[timaji]

Dear Foamers,
What is the method in ignition process of solver XiFoam and engineFoam?
I found that the final results are so sensitive to ignition properties.
in OF ignition is characterized by "strength","duration","radius" in combustionProperties file, what are the true values for them for some ignitor? where can we find these values?

Timaji

[Jacob]

The method can be found in SRC/engine/ignition/ignite.H
here is the formulation:
bEqn.diag()[ignSite.cells()[icelli]] +=
(
ignSite.strength()*ignSite.cellVolumes()[icelli]
*rhou[ignSite.cells()[icelli]]/ignSite.duration()
) /(b[ignSite.cells()[icelli]] + 0.001);


Jacob

[timaji]

Originally Posted by Jacob

The method can be found in SRC/engine/ignition/ignite.H
here is the formulation:
bEqn.diag()[ignSite.cells()[icelli]] +=
(
ignSite.strength()*ignSite.cellVolumes()[icelli]
*rhou[ignSite.cells()[icelli]]/ignSite.duration()
) /(b[ignSite.cells()[icelli]] + 0.001);


Jacob

Hi Jacob

I already saw this equation but the problem is that i dont know how to determine the ignition properties like strength,duration,radious?

according to "Solution adaptive CFD simulation of premixed flame propagation over various solid obstructions" by P.Naamansen, the ignition is carried out by changing the regress variable uniformly in space from one to zero in a sharply defined region.the region has the shape of semicircle in 2D simulation or semi-sphere in 3D simulation, and during the ramping which is a linear function of time no other combustion is allowed to occur.the time it takes to consume the reactants during that period is calculated from the laminar flame speed of gas.
as u see the radius and duration of ignition is proportional to laminar flame speed but there is nothing about the strength! I think the strength is probably the slope of ramp function.
but as i mentioned in previous post the final results are so sensitive to these quantities.

In the article there is no equation for relating the diameter and duration to laminar flame speed!

for example in XiFoam tutorial-moriyoshiHomogeneous- for propane with phi=1 and Su=0.434 how can we evaluate the diameter=0.003 and duration=0.003??


Regards

timaji

[camille131]

Hello Timaji,

Have you finally found the solution to your problem?
because I ask myself the same quesitons today ..

Could you please send me the article by P. Naamansen you mention in your previous post? (camilletienne75@gmail.com)

Thank you in advance,

Cam

[Pier84]

Hi All

It is a shame that there is not a minimum of documentation on that and no answer is given. Only bug reports are welcome for the convenience of the openFOAM(c) distributor.

PO

[sheaker]

Hello.
Because there is lack of information about ignition settings I would like to share with You my little compare that I've done during my studies.

Engine:

conRodLenght

0.150

bore

0.086

stroke

0.086

clearance

0.001

rmp

2000
deltaZ = 0.086
Piston speed = 5.73333 m/s
Vmax = 0.000547039, Vmin = 4.75896e-05
Vmax/Vmin = 11.4949

Plots and ignition settings:
See attachments.

I hope it helps a little for the beginners.
sheaker