CFD/CAD/Thread

General engine tech -- Drag Racing to Circle Track

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Re: CFD/CAD/Thread

Post by SpeierRacingHeads »

I just reread the rules. No welding of any kind in the PR area. So if it doesn't fit in the casting, it's a no go.
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Re: CFD/CAD/Thread

Post by hoffman900 »

To make this design work, a slightly different design is needed for left/right inner/outer are required (4 different ports).
A manifold with perpendicular runners would make that unnecessary and probably improve performance.
Nice, that’s what I expected.
-Bob
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Re: CFD/CAD/Thread

Post by SchmidtMotorWorks »

SpeierRacingHeads wrote: Sat May 20, 2023 7:16 pm I just reread the rules. No welding of any kind in the PR area. So if it doesn't fit in the casting, it's a no go.
Hmmm, what is the max width that can be done?
We will just have to do the best we can, probably lower the floor?
What is the lowest and highest the intake port opening could be measuring from the deck?
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Re: CFD/CAD/Thread

Post by SpeierRacingHeads »

SchmidtMotorWorks wrote: Sat May 20, 2023 8:50 pm
SpeierRacingHeads wrote: Sat May 20, 2023 7:16 pm I just reread the rules. No welding of any kind in the PR area. So if it doesn't fit in the casting, it's a no go.
Hmmm, what is the max width that can be done?
We will just have to do the best we can, probably lower the floor?
What is the lowest and highest the intake port opening could be measuring from the deck?
I will get all that data in the AM. Away from the house.

But yes lowering the floor and even moving over the common wall.
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Re: CFD/CAD/Thread

Post by BLSTIC »

That's some decent long side improvement in the pressure and velocity graphs. There's no dead spot any more. I need to get back to a pc to blow these up properly.

Do you have an easy way to show an overlay of before and after in assorted views?

Thanks btw, this is some great learning, and even if we can't cfd our own port it allows us to visualise flow just that little bit better with good examples like this
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Re: CFD/CAD/Thread

Post by Rick! »

SchmidtMotorWorks wrote: Sat May 20, 2023 4:06 pm Here are some 3D JT files for the images above
The JT with arrows is too large to upload.
If anyone is very interested in that, I can make a shared Google drive (requires that you have a Google account)

streamlines.zip
Is it possible to create the JT's with a CSYS created on the valve face and aligned with the valve stem and bisecting the port entrance?
It would help when creating a cutting plane in the viewer to be oriented with a roughly centered reference.
Default CSYS.png
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Re: CFD/CAD/Thread

Post by SpeierRacingHeads »

SchmidtMotorWorks wrote: Sat May 20, 2023 8:50 pm
SpeierRacingHeads wrote: Sat May 20, 2023 7:16 pm I just reread the rules. No welding of any kind in the PR area. So if it doesn't fit in the casting, it's a no go.
Hmmm, what is the max width that can be done?
We will just have to do the best we can, probably lower the floor?
What is the lowest and highest the intake port opening could be measuring from the deck?
Right now the SSR is all metal and .900 off deck.
The port opening is .525 off deck and .275 is epoxy.
With the pinch at 1.120 wide, I have bubbled the PR relief.
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Re: CFD/CAD/Thread

Post by SchmidtMotorWorks »

Rick! wrote: Sun May 21, 2023 10:47 am Is it possible to create the JT's with a CSYS created on the valve face and aligned with the valve stem and bisecting the port entrance?
It would help when creating a cutting plane in the viewer to be oriented with a roughly centered reference.
Default CSYS.png
I can look into it
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Re: CFD/CAD/Thread

Post by SchmidtMotorWorks »

SpeierRacingHeads wrote: Sun May 21, 2023 12:05 pm Right now the SSR is all metal and .900 off deck.
The port opening is .525 off deck and .275 is epoxy.
With the pinch at 1.120 wide, I have bubbled the PR relief.
Is there any material left to raise the roof?
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Re: CFD/CAD/Thread

Post by SpeierRacingHeads »

SchmidtMotorWorks wrote: Sun May 21, 2023 12:46 pm
SpeierRacingHeads wrote: Sun May 21, 2023 12:05 pm Right now the SSR is all metal and .900 off deck.
The port opening is .525 off deck and .275 is epoxy.
With the pinch at 1.120 wide, I have bubbled the PR relief.
Is there any material left to raise the roof?
I'm .225 from the valve cover rail and the same inside the valve cover area.
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Re: CFD/CAD/Thread

Post by steve cowan »

Good thread and appreciate the time and effort but the casting for the rules and application must be at its limits.
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Re: CFD/CAD/Thread

Post by SchmidtMotorWorks »

This set is conforming the port to the rule that the pushrod hole cannot be modified.
The floor on the inlet is moved down to 0.3 from the deck
The corner radii are 0.375.
The volume is the same as the scanned port.
compare_side 1.png
compare_side 2.png
compare_top 1.png
areas.png
velocity long section.png
voticity long section.png
section_streamlines_velocity.png
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Re: CFD/CAD/Thread

Post by BLSTIC »

I'm gonna bring on something I've seen a couple of times on here that's very much related.

Can you do exhaust flow?

This cfd image of presumably a nascar engine with what appears to be a nearly perfect curve in the exhaust is revealing at worst and revolutionary at best.
exhaustflow.jpg

It's just... If this is representative of reality I can't think of a port and exhaust layout that I've seen that would have full utilisation of the port or even the first few inches of primary. (Except maybe an extremely steep port on an inline engine)

I'm not sure a flow bench would show this at all?
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Re: CFD/CAD/Thread

Post by SchmidtMotorWorks »

BLSTIC wrote: Thu May 25, 2023 6:28 am I'm gonna bring on something I've seen a couple of times on here that's very much related.

Can you do exhaust flow?

This cfd image of presumably a nascar engine with what appears to be a nearly perfect curve in the exhaust is revealing at worst and revolutionary at best.

exhaustflow.jpg


It's just... If this is representative of reality I can't think of a port and exhaust layout that I've seen that would have full utilisation of the port or even the first few inches of primary. (Except maybe an extremely steep port on an inline engine)

I'm not sure a flow bench would show this at all?
Yes, I can do exhaust flow.

Do you have an example that you want to do?
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Re: CFD/CAD/Thread

Post by hoffman900 »

BLSTIC wrote: Thu May 25, 2023 6:28 am I'm gonna bring on something I've seen a couple of times on here that's very much related.

Can you do exhaust flow?

This cfd image of presumably a nascar engine with what appears to be a nearly perfect curve in the exhaust is revealing at worst and revolutionary at best.

exhaustflow.jpg


It's just... If this is representative of reality I can't think of a port and exhaust layout that I've seen that would have full utilisation of the port or even the first few inches of primary. (Except maybe an extremely steep port on an inline engine)

I'm not sure a flow bench would show this at all?

You can see port saturation change from blowdrown to the exhaust stroke. Also note the calculated exhaust mass to the left. It’s a brilliant way of looking at this.

What it highlights to me is that you can’t design an exhaust port without knowing the header geometry (dictated by chassis fitment, etc) and again, depending on how it’s packaged, you might need multiple port designs to maximize. Calvin hasn’t said the port part, but he’s said everything else for decades and no one listens to him still. I don’t know what cylinder number that is, but Cylinder 1 is going to look different than cylinder 4, due to the radii of the manifold to fit in the chassis, and that changes what is happening in the port, plus asymmetry in the intake manifold is going to effect how much mass is in the cylinder to begin with. The strokes are all connected to each other, everything effects everything.

As I said with the intake, the engine doesn’t see the manifolds and ports as separate entities. Where one begins and the other starts is inconsequential to the engine, it only knows the whole duct.

You wouldn’t see this on a flowbench, but the best thing a flowbench person can do (besides cranking it up as much as possible) is to probably have a dummy manifold for the first 8-12” that mirrors the bends being used in the chassis. They’ll likely see flow and velocity go all over the place, and it would also probably show why careful packaging with nice big bend radii is so important (and why crappy tight bend headers need to be bigger than ideal).

I know it doesn’t make sense from a business sense, but buying a head from here, a manifold from there, and an exhaust manifold from another place is absolutely the worst way to maximize a given package, and if you were serious about making the most power, you’d have to sell the intake manifold - head - header as an entirely developed unit.
-Bob
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