• Recap: Lecture 1
–Evaluation scheme
–Applications of gas turbine engines
–Types of gas turbine engines for aviation
Typical multi-stage axial flow compressor
Source: The Jet Engine, Roll Royce Plc, 1996
Typical multi-stage axial flow compressor
A twin turbine and shaft system
3
Source: The Jet Engine, Rolls Royce, 1996
Compressor blade geometry
4
Turbine nozzle and rotor blade geometries
5
Comparison of compressor and turbine flow path
6
Centrifugal compressor
7
Commissioning of world’s first industrial gas
turbine, Neuchatel, 1939 (Stodola at age 80)
8
Frank Whittle and Hans von Ohain
9
First turbojet-powered aircraft – Ohain’s engine on He 178 (1939)
10
Powered the Gloster E28/39
Britain on 15 May 1941.
11
Lect-6
Ideal Brayton cycle
• Brayton cycle is the basic thermodynamic cycle of gas
turbine engines
• The Brayton cycle consists of four internally reversible
processes:
– 1-2 Isentropic compression (in a compressor)
– 2-3 Constant-pressure heat addition
– 3-4 Isentropic expansion (in a turbine)
– 4-1 Constant-pressure heat rejection
12
Lect-6
Ideal Brayton cycle
qin Isobaric 3
P Isentropic
2 3 T qin
2 4
qout
1 4 1
qout
v s
Brayton cycle on P-v and T-s diagrams
13
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect-6
Actual/Real Brayton cycle
Pressure drop
T
3
qin
2a 4a
2s
4s
qout
1
s
Actual Brayton cycle T-s diagram
14
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Lect-7
Ideal cycle for jet engines
Combustion chamber/burner
Diffuser Compressor Turbine Nozzle
a 1 2 3 4 5 6 7
Afterburner
Schematic of a turbojet engine
15
Lect-7
Ideal cycle for jet engines
4
T
5
3
7
2
a
Ideal turbojet cycle (without afterburning) on a T-s diagram
16
Real cycle for turbojetLect-10
engines
6a
T 4
7
5, 6
3
2
a
s
Real turbojet cycle (with afterburning) on a T-s diagram
17
Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay
Examples of gas turbine applications
Military aircraft (Low bypass Turbofan)
Civil aircraft (High bypass Turbofan)
Turboprop
Marine propulsion gas turbine
Land based gas turbine powerplant
Fan
Turbine
Compressor
A modern high bypass turbofan engine
UHBPR Engines, Distributed Propulsion
Higher bypass ratios result in prohibitively
low ground clearance
Source: Hughes, 2014, AIAA Aero Sciences Meeting
Innovative technology for dramatically
reducing noise, emissions and fuel burn
Distributed Propulsion Systems
• Significant fuel burn reduction
compared to current day
aircraft
• Amenable to Turbo-Electric
Propulsion concepts
https://www1.grc.nasa.gov/aeronautics/bli/
20
BLI Propulsion: distortion tolerant fans
Source: Liou et al, 2017; Rosario, 2012
• BLI propulsion calls for innovative fan designs
• Distortion tolerant fans
• Significant inflow non-uniformity
• Effects on fan performance during off-design or
high AoA operations
• Aero-elastic effects (flutter)
• Adaptive fan blades using smart materials
21
