Practical Usage of Gasoline HCCI as an Automotive Powertrain by Using Boosting and Combustion Switching

HCCI combustion can realize low NOx and particulate emissions and high thermal efficiency. Therefore, HCCI combustion has a possibility of many kinds of applications. However, the operational range using HCCI combustion in terms of speed and load is restricted because the start of ignition and the heat release rate during HCCI operation cannot be controlled directly. For the extension of the operational range using either an external supercharger or a turbocharger is efficient. One of the objectives of this research is to investigate the effect of the intake pressure on the HCCI high load limit and HCCI combustion characteristics with blowdown supercharging (BDSC) system for the practical usage. The intake pressure (Pin) and temperature (Tin) were varied as experimental parameter. The intake pressure was swept from 100 kPa (naturally aspirated) to 200 kPa using an external mechanical supercharger. The experimental results showed that the maximum load successfully increased with increasing the intake pressure. The highest load in this study was 935kPa in IMEPg at the condition of 200 kPa in Pin and 32 C in Tin. The maximum load of boosted BDSC-HCCI engine can be achieved comparable to the full load of naturally aspirated SI engine. The other objective is to realize smooth combustion switching between HCCI and SI to enable wide range operation for practical usage. By controlling intake/exhaust throttling, V-TEC system, fuel injection amount, ignition timing and cooled EGR system, smooth switching can be attained.