[amin_u50]

Hello all,

I used NG/diesel mechanism of CONVERGE example file (dual-fuel SAGE). When I validated CONVERGE prediction with experimental data the expansion pressure is higher than that of experimental data. I did validate in different operating conditions. Does anybody have any recommendation?

I think this problem comes from mechanism as combustion phasing is well matched with experimental data.

[tmburton]

Amin,

This problem usually occurs when there is an inconsistent total energy release between experiment and simulation. Are you confident that the total heat release in CONVERGE is consistent with the energy content of the real fuel in the experiment (and that all the fuel burned in both simulation and experiment)?

Best regards,

Tristan

[amin_u50]

Hello Tristan,

Can I have your email and I'll send my validation cases (HRR and in-cylinder pressure)

[amin_u50]

Originally Posted by tmburton

Amin,

This problem usually occurs when there is an inconsistent total energy release between experiment and simulation. Are you confident that the total heat release in CONVERGE is consistent with the energy content of the real fuel in the experiment (and that all the fuel burned in both simulation and experiment)?

Best regards,

Tristan

Could you please send me your email and I will send you my validation case.

[tmburton]

Amin,

Have you determined the energy content of the fuel in the experiment and verified that all the fuel was burned? If the energy content of the fuel you used in CONVERGE is higher than that of the experiment (or if everything burned in CONVERGE but not in the experiment) then you may see over-prediction of the expansion pressure.

Best regards,

Tristan

[amin_u50]

Originally Posted by tmburton

Amin,

Have you determined the energy content of the fuel in the experiment and verified that all the fuel was burned? If the energy content of the fuel you used in CONVERGE is higher than that of the experiment (or if everything burned in CONVERGE but not in the experiment) then you may see over-prediction of the expansion pressure.

Best regards,

Tristan

Tristan,

You are right. When I have over-prediction in simulation, it means more fuel is burned compared to experiment. Also, when I compare the unburned methane emissions of experiment and simulation, it is much lower in the simulation. So, it means most of the natural gas is combusted. So, what do you suggest to sort out this problem?

[mohameditdh]

Hi amin_u50
are you sure about your geometry? compression ratio
i advise you as first step to check the comparison between CFD and simulation before the start of combustion if you have a good monitoring signal pressure

[amin_u50]

Originally Posted by mohameditdh

Hi amin_u50
are you sure about your geometry? compression ratio
i advise you as first step to check the comparison between CFD and simulation before the start of combustion if you have a good monitoring signal pressure

Hello,

Everything is good except expansion pressure. If you send me your email I'll email you my validation case.

[amin_u50]

Originally Posted by amin_u50

Hello,

Everything is good except expansion pressure. If you send me your email I'll email you my validation case.

I solved the problem. I changed the embedding level from 2 to 3 and now the expansion pressure is matched with the experimental data.

[mohameditdh]

Originally Posted by amin_u50

I solved the problem. I changed the embedding level from 2 to 3 and now the expansion pressure is matched with the experimental data.

Good, do you simulate a full cycle or just a combustion phase

[amin_u50]

Originally Posted by mohameditdh

Good, do you simulate a full cycle or just a combustion phase

The whole cycle from IVC to EVO.