O
PERATION
M
ANUAL
VKL
10
/100
V
ERSION
V005-06-2020
9
4.2. The Inlet System and the Mixing Chamber
The details given in the following chapter only apply to VKL 10!
Figure 4.1. shows a cross-section of the dilution stage. Particle-free air with a volume flow
rate V
r
determined by the pre-pressure P, flows through an annular slit around the inlet
nozzle. The resulting under-pressure dP
0
causes the aerosol which is to be diluted, to be
sucked in and to be mixed homogeneously with clean air in the mixing chamber. If the clean
air flow rate is increased, the flow speed within the annular nozzle increases
correspondingly. This causes according to Bernoulli (s. below) the under-pressure dP
0
at the
inlet nozzle to increase, and the flow rate V
an
increases, too. Both flow rates are connected
through the underpressure, and equally depend on it. Consequently, the ratio of the flow
rates remains constant for different pre-pressures, P.
Bernoulli formula:
dP = 1/2 * rho * v²
dP:
pressure drop at a nozzle (here: under-pressure)
rho:
gas density
v:
gas velocity through the nozzle
excess air outlet
excess air
tube connector
outlet nozzle
dP
0
mixing chamber
annular nozzle
inlet nozzle
V
in
V
out
V
r
compressed air
with pre-pressure P
Fig. 4.1.: Cross section of dilution stage