Effect of compression ratio and spark timing on the power performance and combustion characteristics of an HCNG engine

This paper investigates the effect of compression ratio and spark timing on the power performance and combustion characteristics of a hydrogen enriched compressed natural gas engine. The experimental data was conducted under variable compression ratios (i.e. 10:1, 11:1 and 12:1) by varying the spark ignition timing. The engine was kept running at a constant speed of 1200 rpm with a constant excess air ratio of 1.6 and a constant manifold absolute pressure of 50 kPa. It has been found from the results that the higher compression ratio, the higher the indicated thermal efficiency. Increase in compression ratio leads to higher brake torque and lower break specific fuel consumption. But the improvements are weakened between higher compression ratios. The peak pressure is higher with higher compression ratio. Faster heat release rates and lesser coefficient of variations of indicated mean effective pressure can also been observed at higher compression ratios.

► Three pistons of different compression ratios were examined in an HCNG engine.
► Combining the effect of variable spark timing on the performance and combustion.
► Higher compression ratio contributes to better fuel economy and higher power output.
► Combustion rate was increased by increasing compression ratio.