Effects of Different Exhaust Thermal Management Strategies on WHTC Emission for Equivalent NG Engine
The China Ⅵ natural gas engine adopts the emission control technology route of equivalent combustion combined with external cooling EGR and TWC.The conversion efficiency of TWC is an important factor to ensure that the engine emis-sions meet the standards,and the inlet temperature of the catalytic converter is one of the most important influencing parame-ters that determine the conversion efficiency of TWC.However,there is a problem that the inlet exhaust gas temperature of TWC is difficult to meet the high-efficiency conversion requirements of engine and whole vehicle emissions in the cold start stage and under the condition of large temperature drop of exhaust pipe.To address this issue,different exhaust thermal man-agement strategies were investigated on a 4.5 L displacement engine and an urban sanitation vehicle equipped with the engine to study the effects on engine WHTC cycle emissions and whole vehicle operation cycle emissions.The results showed that the ex-haust thermal management strategy with rapid temperature rise could effectively increase the exhaust gas temperature of engine during cold start.The time required for the TWC inlet temperature to reach 300 ℃ during WHTC cycle was shortened by 300 s,which significantly reduced NOx,CH4,and CO cycle emissions with the reductions of 38.5％,38.5％ and 5.8％ re-spectively.The exhaust control strategy that added a metal carrier upstream of TWC produced the reductions of 62.2％,42.8％and 15.7％ respectively in NOx,CH4,and CO cycle emissions during WHTC cycle.Compared with the scheme using ordinary asbestos wrapping,the inlet temperature of TWC increased by nearly 200 ℃ under the whole vehicle operation cycle after using the exhaust thermal management strategy with a special wrapping process for the entire vehicle exhaust pipe,which resulted in a maximum reduction of 60.9％ in the 30 s average value of transient NOx emissions.Accordingly,the emission regulation re-quirements of Beijing's Ⅵ stage can be better met.
NG engineequivalent combustionexhaust thermal managementcold startexhaust temperature
万方数据
维普
