To better describe the engine, we can divide the engine into six different sections:
- The Air inlet,
- The Reduction gearbox,
- The Compressor section,
- The Combustor section,
- The Turbine section, and
- The Exhaust section.
The Air inlet
The air inlet is located at the lower forward side of the engine and functions to direct air onto the compressor section of the engine.
A two stage reduction gear consisting of a planetary gear set and an accessory drive gear set provides gear reduction for the propeller and drives the following engine mounted accessories:
- The Starter-generator,
- The Tachogenerator,
- The Oil pumps,
- The fuel pumps and fuel control unit,
- The Hydraulic pump, and
- The propeller governor.
The reduction gear set is driven by a torsion shaft which drives the engine output to the propeller and also operates the hydromechanical torque meter.
The reduction gear set reduces the engine RPM from 41 730 RPM to 2000 RPM at the propeller with a reduction rate of approximately 20.8:1.
A two stage centrifugal compressor supplies compressed air for engine cooling, combustion, cabin pressurisation, and aircraft pneumatic systems.
The combustion section includes a reverse flow combustion chamber where fuel is introduced into the compressed air for burning and expansion of the gases to derive power for driving the fixed shaft turbines and compressor section.
Other components within the combustion section of the engine include:
- Five primary fuel nozzles for engine start,
- Ten secondary fuel nozzles for engine running, and
- Two high energy igniter plugs used during engine start for initial ignition during the start sequence.
The turbine section utilises three axial flow turbine stages to derive energy from the expanded combustion gases to drive the fixed shaft of the engine.
Approximately 2/3 of the energy extracted from the gases is used to drive the compressor, the propeller and the engine accessories, a majority of which is absorbed by the compressor section.
The exhaust section consists of a duct and cone and an exhaust pipe, which directs the spent gases to the atmosphere.
A small portion of these directed gases will provide direct thrust for forward propulsion of the aircraft.