Sections of Gas Turbine Engine Flashcards
Cold and Hot Section
1
Q
The engine ___________ is built into the airframe or the forward part
of the nacelle installation.
A
air inlet
2
Q
The design of the intake duct is vital to the performance of the
engine under all airspeeds or angles of attack to avoid ________
A
compressor stall
3
Q
Inlet Function
Recover as much ofthe total pressure of the free airstream as possible and deliver this pressure to the compressor.This is known as __________.
A
ram recovery or pressure
recovery
4
Q
Inlet Function
A
Provide a uniform supply of airto the compressor so the compressor can operate efficiently.
Ram / Pressure recovery
5
Q
Types of Inlets
A
Engine Mounted
Wing Mounted
Fuselage Mounted
Subsonic Inlets
Supersonic Inlets
Bellmouth Inlets
6
Q
__________ inlets are
commonly used on wing
mounted and vertical
stabilizer mounted engines
A
Engine mounted
7
Q
located directly in front of the compressor and is mounted to the engine
A
Engine Mounted Inlets
8
Q
They are installed on the
wing’s leading edge,
typically positioned near
the wing root area.
A
Wing Mounted Inlets
9
Q
inlet ducts located just under the
aircraft nose.
A
Fuselage Mounted
10
Q
Atypical subsonic airinlet consists of a fixed geometry duct whose diameter progressively increases from front
to back.
A
Subsonic Inlet
11
Q
This divergent shape works like a venturi in that as the intake air spreads out,the velocity of the air decreases and the pressure increases.
A
Subsonic Inlet
12
Q
On ___________ aircraft a typical airinlet duct has either a fixed or variable geometry whose diameter progressively
decreases,then increases from frontto back.
A
Supersonic Inlet
13
Q
This convergent-divergent shape is used to slow the incoming airflow to subsonic speed before itreaches the compressor
A
Supersonic Inlet
14
Q
have a convergent profile thatis designed specifically for obtaining very high aerodynamic efficiency when stationary or in slow flight. Typically used on helicopters
A
Bellmouth inlets
15
Q
Ways to prevent Foreign Object Damage
A
Inlet screen
Sand and ice separator
Vortex dissipater
16
Q
What are principles or laws that apply when using a sand/ice separator
A
Venturi
Law of Inertia
17
Q
It is the componentthat forces air into the engine
A
Compressor
18
Q
Function of Compressor
A
Its primary functionis to supply air
A secondary function of the compressor is to supply bleed air/customer bleed air
19
Q
To be effective, a modern compressor must increase the intake air pressure __________ times above the ambient air
pressure and move the air at a velocity of _________ feet per second.
A
20 to 30
400 to 500
20
Q
The amount of air passing through the engine is dependent upon
three factors:
A
1.The compressor speed (rpm)
2.The forward speed ofthe aircraft
3.The density ofthe ambient(surrounding) air
21
Q
Bleed air is utilized in a wide variety of ways. Some ofthe current applications of bleed air are:
A
1.Cabin pressurization, heating, and cooling;
- De-icing and anti-icing equipment;
- Pneumatic starting of engines
22
Q
Types of Compressor
A
Centrifugal Flow
Axial Flow
23
Q
Sometimes called a radial outflow compressor.This type of
compressoris one ofthe earliest compressor designs and is still
used today in some smaller engines and auxiliary power units
A
Centrifugal Flow
24
Q
Centrifugal compressors consist of:
A
An Impeller(also called rotor);
Diffuser;
And a Manifold
25
Centrifugal compressors have a high pressure rise per stage that can be around __________. Generally centrifugal compressors are limited to ________ due to efficiency concerns
8:1
two stages
26
The ___________-consists of a forged disk with integral blades fastened by a splined coupling to a common power shaft. Its function is to take air in and accelerate it outward by centrifugal force
Impeller (rotor)
27
Compressors having only
one impeller
Single-stage compressors
28
compressors having two
impellers
Double-stage Compressors
29
When two impellers are mounted back-to back, _____________ is created.
a double-sided or double-entry impeller
30
Process of Centrufugal Flow
Once through the impeller,the air is expelled into a divergent duct
called a diffuser
The diffuser acts as a divergent duct where the air spreads out, slows down, and increases in static pressure.
The compressor manifold distributes the air in a smooth flow to the combustion section.
31
Advantages of Centrifugal Flow
Easy to manufacture, low cost, weight, starting power requirements
32
Disadvantage of Cenrifugal Flow
Large frontal area, limited number of stages for powerful engines
33
In an ____________ compressor,the airflow is along the horizontal axis of the compressor.
axial flow
34
An axialflow compressor has two main elements,
a rotor and a stator.
35
The task of an axial compressoris to _________
raise air pressure rather than air velocity
36
The _____________ consists of rows of blades fixed on a rotating spindle.The angle and airfoil contour of the blades forces air __________ in the same manner as a propeller.
rotor
rearward
37
The rotor blades are usually made of
___________ with the latter stages
being made of __________-.
stainless steel
titanium
38
The design of blade attachment to the rotor disk rims varies, but they are commonly fitted into disks by either:
bulb-type, fir- tree, dovetail
39
Some long fan blades have a mid-span
shroud that helps support the blades,
making them more resistant to the
bending forces created by the
airstream.
Shroud
40
The shrouds, however, do block some of
the airflow and create ____________ that reduces fan efficiency.
additional aerodynamic drag
41
The rotor blades used in an axial flow
compressor have an airfoil crosssection with a ____________
varying angle of
incidence, or twist
42
This ____________ compensates for the blade velocity variation caused by its radius.
twist
43
The ____________, on the other hand, are arranged in fixed rows between the rows ofrotor blades and act as diffusers at each stage, decreasing air velocity and
raising pressure.
stator vanes
44
The set of stator vanes immediately in
front ofthe first stage rotor blades are
called _____________.
inlet guide vanes
45
Stator vanes are normally constructed out of ___________ because those metals have high fatigue strength
steel or nickel
46
Stator vanes are often shrouded attheirtips to _____________
minimize
vibration tendencies.
47
The last set of vanes the compressor air passes through is the __________
outlet vane assembly.
48
These vanes straighten the airflow and eliminate any swirling motion or turbulence.
outlet vane assembly
49
Asingle stage in an axialflow compressoris capable of producing a compressor pressure ratio of only _________
1.25:1
50
Therefore, high compressor pressure ratios are obtained by ____________. In order to add more compressor stages, _____________ are created.
adding more compressor stages
multi-spool compressors
51
Process of Compression (Axial)
The air from the air inletis guided by the inlet guide vanes to the rotors and stators.
Each compressor stage raises the pressure ofthe incoming air while the air's velocity is alternately increased then decreased as airflow proceeds through the compressor
The rotor blades slightly accelerate the airflow then the stator vanes diffuse the air, slowing it and increasing the pressure
The overal lresultis increased air pressure and relatively constant air velocity from compressor inlet to outlet.
The outlet guide vanes will now guide the compressed air into the diffuser to prepare the air mass for combustion.
This process will repeat depending on the number of spools the compressor have.
52
Engine designers devised a way to overcome the limitations of single-spool compressors
Multi Spool Compressor
53
How is the DualSpoolAxial Compressor divided?
N1(LPLS-2STR), N2(HPHS-1STF)
54
How is the Triple Spool Axial Compressor divided?
N1(low speed), N2(intermediate), N3(high pressure)
55
A _____________ occurs when the compressor blades' angle of attack exceeds the critical angle of attack
compressor stall
56
Compressor stalls typically occur when the engine inlet air becomes ________________
turbulent or disrupted
57
____________are severe stalls that can significantly impair engine performance, cause loss of power, and can damage the engine.
Hung stalls
58
Advantages of Axial Flow
small frontal area, high peak efficiencies, high ram efficiency
59
Disadvantage of Axial Flow
high cost, weight and starting power requirements and difficult
to manufacture
60
A ___________ is typically located directly between the compressor diffuser and turbine section.
combustion section
61
All combustion sections contain the same 4 basic elements:
one or more combustion chambers (combustors),
a fuel injection system,
an ignition source,
and a fuel drainage system.
62
The primary function of the combustion section is to _____________
burn the fuel/air mixture,thereby adding heat energy to the air.
63
The ____________ in a turbine
engine are where the fuel and air are
mixed and burned.
combustor chambers
64
A typical combustor consists of an outer
casing with a _____________.
perforated inner liner
65
The ______________ meters the appropriate amount of fuel through the fuel nozzles into the combustors.
fuel injection system
66
__________ are located in the combustion chamber case.
Fuel nozzles
67
Fuel is delivered through the nozzles into the liners in a ______________ to ensure thorough mixing with the
incoming air
finely atomized spray
68
A typical ________ for gas turbine engines is the high-energy capacitor discharge system
ignition source
69
Atypical ignition source for gas turbine engines is the high-energy capacitor discharge system, consisting of an:
exciter unit,two high-tension cables, and two spark igniters.
70
This ignition system produces ______________ ,resulting in a ball offire atthe igniter electrodes.
60to 100 sparks per minute
71
A _____________ accomplishes the important task of draining the unburned fuel after engine shutdown. In addition, draining the unburned fuel helps to prevent ____________ in the fuel manifold, nozzles, and combustion
chambers which are caused by fuelresidue
fuel drainage system
gum deposits
72
Types of Combustion Chamber
Tubular
Annular
Tuboannular
73
consists of a series ofindividual
combustor cans which act as
individual burner units.
Tubular/Multiple
CanType
74
Tubular/Multiple CanType
One ofthe major advantages is that it can be _____________ for inspection.
individually removed
75
There are ___________ cans in a typical
multiple-can combustion section.
8 or 10
76
Consists of a housing and
perforated innerliner, or
basket
Annular Type or Basket Type
77
It must be removed as a single
unit for repair orreplacement.
Annular Type or Basket Type
78
Annular Type or Basket Type
Normally,the ignition source
consists of ___________
similar to the type found in
multiple-can combustors.
two spark igniters
79
From a standpoint ofthermal
efficiency, weight, and physical
size,the annular combustor is the
________________
most efficient.
80
Combination ofthe multiple-can
combustor and the annulartype
combustor
Tuboannular/Can-annular Type
81
Tuboannular/Can-annular Type
It was invented by _______________
and consists of a removable steel
shroud that encircles the entire
combustion section.
Pratt &Whitney
82
Tuboannular/Can-annular Type
This design combines the ___________ and testing ofthe multiple-can arrangement with the ______________ of the annular
combustor.
ease of overhaul, compactness
83
Good Combustion Chamber Characteristics
Best ratio in fuel and air
Burn the mixture as efficiently
Cool combustion gases to make it tolerable forturbines
Distribute hot gases evenly
84
Primary vs. Secondary Air
Primary - combustion air - 25 to 35 percent - support the combustion.
Secondary - Cooling Air - 65 to 75 percent - cools the hot gases
85
The situation wherein an excessively high velocity airflow could literally blow the flame out of the engine/combustion chamber.
Flameout
86
Two Types of Flameout
Lean Die Out
Rich Blow Out
87
usually occurs at high altitude where low engine speeds and low fuel pressure form a weak flame that can die
outin a normal airflow.
Lean Die Out
88
occurs during rapid engine acceleration when an overly-rich mixture causes the fueltemperature to drop
below the combustion temperature or when there is insufficient
airflow to support combustion.
Rich Blow Out
89
Process of Combustion
Air enters the combustion chamber at a velocity up to 500 feet per second
To attain the proper ratio offuel and air, a flame tube is utilized
Approximately 20 percent ofthe air mass flow is taken in by the snout
Immediately downstream ofthe snout are swirl vanes and a perforated flare,through which air passes into the primary combustion zone
It is arranged thatthe conical fuel spray from the nozzle intersects the recirculation vortex at its center
Combustion should be completed before the dilution air enters the flame tube
An electric spark from an igniter plug initiates combustion and the flame is then self-sustained
Fuel is supplied to the airstream by different methods
90
A ___________ transforms a portion ofthe kinetic energy in the hot exhaust gases into mechanical energy to drive the compressor and accessories.
turbine
91
The turbine section of a turbojet engine is located downstream ofthe combustion section and consists of four basic elements;
a case, a stator, a shroud, and a
rotor.
92
The ___________ encloses the turbine rotor and stator assembly, giving either direct or indirect support to the stator elements.
turbine casing
93
A typical case has __________- on both ends that provide a means of attaching the turbine section to the combustion section and the exhaust assembly.
flanges
94
A stator elementis most commonly referred to as the ___________
turbine nozzle, turbine guide vanes, or the nozzle diaphragm
95
located directly aft ofthe combustion section and immediately forward ofthe turbine wheel.
Turine Stator
96
typically exposed to the highest temperatures.
Turine Stator
97
Purpose of Turbine Stator
collect the high energy airflow from the
combustors and direct the flow to strike the turbine rotor at the appropriate angle.
98
The turbine nozzle assembly consists of an ______________ that retains and surrounds the nozzle vanes
inner and outer shroud
99
To allow for expansion,the inner or outer shroud ring is _____________
cut into segments
100
The rotating elements of a turbine section consist of a ______________
shaft and a turbine rotor (wheel).
101
The turbine wheel is a dynamically balanced unit consisting
of blades attached to a _______________-
rotating disk.
102
The _______________ is the anchoring componentforthe turbine
blades and is bolted or welded to the main shaft.
turbine disk
103
itis a phenomena in which extreme stress on turbine blades may cause the turbine blades to grow in length due to severe
centrifugal loads imposed by high rotational speeds.
Growth or Creep
104
The most commonly used method for attaching turbine blades is by ___________slots cut into the turbine disk rim and matching bases cast or machined into the turbine blade base.
fir tree
105
Turbine Blades
Fit _________ into a turbine disk when an engine is cold, but expand
to fit __________ at normal operating temperatures.
loosely, tightly
106
____________ are used on high-speed turbines, while ________ are commonly used on turbines having slower rotational speeds
Open-ended blades, shrouded blades
106
107
To improve the airflow
characteristics around shrouded
turbine blades further, a ___________ is machined around the outside ofthe shroud to reduce air losses atthe blade tip.
knife edge seal
108
the blades merely change the
direction of airflow coming
from the turbine nozzle and
cause relatively no change in
gas pressure or velocity.
ImpulseTurbineBlades
109
Impulse Turbine Blades
The turbine wheel simply
absorbs the force required to
change the direction of airflow
and converts it to______________
to rotary motion.
110
Produce a turning force based on
an aerodynamic action.
Reaction Turbine Blades
111
The result is similar to what
happens to an airfoil, in that the
reduced pressure produces a lifting
force .However, in a turbine,the
force is exerted in the direction ofro
tation.
Reaction Turbine Blades
112
a combination of impulse and reaction
blades, the workload along the length of
the blade is evenly distributed.
Impulse-Reaction Turbine Blades
113
Impulse-Reaction Turbine Blades
The blade base is _______ shaped while
the blade tip is _________ shaped.
impulse, reaction
114
Most common ways of cooling the components in the turbine
section is to use ____________
engine bleed air
115
There are two types of blade
cooling:
convection cooling/film cooling and transpiration cooling.
116
compressor bleed air is
typically directed in through the hollow blades and out through
holes in the tip, leading edge, and trailing edge.
Convection Cooling/Film Cooling–
117
only used on stationary nozzle vanes,
bleed airis ducted into the vanes and exits through the porous
material.
Transpiration Cooling
118
A typical ____________- extends from the rear ofthe turbine section to the point where the exhaust gases leave the engine
exhaust section
119
Exhaust Section
It is comprised of several components including:
the exhaust cone, exhaust duct or tailpipe, and exhaust nozzle.
120
Atypical exhaust cone assembly consists of :
an outer duct, or shell, an inner cone, or tail cone, three or more radial
hollow struts, and a group of tie rods.
121
Purpose of Exhaust Cone
channel and collectturbine discharge gases into a single jet.
122
A ___________ is an extension ofthe exhaust section that directs exhaust gases safely from the exhaust cone to the exhaust, orjet nozzle.
tailpipe
123
Purpose of Tailpipe
protect the surrounding
airframe.
124
Purpose of Exhaust Nozzle
, provides the exhaust gases with a
final boostin velocity.
125
The two types of exhaust nozzle designs used on aircraft are the:
converging design, and the converging-diverging design.
126
Mixer Unit
bypass engine - combine bypass and hot airinto one
127
_____________ are used to accelerate the exhaust gases, which in turn, increases thrust
Afterburners
128
The components that make up an afterburner include the:
fuel manifold, an ignition source, and a flame holder.
129
Most turbojet and turbofan powered aircraft are fitted with ___________ to assist in braking
thrust reversers
130
____________ used on the ground include portable devices which can be positioned near the rear of an engine whenever prolonged ground operation is anticipated.
Noise suppressors
131
132
The _______________ of a gas turbine engine is used to power both engine and aircraft accessories
accessory section, or accessory drive,
133
Accessory section
Secondary functions include acting as an ____________- and ______________
oi reservoir, or sump
housing the accessory drive gears and reduction gears.
134
is a constant speed gas turbine
engine
The Auxiliary Power Unit (APU)
135
APU provides:
Electrical powerforthe aircraft systems,
Bleed airfor engine starting and air conditioning on the ground,
Bleed airfor air conditioning / pressurization and wing anti ice in flight.
136
a self-contained unit,
which enables the aircraftto be
independent of external
pneumatic and electrical power
sources.
The Auxiliary Power Unit (APU)
