A Study on the Effect of De-NOx Device on GHG Emissions

De-NOx 저감장치가 온실가스 배출량에 미치는 영향 연구

Abstract

As increase the number of vehicles, the issue of greenhouse gas that was emitted by them became important. As a result, greenhouse gas (GHG) regulations are being strengthened and efforts are being actively made to reduce greenhouse gas emissions in the automotive industry. In the other hand, regulations for harmful emission of vehicles have been reinforced by step. Especially, the lastly applied step, so called Euro 6, not only decreased NOx limit down to half of Euro 5 but also introduced real driving emission limit for NOx and PN. It is a challenge for manufacturers to meet the recent GHG regulation as well as the latest emission regulation. To overcome these regulations a De-NOx after-treatment system is being applied to diesel vehicles that are known emitting the lowest GHG among conventional internal combustion engines. At the time of the introduction of Euro 6 emission standard in Korea, in the domestic fuel economy certification test, some diesel vehicles emitted more $CH_4$ than Euro 5 vehicles. As a result, it was confirmed that LNT-equipped vehicles emitted a high level $CH_4$ and the level exceeded the US emission standard. In order to determine the reason, various prior literature was investigated. However, it was difficult to find a detailed study on the methane increase with LNT. In this paper, to determine whether the characteristics of vehicles equipped with LNT the affects the above issue and other greenhouse gases, 6 passenger cars were tested on several emission test modes and ambient temperatures with a environment chamber chassis dynamometer. 2 cars of these were equipped with LNT only, other 2 cars had SCR only, and LNT + SCR were applied to remaining 2 cars. The test result shown that the vehicles equipped with LNT emitted more $CH_4$ than the vehicles with SCR only. Also, $CH_4$ tended to increase as the higher acceleration of the test mode. However, as the test temperature decreases, $CH_4$ tended to decreased. $CO_2$ was not affected by kinds of De-NOx device but characteristic of the test modes.

Fig. 1 Vehicle speed schedule of each test mode

Fig. 2 CH₄ emission on WLTC mode by temp

Fig. 3 CH₄ emission on 5-cycle modes

Fig. 4 CH₄ emission on aggressive modes

Fig. 5 CH₄ emission on several test modes

Fig. 6 THC real time emission (Constant volume sample dilution) on WLTC (23℃) modes

Fig. 7 THC real time emission (Constant volume sample dilution) of vehicle A on WLTC modes

Fig. 8 CO₂ emission on several test modes

Table 1 Spec. of test vehicles

Table 2 Spec. of Chassis Dynamometer

Table 3 Spec. of emission analyzer

Table 4 Feature comparison by test mode