Book contents
- Frontmatter
- Contents
- Preface
- 1 INTRODUCTION
- 2 GASDYNAMIC THEORY OF DETONATIONS AND DEFLAGRATIONS
- 3 DYNAMICS OF DETONATION PRODUCTS
- 4 LAMINAR STRUCTURE OF DETONATIONS
- 5 UNSTABLE DETONATIONS: NUMERICAL DESCRIPTION
- 6 UNSTABLE DETONATIONS: EXPERIMENTAL OBSERVATIONS
- 7 INFLUENCE OF BOUNDARY CONDITIONS
- 8 DEFLAGRATION-TO-DETONATION TRANSITION
- 9 DIRECT INITIATION OF DETONATIONS
- Epilogue
- Index
9 - DIRECT INITIATION OF DETONATIONS
Published online by Cambridge University Press: 06 July 2010
- Frontmatter
- Contents
- Preface
- 1 INTRODUCTION
- 2 GASDYNAMIC THEORY OF DETONATIONS AND DEFLAGRATIONS
- 3 DYNAMICS OF DETONATION PRODUCTS
- 4 LAMINAR STRUCTURE OF DETONATIONS
- 5 UNSTABLE DETONATIONS: NUMERICAL DESCRIPTION
- 6 UNSTABLE DETONATIONS: EXPERIMENTAL OBSERVATIONS
- 7 INFLUENCE OF BOUNDARY CONDITIONS
- 8 DEFLAGRATION-TO-DETONATION TRANSITION
- 9 DIRECT INITIATION OF DETONATIONS
- Epilogue
- Index
Summary
INTRODUCTION
Direct initiation refers to the instantaneous formation of the detonation without going through the predetonation stage of flame acceleration. By “instantaneous,” it is meant that the conditions required for the onset of detonation are generated directly by the ignition source rather than by flame acceleration, as in the transition from deflagration to detonation.
Direct initiation was first used to generate spherical detonations because, in an unconfined geometry, the various flame acceleration mechanisms are ineffective (or absent), and hence the transition from a spherical deflagration to a spherical detonation cannot generally be realized. In 1923, Lafitte (1925) used a powerful igniter consisting of 1 g of mercury fulminate to directly initiate a spherical detonation in a mixture of CS2 + 3O2. He also used a planar detonation emerging from a 7-mm-diameter tube into the center of a spherical flask containing the same mixture of CS2 + 3O2. With this method, Lafitte was not successful in initiating a spherical detonation. Using the same powerful igniter of mercury fulminate, spherical detonations were also initiated in 2H2 + O2 mixtures. From the streak photographs taken by Lafitte, the detonation is observed to form instantaneously by the igniter, without a noticeable predetonation period. The detonation of a condensed explosive charge generates a very strong blast wave that decays rapidly as it expands to form the CJ detonation (hence, this mode of initiation is also referred to as blast initiation).
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- Information
- The Detonation Phenomenon , pp. 297 - 372Publisher: Cambridge University PressPrint publication year: 2008