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Research Papers: Design and Analysis

Detonation and Transition to Detonation in Partially Water-Filled Pipes

[+] Author and Article Information
Neal P. Bitter

e-mail: nbitter@caltech.edu

Joseph E. Shepherd

e-mail: joseph.e.shepherd@caltech.edu
Graduate Aeronautical Laboratories,
California Institute of Technology,
Pasadena, CA 91125

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the Journal of Mechanical Design. Manuscript received July 31, 2012; final manuscript received December 18, 2012; published online May 21, 2013. Assoc. Editor: Spyros A. Karamanos.

J. Pressure Vessel Technol 135(3), 031203 (May 21, 2013) (10 pages) Paper No: PVT-12-1111; doi: 10.1115/1.4023429 History: Received July 31, 2012; Revised December 18, 2012

Detonations and deflagration-to-detonation transition (DDT) are experimentally studied in horizontal pipes which are partially filled with water. The gas layer above the water is stoichiometric hydrogen–oxygen at 1 bar. The detonation wave produces oblique shock waves in the water, which focus at the bottom of the pipe due to the curvature of the walls. This results in peak pressures at the bottom of the pipe that are 4–6 times greater than the peak detonation pressure. Such pressure amplification is measured for water depths of 0.25, 0.5, 0.75, 0.87, and 0.92 pipe diameters. Focusing of the oblique shock waves is studied further by measuring the circumferential variation of pressure when the water depth is 0.5 pipe diameters, and reasonable agreement with theoretical modeling is found. Despite the local pressure amplification due to shock focusing, peak hoop strains decreased with increasing water depth. Failure of the detonation wave was not observed, even for water depths as high as 0.92 pipe diameters. Likewise, transition to detonation occurred for every water height.

Copyright © 2013 by ASME
Topics: Pressure , Explosions , Pipes , Water , Waves
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References

Figures

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Fig. 3

Pressure traces for a detonation with water depth h/d = 0.50

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Fig. 4

Two-dimensional wave diagram for a detonation with a wave speed greater than the sound speed of water

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Fig. 2

Pressure traces for a detonation with no water in the test section

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Fig. 1

Schematic of test setup (dimensions in meters). Strain gauges (S7–S22) are oriented in the hoop direction.

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Fig. 5

Pressure contours from a series solution of the equivalent 2D transient problem

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Fig. 11

Contours of pressure P6 (MPa) against time and θ for h/d = 0.50. The bottom of the pipe is denoted θ = 0. Two trials were recorded for each angle, with one plotted as +θ and the other as −θ. Black lines mark the trajectories wall shocks, see Fig. 5.

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Fig. 6

Pressure traces for a detonation with h/d = 0.25

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Fig. 7

Pressure traces for a detonation with h/d = 0.75

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Fig. 8

Pressure traces for a detonation with h/d = 0.92. High frequency oscillations on the bottom trace are due to pressure reflections in a very thin layer of water that spilled over from the water-filled section.

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Fig. 9

Overlaid pressure traces for water heights h/d = 0, 0.5, and 0.87 for transducer P3 (above the water, 1 m from the pipe's endwall)

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Fig. 10

Relationship between peak detonation pressure and water height. Peak pressures are recorded above the water, prior to passage of the reflected shock wave. Each data point corresponds to an individual shot.

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Fig. 12

Baseline pressure traces for DDT with no water in tube

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Fig. 13

Pressure traces for DDT with water depth h/d = 0.50

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Fig. 20

Thermal hoop strain as a function of angle. FEM: Finite element model assuming the temperature distribution shown in the inset diagram. Experiment: Hoop strains after 100 ms compiled from shots rotated at various angles

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Fig. 21

Strain traces for a detonation with a neoprene sheet covering the bottom half of the pipe at the first two strain measurement locations (x = 0.61 and 0.86 m)

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Fig. 14

Pressure traces for DDT with water depth h/d = 0.92

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Fig. 15

Peak pressure below water vs. position for DDT over several water heights

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Fig. 16

Strain traces (hoop direction) for a detonation with no water in pipe

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Fig. 17

Strain traces (hoop direction) for a detonation with h/d = 0.5

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Fig. 18

Dynamic loading factor vs. water depth for both detonations and DDT

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Fig. 19

Strain trace for a detonation with water depth h/d = 0.50

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