Automotive Systems: EPSRC Grant: GR/S97507/01 Zero Constraint Free Piston Energy Converter

EPSRC Grant: GR/S97507/01 Zero Constraint Free Piston Energy Converter, Collaborating Company: Lotus Engineering

PI Paul Stewart



The aim of the project was to realise and demonstrate a completely novel energy conversion technology, which has the potential for high efficiency, low emissions, and low manufacturing cost. Its main applications are likely to be in series hybrid vehicles and portable power generation. The technology is based around a single-cylinder free-piston internal combustion engine (ICE), which is run on a 4-stroke cycle, with an integral linear electromagnetic machine and electromagnetically operated poppet valves. By freeing the piston from crank shaft motion, it removes most of the constraints of crankrod-slider ICEs, and facilitates many advanced combustion strategies – by enabling variable compression ratio operation, throttle-free operation, different piston strokes during compression and expansion, and other previously unattainable piston trajectories. It represents, therefore, a major step change in ICE operating flexibility and offers unparalleled design scope.

Here’s a film of the engine being run as part of an experimental series: