Exhaust emission and fuel consumption of CNG/diesel fueled city buses calculated using a sample driving cycle

In this study the reduction of pollutant emissions from city buses converte d to dual fuel operation was investigated. Exhaust emission and fuel consum ption maps were obtained under laboratory conditions for an engine converte d to CNG/diesel fuel operation. These values are then used in the simulatio n model to predict the total exhaust emission and fuel consumption on a dri ving cycle evaluated from actual recordings. Calculations showed a signific ant decrease in PM emissions as expected while with total CO emissions mino r changes hare been observed. For dual fuel operation NOx emissions were ke pt at the same level as in pure diesel operation with retarded pilot inject ion. Fuel cost calculations showed a decrease up to 30% with current prices of diesel fuel and CNG.