为分析高原环境下柴油机性能下降的原因,应用CFD软件FIRE对不同海拔条件下柴油机燃烧过程进行了三维仿真研究.建立了描述缸内油气混合过程的中间参数,在此基础上定量分析了高原环境对柴油机缸内油气混合过程的影响.着重通过对燃烧放热规律的分析,研究了高原环境对柴油机燃烧过程的影响.结果表明:高原环境下燃烧室近壁面处易形成较浓混合气,燃油附壁较多,燃烧室中心区域空气利用率降低；燃烧后期,高原环境下柴油机缸内仍有大量浓混合气存在,且分布较集中,燃油质量分数均方差大；随着海拔的升高,燃烧中后期缸内高温区域中心逐渐向燃烧室侧壁移动,附壁燃烧严重,凹坑及余隙处易形成油气堆积,促使燃烧恶化；高原环境对柴油机预混燃烧的影响并不明显,但随着海拔的升高,扩散燃烧放热率逐渐降低,燃烧持续期大幅增加,导致严重的后燃.%In order to investigate the reasons for the degradation of dynamic performance of diesel engines under plateau environment, multi-dimensional simulation under different altitudes was conducted to study the combustion process. A set of characteristic parameters accounting for mixing in combustion chamber was established, basing on it, quantitative analysis of the influence of plateau environment on mixing process was conducted. And then the influence of plateau environment on combustion process was investigated mainly by analyzing the heat release rate in the engine. The results show that, under plateau environment , near the wall of combustion chamber easily forms rich mixture, which leads to a reducing of air utilization rate in the center of combustion chamber, a mass of rich mixture still exists at late combustion process. With the rise of altitude, the center area of high temperature moves to the wall of combustion chamber, and causes the deterioration of combustion efficiency. The influence of plateau environment on pre-mixing combustion is not obvious, however, with the rise of altitude, heat release rate of diffusion combustion reduces gradually, and the duration of combustion increases sharply.
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