How to explain this phenomena of hydrodynamics?

[windpowerchina2004]

Hello everyone and happy new year

If my guess was not wrong,the discuss above is talking our web site

http://www.windpower.com.cn/

"Don't these guys in China have any sort of engineering education or even common sense?

If this is really a top research organization over there, maybe they should leave the heavy lifting in the creativity department to western minds.

Then again I guess we have plenty of stupid people with no common sense and advanced degrees here too..."

Oh,the designer is a prof of who teach hydrodynamics in a China university,he has the experience of design some fluid part of the gas turbine of plane,and as a visitor scholar to princeton university in US.

the phenomena had thinked over before we published.

and the below is the continue.

Please visit:

http://www.windpower.com.cn/

for the details.

First please think a QUESTION:

A hollow blade of wind turbine, let the air afflux from the hub, through the hollow blade, jet from the tip, in an opposite direction to its rotating direction, can produce thrust force?

Most and most of us may think the pressure push the too small, and the centrifugal force offer the power so maybe produce resistance, the effect is very small.it is a question that a high school student can solve.

BUT,

the aerodynamics research group in China Shenyang Institute of Aeronautical Engineering(http://www.syiae.edu.cn/syiae/index.htm) developed a serial of wind tunnel test, and the result shown:

this blade-tip jet method can make great thrust force, the rate of increase in the power or power coefficient is over 30% generally.

First of all, they did a compare test, place a hollow blade in the wind tunnel, black up the tip to measure as a prototype data; open up the tip to measure as a compare data, and did many degree setting, and found the rate of increase in the power or power coefficient is great.

At the later test of another blade, compared the prototype data, open up blade-tip data and open up opposite blade-tip data.

Especially when did the opposite blade-tip test they found:With a wind speed of 8 m/s, the rotation speed of the wind turbine can reach more than 1000 rpm without jet, but for opposite blade-tip jet (100% jet flow rate), it can't reach the rating rotation speed of the generator, even through with a wind speed of 23 m/s.

How to explain this phenomena of hydrodynamics?

http://www.windpower.com.cn/

published above more detail.

Althrough this is only concept research, but we can known the great jet force from the test result, and only the pressure of the hub can't reach such great thrust force(pressure force).

The research group also declare:The test result can be more improve, for the test of less 6 degree because may , resolve the best flux match to improve the power is also in deeply research.and a number of comparative experiments with breakage correction,A number of degree,A power meter and several serial-linked loads are used in testing.

How does the Huge jet force generate? only the pressure of the hub can't reach such great thrust force, maybe it is the integrate force include centrifugal force effect, coriolis' force effect,etc.

Maybe a new theory, how to build the modal what can explain and the more deeply mechanism, the research group hope discuss and cooperate with you, and published the BBS and E-mail in the web site.

If my description not very clear, please visit

http://www.windpower.com.cn/

and the above web site has more detail data and others.

webmaster@windpower.com.cn

Apologize for lack english

[skravlinge]

Surprising? The jet they seem to mean comes from the centrifugal forces, and the inlet is in the center of the axis. They  are not using it for extending the speed of the rotor, rather to slow down. I can image the centrifugal forces will increase with speed, and maybe hold the rotation at a resonable speed in high wind. I wonder if the forces are strong so it can hold the overspeeding away, but cannot doubt their result until an other source proof different.

[Ungrounded Lightning Rod]

I've commented on this one before.  The key to why they get their result (and why the concept is faulty) is a little item in the characteristics of the experimental blade:

Blade twist: no

Their blade design is inherently faulty.  The jets partially mitigate the inefficiency from this design flaw.

Efficient blades in HAWTs have to be twisted because an airfoil flys in the "apparent wind" - the vector combination of the true wind's velocity and its own motion.  Near the hub the apparent wind is essentially the true wind.  So the blade has a high pitch to get air flowing correctly over the airfoil and draw power from it.  Near the tip the blade is moving at several times the true wind's speed.  So it needs a very flat pitch to get the wind to push it.

If you have a blade with no twist, as it gets moving the tips stop acting as power collectors and start acting as air brakes.  The section near the hub is pushing, a section farther out is pushing efficiently, a section farther out yet is just flying and providing minimal drag, and the remainder is actually trying to SPEED UP THE WIND, pulling power from the center and feeding it back into the air.  As the blade speeds up further the boundary between turbine and fan effects moves farther inward.  The blade reaches equilibrium speed when all the power pulled by the part near the hub, less any removed by generator load, bearing friction, and air drag, is being used to pull and push air near the tips.  At this point the outer portions of the untwisted blade are slapping the air sideways, with a high pressure on the leading (leaward) face and a low pressure on the trailing (windward) one.

By admintting air near the hub and allowing it out through a "jet" on the trailing edge, the experimenters are breaking the vaccuum on the trailing face of the tips of the blade.  This relieves part (though not all) of the air-braking done by the improperly pitched section, more than making up for the power stolen by accellerating the air as it moves out through the blade.  (Putting the "jet" on the upwind side results in further raising the pressure on that side as well as stealing momentum from the blade, increasing its effectiveness as an air brake, as they observed.)

A high-TSR HWAT with properly twisted blades can easily get within a percent or two of the Betz limit - the theoretical limit on how much power a wind turbine can extract from the air.  (This limit occurs because decelerating the air is necessary to extract its power but it also reduces the amount of air moving through the turbine from which power can be extracted.  So it's unlikely to be found fallacious.  You have to leave some of the power in the air to get rid of it when you're done, and Betz tells you how much that is.)  So even if there were something to be gained by fancy venting arrangements (beyond partially compensating for a misdesigned blade shape), the amount available to be gained would be tiny.  You can get a two percent increase in power from a blade by making it less than one percent longer.  So why bother fabricating complicated air passages and jets?

[windpowerchina2004]

Oh,I will sent your message to zhs@windpower.com.cn

please visit

http://www.fieldlines.com/story/2004/8/7/83459/19915

one said

"Don't these guys in China have any sort of engineering education or even common sense?

If this is really a top research organization over there, maybe they should leave the heavy lifting in the creativity department to western minds.

Then again I guess we have plenty of stupid people with no common sense and advanced degrees here too..."

We welcome agree,we welcome oppose,all of oppose we can anticipation before we send the message,our test is

Most and most of people will laught at it and they can say Super-Lame! Perpetual Motion! but how the data get?

http://www.windpower.com.cn/8_0.htm

http://www.windpower.com.cn/8_50.htm

http://www.windpower.com.cn/8_100.htm

http://www.windpower.com.cn/o6_0.htm

http://www.windpower.com.cn/o6_50.htm

Test! and then you can get the conclusion.

We had done NASA and plane blade,

How you can explain the phenomena of the opposite jet but the blade slowly down?

I recommand you test from the small modal and bit and bit bigger,then to get conclusion for the effect relation with the jet-tip area, direction, etc.

If you think we cheat you, I recommand you accuse to the newpaper, TV, EDU management

you can tell them that we fabricate data to make a Perpetual Motion

[jacquesm]

shoot me, but I don't get it...

[windpowerchina2004]

I published some of the our information not want to supprese any one,and we can't FORCE any one to believe.

I only want say that we know betz limit,TSR and other windpower basic knowledge.

not http://www.fieldlines.com/story/2004/8/7/83459/19915 said.

[jacquesm]

there's no such thing as belief, there are only facts...

I have a hard time trying to make out what the message is here, but from what I get you are suggesting some kind of fundamental breakthrough in windmill design.

Specifically - again, correct me if I'm wrong here - you state that shooting 'jets' of air collected at the root of the machine's blades out through channels in the blade leading to orifices near the tips of the blades.

The tips of the blades revolve at a very high speed, you say you realise about TSR, so let's assume that the windspeed is 30 mph and that your blades are running at a TSR of 5, so tip speed is 150 mph.

That would mean that the jets would have to 'shoot out' of the tips with at least 150 mph for them to give any propulsive effect. But the air is only entering the intake at regular windspeeds so unless it's the centrifugal force that speeds up the air (which robs momentum from the spinning blade) this is no net contribution.

The only possible advantage I can see here is some kind of fluid blade tip, but I'm a bit skeptical about the stated improvements, tip vanes are in use in many commercial windmills (for example the enercon machines) but do not lead to such dramatic improvements.

You claim 'output power' increases of between 30% and 50% relative to baseline, without specifying what that baseline was (for instance, a very small, extremely inefficient machine can be improved upon dramatically, but an already optimized design will show no improvement). One thing I noticed was that your blades have massive drag, they are extremely wide for such an extremely small model, which might account for this effect all by itself. You have to make your comparisions with a baseline, optimized model, not with your own inefficient model.

A few concrete items would give you a lot of credibility:

photographs instead of drawings of prototypes

your real experimental data, and not the pretty graphs

photographs of te test setup

If your claims are real these should be very easy to produce in short order.

Please don't take folks' scepticism here as a lack of 'belief', we have no problem whatsoever with 'breaktrhoughs' of any sort, we'd just like to see in a verifieable way that what you claim is true.

[windpowerchina2004]

concept research!

[rotornuts]

Don't write this guy off just yet. For Underground lightening rod you sould note the blade angle was set at 6 degrees, lack of twist wasn't a signifigant factor. Piping bleed air from a turbofan or conventional jet or ducting air about the wings or fuselage of aircraft has been going on for at least 40-50 years that I'm aware of. Leading edge slats/slots perform a similar job. The purpose is to positively influence the aerodynamic characteristcs of a given area (obviously). It's late so I'm keeping it brief but off the top one could speculate the tip jets may deminish the vortex ring surounding the tip curcumference caused in part by the pressure diff. between the up and down wind sides of the rotor. rotor tips are a significant source of drag (why do you think they produce so much noise?). In my books the idea has merit worth looking into. Don't get hung up on poor translation.

[jacquesm]

check out the width of the blade vs it's span...

the width is 20% of the span, these blades have massive drag.

[Zack]

It boils down to this: Everything in this thread is speculation. It will remain in the realm of speculation until we see a baseline comparison with a properly designed, conventional rotor. Then, assuming the data is based on a real experiment, done with reasonable competence, we will have something with which to make a rational evaluation. Meanwhile, my money is on Ungrounded Lightening Rod's assessment.

[windpowerchina2004]

Airfoil's shape(form) is not the first important factor.

From several test you can get result of blade-tip jet product THRUST or RESISTANCE.

[rotornuts]

I don't have a signifigant problem with this blade design for test purposes. In fact considering it's small size it seems appropriate. Rotor diameter is 23.62". The cord width is 1.97". The blade span is 10.24". The rotors solidity is .09 and considering the pitch angle of 6 degrees is a favorable tip angle and the lack if twist is relatively insignificant at above startup rpm's especially considering the area of duct influence is at the tip and the resulting inefficiecy would be at the blade root. Speculation is the catalist for innovation not derision. The only thing I would like to see is this model scaled up to a working size of about 4' diameter. Something else that may be happening here is the "cheating" of betz theoretical max by injecting air into the area influenced by the rotor reducing the pressure diff. on the two sides of the rotor allowing more air to move through the rotor without deminishing the ability to "capture" the energy. If you could inject air into the downwind air stream you would reduce the amount of influence on the upstream air flow reducing the betz effect without compromising your ability to extract energy but likely increasing it. One thing I can't see though is the ducted air actually pushing the blade around at anything other than start from a dead stand still.

I would suggest some "speculation" may be a good thing.