甲烷-空气预混火焰中OH*标识放热率的数值模拟研究 *

Numerical Evaluation of Heat Release Rate Measurement Using OH* Chemiluminescence in Premixed Methane-Air Flames

关键词:  激发态粒子  化学发光  放热率  定量化  层流预混火焰

Key words:  Excited state radical  Chemiluminescence  Heat release rate  Quantification  Laminar premixed flame

摘要:

为了研究化学发光对放热率的标记特性，得到化学发光与放热率之间的定量关系，对当量比0.8～1.4，流速5～25cm/s的甲烷-空气预混火焰进行了数值模拟。分析了不同基元反应的放热特性及反应速率与放热率的关系；通过研究激发态粒子浓度分布与放热率分布，给出了OH*标识放热率的依据，并获得了放热率峰值与OH*浓度峰值之间的定量关系。结果表明，激发态粒子OH*和CH*都集中分布于热量大量释放的狭窄反应区内；OH*浓度分布随当量比的变化规律与基态粒子HCO相同，在当量比为1.0时峰值浓度最大；OH*可以标识放热率，且效果优于CH*；OH*浓度峰值与放热率峰值呈线性关系，当量比增大，比例系数减小。

Abstract:

An numerical study on laminar methane-air premixed flames was performed to determine the quantitative correlation between the heat release rate (HRR) and chemiluminescence，varying the equivalence ratios from 0.8 to 1.4，flow velocities from 5cm/s to 25cm/s. Different heat release characteristic of elementary reactions and the relationship between net reaction rate and heat release rate are analyzed. The present work investigates the distribution of excited state radical concentration and heat release rate，gives the reason of OH* chemiluminescence mark HRR and determines the precision correlation between the peak concentration of OH* and the peak of HRR. It is found that OH* and CH* are located in the narrow area where severe chemical reactions are happening and lots of heat are released. The variation of OH* concentration distribution with equivalence ratio is similar to HCO，the peak value of concentration reach maximum at equivalence ratio is 1.0. OH* can identify the distribution of the heat release rate. Compared with CH*，OH* is more effective in predicting the heat release rate. The peak of heat release rate as a linear function of the peak concentration of OH*，and with the increase of equivalence ratio，coefficient of proportionality is decreasing.