高原环境对缸内燃烧及壁面油膜的影响研究

为了分析高原环境下缸内燃烧过程及壁面油膜生成规律，采用 CFD 方法对不同海拔条件下柴油机燃烧过程进行了三维仿真计算，着重分析了海拔对壁面油膜的影响。结果表明：随海拔升高，过量空气系数降低，滞燃期延长，着火推迟，燃烧恶化，柴油机性能下降；高原条件对壁面油膜生成有较大影响，壁面累计油膜质量随海拔升高而增大，4500 m 海拔下壁面油膜累计质量最大可达19 mg ，约占总油量的8％；壁面油膜在燃油喷射弹着点处形成，随着时间推移，油膜向活塞边缘扩散，在高海拔条件下，燃烧结束时活塞边缘仍有油膜残留。

Effect of Plateau Environment on In-cylinder Combustion and Wall Fuel Film

In order to analyze in‐cylinder combustion process and wall fuel film forming law under plateau environment ,three‐dimensional simulation and calculation of combustion process for diesel engine were conducted by CFD under different altitudes and the influence of altitude on wall fuel film was mainly analyzed .The results showed that the excess air ratio decreased ,the ignition delay period prolonged ,the ignition delayed ,the combustion deteriorated and the engine performance decreased with the increase of altitude .The plateau environment had a great influence on formation of wall fuel film and the cumulative mass of wall fuel film increased with the increase of altitude .The cumulative mass was up to 19 mg at 4 500 m ,which accounted for a‐bout 8% of total fuel .The wall fuel film formed at the fuel jet impact point ,then diffused toward the edge of piston .There still existed the residual fuel film at the edge of piston at the end of combustion under plateau conditions .