Optimized Design Of Twin-Screw Pump Screw Rotor Profile

Twin-screw pump plays an important role in more and more fields due to its strong self-priming performance,stable liquid transport,no pulsation,low vibration and low noise.The key component of the twin-screw pump is a pair of screw rotors of a twin-screw pump,and its structural parameters directly determine the performance of the twin-screw pump.The research work for twin-screw pump started late in our country.,and there is a certain gap with the advanced twin-screw pump manufacturers in the world.The existing twin-screw pumps are mostly single-headed twin-screw pumps,and the theoretical flow rate is relatively low,which is not suitable for large-displacement applications.The theoretical flow of the double-headed double-screw pump designed in this paper 1s more than double the single-headed double-screw pump,and has broad prospects for development.This paper analyzes several existing twin-screw pump screw rotor profiles,and use cycloid for designing the double-screw twin-screw pump screw rotor original profile.Using the envelope method and coordinate transformation,the conjugate line of the original profile was obtained,and the profile equation of a pair of screw rotors of the twin-screw pump was established.The geometric characteristics of the screw rotor profile,such as the length of the contact line,the area of the leaked triangle,the area between the teeth,and the theoretical flow rate were calculated in detail.The sealing performance of screw profiles was analyzed,and the results show that its radial sealability is good and its axial sealabihty is slightly poor.When the twin-screw pump is in actual operation,there must be a certain gap between the pair of screw rotors and between the screw rotor and the bushing stator.The fluid flows in the gap causes internal leakage,resulting in a reduction in the volumetric efficiency of the twin-screw pump.This paper divides the gap of the twin-screw pump into three types.The leakage is divided into differential pressure flow and shear flow,and the leakage of the circumferential gap and radial gap was calculated.The results show that the direction of the shear flow in the radial gap is the same as that of the differential pressure flow,contrary to the previous judgment.Dividing the leakage in the backlash into leakage along the contact line and leakage from the leakage triangle,the thin-walled hole was used to simplify it.Through the calculation of the theoretical flow and the area of the leaked triangle,its relationship with the screw rotor structural parameters of the twin-screw pump was obtained.In the case of the same theoretical flow rate,select different spiral depths with different the spiral lead,and a larger actual flow rate is obtained by comparing the size of the leakage triangle area.It provides a reference for the selection of the screw rotor structure parameters of the twin-screw pump.