Intake manifold CFD simulation

[Dan Radulescu]

Hello dear colleagues,

My name is Dan and I am a member of the BlueStraemline FSAE racing team from University of Transilvania, Romania. After working on last year's transmission system, It is now my responsibility to design the intake and exhaust system for this year's car. This is all new for me and I want to do a good job.

My plan is to model a time based or crank angle based pressure function for a complete cycle and then use SolidWorks flow simulation or other CFD software to make a CFD simulation to test the design.
I allready did some concepts of the plenum and runners and used the following instructions for it : http://www.youtube.com/watch?v=3C-YG2olxFw

I want to get to do something like this -> http://www.youtube.com/watch?v=vi8I4...q1hF_yUzy3WhtV
however I cannot seem to figure it out.

As initial data I have the engine specifications such as: bore, stroke, crank radius, connecting rod length, valves opening and closing related to crank angle.
With this information I made calculated the displacement volume in relation with the crank angle for a complete cycle of 720 deg.

My goal is to have a table of data with the pressure variation in time during the full cycle of 720 deg at each of the outlets of the intake manifold so that I can begin my CFD study
The current model of the intake system is not supercharged and I intend to make good use of Helmholtz resonance induction method.

I have found interesting materials and P-V diagrams but none of them include the calculation method...I might not see the obvious or I am missing something.

Please give me some tips/directions to materials.

Thank you for your attention and help.
Cheers!

[Screaming V8]

Dan,

To be honest, I would not spend too much time doing the transient simulation in Solidworks. The Solidworks flow sim is not known to give the best results which is why I (as well as others) do not put too much trust in it. Doing some back to back validation using Solidworks flow and physical testing showed that it is quite a bit off compared to Autodesk CFD or Ansys. Since this is new to you, I would spend your time on designing a good restrictor (there is a lot of papers and books that describe this) as well as spend time on the Helmholtz resonance tuning. The Helmholtz calculations will get you close, but there are some assumptions in the calculations that can make them a bit off to what is actually happening in the manifold. You can validate physically on the dyno. Keep in mind, the intake and exhaust should be matched to maximize the benefit. A good 1D simulation program will also get you really close as long as you spend the time to get everything in your model correct. To get proper cylinder balance you can do some steady state CFD and make sure each cylinder is getting good flow. A lot of teams try simulate as much as they can within a certain time frame to get baseline constraints of lengths/volumes ect, then validate everything physically. This is a good way to get a good design implemented in the short time frame that we have.

If you have any other questions feel free to PM me. If you search the forums there are also some other good threads on intake design, as well as recommendations of textbooks to read.

[Dan Radulescu]

Thank you for the tips!