Gas Turbines Flashcards
What does the efficiency of a gas turbine depend on?
The temperature to which the air can be raised
What type of engine is a gas turbine?
Internal combustion, constant flow
What are the different shafts in a gas turbine?
Single shaft
Split shaft
Twin spool shaft
What are the 2 main sections of a gas turbine?
Gas generation section
And
Power section
What are the 3 main components of a gas turbine?
Compressor
Combustion chamber
Turbine
What are the cons of an open cycle turbine?
It has no heat exchanger or regenerator, therefore it has no way to capture the heat from the exhaust gases
This makes the turbine much less efficient
What is a semi-closed cycle turbine?
A turbine that either has a heat exchanger or regenerator attached to it in order to use the waste exhaust heat to assist in heating the expansion of gases before the turbine combustion area.
What is convergence?
Gases coming together in a smaller area
What is divergence?
Gases moving apart into a larger area
How happens to the pressure and velocity inside the turbine compressor?
The pressure will increase and the velocity will decrease
Where is the highest pressure in a gas turbine?
The diffuser
What happens at the first set of nozzles of the gas turbine section?
Pressure is reduced and the velocity is increased
What are the steps/events of a gas turbine?
Intake
Compression
Ignition (also can be in the power section)
Power
Exhaust
Approximately how much of the power developed by a gas turbine is used by the compressor and other accessories?
75%
What happens if the pressure in the combustion chamber becomes higher then the pressure in the diffuser?
The gases can back up and move into the compressor which can cause surging and serious damage to the turbine.
Do you need to filter the air before it enters a gas turbine?
Yes it must have high flow with low restrictions, any restriction to flow can cause surging and catastrophic failure.
What are the 2 types of compressors in a gas turbine?
Radial flow (centrifugal)
Axial flow
These are both dynamic compressors
What are the 3 main parts of a radial flow compressor?
Impeller
Diffuser
Compression manifold
What are the 2 main parts of an axial flow compressor?
Rotor with blades
Stator with blades (stationary)
What accessories controls the variability pitch stator blade system?
The fuel control system
What are variable pitch stator blades?
They are blades that can adjust there pitch by a linkage attached to each stator blade.
They help the turbine engine maintain maximum compressor efficiency over the operating speed of the engine
What are the main parts of a combustion chamber in a gas turbine?
The combustion chamber housing (combustion) is the outside housing.
The combustion chamber liner (flame tubes) is the inside of the housing.
The fuel nozzle (fuel injector, atomizer, vaporizer) injects the fuel.
The igniter ignites the fuel air mixture.
What are the 3 zones of a combustion chamber?
The primary zone
- First part of the combustion chamber liner where fuel injection and ignition begins
The intermediate zone
- Combustion continues and begins to mix with secondary air
The dilution zone
- combustion should be complete, but secondary air is mixed with the burnt gases
Where is the hottest place in a gas turbine?
The combustor
What are the different styles of combustion chambers?
Can type chambers
Annular type chambers
Can-annular chamber
What type of compressor is normally used with a can type combustion chamber?
Most often used with centrifugal compressors
What type of compressor is normally used with an annular type combustion chamber?
Axial flow compressors
What type of compressor is normally used with a can-annular combustion chamber?
Axial flow compressors
When is the turbine igniter used?
Only during start up
After start up the continuous flame ignites the fuel.
What are the 2 categories of fuel used?
Liquid fuels
Gaseous fuels
How are the stationary nozzle vanes cooled on a gas turbine?
They have small holes through out allowing for secondary air to be forced through them for cooling
What kind of seals are used on on gas turbines?
Labyrinth seals
Do gas turbines need large foundations?
No they do not require massive foundations as other prime movers do
What is the purpose of a gas turbine wash system?
Used to remove the buildup on the compressor blades
