maz_side

Hey was just wondering if havin a spiral in the intake runners of a pp would have any affect on power ive just been reading a v8 mag where they use a spiral on carb spacer blocks to increase the velocity of the air fuel charge to enhance fuel atomization was just wondering wat u guys thought of the idea.

cheers jacob

Lynn E. Hanover

No comments on his?





This reminds me of the turbine magic (or whatever its called) that you push into the inlet pipe on your street car, and it is supposed to make your fuel mileage fantastic, (with no supporting data) and paid actors say it feels like I have 50 more HP because of this gizmo. It obviously makes the inlet air spin in the intake.



But..................



Is that what you want?



In some cases yes is the correct answer, but just a bit. You may have noticed the turbulators along the fins (the nonmoving part of the vertical tail) on large airliners. These things are called vortex generators, or VGs. The idea here is to upset a small bit of the airflow over a surface, by setting a little blade at a slight angle so that the air spins leaving the blade and that spinning means that air has been accelerated a bit, and that means that the spinning air has lower pressure relative to the general airflow in that area. So the higher pressure local air flow clamps this spinning flow tight against the surface,

making that surface more powerfull doing what it was designed to do, and that lets you design that piece to be smaller than without the turbulators. If it is smaller, it weighs less, has less drag and the plane goes faster and farther on less fuel. All of those things that airlines love to do.



So, a higher velocity has a lower pressure does it not?



Bernoulli's principal again. The curved surfaces on the aircraft look like 1/2 of a venturi in a carburetter.



In some special cases it is possible to improve on a design that otherwise is a failure buy installing a similar gizmo in some interesting locations. Such as inside intake manifolds. If you are getting flow separation along the inside radius of a turn a well placed sharp edged bur stood up with a punch can get flow reattached to a port wall.



When working on an intake manifold a special flow bench is used called a wet flow bench. Where the air being pulled through the bench has a very light oil mixed in to replicate the mass of a 14/1 FA ratio. So, in a case where a manifold might work well on a dry bench, it might have a runner go to hell on a wet bench. And also in real service. Where the mixture with much higher mass tends to stay along the outside of turns from centrifugal force.



In addition, this can be used to prevent separation (fuel droplets forming) in the mixture at lower velocities.

Clever size and location decisions can then allow for good mixture control at low speeds and monster flow at high speeds.



The turbulators (VGs) may not be obvious as those on the airplanes. (and may not be the same shape)



It may be a bit of mating flange left intruding past the edge of a gasket. It may be a portion of runner that has a slight bulge in it, seeming to intrude on the ID of the runner. It may be one or two punch marks in an odd location. It may be a 1/8" hole drilled on an inside radius. In some cases a small pin sticking out into the flow.



When you get Mr. Bernoulli to help you with things like this, there is a small charge for the service.



That will be in the form of slightly lower velocity in the whole system. When you extract some energy to cause this affect it appears as heat and reduced velocity. So you cannot design a really bad system and then patch it up with a bunch of VG fixes. It will remain a bad system. Good flow attachment (stays on the inside of turns) but poor velocity.



In your particular application, there is a problem. A sphear is ideal for the minimum surface area to enclose any particular volume. And so, the tube is the ideal shape for flow enclosed in the minimum surface area.



The round tube however, is not a good shape for conducting flow through a 90 degree turn. A soft "D" shape is the best for that. Large radius corners on the outside and smaller radius corners on the inside. Makes it look like a "D". If you look at a runner with a "D" shaped turn in it, you can imagine that the flat surface around the inside of the turn, it looks just a bit like the top surface of an airplane wing does it not?



Bernoulli again? Conspiracy?................you be the judge.



If you can maintain close to the same cross sectional area through the turn, you can maintain very close to the same velocity (loose very little) and that is a good thing. Look on Paul Yaws web page and find the picture with the "D" shaped port in it. Then memorize all of his tech articals.



So what the hell was the answer? I almost forgot.



If the device spins the whole mass of the flow in the runner, it removes too much energy and costs flow.

If it is a very small device as described above, upstream of the turn, being used to maintain flow attachment,

it might have some value.



Google velocity generators and read all about them.



www.yawpower.com





Lynn E. Hanover

j9fd3s

this stuff made a lot of sense when we went canoeing last summer. the water on the inside is almost stagnant, its where all the algae grows.

Lynn E. Hanover

So interesting that you noticed that.



Watching a narrow spot in a stream is exactly what started Bernoulli thinking about the rules

of flow dynamics.





Luckily, he was not burned as a witch.





Lynn E. Hanover

j9fd3s

i noticed if you dont paddle a bend in the river will actually spin you around, as the flow is faster on the outside....

Lynn E. Hanover

Also, there will be flow in the oposite direction on the inside of tight turns. The higher velocity on the outside of turns causes rapid erosion, that eats away the banks. Over time the tight turn becomes a large diameter low velocity turn.



That reverse flow on the inside can happen in a manifold too.



Take advantage of the flow bench plans and you can watch it happen by lowering a piece of string into a

test piece with a poorly designed turn in it. Where flow becomes detached like an airplane wing stalling, the detaced flow begines to spin, like the eddies in the stream.



Lynn E. Hanover

BLUE TII

Yes, I was also wondering if the lower drag type vortex generators (pattented, but look like NACA ducts) could be used on the discharge end of the more horizontal type P-port so that there is a more "focused" discharge into the chamber.



Could vortices on the outside of the port flow at the discharge end provide a simulated longer more aerodynamic discharge plume for better chamber fill/less reversion?



I know vortex generators on cars are used to lengthen the rears aerodynamic profile by keeping the flow attached to itself and work even better than a blunt "Cam" tails turbulence.



Also, I pointed my small volume runner/outlet streetport primaries to point accross the large secondaries and toward the rear of the chamber and began to wonder if I swirled the surface like valve faces are done if it would promote the focused discharge I was after.

Lynn E. Hanover

One use for the flow bench is that you can research things like that. I assume you are building a bench from the free plans I posted?



Anyway, clamp a 3" flex hose to the test hole. Just crack open the throttle ans connect the flex hose to a mock up of a Pport made with one housing, one iron and a slightly curved plastic plate to replicate the rotor.



Make a hole in the rotor to draw air through. The flow bench can actually detect improvements to the port in such a lashup. But in this case, the bench is just a low flow vacuum source. Also if one iron is replaced with a plexiglass sheet, you can watch inside a running engine in effect. Tape bits of thread everywhere in the runner and inside the housing. This works for side port irons also.



If possible have the intake and carb or TB installed.



You can get more exotic with some oily rags smoldering in a coffee can with a length of brake line soldered into the lid, a length of plastic line and another piece of brake line as a probe, you can introduce a smoke line into the flow and watch exactly what goes on at any rotor position. A few nail holes in the lid of the can and a method of closing them off will give you any amount of smoke you need.

Use modeling clay to make quick changes. The result will be:



It's damn hard to beat the factory Pport.





Lynn E. Hanover

BLUE TII

Thank you Mr. Hanover!





My girlfriend also suggested the smoke generator to see the affect of my primary ports and possible swirl. She suggested a jug with botom cut out and a hose on the spout. Put the jug in a basin of water, push it down, pull it up w/ hose on a smoke source and then push it down w/ hose in port. A good woman!



Haven't started building a flow bench yet; I am just getting into porting as I am ready to put my first rotary together. I started working off a shops rebuild for my ports and modded them to keep sideseals/apex seals happy- and discovered something.



When I mocked up the sidehousings with manifold, cardboard rotor and partial rotor housing. In certain rotor positions this porter's primary port would blow accross the 2ndary (using low pressure compressed air source) and put a low pressure on it pulling light confetti through the 2ndaries.



I ported my own primary and was able to get this affect through most of the rotor travel.



To do this I had to keep the top of the port at a sharp release angle (no bevel) to keep flow from fanning out toward the sidehousing- it would kill my sideseals this way (early opening port) so I put a small step to the outling of a large scissored port w/ the closing ramp.



I will start a thread w/ pics soon, I waited so long because I didn't want to be discouraged from trying it by others input (conventional wisdom).

inanimate_object

The thing I would like to know is why that woman is your girlfriend and not your wife!



Mark