Experimental analysis of NOx reduction through water addition and comparison with exhaust gas recycling

Abstract

The diesel engine requirements regarding the reduction of exhaust emissions, especially nitrogen oxide (NOx) and particulate matter (PM) are becoming more stringent year by year. A current method used for NOx control is exhaust gas recirculation (EGR). However, this approach significantly increases the production of soot for medium and high rates. Water addition can also be used for NOx control, achieving 50% NOx reduction rates in relation to EGR with a lower production of soot and without additional carbon monoxide (CO) and hydrocarbons (HC) substantially. This paper analyses the weaknesses and the strengths of adding water into the intake manifold with a flow-blurring injector for NOx reduction on a current technology diesel engine with multiple injection thorough a proprietary tool for heat release rate that considered real gas properties. A reduction of NOx emissions around 60–70% was achieved with water injection at different loads and speeds. Besides, a clear relationship was established between the minimum attainable NOx emission and the thermal capacity of the load (air plus water), this result stablish the hard relationship between NOx formation and combustion chamber temperature and therefore shows the strong dependence of the Zeldovich mechanism.