Dilution principle, Figure 6 – M&C TechGroup SP2000H_DIL_BR Operator's manual User Manual
Page 14
14
Gas sampling and gas conditioning technology
2-1.1.7-ME
9
DILUTION PRINCIPLE
The functional principle of the dilution probe is based on ultrasonic flow through a critical orifice (see
Fig. 4). The flow through the orifice is constant when the differential pressure via the orifice is higher
than 500mbar. For the atmospheric inlet pressure (Po
in
= 1020mbar), this means a pressure at the
orifice outlet (P
out
) of less than 520mbar absolute.
The necessary vacuum at the orifice outlet is produced by an injector operated with dilution gas.
Depending on the critical orifice selected, dilution rates can be between 10:1 and 500:1. The table be-
low gives an overview of the dilution factor and sample gas volume using the injector I (480
–
600Nl/h):
Orifice type
a
b
c
d
e
f
g
Dilution ratio
500:1 200:1 100:1 50:1
30:1
20:1
10:1
Volume flow through the critical orifice [Nl/h]
1.4
2.7
5.5
11
19
28
55
* With injector II 50:1 up to 2000:1
Figure 6
Dilution principle
Checking the dilution rates and exact adjustment of the pressure conditions are described in Chapter
14.1.