In a gas turbine engine the power changes are normally made by controlling the amount of ? Choice > assignment
In a free turbine engine ?
In a free turbine engine There no mechanical connection between compressor the power output shaft.
During take off the fan in a high by pass ratio turbofan engine produces ?
During take off fan in a high pass ratio turbofan engine produces The greater part of thrust. At constant fuel flow if engine compressor air bled off engine anti icing or a similar system turbine temperature The greater part of thrust. The ratio of tertiary airflow around combustion flame tube that cools turbine decreases thus less cooling flow as warm air diverted anti icing so egt will increase as a result. A hung abortive start of a gas turbine engine may be caused A too low pneumatic starter pressure.
after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall
hung starts may be caused
starter air pressure too low to accelerate engine to self sustaining speed
premature starter deactivation
fod (foreign object debris) to compressor
faulty pressurizing valves not opening at scheduled fuel pressure setting
incorrect scheduling of hp compressor igv variable stators
turbine section damage. A reverse thrust alert on flight deck occurs when 1 reverser doors are unlocked with reverse lever in stowed position 2 reverser doors are locked with reverse lever in stowed position 3 reverser doors remain stowed with reverse lever in deployed position 4 reverser doors have moved to reverse thrust position with reverse lever in deployed position the combination that regroups all of correct statements A too low pneumatic starter pressure. Boeing fcom
thrust reverser
each engine equipped with a hydraulically operated thrust reverser consisting of left right translating sleeves aft movement of reverser sleeves causes blocker doors to deflect fan discharge air forward through fixed cascade vanes producing reverse thrust the thrust reverser for ground operations only is used after touchdown to slow airplane reducing stopping distance brake wear
when reverse thrust selected an electro mechanical lock releases isolation valve opens the thrust reverser control valve moves to deploy position allowing hydraulic pressure to unlock deploy reverser system an interlock mechanism restricts movement of reverse thrust lever until reverser sleeves have approached deployed position when either reverser sleeve moves from stowed position amber rev indication located on upper display unit illuminates as thrust reverser reaches deployed position rev indication illuminates green the reverse thrust lever can be raised to detent no 2 this position provides adequate reverse thrust normal operations when necessary reverse thrust lever can be pulled beyond detent no 2 providing maximum reverse thrust
downward motion of reverse thrust lever past detent no 1 (reverse idle thrust) initiates command to stow reverser when lever reaches full down position control valve moves to stow position allowing hydraulic pressure to stow lock reverser sleeves after thrust reverser stowed isolation valve closes the electro mechanical lock engages
if reverser doors are unlocked with reverse lever in stowed position or if reverser doors remain stowed with reverse lever in deployed position reverser light illuminates master caution eng system annunciator lights illuminate. In a single spool gas turbine engine compressor rpm The same as turbine rpm. The turbine turning compressor so one turbine one compressor
single spool gas turbine engine. 8 The primary reason a limitation being imposed on temperature of gas flow to Ensure that maximum acceptable temperature at turbine blades not exceeded. The temperatures are highest in combustion chamber but engine most sensitive to high temperatures just behind combustion chamber at turbine high temperatures centrifugal loads can cause turbine blade creep
jt9d engine. 9 One of purposes of bleed valves fitted to axial flow compressors to Reduce tendency to compressor stall. The temperatures are highest in combustion chamber but engine most sensitive to high temperatures just behind combustion chamber at turbine high temperatures centrifugal loads can cause turbine blade creep
jt9d engine. 10 A modern auxiliary power unit apu designed to provide power ground starting of an engine it also supplies both in air subject to certification limitations and on ground Air conditioning electrical services. The temperatures are highest in combustion chamber but engine most sensitive to high temperatures just behind combustion chamber at turbine high temperatures centrifugal loads can cause turbine blade creep
jt9d engine. 11 The disadvantages of axial flow compressors compared to centrifugal flow compressors are 1 more expensive to manufacture2 lower airflow3 greater vulnerability to foreign object damage4 lower pressure ratiothe combination which regroups all of correct answers Air conditioning electrical services.
compared to centrifugal flow compressors axial flow compressors are more expensive to manufacture
due to design function of a compressor engine's air inlet possibility of ingestion of debris always exists this causes significant damage particularly to compressor turbine sections when this occurs it called foreign object damage (fod) typical fod consists of small nicks dents caused ingestion of small objects from ramp taxiway or runway
however fod damage caused bird strikes or ice ingestion can also occur may result in total destruction of an engine
example of a centrifugal compressor
. 12 A stage in an axial compressor Consists of a rotor disc followed a ring of stator blades.
compared to centrifugal flow compressors axial flow compressors are more expensive to manufacture
due to design function of a compressor engine's air inlet possibility of ingestion of debris always exists this causes significant damage particularly to compressor turbine sections when this occurs it called foreign object damage (fod) typical fod consists of small nicks dents caused ingestion of small objects from ramp taxiway or runway
however fod damage caused bird strikes or ice ingestion can also occur may result in total destruction of an engine
example of a centrifugal compressor
. 13 In a turbo jet purpose of turbine to Drive compressor using part of energy from exhaust gases.
compared to centrifugal flow compressors axial flow compressors are more expensive to manufacture
due to design function of a compressor engine's air inlet possibility of ingestion of debris always exists this causes significant damage particularly to compressor turbine sections when this occurs it called foreign object damage (fod) typical fod consists of small nicks dents caused ingestion of small objects from ramp taxiway or runway
however fod damage caused bird strikes or ice ingestion can also occur may result in total destruction of an engine
example of a centrifugal compressor
. 14 The gas turbine illustrated of following type 916 Free turbine centrifugal compressor. For a free power turbine engine turbine driving main rotor transmission mechanically independent from gas generator
radial (centrifugal) compressor (located at front of engine). 15 The control of free turbine engines on turboprops accomplished a propeller control lever used to select 1 propeller rpm2 turbine temperature3 turbine rpm a fuel control lever used to select 4 propeller rpm5 torque6 turbine temperaturethe combination which regroups all of correct statements Free turbine centrifugal compressor. Propeller control lever controls rpm so out of 1 2 3 only 1 correct
fuel control lever controls torque turbine temp so out of 4 5 6 both 5 6 are correct
the correct answer option then 1 5 6. 16 The static thrust of a turbo jet at selection of full power 1 equals product of exhaust gas mass flow and exhaust gas velocity2 obtained pressure of exhaust gas on ambient air3 equivalent to zero mechanical power since aeroplane not moving4 independant of outside air temperaturethe combination which regroups all of correct statements Free turbine centrifugal compressor. Static thrust the measured thrust produced when movement prevented
thrust in its simplest form is
f = m x a
thrust (f) = mass flow rate x (jet velocity tas)
statement 1 it true
2 it a nonsense
statement 3 it true no movement = zero mechanical power
statement 4 wrong static thrust dependant of outside air temperature since mass flow will vary with temperature/density. 17 The purpose of a compressor bleed valve to prevent surging At low compressor rpm.
the compressor bleed valve removes excesss volume of air at low compressor rpm to increase flow over front compressor blades reduce flow over latter stages. 18 Severe compressor stall can be indicated amongst others A rise in turbine gas temperature (tgt) a change in vibration level. A compressor stall means less cooling flow the turbine so egt will increase as a result as a wing vibrations will occur during stall. 19 In a gas turbine engine compressor blades which are not rigidly fixed in position when engine stationary take up a rigid position when engine running due to The resultant of aerodynamic centrifugal forces. The blades are not rigidly fixed one common mehtod of fitting them with 'fir tree root' rotor blades are strong enought to withstand centrifugal forces they take up a rigid position when engine running due to resultant of aerodynamic centrifugal forces
watch videos below
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(you can here at 6 00 'clung' noise of blade falling from their casing)
>phluddufakg
(this for turbine stage but construction similar the compressor stage). 20 The characteristics of a centrifugal compressor are 1 a high pressure ratio stage2 a large diameter3 a low pressure ratio stage4 a small diameterthe combination containing all of correct statements The resultant of aerodynamic centrifugal forces.
axial compressor
radial compressor
the pressure ratio obtained from a centrifugal compressor stage lower than that which can be obtained from axial flow compressor stage
the diameter of a centrifugal compressor usually larger compare to an axial compressor the same flow. Exclusive rights: Content under private and protected license, reproduction prohibited and prosecuted.
