40ty Years of investigation of Diffusion Ignition

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40ty Years of investigation of Diffusion Ignition

• Piotr WolanskiWarsaw University of Technology,
• 00-665 Warsaw, Poland

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Introduction

• Nearly 40 years ago in Chorzow Chemical Plant
  Azoty explosion of synthesis gas killed four
  workers. Explosion happened during failure of
  high pressure gas installation in which mixture
  of hydrogen and nitrogen (3H2 N2), used for
  synthesis of ammonia, was at high pressure (about
  300 bar) and high temperature (about 300 0C).
  Since during expansion gas is cool down and
  selfignition temperature was far above initial
  temperature, search for external ignition source
  was started. No such source was found, so we were
  asked to explain the reason. This was motivation
  to initiate research to found real reason for
  ignition.

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Schematic diagram of experimental test stand
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Streak interferometric pictures of outflow of
hydrogen into oxygen atmosphere
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High speed interferometric pictures (156 250 f/s)
of diffusion ignition of hydrogen flowing out
into oxygen atmosphere
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Frame interferometric and Schlieren syreak
pictures of difusion ignition
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(No Transcript)
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Schematic diagram of high pressure shock tube
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Schematic diagram of observation area
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High speed Schlieren pictures ( 25 000 frames/s)
of diffusion ignition during out flow of high
pressure and high temperature of synthesis gas
into air atmosphere
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High speed Schlieren pictures of diffusion
ignition with obstacle
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Outflow of gas into obstacle
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Direct pictures of flame from Pentazet 16 camera
(3000 frames/s)
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Numerical simulation of diffusion ignition
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Shock tube studies of liquid fuel ignition
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Streak schlieren pictures of ignition of liquid
fuel
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RECENT RESEARCH
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Hydrogen fueled car and refueling station at
Tocho Gas in Japan.
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EXPERIMENTAL TEST STAND
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Lengths and diameters of the tube tested in the
research
L mm D mm D mm D mm
L mm 10 25 32
45 x x x
65 x
75 x
95 x x
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Pressures and signal from photodiode courses.
Extension tube length 45 mm, extension tube
diameter 25 mm, initial hydrogen pressure equal
to 7.6 MPa
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Direct pictures of the hydrogen outflow,
extension tube length 45 mm, extension tube
diameter 32 mm, initial hydrogen pressure equal
to 6.2 MPa. Frame rate 80 000 f/s, shutter
1/182 000 s.
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Direct pictures of the hydrogen outflow,
extension tube length 65 mm, extension tube
diameter 10 mm, initial hydrogen pressure equal
to 7.4 MPa. Frame rate 80 000 f/s, shutter
1/182 000 s.
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Results of the experiments as a function of
pressure and length of the tube. Tube diameter
equal to 10 mm.
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Critical value of the hydrogen pressure required
for ignition as a function of length of the tube.
Tube diameter equal to 10 mm.
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Results of the experiments as a function of
pressure and diameter of the tube. Tube length
equal to 95 mm.
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Number of tests as a function of pressure range
and length of the extension tube
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Reconstruction of the experimental facility.
Initial conditions 1. High pressure hydrogen -
red region on the left hand side of the membrane.
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Reconstruction of the experimental facility.
Initial conditions 2. High pressure hydrogen -
red region on the left hand side of the membrane.
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, explicit. Left - 2 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Comparison of experimental and numerical results.
2nd order upwind, implicit. Left 1 initial
conditions, temperatura distribution (80 bar
initial pressure). Right direct pictures from
experiment (76 bar H2 initial pressure)
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Conclusions (1)

• It was first time shown nearly 40ty years ago
  that outflow of the high pressure combustible gas
  can be a source of ignition. Ignition can be
  obtained both in incident as well as in reflected
  shock wave. In case of reflected shock wave,
  which might be more often case in reality,
  parameters of outflowing gas which can initiate
  explosion are even lower. In case of reflected
  wave, geometry (such as cavities) which might
  focus reflected shock, might additionally lower
  ignition parameters.

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Conclusions (2)

• Also spilled fuel on surface can be potential
  source of ignition. In this case even outflow of
  air or even inert gas can initiate combustion and
  possible explosion. So, research on this
  direction must be continued to evaluate more
  accurately conditions which will lead to ignition
  during outflow of gas from the high pressure
  installation.

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Conclusions (3)

• Hydrogen ignition takes place behind the contact
  surface of the wave generated by hydrogen
  outflowing from high pressure installation, due
  to mixing of air heated by created shock wave
  with expanding hydrogen.
• Geometry of the extension tube significantly
  influences ignition process during outflow of the
  high pressure hydrogen.

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Conclusions (4)

• Ignition process shows stochastic behavior, since
  it depends very much on random processes
  associated with opening of the diaphragm
  (membrane).
• The results of the experimental tests and
  numerical simulations show that geometry of the
  extension tube and the process of the diaphragm
  opening have a significant influence on the
  presence of the hydrogen ignition and the flame
  propagation.

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Conclusions (5)

• More research is necessary to explain
  complicated nature of this phenomenon.

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• THANK YOU FOR YOUR ATTENSION!