A Study on the Optimal Injection Conditions for an HC-LNT Catalyst System with a 12-Hole Type Injector

Abstract

NOx catalytic converter systems periodically require rich or stoichiometric operating conditions to reduce NOx. The HC (hydrocarbon) concentration in a diesel engine is typically so low that the HC is not sufficient for NOx conversion. It was proposed that a rich air fuel ratio in a diesel engine could be realized via post fuel injection or supplemental fuel injection into the exhaust gas. A new method that optimizes the control of an external HC injection to diesel exhaust pipes for HC type LNT (Lean NOx Trap) catalyst systems has been developed. The external injection has other benefits: it can be controlled independently without disturbing engine control, it can be adapted to various layouts for exhaust systems, it has no oil dilution problems, among other benefits. In this study, the concentration and amount of HC can be controlled via control of the external injection. This research investigated the spray behavior of hydrocarbons injected into the transparent exhaust pipe. From this experiment, we obtained useful information about the optimal injection conditions for the HC-LNT catalyst system with an MPI injector.