[adam5743]

Tuan,
I have a calculations tool that I am familiarizing myself with and one application is pressure drop through piping. It is a very powerful tool, but I need information to run a calculation. I was thinking that if you could provide me with a resource or info on data specific to the integra, I could give an example of the difference in exit flow velocity, vol flow rate, pressure drop, etc. My thought is that I might be able to say that for example: MD's GSR has 'X' flow rate at the header collector. If he had 2 1/4 " piping all the way back, his velocity would be 'V'. If he had a 2 1/4 " cat w/ 2 3/8 catback piping the flow would be this much more. If he had 2 1/2" piping from collector, cat, complete exhaust he would get this much more flow. Im not sure how precise this would be to reality, but do you think that we could come up with something useful?
Thanks,
Adam

P.S. I need:
Exhaust flow rate

Typical exhaust gas composition (I really need generic estimates to get a density value. I'll assume exhaust gas composition remains constant w/both diameter piping).
What % of CO2 , NOx, SOx, etc?

Temperature
and pressure @the header collector or from UPstream of wherever we decide to start the calcs
Pipe length (we could assume straight or any # of any type of bends)

Comercial steel or commercial stainless steel

Outlet Pressure and Temp would be normal atmospheric conditions?

Sound Good to you?

 

[MichaelDelaney]

I don't have those numbers...maybe Dave might...contact him (SMSP)....

 

[SMSP]

I hope you have a very good understanding of thermodynamics and a Cray Super Computer at your disposal. This almost sounds like some of the problems we got back in school where we started to make assumptions that this function goes to zero and this one and yet another, then we could solve the question but we had an answer that made far too many assumptions in the first place. It was good for getting a BSME but not always for a real world answer.

I'll give you one variable of the overall equation and I think it would cause a lot of head aches by it self. Gas temperature as a funcion of distance from the head. This will need to take into account tubing material and thickness. Bend radii of the tubing since this effects mixing of the gases. Gases going down a straight tube are cooler nearer the tubing and the hottest gases are in the flow core. When you introduce a bend, it causes the gases to mix, thus moving some hotter gases towards the tubing. This is then repeated at every bend, merge and step. Let's also throw in vehicle speed, higher speed means more air flowing under the car and cooling the exhaust tubing.

My response is not meant as a flame of any sort but some things are better determined by the old method of trial and error. Because that gives you cold hard data.

The same could be said for the effect on a car's handling by changing tire pressures. No equation will give you the correct answer.

 

[adam5743]

Oh I definetly understand what youre saying. I want to totally exclude the header from the equation because of those reasons. When thinking about it, I figured it would be impossible to simulate the header, but I might have a shot at simulating the overall increased flow by using a high flow catalytic converter and catback piping. As far as temperature relating to distance from basically the heat source, I simply need an estimated temp at point A and B as well as pressure at points A and B. I didnt think anyone would have actually taken those measurements (why would anyone?), but I thought it would be worth a shot. This program does in fact have a huge thermodynamics package as well, if I had the data, I could imput gas composition to find a pretty exact gas density as well. The program is actually a proprietary development of the company Im co-oping with this fall - and I shudder to think how many digits were spent on the software. I just thought that hey, while I was familiarizing myself with the software before I got my projects, why not do this little thought experiment? Thanks for the answer though, I would love to see how you design exhaust systems. Although Im pretty week mechanically, Im a chem engr major, I love to learn new things.
Thanks for the thought!

 

[MichaelDelaney]

you guys ever seen the movie the Exorcist? The music for it is called Tubular Bells....that's all I could hear in the background when I read Dave's reply and my eyes glazed over...You can tell I'm not a mechanical engineer.

and I agree with empiricism...cold hard data from trial and error beats 9th order equations and Fourier transforms any day...

 

[adam5743]

shoot Tuan, youve got just as good an understanding of thermodynamics & fluid mechanics as someone that just took the classes + awesome technical mechanical skills not to mention plenty of practical experience. All engineering does is solve problems - you would be great at any field of engineering you took on as throughouly as honda tuning!
I on the other hand have about ZERO experience, my dad wasnt exactly the car tinkering type and I never got a lick of mechanical experience. I guess you could say just about everything Ive leared about cars has come from you Tuan!
BTW, I just took a Heat Transfer course and a reaction kinetics class as well. Neat stuff...

 

[adam5743]

Does anyone know if exhaust flow is laminar, turbulent, or transitional? Im sorry if Im too curious, but I found an EASY Reynolds# calculator here:
Reynolds # Calculator
and something that stuck out to me as a perfect example of an exhaust bottleneck:
Bernoulli's Equation

 

[hootb18]

adam just to let you know that the link to bernoulli's equation is not working. Tuan also mentioned the Bernoulli's effect or something like that ahwile back too.

 

[adam5743]

the link should work now... that site is really great for a wide range of fluid basics

 

[jonny-vtir]

Maybe I'm wrong but I was under the impression that the Bernoulli effect explained lift, i.e. aircraft wings (air moving over the top of the wing has farther to travel thereby creating a low pressure zone that "sucked" the wing upward) not flow dynamics. And Mike/Tuan, you sure as hell know more than most.

 

[adam5743]

I guess you didnt click on my link, here it is again:

URL=http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

Youre thinking of the Bernoulli "effect" which does deal with wings and flight. Slightly different application of the basic ideas - dont forget that air is a 'fluid'!

 

[MichaelDelaney]

...- dont forget that air is a 'fluid'!

and it's a compressible, elastic fluid at that!

 

[br1t1shguy]

Umm, I think I'm gonna go back to bolting stuff together, my heads hurtin.