So the question is what's aircraft
propulsion gonna look like in the future?
Well the driving force behind it is
trying to reduce the environmental
impact, just like it is for all vehicles
that burn fossil fuels, we're trying to
reduce CO2 emissions and for aircraft
NOx. Immediately we're not gonna see a
massive change because if you imagine
there's a large amount of aircraft flying
around the moment, we're not gonna see
you overnight change suddenly to
electric aircraft. It's gonna be a slow
and steady change, but there are a lot of
changes, engineering changes, going
at the moment. So your your standard
aircraft when you go on holiday is
powered by a turbo fan. That front fan
is gonna get bigger, that makes the
aircraft more propulsively efficient so
we can burn less fuel.
If we burn less fuel we produce less
emissions. But if you make that fan
bigger you've got weight issues you've
got all sorts of mechanical issues so
they've been looking at composite materials,
gearboxes, all sorts of heat management
issues. We're also gonna try and push
these cycles, thematic cycles much
further and harder and get hotter
engines so there are gonna be cooling problems.
We're basically taking what we've got at
the moment and pushing it right to its limits.
So perhaps the big changes aren't
gonna happen for the first 10, 15, 20
years but after that we are going to see
electric powered aircraft coming along.
Not a whole electric, it's going to be a
hybrid type aircraft with at least one
jet engine or gas turbine as we like to
call them. That will produce much of the
thrust required for cruise but it'll be
much smaller because we'll be required
for take off. So to help the aircraft get
off the ground we'll have big electric
fans which will be powered by batteries.
At the moment battery technology isn't
quite good enough for this technology so
we're gonna have developed some better
batteries and better energy storage, but
that's the way it will go in the next 20
or 30 years. So as well as going for
higher by bypass ratios between these big
fans, we're also going to change the
combustion system. Obviously that's where
the fuels are burnt and that's where the emissions
are produced. Traditionally we've burnt
our fuels quite rich, so a lot of fuel to air.
We're now going to move towards burning them
in a lean environment, so less fuel
to air. That's problematic in terms of
getting the combustion system to work
but if we can achieve that we'll have a
lot less emissions particularly nasties like
NOx and it can potentially much more
environmentally friendly.
So once we move
towards more electric engines we can
actually make them smaller. If we can make them
smaller we can distribute them around
the aircraft much more which actually
gives us quite a big potential for
efficiency gains. Importantly also we can
start to integrate them into the
airframe, so instead of having the
traditional tube wings and engines
hanging underneath the wings, we'll start
embedding them in the airframe. It's much
better for aerodynamics, much better for
noise. But it is going to require
aircraft manufacturers, not just
engine manufacturers, to work together
and produce this next system of hybrid
aircraft. So we have had aircraft like that
in the past, we've had flying wings, but
now we're looking at what we call
blend wing body aircraft where the
engines are really part of the airframe
design. These sort of aircraft probably
won't be flying you, won't be going on
your holidays these aircraft for another 30, 40, 50 years.
But it's certainly on the horizon.
My name is Dr Duncan
Walker. I'm a senior lecturer in Applied
Aerodynamics here in the Department of
Aeronautics and Automotive engineering.
My particular field of speciality is gas
turbine aerodynamics, and I work very closely
with companies like Rolls-Royce looking
at the next generation of jet engines.
