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以六缸增压中冷发动机为研究对象,采集不同工况下示功图并对NOx排放进行了测试,分析了外特性燃烧特性及排放随转速的变化规律.试验结果表明:在外特性整个转速范围内,瞬时放热率呈先急后缓的趋势,转速越高,瞬时放热率峰值越低;由于低速时滞燃期较长,因此天然气预混燃烧比例较大,各燃烧阶段分界较明显,转速升高到1 100r/min时,滞燃期明显缩短,天然气预混燃烧比例减小,扩散燃烧成为天然气主导的燃烧模式;转速小于900r/min时,NOx排放随转速升高而增加;转速在900~1 600r/min之间时,随转速升高而降低;转速高于1 600r/min时,NOx排放没有明显变化.
Taking the six-cylinder turbocharged intercooled engine as the research object, the kinetic energy diagrams of different operating conditions were collected and the NOx emission was tested, and the variation characteristics of the combustion characteristics and the emission with the rotational speed were analyzed. The experimental results show that: Within the range, the instantaneous heat release rate tends to be lower and lower than before. The higher the speed is, the lower the instantaneous heat release rate is. Because of the longer duration of low-speed lag, the proportion of natural gas premixed combustion is larger. Obviously, when the rotation speed is increased to 1 100 r / min, the ignition delay is obviously shortened, the proportion of natural gas premixed combustion is reduced, and the diffusion combustion becomes the dominant combustion mode of natural gas. When the rotation speed is less than 900 r / min, the NOx emission increases with the increase of rotation speed ; When the rotation speed is between 900 ~ 1 600r / min, it decreases with the increase of rotation speed; when the rotation speed is higher than 1 600r / min, there is no obvious change of NOx emission.