甲醇/正辛醇/HCB混合燃料喷雾燃烧特性

Spray and Combustion Characteristics of Ternary Blends with Methanol,HCB and n-Octanol

基于定容燃烧弹系统,通过纹影法、OH*化学荧光法与背景光消光法及自然辐射光法两套同步光学诊断技术,针对3种不同甲醇添加比例的甲醇/正辛醇/加氢催化生物柴油(HCB)混合燃油,对比分析了不同环境温度、喷射压力下喷雾燃烧特性.结果表明:3种燃油由于反应活性和含氧量的不同,在相同工况下着火延迟期和火焰浮起长度随甲醇比例的增大而增加,使得着火后的喷雾贯穿速度降低.通过对着火延迟期和火焰浮起长度经验公式的拟合,发现混合燃油的着火延迟期、火焰浮起长度与化学当量比的燃油混合分数呈正相关,而火焰浮起长度与燃油的十六烷值呈负相关.所有燃油的火焰浮起长度均小于液相长度,整个燃烧过程中均处于火包油状态,这使得燃烧促进了液相燃油的蒸发,导致着火后液相长度更短.纯生物柴油由于较短的火焰浮起长度和较高的反应活性,其燃烧导致的液相蒸发最为明显.

In order to study the effects of different methanol addition ratio on spray and combustion characteristics of ternary blends with methanol,n-octanol and hydrogenation catalytic biodiesel(HCB),a single-hole nozzle spray was measured within a high-pressure high-temperature constant volume combustion chamber by means of multiple kinds of optical diagnostics,namely high-speed schlieren imaging and OH*chemiluminescence,diffused background-illumination extinction imaging and natural luminosity imaging.The results show that the ignition delay and lift-off length increase with the higher methanol addition ratio,while the spray penetrates more slowly with more methanol blending.After a correlation analysis,it can be concluded that ignition delay and lift-off length in-crease with higher Zst,but effects of Zst on lift-off length are much less important than that of cetane number.A higher cetane number leads to a shorter lift-off length.Because lift-off length is shorter than liquid length for all fu-els under all operating points,the liquid fuel evaporation is enhanced,leading to a shorter liquid length after ignition.The pure HCB presents the most noticeable reduction on liquid length.