[Fyodor]

An interesting article from Flight Global:

https://www.flightglobal.com/news/a...r-achievements-in-hybrid-electric-pro-440602/

... with possible applications outside aviation. Some of this is closer than you think.

 

[Barry]

Interesting catch phrases, but I don't understand the technology based on the information in the article. Pulling 1 MW of power out of a jet engine and then transferring it to an electric motor driven propeller to produce 1 MW of power there does not sound useful in any aircraft I can imagine. There is no time shifting of the power without heavy batteries, the electric motor adds a lot of weight, and combining jet propulsion with propellers on the same aircraft can be problematic, and is probably done more efficiently by directly driving them as in a turboprop. I can see this being useful for other electric power needs such as powering a laser weapon or de-icing equipment, as mentioned, but that does not seem revolutionary. It is just a different form of the generators already in use. There must be more to this that the author did not explain well if they are spending money to develop it.

 

[flyingsherpa]

Interesting catch phrases, but I don't understand the technology based on the information in the article. Pulling 1 MW of power out of a jet engine and then transferring it to an electric motor driven propeller to produce 1 MW of power there does not sound useful in any aircraft I can imagine. There is no time shifting of the power without heavy batteries, the electric motor adds a lot of weight, and combining jet propulsion with propellers on the same aircraft can be problematic, and is probably done more efficiently by directly driving them as in a turboprop. I can see this being useful for other electric power needs such as powering a laser weapon or de-icing equipment, as mentioned, but that does not seem revolutionary. It is just a different form of the generators already in use. There must be more to this that the author did not explain well if they are spending money to develop it.

I believe it's two separate tests:
1) siphon 1MW of electric power from an F-15 engine while still allowing it to be function as an F-15 engine. This will allow high-electric power devices like airborne lasers to be used on those platforms, without need of separate generators (supposedly a 747 requires 6 generators to develop that much power).

2) demonstrate a 1MW electric motor for aviation use, in place of a turboprop. They didn't explain this as well, but the theory I've read is turboprops are usually sized for climb performance, then throttle back quite a bit for cruise. Using a serial hybrid setup with a small battery (used for climb only) would allow using a significantly smaller engine, which can ultimately be more fuel efficient. I think VW has a similar car proposal in the works, a 80 mpg car that is purely serial hybrid with a small battery. The small engine just runs at one super efficient rpm, and the electric side smooths things out and provides adequate power.

I don't think (1) and (2) have anything to do with each other, other than both mention 1 MW envelopes.

 

[Fyodor]

I believe it's two separate tests:
1) siphon 1MW of electric power from an F-15 engine ...

2) demonstrate a 1MW electric motor for aviation use, in place of a turboprop. They didn't explain this as well,...

I don't think (1) and (2) have anything to do with each other, other than both mention 1 MW envelopes.

I agree, this is how I read it. The article could have been better written; it implies more of a link between the two projects. The first is a more efficient generator, the second a more efficient motor. They could presumably be paired somehow, but that doesn't seem to be the intent.

The aircraft projects linked in the article are also very interesting.

 

[Raymondjram]

Somewhere in the past I did read about GE adding a generator/motor inside the turbojet/tubofan system to be used as a starter to spin the turbine and fan, and avoid using an external APU (which is an external starter based on a jet engine itself). The generator will produce electricity for onboard systems, including avionics.

 

[saghost]

Interesting catch phrases, but I don't understand the technology based on the information in the article. Pulling 1 MW of power out of a jet engine and then transferring it to an electric motor driven propeller to produce 1 MW of power there does not sound useful in any aircraft I can imagine. There is no time shifting of the power without heavy batteries, the electric motor adds a lot of weight, and combining jet propulsion with propellers on the same aircraft can be problematic, and is probably done more efficiently by directly driving them as in a turboprop. I can see this being useful for other electric power needs such as powering a laser weapon or de-icing equipment, as mentioned, but that does not seem revolutionary. It is just a different form of the generators already in use. There must be more to this that the author did not explain well if they are spending money to develop it.

You're adding weight and complexity and cost and losing efficiency, no doubt. The question is whether that added weight can give you something useful enough to justify carrying it around.

A couple thoughts come to mind. By putting a propeller at the extreme wing tip rotating outboard, you can reverse the tip vortex, significantly improving lifting efficiency and reducing ground effect.

At the same time, this can reduce Vmc and/or rudder size - assuming you can use one engine to drive the opposite side propeller when needed. In fact, you could put differential propeller thrust into the flight controls as a way of managing low speed stability. Of course, you'd want to stop and feather or possibly stow the tip propellers before you get to higher speeds with an airliner.

For shorter field performance, propellers in front of the wing to provide faster acceleration and more airflow over the wing that are again not used during cruise flight under normal circumstances.