DeflagrationtoDetonation Transition

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Deflagration-to-Detonation Transition (DDT)
P.Barry Butler and K. Ramadan Department of
Mechanical Engineering The University of Iowa
Iowa City - Iowa
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Introduction

• Deflagration
• A Combustion wave moving at subsonic speed.
• Detonation
• A Combustion Wave moving at supersonic
  speed.
• Deflagration-to-Detonation Transition (DDT)
• Transition of the combustion mode from
  deflagration to detonation.
• DDT distance
• The distance traveled by a deflagration wave
  before
• it turns into a detonation front.
• (Also called Run-up length, Pre-detonation
  distance)

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Introduction
Detonation Initiation
Deflagration to Detonation Transition(DDT)
Direct Initiation
High energy supply ( 100kJ)
Weak energy source ( 1mJ)
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Introduction
Phases of the DDT Process
Combustion Initiation Combustion Wave
Acceleration Explosion Centers Development
Into Detonation Front
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Factors Affecting the DDT Process

• Fuel type of the fuel (i.e., fuel reactivity).
• Equivalence ratio.
• Tube diameter/length.
• Initial conditions (pressure and temperature).
  
• Ignition energy.
• The use of turbulizing elements.
• Adding small amounts of a highly detonable
  gas.
• Ignition location

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Summary of Research on DDT
Schelkin spiral Effect of Equivalence
ratio Effect of CO2 Effect of initial Pressure
Fuels H2, C2H4, C3H8
!. Article title Investigation of Deflagration
to Detonation Transition for Applications to
Pulse Detonation Engine Ignition Systems
Author(s) E. Schultz, E. Wintenberger, J.
Shepherd Source Proceedings of the 16th
JANNAF Propulsion Symposium, Chemical Propulsion
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Summary of Research on DDT

• Major Findings/Comments
• Orifice plates and Schelkin spirals.
• Mixing inside the tube
• Energy of the spark plug 35 mJ
• DDT Transition is controlled by
• (1) Spiral geometry
• (2) Initial pressure.

2. Article Title Detonation Studies of
High-Frequencyoperation Pulse Detonation Engine
with Air/Hydrogen. Author(s) F. Y. Zhang, T.
Fujiwara, T. Miyasaka, E. Nakayama, T. Hattori
Source AIAA 41st Aerospace Science Meeting and
Exhibit, 6-9 Jauary 2003, Reno, Nevada, AIAA
2003-1169
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Summary of Research on DDT

• Major Findings/Comments
• Orifice plates and Schelkin spirals.
• Mixing inside the tube
• Energy of the spark plug 35 mJ
• DDT Transition is controlled by
• (1) Spiral geometry
• (2) Initial pressure.

3. Article Title Ignition Effects on
Deflagration-to Detonation Transition Distance in
Gaseous Mixtures Author(s) J. O. Sinibaldi,
C.M. Brophy, LT J. P. Pobinson Source 36th
AIAA/ASME/SAE/ASEE Joint Propulsion Conference,
17-19 July 2000, Huntsville, Alabama. AIAA
2000-3590.
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Summary of Research on DDT

• Summary
• An experimental study about the effects of
• Gas initial temperature together with turbulizing
  elements.
• Effects of the fuel mole fraction
• The detonation tube is 27 cm diameter and 21.3
  meters in length.
• Fuel Hydrogen  
• Major Findings/Comments
• Using periodic orifice plates
• Decreasing the initial mixture temperature
  decreases the run-up distance.
• DDT distance decreases with increasing the mole
  fraction of the fuel up to the stoichiometric
  condition.
• This article reports on a distance of more than
  5 meters for a deflagration wave to accelerate
  to about 1200 m/s.

4. Article Title The Influence of Initial
Temperature on Flame Acceleration and
Deflagration-To-Detonation Transition
Author(s) G. Ciccarelli, J. L. Boccio, T.
Ginsberg Source 26th Symposium
(International) on Combustion/The Combustion
Institute, 1996, pp 2973-2979.
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Summary of Research on DDT
Effects of ignition energy,
equivalence ratio, nitrogen
dilution, ignition location
5. Article Title Ignition Effects on
Deflagration-to Detonation Transition Distance in
Gaseous Mixtures Author(s) J. O. Sinibaldi,
C.M. Brophy, LT J. P. Pobinson Source 36th
AIAA/ASME/SAE/ASEE Joint Propulsion Conference,
17-19 July 2000, Huntsville, Alabama. AIAA
2000-3590.
11
Summary of Research on DDT
6. Article Title Detonation in Pipes and in the
Open Author(s) K. V. Wingerden, D.
Bjerketvedt, J. R. Bakke Source
http//www.safetynet.de/Publications/articles/CMRN
ov99.pdf
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Summary of Research on DDT
References 7 11 High-Speed Deflagration and
Detonation Fundamentals and Control. Editors
G.D. Roy, S.M. Frolov D.W. Netzer A.A. Borisov,
Elex-KM Publishers, Moscow, Russia, 2001
Effects of - turbulizing elements
(spirals, orifices, concave surfaces)
- Fuel concentration
- Sensitizing agents
- Initial temperature
- Initial pressure -
Nitrogen Content
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Summary of Research on DDT
Transient Plasma Ignition System (Corona).
Spatially extensive multi-site ignition
Comparison with the conventional spark plug
ignition in terms of some combustion
characteristics (1) Ignition Delay, (2) Peak
Pressure, (3) Pressure Rise Time. (4) Ignition
Energy 1kJ (5) Ignition of very lean mixtures
(6) Sustain/stabilize combustion
12. Article Title Transient Plasma ignition for
Lean Burn Applications. Author(s)
Jian-Bang Liu, Paul Ronney, L. C. Lee, Martin
Gundersen. Source 41st Aerospace Sciences
Meeting and Exhibit, 6-9 January 2003, Reno,
Nevada,AIAA 2003-877. http//carambola.usc
.edu/research/coronaignition/coronaignition.html
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Recommendations

• Maximize mixing of the fuel and oxidizer
  injector manifold design .
• 
  
• Turbulizing devices in the combustion chamber
  Spirals, orifice plates.
• Increase ignition energy as much as possible
  Spark plug.
• Other important parameters
• Initial gas pressure and temperature.
• Ignition location.
• Sensitizing elements.