[Paolo]

Thanks Pauli,
i already tried to define inlet fuel boundary as you have suggested..
The simulation startes without problems but results are bad:

• the mass fractions in the inlet fuel tube (before combustione zone) are wrong;
• temperature goes to absurd values like 1e+05;
• combustion occurrs in a strange zone: theinlet pipe of the fuel

I think the problem is in defining density of a mixture: in the inlet boundary i define the density of the entire mixture, calculated from the mass fraction and density of single gases which form the syngas.