M15.6 Turbine Section Flashcards
What is the primary function of the gas generator turbine?
To absorb approximately 60 to 70% of the total pressure energy from the exhaust gases.
Where is the turbine section located in a gas turbine engine?
Aft, or downstream, of the combustion chamber.
What are the two types of turbines used in gas turbine engines?
- Radial flow turbine
- Axial flow turbine
What is the advantage of radial flow turbines?
Simple design and easy to manufacture.
What is a disadvantage of radial flow turbines compared to axial flow turbines?
Less efficient due to high aerodynamic losses and small airflow capacity.
Which type of turbine is mainly used on modern gas turbine engines?
Axial flow turbine.
What is the role of stationary turbine nozzle guide vanes?
To direct the gas flow onto the turbine rotor blades.
What distinguishes an impulse turbine from other types?
It makes rotation solely by the impact of gas flow on the rotor blades.
What characterizes the impulse configuration in turbine blades?
Total pressure drop occurs in the fixed nozzle guide vanes, converting all pressure energy to kinetic energy.
What defines the reaction configuration in turbine blades?
Fixed nozzle guide vanes alter gas flow direction without changing pressure.
What is a reaction-impulse configuration in turbines?
Combines both impulse and reaction forces acting on the blade.
What is a common method of turbine blade retention?
Fir tree design.
What materials are commonly used for turbine blades?
Alloy steel or precision-cast metals.
What is the purpose of cooling air in turbine operation?
To relieve thermal stresses and maintain operational limits.
What is creep in the context of turbine blades?
Slow structural deformation caused by prolonged exposure to high stresses.
True or False: Radial flow turbines allow for high airflow and high thrust.
False.
Fill in the blank: The turbine blades convert gas energy from the combustion chamber into _______.
[torque]
What happens to the turbine blades at high temperatures?
They may experience stress rupture cracks and deformation.
What is the significance of the turbine inlet nozzle vanes?
They convert heat and pressure energy to velocity energy for the turbine blades.
What is the function of the turbine shaft?
To transmit the torque from the turbine wheels to the engine components.
What is the effect of uneven workload on turbine blades?
Causes gases to exit from the blade at different velocities and pressures.
What is a common inspection method for turbine blades?
Visual inspection, often aided by dye penetrant methods.
What must be done if stress rupture cracks are found on turbine blades?
An over-temperature condition must be suspected and addressed.
What are the two common methods for connecting the turbine shaft to the turbine disc?
- Welding
- Bolting
What is the role of the turbine inlet guide vanes?
To prepare mass airflow to drive the turbine rotor.
What is the purpose of the grooves or notches in the turbine disc rim?
To allow attachment of turbine blades and accommodate thermal expansion.
What is creep in the context of turbine blades?
Creep is a phenomenon caused by prolonged exposure to high stresses that results in visible dimensional changes to the blades.
Creep increases with temperature, especially in the turbine area of a turbine engine.
What can cause dimensional inconsistency in turbine blades?
Dimensional inconsistency could be caused by creep rather than over-temperature.
Creep leads to gradual deformation of materials over time under constant stress.
How should turbine blades be inspected and measured?
In accordance with the manufacturer’s instructions.
This ensures compliance with safety and performance standards.
What might signs of scoring on the turbine case indicate?
The length of the turbine blades is out of tolerance.
Scoring can be a sign of blade contact or wear that needs to be addressed.
What should be done when observing and measuring blade deformation?
Adhere to all manufacturer’s specifications and replace any damaged turbine blades as specified.
Following specifications helps maintain engine performance and safety.
What should be checked on individual blades and the turbine disc?
Check individual blades for stretch and the turbine disc for hardness and stretch.
This ensures that the components are within operational limits.
What is the protocol for reinstalling blades removed for inspection?
Blades must be reinstalled in the same slots/position from which they were removed.
This maintains the blade’s original orientation and balance.
Before removing blades for inspection, what should be done?
Number the blades before removal.
This helps in correctly reinstalling them in their original positions.
