To provide a means for simulating typical thrust engine environments, two of the GETL engine rigs use a Gnome with the power turbine removed.
The 3rd stage nozzle guide vanes which support the rear bearing have been cut back to reduce swirl and an additional vane set has been provided to reduce swirl still further.
The gas generator can then be run as a turbojet engine generating some 3kN of thrust.
The turbojet rigs allow new nozzle designs to be demonstrated and evaluated. Parameters such as mass flow, thrust, temperature, pressure, fuel flowrate, noise and vibration can be measured.
The thrust can be measured in two axes. Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) can be used to obtain detailed information about the engine flows.
The turbojet rigs provide from small scale up to full scale testing of nozzles depending upon the application (0.16m diameter).
The GETL also has three turboshaft rigs which use the Gnome engine in its conventional format - i.e. with the power turbine. These rigs provide a full scale test capability for helicopter nozzles and their associated installation.
One turboshaft engine is loaded through a Wessex helicopter gearbox using the compressor from another Gnome engine. The other two turboshaft rigs have a bespoke gearbox which means the engine can be fully loaded to 1235SHP.
This in turn provides compressed air which can be used to carry out a number of functions:
- Downwash for helicopter studies (via a bank of small ejectors).
- Provision of bypass flow for the turbojet rig to allow the simulation of turbofan nozzle systems.
- Simulation of high pressure ratio nozzle systems at small scale.