[PRJHA]

Hi,
I am trying to see effect on Tumble for closed cycle combustion simulation.
Does Converge provide any parameter to change tumble inside cylinder.
Where can I find explanation of that?

Thank you
Prabhat

[MFGT]

Hi Prabhat,

Tumble definition is explained in the output file reference, chapter 22, for dynamic.out file. The tumble ratio in x or y direction is defined as the ratio of the angular speed of the flowabout the center of mass in the x or y direction, omega_1 or omega_2 to the angular speed of the crankshaft, omega_crankshaft, as shown in Equation 22.3 of the latest release in the Theory Manuel.

There you have the definition, however its not exactly clear what you want to do? What do you mean by "change tumble inside cylinder"? Its affected by the geometry shape mainly and valve lift i would say. Are we talking about GDI/PFI?

Tobias

[PRJHA]

Hello MGFT,
Thank you for your reply.
I am not simulating intake valve lift profile. I am only simulating for closed cycle. I want to include proper value of tumble inside the cylinder due to affect of geometry effect.

Thank you
Prabhat

[PRJHA]

and I am simulating both cases GDI and PFI.

[MFGT]

Sorry, i still dont get it.
Does your simulation includes the gas exchange (i assume so, otherwise PFI wouldn't work). Then there is nothing you have to do, there is no need to initialize a tumble as it results from the gas exchange. I prefer running from BDC -540 to BDC +180 for a complete cycle.

If you want to increase your tumble you would need to change the port geometry.

[PRJHA]

Hello Tobias,

Thank you again for your reply.
I will try to explain in better way this time
I am doing sector mesh for dual fuel with port injection of gasoline and direct injection of diesel.
So my mesh just include piston, head and liner. It doesn't include valve.
I am only able to do from IVC to EVO due to limitation of computational resources. I wish i can do full cycle simulation for complete engine geometry.
With IVC to EVO simulation is there any parameter i can change to affect my tumble ratio inside my cylinder.
I hope i am clear this time.
and thank you again for taking time to answer my post.

Best Regards
Prabhat

[MFGT]

Okay, so you got premixed gasoline (ic8h18?) and inject diesel, and all as an engine sector with just 3 boundaries.

In these kind of cases, its usually only swirl that can be initialized with initialize.in.
However, in your case i would propably try to go for a full geometry. You could simulate from IVO to IVC only and map the file to you sector geometry.
When mapping, you could modify (scale) charge motion related parameters like velocity and tke. Have a look at the example cases for mesh settings. You might also get away with running a bit coarser.

What are your CPU resources?

[PRJHA]

Thank you , I will try to do that.