Calculation Of Internal Flow Of The Twin-screw Pump And Strength Check Of Its Rotor

The twin screw pump is a kind of positive displacement rotor pump,which is widely used in many engineering and technical fields such as ship equipment,petrochemical industry,food production,etc.It has many advantages such as small pressure pulsation,large flow,wide range of transportable media,strong self-priming performance and compact structure.In 1984,China introduced the twin-screw pump technology.With the maturity of the equipment manufacturing process and the expansion of the application range of the screw pump,the twin screw pump has started to develop in the direction of heavy load,large-scale and medium diversification.The complicated working conditions have posed challenges to the design of twin screw pumps.Therefore,the design and performance optimization of twin screw pumps need to be further improved.The subject takes the B-type twin screw pump which is already in the market as the research object.After a theoretical study and analysis of meshing process of two screws,a series of assumptions of radial force calculation are proposed.The "unbalanced area" method is introduced as a mathematical model of the radial force exerted on the rotor to deduce the variation of radial force with time.The boundary conditions during the operation are analyzed,and the pressure distribution between the screw rotor and the liner is verified by hydraulic calculation to prove the rationality of the hypothesis.Creatively,the radial force is used as the alternating stress to calculate the strength,and the thread pretightening force and the axial force are added to the shaft strength checking process.Compared with the previous strength calculation method,it is proved that the range of radial force and axial force should be considered in the design of the twin screw pump.In this paper,the theoretical derivation and numerical simulation are combined to study the influence of the pressure difference,the number of lead and the ratio of inner diameter to outer diameter on the radial force of the twin screw pump.Through the transient calculation,the pressure distribution information in the internal flow field is obtained.This paper provides a theoretical basis and method for the research on the variation of the radial force of the twin screw pump with time,the vibration and noise of the pump and the calculation of the main shaft strength.It also has certain reference value for the research of other forms of screw pumps.