The Effect of Some Operational and Design Parameters on the Emitted NOx Pollutant of a Spark Ignition Engine

Liquefied petroleum gas and natural gas were used to run a spark ignition type Prodit. Some operational and design parameters effects on the NOx pollutants emitted from the engine were investigated practically. The studied parameters were the equivalence ratio, compression ratio, engine speed and spark timing variation. The resultant pollutants were studied when the engine is running at the higher useful compression ratio, which was 8;1 for gasoline and comparing its results when the engine was run at the higher useful compression ratio for each fuel alone. The results show that the highest value for NOx is laid always on the weak side near the stoichiometric equivalence ratio and its concentrations decreased by going away from that value to run at lean or rich mixtures. NOx maximum concentrations were achieved when the engine was run with LPG at 8:1 compression ratio. This value converges when the engine works on the highest useful compression ratio for each fuel. The major effective parameter on the NOx levels was for the spark timing.