Introduction to pulse detonation combustion and related propulsion.

1. Fundamentals of Pulse Detonation Engine (PDE)
and Related Propulsion Technology
Aerospace Engineering Consulting
Arlington, TX
Dora Musielak, Ph.D.
All rights reserved. No part of this publication may be reproduced, distributed, or transmitted, unless for course participation, in any form
or by any means, or stored in a database or retrieval system, without the prior written permission of the Author. Contact D. Musielak,
dmusielak@uta.edu

2. Pure PDE Cycle
1: Fuel-Oxidizer
Injected and
Mixed
2: Detonation
Initiated by
ignition source
3: Detonation
wave moves
through gas
mixture
4: High
pressure gas
fills detonation
chamber
5: Detonation wave exits
chamber and air is drawn
in by reduced pressure
Thrust is directly proportional to detonation frequency
FILL DETONATE EXHAUST
Repeat
Pulse Detonation Engine (PDE) : type of propulsion system that utilizes detonation waves to combust
fuel and oxidizer mixture. Engine is pulsed because mixture must be renewed from combustion chamber
between each detonation wave initiated .

3. Why PDEs?
Advantages
• Increased Thermodynamic
Efficiency
• Higher Isp
• Reduced SFC
• Design Simplicity
• Increased Thrust-to-Weight Ratio
• Increased Thrust-to-Volume Ratio
• Lower Cost
• Mach Range 0 – 4
• Easy Vehicle Integration
Applications
• Cruise Missiles
• Supersonic Aircraft
• Hypersonic Missiles
• Hybrid Turbine-PDE
• UAV
• UCAV
• SSTO Launch Vehicles
• Precision Guided Munitions
• Drones
3
PDEs potential for easier scaling extrapolates to substantial reductions in
development time, when compared to conventional turbine engines.
Increased cycle efficiency results from quasi-constant volume process

4. Why PDEs?
4
Is it possible to augment gas turbine performance with PDEs
to extend supersonic flight regime?

5. Why PDEs?
5
Is a PDE/SCRAM/PDRE a viable
propulsion system for Spaceplanes?
03-06
PDRE = Pulse Detonation Rocket Engine
SCRAM = Scramjet è supersonic combustion ramjet engine for M > 5

6. Preface
• Revolutionary propulsion is required to achieve high-speed cruise
capability within atmosphere, and for low cost reliable Earth-to-orbit
vehicles.
• Pulse detonation engines (PDEs) have potential performance
advantages over air breathing and rocket propulsion, bypassing
limitations of existing concepts.
• Proposed applications for detonation combustion include
– cruise missiles, UAV, ...
– supersonic aircraft, and
– SSTO launchers.
• This course highlights fundamentals of pulse detonation engines
and other related propulsion concepts, addressing performance
characteristics, enabling technologies, and current R&D initiatives to
develop new propulsion systems.
6

7. Air Breathing PDE Technology – D. Musielak
Nomenclature and Terminology
• A list of common terms and basic definitions is provided in a
separate handout to facilitate communicating the concepts
introduced in the course.
• In 2002, Kaemming, Lidstone, and Sammann proposed a
component nomenclature, station (spatial) designation, process
and event (temporal) designation and terminology for the unique
PDE scheduling characteristics. Ref. AIAA 2002-3631.
• Nomenclature proposal is based on several years of PDE analysis
and testing by Boeing and Pratt & Whitney and is based on
accepted practices, such as SAE Standard AS7551.
• To date, no standard has been formally issued for PDEs, and so
we will follow the recommendations in AIAA paper 2002-3631
7

8. Nomenclature and Terminology
8
See Appendix 1

9. Air Breathing PDE Technology – D. Musielak
Introduction to PDEs
9
• Propulsion Comparison
• A Vision for the Future
• Limits of Turbo-Engines
• Ideal Cycles
• Combustion Modes
• Pure Pulse Detonation Engine
• Detonation for Propulsion
• Modeling a Single Cycle
• PDE Thermodynamic Cycle

10. Propulsion Comparison
fo
sp
mg
F
I
!
=
Need improved SFC performance
Seeking Revolutionary Propulsion Ideas
10
F
m
SFC
f
!
=

11. Air Breathing PDE Technology – D. Musielak
Highest Supersonic Speed: M = 3.2
11
SR-71
Turbofan engines in high performance aircraft such as F-15
“Eagle” fighter can achieve Mach 2.5
F-16 “Fighting Falcon” jet fighter and F-22 “Raptor” are
limited to Mach 2.

12. Air Breathing PDE Technology – D. Musielak
A Vision for the Future
12
q Reduced SFC
q Higher Thermodynamic Efficiency
q Higher Isp
q Design Simplicity
q Increased Thrust-to-Weight Ratio
q Increased Thrust-to-Volume Ratio
q Lower Cost
q Mach range 0 – 10
q Manufacturing Simplicity
q Easy Vehicle Integration
Air Breathing Propulsion Requirements
Develop air-breathing engine capable of
propelling aircraft beyond Mach 2.5.

13. Air Breathing PDE Technology – D. Musielak
Turbine Engine Limits
13
)1(
1
2 4
−
−
=
o
t
o T
T
am
F
γ!
Inlet
Efficiency
Rotational
speed
Compressor exit
temperature limits
pressure ratio
Static pressure
balance
P&W F100 AB Turbofan
• At Mach > 3, compressed air reaches such extreme
temperatures that compressor stage fan blades begin to fail.
• Compressor exit temperature limits pressure ratio.
• Turbine inlet temperature limits thrust.

14. Air Breathing PDE Technology – D. Musielak
Turbofan with Afterburner
• Efficient with continuous afterburner at ~ Mach 3.
• Afterburner provides temporary increase in thrust,
for supersonic flight and take off
• Slower bypass airflow produces thrust more
efficiently than high-speed air from core, reducing
specific fuel consumption.
14

15. Air Breathing PDE Technology – D. Musielak
P&W F-100-
15
Performance
Maximum thrust:
17,800 lbf (79.1 kN) military thrust
29,160 lbf (129.6 kN) with afterburner
Overall pressure ratio: 32:1
Specific fuel consumption:
Military thrust: 0.76 lb/(lbf·h) (77.5 kg/(kN·h))
Full afterburner: 1.94 lb/(lbf·h) (197.8 kg/
(kN·h))
Thrust-to-weight ratio: 7.8:1 (76.0 N/kg)
F-16

16. Air Breathing PDE Technology – D. Musielak
Ideal Thermodynamic Cycle
Brayton cycle: heat addition
at constant pressure
16
in
out
th
Q
Wnet
!
!
=η
inQ! = rate of thermal energy released
= net power out of engineoutWnet !
= thermal efficiency of enginethη
)( 34 TTcmQ pin −= !!
)]([ 2354 TTTTcmWWWnet pctout −−−=−= !!!!
3
2
34
25
34
2354
1
)(
)(
1
)(
)()(
T
T
TT
TT
TT
TTTT
B −=
−
−
−=
−
−−−
=η γγ
η /)1(
23 )/(
1
1 −
−=
pp
B

17. Air Breathing PDE Technology – D. Musielak
Burner Exit Temperature T4
17
• Increasing T4 enlarges useful work output (isobars diverge )
• However, distance between stations 3 and 4 increases also è
more heat has to be added and thus more fuel is needed.
• Thermal efficiency is only dependant on compressor pressure
ratio P3/P2 and does not change with T4

18. Air Breathing PDE Technology – D. Musielak
Higher T4, Lower Efficiency
18
• However, isentropic exponent is not constant but
decreases when temperature increases è
thermodynamic efficiency decreases with T4!

19. Air Breathing PDE Technology – D. Musielak
Heat Addition and Pressure
Can we improve thermodynamic cycle
efficiency with a pressure-gain process?
4
19

20. Air Breathing PDE Technology – D. Musielak
Ideal Thermodynamic Cycle
Humphrey cycle: heat
addition at constant volume
20
1
1
1
3
4
3
4
3
2
1
−
−⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
−=
T
T
T
T
T
T
H
γ
γη
Constant volume
heat addition
inQ!
52
43
3*
Thermal efficiency improves by more
than 15% and as much as 10 to 40%
improvement in Isp (Ref. Bussing (1996);
Heiser & Pratt (2002); Povinelli (2002))

21. Air Breathing PDE Technology – D. Musielak
Pulse Detonation Engine (PDE)
21
Ideal PDE thermodynamic efficiency higher than turbo-
engine because a detonation wave rapidly compresses
mixture and adds heat at ~ constant volume.

22. Air Breathing PDE Technology – D. Musielak
Propulsion Performance
PDEs projected (H2
fuel in air)
PDEs projected (HC
fuel in air)
22

23. Combustion Modes
Deflagration
Subsonic
Combustion
Detonation
Supersonic
Combustion
Unsteady
Pulsed or
Intermittent
Steady or
Continuous
Combustion
Unsteady
Pulsed or
Intermittent
Steady or
Continuous
Ø Pulse Jets Ø Turbojets
Ø Ramjets
Ø Scramjets
Ø PDEs
Ø PDREs
Ø Scramjets ?
Ø RDE
Detonation è supersonic spread of
combustion by shock compression.
Deflagration èsubsonic spread of
combustion by thermal conductivity
F
23

24. Combustion Modes: Detonation and Deflagration
• Deflagrations are subsonic
combustion waves: M1< 1
• Typical deflagrations
propagate at speeds on the
order of 1-100 m/s
• Across a deflagration, the
pressure decreases while the
volume increases, P2 < P1 and
V2 > V1
• Detonations are supersonic
waves: M1 >1
• Typical detonation waves propagate
at a velocity on the order of 2000 m/s
(4 < M1 < 8)
• Pressure increase across a
detonation, while the volume
decreases: P2 > P1, V2 < V1
• Detonations in HC fuel: P2/P1 ~ 20
24
u1
u2
P1 P2

25. Air Breathing PDE Technology – D. Musielak
Deflagration and Detonation
Flame propagates from right
25
• Combustion or burning is sequence of exothermic chemical
reactions between fuel and an oxidant accompanied by production
of heat and conversion of chemical species.
Products
u2
P2, T2, ρ2, M2
P1, T1, ρ1, M1
Reactants
u1

26. Detonation vs Deflagration: Qualitative Differences
• Qualitative differences between upstream and
downstream properties across detonation wave are
similar to property differences across normal shock
• Main differences:
– Normal shock wave: downstream velocity always
subsonic
– Detonation wave: downstream velocity always local
speed of sound
• Note that detonation waves can fall into strong and weak
classes
• Strong detonation: subsonic burned gas velocity
• Weak detonation: supersonic burned gas velocity
26

27. Wave Properties
• Normal shock property ratios are qualitatively similar to those of
detonations and of same magnitude
– Except that for detonation downstream velocity is sonic
• Mach number increases across flame for deflagrations
– Mach number is very small and thus is not a very useful parameter to
characterize a deflagration
• Velocity increases substantially and density drops substantially
across a deflagration
– Effects are opposite in direction as compared with detonations or shock
waves
• Pressure is essentially constant across a deflagration (actually
it decreases slightly), while detonation has high pressure
downstream of propagating wave
• Characteristic shared by shock, detonation, and deflagration is large
temperature increase across wave
27

28. Detonation for PropulsionDetonationwave(DW)
propagationtocreatethrust
28
Oblique Detonation Wave Engine (ODWE)
• Combustible gas mixture velocity equals or exceeds detonation Chapman-
Jouguet (CJ) velocity.
• Detonation waves (DWs) or oblique detonation waves (ODWs) are positioned to
combust injected combustible mixture.
Pulse Detonation Engine (PDE)
• Cyclically detonates fuel and atmospheric air mixtures to generate thrust.
• A shock wave compresses gas and this is followed by rapid release of heat and
a sudden rise in pressure.
• PDE generates thrust intermittently, and it produces a significant pressure rise
in combustor.
• Detonation-generated pressure rise represents primary benefits of a PDE in that
it may reduce engine compression requirements.
Continuous Detonation Engine (CDE)
• Combustible gas mixture is injected along axial direction, and DWs propagate in
azimuthal direction.
• Two directions are independent, DWs can continuously propagate with range of
combustible gas injection velocities and do not require multi-time ignition.

29. Pure PDE Cycle
1: Fuel-Oxidizer
Injected and
Mixed
2: High
pressure
detonation
Initiated
3: Detonation
wave moves
through gas
mixture at
supersonic speed
4: High
pressure gas
fills detonation
chamber
5: Detonation wave exits
chamber and air is drawn
in by reduced pressure
Thrust is directly proportional to detonation frequency
FILL DETONATE
EXHAUST
Repeat

30. Detonation Initiation
• A detonation may form via direct initiation or via deflagration-to-
detonation transition (DDT).
• Direct initiation is dependent upon an ignition source driving a blast
wave of sufficient strength such that igniter is directly responsible for
initiating detonation. It requires extremely large energy.
• DDT begins with a deflagration initiated by relatively weak energy
source which accelerates through interactions with its surroundings
into a coupled shock wave-reaction zone structure characteristic of a
detonation.
• After spark creates a deflagration, transition process can take
several meters or longer and a large amount of time.
30
Key to detonation initiation schemes for PDEs is to shorten distance
and time required for deflagration-to-detonation transition (DDT).

31. PDE Requirements
Ø Ignition and mixing must occur quickly to minimize cycle
time and maximize thrust.
Ø DDT must occur quickly and in a short distance. Shortening
DDT time decreases the detonate part of the cycle, allowing
a frequency increase that is accompanied by a thrust
increase.
Ø Shortening DDT distance decreases necessary thrust tube
length, resulting in weight savings, a great advantage for
propulsion.
31
1 2 3

32. Air Breathing PDE Technology – D. Musielak
PDE Cycle (Basic Cycle Process)
32
1. Initially, chamber at ambient
conditions
2. Propellant injected from
closed end
* Sidewall injection also works
and may improve mixing
3. Ignition from closed end
4. Wave propagation and
transition in chamber
5. Wave exits chamber
6. Exhaust and purge

33. Air Breathing PDE Technology – D. Musielak
Rankine-Hugoniot Combustion Map
Conservation equations for mass, momentum,
and energy for combustion waves in steady,
inviscid, and constant-area flow.
Hugoniot is locus of possible solutions for state 2
from a given state 1 and a given energy release
Rayleigh line relates states 1 and 2.
Solution state is at intersection of Hugoniot and
Rayleigh line.
2211 vv ρρ =
2
222
2
111 vPvP ρρ +=+
2
22
1
2
2
12
1
1 vhvh +=+
M1 M2
111 ,, ρvP 222 ,, ρvP
Combustion
wave
33

34. Air Breathing PDE Technology – D. Musielak
Chapman-Jouguet C-J Condition
• Solution to conservation equations is determined considering:
– For deflagrations, wave structure, and turbulent and diffusive processes
determine propagation speed.
– For detonations, gas dynamic considerations are sufficient to determine
solution.
– Chapman (1899) and Jouguet (1905) proposed that detonations travel
at one particular velocity, which is minimum velocity for all solutions on
detonation branch.
• At solution point (Chapman-Jouguet detonation point), Hugoniot,
Rayleigh line, and isentrope are tangent. Flow behind a C-J
detonation is sonic relative to wave: M2=1.
• C-J points divide Hugoniot into 4 regions:
– Weak deflagrations (subsonic to subsonic)
– Strong deflagrations (subsonic to supersonic)
– Weak detonations (supersonic to supersonic)
– Strong detonations (supersonic to subsonic)
34

35. C-J Velocity
• Chapman-Jouguet (C-J) condition: for an infinitesimal thin detonation,
detonation wave proceeds at a velocity at which reacting gases just
reach sonic velocity (in frame of lead shock) as reaction ceases.
• Assumes chemical reaction takes place at moment when shock
compresses material
• Chapman-Jouguet velocity: velocity of an ideal detonation as
determined by C-J condition: burned gas at end of reaction zone
travels at sound speed relative to detonation wave front.
• C-J velocities can be computed numerically by solving for
thermodynamic equilibrium and satisfying mass, momentum, and energy
conservation for a steadily-propagating wave terminating in a sonic
point.
• C-J velocities in typical fuel-air mixtures between 1400 and 1800 m/s.
35
Speed of sound: 331 m/s in air.

36. Air Breathing PDE Technology – D. Musielak
PDE Thermodynamic Cycle (Heiser & Pratt, 2002
36
• Process 3 è 4 models normal
detonation wave in a PDE (ZND
wave model)
• Entropy generated in detonation
wave heat addition process
is sum of that generated in
process from 3 to 3a (adiabatic
normal shock wave) and that
generated in process from 3a to 4
(constant-area heat addition
process) that follows.
Thermal efficiency of ideal Humphrey cycle is close to, but always
somewhat less than, that of ideal PDE cycle – H&P

37. Summary of Chapter 1
• Revolutionary propulsion is required to achieve high-speed cruise
capability within atmosphere, and for low cost reliable earth-to-orbit
vehicles.
• Pulse detonation engines (PDEs) have potential performance
advantages over air breathing and rocket propulsion, bypassing
limitations of existing concepts.
• Propulsion architectures that use pulsed and continuous detonation
combustion offer more efficient thermodynamic properties, and thus
are expected to exhibit a higher level of performance than more
conventional propulsion that rely simply on deflagration combustion
process.
• Chapter 2 will provide an overview of detonation-based propulsion,
including hybrid turbine-PDE and Continuous Detonation Wave
Engine (CDWE) concepts.
37

38. Air Breathing PDE Technology – D. Musielak
J58
R-R/Snecma
Olympus 593
P&W F100
GE F110
P&W F119
GE F414
P&W
F100-232
Next
Generation
Supersonic
Air Breathing
Engine
38

39. Detonation
• Detonation is a shock wave sustained by energy released by
combustion
• Combustion process, in turn, is initiated by shock wave compression
and resulting high temperatures
• Detonations involve interaction between fluid mechanic processes
(shock waves) and thermochemical processes (combustion)
39