热氛围下水喷射雾化特性试验

摘要

In-cylinder water injection has advantages in suppressing the combustion knock,expanding the operating range and improving the thermal efficiency.In-cylinder water spray characteristics are of great sense to the researches relevant to in-cylinder water injection.By utilizing a thermos-atmosphere system,the spray characteristics of water injection under high temperature conditions were studied.The results show that,for non-flash-boiling sprays,liquid phase spray penetration has a positive correlation with the injection water density,ambient density and injection pressure.Liquid phase spray penetration is mainly affected by injection water density inside break-up length,while outside break-up length the influence of injection water density on liquid phase spray penetration is getting less.Liquid phase spray penetration empirical equations are given for ambient temperature under 350 ℃ (350 ℃ included)and injection water temperature under 125 ℃ (125 ℃ included).Spray cone angle decreases with the increasing of injection water temperature,ambient temperature and injection pressure.The increase of injection water temperature and background temperature accelerates the evaporation of spray,which reduces liquid phase spray cone angle.Liquid phase spray cone angle has a trend to keep stable when injection water temperature and background temperature rise to a certain degree.Liquid phase spray cone angle stabilizes to approximate 11° after injection water temperature reaches 120 ℃ under test conditions.%发动机缸内喷水在抑制爆震、拓宽工作边界和提高热效率方面有很大优势,而缸内喷水喷雾的宏观喷雾特性对缸内喷水相关研究有重要意义.利用热氛围试验系统,对高温环境下水的雾化特性进行了研究.结果表明:在未达到闪急沸腾的情况下,液相喷雾贯穿距与喷射水的密度、环境介质密度和喷射压力正相关,破碎长度内液相喷雾贯穿距主要受喷射水的密度影响,破碎长度外液相喷雾贯穿距受喷水密度的影响减小.给出了环境温度在350℃以下(包含350℃)、喷水温度在125℃以下(包含125℃)的液相喷雾贯穿距经验公式.液相喷雾锥角随喷射压力增加而减小.喷水温度和环境温度的增加都加快喷雾蒸发,使液相喷雾锥角减少,当二者增加到一定程度时,喷雾的液相锥角趋于稳定.试验条件下,喷水温度达到120℃后,液相喷雾锥角稳定维持在11°左右.