Investigations on NO _x and Smoke Emissions Reduction Potential through Water-in-Diesel Emulsion and Water Fumigation in a Small-Bore Diesel Engine 2020-32-2312

In the present work, a relative comparison of addition of water to diesel through emulsion and fumigation methods is explored for reducing oxides of nitrogen (NO_x) and smoke emissions in a production small bore diesel engine. The ratio of water to diesel was kept the same in both the methods at a lower concentration of 3% by mass to avoid any adverse effects on the engine system components. The experiments were conducted at a rated engine speed of 1500 rpm under varying load conditions. For engine studies using emulsion fuels, kinetically stable water-in-diesel nanoemulsions were prepared with 3% water concentration by mass of the total sample. The emulsion fuels formulated using commercial surfactants were transparent in appearance. The droplet size of the nanoemulsions was characterized using dynamic light scattering technique. The fumigation experiments were carried out by injecting water using a low-pressure solenoid operated port fuel injector (PFI) installed in the intake manifold. The timing and duration of PFI were controlled by a National Instruments driver module. The results obtained show that the engine brake thermal efficiency and brake specific fuel consumption are improved by nearly 5% with the emulsion compared to baseline diesel. The peak pressures are higher, and the ignition delay is shorter with emulsion compared to fumigation. Both emulsion and fumigation reduce NO_x emissions, but the reduction is higher with water injection. However, smoke emissions are significantly higher by almost two-fold with fumigation as compared to those with emulsion. Overall, it is observed that utilizing water emulsion has a potential to simultaneously reduce NO_x and smoke emissions along with better engine performance compared to fumigation method.