zeitgeist57 Posted February 16, 2014 Report Share Posted February 16, 2014 As I veg here for a bit on a snowy Sunday (I swear I'll get outside and do some projects in a bit ) I figured a few of you car guys might also ponder the following videos... Fast-forward to 1:00 to avoid the 1991-tastic intro graphics and music... I'm certainly hopeful that jet technology has improved since the '80s, but the idea of unducted fan blades pushing more air from around the nacelle off of the same fuel consumption seems to make a lot of sense to me. The GE engine featured in this video has the exterior, unshrouded "props" being driven off of internal hot-side engine compression...in effect, it's like a turbocharger where the hot exhaust gases spin an additional wheel for more air movement. Back when the video was made, they spoke of $0.50/gal fuel:wtf::no:!!! I'm pretty sure we've seen $8/gal for JetA at OSU Airport, and 100LL for general aviation Cessnas is still around $5-$6+/gal consistently. Can someone tell me why this technology never took off? (pun intended ) Another thought...as energy storage (battery) technology improves and becomes more reliable, I'd love to see a hybrid jet/electric fan system on planes where a jet-fueled engine could be used for take-off and acceleration, and electric ducted fans could then be used for cruising. In power-off situations, the fans can also be used as regenerative motors to recharge onboard batteries. I'd imagine the fuel savings would easily be 33-40%, though you would have to amortize the cost of the battery/electric fan technology over a long time for that to break even. We live in a pretty marvelous time...considering airplane tech hasn't changed dramatically since the '50s - some Cessna designs still date back to post-WWII era, and you can look at Convair jetliners from 1958 and easily see similarities to modern passenger jets - but technology and propulsion is on the cusp of making some pretty major leaps. Looking forward to what the future has in store! Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 16, 2014 Report Share Posted February 16, 2014 I'd be interested to learn why the exposed fan blades would be any more efficient than a modern turbo-fan engine. They operate in the same way but everything is inside the fan cowl. Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 16, 2014 Report Share Posted February 16, 2014 And the second design with the electric motors would require some pretty big improvements in the weight of the batteries before the airlines would be interested. Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 16, 2014 Report Share Posted February 16, 2014 I plead the 5th! Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 16, 2014 Report Share Posted February 16, 2014 I plead the 5th! Do you know something that we don't know? And what are you pleading the 5th on? My comments or the original video? Quote Link to comment Share on other sites More sharing options...
98Formula Posted February 16, 2014 Report Share Posted February 16, 2014 For one its probably a safety concern. If something happens to the fan blades theres nothing to try and stop from ripping into the cabin. Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 16, 2014 Report Share Posted February 16, 2014 Up until the most recent cowling designs they pretty much did that any way and I think between props on reciprocating engines and turbo props we've proven that a blade coming through the fuselage is not much of a concern. Not that it doesnt happen but the chances are pretty slim. Quote Link to comment Share on other sites More sharing options...
Richard Cranium Posted February 17, 2014 Report Share Posted February 17, 2014 This doesn't relate exactly, but I was on a tour of the National Air force museum in Dayton and saw many things that blew my mind. One of those things was a piston driven jet engine that I believe was based on an inline 4-cylinder Honda block. It had a custom cylinder head with long straight exhaust pipes coming off. If I remember correctly the cam was changed out to open the exhaust valve on the up stroke of the engine to pressurize the fuel air mixture which was then detonated as it exited into the exhaust pipe creating the forward thrust. Considering I was looking all around at aircraft that were at one time top secret, I'm a little embarrassed I was that interested in this. The engine was mounted in an airframe that looked like a Long-EZ kit plane. There were 4 pipes running toward the tail from behind the cockpit. These pictures are lousy, but they might have enough detail to show what I mean. http://www.columbusracing.com/forums/picture.php?albumid=590&pictureid=7495 http://www.columbusracing.com/forums/picture.php?albumid=590&pictureid=7496 Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 17, 2014 Report Share Posted February 17, 2014 I believe that is a Olds Quad 4 engine I saw that engine and plane at the 2003 Dayton airshow and only snapped a quick pic of it because I was distracted by everything else going on. Only after getting home and getting my film processed (remember those days) did I realize I should have stopped and asked some questions about that beast. From what I remember it was sort of a pulse jet design hence the long exhaust tubes. Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 17, 2014 Report Share Posted February 17, 2014 Here's a link to all you would ever want to know about the above aircraft: http://stargazer2006.online.fr/aircraft/pages/borealis.htm Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 17, 2014 Report Share Posted February 17, 2014 Do you know something that we don't know? And what are you pleading the 5th on? My comments or the original video? Just a joke. Yes, I know substantially more, but can't say more than what is already public domain, and it tough to say what is and isn't, so I just don't say anything. But yes, both of those programs are great future of flight technologies. Quote Link to comment Share on other sites More sharing options...
buelliganx1 Posted February 17, 2014 Report Share Posted February 17, 2014 Just a joke. Yes, I know substantially more, but can't say more than what is already public domain, and it tough to say what is and isn't, so I just don't say anything. But yes, both of those programs are great future of flight technologies. Well that clears that up then lol Quote Link to comment Share on other sites More sharing options...
98Formula Posted February 18, 2014 Report Share Posted February 18, 2014 Came across this at work. Thought this was cool. http://www.rolls-royce.com/interactive_games/journey03/ Quote Link to comment Share on other sites More sharing options...
Nickey4271647545519 Posted February 18, 2014 Report Share Posted February 18, 2014 Hmm... will have to talk with someone about this. I need to know more! Quote Link to comment Share on other sites More sharing options...
zeitgeist57 Posted February 18, 2014 Author Report Share Posted February 18, 2014 Came across this at work. Thought this was cool. http://www.rolls-royce.com/interactive_games/journey03/ That was HUGELY informative. Thanks for the post. So...looks like the UHB jet from the '80s is similar to this modern jet, with the main fan on the RR Trent is shrouded, and acts as both the compressor for the jet engine AND the bypass fan for pulling air through the nacelle (much like a propeller). One other big difference I hadn't thought about is that many turboprops have variable-pitch prop blades. Most modern jet engines like the RR Trent have fixed blades: HUGE cost/reliability/simplicity benefits to assembly, operation, and maintenance. The external blades still LOOKED cool at least. I had a tough time with his capacity references: "squash cart"? "phone booth"? How much more UK can this guy get? Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 18, 2014 Report Share Posted February 18, 2014 To be clear... EVERY high bypass engine (virtually all commercial jet engines get 90% of their thrust from the fan (what you're calling propellers). Very little of the thrust is from the turbine, that's just what makes the fan spin. And nearly every engine you see the compressor gets it's air from the same fan stage. It's military low bypass engines that get thrust from the turbine. Tomorrow I will post some more basic info and a cross section. I will also gladly explain why an unducted fan is more fuel efficient. (The actual biggest challenge is noise - keeping them quiet enough... The one you have above is much louder in the cabin than the normal engine you hear today. Blade out (when a fan blade breaks off) is actually relatively easy to manage, the bigger challenge there is actually the extreme unbalance it creates in the engine that is spinning Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 18, 2014 Report Share Posted February 18, 2014 BTW, in the hierarchy of the commercial jet engine world. GE is on top, followed by Rolls Royce, followed by Pratt. In the military world, it's Pratt (the last two decades anyway) followed by GE, followed by RR Quote Link to comment Share on other sites More sharing options...
everlight44 Posted February 18, 2014 Report Share Posted February 18, 2014 I'd be interested to learn why the exposed fan blades would be any more efficient than a modern turbo-fan engine. They operate in the same way but everything is inside the fan cowl. Perhaps because they have exposure to more air, so cooling is easier? Not sure either. They also would hit a lot more stuff being exposed (i.e geese) That "journey through a jet engine" made my day Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 18, 2014 Report Share Posted February 18, 2014 It's more efficient because of the high bypass ratio. Higher bypass ratios are more fuel efficient. i.e. For the same fuel consumption a prop/unducted fan will make more thrust. The drawback of the turboprop is that it can't make the same overall thrust and speeds. The unducted turbofan helps resolve that delimma. BTW, here's a bit of info as well: http://en.wikipedia.org/wiki/Propfan Quote Link to comment Share on other sites More sharing options...
Mensan Posted February 18, 2014 Report Share Posted February 18, 2014 BTW, in the hierarchy of the commercial jet engine world. GE is on top, followed by Rolls Royce, followed by Pratt. In the military world, it's Pratt (the last two decades anyway) followed by GE, followed by RR Aircraft? When I was in the military (Navy, non-aircraft), our primary GTGs (propulsion) were GE, secondary (generation) were Allison. Quote Link to comment Share on other sites More sharing options...
JuicedH22 Posted February 18, 2014 Report Share Posted February 18, 2014 Yup, GE pretty much has the navy locked down with the F414. we also lead in helicopters, and marine (ships) The F110 is our biggest most used military engine. What I was more referring to is that the last 2 major jet contracts went to Pratt; the F-20 Raptor and the F-35 Lightning. GE had the alternate engine for the f35, but Pratt successfully lobbied congress to have us pulled to "save money" during the budget crisis and economy problems in 2009, even though in reality the facts showed that over the long run it was cheaper to keep our engine as competition to lower prices... Like I said, Pratt/UTC has a lot of influence in the pentagon and did better lobbying. Quote Link to comment Share on other sites More sharing options...
El Karacho1647545492 Posted February 18, 2014 Report Share Posted February 18, 2014 BTW, in the hierarchy of the commercial jet engine world. GE is on top, followed by Rolls Royce, followed by Pratt. In the military world, it's Pratt (the last two decades anyway) followed by GE, followed by RR My grandfather was an engineer for 35 years in East Hartford for Pratt. I always wanted to follow in his footsteps until I saw the requirements in college and remembered how much I loathed everything about chem and physics in high school. Quote Link to comment Share on other sites More sharing options...
Tindall2006 Posted February 21, 2014 Report Share Posted February 21, 2014 Yup, GE pretty much has the navy locked down with the F414. we also lead in helicopters, and marine (ships) The F110 is our biggest most used military engine. What I was more referring to is that the last 2 major jet contracts went to Pratt; the F-20 Raptor and the F-35 Lightning. GE had the alternate engine for the f35, but Pratt successfully lobbied congress to have us pulled to "save money" during the budget crisis and economy problems in 2009, even though in reality the facts showed that over the long run it was cheaper to keep our engine as competition to lower prices... Like I said, Pratt/UTC has a lot of influence in the pentagon and did better lobbying. 1. What is/was your major? 2. Is your job as cool as it sounds? 3. Would you rather design them, or fly them? 4, if you would rather fly them can we trade jobs? Quote Link to comment Share on other sites More sharing options...
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