Lotus Engineering, the world-renowned automotive
consultancy division of Lotus Cars Limited, unveils
its latest research into engine efficiency at the
79th International Geneva Motor Show. The Omnivore
engine concept has the potential to significantly
increase fuel efficiency for sustainable alcohol
based fuels, which increases the prospect of a
greater amount of vehicle miles travelled using
renewable fuels. On display will be the single
cylinder research engine monoblock that demonstrates
the novel architecture designed for high thermal
efficiency when fuelled on any alcohol based fuel or
gasoline.
The Omnivore concept features an innovative variable
compression ratio system and uses a two-stroke
operating cycle with direct fuel injection. It is
ideally suited to flex-fuel operation with a higher
degree of optimisation than is possible with
existing four stroke engines.
The engine concept features a monoblock construction
that blends the cylinder head and block together
eliminating the need for a cylinder head gasket,
improving durability and reducing weight. In this
case, the application of a monoblock is facilitated
by the absence of the requirement for poppet valves.
A novel charge trapping valve in the exhaust port
allows asymmetric timing of exhaust flow and
continuous variation of the exhaust opening point.
The variable compression ratio is achieved by the
use of a puck at the top of the combustion chamber.
This simple, yet effective system moves up and down
affecting the change in geometric compression
depending on the load demands on the engine.
Mike Kimberley, Chief Executive Officer of Group
Lotus plc said: “We are delighted to unveil this
major milestone in the development of an engine
configuration for a new breed of more efficient
multi-fuel engines. The automotive sector is
focusing on its environmental obligations to improve
efficiency, minimise reliance on fossil fuels and
reduce harmful emissions and Lotus continues to be
an industry leader through our work on all aspects
of future fuels. Sustainable alcohol based fuels
have the potential to reduce the overall CO2
footprint of internal combustion engines towards
zero and for this reason, need to be embraced as
future fuels for road transport.”
In this collaboration with Queen’s University
Belfast and Orbital Corporation Limited Australia,
with sponsorship from DEFRA/DECC and DOE NI through
the Renewables Materials LINK programme, Lotus
Engineering is currently in the final stages of
commissioning the Omnivore single-cylinder research
engine. It uses the Orbital FlexDI™ fuel injection
system which produces fine in-cylinder fuel
preparation irrespective of fuel type, and together
with air pre-mixing allows efficient two-stroke
combustion and low-temperature starting, whilst
offering singular opportunity for advanced HCCI
control.
The Omnivore programme is another development of
Lotus’ research into understanding the complex
combustion processes involved in running an engine
on mixtures of alcohol based fuels and gasoline,
which included the Lotus Exige 270E Tri-fuel,
unveiled at the International Geneva Motor Show in
2008. This research is vitally important for a
successful transition from today’s fuels to the more
efficient sustainable fuels of the future.
Geraint Castleton-White, Head of Powertrain at Lotus
Engineering said, “The absence of poppet valves in
two-stroke engines makes the incorporation of a
variable compression ratio system relatively
straightforward. Our research into these systems on
four-stroke engines has led us to the conclusion
that while thermodynamically it is a desirable
technology to incorporate, practically it is very
difficult, particularly taking into consideration
production feasibility. This two-stroke engine could
solve these practical difficulties and
simultaneously permits a much larger range of
compression ratio adjustment, with the potential to
perform at a much higher efficiency when running on
renewable fuels.”
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