Effect of Water Injection Parameters on Upper Load Limit and Nitrogen Oxides Emissions of a Homogeneous Charge Compression Ignition Engine—A Computational Fluid Dynamics Study

Abstract

<div>Direct water injection inside the cylinder is a promising technique to enhance the upper load limit and reduce nitrogen oxides emissions. The advantage of water injection depends on the percentage of water evaporated inside the cylinder. The percentage of water evaporation depends upon the water injection parameters. Hence, a computational fluid dynamics analysis is done to determine the effect of water injection temperature, water spray cone angle, nozzle hole diameter, and number of nozzle holes on in-cylinder distribution and percentage of water evaporation, engine performance, and emissions of a homogeneous charge compression ignition engine. This analysis considers water injection temperature from 295 K to 385 K, water spray cone angle from 8° to 24°, nozzle hole diameter from 0.14 mm to 0.205 mm, and number of nozzle holes from 4 to 7. The computational fluid dynamics models used are validated from the available experimental data in the literature for the engine considered. Here, the water injector parameters are optimized based on the nitrogen oxides emissions, maximum rate of pressure rise, heat release rate, and distribution of water vapors. This study found that the case of a water injector with a nozzle hole diameter of 0.205 mm, six nozzle holes, 12° spray cone angle, and a water injection temperature of 295 K gave better results than the other cases considered. With the optimum water injection parameters, the indicated mean effective pressure increased from 3.23 bar to 4.39 bar, which is about 35.9% more than the without water injection case, and nitrogen oxides emissions are reduced by about 64.7% compared to without water injection case.</div>