In order to reduce particulate matter emissions from gasoline engines, GPF has become a standard configuration for post-treatment systems. The filtration mechanism of GPF is basically the same as that of DPF. The exhaust passes through a porous wall at a certain flow rate, and this process is called "Wall Flow". The wall flow particle trap is composed of honeycomb shaped ceramics with a certain pore density. By alternately sealing the honeycomb shaped porous ceramic filter, the exhaust flow is forced to pass through the wall of the channel. The particles are captured and filtered through four methods: diffusion, interception, gravity, and inertia. Numerous studies have shown that wall flow filters are currently the most effective means of reducing particle emissions.
