SAE Update - September 2024 - 20

TECH FOCUS:
DECArBONizED AErOSPACE
Here's a cool idea:
Use less hydrogen
However, even at scale, questions
remain whether SAF can be
sufficiently produced
economically, recognizing
that fuel cost is a
major driver in
the financial
Shown: GKN Aerospace's concept aircraft
developed for systems-level research on
hyperconducting technology.
viability
of airlines. Power to liquid (PtL),
which is generally regarded as the
most promising method of
producing SAF, requires a
hydrogen feedstock. This has led
many to question, " Why not save
energy and just use the hydrogen
as fuel? "
Liquid hydrogen has around
three times more energy per unit
mass compared with jet fuel, but
takes up approximately four times
the space. This limits the amount
of fuel that can be carried and
therefore the range. For a
hydrogen aircraft to be feasible,
the configuration must enable
efficient storage but also efficient
consumption of hydrogen to
reduce the overall amount
required for a given mission range.
More-efficient propulsion systems
not only make hydrogen aircraft
more feasible, but reduce the
amount of hydrogen the industry
needs to source.
Overall system efficiency
therefore becomes a major-if
not the major-driver in the
feasibility of hydrogen aircraft.
20
September 2024
With conventional aero engines,
efficiency tends to increase with size of
engine. Engines on small sub-regional platforms are
often in the 25% to 35% efficiency range, whereas
larger turbofans typically exhibit efficiencies in the
35% to 50% range. In both cases, the efficiency in offdesign
conditions can be as low as 15%. These figures
are expected to be similar for hydrogen-burning
engines.
By comparison, typical proton exchange membrane
(PEM) fuel cells tend to be around 50% efficient at
attractive power densities. However, overall
propulsion system efficiency is degraded due to the
challenge of distributing large amounts of electrical
power and the difficulties of efficiently rejecting the
low grade (approximately 80 °C/176 °F) waste heat
they produce. One way to improve this is through the
development of high temperature PEM fuel cells,
which will enable smaller thermal management
systems (because the rate of heat rejection scales
with temperature delta) and the effective use of
thermal energy recovery devices.
But there is another way of looking at the problem.
A cool idea
GKN Aerospace's former airframe OEM (Fokker) and
former engine OEM (Volvo Aero) heritage position the
organization well to evaluate future aircraft concepts
UPDATE
GKN Aerospace

SAE Update - September 2024

Table of Contents for the Digital Edition of SAE Update - September 2024

SAE Update - September 2024 - Cov1
SAE Update - September 2024 - Cov2
SAE Update - September 2024 - 1
SAE Update - September 2024 - 2
SAE Update - September 2024 - 3
SAE Update - September 2024 - 4
SAE Update - September 2024 - 5
SAE Update - September 2024 - 6
SAE Update - September 2024 - 7
SAE Update - September 2024 - 8
SAE Update - September 2024 - 9
SAE Update - September 2024 - 10
SAE Update - September 2024 - 11
SAE Update - September 2024 - 12
SAE Update - September 2024 - 13
SAE Update - September 2024 - 14
SAE Update - September 2024 - 15
SAE Update - September 2024 - 16
SAE Update - September 2024 - 17
SAE Update - September 2024 - 18
SAE Update - September 2024 - 19
SAE Update - September 2024 - 20
SAE Update - September 2024 - 21
SAE Update - September 2024 - 22
SAE Update - September 2024 - 23
SAE Update - September 2024 - 24
SAE Update - September 2024 - 25
SAE Update - September 2024 - 26
SAE Update - September 2024 - 27
SAE Update - September 2024 - 28
SAE Update - September 2024 - 29
SAE Update - September 2024 - 30
SAE Update - September 2024 - 31
SAE Update - September 2024 - 32
SAE Update - September 2024 - 33
SAE Update - September 2024 - 34
SAE Update - September 2024 - 35
SAE Update - September 2024 - 36
SAE Update - September 2024 - 37
SAE Update - September 2024 - 38
SAE Update - September 2024 - 39
SAE Update - September 2024 - 40
SAE Update - September 2024 - 41
SAE Update - September 2024 - 42
SAE Update - September 2024 - 43
SAE Update - September 2024 - 44
SAE Update - September 2024 - 45
SAE Update - September 2024 - 46
SAE Update - September 2024 - 47
SAE Update - September 2024 - 48
SAE Update - September 2024 - 49
SAE Update - September 2024 - 50
SAE Update - September 2024 - 51
SAE Update - September 2024 - 52
SAE Update - September 2024 - 53
SAE Update - September 2024 - 54
SAE Update - September 2024 - 55
SAE Update - September 2024 - 56
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