In naturally aspirated Spark Ignition engine, about 60-80% of total unburned hydrocarbon emissions are produced during initial stage of vehicle operation under cold start or warm up condition. Wall wetting is predominant effect occurs in idle and part load conditions due to impingement or condensing of un-vaporized fuel droplets around the intake wall, combustion chamber liners and top of the piston. These deposits can cause incomplete combustion which will impact on increase in total hydrocarbon emissions. In this study, wall wetting parameters like fuel density, intake duct geometry, wall film thickness, wall film height, mixture preparation, fuel vaporization has been investigated theoretically by considering droplet evaporation and temperature model for cylinder wall film through mathematical equations. The main objective is to control equivalence ratio and to maintain surface temperature is the most effective way to reduce unburnt hydrocarbon emissions due to cold start wall wetting during steady state and transient conditions. This methodology was carried out on four stroke single cylinder Spark Ignition engine, where additives were used with gasoline fuel of different proportions which could intern reduce the intake and combustion chamber deposits during steady state and transient conditions. This experimental analysis was analyzed at different speed and load conditions. Based on these experimental results, Hydrocarbon emissions were reduced by nearly 40% in steady state and 30% in transient state. It is observed that, bi-fuel injection strategy can be implemented for injecting an ample amount of additive in to cylinder before compression stroke at 110 deg of crack angle during cold start, which it enhances the performance and emission characteristics furthermore.
