According to fluid mechanics, the flow of liquid in a pipe is divided into laminar and turbulent flow. The ability of a liquid to remove particles from one surface and carry it down to the downstream is proportional to the energy of the liquid on the surface of the element.
In laminar flow, the surface of the component has a stable layer of liquid, on the surface of the component force is very small, solid particles adhered to the hydraulic pipe on the inner wall is hard to clean, so to improve the washing efficiency, must make the flushing flow state of hydraulic medium in the pipeline for turbulent flow.
The degree of turbulence is determined by Reynolds number:
Re=VDv=4QDV (1) V is the liquid velocity; Q is the pipeline (plastic pipe application and improvement) flow; D is the pipe diameter; V is the hydraulic oil kinematic viscosity.
When the flushing oil is turbulent flow in the pipe, not the whole section is turbulent. In the pipe wall, due to the restriction of the pipe wall and adhesion, there is still a layer of liquid near the pipe wall to maintain laminar flow, that is, the near wall laminar flow layer. Its thickness is greater than the size of the particles attached to the tube wall D, it will affect the washing of particles. Therefore, to obtain a good flushing efficiency, D. must be made
In turbulent flow, the thickness of the laminar flow near the wall in the tube can be calculated by the following empirical formula.
The delta =30DRe approach (2) is the coefficient of drag along the turbulent flow, when 3x103
According to formula (1), (2), the relationship between kinematic viscosity, flow rate, pipe diameter and thickness of near wall laminar flow can be obtained as follows: Q=73.93DvD87 (3)