| EFFECT OF UWS INJECTION AT LOW EXHAUST GAS TEMPERATURE ON NOX REMOVAL EFFICIENCY OF DIESEL ENGINE |
| Joonsoo Han1, Junho Lee2, Youngtaig Oh1, Gyubaek Cho2, Hongsuk Kim2 |
1Chonbuk National University
2Korea Institute of Machinery & Materials |
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| ABSTRACT |
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Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NOx (Nitrogen Oxides) emission standard. The NOx removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 oC. However, a large amount of NOx is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NOx conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NOx removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 oC compared to 200 oC. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition. |
| Key Words:
NOx removal efficiency, Urea SCR (Selective Catalytic Reduction), UWS (Urea Water Solution), NRTC (Non Road Transient Cycle) |
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