正癸烷四步高温总包机理构建与验证

A Four-Step Global Kinetic Mechanism for High-Temperature Combustion of n-Decane

关键词:  正癸烷  总包机理  绝热火焰温度  点火延迟时间  层流火焰速度  本生灯

Key words:  n-Decane  Global mechanism  Adiabatic flame temperature  Ignition delay time  Laminar flame speed  Bunsen burner

摘要:

燃烧数值模拟受控于化学反应机理的物种和反应数量，为减小机理规模，构建了包含8个组分（C₁₀H₂₂，O₂，C₂H₄，CO，H₂，CO₂，H₂O，N₂）并带有修正函数的正癸烷四步高温总包反应机理。以烷烃高温宏观氧化反应路径分析为基础，将正癸烷燃烧过程分解为长链烃裂解为中间烃、中间烃氧化为CO、CO氧化为CO₂等三个宏观过程，其中裂解反应是点火延迟时间的主控因素，而氧化释热过程则对层流火焰速度和点火延迟时间均有显著影响。以点火延迟时间和层流火焰速度为优化目标，通过文献比选并调试得到指定工况下的初始动力学数据；结合两个正癸烷骨架机理的模拟数据，采用以当量比与压力为自变量的二元函数对裂解和氧化过程的Arrhenius公式的指前因子进行修正。在温度T=1000~2000K，压力p=0.1~0.3MPa，当量比Φ=0.5~1.5的工况下，利用Chemkin-Pro软件计算了总包机理的绝热火焰温度、点火延迟时间、层流火焰速度，计算结果与实验数据和骨架机理的计算结果吻合较好。运用该总包机理对本生灯火焰进行数值模拟，取得了与实验一致的火焰温度和组分浓度变化。研究范围内该总包机理满足正癸烷的主要燃烧特性，同时大幅降低了反应规模，适合正癸烷高温燃烧的工程应用。

Abstract:

Combustion numerical simulation is subject to the number of species and reactions in chemical reaction mechanism. In order to reduce the scale of mechanism， a four-step overall kinetic mechanism for the high-temperature combustion of n-decane with modified functions was presented and studied， including eight components （C₁₀H₂₂， O₂， C₂H₄， CO， H₂， CO₂， H₂O， N₂）. Based on the analysis of macroscopic oxidation reaction paths of alkanes at high temperature， the combustion process is decomposed into three macroscopic processes. Firstly， long chain hydrocarbon is cracked into intermediate hydrocarbons， intermediate hydrocarbons are then oxidized to CO， and finally CO is oxidized to CO₂. In these processes， the ignition delay time is mainly controlled by the cracking process， and the oxidation heat release process has an obvious effect on both the laminar flame speed and the ignition delay time. Taking ignition delay time and laminar flame speed as optimization objectives， the initial kinetic data were obtained under specified working conditions through literature comparison and debugging. Based on the simulation data of two n-decane skeleton mechanisms， the pre-exponential factors of the Arrhenius formula for cracking and oxidation processes were modified by binary functions with equivalence ratio and pressure as independent variables. The adiabatic flame temperature， ignition delay time and laminar flame speed were calculated by Chemkin-Pro software under the conditions of temperature （T=1000~2000K）， pressure （p=0.1~0.3MPa）， equivalence ratio （Φ=0.5~1.5）. And the calculated results were in good agreement with the experimental data and the calculation results of the skeleton mechanisms. The numerical simulation of Bunsen burner flame was carried out by this mechanism， and the change of flame temperature and component concentration was obtained in accordance with the experimental results， which verified the feasibility of the application of this global mechanism in combustion simulation. In certain conditions， the global mechanism could predict the main combustion characteristics of n-decane， while greatly reducing the scale of the reaction， which is suitable for engineering applications of n-decane combustion at high-temperature.