摘要
利用定容燃烧弹装置研究了初始压力为3MPa下柴油在乙醇与空气混合气氛围中着火特性,观察和分析了在这两种氛围中柴油的滞燃期和浮起(lift-off)长度随时间和初始温度的变化规律。采用正庚烷-乙醇详细反应机理,利用数值模拟的方法计算了零维模型中正庚烷及正庚烷加乙醇的着火过程。结果表明,乙醇的加入延长了柴油的滞燃期和火焰的lift-off长度,火焰稳定后,乙醇氛围中火焰的lift-off长度随时间的变化比在纯空气氛围中大。在800～900K,随着温度的升高,柴油的滞燃期和火焰的lift-off长度缩短,并且二者在乙醇氛围中对温度的敏感性更大。数值模拟结果表明,乙醇的加入通过抑制OH体积分数延长了正庚烷低温反应的开始时间,从而大大抑制了低温反应的进行,延长了滞燃期,但缩短了高温反应的放热时间,加快了高温反应的进行。
A constant volume bomb was used to study diesel combustion characteristics under air and air- ethanol atmospheres and ambient pressure of 3 MPa. The ignition delay and lift-off length of diesel flame were observed at varied initial temperatures under the two atmospheres. Using zero-dimensional simulation model and the detail reaction mechanism of n-heptane combining ethanol, the ignition process of n-heptane and n-heptane mixing with ethanol was studied. The results show that, ethanol addition increases the ignition delay and lift-off length of diesel flame. For stabilized flame, the lift-off length of flame at the ethanol atmosphere varies greatly compared with that at the pure air atmosphere. Within the temperature range of 800-900 K, the ignition delay and lift-off length of diesel flame decrease with the increase of temperature, and they are more sensitive to the temperature at the ethanol atmosphere. Simulation results shows that, low temperature reaction delay is increased by ethanol addition as the concentration of OH is low, and low temperature reaction is suppressed, however, heat release duration of high temperature reaction is decreased, and high temperature reaction is promoted.
出处
《内燃机学报》
EI
CAS
CSCD
北大核心
2010年第3期207-213,共7页
Transactions of Csice
基金
国家自然科学基金资助项目(50876075)
教育部博士点基金资助项目(200800560040)
关键词
柴油
乙醇
定容燃烧弹
滞燃期
浮起长度
Diesel
Ethanol
Constant volume bomb
Ignition delay
Lift-off length
