柴油喷雾与LPG/柴油混合喷雾的对比研究

以ZH1105W柴油机为模型,采用Jaynes等人提出的雾化液滴尺寸和速度联合数目分布函数,对柴油喷雾和LPG/柴油混合喷雾的燃料液滴尺寸和速度数目分布进行了对比研究;采用液滴蒸发和碰撞模型对液滴尺寸理论数目分布与试验结果进行了对比研究。液滴尺寸和速度联合数目分布的研究结果表明,随着液体喷射速度的增大,液滴尺寸数目分布曲线向小颗粒偏移。随着液滴尺寸的增大,较大颗粒的液滴速度数目分布曲线的峰值先明显增大,到达中等尺寸后又明显减小。由于LPG/柴油混合燃料的闪急沸腾喷雾对燃料液滴具有突爆的加速作用,L30速度分布曲线的峰值速度比柴油的明显增大。累积的液滴尺寸分布和速度数目分布研究表明,由于混合燃料的闪急沸腾喷雾,L30尺寸数目分布曲线峰值相对于柴油向小颗粒方向偏移,L30的峰值大于柴油的峰值。说明L30喷雾所产生的小颗粒液滴多于柴油,雾化质量提高,碳烟排放得以大幅度降低。L30速度分布曲线的峰值比柴油略小一些,且略微向大速度方向偏移。说明与柴油相比,L30燃料较大速度液滴的数目略有增加。液滴蒸发和碰撞模型对于石油液体燃料的研究是可行的,对于液化气体燃料与石油液体燃料的混合燃料的研究,模型还有待于进一步改进。

Comparative Investigation Between Diesel and Mixed Liquefied Petroleum Gas/Diesel Sprays

Comparative studies of ZH1105W diesel engine are computed on the joined fuel droplet size and velocity number distributions between diesel and mixed liquefied petroleum gas(LPG)/diesel sprays by using Jaynes's formula.Comparative investigations are also conducted on the fuel droplet size number distributions between theoretical computation and test data by using Cao's formula.The results of joined fuel droplet size and velocity number distributions indicate that with fuel injected velocity increases,the droplet size number distribution curve moves towards smaller diameters,and with droplet size increases, the peak of droplet velocity number distribution curve of larger drops increases,then decreases at mid-size.Because of exploded effect on fuel droplets of flash boiling injection of mixed LPG/diesel fuel,droplets speed increases,and the peak of droplet velocity number distribution curve of L30 increases significantly compared with diesel.The results of fuel droplet size number distributions and fuel droplet velocity number distributions show that because of flash boiling injection of mixed fuel,the droplet size number distribution curve of L30 moves towards smaller diameters compared with diesel,and the peak of L30 is higher than the peak of diesel.This indicates that smaller drops of L30 are more than those of diesel,spray quality is good,and engine smoke reduces accordingly.The peak of droplet velocity number distribution of L30 is lower than that of diesel slightly,and moves towards higher velocities slightly.This indicates that higher velocity drops of L30 are more than those of diesel.The model of droplet evaporation and coalescence applied on liquid oil fuel sprays is valuable.However,the model needs to improve when it applies on mixed liquefied gaseous fuel and liquid oil fuel.