Turbine Engines

Suck, squeeze, bang, blow... intake, compression, power, exhaust.  The basic sequence of events on a gas turbine is the same as on the 4-cycle reciprocating engines we learned about in Private Pilot ground school.  But the components are different and turbine engines are much more efficient due to continuous flow conditions.  

INTAKE

COMPRESSION

Two types of compressors:

• axial-flow (more efficient)
• rotor blades: air deflected in direction of rotation
• stator vanes: direct and compress the flow of air
• centrifugal-flow (more durable)
• impeller: air directed towards center, then slung outward to diffuser
• diffuser: converts high velocity airflow into high pressure airflow for delivery to combustion section

POWER

Combustion is continuous and self-sustaining

EXHAUST

Turbines are turned by escaping gases, and in turn, drive the compressors through shafts.

Definitions

• bypass ratio: relationship between the mass flow of cold air through the fan to the mass flow of the hot air through the turbine
• engine pressure ratio (EPR): the ratio of turbine discharge total pressure to the total pressure at the compressor inlet (OUT / IN)
• free turbine: there are two separate shafts - one to drive the compressor section and the other to transmit power to the reduction gearbox and thus turn the propeller
• waste gate: controls the amount of exhaust gas which enters the turbine section of a turbo-charger
• flex temperature: the assumed temperature used in calculating the reduced thrust settings for take-off

Lots of systems material to cover... more to come!