Deflagration-to-Detonation Transition in Natural Gas-Air Mixtures

Details

• Personal Author:
  Gamezo VN ; Kessler DA ; Mohamed KM ; Oran ES ; Zipf, R. Karl, Jr.
• Description:
  The gas explosion test facility (GETF) previously used to study detonability of natural gas (NG)-air mixtures was modified for studies of flame acceleration and deflagration-to-detonation transition (DDT). The 73-m-long by 1.05-m-diameter tube was equipped with 15 baffles of varying blockage ratio (BR) = 0.13, 0.25, or 0.50, placed near the closed end of the tube and spaced 1.52-m apart. The remaining part of the tube was smooth. Experiments used mixtures between 5.1% and 15.0% NG-air. Ignition was achieved in NG-air mixtures over the composition range 6.1-14.1%. After passing the 15 baffles, both flame and pressure wave velocity were more than 300 m/s over this range. Flame velocity was increasing over the range 6.2-12.8% NG-air, and it reached the sound speed in the burned gases (800-1000 m/s) over the composition range 8.0-10.8% NG-air. Pressure wave velocity was increasing over the composition range 6.1-14.1% NG-air and had reached sonic velocity over the composition range 6.2-12.6% NG-air. Shock waves with magnitude greater than 1 MPa were measured in all tests over the composition range 6.5-12.4%. DDT within the baffled section of the tube and sustained detonations beyond the baffles in the smooth part of the tube were observed over the composition range 8.0-10.8% NG-air. The observed run-up length to sonic flame velocity normalized by the tube diameter, Xru/D, ranges from 16 to 23 at BR = 0.13, 10 to 21 for BR = 0.25, and 13 to 21 for BR = 0.50. The observed run-up length to DDT normalized by the tube diameter, XDDT/D, ranges from 19 to 23 at BR = 0.13, and 16 to 23 for BR = 0.25 and 0.50. Coal mine safety regulations in the US require mine seals to resist an explosion pressure-time curve that rises instantaneously to 0.8 MPa and remains at that level for 4 s. Pressure-time curves measured in these experiments show that shock waves with near-instantaneous rise time and magnitude greater than 1 MPa can develop from weak spark ignition after passing 15 turbulence-generating obstacles in test mixtures ranging from 6.5% to 12.4% NG-air. [Description provided by NIOSH]
• Subjects:
  Coal Coal Mining Mining Occupational Health Safety Safety Management
• Keywords:
  Author Keywords: Deflagration-to-detonation Transition Coal-mining Explosion Flame Acceleration Flammable-gases Gases Gas Explosions Measurement-equipment Natural-products Natural Gas-air Safety-measures Statistical-analysis

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• Series:
  Mining Publications
• ISSN:
  0010-2180
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  District of Columbia ; Maryland ; OSHA Region 3 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OMSHR - Office of Mine Safety and Health Research
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  161
• Issue:
  8
• NIOSHTIC Number:
  nn:20043984
• Citation:
  Combust Flame 2014 Aug; 161(8):2165-2176
• Contact Point Address:
  Richard K. Zipf Jr., Office of Mine Safety and Health Research, National Institute for Occupational Safety and Health, Pittsburgh, PA 15236
• Email:
  rzipf@cdc.gov
• Federal Fiscal Year:
  2014
• NORA Priority Area:
  Mining
• Peer Reviewed:
  True
• Source Full Name:
  Combustion and Flame
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:7a0f8f3d1aee993bb1e42c470772211ac1d535c520c4dd0b840887d1de3a053b806cd35d89dc41290e31e09fd036ed6b53b43b2e4b4d8f849bb58e3c64d9cc23
• Download URL:
  https://stacks.cdc.gov/view/cdc/228038/cdc_228038_DS1.pdf
• File Type:
  [PDF - 12.82 MB ]