Spark Assisted Compression Ignition (SACI) offers more practical combustion phasing control and a softer pressure rise rate than Homogeneous Charge Compression Ignition (HCCI) combustion, and improved thermal efficiency and lower NOx emissions than Spark Ignition (SI) combustion. Any practical passenger car engine, including one that uses SACI in part of its operating range, must be robust to changes in ambient conditions. This study investigates the effects of ambient temperature and humidity on stoichiometric SACI combustion and emissions. It is shown that at the medium speed and load SACI test point selected for this study, increasing ambient air temperature from 20ºC to 41ºC advances combustion phasing, increases maximum pressure rise rate, causes a larger fraction of the charge to be consumed by auto-ignition (and a smaller fraction by flame propagation), and increases NOx. Increasing ambient humidity from 32% to 60% retards combustion phasing, reduces maximum pressure rise rate, increases Coefficient of Variation of IMEP (COV) of IMEP, reduces NOx, and increases BSFC. These results show that successful implementation of SACI combustion in real-world driving requires a control strategy that compensates for changes in ambient temperature and humidity.
EFFECT OF AMBIENT TEMPERATURE AND HUMIDITY ON COMBUSTION AND EMISSIONS OF A SPARK ASSISTED COMPRESSION IGNITION ENGINE
2016
Aufsatz (Zeitschrift)
Englisch
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