柴油机微粒过滤体内部温度梯度的数值模拟

Numerical simulation of temperature gradient inside diesel particulate filter

基于一维非稳态模型,在最优的流量条件下,研究了在无颗粒层时,过滤体参数(孔目数(CPSI)、壁面厚度δw、过滤体长度L、导热系数λ)和再生条件(再生持续期td、最高再生温度Tmax)对过滤体再生时壁面温度梯度(dT/dx)的影响.研究结果表明:随着CPSI的增加,壁面温度梯度极值((dT/dx)max)逐渐增加;壁面厚度δw对温度梯度有显著影响,当δw<0.3 mm时,(dT/dx)max随δw的增大而减小,且变化显著,而当δw≥0.3 mm时,(dT/dx)max随δw的变化趋于平坦;随过滤体长度L的增加,(dT/dx)max显著下降;当λ<1.0 W.(m.K)-1时,(dT/dx)max随λ的增大而减小且变化显著,而当λ≥1.0 W.(m.K)-1时,随λ的增大(dT/dx)max接近于线性减小;随再生持续期td和最高再生温度Tmax的增大,(dT/dx)max逐渐增大.

Based on the one-dimensional unsteady model, the influences of key parameters on the filter wall temperature gradients were investigated under the optimal flow rate. The key parameters include fil- ter structure parameters of cell per square inch （CPSI） , wall thickness δw, filter length L and thermal conduct factor A and regeneration conditions of regeneration duration td and regeneration temperature Tmax. The numerical simulation results indicate that with the increase of CPSI, the （dT/dx）max gradually increases. The wall thickness δw has remarkable effect on the （dT/dx）max＂ When the δw is less than O. 3 mm, the （dT/dx） decreases with the increase of δw, while the （dT/dx） nearly remains constantly when the δw is more than 0.3 mm. With the increase of filter length L, the （dT/dx） max decreases sharp- ly. When the A is less than 1.0 W （m K） -1, the （dT/dx） significantly decreases as the A increa- ses, the （dT/dx） lineally decreases when the A is more than 1.0 W （m K） -1. With the increases of regeneration duration time td and temperature Tmax, the （dT/dx）max increases gradually.