Representative Turbofan Engine

Prepared under
QIP-CD Cell Project
Lecture-14
Jet Propulsion
Ujjwal K Saha, Ph. D.
Department of Mechanical Engineering
Indian Institute of Technology Guwahati
1
Overview
• Axial-flow turbofan
engine
• Two spool
configuration
• High compression
and bypass ratio
2
Engine Description
•
•
•
•
16 compressor stages
An annular combustion chamber
6 turbine stages
Low pressure system consists of 5-stage
LPC and a 4-stage LPT
• High pressure system consists of 11-stage
HPC and a 2-stage HPT
3
4
Engine Description (Contd.)
• The engine cases form a structurally rigid
support with internal parts supported
through struts and bearings
• First stage of LPC rotor is the fan and it
produces two separate air streams
– The primary (inner) airstream
– The secondary (outer) airstream
5
Engine Description (Contd..)
• Total compression ratio is 30:1
• Bypass ratio is 5:1
• Secondary airflow provides 78% of thrust while
primary airflow provides only 22% of thrust
• Specific fuel consumption is 0.35 lb/lb/h
• The engine is 133in long and 97in across largest
diameter
• Weight is approx. 9200 lb and thrust is 60000 lbt
6
Engine Description (Contd..)
•
Certain specific points along axial profile are identified by station
number to provide ease of reference for items.
7
Main Bearing Numbering and Description
• Bearing No.1 is a thrust ball bearing located
on the LPC turbine shaft coupling
8
Main Bearing Numbering and Description
(Contd..)
• Bearing No.1.5 is a standard non preloaded cylindrical
roller bearing located on the intermediate case. It
supports the turbine shaft coupling.
9
Main Bearing Numbering and Description (Contd..)
• Bearing No.2 is a thrust ball bearing located on
the intermediate case. It supports the rear
compressor front hub.
10
Main Bearing Numbering and Description (Contd..)
• Bearing No.3 is a preloaded cylindrical roller bearing
located on the diffuser case. It supports the rear
compressor rear hub.
11
Main Bearing Numbering and Description (Contd..)
• Bearing No.4 is a standard non-preloaded cylindrical
roller bearing located on the turbine exhaust case. It
supports the front compressor drive turbine shaft.
12
Major Assemblies/Build Groups
•
14 major assemblies, 10 of which are build
groups
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Low pressure inlet (LPC)
Fan cases
Intermediate case
High pressure compressor (HPC)
Diffuser and combustor
Turbine nozzle
High pressure turbine (HPT)
Low pressure turbine (LPT)
Turbine exhaust case (TEC)
Main gearbox
13
Major Assemblies/Build Groups (Contd..)
14
Cold Section
•
•
•
•
Compressor Inlet Cone
Fan Blades
Low Pressure Compressor
Low Pressure Compressor/Low Pressure
Turbine Coupling
• Fan Cases
• Intermediate Case
• High Pressure Compressor
15
Hot Section
•
•
•
•
•
•
Diffuser and Combustor
Turbine Nozzle
High Pressure Turbine
Low Pressure Turbine
Turbine Exhaust Case
Exhaust Nozzle and Plug
16
Compressor Inlet Cone
• It is an aerodynamic
fairing that helps to
create a smooth
airflow into the
engine. The cone is
made of Kevlar and
is constructed in two
pieces with 12 vent
holes
17
Fan blades
• The function of the 38
wide-chord, forged
Titanium fan blades is
to compress the air that
goes into the engine
and to send this air into
the primary and
secondary gas paths
18
Low Pressure Compressor
• The first stage of the
LPC rotor is the fan
stage. The first stage of
the stator assembly is
located behind the fan
blades, while the fan
exit fairing divides the
primary and secondary
airstreams
19
Low Pressure Compressor/Low Pressure Turbine
Coupling
• An LPC/LPT
coupling
connects the
LPC rotor to the
LPT shaft by
means of
splines.
20
Fan Cases- Front and Fan Exit
•
The fan cases consists of
the front fan case and the
fan exit case. The front fan
case contains the fan blade
tip rubstrips and also prevent
the fan blades from going
out of the engine if they
break. The fan exit case
contains 84 exit guide vanes
made of composite material
with metal leading edges.
21
Intermediate Case
• The intermediate case
is the primary structural
component of the
engine and has
attachment points for
many engine parts. It
also supports the two
compressor thrust
bearings.
22
High Pressure Compressor
• The HPC has an 11 stage rotor and stator
assembly. The first stator stage is the inlet
guide vane assembly and first 4 stages are
variable. Bleed air from the HPC is used as
follows:
– Eight stage air for aircraft use
– Ninth stage air for engine operational stability and
turbine cooling
– Twelfth stage air for cooling the No.3 bearing and
parts of the turbine
– Fifteenth stage air to balance the thrust load on the
No. 2 bearing, for airflow sensing, and for aircraft
use.
23
Diffuser and Combustor
• The diffuser straightens
the air flow from the
compressor exit,
increases the static
pressure, reduces the
speed of the primary
air. In the combustor,
the fuel is mixed with
the air and burned to
add energy to the
primary gas path.
24
Turbine Nozzle
• The turbine nozzle
guide vanes send
the hot gases from
the combustion
chamber to the first
stage turbine blades
at the correct angle
and speed
25
High Pressure Turbine
• The 2-stage HPT
supplies the force to
turn the HPC. The 60
first stage blades are
made by using a single
crystal material, while
the 82 second stage
blades are made of
directionally solidified
material.
26
Low Pressure Turbine
•
The 4-stage LPT supplies
the force to turn the LPC
(incl. the fan) through a drive
shaft. Internal cooling air
from the HPC ninth stage is
supplied to the LPT to
reduce the temperature at
the inner wall of the
transition duct, the 3rd, 4th
and 5th stage stators and the
inner seal areas.
27
Turbine Exhaust Case
• The purpose of the
turbine exhaust case is
to support the no. 4
bearing, hold the
exhaust nozzle and
plug, and transmit the
turbine-discharge
gases through its
struts to the exhaust
nozzle and plug.
28
Exhaust Nozzle and Plug
• The exhaust nozzle,
which is made up of
Inconel honeycomb with
an acoustically treated
inner skin and an
Aluminum-titanium
outer skin, changes the
engine’s primary gas
flow energy into primary
thrust.
29
Gearboxes
• Angle and main gearboxes
The angle gearbox is driven by the tower
shaft, which is turned by the HPC. The
Angle gearbox, in turn, turns the
horizontal layshaft (gearbox drive shaft),
which drives the main gearbox.
30
Gearboxes
•
w conical shaft. The shaft has an external spline that engages with the
compressor rotor rear stub shaft.
31
References & Web Resources
1.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
Treager, I.E., (1997), Aircraft Gas Turbine Engine Technology, Tata
McGraw Hill.
http://www.soton.ac.uk/~genesis
http://www.howstuffworks.co
http://www.pwc.ca/
http://rolls-royce.com
http://www.ge.com/aircraftengines/
http://www.ae.gatech.edu
http://www.ueet.nasa.gov/Engines101.html
http://www.aero.hq.nasa.gov/edu/index.html
http://home.swipnet.se/~w65189/transport_aircraft
http://howthingswork.virginia.edu/
http://www2.janes.com/WW/www_results.jsp
http://www.allison.com/
http://wings.ucdavis.edu/Book/Propulsion
http://www.pilotfriend.com/
http://www.aerospaceweb.org/design/aerospike
http://www.grc.nasa.gov
http://www.hq.nasa.gov/office/pao/History
http://membres.lycos.fr/bailliez/aerospace/engine
http://people.bath.ac.uk/en2jyhs/types.htm
http://roger.ecn.purdue.edu/~propulsi/propulsion/rockets
http://www.waynesthisandthat.com/ep2.htm
http://www.answers.com/main
http://www.astronautix.com
32