Experimental investigations of effects of cycle time on NOx emission in a hydrogen fueled multi-cylinder automotive spark ignition engine

Abstract

The present study deals with the influence of cycle time on NOx emission in a hydrogen-fueled multi-cylinder automotive spark-ignition engine. The engine was operated at a constant torque of 70 Nm in the speed range of 1000–1900 rpm with a step interval of 300 rpm. FT-IR spectrometer was used to measure the real-time regulated (NO, NO2) and non-regulated (N2O, HCN) emissions. The peak in-cylinder pressure and convective heat transfer rate decreased till cycle time of 75 ms due to reduced available time for combustion and heat exchange resulting in lower NO emission. However, as the cycle time decreased to 63 ms, NO emission shot up. NO emission drastically increased about five times higher at an engine speed of 1900 rpm compared to lower engine speeds due to an increase in peak in-cylinder gas temperature (above 1700 K). Percentage apportionment of NO2 to NOx emission is by half at 1900 rpm due to the rise of NO emission at higher engine speeds. The increasing trend of HCN and NMHC emissions with engine speed indicates the possibility of lubricating oil burning.