Research And Simulation On The Gap Type Servo Hydraulic Cylinder Seals

As the implementing component of hydraulic servo control system, servo-hydraulic cylinder is the last link of the whole control system and it is the the lowest part of the dynamic response. The Seals will directly affect the control accuracy and response speed of the system. Therefore, it is important to research the sealing characteristics of the servo-hydraulic cylinder. In this paper, it is about the seals of one kind of the gap type servo-hydraulic cylinder, also the size of leakage and friction is given.The gap type seal is one kind of the non-contact seal form. In the first part of this thesis, the three sealing structure forms were put forward, the pure gap seal, the gap seal with rectangular or triangular grooves. The pressure and velocity distribution property in the filed were also given by comparing couette flow with pressure flow. Through the analysis of the impact of gap width, concentric, eccentric, and the relative velocity on the leakage and viscous friction from theory, the approximate calculation method of them was deduced.In the second part of this thesis, the modeling and simulation of three gap seal structures were given with the application of Fluent software. The geometric model was bTuilt up and meshed with the Gambit. Because of the differences of the model geometry dimension in three direction, nodes in each direction needed to be setted intervals separately. Models with rectangular or triangular grooves were divided by varying intervals and meshed with the sub-block partition method for the body grid. By using three-dimensional double-precision solver and choosng laminar flow as the physical model in Fluent, the model simulation was given and the appropriate relaxation factor and convergence precision should be setted based on the body grid characteristic. Through the simulation, the value of leakage and viscous friction were given, and the feasibility of the model was analysed by comparing with the theoretical. Those provided the basis for determining performance parameters of the servo-hydraulic cylinder leakage and friction.