Abstract
NOx catalytic converter systems periodically require rich or stoichiometric operating conditions to reduce NOx. The hydrocarbon (HC) concentration in a diesel engine is typically too low for NOx conversion. A post or supplemental fuel injections into the exhaust gas have been proposed to achieve the HC rich operating condition. A new method that optimizes the control of external HC injection to diesel exhaust pipes for a hydrocarbon-type lean NOx Trap (HC-LNT) catalyst system was developed. The system has a secondary injector that injects diesel fuel (HC) into an exhaust pipe. The typically high temperatures (250 ~ 350℃) in the exhaust pipe affects spray behavior of the secondary injector which makes it difficult to achieve uniform distribution of the reducing agent in the manifold. The effects of a variety of mixer-types on the spatial distribution of the LNT reducing agent were investigated to promote performance of the LNT catalyst system. While the LNT reducing agent was directly injected against the mixers in a transparent manifold, spray images were taken with a high speed camera, and the spatial distribution of the spray was analyzed using image processing techniques.
Keywords: Mixer, Reductant, RMS (Root Mean Square) Image, Lean NOx Trap, Diesel Engine