CFM Rise

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TomcatViP

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GE Aviation and France's Safran together produce some of the most commonly used aircraft engines under their CFM joint venture. Together they launched a new program, called CFM Rise, that will develop and test new technology that could enter service in the mid-2030s, the companies said.
[...]
The RISE program will work on technology that could reduce fuel consumption by more than 20% and also be compatible with sustainable aviation fuel and hydrogen, they said.

The companies plan to design an engine that is open fan, which is unlike the covered jet-engines on commercial aircraft.
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rotor-1_cfm-monday-promo.jpg



www.cnbc.com

GE, Safran developing cleaner energy aircraft engines that could work with hybrid technology, hydrogen

General Electric's aviation unit and joint venture partner Safran plan to develop new aircraft engines that would require more than 20% less fuel.
www.cnbc.com www.cnbc.com
 
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AV Week story on RISE

CFM Unveils ‘Open Fan’ Demonstrator Plan For Next-Gen Engine | Aviation Week Network

CFM International joint venture partners GE Aviation and Safran have launched an aggressive technology development program to pave the way for a new generation of fuel-efficient unducted—or open fan—engines to enter service around the mid-2030s.
aviationweek.com aviationweek.com


The non-rotating, variable-pitch stators behind the fan are a fascinating development.

If the current Administration is able to make funding for a TBW x-plane happen, I'd want to see NASA put RISE (or equivalent) on it at some point during the test program. A truss-braced high aspect ratio wing combined with this open-fan concept would be a hell of a thing to see.
 
I am wondering what core it will be based on.
Norris mention test being done with the M88. But what's next?
 
Smaller diameter = lower tip speed = less noise.
Idem for the core size (smaller, less tip speed, less noise + plus you need a small core to have a small diameter prop).
The stator behind the rotor might not be that really static (beyond pitch).I think they have put their finger on something really interesting for the future of subsonic propulsion.
:rolleyes:
 
I'd be interested to see if the gearbox allows them to get the fan speed down lower than GE36, despite the loss of the second fan.
 
TomcatViP said:
Smaller diameter = lower tip speed = less noise.
Idem for the core size (smaller, less tip speed, less noise + plus you need a small core to have a small diameter prop).
The stator behind the rotor might not be that really static (beyond pitch).I think they have put their finger on something really interesting for the future of subsonic propulsion.
:rolleyes:
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Smaller diameter = less thrust. To get more thrust out of a smaller diameter fan, usually the fan speed is increased. And a larger-diameter core tends to be more efficient (lower thermal losses).

So decreasing the engine diameter goes against the entire line of development from the TF39 and Conway to today's high-bypass engines. It'll be interesting to see how they intend to resolve this.
 
Over the last 50 years, we’ve learned how to make the open fan engine design simpler and lighter. Stationary outlet guide vanes replace previous two-stage, counter-rotating fan blades in our latest designs. This change is significant because we can direct air flow and fly at speeds consistent with conventional turbofan engine architectures.

More recently, we’ve made significant improvements in acoustics, which had been an inhibiting factor. Open fan acoustics are where we need them to be for commercial service and we are actually on the lower end for noise certification.

While ducts (or fan cases/nacelles) perform some aerodynamic function, their primary function is structural. But they weigh a ton. Literally. And when you take most of that weight away with the open fan design, you also remove propulsion drag.

We joke that removing the nacelle lets a fan blade be a fan blade. When there is a nacelle, you have to decide how big you want the fan to be. But when you remove the nacelle, the fan is able to be as big as it needs to be from an aerodynamic standpoint. Even with larger blades, the open fan is not much bigger than the nacelle we have around the CFM LEAP engine today. In fact, the blades for the RISE Program’s open fan are not much bigger than the GE9X fan blades.

blog.geaviation.com

Why the Time for Open Fan is Now - The GE Aerospace Blog | Aviation & Flight News

As the GE Aviation rises to the aviation industry’s challenge to achieve net zero CO2 emissions by 2050, GE Aviation's Chief Engineer Chris Lorence outlines why open fan engine architecture is the radical change aviation needs to achieve its goals.
blog.geaviation.com blog.geaviation.com
 
"variable-pitch stators"

Thank you. I'd missed that...

Can they get away with one ring, or will they iterate to two ??
 
I might be wrong, but my idea was, that counter rotating enables to use lower rpm on the props (my personal estimation 50% of a single blade plus stator) than using a single open fan in combination with a stator. In this case, the tip speed could be much lower in a counter rotating configuration, am i wrong?

I thought this would be the reason why nobody ever used a single open fan with a stator. BTW. In ships pre swirl devices are becoming more popular (e.g. the Mevis duct).
 
View: https://www.youtube.com/watch?v=CDA1mQjC8LE

https://twitter.com/x/status/1567159710050123778
View: https://twitter.com/GEAviation/status/1567159710050123778

blog.geaviation.com

Passion in 3D: Aviation Hobbyist Prints CFM RISE Open Fan Model From Scratch - The GE Aviation Blog | Aerospace & Flight News

When Alex Hills first saw the video rendering of the #CFMRISE open fan engine demonstrator he thought, "Wouldn't it be cool if there was a physical model?" So he decided to reverse engineer one.
blog.geaviation.com blog.geaviation.com
 
Just yesterday I found a good video, representing history and current stage of Unducted Fans' development- namely CFM RISE.

Revolutionizing Flight! The Amazing Potential of the CFM RISE Engine

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I still wonder, how such combination of rotor and stator works. Nearly century classic propellers works without any type of devices, that align their stream. However, such feature is the basis of all turbojets. I would kindly apperciate a good explanation of such different layouts.
 
You will surly know, that every (single) propeller not only accelerates the air in the desired direction, but also produces an unwanted spin which means lost energy. To avoid that spin, you can use e.g. counter rotating props or a non-rotating device which eliminates the spin and will hopefully produce thrust out of the otherwise wasted energy. Of course, the additional device will also produce losses, so that it is not an easy task to make a real benefit. I believe it simply wasn’t regarded as worth the effort, especially when conventional propeller can already archive about 85 % efficiency. It might be different at higher Mach numbers. My idea is, that at higher subsonic Mach numbers, the inclination of the prop blades has to be increased to reduce the prop blades tip speed and in doing so, the losses due to rotational energy are increased. So the relation between additional losses and recovered energy is more positive at higher speeds. These guide vans are variable, to work as good as possible at every speed/power output and flight height but will very likely be optimized for cruise flight.
 
This engine concept annoys the hell out of me. They are basically saying "a counter-rotating gearbox is too difficult so we are going to try and get as close to that as we can by using a simpler technology" technological laziness is what the CFM RISE is. This engine is the "patron saint of mediocrities" for the open rotor world. The stators can only partially make up for the loss of counter rotation and so this will inevitably have to have a larger diameter than CROR and will have lower propulsive efficiency. Period. Why compromise when you don't have to? Makes absolutely no sense.
 
Counter rotating props with variable pitch are nothing new and the benefits are well understood, despite that, such a system never became a commercial success. Focusing only on max. efficiency and ignoring all other aspects is rarely the best way to go. The non rotating variable pitch guide blades are a much simpler concept which might be much more viable than counter rotating props. I expect, that counter rotating is only better at high speeds, because it allows lower tip velocity.

On the other hand, I never understood, why counter rotating props (even in combination with a swashplate) are doing fine in helicopters but were too troublesome for planes.
 
Moose said:
A truss-braced high aspect ratio wing combined with this open-fan concept would be a hell of a thing to see.
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Has anyone put control surfaces on trusses to handle intake airflow going to such nacelles—-nothing you would want to use at speed mind you.
 
Im thinking on a pusher plane were the tailplane could act as a non rotating guide vanes.
 
Early days, but interesting differences to to concept images they've shown previously. Almost looks like this has returned to counter-rotating fans rather than Fan+stator.
 
Moose said:
Early days, but interesting differences to to concept images they've shown previously. Almost looks like this has returned to counter-rotating fans rather than Fan+stator.
Click to expand...

Why do you think that is the case? The two groups of blades (fan + stator or fan + fan) are still looking like they were made out of different materials. I guess, the fan are made out of Carbonfibre and the stator out of metall, which would make sense, since weight it not as important on the stator and metalls might allow to make them thinner which might make them more effective.
 

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