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Does a turbine run better with inlet ducting

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Does a turbine run better with inlet ducting

Old 04-15-2011, 02:24 AM
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BaldEagel
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Default Does a turbine run better with inlet ducting

As the title is there any proof that inlet ducting improves the running of a turbine.

Mike
Old 04-15-2011, 03:05 AM
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Mark H
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Default RE: Does a turbine run better with inlet ducting

Mike have you ever run a bypass.
If so in what aircraft.
Old 04-15-2011, 03:07 AM
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Default RE: Does a turbine run better with inlet ducting

Sure it's better ! If you can have some well canalysed and not turbulent air at engine inlet, this one will be more efficient. It's the same effect as with bypass setups.

A friend have this effect few weeks ago with an electric ducted fan on E-flite F-86 : This is the same setup as on Habu, but on the F-86 it is all ducted from nose to tail cone. It run more quieter with a very different sound and with more efficiency. Why it should be different with kero turbines ?
Old 04-15-2011, 03:10 AM
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Mark H
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Default RE: Does a turbine run better with inlet ducting

Correct just a little more work.
No need for bypass on back of boomerang though.
Regards.
Old 04-15-2011, 03:29 AM
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Default RE: Does a turbine run better with inlet ducting

Its well documented that EDF's need a good free flow of air in fact more than the outlet, the radius of the inlets also has to be correct, turbines are a lot more efficient than EDF's and will take in as much air as they need to combust efficiently, what I am looking for is some implacable information on the efficiencies of an inlet duct compared to the Boomerang type of inlet.

Mike
Old 04-15-2011, 03:38 AM
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: Nhalyn

A friend have this effect few weeks ago with an electric ducted fan on E-flite F-86 : This is the same setup as on Habu, but on the F-86 it is all ducted from nose to tail cone. It run more quieter with a very different sound and with more efficiency. Why it should be different with kero turbines ?
I have the E-Flight F-86 and compared to the Habu its a dog, compared to the foam ViperJet its two dogs, sits in my workshop unused and unloved, this brings up an interesting fact, the F-86 has smooth inlets and outlets the Habu has just foam surface's in both, this would seem to indicate that the foam uneven surface is more efficient in air flow, now this could be the boundary layer of a rough surface attaching to said surface is more efficient and thiner, therefore, allowing smooth airflow over it, a smooth surface may have a thicker boundary layer, before allowing a smooth transition, I remember reading something on this from Carol Shelby on a bead blasted surface in an inlet manifold, all interesting stuff.

Mike
Old 04-15-2011, 04:07 AM
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Mark H
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Default RE: Does a turbine run better with inlet ducting

Mike could also be the fact that the F86 is just a woofer compared to the Habu.
I know when I first flew the H I was taken aback by it's total performance. Same as the little F16 from Phase3, look
At it's performance on a 2500, I think you are looking at two different packages not just the intake duct.
As for turbines I always try to duct where possible to as close to the intake as possible but always leave a good supply
Around the turbine case to cool both engine and tail pipe. I have seen some total tight installs that scare me in the past.
Mark.
Old 04-15-2011, 04:24 AM
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Nhalyn
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: BaldEagel
Its well documented that EDF's need a good free flow of air in fact more than the outlet, the radius of the inlets also has to be correct, turbines are a lot more efficient than EDF's and will take in as much air as they need to combust efficiently, what I am looking for is some implacable information on the efficiencies of an inlet duct compared to the Boomerang type of inlet.
Mike
Hi Mike,

It's the same for kero turbine. It's a matter of efficiency. With our modern kero turbine we have always enough power, nor we put a P180 or P200 intead of a P160 and that's it. With electric ducted fan we have to work on efficiency as we have a limited power source, the batteries, and a power to weight ratio really lower than kero jets. We can't work many more on engine (with 85% efficiency) or complete electric chain (good speed controllers, accus 45C, good plugs, etc).

Turbulent air in front of the engine cost a lots of efficiency, as you said we are well documented on that subject with electric. If it cost efficency (= power !) with an electric ducted fan why does it should not cost the same with a kero burner... If inlet compressor can work in laminar air, it will be far better.

As our kero turbine are not (at all !) consuption efficients (4 to 5 liters for a P160SX 10 minuts flight ? With 1 liter gazoline on my zenoah ZG 62, I can fly for minimum 30 minuts !) with that single stage compressor, it's not the first work to do that working on bypass and inlet quality. When multiple stage turbine will be ready for business, it will be time to look at the other parameters !

Your question is really good in fact...
Old 04-15-2011, 04:30 AM
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Default RE: Does a turbine run better with inlet ducting

Mark

I know what you are saying, but the F-86 uses the same equipment and weighs about the same as the Habu, I would have thought the F-86 having a straight through duct installation would be more efficient than the Habu, but performance says otherwise.

It would still be nice to get some Empirical data on ducted installations in turbine installs, I have seen a smoke test on the airflow into a turbine and the air seems to straighten itself out into the inlet no matter what is in the way or where the air is comming from, I am assuming the suction from the turbine is such that it will take in the amount of air it needs to satisfy the fuel being burnt, this is mostly superstition on my part and was looking for some substantiated evidence.

Mike
Old 04-15-2011, 04:42 AM
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Default RE: Does a turbine run better with inlet ducting

i dont think it afects turbine , just less "inner" drag
Old 04-15-2011, 04:43 AM
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Default RE: Does a turbine run better with inlet ducting

Hi together,
I am totally convinced that a clean ducting, be it for EDF or turbine, will have a positiv influence on ALL the above mentioned factors !!
Personally, I always spend a lot of thoughts and manhours to keep this airflow as laminar as possible !
This is done not only to the inlet, but as well in the thrust duct ( tailcone for the EDF with a nice airfoil-shaped extension to guide those wires out of the airstream ).
On a turbine install, I believe that it is important to keep all these tubes and wires out of the circumference of the compressor wheel !
You just have a look at the real jet aircraft : never seen any without a nice and clean ducting or a nice and very flush nacelle without having any gaps !!
see you
Hans
Old 04-15-2011, 05:50 AM
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Default RE: Does a turbine run better with inlet ducting

ORIGINAL: BaldEagel
I have seen a smoke test on the airflow into a turbine and the air seems to straighten itself out into the inlet no matter what is in the way or where the air is comming from, ......
Mike
Does this test has been done in a wind tunnel with the proper flight speed simulated ?

My thought is that if you put a jet in static on ground and just put smoke behind the inlet, there is only suction from the engine, but not the great debitment of air due to the speed, and that would change how thing goes aroud...

That's not the same difficulty to test !!!

Edit : totaly agree with Hofer !
Old 04-15-2011, 06:09 AM
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Default RE: Does a turbine run better with inlet ducting

The test was by RR in their wind tunnel, having a jet on the ground and putting smoke behind it will not give a true indication due to the ground effecting the airflow into the underside of the inlet, thier premiss was that as speed increases the airflow into the turbine has less influence on the turbine due to the ram effect, in fact they went into all sorts of fuel efficiency data above certain Mach speeds, but that is getting way off the point of this thread and our small turbines.

I suppose what all this boils down to is that most turbine users don't take as much notice of airflow into our motors as the EDF chaps do, but it seems sensible that if we have a smooth airflow into our turbines it must make its combustion more efficient, therefore decrease fuel consuption and increase thrust for the same fuel usage, well I seem to have answered my own question with the help of your thoughts chaps, thanks for your contributions.

Mike
Old 04-15-2011, 07:06 AM
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Default RE: Does a turbine run better with inlet ducting

Well, I have nothing really scientific to back this up but......

I have noticed that on my JMP Firebird, when I first ran the engine, I did so with the bypass cover off, that dirties up the air. When it was placed on, the turbine ran cooler, same thing with my old Super Bandit.
In my mind, cooler temperatures mean parts should last longer.
Jets that are fully ducted (with a bypass) are almost always quieter than an open installation as well which is a bonus in my opinion.

I think that it could be perceived as more power is available in a fully ducted situation as performance generally improves, though I feel this is more about drag from the inside of the airplane as opposed to making more power, but again, with a lower temp, perhaps the turbine does make a little more power, would it be enough to be noticeable, probably not, but who knows.
Old 04-15-2011, 09:46 AM
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Default RE: Does a turbine run better with inlet ducting

Running better is a hard to define thingy. You can not really compare an EDF with a turbine in that way. An EDF application with restricted inlets would just perform worse, while a turbine with too little air would run in to compressor stall http://www.youtube.com/watch?v=-BnrL...4DA02E30E8A038

Where an EDF will have too little air (scale jet airplane for example) a turbine setup with simmular thrust will do fine as the turbine uses less air for the same thrust.
Old 04-15-2011, 01:48 PM
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Default RE: Does a turbine run better with inlet ducting

The best advice I got was from Eddie Weeks.

http://www.rcuniverse.com/forum/fb.asp?m=5017504

I was setting up a P-180 in an unproven bypass/pipe combination.

I checked the free air exhaust temps, then installed it and checked to see that I was pulling similar temps. The Tam pipe was spot on (Tam knows pipes, period)

If you get a lower temp when installed, you constrict the exit diameter of the pipe to regain the temp (and power). Lower temp is of course easier on the turbine, his theory is that too large of a pipe exit diameter was actually creating low pressure directly aft of the turbine nozzle, therefore making it work less hard (and less thrust)

Constrict the exhaust and the temps come right back, as does the thrust.

For those looking ahead in the chapter, you can figure a cool product would be a controllable nozzle, I had one on my old Viper DF, I have not seen a real one on a turbine but no doubt some German is working on one!!

I think Wren came up with an expanding pipe that increased thust so I don't know how there work jives with what Eddie said. YMMV
Old 04-15-2011, 04:23 PM
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Default RE: Does a turbine run better with inlet ducting

No offense to you or Eddie, Matt. But I'm taking that with a grain of salt because to me it makes no sense at all. Just......none. Without a thermo/fluid dynamics background all I have to stand on is instinct tho. Seems to me that unless you're up against an rpm limit reducing the EGT will enable a higher ff (fuel flow) until the limit is again reached. And when RPM is the limit, consricting the exhaust will raise the thrust and EGT to the even as the ff remains constant.

Perhaps someone with an education in the matter can weigh in and clarify
.
Old 04-15-2011, 04:39 PM
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Default RE: Does a turbine run better with inlet ducting

what does "ff" refer too?
Old 04-15-2011, 04:44 PM
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Default RE: Does a turbine run better with inlet ducting

Not meaning to call him out because I have not posted myself much in the last year, but I saw Eddie logged in a couple of weeks ago.

Come on Eddie, chime in here!
Old 04-15-2011, 04:53 PM
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: mr_matt

what does ''ff'' refer too?
Sorry Matt, habit from work where abbreviation ff= Fuel Flow.

I will edit the post for clarity.
Old 04-15-2011, 06:18 PM
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: highhorse

Seems to me that unless you're up against an rpm limit reducing the EGT will enable a higher ff (fuel flow) until the limit is again reached.

AFAIK, all modern turbines are RPM limited. Much like an IC motor, if there is no load, they will reach RPM limit while making little power

ORIGINAL: highhorse

And when RPM is the limit, consricting the exhaust will raise the thrust and EGT to the even as the ff remains constant.
Don't understand this.

Old 04-15-2011, 11:10 PM
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: mr_matt


ORIGINAL: highhorse

Seems to me that unless you're up against an rpm limit reducing the EGT will enable a higher ff (fuel flow) until the limit is again reached.

AFAIK, all modern turbines are RPM limited. Much like an IC motor, if there is no load, they will reach RPM limit while making little power

ORIGINAL: highhorse

And when RPM is the limit, consricting the exhaust will raise the thrust and EGT to the even as the ff remains constant.
Don't understand this.

You're saying that the ECU's don't limit ff as the egt limits are reached? On a hot day, for instance? Or are you saying that there is no egt limit at all? How can a turbine not be "loaded" and make "little power" while running at it's limit rpm? Please elaborate? And I don't understand what you don't understand....constricting the exh raises the thrust and the egt, does it not?
Old 04-17-2011, 01:44 PM
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Default RE: Does a turbine run better with inlet ducting


ORIGINAL: highhorse

You're saying that the ECU's don't limit ff as the egt limits are reached?
Well some are different than others (I think the AMTs do not look at EGT after the turbine starts) but that was not my point. I was stating the case where you hit your RPM limit and the temps are low so by definition you are not near an EGT cutoff, if your ECU has an EGT limit function.


ORIGINAL: highhorse

How can a turbine not be ''loaded'' and make ''little power'' while running at it's limit rpm? Please elaborate?

I don't understand the physics behind it, buit what I took from Eddie was that some combinations of bypasses and pipes produce a low pressure aft of the turbine, and this low pressure lets the turbine have it easier at a given RPM. So if you go to full throttle, the RPM would max out but the EGT would be low (and I would guess the ff would be low as well, but he did not speak of that).
Old 04-17-2011, 03:30 PM
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Default RE: Does a turbine run better with inlet ducting

OK, I guess I've gotta add to my list of things I'm never gonna understand. In descending order of complexity, they are:

1) Some Women
2) Other Women
3) The rest of the Women
4) The Theory of Relativity
5) Nuclear Physics
6) Thermo/fluid dynamics of tubine exhausts
Old 04-17-2011, 04:11 PM
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Default RE: Does a turbine run better with inlet ducting

Imagine yout put your car into first gear and floor it. You have a rev limiter. Off you go up to the limit of the rev limiter, clearly.

Now get on the freeway, in overdive, much higher drag, hit the rev limiter again, this time.......the motor is clearly working harder.

RPM the same in both cases......

You have to disconnect the idea of RPM from power produced.

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