Automotive Engineering - October 2021 - 23

ADVANCED PROPULSION FEATURE
EXTENDING THE WANKEL'S FUTURE ON
HYDROGEN
FUEL
Baseline for Garside's modular series of hydrogen
rotaries is a 225-cc single-rotor engine with
an initial test power rating of 16 hp based on a
UAV engine weighing 22 lb. Applications would
include urban taxis and cargo vans.
Proven in thousands of military drone
aircraft, the lightweight and power-dense
Wankel rotary still aims for a future...as
a zero-emission range extender.
by John Kendall
C
ould the Wankel rotary engine have a major
future as a hydrogen-fueled, zero-emissions
range-extender engine? Fuel cells are still under
development and there are technical hurdles
and production costs to overcome. Reciprocating engines
are generally too heavy and complex for rangeextender
application, experts believe. Furthermore,
hydrogen fuel - necessary for zero emissions - presents
many difficulties when used in reciprocating engines.
These issues are evaded in the rotary engine
where the cool intake chamber is remote from the
combustion zone.
" The overall objective is to create a range-extender
power unit that exceeds the efficiency of the best fuel
cells; with lower weight, higher TBO [time between
overhauls] and at a fraction of the manufacturing
cost, " said veteran Wankel development engineer
David Garside. He expects that after 2030, the majority
of the world's larger electric vehicles will be fitted
with range extenders of this type.
The proposed basic technology for the rotary has
for many years been extensively used in the engines
for powering military UAVs (unmanned aerial vehicles,
AUTOMOTIVE ENGINEERING
or drones), but further key technical advances now are incorporated.
Garside has been involved with rotary-engine R&D since 1964, initially
working at Rolls-Royce. He notes the design can make a major
contribution as a hydrogen-fueled range extender. Having developed
the successful Norton and UAV rotaries (see sidebar), Garside, now
formally retired, has continued his involvement in rotary engine technologies.
The Norton and UAV engines used air to cool the rotor, in
place of oil-cooling systems used in automotive applications.
Particularly in the UAV engines, this resulted in some wet oil mist being
emitted, making them unsuitable for ground use.
In 2008, Garside patented a self-pressurized air-rotor cooling system
(SPARCS) which eliminated that problem. " The internal cavity of
the rotor becomes part of a closed cooling system " he explained. " A
small engine-shaft-mounted centrifugal fan circulates the air at high
speed through the rotor, where heat is gathered and through an air/
water heat exchanger where it is rejected. The advantage is that the
circulating gas becomes pressurized to the average pressure in the
engine working chambers via the very small two-way leakage of gases
past the rotor side seals. "
In an engine at wide-open throttle, the cooling system is pressurized
and hence densified, to about five to six bar (72.5 psi - 87psi),
Garside noted. " Since the rate of heat transfer is proportional to gas
density to the power of 0.8, we obtain a gain of more than two or
October 2021 23
DAVID GARSIDE
Automotive Engineering - October 2021

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