【作者】 张华；

【导师】 乔信起；

【作者基本信息】 上海交通大学 ， 动力机械及工程， 2007， 硕士

【摘要】 燃油喷雾碰壁作为中小型柴油机中不可避免地存在的现象,往往造成燃油沉积壁面,形成近壁浓混合气,导致高的燃油耗及CO和HC排放。但喷雾碰壁合理利用可改善燃油雾化,促进油气混合,从而降低燃油耗和排放。斗笠状喷雾燃烧系统即是一种新型的基于此思想开发出的燃烧系统。本文采用试验和计算方法,研究了二冲程柴油机采用该燃烧系统的燃烧、性能和主要因素的影响规律。在高压油泵试验台上,采用高速摄影技术和电控共轨燃油喷射系统,建立了喷雾特性试验台,测试了斗笠状喷雾的宏观特性,研究了碰撞环尺寸、喷射压力、碰撞距离等的影响。结果表明,当共轨压力大于等于90MPa时,随其上升,喷雾锥角上升,喷射后期贯穿距变化不大;碰壁明显缩短喷射结束时刻喷雾行进的总距离,增大喷雾最大宽度;喷射压力上升,碰壁后贯穿距离及喷雾最大宽度均上升;增加碰撞环高度,相同喷射时刻下,碰壁后贯穿距降低,喷雾行进的总距离增加,但喷射结束时刻仍低于自由喷雾的贯穿距,喷雾最大宽度下降。将一台1E150C型二冲程船用中速柴油机的燃烧系统改为斗笠状喷雾燃烧系统,建立了试验台,采用柴油和柴油-DMC混合燃料,进行了燃烧和性能试验。利用测得的缸内压力,计算了放热率和累计放热率。燃用柴油的研究表明,在8×0.25、8×0.30、8×0.35及5×0.42四个喷油嘴中,8×0.30喷油嘴NOx排放最高,但是燃油消耗率及烟度最低,综合性能最好。8×0.25喷油嘴在最大转矩下具有扩散燃烧峰值大于预混合燃烧峰值的放热规律;使用8×0.30喷油嘴,喷油嘴端伸出量为2.5mm时,综合性能较好;碰撞环外径不宜过大;供油提前能够改善烟度,但会升高NOx排放。启喷压力增大,燃烧始点推迟。启喷压力过高过低对性能都不利。扫气压力增大,则燃油消耗率、烟度及NOx排放均降低。转速升高,则最大爆发压力降低,预混合放热峰值升高,扩散燃烧峰值降低。随着负荷上升,NOx排放、烟度及排温上升。燃用柴油-DMC混合燃料的研究表明,采用含氧燃料能明显降低碳烟排放,降低燃油耗,改善发动机工作平稳性。随着DMC比例上升,燃烧始点略为推迟,燃烧结束点提前,燃烧持续期缩短。添加DMC后,最佳燃油消耗率对应的供油定时提前。更多还原

【Abstract】 Spray impingement on wall as an avoidless phenomenon in middle and small cylinder bore diesels will cause accumulation of fuel on the wall of the combustion chamber, which results in high brake specific fuel consumption and HC & CO emissions. But it also can be used rationally to improve the fuel mixing with air, and improve in-cylinder combustion. Bamboo-hat shaped combustion system is a new one of those systems taking advantage of spray/wall interaction, and it’s combustion, performance and main factors were studied on a two-stroke diesel engine.A spray characteristics-measuring system was established on a fuel injection pump test-bench equipped with electrical-controled high pressure common rail injection system and high-speed video camera. The effects of the diameter of the impingement ring, common rail pressure and impaction distance were studied. The experimental results indicate that, when common rail pressure is above 90MPa, the spray cone angle increases as common rail pressure rise, and the penetration varies slightly during the final stage of the injection. The impaction observably shortens the distance that the spray penetrates during the injection, and extends the maximal spray width. The penetration after impingement increases and the maximal spray width extends with the rise of the common rail pressure. Increase of the height of the impingement ring follows a reduction of the penetration after impingement at the same injection timing, while the distance that the spray penetrates during the injection increases, but still less than the penetration of free spray. Increasing impingement ring height also reduces the maximal width of the impingement spray.The combustion system of a two-stroke marine diesel engine 1E150C was retrofitted to bamboo-hat-shaped spray combustion system and test apparatus established. The combustion and performance experiments were conducted with diesel fuel and its blend with DMC. The heat release rate and更多还原