Trouble in using Cantera in DWSIm

[Pietro]

Dear all,
I am trying to run the following script in Script Manager with Python.net as execution engine:

import cantera as ct
import numpy as np
import System
from System import IO

ct.add_directory(IO.Path.GetDirectoryName(Flowsheet.FilePath))
gas = ct.Solution('C:\Users\User1\AppData\Local\DWSIM6\samples\ChemDetailed.cti')

Previously I did the following:
1) I installed the portable Python distro as suggested by Daniel in this post (https://sourceforge.net/p/dwsim/discussion/844529/thread/652ccd224d/?limit=25.)
2) I installed cantera in the portable Python distro and made sure that Cantera works, by running a simple Cantera example in the Python console of the distro.
3) I set the directory C:\Users\User1l\Desktop\WPy64-3980\python-3.9.8.amd64 as Python 3.x DLL Directory in DWSim>General Settings>Other

Now, by running the script with the line "gas=..." hidden, the script is computed successfully. Thus, I assume that cantera is successfully imported. When I run the script including the line "gas=...", an additional DWSim interface opens (the "Welcome to DWSim" interface). Afterwards, the script is processed for quite long time until DWSim crashes.

Do you have an idea about what happens? Why a new Dwsim interface opens? Could you please help me in solving this bug?

Thank you so much,
Pietro

[Pietro]

I found a solution: I substituted ChemDetailed.cti with ChemDetailed.yaml and it works. But couldn't say why...

[Pietro]

But unfortunately I face another issue: I am still trying to model a unit operation using Python.Net as interpreter. When I run the lines

import System
oms1.Phases[0].Properties.temperature = System.NullableSystem.Double

I get the error:

2   08/01/2022 10:49:31 Error   module 'System' has no attribute 'Nullable'

File "<string>", line 5, in <module>
at Python.Runtime.PythonException.ThrowLastAsClrException()
at Python.Runtime.PythonException.ThrowIfIsNull(BorrowedReference ob)
at Python.Runtime.PythonEngine.RunString(String code, BorrowedReference globals, BorrowedReference locals, RunFlagType flag)
at Python.Runtime.PythonEngine.Exec(String code, Nullable1 globals, Nullable1 locals)
at DWSIM.UnitOperations.UnitOperations.CustomUO.Calculate(Object args) in C:\Users\Daniel\source\repos\DanWBR\dwsim6\DWSIM.UnitOperations\UnitOperations\PythonScriptUO.vb:line 347 </module></string>

If I set IronPython as Interpreter I don't get this error.  For now,  I can't find any explaination...
I use DWSIm version 6.7 and set C:\Users\User1l\Desktop\WPy64-3980\python-3.9.8.amd64 as Python 3.x DLL Directory in DWSim>General Settings>Other

Any help is very appreciated....Thank you so much!!!

[Pietro]

Hi guys,

I realized a typing error in the previous post. The code I run is:

import System
oms1.Phases[0].Properties.temperature = System.Nullable [ System.Double ] (T)

I also installed in my PC the version 3.6.8 of the portable Python (https://sourceforge.net/projects/winpython/files/WinPython_3.6/3.6.8.0/) and set it in the as Python 3.x DLL Directory in DWSim>General Settings>Other. Still I get the error:

module 'System' has no attribute 'Nullable'

At this point, for now I don't have a clue on how to go on. Any help is very deeply appreciated!

By the way, what is "System" in DWSim?

Thank you so much again for your support!!!

[Daniel Medeiros]

To set the temperature, you can now use this command:

oms1.SetTemperature(T)

[Pietro]

Thank you so much for the reply! Can I use the command
oms1.SetTemperature(T) with Python.NET as python Execution Engine?

I run:

T = ims1.Phases[0].Properties.temperature
oms1.Phases[0].Properties.temperature = oms1.SetTemperature(T)

And I still get the error

Error must be real number, not str
File "<string>", line 67, in <module>
at Python.Runtime.PythonException.ThrowLastAsClrException()
at Python.Runtime.PythonException.ThrowIfIsNull(BorrowedReference ob)
at Python.Runtime.PythonEngine.RunString(String code, BorrowedReference globals, BorrowedReference locals, RunFlagType flag)
at Python.Runtime.PythonEngine.Exec(String code, Nullable1 globals, Nullable1 locals)
at DWSIM.UnitOperations.UnitOperations.CustomUO.Calculate(Object args) in C:\Users\Daniel\source\repos\DanWBR\dwsim6\DWSIM.UnitOperations\UnitOperations\PythonScriptUO.vb:line 347 + Info</module></string>

Must T be a double?

[Pietro]

Ok, I found the problem.
oms1.Phases[0].Properties.temperature = oms1.SetTemperature(T)
is simply wrong.
I just have to run
oms1.SetTemperature(T)
as suggested.

Thank you so much for the support! And sorry for the spam...

[Pietro]

Ok, I found the problem.
oms1.Phases[0].Properties.temperature = oms1.SetTemperature(T)
is simply wrong.
I just have to run
oms1.SetTemperature(T)
as suggested.

Thank you so much for the support! And sorry for the spam...

[Nik]

Hi everyone,
I am new to DWSIM and I am trying to set a model based on Cantera Interop.
I am using python 3.9 (portable version as suggested by Daniel) and have checked already that Cantera is installed and functioning. All good till here.

The issue I have is similar to what Pietro reported here above a couple of years back:

when running:
"oms1.Phases[0].Compounds['Methane'].MoleFraction = System.NullableSystem.Double"

I get an error message saying:
"Error in 'Python.Runtime': module 'System' has no attribute 'Nullable'"

I have checked directly in python and "System" works well.
I have also set the new way of passing macro variables like T and P usign setTemperature, which work well.

I am stucking when setting the composition as I am not able to find neither a solution to "System" nor an alternative as for SetTemperature or SetPressure.

Any suggestion?

Thanks a lot
Nik

[Daniel Medeiros]

try using

oms1.SetOverallCompoundMolarFlow('Methane', methane_molar_flow)

[Nik]

Thanks, Daniel.
I got another error saying "an integer is required".
I can go around the issue by rounding the number but that would not be numerically correct. Something I should do to troubleshoot the code?

Set the properties on the Outlet Material Stream connected to Port 1(oms1)

oms1.Clear()

Set operative conditions

oms1.SetTemperature(T)
oms1.SetPressure(P)
oms1.SetMassFlow(WF)

Read mass fractions from cantera mixture. See the original 'gri30.yaml' file to inspect compound indexes in the array

outYCH4 = gas1.Y[13]
outYH2O = gas1.Y[5]
outYCO = gas1.Y[14]
outYCO2 = gas1.Y[15]
outYH2 = gas1.Y[0]
outYO2 = gas1.Y[3]

Calculate mass fractions

outWFCH4 = WFoutYCH4
outWFH2O = WFoutYH2O
outWFCO = WFoutYCO
outWFCO2 = WFoutYCO2
outWFH2 = WFoutYH2
outWFO2 = WFoutYO2

Set compound mass flow

oms1.SetOverallCompoundMassFlow('Methane', round(outWFCH4))
oms1.SetOverallCompoundMassFlow('Water', round(outWFH2O))
oms1.SetOverallCompoundMassFlow('Carbon monoxide', round(outWFCO))
oms1.SetOverallCompoundMassFlow('Carbon dioxide', round(outWFCO2))
oms1.SetOverallCompoundMassFlow('Hydrogen', round(outWFH2))
oms1.SetOverallCompoundMassFlow('Oxygen', round(outWFO2))

In the history log I got:
This error was raised during the calculation of a Unit Operation or Material Stream.

System.Exception: No method matches given arguments for MaterialStream.SetOverallCompoundMolarFlow: (<class 'str'="">, <class 'numpy.float64'="">) ......</class></class>

[Daniel Medeiros]

maybe it is because this function has two variations and python only sees the one where the first argument is the compound index. also be careful to not misunderstand mass/molar and flow/fraction.

[Nik]

Thanks, Daniel.
I will correct the calculations above to make sure mass and molar balances are respected.

About the compound index, I guess it is the one defined in DWSIM: how can I get to know compound indexes? is there any function I could call?

Anyhow, the note on the function says "String". see attached screenshot

Thanks a lot

[Nik]

Hi again,
I have tried with creating a project from scratch without involving Cantera and the function i.e. oms1.SetOverallCompoundMassFlow('Methane',outCH4) works as expected.

Is there a way to print outputs from a Python script for debugging?

thanks a lot

[Nik]

Solved using "float" in the Set function:
oms1.SetOverallCompoundMassFlow('Methane',float(outWFCH4))