Page 46 - Fluid Power Engineering

Hydraulic Oils and Theor etical Backgr ound 23

FIGURE 2.6
Radial clearance
with eccentric
mounting.

FIGURE 2.7
Long-thin-slot
orifi ce.

Fluid Flow in the Clearance Between a Circular Nozzle and a Plane
Surface The flow rate in the clearance between the plane face of a
nozzle and a plane surface (see Fig. 2.8), is given by the following
relation:

π( d + d h 3
)
Q = 1 2 Δ P (2.24)
12 ( d − d μ
)
1 2
Viscous Friction and Damping Effect The parts moving in oil are sub-
jected to viscous friction forces due to the shear stress resulting from
the oil viscosity. Figure 2.9 shows a spool moving axially. The cylindrical

FIGURE 2.8
Nozzle controlled
by a plane surface
at distance h.