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Electric Jet Ducted Fan?

by violin_writer
Tags: ducted, electric
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mheslep
#19
Aug2-09, 09:26 PM
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Nuclear power case

Appears the old nuclear aviation case is feasible with HTS electric fans:
-737 fuel load = 26 tons
-737 engine power cruise (x2): 5.5MW [24kN * 228m/s]
-Replace fuel load w/ Hyperion 25MW(e) small reactor. Weight, size: 15-20 tons, 1.5M OD x 2M

Range: Five years aloft
Cyrus
#20
Aug2-09, 09:54 PM
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Quote Quote by mheslep View Post
Nuclear power case

Appears the old nuclear aviation case is feasible with HTS electric fans:
-737 fuel load = 26 tons
-737 engine power cruise (x2): 5.5MW [24kN * 228m/s]
-Replace fuel load w/ Hyperion 25MW(e) small reactor weight, size: 15-20 tons, 1.5M OD x 2M

Range: Five years aloft
Nuclear powered aircraft were seriously looked into by skunk works back in the 60s. The idea never got off the ground because the amount of lead shielding needed to protect the pilots was too heavy.

See: Skunk Works, Ben L. Rich for more good info on this.
mheslep
#21
Aug2-09, 09:59 PM
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Quote Quote by Cyrus View Post
If your numbers are right, that's terrible performance.
Yes, certainly. Max range of that aircraft is normally 1720 miles. Though here's the key interest for battery power: assuming the HTS fans can be made cheaply, the battery powered aircraft is about the same cost per mile as the Jet-A powered one, including the battery cost, even at today's battery prices. Battery prices will go down, Jet-A will only go up.
Cyrus
#22
Aug2-09, 10:34 PM
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Quote Quote by mheslep View Post
Yes, certainly. Max range of that aircraft is normally 1720 miles. Though here's the key interest for battery power: assuming the HTS fans can be made cheaply, the battery powered aircraft is about the same cost per mile as the Jet-A powered one, including the battery cost, even at today's battery prices. Battery prices will go down, Jet-A will only go up.
An airplane that has a range of 150n.m. is an epic failure, no matter how cheap per mile it costs.
mheslep
#23
Aug10-09, 06:51 PM
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Quote Quote by Cyrus View Post
An airplane that has a range of 150n.m. is an epic failure, no matter how cheap per mile it costs.
How do you measure failure? One can imagine the case that an for say, 20% lower operating costs an airline might use a similar plane to do nothing but make the shuttle run from NYC to Boston five times a day. And, it might offer be able to operate at night because of reduced noise, thus opening up time slots not available to traditional aircraft.

Realistically, I suppose that the costs of certifying a radically new technology aircraft for a small market segment make the 'electric shuttle to Boston' unaffordable.
mheslep
#24
Aug10-09, 06:59 PM
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Quote Quote by Cyrus View Post
Nuclear powered aircraft were seriously looked into by skunk works back in the 60s. The idea never got off the ground because the amount of lead shielding needed to protect the pilots was too heavy.

See: Skunk Works, Ben L. Rich for more good info on this.
Thanks, I've seen some discussion, but are you sure this is a relevant source? I searched Skunk Works for 'nuclear', 'lead', 'shielding', and 'radiation': all the hits were about weapons.
Cyrus
#25
Aug10-09, 07:10 PM
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Quote Quote by mheslep View Post
Thanks, I've seen some discussion, but are you sure this is a relevant source? I searched Skunk Works for 'nuclear', 'lead', 'shielding', and 'radiation': all the hits were about weapons.
How did you search the book, do you have it in pdf format?
Cyrus
#26
Aug10-09, 07:11 PM
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Quote Quote by mheslep View Post
How do you measure failure? One can imagine the case that an for say, 20% lower operating costs an airline might use a similar plane to do nothing but make the shuttle run from NYC to Boston five times a day. And, it might offer be able to operate at night because of reduced noise, thus opening up time slots not available to traditional aircraft.

Realistically, I suppose that the costs of certifying a radically new technology aircraft for a small market segment make the 'electric shuttle to Boston' unaffordable.
You're taking an existing aircraft and reducing its range by an order of magnitude. That's always bad - really - really bad.
mheslep
#27
Aug10-09, 07:27 PM
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Quote Quote by Cyrus View Post
How did you search the book, do you have it in pdf format?
online search at the Amazon link you provided, thanks again.
mheslep
#28
Aug10-09, 07:30 PM
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Quote Quote by Cyrus View Post
You're taking an existing aircraft and reducing its range by an order of magnitude. That's always bad - really - really bad.
<shrug>. I'm talking the feasibility of turning a profit in aviation w/ electric aircraft.
mheslep
#29
Aug10-09, 08:10 PM
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Regarding nuclear powered aviation, after reviewing some history I doubt the shielding would be major problem any more. A jumbo sized aircraft can afford to carry 10-15 tons of shielding. I expect the forever insurmountable problem is the risk of nuclear contamination in the event of a crash.
Cyrus
#30
Aug10-09, 09:05 PM
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Quote Quote by mheslep View Post
<shrug>. I'm talking the feasibility of turning a profit in aviation w/ electric aircraft.
You would have to do a cost benefit analysis to see if it's worth while to do such a thing.
FredGarvin
#31
Aug10-09, 10:41 PM
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Look up "Project Pluto" for the nuclear propulsion R&D effort.

In terms of electrics, I think the idea will come in some form, some day. There are too many benefits to not chase after them. In part of my company's business, customers would go gaga at the chance for an extremely quiet ride. Of course, a ducted fan would have to be quite a bit larger in diameter to get the roughly the same amount of thrust.
There are hurdles that are on the scale of putting a man on Mars to overcome though. I always wince when I read a paper that the only benefit/output is a "model" to help in the conceptual design of something that can not exist at the current point in time.
mheslep
#32
Aug11-09, 08:58 AM
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Thanks for the response Fred
Quote Quote by FredGarvin View Post
...
In terms of electrics, ... Of course, a ducted fan would have to be quite a bit larger in diameter to get the roughly the same amount of thrust.
That was my first thought, but then I read that in today's high bypass turbo fan engines the majority of thrust already comes just from the bypass, i.e, the majority of propulsion comes from the low pressure compressor fan and not directly via the combustion gasses. Is that true?

Edit: found my source. The Luongo paper claims in existing turbo fans, the fan produces 85% of thrust, jet produces 15% of thrust. Example: GE90 has a BPR of 9:1
FredGarvin
#33
Aug11-09, 09:53 AM
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You're right on that. The fan does produce the majority of the thrust.
mheslep
#34
Aug11-09, 10:57 AM
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Overview of the basic propulsion concept from an earlier Masson, Luongo paper

A. Propulsion
In most modern airliners, propulsion is done through the combustion of jet fuel in turbofans in which, thrust is generated by both exhaust of hot gas and rotation of a large ducted fan generating an airflow bypassing the turbine. In modern engines, most of the thrust comes from the fan and only a fraction, less than 10%, comes form the exhaust. Therefore, it should be possible to replace the turbine by an electric motor and generate the full thrust using a large fan. This concept is presented in Fig. 4.

The duct and fan can be kept almost identical if an electric motor of the same shape and size as the original turbine is designed. The low rotation of the fan being limited to about 2,600 RPM, a propulsion motor will have to exhibit both high power density and high torque density. ...
Figure 14 shows the over all power system, in this case it is based on traditional gas turbines driving generators. A fuel cell system would replace the generator and gas turbine. I posit that a small battery supplement could have large advantages, though the authors don't address batteries. The key given the various new onboard boxes in fig 14 is low weight motors and generators. Superconductor tech. facilitates this, hence this research and the body of the paper.
Attached Thumbnails
Fig4.png   Fig14.png  
mheslep
#35
Aug11-09, 11:39 AM
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Powerpoint overview from the authors, better graphics.
http://www.masbret.com/asc08/ASC08_T...c_Aircraft.ppt
FredGarvin
#36
Aug11-09, 11:49 AM
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That is all pretty much true. It would be something worth striving for to be sure, but it's not going to happen in our lifetime. This paper reminds me of this cartoon:



If we just get these super conductors...and then if we just get these super batteries...and then we just get these super high powered motors designed...For me, reading papers like that gets old pretty quick. I guess that's why I am in the engineering trenches and not doing pure research.


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