Learning Forum

[Akshayg]

I am simulating for simple combustion of air-fuel mixture at different temperatures and equivalence ratios. The primary fuels that I’m using are- m-Xylene and n-Dodecane

 

1. JSRPFR model problem

In this model I have a Perfectly stirred reactor followed by two Plug flow reactors. The error that occurs is-

FATAL ERROR: SINGULAR JACOBIAN MATRIX"  and "TWOPNT: FAILURE. NO SOLUTION WAS FOUND. PSR FATAL ERROR:Twopnt reports no success in solving the problem"

The same problem is running well for equivalence ratios less than 2. This means there is no problem in the mechanism and set up of the problem. I want to use equivalence ratios more than 2. From what I have read, it seems changing initial guesses can help relieve the singular jacobian matrix error. Can you please guide how to do so or help me troubleshoot the problem? Can you please give tips about what might be the problem and what might be the path to solution?

 

2. Burner stabilized flame-

Again, there’s nothing complicated here. I am using the same fuel-air combustion problem. The SERDP mechanism runs well when I input n-Dodecane fuel. But, when I input m-Xylene fuel it gives error- " ERROR: FAILURE. NO SOLUTION WAS FOUND. ERROR: Particle solver failed".

 

3. Closed homogeneous reactor

Here the case is even simpler. I am trying to simulate combustion of the same fuels in closed homogeneous reactor model. The error this gives here is- WARNING: Growth rate is negative, but an etching keyword was not input for this phase. This growth rate is regarding soot.

 

[wcao]

 Hi,

I have a couple of questions regarding your issues:

1. JSRPFR model problem:

I wonder what kind of fuel are you using? What is the residence time you set? Have you checked the flammability limit of the fuel or do you have some physical test data under the same conditions (equivalence ratio etc.)? 

2. Burner stabilized flame:

Is it possible to share the SERDP mechanism?

3. Closed homogeneous reactor

Does the warning come only under certain conditions or it is always there?

 

Please kindly let me know. Thank you.

Best,

Weiyu

[Akshayg]

Hello,

 

1. I am using n-Dodecane and m-Xylene fuels. I have tried 3 different residence times- 0.01 sec, 0.05 sec, 0.001 sec for 1600 K temperature and 1 atm pressure. I don't have the physical test data for the flammability limit.

2. I am sending the link for the mechanism-

https://drive.google.com/file/d/1XBWX7dHQqxc7pAGQu8h0uncQVsshKf04/view?usp=sharing

Please request access with your email.

3. No, the warning comes only sometimes for specific random cases.

Thank you!

[wcao]

 Hi Akshayg,

Thank you for your reply. I am sorry for replying late. I have tried several cases on my side but yet able to reproduce your issues. Can you please share the files with me? I will send you a secure file transfer link where you can drop your files. Thank you.

Best regards,

Weiyu

[Akshayg]

Hello,

Please see the attached files in the dropbox reply.

Thanks!

Akshay

[wcao]

Hi Akshay,

Sorry for replying late. I have checked through the three case you sent in 2019R3. While I can not reproduce the error in the JSRPFR model problem and the Closed homogeneous reactor, I do see the particle solver issue for the Burner stabilized flame. It might be some issue with the soot solver that our developer is working on. Please allow us some more time to figure it out.

I am not sure which version of chemkin you are using but could you please try the other two models in the latest release? Thank you.

Regards,

Weiyu