The mathematical expression for the Reynolds number re when a liquid or gas flows through a conduit of a circular section is:
The expression is:
In a dry sandblasting machine, the flow rate of compressed air q>1000 l min and the nozzle diameter d=08-1.2cm, movement of the compressed air.
The viscosity is 1cst at 20 degrees, so that the Reynolds number RE value of the dry blasting machine during the jet can be obtained according to Equation 5-2.
For the 999999, hence the re"rec, therefore, the jet of dry blasting is a turbulent jet.
In a liquid sandblasting machine, the jet of liquid sandblasting is also a turbulent jet.
That is, the jets we are talking about are all turbulent flows.
Turbulent jet refers to the fact that when the fluid is flowing, the fluid particles are both moving along the direction of the jet and perpendicular to the direction of the jet.
transverse movement, or a mixture that produces small swirls. Disordered mixed movements. The collision between the abrasive particles in the abrasive jet and the mixing of compressed gas and water further aggravate the turbulent state of the jet. Let's analyze each of them according to Figure 5-1.
The state and generation process of the same jet segment.
In the core segment 1, although the jet is in a turbulent state, it is confined by the inner wall of the nozzle, and at the same time, the jet.
It is also isolated from the outside atmosphere, so the jet is relatively tight, as can be seen from Figure 5-1, when the jet is ejected out of the nozzle exit plane.
The velocity of the jet decreases with the increase of the jet length, centered on the jet axis, forming a cone-shaped isokinetic nucleus. This is.
This is because, as soon as the turbulent jet comes into contact with the air or loses its restraint, the lateral motion properties are activated and immediately mix with atmospheric air.
The so-called gas-doped boundary layer is formed, which is also formed gradually, so that the formation speed of the boundary layer is combined with the jet velocity to form the actual tapered isokinetic nucleus of the core segment. The aerated boundary layer is actually the diffusion of jet particles into the atmosphere, therefore, aeration.
The diameter of the boundary layer changes from large to small, and finally converges on the jet axis, but this actual conical isokinetic nucleus does not affect us.
Therefore, we still assume that in the isovelocity segment, the velocity of the jet is equal in the various sections, the core segment.
Also known as isokinetic nucleus or isokinetic segment.