Part 1 - Fundamentals Flashcards
what does the adiabatic process mean?
- expansion or contraction is adiabatic when
- no loss or gain of heat by the working fluid
what does the isothermal process mean?
- expansion or contraction is isothermal when
- the condition of the gas is changed at constant temperature
- heat is gained or lost
what is momentum thrust?
thrust due to the change of momentum of the gases through the engine
what is pressure thrust?
thrust produced by a choked nozzle condition causing a pressure difference across the nozzle
what is gross thrust?
- thrust produced by the total work done on the gas stream
- is a combination of momentum thrust and pressure thrust
- i.e. momentum thrust + pressure thrust = gross thrust
what is momentum or intake drag?
drag due to the momentum of the air passing into the engine relative to aircraft speed
what is net thrust?
gross thrust minus momentum drag
what is ram ratio?
the ratio of engine intake pressure to static pressure at the aircraft intake
what is total head pressure?
- pressure of the air when brought to rest ahead of the intake supersonic flow
- compressor inlet pressure should be as near as possible to total pressure
what is effect of humidity?
- humid air will give less thrust
- water vapour less dense than air
- therefore weight of air entering engine is less
what is compressor efficiency?
- determined by temperature rise through the compressor
- large temperature increase could indicate an inefficient compressor
what is a plenum chamber?
- chamber or enlargement of a duct in an air intake system
- used to smooth or dampen out pulsations in a flow of air
- so that the air is supplied at a constant value
what is a power turbine?
- sometimes referred to as a free turbine
- a turbine assembly not mechanically connected to a compressor
definition of mass
- basic property of matter
- generally associated with force required to overcome inertia of a body
- called weight when that inertia is associated with gravity
definition of acceleration
rate of change of velocity of a body
definition of momentum
- measure of quantity of motion
- product of mass and velocity on a body
- determined by length of time a constant force must act on that body to bring it to rest
- momentum is a vector quantity and is parallel to the velocity vector
- loosely speaking, momentum is the force built up by a moving body
definition of power
- rate of charging energy from one form to another or the rate of doing work
- power = energy/time
SI units of power
watts (W) or Joules per second (J/s)
Boyle’s law
- volume of a given mass of gas
- whose temperature is maintained constant
- is inversely proportional to the gas pressure
Charles’ law
- if the pressure of a given mass of gas is maintained constant
- the volume of gas increases as its temperature is increased
what is the ideal gas law?
P1V1/T1 = P2V2/T2
effect of adding heat energy at a constant volume
- increase in pressure
- this condition exists in a piston engine
effect of adding heat energy at a constant pressure
- increase in volume
- this condition exists in a gas turbine engine
energy cannot be…
created nor destroyed
what is entropy?
flow of energy to an even level
what are six forms of energy?
- heat
- fuel
- kinetic
- potential
- electrical
- pressure
heat energy is regarded as __________ energy
heat energy is regarded as DISORDERLY energy
heat energy travels through which three methods?
- convection
- conduction
- radiation
fuel energy is also known as _________ energy
fuel energy is also known as CHEMICAL energy
fuel energy is regarded as _________ energy
fuel energy is regarded as ORDERLY energy
kinetic energy is the energy a body possesses by virtue of its _______
kinetic energy is the energy a body possesses by virtue of its MOTION
potential energy is energy caused by the _________ of a body
potential energy is energy caused by the POSITION of a body
electrical energy is the flow of atoms from a ________ charge to a ________ charge
electrical energy is the flow of atoms from a NEGATIVE charge to a POSITIVE charge
pressure energy; a fluid under compression will attempt to flow from a ____ pressure to a ___ pressure and, in doing so, will or can do _____
pressure energy; a fluid under compression will attempt to flow from a HIGH pressure to a LOW pressure and, in doing so, will or can do WORK
a thermodynamic engine is a machine where ____ energy is changed into work
a thermodynamic engine is a machine where HEAT energy is changed into work
a thermodynamic engine is NEVER ___% efficient
a thermodynamic engine is NEVER 100% efficient
in temperature scales:
- C = ?
- F = ?
- K = ?
- R = ?
in temperature scales:
- C = CELSIUS
- F = FAHRENHEIT
- K = KELVIN
- R = RANKINE
rankine = fahrenheit + ___
rankine = fahrenheit + 460
kelvin = celsius + ___
kelvin = celsius + 273
fahrenheit = (9/5 celsius) + __
fahrenheit = (9/5 celsius) + 32
celsius = 5/9 (Fahrenheit - __)
celsius = 5/9 (Fahrenheit - 32)
what is newtons first law?
a body at rest will remain at rest…
what is newtons second law?
rate of change of momentum of a body is proportional to the size of force and acts in direction of applied force
what is newtons third law?
every action has an equal and opposite reaction
what does Bernoulli’s theorem state?
energy can’t be created or destroyed
what happens to pressure, temperature and velocity in a convergent duct?
- pressure decreases
- temperature decreases
- velocity increases
what happens to pressure, temperature and velocity in a divergent duct?
- pressure increases
- temperature increases
- velocity decreases
with a piston engine, combustion (power) is __________, whereas in the gas turbine, each process is __________
with a piston engine, combustion (power) is INTERMITTENT, whereas in the gas turbine, each process is CONTINUOUS
in a gas turbine system, combustion takes place at a constant ________
in a gas turbine system, combustion takes place at a constant PRESSURE
gas turbine engine fuel is ________ and less _________ than piston engine fuel
gas turbine engine fuel is CHEAPER and less DANGEROUS than piston engine fuel
the power to weight ratio of the average turbo propeller engine is ______ times better than its equivalent piston engine; there is ________ frontal area; the efficiency is ________
the power to weight ratio of the average turbo propeller engine is THREE times better than its equivalent piston engine; there is REDUCED frontal area; the efficiency is SUPERIOR
thrust in a gas turbine engine is felt on…
all static and rotating components
the compressor provides mass ____ and at the same time increases its ________
the compressor provides mass FLOW and at the same time increases its PRESSURE
the combustion system is designed to burn the fuel as efficiently as possible over the whole range of engine _________ conditions. it must do so without any increase in _________
the combustion system is designed to burn the fuel as efficiently as possible over the whole range of engine OPERATING conditions. it must do so without any increase in PRESSURE
what is a disadvantage of single spooled engines?
single, heavier spools taking too long to accelerate (spool up)
the high bypass turbofan engine is essentially a fix-______, multi-_______, ducted _________
the high bypass turbofan engine is essentially a fix-PITCHED, multi-BLADED, ducted PROPELLER
high bypass engine ratios range from 1:1 to .:1
high bypass engine ratios range from 1:1 to 6.5:1
the weight reduction on a typical low by-pass engine over a pure jet of similar mass flow is around __%
the weight reduction on a typical low by-pass engine over a pure jet of similar mass flow is around 20%
on most modern turboprop engines, the amount of energy available for jet thrust is approximately __% at sea level
on most modern turboprop engines, the amount of energy available for jet thrust is approximately 10% at sea level
a turbo prop usually has ____ stages than a turbo-jet engine
a turbo prop usually has MORE stages than a turbo-jet engine
what is meant by a “free turbine”?
- drive with no mechanical linkage to the “core engine”
- separate turbine drives shaft, driven by hot gases
the majority of turbo prop engines are now “____ turbines”
the majority of turbo prop engines are now “FREE TURBINES”
with respect to engine notations, what temperatures, pressures and speeds are the following referring to:
- P0, T0?
- P1, T1?
- P2, T2?
- P3, T3?
- P4, T4?
- P5, T5?
- P6, T6?
- P7, T7?
- N1, N2 AND N3?
with respect to engine notations, what temperatures, pressures and speeds are the following referring to:
- P0, T0 = ambient pressure and temperature
- P1, T1 = compressor inlet P&T
- P2, T2 = LP compressor delivery P&T
- P3, T3 = HP compressor P%T
- P4, T4 = turbine entry P&T
- P5, T5 = HP turbine outlet P&T
- P6, T6 = LP turbine outlet P&T
- P7, T7 = exhaust P&T
- N1, N2 AND N3 = LP, IP and HP spool speeds
installed turbine engines which are out of use for up to _____ days require no special protection aside from _________ off apertures to prevent moisture/FOD ingress
installed turbine engines which are out of use for up to SEVEN days require no special protection aside from BLANKING off apertures to prevent moisture/FOD ingress
short term engine storage is regarded as periods up to ___ month
short term engine storage is regarded as periods up to ONE month
with regards to fuel systems, oil systems and external treatment, what must be done to satisfactorily store an engine on a short term basis?
- fuel system - inhibited to prevent corrosion depending on whether installed or not
- oil system - WRT maintenance manual, remove and clean filters or fill system to normal level with clean system or storage oil
- external treatment - clean, dry with compressed air and inspect for corrosion and treat corrosion if necessary. desiccant or vapour phase inhibitor should be placed in intake. blank off engine
long term engine storage is regarded as periods up to ___ months. after a six month storage period, the engine should be re-________ for a further six months if necessary. alternatively, the engine can be removed from the aircraft and placed in a _______ _______ ______ (MVP) bag
long term engine storage is regarded as periods up to SIX months. after a six month storage period, the engine should be re-PRESERVED for a further six months if necessary. alternatively, the engine can be removed from the aircraft and placed in a MOISTURE VAPOUR PROOF (MVP) bag
for long term storage, in addition to measures taken for short term storage, the following action should be taken:
- _______ all control rods and fittings
- ______ off all vents and apertures on the engine, and, after covering ______ parts with greaseproof paper, spray a thin coat of preservative over the whole engine _______ of the exhaust
for long term storage, in addition to measures taken for short term storage, the following action should be taken:
- GREASE all control rods and fittings
- BLANK off all vents and apertures on the engine, and, after covering RUBBER parts with greaseproof paper, spray a thin coat of preservative over the whole engine FORWARD of the exhaust
why is fuel system inhibiting carried out in stored engines?
fuel contains water which can cause corrosion
briefly explain motoring method of fuel system inhibiting
- used on installed engines where engine can be turned through normal trying system
- header tank supplies oil to engine, connected to LP fuel inlet, LP cock should be closed
- after draining engine fuel filter, motoring run should be carried out, bleeding the HP pump and FCU and operating HP cock several times whilst engine turning
- neat inhibiting oil will eventually be discharged through combustion chamber drains
- seal off apertures after motoring run
when should gravity fuel system inhibiting be carried out?
- only when motor driven rig not available
- gravity fed results less effective
what does a motor driven fuel system inhibiting rig consist of?
- tank capacity of at least 5 imperial gallons
- motor driven had pump capable of 2gpm at 300 psi
- 500 psi pressure gauge
- filter
what does a gravity feed fuel system inhibiting rig consist of?
- tank capacity of at least 5 imp gallons
- mounted at least 3ft above highest point in fuel system
- pipe of 1” bore fitted with shut off cock
- filter
briefly explain pressure rig method of fuel system inhibiting
- installed or uninstalled engines
- pressure rig circulates oil through system at high pressure
- drain fuel filter and LP cock closed
- inlet and outlet connected to HP fuel pump pressure tapping and system LP inlet
- bleed components and operate HP cock several times whilst oil flowing
- neat inhibiting oil will eventually be discharged through combustion chamber drains
- seal off apertures
briefly explain gravity method of fuel system inhibiting
- used when engine cannot be turned
- connected to HP pump pressure line, FCU pressure line, burner manifold and LP inlet pipe
- neat oil should run from components
- blank off
when storing fuel system components, they should be ________ as soon as possible prevent internal corrosion
when storing fuel system components, they should be INHIBITED as soon as possible prevent internal corrosion
indicator paper accompanying engines stored and wrapped in ___________ sealed bags should be _____ when not contaminated and ____ if contaminated
indicator paper accompanying engines stored and wrapped in HERMETICALLY sealed bags should be BLUE when not contaminated and PINK if contaminated
engines stored on a long term basis should be mounted on __________ stands, with associated _________ and information. if the engine has been removed because of failure, ______ from filters, _______ blades, or other evidence should also be packed for examination during overhaul
engines stored on a long term basis should be mounted on TRANSPORTATION stands, with associated DOCUMENTS and information. if the engine has been removed because of failure, METAL from filters, BROKEN blades, or other evidence should also be packed for examination during overhaul
components should be stored in conditions which are dry and free from _________ fumes
shafts of fuel ______ and _____ flow regulators should be turned and part checked for satisfactory ___________ state
when life-ex, components should be subjected to ________ or testing IAW manufacturers instructions
components should be stored in conditions which are dry and free from CORROSIVE fumes
shafts of fuel PUMPS and FUEL flow regulators should be turned and part checked for satisfactory MODIFICATION state
when life-ex, components should be subjected to OVERHAUL or testing IAW manufacturers instructions
