Potential for Improving the Efficiency of a Spark Ignition Engine for Natural Gas Fuel

Experimental data were obtained on a single cylinder spark ignition engine to determine the relationships between compression ratio, air-fuel ratio, performance, thermal efficiency and emissions using natural gas as fuel. The study was carried out using minimum spark timing for best torque (MBT) with air-fuel ratio varied from rich to the lean limit and compression ratios ranging from 8.4:1 to 18.5:1 while using natural gas. Data on thermal efficiency and emissions from the natural gas tests at optimized compression and air-fuel ratios are compared with similar data from gasoline and natural gas at the baseline compression ratio of 8.4:1.