Emission of hydrophilic soot precursor particulates from small gasoline engine at different load conditions, Journal of the Energy Institute, Volume 86, Number 2, p78-84

An experimental study has been performed to analyse the emission of hydrophilic particulates in nanometre size range in the exhaust gas of a small non-road gasoline engine. Such engines are widely used in agricultural and farmland applications, and emission from them is receiving serious attention from environment protection agencies in recent times. The engine coupled with an eddy current dynamometer was operated at different loads while maintaining the speed constant. A small portion of the exhaust gas was extracted and passed through deionised water to disperse any hydrophilic substance to form a colloidal suspension. Any volatile compound and low boiling point liquid are removed from the samples by continuous sparging before analysis. Absorption and fluorescence studies of the hydrosol confirm the existence of combustion generated nanosized soot precursor particles in the sample. The particle size distributions at different loads were studied using dynamic light scattering, and the number concentration of the particles in the exhaust gas has been evaluated using the absorption results. It has been found that as the engine load increases, the particle size in the exhaust gas increases, while the number concentration of the particles decreases. This phenomenon is attributed to the increased rate of particle coagulation at higher load.