Influence of MFB50 control on emission dispersions according to engine parameter changes for passenger diesel engines

Combustion phase variations in diesel engines due to production tolerance, engine aging, and different combustion conditions cause performance deterioration of fuel economy, torque, and emissions. Therefore, the combustion phase should be controlled by feedback information. A well-known method to control the combustion phase is mass fraction burnt 50% (MFB50) control using in-cylinder pressure. MFB50 control can retain performance through combustion phase compensation despite production tolerance, engine aging, and different combustion conditions. However, MFB50 can compensate only for variations caused by combustion phase changes; therefore, further study is required to supplement the limitation of MFB50 control. In this study, to analyze the effect of MFB50 control on combustion, MFB50 is controlled by adjusting the main injection timing using in-cylinder pressure at 1500 rpm and a BMEP of four bar according to engine parameter changes. The parameters are fuel rail pressure, boost pressure, mass air flow, swirl valve open, main injection quantity, pilot injection timing, and quantity. While the engine parameters were changing, the influence of MFB50 control on the combustion and emissions was analyzed to establish improvement points for combustion feedback control. Our experiments demonstrated that MFB50 control reduced NOx dispersions but at the cost of increasing PM dispersions. Therefore, to improve MFB50 control, a control algorithm that can handle PM emission dispersion needs to be considered.