Emissions from diesel engines, particularly NOx and TPM emissions are harmful to the environment. Reduction of NOx emissions from diesel engines is of increasing concern. In 1998, a novel approach called Selective NOx Recirculation (SNR) was used to reduce NOx emissions in diesel engines. The SNR concept relies on two major parts, one to collect the NOx emissions from the exhaust by an adsorber, and another to decompose NOx using the in-cylinder combustion process by injecting the collected NOx emissions into the intake manifold at an elevated concentration. This paper deals with the destruction rates during the combustion process.
A 1992 DDC series 60, 350 hp, 12.7 liter engine was connected to a 500 hp DC dynamometer. A full-scale dilution tunnel and analyzers capable of measuring continuous NOx, CO2, CO, HC, and PM in the exhaust were used. Bottled nitric oxide (NO) gas was injected into the intake manifold through a mass flow controller in order to assess NOx decomposition at various loads and concentrations. By comparing the integrated values of NO injected into the intake and exhaust (as a control), the destruction rates of NOx were calculated.
NO was injected for 20 seconds at each mode into the intake and exhaust manifold. Data show that 57% of NO injected was destroyed when the engine was operated at the intermediate speed (1200 rpm) and 100% load point (1310 ft-lb).