Abstract

This paper evaluated the dynamic response of the compression ignition engine's performance parameters and emissions when water was injected into the intake manifold at different water ratios. This technique effectively decreased NOx emissions and mitigated knock intensity when the engine ran at dual fuel mode. With a WR = 143 %, NOx emissions were reduced by 52 % at 100 % diesel operation, whereas with a WR = 132 %, NOx emissions were reduced by 57 % at dual fuel mode operation. The knock intensity decreased from 1.52 V to 1.12 V using a water ratio of 133 % when the engine operated with a substitution of diesel by LPG of 50 % on a mass basis. The results also revealed that water injection increased HC emissions from 220 +/- 1 ppm to 430 +/- 1 ppm, whereas the Particle Matter (PM2.5) increased from 42.4 mu g/kWh to 127.3 mu g/kWh at 100 % diesel operation. When the engine operated at dual fuel mode PM2.5 increased from 42.4 mu g/kWh to 84.3 mu g/kWh. Finally, two First Order plus Dead Time models were deduced through the system identification technique to simulate the dynamic response of Knock Intensity when a step change of water ratio was made. These models play a key role in tuning system controllers for knock suppression.