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14-7 2412-02 1. OVERVIEW The low emission vehicle is being sold increasingly in the market as a countermeasure for complying with the environment regulations such as a special act on Seoul metropolitan air quality improvement and for reducing the PM (Particulate Material) from the diesel-powered vehicle. For the CDPF system, the DOC (two-way catalytic converter or catalytic combustion system) fitted to the conventional diesel engine has the high purification rate for HC or CO but not have a high reduction rate for the PM. For this reason, a necessity has been raised in order to consider a countermeasure to reduce the PM since the existing DOC can't meet the regulation, which is getting tighter. This results in a development of the CDPF (Catalyst & Diesel Particulate Filter) that is combination of the existing DOC (Diesel Oxydation Catalyst) and DPF (Diesel Particulate Filter). While the DOC converts the CO and HC into the CO2 and H2O - unharmful to human body - using a oxidation reaction, the DPF collects the PF (Particulate Material) for regeneration of it. However, each of these devices can only reduce a part of the exhaust gas. This evoked the necessity of the CDPF with both features. The DOC capacity is more on the manual transmission than the automatic transmission. DOC(Diesel Oxidation Catalyst) ▶ It is called as a oxidation catalyst, which purifies CO and HC in exhaust gas. The three-way catalyst is used for the gasoline vehicle. But, the diesel engine oxidates CO and HC excepting NOx into H2O and CO2 in order to purify the exhaust gas since the exhaust gas has a rich oxygen at all times. DPF(Diesel Particulate Filter) ▶ It consists of mainly the aluminum and titanium and there is a porous thin film, which emits the exhaust gas but does not emit the PM in it. It emits the exhaust gas generated during combustion and filters the PM which is a byproduct of combustion to burn it when a certain amount of it is collected in the filter. When a certain amount of the PM builds up, exposure to high exhaust gas causes carbon, the fundamental ingredient in PM, to burn and release into the atmosphere in form of CO2. |