Truck & Off-Highway Engineering - October 2021 - 7

TECHNICAL INNOVATIONS
End plates (left) and main shaft of a development engine showing
rolling-element bearings. Apex seals are made from Si3N4 material.
Garside notes that this technology is key to the aircooled-rotor
Wankel's future successful application as a hydrogen-fueled
range-extender engine, especially when compared
to rotary designs using oil-cooled rotors. He lists
these as more compact geometry, higher mechanical efficiency,
reduced size, weight and production cost, improved
combustion efficiency and hence overall brake thermal efficiency
(BTE).
Single-rotor design
This fits well with the engine characteristics that Garside has
identified as necessary in providing a lightweight, low-cost
range-extender engine with zero NOx and negligible HC
emissions. All sizes of the engine use just a single rotor, which
only ever operates at a single load and single speed. Provision
of a weak (50% excess air) hydrogen fuel/air mixture results
in both zero NOx and excellent thermal efficiency.
A single-rotor design with a larger chamber size has fewer
components and reduced heat losses and gas leakage, contributing
to the high BTE. Such an engine still has zero radial
vibrations and the same instantaneous torque vibrations as a
3-cylinder reciprocating engine. It can be rigidly mounted,
saving cost and space, and is ideal for driving an integrated
electrical generator.
" A single-rotor Wankel's large-diameter output shaft allows
the generator rotor to be compactly cantilever-mounted
on the engine shaft without additional bearings, "
Garside detailed.
Since speed and load remain constant in operation, the
quantity and timing of hydrogen injected per cycle also remain
constant, permitting the use of a rotary valve operating
at half engine speed to control the supply of hydrogen gas to
the engine. The valve opens precisely as the engine air intake
port closes, with injection operating at about 3 bar (43.5 psi)
pressure and completed within approximately the first 15% of
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200901_HEN_Anzeige_Bluemaxx-85x244_Ansicht.indd 1
02.09.2021 12:15:40
DAVID GARSIDE
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Truck & Off-Highway Engineering - October 2021

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