低转速工况下喷油量对柴油机缸内压力振荡和排放特性的影响  

Influence of Fuel Injection Quantity on In-Cylinder Pressure Oscillation and Emission Characteristics of Diesel Engine at Low Speed

作　　者：黎一锴[1] 薛泽峰 王东方 史中杰 谢勇 李耀宗 LI Yikai;XUE Zefeng;WANG Dongfang;SHI Zhongjie;XIE Yong;LI Yaozong(School of Mechanical Engineering,Beijing Institute of Technology,Beijing 100081,China;China North Engine Research Institute(Tianjin),Tianjin 300406,China)

机构地区：[1]北京理工大学机械与车辆学院,北京100081 [2]中国北方发动机研究所(天津),天津300406

出　　处：《车用发动机》2023年第6期1-9,共9页Vehicle Engine

基　　金：北京市自然科学基金资助项目(3212022);北京理工大学科技创新计划创新人才科技资助专项计划(2022CX02021);国家自然科学基金资助项目(51976011);博士后科学基金资助项目(2020M680378)。

摘　　要：缸内压力高频振荡现象对发动机低速、低负荷起动过程的燃烧稳定性、运行可靠性和排放物水平有着重要影响。为探明在柴油机低转速工况下喷油量对缸内压力振荡和排放特性的影响规律,基于单缸柴油机试验平台获取了低转速工况(800 r/min)下,喷油压力为40 MPa,喷油脉宽为3500~6000μs时的缸内燃烧压力、放热率、平均指示压力以及NO_(x)和Soot排放量。试验结果表明:在低转速工况下,随着喷油量的增大,缸内压力峰值逐渐增大;压力高频振荡的幅值呈现先增大后减小的非单调变化规律,当喷油脉宽为5000μs时,缸内压力高频振荡幅值达到最大值0.84 MPa。缸内燃烧放热各指标如压力升高率、放热率、滞燃期和平均指示压力与缸压振荡的变化规律呈现高度一致性,缸内压力振荡最大值大致对应上述指标的最佳值。适当强度的缸压振荡有利于缸内燃烧效率的提高。此外,随着喷油量的增大,Soot的排放量呈现两阶段非线性增加的变化规律,NO_(x)的排放量呈现先增大后减小的非单调变化规律,增加喷油量与缸内压力振荡导致的缸内当量比浓度转变造成了上述变化。The phenomenon of in-cylinder pressure high-frequency oscillations has an important impact on the combustion stability,operating reliability and emission levels of diesel engine.In order to explore the influence of fuel injection quantity on the in-cylinder pressure oscillation and emission characteristics at low speed,a single cylinder diesel engine test platform was used to obtain the combustion pressure,heat release rate,IMEP,and NO_(x) and Soot emissions under the conditions of injection pressure of 40 MPa and injection pulse width of 3500~6000μs at low speed(800 r/min).The test results show that the peak pressure in the cylinder gradually increases with the increase of fuel injection quantity under low speed conditions.The amplitude of pressure high-frequency oscillations exhibits a non-monotonic variation pattern of increase first and then decrease.When the injection pulse width is 5000μs,the amplitude of in-cylinder pressure high-frequency oscillation reaches the maximum value of 0.84 MPa.The variations of heat release indicators such as pressure rise rate,heat release rate,ignition delay and IMEP are highly consistent with those of cylinder pressure oscillation.The maximum value of in-cylinder pressure oscillation roughly corresponds to the optimal value of the above-mentioned indicators.Proper intensity of cylinder pressure oscillation is beneficial to improving combustion efficiency.In addition,the Soot emissions exhibit a two-stage nonlinear increase pattern with the increase of fuel injection quantity,and the NO_(x) emissions exhibit a non-monotonic change pattern of increase first and then decrease.These changes are caused by the change of in-cylinder equivalent ratio concentration led by increased fuel injection and in-cylinder pressure oscillation.

关 键 词：柴油机 喷油量 压力振荡 燃烧过程 排放 

分 类 号：TK421[动力工程及工程热物理—动力机械及工程]