基于液压驱动气门的柴油机性能优化研究

摘要

The original cam driven valve system was replaced by a hydraulic driven valve system and the model of diesel engine was built with GT-Power .With the model ,the influences of intake retarded angle ,exhaust advance angle and valve overlap an-gle on diesel engine power performance were analyzed ,the valve timing was optimized aiming at the maximum output torque , and EGR rate and NOx emission under different loads for two kinds of internal EGR were compared .The results showed that diesel engine with a hydraulic driven valve system had better power performance and fuel economy in low and medium speed with full load .The torque increased by 5 .6% and the specific fuel consumption rate decreased by 5 .1% .However ,the im-proved effects would become less obvious with the increase of speed .Compared with the exhaust valve early closing ,the ex-haust late closing was more likely to promote the increase of EGR rate and the reduction of NOx emission at 2 000 r/min .Under the operating condition of 50% load ,the maximum reduction of NOx emission was 23 .8% .%在某柴油机上将传统凸轮驱动气门机构改进设计为液压驱动气门机构 ,利用仿真软件GT-Power建立液压驱动气门柴油机模型 ,分析进气滞后角、排气提前角和气门重叠角对柴油机动力性的影响 ,然后以扭矩最大为目标对配气正时进行联合仿真优化 ,最后对比两种内部 EGR实现方法在不同负荷下的EGR率和对 NOx 排放量的改善效果.研究结果表明 ,在外特性下 ,液压驱动气门柴油机在中低转速时的动力性和经济性有了明显改善 ,扭矩比原机提高了5.6% ,燃油消耗率降低了5.1% ;但由于液压气门响应滞后 ,随着转速的升高 ,改善效果逐渐降低.在转速2 000 r/min时 ,排气门晚关比排气门早关可以获得更大的EGR率 ,NOx 排放量降幅也比排气门早关的大 ,在50% 负荷时 ,N O x 排放量降幅最大为23 .8% .