SSR and Coanda effect

[jfholm]

Good article on coanda effect

I did a video today to show how the Coanda effect works. It is interesting and can be applied to our cylinder heads.

John

[jfholm]

any thoughts on this?

[bruce]

You need to stay out of the kitchen!!

Do we all think like this? ???

[jfholm]

My wife is getting suspicious about "too much head stuff" going on in the kitchen.

[blaktopr]

Thats funny cause I was watching the effects water had over the base of a wine glass. Just like an intake valve.

[49-1183904562]

Chris,

Did you crack the stem off the Glass?

Or accidently drop it?

John you itchin to have to do the dishes!.

Rick

I have a good video on this also i will try to find and post



Edited By 1960FL on 1242086181

[blaktopr]

[Flash]

Thanks John.


What i found interesting was, the short radius attracted more water then the large.........Hmm

I always was told that you keep the radius as large as possable..............?

[jfholm]

A good way to tell if you need to work on the SSR is if the flow stalls or goes backwards at the convergence lift point. That is 25% of the valve diameter. So if you had a 2.00" intake valve the convergence lift would then be .500" - if at that point the flow drops then you need to look at the SSR

On mine I did have to lay it back and make the radius bigger. When I did that I went from 221 cfm to 263 cfm - makes a big difference.

Video was for things that make you go "hmmm..."

John

[Flash]

[jfholm]

here is a drawing I have posted before on the forum on how I modified my SSR on my Dart Iron Eagle heads. Red lines are the new port profile.
John

[slracer]

[color=#000000]John, I have been reading this post and trying to figure out how the Coanda effect would work here. Try to lay some flow lines on your drawing and see if you can. If you look at the effect in your video, a tangential flow does almost nothing, but an intersecting flow attaches and turns. Unless you add a bump or your upstream flow is really messed up, flow to the SSR will be tangential, therefore creating little help turning the corner.

As you know, I was an aerospace engineer before I retired. In the late 60's and early 70's I worked on a program which became the AMST. Boeing had an AMST version called the YC-14 which used upper surface blowing (USB) to create the Coanda effect for improved low speed lift. They built and flew the vehicle quite successfully (against the McDonnell-Douglas YC-15, which later became the C-17 being built today). In their testing prior to build, Boeing discovered this problem of small effect with tangential flow. The quote below is from Wikipedia about their wind tunnel model testing. The term "flow separation" means the flow didn't follow the flaps (it didn't turn the corner on the SSR).



"Two major problems were found and corrected during testing. The first was a problem with air circulating around the wing when operating at low speeds close to the ground, which had a serious effect on the spreading of the jet flow though the nozzle. This led to flow separation near the flap, and a decrease in effectiveness of the USB system. In response, Boeing added a series of vortex generators on the upper surface of the wing, which retracted when the flap was raised above 30

[49-1183904562]

[color=#000000]How about a twist on this theory, what if we did not look at the Coanda effect as to the port itself,

[slracer]

Interesting thought Rick, but I think that the result might be the reverse of what you want. In the attached pic, I have drawn some "estimated" flow lines (solid lines). The flow is still tangential to the SSR wall so the Coanda effect probably won't benefit. Conversely, if the flow does separate from the SSR wall, it will intersect the long wall and MIGHT induce some coanda on that side of the valve (which is usually carrying more flow than desired already).

My comment about using the valve guide is illustrated using the dotted flow line. Shaping the valve guide to redirect part of the flow back into the SSR (and getting it to reattach!) COULD provide more flow out that side of the valve resulting in better distribution, a more even mixture in the chamber, better burn and more power. It could also create a mess that loses everything. Trying to visualize 3D flow in a tube is for computers, not mere mortals such as ME! It would be an "interesting" test program, but would have to be dynoed to determine if the "improved" flow didn't have some other effect on mixture and/or distribution which cancelled any gains! Any takers? Again, JMO. -- Doug

[200cfm]

When I check the SSR air speeds they are always much higher as the air falls over the turn in comparison to the speeds on the long side. Would the air speed measurement indicate the air is "sticking" to the SSR or "coanda effect"? And if air sticks to turns, then it could also be sticking to the turns on the backside of the valve head itself, especially if the valve has a tulip backside. Then you would have two turns that are producing "coanda effect" in a limited throat area. Can air ever go so fast that it can unstick the coanda effect on say the backside of a spoon? Then there is the behavior of the fuel which is liquid and not in a gas state. Interesting topic.