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3 500~6 000 μs 时的缸内燃烧压力、放热率、平均指示压力以及NOx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5 000 μs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，NOx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。
Abstract
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 NOx and Soot emissions under the conditions of injection pressure of 40 MPa and injection pulse width of 3 500~6 000 μs 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 5 000 μs, 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 NOx 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
Key words
diesel engine /
fuel injection quantity /
pressure oscillation /
combustion process /
emission
黎一锴，薛泽峰，王东方，史中杰，谢勇，李耀宗.
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[J]. 车用发动机. 2023, 0(6): 1-9 https://doi.org/10.3969/j.issn.1001-2222.2023.06.001
LI Yikai，XUE Zefeng，WANG Dongfang，SHI Zhongjie，XIE Yong，LI Yaozong.
Influence of Fuel Injection Quantity on InCylinder Pressure Oscillation and Emission Characteristics of Diesel Engine at Low Speed[J]. Vehicle Engine. 2023, 0(6): 1-9 https://doi.org/10.3969/j.issn.1001-2222.2023.06.001
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