[o_cean]

hello

I did engine combustion analysis with CONVERGE 3.0 version.

The combustion model was analyzed using the SAGE model.

I'm in the process of organizing and analyzing the results after analysis, but it is difficult to obtain the mass fraction burned (MFB).

How did you calculate the MFB of engine fuel while doing CFD analysis?

I would be grateful if you could tell me in detail

In addition, can engine performance factors such as torque and IMEP be calculated within CONVERGE? If you can calculate it, please tell me how.

Or, if the performance factor needs to be calculated through post-processing, I would appreciate it if you could tell me how to calculate the post-processing.

Thanks.

[ksrivast]

Hello Sehyun,

CONVERGE outputs species_mass_frac.out/species_mass_frac_region*.out which contains values for mass fractions of all species listed within mech.dat and species.in, averaged over the entire domain and individual regions. Enable this output in STUDIO under Output/Post-Processing > Output files > Species output > All species > 2- Mass fraction (or species_output_flag = 2 in inputs.in). Identify your burned gas species (CO2, H2O, etc) and add the values up to obtain mass fraction of burned gases. This operation can be done within STUDIO's Line Plotting module.

Within STUDIO's Line Plotting module, under Tools > Engine Performance Calculator, you can evaluate engine performance factors such as IMEP using a thermo*.out file from your CONVERGE simulation. Please refer the CONVERGE STUDIO manual for more details.

Hope this helps.

Sincerely,

[o_cean]

ksrivast, thank you so much for your help.

Your answer was really helpful. I calculated the engine performance perfectly while looking at the studio manual.

By the way, I'm trying to calculate the MFB, but I have a question about the method you gave me.

I don't know how to get the sum of combustion products (CO2, H2O, OH, etc...) in CONVERGE line plotting.

I would like to know if there is a way to find the sum of the mass fractions of the burned gas in line plotting and how to export the MFB data obtained in this way.

Thank you so much for your help.

[ksrivast]

Hello Sehyun,

Within species_mass_frac*.out, the mass fractions of every species present in your CONVERGE simulation is outputted as separate columns. Using STUDIO's line plotting module, you can perform custom plot operations which include adding values from different columns within the same *.out file or across different *.out files. A new plot can then be created whose values are the sum of the mass fractions of all burned gas species from species_mass_frac*.out. To learn how to perform such plot operations, please refer our STUDIO manual (Chapter Line Plotting > Plotting Dock > Dataset Editor > Plot operations)

Once a new plot has been created, you can export data View > Preview plot data > Export to file. This has been described in our STUDIO manual as well.

Sincerely,

[o_cean]

Hello Kislaya.

Thanks to your help, I've been able to solve most of my anxieties.

I'm familiar with most of the uses for CONVERGE line plotting.

However, in the process of calculating the MFB, there is a part that has not been accurately calculated.

Hydrogen is used as fuel, and I calculated the MFB with the method you told me using the hydrogen combustion reaction equation and chemical equilibrium by referring to various literature, but I think something is wrong. MFB doesn't seem to be calculated correctly. It's out of range on the Y-axis I was expecting.

So I'm looking in the wrong place.

When I looked at the engine performance calculation results in the engine performance dock using the method you taught me, I was able to confirm that the MFB came out as 10, 50, and 90.

When calculating MFB in the engine performance dock, where can I find out what data and how to calculate it?

Thank you so much for your help.

[ksrivast]

Hello Sehyun,

You will not use the Engine Calculator to evaluate MFB. If you take hydrogen combustion/oxidation reaction, your fuel species is H2. You can look in species_mass_region*.out for your cylinder region to evaluate mass of H2 right before and after combustion. And that will help you evaluate how much % of H2 was consumed.

If you continue to face issues, please reach out to us at support@convergecfd.com. Please use your official email for all correspondence with Convergent Science. Please mention your issue, attach your case setup and add the cfd-online thread, as reference.

Sincerely,

[o_cean]

Hello Kislaya,

Thank you very much for your kind reply.

Once I calculate it, if it doesn't work out, I'll contact you via the email you let me know.

Your sincerely,

[o_cean]

Hello Kislaya,

I'm going to look at other tasks and try to calculate again. Can you help me again?

Now you know how to use line plotting.

However, when I get the MFB, I try to input the fuel before combustion and the fuel after combustion in Operations of the direct editor, but it doesn't go well.

If you don't mind, can you tell me the process of calculating MFB?

For reference, I interpreted the hydrogen engine.

And in line plotting, if you calculate the engine performance in Tool -> Engine calculators -> Engine performance, you can see that it is calculated as CAD10, 50, and 90. Can you tell me what formula it is calculated with?

Sincerely,

[ksrivast]

Hello Sehyun,

On your plot window, you can use the cursor to find the values before combustion and after combustion. This will help calculate a single value of MFB over the entire combustion process. If you want to visualize how the consumption varies over time, then you can use the Operations panel in the Dataset editor and normalize the fuel mass based on maximum value seen in the cycle. The STUDIO manual demonstrates how to apply operations to the plot.

CADXX is the crank angle at which the amount of burned fuel reaches XX percent of its
maximum value for the cycle. We report values for 10%, 50% and 90% consumption.

Hope this helps.

Sincerely,