Lubrication System & Thrust Reverser Flashcards
(89 cards)
1
Q
Purpose of Lubricants
A
Reduce friction between moving parts
Cooling
Collect foreign matter
Protect from corrosion
2
Q
Lubricating Systems
A
Full Flow System
Pressure Relief Valve System
Total-Loss (Expendable) System
3
Q
Pressure Relief Valve System
A
turboprop engines
good with engine that has low bearing chamber pressure
bearing chambers is controlled by limiting the pressure
Constant Pressure
4
Q
Full Flow System
A
turbofan engines
high bearing chamber pressure
oil flow rates dispensing with the pressure relief valve and allowing the pressure pump
Pressure varies with engine speed
5
Q
Total Loss (Expendable) System
A
engines which run for periods of short duration, such as booster and vertical lift engines.
6
Q
Oil System Components
A
Oil Tank
Oil Pump
Oil Jets
Oil Cooler
Magnetic Plugs
Oil Vents
Oil Filters
Oil
7
Q
usually mounted on the engine and is normally a separate
unit although it may also be an integral part of the external
gearbox.
A
Oil Reservoir/Tank
8
Q
Oil Reservoir/Tank
It must have provision to allow the lubrication system to be
______ and _________.
A
drained and replenished
9
Q
A ____________ must also be incorporated to allow the oil system contents to be checked.
A
sight glass or a dipstick
10
Q
____________ is designed to supply oil under pressure to
the parts of the engine that require lubrication, then
circulate the oil through coolers as needed, and return
the oil to the oil tank
A
oil pump
11
Q
OilPumps
vital to the efficient operation of the engine. Failure of the pumps will necessitate a __________.
A
rapid shutdown of the engine
12
Q
Typesof Oil Pump
A
Gear - Oil is picked up by the gears
Vane - uses sliding vanes in an eccentric rotor to move fluid
Gerotor - engine-driven spur gear that rotates within a free-spinning rotor housing
Scavenge - return oil to the reservoir
13
Q
can deliver lubrication oil as a solid oil spray or an air-oil mist.
A
Oil jets
14
Q
is considered adequate for some
types of bearings,
A
air-oil mist
15
Q
typically provides better lubrication.
A
a solid oil spray
16
Q
is required in engines that use oil dampened bearings to reduce rotor vibrations and
compensate for slight rotor misalignments
A
Solid oil spray
17
Q
Two basic types of oil coolers
A
aircooled and fuel-cooled.
18
Q
used in the lubricating systems of some turbine engines to reduce the temperature of the oil to a degree suitable for recirculation through the system
A
Air-oil coolers
19
Q
Normally installed at the forward end of the engine and is usually included in a dry-sump oil system.
A
Air-oil coolers
20
Q
acts as a fuel-oil heat exchanger in that the fuel cools the hot oil and the oil heats the fuel for
combustion. It consists of a series of joined tubes with
an inlet and outlet port. The oil enters the inlet port, moves
around the fuel tubes, and goes out the oil outlet port.
A
Fuel-Oil Coolers
21
Q
They are fitted on scavenge return side to collect ferritic
debris from each bearing chamber.
A
Magnetic Plugs
22
Q
Functions of chip detectors/magnetic plugs
A
prevents metal particles attracted to the detector from circulating
provide valuable information
23
Q
- To prevent excessive air pressure within the oil tank,
gearboxes and bearing chambers
A
Centrifugal Breather
24
Q
Oil Vents
Any oil droplets in the air
are ________ by a centrifugal breather prior to the air being vented overboard.
A
separated out
25
To prevent foreign matter from continuously circulating
around the lubricating system, a number of filters and
strainers are positioned within the system.
OilFilters
26
- are usually fitted at the outlet of the oil tank or immediately prior to the inlet of the oil pumps to prevent debris from damaging the pumps.
Coarse strainers
27
A _________ is fitted at
the pressure pump outlet which
retains any small particles
which could block the oil feed
jets
fine pressure filter
28
___________ are often fitted as a 'last chance' filter immediately upstream of the oil jets
Thread-type filters
29
________ are
fitted in each oil return
line to collect any debris
from the lubricated
components.
scavenge filters
30
Oils or Lubricating Oils
Most gas turbines use a ___________ due to the absence of reciprocating parts and heavy duty gearing.
This _____________ for starting,
particularly at low temperatures.
low viscosity oil; reduces the power required
31
Oils or Lubricating Oils
In fact normal starts
can be made in temperatures as low as __________ without having to pre-heat the oil.
-40 deg. C
32
Thrust Reversal
A simple and effective way to reduce the aircraft landing run
on both dry and slippery runways is to _____________, thus using engine power as a deceleration force.
reverse the direction of the exhaust gas stream
33
has been used to reduce airspeed in flight but it is not commonly used on modern
aircraft.
Thrust reversal
34
Thrust Reversal Systems
Clamshell Door System
Bucket Target System
Cold Stream Reverser System
35
is a pneumatically operated
system. Normal engine operation is not affected by the
system, because the ducts through which the exhaust
gases are deflected remain closed by the doors until
reverse thrust is selected by the pilot.
Clamshell Door System
36
On the selection of reverse thrust, the doors rotate to
uncover the ducts and close the normal gas stream exit.
Cascade vanes then direct the gas stream in a forward
direction so that the jet thrust opposes the aircraft motion.
Clamshell Door System
37
Hydraulically actuated and uses bucket-type doors to reverse the hot gas stream.
Bucket Target System
38
The thrust reverser doors
are actuated by means of a conventional pushrod
system. A single hydraulic powered actuator is connected to a drive idler, actuating the doors through a pair of pushrods (one for each door).
The reverser doors are kept in synchronization through the
drive idler. The hydraulic actuator incorporates a mechanical lock in the stowed (actuator extended) position.
Bucket Target System
39
The _____________ can be actuated by an
air motor, the output of which is converted to
mechanical movement by a series of flexible drives,
gearboxes and screwjacks, or by a system incorporating
hydraulic rams.
Used on turbofan engines
cold stream reverser system
40
The maximum power output of a gas turbine engine
depends to a large extent upon the _____________ passing through the engine
density or weight of
the airflow
41
The maximum power output of a gas turbine engine
depends to a large extent upon thedensity or weight of
the airflow passing through the engine.
Therefore,there would be a reduction in thrust or shaft
horsepower as the
_____________, and/orthe ambient airtemperature
increases
atmospheric pressure decreases with altitude
42
Performance Augmentation
Water Injection System
Water Methanol Injection System
Afterburners
43
Power available of your
turbojets are restored
back to 100% even after
exceeding 25 deg. C.
Water Injection System
44
Power available of your
turboprops are boosted
by 15%
Water Methanol Injection System
45
Improve takeoff and
climb or combat
performance
Afterburners
46
In conditions ofhigh altitude and/orhigh temperature the
use of ________ can restore the thrust of a turbo-jet
engine andboost the output of a turbo-prop engine.The
_____________ is typically activated by moving the throttle to the take-off position.
water injection system
47
The amount of water which is carried can be large,theBoeing
707 carry approximately _________ of water injection fluid
per engine which must
________________
300 gallons; all be used up in a three minute take
off and climb
48
WaterInjection
This equates to a water flow rate of ___________ per minute.
The fuelflow through each engine at this time is ___________.This gives a water flow to fuel flow ratio of ________.
100 gallons; 9,000
lbs/hour(22gallons/minute); 4.5:1
49
limits the engine power so that it does notincrease above its flatrated 100% power
Power limiter circuit
50
The ___________, must
be limited to preventthe engine carcass splitting under
excessive stress.
maximum compressor outlet pressure (P3)
51
Apure waterinjection system does have some _________, because the water must all be used up on take-offifitis notto freeze in the tanks as the aircraft climbs to altitude.
drawbacks
52
It would be logicalto require an injection fluid that did not
freeze,thus _________ is added to the water.This serves
primarily as an _______,there is however an additional
bonus achieved by using methanol.
methanol; anti-freeze
53
By injecting coolantinto the combustion chamber,the
TGT(turbine gas temperature), is ___________ which somewhat _______ the power available (remember that the turbojetis a heat engine).
lowered dramatically; lowers
54
being an alcoholfuel, burns, and adds to the
temperature of the gases,raising theTGTback to its
original level
Methanol
55
In orderto regulate the amount of heat added,the quantity of
water methanol injected into the engine must be carefully
regulated,this is done by a _____________. The proportion of methanol added to the water must also be carefully controlled, a ratio of ________ ensures thattheTGTlimits should never be exceeded during use ofthe water methanol system.
water methanol control system; 40% methanol to 60% water
(by volume)
56
Methods of Injection
Some centrifugal compressor engines, and some small
American designed axial flow compressor engines, injected
the water into the _______ or also known as the ___________. Unfortunately, water distribution was not of
the best and the quantity of water had to be limited so as not to cause an ___________.
engine intake; compressor inlet; engine flame out
57
Methods of Injection
As was mentioned in the previous paragraph, injection of
water into the _________ increases the mass flow through the turbine relative to thatthrough the compressor. Because the turbine has no extra work to do to obtain this increase mass flow,there is a related decrease in the pressure drop across it. This results in an increase in the amount of power available,
either to drive the propellerthrough a _________, or as an increase in the ____________
combustion chamber; free turbine; jet pipe pressure
58
The compressor inlet injection system as shown in the figure
below is a typical system for a turbo-propeller engine.When
the injection system is switched on, _____________ is pumped from an aircraft mounted tank to a control unit.
water/methanol mixture
59
compressor inlet injection
The control unit ________ to the compressor inlet through a metering valve thatis operated by a servo piston.
meters the flow of mixture
60
compressor inlet injection
The __________ uses engine oil as an operating medium, and a servo valve regulates the supply of oil.
servo system
61
compressor inlet injection
The ____________ is set by a control system thatis sensitive to propeller shaft torque oil pressure and to atmospheric air pressure acting on a capsule assembly.
degree of servo valve opening
62
compressor inlet injection
The control unit high pressure oil cock control lever is ___________ in such a
mannerthat, untilthe throttle is moved towards the __________,the oil cock remains ______, and thus the metering
valve remains _________, preventing any mixture flowing to the compressor inlet.
interconnected to the throttle control system; take-off
position; closed; closed
63
compressor inlet injection
Movement of the throttle control to the take-off position
_____ the oil cock, and the oil pressure passes through the
servo valve to open the ______ by means ofthe
servo piston.
opens; metering valve
64
The combustion chamberinjection system shown in the figure shown below is a typical system for a turbojet engine.
The coolant flows from an __________ to an air driven turbine pump that delivers it to a __________.The water passes from the sensing unit to each
fuel spray nozzle and is sprayed from ____________,thus cooling the air passing into the
combustion zone.
aircraft-mounted tank; water flow sensing unit; two jets onto the flame tube swirl vanes
65
The water pressure between the sensing unit and the
discharge jets is sensed by the ______________, which
automatically resets the engine speed governor to give a
______________.
fuel control system; higher maximum engine speed
66
The water flow sensing unit opens only when the___________ between compressor
delivery air pressure and water pressure. The system is
brought into operation when the engine throttle lever is
moved to the ________, causing ______ to operate and select the air supply forthe turbine pump
correct pressure difference is obtained; take-off position; micro switches
67
The sensing unit also forms a _________ to prevent air
pressure feeding back from the discharge jets and provides
forthe operation of an indicatorlightto show when wateris flowing.
non-return valve
68
makes use of the unburnt oxygen in the exhaust to release more heat
energy by burning more fuel between the turbine and the
propelling nozzle
Thrust augmentation by afterburning
69
is used to improve takeoff and climb or combat performance, mainly restricted to military aircraft.
Afterburning
70
________ are used to accelerate the exhaust gases,
which in turn, increases thrust.
Afterburners
71
currently the only
supersonic passenger carrying aircraft using fourlow bypass ratio turbojets with afterburners
Concorde
72
The velocity ofthe gas stream from the turbine is __________
before entering the afterburner section to _________ the
velocity sufficiently to enable the afterburnerflame to remain
____________
diffused; reduce; stable
73
is introduced into the jet pipe through the burners and ignited by an igniter plug or a hot streak of
flame from the combustion chamber.
atomized fuel spray
74
Once combustion is established the gas temperature
increases and the expanding gas __________ through the
open propelling nozzle providing __________.
accelerates; additional thrust
75
As can be imagined the fuel consumption goes up
dramatically so use ofthe afterburneris normally limited to ___________
short periods
76
Operations of Afterburning
The gas stream from the engine turbine enters the jet pipe at a
velocity of _______________, but as this velocity is far too high for a stable flame to be maintained,the flow is
________ before it enters the afterburner combustion zone,
i.e.the flow velocity is reduced and the pressure is increased.
750 to 1,200 feet per second; diffused
77
Operations of Afterburning
However, as the speed of burning kerosene at normal mixture ratios is only a few feet per second, any fuel lit even in the diffused air stream would be blown away. A form of _________ is,therefore, located downstream of the fuel burners to provide a region in which ________ are formed to assist combustion and where the local gas velocity is further _____ to a figure at which flame stabilization occurs whilst combustion is in operation.
flame stabilizer (vapor gutter); turbulent eddies; reduced
78
An __________ is fed into the jet pipe through a number of burners, which are so arranged as to distribute the
fuel evenly overthe flame area.
atomized fuel spray
79
Combustion is then initiated by a __________________, which
creates a flame as a result ofthe chemicalreaction ofthe
fuel/air mixture being sprayed on to a __________________
catalytic igniter; platinum-based
element
80
by an igniter plug adjacentto the burner, or by a hot
streak offlame that originates in the engine combustion
chamberthis latter method is known as ______________.
'hot-shot' ignition
81
Once combustion is
initiated, the gas
temperature
__________ and the
expanding gases
__________ through
the enlarged area
propelling nozzle to
provide the _______
increases; accelerate; additional
thrust
82
The increase in thrust due to afterburning depends solely
upon the _______________
ratio of the absolute jet pipe temperatures before and after the extra fuel is burnt
83
Engine Station Numbering
0- InletAirflow
1 - Inlet Diffuser
2- Inlet Duct
3- Fan
4- Compressor
5-Burners
6-Turbine
7 -Exhaust Duct
8-Exhaust Nozzle
9-ExhaustAirflow
84
Those engines withbypass ducts are designated in the same
manner but have ___________
two numbers instead of one
85
Fundamental Station Numbers
AMB Ambient conditions
0 Ram conditions in free stream
1 Engine intake front flange, or leading edge
2 First compressor/fan front face
3 Last compressor exit face
4 Combustor exit plane
5 Last turbine exit face
6 Front face of mixer, afterburner etc.
7 Propelling nozzle inlet
8 Propelling nozzle throat
9 Propelling nozzle or exhaust diffuser exit plane
86
Parameters
Po or To - Ambient pressure or temperature
P1 or T1 - Pressure or temperature at engine intake front flange, or leading edge
P2 or T2 - Pressure or temperature at the low pressure compressor delivery or at the first compressor/fan front face
P3 or T3 - Pressure or temperature at the high
pressure compressor delivery at the last compressor exit face
P4 or T4 - Pressure or temperature at the turbine entry or at the combustor exit plane
P5 or T5 - Pressure or temperature at the high
pressure turbine exit or at the last turbine exit face
P6 or T6 - Pressure or temperature at the low
pressure turbine exit or at the front face of mixer
P7 or T7 - Pressure or temperature at the exhaust
P8 or T8 - Pressure or temperature at the
propelling nozzle
87
Intermediate station numbers most commonly used for a
two spool turbojet
24 First compressor exit
26 Second compressor front face
31 Compressor outlet diffuser
exit/combustor inlet
405 First turbine nozzle guide vane throat
41 Stator outlet temperature
44 First turbine exit
45 Second turbine nozzle guide vane leading edge
88
For a turbofan with separate jets, common bypass duct station numbers include:
12 Fan tip front face, if conditions are different from the fan root front (station 2)
13 Fan exit
17 Cold propelling nozzle inlet
18 Cold propelling nozzle throat
89
In the more complicated instance of mixed streams and an afterburne rthe following numbers are usually used through these components:
16 Cold mixer inlet
6 Hot mixer inlet
65 Mixer outlet/afterburner inlet
7 Afterburner outlet/propelling nozzle
inlet
