用加速量热仪研究参比燃料的低温氧化特性(Ⅱ)

Oxidation Characteristics at Low Temperature for Primary Reference Fuels by Accelerating Rate Calorimeter (Ⅱ)

基于用加速量热仪(ARC)对参比燃料与空气的混合物在低温条件下的氧化特性的实验结果,对ARC实验结果进行了热力学和化学动力学分析.根据能量平衡方程,推导出在较小的样品质量下,考虑到密闭容器中各种基本反应物质的比热容随温度变化时,热惰性因子的准确表达式,算出参比燃料在反应过程中的实际自放热率,并根据化学动力学分析求出正庚烷和异辛烷低温氧化动力学参数.对正庚烷和异辛烷的自放热率分析发现,它们都出现双峰现象,并分别在 589. 4K和 585. 7K时有最大放热率,随后在 598. 5K和 594. 8K结束自放热.

According to the experimental results of oxidation characteristics for primary reference fuels (PRFs) at lower temperature ranged from 450 K to 650 K, both the thermal and chemical kinetics analyses on self-heating rate of oxidation for PRFs were made. Based on energy balance equation, the exactly equations of the thermal inertia factor, activation energy, and reaction order,considering the effect of temperature on heat capacity and the sum of reaction substance,were deduced.By using these equations, the basic chemical parameters for n-heptane and iso-octane at the pressure of 1.5 MPa, (equivalence) ratio of 0.52, and the temperature at 450 K^650 K were calculated. The results show that the self-heating rates of both n-heptane and iso-octane have the two-peak phenomenon. The maximum self-heating rates are detected at (589.4 K) and 585.7 K,and after that, the self-heat reaction terminates respectively at 598.5 K and 594.8 K for n-heptane and iso-octane.