刘光义，孙德增，邬斌扬，苏万华.柴油机WHTC冷起动过程SCR温度热管理技术研究[J].内燃机工程,2017,38(6):145-151.
柴油机WHTC冷起动过程SCR温度热管理技术研究
Study on SCR Thermal Management for Diesel Engines during Cold Start WHTC Process
DOI：
关键词:排气热管理  SCR温度控制  SCR转化效率  WHTC测试循环  排放
Key Words:exhaust temperature management  SCR temperature control  SCR efficiency  WHTC test cycle  emissions
基金项目:国家自然科学基金项目（51236005，51506144）
作者单位
刘光义，孙德增，邬斌扬，苏万华 天津大学 内燃机燃烧学国家重点实验室，天津 300072 
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摘要:研究了低速低负荷工况下可变几何截面增压器（variable geometry turbocharger，VGT）开度、进气门晚关机构（retard intake valve closing auction, RIVCA）和后喷技术对提升选择性催化还原（selective catalytic reduction, SCR）后处理器温度的作用，并从温度提升幅度、发动机油耗率和排放等方面对各技术进行了分析比较。试验结果表明，采用后喷技术、增大VGT开度和利用进气门晚关可以有效提高SCR后处理器温度。但相比于后喷技术，增大VGT开度和运用进气门晚关技术造成的油耗损失较小。试验对后喷策略和VGT RIVCA策略进行了全球统一瞬态试验循环（world harmonized transient cycle, WHTC）冷起动对比试验。试验结果显示，在使SCR后处理器的起燃时间缩减至循环第600 s附近时，后喷策略造成的油耗损失为3.5%，而VGT-RIVCA策略造成的油耗损失仅为1.1%。在验证了VGT控制策略的优越性后，通过设定不同VGT开度的对比试验，最终得到了一套优化的VGT-RIVCA控制策略，运用该策略可以使SCR后处理器的起燃时间由1300 s缩减至540 s，NOx排放量由1.78g/(kW•h）降低至0.929g/（kW•h），同时发动机油耗仅有1.4%的恶化。
Abstract:The effects of variable geometry turbocharger (VGT) opening, retarded intake valve closing timing and post injection strategy on the promotion of SCR temperature were experimentally studied in detail, and the comparative analysis of the above approaches was made with regard to SCR temperature rise, emissions and engine operation economy. Experiment results show that using the post injection, increasing the VGT opening and taking the advantage of RIVCA (retarded intake valve closing auction) can effectively increase the SCR temperature. Compared with the post injection strategy, increasing the VGT opening and using the RIVCA make the engine have lower fuel consumption. Based on the above steady state test results, the post injection strategy and VGT-RIVCA strategy were selected and the further comparison was carried out by cold-start of WHTC test. Results show that both strategies can reduce the SCR light-off time to around the 600th second of the test cycle, and at this point the post injection strategy worsens the fuel economy by 3.5%, while the VGT-RIVCA strategy by only 1.1%. Through the contrast test of different VGT openings, an optimized VGT-RIVCA control strategy was obtained. With this strategy, the SCR temperature can reach 190℃ at the 540th second of the test cycle, NOx emission is reduced to 0.929 g/(kW•h） from 1.78g/(kW•h）, and the engine fuel consumption increases by only 1.4%.
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