Air is admitted into the compressor axially through an inducer. To ensure a smooth acceleration of the air into the compressor impeller blades, a short air horn is fitted to the inducer. The open end of the horn is provided with a mesh (on the advice of many dtt subscribers) to prevent ingestion of items such as leaves, fingers, dogs and small children (copyright Chris "Kamikaze" Bennett).
The air horn is partially hidden by the aluminium ring which secures the compressor inducer to the rig frame. Just visible behind the mesh is the compressor nut, and the tacho probe.
There are three bayonet pegs on the rim of the mesh frame, to engage with the slots in the duct from the starter blower. For test purposes, a venturi can be attached in series with the blower to measure the turbine massflow.
The venturi is shown attached above. A differential pressure measuring device can be fitted to the connections on the venturi.