Abstract
The theoretical analysis of the charge exchange process in a spark
ignition engine has been presented. This process has significant impact on
the effectiveness of engine operation because it is related to the
necessity of overcoming the flow resistance, followed by the necessity of
doing a work, so-called the charge exchange work. The flow resistance
caused by the throttling valve is especially high during the part load
operation. The open Atkinson-Miller cycle has been assumed as a model of
processes taking place in the engine. Using fully variable inlet valve
timing the A-M cycle can be realized according to two systems: system with
late inlet valve closing and system with early inlet valve closing. The
systems have been analysed individually and comparatively with the open
Seiliger-Sabathe cycle which is a theoretical cycle for the classical
throttle governing of the engine load. Benefits resulting from application
of the systems with independent inlet valve control have been assessed on
the basis of the selected parameters: fuel dose, cycle work, charge
exchange work and a cycle efficiency. The use of the analysed systems to
governing of the SI engine load will enable to eliminate a throttling
valve from the system inlet and reduce the charge exchange work,
especially within the range of part load operation.
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