The Effects of Combustion Duration on Engine Emission Characteristics

The purpose of this research is to study how the combustion durations get effect on engine emission characteristics. To achieve this goal, an experimental system is installed with dynamo testing system and a simulation model is established using AVL-Boost software. The simulation model is used to determine the residual gas ratio and engine emission characteristics. In this research, the combustion duration will be increased from 40 deg to 110 deg of crank angle and engine testing speeds are 6000 rpm, 7000 rpm and 8000 rpm. The results show that: the combustion durations get big effect on residual gas ratio, effective real energy and engine performance. When combustion duration is changed, the residual gas ratio and effective real energy are changed in various trends of engine speeds. At the engine speed is 6000 rpm, the minimum residual gas ratio is 0.22% at 80 deg combustion duration and maximum effective real energy is 0.826 KJ at 60 deg combustion duration. With the engine speed is 7000 rpm and 8000 rpm the minimum residual gas ratio is 0.14% and 0.15%. The residual gas affected the release energy and CO emission. The trend of residual gas was opposite those of effective release energy and CO emission. If the residual ratio was increased, then the effective release energy decreased and CO emission increased, and vice versa. The NOx and HC emission has decreased when the combustion duration increased.