Chapter 1.2: Intro to Turbofan engine Flashcards
what is bypass air?
air that goes around core engine and produce 80% of thrust
will not go through core stages
what is bypass air used for?
cooling engine components & producing thrust
what is primary air?
core air that goes into internal stage
how many percent of thrust is produced by primary air?
20%
how does core air help to produce thrust?
core air turns turbine > turns compressor and fan blades > fan blade turns means bypass air flow through > majority of thrust produced
what is fan blade responsible for?
producing majority of thrust from fan air
what is compressor responsible for?
compressing core air so internal energy of gas is increased
what does LPT energy drive?
LPC & fan blade
what is connected on the same shaft with LPT?
fan blade & LPC
what does HPT do?
extracts energy from gas coming out of combustor
what does LPT do?
extracts energy from gas that comes out of HPT
what does HPT’s energy drive?
HPC
what are the triple spools naming configuration?
low pressure - N1
intermediate pressure - N2
high pressure - N3
if no IP:
LP - N1
HP - N2
what is HPC responsible for?
compressing core air from LPC before going into combustor
what is the best mach number for turbofan?
M0.85
reason for split spool
first blade is biggest and slowest, split to not drag down blades that are behind and smaller, allowing them to run faster
rank compressors in terms of rpm
HPC > IPC > LPC
why is triple spool engine not good?
more bearings needed > reliability decreases & maintenance needed higher
which component is weakest in engine and why?
bearings
high stress & heat, if 1 ball bearing break, will cause vibration and domino effect on other bearings)
bypass ratio formula
mass of bypass airflow / mass of primary airflow
what is engine pressure ratio?
total pressure ratio across engine
what is the range of EPR?
1 < EPR < 2
