Establishment of unified parametric equation and performance analysis of screw motor stator and rotor linetype

Abstract

Aiming at the screw motor stator and rotor linetype parameter equations are not uniform and the linetype characteristics have not been completely studied, resulting in the linetype design and selection method is not perfect and poor interchangeability and so on. In this paper, the unified parameter of linetype equation of the screw motor stator and rotor and the thermo-mechanical coupling model and the shell-bushing cohesive zone model of the 5/6 screw motor under the three linetypes of equidistant hypocycloid, equidistant epicycloid and hypocycloid and epicycloid are established. The relationship between the three linetypes of stator and rotor and the lagging heat generation of the bushing, drilling fluid pressure, downhole temperature and shell-bushing bonding performance is studied. The results show that the stator temperature rise of the equidistant epicycloid method is 22%–30% lower than that of the other two types of stator. The stator with equidistant epicycloid is less affected by drilling fluid pressure and is more conducive to forming conjugate sealing cavity in deep wells. The downhole temperature has a certain influence on the stator linetype, which needs to be considered in the design. The CSMAXSCRT value of the bonding interface of the screw motor using the equidistant epicycloid method is 6.1%–10.1% higher than that of the screw motor using the other two linetypes, which is prone to bonding failure. When the interference is small, the equidistant hypocycloid method and the hypocycloid and epicycloid method can be used, and the equidistant hypocycloid method is recommended when the interference is large. The research in this paper provides a theoretical basis for the design and selection of screw motor linetypes, and has important engineering practical significance for realizing product interchangeability.