An Experimental Investigation of Shock Initiated Detonation Waves in a Flowing Combustible Mixture PDF Download
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Author: Leonard Anthony Hamilton
Publisher:
ISBN:
Category : Shock waves
Languages : en
Pages : 0
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Author: Leonard Anthony Hamilton
Publisher:
ISBN:
Category : Shock waves
Languages : en
Pages : 0
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Author: United States. Air Force. Office of Aerospace Research
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 586
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Author: Robert B. Driscoll
Publisher:
ISBN:
Category :
Languages : en
Pages : 105
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An experimental investigation was carried out to study the travel of a shockwave through a crossover tube and analyze the ability to cause shock initiated detonation. This concept involved using a pulse detonation engine (PDE) as a driver to produce a shockwave. This shockwave travelled to a second, adjacent detonation tube. In this driven PDE, the shockwave would reflect off of the inner, concaved wall causing shock initiated detonation. A preliminary study using a dual PDE crossover tube system yielded experimental results that have shown successful cases where reflected shockwaves are used to cause direct detonation initiation. For that study, two reactant-filled PDEs were connected through an air-filled crossover tube, with the driver PDE ignited. High speed pressure sensors were used to verify combustion wave speeds. Preliminary results showed shock initiated detonation to be possible when using a dual PDE crossover system. Additionally, a parametric study was carried out to investigate shock initiated detonation within a dual PDE crossover system. Shockwaves produced by a driver PDE were carried through crossover tubes of varying lengths and bends to the driven PDE. The driving PDE was ignited using a traditional spark plug. From burning wave speeds measured by high speed pressure sensors, results have shown a transferred shockwave reflecting off the wall of the driven PDE will achieve shock initiated detonation. However, the results have also yielded cases where the initial shockwave reflection does not directly initiate a detonation in the driven PDE, but rather causes ignition leading to accelerated deflagration to detonation transition (DDT). Overall results have shown that for specific tube geometries, there is a maximum effective crossover tube length in which shock initiated detonation is possible. Furthermore, shadowgraph techniques were used to capture and study the propagation of a transferred shockwave produced by a driving detonation tube. To accomplish this, a single PDE was used to drive a shockwave through a clear, composite, transfer tube. Shock attenuation data was gathered during this study. This information created a relation between shock strength and crossover tube length. Also, regardless of the filling conditions of the transfer tube, all shock waves reach similar attenuation rates at relatively the same transfer tube length. Moreover, a vortex plume study was carried out to capture and study shock Mach number decay as a planar shockwave transitions to a spherical shockwave at the exit of a transfer tube. Transfer tubes of varying lengths and bends were used in the study. General Attenuation Law was used to further understand the relation between spherical shock strength and propagation distance. Results showed that a bend placed at the end of the transfer tube enhances the strength of a planar shockwave. Finally, with the aid of the two shadowgraph experiments, a correlation between maximum effective crossover tube length and shock strength was created. Performance in the driven PDE begins to decrease when the incident shock strength decreases below M = 2.0.
Author: Rohit Ranjan Bhattacharjee
Publisher:
ISBN:
Category : Detonation waves
Languages : en
Pages :
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Detonation waves are supersonic combustion waves that have a multi-shock front structure followed by a spatially non-uniform reaction zone. During propagation, a de-coupled shock-flame complex is periodically re-initiated into an overdriven detonation following a transient Mach reflection process. Past researchers have identified mechanisms that can increase combustion rates and cause localized hot spot re-ignition behind the Mach shock. But due to the small length scales and stochastic behaviour of detonation waves, the important mechanisms that can lead to re-initiation into a detonation requires further clarification. If a detonation is allowed to diffract behind an obstacle, it can quench to form a de-coupled shock-flame complex and if allowed to form a Mach reflection, re-initiation of a detonation can occur. The use of this approach permits the study of re-initiation mechanisms reproducibly with relatively large length scales. The objective of this study is to experimentally elucidate the key mechanisms that can increase chemical reaction rates and sequentially lead to re-initiation of a de-coupled shock-flame complex into an overdriven detonation wave following a Mach reflection. All experiments were carried out in a thin rectangular channel using a stoichiometric mixture of oxy-methane. Three different types of obstacles were used - a half-cylinder, a roughness plate along with the half-cylinder and a full-cylinder. Schlieren visualization was achieved by using a Z-configuration setup, a high speed camera and a high intensity light source. Results indicate that forward jetting of the slip line behind the Mach stem can potentially increase combustion rates by entraining hot burned gas into unburned gas. Following ignition and jet entrainment, a detonation wave first appears along the Mach stem. The transverse wave can form a detonation wave due to rapid combustion of unburned gas which may be attributed to shock interaction with the unburned gas. Alternatively, the Kelvin-Helmholtz instability can produce vortices along the slipline that may lead to mixing between burned-unburned gases and potentially increase combustion rates near the transverse wave. However, the mechanism(s) that causes the transverse wave to re-initiate into a detonation wave remains to be satisfactorily resolved.
Author: J. A. Nicholis
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Author: William Wilfred McKenna
Publisher:
ISBN:
Category : Explosions
Languages : en
Pages : 0
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The study of detonation waves in a flowing combustible mixture of gas could lead to a better understanding of combustion instability in rocket motors and to possible application to supersonic combustion. Apparatus was designed to measure the relative wave velocity and to photograph the wave profile as a fully developed detonation wave propagated against a flow of stoichiometric mixture of hydrogen-oxygen gases. The Mach number of the flowing gas was varied from 0.14 to 4. The subsonic flow results indicated that the absolute detonation wave velocity relative to the gas was independent of the speed of the flowing gas. But, the supersonic flow results indicated a strong wave which was contributed to the particular pressure profile in the tube during the supersonic flows. The schlieren photographs of the wave indicated propagation into the boundary layer and a convex curvature of the complete wave front was observed in the Mach 4 flow. Velocity measurements indicated that the detonation wave was steady but it is believed that retonation waves were observed in some experiments.
Author: William Wilfred McKenna
Publisher:
ISBN:
Category : Shock waves
Languages : en
Pages : 230
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Author: Thomas John Krusic
Publisher:
ISBN:
Category :
Languages : en
Pages : 96
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The purpose of this work was to develop an experimental apparatus for the study of the initiation of detonation in a gaseous medium as a result of shock compression. The design of the apparatus is described, and results of some preliminary experiments are reported. They indicate that the mechanism of the initiation process behind reflected waves in a shock tube is essentially different than that caused by an accelerating flame. (Author).
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 836
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Author: Tim Gardiner Adams
Publisher:
ISBN:
Category : Explosions
Languages : en
Pages : 302
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