GE's new jet engine

[ChuckMK23]

Re-engine the B-52... that's a good use for it. Would cut the number of engines from 8 to 4, maybe possibly 2? I can see that happening. Less fuel + longer range + less engines = better aircraft.

But alas, that would make sense, and we all know that if the military did anything that made sense, it's instantaneously mink out of existance and be replaced by something even more bizzare and inexplicable... (does anyone get the reference?)

You know that does make sense - re-engining the B-52 like that. I doubt we will ever not have B-52's in the inventory.

 

[phrogdriver]

We got anyone on here who can discuss the possibility of converting this for application in engines that might someday replace the props / rotors on the MV-22 Osprey? Or maybe just helo engines in general...?

Pretty big for an Osprey. I'm not sure you'd want to point an engine like this right at the ground. It would have to be very high bypass. Even a turboshaft engine like the Osprey's, which has relatively negligible exhaust, uses a "coanda" system to prevent exhaust from directly hitting the ground, and it's still pretty warm.

 

[jamnww]

Pretty big for an Osprey. I'm not sure you'd want to point an engine like this right at the ground. It would have to be very high bypass. Even a turboshaft engine like the Osprey's, which has relatively negligible exhaust, uses a "coanda" system to prevent exhaust from directly hitting the ground, and it's still pretty warm.

Thanks thats exactly the information I was looking for...

 

[Pags]

True as it may be, you also have to look at the technology... Yes, something that large is impractical in most military airframes (save USAF cargo planes). However, the technology used in the engine... i.e. the curved fan blades on the intake that make the engine more efficient, can be scaled down and use in smaller engines that may be practical for military aviation.

I think the real value in this engine isn't just its size or power, but also the technological advances it encompasses that can be scaled down for use on smaller aircraft.

-More of Bubba's $0.02

Nothing scales linearly. You can't just shrink an engine and hope it works the same when you make it smaller. I have no clue how well it would work if you shrunk it down to something the size of an S-3 engine, but it wouldn't work the same. And I doubt it would have the same benefits in an engine with a lower bypass.

 

[highlyrandom]

Correct me if I'm wrong, but you can't do an auto with a jet engine...

Helo guys confirm? I figure the way helos and Osprey work, one can lift more stuff with a running takeoff due to rotor aerodynamics (works a little like a wing), but with a constant amount of thrust pointed at the ground, you get no benefit from a running takeoff.

A windmilling jet engine gets you jack in the way of effective lift.

 

[phrogdriver]

The Osprey has a wing, too, so it would still benefit from forward airspeed. I don't think you'd get any benefit from ground effect in a hover with a jet, though you'd still get it close to the ground in forward flight.

Pointing jets at the ground has its limits, which is probably why it hasn't been done to this point. Witness the JSF, which uses a clutched turboshaft to drive a fan for vertical propulsion. Previous VTOL aircraft, like the Harrier, have extremely limited hover times and weights. There's just a lot of efficiency lost there.

 

[Pags]

Does the osprey benefit from translational lift like a helo does?

 

[highlyrandom]

There's no way it doesn't...it's like a sideways -46 with wings when it's taking off, and those blades are huge. Since I'm no aeronautical engineer, I'm just gonna stick with the autorotation part, since the blade pitch can be manually changed from "shallow" for blade acceleration to "coarse" for that last bit of thrust prior to touchdown. Or however you guys do autos.

In other words, no idea.

 

[phrogdriver]

Yes, the Osprey does get translational lift, like a helo. Obviously, the faster you go, the more the wing becomes a player. You are right that you couldn't auto a turboFAN engine, but I don't think that's really why it's not used. I think it has more to do with jet blast and thrust efficiency.

 

[squeeze]

The Osprey has a wing, too, so it would still benefit from forward airspeed. I don't think you'd get any benefit from ground effect in a hover with a jet, though you'd still get it close to the ground in forward flight.

Pointing jets at the ground has its limits, which is probably why it hasn't been done to this point. Witness the JSF, which uses a clutched turboshaft to drive a fan for vertical propulsion. Previous VTOL aircraft, like the Harrier, have extremely limited hover times and weights. There's just a lot of efficiency lost there.

With the Harrier you don't really get ground effect per se, but you get the benefit of the jet fountain deflecting off the ground. The Harrier has a Lift Improvent Device System (LIDS) that helps to 'capture' the fountain and provide ~1200# of lift in the hover. Jets do have their limits in hovering flight. Harriers are limited by weight and a max of 5 minutes of sustained engine bleed (bleed air powers the reactive control system (RCS) ducts that control movement in jetborne/semi-jetborne flight). FOD is also more of an issue with jets, which is why we don't do sustained hovering below 50'. Lower than that you have reingestion of exhaust gases and with it, FOD issues.

 

[highlyrandom]

Here's your vertically mounted turbofan.

"Arrest the drift, cushion the landing...with pogo sticks!"

 

[TheBubba]

Nothing scales linearly. You can't just shrink an engine and hope it works the same when you make it smaller. I have no clue how well it would work if you shrunk it down to something the size of an S-3 engine, but it wouldn't work the same. And I doubt it would have the same benefits in an engine with a lower bypass.

Talking concepts... sure if you used curved blades in a smaller engine, you'd have to change a buch of the blade specs. The same with any number of things on GE's engine.

However, if you take the technological concept and scale it correctly, making any neccessary adjustments, you may end up with an engine that can be used in military aviation.

It may not work, it may work. But ya gotta try...

 

[TurnandBurn55]

So the B-52 with 8 engines... does it have 8 throttles? What, are they all like mechanically linked in one ungodly assembly? I can only imagine EPs in that behemoth... "uhhh... throttle affected engine off... hrmmm"

 

[squeeze]

So the B-52 with 8 engines... does it have 8 throttles?

Does that answer that?

 

[Jaxs170]

Check out this web site from GE to get the full view of what they are working on: http://ge.ecomagination.com/

While the -115B is a great engine, the GEnx is the wave of the future. You'll find both under transportation aircraft, but if you have time the rest of the site is worth checking out as well, a true preview of what is to come.