chemical mechanism for blending CH4 with H2

[rober]

Hello I'm working for gas turbine which uses CH4 with H2 for a fuel. I use gri3.0 chemical mechanism but it doesn't work over some portion of hydrogen. Can somebody recommend some chemical mechanism for blending CH4 with H2?? 

[SERGIO SANCHEZ MARTINEZ]

Hello Rober, not sure 100% it may be useful for you but, Have you tried the NUIGMech from the Combustion Chemistry Centre (C3)? 

Please see the next link:

https://www.universityofgalway.ie/combustionchemistrycentre/mechanismdownloads/

Once you download the version you would like to use, you can extract the C1 mechanism, either with Chemkin or Cantera. Then you can test it and do any changes you need. 

I hope it helps, the best, good luck and have fun!

Sergio.

On Tue 7 Nov 2023, 10:35 rober, <rober...@g.hongik.ac.kr> wrote:

Hello I'm working for gas turbine which uses CH4 with H2 for a fuel. I use gri3.0 chemical mechanism but it doesn't work over some portion of hydrogen. Can somebody recommend some chemical mechanism for blending CH4 with H2?? 

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[K G-A]

I have developed a gas turbine model which also uses blends of Methane and Hydrogen using the GRI3.0 and the San Diego Mechanisms. 

I am getting very very high cycle efficiencies above one (1). 

I have checked both mechanisms and they give similar results so it is not the mechanism since I am using the GRI3.0 Mechanism that comes with Cantera.

Can someone assist me to verify the model?

Thank you in advance.

Kofi.

[Steven DeCaluwe]

Hi Kofi,

Did you mean to attach a file that includes your model and your efficiency calculation?

Thanks,

Steven

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[K G-A]

Attached is the model in Jupyter Notebook.

Thank you 

Kofi.

[K G-A]

Hello,

Any progress on verifying my model?

I am changing my model to calculate the Air-Fuel Ratios manually without using Cantera's stoich_air_fuel_ratio(fuel, oxidizer, basis='mole') function to compare the results.

Regards,

Kofi

[John Leylegian]

Hello,

This notebook has some errors in the code apart from Cantera. The calculation of compressor work has an incorrect implementation of the isentropic efficiency, and your sign convention isn't taking into account how work crosses the system boundary. I would go back, review everything, print out all intermediate values, including units (make sure you're reckoning mass flow rates correctly), and consult an engineering text to make sure you're not flipping signs...

Once all of that works, then look at Cantera for other possible issues. Good luck

[K G-A]

Thank you John.  I followed your advice and got more reasonable change in enthalpies. 

But now I need to simulate the combustor in the gas turbine. None of the equilibrate() combinations below adequately simulates the combustion in the combustor. since temperature, entropy, internal energy and volume are not constant. The equilibrate() holds the pair in the bracket constant.

gas1.TP
gas1.TD
gas1.HP
gas1.UV
gas1.SP
gas1.SV

If I equilibrate (HP) since the combustion in a gas turbine is at constant enthalpy and constant pressure to get the adiabetic flame temperature and the equilibrate again at constant pressure and constant temperature at the adiabetic temperature to obtain the new enthalpy. Will this be a good representation of the combustion in a gas turbine combustor?

I have attached the updated model in Jupyter Notebook.

Regards,

Kofi.

[John Leylegian]

If you equilibrate a mixture that is already in equilibrium, nothing more will happen. One thing you could do is find the enthalpy at the equilibrium temperature, then bring the equilibrium mixture down to your initial temperature (the compressor exit temperature). That would tell you how much energy was converted from chemical to sensible enthalpy.

Good luck.

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[K G-A]

Thank you John. I noticed it. My model is working as expected now.

Regards,

Kofi.

[John Leylegian]

Great, glad I could help.

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