Unable to get a certain mass of gas to enter a cosntant volume chamber, build up pressure then leave to go into the rest of the system.

[Yifeng Tang]

Could you please explain your question better so the community can better understand and help you?

Answer 1

[Pramil]

Assuming the value of variable "ptankVolume" to be "1", there are some changes required in your model in order to tackle the warnings you are getting.

1st Warning: "First solve for initial conditions failed to converge. Trying again with all high priorities relaxed to low".

• As the warning suggests, the solver is not able to find a solution for high priority values.
• This can be addressed by simply setting the priority of the target, in this case pressure in the "Volume Chamber" to low.

2nd Warning: "Solver was unable to reduce the step size without violating the minimum step size value of 3.55271E-14 for 1 consecutive times at time 10".

• This error is due to the sudden change in flow rate due to which the solver is not able to compute the values at timestep "10".
• Inorder to have a smooth transition and allow solver to be able to calculate the value, you can add the "Rate Limiter" block. This prevents the sudden change in value and hence get rid of the warning as well.

You can refer this documentation to know more about the "Rate Limiter" block:

https://www.mathworks.com/help/simulink/slref/ratelimiter.html

I have also attached the updated model for your reference, if you have any doubts, feel free to drop them in comments here.