[D_Timbota]

Hi.

I am running a ICE GDI simulation, using Hydrous Ethanol as a fuel, with various ethanol/water ratios. The GDI model it is set up at 1440 CAD as default, therefore incurring 2 combustion processes, however, my results are different for every combustion(I was expecting to get a repeated behavior of spikes depicted on the graph). Please see the picture attached. P.S.: I was trying to run a simulation including 4* 720 CAD to see if there is any change, but the emissions are following same trend. Also I can't find how to read in-cilinder pressure( from outputs, I can only see the in-flow pressure at around 2.5 bar)
Thank you!
Regards, Dumitru Timbota

[alireza.mashayekh]

Hi;

We usually recommend neglecting the results of your 1st simulation cycle as they are strongly affected by your initialization. Additionally, cyclic variation is expected in simulations just as they are in the real engine. If you would like to get repeatable results, you can refer to our Tumble_GDI_SAGE_repeatable example case for the case setup recommendations.

Let's assume that your combustion chamber is region 0. In this case, all the averaged data for the chamber region are stored in thermo_region0.out file. You can plot Pressures, Min/Mean/Max Temperature and many more variables that are written in this file for the chamber region. You have the same files w/ the same variables for other regions as well.

Thanks,

[D_Timbota]

Dear Alireza,

Thank you, I ran a simulation based on repeatable and got similar cycle to cycle results. I have 2 issues which I am trying to solve now:
1. I am trying to adjust engine load, but I don't know how to change Lambda ( I was trying through Regions and Initialization -> +Combustion Products but I can not select Ethanol as a species as it can not be found in Species Drop-down menu. However I don't know if this is the right approach? Another approach I was thinking of is to adjust the injected mass ( Under Injection function) to force the mixture to change its air-fuel ratio ( although this is rather a desperate approach as I believe is the wrong one). I have attached a Graph highlighting the issue.
2. The pressure I car read from output files is around 2-2.5 bar, I am expecting it to be about 20 times higher. Where am I getting it wrong?
P.S.: Thank you for your quick answer to initial thread and I apologize that I did not replied earlier, It was a tough week.

Regards,
Dumitru Timbota

[tmburton]

Dumitru,

If ethanol is not in your mech.dat and therm.dat files, then you will not be able to use it in CONVERGE.

The pressure output you showed in in MPa, not bar.

Best regards,

Tristan

[D_Timbota]

Dear Tristan,

I have Ethanol in both therm.dat and mech.dat. Regarding the pressure, the unit is not as important, it easily can be converted in bar, but the value I obtain is way too small and I have no idea on how to get it right
Thank you!

[tmburton]

Dimitru,

I opened our SI8_engine_premix_E85 example case and went to the Regions and initialization section and selected the +Combustion products button. Ethanol is available for me to select as a Fuel Species, see attached image.

The image you shared showed 2.5 MPa pressure peaks which are 25 bar pressure peaks. Are you saying that you're still low by a factor of 20?

Best regards,

Tristan

[D_Timbota]

Hi!

I realised my explanations were incomplete. I can find Ethanol under the species button, but I can not find them under Equivalence Ratio( the option on the left), the most I can find is Ethyl and I don't know how to set the A/F ratio for them. If I select Ethanol and Water(I am working with Hydrous Ethanol) under Species in +Combustion Products, it will populate the box in Regions and Initialisation field with the chosen species, deleting the air. Here is where I am getting lost. On other side, to play with Equivalence ratio coefficient under +Combustion products, I need to populate the top half box of the function with species, to ask CONVERGE what to calculate. I'm going to read through AdvICE training on your site to see if I'll find anything.
Thank you!

[MFGT]

Originally Posted by D_Timbota

1. I am trying to adjust engine load, but I don't know how to change Lambda ( I was trying through Regions and Initialization -> +Combustion Products but I can not select Ethanol as a species as it can not be found in Species Drop-down menu. However I don't know if this is the right approach? Another approach I was thinking of is to adjust the injected mass ( Under Injection function) to force the mixture to change its air-fuel ratio ( although this is rather a desperate approach as I believe is the wrong one). I have attached a Graph highlighting the issue.

If you are trying to adjust engine load, the initialization is the wrong way, as this would only affect your 1st cycle.


Easiest way is to have a GT-Power simulation model where you use the same fuel properties. Then you can take pressures from the ports and fuel mass from injector to simulate various operation points.


If you dont habe a GT-Power model, another approach could be to run a coarse (gridscale value set to -1 or even -2) simulation and increase fuel mass by estimiation until you reach your target lambda. Or you simply calculate your additional fuel mass if you know the stoichiometric value and assume constant air mass.

[D_Timbota]

Originally Posted by tmburton

Dimitru,

I opened our SI8_engine_premix_E85 example case and went to the Regions and initialization section and selected the +Combustion products button. Ethanol is available for me to select as a Fuel Species, see attached image.

The image you shared showed 2.5 MPa pressure peaks which are 25 bar pressure peaks. Are you saying that you're still low by a factor of 20?

Best regards,

Tristan

I got access to a computer and I could better see what you are talking about, I opened same example case as you and indeed I can find the species. I will run a simulation to get generated therm.dat file and compare it with what I have, however I have seen Tobias comment an I am trying to see if I can figure out how to follow all steps correctly. Thank you again.

Regards,
Dumitru Timbota

[D_Timbota]

Originally Posted by MFGT

If you are trying to adjust engine load, the initialization is the wrong way, as this would only affect your 1st cycle.


Easiest way is to have a GT-Power simulation model where you use the same fuel properties. Then you can take pressures from the ports and fuel mass from injector to simulate various operation points.


If you dont habe a GT-Power model, another approach could be to run a coarse (gridscale value set to -1 or even -2) simulation and increase fuel mass by estimiation until you reach your target lambda. Or you simply calculate your additional fuel mass if you know the stoichiometric value and assume constant air mass.

Dear Tobias,

Could you recommend me the relevant support literature on how to set up the case? Basically What I have to simulate is the use of Hydrous ethanol in a GDI. The plan is to run a simulation with Iso-octane as reference fuel and various ethanol water ratios (E94W6,E80W20,E70W30,E60W40,E50W50) and compare the combustion behavior and emissions.
P.S.:I am currently reading through AdvICE courses from CONVERGE website.

Regards,
Dumitru Timbota

[MFGT]

I dont have literature for that, that is personal experience


Since you want to compare fuels and various ethanol water ratio, you could also calculate LHV´s and:
a) adjust fuel mass for constant fuel energy
b) keep fuel masses the same
c) ...


Its up to you, what you want to investigate in detail and where to focus on your comparison.

[D_Timbota]

Originally Posted by tmburton

Dimitru,

I opened our SI8_engine_premix_E85 example case and went to the Regions and initialization section and selected the +Combustion products button. Ethanol is available for me to select as a Fuel Species, see attached image.

The image you shared showed 2.5 MPa pressure peaks which are 25 bar pressure peaks. Are you saying that you're still low by a factor of 20?

Best regards,

Tristan

I am expecting a pressure of 4-8 MPa, depending on load, clearly I am not getting everything right.