DEVELOPMENT OF A NATURAL-GAS SPARK-IGNITION ENGINE FOR OPTIMUM PERFORMANCE

A 4 litre displacement, six cylinder, fuel injected petrol engine was modified to natural gas (NG) fuelling. Experimental investigation was carried out with various mixture controls and compression ratios over a wide range of operating conditions. As a strategy for combustion cha mber shape modification, the compression ratio was raised with simulta neous enhancement of in-cylinder turbulence through squish motion. A f ast burning chamber for the combustion of lean mixtures of natural gas and air was developed. Brake thermal efficiency in excess of 40 per c ent and brake torque in excess of the peak base torque with petrol wer e achieved. The research provides the foundation for the implementatio n of NG cars that will emit only about 65 per cent of the carbon dioxi de (CO2) of their petrol engine counterparts, with the prospect of ext ending the limited range of NG cars by up to one-third and producing l ow hydrocarbon (HC) and nitrogen oxide (NOx) emissions.