LOTUS OMNIVORE RESEARCH ENGINE Lotus Engineering, the renowned automotive consultancy division of Lotus Cars, unveils its latest research into engine efficiency at the International Geneva Auto 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 traveled using renewable fuels.
On display will be the single cylinder research engine mono-block that demonstrates the novel architecture designed for high thermal efficiency when fueled 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 optimization than is possible with existing four-stroke engines.The engine concept features a mono-block 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 mono-block 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.
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 program, 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 program 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 Geneva Show in 2008. This research is vitally important for a successful transition from today's fuels to the more 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."