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"Thomas Schoene" wrote in message link.net... George Ruch wrote: I remember what may be the same picture, a DC-9 fitted with a high-bypass turbofan, and multiple scimitar-shaped fan blades extending from the first-stage fan. Damned if I can find it now, though. Nothing like it so far on the NASA Dryden site. Any other ideas? They called in an unducted fan or ultra-high bypass turbofan. Pictures: http://www.b-domke.de/AviationImages/Rarebird/0809.html http://www.nurflugel.com/Nurflugel/NASM/Img0052.jpg Russian prop benders were on site for the program. The engine saves about 23% of fuel compared to regular high bypass engines, of the time. (pre tripple spool compressor) |
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On Thu, 04 Dec 2003 16:37:38 GMT, Scott Ferrin
wrote: Or both as per Dornier 335, hmmm 2 x Bear engines (15,000hp each) might be a bit much. I imagine it might be a bit large too :-) Make for interesting an interesting piece of flying boom refuelling also. greg -- In the beginning. Back in nineteen fifty-five Man didn’t know about a rock ’n’ roll show And all that jive. |
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I recall seeing GE tested scimitar shaped pusher prop engines, I think
it was on a 727. I seem to recall it being on the right engine of a DC-9. I wonder what became of that idea. "Unducted fans" or "propfans" were, I believe, tested on both a 727 and an MD-80. See for instance http://www.jsc.nasa.gov/er/seh/profan.html (contemporary article from midway through the program) http://www.aerospaceweb.org/question...on/q0067.shtml (survey article; pix) http://www.aviation-history.com/garb...g/udf-2_f.html The goals were, I think, a combination of fuel efficiency and some internal simplifications. I'm not exactly sure why they aren't much in use. Hypotheses I've read include greater risk to the passenger cabin from uncontained failures (I wonder if it is coincidence that both the testbeds were the sort of jets with aft-mounted engines); undesirable "propeller" image; noise; and parallel improvements in high-bypass turbofans of the usual ducted design. Cheers, --Joe |
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About 15 yrs ago BAe messed around with a project called SABA ('small
agile battlefield aicraft') one of the designs touted was a v. lightweight pusher UDF propellor craft with about a 2 ton warload. Looked pretty cool. I think it was mainly an anti-tank craft designed to fill the void between attack helicopters and full-blown ground attack aircraft. David Sounds a lot like the Rutan ARES. Ron Pilot/Wildland Firefighter |
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"Ad absurdum per aspera" wrote in message om... I recall seeing GE tested scimitar shaped pusher prop engines, I think it was on a 727. I seem to recall it being on the right engine of a DC-9. I wonder what became of that idea. "Unducted fans" or "propfans" were, I believe, tested on both a 727 and an MD-80. See for instance http://www.jsc.nasa.gov/er/seh/profan.html (contemporary article from midway through the program) Thanks for these links. They all seem to think that a Mach 0.85 for a scimitar blade contra-rotating coaxial "prop-fan" is possible and indeed fuel efficient. Given that there was in a German 1940s study suggesting 584 mph with twin piston engines I think its fairly believable. I find the idea of a Mach 0.85 diesel or spark ignition engine fascinating. There is also the Soviet An 70 http://www.geocities.com/CapeCanaver...5/antonov1.htm I would be interesting to read what the Russian desginers thought that they gained with this designe of a straight jet or prop. I know that a C-17 got bogged at a Sarajevo airport on a bit of wet grass and that this lack of grunt is due to the use of jets instead of props. Either way the Russians are ready to go apparently! Another fascinating possibility is the use of SOFC (Solid Oxide Fuel Cells). Many people beleive these will match piston engines in cars in terms was weight. If turbo supercharged they should have an amazing efficiency of 85%. They opperate at 800C at which point the metal oxide membranse can conduct oxygen ions (instead of hysrgen ions) and thus burn hydrocarbon fuels. The high temperature (still only 1/3rd that of a pertrol engine) means that no catalyst is needed. They are running in the lab at 60% efficient unburdened but becuase they exhaust at 800-1000C they can be trubo-supercharged and excess shaft power extracted. These SOFCs should achieve the same power to weigh ratio of petrol engines and thus be able to propell aircraft. Potentialy their engine and cell life will be so high that they compete with gas trubines. They would require only modes cooling and would require light propellors since no piston torgue vibarations would be present. I'm not exactly sure why they aren't much in use. Hypotheses I've read include greater risk to the passenger cabin from uncontained failures (I wonder if it is coincidence that both the testbeds were the sort of jets with aft-mounted engines); undesirable "propeller" image; noise; and parallel improvements in high-bypass turbofans of the usual ducted design. Cheers, --Joe I think there were some noise issues (not major), blade safety I think could be handled (the scimitar shaped much add unusual stresses), then there is the issue of gear boxes. These are high maintain items. (The only geared turbo fan in sevice is that unit (Allison) on the BAE avro regional/ BAE146 series jet I think) It will be interesting to see if Pratt+Whitney's PW8000 geared turbofan for airbus changes the anti-gearbox mindset. http://www.aerospaceweb.org/question...on/q0067.shtml (survey article; pix) http://www.aviation-history.com/garb...g/udf-2_f.html The goals were, I think, a combination of fuel efficiency and some internal simplifications. |
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On Wed, 03 Dec 2003 23:11:57 -0700, George Ruch
wrote: I remember what may be the same picture, a DC-9 fitted with a high-bypass turbofan, and multiple scimitar-shaped fan blades extending from the first-stage fan. Damned if I can find it now, though. Nothing like it so far on the NASA Dryden site. Any other ideas? We put ours on the spine of the Jetstar and drove it with bleed air. That DC-9 you recall probably belonged to GE, which has a test facility in Mojave. Mary -- Mary Shafer Retired aerospace research engineer |
#30
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Chad Irby wrote:
In article , George Ruch wrote: (B2431) wrote: From: "The Enlightenment" snip I recall seeing GE tested scimitar shaped pusher prop engines [snip] I remember what may be the same picture, a DC-9 fitted with a high-bypass turbofan, and multiple scimitar-shaped fan blades extending from the first-stage fan. Damned if I can find it now, though. Nothing like it so far on the NASA Dryden site. Any other ideas? The one thing I can remember about the program was that the suckers were too loud to fly over most cities in the US. Probably so. Something like flying next to a TU-95 (migraine headache number 43, or so I've heard). /------------------------------------------------------------\ | George Ruch | | "Is there life in Clovis after Clovis Man?" | \------------------------------------------------------------/ |
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