A study on the spray characteristics of a 12-hole type injector for use in HC-LNT catalyst system

Abstract

NOx catalytic converter system needs rich or stoichiometric operating condition periodically to reduce NOx. The HC(hydrocarbon) concentration in a diesel engine is so low that the HC is not sufficient for NOx conversion. It was proposed that a rich air fuel ratio in a diesel engine was realized by post fuel injection or supplemental fuel injection into the exhaust gas. A new method that optimizes a control of external HC injection to diesel exhaust pipe for HC type LNT(Lean NOx Trap) catalyst system has been developed. These catalysts are called the HC-LNT catalyst in this paper. The external injection has prior benefit; can be controlled independently without disturbing engine control, can be adapted to various layout of exhaust system, has no oil dilution problem, and etc. In this study, concentration and amount of HC can be controlled with the control of external injection. This research investigated spray behavior of hydrocarbons injected into the transparent exhaust pipe. From this experiment, we obtained useful information about the optimal injection condition for HC-LNT catalyst system with a MPI injector.