Titel der Prsentation - PowerPoint PPT Presentation

Loading...

PPT – Titel der Prsentation PowerPoint presentation | free to download - id: 100635-ZDc1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Titel der Prsentation

Description:

preliminary results of ENACCEF Benchmark ... (Enceinte d'ACCEl ration de Flamme) The upper dome part with a total volume of 0.66 m3 ... – PowerPoint PPT presentation

Number of Views:38
Avg rating:3.0/5.0
Slides: 25
Provided by: MICA8
Learn more at: http://www.sar-net.org
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Titel der Prsentation


1
Hydrogen combustion with concentration gradients
in experiments and simulations preliminary
results of ENACCEF Benchmark
Ahmed Bentaib, Alexandre Bleyer, Heinz Wilkening,
Daniele Baraldi, Eveliina Takasuo and Risto
Huhtanen
2
Topics of the EUSAFE PIRT addressed in WP 12-1
Hydrogen Combustion (HC)
3
Hydrogen Behaviour in Containment (HBC)
  • Containment Atmosphere Mixing (CAM)
  • Non-homogenous atmosphere
  • hydrogen gradients
  • PARs

Hydrogen Combustion (HC) Ignition Flame
acceleration Recombiner Self ignition in
recombiners
4
Hydrogen Dispersion in a Reactor Containment
Typical hydrogen distribution in a NPP during a
severe accident. 1000 s and 1500 s after release
starts. Total amount released 1000 kg in 1000 s.
5
The ENACCEF test facility (Enceinte
dACCElération de Flamme)
The vertical facility ENACCEF allows to study
the effect of hydrogen gradients on flame
acceleration and deceleration. These gradients
are typical for real accident situation. 3
experiments on flame acceleration with defined
hydrogen concentration gradients are available
for SARNET partners and used in a CFD code
benchmark.
The upper dome part with a total volume of 0.66
m3
The lower driver tube with a length of 3.2 m and
a diameter of 0.154 m
6
Experimental Facility ENACCEF
1.7 m i.d. 0.74 m
Total Volume 0.72 m3 Vol.. (Dome)/Vol. (Tube)
10.6
DOME
3.3 m i.d. 0.15 m
9 Ring Shape Obstacles (BR0.63) section
TUBE
Spark ignition
7
ENACCEF FACILITY Diagnostics
  • 16 Photomultiplier Tubes
  • Flame front position
  • 9 Pressure Transducers
  • Pressure Built-up in the facility
  • Flame front position
  • 6 Gas Sampling Analysis GC/TCD
  • H2 Gradient

8
Experimental Conditions
  • Room Temperature and 100 kPa
  • Uniform / Stratified Mixtures in the Tube
  • Positive H2 gradient (d(H2)/dx gt 0, x0
    Ignition Point)
  • Negative H2 gradient (d(H2)/dx lt 0, x0
    Ignition Point)

Open tests (SARNET, OECD)
9
Homogenous mixture flame acceleration
Evaluation of flame speed from photomultiplier
sensors and reproducibility of experiments
(uniform 13 H2 case)
10
Codes used in the ENACCEF benchmark
11
Computational Grids
12
REACFLOW simulation of flame front (top)
(temperature distribution) and pressure
distribution (right) in the dome of the ENACCEF
facility (13 Vol.. hydrogen in air). Adaptation
is based on flamefront and pressure.
13
TONUS model - results
Dome part Fast combustion near the axis due to
strong connection between mesh density and
combustion rate in CREBCOM model
Hydrogen mass fraction at selected simulation
times (uniform 13 H2 case)
14
FLUENT model -results
  • Reaction rate at selected time steps (13 H2 case)

15
FLUENT model - results
Velocity magnitude at selected time steps (13 H2
case)
16
Comparison flame speed
ENACCEF Benchmark Comparison of flame velocity
between experiments and codes Uniform mixture 13
H2 87 Air
17
Comparison flame speed
ENACCEF Benchmark Overpressure history plots
comparison between experiments and codes at a
distance 2.877 m from ignition point, uniform
mixture 13 H2 87 Air
18
H2 Gradient EstablishmentNegative hydrogen
gradient
  • Lower injection of premixed gas (10.5h2 and
    89.5 air )up to 99725 Pa
  • Pure hydrogen is injected during 2 minutes in
    the bottom of the facility with rate of 0.5l/min
    up to 1 bar
  • Waiting Time (about 5 min)
  • For H2 gradient establishment in Tube
  • Homogeneous Charge in Dome
  • Gas sampling (at the wall) with relative
    uncertainty lower than 3 in mass

19
COMPARISON 2004-2006
20
Comparison Flame speed (neg. grad.)
ENACCEF Benchmark Comparison of flame velocity
between experiments and negative gradient
mixture, flame starts at 13.17 H2 (tube) and
ends at 10.63 H2 (dome)
21
H2 Gradient EstablishmentPositive hydrogen
gradient
  • Lower injection of premixed gas (13h2 and 87
    air ) up to 89325 Pa
  • During 9 minutes, lower injection with rate of
    7.2l/min of mixture composed by
  • Ø  13 H2 and 87 air during the first 180
    seconds,
  • Ø  12 H2 and 88 air from 181 to 300 seconds,
  • Ø  11 H2 and 87 air from 301 to 420 seconds,
  • Ø  10.5 H2 and 89.5 air from 421 to 540
    seconds,

13 H2
10,5 H2
22
COMPARISON 2004-2006
23
Comparison Flame speed (pos. grad.)
ENACCEF Benchmark Comparison of flame velocity
between experiments and positive gradient
mixture, flame starts at 10.75 H2 (tube) and
ends at 12.76 H2 (dome)
24
Conclusion
  • Simulation results from three CFD codes FLUENT,
    TONUS and REACFLOW have been compared against
    ENACCEF experimental results.
  • All codes are able to predict flame speed and
    pressure for a homogenous hydrogen air mixture
    (also valid for positive hydrogen gradient).
  • Nevertheless when the hydrogen gradient is
    negative, the flamespeed is generally
    overpredicted.
  • TONUS CREBCOM (Forest Fire) simulation showed
    some grid dependence in flame acceleration
    direction.
  • Improved combustion models are needed to predict
    hydrogen combustion with hydrogen gradients.
  • Scaling effects remain unclear.
About PowerShow.com