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# CFD For Engines5

## CFD For Engines

(OP)
Hello all.

I have been on a quest to put more of my ideas into reality, and do it efficiently.

Right now, I need advice on choosing a CFD program to learn with. My main intents and purposes for this are to analyze engine intake systems on an engine, prove/illustrate concepts, then proceed with a more concise prototyping process. I don't need to analyze with precision. I simply want to observe an approximation of the flow so that I can possibly size the system close to the engine's demands.

Are there any high level programs that would allow me to make simple models? I have the system modeled in Autodesk inventor 2014, but I have not yet tried any CFD modeling. Let me know of any programs that stand out as the best CFD program for somebody who learns alone.

Thank you.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

### RE: CFD For Engines

You may qualify for a free single cylinder version of Lotus engine simulation, which claims to model the gas dynamics in the engine manifolds and enables the complex operating modes used in modern engines to be simulated.
http://www.lotuscars.com/engineering/engineering-s...

### RE: CFD For Engines

(OP)
Thanks for the link. That program has the option to change the cam profile, which is an integral part of what I'm doing. I'm going to look into it further

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

### RE: CFD For Engines

Hey Panther,

For those operating simulations you've noted above I think you need a mix of both simple CFD and the 1D simulation software.

Trying to run CFD on a full cylinder cycle with moving intake/exhaust valves is the stuff of PHD theses/heavy heavy calculations. YOu need things like those fancy 'stretching' meshes to take into account the changing flow domain size, or to remesh the domain at certain time-steps, etc - that kind of thing is incredibly computationally expensive.

You could try to use a mix of steady state, fixed domain simulations in 3D CFD (Solidworks) to get an estimate of valve flow coefficients at different amounts of lift, then use that data in the 1D simulation to see how that affects the whole engine cycle. I get the feeling this approach is the exact reason 1D software like GTpower exist - it's easier to take this approach than to try and model a full working cycle in 3D CFD like Solidworks and ANSYS. Probably better to try to start with the simplistic models and software as well, since the major CFD packages to do this kind of work are super expensive.

I'm certainly no expert in this (I haven't used the 1D softwares before but read about them where I can), but when I was doing CFD stuff at university some years ago, all of the trainings we got from ANSYS were showing just how 'cool' their moving/stretching mesh stuff was; but to get to the point where those models work and are accurate enough would be an incredible amount of

Good luck though!

### RE: CFD For Engines

I'd like to recommend the Yoshimura Dual Stack (http://shop.yoshimura-jp.com/files/img1/765-T2--06...), as an intake upgrade. I made my own, but that shows the concept.

From my own research & development using the idea, it is possible to have the shortest possible intake runner length, i.e. the metal head intake tract with just a nice rounded/ellipse feed lip. Then a dual or even triple stack beyond this. When the inner end of one is in the correct position relative to the outer of the one below, the gas pulse bridges the gap & thus it acts as a longer runner at low rpm & a shorter one at high rpm.

Adding these to my project bike, added 6hp at peak power rpm, with no other mods, due to the shortening of the intake tract, but with the dual stack, there were NO losses at lower RPM. The other advantage was the the torque curve that flattened & dropped after 8500rpm, stayed flat to 10,500rpm before falling more gradually. Thus there was a larger area under the torque curve !

### RE: CFD For Engines

(OP)
Thank you guys. I didn't know that about EAA memberships. I went to the EAA airventure airshow in Oshkosh, Wi last year. It was fascinating. I'm going to join that organization.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

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