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The diffuser in a centrifugal compressor is a device in which the ? Theoretical > lift > off

exemple question 167
Pressure rises velocity falls. Diffuser = stator a compressor in case of a compressor velocity falls the pressure increases in stator (the diffuser).


The thrust reversers of jet engines may use clamshell doors in order to ?

exemple question 168
The thrust reversers of jet engines may use clamshell doors in order to Change direction of exhaust gas stream. Diffuser = stator a compressor in case of a compressor velocity falls the pressure increases in stator (the diffuser).


By pass turbine engines are mainly used in commercial aviation because ?

exemple question 169
By pass turbine engines are mainly used in commercial aviation because At high subsonic airspeeds they have a better propulsive efficiency than propeller or straight jet engines. Diffuser = stator a compressor in case of a compressor velocity falls the pressure increases in stator (the diffuser).


exemple question 170
Engine auxiliary gearboxes Provide drives a wide variety of services may even provide the support of engine in airframe. the accessory gearbox driven a radial shaft that meshes with a bevel gear driven the n2 (or gas producer rotor) is used to drive essential engine components such as fuel pump oil pump fuel control unit generators hydraulic pumps the accessory gear box also used to drive engine rpm feedback tacho generators is means which starter drives engine these are systems which must operate as soon as engine starts structure containing gearbox can be utilised as a support as well each component that attaches to accesssory gearbox has its own mounting pad with its unique gear reduction speed rotational direction.


exemple question 171
The greatest risk created a free turbine overspeed Bursting of free turbine disk. In case of turbine overspeed centrifugal force can be so great that turbines rotor blades can detatch during a high powered engine run this 767 had a engine failure piece of turbine seen above lodged in outboard side of engine the photo above shows gash made on lower part of fuselage in air conditioning bay when a piece of turbine exited engine ended up embedding in engine.


exemple question 172
The thermal efficiency of a gas turbine engine will increase with a Decrease in ambient air temperature. Thermal efficiency the ratio of useful work to heat put in expressed as a percentage the power output of a gas turbine engine depends on mass airflow a cold air mass has higher density thermal efficiency increases with cold ambient air temperature.


exemple question 173
Creep of turbine blades caused High blade temperature whilst under centrifugal loading. Blade creep the increase in length of turbine rotor blades during their operating life due to heat stress.


8
By pass ratio in a turbine engine the ratio of Cold air mass flow to hot air mass flow. bypass ratio = bypass mass flow / hp compressor mass flow by pass mass flow cold air mass flow hp compressor mass flow the hot air mass flow.


9
On landing and prior to shut down a gas turbine engine should be r at 'ground idle' a short period this allows The core temperature to diminish. bypass ratio = bypass mass flow / hp compressor mass flow by pass mass flow cold air mass flow hp compressor mass flow the hot air mass flow.


10
Both gas turbine and piston engines utilise a cycle of induction compression combustion and exhaust however in gas turbine these processes are i and combustion occurs at ii respectively i and ii are (i) continuous (ii) constant pressure. Piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure.


11
For a subsonic airflow in a divergent duct Pressure increases velocity decreases temperature increases. Piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure.


12
An engine pressure ratio epr can be defined as ratio of Jet pipe total pressure to compressor inlet total pressure. Epr defined as ratio of total turbine outlet pressure to total compressor inlet pressure 'total turbine outlet pressure' 'jet pipe total pressure'.


13
For a fan jet engine by pass ratio the Cold air mass flow divided the hot air mass flow. bypass ratio = bypass mass flow / hp compressor mass flow by pass mass flow cold air mass flow hp compressor mass flow the hot air mass flow.


14
The pass air in a pass type gas turbine engine promotes lower specific fuel consumption causing an overall Decrease in exhaust gas flow average velocity higher propulsive efficiency. Bypass engines have a number of advantages the bypass air does not need to be combusted to achieve its acceleration since no fuel needed to heat air design inherently more thermally efficient the bypass air given a smaller acceleration so its propulsive efficiency greater at lower speeds the reason that answer decrease in combustion chamber temperature higher thermal efficiency not correct that although engine more thermally efficient combustion chamber temperatures are not reduced.


15
In airflow through a single spool axial flow turbo jet engine axial velocity of air greatest On exit from propelling nozzle. single spool axial flow turbo jet engine the term 'single spoo refers to fact that there only one shaft this shaft connects one turbine section to one compressor section all jet engines in current use are axial flow engines meaning that compression phase done axially (parallel to axis of engine) as air flows through compressor axial flow engines are different from early jet engines which compressed air in a centrifugal compressor the axial velocity of air greatest on exit from propelling nozzle (exhaust of propulsive gases).


16
In a jet engine propelling nozzle Must be designed to obtain correct balance of pressure velocity to prevent flow separation. single spool axial flow turbo jet engine the term 'single spoo refers to fact that there only one shaft this shaft connects one turbine section to one compressor section all jet engines in current use are axial flow engines meaning that compression phase done axially (parallel to axis of engine) as air flows through compressor axial flow engines are different from early jet engines which compressed air in a centrifugal compressor the axial velocity of air greatest on exit from propelling nozzle (exhaust of propulsive gases).


17
In a multi spool turbofan engine fan driven The rearmost turbine. The high pressure turbine drives high pressure compressor the low pressure turbine drives fan the low pressure compressor therefore we can say that fan driven from rearmost turbine a shaft.


18
After air has passed through compressor of a gas turbine engine Temperature will be higher than inlet temperature. Compression of air generates heat air warmer after compression 1 compressed air high pressure flows toward low pressure 2 the compressor sections are in front of engine the turbine in rear 3 the compressors are attached to turbines via shafts 4 between compressor turbine sections the combustion chamber where fuel mixed with compressed air iginited the compressor section made up of alternating rows rotating blades stationary vanes that are shaped like wings curved on one side flat on other they function like wings too airflow creates low pressure on curved side high pressure on flat this imparts direction of airflow toward rear of engine high pressure flows toward low pressure the leading edges of these rotating blades face leading edge of stationary blades as air cascades through each pair of rotor stationary vanes it becomes more more compressed the air enters combustion chamber is rapidly heated wants to expand (but there only so much room expansion which another form of compression) so it continues to rear of engine where pressure lower it meets turbines the turbine are like pinwheels the fast flowing compressed air strikes turbines causes it(them) to spin add more fuel more heat compressed air expands faster the turbines spin faster because they are attached to compressor section via shaft compressor spins faster too which compresses incoming air faster even more air does not like to be compressed it likes to be in its normal state so it roars past turbines out back of engine the reaction thrust of exhaust against engine itself causes propulsion.


19
To achieve reverse thrust on a turbine engine with a high pass ratio generally The fan flow deflected. Compression of air generates heat air warmer after compression 1 compressed air high pressure flows toward low pressure 2 the compressor sections are in front of engine the turbine in rear 3 the compressors are attached to turbines via shafts 4 between compressor turbine sections the combustion chamber where fuel mixed with compressed air iginited the compressor section made up of alternating rows rotating blades stationary vanes that are shaped like wings curved on one side flat on other they function like wings too airflow creates low pressure on curved side high pressure on flat this imparts direction of airflow toward rear of engine high pressure flows toward low pressure the leading edges of these rotating blades face leading edge of stationary blades as air cascades through each pair of rotor stationary vanes it becomes more more compressed the air enters combustion chamber is rapidly heated wants to expand (but there only so much room expansion which another form of compression) so it continues to rear of engine where pressure lower it meets turbines the turbine are like pinwheels the fast flowing compressed air strikes turbines causes it(them) to spin add more fuel more heat compressed air expands faster the turbines spin faster because they are attached to compressor section via shaft compressor spins faster too which compresses incoming air faster even more air does not like to be compressed it likes to be in its normal state so it roars past turbines out back of engine the reaction thrust of exhaust against engine itself causes propulsion.


20
An aircraft flying in conditions of continuous heavy rain and high ambient temperatures may require precautionary use of The fan flow deflected. Normally in flight no igniters are in use as combustion self sustaining during engine start for take off landing igniters are in use you have to use igniters in case of moderate or severe precipitation turbulence or icing or an in flight relight.



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