Exploring the Potential of Ethanol, CNG, and Syngas as Fuels for Lean Spark-Ignition Combustion - An Experimental Study

Abstract In this study, experiments were carried out on a single-cylinder Cooperative Fuel Research (CFR) engine with different fuel-air equivalence ratio (φ) and compression ratio to explore its performance and emissions using four different fuels, E10, natural gas, ethanol, and syngas, at 1200 rev/min and 75 kPa intake pressure. The compression ratio was varied from 9 to 11 for E10 and syngas, and from 9 to 13 for natural gas and ethanol. The combustion characteristics were analyzed on the basis of enabling lean flame propagation. It was found that higher compression ratio resulted in higher engine efficiency and improved lean burn capability for all fuels studied. However, the use of ethanol, natural gas, and syngas helped to extend the lean misfire limit. Syngas enabled combustion at considerably lean operating conditions and achieved the leanest misfire limit. Spark ignition combustion with natural gas showed better lean combustion capability than gasoline and ethanol. Ethanol offered a wider lean limit than E10 and achieved higher fuel conversion efficiency than E10 and natural gas. Combustion with E10 was limited by end gas knock at high compression ratio, which necessitated spark retard and reduced engine efficiency and performance.