Study On Cavitation Characteristics In Multistage Series Parallel Venturi

Cavitation is a kind of complex multiphase flow phenomenon between gas and liquid.Its essence is the whole process of bubble generation,growth and collapse caused by local low pressure in the process of fluid flow.During the cavitation process,there will be high temperature above 5000 K and high pressure of 50 MPa,accompanied by strong shock wave and water jet with speed up to 400km/h.Therefore,reasonable use of these characteristics generated by cavitation has become the starting point to explore the phenomenon of hydraulic cavitation.In this article,the venturi tube was used as the carrier of cavitation research.The numerical simulation of single-stage,series and Parallel Venturi tubes was carried out.Combined with experimental verification(mung bean seed water absorption experiment),the cavitation characteristics of multi-stage series and Parallel venturis under different operating conditions(inlet pressure and temperature),and different throat size and outlet cone angle were explored.The average gas holdup(the ratio of gas volume to total volume of Venturi)is used as the Parameter to characterize the cavitation effect,and the relationship between the above factors and the cavitation effect in multi-stage series and Parallel Venturi tubes was obtained.Theoretical aspect: Based on the three conservation equations of mass,momentum and energy,the pressure loss model and water vapor two-phase dynamic cavitation model in the venturi were derived,and the structural design model of the geometric model of the venturi was established.According to the cavitation dynamic equation and the variable dimension of cavitation number,combined with the cavitation characteristics in the venturi,the reasonable numerical simulation control equation and turbulence model of Venturi were established.Numerical simulation: ICEM was used to mesh the multi-stage series and Parallel venturi models,and then the numerical calculation method and boundary conditions of the venturi in FLUENT software were set;the established venturi model was used to verify the numerical calculation method,and reliable numerical calculation results of Venturi were obtained;and the transient cavitation process was described quantitatively.Experimental research: a reasonable venturi cavitation device was established,and the cavitation effect of multi-stage series venturi,parallel venturi and singlestage and series venturi with different outlet cone angles were verified under the same operating pressure.The cavitation effect in Venturi was comprehensively analyzed by measuring the temperature and conductivity of cavitation water samples,and the water absorption experiment of mung bean seeds.The results are consistent with the numerical simulation,which provides a theoretical reference for the practical application of venturi.