Learning Forum

[ed12s6w]

Has anyone been successful in getting the Chemkin DI engine model to run with engine specifications that are different to the tutorial? When I have changed the engine specifications to match the engine I want to model, I repeatedly get the following error message.

Error: BAD AIR ZONE VARIABLE VALUE and Error: LOW AIR ZONE TEMPERATURE

Trying the suggested fixes does not seem to work. Any hints or ways to get it to work would be greatly appreciated!!

  *** Please try the following:
       1. increase the min. air zone mass
       2. decrease the air entrainment coeffs
       3. decrease the max solver time step size

[Judy Cooper]

Hi:

 

Your question is a bit unclear as to exactly what changes were made to the setup, but the tutorial runs quite quickly as it is, so I am curious about the purpose of the changes? Most of the tutorials were created with older versions of Chemkin and so may not work optimally in newer versions where some of the numerics have changed.

Below are the current default settings for DI engine.  If a project has been updated to a current version of Chemkin, these sometimes may work better than the original settings.  The solver absolute tolerance can occasionally be increased to 1.0e-08 to allow convergence; this is still adequate to capture species concentrations.

 

[ed12s6w]

Hi There,

I am trying to model a specific diesel engine and not the one used in the tutorial. When I have changed the engine specification to match that of the engine I want to model from the tutorial values I get the error messages shown in my original post. The tutorials run perfectly fine with the exisiting engine specification, but when I change the cylinder bore and stroke to that of a different engine it crashes, even with using the disel 1 component mechanism used in the tutorial. When I have changed the other engine parameters such as speed and compression ratio there has been no trouble, but when I want to use a different engine geometry there are these failures. 

I always adjust the parcel gas volume to account for the change in the cylinder volume but this has not seemed to helped either.

Any help would be great.

Thanks

[Judy Cooper]

How does the run fail and during what part of the cycle?  Is the run failing with the  message shown below ?

BAD AIR ZONE VARIABLE VALUE and Error: LOW AIR ZONE TEMPERATURE

[ed12s6w]

It usually is failing upon the point of the fuel injection, where I have defined the crank angle at which the fuel should be injected. And yes it is failing with those error messages.

[ed12s6w]

Is there any further update on a potential solution for these errors with the DI engine model? Is there anyway around the error messages of BAD AIR ZONE VARIABLE VALUE and Error: LOW AIR ZONE TEMPERATURE?