Keywords: vehicle exhaust, petrol, CNG, emissions reductions, Cairo, natural gas
Natural gas as a promising alternative fuel for passenger cars
The present work (as a field study) investigated the role of compressed natural gas (CNG), as an automotive fuel in CO, HC and CO2 emissions in vehicle exhaust. Besides evaluating the influence of the fuel-feed systems into their cylinders on a vehicular emission level, two different systems were examined; electronic fuel-injection and well-carburetted engines. The chosen vehicles were already in service without catalytic converters and alternately operating on either petrol or CNG fuel. Their equivalence ratios were very near to the integer unit and they were of the same model and capacity (1800 cc) but differed in their manufacturing date. CO, HC and CO2 concentrations were determined by using the exhaust analyser (SNAP). The output results illustrated that, compared to petrol, CNG has a vital potential to reduce CO, HC and CO2 concentrations in exhaust released from the electronic fuel-injection and well-carburetted engines by an average of 73% and 66%, 39% and 31% and 21% and 19%, respectively. Furthermore, compared to the well-carburetted engine's emissions, the use of vehicles with the electronic fuel-injection system reduced the concentrations of the same investigated pollutants in CNG and petrol exhausts by an average of 78% and 70%, 52% and 45% and 17% and 12%, respectively. The results confirmed that auto exhaust air pollutant levels could be reduced by replacing conventional petrol by CNG and using vehicles with electronic fuel-injection systems in all activities.