Explanations: Turbine Engines Flashcards
(35 cards)
The compressor outlet is the same as the what?
the burner inlet.
In what direction does the nozzle diaphragm in a turbine engine deflect the gases?
In the direction of turbine wheel rotation.
What is the purpose of profiling a compressor blade?
Profiles prevent serious damage to the blade or the housing if the blade should contact the compressor housing.
What is the Brayton cycle?
It is the energy exchange cycle used in a turbojet engine. The pressure of the air remains relatively constant as the energy from the burning fuel is added to it. Since the pressure is constant as the volume of the gas increases, its velocity increases.
What is the difference between a turboprop and turbojet engine?
In summary, turboprop engines are more efficient at lower speeds and are suitable for shorter-range flights, while turbojet engines are optimized for high-speed flight and are used in high-performance aircraft requiring supersonic capabilities.
What is a two-spool (split-spool) compressor?
The compressor and high-pressure turbine are both split into two segments. Each compressor segment is driven by its corresponding turbine using two separate drive shafts, with one inside the other.
The high pressure rotor is governed for speed, but the low-pressure rotor is free to operate at its own best speed.
As the density decreases at altitude, the compressor load decreases and the low-pressure rotor increases its speed.
What sort of duct is the exhaust cone aft of the turbine jet engine?
It is a divergent duct, increasing pressure and lowering velocity.
What are the stator vanes at the end of the discharge of an axial-flow compressor called?
straightening vanes.
What are the n1 and n2 compressors in a dual axial flow or twin spool compressor system.
The n1 compressor is the low-pressure compressor and
the n2 compressors is the high-pressure compressor.
What names does the stator element of a turbine assembly have?
turbine inlet nozzle vanes, turbine inlet guide vanes, and nozzle diaphragm vanes are the three most commonly used.
They are located directly aft of the combustion chambers and immediately forward of the turbine wheel. This is the highest or hottest temperature that comes in contact with metal components in the engine.
What is a hung start?
When an engine is unable to accelerate to a speed high enough to keep running without help from the starter.
What are the two basic elements of a gas turbine engine?
Stator and rotor.
What do the impeller and diffuser do in a centrifugal compressor?
The impeller adds energy to the air flowing through the engine and speeds it up. The diffuser slows the air down and increases its pressure.
What does trimming a gas turbine engine consist of?
adjusting the fuel control to give the engine the correct idle and maximum RPM.
What will happen is a bearing is allowed to retain it’s magnetism?
they will be damaged by foreign ferrous materials they attract.
What is Tt7 and what is Pt12
Tt7 is turbine discharge total temperature
Pt12 is compressor inlet total pressure.
What is TBO?
The recommended operating time between overhauls.
Why must the materials used to mark the components in the hot section be carefully chosen?
so that they do not contaminate the structure of the metal when it is exposed to high temperatures.
What is a compression ratio in turbine engines?
The ratio of the pressure of the air at the discharge of a turbine engine compressor to the pressure of the air at its inlet.
What are impulse, reaction, and impulse-reaction turbine blades?
Impulse - The airflow strikes the blades, transferring its momentum to the blades
Reaction - the air flows energy is converted to rotational motion as it flows over the turbines. The pressure difference between the inlet and outlet of the turbine cause the rotation.
Impulse-reaction- combines both elements of the two design.
What is the difference between the thrust produced by a turbojet or turbofan engine and that produced by a turboprop engine?
An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air, and a turbojet/fan imparts a greater amount of acceleration to a smaller mass of air.
Almost all of the useful heat energy in a turboprop engine is used to drive the compressor and the propeller, and very little is used to provide exhaust thrust.
What is a can type combustion chamber?
It consists of an outer case, and inside is a perforated stainless steel combustion chamber or liner. Both are removed as a unit for routine maintenance.
Each can has its own fuel injector, igniter, liner, and casing.
How does turbine engines deal with airborne particulates?
There is normally efficient dust and particle separators in the induction sections.
Why are turbine outlet temperatures monitored?
Because it is impractical to measure TIT, so TOT must be monitored. If TOT is within range, it is reasonable to assume TIT is also.
