Experimental And Numerical Simulation Study On The Effect Of Water Temperature On Cavitation

Based on the requirements of the carbon peaking and carbon neutrality goals,hydraulic machinery is aimed at stable and efficient operation to provide a guarantee for the efficient use of energy.The cavitation problem of hydraulic machinery is an important obstacle to its efficient and stable operation,and is also a hot spot and difficult area of scientific research.Cavitation research in hydraulic machinery is usually carried out under room temperature conditions,but in practical engineering,hydraulic machinery in abnormal atmospheric temperature water media has an increasingly wide range of applications.The cavitation phenomenon itself has thermodynamic effects and is significantly influenced by the ambient temperature.Therefore,cavitation flow studies that consider the effects of temperature are necessary.Firstly,the experimental study of venturi cavitation flow at different water temperatures is carried out,and the cavitation characteristics of venturi at different water temperatures and different flow conditions are obtained by recording the cavitation phenomenon with high-speed camera technology.The relationship between the flow characteristics and temperature-related parameters is quantitatively analysed to obtain the Reynolds number,flow coefficient and thermodynamic parameters with temperature at different water temperatures.Secondly,a numerical simulation study of venturi cavitation flow at different water temperatures is carried out based on experimental conditions.The Zwart-Gerbera-Belamri(ZGB)cavitation model commonly used in engineering and the Thermodynamic Zwart-Gerbera-Belamri(TZGB)cavitation model modified to take into account the effect of temperature are compared,and the applicability of the TZGB cavitation model to different water temperatures is verified based on the experimental results,and the numerical calculation results of the cavitation flow field under different water temperatures and different flow conditions are obtained.The cavitation phenomena are compared between numerical calculations and experiments,the dimensionless cavity length is quantified and the variation of cavitation phenomena in the venturi with water temperature under different operating conditions is summarised.Finally,the TZGB cavitation model,modified to take into account the effect of temperature,is used for the numerical simulation of centrifugal pumps under different water temperature conditions.As the water temperature increases,the critical cavitation number increases as the head of the centrifugal pump decreases and cavitation occurs earlier.Combined with entropy production theory for energy characteristics analysis,summarise the relationship between cavitation characteristics and energy loss.Under different water temperature conditions,the cavitation region and transient characteristics within the impeller of the centrifugal pump are compared,and the pressure pulsation characteristics are analysed to investigate the influence of water temperature on the pressure pulsation of cavitation flow.The research results obtained in this thesis lay the foundation for the reasonable prediction of cavitation flow field under different water temperatures,which is of great significance to reveal the cavitation characteristics inside the centrifugal pump under different water temperatures,provide theoretical guidance for the operation of fluid machinery in practical engineering considering the influence of water temperature,and provide technical support for the prediction of cavitation flow under different water temperatures.