Powerplant Theory & Maintenance: Turbine Engines 🔊 Flashcards
What are the major components of a typical gas turbine engine?
An air inlet, compression section, combustion section, turbine section, exhaust section, and accessory section.
What are two principle types of compressors used in turbojet aircraft?
Centrifugal flow and axial flow types.
What are the four combustion chamber systems?
Can, can-annular, annular, and reverse flow annular types.
What is the purpose of the interconnector tubes between can type combustion chambers?
To spread the flame to the combustion chambers that are not equipped with igniter plugs during engine starting.
What prevents burning of the liner walls in a can type combustion chamber?
Louvers are provided along the axial length of the liners to direct a cooling layer of air along the inside wall of the liner.
What types of damage may be found when inspecting compressor blades?
Dents, scratches, gouges, galling, burns, burrs, pitting, and cracks.
What is the location and function of the diffuser section in a turbine engine?
It is the divergent section of the engine located between the compressor section and burner cans. Its function is to change the high velocity compressor discharge air to static pressure.
Where are stress rupture cracks most likely to occur on turbine blades?
As small hairline cracks on or across the leading or trailing edge of the blades. They appear at right angles to the edge length.
How are compressor blades attached to a disk-type rotor?
They are fitted into the disks by either bulb-type, fir-tree, or dove tail type roots. They are then locked by means of screws, peening, locking wires, pins, or keys.
What is the purpose of the nozzle diaphragm or turbine nozzle?
The turbine nozzle prepares the combustion mass airflow to drive the turbine rotor. First, they change a portion of the heat and pressure energy to velocity energy. The fixed vanes are shaped and set at such angles that they form several small nozzles that discharge the gases at extremely high speeds. Second, they deflect the gases so they strike the turbine at the most efficient angle for maximum turbine rotation.
What is the major difference between turboprop and turbojet engines?
A turboprop engine usually has more turbine stages than the turbojet. In addition to operating the compressor and accessories, the turboprop turbine must also drive a propeller.
What is a turbofan engine?
It is the same as a turboprop, except that the propeller is replaced with a duct-enclosed axial flow fan.
What is the effect of air density on the thrust of a turbine engine?
Air density determines the mass of air that is used by a jet engine. If density increases, thrust increases and vice versa. An increase in air temperature entering an engine will cause a decrease in air density and thrust.
What are the two most common types of thrust reversers?
Mechanical blockage type and aerodynamic blockage type.
What is a split compressor system in a turbine engine?
It requires two concentric shafts joining the turbine stages to their respective compressors.
