The axial compressor is ﬂexibly coupled to the compressor turbine and the complete rotating assembly is supported in three bearings. These are carried in the rigid stator casings, which are split horizontally along the centre line of the rotor shaft to facilitate inspection of both the rotor and stator blades and bearings. A single large diameter combustion chamber is used, capable of burning a wide range of fuels.
The thirteen-stage compressor is a subsonic aerodynamic design with a pressure ratio of 4:1 at full load. Two sleeve bearings are used to carry the rotating assembly supported by the stator casing at the turbine end and the inlet casing at the compressor end. An anti-whirl type bearing is ﬁtted at the compressor turbine end of the assembly and thrust loads are taken by a white metal lined double acting tilting pad bearing. Separate grooved discs are clamped together with a single through bolt to make up the rotor assembly. Stator blades are retained by dovetail roots in grooves machined on the stator casing which is split on the horizontal centre line to facilitate inspection of the rotor and stator assemblies.
The two-stage turbine which is ﬂexibly coupled to the compressor rotor, has a full load speed of approximately 12,000rev/ min.
The discs of the two-stage free power turbine and the rotor blades are manufactured from alloys to meet the engine duty. The blades are ﬁxed into the discs by the traditional ﬁr tree root method and secured by peening. The use of two stages gives low stress levels and maintains a safe overspeed capability. There are no critical speeds within the operating speed range. Two sleeve bearings support the power turbine rotor shaft which are carried in the robust gear casting to which is secured the support arm for the stator casing. Thrust loads are taken by a white metal lined tilting pad thrust bearing.
The compensating hydraulic governor, that controls the quantity of fuel delivered to the combustion chamber, is gear driven from the power turbine. It controls the turbine over the full power range and allows output speed to be controlled. Starting may be either from a 24-volt D.C. electric motor or by a gas starter motor driving through a Bendix drive on to the turbine axial compressor shaft. When operating on gaseous fuels the pilot igniter can be supplied with gas from the main fuel system via a pressure reducing valve. For engines burning liquid fuel the igniter gas supply is taken from a gas bottle or similar source of supply. The control equipment is housed in two cabinets mounted in the turbine under base, the hydraulic control cabinet housing the engine instruments, pressure switches a servo system component while the electrical control cabinet contains the associated relays, timers, wiring and terminals, the selection switches, the annunciator panel, and the T Max temperature indicator.
The turbine is fitted with devices to shut down the turbine in the event of:
- Low lubricating oil pressure
- High lubricating oil temperature
- High cycle temperature
- Over speed
- Flame failure
In the event of high lubricating oil temperature or high cycle temperature, a visual and audible warning is given before shutdown values are reached
During starting and for the cooling period after shutdown, lubricating oil is supplied by a D.C. electric motor-driven auxiliary lubricating oil pump. The main engine pump is driven through the auxiliary gear train from the output shaft. Oil cooling is by either an air blast or water-cooled cooler to meet site requirements. The double helical gears have hardened teeth and are precision ground to ensure silent running and long working life. For direct drive to centrifugal pumps and compressors a shaft speed of 6,600 rev/min is provided. The engine is mounted on an under base with extended platforms on which the auxiliary components are installed. This also forms the lubricating oil tank.