I think there are startups making a similar sort of engine for general aviation. It's good to see that there is development of the same idea for commercial aviation.
This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly during cruise if needed.
This means that the battery is quite small and light, having only enough charge to take off and get to altitude.
I suspect that this system probably improves safety as well, if architected properly. If one or both of the gas engines fail, so long as they are not seized, that electric motor can still provide some power for diversion.
kspacewalk2 26 minutes ago [-]
>This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly during cruise if needed.
Isn't that exactly what hybrid cars (e.g. Prius) are? Extremely efficient gas engine for highway cruising, but insufficient for acceleration, which is aided by electric motors?
Tade0 15 minutes ago [-]
The Prius uses a planetary gear set to blend power of the engine with that of the two motor-generators.
Both the engine and motors are used at all speeds. Particularly during highway acceleration the entire assembly rotates in the same direction.
arijun 22 minutes ago [-]
The Prius is in series, or something like it.
idontwantthis 5 minutes ago [-]
No it’s not. The majority of power comes from the engine. It drives the electric motor mechanically, using it as a transmission. It is not just charging the battery.
idontwantthis 3 minutes ago [-]
Hybrid cars are mostly parallel hybrids. Only the Chevy Volt comes to mind as a serial hybrid.
SoftTalker 52 minutes ago [-]
The fuel burn of take-off and climb substantially lightens the aircraft for cruise. Electric batteries have no such effect, you're carrying all that dead weight for the rest of the flight. This reduces the passenger or cargo capacity of the aircraft, which reduces potential revenue.
And what if you need two go-arounds?
arijun 10 minutes ago [-]
> you're carrying all that dead weight for the rest of the flight
If you're recharging the batteries for extra go-arounds during landing, they are as dead weight as the fuel you would otherwise reserve for that purpose. And if you have 30% more efficient engines, meaning less fuel and smaller engines, it's possible you could come out ahead, weight-wise.
> what if you need two go-arounds
I assume that a go-around requires less sustained power output than a full climb from takeoff, so you will probably get more than one go-around anyway, and we don't know how much over-capacity they're designing for. In any case, any design will require tradeoffs in safety, and having more engine-out capabilities might improve safety enough to overcome the higher risk with go-arounds.
Not saying this project is will work out or that you're even wrong necessarily (this could be the equivalent of a concept car for Pratt & Whitney).
0cf8612b2e1e 37 minutes ago [-]
Energy density of liquid fuels cannot be beat by batteries, so this is not competitive if you are looking to maximize cargo. However, there are plenty of short haul flights: private jets, island hopping, regional routes where you need to move little mass.
xattt 33 minutes ago [-]
Exactly. A hybrid passenger car can tolerate unpredictable power output that may come with an auxiliary power setup that may or may not be available when stronger dynamics are called for.
A plane doesn’t have this luxury and needs predictable output. The fossil fuel engine either needs a sacrificial “overboost” mode for emergencies (at the cost of wear/long-term longevity), or has to be sized for full power at the ultimate cost of efficiency.
Tade0 14 minutes ago [-]
On anything but very short flights most of the fuel is spent on cruising.
hobonation 21 minutes ago [-]
Valid.
Perhaps it's not all negative: the electric portion could give a pilot a bit more glide than the gas portion dies.
Someone 2 hours ago [-]
Not “30% fuel efficiency”, but an improvement of 30%.
FTA: “The project aims to demonstrate up to 30% improved fuel efficiency for a typical 250-nautical-mile regional turboprop mission”
c0n5pir4cy 43 minutes ago [-]
I was so confused by the title - I thought jets were fairly efficient at ~40%-50% of theoretical maximum and turbofans can't be that far behind. It would maybe make sense for a single prop aircraft.
30% improvement makes much more sense.
soperj 51 minutes ago [-]
Only AI stories show up now, so they had to call it an Ai craft I guess.
xnx 1 hours ago [-]
[dead]
Rendered at 17:13:51 GMT+0000 (Coordinated Universal Time) with Vercel.
This isn't like a hybrid car. It's a parallel hybrid, where the gas engine is just big enough for efficient cruise at altitude, and the electric motor/generator provides extra power for takeoff and ascent (or go-around power), and then charges slowly during cruise if needed.
This means that the battery is quite small and light, having only enough charge to take off and get to altitude.
I suspect that this system probably improves safety as well, if architected properly. If one or both of the gas engines fail, so long as they are not seized, that electric motor can still provide some power for diversion.
Isn't that exactly what hybrid cars (e.g. Prius) are? Extremely efficient gas engine for highway cruising, but insufficient for acceleration, which is aided by electric motors?
Both the engine and motors are used at all speeds. Particularly during highway acceleration the entire assembly rotates in the same direction.
And what if you need two go-arounds?
If you're recharging the batteries for extra go-arounds during landing, they are as dead weight as the fuel you would otherwise reserve for that purpose. And if you have 30% more efficient engines, meaning less fuel and smaller engines, it's possible you could come out ahead, weight-wise.
> what if you need two go-arounds
I assume that a go-around requires less sustained power output than a full climb from takeoff, so you will probably get more than one go-around anyway, and we don't know how much over-capacity they're designing for. In any case, any design will require tradeoffs in safety, and having more engine-out capabilities might improve safety enough to overcome the higher risk with go-arounds.
Not saying this project is will work out or that you're even wrong necessarily (this could be the equivalent of a concept car for Pratt & Whitney).
A plane doesn’t have this luxury and needs predictable output. The fossil fuel engine either needs a sacrificial “overboost” mode for emergencies (at the cost of wear/long-term longevity), or has to be sized for full power at the ultimate cost of efficiency.
Perhaps it's not all negative: the electric portion could give a pilot a bit more glide than the gas portion dies.
FTA: “The project aims to demonstrate up to 30% improved fuel efficiency for a typical 250-nautical-mile regional turboprop mission”
30% improvement makes much more sense.