CNG LOW EMISSION CITY BUSES

A stoichiometric Compressed Natural Gas (CNG) s.i. 9.5 litre engine with a 3-way catalyst has been developed for achieving very low emission figures. The basic engine layout is as follows: Heron type combustion chamber with gallery cooled piston; 10 compression ratio; low oil consumption; water cooled turbocharger plus waste gate; and closed loop control of the stoichiometric mixture by means of oxygen sensor. An engine configuration with a rated power output of 165 kW at 2100 rpm and a peak torque of 870 Nm at 1400 rpm has been examined. Emissions obtained under the European 13-mode procedure have been obtained. A general comparison among reciprocating internal combustion engines using different fuels (natural gas, gasoline, methanol and Diesel fuel) as far as brake thermal efficiency and carbon dioxide are concerned is presented. (A) For the covering abstract of the conference see IRRD 853181.