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.
