Experimental Investigation of The Performance Response of A Spark Ignition Engine to Adding Natural Gas to Gasoline in Lean-Burn Condition

Considering the disadvantages of gasoline and natural gas as mono-fuel in SI engines has made the researchers to improve the performance and reduce the pollutant as the advantages of the application of dual fuel engines. On the other hand, lean-burn in engine may lead to the reduced pollutant. In the present study various mixtures of gasoline and natural gas with the gasoline as the dominant fuel, including 100‎‎ ‎‎‎%‎‎‎, 87,5%, 75‎‎% and 62.5% in weight-base gasoline and the rest natural gas (respectively named as G100, G87.5, G75, G62.5) in lean-burn condition with 0.9 as the equivalence ratio are investigated. At 1800 rpm and 11 compression ratio, cylinder pressure variations of 350 successive cycles of each mixture were recorded using a single cylinder research engine. First of all, the raw data were processed and the optimized knock-free advance for each individual mixture was determined. Later on the performance of all four mixtures in the corresponding optimized advance was explored. The results revealed that by increasing the amount of natural gas in the mixture, the CO pollutant reduced however the amount of HC initially increased which was followed by a decreasing trend. The amount of NOx had a direct relation with the appearance of the natural gas. In the lean-burn condition, a better performance was observed for G75 in compare with G100 and the other mixtures.