Fire suppression model

[shhe]

Hi

I am trying to suppress the fire with water mist. From physical point
of view, we should not need extra model for fire suppression.
Furthermore, I started my simulation with and without suppression
model. In both cases, I have gotten the same results. What I mean by
same result that the there are decreasing in temperature and heat
release.

I have some questions relating to that issue:

Have I to activate suppression model or not?

DEACTIVATION as follows:

&MISC SUPPRESSION=.FALSE./
&REAC ID='Propane fuel',
C=3.00,
H=8.00,
O=0.00,
N=0.00,
X_O2_LL=0.00/

[Kevin]

SUPPRESSION=.FALSE. makes X_O2_LL meaningless. I suggest you use
SUPPRESSION=.FALSE. to save on some CPU time. It prevents FDS from
going through that algorithm.

[JWilliamson]

Oxygen displacement can cause your reaction to move no matter what
suppression model you use. In some cases, your fuel will escape the
domain before reacting. Have you checked oxygen concentrations?
Justin

On May 28, 8:51 am, shhe <entsa...@hotmail.com> wrote:

[shhe]

Unfortunately, Oxygen concentration has been already increased. I
think there is a confusion with me. However, I am trying to use FDS
with watermist suppression as in the following article:

"A Numerical study of water-mist suppression of large scale
compartment fires", Fire Safety Journal 37 (2002) 569-589.

I have already compared the above case with experimental results
without injecting water mist. The results were compared good. Propane
fuel was supplied at a steady rate to obtain 980 kW. However, the fire
is ignited at t = 0 s and is alowed to develop fully till time t =
1810 s. At this time the water mist is injected through four nozzles
to about 50 s.

&PART ID='Water',
WATER=.TRUE.,
AGE=60.00,
QUANTITIES='DROPLET TEMPERATURE','DROPLET DIAMETER'/

&REAC ID='Propane fuel',
C=3.00,
H=8.00,
O=0.00,

N=0.00/

&SURF ID='burner',
COLOR='RED',
HRRPUA=1.3168000E003,
RAMP_Q='burner_RAMP_Q'/
&RAMP ID='burner_RAMP_Q', T=0.00, F=0.00/
&RAMP ID='burner_RAMP_Q', T=1.00, F=1.00/
&RAMP ID='burner_RAMP_Q', T=1.8000000E003, F=1.00/
&RAMP ID='burner_RAMP_Q', T=1.8010000E003, F=0.00/

&RAMP ID='CTRL_RAMP', T=1.8097500E003, F=-1.00/
&RAMP ID='CTRL_RAMP', T=1.8102500E003, F=1.00/
&PROP ID='Water Spray', PART_ID='Water', FLOW_RATE=3.0000000E003,
DROPLET_VELOCITY=1.00, SPRAY_ANGLE=30.00,80.00/
&DEVC ID='O2', QUANTITY='oxygen', XYZ=1.85,1.25,1.25/
&DEVC ID='NOZZLE1', PROP_ID='Water Spray', XYZ=0.70,0.70,2.50,
ORIENTATION=1.00,1.00,-1.00, LATCH=.FALSE., QUANTITY='CONTROL',
CTRL_ID='CTRL'/
&DEVC ID='NOZZLE2', PROP_ID='Water Spray', XYZ=0.70,1.70,2.50,
ORIENTATION=1.00,-1.00,-1.00, LATCH=.FALSE., QUANTITY='CONTROL',
CTRL_ID='CTRL'/
&DEVC ID='NOZZLE3', PROP_ID='Water Spray', XYZ=3.00,0.70,2.50,
ORIENTATION=-1.00,1.00,-1.00, LATCH=.FALSE., QUANTITY='CONTROL',
CTRL_ID='CTRL'/
&DEVC ID='NOZZLE4', PROP_ID='Water Spray', XYZ=3.00,1.70,2.50,
ORIENTATION=-1.00,-1.00,-1.00, LATCH=.FALSE., QUANTITY='CONTROL',
CTRL_ID='CTRL'/





On May 28, 4:19 pm, JWilliamson <williamson.justin.w...@gmail.com>
wrote:

[JWilliamson]

&RAMP ID='burner_RAMP_Q', T=1.8000000E003, F=1.00/
&RAMP ID='burner_RAMP_Q', T=1.8010000E003, F=0.00/

It appears that you are turning your burner off before you activate
the mist.
Justin

[shhe]

I have already modified them as follows:

&RAMP ID='burner_RAMP_Q', T=1.8000000E003, F=1.00/
&RAMP ID='burner_RAMP_Q', T=1.8010000E003, F=0.00/

&RAMP ID='CTRL_RAMP', T=1.7997500E003, F=-1.00/
&RAMP ID='CTRL_RAMP', T=1.8002500E003, F=1.00/

Where CTRL_RAMP for nozzles. I found that the temperature has
decreased suddenly within the first 5 second to the ambient
temperature. Furthermore, the Oxygen concentration has increased too.
Are these reasonable results??

Temperature and Oxygen concentration in File sectionsas follows:

Temperature_with_watermist.jpg
Oxygen_concentration.jpg

shhe

On May 28, 7:03 pm, JWilliamson <williamson.justin.w...@gmail.com>
wrote:

[JWilliamson]

You are turning the nozzles on at ~1800s and turning your burner off
at ~1800s.
It is reasonable that your temperature will decrease and oxygen
concentration will increase. I don't know enough about your scenario
to say that the quantities you see are reasonable, but they are
possible.
Are you certain that you want to turn the nozzles on and the burner
off at the same time? You do not appear to be simulating suppression,
but burnout.
Justin