Influence of PCHE channel shape on oxidation coking characteristics of aviation kerosene
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摘要:
数值计算了直形、Z形PCHE（印刷电路板式换热器）流道航空煤油氧化结焦过程，分析了不同质量流量及热流密度下流道形状对航空煤油氧化结焦特性的影响规律及内在机理。结果表明：当流道转折角从0°（直形）逐渐增大到25°（
Z 形），结焦总量先减小后增大，沿程分布呈现多峰值特征。小转折角时，高温边界层诱发结焦机制主导结焦过程，转折引发的二次流随角度变大而逐渐增强，导致换热强化，结焦得到抑制；大转折角时，高温度梯度诱发结焦机制占主导地位，二次流会增大温度梯度，导致结焦速率沿程分布的不均匀性变强，加剧了转折角处的结焦沉积。结焦量随质量流量的增大而下降，随热流密度的增大而升高，转折角越大，提升质量流量抑制结焦的效果越明显。-
关键词:
- 印刷电路板式换热器（PCHE） /
- 航空煤油 /
- 氧化结焦 /
- 流道形状 /
- 二次流
Abstract:The oxidation coking process of aviation kerosene with straight and Z-shaped PCHE (printed circuit heat exchanger) channels was numerically calculated. The influences of the shape of the channels on the oxidation coking of aviation kerosene with different mass flow and heat flux were analyzed. The results showed that, when the turning angle of the channel gradually increased from 0° (straight) to 25° (Z-shaped), the total mass of coking decreased first and then increased, and the distribution along the channel presented multi-peak characteristics. When the angle was small, the coking mechanism induced by the boundary layer at high temperature dominated the coking process, and the secondary flow induced by the transition gradually increased with the increase of the angle, resulting in the inhibition of heat transfer and enhanced coking. When the turning angle was large, the coking mechanism induced by high temperature gradient was dominant, and the secondary flow could increase the temperature gradient, which led to the uneven distribution of coking rate along the way, and intensified the coking deposition at the corner. The coking mass decreased with the increase of mass flow rate and increased with the increase of heat flux. The larger turning angle indicated the more obvious effect of increasing mass flow rate on inhibiting coking.
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图 6 直形流道内结焦反应中间产物沿程分布
Figure 6. Intermediate products distribution of coking reaction along straight channel
图 7 直形流道底面与棱角处沿程结焦速率
Figure 7. Coking rate at the bottom and corner of straight channel
图 9 Z形流道内结焦反应中间产物沿程分布
Figure 9. Intermediate products distribution of coking reaction along Z-shaped channel
图 13 不同转折角流道375 mm处二次流
Figure 13. Secondary flow at 375 mm position in different angle channels
图 14 不同转折角流道2 h结焦量随质量流量变化
Figure 14. 2 h coking mass varies with the mass flow rate at different angle channels
图 15 不同转折角流道2 h结焦量随热流密度变化
Figure 15. 2 h coking mass varies with the heat flux density at different angle channels
表 1 计算工况
Table 1. Computational boundary condition
序号 入口
温度/K流量/
（g/s）压力/
MPa热流密度/
（ kW/m2）1 300 1 3 340 2 300 1 3 280 3 300 1 3 220 4 300 1 3 160 5 300 1.5 3 340 6 300 2 3 340 7 300 2.5 3 340 
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反应类型 序号 反应过程 指前因子A 活化能E/106 空间反应 R1 F+O2$\longrightarrow $P 0.083 0.2 R2 P$\longrightarrow $S 500 41.861 R3 P$\longrightarrow $IN 2 8.4 壁面反应 R4 F$\longrightarrow $D 2×10−11 8.6 R5 IN$\longrightarrow $D 10 50 R6 P$\longrightarrow $D 480 85
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