Research on Misfire and Additional Spark Ignition at First Combustion Cycle during Cold Start based on a Modified Form Tandem Ion Current Detection System on a PFI/GDI Engine

摘要

This paper focuses on the first firing cycle of a cold start process as a means to improve combustion performance and reduce emissions during the cold start of a combined injection strategy engine. A novel additional firing strategy, based on a modified form tandem ion current (IC) signal detection system, was applied to avoid an in-cycle misfire condition. Specifically, by detecting the misfire with the IC signal and then using an additional injection and spark ignition strategy, misfire can be avoided in the current cycle by successful survival combustion. However, if the quantity of additional injection fuel is improper, a misfire may still happen even if this strategy is applied. Furthermore, the requirement for additional fuel was found to be sensitive to the primary ignition timing. Thus, the effects of different ignition timings on the combustion and emissions of the first cycle were also studied. If the additional injection occurs near top dead centre, less fuel needs to be injected to avoid misfire. Having the additional injection timing occur too early or too late were both disadvantageous for additional spark ignition. Increasing the amount of additional injection fuel can stabilize combustion but this also increases the hydrocarbon (IIC), particulate number (PN) and particulate mass (PM) emissions. If the additional spark ignition fails to cause the combustion after additional injection and ignition, the HC emissions will not dramatically increase compared with basic misfire operation, but the PM will. However, the PM emissions are still at the same level as in normal combustion because the basic misfire condition causes ultra-low PM emissions.