Research On Pressure Fluctuation Characteristics Of Cavitation Impinging Stream Field

The cavitation-impinging stream is a novel flow field structure,which has the characteristics of efficient macro mixing,micro mixing and strong pressure fluctuation.In this paper,in order to reveal the pressure fluctuation law of cavitation-impinging stream field and its influencing factors,with the help of self-developed cavitationimpinging stream reactor,the characteristics and distribution of pressure fluctuations in cavitation-impinging stream field were studied from three aspects: theoretical analysis,numerical simulation,and experimental research.It is the basic work of the development and application of cavitation-impinging stream technology.In this paper,the physical and mathematical models of cavitation-impinging stream is established by theoretical analysis firstly.The fluid is regarded as composed of countless fluid micelles,and the trajectory equation,velocity distribution function and pressure distribution function of the micelles are obtained respectively,provide a theoretical basis for the study of pressure fluctuation characteristics of cavitationimpinging stream field.Next,a numerical simulation of the cavitation-impinging stream field was performed.The simulation results showed that the velocity of the fluid on the impact surface was zero and the pressure was the maximum value;There is an elliptical highpressure impact area with a long axis of 20 mm and a short axis of 10 mm in the impact center.The size of this area does not change with the impact speed,and the pressure value in the flow field gradually decreases outward along this area.Finally,through experimental research,a complete set of cavitation-impinging stream field pressure fluctuation measurement device was established.For the first time,high-precision pressure sensor and dynamic signal analysis system were used to measure the amplitude and frequency of pressure fluctuation at different positions of flow field in the reactor under different flow rates.By analyzing the measured amplitude,the results show that there is a cube cavitation impact area with a side length of about 10 mm,and the pressure amplitude in this area is stronger than others.When the flow rate reaches 1000L/h,the amplitude in this area can reach up to 640 kPa.The amplitude value of the pressure fluctuation in the flow field gradually decreases outward along this impact zone.By analyzing the fluctuation frequency at different locations and different flow rates,the results show that the fluctuation frequency on the impact surface is much stronger than other locations,it changes frequently and can not remain stable,the highest frequency can be achieved to 50 Hz.As it moves away from the impact surface,the frequency of the flow field fluctuation caused by the impact gradually weakens.By numerically fitting the fluctuation frequency to the flow rate,the relationship between the fluctuation frequency and the flow rate is a cubic power function.In summary,through this study,around the impact center,there is a cavitation impact zone in the cavitation-impinging stream field that does not change with the impact velocity and it has strong pressure fluctuation.The amplitude of pressure fluctuations in this area is strong,the fluctuation frequency changes frequently and cannot be stable,the pressure fluctuation in the flow field gradually decreases outward along this area.