Study On The Evolution Process Of Cavitation In Venturi And Its Influencing Factors

As a complex hydraulic phenomenon,the harm caused by cavitation has always been the focus of attention.But it can not be ignored that the collapse of cavitation bubbles will produce instantaneous high temperature,high pressure and high-speed jet phenomena,that is to say,this process contains huge energy.It not only strengthens physical and chemical processes,but also achieves the goal of energy saving and efficiency improvement.At present,no breakthrough has been made on how to effectively generate cavitation,what kind of efficient cavitation equipment is used,and how to accurately quantify cavitation effects.Therefore,it is of great significance to study the evolution process of cavitation and the influencing factors of cavitation effect.In this paper,the venturi tube of hydrodynamic cavitation generator is used as the research carrier,and the evolution process of internal cavitation and the influencing factors of cavitation effect are studied by theoretical analysis,numerical simulation and experimental testing.Theoretical aspects: Firstly,three conservation equations of fluid mass,momentum and energy are established from macroscopic fluid;Then,the bubble dynamics model is established from microscopic individuals;Finally,considering the deficiency of the current steady-state cavitation model and the cavitation bubble source generated by hydraulic cavitation,the water-vapor two-phase dynamic cavitation model of the Venturi tube is established,which provides theoretical support for the cavitation evolution process in the Venturi tube.Numerical simulation:Firstly,the geometric model of the internal fluid domain of the venturi tube is built in CREO,and the structured grid of Venturi tube is divided in ICEMCFD;Then,in the fluid simulation software FLUENT,the cavitation of Venturi tube under different structural parameters(inlet cone angle,outlet cone angle,throat diameter,cross section shape),physical parameters(initial gas content,surfaceroughness)and operating conditions(inlet pressure,temperature)is simulated,and the vapour rate is used to judge the pros and cons of the cavitation effect.The relationship between the above influencing factors and the cavitation effect in the Venturi tube is obtained.Experimental testing:Established experimental reaction devices including pumps,motors,water storage tanks,pressure gauges,venturi tubes,piping,etc.And an experimental detection device(visible spectrophotometer)was established in the laboratory.By measuring the change in absorbance(concentration)of methylene blue solution before and after the reaction,the cavitation situation of Venturi tube under different conditions is obtained,and verifies the theoretical analysis and simulation.The results show that the change of the length of the venturi tube has different effects on the cavitation effect under the same structural parameters,which provides a strong basis for the practical application of the venturi tube.