Abstract
To clarify the mechanism of high brake thermal efficiency of HCCI combustion compared to SI combustion, the contributions of pumping loss, friction loss and gross indicated thermal efficiency were investigated. Also, independent effects of heat loss, specific heat ratio, heat release profile and combustion timing on gross indicated thermal efficiency in HCCI combustion were analyzed in detail. As a result, high gross indicated thermal efficiency is found to be the main contributors to improvement in brake thermal efficiency. Also, it is found that heat loss in HCCI combustion is lower than SI combustion leading to the increase in gross indicated thermal efficiency. The improvement in gross indicated thermal efficiency in HCCI operation is mainly caused by lower heat loss in HCCI compared to SI combustion.
