| Summary: | Internal combustion (I.C.) engines typically exhibit a characteristic ef ciency pro le which varies with
operating load and engine speed, and it is widely known that the operating ef ciency is poor under low
loading conditions. The objective of this project is to investigate whether an energy storing and recover-
ing process, involving compressing air and subsequently using it for propulsion, could be used to achieve
better overall ef ciency. An engine so modi ed would operate in two alternate modes. When using fuel,
the engine operates as close to maximum ef ciency as practicable, with the excess of engine output
over driving requirements being absorbed by air-compression loading - driving an external compressor,
charging air into a receiver. Later, under low driving requirements, this air is expanded - using the engine
cylinders - as a source of propulsion. Heat transfer from the exhaust gases to the stored compressed air
is used to improve engine ef ciency. Through modelling and simulation, an overall ef ciency improve-
ment of 10% over standard engine operation is predicted to be realisable by applying this modi cation,
and scope exists to further improve this gure through improved heat recovery from exhaust gases and
improved loading capability.
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