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M15 Ryan > M15.6 > Flashcards

M15.6 Flashcards

(79 cards)

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1
Q

What are the 2 types of turbines?

A

Radial flow
Axial flow

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2
Q

What is the main purpose of the turbine?

A

To provide power to drive the engine compressor and gear box

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3
Q

What is the turbine made up of?

A

Rotors
Stators

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4
Q

Radial turbines are always what?

A

Single stage turbines

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5
Q

Where are radial flow turbines used?

A

On small GTE’s such as APU

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6
Q

What are the disadvantages of a radial flow turbine?

A

Small efficacy
Small airflow

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7
Q

What is the advantage of radial flow turbine?

A

Simple design

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8
Q

The axial flow turbine is mainly used on what?

A

Modern GTE’s

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9
Q

What is the advantage of axial flow turbines?

A

Allow for very high airflow

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10
Q

What is the operation of a turbine?

A

To convert gas into torque

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11
Q

What’s the purpose of the convergent duct?

A

To accelerate the air and create more pressure energy

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12
Q

What is a impulse turbine?

A

Makes rotation only by impact of gas flow on rotor blades

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13
Q

Where are impulse turbines usually found?

A

On very old GTE’s

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14
Q

Where is the highest heat to metal contact in the engine?

A

1st stage of hp compressor

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15
Q

What are the 2 types of turbine blades?

A

Impulse
Impulse - reaction

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16
Q

The force at the outlets acts in what direction?

A

Opposite to discharge gas flow

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17
Q

What is done by the pilot to try and reduce heat in the turbine?

A

High throttle is kept to a min

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18
Q

Why must the correct jet fuel be used?

A

Prevent corrosion from sulphuric acid

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19
Q

What are the 3 factors that contribute to creep?

A

Time
Temp
Centrifugal forces

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20
Q

When does creep occur?

A

When centrifugal forces are applied for a long time in high temps

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21
Q

What is the only way to reduce creep?

A

To keep material as cool as possible

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22
Q

What are the 2 reasons to cool turbines for?

A

Increase service life
Better turbine efficiency

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23
Q

What are the nozzle guide vanes and rotor blades cooled from?

A

Air from hp compressor

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24
Q

What is convention cooling?

A

Passing cool airflow through the hollow turbine materials while air is also passing inner wall of turbine aero foil

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25
What is the easiest method of cooling?
Convection cooling
26
What is the best cooling method for nozzle guide vanes no rotor blades?
Impingement cooling
27
What is the most effective method of cooling?
Film cooling
28
What is the principle of film cooling?
Prevents direct contact of hot gas flow with turbine materials
29
What method is used to cool second stage hide vanes?
Convection Impingement
30
What method is used to cool second stage rotor blades?
Convection
31
What is tip clearance?
The gap between the tip of the rotor blade and the casing
32
Why does a large tip clearance decrease the efficacy of the turbine stage?
Because a large amount of gas passes through the gap between the rotor blades and turbine casing
33
What are the 2 types of turbine clearance control systems?
Passive clearance control Active clearance control
34
How is vibration reduced in LP turbine blades?
With shrouds
35
What causes stress rupture cracks in the turbine section?
Metal fatigue and corrosion
36
When does the active clearance control system operate on engines fitted with hydro mechanical fuel control systems?
During climb and cruise
37
What does the passive clearance control system use for cooling?
Fan air
38
What controls clearance control valves? And what are they actuated by?
Engine control unit Actuated by the fuel pressure from the hydro mechanical unit
39
Are the LP turbine blades cooled?
No
40
FADEC?
Full Authority Digital Engine Control
41
What works out the tip clearance?
ECU
42
What loads does the turbine frame carry?
Bearing loads of aft end of the LP turbine
43
The case of the HP turbine is bolted to what?
Rear flange of combustion case
44
How many pieces make up the HP turbine case?
1
45
Why is the HP turbine case made up of a abradable ceramic surface?
To give thermal resistance
46
How many nozzle guide vanes are in a nozzle guide vane segment?
2
47
What are the gaps between the nozzle guide vane segments sealed with?
Sealing metallic strips
48
What does the interstate seal do?
Prevents airflow between the rotor and stator gap
49
Where is the HP turbine case bolted to?
The rear flange of HP turbine
50
The LP turbine case is made of how many pieces on modern engines?
1
51
Where are the inner air seals located?
On the inner surface of the nozzle guide vane segments
52
How many vanes make up the nozzle guide vane segments?
6 or 7
53
The HP turbine rotor is attached to what?
The rear shaft of the compressor
54
What is the function of a disc on the turbine?
To hold the rotor blades and transfer torque
55
Why is the cross sectional area of the disc very large?
So the disc withstands high centrifugal forces
56
On HP turbines what must the interstate seal do?
Help transfer torque from stage 2 disc to stage 1 disc
57
What does the interstate seal do?
Act as a space between the 2 discs
58
What’s the purpose of the blade retainers?
Hold turbine blades in place
59
What does the seal lip do on the blade retainers?
Act as air seal
60
Why is the fur tree root fitting so efficient?
Has many contact surfaces
61
What is the fitting like on fur tree roots when the engines not running?
Loose
62
What is the most common method for attaching turbine rotor blades?
Fir tree root
63
What advantage does the axial flow turbine have over radial flow turbines?
They can be built with as many stages as required and allow for a very high flow rate
64
What is the primary air sources for a passive clearance control system?
HPC air for the HPT and fan air for LPT
65
What are the 2 types of rotor assembly?
Open ended blades Shrouded blades
66
What type of blade is used in HP turbines?
Open ended blade
67
What’s the disadvantage of shrouded blades?
More weight
68
What’s the purpose of the knife edge seal on shrouded blades?
Helps reduce air loses at the tip of blade
69
Where are shrouded blades usually found?
LP turbines
70
How are turbine discs attached to the shaft?
Either splined or bolted
71
How are the HP turbine blades cooled?
Internally with air from HP compressor
72
What type of structure is the turbine frame?
Major
73
What does the turbine frame do?
Supports 1 or 2 turbine rotors and provides attachment points to rear engine mount
74
How are the turbine struts shaped?
Aerodynamically to cause a little drag as possible
75
What are the 2 types of strut?
Radial strut Tangential strut
76
The radial strut is what?
Thick and hollow
77
What does the tangential strut do to minimise stress from thermal expansion?
Expands
78
On engine shut down what is the contraction sequence of the turbine and casing?
Rotor shrinks Then Casing
79
On what stage of a turbine would open turbine blades normally be found?
On the HP turbine stage

M15 Ryan (17 decks)

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