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A Study of Newly Developed HCCI Engine With Wide Operating Range Equipped With Blowdown Supercharging System
Abstract:
To extend the operating range of a gasoline HCCI engine, the
blowdown supercharging (BDSC) system and the EGR guide were
developed and experimentally examined. The concepts of these
techniques are to obtain a large amount of dilution gas and to
generate a strong in-cylinder thermal stratification without an
external supercharger for extending the upper load limit of HCCI
operation whilst keeping dP/dθmax and NOx emissions low.
Also, to attain stable HCCI operation using the BDSC system with
wide operating conditions, the valve actuation strategy in which
the amount of dilution gas is smaller at lower load and larger at
higher load was proposed. Additionally to achieve multi-cylinder
HCCI operation with wide operating range, the secondary air
injection system was developed to reduce cylinder-to-cylinder
variation in ignition timing. As a result, the acceptable HCCI
operation could be achieved with wide operating range, from IMEP of
135 kPa to 580 kPa. Compared to conventional SI operation, BSFC was
improved by 14% ~ 35% with more than 99% reduction in NOx
emissions.