Comparative Study of Low Octane Gasoline Multiple Premixed Compression Ignition and Conventional Diesel Combustion

Abstract

This article proposes a novel combustion mode, namely “multiple premixed compression ignition” (MPCI), in gasoline direct-injection compression ignition (GDICI) regime. Its predominant feature is the multiple premixed combustion processes in a sequence of “spray–combustion–spray–combustion” around the compression top dead center. The multiple-stage premixed combustion decouples the pressure rise with the pollutant formation process. With optimization, it can lower the rate of pressure rise and emissions simultaneously while achieving high thermal efficiency. The experimental study has been carried out in a single-cylinder research engine with a compression ratio of 18.5. Gasoline with the research octane number of 66 was tested under MPCI mode with different exhaust gas recirculation rates and injection timings. Compared to the single-stage diffusion combustion mode of conventional diesel engines, the low octane gasoline MPCI mode achieves lower emissions of smoke, NO, and CO as well as greater thermal efficiency, with a penalty of greater total hydrocation emissions.

Keywords:

• Gasoline direct-injection compression ignition (GDICI)
• High efficiency
• Low octane gasoline
• Low pollutants
• Multiple premixed compression ignition (MPCI)

ACKNOWLEDGMENTS

The authors acknowledge the General Program of the National Natural Science Foundation of China (NSFC 51276097), the Key Program of the National Natural Science Foundation of China (NSFC 51036004), and the Joint Research Program between General Motors Corporation and Tsinghua University for funding this research.