[tom634]

Hello,
I am modelling Spark Ignition engine work (compress, combustion, work). I set:
Pressure based, Transient Solver
Energy Equation- On
Species- Partially Premixed Combustion with PDF Table (CH4 (methane)- 1 in mass fraction and N2- 0.767 and O2- 0.233 in mass fraction), with compressibility effects and calculated PDF Table.
Spark Ignition- Fixed Spark Size with Start at 360 degrees.
Materials- remove Air, remains PDF Mixture and Solid Aluminium.
I am modelling Dynamic Mesh working as piston.
Solution Methods- Green Gauss Cell Based, Pressure PRESTO!, rest First Order Upwind.
Solution Initialized with Mean Mixture Fraction 0.03.

I have such calcuations:


At crank angle 199 degrees:

At crank angle 369 degrees:


My problem is that, combustion is at about crank angle 120 degrees, when it should be at crank angle 360 degrees by spark ignition (I have 720 time steps). What to do to have spark ignition at crank angle 360?

[mokrane]

hi.
please if you have solved your proplem please helpe me.
could you please tell me how you choose the mean mixture fraction 0.03.
i am doing a simulation of biogas in si engine using FLUENT.
thanks.