﻿ 柴油车碳化微米长木纤维DPF尾气排放的压降梯度
 林业科学  2009, Vol. 45 Issue (12): 118-123 PDF
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#### 文章信息

Ma Yan, Guo Xiurong, Wang Fenghu, Du Danfeng

Pressure Drop Gradient of Carbonized Micro-Length Wood Fiber DPF

Scientia Silvae Sinicae, 2009, 45(12): 118-123.

### 作者相关文章

Pressure Drop Gradient of Carbonized Micro-Length Wood Fiber DPF
Ma Yan, Guo Xiurong, Wang Fenghu, Du Danfeng
Northeast Forestry University Harbin 150040
Abstract: Diesel powered vehicles produce a considerable amount of particulate laden exhaust gases, which is thought to be the main source of air pollution and also cause lung cancer. The diesel particulate filter(DPF) is one of the leading technologies for reducing diesel PM(particulate material). In this paper, utilizing carbonized micro-length wood fiber(CMLWF) as filter material of DPF is presented and a corresponding mathematic model is built for the first time. Theory and test prove that the filter efficiency of the CMLWF DPF is high, the pressure drop gradient low and performance life long, which can successively open up a new direction for reducing diesel PM.
Key words: carbonized micro-length wood fiber(CMLWF)    diesel particulate filter(DPF)    particulate material(PM)    pressure drop gradient

1 碳化微米长木纤维

2 碳化微米长木纤维DPF压降梯度理论计算方法

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 图 1 简化的立体框架结构及其二维示意 Figure 1 Simplified three and two dimensional geometrical model
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Rep≤2 000时, λ=64/Rep。对于形阻系数CD, 要根据简化的框架结构来解决, 因迎风形状阻力是由垂直于流动方向的六棱柱产生的, 这属于管内有阻碍物的流动阻力问题(华绍曾等，1985), 其阻力与阻碍物的截面形状、大小及其在管内的位置有关, 其形阻系数经简化表示为：

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Cx可在有关流阻手册中查到(Masoudi et al., 2000; Konstandopoulos, 2003)，根据实践经验，本文取ζ=0.7。在一单元体中, 进、出口阻流支杆总迎风面积为：

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3 渗流速度对DPF压降梯度的影响 3.1 试验设备与材料

3.2 压降梯度理论计算结果与试验结果比较

 图 2 滤芯上压降梯度与渗流速度的关系 Figure 2 Relation between pressure drop gradient and seepage velocity —计算结果Result；●过滤体Ⅰ Flter Ⅰ；▲过滤体Ⅱ Filter Ⅱ；★过滤体Ⅲ Filter Ⅲ.下同The same below.

4 滤体长度对微粒捕集效率及压降梯度的影响

 图 3 过滤体长度对微粒捕集效率和压降梯度的影响 Figure 3 Impact of the filter length upon the PM arresting efficiency and exhaust pressure drop gradient
5 滤体横截面积对微粒捕集效率及压降梯度的影响

 图 4 过滤体横截面积对微粒捕集效率和压降梯度的影响 Figure 4 Impact of the filter cross-sectional area upon the PM arresting efficiency and exhaust pressure drop gradient

 图 5 改进后的过滤体对PM捕集效率及压降梯度的影响 Figure 5 Impact of the modified filter upon the PM arresting efficiency and exhaust pressure drop gradient

6 结论

1) 在设计DPF滤芯时需慎重选择合适的孔径，并且在外形结构允许的情况下，可以优先考虑孔隙直径较大、轴向长度较长的过滤介质。

2) 增加过滤体长度，微粒捕集效率提高；但压降梯度也近乎直线上升。过滤体长度对细孔CMLWF DPF过滤体排气背压的影响更加显著。

3) 增加过滤体的横截面积，微粒捕集效率提高，同时压降梯度下降；细孔CMLWF滤体的微粒捕集效率和压降梯度受过滤体横截面积的影响较大。

4) 为解决细孔碳化木过滤体阻力大、微粒仅沉积在过滤体气流入口端附近的问题，本文采用特殊工艺加工出从进口端到出口端孔径由大到小过渡的碳化木过滤体。试验结果表明，改进后的过滤体的微粒捕集效率略有下降，但随着过滤体长度的增加，微粒捕集效率的损失逐渐减小；压降梯度则随着过滤体长度的增加而大幅度下降。

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