Abstract: The exhaust gas recirculation (EGR), coupled with a high-collection
efficiency particulate trap to simultaneously control smoke and NOx emissions
from diesel engines were studied. This ceramic trap developed previously
provided the soot cleaning efficiency of 99%, the regeneration efficiency
reaches 80% and the ratio of success reaches 97%, which make EGR used in diesel
possible. At the presence of EGR, opening of the regeneration control valve of
the trap was over again optimized to compensate for the decrease of the oxygen
concentration in the exhaust gas resulted from EGR. The results indicated the
cleaning efficiency and regeneration performance of the trap were maintained at
the same level except that the back pressure increased faster. A new EGR system was developed, which is based on a wide range
oxygen(UEGO) sensor. Experiments were carried out under steady state conditions
while maintaining the engine speed at 1600 r/min, setting the engine loads at
0%, 25%, 50%, 75% and 100% respectively. Throughout each test the EGR rate was
kept at nine different settings and data were taken with the gas analyzer and
UEGO sensor. Then, the EGR rate and engine load maps, which showed the
tendencies of NOx, CO and HC emissions from diesel engine, were made using the
measured data. Using the maps, the author set up the EGR regulation, the
relationship between the optimal amounts of EGR flow and the equivalence ratio,
σ, where σ = 14.5/AFR.
