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|Title: ||Gas explosions in process pipes|
|Authors: ||Kristoffersen, Kjetil|
|Issue Date: ||2004 |
|Abstract: ||In this thesis, gas explosions inside pipes are considered. Laboratory experiments and
numerical simulations are the basis of the thesis.
The target of the work was to study gas explosions in pipes and to develop numer-
ical models that could predict accidental gas explosions inside pipes.
Experiments were performed in circular steel and plexiglass pipes. The steel pipes
have an inner diameter of 22.3 mm and lengths of 1, 2, 5 and 11 m. The plexiglass
pipe has an inner diameter of 40 mm and a length of 1.9 m. Mixtures of propane,
acetylene and hydrogen with air at various equivalence ratios were used. Pressure
was recorded by Kistler pressure transducers and ame propagation was captured
by photodiodes, a SLR camera and a high-speed camera. The experiments showed
that acoustic oscillations would occur in the pipes, and that the frequency of these
oscillations are determined by the pipe length. Several inversions of the ame front
can occur during the ame propagation in a pipe. These inversions are appearing due
to quenching of the ame front at the pipe wall and due to interactions of the ame
front with the longitudinal pressure waves in the pipe. Transition to detonation was
achieved in acetylene-air mixtures in a 5 m steel pipe with 4 small obstructions.
Simulations of the ame propagation in smooth pipes were performed with an 1D
MATLAB version of the Random Choice Method (RCMLAB). Methods for estimation
of quasi 1D burning velocities and of pipe outlet conditions from experimental pres-
sure data were implemented into this code. The simulated pressure waves and ame
propagation were compared to the experimental results and there are good agreements
between the results.
Simulations were also performed with the commercial CFD code FLACS. The code
was tested for gas explosions in smooth pipes and the results compared to experimental
results. To properly handle the longitudinal pressure oscillations in pipes, at least 7
grid cells in each direction of the pipe cross-section and a Courant number (CFLC)
of maximum 1 should be used. It was shown that the current combustion model in
FLACS gave too high ame speeds initially for gas explosions in a pipe with an inner
width of 40 mm.|
|Publisher: ||Høgskolen i Telemark|
|Document type: ||PhD thesis|
|Appears in Collections:||Doktorgradsavhandlinger i prosess- energi og automatiseringsteknikk|
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