Jung-Mo Oh

Spray characteristics of four-hole injectors used for a hydrocarbon lean nitrogen oxide catalyst system in a diesel engine

Among emission reduction technologies, a hydrocarbon lean nitrogen oxide trap is a cost-effective solution for nitrogen oxide emission control in light-duty vehicles. However, the hydrocarbon lean nitrogen oxide trap leads to high fuel consumption because diesel fuel is normally used as a reducing agent (i.e. a reductant). It is necessary to establish injection conditions corresponding to the maximum nitrogen oxide conversion in the hydrocarbon lean nitrogen oxide trap system. A uniform distribution of the reducing agent is desirable, and the spray characteristics of the reductant, such as atomization and penetration, must be well understood in order to establish a good performance of the hydrocarbon lean nitrogen oxide trap. With this goal in mind, the spray characteristics and behaviour of a port fuel injector with four holes were analysed using visualization and r.m.s. image-processing techniques. The Sauter mean diameter distribution of the injector was measured using a Malvern system. The liquid agents employed in this study were ISO 4113 and n-heptane, which have properties similar to those of diesel and gasoline fuels respectively. These results elucidated the feasibility of a secondary injection system for the hydrocarbon lean nitrogen oxide trap.

Study on the Optimal Injection Condition for HC-LNT Catalyst System for Diesel Engines with a Gasoline PFI Type Injector

NOx (Nitrogen Oxide) reduction system periodically needs a rich or stoichiometric operating condition to reduce NOx. A new method that optimizes the control of external HC injection into a diesel exhaust pipe for HC-type LNT (Lean NOx Trap) catalyst system has been developed. In this paper, these catalysts are called HC-LNT catalysts. The concentration and amount of HC can be controlled by controlling the external injection. In this study, we investigated the relationship between the spray behavior of hydrocarbons injected into the transparent exhaust pipe and NOx reduction characteristics. From the results of this experiment, we obtained useful information about the optimum injection and position of HC injector to the exhaust pipe. Further, we obtained useful information about the optimal injection condition for an HC-LNT catalyst system with a gasoline PFI (port fuel injection) typeinjector.

NOx Conversion Characteristics of HC-LNT System according to Secondary Injection Conditions in a Diesel Engine

Automotive engines need strategies to satisfy with the emission regulations in terms of PM and NOx. HC-LNT (Hydrocarbon-Lean NOx Trap) with secondary injection system is considered as more practical technology in order to cope with emission regulations. The HC-LNT system, which is using diesel fuel itself as a reducing agent, absorbs NOx in lean exhaust gas condition and releases NOx in rich exhaust gas conditions. In this system, inappropriate amounts of reducing agent will slip through the LNT without the profits of conversion and cause additional emission problems. Therefore, the suitable amount of reducing agent should be supplied into the catalytic converter. In this research, engine emission test was conducted to optimize injection quantity at the various engine test conditions. Different exhaust layouts and catalyst shapes have been studied and extension unit which makes better uniformity of exhaust gas was used for HC-LNT system. From this results, the effect of secondary injection conditions on NOx conversion characteristics of HC-LNT was clarified.

The Spray Characteristics and Spray Behavior Characteristic in Exhaust Gas Flow of Urea Solution Injector

Recently, many technologies have been developed in order to satisfy stringent emission regulations. However, in the case of diesel engines, the stringent emission regulations with respect to NOx and PM have not yet been satisfied. A dramatic reduction in the NOx and PM emissions could be achieved by using after-treatment systems such as lean NOx trap (LNT) and urea-SCR systems. However, the high temperature in the exhaust pipe affects the spray behavior of the secondary injector, which is used for supplying the Urea-SCR. Because of this high temperature, it is difficult to achieve uniform distribution of the reducing agent in the manifold. In this paper, the characteristics of a urea-SCR injector used for injecting in the exhaust pipe are presented. The purpose of this study was to investigate the spray characteristics of the injector, such as the spray angle, injection quantity, and SMD. In addition, laser diagnostics and high-speed-camera images were used to analyze the injector spray characteristics and to present a distribution of reduction in the transparent manifold.