A control strategy for cold starting of a diesel engine with common rail fuel injection system

In the dissertation a new control strategy has been developed for injection strategy of a diesel engine with common rail fuel injection system to improve diesel engine cold startability, to reduce fuel delivery per cycle by using split-main injection and to reduce HC emissions (or white smoke) during cold starting. And a new simulation based calibration (SBC) method to arrive at the above strategy has also been developed to predict the combination of injection parameters to produce the highest IMEP. A single cylinder simulation model based on a commercial code and embedded with the author developed submodels: a modified AI model, a fuel injection system model and a blow-by model is well correlated and validated in a 4-cylinder, direct injection DIATA diesel engine during cold starts. Then the model is applied to develop IMEP control maps at various ambient temperatures. Limited experimental data shows the injection strategies based on the selection of higher IMEP significantly improve diesel engine cold startability, greatly reduce total fuel mass injected per cycle and HC emission (or white smoke) over a wide range of ambient temperatures. The model or developed IMEP control maps are one of the most effective tools for engine cold starting calibration. Also, the maps give a wide range of selections of control strategies during cold starting, which will be beneficial to emission study and NVH study during cold starting.; The analysis of the experimental data and parametric studies on combustion failure at ambient temperature lower than 0°C indicated that (1) Engine combustion fails when compression temperature is lower than 540K for DF2 diesel fuel. (2) Injection pressure has no influence on IMEP control maps and higher injection pressure at lower ambient temperature is detrimental to engine cold startability because of the increase of FMEP and drop of cranking engine speed. (3) Split-main injection strategy is not applicable to improve engine cold startability when compression temperature is lower than 540K.