【摘要】 通过三维计算模型研究了航空煤油喷雾液滴直径不均匀度对四冲程低压直喷航空发动机缸内混合气形成过程的影响.结果表明:随着航空煤油喷雾液滴直径不均匀度增加,在航空发动机压缩行程中燃油重聚效果更加明显,点火时刻缸内未蒸发燃油直径逐渐增大,大直径液滴数量增加,且大直径液滴多出现在火花塞附近或气缸边缘,使燃烧不稳定,易形成积碳;同时,航空煤油蒸发量逐渐降低,缸内混合气分布也受到影响,气缸中央的混合气变稀,使得火焰传播速度下降,增加爆震倾向.当航空煤油喷雾索特平均直径(SMD)超过10μm之后,不均匀度对缸内未蒸发燃油液滴SMD和燃油蒸发量的影响更加显著.喷雾SMD为15μm的计算结果中,不均匀度由1.6增加到2.2时,缸内未蒸发燃油液滴SMD增加了27%,燃油蒸发量减少了19%.更多还原

【Abstract】 The influence of the unevenness of aviation kerosene spray droplets diameter on the mixture formation process in the cylinder of a four-stroke low-pressure direct injection aviation engine was studied by threedimensional modelling calculation. The research results show that,with the increase of the unevenness of aviation kerosene spray droplets,the effect of fuel recombination in the compression stroke is more obvious,the droplets diameter and the number of large droplets of the non-evaporated fuel is bigger,the evaporation amount is gradually reduced and the mixture gas in the center of the cylinder is thinned. Large droplets appear mostly near the spark plug or at the edge of the cylinder,making the combustion unstable and easily forming carbon deposits. The dilution of the mixture in the middle of the cylinder reduces the flame propagation speed and increases the tendency to knock. The analysis shows that after the Sauter mean diameter(SMD)of aviation kerosene spray exceeds 10 μm,the effect of unevenness on the average spray droplets diameter of the un-vaporized fuel in the cylinder and the amount of fuel evaporated is more significant. For the spray SMD of 15 μm,the results show that as the unevenness increases from 1.6 to 2.2,the average fuel droplets diameter in the cylinder increases by 27% and the fuel evaporation is reduced by 19%.更多还原