Index revision : F - November 2017
18
7012
2.5.1. Turbine Rotation Speed
An acoustic method is used to measure rotation speed.
The air arrives at the injector holder. The channel machined in the ’microphone reader”
located on the bellcup allows air to pass each time the bell cup rotates
This pressure variation induces a noise, or "frequency signal" which passes across the injector
holder to reach a microphone.
This microphone converts the acoustic frequency signal into an electrical frequency signal for
processing by the turbine speed regulation module.
2.6. Shaping air
This air supply circuit is used to modify the pattern size. If the shaping air pressure is increased,
the pattern is narrowed and if it is decreased the pattern is widened (an O-ring provides a seal
between the turbine and the inner surface of the shroud).
The shaping air arrives on the turbine side, passes through the holes on the shroud and is then
directed towards the bellcup
DES01241
Outer dia.
1/4”
Maximum length
8 m
Required minimum length
4.5 m
Microphone inlet
Required pressure
1.9 - 3 bar
