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  #1  
Old 04-30-2005, 04:28 AM
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PeteK PeteK is offline
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Default Turbo Bleed Air

I think it would be fun to use turbo bleed air for various purposes. It might be a Rube Goldberg type of solution, but what the heck, this is experimental, right?

If a fuselage were designed for pressurization, you could use it for that. How about heating, or using it through a check valve to pressurize a pneumatic system? You could use it for inflating a canopy seal or something too I suppose. Again, maybe overly complex....

Anywayyyy, would bleeding air from the turbo reduce its efficiency too much? What other problems (or opportunities) for bleed air fun can you think of? What sort of temps are we talking about?
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  #2  
Old 04-30-2005, 05:00 AM
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Quote:
Anywayyyy, would bleeding air from the turbo reduce its efficiency too much?
Not in my case. I have way more boost than I can use. Too much bleed can, however, lead to overspeeding the turbo (Ask me how I know this )

Typical intake temps I've seen so far have been about 130F.

Quote:
What other problems (or opportunities) for bleed air fun can you think of?
A whoopie cushion for the unsuspecting passenger
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  #3  
Old 04-30-2005, 05:06 AM
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Default Pressurizing the Fuselage

Quote:
Originally Posted by PeteK
I think it would be fun to use turbo bleed air for various purposes. It might be a Rube Goldberg type of solution, but what the heck, this is experimental, right?

If a fuselage were designed for pressurization, you could use it for that. How about heating, or using it through a check valve to pressurize a pneumatic system? You could use it for inflating a canopy seal or something too I suppose. Again, maybe overly complex....

Anywayyyy, would bleeding air from the turbo reduce its efficiency too much? What other problems (or opportunities) for bleed air fun can you think of? What sort of temps are we talking about?
As far as pressurizing the fuselage is concerned, see my thread "Pressurized AeroCanard ?" of 04/04/2005, and the answers that made everything clear to me.
Kumaros
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  #4  
Old 04-30-2005, 04:43 PM
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Quote:
Originally Posted by Kumaros
As far as pressurizing the fuselage is concerned, see my thread "Pressurized AeroCanard ?" of 04/04/2005, and the answers that made everything clear to me.
Kumaros
It's all Greek to me
I'll check it out. I know that massive redesign would be required, I was just using it as an example. I think the best use of bleed air would be for heat.
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  #5  
Old 04-30-2005, 07:48 PM
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It's already been answered, but yes, you can use bleed air for many purposes.
Plenty of pressurised piston props use a bleed air system for pressurisation. A multitude of pressurised gas turbine aircraft use bleed air for heating, air conditioning, wing de-icing. I believe the Fokker Friendship turbo prop has a pneumatic system where all the flight controls, flaps, gear, even windscreen wipers are operated using bleed air.

As for pressurising a homebuilt, very tricky.

Was it Payne Stewart the golfer who died from asphyxia when his bizjet developed a slow leak in the windshield? The plane full of corpses flew for several hours on autopilot until it ran out of fuel and landed in the ocean.
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Old 05-01-2005, 04:00 AM
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Default Not quite...

Quote:
Originally Posted by no4
Was it Payne Stewart the golfer who died from asphyxia when his bizjet developed a slow leak in the windshield? The plane full of corpses flew for several hours on autopilot until it ran out of fuel and landed in the ocean.
Payne Stewart died in a Learjet.. and presumably from asphyxia.. but if not from that, definately from the crater it made when it lawn-darted itself into the middle of South Dakota.

I have flown in several Lears..as a passenger. ALL are supposed to have cabin altitude alarms.. The alarm was audible in the CVR's tape on the accident plane. I will also snitch on my coworkers.. regs require oxygen to be either worn, or in the "quick donning" position at the high altitudes.. but the crews i flew with never did. At very high altitudes, your time of consciousness is measured in seconds.. if both guys fumbled for the masks (quick don or otherwise) they may have not been able to react futher when they passed out.

The NTSB Factual for Payne's plane is at the following addy:

http://www.ntsb.gov/publictn/2000/AAB0001.htm
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Old 05-01-2005, 12:20 PM
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Quote:
Originally Posted by no4
Was it Payne Stewart the golfer who died from asphyxia when his bizjet developed a slow leak in the windshield? The plane full of corpses flew for several hours on autopilot until it ran out of fuel and landed in the ocean.
I recalled a foggy windscreen but the root problem was a malfunctioning pressurization system. Going down to the bottom 1/3 of the NTSB report talks about it.
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  #8  
Old 05-01-2005, 12:51 PM
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I didn't read the NTSB, but caught a short special about it on TV. The O2 system has a shutoff for when the plane is on the ground. It was never turned on. Supplemental would not work if the pilots were able to figure out the problem in time.

The frozen (fogged) up windsheild was how the military pilots were able to determine that the Lear had a no pressurization problem and that everyone on board, even though still flying, was basically a popsicle.
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  #9  
Old 05-01-2005, 07:47 PM
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Default Maybe you should read the NTSB then..

Quote:
Originally Posted by MarbleTurtle
I didn't read the NTSB, but caught a short special about it on TV. The O2 system has a shutoff for when the plane is on the ground. It was never turned on. Supplemental would not work if the pilots were able to figure out the problem in time.

The frozen (fogged) up windsheild was how the military pilots were able to determine that the Lear had a no pressurization problem and that everyone on board, even though still flying, was basically a popsicle.

Cause both of those assertions are incorrect: The oxygen system was found in the ON position ... and the pressurization system was found to not be operating properly. The pressurization/bleed air system also provides the "defroster" to the windscreen so that even in an rapid decompression, the windscreen is kept clear to permit visual reference. The addy for the NTSB is in my post two links above.

Dave
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  #10  
Old 05-02-2005, 02:35 PM
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back to turbo bleed air - that is how i am planning to heat my cozy, plenty of 150 to 300 F air to keep my tosies warm.

Common practice in certificated planes for heat and pressurization. just a pump that heats air
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  #11  
Old 05-02-2005, 08:11 PM
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whoops... getting too confrontational. Original message removed to spare the unnecessary agrivation...
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  #12  
Old 05-02-2005, 11:42 PM
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Default Sorry....

MT:
I apologize if I was starting to push buttons.. I come across a little rough sometimes, and I will try to moderate that a little better on my own. I didn't see the original post, but if it was in response to me, and you felt the need to self edit, then I likewise need to "check myself" before I elicit those responses.

Dust:
Bleed air would be a great heating source provided it is available... just remember that you have this "hot" air because its compressed. You will likewise lose heat when that compressed air undergoes expansional cooling.

Case in point, if I take a scuba tank (or any other pressure vessel) and take it from empty to full (>2000 psi) it will get HOT.. Compression-related heating. Now.. bleed that HOT tank to the atmosphere and empty it.. the valve stem will be COLD, and in a humid environment will either "sweat" or get frost. Bleed air environmental systems are a few stages more complex than simply taking a feed off the 1st stage/upper deck. Complexity usually means weight and failure points. Bleed air will also "take" some power from the engine.. if its needed, performance will suffer. If its surplus, then the turbo is working harder to make that surplus bleed air. The NTSB report that got mentioned delved into the complexities of the environmental control system.

Maybe what you are describing will work fine.. maybe it will need some fine tuning.. Just be aware of the rube goldberg outcomes that may result from a "simple" mod. Hope it works. IF you can make a simple feed from the Upper deck to the ducting work for you, that would be a good data point for the rest of us to use, but I am going to have to remain skeptical out of "theoretical ignorance".

Dave

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Old 05-02-2005, 11:53 PM
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Yes the engine will work a little harder, but very, very little harder, consider, if the compressor i put in will handle 25000 feet at a 3 to one compression ratio, then the volume of air would be 2400RPM / 2 (4 stroker) x 360 cubic inches /4 x3 ABOUT. a cursory review of those numbers is that it is a huge volume of air.

it will need to be regulated for amount and for mixing with cool air, it will not have to be preasurized to reach my toes.

It will be interesting
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  #14  
Old 05-03-2005, 01:54 PM
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As I noted in another thread.... bleed air heat seems to work wonderfully in turbine aircraft, however the piston aircraft I have been in that use it seem to be rather lacking in the heating department. Mostly they just give off luke warm air, and still require the use of an additional heater. On those days where it is kinda inbetween warm and cold it might work well, but on truely cold days it is just frustrating.
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  #15  
Old 05-03-2005, 02:17 PM
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The amount of heat available to me will increase as altitude increases, i have the "formulas" of turbo output air temps at all boost levels and since i am going to only boost to normalize, the available heat will be meager at sea level

at take off i will start off with just about 4 IM boost to bring manifold to 31.5 MAP, this will not create much heat

The turbo bleed air will work best at high altitude cruise, my biggest concern.

If i need help at lower levels, then I'll just have to figure it out

That is another reason i will fly for a year or so in primer, to work the kinks out
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