Experimental and modeling study of the effect of cetane improver-coupled EGR on RP-3 kerosene spray ignition and emissions

Abstract

ABSTRACT To improve the ignition quality of RP-3 kerosene as a single fuel for application in direct injection diesel engines, the effect of ignition improvers and exhaust gas recirculation (EGR) on the ignition and emission of RP-3 fuel was investigated. The ignition delays of three sets of fuels, pure RP-3, 1,2-dimethoxyethane(1,2-DME)/RP-3, and 2-ethylhexyl nitrate(2-EHN)/RP-3, were measured experimentally in a constant volume combustion chamber. The exhaust emissions (CO, CO2, HC, and NOx) were measured under different operating conditions, and the effect of EGR was evaluated. The kinetic analysis was performed by merging a new model. The results showed that the ignition delay of pure RP-3 fuel was shortened by 22.4% on average as the ambient pressure varied from 2.2 MPa to 4 MPa. 2-EHN promoted RP-3 ignition more effectively than 1,2-DME. The introduction of EGR in low-temperature and low-pressure conditions is more favorable for shortening the ignition delay. The addition of ignition improvers weakens the effect of EGR on ignition. Lower ambient pressures bring higher levels of emissions. 2-EHN has a more significant positive effect than 1,2-DME to reduce HC and CO emissions. 1,2-DME-doped fuels are prone to bring about a spike in NOx under high ambient temperatures. Kinetic analysis reveals that 2-EHN has a more significant effect on the first stage of ignition. For 1,2-DME/RP-3, the OH radical formation pathway is enriched with more low-temperature branched chain reactions originating.