A study on the exhaust characteristics of catalyst coated GPF in GDI engine vehicle

Abstract

Unlike the PFI engine that injects fuel at the intake port, the GDI engine directly injects the fuel into the cylinder, thereby improving the fuel efficiency by increasing the volumetric efficiency and compression ratio due to fuel evaporation. However, incomplete combustion due to wall wetting by fuel adsorbing to the cylinder and the piston causes a problem of generating more fine particles than the PFI engine. As a countermeasure for reducing the fine particles emitted from the GDI engine, a method of mounting GPF has been actively studied. GPF can be categorized as "Add on GPF" and "Integrated GPF" depending on the role. "Add on GPF" is a function to filter out particulate matter. "Integrated GPF" is a type that performs both the role of filtering particulate matter and the role of TWC by the catalyst is coated. In case of "Add on GPF", it is advantageous to simply mount it to existing exhaust aftertreatment system, and "Integrated GPF" is advantage that it can simplify the entire exhaust aftertreatment system. In this study, "Integrated GPF", which is easy to simplify the exhaust system, was used for experiment. We configured three systems, System A is reference system, System B is the system of “Integrated GPF” mounted on the CCC position, and System C is the system of “Integrated GPF” mounted on the UCC position. For comparison with the reference, when GPF is attached to the CCC position and the UCC position, exhaust gas and engine performance tests in various driving modes such as CVS-75, WLTP, and US-06 are performed using a chassis dynamometer respectively. As a result, there is no significant effect on the engine performance when mounting GPF by back pressure and fuel consumption data. But it is found that the System C reduced more PM, PN than System B. It is because the System C GPF mounted position is relatively backward than System B GPF mounted position, the flow velocity and flow are more stable. The System C is more appropriate mount position than the System B when considering the regulations and the actual road driving conditions that are strengthened.