Optical Pyrometry System (Rotamap II)
Oscillating Mirror Sight Tubes
The oscillating mirror pyrometer is mainly used for blade thermal mapping in military and civil aeroengines. The sight tube has a rest position where it is parked outside the gas stream.
On demand the sight tube is pneumatically inserted into the gas stream and once located the mirror is articulated and data collection begins. At maximum insertion the mirror drive is reversed and the scan repeated in the opposite direction.
• An oscillating mirror sight tube and electro-mechanical actuator assembly with actuator environmental cover removed for clarity.
On completion the sight tube is extracted into its rest position clear of the gas stream. As data is collected continuously each sight tube cycle provides two full scans of the measured turbine area.
Oscillating mirror sight tubes can be permanently attached to the actuator or be ‘detachable’. The detachable sight tube design enables different sight tubes to be used with the same actuator and Rotamap II system thus saving on costs where several positions in an engine have to be thermally mapped.
Fixed Mirror Sight Tubes
In this system the sight tube is inserted directly into the gas stream for a distance dependent on gas stream conditions and engine blade height dimensions.
Two fixed mirror sight tube insertion systems are available:
(i) A compact pneumatically actuated sight tube designed to operate under engine turbine cowlings and having sight tube outside diameters from 8.0 mm diameter upwards.
(ii) A electro-mechanically actuated sight tube designed to operate above engine turbine cowlings and having sight tube outside diameters from 12.0 mm diameter upwards.
(i) is mainly used for large aero-engine blade thermal mapping and (ii) for power generating gas turbine blade thermal mapping.
Similar to the oscillating mirror system, the fixed mirror sight tube is traversed fully into the gas stream over a time period and under precise control, collecting data continuously. The probe has a viewing ‘spot’ of approximately 2 mm outside diameter, so that a complete in/out sight tube traverse permits observation of the blade airfoil surface in small overlapping increments. Blade radiance is collected and processed in the same way as the oscillating mirror system.
