Study On Hydrodynamic Cavitation Degradation Of Rhodamine B In Alcohol Aqueous Solution

Cavitation bubbles produced in the process of hydrodynamic cavitation can release huge energy and form local extreme environment in the liquid.The intensification of some physical and chemical reactions can be achieved by utilizing the extreme environment and energy in this process.In order to clarify the influence of structural parameters of throttling device,liquid saturated vapor pressure and other factors on the intensity of hydrodynamic cavitation and organic degradation effect,so as to realize the purpose of optimizing the structure of throttling device and liquid selection.In this paper,hydrodynamic cavitation is studied in the following aspects:1.Numerical simulation method is used to simulate the influence of structural parameters of venturi cavitation.The simulation results show that the structural parameters have different effects on hydrodynamic cavitation.(1)With the increase of the Angle of the contraction segment,the cavitation area firstly increases and then decreases;When the half Angle of the contraction segment is 10°,the cavitation area is the largest.(2)When the diffusion Angle varies from 2.5° to 10.5°,the larger the Angle,the smaller the cavitation area.(3)When the throat diameter increases from 2 mm to 36 mm,the cavitation area increases first and then decreases.When the throat diameter is22 mm,the cavitation area formed at the same pressure condition is the largest.(4)The length of cavitation throat restricts the effect of hydrodynamic cavitation.The longer the throat,the smaller the cavitation area.2.The hydrodynamic cavitation experiment device was designed and built.The optimal concentration of Rh B is 5.0 mg/L.The degradation experiment of rhodamine B(Rh B)is carried out by using this device.The experimental results show that the degradation effect can be affected by operating conditions.When p H=3.5,the degradation effect can be increased by 42.59% compared with neutral environment,proving that acidic condition is more conducive to the improvement of cavitation effect.The difference of degradation effect can reach 5.03% by changing the inlet pressure of cavitation.The influence of cavitation inlet pressure,solution p H and Rh B initial concentration on degradation effect can be ranked as: solution p H>Rh B initial concentration>Inlet pressure.The use of methanol,ethanol,ethylene glycol and glycerin inhibited the degradation effect,and the maximum reduction of degradation rate is45.31% when 0.5 Vol.% is used.When alcohol additives with high saturated vapor pressure are used,the optimal experimental pressure moves towards low pressure.The optimum experimental pressure moves towards the high pressure direction with alcohol additives depressed by saturated steam.3.Vibration signals induced by cavitation flow were collected and analyzed,and the position of characteristic peak of vibration signals induced by cavitation process is determined to be at 12500 Hz.The intensity of cavitation induced vibration characteristic peak increases with the increase of cavitation inlet pressure.After adding four different alcohol additives,the position of cavitation induced vibration characteristic peak don’t change,but the peak value decreased with the increase of the concentration of alcohol additives,which is consistent with the inhibition effect of adding alcohol additives in the degradation experiment.The vibration time domain signal in cavitation is stochastic and repetitive.After the use of alcohol additives,the impact intensity of high amplitude acceleration impact signal is weakened and the frequency of occurrence is reduced.