction. ④ optimize the operating conditions of the process conditions permitting, change the pump flow, lift, speed and medium operating temperature and other operating parameters, to avoid the occurrence of cavitation. However, due to the limitation of the process conditions, the optimization of the process operation conditions has great limitations, and the effect is not significant in most cases. Therefore, this method can be used as a secondary solution to cavitation problems. 2.4 program to determine Through the analysis and comparison of the above programs, without affecting the normal production under the premise of the pump to solve the problem of cavitation should be preferred at its entrance to install induction wheel. 3 Induction wheel design When the liquid flows through the induction wheel, the induction wheel does work on the liquid, which is equivalent to the liquid entering the impeller behind to boost the pressure, thereby increasing the pressure. Although this method increases the load on the motor, the power of the motor is usually relatively large (usually 20-30% larger than the shaft power of the centrifugal pump), and the size of the inducer is affected by the diameter of the suction port. The supercharging range limited. The motor can still meet the general requirements, do not need to replace the motor. Due to the current understanding of induction wheel is still in the exploratory stage, there is no unified view on some theoretical issues. Therefore, the induction wheel design is largely based on experience, combined with the actual structure of the pump carried out. The 217-J / JA (model D1011 3 × 11/2 × 8) pump (Figure 1) will be taken as an example to introduce the design method of the inducer and provide some references for solving the pump cavitation problems in the field.