EPA emissions standard strongly force engine manufactures to develop advance technical system for reducing NOx and PM. New advance combustion concepts have been developed to reduce NOx and PM simultaneously by many researchers but, the limitation of operating range and combustion control is still unsolved. One promising methods to overcome the limitation of advanced combustion concepts to meet strict emission standards with after-treatment system is to use mixed mode combustion.
In this study, two High Speed Direct Injection (HSDI) diesel engines were used for transient tests at constant speed with increasing load and constant torque with increasing speed to explore transient emissions with fast response emissions analyzers by applying a step fuel change and linear fuel change for preliminary tests. The effects of injection parameters, start of main and pilot injection timing, EGR, rail pressure and multiple injections, were explored to study the behavior of transient emissions in constant speed and constant torque cases. Transient tests between premixed charged combustion at low load and diffusion combustion (Conventional Diesel Combustion) at high load to study transitions of transient emissions were performed with a 1.9L Common Rail Direct Injection (CRDI) diesel engine. A step load change (rapid fuel quantity change) was applied to study the transitions of transient emissions at constant speed. The peak emissions during transitions of combustion were observed.
This study is the initial stage of the experimental work for transient emissions and mixed mode combustion. More specific and intensive study should be required for future work.