purple82

No hating or flaming at all. Discussion is the source of good ideas. The only way to find the truth is to be skeptical and prove out the theory. There's nothing wrong with heated discussion as long as it doesn't get personal as blake is starting to do, unfortunately. I mention my degree for credibility and background. You've done the same many times blake. By the way, I'm 31 and have been working in ballistics and thermal solutions for 7 years. I can direct you to my SAE papers and thesis if you'd like to PM me.

I've asked a number of times and no one has shown a dyno sheet or acceleration improvement to me. That's all I'm looking for. I've done flow simulation out of curiosity and Yaw did experiments and neither shows flow improvement. Prove me wrong and I'll accept it.

Manntis

In the link you posted, you state that the water going around the inside of a riverbend (as an example of air going around a 90 degree bend - not accurately analogous) is high pressure, but you also to claim it's faster than the water going around the outside. You use the example of cars going around a bend, and how the inside one, covering less ground, goes 'faster' according to you because it emerges from the turn first.

The car example is flawed, as two cars going the same speed through such a bend would demonstrate that result. The car going around the outside covers a greater distance than the one on the inside - that is why the inside car emerges first. Furthermore, the car example fails to take into account that, in a river bend, water can only go as fast as the water in front of it. The water on the outside, covering a greater distance, has water getting out of its way faster than water on the inside, allowing increased velocity.

Just as your example is flawed, so are your statements about fluid dynamics. While you assert that water going around the inside moves faster and has a higher pressure, Daniel Bernoulli, who's work has been widely accepted by the scientific community for a few years longer than you've had your degree, tells us these cannot both be true.

If what you postulated was true, carburetors wouldn't work. Higher speed fluid results in a pressure drop, not increase.

From my experiences with fluid dynamics I say you're right about the pressure, wrong about the velocity. Since you've a master's and I have but a humble engineering degree I'll bring in a chart of velocity vectors modeled from data from river meander research by J.F. Friedkin, 1945, at the US Army Engineer Waterways Experiment Station, to back up my assertation:



Notice the velocity is greater at the outside, not inside, of the bend. (green = riverbed velocity, black=surface). If velocity is greater at the outside of the bend, your claim that water moves faster around the inside is incorrect. If you can be wrong about basic waterflow dynamics, is it not possible that you are also wrong about your presumptions concerning Pineapple's racing sleeves?

mar3

iTrader: (8)

The combustion event in an internal combustion engine is no more an explosion than a wildfire running up the mountainside is a "controlled explosion." Except for the fuel source, they are exactly the same kind of physical process. How can you call a wildfire an explosion? That's why you can't characterize the controlled burn in a rotary or piston engine an explosion...

Carl, this 6 month old baby has turned out to be a high maintenance girl already...between wiffey's crazy hours at Sears and juggling the 4 year old boy, I can't even work on my cars except to keep them going......realizing how things are going, I've sold the white '68 Pro-Street Firebird to a close friend and also dumped the '84 GS that was my main ride so I could finish Furious the way I wanted to. Now, all that's hit the bricks, even finding an hour or two to play on the 'Net has become a rarity....I drop in just to see what's going on, but I can't even process my pics and post to update my own little thread buried deep in this corner...the only thing that keeps me sane is thought that I could have been living in Florida....

Blake

I'm not trying to get personal, but you *are* attacking my credibility. I have told you that I have personally seen proof positive of the benefits of the inserts. You are calling me a liar and basing this conclusion entirely on your apparently tenuous grasp of the subject...a theory that does NOT reflect reality. I could understand if you were simply skeptical and reserving judgement but, instead, you have stated flatly that they do not work...an accusation I find unacceptable from a professional who should know better than to jump to conclusions with no practical experience to back up the theory. You have crossed the line from skepticism to condemnation, which should shift the burden of proof to you.

Did you asked Pineapple Racing for proof before launching off on your condemnation of the product? What you are saying -- particularly because of your apparent professional expertise -- is, to my mind, defamation. Rob lives and dies by his reputation and chickenshit accusations by someone claiming expertise can harm his business.

BTW, I sure hope you are not trying to use a flowbench on rotary engine ports! That is a dead end, as the dynamics are totally different than anything you could possibly simulate. Rob has a flowbench, which he uses for piston engine heads and manifolds, but he and just about everybody else who've been in the field for 20+ years concluded long ago that they are next to useless for determining port flow on rotary engines. The proof is in years and years of trial and error; stacks of timeslips, dynocharts, laptimes, etc. Again, when the theory and reality conflict, the *theory* must be discarded. Rob has 20+ years experience and a thriving business built upon his reputation; you have a degree and no experience. Even if I hadn't seen the proof, I'd side with him *every* time.

Elysian

i've met rob, i've also talked to him over the phone many times, and i would also side with him over most anyone. he's one hell of a smart guy, and not just about rotary engines, about everything... if there were such thing as a know it all, rob would be it lol

Blake

I never said they flowed better because they looked pretty. I concluded they flow better because of the timeslips and dyno charts I've seen. In this case elegance and function just went hand in hand. I have also done something similar, myself, with Teflon (no sleeves) and the performance was incredible...I just didn't have back-to-back testing to confirm the results objectively (this was a port/rebuild job and the Teflon was not removable).



I have the Pineapple sleeve inserts in my Rotary Truck, but that project has been delayed by further development of my "RX-7.5" trailer and work on my Porsche 914-RE with the RENESIS.

Blake

Oh, BTW, if there is no benefit, why did Mazda start radiusing the ends of the auxiliary sleeves starting with the new RENESIS 13B?

Rx7carl

Purple82 I was kidding about the hating part.



Damn Blake, your a busy guy! That 914 is gonna be a badass car I bet. You mistook what I was saying though. All I am saying is that what looks like a good flowing piece aerowise isint always the best flowing in reality. It was just a general statement of fact, not an opinion about the sleeves.

And my trial and error work on the flowbench is inching forward and giving me a much better understanding about internal airflow of the rotary.

Manntis

to add to the airflow debate - it's long been thought that a smooth wing resulted in better laminar flow. However one aerodynamicist noticed the bumps on the leading edges of humpback whale fins, and incorporated them into wing design. His experiments this year are giving us new understanding on how to direct a compressible, like air, along a desired path.

Wind tunnel tests of scale-model humpback whale flippers have revealed that the scalloped, bumpy flipper is a more efficient wing design than is currently used by the aeronautics industry on airplanes. The tests show that bump-ridged flippers do not stall as quickly and produce more lift and less drag than comparably sized sleek flippers...
...As whales move through the water, the tubercles disrupt the line of pressure against the leading edge of the flippers. The row of tubercles sheers the flow of water and redirects it into the scalloped valley between each tubercle, causing swirling vortices that roll up and over the flipper to actually enhance lift properties.

"The swirling vortices inject momentum into the flow," said Howle. "This injection of momentum keeps the flow attached to the upper surface of the wing and delays stall to higher wind angles."

Elysian

looks like rob's shop in the background eh

cdrad51

I can take care of that for you, just send it to me

purple82

Manntis, first let me say that I appreciate your questions and the respectful manner in which you ask them.

I stated that the inside corner of the bend is high pressure, that's incorrect and mis-spoken on my part. I think I corrected that statement later in the thread. It's a low pressure, high velocity region.

You're right that this port isn't exactly analogous to flow around a bend since the port isn't a smooth inner bend. As the flow tries to turn, it will separate from the wall of the bend and shoot towards the back of the port, but the airstream will be inside the chamber by the time it reaches that distance.

My point, however, is that most of the dynamic energy of the flow is on the inside of the bend, decreasing as you go to the outside of the bend.

Here's why the car analogy isn't as flawed as you might think. Think of a stream of cars 10 wide and 10 deep all moving towards a corner. The cars behind can only go as fast as the cars in front as you mentioned, these are reffered to as streamlines in fluid dynamics. As the cars go around the corner, the insided cars are forced into their line by the outside cars. They can't cross over each other, so the inside cars are forced to accelerate faster than the outside cars, this is known as streaklines in fluid dymanics. The cars along the outside of the bend don't need to stay in the same row with the cars along the inside of the bend, and they don't.

I realize that is seems counter-intuitive, but if you think about it, it does make sense. I sent Rotarygod a link to a really good example of this but I can't find it anymore. Maybe he'll read this and post it. Hopefully you can see that this isn't flawed anymore. If not, I'll try to find some info on the web for you (guys)

The bernoulli principle states that as velocity goes up, static pressure goes down and stagnation pressure remains constant for an incompressible fluid flow. The inside corner is low pressure/high velocity, the outside is high pressure/low velocity. In the bulk flow, wall effects neglected.

Yup

Ahh, you are looking at flow separation from the sides of the stream. In some cases, the bulk flow has enough energy that it will "separate" or pull away from the inner wall of the bend. That's what's going on in this picture. The resolution of the arrows to too small to see what's going on in the bulk flow.

I'm sure separation is going on in the ports as well, but like I said in the other threads, the flow sets up a high pressure zone in the outside corner of the port and will flow around it anyway. I love talking about this stuff so ask more questions! I'm a geek.

purple82

That's convenient.

purple82

This is due to a boundary layer phenomina. A laminar flow boundary layer has more drag than turbulent. Laminar flows can be "tripped" into turbulence to reduce drag without really effecting lift. Also, laminar boundary layers can be unstable and go back and forth to turbulent unpredictably, leading to strange disruptions in the bulk flow.

kleinke

High pressure/low velocity vs. low pressure/high velocity, is not the net energy at any point of the bend the same?

Rx7carl

Exactly. We use boundary layer destroyers on commercial jet wing surfaces. Look out the window next time, youll see little fins on the top surface on many aircraft. Actually they are also used in other places on an aircraft where they want to keep the boundary layer thin or nonexistant as possible. I wish I was a geek. I have to learn all this stuff the hard way, and thats always slower.

Manntis

Actually, no. What is going on in the picture is exactly what the author said was going on in the picture - the velocity on the outside of the bend is greater than the velocity on the inside. I suggest you research the report I cited.

Rx7carl

Makes sense to me. It has less restriction to its flowpath (longer radius). The inner side would have a harder time negotiating the sharp turn and would be forced to slow down since it cant muscle in on the water thats occupying the outer portion of the bend. Go stand in a stream and you can feel this effect.

bouis

I've been fishing enough times to know that the speed of the water (at least at the surface) isn't always faster or slower on the inside or outside of a bend; it depends on a lot of factors.

kettlman

iTrader: (2)

man this topic has sure gone OFF TOPIC

Jeff20B

iTrader: (13)

Yeah, you said it. All this flow stuff is fascinating though. At least we now know that DLIDFIS isn't a myth. It may not add power to an engine that already has an adequate intake/ignition system, but it does help in other ways.

I spoke with my friend this evening who owns the '77 REPU. His air fuel meter does indeed run one LED to the rich side of 14.7 where before it would fluctuate up to three LEDs all the time. It's now a steady 14.0 or whatever that LED represents. He's happy.

We can't wait to see how the S5 T2 engine will run.

purple82

Sorry about being so far off topic. It's my fault.

Manntis, I will go to read the study that you're citing. In the meantime, I ran a quick simulation to show you what I'm talking about.

These screen shots show the speed increase of the flow at the inner sides of the bends. The pressures are also highest at the outer sides of the bends.

Elysian

interesting... could you do one where you had a radius'd top part? instead of the 90 degree bend?

Kenku

*whistles* Man, this turned into a port flow discussion. I think I'm going to stay out of that... though I've done a lot of research on CFD models of flows in rotary engines and think I have a pretty good grasp on things... but really I think the argument's being well handled by people with far better resumes than I.

About the ignition though. We moved up to an MSD box firing dual lead coils a year or so back on the race car. I sincerely doubt it made any more power. What it did though is vastly improve cold starting, especially with the cold race plugs (which we previously had to swap in after it was warmed up as it absolutely would not start on them). It starts right away every time, no matter the temperature or anything else whereas previously with the stock system and all new components, cold starting was... iffy. It starts it hot, it starts it cold, it starts it when one rotor is completely blown and the other only has 40psi of compression (albeit, lap times sucked... as you might imagine).

For this reason, I like the upgraded ignition and think it worth the money even if it doesn't have any performance benefits whatsoever.

mar3

iTrader: (8)

Yet another good reason for the DLIDFIS set-up if you're running nitrous on the street...now you don't have to change plugs for a 100 shot...anytime you can save an engine, that upgrade is worth its weight in gold and well worth the effort and expense when you start going after serious performance modifications.