Billowing Hot Air: A Brief Analysis of Fluid Dynamics in Exhaust Systems

[BigTyla]

So perhaps the expansion is simply there to allow for a larger filter and reduce pressure drop

I KNEW there had to be something inside that thing!

[AdamVR4]

I miss being spoon fed information like this. Bravo, sir.

[CoopKill]

Awesome stuff, though some is over my head without some serious reading.

Thanks guys!

[j2k4]

Tyler - would it be fair to call the common chamber linking your laminar to your turbulent flows a buffer, considering it's force-fed?

Sized with no consideration apart from providing In = Out?

[BigTyla]

In the example above, it appears the true reason for it's shape is to house the filter, nothing more. The long pipe is kind of like a duct to receive colder ambient air and feed it to the intake.

[mb3000]

In the example above, it appears the true reason for it's shape is to house the filter, nothing more. The long pipe is kind of like a duct to receive colder ambient air and feed it to the intake.

But now you've got me wondering.

[BigTyla]

I did a little more thinking of exhaust manifold optimization over the past couple of weeks and it occured to me that the cheapest solution (in terms of testing) would be to utilize some sort of genetic algorithm to find the best design for a particular engine. After a two-minute Google search, I found my diamond:

http://www.ifs.tohoku.ac.jp/edge/lib...(kanazaki).pdf

As you can see, this is not a simple problem by any means, but it is at least achievable with no laboratory testing, which means less money spent on labor and materials for empirical trial-and-error runs. It would require some cycling simulation of our engine which would be difficult, but what part of this wouldn't be?!

Also, note the goal of the GA stated in the paper:

The objective functions considered here are to maximize the gas temperature at the end of the exhaust pipe at 1,500 rpm and to maximize the charging efficiency at 6,000 rpm, where the charging efficiency indicates the engine power.

Just wanted to share that part to try to hammer this home. More heat is better!

[MR2]

Does not seem to cover info on Turbo's and how they effect exhaust design?

[BigTyla]

Does not seem to cover info on Turbo's and how they effect exhaust design?

Nope.

[green-lantern]

How did I miss this thread?! Awesome write-up. Thank you, Tyler, for a superb addition to the knowledge base.

Jeremy

It appears I did too, very good info.