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keesje
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A320 & Boeing 737 Successor, Open Rotor?

Thu Jul 16, 2009 9:22 pm

The Boeing 737 has been around for 40 years and has seen major upgrades in the mid eighties and late nineties. The A320 also has passed 20 yrs. Both Airbus and Boeing indicate they don’t see the need for new narrow body aircraft being developed before 2020 earliest.

Question is what the airlines will think if oil goes through the roof again. Who will buy Boeing 737/A320's from 2017 for use until 2042? Is it still a good investment? Public & government pressure to reduce levels of green house gas emissions are also growing.

Counter rotating open rotor technology (CROR) promises 25 % fuel efficiencies improvements over todays engines..


Source : http://www.nlr.nl/smartsite.dws?id=12618
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MSNDC9
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RE: A320 & Boeing 737 Successor, Open Rotor?

Thu Jul 16, 2009 10:03 pm

Not a chance. Too much noise.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Thu Jul 16, 2009 10:25 pm

I'm more of a believer that eventually making laminar flow through the engine will be where we go. Open rotor technology isn't that impressive. It doesn't get you much more than a high bypass engine does. Open rotors were a good thing to look at when engines were lower bypass as in the 727/DC9 days. The new engines with less than 10% going through the core defeat the purpose of open rotor in my opinion. If you want to go towards higher efficiency, then go for a full turboprop, and not a basterdized more efficient low bypass engine. The open rotor concept was really popular in the 80s for development, but the noise, lower altitude, lower speed could not help it overcome the fuel improvement, especially when the ultra high bypass engines gave almost the same improvement.

Now where we can see some big gains is if we go towards laminar flow. The technology has been around for decades on submarines, and Pratt & Whitney is trying to do it with air. Changing the speed of the fan blades is not an easy task though. Getting reliability out of all those extra moving parts operating at the extreme conditions in an engine will be an incredible challenge. They'll certainly blow a lot of stuff up in the process. If someone can do it and get it to work though, they are going to have a huge money maker, although the risk and cost are probably as high to an engine manufacturer as the 747 was to Boeing. It appears though that Pratt & Whitney is willing to bet the company. The others still seem to believe that the bigger the fan, the better off you are.

[Edited 2009-07-16 15:44:55]
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tdscanuck
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 3:59 am



Quoting Keesje (Thread starter):
Who will buy Boeing 737/A320's from 2017 for use until 2042?

Everyone, unless somebody comes out with a viable competitor. Although using an older technology aircraft isn't a great value proposition for an airline, it's better than having no aircraft. That's assuming you actually want to have an airline at all. Thus the old joke about how to make a fortune in the airline business...

Quoting Keesje (Thread starter):
Is it still a good investment?

Relative to what? If it's the only option then it's the only investment...unless you choose to exit the business, you need aircraft.

Quoting Keesje (Thread starter):
Counter rotating open rotor technology (CROR) promises 25 % fuel efficiencies improvements over todays engines..

*If* they can solve all the integration issues. CROR promised exactly the same thing in the 80's with and it never went anywhere.

Quoting MSNDC9 (Reply 1):
Not a chance. Too much noise.

Last month, RR claimed their latest open rotor would meet Stage IV by a comfortable margin.

Quoting RoseFlyer (Reply 2):
If you want to go towards higher efficiency, then go for a full turboprop, and not a basterdized more efficient low bypass engine.

That kills your speed worse than an open rotor. If fuel really goes through the ceiling the time/fuel trade might drive us that way, but the open rotor is an attempted compromise to get a step change in fuel burn while fitting in the same route/schedule structure as the existing products.

Of course, by the time we replace the A320/737, the A400M engines will finally be available and we'll have a nice big turboprop to play with...

Tom.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 4:18 am



Quoting Tdscanuck (Reply 3):
Last month, RR claimed their latest open rotor would meet Stage IV by a comfortable margin.

Yes, but fans are doing so by a wide margin.
 
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keesje
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 8:24 am



Quoting RoseFlyer (Reply 2):
Open rotor technology isn't that impressive. It doesn't get you much more than a high bypass engine does. Open rotors were a good thing to look at when engines were lower bypass as in the 727/DC9 days. The new engines with less than 10% going through the core defeat the purpose of open rotor in my opinion. If you want to go towards higher efficiency, then go for a full turboprop, and not a basterdized more efficient low bypass engine.

I think counter rotating open rotor technology is more efficient then a single prop. A single prop creates a swirling airstream. A CROC a more straight one. That should be good enough for an additional 5% energy effieciency. I think CROR have a bypass ratio in term of 1 to 30/40 so only 3-4% of the air going through the core.

CFM and Pratt are developing the LEAPX and the Geared Turbo Fan (GTF). Both these engines could fit under the wings of A320 and 737 (though with considerable modifications). Those engines promise fuel consumption reduction of around 15%.

However a further 10% improvement could be achieved by introducing counter rotating open rotors (CROR) as shown on GE stand at the Paris airshow (CFM LEAPX prototype in front).



So the promises of the new improved CROR are high. Last month GE / Safran were openly claiming its 10% better then their LEAPX (in front).
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Faro
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 11:40 am



Quoting RoseFlyer (Reply 2):
Now where we can see some big gains is if we go towards laminar flow. The technology has been around for decades on submarines, and Pratt & Whitney is trying to do it with air. Changing the speed of the fan blades is not an easy task though. Getting reliability out of all those extra moving parts operating at the extreme conditions in an engine will be an incredible challenge. They'll certainly blow a lot of stuff up in the process. If someone can do it and get it to work though, they are going to have a huge money maker, although the risk and cost are probably as high to an engine manufacturer as the 747 was to Boeing. It appears though that Pratt & Whitney is willing to bet the company. The others still seem to believe that the bigger the fan, the better off you are.

Very interesting, first time I've heard of laminar flow in the context of jet engines. Is this a direct result of GTF and a slower turning fan? Can it be applied to compressor/turbine flow too or only to the fan? Are we talking of all engine surfaces including the nacelle duct or the aerodynamic airfoils only?

Also, why would it be a bet-the-company innovation for PW? What is so difficult to implement about laminar flow in a fan engine?

Faro
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MSNDC9
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 3:40 pm



Quoting Keesje (Reply 5):
I think counter rotating open rotor technology is more efficient then a single prop. A single prop creates a swirling airstream. A CROC a more straight one. That should be good enough for an additional 5% energy effieciency. I think CROR have a bypass ratio in term of 1 to 30/40 so only 3-4% of the air going through the core.

But an ultra high bypass fan combined with bio-fuel makes the open rotor idea relatively dead idea, yet again...
 
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keesje
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 7:24 pm



Quoting MSNDC9 (Reply 7):
But an ultra high bypass fan combined with bio-fuel makes the open rotor idea relatively dead idea, yet again...

The most ambitious turbofans at this moment have bypass ratios of about 1:10-12. Making them even bigger makes cowlings very heavy.

The most modern turbofan currently under development and to enter service around 2015 is the LEAPX, it has a BPR of about 10. GE and Safran hope it will have provide a fuel efficiency improvement of about 16%.



Still CORC offers a 10% advantage, to much to ignore. That's why despite the LEAPX, GE are investing in it, together with NASA. http://www.gereports.com/ge-and-nasa...est-open-rotor-jet-engine-systems/

Biofuel or whatever alternative fuel can also be put in an CROC, that's not the issue.
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 7:39 pm



Quoting Keesje (Reply 8):
a fuel efficiency improvement of about 16%.

I have a question. When engine manufacturers state percentages like this, are they using common definitions and conditions?

In other words, when an engine manufacturer says an engine will be 16% more efficient than a certain engine in service today, do they mean:

- The new engine will burn 16% less fuel in a ground-based test stand at XX% N1

or do they mean:

- The new engine will burn 16% less fuel when mounted on an aircraft and flown from airport A to airport B

As I understand it, there is a significant difference. Awhile back, I read an interview with an opponent of open-rotor technology (proponent of the GTF), and if I recall correctly, he stated that the open-rotor can exhibit lower fuel burn in the stand, but due to other factors, the advantage decreases or disappears on actual flights. Possibly because the open-rotor must be throttled up for a longer period of time...maybe due to weight and/or aerodynamics.

So which conditions does everyone refer to? Test stand or point-to-point? And does it really matter?

2H4
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MSNDC9
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 8:51 pm

Quoting Keesje (Reply 8):
The most ambitious turbofans at this moment have bypass ratios of about 1:10-12. Making them even bigger makes cowlings very heavy.

Size of the cowling is moot compared to the diameter of unducted blades. Your argument makes no sense.

Quoting Keesje (Reply 8):
The most modern turbofan currently under development and to enter service around 2015 is the LEAPX, it has a BPR of about 10. GE and Safran hope it will have provide a fuel efficiency improvement of about 16%.

The PW GTF is a 20% per seat burn improvement over the 717-200 and A-318. Your point is again moot.

Quoting Keesje (Reply 8):
Still CORC offers a 10% advantage, to much to ignore. That's why despite the LEAPX, GE are investing in it, together with NASA. http://www.gereports.com/ge-and-nasa...tems/


Waste of time and money.

Quoting Keesje (Reply 8):
Biofuel or whatever alternative fuel can also be put in an CROC, that's not the issue.

Irrelivant. The point is the fan gains coupled with biofuel being enough to relegate the open rotor to the dust box again. You might see it on a nextgen RJ but you are seriously out of touch if you think you're going to see it on a 150 seater.

Just because you can, doesn't mean you should.

[Edited 2009-07-17 14:03:37]
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Jul 17, 2009 9:37 pm

During the last year Rolls Royce has been doing extensive testing on new open rotor concept.

Strategic Marketing Manager-Future Programs Paul Randall said the open rotor is "the true game-changer" and could provide a 25%-30% fuel efficiency gain over turbofans powering narrowbodies today and be 10%-15% more fuel efficient than advanced turbofans that may come on line in the next decade. "Now the open rotor has moved from being a physics problem to an engineering problem," he said. "It is real and it is being realized."
http://www.atwonline.com/news/story.html?storyID=16749



RR open rotor being tested in large wind tunnel in the Netherlands last yr.

I think progress has been been made with the help of CFD that wasn't there 20 yrs ago. Wing tip vortexes don't hit each other anymore and smart ways to manage engine pylon wake are developped.
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MSNDC9
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 3:02 am



Quoting Keesje (Reply 11):
"Now the open rotor has moved from being a physics problem to an engineering problem," he said.

Thats a big problem.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 3:30 am



Quoting MSNDC9 (Reply 12):
Thats a big problem.

Historically, it's been easier to overcome engineering challenges than it has been to overcome laws of physics.

2H4
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 3:50 am



Quoting 2H4 (Reply 13):
Historically, it's been easier to overcome engineering challenges than it has been to overcome laws of physics.

2H4

Unless the engineering problem winds up turning in to a new physics problem once you attach it to an airframe.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 3:52 am



Quoting MSNDC9 (Reply 14):
Unless the engineering problem winds up turning in to a new physics problem once you attach it to an airframe.

Precisely! In the end, it's the physics problem that is most difficult to overcome, and is the limiting factor.  yes 

2H4
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tdscanuck
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 3:55 am



Quoting Keesje (Reply 5):
I think counter rotating open rotor technology is more efficient then a single prop. A single prop creates a swirling airstream. A CROC a more straight one.

This is true from a purely aerodynamic point of view, but the CROC has to be much much heavier and more complex in order to achieve the aerodynamic gain. At the moment, CROC's can't beat turboprops on installed efficiency, although the gap will eventually close up since a CROC taken to its extreme is just a counter-rotating turboprop, which is ~50 year old technology.

Quoting 2H4 (Reply 9):
As I understand it, there is a significant difference. Awhile back, I read an interview with an opponent of open-rotor technology (proponent of the GTF), and if I recall correctly, he stated that the open-rotor can exhibit lower fuel burn in the stand, but due to other factors, the advantage decreases or disappears on actual flights. Possibly because the open-rotor must be throttled up for a longer period of time...maybe due to weight and/or aerodynamics.

I've heard that as well, although not due to weight or aerodynamics but due to integration problems. You need to do a lot of things to the airframe to accomodate the open rotor and, apparently, those compromises eat up most of the initial advantage that the engine had in isolation on the test stand.

Quoting 2H4 (Reply 9):

In other words, when an engine manufacturer says an engine will be 16% more efficient than a certain engine in service today, do they mean:

- The new engine will burn 16% less fuel in a ground-based test stand at XX% N1

or do they mean:

- The new engine will burn 16% less fuel when mounted on an aircraft and flown from airport A to airport B

Typically the former. The engine makers usually wash their hands of the airframe integration problems, which is where most of the difference between the two comes from.

Tom.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 4:00 am



Quoting Tdscanuck (Reply 16):
Typically the former. The engine makers usually wash their hands of the airframe integration problems, which is where most of the difference between the two comes from.

Very interesting, indeed. Thanks for the info.

2H4
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Jul 18, 2009 9:20 am



Quoting Keesje (Reply 11):
During the last year Rolls Royce has been doing extensive testing on new open rotor concept.

CFD may be a boost to the progress achieved with the CROR concept but the pic of the Rolls Royce set-up resembles the Kuznetsov MK-12 as installed on the Tu-95/Tu-114. I wonder whether this older technology installation is to a certain extent being refined with today's CFD tools.

Faro
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keesje
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sun Jul 19, 2009 7:50 pm



Quoting Faro (Reply 18):
CFD may be a boost to the progress achieved with the CROR concept but the pic of the Rolls Royce set-up resembles the Kuznetsov MK-12 as installed on the Tu-95/Tu-114. I wonder whether this older technology installation is to a certain extent being refined with today's CFD tools

The RR testconfiguation is for accoustic testing. Extensive CFD modelling and testing let to significant noise and efficiency improvements compared to late eighties research. Blade tip vortex streams are among the key research areas. Shapes, lenghts, numbers, speeds of these rotor are incomparable to previous generations.

Progress has been made. Thats why GE and RR are investing and developping. 10 Percent on top of new gen turbofans within noise regulations cannot be ignored. PW is nervous. GE, Safran and RR are betting on two horses.
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RE: A320 & Boeing 737 Successor, Open Rotor?

Mon Dec 14, 2009 2:58 pm

What about the design of NK-93? I guess the ducting of the counter rotating fans greatly reduces the noise but it still has all the savings of the open rotor concepts. It surprises me that noone else have tried this solution. This also facilitates the mounting under the wings which would be a problem with the open rotor.
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RE: A320 & Boeing 737 Successor, Open Rotor?

Mon Dec 14, 2009 3:18 pm

You're still going to need a pretty large duct around the rotor, so you either need a high-mounted wing or stilts for landing gear.

Open Rotor does have a fuel advantage over "traditional turbine" and GTF designs in a laboratory environment, but Pratt is pretty confident that once you actually attach it to an airframe and put it into revenue service, the extra weight of the mounting unit and extra insulation and armor for the cabin/control surfaces will negate much of that.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 15, 2009 2:09 pm

But with the current NK-93 design the fan diameter is 290mm which would be about the same as the GE90 and I would guess you would be able to scale it somewhat.. All newer designs are growing the fan compared to the compressor itself so I guess no matter how you spin it you'll need more space underneath the wing eventually or go for a mounting on top of the empannage.?

My technical knowledge is restricted when it come to this, but since the NK-93 at it's current form has a output of ca 16t.. What would be the equivalent GE/RR/PW engine?
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Stitch
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 15, 2009 3:22 pm

According to Pratt, an Open Rotor providing 24,000 to 30,000 pounds of thrust would require between 450 and 500 centimeters of clearance. You're not going to be able to do that with a low-mounted wing unless you're undercarriage is modeled after a stork's.  Smile

They claim a GTF could do that with a nacelle diameter under 250 centimeters and that they could squeeze it under a 737NG (thanks to a more forward mounting position allowing them to lift the top of the nacelle up close to the wing's leading edge, which evidently brings it's own benefits.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 15, 2009 4:24 pm



Quoting Keesje (Thread starter):
Counter rotating open rotor technology (CROR) promises 25 % fuel efficiencies improvements over todays engines..

And 300% more troubles for the noise.... so that's not convenient
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 15, 2009 8:02 pm



Quoting Stitch (Reply 23):
According to Pratt, an Open Rotor providing 24,000 to 30,000 pounds of thrust would require between 450 and 500 centimeters of clearance. You're not going to be able to do that with a low-mounted wing unless you're undercarriage is modeled after a stork's

I think the configurations in the opening post & GE presentation are no coincidence.

Quoting Max777geek (Reply 24):
And 300% more troubles for the noise.... so that's not convenient

RR says they made progress due to new configurations, shapes and CFD. Most likely the noise will be worse then the latest Turbofans. That brings us to the unconvinient trade-off for the next decade. Do we want more environmental friendly OR silent engines. The polar bears don't die from the noise around FCO.. maybe it's comfort vs environment..
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RE: A320 & Boeing 737 Successor, Open Rotor?

Wed Dec 16, 2009 12:38 am



Quoting Keesje (Reply 25):
I think the configurations in the opening post & GE presentation are no coincidence.

Indeed.  checkmark 

Quoting Keesje (Reply 25):
Do we want more environmental friendly OR silent engines. The polar bears don't die from the noise around FCO.. maybe it's comfort vs environment..

However, NIMBY's concern for the plight of polar bears end in their backyards.

So they're going to be interested in reducing both fuel consumption and noise over just reducing fuel consumption and not noise. And they will almost certainly be against reducing fuel consumption while increasing noise.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Wed Dec 16, 2009 12:02 pm



Quoting Stitch (Reply 23):
They claim a GTF could do that with a nacelle diameter under 250 centimeters and that they could squeeze it under a 737NG (thanks to a more forward mounting position allowing them to lift the top of the nacelle up close to the wing's leading edge, which evidently brings it's own benefits.

Ok, so after browsing what little info I could find on the NK-93 I found that the 18t (not 16t) of thrust equals about 35-40.000 pounds of thrust. So putting an engine like this, with it's current forecasted savings, would in the case of a narrowbody like the 737 or A320 mean a calculated 20% more fuel efficient over current technology as opposed to a calculated 10-16% from GTF or LEAPX. And this with a 290cm (not mm) diameter fan (approximately how much extra would be needed for the nacelle?).. Understandably the extra ≈50cm would be hard to accommodate on current designs but that's what we have engineers for right?

Also, concurrently with the testing and development of the NK-93 Kuznetsov is also developing the NK-94 which is basically the same engine but driven by LNG fuel instead. Thus even more environmentally friendly (once there's a viable way to carry it onboard)..

I also found some data that the expected life of a NK-93 would be 15000 hours, and 7500 between overhauls. How would that stack up to the "western" competition?

I'm not necessarily saying that we should all go to the russians and buy our engines henceforth but since they do have some great ideas maybe one should start thinking in the terms of collaboration.. This would be a way to save the polarbears without having the NIMBY's crying too, right?

Sources:
http://motor-s.ru/NK93_en.htm

http://www.janes.com/articles/Janes-...tsov-NK-93-Russian-Federation.html
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RE: A320 & Boeing 737 Successor, Open Rotor?

Wed Dec 16, 2009 1:59 pm

I think that the UDF is always going to come up short against turbofans, for two reasons. One is noise, and the other is speed. Fuel efficiency alone is not going to compensate for noisier aircraft flying considerably slower. And while advances are being made on the UDF, they are also being made on turbofans, and the turbofan will always be quieter and faster. On top of that the most efficient place for engines has been found to be under the wing, for a variety of reasons, and that is a much less desirable place for UDF's. The disadvantages of tail-mounted engines probably will cancel out much of the efficiency gains of the UDF, as Tdscanuck points out.
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RE: A320 & Boeing 737 Successor, Open Rotor?

Wed Dec 16, 2009 3:54 pm

Even with all the problems of noise and structure, the savings on fuel consumption may well be of enough importance to think about this propulsion system as the one for the next generation of 737 and A320. Not that I know much about it, I say this because both Airbus and Boeing are doing serious studies and putting a considerable effort on it...
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Stitch
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RE: A320 & Boeing 737 Successor, Open Rotor?

Wed Dec 16, 2009 4:54 pm

For a 737/A320 thrust range, the GTF's fan is 203 cm, so you'd probably be looking at 340+ cm for an NK-93 with nacelle?

[Edited 2009-12-16 08:54:44]
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Thu Dec 17, 2009 10:01 pm



Quoting Stitch (Reply 30):
For a 737/A320 thrust range, the GTF's fan is 203 cm, so you'd probably be looking at 340+ cm for an NK-93 with nacelle?

Ouch.. Well, I guess that's out of the picture unless they can refine that technology. I do think that the whole counter rotating and variable pitch idea would be interesting if they find a way to put it inside a nacelle, with a 20% or better improvement in fuel economy I think it's very important.. Be it GE, PW or RR.. Really, who cares about who develops the technique the important thing is that we start looking beyond todays technology..

I want a BWB with 4 ducted counter rotating variable pitch fan-jet.. (wow, that's a mouthful)

Cheers!
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Dec 18, 2009 2:03 am



Quoting SEPilot (Reply 28):
I think that the UDF is always going to come up short against turbofans, for two reasons. One is noise, and the other is speed.

Aviation Week & Space Technology had an interesting article on this topic this week...in an nutshell, they've got GE on record as claiming they can get an open rotor as quiet or quieter than current technology and "definitely meet Stage 4 noise regulations."

Tom.
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Dec 18, 2009 3:45 pm

Didn't the GE36 eventually meet Stage III noise regulations?
 
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Dec 19, 2009 2:08 pm



Quoting Tdscanuck (Reply 32):
Aviation Week & Space Technology had an interesting article on this topic this week...in an nutshell, they've got GE on record as claiming they can get an open rotor as quiet or quieter than current technology and "definitely meet Stage 4 noise regulations."

That will be very interesting if they can do it; but that still leaves the problem of speed. I do not see how they can even approach the current speed of jetliners without the blades of the open rotor going seriously supersonic, and that will cause not only noise but efficiency problems. And the problem of speed is not just passengers in a hurry; it is aircraft utilization and return on investment. So it is definitely worth burning more fuel to go faster; the question becomes where is the break point. As Boeing found out with the SonicCruiser, there definitely is one. If the open rotor can go 80% as fast on 80% as much fuel, that might do it. But I suspect that it might end up being more like 70% as fast on 90% as much fuel, and I don't think that will cut it.
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Dec 19, 2009 7:49 pm



Quoting SEPilot (Reply 34):
. As Boeing found out with the SonicCruiser, there definitely is one. If the open rotor can go 80% as fast on 80% as much fuel, that might do it. But I suspect that it might end up being more like 70% as fast on 90% as much fuel, and I don't think that will cut

Both GE claims 26% fuel saving over their CFM56 (market standard) and about 10 % over their future LEAPX concept, as can be seen in early replies. RR is aiming at about 0.76 Mach with its open rotor. http://www.flightglobal.com/articles...1/open-rotor-how-does-it-work.html
"Never mistake motion for action." Ernest Hemingway
 
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SEPilot
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RE: A320 & Boeing 737 Successor, Open Rotor?

Sat Dec 19, 2009 7:53 pm



Quoting Keesje (Reply 35):
RR is aiming at about 0.76 Mach with its open rotor.

If they can achieve this then it may be viable, provided the noise targets are met. That is assuming that they do not make more advances on fanjets in the meantime that will shave the fuel consumption margin more.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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DocLightning
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RE: A320 & Boeing 737 Successor, Open Rotor?

Mon Dec 21, 2009 6:15 pm



Quoting Keesje (Reply 35):
RR is aiming at about 0.76 Mach with its open rotor.

Which is fine for flights under about 2000 statute miles. But for a flight like JFK-SFO, you'll still want turbofans.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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Okie
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 22, 2009 4:57 am

Mount a single MTU off the A400M on the nose of a 37, that ought to pull a 37 about 330kts.

Okie
 
Fly2HMO
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 22, 2009 6:39 am



Quoting Okie (Reply 38):
Mount a single MTU off the A400M on the nose of a 37, that ought to pull a 37 about 330kts.

Now now, we have to keep aesthetics into account. It may work but I don't even want to picture how ugly that would look  liar 
 
tdscanuck
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 22, 2009 6:56 am



Quoting FLY2HMO (Reply 39):
It may work but I don't even want to picture how ugly that would look

It would sure show those Canada Geese who's boss. You want to take down an A320? Well how about *these* apples!

Tom.
 
erchen
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 22, 2009 8:12 am

Approximately how big is the difference in noise in dB?
 
Okie
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RE: A320 & Boeing 737 Successor, Open Rotor?

Tue Dec 22, 2009 1:49 pm



Quoting Erchen (Reply 41):
Approximately how big is the difference in noise in dB?

I am not sure exactly, but living close to an Air Force Base, I can tell you there is a significant difference between some of the older low bypass engines, and the newer high bypass engines.
I am not complaining just stating there is a profound difference. The fighters and turbo-props just come in and out of here and refuel only, they do their touch and goes elsewhere, typically straight in and straight out.

Okie
 
sirtoby
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RE: A320 & Boeing 737 Successor, Open Rotor?

Fri Mar 12, 2010 8:44 am

Quoting Tdscanuck (Reply 3):
Last month, RR claimed their latest open rotor would meet Stage IV by a comfortable margin.

By the time an open rotor would enter service, we will have eventually Stage V - should be another 10dB below Stage 4, what makes it hard to believe and open rotor can also make that!

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