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车用增压柴油机VNT和EGR系统匹配试验研究
本论文在CA498Z 柴油机上进行电控VNT 和EGR 匹配，旨在降低发动机的 排放，使之达到欧II 排放标准。 可变喷嘴增压器（VNT）能在所有的工况点与发动机都有良好的匹配，使 发动机的性能达到最佳。配有一可调节的喷嘴环，它能通过调节喷嘴环上的可 变舌片位置而改变涡轮的流通截面。从而使它在低速时像一快速反应的小涡轮 而在高速时像一高效率的大涡轮。通过减少涡轮流通截面它能最大程度的减少 涡轮滞后现象。也能在高速流动时减少废气的摩擦而使发动机输出更大功率。 使用可变喷嘴增压器，能提高发动机的低速扭矩性及加速性能，并大幅度的降 低发动机的微粒。 废气再循环（EGR）对降低发动机排气中NOx 十分有效，此技术是将一部 分废气引入发动机的进气系统，使得进气充量中惰性气体（H2O 蒸气，N2 和CO2 等）的比例增加。由于这些惰性气体具有较高的比热容，使得经再循环废气稀 释的混合气的比热容增高，致使发动机最高燃烧温度下降，同时EGR 的稀释作 用也降低了混合气中的氧浓度，从而破坏了NOx 的生成机理，以致有效的抑制 了NOx 的生成。但废气再循环也会使发动机的微粒排放会有较大增加，特别是 在大负荷。研究显示冷的EGR 对减少微粒特别有效。 本论文主要研究发动机的各个工况下不同VNT 叶片位置及EGR 率对柴油机 性能和排放的影响，确定各工况点下最佳VNT 的叶片位置和EGR 率，制成电控 脉谱。 通过认证试验，可知匹配VNT 和EGR 系统后CA498Z 的排放大幅度降低， 达到了欧II 排放法规。 关键词：CA498Z 柴油机，排放控制，优化匹配，可变喷嘴增压器，废气再循 第一章 绪 论·······································································································1 1.1 车用柴油机的发展状况····························································································· 5 1.2 车用柴油机的排放法规和发展目标·········································································· 6 1.3 降低柴油机主要排放污染物的措施········································································· 7 1.4 采用电控EGR、VNT 系统降低柴油机NOX、PM 的排放·································· 10 1.4.1 采用电控EGR 降低柴油机NOX 的排放······················································ 10 1.4.2 采用电控VNT 系统降低PM 的排放··························································· 10 1.5 本论文研究的主要内容··························································································· 11 第二章 CA498Z 柴油机VNT 系统·······································································9 2.1 涡轮增压器及其在发动机上的应用········································································· 9 2.1.1 车用涡轮增压器的种类··················································································· 9 2.1.2 可变喷嘴增压器在发动机上的应用····························································· 12 2.1.3 柴油机匹配不同增压器的性能的对比······················································ 13 2.1.4 CA498Z 柴油机VNT 系统········································································· 14 2.2 可变喷嘴涡轮增压器与发动机的匹配性能···························································· 15 2.2.1 车用发动机对增压器的要求········································································· 15 2.2.2 涡轮增压发动机的运行性能和匹配设计点的确定······································ 16 2.2.3 可变喷嘴涡轮增压发动机的运行特点························································· 18 2.2.4 可变喷嘴涡轮增压器的匹配········································································ 20 2.6 本章小结·················································································································· 21 第三章 CA498Z 柴油机EGR 系统·····································································24 3.1 NOx 生成机理及EGR 系统降低NOx 机理························································· 24 3.1.1 NOx 生成机理······························································································· 24 3.1.2 EGR 系统降低NOx 排放的机理································································ 25 3.2 EGR 系统的布置··································································································· 26 3.2.1 EGR 系统取气方式的选取············································································ 26 3.2.2 EGR 动力回流措施······················································································· 27 3.2.3 EGR 系统的布置··························································································· 28 3.3 EGR 系统的组成结构························································································· 28 3.3.1 EGR 阀··········································································································· 28 3.3.2 EGR 冷却器··································································································· 31 3.3.3 文丘里混合器······························································································· 35 3.3.4 EGR 系统的总体布置················································································· 37 3.4 柴油机EGR 系统所引发的问题及解决措施: ························································· 38 3.5 本章小结·················································································································· 38 第四章 试验方案的设计·······················································································37 4.1 试验方案················································································································· 37 4.1.1 试验发动机及测量设备················································································· 37 4.1.2 法规简介······································································································· 38 4.1.3 试验内容和方法··························································································· 39 4.2 EGR 阀和VNT 的控制···························································································· 40 4.2.1 试验用传感器简介······················································································· 40 4.2.2 信号输入电路································································································ 41 4.2.3 VNT 和EGR 系统的电控调节······································································ 42 4.4 试验系统布置········································································································· 44 4.5 本章小结··············································································································· 45 第五章 CA498Z 柴油机VNT 及EGR 匹配试验结果·······································46 5.1 VNT 匹配试验······································································································· 46 5.1.1 VNT 叶片位置对发动机外特性的影响························································ 46 5.1.2. CA498Z 柴油机匹配VNT 自由加速烟度试验··········································· 50 5．1．3 CA498Z 匹配VNT 与TB28 的性能比较·············································· 52 5．1．4 VNT 与原TB28 柴油机万有特性对比················································ 55 5．2 CA498Z 柴油机EGR 系统匹配试验································································· 57 5.2.1 EGR 冷却器试验··························································································· 57 5.2.2 文丘里混合器的试验···················································································· 59 5．2．3 EGR 率CA498Z 性能及排放的影响··················································· 63 5.2.3. CA498Z 柴油机最佳EGR 率时与原机性能对比········································ 73 5.2.4 TB28 和VNT 最大EGR 率对比·································································· 78 5.3 CA498Z 柴油机VNT 及EGR 综合匹配试验······················································ 80 5．4 CA498Z 柴油机匹配VNT 及EGR 系统后欧II 十三工况综合测试················ 86 5.5 本章小结·················································································································· 87 第六章 结论和展望·······························································································87 
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