Will a helical surface improve airflow?

[uGlay]

I am sorry if this is the wrong forum but i did not want to put this in the mechanical forum because this has to do with wind speed and displacement and not so much the mechanical aspect of the part.

I am designing a throttle body spacer for a 4 cylinder engine. This part is 1" thick aluminum and will be placed between the throttle body and plenum. The inside diameter of the spacer is 2.5"

Now, there is a lot of controversy regarding whether a helical surface would be better than a smooth polished surface. So my question is, will a helical surface create a fast flowing vortex as opposed to a smooth surface?

Or am i looking at a negligible difference and its not worth pursuing.

Here is an example of what i am looking to make.

http://premium1.uploadit.org/telegon80//Dsc02403.jpg

 

[patprimmer]

No.

Think about the laws of conservation of energy.

There is a specific amount of energy available to draw air into the plenum. This energy can accelerate a given mass of air to a given velocity. If some of that energy is diverted to rotational velocity, it must come from reduced mass or reduced velocity of the air in the other plane.

A bigger cross section will allow a larger mass of air as it will require less acceleration as the airspeed will be lower

Regards

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[uGlay]

that is interesting. So besides from making the air spin, a helical surface also slows the air down. Considering the air stream gets broken down into 4 streams leading to each intake runner, then there isn't really a point to making the air flow in a vortex.

 

[BiPolarMoment]

I think people used this to some effect with carburetors to allegedly improve fuel mixture with the intake air. However, it seems more intuitive to me in a carb'd setup that if you aren't getting a good mixture to induce (more)turbulence as it enters the cylinder, not spin it. Someone more familiar with this might be able to clarify. (I'd like to know for certain as well)

In either case, I cannot see any benefit in your application--especially not for flow rate.

I think you may have been mislead by those commercials for a similar product that claims the air would actually flow faster. The example they present, with the 2-liter bottles (one filled with air, one water), however, is not an accurate model of what is happening in this case. In the bottle example there is 2-way flow where the displaced air in the second bottle (and the vacuum created in the top bottle by the exiting water) is trying to equalize and the air needs to backflow through the water to do so. In your case, short of the pressure wave caused by the intake valve closing, there is nothing that is trying fight its way back through the incoming air--and the vacuum is on the engine side of the throttle body, sucking the air in. Of course, maybe that's not where you got this idea--but I've heard it come up before.

In conclusion, like the other poster implied--spend the money on a bigger throttle body if you want to see better flow.

 

[patprimmer]

In my opinion, spinning air under a carburettor might help break up fuel droplets, but as the liquid drops are many times heavier than air, it also throws them outward toward the manifold walls where they collect and eventually come back off as vapour or large drops or a mixture of each, but at a different time to required, upsetting mixture consistency and distribution.

Expanding from something I read in a recent post on the subject of swirl, to better disperse and atomise fuel air, do it in the cylinder with many small eddies so the fuel throws back and forward between them, not to an outside wall like the cylinder bore.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Kohut]

Maybe I can shed a little light on the subject. In the sixty's one often polished the inlets and experienced an increase in bhp. Currently, auto manufacturers are creating turbulence within the cylinder to maximize the fuel-air mixture. The issue is getting as much in the cylinder as quickly as possible, and getting the best mixture. Mind you the grooves within the new cylinders are "engineered" and machined, where as most DIY carb jobs are not. In my opinion, unless you devote considerable time and money to determine the best solution, the effects will be negligible. I'd be interested to know the outcome.

 

[Rob45]

There's a simple answer to this question:

No.

 

[OP800]

Further, if the point the sweril is introduced is to far away from the inlet valve any effect would be all but lost by the time the air gets to the valve.
In fuel injection, the fuel is introduced near the valve at about the last part of the total tract and would see little effect by that point.
In fuel injection engines the inlet tract length between the throttle body and the inlet valve is usually quite a distance to use tuning resonances for enhanced low end torque from ram tuning effects the cylinder inherently can produce.
Trying to make it sweril and keeping it in that mode thruout all the turns and direction changes would be quite a trick, in addition.