Application of a New Selective Noncatalytic NO Reduction System to Diesel Exhaust(<Special Issue>Recent Combustion Technology in Internal Combustion Engines)

The chemical gas-phase reduction process used to reduce nitric oxide (NO) in diesel engine exhaust has been applied to a high-speed, light-duty diesel engine. The chemical gas-phase reduction process involves adding methylamine (CH_3NH_2) in water solution to the exhaust gas as an NO reduction agent. In this study, an experimental selective noncatalytic NO reduction system designed to be used with a diesel engine was applied to evaluate this technique for practical use. The NO_x reduction ratio (R_<No_x>) of methylamine processes with and without the installation of a particulate filter was investigated. Two different mixing chambers with different volumes and residence times (0.1 s and 0.17 s) were also tested. Longer residence times were required to achieve a given level of NO_x reduction in unfiltered exhaust, suggesting that the presence of particulate matter inhibits NO reduction. For the standard residence time (0.1 s), the process achieved 64% NO reduction in unfiltered diesel exhaust, which increased to 80% NO reduction when a particle filter was fitted to the system.